Journal of Engineering Geology

---

In seismic prone areas, earthquakes happen more than just main shocks which are happen with sequences of shocks include of different intensity of aftershocks. In technical documents, these kinds of several earthquakes are called mainshock-aftershock ground motions. In this study, seismic behavior of RC frame under mainshock-aftershock with different ratios of maximum acceleration of aftershock to maximum acceleration of mainshock was evaluated. In this paper, nonlinear time-history analysis of frame were performed under mainshock-aftershock sequences and then the residual interstory drift ratio for comparing response of frame under seismic sequences was evaluated. The results show that, residual interstory drift ratio of frame, related to intensity of aftershocks to mainshock and enhance of intensity of aftershock due to increase residual interstory drift ratio of frame. Although, growth of residual interstory drift ratio of top stories more significant than below stories of frame.

---

With regard to the increase of computing power in the past decades, finite element methods have been used to obtain the graphs of rotational moment curves which reflect non-linear effect in connections response. Several common semi-rigid connections are modeled and their behavioral properties are briefly reviewed, then the details related to a new semi-fixed connection have been provided. The behavioral properties like hardness, ultimate capacity and ductility are investigated and compared to other simulated connections. To perform non-linear analyses of connection, finite element software ABAQUS is used. In this simulation, it has been tried to have inter-component interactions according to reality as much as possible. Bolted connections are modeled exactly and the interaction among the bolt surface and hole is modeled as a hard friction with friction coefficient 0.3 with the ability of separating after loading. Also, fillet welds are modeled as a prism with triangular section. Where a groove weld is applied, since the strength in this type of welding is like base metal, two connection parts are stuck together. To mesh the element, C3D8R element is used. The proposed connection n1 has the most rigidity values among semi-rigid connections. Reducing the number of connection bolts has more reducing impact on connection rigidity value, so that with the half thickness of upper and lower sheets, rigidity rate is reduced only 9%, but with the half number of bolts, rigidity rate is reduced about 64%. Also the connection n3 have lowest rigidity rate and its rigidity amount is in the class of bolted connection in seat angle to web angle.

---

Previous earthquakes have shown that topographic irregularities have significant impacts on the site seismic response and increasing structural damage by amplifying seismic responses. Studies on seismic behavior of slope topographic have shown that dynamic response of free field and soil-structure system is severely on the influence of topography shape and soil properties. Angle and height of slope, frequency of excitation, nonlinear behavior of soil and depth of bedrock are other parameters that affect on the response of the entire system. Furthermore the studies have shown that presence of structure adjacent to slope is very effective on variation of seismic behavior pattern of this topography but these studies are very limited. In this study the effect of existing structure adjacent to slope to seismic behavior pattern of slope topography have been investigated. The parameters that have studied in this article comprise slope angle and frequency content of excitation. The results show that the presence of structure adjacent to the slope, causes an increase to the response of free field and transmitting maximum response to distance away from structure position.

---

Consecutive impacts of pile driver hammer on a precast pile head for pile installation in the ground is called impact pile driving. Nowadays, the widespread use of impact pile driving in pile foundations construction is undeniable; As a result, pile driving is the most common source of construction vibrations among the sources of producing ground vibrations. The ground vibrations during pile driving is the most important factor of limiting the use of this method. Thus, to avoid structural damages, acceptable prediction of ground vibration before any project implementation is necessary. For this purpose, numerical modeling is undoubtedly the most accurate, economical and fastest way; but up to now, correct modeling of pile installation process has been the main problem in numerical modeling of pile driving. This study aims to achieve better match of ground vibrations with field results compared to the previous numerical results in terms of peak particle velocity by modeling impact pile driving operation through ABAQUS finite element software from ground surface to a desired depth without considering previous researchers assumptions and considering the details of practical works.

---

Due to increasing speed and mass of trains and vehicles, the errors arising from utilizing moving force method to obtain dynamic response of bridges cannot be neglected. In this paper, dynamic response of bridges under moving loads is studied. The bridge is modeled as simply-supported Euler-Bernoulli beam. Since in modeling moving loads by moving force method, inertial forces are neglected, this method is valid for a limited range of influential parameters (speed and mass). By considering inertial forces between the moving load and supporting structure, moving mass method can be utilized to extract dynamic governing equations. Numerical results reveal that by increasing speed and mass of the moving load, midpoint dynamic deflection of bridge obtained by two distinct methods differ considerably.  For example, for mass ratio of 0.15 and speed ratio of 0.8, 11 percent difference is observed in midpoint dynamic deflection calculated by two aforementioned methods.

---

./files/site1/files/6Extended_Abstract.pdfExtended Abstract
(Paper pages 115-134)
Introduction
Different factors should be considered in investigating soil- structure interaction for which we can refer to underground layers material properties, site shape and topography and entry motion. It has been showed that seismic waves will be reflected and makes more strange seismic waves in comparison with the state of without slope. To investigate the topography effects the various assumptions such as considering the rigid and compliant bedrock, half space, stimulations with different frequencies, slopes with different angles, different heights of slopes, and soil type were evaluated.  In this study topography effects on interstory drift of three structures with steel moment resistant frame system is considered, for this aim 6 combined model of soil- structure and topography is investigated. Three structures of 6, 9 and 12 story placed in near and far from of crest of a slope and 10 earthquake on bedrock has been applied to models. Interstory drift is considered as a criteria for investigating topography effect.
Material and Methods
This paper examines 3 planar steel moment resistant frame (SMRF) which have been previously designed by Karavasilis et al (2007) according to EC3 and EC8. These structures have 3 bays, and 6, 9, 12 stories. The length of each bay and the height of each story are 5 and 3 m, respectively. Furthermore, the amount of dead and live loads are considered in accordance with the current study (Minasidis et al 2014). The study frames were modeled in ABAQUS software in the form of two-dimensional (Figure 2). A36 steel is used in the models and the yield strength of steel is 235 MPa. Modeling of the behavior of steel was implemented using the yield criterion of VON MISES and taking into account the non-linear behavior of materials and Poisson's ratio of 0.3. A kinematic material hardening of 3% is assumed for the nonlinear elements and a Rayleigh damping of 5% is assumed for the first two modes of each frame.
In this study,   a slope with α=20 is considered. The characteristics of the slope and the soil of the region are obtained by borehole in different point based on Ghanbari et al 2011 study.




Figure1. Growth percentage in average amount of interstory drift
The desired slope has a height of 30 m. The depth of the bedrock is considered equal to 60 m. The numerical analyses were performed with the Finite element method, for nonlinear soil with VS=238 m/s, Poisson’s ratio v=0.35 and mass density ρ=1800 kg/m3. Moreover, to estimate the distribution of response, 10 records located on the bedrock (shear wave velocity is more than 650 m/s) have been used. To reduce the near source effect records are selected in such a way that they have no pulse in velocity time history and Distance from source to site greater than 10 km considered
Result
Result showed that interstory drift of structures increases due to topography effects, but this increase varies for different structures and earthquakes. Growth percentage in average amount of interstory drift are 25, 15 and 6 percent for structures with 6, 9 and 12 story respectively. Also for structure 9 and 12 story, interstory drift was decrease in some stories.
 

