scholarly journals Multiscale effects caused by the fracturing and fragmentation of rock blocks in rock mass movement: Implications for rock avalanche propagation

2021 ◽  
Author(s):  
Qiwen Lin ◽  
Yufeng Wang ◽  
Yu Xie ◽  
Qiangong Cheng ◽  
Kaifeng Deng
Keyword(s):  
Rock Mass ◽  
Elastic Strain ◽  
Strain Energy ◽  
Mass Movement ◽  
Elastic Strain Energy ◽  
Rock Avalanche ◽  
Strain Energy Release ◽  
Rock Block ◽  
Positive Trend ◽  
Mass System

Abstract. Fracturing and fragmentation of rock blocks are important and universal phenomena during the propagation of rock avalanches. Here, the movement of a rectangular rock block characterized by different joint sets along an upper inclined and lower horizontal traveling path is simulated, aiming to quantify the fracturing and fragmentation effect of the block in propagation. The preset of the joint sets allows the block to break along the weak joint planes at the very beginning of fragmentation. With this design, the fracturing and fragmentation processes in the sliding rock block and their influences on energy transformation in the system are investigated. The results show that fragmentation can alter the horizontal velocities and kinetic energies of fragments in the block system with the front subblocks being accelerated and the rear part being obviously decelerated. Such energy conversion and transfer between the front and rear subblocks is attributed to the elastic strain energy release and transformation caused by fragmentation. The energy transfer induced by fragmentation is more efficient than that induced by collision. A positive trend between the kinetic energy increase of the front subblocks induced by fragmentation and the rock strength can be fitted well with a linear function. However, no good relationship is reached between the strain energy incremental ratio and travel distance, which implies that the fragmentation effects may be weakened with the increasing complexity of the fragmenting rock mass system. Three elastic strain wave release effects caused by rock fragmentation are further inferred and discussed based on simulation results.

scholarly journals Effect of Joint Density on Rockburst Proneness of the Elastic-Brittle-Plastic Rock Mass

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Jiliang Pan ◽  
Fenhua Ren ◽  
Meifeng Cai
Keyword(s):  
Rock Mass ◽  
Elastic Strain ◽  
Strain Energy ◽  
Elastic Strain Energy ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Joint Density ◽  
Dissipated Energy ◽  
Uniaxial Compression Test ◽  
Plastic Rock

The prediction of rockburst proneness is the basis of preventing and controlling rockburst disasters in rock engineering. Based on energy theory and damage mechanics, the quantitative functional relationship between joint density and energy density was derived. Then, the theoretical results were verified by numerical simulation and uniaxial compression test, and the effect of joint density on rockburst proneness of the elastic-brittle-plastic rock mass was discussed. The results show that the relationship between the joint density and the dissipated energy index of the jointed rock mass is a logarithmic function. With the same total input energy, the higher the joint density, the more the damage dissipation energy. Even in the case of high joint density, the rock mass still has limited resistance to external failure. Under the same joint density, the strength of parallel jointed rock mass is better than that of the cross-jointed rock mass, and the parallel jointed rock mass can accumulate more elastic strain energy and has higher rockburst proneness. The joint density is closely related to the ability of the rock mass to store high strain energy. The higher the joint density is, the weaker the ability to accumulate the elastic strain energy of rock mass is and the lower the rockburst proneness is. It is helpful to predict rockburst proneness by investigating and studying the properties of geological discontinuities. The research results have some theoretical and engineering guiding significance for the prediction of rockburst proneness of the jointed rock mass.

scholarly journals Stability Analysis of Water-Resistant Strata in Karst Tunnel Based on Releasable Elastic Strain Energy

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Qin Liu ◽  
Lai Wei ◽  
Jianxun Chen ◽  
Yanbin Luo ◽  
Pei Huang ◽  
...  
Keyword(s):  
Rock Mass ◽  
Elastic Strain ◽  
Strain Energy ◽  
Elastic Strain Energy ◽  
Instability Criterion ◽  
Distribution Law ◽  
Critical Instability ◽  
Concealed Karst Cave ◽  
Rock Mass Failure ◽  
Energy Instability

In this paper, the energy instability criterion of water-resistant strata and rock mass failure index (RMFI) are proposed, respectively, based on releasable elastic strain energy Ue. RMFI is employed to represent the damage extent of water-resistant strata. When RMFI<1.0, rock mass is stable. When RMFI=1.0, rock mass is in the critical instability state. When RMFI>1.0, rock mass is unstable. The releasable elastic strain energy Ue and RMFI program is performed by FISH programming language of Flac3D software. Then, the authors apply Flac3D software to analyze the distribution law of releasable elastic strain energy Ue and failure zone under different width of concealed karst cave. Finally, combined with the numerical analysis, a case study is carried out to illustrate the rationality, effectiveness, and feasibility through using RMFI to predict safe thickness of water-resistant strata.

