Undrained Deformation Characteristics of Soft Marine Clay Subjected to One-Way Cyclic Loading with Variable Confining Pressure

To gain a better understanding of the undrained deformation characteristic of saturated marine clay soil subjected to vehicle cyclic traffic load, a sophisticated dynamic triaxial was used to conduct a variety of undrained one-way compression cyclic experiments with variable confining pressure (VCP) as well as constant confining pressure (CCP). The results indicate that, compared to CCP test results, VCP is helpful to raise the axial resilient modulus (Mr) and restrain the permanent plastic strain ( ε a p ) development of the specimens. By normalization analysis of the measured data of Mr and ε a p , the virtually unique correlation between normalized average resilient modulus, normalized permanent axial strain after 1,000 loading cycles, and normalized mean normal stress is established, respectively, regardless of the values of CSR. Additionally, the VCP influence on ε a p is quantified and fitted by a power law function, which can be used for subsoil deformation prediction and provides new insights into the mechanics of strain accumulation under undrained cyclic loading conditions.

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Strain Accumulation in Soft Marine Clay due to One-Way Cyclic Load with Variable Confining Pressure

Advances in Civil Engineering ◽

10.1155/2021/6624270 ◽

2021 ◽

Vol 2021 ◽

pp. 1-13

Author(s):

Lei Sun

Keyword(s):

Axial Strain ◽

Soft Clay ◽

Deformation Characteristic ◽

Confining Pressure ◽

Deviatoric Stress ◽

Strain Accumulation ◽

Marine Clay ◽

Traffic Loading ◽

Wide Range ◽

Variable Confining Pressure

The effect of variable confining pressure on the strain accumulation in soft marine clay was investigated to gain a better understanding of the deformation characteristic in the subgrade of pavements due to traffic loading. A series of variable confining pressure (VCP) experiments and corresponding constant confining pressure (CCP) experiments were conducted on Wenzhou soft clay using an advanced cyclic triaxial apparatus. A wide range of deviatoric stress amplitudes (qampl), combined with different isotropic stress amplitudes (pampl), and partially drained conditions are simulated in the experiments. The test results indicate that the variable confining pressure significantly influences the permanent axial strain and might exacerbate the potential of subgrade invalidation in soft marine clay area. The normalized permanent axial strain ( ε a , 1000 p / ε a , 1000 p , C C P ) after 1000 cycles is logarithmic with the normalized stress path length (L/LCCP), and one-unit increment in the amplitude of cyclic confining pressure will induce an increment of 0.0213% in the permanent axial strain regardless of the CSR values. Based on the data from the CCP tests, a cyclic deviatoric stress ratio threshold is determined to be about 0.7, which may suggest that the upper bound of criterion will limit the cyclic traffic loadings on soft marine clayey deposit. Finally, the effect of variable confining pressure on the permanent axial strain is quantified and incorporated in a logarithmic model for the subsoil deformation prediction under traffic loading.

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Effect of Variable Confining Pressure on Cyclic Triaxial Behavior of K0-consolidated Soft Marine Clay

Civil Engineering Journal ◽

10.28991/cej-0309130 ◽

2018 ◽

Vol 4 (4) ◽

pp. 755

Author(s):

Lei Sun

Keyword(s):

Pore Water ◽

Pore Water Pressure ◽

Axial Strain ◽

Water Pressure ◽

Confining Pressure ◽

Stress Path ◽

Cyclic Stress ◽

Marine Clay ◽

Stress Ratios ◽

Variable Confining Pressure

The effect of variable confining pressure (VCP) on the cyclic deformation and cyclic pore water pressure in K0-consolidated saturated soft marine clay were investigated with the help of the cyclic stress-controlled advanced dynamic triaxial test in undrained condition. The testing program encompassed three cyclic deviator stress ratios, CSR=0.189, 0.284 and 0.379 and three stress path inclinations ηampl=3,1 and 0.64. All tests with constant confining pressure (CCP) and variable confining pressure (VCP) have identical initial stress and average stress. The results were analyzed in terms of the accumulative normalized excess pore water pressure rqu recorded at the end of each stress cycle and permanent axial strain, as well as resilient modulus. Limited data suggest that these behavior are significantly affected by both of the VCP and CSR. For a given value of VCP, both of the pore water pressure rqu and permanent axial strains are consistently increase with the increasing values of CSR. However, for a given value of CSR, the extent of the influence of VCP and the trend is substantially depend on the CSR.

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Triaxial Characterization of Minnesota Road Research Project Granular Materials

Transportation Research Record Journal of the Transportation Research Board ◽

10.3141/1577-04 ◽

1997 ◽

Vol 1577 (1) ◽

pp. 27-36 ◽

Cited By ~ 23

Author(s):

Navneet Garg ◽

Marshall R. Thompson

Keyword(s):

Shear Strength ◽

Granular Materials ◽

Resilient Modulus ◽

Axial Strain ◽

Confining Pressure ◽

Engineering Properties ◽

Shear Tests ◽

Road Project ◽

Load Tests ◽

Repeated Load

Six granular materials were used as base and subbase materials in the flexible pavement test sections for the Minnesota Road Research (Mn/ROAD) project. Crushed/fractured particles are not allowed in aggregate classes CL-1Fsp, CL-1Csp, CL-3sp, and CL-4sp. Ten to 15 percent crushed/fractured particles are required for CL-5sp. One hundred percent crushed/ fractured particles are required for CL-6sp. A comprehensive laboratory testing program was established to determine pertinent engineering properties of the granular materials. Rapid shear tests and repeated-load tests were conducted to determine the shear strength parameters (friction angle and cohesion), resilient modulus, rutting potential, stress history effects on shear strength, and moisture susceptibility. The results from the rapid shear tests and permanent deformation tests show that the rutting potential of a granular material can be characterized from rapid shear test at a confining pressure of 15 psi (103.35 kPa). The rutting parameter A was a function of the shear strength of the granular materials. The shear strength results obtained from rapid shear tests performed at a confining pressure of 15 psi reflect the rutting trends observed in the low-volume road test sections at the Mn/ROAD project. Results from repeated-load tests were used to develop the parameters for K-θ, UT-Austin, and Uzan’s models for evaluating the resilient modulus of granular materials. The axial strain values calculated from the resilient modulus models appear to be in good agreement with the measured axial strain values, except for the very low shear strength material CL-1Csp.