---

./files/site1/files/7Extended_Abstract.pdfExtended Abstract
 (Paper pages 135-156)
Introduction
Many civil structures (e.g. tunnel walls, bridge pillars, dam abutments and road foundations) are subjected to both static and dynamic loads. Cyclic loading leads to occurring fatigue phenomenon. Fatigue is the tendency of materials to break, or the process of damage accumulation, under cyclic loading. It was found that the dynamic fatigue strength can be reduced by 30-70 percent on average compared to uniaxial compression strength. Different materials show different response when they are subjected to cyclic loading. Some materials become stronger and more ductile, while others become weaker and more brittle. Although it is clear that the mechanical properties of rock under dynamic loads varied dramatically from those under static loads, the nature of dynamic failure in rock remains unclear, especially in cyclic loading condition. Fatigue behavior of rocks was rarely studied in respect to other materials such as steel and soil. The performed researches on fatigue behavior of rocks indicated that fatigue life will be decreased by increasing load amplitude in logarithmic and exponentially pattern. Also, strain softening is the dominated behavior of rocks against cyclic loading. Furthermore, some parameters such as maximum load level, confining pressures, amplitude, and loading frequency have considerable effects on fatigue behavior of rocks. However, available data on fatigue behavior remain insufficient for solving the practical tasks of predicting rock bursts and earthquakes. Obtained results are inconclusive and sometimes discordant. The aim of the current work was to assess tonalite rock fatigue behaviour under different loading conditions to describe the fatigue damage process of the granitic rock.
Material and methods
Several core samples were prepared to perform this research. The core samples were prepared with a L/D ratio of 2.5 with an average diameter of 54 mm. Before the fatigue tests, the physical and mechanical properties of the rocks were measured. Uniaxial compressive strength test (UCS) has been done on 5 core samples. The tests were performed in the load-control mode with a 1.6 kN/s loading rate. The tests were conducted to obtain the physico-mechanical parameters of the rocks in static loading condition, and provided a reference for subsequent dynamic tests. The cyclic tests were performed in both load and displacement control modes. To record axial and lateral strains during the fatigue tests, four strain gauges have been employed with arrangement of two axial and two laterals. Also, three acoustic emission sensors were installed on top, mean and bottom of the core samples to record cracking sound. In order to doing the tests a servocontrol Instron machine with 500 kN capacity was employed. The fatigue tests were conducted with three different maximum loads, 1 Hz frequency, and constant amplitude (0.82 of uniaxial compressive strength). The maximum stress level (the ratio of maximum cyclic stress to static strength) was varied 0.80, 0.85, and 0.90. The amplitude level (the ratio of amplitude stress to static strength) ranged from 0.50 to 0.70 and 0.90. Finally, Multi stages loading with increasing amplitude were applied for the displacement control tests. The results of fatigue tests have been evaluated by fatigue damage parameters including maximum and minimum axial strain, maximum and minimum lateral strain, tangent and secant modulus, toughness and hysteresis energy.
Results and discussion
The obtained results indicated that during fatigue process failure occurs below the maximum strength loading condition as a result of accumulative damage. Analysis of the fatigue test results showed that the fatigue failure consisted of three stages: fatigue crack formation (initiation phase I), stable crack propagation (uniform velocity phase II), and unstable crack propagation resulting in a sudden breakdown (accelerated phase III). By comparing the axial and lateral deformation, it was found that lateral deformation is more sensitive to fatigue. At higher stress levels, considerable part of fatigue life is response to crake development, whereas at lower stress levels, crack acceleration phase of fatigue life is distinguishable. Descending trend of loading and unloading tangent modulus shows a scatter pattern. This behavior may be related to the calculation method and loading condition, as well as microstructure and behavior of the rock mass. In spite of tangent modulus results, the three-stages of damage process (especially phase I and II) for secant modulus in both loading and unloading conditions are clear. The result is due to the method of calculation and increase in axial strain with increasing number of cycles. Brittle behavior of this type of rock leads acceleration phase to be hidden and unclear in most of fatigue damage parameters. A dramatic decrease of toughness and hysteresis energy in the first few cycles is due to the closing of pre-existing micro fractures. In fact, during the initial cycle, the rock behaves in a more ductile fashion than in the next few cycles. Thereafter, toughness begins to increase slowly, then steadily, and finally rapidly. A similar behavior was found for hysteresis energy as well. This fact indicated that cracks generated in parallel to loading direction. Fatigue displacement control tests show a strain softening behavior for the granitic rocks. This behavior is highlighted in variation of maximum stress during the tests. This parameter, especially in final step of loading, shows distinguishable decreasing trend.
Conclusion
The tonalite rocks were subjected to uniaxial cyclic loading in both load and displacement control mode. The following conclusions were drawn from this research.
-Accumulated fatigue damage occurs in an obvious three-stage process. This is the result of the micro-fracturing mechanism in the fatigue process.
-By comparing axial and lateral strain damages, it was found that crack propagation occurred in the loading direction and crack opening occurred in the lateral direction. So, among fatigue damage parameters, lateral strain shows the best three-stage fatigue damage behavior.
- Strain softening was found as rock response to cyclic displacement control loading.

---

./files/site1/files/3Extended_Abstract.pdfExtended Abstract
(Paper pages 51-72)
Introduction
Value engineering is considered an efficient alternative to improve design and construction process of urban tunneling projects. Application of value engineering techniques can provide investigating all aspects of a project in a team work, creative and short-time manner which contribute to precisely identify a project’s quality improvement issues, construction time and costs.
Hakim Expressway one of the capital's main highways in Tehran metropolis with 9 Km in length, starts from the junction of Resalat expressway and Kurdistan expressway after Resalat tunnel and ends in Lashgari expressway. The west extended this highway passing through the area of Chitgar forest park. Due to environmental constraints, the Hakim twin tunnels with cross-section of 186 m² excavation areas and total length of 3256 m to the NATM/SEM method in this area were excavated (Figure 1).
In preliminary design of Hakim tunnel project, on category of excavation and support system was suggested. During the tunnel^’s excavation operation, the behavior and classification of the tunnel were investigated from field observation, instrumentation and monitoring of geological models and subsequently, further excavation process was modified in accordance with value engineering. The aim of using value engineering approach in this project was to reduce the costs without any decrease in quality, employer satisfaction along with minimum risk and as well as improving operational and practical aspects. Ultimately, establishment of the value engineering approach on Hakim tunneling project leads to 10% reduction in construction costs as well as relevant quality with the least challenges (Figure 2).
General Geology
The city of Tehran is founded on Quaternary alluvium, which has been geologically classified by Rieben [1]. The city is located at the foot of the Alborz mountain range, which is basically composed of Eocene pyroclastic deposits (green tuff) and other volcanic rocks. The geology and the morphology of the Tehran region is similar to that for other cities located at the foot of mountains.
Rieben (1966) divided the Tehran coarse-grained alluvia into four categories, identified as A, B, C and D, where A is the oldest and D the youngest (Figure 3).
Hakim tunnel project locates on foothills of northern Tehran, crossing the hills of Chitgar forest park. Results of field surveys indicate that alluvial deposits in tunnel track belong to C (ramps and tunnel portal) and A formations (in most parts of tunnel track).



