Energy Dissipation Analysis on Unloading Confining Pressure Failure Process of Rock Material

2012 ◽  
Vol 256-259 ◽  
pp. 398-401 ◽  
Author(s):  
Fu Jiang Chen ◽  
Hong Xia Li ◽  
Ze Qi Zhu
Keyword(s):  
Energy Dissipation ◽  
Rock Sample ◽  
Failure Process ◽  
Strain Curve ◽  
Confining Pressure ◽  
Rock Material ◽  
Test Machine ◽  
Lateral Deformation ◽  
Unloading Confining Pressure ◽  
Pressure Failure

The energy dissipation law of rock material are analyzed comprehensively by studying the energy exchange between test machine and rock sample in two typical stress-strain curve of unloading tests. The relationships between energy, deformation and confining pressure in unloading confining pressure failure process are expected to be found based on energy dissipation analysis. It shows that the energy dissipation is greatly related to the failure characteristic of rock material and confining pressure. Both two unloading tests show that energy dissipation has a nonlinear relationship with time and linear relationship with lateral deformation. The much the confining pressure is in unloading condition, the more the energy dissipation is under the same lateral deformation, and the obviously the rock sample suffers brittle failure.

scholarly journals Research on Energy Conversion and Damage Features of Unloading Instability of Sandstone under High Stress

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Zhiyuan Hou ◽  
Chuanbo Hao ◽  
Fukun Xiao ◽  
Gang Liu
Keyword(s):  
Energy Conversion ◽  
Elastic Energy ◽  
Failure Process ◽  
High Stress ◽  
Confining Pressure ◽  
Dissipated Energy ◽  
Radial Deformation ◽  
Sandstone Sample ◽  
Surplus Energy ◽  
Unloading Confining Pressure

In order to explore the failure characteristics of sandstone under unloading conditions in deep zone with high stress, constant axial pressure and unloading confining pressure tests were conducted on a yellow sandstone sample under different initial confining pressures using the French ROCK600-50 triaxial tester, and the mechanical properties, energy conversion characteristics, and damage evolution law of sandstone failure under unloading conditions were obtained. The test results showed that the axial deformation, the confining pressure for failure, and the shear fracture energy during the failure process of sandstone under the unloading state were positively correlated with the initial confining pressure; the dilatancy amount and speed and the radial deformation were negatively correlated with the initial confining pressure, exhibiting the characteristics of dilatancy under low confining pressure and compression under high confining pressure. Before the unloading point, almost all the energy absorbed by the rock under low initial confining pressure was converted into elastic energy, while part of the energy absorbed under high initial confining pressure was converted into dissipated energy, and the higher the confining pressure, the greater the proportion of the dissipated energy converted. The higher the initial confining pressure, the greater the elastic energy, radial deformation energy, and dissipated energy at the rock fracture point. The larger the unloading confining pressure, the greater the postpeak failure energy and surplus energy of sandstone, and the greater the increase in the proportion of elastic energy converted into surplus energy. The higher the confining pressure, the larger the damage value at the unloading point; the damage speed in the unloading stage was significantly greater than that in the loading stage.

scholarly journals Seepage Damage Statistical Model of Filled Fractured Rock considering Structural Surface and Failure Characteristic

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Xinyu Liu ◽  
Yuan Tian ◽  
Zhende Zhu
Keyword(s):  
Elastic Modulus ◽  
Weibull Distribution ◽  
Statistical Model ◽  
Fractured Rock ◽  
Failure Process ◽  
Strain Curve ◽  
Confining Pressure ◽  
Tensile Failure ◽  
Whole Process ◽  
Structural Surface

