scholarly journals Theoretical Analysis on Safety Thickness of the Water-Resistant Rock Mass of Karst Tunnel Face Taking Into Account Seepage Effect

2021 ◽  
Author(s):  
Jiaqi Guo ◽  
Wenlong Wu ◽  
Xiliang Liu ◽  
Xin Huang ◽  
Zhengguo Zhu
Keyword(s):  
Rock Mass ◽  
Theoretical Analysis ◽  
Karst Tunnel ◽  
Tunnel Face ◽  
Safety Thickness

scholarly journals Theoretical Analysis of Safety Thickness of the Water-Resistant Rock Mass of Karst Tunnel Face Taking Into Account Seepage Effect

2021 ◽  
Author(s):  
Jiaqi GUO ◽  
Wenlong Wu ◽  
Xiliang Liu ◽  
Xin Huang ◽  
Zhengguo Zhu
Keyword(s):  
Rock Mass ◽  
Influencing Factors ◽  
Water Pressure ◽  
Water Inrush ◽  
Surrounding Rock ◽  
Karst Water ◽  
Seepage Force ◽  
Karst Tunnel ◽  
Tunnel Face ◽  
Safety Thickness

Abstract This paper took into account the adverse influence of the karst water seepage effect on the water-resistant rock mass. Based on the upper-bound theorem of limit analysis and the Hoek-Brown failure criterion, through a series of formula derivation, the expression of critical safety thickness of water-resistant rock mass of karst tunnel face was finally obtained. The paper carried out a feasibility analysis, an analysis of influencing factors and a comparative analysis with previous related research achievements of this method. The results showed that: (1) With the decrease of surrounding rock grade, the safety thickness of water-resistant rock mass gradually increased, and the safety thickness of surrounding rock at all grades remained within a reasonable range. (2) The safety thickness decreased as the compressive strength, the tensile strength and parameter A increased, and it increased as the karst water pressure, the tunnel excavation height, and parameter B increased. (3) The change trend of the safety thickness with the influencing factors was completely consistent under the two conditions of considering and without the seepage effect, and the safety thickness with considering the seepage force was greater than that without considering the seepage force. Taking the Yunwushan tunnel of Yiwan railway as an example, the critical safety thickness of the water-resistant rock mass was calculated and the calculated value was in good coincidence with the safety thickness adopted in the actual project. The research results are of great significance to prevent the occurrence of high pressure filling karst geological disasters such as water inrush in tunnels.

scholarly journals The Minimum Safe Thickness and Catastrophe Process for Water Inrush of a Karst Tunnel Face with Multi Fractures

Processes ◽  
2019 ◽  
Vol 7 (10) ◽  
pp. 686 ◽  
Author(s):  
Jiaqi Guo ◽  
Yuan Qian ◽  
Jianxun Chen ◽  
Fan Chen
Keyword(s):  
Rock Mass ◽  
Water Pressure ◽  
Water Inrush ◽  
Karst Water ◽  
Karst Tunnel ◽  
Tunnel Face ◽  
Measuring Point ◽  
Karst Cavity ◽  
Study Results ◽  
Safe Thickness

Water inrush of tunnel face is one of the most common geological disasters during tunnel construction in China. Aiming at the rock mass with multi fractures in water-resistant strata ahead of karst tunnel, the compressive-shear cracking property is analyzed by fracture mechanics theory and the change law of rock bridge shear strength with branch crack propagated length under karst water pressure and geo-stress is studied according to Mohr-Coulomb strength criterion. Moreover, the critical water pressure of water-resistant strata with multi fractures under tension-shear failure is deduced. The safe thickness of water-resistant strata with multi fractures ahead of karst tunnel is established based on two band theory and critical water pressure, and the influence of karst water pressure, initial crack length, crack spacing, array pitch of cracks, lateral pressure coefficient and the angle between the crack and the maximum principal stress on the minimum safe thickness of water-resistant strata are discussed. A 3 Dimension Distinct Element Code (3DEC) considering the fluid-solid coupling effect and structural characteristics of rock mass is adopted to study the catastrophe process and the influence of karst cavity scale on displacement and seepage field in water-resistant rock mass ahead of tunnel in the process of sequential excavation. The numerical simulation results show that: The transition from the single effect of unloading on the extrusion displacement of karst tunnel face to combined action of unloading and karst water pressure occurs with the tunnel face advance; The displacement at each measuring point in water-resistant strata continues to increase in the process of tunnel excavation; The extrusion displacement and water flow velocity in tunnel face suddenly increase when the water inrush pathway is about to form; With the increase of karst cavity size, the minimum thickness of water-resistant strata, the displacement of measuring point and pore pressure of crack increase. The study results provide a reference for early warning and prevention of water inrush in karst tunnel face.

scholarly journals Evolution Pattern and Matching Mode of Precursor Information about Water Inrush in a Karst Tunnel

Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1579
Author(s):  
Jie Song ◽  
Diyang Chen ◽  
Jing Wang ◽  
Yufeng Bi ◽  
Shang Liu ◽  
...  
Keyword(s):  
Rock Mass ◽  
Stress Field ◽  
Displacement Field ◽  
Water Inrush ◽  
Seepage Field ◽  
Karst Tunnel ◽  
Rock Mass Structure ◽  
Evolution Pattern ◽  
Water Blocking ◽  
Precursor Information