Geotechnical characterization
Table1 summarizes soil input parameters. Two soil types were considered for the model with 8- meter-height overburden. First layer (No.1) starts from surface with a 1 meter thickness. Second layer (No. 2) has 7 meter thickness.
Table1. Summary of the geotechnical parameters

Parameter	Unit	Layer No. 1	Layer No. 1
Internal friction angle (CU)	Deg.	29	33
Cohesion (CU)	Kg/cm2	0.15	0.45
Density	Kg/cm3	18.5	20
Poisson ratio of unloading/reloading	Kg/cm2	0.2	0.2
Secant deformation modulus	Kg/cm2	550	900
Power of stress level of stiffness		0.5	0.5
Stiffness unloading	Kg/cm2	1650	2700

During tunnel excavation using field observations, the results of the monitoring and reviewing the geological model, ground behavior and classification were re-examined to optimization of the excavation and support class (Figures 4, 5).
Detailed analysis before excavation and continuation of studies led to two excavation and support classes purposed for Hakim tunnel. Both classes of excavation and support due to ground conditions are modeled and analyzed using software Plaxis. For verification, the results of numerical analysis using monitoring and field observations were compared during the tunnel excavation. The results of monitoring compliance with the results of numerical analysis were appropriate.
Implementation and construction costs were calculated for different sections of two excavation and support classes in accordance to contraction documents to evaluate the effect of optimization in design (Figures 6, 7)
 

Figure4. Excavation sequence in excavation and support class “A”



Results
Results indicate that in both classes maximum costs are related to excavation section while minimum costs are for invert and mucking. In all concrete spray operations there was just a %3.5 increase in costs. Overall savings in excavation and support was about %10 which is significant (Figure 8).


Figure8. Savings percentage comparison in excavation and support classes A and B



 

---

./files/site1/files/4Extended_Abstract.pdfExtended Abstract
(Paper pages 73-90)
Introduction
Up to now, various indexes and methods have been presented for evaluating the abrasivity of rocks. In total, these methods can be divided to two main groups; the methods based on nature of rocks, methods based on heuristic tools. Schimazek F-abrasivity index is one of the most powerful and applicable indexes for evaluating the rock abrasiveness. This index uses the grain size, Brazilian tensile strength and equivalent quartz content for abrasivity analysis. Since the values of these parameters are equal in Schimazek index, therefore, in some cases this index doesn't have suitable ability to distinguish and classify the rock abrasiveness. This paper tries to modify the Schimazek index considering the weights of its applied parameters.
Material and Methods
In this research, Fuzzy Delphi Analytical Hierarchy Process (FDAHP) has been used to calculate the weight of dominant parameters in rock abrasivity. For this purpose several questioners have been distributed and the expert opinions were collected. The results showed that the quartz content, grain size and tensile strength have the weight of 0.4, 0.31 and 0.29 respectively and new Schimazek F-abrasivity index is as presented in equation (1).
    
In the next stage, in order to facilitate the application of new index, a new classification system was developed. This classification and related weighing graphs (Figure 1) help to change the discontinuous classification to continuous one.
Results and discussions
In order to verify the application of the new developed index, ten ornamental stones have been studied and the old and modified Schimazek indexes were calculated for all of them. Then, the cutting rate (sawing rate) of each stone was recorded in laboratory and the mathematical relationships between new and old indexes have been achieved. The results show that the new Schimazek abrasivity index has higher ability to predict the cutting rate than old one (Figure 2). 

 
Figure1. Continuous weighting for parameters of Schimazek F-abrasivity index


Figure2. Regression of old and new Schimazek F-abrasivity index with cutting rate of granite ornamental stones
Conclusion
Generally it could be concluded that, the main weakness of Schimazek F-abrasivity index which is the equality of parameters’ importance, has been removed by idea developed and confirmed in this study. The different weights which allocated to grain size, Brazilian tensile strength and equivalent quartz content in study, improves the Schimazek index applicability in rock engineering applications specially rock cutting and drilling. Therefore, it is recommended to use new method instead of old one in future applications.
 




 

---

./files/site1/files/5Extended_Abstract.pdf Extended Abstract
 (Paper pages 91-114)
Introduction
Due to possibility of occurrence in various natural environments and the variety of natural and artificial factors that affect landslides, landslide has special importance in natural hazards. Depending on the landform, several factors can cause or accelerate the landslide. According to previous researches, Human activities, land morphology, geological setting, slope, aspect, climate conditions, proximity to some watershed features such as rivers and faults are the most important parameters. Landslides occur frequently each year and they can cause heavy losses which compensating some of them requires a lot of money and time.
Assessing landslide related hazards with only limited background information and data is a constant challenge for engineers, geologists, planners, landowners, developers, insurance companies, and government entities.
The landslide occurrence in terms of time and place are not easily predictable, for this reason, Landslide Hazard Zonation (LHZ) or Landslide Susceptibility Zonation (LSZ) maps are used to predict the happening of landslides. A landslide susceptibility map depicts areas likely to have landslides in the future by correlating some of the principal factors that contribute to landslides with the past distribution of slope failures. These maps are basic tools for land-use planning, especially in mountain areas. Landslide susceptibility mapping relies on a rather complex knowledge of slope movements and their controlling factors. The reliability of landslide susceptibility maps mostly depends on the amount and quality of available data, the working scale and the selection of the appropriate methodology of analysis and modeling.
Such maps are obtained by dividing of a region into near-homogeneous domains and weighting them according to the degree of possible hazard of a landslide. There are two ways to do landslide hazard zonation: (i) a qualitative approach that is based on expert knowledge of the target area and portrays susceptibility zoning in descriptive terms; and, (ii) a quantitative approach based on statistical algorithms. In the present study of landslide susceptibility zonation, bivariate statistical methods (information value, density area, LNRF, frequency ratio) were used. In bivariate statistical analysis, each factor map is combined with the landslide distribution map and weighting values based on landslide densities are calculated for each parameter class.
Materials and Methods
The best method for studying landslides, which has long been of interest to researchers, is hazard zonation. In this method due to the affecting factors in landslide occurrence, the study area is classified into areas with low to very high risk. Such zonation could be of great help in regional planning. Different methods have been developed for this purpose. In this research four bivariate statistical methods namely information value, density area, LNRF, and frequency ratio are used to investigate the hazard zonation in Poshtdarband region, Kermanshah province. The study began with the preparation of a landslide inventory map. The instability factors used in this study included geology, land use, normalized difference moisture index (NDMI), slope gradient, aspect, distance from faults, distance from surface water, distance from roads, profile curvature and plan curvature. Landslide area ratio was calculated in classes of effective factors maps and weighted by four bivariate statistical methods. In addition, landslide hazard zonation maps were obtained from algebraic sum of weighted maps with regard to breakpoints of frequency curve. Finally, by using density ratio (D_r) Index through all four methods hazard classes were compared and with the help of quality sum (Q_s) and precision (P) indexes these four methods were compared and evaluated.
Results and Discussion
If the landslide susceptibility analyses are performed effectively, they can help engineers, contractors, land use planners, etc. minimize landslide. In this study, bivariate statistical methods were applied to generate landslide susceptibility maps using the instability factors. The bivariate approach computes the frequency of landslides with respect to each input factor separately, and the final susceptibility map is a simple combination of all the factors irrespective of their relative significance in causing landslides in a particular region.
In table 1 subclasses of instability factors which had the highest value in different methods, are summarized.
The density ratio indexes (D_r), quality sum indices (Q_s) and precision indices (P) were used to compare the methods. By overlaying the landslide inventory map of the study area and landslide hazard zonation maps, quality sum (Q_s) and precision (P) indices introduce a suitable model for the studied region, and density ratio index (D_r) introduces division precision among the zones or hazard classes in each zonation model.
Table1. subclasses of instability factors in different methods which had the
highest value

factor methods	aspect	Slope	distance from surface water	land use	plan curvature	profile curvature	distance from fault	distance from the roads	NDMI
information value	N, NE	>40	>1000	forest	concave	concave	<500	>1000	-0.17_ -0.408
density area	N, NE	>40	>1000	forest	concave	concave	<500	>1000	-0.17_ -0.408
LNRF	SW, S	10-20	>1000	pasture	Convex	convex	<500	>1000	-0.17_ -0.408
frequency ratio	N, NE	>40	>1000	forest	concave	concave	<500	>1000	-0.17_ -0.408

