Maryam Yazdi, Ali Komak Panah,
Volume 9, Issue 4 (3-2016)
Abstract
As usage of reinforced soil structures is highly increased in seismic active zones, the analysis of dynamic behavior of these structures begins to be of great significance. The present paper is an attempt to study the seismic behavior of reinforced soil retaining walls with polymeric strips. The consequences of the most principal parameters counting the length of reinforcement, reinforcement arrangements (zigzag vs. parallel), maximum base input acceleration and wave frequency on the wall displacement have been investigated for sensitivity analyses. The main drawback of numerical methods in dynamic analysis is being very time consuming. Therefore, determination of equivalent coefficients is a suitable, easy and beneficent approach to converge results of pseudo-static and dynamic methods. In this case, a relatively accurate design is achieved by using pseudo-static method that takes less time. To this end, an earthquake equivalent horizontal acceleration coefficient is proposed by considering horizontal displacement of the wall as the basis for comparison
, , Gholam Lashkaripour, ,
Volume 10, Issue 1 (8-2016)
Abstract
Kerman city and its surrounding towns in terms of morphology, consist of a flat alluvial plain of fine silt and clay materials. These sediments have very gentle slope, and constitute the city's main infrastructure. Natural soils generally are structured by passing times due to the influence of environmental factors. Geological factors in Kerman alluviums have caused fine structure after deposition. This paper studies briefly sedimentary basin Kerman, mineralogical and geotechnical properties of the sediments of these areas.semi-qualitative analysis of samples has shown that the mineral deposits in Kerman are mainly illite, chlorite, smectite and calcite. then In order to evaluate the effect of depositional environments and geological history of the engineering properties of the sediments of the Kerman city, A large number of triaxial tests on reconstituted soil moisture greater than LL and different confining pressures, consolidated drained and consolidated undrained is done . In order to evaluate the applicability of soil behavior in normal conditions and the reconstructed curves and stress - strain sensitive soils and soil structure compared with standard sensitivity and then their resistance have been investigated. The results of triaxial tests can be used to interpret the depositional environments and geological history. Comparing the curves of stress - strain in natural and reconstituted samples indicates that in many cases the behavior of intact and reconstituted soils were similar and cementation and soil structure have not been much development. Also Comparison of electron microscopy images of reconstituted and intact samples, not random arrangement of particular structure and soil compaction within the city limits have confirmed. therefore, soils of Kerman are relatively similar by the influence of depositional environments and geological history. these soils have a lot of structure and cementation and are generally compact and strengthening.
, Mohamad Ghafoori, Javad Ahmadzadeh, Salameh Afshar,
Volume 10, Issue 1 (8-2016)
Abstract
In tunnelling in soil mass, in groundwater existing mode, liquefaction, elastic displacements and settlement in soils upon the tunnel, are the risks may attack the excavated underground space stability. In this case study that were performed on second line of Mashhad city subway route, information catched from Standard Penetration Test, in situ and laboratorial tests, were used to optimum numerical values search for soil engineering parameters that could optimize the TBM stationing level. In order to this goal attaining, intelligent, numerical and probabilistic methods were used and the reliability of intelligent and numerical methods with the Safety Factors of tunnel stability, investigated simultaneously. The results were denoting the accordance of intelligent models such as Genetic Algorithm (GA) and Multi objective Genetic Algorithm with Finite Element model's output. So these models could be complement of each others in planning and designing of tunnels and using of them advised in tunneling and excavations.
, ,
Volume 10, Issue 1 (8-2016)
Abstract
The in-situ stress is one of the most important parameters in the design of underground structures. Conventional methods such as in-situ stress measurements using hydraulic fracturing method has two main disadvantages are time and cost of this methods. Acoustic emission is one of the indirect in-Situ stress measurement methods which is based on the theory of the Kaiser effect. When a rock is stressed, it release acoustic signals this phenomenon is called acoustic emission. Kaiser Effect is defined as lack of acoustic signals in the lower stress levels than the previous maximum stress level. In other words, as long as rock is not reached to the previous maximum stress level, do not show significant acoustic emission. Several factors affect on Kaiser Effect such as delay time, temperature, rock fabric, porosity, discontinuities, joints and geological structure. In this paper, effect of the delay time on Kaiser Effect has been presented. The time between coring operations and acoustic emission test is called delay time. The limestone rock is selected as main samples of test and after preloading, reloading and acoustic emission test were carried out with different delay times. The results showed that the felicity ratio is less than 1, when delay time is about 20 days and after three months has increased to be more than one.
