Journal of Engineering Geology

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Discontinuities have properties such as orientation, number of set and frequency that can affect the rock strength. Rock specimens having one, two and three cross- sets of discontinuities, various frequencies and orientations of 0, 30, 45, 60 and 90 degrees were prepared. The numbers of rock pieces increased progressively with an increase of frequency and set of discontinuities. As specimens having three sets of discontinuities that one of their sets had four number of parallel discontinuities were consisted 20 rock pieces and they represented jointed rock mass. Joint factor, uniaxial compressive strength and friction angle along the discontinuity surface in direct shear were determined. The uniaxial compressive strength of specimens having one, two and three sets of discontinuities in horizontal and vertical direction was less than the uniaxial compressive strength of intact rock. The uniaxial compressive strength of specimens approached approximately to zero value particularly when the orientation of discontinuities was 60 degrees. This considerable decrease of strength was occurred also for specimens having two and three sets of discontinuities at orientation of 30 degrees. The analysis of results showed that the relationship between ratio of uniaxial compressive strength of jointed specimens to the uniaxial compressive strength of intact rock specimens (anisotropy factor) and joint factor of this research is considerably different with the suggested relationship by Ramamurthy. Properties of discontinuities have altogether essential role on the strength of rock mass.

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Shear wave velocity (Vs) is a basic engineering soil property implemented in evaluating the soil shear modulus. Due to a few limitations, sometimes it is preferable to determine Vs indirectly by in situ tests, such as standard penetration test (SPT). However, inaccuracies in measurement or estimation of the influencing parameters have always been a major concern, and thus various statistical approaches have been proposed to subdue the effect of such inaccuracies in predictions of future events. In this article, an innovative approach based on robust optimization has been utilized to enumerate the effect of such uncertainties. In order to assess the merits of the proposed approach a database containing 326 data points of case histories from Adapazari, Turkey were gathered from renowned references. The identification technique used in this article is based on the robust counterpart of the least square problem which is a second order cone problem and is efficiently solved by interior point method. A definition of uncertainty based on frobenius norm of the data is introduced and examined against correlation coefficient of various correlation parameters and optimum values are determined. Finally the results of new correlation are compared with those utilizing a commonly used statistical method and the advantages and possibilities of the proposed correlation over the conventional method are highlighted

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In this study using finite element procedure was used to simulate the dynamic behavior of reinforced soil walls, to evaluate their dynamic response on all types of deformation modes, different mechanisms of failure detection and identification of parameters in each of the modes and the mechanisms. Detailed numerical modeling, behavioral models and materials were described and Dynamic response of the physical model has been validated experimentally. Parametric study has been of the wall height of 5 meters by the effective parameters such as hardness, length to height ratio, the vertical reinforcement, wall height, and acceleration inputs. Three modes of deformation were observed. The study showed that occur bulging deformation mode while the use of flexible reinforcement and occur overturning deformation mode while the use of stiffness reinforcement. Stiffness reinforcements have the most effective in changing the type of deformation. Length to height ratio of reinforcements has the minimum effective in changing the type of deformation.

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Determination of stress in earthfill dams is one of the most important parameters in dam safety studies. Stress monitoring can be done using total pressure cells which are typically installed during construction. The cell is installed with its sensitive surface in direct contact with the soil to measure total stress of soil and in combination with piezometers to measure pore-water pressure acting in the soil mass. Total pressure cells needs to be installed with care to get reasonable measurements. However, measurements are often incompatible with the theoretical predictions such that pressure cell results usually have some inaccuracies. There are several parameters effecting pressure cell errors. However, in the present paper it is only focused on the height of embankment and the duration of dam construction. For this purpose, a case study, namely Alborz embankment dam located in northern part of Iran was studied. It is an earth dam with clay core with a height of 78 m. Using the monitoring data and considering the effect of embankment height and construction period parameters, a model is presented to predict the pressure cells error with Gene Expression Programming (GEP) procedure by GeneXProTools 4.0 software. The computed coefficient of correlation (R²) for the proposed model is 0.98 showing a good agreement with the monitoring data. The obtained results indicate that the ratio of height difference to time difference for Alborz dam has a significant role in dam pressure cells errors

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The choice of a suitable bearing capacity of soil becomes the most important issue to be considered in any project. This paper describes analytical investigation conducted to evaluate the ultimate bearing capacity of adjacent footings in various spacings of footings. Bearing capacity of adjacent footings is determined based on virtual retaining wall method by applying equilibrium between active and passive forces. Results indicate the ultimate bearing capacity of each foundation changes due to the interference effect of the failure surface in the soil and it depends on footings spacing. In the present study, effect of soil type, depth of adjacent footings and reinforced soil is investigated on bearing capacity of adjacent footings. Results indicate closely spaced footings, can decrease or increase bearing capacity of adjacent footings with respect to single footings. Also, reinforced soil increases bearing capacity of closely spaced footings with respect to single footings on unreinforced soil, it depends on footings spacing. Finally, the predicted results are compared with those reported from experiments, analytical and numerical results performed by others, indicating an acceptable agreement.
 

