Search published articles

Showing 17 results for Triaxial Tests

Baziar M.h., Asna Ashari M.,
Volume 2, Issue 3 (9-2004)

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)

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.
M. Naderi,
Volume 3, Issue 1 (3-2005)

Having observed the costly failures of different cutoff walls, that had been constructed according to the mix design specified by reputable consultants in Iran, a research programme was conducted to study the effects of constituent materials on the properties of plastic concrete. The main properties, such as compressive strength, biaxial and triaxial strains, permeability, and modulus of elasticity have been investigated using different mixes, obtained from prototype production line plant, situated on site, because it was realized that the site production line and the systems employed have major effects on the properties of plastic concrete. Statistical analysis of the results, revealed the coefficients of influence of main constituent materials of plastic concrete namely cement, bentonite, aggregate and water on its compressive strength and modulus of elasticity. Having realized the cancelling effects of bentonite and aggregates on the measured properties, some equations relating the quantities of cement and water to the compressive strength and modulus of elasticity are introduced. Effects of clay and hydrated lime powder, as fillers were also investigated leading to the proposal of limits for their safe and economic use. Since most of the cutoff walls are buried structures, failure strains under both uniaxial and triaxial tests, with values of cohesion and internal friction, are also presented in this paper.
Saleh Zadeh H., Procter D.c., Merrifield C.m.,
Volume 3, Issue 3 (9-2005)

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. Soltani-Jigheh, A. Soroush,
Volume 4, Issue 3 (9-2006)

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)

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.
M.a. Khan, A. Usmani, S.s. Shah, H. Abbas,
Volume 6, Issue 2 (6-2008)

In the present investigation, the cyclic load deformation behaviour of soil-fly ash layered system is

studied using different intensities of failure load (I = 25%, 50% and 75%) with varying number of cycles (N =

10, 50 and 100). An attempt has been made to establish the use of fly ash as a fill material for embankments of

Highways and Railways and to examine the effect of cyclic loading on the layered samples of soil and fly ash.

The number of cycles, confining pressures and the intensity of loads at which loading unloading has been

performed were varied. The resilient modulus, permanent strain and cyclic strength factor are evaluated from

the test results and compared to show their variation with varying stress levels. The nature of stress-strain

relationship is initially linear for low stress levels and then turns non-linear for high stress levels. The test

results reveal two types of failure mechanisms that demonstrate the dependency of consolidated undrained

shear strength tests of soil-fly ash matrix on the interface characteristics of the layered soils under cyclic

loading conditions. Data trends indicate greater stability of layered samples of soil-fly ash matrix in terms of

failure load (i) at higher number of loading-unloading cycles, performed at lower intensity of deviatoric stress,

and (ii) at lower number of cycles but at higher intensity of deviatoric stress.

Mahmoud Hassanlourad, Hosein Salehzadeh, Habib Shahnazari,
Volume 6, Issue 2 (6-2008)

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)

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. Soltani-Jigheh, A. Soroush,
Volume 8, Issue 2 (6-2010)

Mixed clayey soils occur as mixtures of sand (or gravel) and clay in widely varying proportions. Their

engineering behavior has not been comprehensively studied yet. An experimental program, comprising monotonic,

cyclic, and post-cyclic triaxial tests was undertaken on compacted clay-granular material mixtures, having different

proportions of clay and sand or gravel. This paper presents the results of cyclic triaxial tests and explains the behavior

of the mixtures based on number of loading cycles, cyclic strain amplitude, granular material content, grain size, and

effective confining pressure. The results indicate an increase in degree of degradation and cyclic loading-induced pore

water pressure as the number of loading cycles, cyclic strain and granular material content increase. Also the results

show that the grain size has no significant effect on the degree of degradation and cyclic loading-induced pore water

pressure in the specimens. The effect of granular material content on pore water pressure during cyclic loading in

equal-stress-level was also examined. The pore water pressure increases with the increase of granular material