, Mojtaba Rabiei Vaziri, Hamidreza Mohammadi Azizabadi,
Volume 10, Issue 1 (8-2016)
Abstract
Hoek and Brown suggested a method to estimate the strength and deformation modulus parameters of rock masses. The method was then widely used in rock engineering designs. In such designs, the mean values of Hoek and Brown parameters are often used which are not proper values due to the variability of rock mass properties within a great range of values. In such cases, probability analysis of rock mass properties is highly important. The geological strength index is one of the most important parameters in Hoek and Brown equations. Determination of this parameter includes greater uncertainties than determining other parameters. In this paper, based on the results of rock mechanical tests carried out on rock samples of Gol-Gohar iron ore mine, and the required field surveys, the sensitivity of rock mass geomechanical properties on the type of the statistical distribution function of the geological strength index in statistical analysis of these parameters using Monte Carlo simulation method was investigated. The results showed that the sensitivity of Hoek and Brown equations to determine different rock mass geomechanical parameters varies as the type of the statistical distribution function of the geological strength index changes. The sensitivity of geomechanical parameters such as internal friction angle, cohesion, total strength and rock mass modulus on the type of the statistical distribution function of the geological strength index is much less than parameters such as uniaxial compressive strength and tension strength of rock mass. The greatest variations based on changes of the type of the statistical distribution function of the geological strength index are less than 5% for the internal friction angle, cohesion and total strength, less than 10% for the modulus, and less than 25% for the uniaxial compressive strength and tension strength.
Mh Ghobadi, R Babazadeh,
Volume 10, Issue 1 (8-2016)
Abstract
Strength and durability of sandstones and their influences from natural conditions, are the most important factors which should be considered as engineering materials. In this study, the effect of freeze-thaw and salt crystallization phenomena on strength and durability of upper red formation sandstones collected from southern part of Qazvin province was investigated. Nine specimens of sandstones (specified by A, B, C, CG, S, S1, Tr, Min and Sh) were collected from different part of studied area, then their physical and mechanical characteristics were determined. In order to assessing the effect of freeze-thaw on physical and mechanical characteristics of sandstones, 60 cycles of freeze-thaw test was performed. Also in order to investigate the effect of salt crystallization on strength of studied sandstone, sodium sulphate crystallization test (100% weight solution of Na2SO4) was carried out in 20 cycles. Physical and mechanical characteristics of sandstones such as point load index, Brazilian tensile strength, wave velocity (Vp) and weight loss were computed after different cycles. To evaluate the effect of freeze-thaw and salt crystallization phenomena on durability of sandstones, slake durability test was conducted on specimens subjected to mentioned processes and changes occurred in slake durability index in 15 cycles were investigated. Based on results obtained from current study, it could be concluded that in comparison to freeze-thaw, salt crystallization can considerably reduce the strength and durability of sandstones and deteriorate them. Also it was found that index tests such as point load index, Brazilian tensile strength, wave velocity (Vp) and weight loss can predict the behavior of sandstones in different cycles of freeze-thaw and salt crystallization tests.