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Today the effects of grouting are usually confirmed by the results of permeability tests but this method is not enough to show the changes in mechanical properties of rock masses. Although many investigators use the in situ tests for evaluation of rock mass mechanical property improvement. But this tests are time consuming and expensive. Grouting reduces the permeability and improves the condition of joints and ultimately increases the rate of rock mass classification in rock engineering. So with measurement of rock mass quality index values (Q-value) in cores obtained from grouted boreholes, the efficiency and success in improving the mechanical properties of rock mass can be showed. This paper for first time introduces Q-logging as a simple method to assess the impact of grouting in improvement of the rock mass quality. Here in, the results of Q-Logging in trial injection panels in the Bakhtiary, Bazoft and Khersan II dams have been examined. The deformation modulus were calculated from the Q-Logging for before and after of grouting. Results show that there is a good agreement between calculated rock mass parameters based on the Q-Logging method and the measured from in-situ test in the studied site. This agreement confirms the efficiency and applicability of the Q- Logging method for assessment of grouting success as well as the estimation of the rock mass parameters in grouted areas. Also it has been shown that the deformation modulus in weak rock mass with low quality has been more improved than rock mass with beater quality.

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One way of reduction of leakage from beneath of earth dams is using of one contact clay layer with very low permeability and intermediate to high plastisity and connectig it to core of dam. Since, most of fine-grained soil in environtment of dam have low plastisity and preparing it from another place is not economic, use of bentonite in order to improvement of engineering characteristic of borrowed clay is suitable way.
In this search effect of bentonite on geotechnical properties of fine-grained soils with low plastisity are evaluated. Results of this research show that hydraulic conductivity, consolidation coefficient, dry density, colifornia bearing ratio (CBR),.....are decreased with increase in bentonite content but optimum moisture , Aterberg limits , cohession and so on are increased with bentonite addition. Finally, with analysis of obtained result, optimum percent of bentonite is offered in order to improve of engineering properties of used clay in contact region.

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The in situ measurement of discontinuity geometry of rock mass exposures is a time consuming and sometimes hazardous process. Moreover, a large proportion of the exposure is often inaccessible. Thus, a fast and safe tool is required in order to acquire the information which characterizes the geological/structural regime. Digital image processing techniques provide the necessary tools for realizing this goal. This paper presents a methodology for automated discontinuity trace detection in digital images of rock mass exposures. In this study at first based on difference in gray level discontinuities with the face, fracture traces detected in images of rock face. Then some parameters of discontinuities geometry such as spacing, linear joint density, persistence, trace angle of joints and value of RQD are obtained. The Automated discontinuity geometry analysis system including: 1- Providing a digital image from rock face 2- The pre-processing on the images 3- Detection of edge or joint traces by the canny detector 4- Description of the edges using line detector by the Hough transform 5- The joint sets estimation using fuzzy methods and 6- Description the rock mass geometry properties.

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Evaluation of strong ground motion up beneath the construction is important in both geotechnical engineering (site effect) and earthquake engineering aspects (analysis of earth behavior). The common methods of microzonation in geotechnical engineering are based on one dimensional dynamic analysis, in which ground surface is assumed to be horizontal. However in many cases, because of variety of topography conditions, recorded responses are different on the top of hills and their corners. In this study, FLAC 2D software, as finite difference software, is used to analysis the trapezoidal hill with different shape ratios. These topography models are analyzed by far field earthquake records, and their dimensionless amplification ratios are compared with the obtained results of one dimensional analysis. Assessment of these two analyses methods in some points on the topography and around it, demonstrated considerable differences that show the necessity of two dimensional analysis in earthquake geotechnical engineering.

