Studies on Mode II Rock Crack Propagation on Different Loading Environments

2016 ◽  
Vol 713 ◽  
pp. 305-308
Author(s):  
C. Cheng ◽  
M.X. Li ◽  
Y. Liu ◽  
X. Zhang ◽  
Y.Y. Cheng ◽  
...  
Keyword(s):  
Crack Propagation ◽  
Confining Pressure ◽  
Element Model ◽  
Mode Ii ◽  
Geological Exploration ◽  
Underground Engineering ◽  
Different Temperatures ◽  
Confining Pressures ◽  
New Type ◽  
The Stability

In this paper, a new type of specimen, which can be easily made by rock core through geological exploration, of mode II rock crack has been designed and processed. The crack propagation forces F of the specimen are measured under different temperatures and different confining pressures. The crack extension patterns are observed. The 3D finite element model of the specimen is established. The stresses near crack tip are calculated to get the value of KIIC when the crack initiation. The variation of KIIC of the model II rock crack is obtained under different temperatures and confining pressures. The experiments and numerical results show that temperature and confining pressure have obviously influence on KIIC, the value of KIIC decreases with the temperature increasing, and increases with the confining pressure increasing. The results of the paper can provide an important reference for analyzing the stability of the rock cracks in underground engineering.

Experimental Study on Mechanical Property of Thermo-Mechanical and Hydro-Mechanical Coupling Condition for a Sandstone

2006 ◽  
Vol 326-328 ◽  
pp. 1797-1800 ◽  
Author(s):  
Qing Chun Zhou ◽  
Hai Bo Li ◽  
Chun He Yang ◽  
Chao Wen Luo
Keyword(s):  
Pore Pressure ◽  
Deformation Modulus ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Underground Engineering ◽  
Coupling Condition ◽  
West China ◽  
Mechanical Coupling ◽  
North Water ◽  
Confining Pressures

The mechanical properties of rock under high temperature, high geostress and high pore pressure are the basic and important information to assess the safety of underground engineering in west China. Based on the environmental conditions of the west route of south-to-north water transfer project in west China, a series of triaxial tests at confining pressures (0 to 60MPa) and temperatures (25°C to 70°C) as well as pore pressure (0 to 10MPa) have been conducted for a sandstone. It is reported that under the temperatures varying from 25°C to 70°C, the strength of the rock increases with the increment of confining pressure, while the deformation modulus of the rock doesn’t change distinctly with the increment of confining pressures. It is also indicated under the temperatures condition in the experiments, when the confining pressure is lower than 40MPa, the strength of the rock increases with the increment of temperature, whereas when the confining pressure is higher than 40MPa, the strength of rock tend to decrease with increment of temperature. It is further shown that the strength decreases with increasing pore pressure, and the decreasing rates tend to decrease with the increment of confining pressures.

The Stability of 3D-Geomat in Different Slope Gradient

2014 ◽  
Vol 580-583 ◽  
pp. 782-786
Author(s):  
Guang Yue Wang ◽  
Jian Peng Zhang ◽  
Yuan Shuai Sun
Keyword(s):  
Water Conservation ◽  
Element Model ◽  
Slope Gradient ◽  
Slope Surface ◽  
Engineering Construction ◽  
Ecological Protection ◽  
New Type ◽  
The Stability ◽  
The Finite Element Model ◽  
Soil And Water

3D-geomat protective slope is a new type of protective slope form which combines the 3D-geocell with the planting grass. Because the complex and dense spatial structure can tie the slope soil and has a reinforced effect on the slope surface, it has the advantage in soil and water conservation and ecological protection, and it gets more and more widely used in the present engineering construction. By using the finite element model, we compare the whole stability in the 3D-geomat slope and unprotective slope under the condition of different slope gradient. And then we get the relative results.

scholarly journals Experimental study on the thermal damage characteristics of cement stone