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Modeling permanent strains of granular soil under cyclic loading with variable confining pressure

Acta Geotechnica ◽

10.1007/s11440-019-00868-w ◽

2019 ◽

Vol 15 (6) ◽

pp. 1409-1421

Author(s):

Qi Sun ◽

Quanyang Dong ◽

Yuanqiang Cai ◽

Jun Wang

Keyword(s):

Cyclic Loading ◽

Confining Pressure ◽

Granular Soil ◽

Variable Confining Pressure

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Effect of Geotextile Encapsulation on Lime Column Axial Stress in Pontain Marine Clay

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.773-774.1402 ◽

2015 ◽

Vol 773-774 ◽

pp. 1402-1406

Author(s):

Siaw Yah Chong ◽

Khairul Anuar Kassim ◽

Kenny Tiong Ping Chiet

Keyword(s):

Axial Stress ◽

Axial Strain ◽

Soft Clay ◽

Confining Pressure ◽

Marine Clay ◽

Loading Test ◽

Lime Stabilization ◽

Multi Stage ◽

Surrounding Soil ◽

Lime Column

Previous researchers reported that problematic soft clay can be improved by deep lime stabilization. However, due to low confining pressure of surrounding soil, problems often occurred at top part of column which reduced the performance of lime column, such as: crushing at column head and higher settlement for surrounding soil at the upper part of column. Geotextile encapsulated lime column (GELC) was proposed in this study. The stresses on column are essential in the analysis on columnar improved soil. Multi-stage loading test was conducted on lime column and GELC stabilized Pontian marine clay aged 14 days, 28 days and 56 days in order to investigate axial stress on lime column and GELC stabilized Pontian marine clay. Geotextile encapsulation increased the compressive strength of lime column about 70 percent at axial strain of 8 percent.

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Deformation and Acoustic Emission Characteristics of Cracked Granite during Creep

Advances in Materials Science and Engineering ◽

10.1155/2020/7075287 ◽

2020 ◽

Vol 2020 ◽

pp. 1-11

Author(s):

Chunping Wang ◽

Jingli Xie ◽

Jian Liu

Keyword(s):

Acoustic Emission ◽

Axial Strain ◽

Failure Process ◽

Deformation Characteristic ◽

Temporal Distribution ◽

Confining Pressure ◽

High Energy ◽

Lateral Strain ◽

Creep Tests ◽

Confining Pressures

A series of multistage creep tests under different confining pressures with acoustic emission monitoring have been performed to investigate the deformation characteristic and failure process of cracked granite during creep. The critical axial strain of cracked sample showed an increasing tendency with the increase of confining pressure. In contrast, critical lateral strain experienced a process of descending first at low confinement and then remaining nearly constant at high confinement. Compared with loading-cracked specimen, smaller critical axial strain, greater critical lateral strain, and higher lateral creep strain rate were found for unloading-cracked specimen. Based on the spatial and temporal distribution of acoustic emission events, the cracking process during creep was analysed. The AE events with high energy are mainly concentrated at the final fracture area of the specimen. The higher the confining pressure, the more the AE events with low energy. Compared with the loading-cracked specimen, the percentage of AE events with high energy is relatively small for the unloading-cracked specimen.

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Empirical Method for Evaluating Resilient Modulus of Saturated Silty Clay under Cyclic Loading

Advances in Civil Engineering ◽

10.1155/2020/8846895 ◽

2020 ◽

Vol 2020 ◽

pp. 1-12

Author(s):

Zhen Zhang ◽

Yong Chen ◽

Guanbao Ye ◽

Peilin Xiang ◽

Yan Xiao ◽

...

Keyword(s):

Cyclic Loading ◽

Stress Ratio ◽

Resilient Modulus ◽

Dynamic Properties ◽

Damping Ratio ◽

Empirical Method ◽

Traffic Load ◽

Triaxial Tests ◽

Silty Clay ◽

Test Results

Resilient modulus of soil is crucial for the design of a structure on a foundation subjected to a cyclic loading (e.g., traffic load or machine vibration load). This paper conducted a series of dynamic triaxial tests of saturated silty clay, considering the influence of the factors of cyclic stress ratio (CSR), static deviatoric stress ratio (SDR), and overconsolidation ratio (OCR) on the resilient modulus and dynamic damping ratio of the soil. A cyclic loading with a form of half sine wave was used to model the traffic loading. The results showed that the soil was prone to failure under a higher SDR, even though the applied CSR was less than the critical CSR. The saturated silty clay performed a strain softening behavior and its dynamic properties deteriorated significantly when higher CSR and SDR and lower OCR were involved. Based on the test results, an empirical method with a form of exponential function was proposed to evaluate the resilient modulus of the soil, considering the combined effects of CSR and SDR and OCR. The proposed method was verified through a comparison with the test results in this study and from literatures, and some recommendations for its application were offered.

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