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Showing 76 results for Sand

Baziar M.h., Ziaie Moayed R.,
Volume 1, Issue 1 (9-2003)
Abstract

An experimental study was carried out to evaluate the influence of silt content on cone penetration measurements and its implication for soil classification. The investigation includes twenty-seven peizocone tests in saturated salty sand samples, which had been prepared in a big rigid thick walled steel cylinder-testing chamber. The samples were prepared with several different silt contents ranging from 0 to 50 percent and were consolidated at three-overburden effective stresses including 100, 200 and 300 kPa. This study showed that, the amount of silt content in sand is an important parameter affecting CPT results. As the silt content increases, the cone tip resistance decreases. The recorded excess pore water pressure during sounding was increased with increasing silt content. It is also concluded that friction ratio, in general, increases with increasing silt content. The method presented by Robertson and Wride [25] and Olsen [17] to evaluate soil classification are also verified.
Pakbaz M.c., Ahmadi C.,
Volume 1, Issue 2 (12-2003)
Abstract

This research include, more than 400 erosion tests performed on coarse and fine grain suspension materials. The purpose of tests was to determine erosion characteristics of mixtures of different materials. Samples of the .same constituents in different groups were cured tit two different setting time of // and 16 !tours before they were subjected to the constant hydraulic heads of 20 and 40 cm for ct time period of 30 urinates. The amount of erosion was measured as the weight loss of the samples offer the test. /n general the lower setting tune and the higher hydraulic head for a large group of samples showed higher erosion. For uniform sand samples when the cement content was 60-70 % the percentage of erosion (PE) was below 2. For the mixture of sand-cement, with the clay content below, 20% the percentage of erosion was below 2 and it increased to 15.5 for the clan, content of 58dc. Die addition of bentonite in the soil-cement mixtures in general did not affect the erosion.
Shooshpasha I.,
Volume 1, Issue 2 (12-2003)
Abstract

This study was designed to investigate the local volume changes induced by swelling pressure in unsaturated stand-bentonite bused buffer material. A laboratory mixture of sodium bentonite (lilt/ well graded silica stool in equal proportion by do weight was used for moisture floss experiments in both ambient and elevated temperatures. Experimental results have shown that tit high water content locations within the tested specimens, the density was reduced by .3.57% from its initial values clue to swelling. The swelling pressure was calculated by 4 different models as a function of distance. The calculated results have indicated that the density distribution within the .specimen is affected by swelling potential distribution. The calculated swelling pressure values van as u function of water content, reaching I MPa at the source of water intake, i.e., at high water content :.one, and 2 MPa cot the heater .side, i.e., cot low water content .one.
H. Ghiassian,
Volume 2, Issue 1 (3-2004)
Abstract

A study of bearing capacity and compressibility characteristics of cohesive soil, reinforced by geogrid and supporting square footing loads has been conducted. The lack of adequate frictional resistance between clay and reinforcing elements was compensated by using a thin sand layer (lens) encapsulating the geogrid sheet. In this way, tensile forces induced in the geogrid were transferred to the bulk clay medium through the sand particles and soil reinforcement was improved Experiments were conduced on two sets of specimens, one set of 1 x 1 x 1 m dimension and the footing size of 19 x 19 cm (series A), and the other set of 0.15 x 0.15 x 0.15 m dimension and the footing size of 3.7 x 3.7 cm (series B). The loading systems for the above specimens were stress controlled and strain controlled respectively. All specimens were saturated and presumably loaded under an undrained condition. The results qualitatively confirmed the effectiveness of the sand lens in improving the bearing capacity and settlement characteristics of the model footing. In series A, the maximum increase in the bearing capacity due to the presence of the sand lens was 17% whereas in series B, the amount of increase was 24%. The percentage reductions in the settlement for these results were 30% and 46% respectively.
Baziar M.h., Asna Ashari M.,
Volume 2, Issue 3 (9-2004)
Abstract