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Direct observation and experience of past earthquakes together with modeling carried out by researchers, has shown that ground motion acceleration and frequency is affected by the nonlinear behavior of site soil. In the process of assessing the seismic response of structures and lifelines, it is essential to understand the nonlinear behavior of the soil and how it can affect the results. In this paper, the nonlinear behavior of Urmia's subsurface soil is studied by performing one dimensional nonlinear site response analysis in time domain. Artificial acceleration time histories that were synthesized based on the result of seismic hazard analysis, conducted over three return periods, are used as input motion. Spectral acceleration at the ground surface is compared with those calculated for seismic bedrock, and spectral acceleration amplification curves are obtained. These curves show that, the amplification is greater in the central and eastern regions of the city than those for other regions of the city because of a deeper soil profile. The results show that the maximum amplification for higher return period is smaller because of greater soil nonlinear behavior

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The collapsible soils are usually known as soils with open structure and weak bonding between particles. The behavior of such soils is similar to very loose soils. These types of soils, when saturated without any changes in loading or subjecting vibratory loads, experiences huge settlements. The present research deals with investigation on collapsible soils located in the North East of Mashhad. The results of laboratory and in situ tests show that collapsible soil in this region was very sensitive to the increasing of moisture content. This means that an increase in soil moisture content, significant excess settlement occurs during a short time. This indicates that the soil in this region suffers from high potential collapsibility. The huge soil settlement will lead to the stability of existing structures to be at risk. It is, therefore, necessary for the collapsible soil in the region to be improved. For soil improvement, many techniques including moisture mitigation and soil replacement or compaction may be employed. Also stabilization of soil with lime, cement or coarse aggregates are practical methods. Which The results of the present research indicate that stabilization of soil lime is the most appropriate method for increasing bearing capacity of soil and reducing structural settlement.

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One of the most useful procedures in soil stabilization is lime. Soil improvement using lime is a quick and simple approach which could be included in large and small projects. The objective of soil ‘Improvement’ with quicklime is to achieve an immediate reaction, which significantly strengthens the soil due to the removal of moisture and a chemical change in clays. In order to do a parametric study on the influence of the lime on shear strength preparing the samples is important. In this paper, in addition to considering a method of samples preparation, the effect of lime content, water content and processing time on the shear strength of clay using direct shear test is investigated. The results indicate that the method of samples preparation is effective and is identified that there is an optimum lime and moisture content which maximize shear strength.

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The objective of this paper is to investigate the bearing capacity of strip foundations next to sand slope. A series of laboratory model tests has been carried out and a new correlation coefficient to estimate the bearing capacity of shallow foundations near slopes is presented. The sand layers were prepared in a steel test tank with inside dimensions 500 ´ 200´ 250 mm. After vertical loading, the applied load and displacement of foundation were recorded and stress-settlement curve is drawn. Finally, the load at which the shear failure of the soil occurs is recorded as ultimate bearing capacity of foundation. The test sand used in this study was Babolsar sand with relative density of 50%. The relative performance of different distance of foundation from the edge of slope and inclination angle of slope are compared using same quantity of soil properties in each test. The results indicate that with increasing distance from the edge of the slope, bearing capacity increases linearly. Also with increasing slope angle, the bearing capacity has declined linearly

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The present study aims to employ intelligent methods to predict shear wave velocity (V_s) in limestone. Shear wave velocity is one of the most important rock dynamic parameters. Direct determination of this parameter takes time, cost and requires accuracy as well. On the other hand, there is no precise equation for indirect determination. This research attempts to provide some simulations to predict V_s using the information obtained several dams located in Iran, using different approaches, including adaptive neuro-fuzzy inference system (ANFIS) and gene expression programming (GEP). 136 datasets were utilized for modeling and 34 datasets were used for evaluating its performance. Parameters such as Compressional wave velocity (V_p), density (g) and porosity (n) were considered as input parameters. The values of R² and RMSE were 0.958 and 113.620 for ANFIS, where they were 0.928 and 110.006 for GEP respectively. With respect to the accuracy of the intelligent methods, they can be recommended for future studies

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This paper describes triaxial compression tests conducted to determine the effect of fiber inclusion on stiffness and deformation characteristics of sand-gravel mixtures. Tested soil was a mixture of Babolsar sand from the shores of the Caspian Sea and Karaj River gravel. Portland cement was used as the cementing agent and fibers 12mm in length and 0.023mm in diameter at 0%, 0.5% and 1.0% were added to the mixtures. Triaxial tests were performed on saturated samples in consolidated drained and undrained conditions at confining pressures of 100, 200 and 300 kPa. Deviatoric stress-axial strain, volumetric strain-axial strain, pore pressure-axial strain curves with deformation and stiffness characteristics were investigated. Tests results show that fiber addition increased peak and residual shear strength of the soil. Fiber addition resulted in an increase of the maximum positive and negative volumetric strains. In undrained condition, fiber inclusion caused increase in initial positive pore pressure and final suction. It has also been observed that fibers decreased initial tangent stiffness of the cemented sand-gravel mixture.

