scholarly journals Effects of Unidirectional In Situ Stress on Crack Propagation of a Jointed Rock Mass Subjected to Stress Wave

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Zhanfeng Fan ◽  
Jianhua Cai
Keyword(s):  
Wave Propagation ◽  
Rock Mass ◽  
Crack Propagation ◽  
Stress Wave ◽  
Large Scale ◽  
Jointed Rock ◽  
In Situ Stress ◽  
Jointed Rock Mass ◽  
Stress Wave Propagation

This paper proposes a large-scale experiment combined with multiple cement mortar blocks to simulate stress wave propagation across a jointed rock mass under unidirectional in situ stress. Two identical mortar block models with smooth, dry, and unfilled joints were poured. The stress waves in Model 1 and Model 2 were generated by an electric spark source and a blast-induced source, respectively. The effects of these two excitation sources on stress wave propagation were compared through crack propagation experiments. The experimental results show that the peak value of the transmitted strain wave decreases as the in situ stress increases. The unidirectional in situ stress has a certain inhibitory effect on the stress wave propagation. It also indicates that for Model 1 with the electric spark source, no cracks on the upper surface, but a Livingstone blasting crater at the bottom is generated. For Model 2 with the blast-induced source, cracks on the upper surface and a blasting crater at the bottom are produced. The results verify the similarity between the electric spark source and the explosive source. The two-dimensional finite element program (ANSYS/LS-DYNA) was applied to further simulate the crack propagation of a jointed rock mass under different in situ stresses. The results of numerical simulation verify that the in situ stress has a clear guiding effect on the crack propagation.

scholarly journals A Numerical Simulation of Blasting Stress Wave Propagation in a Jointed Rock Mass under Initial Stresses

2021 ◽  
Vol 11 (17) ◽  
pp. 7873
Author(s):  
Qian Dong ◽  
Xinping Li ◽  
Yongsheng Jia ◽  
Jinshan Sun
Keyword(s):  
Wave Propagation ◽  
Rock Mass ◽  
Initial Stress ◽  
Stress Wave ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Stress Waves ◽  
Initial Stresses ◽  
Stress Wave Propagation ◽  
Rock Masses

The initial stresses have a strong effect on the mechanical behavior of underground rock masses, and the initial stressed rock masses are usually under strong dynamic disturbances such as blasting and earthquakes. The influence mechanism of a blasting excavation on underground rock masses can be revealed by studying the propagation of stress waves in them. In this paper, the improved Mohr-Coulomb elasto-plastic constitutive model of the intact rock considering the initial damage was first established and numerically implemented in Universal Distinct Element Code (UDEC) based on the variation of the experimental stress wave velocity in the initial stressed intact rock, and the feasibility of combining the established rock constitutive model and the BB (Bandis-Barton) model which characterizes the nonlinear deformation of the joints to simulate stress waves across jointed rock masses under initial stress was validated by comparing the numerical and model test results subsequently. Finally, further parameter studies were carried out through the UDEC to investigate the effect of the initial stress, angle, and number of joints on the transmission of the blasting stress wave in the jointed rock mass. The results showed that the initial stress significantly changed the propagation of the stress waves in the jointed rock mass. When the initial stress was small, the transmission coefficients of the stress waves in the jointed rock were vulnerable to be influenced by the variation of the angle and the number of joints, while the effect of the angle and the number of joints on the stress wave propagation gradually weakened as the initial stress increased.

scholarly journals Influence of In-Situ Stress on the Energy Transmission of Blasting Stress Wave in Jointed Rock Mass

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Qian Dong ◽  
XinPing Li ◽  
TingTing Liu
Keyword(s):  
Rock Mass ◽  
Stress Wave ◽  
Static Load ◽  
Jointed Rock ◽  
In Situ Stress ◽  
Jointed Rock Mass ◽  
Energy Transmission ◽  
Explosive Energy ◽  
In Situ Stresses