The density ratio for information value method in the very high hazard class is accounted 1.700495. These values for density area, frequency ratio, and LNRF methods are, 3.407827, 3.402257, and 1.694628 respectively.
Method precision (P) values for information value, density area, frequency ratio, and LNRF methods are 0.160826, 0.241024, 0.240672 and 0.16942 respectively.
Conclusion

• Frequency ratio, density area and information value methods showed that forest land use, slope and slope shape factors have the highest impacts on a landslide occurrence.
• The LNRF method showed that geology factors, pasture land use and distance from surface water had the greatest role in landslide making.
• For frequency ratio, information value, and density area methods, the effective factors in landslide are the same, however through the LNRF method, the three factors which have the greatest impact on landslide happening, are generally different from the three other methods.
• The density ratio values show that density area and frequency ratio methods respectively have more accuracy and applicability within all used methods for separating hazard classes in the study area.
• The quality sum (Q_s) results indicate that although there are minor differences, the frequency ratio compared to the density area method was more accurate and more applicable for separating landslide hazard in the Poshtdarband region.
• The calculated results of P index indicated that among the used methods, the density area method with a nuance of the frequency ratio method is the most suitable method for the study area.

---

./files/site1/files/1.pdfExtended Abstract
(Paper pages157-174)
Introduction
Considering the fact that the estimation of mode  fracture toughness by testing is time-consuming and expensive. It might be associated with certain practical difficulties. Therefore, many researchers have attempted to propose experimental relationships in order to capture these problems. Gunsallus et al. (1984) and Bhagat (1985) experimentally found that mode  fracture toughness is related to tensile strength. Whittaker et al. (1992) have also proposed a number of relationships between mode I fracture toughness, tensile strength, point load index, uniaxial compressive strength and the velocity of sound waves. Bearman (1999) obtained an experimental relationship between mode I fracture toughness and point load index, while Brown et al. (1997) presented an experimental relationship between this parameter and density. Up to now no significant research effort has been made in this field in Iran, only Ayatollahi and Fatehi addressed rock fracture toughness. Although, Ayatollahi has not presented any experimental relationships. In the present research the three-point bending test was used on a cylindrical specimen containing a straight crack in order to determine the mode  fracture toughness, and the Brazilian test was employed to determine tensile strength.
Materials and Methods
The tests were carried out on six types of rocks, namely gray sandstone,
tuff, lithic tuff, travertine, andesite, and limestone. Sandstone, travertine, and limestone are sedimentary rocks, while andesite is an extrusive igneous rock, and tuff and lithic tuff are pyroclastic rocks (pyroclastic rocks resulting from volcanic eruptions that harden by sedimentation). Therefore, the studied rocks have different origins. In order to carry out the Brazilian and the three-point bending test, cores were prepared from these blocks. In order to perform the three-point bending test, specimens with diameter of 73 mm with a thickness of 30 mm were used. The samples were cut in two semicircular by a cutting machine, and a notch with length of 15 mm is created by a diamond saw.  Notch is vertical in the center of the semicircular samples.
The Brazilian test was performed on disc shaped specimens. In order to perform the Brazilian test, specimens with diameter of 51 mm and thick of 25 mm were used. The specimens are carefully placed under the curved jaws of the machine and then loaded until fracture.
Results and Discussion
A summary of the Brazilian and the three-point bending test results are presented in Table 1. The average value of test result pertaining to each rock is reported in Table 1.
Table 1. Summary of the Brazilian and the three-point bending test results

Specimen	Tensile Strength (MPa)	Fracture Toughness (MPa√m)
Limestone	3.74	1.23
Sandstone	7.14	1.63
Tuff	16.36	2.17
Lithic Tuff	4.34	1.01
Andesite	13.25	1.86
Travertine	8.27	1.14

In this study, it was attempted to propose an experimental relationship between mode I fracture toughness and the tensile strength of the rock.
In order to determine the relationship between the tensile strength and the fracture toughness, the tensile strength vs. fracture toughness diagram was plotted in Excel to obtain Eq. 1 and the coefficient of determination (R²) (Figure 1).

The coefficient of determination (R²) in Eq. 1 shows that almost 80 percent of the mode I fracture toughness variations can be estimated using the linear relationship (Eq. 1). The relationship is applicable for determining the mode I fracture toughness resulting from the three-point bending test on semicircular specimens containing a straight crack.

In the following, the results of this study are compared to those reported by Whittacker (1992) and Zhang (2002).
In order to examine the accuracy of the presented relationships, the Root Mean Square Error (RMSE) measure was used which is computed from Eq. 2. In the best case, RMSE is zero. 

In the relationships,   represents the fracture toughness obtained from testing while  is the fracture toughness estimated using the relationships.
Comparison of the obtained results indicate that the proposed relationship has the capability of precise estimation of the mode I fracture toughness of rocks.
Conclusion
Given the many difficulties associated with the direct estimation of fracture toughness, indirect estimation methods have been proposed. One of such methods is the estimation of mode I fracture toughness using tensile strength. A linear relationship with a coefficient of determination of 0.7977 was proposed. The accuracy of this relationship has been verified by comparing its results to those from previous studies.

 

