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Showing 109 results for Subject: En. Geology

, ,
Volume 2, Issue 1 (9-2007)
Abstract

Considering the seepage and choosing an efficient sealing method is very important in dam projects. This issue has a close relationship with engineering geological properties of the dam site. Chapar-abad dam is an inhomogeneous earth-fill dam of 44.5 meters height, crest length about 427 meters and a reservoir capacity of 127 million cubic meters. The dam project is under construction and is located about 75 Km southeast of Uromieh city, in West Azerbaijan Province. The foundation materials include 60 meters of alluvium deposits overburden bedrock layers of carbonate units. The abutments consist of carbonate and schistose layers of Precambrian age. In order to control the seepage through the Alluvial foundation, several sealing methods were considered. The methods include grout curtain, cutoff-wall, impervious blanket, open compacted trenches, and the use of geosynthetics are evaluated. In this research using a finite element package named Plaxis was utilized. The results indicate that although the cutoff-wall is usually considered as the best method for this type of geological condition, but due to the instability of granular soils and the possibility of liquefaction capability, the grout curtain is proposed as to be an efficient method.


, ,
Volume 2, Issue 1 (9-2007)
Abstract

Saymareh dam and hydro-power plant are under construction on Saymareh River in Ravandi anticline, Ilam province. During boring the power tunnel which crosses the anticline, a large volume of water was encountered. This volume of water was not observed in the past. Considering the water quality of springs, water level of dam site piezometers, geological and hydrogeological inspections, isotope analysis, tracing experiments and water balance, it was concluded that the main portion of water is not supplied by the Ravandi anticline. The neighboring Veizenhar, Gavar and Milleh anticlines contribute to providing the main body of water. The most probable paths of water are not cross the dam reservoir and a localized conduit flow is not established in this area. Therefore, water leakage from the reservoir is not expected.


, , ,
Volume 2, Issue 1 (9-2007)
Abstract

Groundwater is the sole source of accessible resource for agriculture in Zeviercherry- Kherran plains and water quality often falls in brackish group. In order to determine the source of salinity and hydrochemical processess affecting groundwater environment of the area, 61 groundwater samples were taken for hydrochemical analysis and composite diagrams (two variant diagrams of total concentration verses concentration of major ions and two variant diagrams of chloride verses concentration of bicarbonate, sulfate and sodium), Factor analysis and saturation index of calcite, dolomite and gypsum were applied. The data indicated that groundwater is supersaturated with respect to calcite and dolomite and with respect to gypsum saturated to under saturation. Regional dissolution of gypsum, anhydride and local dissolution of sodium chloride are important controlling factors of groundwater salinity of the area. 


, , ,
Volume 2, Issue 1 (9-2007)
Abstract

Results of velocity structure modeling in the Earth's crust using a comparison approach of receiver function analysis and joint inversion of receiver functions with surface wave dispersion data are presented in this paper. Seismograms of the teleseismic events that have been recorded on a broadband seismic station in the central Alborz were used for data processing. Velocity models that were computed by using both modeling methods show analogy the depth  discontinuities but differences in the absolute values of velocity. In addition, differences between computed models using different initial velocity models confirms that receiver function results are not a unique modeling method compared with the joint inversion results which show reasonable and stable values. Both methods show 56km depth for the Moho discontinuity.


, ,
Volume 2, Issue 1 (9-2007)
Abstract

This paper describes the results of a study which was primarily directed to the determination of geotechnical properties of fine and coarse grain soils stabilized by lime obtained from Taleghan, northwest of Tehran to assess its suitability as construction material. Soils were treated with lime mixtures in various portions between 3 to 9 percents by weight. The samples were cured for different periods of time up to 90 days under 30°c and 60 percent relative humidity. The geotechnical properties were investigated by: (a) compaction characteristics, (b) compression tests and (c) direct shear tests. The results indicated soils maximum dry densities decreased while the optimum water contents increased. The compressive and shear strength of admixtures depicted an increasing trend. It was observed that addition of 6 percent of lime caused a significant increase in strength properties of CL and SC grain soils. However, the SC soil yielded the best results.


