Experiment Study of Rock Damage and Permeability Meso-Mechanical Coupling Failure Model under Complex Condition

2010 ◽  
Vol 40-41 ◽  
pp. 354-360
Author(s):  
Ji Kun Zhao
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Confining Pressure ◽  
Coupling Mechanism ◽  
Mechanism Analysis ◽  
Force Transmission ◽  
Mechanical Coupling ◽  
Compression Sample ◽  
Weak Part

Pore water pressure and the changes of crustal deformation, fault rupture and seismic activity has important influence. So the pore water pressure and load rock stress – hydro-mechanical coupling mechanism is very important. This paper mainly studies the rock specimens of hydraulic crack damage simulation. This study found: with the increase of the axial compression, sample is on the surface crack. Crack characteristics is smooth and continuously expanding. With the load increasing at the same time, the number of samples is also increased damage elements. The sample was through the cracks. This is due to the effect of water pressure to reduce the size of confining pressure .From the failure mechanism analysis, the distribution of stress non-uniform material will not uniformity, reflected in the actual rock because of the grain and the defects of the random distribution. When the load, the composition of force transmission effect of different deformation and stress in rock, the internal non-uniform stress concentration, local, it will directly cause the weak part, and micro cracks generated change the failure mode of materials.

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.

scholarly journals Mechanical properties and acoustic emission characteristics of granite under thermo-hydro-mechanical coupling

2021 ◽  
Vol 25 (6 Part B) ◽  
pp. 4585-4596
Author(s):  
Xin-Zhong Wang ◽  
Dong Wang ◽  
Zhe-Wei Wang ◽  
Xiao-Juan Yin ◽  
Xue-Jun Zhou ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Acoustic Emission ◽  
Elastic Modulus ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Thermal Cracking ◽  
Confining Pressure ◽  
Mechanical Coupling ◽  
Increasing Temperature

Exploring the mechanical properties and thermal cracking characteristics of rock under thermo-hydro-mechanical coupling in detail is of great importance for the safe excavation and stability of deep rock engineering. The mechanical properties and thermal cracking characteristics of granite under burial depths of 1000 m (confining pressure of 25 MPa) and 1600 m (confining pressure of 40 MPa) at a temperature of 110?C and a pore water pressure of 10 MPa were studied. The results show that the elastic modulus decreases with increasing temperature under a confining pressure of 25 MPa, whereas under a confining pressure of 40 MPa, the elastic modulus increases with increasing temperature. As the pore water pressure increases, the elastic modulus decreases slightly. Poisson?s ratio increas?es with increasing temperature below 40?C but decreases from 50-110?C. Pois?son?s ratio increases as pore water pressure increases. During the heating process, acoustic emission activity is first detected at 30-40?C and is relatively stable from 40-90?C. The acoustic emission activity increases sharply at 90-110?C, and the thermal cracking threshold of granite under thermo-hydro-mechanical coupling is approximately 95?C.

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.

scholarly journals Study on Dynamic Response Characteristics of Saturated Asphalt Pavement under Multi-Field Coupling

Materials ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 959 ◽  
Author(s):  
Yazhen Sun ◽  
Rui Guo ◽  
Lin Gao ◽  
Jinchang Wang ◽  
Xiaochen Wang ◽  
...  
Keyword(s):  
Dynamic Response ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Asphalt Pavement ◽  
Water Pressure ◽  
Moving Load ◽  
Transverse Stress ◽  
Middle Point ◽  
Mechanical Coupling ◽  
Temperature Load

To study the dynamic response of saturated asphalt pavement under moving load and temperature load, 3-D finite element models for asphalt pavements with hydro-mechanical coupling and thermal-hydro-mechanical coupling were built based on the porous media theory and Biot theory. First, the asphalt pavement structure was considered as an ideal saturated fluid–solid biphasic porous medium. Following this, the spatial distribution and the change law of the pore-water pressure with time, the transverse stress, and the vertical displacement response of the asphalt pavement under different speeds, loading times, and temperatures were investigated. The simulation results show that both the curves of the effective stress and the pore-water pressure versus the external loads have similar patterns. The damage of the asphalt membrane is mainly caused by the cyclic effect of positive and negative pore-water pressure. Moreover, the peak value of pore-water pressure is affected by the loading rate and the loading time, and both have positive exponential effects on the pore-water pressure. In addition, the transverse stress of the upper layer pavement is deeply affected by the temperature load, which is more likely to cause as transverse crack in the pavement, resulting in the formation of temperature cracks on the road surface. The vertical stress at the middle point in the upper layer of the saturated asphalt pavement, under the action of the temperature load and the driving load, shows a single peak.