Damage theory studies the whole process of initiation, propagation, and instability of microcracks in materials and provides an important basis for the estimation of the risk of materials. Therefore, it is assumed that the rock microunit strength is the damage variable of the medium and obeys the Weibull distribution. According to the tensile failure characteristics of filled fractured rock under the action of seepage stress, the maximum tensile strain criterion is used to define the rock microunit strength parameters, and the equivalent elastic modulus of the fractured rock is used to establish a new damage statistical model. This paper mainly studies the rationality and feasibility of using this new constitutive model to describe the seepage failure process and damage characteristics of filled fractured rock. The results indicate that (1) the accuracy of the equivalent elastic modulus is affected by the confining pressure and the characteristics of the structural surface. In the elastic phase, using the equivalent elastic modulus, E V R H has better fit. In the plastic phase, it is better to use the E V parameter. (2) The established Weibull distribution statistical model can better calculate the stress-strain curve of fractured rocks with weak and soluble fillings. (3) The rock strength characteristics affected by different stress conditions and different filling fracture states calculated by the model are the same as the experimental data. (4) The model using equivalent elastic modulus parameters reflects the threshold characteristics of rock failure and the damage evolution process. After comparison, it is found that the model can accurately calculate the final damage value of the fractured rock with weak and soluble filling. However, the final damage value used to calculate the fractured rock of the hydraulic material filling is much higher and inaccurate.

Numerical Simulation of Compressive Experiment for Rock with a Natural Interlayer

2012 ◽  
Vol 217-219 ◽  
pp. 1389-1392
Author(s):  
Feng Shan Han ◽  
Li Song
Keyword(s):  
Numerical Simulation ◽  
Compressive Strength ◽  
Process Analysis ◽  
Failure Process ◽  
Peak Load ◽  
Strain Curve ◽  
Confining Pressure ◽  
Physical Experiment ◽  
Stress Strain Curve ◽  
Rock Failure Process

It is difficulty to make physical experiment for compressive experiment of rock with a natural interlayer I Natural interlayer affect greatly on mechanical property of rock. In this paper, Rock Failure Process Analysis Code RFPA is used to simulate influence of natural interlayer to compressive strength of rock by numerical simulation under compression. Through numerical simulation complete stress strain curve and peak load can be obtained for compressive experiment of rock with a natural interlayer. RFPA can be effectively used to investigate anisotropy of compression for rock with natural interlayer under different confining pressure. Numerical simulation show that anisotropy of compressive strength of rock with a natural interlayer varies with inclination of natural interlayer, as the confining pressure increase, the compressive strength, the plasticity and ductility increase for rock with a natural interlayer. That provides new method to analyze and investigate mechanical behavior for multilayer composite material such as rock mass with a natural interlayer，finally Index of Anisotropy for rock with a natural interlayer are put forward

scholarly journals Experimental Study on Mechanical and Acoustic Emission Characteristics of Rock Samples under Different Stress Paths

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Tao Qin ◽  
Hongru Sun ◽  
Heng Liu ◽  
Junwen Zhang ◽  
Tao Li ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Failure Mode ◽  
Shear Failure ◽  
Rock Specimen ◽  
Axial Strain ◽  
Failure Process ◽  
Confining Pressure ◽  
Stress Path ◽  
Initial Value ◽  
Unloading Confining Pressure

A series of tests on characteristics of acoustic emission have been performed on sandstone under uniaxial, conventional, and triaxial conditions and the unloading confining pressure path. The failure mode of rock specimen has been scanned by CT and a three-dimensional reconstruction was made. The differences on characteristics of AE, mechanics, and the failure mode of sandstone during the failure process under three paths are studied. The results show that the deformation of rock specimen is bigger, and axial strain and circumferential strain have a deformation platform at peak point of stress under the unloading confining pressure path. Characteristics of AE ringing are significantly affected by the confining pressure and stress path. AE ringing counts peak value, and accumulative ringing on the breaking moment as well as cumulative release energy is higher, which indicates that the rock failure is more violent under the unloading confining pressure path. The failure mode of rock specimen was dominated by shear failure under the conventional triaxial stress path. The tension failure is the main form at a lower initial value of unloading confining pressure, and the shear failure is more prominent at a higher initial value of unloading confining pressure.