,
Volume 4, Issue 1 (11-2010)
Abstract

Distribution of static active earth pressure on an inclined retaining wall, with frictional or cohesive-frictional backfill, has been studied in the present research. Based on the limit equilibrium concept, and by implementing the horizontal slices method (HSM), two formulations have been proposed for determination of critical failure wedge. Results obtained from these formulas and results of the suggested equations by other researchers have been compared. Findings of current study show that horizontal slices method is capable of predicting the stress distribution and angle of failure wedge for inclined walls with high degree of accuracy. In addition, this method is applicable for various conditions of soil and wall and is able to consider the slope of backfill, friction between soil and wall, cohesion of soil and the effect of surcharge, simultaneously. Application of achieved formulation from horizontal slices method reveals that active earth pressure on inclined walls is nonlinear for both frictional and cohesive-frictional soils and the center of mass point of the resultant force would be located in an elevation less than one third of the height of wall.
, ,
Volume 4, Issue 1 (11-2010)
Abstract

One of the major problems in urban subway tunnels is tunnel stability analysis and determination of the safety factor, and the prediction of the settlement that caused to provide stability during the performance, and then at the time utilization structure. The objectives of this study is using different methods to predict and development of these methods by use of each other. In this  paper, analyze and evaluate the stability of Tabriz Metro tunnel- Line 1 has been carried out using numerical methods, artificial neural networks and empirical  equations. The two excavating methods used in Tabriz Metro tunnel- Line 1 (using machine TBM tunnel method and NATM). In the first part of this  research, the excavated zone of the tunnel with NATM method has been analyzed  using numerical method and surface settlement and amount of tunnel convergence in the tunnel walls have been predicted by this method. After that, surface settlement has been predicted using artificial neural networks and then it has  been compared with obtained value from numerical method analysis and empirical relations.  Then, based on these results, empirical relations of convergence - settlement have been modified for Tabriz Metro tunnel- Line 1. In the second part of the research, the TBM penetration rate was predicted by use of neural network which is an important parameter, when one faced with troublesome areas and is very useful to use appropriate pressure EPB for TBM.  
Zohreh Safipoor Rashvanlu, Ali Ghanbari, Seyed Jamal Zakariaee,
Volume 5, Issue 1 (9-2011)
Abstract

The ever increasing growth and development of the metropolitan city of Karaj in recent years has placed implementation of basic studies on Alluvium of Karaj Plain on the top of significant priorities of the region’s development projects. Therefore, in the present paper, the alluvium of South Karaj was studied based on relevant numerous geotechnical laboratory and field tests. In this regard, an area from Pol-e Fardis to Serāh-e Andishe with a length of 10 km is selected and the geotechnical engineering features of this area were taken into careful consideration and study. The carried out studies divide South Karaj Alluvium into five independent parts whose engineering description are presented. On the other hand, since the results of most of relevant laboratory and field tests have been collected, some relations for calculating Elasticity Modulus, Soil Inner Friction Angle as well as other geotechnical parameters in South Karaj Alluvium are introduced. Finally, the process of soil classification in South Karaj Alluvium is compared with the same process in other regions of Karaj, and, given the soil engineering features of Southern part of South Karaj Alluvium, some suggestions are presented for optimization and facilitation of future development projects in south Karaj Alluvium. Geotechnical studies.
, D Fereidooni,
Volume 5, Issue 1 (9-2011)
Abstract