---

./files/site1/files/3.pdfExtended Abstract
(Paper pages 201-224)
Introduction
Soil nails are traditionally designed with uniform length and equal spacing to stabilize slopes which do not meet safety requirements. However, nails with uniform layout in a slope may not be the optimal design if the construction cost is taken into account. The optimal layouts lead to a minimum usage of nails and satisfies the allowable factor of safety and wall deformation.
In this study a decreasing trend of nails length along the wall height was considered to investigate the stability and the performance of the wall in different nail patterns. Then nail density was introduced as an important factor on the overall stability and deformation of the wall. It can be beneficial in the preliminary estimation of the required nail length at the beginning of a project.
Findings of this study are helpful for effective design of soil–nailed slopes.
Materials and Methods
The finite element analyses were conducted to investigate the effects of nails pattern on the overall stability and deformation of soil–nailed walls. Slope/W software was used to obtain the Factor of safety and Plaxis 2D was used to calculate the deformation of the soil nail walls. Soil hardening model was used to simulate the behavior of soil. In this study, various walls with different specifications were modeled and analyzed. As an example, a 10 m deep soil nail wall with C=10 kN/m², ?=25 deg, E_oed=20000 kN/m² is discussed here to monitor the trends (C represents cohesion, ? is the angle of friction and E_oed is the modulus of elasticity of the soil).
As it is shown in Figure 1, by considering the decreasing trend of nail length along the wall height, an ordered arrangement (pattern) is introduced by presenting “L” as the base nail length and “” as the inclination of stabilized zone border then, the effect of nail arrangement on the safety factor and deformation of nailed wall is investigated. The nails were installed with an angle of 15 degrees relative to the horizon. According to FHWA a minimum value of 1.35 is considered for the factor of safety. Circular failure surfaces are assumed and the tensile and pullout resistance of the nails crossing the failure surfaces are considered as the governing stabilizing forces.
Results and discussion
In this study, soil nails pattern effects on the performance and the stability of the soil nail wall are investigated. In Figure 2 variation of safety factors caused by different soil nails arrangements is illustrated. Generally three separated trends are observed in each curve. It demonstrates that at lower values of  with small bond length, the factor of safety is constant. As  increases the bond length behind the slip surface becomes longer and the safety factor is increases gradually. Eventually it reaches a point that the nails are long enough that increasing the nails length is not influential in the stability of the wall. Hence, nails at different elevations of a slope have different contribution to the overall stability of soil–nailed slopes.
Wall deformations need to be controlled by the allowable deformation level in designing the soil nailed wall especially when buildings or other underground facilities exist near the excavation. One of the most important parameters on soil nailed wall deformations is the arrangement of nail lengths.
Figure 3 shows the effect of nail arrangements on the wall horizontal deflection. In general, as and L increase, horizontal deflection of the wall decreases. The rate of this reduction is higher in lower base length. As it is
 


illustrated in Figure 3, by increasing the length of the nails, the deflection is decreased till no significant reduction is observed.
As it is shown the arrangement and the layout of the nails are influential on the stability and deformation of the soil nailed walls. However, it is important to identify an optimal layout in a way that with optimum nail length, allowable stability is reached and the wall deformation stay in an allowable range.
Nail density is defined as the ratio of the required nail length per the unit area of the wall surface and defined as below:

where L_i is nail length of each row and A is the stabilization area. Hence, estimating the nail density can be beneficial for the engineers to have a preliminary estimation of the costs of the project at beginning of the project.
Figure 4 indicates that the nail density governs the wall deformation. As it is seen, for different layouts with the same nail density, the resulted deflections are so close. Hence, it can be concluded that nail density is a key factor in determination of the wall deflection. It is also illustrated that, as the nail density increases, the reduction rate of the deflection is decreased. Effective nail density is defined as a threshold point that increasing the nail density is no longer effective on deformations.


As it is demonstrated in Figure 5, different layouts with a similar nail density have close values of safety factors. In walls with higher nail density increasing the nail length is fruitless and at lower nail density nails are not effective. So Optimum designation should be somewhere at the middle part with an allowable factor of safety. In the middle part the variation of factors of safety is more tangible.
Horizontal deflection profile
During the construction process the wall tends to move outward. Figure 6 illustrates the effect of soil nails arrangements on the deformation of a 10 m deep wall for a constant base length. As it is shown, by increasing  the horizontal deflection at the top of the wall decreases in a way that at higher  values, the wall deformation mode changes from overturning mode to bulging mode.
Conclusion
In this paper the effects of soil nail arrangement on the stability and performance of the wall was investigated. An ordered arrangement of the nails was introduced and the effect of various nail lengths at different elevations of the wall was discussed. Major findings concluded from this research are summarized as follows:


Nail density was defined as a key parameter and the findings demonstrate that nail density plays an important role in controlling the stability and the performance of the soil nail walls, in a way that patterns with the same nail densities but different arrangements, result in the almost similar factors of safety and deformations. Therefore based on the allowable factor of safety and deformation, nail density can be concluded and the nail arrangement which meets the standards, is selected.
Threshold nail density is defined as a value of nail density which no significant reduction of deflection happens afterward.
Uniform distribution of the nails and lower values of  generates the maximum deflection at the top of the wall. As  increases, the bond length in the upper parts of the wall controls the deformation. In that case, the deflection value is bounded and the maximum deflection occurs at the middle depth of the wall. Therefore the mode of deformation changes from overturning mode to bulging mode. As a result, in the projects which their adjacent structures are of high importance, it is recommended to use more 
 

---

./files/site1/files/4.pdfExtended Abstract
(Paper pages 225-246)
 Introduction
Soil has always been a major material in civil projects. Due to progress in science, different studies on the behavior of soil and its engineering characteristics have been conducted. As mentioned, there are different types of soil in nature; a small change in their structure and fabric under different environmental conditions or loading causes high deformation and settlements, which result in a reduction of strength and bonding between soil particles. Also, in this regard, some soft soils exist that are mostly composed of clay particles, with small shear strength and big settlement under low stress. With respect to the above-mentioned characteristics, these soils are referred to as problematic soils. The problematic soils consist of a silicate combination, whose major parts are clay minerals formed under weathering of rocks. Additionally, the precipitation of some soils and ground activity near the surface causes them to become problematic (Beckwith and Hansen [1]). Principally, in engineering, those soils on which construction is not safe, and which are affected by different environmental conditions, are defined as problematic soils. Collapsible soils are some of the most important of these problematic soils. The collapsibility phenomenon is defined as a sudden collapse of soil caused by the loss of the shear strength of soils. The collapsible potential depends on the initial void ration of soils. A few silty strata that are exposed to arid weather are susceptible to considerable volume decrease or collapse under soil saturation. Therefore, it is possible that surface water penetration in an irrigation form, pipe leakage and rise in ground water level may lead to great settlement.
In the last decade, the use of nanotechnology based on the science of production and nano-scale particles usage has become prevalent in many sciences. It can be said that nanoparticle application has made considerable progress, apart from nanotechnology, in recent years and has been one of its main aspects of this study. In this regard, the variety of nanoparticle depends on different applications.
The use of nano-materials has drawn the attention of various researchers in geotechnical engineering. One of the important nano-materials is nanoclay which, with respect to its characteristics, has had a wide range of applications in soil improvement techniques. Taha and Taha [2] and Majid et al. [3] have studied the effects of nano-materials, such as nanoluminum, nanocopper and nanoclay, on the swelling and shrinkage behavior in fine grain-size soils. Also, the compressive strength and permeability of soils increase and decrease with the addition of nanoclay, respectively, and are subjected to change of elastic to plastic behavior (Burton et al. 2009 [4], Gallagher and Lin [5], Persoff et al. [6]).
In this research, the main objective is to investigate the addition of nanoclay on the behavior of fine grain-size soil with experimental studies and to evaluate the different parameters on the soils’ modification mechanisms.
Material and methods
Given the importance of this subject and the practical use of the results of this research in the improvement of problematic soils, as well as the field assessment conducted, it was observed that, in many parts of the main irrigation channels of Gonbad dam in northeastern Iran, which is an arid and semi-arid region of Iran, due to the specific geotechnical conditions and loess soils, large and non-uniform subsidence of soil has occurred around dewatering channels. This has caused large cracks to occur in the concrete channel coverage and subsoil and the surrounding wall soil, which ultimately will lead to the destruction of large parts of the channel mentioned above. Remarkably, given the nature of loess soils in the study area, dangers such as collapsibility, dispersivity, landslides, sinkholes and subsidence can be noted. In order to evaluate the effect of soil improvement with the help of nanoclay in field conditions, all the tests and geotechnical studies on soil samples located in the channels were performed under valid standards. In this regard, a number of exploratory boreholes were bored in the walls and floors of the considered channel. During this procedure, sampling was carried out in different depths of layers of soil in order for laboratory tests to be carried out and for identification of the soil. The undisturbed samples were also taken by a Shelby Tube Sampler for necessary tests. In order to determine the initial physical and mechanical properties of the used soils, various tests such as particle size analysis, Atterberg limits, specific gravity and standard compaction were conducted. Table 1 summarizes the characteristics of the used soils.
Table 1. Soil  specifications