The study of influence of in-situ stress on energy transmission of blasting stress wave in jointed rock mass is the basis for improving the utilization rate and optimizing the distribution of explosive energy in underground rock mass during blasting excavation. Thus, a model test was carried out to explore the energy transmission of blasting stress wave in jointed rock mass under different in-situ stresses, and the energy transmitting coefficients of the blasting stress wave were derived. Then, the influencing factors such as the scale and distribution of in-situ stresses and the angle and number of joints were discussed, respectively. The results showed that the energy transmission of blasting stress wave in jointed rock mass was affected by both the intact rock and joints, and the energy transmitting coefficients first increased and then decreased with the rise of static load and lateral static load coefficient, indicating that the lower in-situ stress can enhance the energy transmission of stress wave in rock mass to some extent. While the in-situ stress was relatively large, the stress wave energy dissipation in intact rock was dominant. The number and angle of joints also had a remarkable impact on the energy attenuation of the stress wave; when the stress wave was vertically incident on the joints, the energy transmitting coefficient was the largest. For underground engineering, the orientation of the dominant structural plane and the in-situ stress state of rock mass should be determined firstly, and the blasting parameters can be optimized to improve the utilization of explosive energy and achieve the designed blasting effect.

Analysis of TBM Tunnel Behavior in Jointed Rock Mass

2011 ◽  
Vol 90-93 ◽  
pp. 2033-2036 ◽  
Author(s):  
Jin Shan Sun ◽  
Hong Jun Guo ◽  
Wen Bo Lu ◽  
Qing Hui Jiang
Keyword(s):  
Rock Mass ◽  
Numerical Models ◽  
Jointed Rock ◽  
In Situ Stress ◽  
Jointed Rock Mass ◽  
Joint Orientation ◽  
Joint Spacing ◽  
Factors Affecting ◽  
Dip Angle

The factors affecting the TBM tunnel behavior in jointed rock mass is investigated. In the numerical models the concrete segment lining of TBM tunnel is concerned, which is simulated as a tube neglecting the segment joint. And the TBM tunnel construction process is simulate considering the excavation and installing of the segment linings. Some cases are analyzed with different joint orientation, joint spacing, joint strength and tunnel depth. The results show that the shape and areas of loosing zones of the tunnel are influenced by the parameters of joint sets and in-situ stress significantly, such as dip angle, spacing, strength, and the in-situ stress statement. And the stress and deformation of the tunnel lining are influenced by the parameters of joint sets and in-situ stress, too.

scholarly journals Model Test Study on Cylindrical Blasting Stress Wave Propagation across Jointed Rock Mass with Different Initial Stresses

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Qian Dong ◽  
XinPing Li ◽  
JunHong Huang
Keyword(s):  
Rock Mass ◽  
Transmission Coefficient ◽  
Stress Wave ◽  
Confining Pressure ◽  
Jointed Rock ◽  
Cylindrical Wave ◽  
Jointed Rock Mass ◽  
Initial Stresses ◽  
Stress Wave Propagation ◽  
Intact Rock Mass

In the drilling and blasting excavation of underground rock mass, the stress wave produced by the blasting holes usually propagates in the form of cylindrical wave, while the rock mass surrounding the underground engineering is initially subjected to the in situ stress. To explore the propagation and attenuation law of cylindrical stress wave in the in situ stressed rock mass, a model test of cylindrical blasting stress wave propagation across the intact and jointed rock mass under different initial stresses was carried out. First, the attenuation law of the cylindrical stress wave in the intact rock mass under different confining pressures is analysed, and then the influence of the confining pressure scales, the angle, and the number of joints on the propagation law of the cylindrical blast wave in the jointed rock mass is studied. The experimental results show that the physical attenuation of the cylindrical wave in the intact rock mass decreases and then increases as the confining pressure increases from zero. Under zero confining pressure, the transmission coefficient of the cylindrical wave in the jointed rock mass decreases with the increase of joint angle, and the transmission coefficient increases with the increase of the joint angle under confining pressure. As the confining pressure increases from zero, the transmission coefficient shows a trend of increasing firstly and then decreasing.

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