HCA Study of Permanent Deformation of Sand Under Train-Induced Stress Path Considering Variable Confining Pressure

2020 ◽  
pp. 347-357
Author(s):  
Juan Wang ◽  
Yanfei Xiong ◽  
Dariusz Wanatowski
Keyword(s):  
Permanent Deformation ◽  
Confining Pressure ◽  
Stress Path ◽  
Induced Stress ◽  
Variable Confining Pressure

Effect of variable confining pressure on cyclic behaviour of granular soil under triaxial tests

2017 ◽  
Vol 54 (6) ◽  
pp. 768-777 ◽  
Author(s):  
Qi Sun ◽  
Yuanqiang Cai ◽  
Jian Chu ◽  
Quanyang Dong ◽  
Jun Wang
Keyword(s):  
Initial Stress ◽  
Stress Ratio ◽  
Permanent Deformation ◽  
Confining Pressure ◽  
Stress Path ◽  
Average Stress ◽  
Triaxial Tests ◽  
Cyclic Behaviour ◽  
Different Strains ◽  
Variable Confining Pressure

Previous studies were performed to use combined cyclic deviatoric stress and confining pressure to simulate cyclic vertical and horizontal normal stresses under traffic loading. The effect of variable confining pressure (VCP) on the permanent deformation of soils was investigated. However, some studies concluded VCP could promote the development of permanent deformation compared to the tests with constant confining pressure (CCP), while others drew the opposite conclusions. In this study, three types of CCP and VCP tests with identical maximum stress, identical average stress, and identical initial stress were conducted. Test results showed VCP tests accumulated more permanent strains when CCP and VCP tests had identical maximum or average stress, and the permanent strains increased with the decrease in the inclinations of stress paths, while similar permanent strains were generated when CCP and VCP tests had identical initial stress. In addition, larger permanent strains were generated with the increase in stress ratio or length of stress path in both CCP and VCP tests. Considering that different strains were cumulated in CCP and VCP tests with the same stress ratio, it is recommended that both stress ratio and length of stress path be considered to assess the permanent deformation.

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

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.

Unbound Aggregate Rutting Models for Stress Rotations and Effects of Moving Wheel Loads

2005 ◽  
Vol 1913 (1) ◽  
pp. 41-49 ◽  
Author(s):  
In Tai Kim ◽  
Erol Tutumluer
Keyword(s):  
Test Data ◽  
Permanent Deformation ◽  
Confining Pressure ◽  
Stress Path ◽  
In Situ Stress ◽  
Triaxial Tests ◽  
Wheel Loading ◽  
Stress States ◽  
Granular Layers ◽  
Unbound Aggregate

The latest research findings on stress rotations caused by moving wheel loads and their effects on permanent deformation or rut accumulation in pavement granular layers are presented. Realistic pavement stresses induced by moving wheel loads were examined in the unbound aggregate base and subbase layers, and the significant effects of rotation of principal stress axes were indicated for a proper characterization of the permanent deformation behavior. To account for the rutting performances of especially thick granular layers, a comprehensive set of repeated load triaxial tests was conducted in the laboratory. Triaxial test data were obtained and analyzed from testing aggregates under various realistic in situ stress paths caused by moving wheel loading. Permanent deformation characterization models were then developed on the basis of the experimental test data to include the static and dynamic stress states and the slope of stress path loading. The models that also considered the stress path slope variations predicted the stress path dependency of permanent deformation accumulation best. In addition, multiple stress path tests conducted to simulate the extension–compression–extension type of rotating stress states under a wheel pass gave much higher permanent strains than those of the compression-only single path tests. The findings indicated actual traffic loading simulated by the multiple path tests could cause greater permanent deformations or rutting damage, especially in the loose base or subbase, when compared with deformations measured from a dynamic plate loading or a constant confining pressure type laboratory test.

scholarly journals Deformation, Permeability and Acoustic Emission Characteristics of Coal Masses under Mining-Induced Stress Paths

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2233 ◽  
Author(s):  
Yi Xue ◽  
Faning Dang ◽  
Zhengzheng Cao ◽  
Feng Du ◽  
Jie Ren ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Coal Seam ◽  
Coal Mining ◽  
Confining Pressure ◽  
Stress Path ◽  
Coal Mass ◽  
Emission Characteristics ◽  
Induced Stress ◽  
High Confining Pressure ◽  
Pillar Mining