Study of Deformation Rule of Ordovician Limestone in Unloading of High Confining Compress

2014 ◽  
Vol 488-489 ◽  
pp. 333-336
Author(s):  
Yu Chun Yang ◽  
Xiang Min Cheng ◽  
Guo Bin Zhao ◽  
Zhi Yong Qu ◽  
Shu Wen Chen
Keyword(s):  
Loading Condition ◽  
Rock Sample ◽  
Deformation Modulus ◽  
Strain Curve ◽  
Lateral Deformation ◽  
Bulk Deformation ◽  
Stress Strain Curve ◽  
Ordovician Limestone ◽  
Loading And Unloading ◽  
Peak Value

Under unloading condition, the characteristics of rock are different from them under loading condition. This paper talks about the characteristics of Ordovician limestone under loading and unloading condition of high compress which were taken from North Tian Mountain. The testing results indicated that: The lateral deformation and bulk deformation of rock sample are clearly in the process of unloading. Plastic deformation is not notability in the unloading condition. After the peak value in the stress-strain curve, the stress decrease quickly, it is showed that the brittleness characteristic is the better remarkable under unloading condition than loading condition. Under unloading condition, deformation modulus E50 and Possion ratio μ is quadric with the confining compress.

scholarly journals Discrete Element Simulation Analysis of Biaxial Mechanical Properties of Concrete with Large-Size Recycled Aggregate

2021 ◽  
Vol 13 (13) ◽  
pp. 7498
Author(s):  
Tan Li ◽  
Jianzhuang Xiao
Keyword(s):  
Mechanical Properties ◽  
Stress State ◽  
Strain Curve ◽  
Confining Pressure ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Aggregate Model ◽  
Large Size

Concrete made with large-size recycled aggregates is a new kind of recycled concrete, where the size of the recycled aggregate used is 25–80 mm, which is generally three times that of conventional aggregate. Thus, its composition and mechanical properties are different from that of conventional recycled concrete and can be applied in large-volume structures. In this study, recycled aggregate generated in two stages with randomly distributed gravels and mortar was used to replace the conventional recycled aggregate model, to observe the internal stress state and cracking of the large-size recycled aggregate. This paper also investigated the mechanical properties, such as the compressive strength, crack morphology, and stress–strain curve, of concrete with large-size recycled aggregates under different confining pressures and recycled aggregate incorporation ratios. Through this research, it was found that when compared with conventional concrete, under the confining pressure, the strength of large-size recycled aggregate concrete did not decrease significantly at the same stress state, moreover, the stiffness was increased. Confining pressure has a significant influence on the strength of large-size recycled aggregate cocrete.

scholarly journals Hopkinson rod test results and constitutive description of TRIP780 steel resistance spot welding material

Open Physics ◽  
2020 ◽  
Vol 18 (1) ◽  
pp. 961-967
Author(s):  
Xiaomin Li ◽  
Jianrong Zhang
Keyword(s):  
Spot Welding ◽  
Steel Strip ◽  
Strain Curve ◽  
Test Machine ◽  
Strain Rates ◽  
Test Results ◽  
Welding Material ◽  
Static Tensile ◽  
Split Hopkinson ◽  
Brittle Fractures

Abstract A quasi-static tensile test was performed on a 1.4 mm-thick TRIP780 steel strip with welding points. An MTS810 material test machine was used in the test, and a Split Hopkinson tension bar device was used in performing impact stretch loading at different strain rates. The dynamic tensile stress–strain curve of the spot welding material with different strain rates was obtained through the finely designed Hopkinson rod test, and the strain rate dependence of a TRIP780 steel spot welding material was discussed. According to the dynamic constitutive equation of the TRIP780 steel spot welding material, the test results were numerically simulated, the constitutive description and test curves were compared, and the simulation results and test results were discussed and analyzed. The fractures of the test recovery specimen were scanned with the scanning electron microscope, and the fracture mechanism of the TRIP780 steel spot welding material was explored by observing the fractures. The surfaces of the fractures surface showed obvious cleavage river patterns, and the evolution process of microcracks was determined and used in characterizing brittle fractures in specimen spot welding sample subjected to dynamic stretch loading.