Mohammad Adampira, Hamid Alielahi, Mehdi Panji, Hamid Koohsari,
Volume 10, Issue 2 (11-2016)
Abstract
Due to the increasing importance of geomorphologic conditions on the seismic ground response, the effect of liquefiable soils on seismic ground surface response is discussed. At first, the equivalent linear analysis based on total stress model in the frequency domain is carried out and then the nonlinear analyses based on total stress, effective stress model and considering the pore water pressure development in time domain are done in order to evaluate the differences between the several types of ground response analysis methods. DEEPSOIL.Ver5 software is used based on the latest achievements and various techniques in both solution domains. LNG port project in Assaluyeh, situated in south of Iran, is considered as a case study. Due to lack of the real data recorded near-field fault at the project site, the simulated method is used in order to create the artificial earthquake. Also three far-field earthquakes have been selected based on conventional seismic hazard studies for the seismic ground response analysis. Then, in order to better understanding of the obtained responses, the resulted responses spectra are compared with the acceleration design spectra provided in some valid codes. The result of this study indicates that the pulse effect in the horizontal component of acceleration perpendicular to the fault plane direction, affects severely the surface ground response of the near-field earthquake. The obtained results of the nonlinear modeling of the soil with excess pore water pressure build-up in the time-domain are extremely different from those of frequency-domain responses based on the equivalent linear method. In addition, because of the inherent linearity of equivalent linear analysis which can lead to spurious resonances in ground responses, the peak ground acceleration in the time-domain is lower than the frequency-domain.
Ahmadzadeh, R Bagherpour, Saeed Mahdevari,
Volume 10, Issue 2 (11-2016)
Abstract
Because most part of Iran country is located in a dry climate, construction of water conveyance tunnels is inevitable. One of the major challenges in the construction of these tunnels is inflow of water into the tunnel during the construction and operation phase. The Rozieh water conveyance tunnel whose length is 3200 meters is a part of water conveyance project to the Semnan city and it is located 30 k NE of Semnan city. In accordance with the drilled boreholes, the tunnel route has been classified into eight zones from the geotechnical view. Then the permeability coefficients of host rock were calculated using back analysis approach on the basis of numerical simulation results and water inflow quantity during the construction phase. A parametric study was done on the lining and cement injection zone permeability and the thickness of cement injection zone. According to this study, the effect of injection zone thickness variation on the water inflow quantity is negligible. So with the assumption of 3 meters thickness for the injection zone, the permeability coefficient of host rock after injection were evaluated. Dependent on the initial rock permeability, cement injection could reduce the rock permeability 10 to 1000 times. In addition, the water inflow into the tunnel was calculated using hydro-mechanical coupling analysis. According to this analysis, the water inflow calculated by the hydro-mechanical coupling analysis is 50 to 70 percent less than the hydraulic analysis.
, , ,
Volume 10, Issue 3 (2-2017)
Abstract
The Bakhtiari dam has located on Bakhtiari River in province of Lorestan. In order to access the crest of the dam, the excavation of a spiral tunnel is being studied. There are other access tunnels which are branched from this tunnel in different levels and are connected to grout galleries. According to the fact that this tunnel will also be used during the operation of the dam,The correct determination of mechanical parameters of rock masses for tunnel design and stability Analysis is very important. In order to analyse the stability of the underground rock structures, the mechanical and engineering parameters of the rock mass must be known. Accurate rock mass properties can only be obtained from large in situ tests. Such tests are seldom carried out as they are very expensive and time consuming. Sensitivity analysis of parameters can be applied for the optimisation of testing schemes. Sensitivity analysis helps to avoid mistakes due to subjective conjecture. In this article, after the introduction of regional geology and determination critical section on the tunnel path, the mechanical parameters of the rock mass surrounding the tunnel are modelled and analyzed by using FLAC3D software (numerical finite difference method). Parameters conducted in the analysis include the elasticity modulus (E), cohesion of the rock mass (C), friction angle (ϕ), coefficient of lateral stress (K) and tensile strength (&sigmat). Ultimately, according to the result of numerical modelling and parametric analysis, parameters affecting the stability are prioritized. The result of analysis showed that in this project, tensile strength of the rock mass does not affect the stability of the tunnel, and Also, in order of priority, E, ϕ, C, k parameters are important in design. The amount of field tests for rock parameters can be rationalised according to their sensitivity factors.