The geomechanical and seepage evolution characteristics of coal masses during mining are the key factors that affect the drainage of coalbed methane and the safety of coal mining. Nevertheless, the influence of mining paths on coal seam permeability is rarely investigated given the complexity of mining-induced stress experiments. To study the effect of mining-induced stress on coal mining, the mechanical properties, acoustic emission characteristics and energy evolution of coal masses were experimentally evaluated through mining-induced stress experiments. Experimental results indicated that at peak intensity, the deviatoric stress and axial strain of coal samples under the stress path of protective coal-seam mining are lower than those of coal samples under the non-pillar stress path. The unloading ratio of confining pressure is large under a stress path of non-pillar mining, and the elastic energy, the absorbed energy, and the dissipated energy of coal mass are low during destruction. The effect of high confining pressure on AE events is pronounced under the non-pillar mining path. The overall b value under high confining pressure is smaller than that under low confining pressure, and AE events generally have high energy. The fracture structure of coal mass is complex, and the fractal size of coal is large under high unloading rates of confining pressure, which induce the increase of permeability after coal destruction.

Permanent deformation characteristics of saturated sand under cyclic loading

2015 ◽  
Vol 52 (6) ◽  
pp. 795-807 ◽  
Author(s):  
Yuanqiang Cai ◽  
Qi Sun ◽  
Lin Guo ◽  
C. Hsein Juang ◽  
Jun Wang
Keyword(s):  
Shear Stress ◽  
Stress Ratio ◽  
Permanent Deformation ◽  
Confining Pressure ◽  
Stress Path ◽  
Deviatoric Stress ◽  
Loading Path ◽  
Triaxial Tests ◽  
Deformation Characteristics ◽  
Torsional Shear

The loading path involving principal stress rotation (PSR) during shear is an important phenomenon encountered in many field conditions. Typically for traffic loading, both the magnitude and direction of principal stresses may vary with time due to the motion of vehicles, and the stress path can be mimicked by a heart shape in the deviatoric stress space. Conventional triaxial tests are not suitable to recreate this type of stress path in that no torsional shear stress can be applied on the test samples. To overcome this limitation, a series of tests using a hollow cylinder apparatus were conducted on sand to investigate the permanent deformation characteristics under drained conditions with different levels of confining pressure (σc), cyclic vertical stress ratio (CVSR), and cyclic torsional stress ratio (η). The results clearly show an increase in the permanent deformation with η, indicating that the PSR effect on permanent deformation cannot be ignored. Both σc and CVSR were found to also affect permanent deformation, which was more pronounced when PSR was coupled into the test. A five-parameter formulation that accounted for the effect of confining pressure, deviatoric stress, torsional shear stress, and number of loading cycles was subsequently established to analyze the permanent strain. The formulation coefficients were first determined and then used to explain the effects of stress variables on the permanent deformation. Validation studies were performed to address the adequacy of the formulation to predict permanent deformation.

Injection-induced seismicity: strategies for reducing risk using high stress path reservoirs and temperature-induced stress preconditioning

2019 ◽  
Vol 220 (2) ◽  
pp. 1436-1446 ◽  
Author(s):  
B Fryer ◽  
G Siddiqi ◽  
L Laloui
Keyword(s):  
Seismic Event ◽  
Shear Failure ◽  
High Stress ◽  
Stress Path ◽  
B Value ◽  
Large Magnitude ◽  
Differential Stress ◽  
Induced Stress ◽  
Reverse Faulting ◽  
New Strategy

SUMMARY It is suggested that fluid injection in normal faulting stress regimes can stabilize a reservoir if the stress path is high enough. This stabilization is not seen when the reservoir is significantly cooled as a result of injection. Further, a new strategy is suggested for stimulating reservoirs in shear with a reduced chance of inducing a large magnitude seismic event. The version of this methodology presented here is applicable for reverse faulting stress regimes and involves an initial stress preconditioning stage where the reservoir is cooled and the pressure increase is limited. This process reduces the horizontal total stress and thereby also the differential stress. Next, the reservoir is stimulated with a rapid increase in pore pressure, resulting in shear failure at a lower differential stress than was initially present in the reservoir. Due to the connection seen between the Gutenberg–Richter b-value and differential stress, it is suggested that reservoirs stimulated in this fashion will exhibit higher b-values and thereby also have a reduced chance of hosting a large magnitude event. It is suggested that adaptations of this methodology are applicable to both normal and strike-slip faulting stress regimes.

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