Study on Static Strength of Aeolian Sand before and after Cyclic Loading

2014 ◽  
Vol 580-583 ◽  
pp. 191-194
Author(s):  
Da Peng Liu ◽  
Xiao Hua Yang ◽  
Jing Wang ◽  
Zheng Jun Mao
Keyword(s):  
Cyclic Loading ◽  
Confining Pressure ◽  
Static Strength ◽  
Triaxial Tests ◽  
Aeolian Sand ◽  
Desert Region ◽  
Deviator Stress ◽  
Before And After ◽  
The Stability ◽  
Engineering Practices

Aeolian sand is one commonly used subgrade filling in Xinjiang Oasis-desert region, engineering practices also proved its applicability as subgrade filling. In order to find the law of Aeolian sand subgrade static strength after cyclic loading, the paper studied the static strength of Aeolian sand before and after cyclic loading through the dynamic and static triaxial tests. It is concluded that the greater cyclic loading is, the more Aeolian sand static strength peak decreases. When cyclic loading is small, the bigger confining pressure and consolidation ratio are, the static strength peak increases more after cyclic loading. The bigger initial static deviator stress is, the more Aeolian sand static strength peak reduces. The frequency of cyclic loading has little effect on static strength. In order to keep the stability of low embankment, we should restrict overload , ensure subgrade and foundation consolidation adequately, at the same time using gravel or geosynthetic materials to package edge of roadbed, so as to increase confining pressure. The research results can provide reference for the design and construction of Aeolian sand low subgrade in Xinjiang Oasis-desert region.

scholarly journals Experimental Study on Dynamic Resilient Modulus of Lime-Treated Expansive Soil

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Zheng Lu ◽  
Yang Zhao ◽  
Shaohua Xian ◽  
Hailin Yao
Keyword(s):  
Moisture Content ◽  
Environmental Changes ◽  
Resilient Modulus ◽  
Expansive Soils ◽  
Expansive Soil ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
The Stability ◽  
Compaction Degree

Dynamic resilient modulus is the design index of highway subgrade design code in China, which is significantly affected by the traffic loads and environmental changes. In this study, dynamic triaxial tests were conducted to investigate the influence of moisture content, compaction degree, cyclic deviator stress, and confining pressure on lime-treated expansive soil. The suitability of UT-Austin model to lime-treated expansive soils was verified. The results indicate that the dynamic resilient modulus of lime-treated expansive soils increases nonlinearly with the increase of compaction degree, while decreases nonlinearly with the increase of dynamic stress level. The dynamic resilient modulus decreases linearly with the increase of moisture content and increases linearly with the increase of confining pressure. Moreover, the moisture content has a more significant effect on the dynamic resilient modulus of lime-treated expansive soil. Therefore, it is necessary to ensure the stability of soil humidity state and its excellent mechanical properties under long-term cyclic loading for the course of subgrade filling and service. Finally, the calculated results of the UT-Austin model for dynamic resilient modulus show a good agreement with the test results.

Influence of cycling pore-water pressures and principal stress ratios on drained deformations in clay

1992 ◽  
Vol 29 (2) ◽  
pp. 326-333 ◽  
Author(s):  
K. D. Eigenbrod ◽  
J. Graham ◽  
J.-P. Burak
Keyword(s):  
Cyclic Loading ◽  
Pore Water ◽  
Seasonal Changes ◽  
Triaxial Tests ◽  
Strain Rates ◽  
Natural Clay ◽  
Groundwater Levels ◽  
Deviator Stress ◽  
Pore Water Pressures ◽  
Stress Ratios

Seasonal changes in groundwater levels affect the rate of downhill creep movements in slopes. This process has been studied in triaxial tests on undisturbed specimens of a natural clay from Bluefish Lake, 50 km north of Yellowknife, N.W.T. Specimens were first anisotropically consolidated to low stresses that correspond to conditions at shallow depths in creeping slopes. Pore-water pressures (back pressures) in the specimens were then cycled systematically (over periods lasting 4–48 h) with the drainage leads open. Resulting axial and volumetric strains were measured, and shear and lateral strains deduced from them. Strain rates decreased with increasing total times of testing. They increased with increasing values of the ratio Δu/Δuf, with increasing values of deviator stress q, and with decreasing values of [Formula: see text]. Systematically increasing the pore-water pressures in the specimens produced clear estimates of failure at low stresses. Key words : slope, clay, creep, cyclic loading, ground water, triaxial.

scholarly journals Influence of Humidity State on Dynamic Resilient Modulus of Subgrade Soils: Considering Repeated Wetting-Drying Cycles