R. Mahin Roosta, A. Alizadeh,
Volume 10, Issue 2 (6-2012)

In the first impounding of rockfill dams, additional settlements occur in upstream side in saturated rockfills due to collapse
phenomenon even high rainy seasons can cause additional deformation in the dumped rockfills. Unfortunately these
displacements are not taken into account in the conventional numerical models which are currently used to predict embankment
dam behavior during impounding. In this paper to estimate these displacements, strain hardening-strain softening model in Flac
is modified based on the laboratory tests, in which same impounding process in such dams is considered. Main feature of the
model is reproduction of nonlinear behavior of rockfill material via mobilized shear strength parameters and using collapse
coefficient to display induced settlement due to inundation. This mobilization of shear strength parameters associated with some
functions for dilatancy behavior of rockfill are used in a finite difference code for both dry and wet condition of material. Collapse
coefficient is defined as a stress dependent function to show stress release in the material owing to saturation. To demonstrate
how the model works, simulation of some large scale triaxial tests of rockfill material in Gotvand embankment dam is presented
and results are compared with those from laboratory tests, which are in good agreement. The technique could be used with any
suitable constitutive law in other coarse-grained material to identify collapse settlements due to saturation

A. H. Eghbali, K. Fakharian,
Volume 12, Issue 1 (1-2014)

Portland cement can be mixed with sand to improve its mechanical characteristics. Many studies are reported in literature on this topic, but the effect of principal stress rotation has not been investigated yet. Considering the inherent anisotropy of most sands, it is not clear whether the added cement shall contribute to equal increase in strength and stiffness at vertical and horizontal directions or not. Furthermore, it is not well understood how the cement as an additive in non-compacted (loose) sand compared to compacted (dense) sand without cement, contribute to improving the material behavior in undrained condition such as limiting the deformations and the liquefaction potential. In this research, undrained triaxial and simple shear tests under different stress paths are carried out on different mixtures of Portland cement (by adding 1.5, 3 and 5 percent) with clean sand to investigate the effect of principal stress rotations. The triaxial test results revealed that the cement mixture reduces the anisotropy, while it improves the mixture mechanical properties compared to compacted sand without cement. The results of the simple shear tests validated the triaxial test results and further clarified the effect of the  parameter or rotation of principal stresses on the behavior of cemented sand mixtures.
S.h.r. Kargar, H. Shahnazari, H. Salehzadeh,
Volume 12, Issue 4 (12-2014)

In this study, a researching program is conducted by cyclic triaxial test to determine the post-cyclic behavior of Bushehr carbonate sand retrieved from the north of the Persian Gulf, under anisotropic consolidation at 200 kPa confining pressure. The article compares the post-cyclic monotonic strength and excess pore water pressures generated after the test with the pre-cyclic monotonic results. The results attest to the existence of a relationship between CSR (Cyclic Stress Ratio) and the frequency of failure cycles. The article also investigates the relationship between the amount of excess pore pressures generated during both the cyclic and post-cyclic loading, revealing an increase in the post-cyclic strength and stiffness of sand retrieved from Bushehr. Also the effect of multi stages cyclic loading, density, pore pressure and stain history in post cyclic strength and stiffness is evaluated. The increasing in post cyclic strength and stiffness depends on excess pore pressure generated during cyclic loading and stain history. This article also reveals that a distinct trend in the relation between post cyclic behavior and crushing value does not exist at lower confining pressure.

M. Karimpour Fard, N. Shariatmadari, M. Keramati, H. Jafari Kalarijani,
Volume 12, Issue 4 (12-2014)

Due to the existence of fibrous materials such as plastic fragments, the strength anisotropy of Municipal Solid Waste

(MSW) materials is the main source of differences between their mechanical response in direct shear and triaxial apparatus.

