فهرست مطالب mansour parvizi

The issue of water seepage from foundations and abutments is one of the main challenges related to the design and construction of dams. One of the most important parameters in dam design in the study of seepage is to determine the permeability of the dam site, especially in rock formations. In this study, first, the permeability of Haigher roller compacted concrete dam site, located in Fars province, was determined through extensive Lugeon tests before and after the grout curtain. Then, using PLAXIS 3D FEM software, the site topography was modeled in three dimensions and three-dimensional dam seepage analysis was performed. The efficiency of the grout curtain was evaluated using numerical analysis. The results show that the total seepage discharge in the Haigher dam construction site without grout curtain is 1.075 * 10-2 and after the construction of the grout curtain is reduced to 2.305 * 10-3 m3/s, which indicates a reduction of about 80% seepage discharge due to construction of grout curtain. The results of the parametric study showed that with increasing the depth of the grout curtain, the seepage flow decreases and with increasing the upstream water level, the seepage flow rate from the dam increases linearly.

Nowadays, the lack of suitable ground in urban areas has raised and solving the problems in loose areas is one of the main concerns of geotechnical engineers. In recent years, the use of polymeric reinforcements such as geocells in geotechnical engineering has increased significantly. In the present study, the effect of geocell on the bearing capacity of the shallow foundation located on sandy soil under inclined load has been investigated using PLAXIS 3D finite element software. Thus, after verifying the numerical model, the effect of parameters such as the presence of shear force as well as the optimal arrangement of the reinforcing layer on the bearing capacity of the foundation has been studied. The results of the analysis are plotted in the form of diagrams and based on that, the optimal dimensions as well as the optimal depth of geocell reinforcement layer are determined. The results of the analysis indicate that, with the addition of the geocell layer, the bearing capacity of the foundation under the inclined load increases 500 % and 210% in shear and vertical bearing capacity, respectively. The extent of this effect depends on the arrangement of the reinforcing layer. Also, the optimal placement depth, width and height of the reinforcing layer to obtain the maximum bearing capacity in the inclined load condition in the present study are equal to 0.025B, 4B and 0.6B, respectively.

The sheet piles are used below hydraulic structures to reduce seepage flow rate and hydraulic gradient at the outlet of such structures rested on permeable foundations. Up to now, for analysis of seepage under hydraulic structures much research work has been carried out in the form of numerical models. However, less field and laboratory works have been performed to study and compare boiling phenomena for evaluating of the numerical models. By simulating an experimental model of a sheet pile inserted in a sand foundation by computer code FLAC based on the finite difference method, the soil behavior mechanism flow has been investigated under seepage effect. The results indicate that computer code FLAC underestimated uplift pressures compared to the experimental data. In order to study the boiling, the soil treatment analyzed at the most critical condition as well. The numerical model presented in computer code FLAC, is properly able to simulate the soil and foundation behavior. Comparing the results obtained from numerical model with experimental data also confirms well, because this model predicts the boiling observations with reasonable accuracy and it was possible to predict heaving mechanism based on the stress analysis before performing the plan.

The purpose of this study is to find a method for obtaining all soil dynamic parameters numerically. Moreover, it is intended to predict the dynamic parameters after each impact, and to obtain the predicted compaction as well as the desired dynamic parameters after a certain number of impacts. In the study, four hammers with different dimensions are modeled on sandy soil using ABAQUS. Additionally, the activated wave stiffness test is used to extract the dynamic parameters of each hammer for loose sand, and it is shown that which hammer under what conditions yields the highest efficiency. The peak particle velocity is obtained using the finite element technique for each hammer, and the results are used to determine the safe distance after each blow. The results indicate that the unsafe distance of compactor from the location of impact increases with the weight of the compactor. In the study, a hammer with a mass of 875 kg, falling through a distance of 1 m. horizontal safe distance of 3.80 m, and a vertical safe distance of 2.30 m is designed to deliver five blows to achieve the maximum stiffness with an improved depth under the foundation from 0.9 to 1.2 m in a loose soil and a relative error of 5% is obtained. The improvement depth obtained numerically is in good agreement with the experimental results of centrifuge tests at accelerations of 1, 10, 20, and 30 g as well as the field results of Parvizi and Merrifield, Allen, Maxwell and Briaud.