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Gongfeng Xin ◽  
Anshun Zhang ◽  
Zijian Wang ◽  
Quanjun Shen ◽  
Minghao Mu
Keyword(s):  
Resilient Modulus ◽  
Confining Pressure ◽  
Service Performance ◽  
Triaxial Tests ◽  
Road Engineering ◽  
Groundwater Level Fluctuations ◽  
Subgrade Soils ◽  
Deviator Stress ◽  
Complicated Conditions ◽  
Satisfactory Prediction

The service performance of subgrade depends on the dynamic resilient modulus (MR) of subgrade soils. Meanwhile, due to complicated conditions such as rainfall infiltration, high temperature evaporation, and groundwater level fluctuations, it can be safely said that the humidity state and repeated wetting-drying (WD) cycles affect the MR of subgrade soils. The object of this study is to conduct a series of dynamic triaxial tests after WD cycles to investigate the characteristics of the MR under various factors. The main results are as follows: (i) the MR decreased with the increase of deviator stress and rose with the growth of confining pressure; (ii) the humidification effect caused by the increase in moisture content attenuated the MR; (iii) the accumulation of WD cycles damaged the MR; however the decline rate was gradually retarded until it was stable with WD cycles 5 times; (iv) the satisfactory prediction model for the MR of subgrade soils considering WD cycles was proposed and verified. It is expected that the findings can provide valuable contributions for road engineering.

Stability threshold for cyclic loading of saturated clay

1989 ◽  
Vol 26 (1) ◽  
pp. 122-131 ◽  
Author(s):  
Guy Lefebvre ◽  
Denis LeBoeuf ◽  
Benoît Demers
Keyword(s):  
Shear Strength ◽  
Cyclic Loading ◽  
Strain Rate ◽  
Undrained Shear Strength ◽  
Triaxial Tests ◽  
Repeated Loading ◽  
Loading Test ◽  
Stability Threshold ◽  
The Stability ◽  
Undrained Shear

This paper presents the results of an experimental investigation performed to study the stability threshold under cyclic (repeated) loading, and the postcyclic static strength of a sensitive clay from the Hudson Bay region. The strain rate and structure effects were also studied by carrying out monotonic and cyclic triaxial tests at both slow and rapid strain rates or frequencies, and at confining pressures above and below the apparent preconsolidation pressure. The stability threshold for both structured and normally consolidated Grande Baleine clay is about 60–65% of the original undrained shear strength measured at the same strain rate as that used in the repeated loading test. The undrained shear strength and the failure envelope remain essentially unchanged if the repeated preloading is kept below the threshold. The clay structure remains unaltered by this preloading. Key words: clay, stability threshold, cyclic loading, earthquake, postcyclic strength.

Liquefaction and Pore Water Pressure Generation in Sand

2012 ◽  
Vol 3 (1) ◽  
pp. 57-85 ◽  
Author(s):  
T. G. Sitharam ◽  
B. V. Ravishankar ◽  
S. M. Patil
Keyword(s):  
Relative Density ◽  
Shear Strain ◽  
Pore Pressure ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Cyclic Strain ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Before And After ◽  
Reconstituted Soil

Cyclic strain controlled laboratory triaxial undrained tests were performed on sand samples collected from earthquake affected Ahmedabad City of Gujarat (India). To study the factors controlling the liquefaction potential and pore pressure generation, cyclic strain controlled triaxial tests were carried out on (a) base sand, (b) pure sand, and (c) pure sand and non plastic silt mixture. All the tests were conducted on reconstituted soil samples and consolidated isotropically to different effective confining pressures. Base sand, clean sand and sand with non-plastic fines were tested using cyclic strain controlled triaxial undrained tests for different combination of shear strain amplitudes, initial effective confining pressure, and relative density (RD). In case of base sand and pure sand both have qualitatively the same liquefaction and pore pressure generation behaviors. For sand with non plastic fines, basic concept of limiting fines content (LFC) is justified and shown that how the behavior of mixture undergoes transition before and after LFC. This transitional behavior is observed both in the liquefaction strength and pore pressure generation. To obtain a mean relationship between liquefaction strength, pore pressure generation on relative density, confining pressure and shear strain amplitude, approaches previously adopted by Talaganov (1996) are used.

scholarly journals Mechanical Behavior and Damage Evolution for Granite Subjected to Cyclic Loading

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Zhiliang Wang ◽  
Jikang Yao ◽  
Nuocheng Tian ◽  
Jingbin Zheng ◽  
Peng Gao
Keyword(s):  
Cyclic Loading ◽  
Mechanical Behavior ◽  
Damage Evolution ◽  
Confining Pressure ◽  
Test System ◽  
Triaxial Tests ◽  
Dissipated Energy ◽  
Granite Sample ◽  
Cycle Number ◽  
Four Levels

