scholarly journals Three-Dimensional Numerical Investigation of Coupled Flow-Stress-Damage Failure Process in Heterogeneous Poroelastic Rocks

Energies ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 1923 ◽  
Author(s):  
Shikuo Chen ◽  
Chenhui Wei ◽  
Tianhong Yang ◽  
Wancheng Zhu ◽  
Honglei Liu ◽  
...  
Keyword(s):  
Rock Mass ◽  
Flow Stress ◽  
Failure Mechanism ◽  
Hydraulic Properties ◽  
Failure Process ◽  
Three Dimensional ◽  
Permeability Evolution ◽  
Heterogeneous Rocks ◽  
Hydraulic Conditions ◽  
Stress Damage

The failure mechanism of heterogeneous rocks (geological materials), especially under hydraulic conditions, is important in geological engineering. The coupled mechanism of flow-stress-damage should be determined for the stability of rock mass engineering under triaxial stress states. Based on poroelasticity and damage theory, a three-dimensional coupled model of the flow-stress-damage failure process is studied, focusing mainly on the coupled characteristics of permeability evolution and damage in nonhomogeneous rocks. The influences of numerous mesoscale mechanical and hydraulic properties, including homogeneity, residual strength coefficient, loading rates, and strength criteria, on the macro mechanical response are analyzed. Results reveal that the stress sensitive factor and damage coefficient are key variables for controlling the progress of permeability evolution, and these can reflect the hydraulic properties under pre-peak and post-peak separately. Moreover, several experiments are conducted to evaluate the method in terms of permeability evolution and failure process and to verify the proposed two-stage permeability evolution model. This model can be used to illustrate the failure mechanics under hydraulic conditions and match different rock types. The relation of permeability with strain can also help confirm appropriate rock mass hydraulic parameters, thereby enhancing our understanding of the coupled failure mechanism in rock mass engineering.

Three-Dimensional Micro Flow-Stress-Damage (FSD) Model and Application in Hydraulic Fracturing in Brittle and Heterogeneous Rocks

2010 ◽  
Vol 452-453 ◽  
pp. 581-584 ◽  
Author(s):  
G. Li ◽  
C.A. Tang ◽  
L.C. Li
Keyword(s):  
Flow Stress ◽  
Damage Mechanics ◽  
Process Analysis ◽  
Failure Process ◽  
Numerical Code ◽  
Mesoscopic Scale ◽  
Fracture Development ◽  
Heterogeneous Rocks ◽  
Stress Dependent ◽  
Stress Damage

In order to investigate the hydraylic fracture development of the specimens and simulate the cracks drived by fluid flow in rocks, a flow-stress-damage (FSD) model, implemented with parallel Rock Failure Process Analysis code (parallel -RFPA3D), is presented. The numerical code is based on linear elastic damage mechanics on mesoscopic scale and FEM. For simulating the complete progressive 3D failure and macroscopic mechanical behaviors of rock materials, rock properties such as elastic constants, peak strength, and poisson ratio are randomly distributed to reflect the initial random distributed weakness in mesoscopic scale. The FSD model is used to represent the permeability variation at the two stages, that is stress-dependent permeability for pre-failure and deformation-dependent permeability for post-peak stage of rock at the elemental scale. The results of the simulation with 680,000-element cylindrical rock specimen coincide well with reported experimental results and the process of crack from initiation to the instability extensions is captured vividly. The results and the process indicate that the FSD model works well and parallel-RFPA3D incorporated with FSD model is a valid tool of understanding the physical essence of the evolution of fracture with large-scale elements and fluid flows in rocks.

scholarly journals Investigating the Failure Mechanism of Jointed Rock Slopes Based on Discrete Element Method

2020 ◽  
Vol 2020 ◽  
pp. 1-19
Author(s):  
Chao Peng ◽  
Qifeng Guo ◽  
Zhenxiong Yan ◽  
Minglong Wang ◽  
Jiliang Pan
Keyword(s):  
Rock Mass ◽  
Failure Mechanism ◽  
Failure Process ◽  
Structural Complexity ◽  
Jointed Rock ◽  
Research Area ◽  
Open Pit ◽  
Particle Model ◽  
Rock Slopes ◽  
Synthetic Rock