Incheberon Area	Gonbad    Area	Soil Properties
CL-ML	CL-ML	Unified soil classification system
2.55	2.54	Particle specific gravity
18	16	Plastic limit (%)
23	22	Liquid  limit (%)
5	6	Plasticity index (%)
86	95	Passing No. 200 sieve (%)
0.04	0.006	Average particle size  (D50) (mm)
16	15	Optimum water content (%)
1.60	1.54	Maximum dry unit weight (g/cm3)

The nano-materials used in this study have comprised nanoclay prepared by Sigma-Aldrich Company Ltd with the brand clay montmorillonite K(10).
Results and discussion
By adding nanoclay to the soil, it is observed that the liquid limit and plasticity limit of samples gradually increases as can be seen in Figure 1.


Figure 1. Effect of nanoclay addition on the Atterberg limits test of soil samples
Based on the obtained results by adding different amounts of nanoclay to the soil, the maximum dry density and optimum moisture content decreased and increased, respectively. By adding nanoclay to the soil, strain increases at the moment of failure due to increased plasticity and changes in soil structure. It is worthy to note that the unconfined compressive strength in samples stabilized with nanoclay has been increased in comparison with the plain soil.  Plain and improved soil samples were tested with different amounts of nanoclay under unconsolidated undrained conditions at different confining pressures.
To study the impact of nanoclay on the collapsibility potential of the soil, double consolidation tests were conducted to determine the deformation of plain and stabilized samples with various amounts of nanoclay under different vertical pressures. The test results showed that adding nanoclay has reduced the collapsibility potential of samples.
Conclusions
Due to existence of large areas of collapsible soils in Iran, improvement of these soils is necessary in civil projects. With considering the advances of nanotechnology sciences, in this research aiming to understand the impacts of different amounts of nanoclay on above mentioned soils have been studied. The soil samples used in experiments were collected from Golestan province including Boston dam of Gonbad and Incheboron near Gorgan city. In order to assessment of geotechnical behavior of soils, samples were mixed with varying percentages of nanoclay and different tests such as Atterberg limits, standard compaction, unconfined compressive strength, unconsolidated undrained triaxial and double consolidation were conducted. The results showed that nanoclay particles have a significant effect on the plasticity and strength behavior of used soils. Also, it was found that collapsibility index of soils decrease with adding nanoclay and it depends on the type of soil. 
Keywords: Nanoclay,‎‏ Collapsibility, Improvement, Fine-grained Soils.
 
1. Beckwith, C., Hansen, L.A., Identification and characterization of the collapsible alluvial soils of the western United States, Foundation Engineering, Current Principles and Particles, ASCE, (1989) 143-160.
2. Taha, M.R., Taha, O.E., Influence of nano-material on the expansive and shrinkage soil behavior, Journal of Nanoparticle Research Vol. 14(10) (2012) 1-13.
3. Majeed, Z.H., Taha, M.R., Jawad, I.T., Stabilization of soft soil using nanomaterils, Research Journal of Appiled Sience, Engineering and Technology Vol. 8(4) (2014) 503-509.
4. Burton, C., Axelsson, M., Gustafson, G., Silica sol for rock grouting: laboratory testing of strength, fracture behavior and hydraulic conductivity, Tunneling and Underground Space Technology (2009) 603-607.
5. Gallagher, P.M., Lin, Y., Column testing to determine colloidal silica transport mechanisms, Proceedings Sessions of the Geo-Frontiers Congress of Innovations in Grouting and Soil Improvement, Texas Vol. 162 (2005) 1-10.
6. Persoff, P., Apps, J., Moridis, G., Whang, J.M., Effect of dilution and contaminants on strength and hydraulic conductivity of sand grouted with colloidal silica gel, Journal of Geotechnical and Geoenvironmental Engineering Vol. 125 ( 6) (1999) 461-469.

 

 