This paper focuses on the mechanical behavior and damage evolution of Huashan granite subjected to cyclic loading. Four levels of confining pressure (0, 15, 25, and 35 MPa) were applied during cyclic axial loading by using a Rock Test System (MTS815) along with an acoustic emission (AE) monitoring device. Experimental results indicate that the number of AE activities is higher under cyclic triaxial loading compared to that under cyclic uniaxial loading. The measured stress-strain curves of both uniaxial and triaxial tests under cyclic loading are concave-up, but the degree of concavity is mild for the latter. As the cycle number rises, elastic modulus of the granite sample under different confining pressures increases. The slope of the peak strength versus confining pressure plot for the cyclic loading is larger than that for the monotonic loading. Besides, it is found that the dissipated energy increases with the increase of cyclic stress, but it hardly increases in proportion with the confining pressure. The damage parameters defined in terms of the plastic strain can be extended for the whole cyclic loading process, and they agree well with the energy-based damage parameters.

Improvement of sensitive silty clay by electroosmosis

1985 ◽  
Vol 22 (1) ◽  
pp. 17-24 ◽  
Author(s):  
Derek V. Morris ◽  
Sydney F. Hillis ◽  
Jack A. Caldwell
Keyword(s):  
Cyclic Loading ◽  
Water Content ◽  
Soil Improvement ◽  
Static Strength ◽  
Triaxial Tests ◽  
Silty Clay ◽  
Cyclic Testing ◽  
Test Program ◽  
Results Of Treatment ◽  
Liquidity Index

A laboratory test program was undertaken in order to assess the probable effectiveness of electroosmotic treatment in the field in reducing the water content and sensitivity of a deposit of soft sensitive silty clay. The results of treatment on tube samples indicate that substantial reductions in water content and liquidity index would be expected, particularly close to the anode. Static and dynamic triaxial tests on both treated and untreated specimens indicated major improvement in both static strength and the resistance to cyclic loading of the soil. Both of these are necessary if construction of a major embankment on this material is to proceed. Key words: electroosmosis, soil improvement, sensitive soils, cyclic testing.

Research on Shear Failure Criterion for Layered Rock Mass

2012 ◽  
Vol 446-449 ◽  
pp. 1491-1496 ◽  
Author(s):  
Zhi Zeng Zhang ◽  
Lan Lan Zhou ◽  
Zhen Xia Yuan ◽  
Zhong Hua Sun
Keyword(s):  
Rock Mass ◽  
Failure Criterion ◽  
Shear Failure ◽  
Three Dimensional ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Layered Rock ◽  
Layered Rock Mass ◽  
The Stability ◽  
Confining Pressure Effect

In order to study the stability of layered rock mass, a shear failure criterion for layered rock mass is presented and its program is compiled in C language. The shear failure criterion consists of two parts: firstly, four empirical expressions are suggested in which shear strength parameters vary with the direction; secondly, a pilot calculation method is developed to judge whether a shear failure plane in layered rock mass occurs or not and give its occurrence under three dimensional stress condition. A triaxial numerical experiment on layered rock mass is designed to test the shear failure criterion, and its results reflect the characters including obliquity effect, confining pressure effect and failure mode which conform to the previous triaxial tests.

scholarly journals Experimental Study on Stiffness Softening of Soil-Rock Mixture Backfill under Metro Train Cyclic Load

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Zuliang Zhong ◽  
Hong Zou ◽  
Xiangxiang Hu ◽  
Xinrong Liu
Keyword(s):  
Cyclic Loading ◽  
Soil Layer ◽  
Confining Pressure ◽  
Factors Affecting ◽  
Chongqing City ◽  
Degree Of Consolidation ◽  
The Stability ◽  
Number Of Cycles ◽  
Consolidation Degree ◽  
Stiffness Softening

Due to the thick soil layer, short backfill time, and low degree of consolidation of the soil-rock mixture backfill in Chongqing city, metro train tunnels passing through this type of strata are prone to large settlements during operation, which greatly affects the stability of the tunnel and the safety of metro train operations. In response to this problem, the dynamic triaxial test of the soil-rock mixture backfill under cyclic loading was carried out to study the dynamic characteristics of the soil-rock mixture backfill under cyclic loading. The effect of initial consolidation degree, effective consolidation confining pressure, and rock content on the stiffness softening of soil-rock mixture backfill was analyzed. The results show that the initial consolidation degree, effective consolidation confining pressure, and rock content are all important factors affecting the stiffness of soil-rock mixture backfill under cyclic loading. As the number of cycles increases, the lower the initial consolidation degree and effective consolidation confining pressure, the faster the attenuation of the softening index, and the larger the amplitude. As the rock content increases, the softening index increases and the stiffness of the backfill changes from softening to hardening. Based on the test data, the softening-hardening model of the soil-rock mixture is established, which is in good agreement with the field test results. This study can provide a reference for predicting and controlling the postconstruction settlement of the metro tunnel in the soil-rock mixture backfill.

Sign in / Sign up

Export Citation Format

Share Document