Numerical Simulation Study on the Delay of Rockburst Based on Rock Mass Stress Release Rate

2014 ◽  
Vol 501-504 ◽  
pp. 20-26 ◽  
Author(s):  
Cheng Lin Yao ◽  
Jie Chen ◽  
Li Peng Liu
Keyword(s):  
Numerical Simulation ◽  
Rock Mass ◽  
Energy Distribution ◽  
Release Rate ◽  
Elastic Strain ◽  
Strain Energy ◽  
Elastic Strain Energy ◽  
Simulation Software ◽  
Stress Release ◽  
Shear Field

Rockburst is a phenomenon of geological hazard due to excavation in brittle rockmass of high in-situ stress which endanger to the engineers and construction equipments with unexpectedly damaged. At present, researchers and engineers mainly concentrate to the requirement of rockburst and whether to arise. Although the delay characteristic of rockburst (DCR) has been realized and recorded, but the knowledge of the mechanism of this feature is insufficient. In the paper, the delay characteristic was researched from the stress release rate (SRR) of the excavation rock mass using the numerical simulation software. Firstly, using the core replacement technique, the relation of the SRR and core modulus reduction (CMR) was determined. Secondly, the mechanism of the DCR was analyzed from the elastic strain energy distribution and the plastic strain energy distribution in the different SRR. Finally, the plastic field shape and range under different SRR was contrasted and analyzed. Conclusions can be drawn as follows: with the increase of CMR value, the SRR shows increase trend in the form of exponent. In the process of excavation, the rockmass elastically deform under the low SRR value. When the SRR value equals certain degree, the portion of rockmass will be plastic field and behind the plastic region there will be arise a elastic strain energy centralized phenomenon. Under the different the SRR value, the field style change to the tension-shear field from the shear field in the rock mass and the rockburst rank obviously different.

scholarly journals Brittle Characteristic and Microstructure of Sandstone under Freezing-Thawing Weathering

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Songtao Yu ◽  
Junren Deng ◽  
Hongwei Deng ◽  
Feng Gao ◽  
Jielin Li
Keyword(s):  
Elastic Modulus ◽  
Energy Release Rate ◽  
Release Rate ◽  
Elastic Strain ◽  
Strain Energy ◽  
Strain Energy Release Rate ◽  
Elastic Strain Energy ◽  
Strain Energy Release ◽  
Peak Stress ◽  
Brittleness Index

As an important property of rock material, brittleness plays a vital role in rock engineering. This paper raised the concept of elastic strain energy release rate and proposed an elastic strain energy release rate based brittleness index based on the most acceptable definition of brittleness. Mechanical and Nuclear Magnetic Resonance parameters of sandstone under various Freezing-Thawing (F-T) cycles are also acquired and analyzed. Then, the proposed brittleness index is used to compare with two recently proposed brittleness indices to verify its correctness and applicability. Finally, the brittleness index is applied to evaluate the brittle behavior of F-T cycles treated sandstone under uniaxial compression. The results show that elastic modulus, value of the postpeak modulus, and peak stress decrease with F-T cycles, and the porosity and microstructure develop with F-T cycles. The proposed brittleness index is highly related to F-T cycles, peak stress, porosity, and elastic modulus of sandstone that suffered recurrent F-T cycles. It declines exponentially with F-T cycles and porosity increase while growing exponentially with peak stress and elastic modulus increase.

scholarly journals A New Bursting Liability Evaluation Index for Coal –The Effective Elastic Strain Energy Release Rate

Energies ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3734
Author(s):  
Zhiguo LU ◽  
Wenjun JU ◽  
Fuqiang GAO ◽  
Youliang FENG ◽  
Zhuoyue SUN ◽  
...  
Keyword(s):  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Elastic Strain ◽  
Strain Energy ◽  
Strain Energy Release Rate ◽  
Elastic Strain Energy ◽  
Strain Curve ◽  
Strain Energy Release ◽  
Stress Strain Curve

Because both faults and cleats exist in coal, sharp stress drops occur during loading when coal is deformed. These drops occur during the pre-peak stage and are accompanied by sudden energy releases. After a stress drop, the stress climbs slowly following a zigzag path and the energy accumulated during the pre-peak stage is unstable. A stress–strain curve is the basic tool used to evaluate the bursting liability of coal. Based on energy accumulation in an unsteady state, the pre-peak stress–strain curve is divided into three stages: pre-extreme, stress drop, and re-rising stage. The energy evolution of the specimen during each stage is analyzed. In this paper, an index called the effective elastic strain energy release rate (EESERR) index is proposed and used to evaluate the coal’s bursting liability. The paper shows that the propagation and coalescence of cracks is accompanied by energy release. The stress climb following a zigzag path prolongs the plastic deformation stage. This causes a significant difference between the work done by a hydraulic press during a laboratory uniaxial compression experiment and the elastic strain energy stored in the specimen during the experiment, so the evaluation result of the burst energy index would be too high. The determination of bursting liability is a comprehensive evaluation of the elastic strain energy accumulated in coal that is released when the specimen is damaged. The index proposed in this paper fully integrates the energy evolution of coal samples being damaged by loading, the amount of elastic strain energy released during the sample failure divided by the failure time is the energy release rate. The calculation method is simplified so that the uniaxial compressive strength and elastic modulus are included which makes the new index more universal and comprehensive. Theoretical analysis and physical compression experiments validate the reliability of the evaluation.

Elastic strain energy release from fragmenting grains: Effects on fault rupture

2012 ◽  
Vol 38 ◽  
pp. 265-277 ◽  
Author(s):  
Timothy R.H. Davies ◽  
Mauri J. McSaveney ◽  
Carolyn J. Boulton
Keyword(s):  
Energy Release ◽  
Elastic Strain ◽  
Strain Energy ◽  
Elastic Strain Energy ◽  
Strain Energy Release ◽  
Fault Rupture
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