An experimental study was carried out to evaluate the liquefaction resistance of silty sand utilizing laboratory techniques. In this study, liquefaction potential of silty sand by using cyclic triaxial tests on frozen samples retrieved from calibration chamber and constructed samples by dry pouring method were investigated. Correlation between cone penetration resistance and cyclic strength of undisturbed silty sand samples are also examined using CPT calibration chamber and cyclic triaxial tests. The cone penetration tests were performed on silty sand samples with fine contents ranging from 0% to 50% and overburden stresses in the range of 100-300 kPa. Then the soil sample in calibration chamber, in the same way that soil samples were prepared during CPT sounding, was frozen and undisturbed soil specimen retrieved from frozen soil sample were tested using cyclic triaxial tests. Analysis of results indicates that the quality of frozen samples is affected by fine content and overburden pressures. Also, using data obtained in this research, the relationship between cone tip resistance and cyclic resistance ratio (CRR) for silty sand soils will be presented. These correlations are in relatively good agreement with field case history data. Also increasing confining pressure in silty sand material increases the cone tip resistance and generally, cyclic resistance ratio increases by increasing silt content.
Saleh Zadeh H., Ghazanfari E.,
Volume 2, Issue 4 (12-2004)
Abstract

To study the behavior of carbonate sands parametrically, some monotonic triaxial testswere carried out on Kish carbonate sand. The sample was provided from Kish Island beach. Inorder to examine the effect of density and confining pressure, samples in loose and dense stateswere tested under different confining pressures. For studying the effect of drainage andconsolidation, different stress paths were followed. Also to study the effect of particle crushing indrained tests all samples were graded before and after testing. Comparison between loose anddense samples in both drained and undrained tests showed that with increasing confiningpressure, the reduction in shear resistance in loose samples is less than dense samples and theincrement rate of particle crushing in loose samples is more than dense samples. In the range oflow confining pressures both loose and dense samples showed dilation response. With increasingconfining pressure, the loose samples tended to exhibit contraction and the rate of dilation indense samples reduced. Because recovering undisturbed sample of carbonate sediments is veryhard or even impossible so the effect of soil disturbance is not studied in this research.
Soroush A., Koohi Sh.,
Volume 2, Issue 4 (12-2004)
Abstract

Lateral spreading of liquefied saturated sandy deposits happens during and shortly afterearthquakes. This paper first reviews this phenomenon by means of reviewing and comparingobservations on case histories and experimental works. Based on the results from the review andcomparison, a mechanism for describing lateral spreading will be suggested. The Finn model,adopted in the Computer code FLAC is employed to carry out numerical analyses of lateralspreading of the Wildlife Site, happened during the 1987 Superstition Hills earthquake. First themodel is calibrated by means of numerical analysis of the first centrifuge model test of theVELACS Project. For the Wildlife site, three types of analysis are carried out: a) coupledliquefaction-consolidation analysis using the coefficient of permeability (K1) of the liquefiedlayers, as reported in the literature b) analysis type (a), but with K equal to 0.1K1, and c) a fullyundrained liquefaction analysis. The analyses results, in forms of excess pore water pressures andsurface displacements, indicated that the fully undrained behavior of the liquefied layers betterrepresents the behavior and response of the site during the earthquake.
Mohammad C. Pakbaz, M. Lorestani,
Volume 3, Issue 2 (6-2005)
Abstract

The main purpose of this research is evaluation of effect of chemicals on permeability of sand- bentonite mixtures. The coefficients of permeability of sand- bentonite mixtures in water, solutions of sodium and calcium chlorides, sodium hydroxide, acetic acid, methanol and carbon tetrachloride were calculated using parameters obtained in 1- D consolidation test and Terzaghi’s theory. At each void ratio permeability of samples in water is the lowest and that for carbon tetrachloride is the highest. For all fluids the permeability index Ck is decreased as the percentage of sand is increased. The largest Ck belongs to the samples tested in water and the smallest Ck belongs to the samples tested in carbon tetrachloride.
Ali Noorzad, H.b. Poorooshasb,
Volume 3, Issue 3 (9-2005)
Abstract

