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A GOOD MESH CHARACTERISTICS IN FLAC3D CRACK
The AE cumulative energy is more suitable for determining crack strength and damage strength of coal reservoirs. studied the fracture behavior and crack propagation features of coal to evaluate the dynamic failure of coal and considered the effects of the static axial prestress and loading rate on the dynamic tensile strength and crack propagation characteristics of BD coal specimens. Water softened rocks and reduced their mechanical properties, and the tunnel model in the saturated state exhibited a lower dynamic failure rate, leading to quicker static failure. studied the rock burst in tunnel under dry and saturated conditions and investigated the influence of water contents on rock burst in tunnel. In summary, studies on the stability of horseshoe-shaped tunnel are rare, and the magnitude and direction of tectonic stress are two important factors affecting the stability of such tunnels. Hui considered dynamic testing as an impact factor behind the stability of horseshoe-shaped tunnels and studied the dynamic response of lateral blasting effect on horseshoe shape.
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The horizontal stress had a great effect on the floor heave failure, and the rock mass failure was accompanied with abnormal temperature change. investigated the floor heave and failure by the combined analyses of the acquired infrared images, video photographs, and straining field variations. The horizontal and vertical stresses influence the faults, and higher stresses are concentrated near the ends of the two faults. Islam and Shinjo used the boundary element method (BEM) to analyze the stress characteristics and deformation around the faults.
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Then, the macroscopic tensile failure occurs along the direction of the maximum principal stress. The damage section of the horseshoe-shaped tunnel starts with the meso-unit tensile. used the lateral pressure coefficient for a thorough analysis of the field of tunnel stability. To explain the meaning of the horseshoe-shaped tunnel, Li et al. In some cases in the literature, the straight wall arch section is used instead of the horseshoe section mainly because of the blindness and difficulty of modeling a horseshoe-shaped tunnel. The horseshoe-shaped tunnel is used in engineering sites, where the surrounding rock is soft, the top and side pressures are high, and the bottom is under pressure due to its superior loading capacity. In the environment of high ground stress and high geothermal heat, rocks undergo brittle-duct or brittle-plastic transformation, and the horseshoe-shaped section is widely used in deep tunnels.
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With the continuous development of economic construction, science, and technology, the development of underground space has increasingly broadened, even to the Earth’s deep interior. In addition, the orientation of the tunnel should be arranged along the maximum direction of principal stress. The direction of tectonic stress mainly reflects the orientation of the tunnel. Similarly, the magnitude of tectonic stress can significantly affect the deformation state of the tunnel. The magnitude and direction of tectonic stress greatly affect the stability of the horseshoe-shaped tunnel. Results show that the stress concentration phenomenon is easily focused on the left, right, and bottom sides of the tunnel these places should therefore be the focus of attention of tunnel stability analysis. Finally, the security support of the tunnel is discussed. The numerical model of the tunnel is built by FLAC3D, and the influence of the magnitude and direction of structural stress on the horseshoe-shaped tunnel is studied in detail. An elastic-plastic model is analyzed by complex function theory in accordance with the deformation characteristics of a horseshoe-shaped tunnel in an engineering site. While the tunnel is in the high tectonic stress environment and surrounding rock of tunnel has the characteristics of soft texture and stronger expansion, the preference of tunnel shape is horseshoe.