scholarly journals Effects of Initial Shear Stress and Vibration Frequency on the Dynamic Pore-Water Pressure of Saturated Sands

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Jian Zhang ◽  
Jiuting Cao ◽  
Sijie Huang
Keyword(s):  
Shear Stress ◽  
Pore Water ◽  
Vibration Frequency ◽  
Dynamic Stress ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Confining Pressure ◽  
Model Parameters ◽  
Saturated Sand ◽  
Isotropic Consolidation

The cyclic triaxial system is used to investigate the effects of confining pressure, initial shear stress, vibration frequency, and dynamic stress on the pore-water pressure characteristics of saturated sand in the Wenchuan area. Results show that the initial shear stress has a remarkable effect on the development of the dynamic pore-water pressure of saturated sand. The greater the initial shear stress, the slower the development curve of the pore-water pressure of saturated sand and the higher the number of cycles required to reach the same pore-water pressure. The larger the initial shear stress, the smaller the dynamic pore-water pressure when the sample is destroyed. Moreover, the maximum pore-water pressure ratio decreases linearly with the increase of the consolidation ratio. The normalised relationship curve between the dynamic pore-water pressure and failure time of vibration is consistent with the development law of the power function. The power function model parameters are affected by the initial shear stress and confining pressure. At the time of isotropic consolidation, the accumulation law of pore-water pressure presents a growth pattern of “fast-stable-intensified.” A modified pore-water pressure model considering vibration frequency is proposed on the basis of the Seed pore-water pressure model, and the model parameters are linear with the vibration frequency. When the vibration frequency remains unchanged, the parameter does not change with the confining pressure and dynamic stress. This modified model can predict the change rule of pore-water pressure with the frequency under isotropic consolidation.

A Practical Saturated Sand Elastic-Plastic Dynamic Constitutive Model and Application

2012 ◽  
Vol 446-449 ◽  
pp. 1621-1626 ◽  
Author(s):  
Yan Mei Zhang ◽  
Dong Hua Ruan
Keyword(s):  
Constitutive Model ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Stone Columns ◽  
Saturated Sand ◽  
Multidimensional Model ◽  
Excess Pore Water Pressure ◽  
Elastic Plastic ◽  
Excess Pore

A practical saturated sand elastic-plastic dynamic constitutive model was developed on the base of Handin-Drnevich class nonlinear lag model and multidimensional model. In this model, during the calculation of loading before soil reaches yielding, unloading and inverse loading, corrected Handin-Drnevich equivalent nonlinear model was adopted; after soil yielding, based on the idea of multidimensional model, the composite hardening law which combines isotropy hardening and follow-up hardening, corrected Mohr-Coulomb yielding criterion and correlation flow principle were adopted. A fully coupled three dimension effective stress dynamic analysis procedure was developed on the base of this model. The seismic response of liquefaction foundation reinforced by stone columns was analyzed by the developed procedure. The research shows that with the diameter of stone columns increasing, the excess pore water pressure in soil between piles decreases; with the spacing of columns increasing, the excess pore water pressure increases. The influence of both is major in middle and lower level of composite foundation.

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.

scholarly journals Experimental Study on the Variation Law of Excess Pore Water Pressure at the Bottom of the Foundation Pit for Excavation

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Qizhi Hu ◽  
Qiang Zou ◽  
Zhigang Ding ◽  
Zhaodong Xu
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soft Soil ◽  
Confining Pressure ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Excess Pore Water Pressure ◽  
Accurate Expression ◽  
Excess Pore

The excavation unloading of deep foundation pits in soft soil areas often produces negative excess pore water pressure. The rebound deformation of soil on the excavation surface of the foundation pit can be predicted reliably through the accurate expression of relevant variation laws. In combination with the principle of effective stress and the general equation of unidirectional seepage consolidation, an equation for calculating the rebound deformation from the bottom in the process of foundation pit excavation unloading was obtained. Additionally, a triaxial unloading test was adopted to simulate the excavation unloading processes for actual foundation pit engineering. After studying the variation law of the excess pore water pressure generated by excavation unloading, it was found that the negative excess pore water pressure increased with increasing unloading rate, while the corresponding peak value decreased with increasing confining pressure. The equation for rebound calculation was verified through a comparison with relevant measured data from actual engineering. Therefore, it is considered that the equation can reliably describe the rebound deformation law of the base. This paper aims to guide the design and construction of deep foundation pits in soft soil areas.