Amin Keshavarz, Mehdi Nemati,
Volume 10, Issue 3 (2-2017)
Abstract
In this paper, the bearing capacity of strip footings on fiber reinforced granular soil has been studied. The stress characteristics or slip line method has been used for the analysis. In the selected failure criterion, the orientation of the fibers are isotropic and fibers are not ruptured. Seismic effects have been considered in the equilibrium equations as the horizontal and vertical pseudo-static coefficients. The equilibrium equations have been solved using the finite difference method. The provided computer code can solve the stress characteristics network and calculate the bearing capacity. The bearing capacity has been presented as the bearing capacity factors due to the unit weight of the soil and surcharge. Several graphs have been prepared for the practical purposes. Also, a closed form solution has been presented for the bearing capacity factor due to the surcharge. By the parametric studies, the effects of the geometry and soil properties have been investigated. Results show that the bearing capacity increases with an increase on the average concentration and aspect ratio of the fibers, the fiber/matrix friction angle and the soil friction angle. Furthermore, the extent of the failure zone is increased with increasing the pseudo-static coefficients and decreasing the surcharge.
M. R Baghban Golpasand , M. R Nikudel , A Uromeihy ,
Volume 10, Issue 3 (2-2017)
Abstract
Ground settlement due to tunneling and the effects of the engineering geological factors on its dimensions and extensions, is a very important problem in shallow tunnel excavation projects in urban areas. Empirical method is one of the usual methods to study this subject. The empirical and dimension-less parameters of VL and k are the most important parameters in relation to this method that are estimated according to engineering geological factors. In this research, the values of these parameters were initially estimated based on preceding studies and the ground settlement was predicted using these estimated values of VL and k. In next stage, the results of predictions were compared with the real (measured) settlements happened due to Abuzar tunnel excavation. As the real settlements are less than the predicted ones, it was concluded that the real VL must be lower than the predicted values or the real k must be higher than the predicted values. With regard to the high dependency of these parameters to the soil cohesion, it seems natural cementation of Tehran alluvia has acted as a factor to increase the soil cohesion and has caused to decrease ground settlement due to excavation of Abuzar tunnel. For validation of this hypothesis, preceding findings about alluvia cementation were reviewed and the results of in-situ and laboratory shear and triaxial tests were compared with together. Then it is concluded that the higher cohesions of in-situ shear tests are occurred due to natural cementation of materials existing in Abuzar tunnel route
N Salimi , M Fatemiaghda , M Teshnehlab , Y Sharafi ,
Volume 10, Issue 3 (2-2017)
Abstract
Landslides are natural hazards that make a lot of economical and life losses every year. Landslide hazard zonation maps can help to reduce these damages. Taleghan watershed is one the susceptible basin to landslide that has been studied. In this paper, landslide hazard zonation of the study area is performed at a scale of 1:50,000. To achieve this aim, layers information such as landslides distribution, slope, aspect, geology (lithology), distance from the faults and distance from rivers using artificial neural network-based Radial Basis Function (RBF) and perceptron neural network (MLP), has been studied. Principal of RBF method is similar to perceptron neural network (MLP), which its ability somewhat has been identified up to now and there are several structural differences between these two neural networks. The final results showed that the maps obtained from both methods are acceptable but the MLP method has a higher accuracy than the RBF method.
, ,
Volume 10, Issue 4 (5-2017)
Abstract
There are various methods for the analysis of the interactional behavior of the surrounding land, using the lining structure which is the most common method of deigning lining structure tools for the static loads by using the hyper static methods. In recent years, there has been a question that depicts whether this method provides the best results in designing the tunnel structure or not.Due to the nonlinear behavior of the earth surrounding the lining structure, utilizing the lining method could lead to conservative results in the design. If it is possible to somehow find the forces caused by the real behavior of the land surrounding the lining structure influencing the structure and conduct the design based on them, more optimal results would be obtained. This study is based on the actual behavior of the land surrounding the lining structure and the displacement of the structure caused by forces with linear behavior in the static design according to the non-linear behavior of the land around the tunnel structure. The behavior is modeled using the non-linear programs and the forces affecting the lining of the structure will be inference. Also there is a case study based on this method in which the soil interaction with the tunnel analysis and designing the lining structure was first performed and eventually the obtained results were compared with the hyper static method. In this paper, analysis of maintenance system with lower thicknesses considering land-shield, indicated that applying the reinforced concrete with 40cm thickness has the potential to tolerate the applied load but lining with 45cm thickness is capable of tolerating the loads of design and it can be concluded that applying the simulation method combined with the soil and structure besides considering the nonlinear behavior of the soil leads to more economical results in a project.
