International Journal of Civil Engineering
Volume:14 Issue: 4, 2016

This paper is a comprehensive analysis on various experimental and numerical studies on slopes. Small-scale physical modeling of slopes under surcharge loads was performed on loose sand slopes. Digital images were captured during the incremental loading from the model’s side. Particle image velocimetry and 3D numerical model were applied to investigate the slope under surcharge loading; several important factors that control pile performance are investigated. Safety factors and location of critical failure surfaces of various reinforced and unreinforced slopes are obtained and compared. The results shows, the 3D failure surface shape in front of the piles is triangular for stabilized homogenous slopes, which is different from its conical shape in laterally loaded piles. This paper also analyzes the effects of soft bound interlayer, soil properties, pile spacing, pile position, and surcharge distance on the safety factor and slip surface shape of the stabilized and non-stabilized slopes. The results indicate that the distance of soft soil layer from ground surface and its horizontal direction angle strongly influence the optimum location of the piles. The numerical modeling results show that increasing the distance between the piles prevents the arching phenomenon from developing, and instead, increases the failure volume in the slope.

Complete recognition of calcareous sediments engineering behavior considering their local expansion and wide variety of engineering properties is very important. In south parts of Iran, there are some carbonate hydrocarbon reservoirs which are covered by calcareous deposits. Hormuz Island in is one of the most strategic areas in Hormuz Strait between the Persian Gulf and Oman Sea. In this study, a series of undrained monotonic and cyclic simple shear tests was performed on saturated Hormuz calcareous sand specimens using hollow cylinder torsional apparatus. The tests were carried out on specimens with various relative densities under different effective consolidation stresses. Based on the results, pore pressure generation, shear strain development, stress–strain characteristics of the specimens are presented and compared with the technical literature. In addition, dissipation of strain-based energy during the cyclic loading and its relation to excess pore water pressure is described. The cyclic resistance curves of specimens with different initial conditions are plotted. Also the results of monotonic and cyclic tests are compared together for better interpretation of Hormuz calcareous sand under undrained torsional loading.

The behavior of Chamkhaleh sand and three other recognized sands namely, Babolsar, Firouzkuh, and Standard (Ottawa) sands are compared using triaxial apparatus under undrained monotonic loading conditions. Chamkhaleh and Babolsar sands are supplied naturally from southern Caspian Sea shorelines, whereas artificial Firouzkuh and Standard sands were supplied commercially. Samples were prepared using wet tamping with regard to the reduced compaction effect at relative density of 15 % under isotropic consolidation pressures of 100, 300, and 500 kPa. The results of triaxial tests have indicated that Chamkhaleh sand has much more dilation tendency than the other sands. To evaluate the reasons behind this behavior, the sphericity and roundness of all the four sand particles were measured using an image processing method. It was revealed that the sphericity of the four sands is not much different, but Chamkhaleh sand is more angular than the other sands. For comparison of the dilative response of the sands in undrained triaxial tests, a “dilation tendency index” is introduced. This index may be used as a criterion for measuring the dilation of sands in undrained tests. Results have shown that the internal friction angle under the steady-state condition is more dependent on the shape of particles than the maximum strength condition. For sphericities greater than 0.5, the dependency rate of sand behavior on the roundness is decreased.

In this paper, the results of a comprehensive numerical parametric study on the seismic response of the half-plane with subsurface cavity have been presented. For analysis purposes, a numerical time-domain analysis is performed by utilizing a robust numerical algorithm based on time-domain boundary element method. It is observed that an embedded cavity under the ground surface can create a highly variable amplification pattern on the half-plane. Some preliminary simple relationships and tables are presented which could be used while introducing simple preliminary ideas for modification of the standard design spectra in building codes and seismic microzonation studies.

To meet construction demands, reinforcement and stabilization methods have been widely used to improve properties and mechanical behavior of clays. Although cement stabilization increases soil strength, at the same time reduces ductility which is of paramount importance in roads, landfill covers, etc. In the current study, kaolinite was stabilized with 1, 3, and 5 % cement and mixed with 0.05, 0.15, 0.25, and 0.35 % polypropylene fibers to increase ductility. Samples were cured at 35 °C for 1, 7, and 28 days and subjected to unconfined compression tests. Results showed that the inclusion of discrete fibers to uncemented and cemented kaolinite reduced stiffness and the loss of post-peak strength and changed brittle behavior of cemented samples to a more ductile behavior. Cement and fiber contents as well as curing period were found to be the most influential factors, and fiber–soil interaction was influenced by binding materials.

This paper presents a numerical model based on explicit finite difference method for contaminants transport under electrokinetic remediation process. The effect of adsorption, precipitation and water auto-ionization reactions was considered with a set of algebraic equations. Also the effect of electrolysis reaction in anode and cathode cells was considered with appropriate boundary conditions. The model predictions are compared with experimental results of electrokinetic lead removal from kaolinite in the literature. The coefficient of determination and index of agreement between the lead concentration of experimental result and model prediction were 0.974 and 0.884, respectively. The coefficient of determination and index of agreement between the pH value of experiment and the pH prediction were 0.975 and 0.976, respectively.