Schmidt hammer is used for calculation of joint compressive strength and elasticity modulus of rocks. Today, application of Schmidt hammer is a common method in evaluation of properties of rocks. This method is quick, inexpensive and non-destructive which are benefits of this method. In this regard, different experimental equations proposed by Barton & Choubey (1977), Deere (1960), Keadbinski (1980), Aufmuth (1973) and ISRM (1981) can be employed in order to calculate the Joint Compressive Strength (JCS) of rocks. Due to the importance of this research, new experimental equations are introduced. Using this equations show a very good results in comparison with the results of other researchers. It should be noted that this equations are achieved from 827 records of Schmidt Hammer results from different types of hard rocks such as granite, diorite and hornfels from the Ganjnameh-Shahrestaneh road in Hamedan province, west of Iran.
, A Sorosh, S Hashemi Tabatabaee, A Ghalandarzadeh,
Volume 5, Issue 2 (4-2012)
Abstract

All rockfill materials subjected to stresses above the normal geotechnical ranges exhibit considerable particle breakage. Particle breakage and crushing of the large particles to smaller ones result in a lower strength and higher deformability. The breakage of particle that is observed in the large scale triaxial tests, is usually expressed quantitatively by the Marsal breakage index, . This paper presents a method for calculating at any axial strain level in the large triaxial tests. The model used Rowe’s minimum energy principle ratio. The key parameter in modeling , is the friction angle which excludes dilation and breakage effects, . The results indicate that the internal friction angles at confining pressure equal and less than 200 kPa at the constant volume state is a unique value. Moreover, there is a linear relationship between the variation of energy spent on particle breakage to Marsal Breakage index with confining pressure, at failure axial strain.
, Gholam Lashkaripour, M Akbari,
Volume 5, Issue 2 (4-2012)
Abstract

Tunnel boring machines (TBM) are widely used in excavating urban tunnels. These kinds of machines have different types based on supporting faces and tunnel walls. One type of these machines, is the Earth Pressure Balance (EPB) type that was used in excavating the Line 1 Tunnel of Tabriz Metro. Different parameters such as geological conditions, rock mass properties, dip and machine specifications affect the efficiency of the machine. One method of predicting the efficiency of these machines is to estimate their penetration rates. In this study the value of TBM penetration rates are predicted by an artificial neural network. Predicting of this parameter is so effective for conducting in high risk regions by understanding the time of facing to these regions. The main result of this study is to forecast the penetration rate with an acceptable accuracy and to determine the effective parameters through sensitivity analysis measured by an artificial neural network.
, , ,
Volume 5, Issue 2 (4-2012)
Abstract

The development of large cities requires the use the underground networks for the construction of transportation infrastructures and facilities. Construction of tunnels in soft grounds induces generally soil movement, which could seriously affect the stability and integrity of existing structures. In order to reduce such movements, in particular in urban areas, contractors use more and more the tunnel boring machines (TBM) for the construction of tunnels. Hence in urban environment, Prediction of the ground movements caused by the tunnel excavation is a major engineering challenge. In this paper is used a three-dimensional numerical model and ABAQUS cod for the prediction of soil movements induced during tunnel construction in part of the line 3 of Tehran subway using EPB excavation machine. This investigation include most shield tunneling components such as face pressure, the grouting pressure, excavation machine and frictional contact with soil and shield. Observations of the results demonstrate that the maximum surface settlement in this section is 2.5 cm that is 0.5 cm more than the its allowable value. Simultaneously with surface settlements occur horizontal movements within soil mass, which have different forms in two horizontal directions, and with the expansion of depth they increasing.
H Ghasemzadeh, ,
Volume 5, Issue 2 (4-2012)
Abstract