2020 ◽  
pp. 317-317
Author(s):  
Feng Xu ◽  
Bowen Qian ◽  
Ling Tan ◽  
Jianqiang Xu ◽  
Shengchuan Tang ◽  
...  
Keyword(s):  
Strain Curve ◽  
Horizontal Wells ◽  
Friction Angle ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Cement Stone ◽  
Different Temperatures ◽  
Confining Pressures ◽  
Southwest Region ◽  
Sealing Failure

Aiming at the problem of cement ring sealing failure during deep high-temperature shale gas exploitation, comprehensively considering the influence of the characteristics of multi-cluster fracturing of multiple horizontal wells and formation temperature, the cementing cement the southwest region is taken as the research object. After exposure to different temperatures (95?C and 135?C) and for different times (5, 10 and 20 times), axial and triaxial tests with different confining pressures (0, 5 MPa, 15 MPa and 30 MPa) were carried out. The research shows that: (1) the stress-strain curve of cement stone after heat treatment can be divided into four stages: compaction, elastic, yield and post-peak stage. As the confining pressure increases, the compaction phase disappears, the yield phase increases, and we see the transition from brittle to ideal plasticity after the peak; (2) as the temperature and number of thermal cycles increase, the cohesive force decreases significantly, and the internal friction angle shows a slight increase. The elastic modulus and the peak strength decreased.

IMPACT OF WATER AND CO2 ON THE MECHANICAL PROPERTIES OF LOW PERMEABLE ROCKS

2021 ◽  
Vol 7 (2) ◽  
pp. 130-146
Author(s):  
Anatolii A. KISLITSYN ◽  
Nikita V. Lipatov
Keyword(s):  
Mechanical Properties ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Strength Properties ◽  
Pore Fluid ◽  
Co2 Injection ◽  
Core Samples ◽  
Different Temperatures ◽  
Confining Pressures ◽  
Temporary Decrease

This article features experiments on triaxial compression of low-permeable dolomite samples with different confining pressures (2-20 MPa), different pore fluids (dry air, water, CO2), and different temperatures (25-150 °C). The authors have studied the effect of confining pressure, pore fluid and temperature on the strength properties of the studied samples. The results show an increase in the strength with grwoing confining pressure. When the confining pressure increases from 2 to 20 MPa, the compressive strength increases from 86 to 370 MPa. Temperature has a significant effect on rock strength under low confining pressure conditions. With the increasing confining pressure reaching 15 MPa, increasing temperature has little effect on the strength of dolomite samples. Under an effective confining pressure of 5 MPa, the temperature weakening occurs on the dolomite specimens when the temperature exceeds 90 °C. During compression, liquid diffusion occurs in the specimens. Higher water viscosity can cause a temporary decrease in effective confining pressure, which can increase the strength of the rock. More prominent fractures are observed in the samples, and more fluid is injected under CO2 injection conditions, which may be useful for increasing the permeability of the geothermal reservoir. Two groups of experiments have been performed on the samples in this study: the first group of experiments investigated the effect of confining pressure on the fracture stress of core samples, without pore fluid injection; the second group of experiments investigated the effect of water or CO2 and temperature on the mechanical properties of core samples.

scholarly journals Experimental Study on Mechanical Properties of Deep Buried Granite under Different Confining Pressures

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Jun Zhao ◽  
Tan Zhang
Keyword(s):  
Cyclic Loading ◽  
Confining Pressure ◽  
Surrounding Rock ◽  
Underground Engineering ◽  
Failure Characteristics ◽  
Deformation And Failure ◽  
Cyclic Loading And Unloading ◽  
Confining Pressures ◽  
Crack Damage Stress ◽  
Loading And Unloading