As an extension of earlier research on the mechanical behavior of MSW using a large traixail apparatus, results presented in

Shariatmadari et al. [1] and Karimpour-Fard et al. [2], the current study was programmed and executed. MSW samples were

tested using a computer controlled large shear box apparatus with normal stress levels ranging between 20 to 200 kPa. The

effect of fiber content, fiber orientation, aging and shearing rate on the response of MSW were addressed. The results showed

that shear strength of MSW increases with normal stress, although, in spite of the presence of reinforcement elements in MSW

and unlike the results from triaxial tests, no strain hardening could be observed in their mechanical response. An increase in

the shear strength of MSW was observed with increasing the shearing rate. Increasing the shearing rate from 0.8 to 19

mm/min, enhanced the shear strength of samples from 16 to 27% depending on the shear displacement level. Although, the

same trend was investigated in traixial tests, but lower rate-sensitivity in the mechanical response of MSW in direct shear tests

were observed.

Unlike the results of triaxial tests with aging process, mobilized shear strength level of MSW samples tested under direct

shearing decreased comparing fresh samples. It was also observed that altering the fiber content and their orientation could

affect the mechanical response and shear strength of the MSW. Additionally, there is an optimum fiber angle in MSW which

yields the highest level of shearing strength.

A.a. Heshmati, A.r. Tabibnejad, H. Salehzadeh, S. Hashemi Tabatabaei,
Volume 13, Issue 1 (3-2015)

To investigate the saturation induced collapse deformation behavior of rockfill material, a set of large-scale triaxial tests were conducted in saturated and dry-saturated conditions. Specimens were tested under various confining pressures. For dry-saturated tests, specimens were sheared in various stress levels. Results of all dry saturated tests indicate a sudden reduction in the specimen volume during the submerging process. The ratio of the minimum axial strength of a submerged specimen (at the end of the saturation process) to the shear strength of the specimen before saturation is defined as the coefficient of stress recovery, Csr. Results show that this ratio increases as the confining pressure increases, and decreases as the shear stress level increases. According to the results of dry-saturated tests, reduction values of the internal friction angle caused by saturation (c), the ratio of the elasticity modulus of the material after saturation to its elasticity modulus in dry condition, i.e., Ewet/Edry, and the saturation induced sudden volumetric strain (vc) decrease as the confining pressures increase. However the shear stress level does not have any meaningful effect on the variation of c, Ewet/Edry and (vc).
M. Alibolandi, Dr. R. Ziaie Moayed,
Volume 13, Issue 3 (12-2015)

In this study a series of cyclic triaxial tests were performed to examine the undrained dynamic resistance of silty sand reinforced with various arrangements of geotextile layers. The silt content of samples varies in percentage from 0, 10, 20, 30, 40 and 50%. A total of 32 laboratory cyclic triaxial tests have been performed on silty sand samples reinforced with geotextile layers in different depths. All tests were performed with 100 kPa confining pressure, subjected to an isotropic consolidated undrained (CIU) condition. The tests were conducted at a frequency of 2 Hz. Results indicate that both the geotextile arrangement and the silt content were most essential in the liquefaction potential of reinforced sands. An increase in the number of geotextile layers enhanced the cyclic resistance of reinforced samples against the liquefaction potential. It was also found that when the geotextile layer was posited near the top of the specimen (load application part) the liquefaction resistance would increase (e.g. for clean sands, the improvement of liquefaction resistance caused by the geotextile layer had a 0.2 depth, and the sample height was 5.5 times greater than the geotextile layer inserted in mid height of sample H). Based on the obtained results, effects of geotextile on liquefaction resistance decreased as fines content increased to about 33%. Further increase in the fines content however, would lead to higher in reinforcement advantages. The liquefaction improvement is more effective with a higher number of geotextile layers. The results also revealed that the reinforcement effect in FC≈33 % is at its lowest amount. 

Kazem Fakharian, Ali Borhani,
Volume 14, Issue 4 (6-2016)

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. In order to evaluate the reasons behind this behavior, the spherecity and roundness of all the four sand particles were measured using an image processing method. It was revealed that the spherecity 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 spherecities greater than 0.5, the dependency rate of sand behavior on the roundness is decreased.

Page 1 from 1     

© 2019 All Rights Reserved | International Journal of Civil Engineering

Designed & Developed by : Yektaweb