Softening of the Clayey Seabed Foundation due to Earthquakes

1988 ◽  
Vol 110 (1) ◽  
pp. 17-23 ◽  
Author(s):  
N. Mori ◽  
Y. Ishikawa ◽  
A. Hirayama ◽  
K. Tamaoki ◽  
H. Kobayashi
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Confining Pressure ◽  
Offshore Structures ◽  
Model Tests ◽  
Shaking Table ◽  
Earthquake Response ◽  
Response Analysis ◽  
Earthquake Response Analysis

Offshore structures are subjected to repeated loads from earthquakes and waves which may cause softening of the clayey seabed foundation. Carrying out a series of model tests on a shaking table, the following results are obtained. Settlement and inclination of a model of the base-part of the structure occur when the excess pore water pressure beneath the model rises to about 5 percent of the initial confining pressure. The earthquake response analysis even taking the nonlinearity of the soil into account cannot predict the results of the model test when the pore water pressure does generate and accumulate. Model tests show that the values of the pore water pressure are about twice as large as those predicted by calculation. From these results, rough evaluation of earthquake stability of the clayey seabed under offshore structures are obtained.

Analysis of One-Dimensional Thermal Consolidation of Saturated Soil with and without Thermo-Mechanical Coupling

2012 ◽  
Vol 594-597 ◽  
pp. 335-338
Author(s):  
Xue Shen ◽  
Rui Qian Wu
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Saturated Porous Medium ◽  
Water Pressure ◽  
Saturated Soil ◽  
Excess Pore Water Pressure ◽  
One Dimensional ◽  
Mechanical Coupling ◽  
Thermal Consolidation ◽  
Excess Pore

Based on a one-dimensional thermal consolidation formulation with and without thermo-mechanical coupling of saturated porous medium, problems of one-dimensional thermal consolidation of saturated soil were investigated. For the condition with instantaneous constant surface temperature and uniform initial pore-pressure, analytical solutions of excess pore-water pressure and temperature increment were derived respectively by the method of finite Fourier transform and inverse transform. A relevant computer program was developed, and the excess pore-water pressure was compared in detail. The results show that the thermo-mechanical coupling item in the thermal consolidation equation can be ignored.

Strain Soft Numerical Simulation for Destroy Process of Subsea Rock with High Ground Stress and Hydraulic Pressure

2011 ◽  
Vol 204-210 ◽  
pp. 341-345 ◽  
Author(s):  
An Nan Jiang ◽  
Zhan Ping Song ◽  
Jun Xiang Wang
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Confining Pressure ◽  
Surrounding Rock ◽  
Zonal Disintegration ◽  
Hydraulic Pressure ◽  
Invasion Risk ◽  
High Confining Pressure ◽  
Ground Stress

Aiming at the characters of high ground stress and high pore water stress, which resulting in water invasion risk in excavation of subsea rock, FLAC is adopted to simulate the strain localization phenomena of surrounding rock with different pore water pressure and confining pressure. In calculation, the strain soft constitutive relation and “first loading then unloading” pattern are used. Simulation result states that, the bigger the confining pressure is the more destruct the surrounding rock is, and the water invasion risk is more serious. In high confining pressure condition, shortly after excavation, the destroy zone is thin ring, subsequently, the arc shoulder and arc bottom occurs shallow hole, the destroy zone increasing, which presents zonal disintegration. Pore pressure has obvious influence at plastic strain of rock, the high pore water pressure results in surrounding rock destroy zone enlarging, which changing the seepage field of rock, and probably lead to seepage instability.

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