---

./files/site1/files/2.pdfExtended Abstract
(Paper pages175-200)
Introduction
In weak soils with low bearing capacity, the load transfer is done using piles. Therefore, by creating an interposed layer separating the pile from the raft, reactions between raft and pile head will be reduced and the load-bearing role of shallow soil will be more than contact pile situation. Normally, the pile head and shallow soil have a settlement equal to the raft. Thus, the relative settlement of pile and soil in pile head is equal to zero and at the bottom is high and the body friction mobilizes upward. In addition, a portion of load is tolerated by shallow soil and the other portion is tolerated by the pile head, which would be transferred to deeper soil layers. In noncontact state, with the formation of a hard soil layer on which the raft is located, soil mechanical parameters will be improved; while in contact state, the settlement will be decreased by reducing the amount of transferred load to the shallow soil. The transferred load to the shallow soil increases vertical and horizontal stress around piles, so bearing capacity of piles is increased.
Methodology
In this study, a parametric study has been performed concerning contact and noncontact piles using finite element software namely, ABAQUS/CAE software version 6.13.1 and the obtained results were compared (with what? The sentence is incomplete). Thus, simulations are is done for states of 0, 1, 4 and 9 piles for each of the contact and noncontact piles (total of 8 simulations). In the present research two models were taken to investigate the optimum mesh sizes, 12 models for parametric studies on parameters of piles’ length, piles’ diameter, thickness of the raft and interposed layer and one model for verification study. Models in both contact and noncontact have been considered with a one meter interposed layer. Raft width and thickness were selected 7.5 and 1.6 m, respectively. Width and depth of the soil mass used in the model were 32 and 26 m, respectively, and the distance between the bottom of the pile and the soil mass was 13 m. In all cases, the diameter of piles was 0.5 m and distance between piles were 5 and 2.5 m in 4 and 9 states, respectively. The geotechnical parameters and model dimensions used, were selected according to the Fioravante & Girettis (2010) [1]. Sand and silica-sand with the defined properties were used for the soil mass and the interposed layer, respectively. Since Drucker-Prager criteria has better ability to express the behavior of coarse-grained soils, this criterion was used in the modeling [2]. The purpose of this study is to investigate the influence of interposed layer on bearing capacity and settlement of pile. Hence, because of simplifying the process of modeling, parameters of main soil and interposed layer are mostly similar. Piles and raft are made of concrete with an elasticity modulus of 21 GPa, Poisson's ratio of 0.2 and density of 2300 kg/m³. The crack growth analysis with the compressive stress-plastic strain was used to express the fracture behavior of concrete [2, 3 & 4]. In the present study, frictional and vertical contacts between surfaces were considered for conducting interactions between different materials. For frictional contact, the penalty formulation with the fixed friction coefficient of tanδ was used where δ is the angle of friction. The penalty formulations and hard contact were applied between two surfaces for the normal contact. Interactions were considered in the modeling including raft-soil mass, raft-interposed layer, pile-raft, interposed layer-soil mass, interposed layer-pile and the soil-pile [5 & 6]. Coefficient of soil lateral pressure used in this study corresponds to k₀=0.65 which is introduced in many geotechnical conditions [7]. A uniform distributed vertical load 500 kPa was applied on the raft. For getting results in every portion of loading time, this amount is applied in order of 5 kPa in each time interval. To accelerate the process of analysis and because of the symmetry of all models in two directions of X and Y, the quarter model technique was used, so that movements in the direction perpendicular to the sheet and rotation around perpendicular axes on the sheet were not allowed on the border of symmetry. The boundaries of the models due to the enough distance from the piles were considered in a way that lateral displacement and rotation around the vertical axis was not allowed. Furthermore, the bottom of the soil mass was considered as complete fix due to the enough distance from the pile foot.
Conclusion
In this research, a numerical – parametric study is performed on special kind of piles named noncontact piles and results are compared with contact piles. Results of this study can be summarized as follows:
1. By increasing the number of piles from 1 to 9, the settlement reduced more in a noncontact state showing more effectiveness of implementing 9 contactpiles and thus requiring more piles in this case.
2. Soil surface stress differences in noncontacts states from 4 to 9 piles was less than contact state (approximately 1/7) indicating that more piles is needed to conduct the contact state.
3. Stress changes in the soil under the pile in noncontact state by adding piles from 1 to 4 was higher than adding piles from 4 to 9 indicating the suitability of using 4 noncontact piles; while, in the contact state, the stress changes in the soil under the pile in both cases from 1 to 4 piles and from 4 to 9 piles was noteworthy showing the necessity of using the ninth pile.
4. Unlike the states of 4 and 9 piles, the negative friction in noncontact state and 1 pile was seen along the piles, which can be due to the fewer piles and the effect of interposed layer density as well as soil mass at greater depthsbecause of lesser effect of piles in load-bearing.
5. The ratio of heads load in the contact to the noncontact piles was about 2.5 to 4 reflecting the positive impact of using interposed layer on load reduction and smaller cross-layer design for piles. In addition, the ratio of heads load in the contact to the noncontact piles was higher for 4 piles than 9 piles that represented the suitability of using 4 piles.
6. Based on the results of geometric parametric studies it is found that:
(A) By resizing the elements from 0.25 to 0.5 m, the results had not changed and only time of analysis was increased.
(B) Among three values of 0.5, 1 and 1.5 m for interposed layer thicknesses, the thickness of 1 m was enough and had a good effect on the stress distribution and involving shallow soil in bearing vertical stress.
(C) The raft thickness of 1.6 m was appropriate so that with this thickness, the resultant effect of increasing vertical loads (raft weight) and increased rigidity due to increased raft thickness caused the stress and settlements remain in a reasonable range.
(D) Due to the increased friction by increasing in diameter, the optimal diameter of 0.5 m was achieved for piles which reduced the settlement by receiving more load.
(E) Among three pile lengths of 10, 19 and 25 m, the optimal length was 19 m; so that by further increase in the length, stresses and settlements were not noticeably changed.In total, noncontact piles had better performance compared to contact piles in similar conditions.
Reference
1. Fioravante V., Giretti D., "Contact versus noncontact piled raft foundations", Can. Geotech. J. 47 (2010) 1271-1287.
2. Saba H., "Verification of nonlinear condition of anchored walls in various loading", Thesis document of Amirkabir University of Tehran, Iran (2003).
3. Fioravante V., "Load transfer from a raft to a pile with an interposed layer", Geotechnique 61, No. 2 (2011) 121-132.
4. Dastani H., Shariati M., "Numerical and experimental analysis of controlling of crack propagation route in a plane under cyclic uniaxial loading by creating openness", Thesis document of Shahrood Industrial University of Shahrood, Iran (2014).
5. Randolph M. F., Wroth C. P., "Application of the failure state in undrained simple shear to the shaft capacity of driven piles", Geotechnique, Vol. 31, 1 (1981) 143-157.
6. Poulos H. G., Small J. C., Ta L. D., Sinha J., Chen L., "Comparison of some methods for analysis of piled rafts", Proc. 14th Int. Conf. Soil Mech. Found. Engng, Hamburg, Balkema, Rotterdam, Vol. 2 (1997) 1119-1124.
7. mottaghi A., "3D static and dynamic analysis of pile group with considering soil-pile interaction", 6th National Congress of Civil Engineering, Iran, Semnan (2012).

---

./files/site1/files/5.pdfExtended Abstract
(Paper pages 247-276)
Intro

---

./files/site1/files/6.pdfExtended Abstract
(Paper pages 277-298)
Introduction
Preparation of uniform and repeatable reconstituted sand specimens of required density is a prerequisite for obtaining reliable results from experimental studies. Among different methods of reconstituted specimens, sand pluviation technique is widely adopted by researchers because of its unique advantage. In this study, a new curtain traveling rainer (CTR) is developed for large model sand bed preparation in experimental studies. CTR is a simple and low-cost system which is worked on the principle of air pluviation of sand. It provides specimens with wide range of relative density of sand bed (viz, 30%-90%) and very high degree of spatial uniformity of density distribution while reducing the time of preparation the specimens. A series of laboratory tests is carried out in order to study the performance of the proposed system and the effect of the curtain speed, curtain width, height of the fall and flow rate on the relative density and uniformity of sand specimens. For the sand used in the present study, it was observed that the relative density increases with an increase in the curtain speed and height of the fall. Furthermore, increasing the curtain width results in reducing the relative density.
Material and Methods
The calibration of geotechnical in situ tests in granular soil requires the preparation of large, uniform, and replicable specimens of a desired density. When preparing calibration chamber specimens, the adoption of techniques such as chemical impregnation and the freezing method in order to obtain undisturbed granular specimens becomes unfeasible due to the technical limitations and relatively high expense of these techniques. Conversely, the pluviation method has been widely used because of its ability to simulate the depositional mechanism of the soil and because of its applicability to a wide range of specimens, from small specimens for triaxial tests to large specimens for calibration chamber tests. 
soil sample was chosen from natural white-yellow silica sand mines of Firouzkooh, which can be categorized as poorly graded sand (SP) based on unified classification system (USCS). In order to control sand flow rate at the end of the pluviation path, a series of plates is designed to have rectangular openings with a width range of 2 to 4.5 mm. It should be noted that a sand reservoir is included in the transformer, which enables a uniform sand flow over the rectangular opening. the raining height is set at 100 mm to 500 mm with 100 mm steps. For more accuracy an extra test with  height fall equal 150 mm is performed.
A contiguous system of wheel-rail is operated for effective transmission of the traveling funnel over the entire sample surface in the circular container. The device’s jacking system and its related components are the cause of several limitations, which lead to the implementation of two-joint methods for keeping the sand rain height constant during the pluviation and sample preparation process.
Results and discussion
The CTR system comprises sand transfer compartments from the main hopper to the sample container and a rectangular opening at the bottom of the hopper, which controls the pluviation flow rate. The main concept driver of this research is to reproduce large samples in the most efficient time.  In order to recognize the uniformity of the reconstituted specimen in the vertical and horizontal directions, the variation of density is evaluated by placing 20 cylindrical molds within the specimen.
In this paper the effect of deposition intensity and the effect of height and flow rate on the sample relative density are evaluated.
Calibration of the sample preparatory device is very important in order to produce optional and repeatable samples with a specified relative density, in experimental studies and laboratory models. According to the test results, the effects of drop height and flow rate are investigated. Calibration graphs are presented in Figs. 1 and Fig. 2 for the proposed system in the case of 2.5 cm and 5 cm layer thickness.