This paper presents a comprehensive engineering method to investigate the failure mechanism of the jointed rock slopes. The field geology survey is first carried out to obtain the slope joint data. A joint network model considering the structural complexity of rock mass is generated in the PFC software. The synthetic rock mass (SRM) approach for simulating the mechanical behavior of jointed rock mass is employed, in which the flat-jointed bonded-particle model (FJM) and smooth joint contact model (SJM) represent intact rock and joints, respectively. Subsequently, the effect of microparameters on macromechanical properties of rock is investigated for parameter calibration. Moreover, the scale effect is analyzed by multiscale numerical tests, and the representative elementary volume (REV) size in the selected research area is found as 16 m × 16  m × 16 m. The microparameters of the SRM model are calibrated to match the mechanical properties of the engineering rock mass. Finally, an engineering case from Shuichang open-pit mine is analyzed and the failure process of the slope during the excavation process from micro- to macroscale is obtained. It has been found that failure occurs at the bottom of the slope and gradually develops upwards. The overall failure of the slope is dominated by the shallow local tension fracture and wedge failure.

scholarly journals Experimental and Numerical Investigation on C/SiC Composite Z-Pinned/Bonded Hybrid Single-Lap Joints

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1130
Author(s):  
Yao Wang ◽  
Xiaodong Wang ◽  
Zhidong Guan ◽  
Jifeng Xu ◽  
Xia Guo
Keyword(s):  
Failure Mechanism ◽  
Composite Structures ◽  
Mechanical Performance ◽  
Failure Process ◽  
Three Dimensional ◽  
Discrete Distribution ◽  
Lap Joints ◽  
Single Lap Joints ◽  
Load Peak ◽  
Two Peaks

Z-pinned/bonded joints are great potential connection components that have been used in the 2D C/SiC composite structures; however, the hybrid joints present complex failure mechanism considering the secondary deposited SiC matrix in the clearance. Therefore, the mechanical performance and failure mechanism of the joints are investigated through experimental and numerical methods in this paper. Experiment results show that two peaks exist in the load–displacement curves. The first load peak is 2891–4172 N with the corresponding displacement of 0.10–0.15 mm, and the second load peak is 2670–2919 N with the corresponding displacement of 0.21–0.25 mm. Besides that, the secondary deposited SiC matrix exhibits discrete distribution, and it has significant effects on the failure mechanism. Validated by experimental data, the proposed three-dimensional numerical model based on modified Hashin’s criterion and fastener element can predict the mechanical performance and failure process. The numerical results indicate that the first load peak is dominated by the deposited SiC matrix near the edge, while the second peak is dominated by the z-pin and the SiC matrix near the z-pin. Moreover, the effects of the deposited SiC matrix’s strength and distribution are discussed, which is meaningful to the optimal design of C/SiC composite z-pinned/bonded hybrid single-lap joints.

Investigations of Hydraulic Properties in Crystalline Rock.

1983 ◽  
Vol 26 ◽  
Author(s):  
Leif Carlssn ◽  
Anders Winberg ◽  
Björn Rosander
Keyword(s):  
Rock Mass ◽  
Hydraulic Conductivity ◽  
Hydraulic Properties ◽  
Water Injection ◽  
Three Dimensional ◽  
Crystalline Rock ◽  
Fracture Frequency ◽  
Effective Hydraulic Conductivity ◽  
Constant Head ◽  
Total Fracture

ABSTRACTHydraulic properties of crystalline rock from four potential repository sites in Sweden were analysed. The hydraulic conductivity of the bedrock was established by means of transient water-injection tests with constant head conducted in 25 m sections. The bedrock at the sites was divided into different hydraulic units. An effective hydraulic conductivity was calculated for the rock mass at each site. This was done on the basis of the frequency distribution of all measured values within this unit. A log-nornal distribution was found to fit the data reasonably well. Regression analysis of hydraulic conductivity as a function of depth indicated similar relationships between the four sites. At a depth of 500 m the effective hydraulic conductivity for three-dimensional flow was about 5.10-11 m/s.The fracture frequency of the sites was established from existing core-logs. At depths of about 500 m the mean fracture frequency of the rock mass at the four sites was 1.8-2.5 fractures per meter. Of this total fracture frequency only a a certain proportion is considered to be hydraulically conductive. This proportion was established from results of hydraulic tests perforned in 2 or 3 m sections. Results obtained indicated a frequency of hydraulically conductive fractures of 0.1-0.3 fractures per meter in the rock mass at depths below 300 m.

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