Seyed Hamed Moosavi, M Sharifzadeh ,
Volume 10, Issue 4 (5-2017)
Abstract
Combination of Adoptive Network based Fuzzy Inference System (ANFIS) and subtractive clustering (SC) has been used for estimation of deformation modulus (Em) and rock mass strength (UCSm) considering depth of measurement. To do this, learning of the ANFIS based subtractive clustering (ANFISBSC) was performed firstly on 125 measurements of 9 variables such as rock mass strength (UCSm), deformation modulus (Em), depth, spacing, persistence, aperture, intact rock strength (UCSi), geomechanical rating (RMR) and elastic modulus (Ei). Then, at second phase, testing the trained ANFISBSC structure has been perfomed on 40 data measurements. Therefore, predictive rock mass models have been developed for 2-6 variables where model complexity influences the estimation accuracy. Results of multivariate simulation of rock mass for estimating UCSm and Em have shown that accuracy of the ANFISBSC method increases coincident with development of model from 2 variables to 6 variables. According to the results, 3-variable model of ANFISBSC method has general estimation of both UCSm and Em corresponding with 20% to 30% error while the results of multivariate analysis are successfully improved by 6-variable model with error of less than 3%. Also, dip of the fitted line on data point of measured and estimated UCSm and Em for 6-variable model approaches about 1 respect to 0.94 for 3- variable model. Therefore, it can be concluded that 6-variable model of ANFISBSC gives reasonable prediction of UCSm and Em.
Ibrahim Naeimifar, Shahaboddin Yasrobi, Ali Uromeie, Hatef Hashemi,
Volume 10, Issue 4 (5-2017)
Abstract
Evaluation of the excavation-induced ground movements is an important design aspect of supporting system in urban areas. This evaluation process is more critical to the old buildings or sensitive structures which exist in the excavation-affected zone. Frame distortion and crack generation are predictor, of building damage resulted from excavation-induced ground movements, which pose challenges to projects involving deep excavations. Geological and geotechnical conditions of excavation area have significant effects on excavation-induced ground movements and the related damages. In some cases, excavation area may be located in the jointed or weathered rocks. Under such conditions, the geological properties of supported ground become more noticeable due to the discontinuities and anisotropic effects. This paper is aimed to study the performance of excavation walls supported by nails in jointed rocks medium. The performance of nailed wall is investigated based on evaluating the excavation-induced ground movements and damage levels of structures in the excavation-affected zone. For this purpose, a set of calibrated 2D finite element models are developed by taking into account the nail-rock-structure interactions, the anisotropic properties of jointed rock, and the staged construction process using ABAQUS software. The results highlight the effects of different parameters such as joint inclinations, anisotropy of rocks and nail inclinations on deformation parameters of excavation wall supported by nails, and induced damage in the structures adjacent to the excavation area. The results also show the relationship between excavation-induced deformation and the level of damage in the adjacent structure.
M Moradi , A Hamidi , Gh Tavakoli Mehrjardi ,
Volume 10, Issue 4 (5-2017)
Abstract
Consolidated-drained triaxial compression tests were conducted to compare the stress-strain and volume change response of sands and clayey sands reinforced with discrete randomly distributed poly-propylene fibers. The influence of various test parameters such as fiber content (0.0%, 0.5% and 1.0% by weight), clay content (0%, 10% and 20% by weight), relative density (50% and 90%) and confining pressure (100 kPa, 200 kPa and 300 kPa) were investigated. It has been observed that addition of clay particles to the sands decreased the shear strength of samples. Also, increase in clay content reduced dilation and increased compressibility of the mixed soil. Addition of the fiber to both sands and clayey sands samples improved the shear strength and increased ductility and axial strain at failure point.