In this paper, using Mononobe & Okabe method, seismic force and its effects on thin masonry retaining wall inside structural frame (Masonry retaining infill) are presented. In this method, retaining wall has been assumed to be rigid and the prevailing failure mode is sliding of wall bed joint or wall rotation around its toe, whereas the prevailing failure mode of masonry retaining infill is usually flexural cracking in middle zone of wall under out of plane seismic force. In this case, the seismic force distribution is important. Accordingly in this paper, a distribution for seismic forces on masonry retaining infill has been proposed. Also with regard to out of plane behavior of masonry retaining infill in terms of strength and acceptance criteria aspect, failure in body of wall due to out of plane loads has been analyzed. Then, the desired seismic rehabilitation method in case of vulnerable masonry retaining infills has been presented and as a practical example, results of the proposed method with the results of numerical software have been controlled. Finally, according to various conditions predicted for masonry retaining infills, Seismic Retrofit solutions are presented for practical applications.
S Afshar, M Ghafori, Gr Lashkaripur, M Arian, M Musavimadah,
Volume 6, Issue 1 (11-2012)
Abstract

With respect to development of underground structures and their high construction costs in intra- and inter-municipal transportation, it is necessary to study the stability of such structures. In this research, tunnel stability of Mashhad Metro line 2 with 17 km length is studied. First, the type of sediments and geotechnical properties in Mashhad Plain are investigated. The SPT profiles were prepared using Rock Work 2006 software. The soil classification tests and XRD results show that the soils in this line are mostly clay such as Illite and Kaolinite types. Afterwards, because most of the soils in this line are characterized as fine grained, the ground settlement using PLAXIS V8 software was performed. According to the numerical modeling and the depth of tunnel, the optimum depth for tunnel was determined.
Akbar Cheshomi, Ebrahim Ahamadi Sheshde,
Volume 6, Issue 1 (11-2012)
Abstract

Determination of uniaxial compressive strength (UCS) of intact rock is an important mechanical parameter required for many engineering projects. In some engineering projects, for example, well drilling has been accomplished for petroleum. The requirement of deep well to take samples to obtain rock core sample for determination of UCS is a difficult task. On the other hand, determination of this parameter is essential in order to analyze well wall stability and well development program. Therefore, the idea of using drilling cuttings is proposed for determination of UCS. In this paper, in order to develop relationship between UCS and single compressive strength (SCS) 7 block sample of microcrystalline limestone from Asmari formation were used. Then UCS test was performed and uniaxial compressive strength was determined. Next, these samples were crushed and 420 single particles were prepared. Then SCS for each particle was determined. Since the shape of particles affects particle strength, shape of particles was modified.  The total particles used for determination of SCS were spherical. In order to study the effect size of particle, particles with diameters 2, 3 and 4 millimeters were prepared and the SCS for each particle has been determined. With the increase of diameter of particles, the SCS has been increased too. In order to eliminate the effect of size of particles, it is defined variable size and strength and proposed chart between them. Coefficient of correlation between SCS and UCS is more than 0.91 which indicates a high correlation between them.
, Ar Taleb Beydokhti, A Asiabanha,
Volume 6, Issue 1 (11-2012)
Abstract

Slake durability of rocks is an important engineering parameter for evaluating deterioration of rocks in chemical and physical agents that are related to mechanical properties of rock. The main purpose of this study is to assess the influence of the number of drying and wetting cycles under variable pH conditions and controls of mineralogical composition on durability. For this purpose, five different types of tuff were selected from different parts in north Qazvin city. The samples were subjected to multiple-cycle slake durability testing with different pH values solution. Also the slake durability tests in saturated condition on samples, petrographical analyses and basic physical - mechanical test were performed. In addition, to assess the influence of mineralogical composition on durability, the mineral contents of the original material and the material passing from the drum of the slake durability apparatus after fifteen cycles were also determined by XRD analyses. It was concluded that the slake durability of tuff is independent of the pH in acidic solution circumstances. Mineralogical composition, fabric and weathering rate are considered to have a greater influence on the slake durability of tuff. A strong relationship between the point load strength and the fifteenth-cycle slake durability index is found in the rock types studied.
, ,
Volume 6, Issue 1 (11-2012)
Abstract