Brittle failure of hard rock poses a serious threat to the stability of surrounding rock in deep underground engineering. In order to study the deformation and failure characteristics of deep buried granite under high confining pressure cyclic loading and unloading, MTS815 electro-hydraulic servo rock test system was used to conduct cyclic loading and unloading tests under confining pressures of 15 MPa, 35 MPa, 45 MPa, and 55 MPa, and the corresponding stress-strain curves and deformation failure characteristic curves were obtained. The experimental results show the follows: (1) under the same confining pressure, the peak strength, crack initiation stress, crack damage stress, and Poisson’s ratio of the specimens under cyclic loading and unloading are larger than those under conventional triaxial loading and unloading, and the unloading elastic modulus is smaller than that, under conventional triaxial compression; (2) the results show that, under different confining pressures, the granite samples show obvious brittle failure characteristics, the elastic modulus and crack initiation stress increase first and then decrease with the confining pressure, the peak strength and crack damage stress of the samples increase linearly with the confining pressure, and Poisson’s ratio increases first and then remains unchanged with the confining pressure; (3) under the two kinds of stress conditions, the macroscopic failure of the samples is mainly shear failure. The deformation and failure law of granite samples revealed in this study has significant reference value for the selection of rock mass mechanical model of surrounding rock stability of underground engineering, the formulation of surrounding rock support countermeasures, and the evolution law of mechanical parameters with damage variables.

scholarly journals Investigation on the Influence of Temperature and Confining Pressure on the Hydraulic Conductivity of the Integrated and Fractured Jurassic Conglomerates

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Dingyang Zhang ◽  
Wanghua Sui ◽  
Jiawei Liu
Keyword(s):  
Hydraulic Conductivity ◽  
Shear Failure ◽  
Negative Relationship ◽  
Confining Pressure ◽  
Regression Equations ◽  
Intact Sample ◽  
Triaxial Cell ◽  
Different Temperatures ◽  
Confining Pressures ◽  
Constant Head

This paper presents an experimental investigation on the properties of hydraulic conductivity and permeability of conglomerates under different temperatures and confining pressures with integrated samples and samples with shear failure. Constant head tests were carried out in a temperature-controlled triaxial cell with samples obtained from the Zhuxianzhuang Coal Mine. Five levels of temperatures (10°C, 20°C, 28°C, 35°C, and 50°C) and three levels of confining pressures (3 MPa, 5 MPa, and 7 MPa) were chosen for the tests. The results show that there is a negative relationship between hydraulic conductivity and confining pressure with both original and shear failure samples. An inflection point of 35°C is found in the relationship between the flow rate and temperature. However, with increasing temperature conditions, hydraulic conductivity first increases and then decreases at 50°C with the intact sample, while hydraulic conductivity first decreases from 20°C and then increases with the shear failure sample. Finally, nonlinear regression equations of hydraulic conductivity and temperature were obtained under different confining pressures.

scholarly journals An Experimental Investigation of the Progressive Failure of Sandstone and Its Energy Evolution Characteristics

2018 ◽  
Vol 2018 ◽  
pp. 1-12
Author(s):  
Yan Chen ◽  
Baohua Guo
Keyword(s):  
Crack Propagation ◽  
Crack Closure ◽  
Progressive Failure ◽  
Axial Strain ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Energy Evolution ◽  
Evolution Characteristics ◽  
Confining Pressures ◽  
The Relationship

In this research study, the progressive failure and energy evolution characteristics of sandstone samples with different sizes were explored under uniaxial and triaxial compression conditions. The characteristic stresses and strains were captured using the crack axial strain levels and dissipative energy. The results showed that, with the increase in the ratios of the height to diameter (H/D), the crack closure stresses increased, while the crack damage stresses decreased. However, the levels of both the crack closure stresses and crack damages were observed to increase with the H/D. With increase in the confining pressure, it was found that the crack closure and crack damage stresses increased, while their levels decreased. The strains of the crack closures, peak crack axial, and crack propagation were observed to decrease with the H/D, while the crack closure strain levels increased. Also, the crack propagation strains were observed to increase with the confining pressures, while the crack closure, peak crack axial, and crack closure strain levels decreased. The progress failure of the sandstone samples was also obtained based on the evolution characteristics of the dissipative energy. The relationship between the energy densities during each phase and the H/D was also analyzed. It was determined that, with the increasing of the H/D, the input, elastic, and dissipative energy densities displayed different evolution characteristics. Furthermore, with the increases in the characteristic stresses, the input and elastic energy densities were found to increase. The dissipative energy density displayed a slight increase with the increases in the peak strength, which resulted in variations with regard to the crack closures and crack damage stresses.