In building design codes, no attention has been paid to the interaction effect of underground structures and the building, which can change the amount of applied forces on the building. Therefore, in the present study, by using numerical modeling with FLAC 2D software, the effect of tunnel and building interaction on the seismic response of building stories has been investigated in order to have more accurate assessments of seismic forces on the building when we want to design it. In this study, the model was first stimulated in the case of presence of building alone (SF model) by harmonic shear SV waves and the real earthquake waves. Then, by adding a tunnel to the model (STF model), the system was analyzed. By comparing the result of the maximum acceleration of buildings floors in case of STF to the SF model, the effect of tunnel and building interaction on stories acceleration have been investigated. In low frequencies, the negative effect of tunnel on the acceleration response of the building stories was observed. In high frequencies, the positive effect of tunnel on the acceleration of the stories was observed. It was also concluded that the harmonic waves with the frequency equal to the dominant frequency of the real motions, applied to the models, have created more amplification in acceleration response of buildings.

In the present study, laboratory methods were used to investigate the drainage conditions of the steady-state with the surface recharging. In the study, fine and coarse sandy soil samples were used to study changes in groundwater level. The test specimen was poured into a large-scale flume, with 5.4 m long, which led to uniform vertical precipitation and vertical drainage on both sides. The parameters of precipitation rate, soil gradation and water level within the drains were investigated as variables in this study. The results showed that the maximum change in water height in coarse sand due to increasing water height in drains from 0 to 40 cm is equal to 56.9 cm and 72.5 cm, respectively, which caused an increase of 15.6 cm. However, in fine sand these changes are very small (2 cm) and equal to 87.2 cm in free drainage conditions and equal to 89.2 in water conditions of 40 cm inside the drains. The obtained laboratory results were compared with the Dupuit-Forchheimer analytical relationship, according to which this relationship is able to accurately predict the level of water in the fine sand, but in coarse sand, the relationship underestimates the water table height in the soil.

In this study, the effect of geogrid on the ultimate bearing capacity of strip footing, which was imbedded on sandy soil and under eccentric loads (VM) was investigated by using PLAXIS 2D finite element software. After numerical verification, the effect of parameters, such as the amount of eccentricity, applied vertical force, the number of reinforced layers and layout of the layout of geogrid layers on the ultimate bearin capacity of strip footing were studied. The results of analyzes were presented in the form of dimensionless graphs. Based on the analyses result, the optimum depth of first geogrid layer from foundation (u), the vertical intervals of the layers (h), the number (N) and layout of the geogrid layers have been determined. The results of the analysis show that by adding the geogrid layers, the bearing capacity of footing under the eccentric load increases significantly. The amount of the effectivity is related to the layout of layers and and the amount of the eccentricity. In the optimum layout of the layers, the position of geogrid layers depends on the number of layers. Also, the optimum number of layers for obtaining the maximum bearing capacity at eccenric load condition was obtained to be 4 layres in the present study. The optimum depth for the first, second, third and fourth layers, at the optimal layout, was 0.5, 0.7, 0.3 and 0.9 meters from the base of the footing, respectively.