V Shirgir , A Mohammad Amiri , A Ghanbari , M Derakhshandi ,
Volume 10, Issue 4 (5-2017)
Abstract
Free vibration of soil often occurs during earthquakes. Since the vibration caused by earthquake does not have (steady state harmonic vibration) continuity, the alluvium vibrates with its natural frequency between two natural seismic waves. This study evaluates the effect of piles on the period of free vibration of a soil layer using numerical method. In the first stage, using analytical equations for calculation of vibration period of a soil layer and a column with continuous mass, the results were analyzed by the software. In the second step, piles with the same dimensions and distance were added step by step, and the vibration period for the soil layer with piles was calculated. The friction or floating effects of the piles on alluvial soil vibration period was also examined. The results show that as the number of piles increases, the differences between the results of one dimensional analysis of alluvium soil and the results of the software become different, and this creates the need for specific arrangements for seismic analysis of this kind of alluvium (with inserted piles). The results also suggest that end-bearing piles have a greater effect on alluvial soil vibration period, and with increased amount of the floating of these piles, these effects decline.
Mh Ghobadi, M Kapelehe ,
Volume 10, Issue 4 (5-2017)
Abstract
Durability is a significant parameter in engineering geology and it shows the extent of the degradability of rocks as the result of mechanical and chemical breakdowns. This phenomenon is closely linked to the composition, porosity and texture of rocks. To understand the relationship between the chemical composition of rocks and their durability the mineralogical properties of the rocks along with durability tests under both acidic and alkaline pH environments were determined. Five samples of limestone and three samples of marl were analyzed. The results revealed that rocks containing high levels of CaCo3 were affected in the acidic conditions while rocks containing high levels of SiO2 were not affected by variance in the pH of the environment. These second groups of rocks were more dependent on the texture of their constituent minerals.
M.a Eskandari , P Homami ,
Volume 10, Issue 5 (7-2016)
Abstract
Most of masonry buildings are vulnerable against earthquakes and need to be rehabilitated. One of the pragmatic methods for strengthening is to utilize shotcreting the masonry walls. In this paper the effects of the soil type (in view of seismic behavior) on the rehabilitation of the masonry building by shotcrete are investigated. Three types of masonry buildings are simulated by ABAQUS software and analyzed against three earthquake records to find their reporses and seismic demands. Using five types of shotcrete configuration consisted of shotcrete strips in vertical and horizontal directions for rehabilitation are studied to find the appropriate method for damage mitigation. The suitable method for rehabilitation are used to study the effects of soil type on the rehabilitated buildings. Three records of the Tabas (1979) earthquake which were recorded on different types of soils (Type I, II and III based on the Iranian seismic design regulations) are considered to analyze the sample masonry building. The results show that the shotcrete method is more effective for buildings which are relying on the softer soils and in stiff soils it is recommended to combine the shotcrete method with other rehabilitation methods which are able to strengthen the building without increasing the stiffness of the building, like utilizing post tensioning cables.
H Hataminia , M Khanmohammadi , A Ghalandarzadeh ,
Volume 10, Issue 5 (7-2016)
Abstract
Tanks are structures for storing fluids that are made in different sizes, shapes and genera. Today using of tanks for water, petroleum products storage, and industrial wastes, has been developed significantly. The buried rectangular concrete tanks are used for water supply in most cities in our country. Soil-structure interaction is one of the most important issues in seismic behavior of buried tanks. With respects to code 123 that has suggested Mononobe-Okabe equation for dynamic pressure of earthquake excitation, the purpose of this research is to achieve the dynamic pressure of soil during earthquake. The obtained results have been compared to analytical and other experimental researches. Therefore, a series of small-scale experimental tests were conducted using 1g shaking table testing in the laboratory of physical modeling at University of Tehran. The results illustrate that dynamic force and pressure from Mononobe-Okabe and Wood equation are greater than experimental testing results. However Seed-Whitman equation is closer to experimental results.