Theoretical prediction of rutting in flexible pavement subgrades

1992 ◽  
Vol 29 (5) ◽  
pp. 765-778 ◽  
Author(s):  
D. V. Ramsamooj ◽  
R. Piper
Keyword(s):  
Pore Water ◽  
Critical State ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Permanent Deformation ◽  
Flexible Pavement ◽  
Load Test ◽  
Model Parameters ◽  
Silty Clay ◽  
Rate Of Development

The theoretical model for predicting the cyclic response of soils is extended to handle the generation and dissipation of pore-water pressures and to predict the rutting of the subgrade of a flexible pavement. The model utilizes multiyield surfaces and the concepts of critical state mechanics to predict the permanent deformation of the subgrade under vehicular loading. The theoretical solution also considers the effects of the drainage characteristics of the subgrade soil on the rate of development of the permanent deformation. Experimental verification of the model concepts are presented for a drained cyclic load test on Ottawa sand and for undrained cyclic loading on Newfield clay using published experimental data. An illustrative example is given for the prediction of rutting in a silty clay subgrade. The model parameters for the silty clay are obtained from triaxial and consolidation tests. These parameters are then put into a computer program that determines the rut depth, pore-water pressure, and the ratio of the vertical deformation and the rut depth as functions of the number of vehicular loads for a flexible pavement for various conditions of drainage ranging from undrained to fully drained. The role of the coefficient of consolidation of the subgrade in controlling the rate of development of the rut depth is highlighted. Key words : critical state soil mechanics, multiyield surfaces, rutting, silty clay subgrade, drainage, vehicular loading.

scholarly journals Progressive Failure and Fracture Mechanism of Sandstone under Hydraulic-Mechanical Coupling

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Yingming Li ◽  
Gang Liu ◽  
Tao Qin ◽  
Zhupeng Jin ◽  
Chengxing Zhao ◽  
...  
Keyword(s):  
Pore Water ◽  
Fracture Mechanism ◽  
Pore Water Pressure ◽  
Progressive Failure ◽  
Water Pressure ◽  
Confining Pressure ◽  
Experimental Results ◽  
Type I ◽  
Volume Deformation ◽  
Mechanical Coupling

Hydraulic coupling often leads to progressive rock failure accidents. Mechanical tests were performed over a range of combined pore water pressure and confining pressure stress path conditions to study the progressive failure characteristics of sandstone under hydraulic-mechanical coupling and explore the crack initiation and pore water fracture mechanism. The closure stress and damage stress were determined by the axial deformation stiffness and volume deformation stiffness. The experimental results indicate that confining pressure is the main controlling factor in the crack propagation stage, and pore water pressure enhances crack evolution. With increasing effective confining pressure, the effective peak deviatoric stress strongly increases and the characteristic stress increases linearly. The initiation stress and damage stress decrease with increasing pore water pressure. The moduli in stages I, II, and III are similar to the law of the transverse and radial deformation ratio with notable differences in stage IV. The fracture trend angle was determined by the ratio of axial crack strain and radial crack strain. Compared with the experimental results, the internal cracks in the sandstone samples are mainly type-II cracks, and type-I cracks are also locally present. After stress damage, the cracks expand and extend at an angle close to the real fracture.

Dynamic Behaviors of Mucky Clay Material under Cyclic Loads

2016 ◽  
Vol 703 ◽  
pp. 345-348
Author(s):  
Zheng Lu ◽  
Zhi Hu ◽  
Hua Wang ◽  
Hai Lin Yao
Keyword(s):  
Pore Water ◽  
Dynamic Stress ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Triaxial Tests ◽  
Clay Material ◽  
Dynamic Behaviors ◽  
Accumulated Strain ◽  
Mucky Clay ◽  
Number Of Cycles

A series of consolidated-undrained (CU) triaxial compression tests and dynamic triaxial tests on mucky clay material were performed in the present paper, and the dynamic behaviors of mucky clay material for different dynamic stress amplitudes and initial static deviator stresses were studied. It is indicated that both the accumulated strain and the pore water pressure increase rapidly with increasing number of cycles. While after a certain number of cycles, the accumulated strain tends to be stable and there is enough time for the equilibrium of pore water pressure. Results also show that the influences of dynamic stress amplitudes and initial static deviator stresses on the accumulated plastic strain and pore water pressure of the mucky clay material are significant.

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