The CANAsand constitutive law in conjunction with the ID technique is used to study the flow phenomenon in a cohesionless granular medium placed between two parallel, rough vertical walls. It is shown that the development of flow is influenced by the geometry of the case. However the main factor is the void ratio of the medium: i.e. arching will prevent the free flow of the material if its void is close to the compact state. The study is extended to cover the axisymmetric situation. Here the flow of bulk solids through a circular opening at the base of a cylindrical tank is examined.
Saleh Zadeh H., Procter D.c., Merrifield C.m.,
Volume 3, Issue 3 (9-2005)
Abstract

The unique behaviour of carbonate materials under shear loading has stimulated in investigating of their geological and engineering properties.Carbonate soils composed of calcium or other carbonates and most abundant in tropical marine environments are of interest from geotechnical view, especially for offshore engineers engaged with Fossil-based fuel exploitation. This was initiated in the early 1960's, when the first offshore borings in the Persian Gulf identified layers of calcarenite and thick layers of sand containing visible shell fragments.For the purpose of exploiting gas and oil resources in hot and temperate climates (e.g. Persian Gulf) off-shore structures have been placed on carbonate soils. The carbonate sediments are high crushable compared with low crushable sediments such as quartzic soils.To examine the crushability of these problematic sediments a series of monotonic compression, extension and post-cyclic triaxial tests under different densities and confining pressures was carried out to study the crushing behaviour of "Rock" carbonate sand obtained from Cornwall, England.It was shown that crushing coefficient decreases with increasing in maximum principal effective stress ratio for both loose and dense states. It seems that for skeletal carbonate sand maximum and minimum dry densities will be changed during shearing loading. In other words, even though the sample has experienced an increase in density, it may also have experienced a reduction in relative density.
H. Salehzadeh, D.c. Procter, C.m. Merrifield,
Volume 4, Issue 1 (3-2006)
Abstract

Carbonate materials are mostly found in tropical areas, where exploiting gas and oil resources are of high concern. Their unique behavior under shear loading first was recognised during oil resources investigations in the Persian Gulf. Off-shore structures have been placed on carbonate soils which are highly crushable.During storms cyclic loading imposes on the bases of structures lied down on seabed. Cyclic loading, therefore, may trigger liquefaction phenomenon which leads to soil collapse and a catostrophic event. Therefore, stability of these expensive structures need to be investigated. To this aim carbonate sand in medium dense to medium dense state was considered and its response under varied cyclic shear stress ratio was studied.
M.h. Baziar, R. Ziaie_moayed,
Volume 4, Issue 2 (6-2006)
Abstract

This paper highlights the effect of silt content on cone tip resistance in loose silty sand. In this study, twenty-seven cone penetration tests are performed in saturated silty sand samples with several different silt contents ranging from 10 to 50 percent. The samples are consolidated at three overburden stresses including 100, 200 and 300 kPa. It is shown that, as the silt content increases, the cone tip resistance decreases. In high percent of silt (30-50%), the cone tip resistance decreases more gently compared with low percent of silt (0-30%). It is also concluded that the method proposed by Olsen (1997) for stress normalization of cone tip resistance compared with the Robertson and Wride (1998) method has better agreement with the obtained results. To evaluate liquefaction potential of loose silty sand, the method presented by Robertson and Wride (1998) is also studied. The results showed that the use of Robertson and Wride (1998) method to estimate the fine content from CPT data causes some uncertainty especially for high silt content (FC>30%).
H. Soltani-Jigheh, A. Soroush,
Volume 4, Issue 3 (9-2006)
Abstract

This paper presents the results of a series of monotonic and post-cyclic triaxial tests carried out on a clay specimen and three types of clay-sand mixed specimens. The focus of the paper is on the post-cyclic mechanical behavior of the mixed specimens, as compared to their monotonic behavior. Analyses of the tests results show that cyclic loading degrade undrained shear strength and deformation modulus of the specimens during the post-cyclic monotonic loading. The degradation depends on the sand content, the cyclic strain level and to some degrees to the consolidation pressure.
S.a. Naeini, R. Ziaie-Moayed,
Volume 5, Issue 2 (6-2007)
Abstract