Research on Post-Peak Characteristics of Elastic-Plastic Strain-Softening Model Based on Mohr-Coulomb Strength Criterions

2011 ◽  
Vol 261-263 ◽  
pp. 1439-1443
Author(s):  
Shao Qing Niu ◽  
Shuang Suo Yang ◽  
Lei Cui
Keyword(s):  
Rock Mass ◽  
Strain Softening ◽  
Triaxial Compression ◽  
Dynamic Change ◽  
Confining Pressure ◽  
Strength Parameters ◽  
Underground Engineering ◽  
Coulomb Failure ◽  
Confining Pressures ◽  
Damage Extent

Considering the characteristic that rock mass can transform from brittleness to plasticity and the dynamic change of post-peak strength parameters of the rock mass, the invariability of elastic modulus and poisson's ratio, constitutive model of rock mass could be described with the characteristic that strength parameters obey different Mohr-Coulomb failure criterions under different plastic strains. This model may reflect the post-peak subsequent characteristics of rock mass and the fact that rock mass can transform from brittleness to plasticity with the increase of confining pressure. Numerical calculation is applied to simulate the triaxial compression test under different confining pressures and underground engineering example, which proves that this model has the characteristic of reflecting the damage extent of surrounding rock.

scholarly journals Influence of “X” Fracture, Confining Pressure, and Temperature on Rock Masses’ Failure Process

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Yunjuan Chen ◽  
Yi Jing ◽  
Yanchun Yin ◽  
Fuqiang Yin ◽  
Chenglong Zhao
Keyword(s):  
Crack Propagation ◽  
Similarity Theory ◽  
Failure Process ◽  
Confining Pressure ◽  
Discontinuous Deformation Analysis ◽  
Deformation Analysis ◽  
Confining Pressures ◽  
Discontinuous Deformation ◽  
Loading And Unloading ◽  
Cracking Process

Based on the similarity theory, sandstone was taken as the prototype, and rock-like specimens were made with the strength ratio of 1 : 1. Single “X” fracture and double “X” fractures were prefabricated in rock-like specimen, and crack propagation was studied through the compressive test. An improved discontinuous deformation analysis method (DDARF) was adopted to simulate on the cracking process. Further, other factors should not be ignored such as confining pressure and temperature, which were considered: rock’s crack propagations under loading and unloading with different confining pressures were studied; influences of temperature from 20°C to 300°C on crack propagation were analyzed.

scholarly journals Research on the Performance of a New External Occlusion Device for Pressure Vessel Leakage

2020 ◽  
Vol 66 (11) ◽  
pp. 668-676
Author(s):  
Hongwei Yan ◽  
Xiong Yang ◽  
Xiangrong Hou ◽  
Lu Wang ◽  
Pengcheng Li
Keyword(s):  
Pressure Vessel ◽  
Simulation Analysis ◽  
Element Model ◽  
Self Healing ◽  
Connecting Rod ◽  
Advantages And Disadvantages ◽  
Occlusion Device ◽  
New Type ◽  
The Stability ◽  
Sealing Device

Given the advantages and disadvantages of the existing plugging technology, a new type of external sealing device for pressure vessel leakage is proposed, which has the advantages of fast installation speed, small installation resistance, and stronger adaptability to the leakage surface. The connecting rod propulsion mechanism provides power, uses the fluidity of materials in the annular cavity to adapt to the complex curved surface, and carries out real-time monitoring and self-healing of the plugging process. Through the establishment of a finite element model of conventional top pressure plugging and the new type of external sac plugging method, simulation analysis of the leakage point and the pressure distribution around the crack leak has shown that: in the installation process of the new type of external liquid sac plugging device, a pressure-equalizing contact area and a sealing area are formed around the leakage point, and there is no obvious stress concentration phenomenon. When the thickness of the gasket is low, the deformation is uniform, which overcomes the problems of insufficient adaptability of the gasket in the conventional jacking method, and enhances the stability and reliability of emergency plugging.

Sign in / Sign up

Export Citation Format

Share Document