Strength and Deformation Characteristics of Stabilized Silty Soil

2012 ◽  
Vol 594-597 ◽  
pp. 512-515
Author(s):  
Zheng Rong Zhao ◽  
Hong Xia Yang
Keyword(s):  
Internal Friction ◽  
Brittle Failure ◽  
Yellow River ◽  
Strain Curve ◽  
Friction Angle ◽  
Confining Pressure ◽  
Alluvial Plain ◽  
The Yellow River ◽  
Stress Strain Curve ◽  
Silty Soil

Combined with the silty soil characteristics of the Yellow River alluvial plain and the subgrade filling of Ji-He expressway, the paper discusses silty soil, stabilized silty soil strength and stress-stain characteristics through the indoor triaxial shear test. The results show that the remodeling silty soil has obvious peak, brittle failure, low residual strength after being destroyed and the stress-strain curve shows a softening type in confining pressure 100kPa lower stress level. In the confining pressure 400kPa higher stress level, soil samples peak is not obvious,mainly plastic failure and the stress-strain curve is close to a hardening type. Compared to mixed with 8% lime, stabilized silty soil of mixed with 4% cement and 4% lime shows that the partial stress peak is more obvious when destroyed and the residual strength is drastically reduced and more incline to brittle failure. In different the age, compared to mixed with 8% lime, stabilized silty soil of mixed with 4% cement and 4% lime shows that internal friction angle becomes larger and cohesion improves gradually whose amplitude is much larger than internal friction angle. Therefore, a more effective way to stabilize the silty soil of the Yellow River alluvial plain is to select silty soil mixed with 4% cement and 4% lime.

scholarly journals Energy Evolution Law of Marble Failure Process Under Different Confining Pressures Based on Particle Discrete Element Method

2021 ◽  
Vol 8 ◽  
Author(s):  
Yan-Shuang Yang ◽  
Wei Cheng ◽  
Zhan-Rong Zhang ◽  
Hao-Yuan Tian ◽  
Kai-Yue Li ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Energy Dissipation ◽  
Axial Strain ◽  
Triaxial Compression ◽  
Failure Process ◽  
Rock Failure ◽  
Biaxial Compression ◽  
Energy Evolution ◽  
Confining Pressures ◽  
Energy Dissipated

The energy dissipation usually occurs during rock failure, which can demonstrate the meso failure process of rock in a relatively accurate way. Based on the results of conventional triaxial compression experiments on the Jinping marble, a numerical biaxial compression model was established by PFC2D to observe the development of the micro-cracks and energy evolution during the test, and then the laws of crack propagation, energy dissipation and damage evolution were analyzed. The numerical simulation results indicate that both the crack number and the total energy dissipated during the loading process increase with confining pressures, which is basically consistent with the experiment results. Two damage variables were presented in terms of the density from other researchers’ results and energy dissipation from numerical simulation, respectively. The energy-based damage variable varies with axial strain in the shape of “S,” and approaches one more closely than that based on density at the final failure period. The research in the rock failure from the perspective of energy may further understand the mechanical behavior of rocks.

Composite Material of Concrete Meso-Failure Test

2010 ◽  
Vol 160-162 ◽  
pp. 135-139
Author(s):  
Ji Kun Zhao
Keyword(s):  
Dynamic Load ◽  
Main Crack ◽  
Failure Process ◽  
Strain Curve ◽  
Static Modulus ◽  
Starting Point ◽  
Beam Shear ◽  
Concrete Damage ◽  
Extension Direction ◽  
Static Modulus Of Elasticity

With static and dynamic load for the research background, this paper conducted a four-phase composite model for concrete damage test simulation of micro-mechanics. The two kinds of three-point bending beam load ware studied in case of failure process. The study found that the location of the main crack in the most disadvantaged section of beam shear in the vicinity. Crack is always along the aggregate and the mortar bond zone be extended. The main crack extension direction is always toward the load point. The main crack is showing a tortuous shape. Dynamic load and static load the stress - strain curve is basically similar shape, but basically the same as the starting point of the initial fracture. Stress wave in the sample after multiple visits, is the main reason leading to the breakdown of the sample. Dynamic load cases, the concrete elastic modulus higher than the static modulus of elasticity, numerical simulation results agree well with the experimental results.

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