According to increasing demand of box-shaped tunnels in transportation networks, which are mainly built as cut and cover tunnels, the impact of natural hazards such as earthquakes on these geotechnical structures and seismic load reduction methods of these types of structures is more important than before. Nowadays, the use of lightweight materials such as geofoam plays fundamental role in civil engineering and has solved many of the challenges of civil engineering. In the present study, the role of geofoam materials as embankments for cut and cover tunnels on the internal forces of the tunnel structure during the earthquake have been investigated. The numerical modeling was performed by two-dimensional finite difference software, FLAC 2D v7.0. The results of an experimental study were used to verify the numerical model. Time histories of acceleration and bending moments for Kobe and Northridge earthquakes were examined. Based on the analysis, it was observed that the software was able to predict the results of the centrifugal experiment well and provided reliable results. EPS19 has been used as a geofoam embankment in the analyzes. The acceleration time history of the Kobe and Northridge earthquakes with a maximum acceleration of 0.3 g has been used in the analysis. In the numerical model of the present study, the equivalent linear model (ELM) has been used to model the behavior of the geofoam. Mohr-Coulomb elastoplastic model was used in soil behavior modeling for static analysis. The behavior of the soil in dynamic analyses was considered as nonlinear and modeled with hysteretic damping. The results are determined in the form of bending moment and shear force diagrams for the roof and wall of the tunnel. The diagrams were provided for static and seismic loading conditions. According to the results of numerical studies, it was observed that the geofoam model has a very good performance in reducing the bending moments and shear forces in static and seismic conditions. Present study shows that geofoam, as the cover material of the cut and cover tunnel, is able to reduce internal forces of the tunnel structure in static, seismic loading condition compared to the soil. Based on the results, it was concluded that geofoam is a suitable material for retrofitting the cut and cover tunnels during earthquakes.

The present study has mainly focused on the modification of the hyperbolic model formulation so that the shortcomings of the said model can be corrected and more conformity with the experimental results can also be provided. This model, also known as Duncan-Chang model, is a two parameter model for obtaining the stress-strain curve of the triaxial test. The hyperbolic model which is indicative of the ideal characteristics of the soil is particularly advantageous in that it does not require the presence of extensive test programs and can easily be implemented through computer programs. As the results show, although numerous studies have already been carried out to address the model shortcomings, this model fails to predict the plastic behavior of the subsaturated soils. Among the shortcomings of the said model are the insufficiency of the hyperbolic model relations for the analysis of the stage related to the soil instability, uselessness of the relations in case of soil volume variation, experimental nature of the used coefficients in the relation. Hyperbolic relations are useful in solving different problems of engineering and geotechnics since numerical values of hyperbolic model parameters can be extracted from the experimental results and all the relations that are used for the drained soils can also be applied to non-drained and unstable soils. Furthermore, numerous values of parameters have been tested and utilized for different kinds of soil over the past thirty years. Therefore, a rich source is available for comparison and interpretation of the obtained results from different projects.

Fast growing of engineering infrastructure to meet human requirements is directly related to the need for a resistant soil to carry out construction load. On the other hand, the importance of environmental issues has led to an ever-increasing demand for new and environmentally friendly methods for soil remediation. The method of microbial induced calcium carbonate precipitation (MICP) is considered by the researchers as one of the most environmentally friendly methods. The purpose of this study was to investigate the effect of MICP on the uniaxial strength of carbonate sand. Therefore, samples of Bushehr carbonate sand were cured after the injection of bacteria and cement solution. Then a uniaxial compression tests were carried out to evaluate the compressive strength. Also, the effect of cement solution concentration and curing time on the results of MICP method was investigated. The results show that maximum uniaxial strength of sand stabilized with MICP is about 3.5 kg/cm2, which indicates the proper performance of MICP method for stabilization of carbonate sand. The UCS of the samples depends on the concentration of cement solution. Stabilized samples with a higher cementation of concentration solution had more uniaxial resistance than samples with lower cement concentrations. The curing time more than 14 days did not significantly affect the uniaxial resistance.

Microbial induced carbonate precipitation (MCIP) is an environmentally and suitable method for soil remediation. In this method, urea is hydrolyzed by the urease enzyme, that is splashed from Sporosrcina Pasteurii bacteria. The calcium carbonate is formed in the presence of calcium ion. Calcium carbonate connects the soil particle like a bridge and improve its engineering characteristics. In the present research, the effect of MICP on the permeability of carbonated sand was investigated. The effect of factors such as concentration of the cementation solution, curing time and relative density on soil permeability have been studied. To consider the effect of different factors on the MICP performance, number of samples have been treated with MICP method and then constant head permeability test were conducted on the treated samples. the results show that as the concentration of cement solution was increased, the permeability of the samples was decreased. Loose Samples resulted in more decrease in permeability with respect to the dense samples. Also, bacterial activity was increased with time and after 14 days the variation in permeability was reduced. The highest rate of permeability reduction was around 60% for the sample prepared in loose state and cured with one molar concentration of cementation solution for 28 days