Conclusion
This paper aims to extend the existing apparatus to achieve consistent low and high relative density sand samples. The preparation of low relative density samples is particularly important in liquefaction studies in geotechnical earthquake engineering. The comprehensive design and calibration of the CTR system can be concluded in the following points. The proposed method can easily be deployed to produce any arbitrary sample with a wide range of relative densities. Increasing the flow rate given a constant drop height leads to decrease in the relative density and is independent of layer thickness. Keeping constant the drop height and flow rate, higher relative densities can be achieved by increasing the curtain traveling velocity. There is a direct relationship between drop height and relative density. The  results  give  some  information  about  the  deposition  process  and  in particular about the terminal falling height. It can be henceforth stated that the performance of the proposed system is reliable and very acceptable due to high uniformity across the entire sample. 

 

---

./files/site1/files/7.pdfExtended Abstract
(Paper pages 299-318)
Introduction
Bentonite has been used industrially in various construction projects. This material is used, due to its limited hydraulic conductivity, in some cases such as landfill, sealing walls and nuclear waste disposal tanks. Recently, many researchers have investigated the use of bentonite slurry systems for injection into granular soils under static and dynamic loading conditions in order to improve soil engineering performance. In this condition, bentonite slurry is deposited in a loose soil with low pressure and without disturbance in the structure of the soil under injection. Due to the nature of the thixotropy of the bentonite slurry, the injected material is deposited in the form of gel structures in the soil and leads to increasing soil resistance to static and dynamic loads. For suitable soil engineering properties in granular soil, the use of concentrated bentonite slurry is appropriate; high concentrations will limit the penetration of bentonite due to low soil permeability. In order to overcome this limitation, slurry rheological properties such as viscosity must be corrected in order to increase the depth of sand penetration. Other researchers observed that with the reduction of viscosity in the cement slurry with micro-size particles, the amount of its penetration in the sand column significantly increased.
In present paper, due to the lack of studies on the penetration rate of bentonite in sand and also the effective role of bentonite in the mechanical properties of sandy soils, the permeability of sandy soils by bentonite under the influence of change factors such as concentration of bentonite in injection suspension were investigated.
Material and Methods
In the present study, Firoozkooh sand samples with the traditional names of 131, D11 and D1 were used for testing. Different concentrations of bentonite slurry which is used in this study are 3, 5 and 7% of the bentonite to water ratio.
Figure 1 shows the location of the reading of the penetration length and Figure 2 shows variations in the length of infiltration against time for different heights of the pressure head.


Figure 1. The reading point of the penetration length in the sample


Figure 3 shows the variations of penetration length versus pressure heads for samples with a relative density of 70% at concentrations of bentonite slurry of 3, 5 and 7% in different aggregates. It can be stated that while the concentration of bentonite to water increases, the longitudinal penetration of the injected substance into the sample is reduced. For example, in sand 131 with Dr=70% the penetration value at a pressure head of 130 cm for suspension containing 3% bentonite slurry is 100 cm. The same values for samples containing 5% and 7% bentonite are 45 and 20 cm respectively. This is due to the increase in the presence of bentonite slurry (solid substance) in the suspension. The greater amount of solids inside the suspension causes the greater contact between sand grains with solid particles of suspensions. As a result, it causes increasing friction for longitudinal motion. Therefore, with increasing the concentration of suspension the length of its movement in the soil is reduced. Also, due to the increased viscosity of the injectable substance with increasing the amount of bentonite, the forward movement of the suspension under constant pressure is reduced. This is another important parameter that leads to a reduction in the length of the injection by increasing the concentration of the bentonite slurry.
 It is also observed that the variation of penetration in higher concentrations is less than the low concentration. For example, in sand D1 (coarse sand) at a pressure height of 100 cm, the penetration rate at a concentration of 5% increases by 35% compared to a concentration of 3% and at a concentration of 7% increases by 300% compared to the sample containing 3% bentonite. This indicates that at less than 5% concentration the presence of bentonite in the sample is less effective, and the suspension can be more easily move between the pores. This result indicates that by reducing the pores inside the sand, the effect of changing to the suspension concentration is reduced. 


Figure 3. Penetration length versus pressure level for specimens with a Dr=70% in concentrations of bentonite of 3, 5 and 7% in different aggregates; a) fine sand (sand 131); b) moderate sand (sand D11); c) coarse sand (sand D1)

 

---

The results of an ongoing FEM parametric study are presented regarding the dependence of the resulting piled raft behavior under lateral load and combination of loads on pile diameter, pile length, arrangement of piles and raft thickness. Taguchi method with Analysis of Variance (ANOVA) was employed to calculate the contribution ratio of these factors on the lateral displacement of piled raft. The obtained results of this study show that the pile diameter is an effective factor in horizontal deformation of the piled raft under pure horizontal load. However, in the case of load combinations, the pile length has the highest participation ratio in reducing the horizontal deformations.
 

 

---

In many rock engineering projects, accurate identification of rock strength properties is very important. Uniaxial compressive strength is one of the most important features to describe the resistive behavior of rocks which is used as an important parameter in the design of structures especially underground openings. Determination of this parameter using direct methods, including uniaxial compressive strength tests is costly and time-consuming, and also sometimes preparation of standard samples in many rocks is difficult. In such cases, the implementation of some simple and non-destructive tests and using empirical relations can increase the evaluation speed and reduce costs. These relations even regional or local (For example within a geological formation or a single lithology) can help in the estimation of these parameters in order to be used in geotechnical projects. In this study, samples of existing limestones in south west of Tehran (Capital of Iran) were prepared and uniaxial compressive strength, point load, Schmidt hammer and Shear wave velocity tests on which have been performed. Then by the statistical evaluations of the results, the empirical relations between uniaxial compressive strength and the results of other tests are obtained. The comparison between the predicted and observed values of uniaxial compressive strength represents the validity of obtained empirical relations. The application of the proposed relations for limestones in the study area and those with similar geological conditions will provide acceptable results.

---

In recent decades many researchers have studied on the damage assessment of structures after a seismic event. To assess the damage of structures under an earthquake, it is so important to study the correlations between earthquake parameters and damages of the structures. A lot of seismic parameters have been defined by researchers to characterize an earthquake. Spectral parameters of an earthquake convey a variety of information about ground motion, so they can properly characterize an earthquake. Also a lot of damage indices were proposed by researchers to quantify the damage of the structures or to rank their vulnerability relative to each other. Park-Ang index is one of the best indices to describe the damage of a structure. In this paper, the correlations between spectral parameters of earthquakes and Park-Ang indices are studied. Three RC frames with different height are analyzed under far-fault earthquake records by nonlinear dynamic analyses. The correlations between spectral parameters and Park-Ang indices of the frames are calculated. The results show that in all the frames most of spectral parameters have strong correlations with damage intensity. In order to estimate the damage potential of an earthquake, some spectral parameters which have high correlations with damage intensity can be proper indices. Housner intensity, acceleration spectrum intensity and velocity spectrum intensity are shown to have strong correlations with damage intensity. In this paper, a new spectral parameter which has high correlation with damage intensity is achieved.