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Collapsible soils could widely be found in central part of Iran and has caused lots of problems for roads and railroads in that region. Appearance of wide cracks in the collapsible soil near the Tehran-Semnan railroad tracks has caused some worries regarding the safety and performance of the railroad. However, due to the high traffic of the railroad, it is impossible to block the road for remedy. Therefore using injection method was found the most suitable alternative to improve the soil along railroad. The results of field and laboratory tests revealed that the injection of lime has better effects on improving soil characteristics than the other materials. It will significantly decrease the collapsibility potential of soil in saturated condition and will cause an increase in loading capacity of soil. Lime injection was suggested as the most appropriate solution for projects with similar geological condition. 

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This paper aims to present an experimental and numerical study on the effect of wetting-drying cycles and plasticity index on the California Bearing Ratio (CBR) of lime stabilized clayey soils. The numerical analysis was carried out based on finite element method for comparison between results of experimental and numerical studies. Three clays with different plasticity indices were mixed with various amounts of hydrated lime and compacted at optimum water content. The CBR tests were conducted to the soils and admixtures after specified curing time and various numbers of wetting-drying cycles. The experimental results indicate that addition of lime content up to 4% causes significant increase in the CBR values. Based on the obtained results the CBR decreases during the wetting phase and increases during the drying phase of each cycle. After 3 cycles the CBR values of lime stabilized clayey soils are increased. Also, for stabilized clays by increasing the plasticity index, the CBR values resulted by increase of lime content are decreased. The comparison between numerical and experimental analyses indicates a good agreement between results.

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In present research, landslide hazard zonation of Latian dam watershed area has been carried out using Analytic Hierarchy Process (AHP), Valuing area accumulation, Factor overlay and Information value methods. At first, different maps comprising slope, aspect, altitude, faults, drainage network, access roads, lithology, land use and friction angle maps were prepared digitally using GIS. Afterward affecting factors were evaluated using old landslides. The results of evaluation show that seven parameters are important effective factors on sliding in this area. These parameters were leaded to landslide zonation maps. These maps show that potentially high risk zones point of view landslides are located near the central and western boundaries of the reservoir. Performance of four used classification methods were evaluated and compared. The evaluation results show that Valuing area accumulation and Factor overlay are precise methods for evaluating landslide potential in the study area respectively

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Buried pipeline system form a key part of global lifeline infrastructure and any significant disruption to the performance of these systems often lead to undesirable impact on regional business, economies or the living condition of citizens. In this paper the response of buried pipelines at fault crossings are studied. A fault movement can be resolved into an axial component, a lateral component in the horizontal plane, and a vertical component. Applying finite element method, the effect of various parameters such as anchored length, internal friction angle of surrounding soil, fault movement and fault crossing angle on the behavior of buried pipeline were studied. Nonlinear behavior for pipe and surrounding soil are assumed using beam-spring model. Results showed an increase in internal friction angle of surrounding soil increases strain and also normalized bending moment and axial force. Comparing bending moment at friction angle of 20^° and 40^° shows about 30% differences with certain crossing angle we can prevent producing large strain and bending moment on pipeline

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One of the major problems associated with the clayey soils is the swelling potential due to moisture absorption, which results in applying high pressure on the superstructures, and may cause failure or large deformation of the structures. Among the solutions to mitigate the swelling problem of clayey soils is their stabilization using additives. This study aims to compare the effects of three types of additives on the reduction of swelling potential of two types of clayey soils, with two different plasticity indexes. The additives used in this research include two traditional additives namely, cement and lime, and one type of nontraditional stabilizer namely, CBR PLUS nano polymer. These additives were added to the soils in different contents, and the Atterburg limits, and the swelling of the soils were measured at different times after addition of the additives. The results show that the CBR PLUS is more effective in reducing the swelling potential of the soil with high plasticity index, by which, the swelling was reduced by 1500%, while the addition of  lime and cement reduced the swelling about 1000%. For the soil with low plasticity index, the cement is found to be more effective than the lime and CBR PLUS in reducing the swelling potential. The addition of 7% of cement resulted in 1400% of reduction in swelling, against 600% reduction for the addition of the same content of lime. In addition, it is found that the CBR PLUS and cement are, respectively, more effective in reducing the plasticity index of the soil with high and low plasticity index