Series of undrained monotonic triaxial tests and cone penetration tests were conducted on loose silty sand samples to study correlation between undrained shear strength of silty sands (Sus) and piezocone test results. CPT tests were conducted at 27 silty sand samples in calibration chamber. The results indicate that, in low percent of silt (0-30%), as the silt content increases, the undrained shear strength (Sus) and cone tip resistance (qc) decreases. It is shown that, fines content affects undrained shear strength (Sus) and cone tip resistance (qc) similarly. On the basis of obtained results, equations were proposed to determine the normalized cone tip resistance (qc1n) and undrained shear strength (Sus) of silty sand in term of fines content. Finally based on those equations, a correlation between normalized cone tip resistance and undrained shear strength of silty sand is presented. It is shown that the normalized undrained shear strength and normalized cone tip resistance of loose silty sands (F.C. <30%) decreases with increase of silt contents.
S.n. Moghaddas Tafreshi, Gh. Tavakoli Mehrjardi, S.m. Moghaddas Tafreshi,
Volume 5, Issue 2 (6-2007)
Abstract

The safety of buried pipes under repeated load has been a challenging task in geotechnical engineering. In this paper artificial neural network and regression model for predicting the vertical deformation of high-density polyethylene (HDPE), small diameter flexible pipes buried in reinforced trenches, which were subjected to repeated loadings to simulate the heavy vehicle loads, are proposed. The experimental data from tests show that the vertical diametric strain (VDS) of pipe embedded in reinforced sand depends on relative density of sand, number of reinforced layers and height of embedment depth of pipe significantly. Therefore in this investigation, the value of VDS is related to above pointed parameters. A database of 72 experiments from laboratory tests were utilized to train, validate and test the developed neural network and regression model. The results show that the predicted of the vertical diametric strain (VDS) using the trained neural network and regression model are in good agreement with the experimental results but the predictions obtained from the neural network are better than regression model as the maximum percentage of error for training data is less than 1.56% and 27.4%, for neural network and regression model, respectively. Also the additional set of 24 data was used for validation of the model as 90% of predicted results have less than 7% and 21.5% error for neural network and regression model, respectively. A parametric study has been conducted using the trained neural network to study the important parameters on the vertical diametric strain.
S.n. Moghaddas Tafreshi, A. Asakereh,
Volume 5, Issue 4 (12-2007)
Abstract

Conventional investigations on the behavior of reinforced and unreinforced soils are often investigated at the failure point. In this paper, a new concept of comparison of the behavior of reinforced and unreinforced soil by estimating the strength and strength ratio (deviatoric stress of reinforced sample to unreinforced sample) at various strain levels is proposed. A comprehensive set of laboratory triaxial compression tests was carried out on wet (natural water content) non-plastic beach silty sand with and without geotextile. The layer configurations used are one, two, three and four horizontal reinforcing layers in a triaxial test sample. The influences of the number of geotextile layers and confining pressure at 3%, 6%, 9%, 12% and 15% of the imposed strain levels on sample were studied and described. The results show that the trend and magnitude of strength ratio is different for various strain level. It implies that using failure strength from peak point or strength corresponding to the axial-strain approximately 15% to evaluate the enhancement of strength or strength ratio due to reinforcement may cause hazard and uncertainty in practical design. Hence, it is necessary to consider the strength of reinforced sample compared with unreinforced sample at the imposed strain level. Only one type of soil and one type of geotextile were used in all tests.
Habib Shahnazari, Hosein Salehzadeh, Amin Askarinejad,
Volume 6, Issue 1 (3-2008)
Abstract