In this paper, subsurface water profile and seepage discharge through fine porous media were modeled experimentally and their results were compared with the data of Dupuit- Forchheimer, Chapman, Bear and Castro- Orgaz et al. methods. Laboratory model consist of fine porous media having 5 m long, 0.6 m wide and 1 m deep. For different water levels. The seepage discharge and water profiles were measured and then were compared with analytical relationship. The values of relative error percent and NOF function for computed and measured variables were compared. After comparison of experimental results and analytical solutions, the drawbacks and capabilities of each method has been revealed. After comparing the results of the discharge experimental with the analytical relationship based on Dupuit- Forchheimer assumption analytical the relative error was between 4.2 to 6.4 percent. By the comparison of the experimental results with analytical solution for subsurface flow profile, the NOF for analytical method were between 0.012 to 0.048 for Chapman, 0.011 to 0.081 for Bear and 0.011 to 0.078 for Castro- Orgaz et al, respectively, which indicated a proper confirmation.

The sheet piles are used below hydraulic structures to reduce seepage flow rate and hydraulic gradient at the ýoutlet of such structures rested on permeable foundations.ýþ þSo far, for analysis of seepage under hydraulic ýstructures much research work has been conducted in the form of numerical models. However, less field and ýlaboratory works have been done to study boiling phenomena for evaluating of the numerical models. In the ýpresent research work, a laboratory model was made to simulate seepage and its controlling measures under ýcoastal dikes. The model consist of a flume 2.2m long, 0.8m deep and 0.4m wide, in which vertical sheet pile ýwere provided by Perspex sheets. The flume was made of steel frame and Perspex as well as thick glass ýsheets. The foundation material was made of clean, fine sand, compacted to a uniform density and covered ýthe bottom 40cm of flume. Perspex sheets were employed sheet pile variable depth. The piezometric heads at ýthe both downstream and upstream side of dike were measured using small diameter clear plastic tubes. The ýeffect of position and depth of the sheet pile on the seepage flow and exit gradient have been demonstrated in ýform of dimensionless curves. The results show that the depth of the sheet piles d/D=0.46 with the maximum ýupstream water level h/hm=1.0 boiling phenomenon does not occur and the seepage rate and hydraulic ýgradient in the area are favorable.ý

In this paper, subsurface water profiles through coarse porous medium are investigated ýnumerically and then are compared with experimental data. Numerical simulations have been ýconducted using SEEP/W model which is based on the finite element method. Laboratory model of ýthe porous medium has 6.4m length, 0.8m width and 1m height. Crushed materials were used as ýporous media. Modeling scenarios were conducted for different values of flow discharges and ýthree bed slopes of 0, 4 and 20.3 % and then flow profiles and discharges were computed and ýcompared with those provided form experimental. The results indicated that application of ýSEEP/W model for simulating flow properties through coarse materials and rockfill structures do ýnot always present satisfactory outputs, wherein in most cases specifically in low slopes ýunderestimated subsurface water profiles ( seepage line) compared to observed profiles. Also ýcomputed flow discharge give a different behavior depend on bed slope and kind of materials. The ýresults of numerical model showed a good agreement in steep slope comparing to low slopes. ý

In this paper we investigate the mechanism of internal erosion caused in the right abutment of the Shahghasem dam’s spillway. Shahghasem dam is an earthen dam located in Yasouj, in southwest of Iran. A significant hole and pipe have been observed in the corner of the right abutment from upstream view. The foundation is Marlstone, which has low cohesion and susceptible for internal erosion and piping in some conditions. Going through details of the design maps has shown that Lane’s criteria for selecting safe dimensions of the seepage control measures have not been considered properly. A series of the supportive walls are designed to attach to the right part of the spillway in order to increase the length of seepage. The pipe route of the erosion should also be grouted with high quality concrete.