The Water infiltration rate of a catchment area depends on a number of parameters. Each catchment area has its own peculiar infiltration features, depending on its climate and soil structure This research is a study and comparison of the banks of two permanent rivers of Bushehr Province (Iran), namely, the Mond and the Bahoosh, in the County of Tangestan. In order to determine and check the best penetration model and to calculate the infiltration coefficients of the Kostyakov-Lowese, SCS, and Philip models, the vertical water penetration rate of the soil was measured using field Double Ring tests (repeated for three times) in 60 test pits. Using computing software, the infiltration and aggregate infiltration rates’ curves were drawn and a Visual Basic software program was used for each model to specify the best coefficients, that is, those with the highest correlation with the curves. Results show that, for the Bahoosh riversides, the American SCS infiltration model has less errors than the Philip and Kostyakov-Lowese models, and for the Mond riversides, the Philip model is better than the Kostyakov-Lowese and American SCS models.
Mahmoud Ghazavi, M Moshfeghyeganeh,
Volume 6, Issue 2 (4-2013)
Abstract

The shape of slip surface of the wedge creating lateral thrust on rigid retaining walls plays an important role in the magnitude, distribution, and height of point of application of lateral thrust.  Considering the shape of slip surface as linear, circular, logarithmic spiral, or a combination of them has been used in the literature. In the Coulomb lateral earth pressure method, a linear distribution of soil pressure on retaining walls is tentatively assumed and thus the point of application of total thrust is placed at one third of the wall height from the wall bottom. However, some experimental studies have revealed non-linear distribution of lateral earth pressures and that the point of application of resultant thrust is placed upper than one third of the wall height. In the present study, a plasticity equation is used to determine the reaction of the stable soil on cohesionless backfill supported by a retaining wall using an empirical equation derived from experiments performed in the field by others. A new analytical solution for determining the total resultant thrust on the wall is introduced and the distribution of pressures and the point of application of total thrust are computed. The results have been compared with some analytical methods, experimental data, and also with available data reported from field, demonstrating the accuracy and capability of the developed method. The results show that the distribution of the active lateral earth pressure is nonlinear and the point of application of total thrust is located about 0.42H from the wall bottom (H=wall height). In addition, the application point of total thrust is nonlinear function of soil-soil, wall-backfill soil friction angels and the height of the wall
Ali Ghanbari, Mohsen Mojezi, Meysam Fadaee,
Volume 6, Issue 2 (4-2013)
Abstract

Construction of asphaltic core dams is a relatively novel method especially in Iran. Iran is located in a region with high seismicity risk. Therefore, many researchers have focused on the behavior of such types of dams under earthquake loading. In this research, the behavior of asphaltic core rockfill dams (ACRD) has been studied under earthquake loading using nonlinear dynamic analysis method and a new method is presented to assess seismic stability of these types of dams in earthquake conditions. Based on nonlinear dynamic analysis, the current study attempts to provide an appropriate criterion for predicting the behavior of earth and rockfill dams considering real behavior of materials together with actual records of earthquake loading. In this method, the maximum acceleration of the earthquake record (PGA) increases until instability conditions. Finally, a new criterion is presented for evaluating seismic safety of ACRDs via demonstrating curves of the crest's permanent settlement and maximum shear strain against maximum earthquake acceleration. Results of the proposed criteria can assist designers of asphaltic core dams to predict dam stability during earthquake event
Amir Hamidi, P. Yarbakhti,
Volume 6, Issue 2 (4-2013)
Abstract

In this paper, a constitutive model is proposed for prediction of the shear behavior of a gravely sand cemented with different cement types. The model is based on combining stress-strain behavior of uncemented soil and cemented bonds using deformation consistency and energy equilibrium equations. Cement content and cement type are considered in a model as two main parameters. Based on the proposed method, the behavior of cemented soil with different cement types is predicted for conventional triaxial test condition. Porepressure developed during undrained loading besides volumetric strains in drained condition are also modeled according to this framework. Comparison of model results with experimental data indicates its reasonable accuracy.

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