Classical soil mechanics involves the study of fully saturated soils. However, many problems encountered in geotechnical engineering practice involve unsaturated soil, in which behavior is significantly different from classical saturated soil. Negative pore pressure and capillary forces develop a virtual cohesion between the grains of semi saturated soils. This kind of cohesion is dependent on different factors such as grain size, saturation degree, soil-water characteristic curve and relative density of the soil. In this research the virtual cohesion of fine silty sand with 5% water content and a saturation degree of 17% is estimated. A vertical slope is constructed and is accelerated in the geotechnical centrifuge until failure. During the test, the model was monitored by a wireless video camera, attached to the strong box. The cohesionless tested sand was unsaturated. Based on the scaling laws and considering parameters such as sample unit weight, failure acceleration and the sample dimensions, a slope stability analysis was performed, and the virtual cohesion generated in the sample was calculated. The factor of safety of the prototype modeled in the centrifuge is calculated either by Finite Element Method and Finite Difference Method by using the resulted virtual cohesion from physical modeling. Results of this research show the validity of physical modeling for calculating the virtual cohesion in unsaturated silty sand.
Mahmoud Hassanlourad, Hosein Salehzadeh, Habib Shahnazari,
Volume 6, Issue 2 (6-2008)
Abstract

In this paper shear behavior of two calcareous sands having different physical properties are

investigated using drained and undrained triaxial tests. The investigated sands are obtained from two different

zones located in Persian Gulf, Kish Island and Tonbak region. Analysis based on energy aspects show that

friction angle in these soils, having crushable particles, is formed of three components: substantial internal

friction angle, dilation and particle breakage angle. Dilation component is available in the two investigated

sand. Particle breakage component is a function of grains hardness, structure and geometry shape. Particles

breakage decreases the volume of sample during drained tests and creates positive pore water pressure during

undrained tests. Two investigated sands show different amount of dilation and particle breakage under similar

conditions. Simultaneous dilation and particles crushing and different amount of them result in different shear

behavior of the two studied sands. Energy aspects are used to determine the effect of particle crushing on the

shear strength. There is a suitable compatibility between relative breakage of grains and consumed energy

ratio for particle breakage.


Amir Hamidi, S. Mohsen Haeri,
Volume 6, Issue 3 (9-2008)
Abstract

The deformation and stiffness characteristics of a cemented gravely sand was investigated using triaxial equipment. The triaxial tests were conducted in both dry and saturated undrained conditions. Artificially cemented samples are prepared using gypsum plaster as the cementing agent. The plaster was mixed with the base soil at the weight percentages of 1.5, 3, 4.5 and 6. The applied confining pressure varied between 25 to 500 kPa in triaxial tests. The process of yielding of the soil was investigated for the considered soil and the bond and final yield points were identified for the cemented soil with different cement contents. The variations of deformation and stiffness parameters with cement content and confining stress were studied as well. Some of the parameters were determined for both drained and undrained conditions to investigate the effect of drainage condition on the stiffness and yield characteristics of the tested cemented gravely sand. According to the results, the difference between drained and undrained tangent stiffness decreases with increase in confining stress. Finally the effect of cement type was investigated as an important parameter affecting the stiffness at bond yield. The rate of increase in tangent stiffness at bond yield changes with cement content for different cementing agents.
H. Salehzadeh, M. Hassanlourad, D.c. Procter, C.m. Merrifield,
Volume 6, Issue 4 (12-2008)
Abstract

The unique behaviour of carbonate sediments under shear loading has stimulated in investigating of their geological and engineering properties. Their shapes are very different varying from needle shaped to platy shaped. Hence, it is important to examine their fabric effect on soil response under shearing condition. To this aim a series of small scale laboratory element testing were carried out on North Cornwall Rock" beach sand. Non-cemented and cemented Carbonate sand response under compression and extension loading and different initial density and confining pressure with samples allowed to be drained were investigated and compared. The results show that the sand shear strength under Extension loading is lower than compression regarding to anisotropic fabric due to platy and needle shape of grains. The anisotropy is reduced with increasing the confining pressure and initial relative density with non-cemented sand. Furthermore, present of cement bounds reduces the anisotropy especially in low confining pressures.

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