The water inrush of the Shangjiawan karst tunnel is used to study the evolution pattern of precursor water inrush information in water-filled caves and to further reveal the matching mode of the information. The three-dimensional numerical method FLAC3D was used to simulate the evolution process of water inrush after damage to a water-blocking rock mass structure in a water-filled cave and to obtain the evolution pattern of precursor water-inrush information caused by the damage. The results show that the multifield response to the characteristic precursor information of the water-inrush pattern after the fracture of the water-blocking rock mass follows the order of stress-field displacement-field seepage-field. Further, the matching pattern of the information shows that the stress field increased first and then decreased, the displacement field always increased, and the seepage field increased first and then decreased.

scholarly journals Dynamic Analysis for the Hydraulic Leg Power of a Powered Roof Support

Energies ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5715
Author(s):  
Dawid Szurgacz
Keyword(s):  
Rock Mass ◽  
Theoretical Analysis ◽  
Dynamic Analysis ◽  
Experimental Studies ◽  
Geological Structure ◽  
Basic Element ◽  
Bench Test ◽  
Dynamic Power ◽  
The Impact ◽  
Roof Support

This paper presents the results of a study conducted to determine the dynamic power of a hydraulic leg. The hydraulic leg is the basic element that maintains the position of a powered roof support. It is located in the structure between the canopy and the floor base. The analysis assumes that its power must be greater than the energy of the impact of the rock mass. The energy of the rock mass is generated by tremors caused mainly by mining exploitation. The mining and geological structure of the rocks surrounding the longwall complex also have an influence on this energy generation. For this purpose, stationary tests of the powered roof support were carried out. The analysis refers to the space under the piston of the leg, which is filled with fluid at a given pressure. The bench test involved spreading the leg in the test station under a specified pressure. It was assumed that the acquisition of dynamic power would be at the point of pressure and increase in the space under the piston of the leg under forced loading. Based on the experimental studies carried out, an assessment was made with the assumptions of the methodology adopted. The results of the theoretical analysis showed consistency with the experimental results.

Multiple Artificial Geothermal Cracks in a Hot Dry Rock Mass for Extraction of Heat

1985 ◽  
Vol 107 (2) ◽  
pp. 274-279 ◽  
Author(s):  
Y. Shibuya ◽  
H. Sekine ◽  
Y. Takahashi ◽  
H. Abe´
Keyword(s):  
Rock Mass ◽  
Stress Distribution ◽  
Theoretical Analysis ◽  
Boundary Conditions ◽  
Singular Integral ◽  
Inversion Formula ◽  
Singular Integral Equations ◽  
Fluid Temperature ◽  
Two Dimensional ◽  
Dimensional Theory

Theoretical analysis is made for multiple geothermal cracks. A periodic array of two-dimensional cracks is considered as a model of the multiple geothermal cracks, and is anlayzed on the basis of the two-dimensional theory of quasi-static thermo-elasticity. The singular integral equations are derived from the boundary conditions, and they are solved by applying the combination of inversion formula and collocation method. Numerical results for the fluid temperature at an outlet, the rock mass temperature, the shape of the geothermal cracks and the stress distribution around the geothermal cracks are shown in graphs.

Study on Safe Thickness of Comparatively Intact Rock Ahead of Karst Tunnel Face

2011 ◽  
Vol 90-93 ◽  
pp. 2456-2459 ◽  
Author(s):  
Jia Qi Guo ◽  
Lian Wei Ren ◽  
Xi Liang Liu
Keyword(s):  
Mechanical Model ◽  
Water Pressure ◽  
Water Inrush ◽  
Intact Rock ◽  
Tensile Fracture ◽  
Karst Tunnel ◽  
Tunnel Face ◽  
Rock Wall ◽  
Safe Thickness ◽  
Tension Strength

Under the effect of water pressure in karst cave before tunnel face, water inrush happens when excavation face enters into the minimal value of safe thickness. Aiming at comparatively intact rock ahead of karst tunnel face, rock wall often appears to be tensile fracture. With some hypotheses, a mechanical model of water inrush for tunnel face instability has been established, furthermore, the analytical expression to calculate safe thickness of rock wall has been given based on the criteria of tension strength through elastical theories. Combined with Maluqing tunnel in Yiwan line, applicability and reliability of formula is discussed.

Stability of Geotechnical Material by Safety Factor of Rock Mass Element

2012 ◽  
Vol 446-449 ◽  
pp. 1506-1509 ◽  
Author(s):  
Xiong Gang Xie ◽  
Zhao Yang Yu ◽  
Zhang Yin Dai
Keyword(s):  
Rock Mass ◽  
Theoretical Analysis ◽  
Engineering Design ◽  
Safety Factor ◽  
Factor Of Safety ◽  
Sensitivity Study ◽  
Influential Factors ◽  
Design Decision ◽  
Significant Parameter ◽  
Mass Element

In order to study the safety situation in each part of rock mass, the element safety factor Fe is introduced to estimate the micro-stability of rock mass; the equation for the element safety factor is deduced by the theoretical analysis. Rather than base an engineering design decision on a single calculated factor of safety, an approach which is frequently used to give a more rational assessment of the risks associated with a particular design is to carry out a sensitivity study. This involves a series of calculations in which each significant parameter is varied systematically over its maximum credible range in order to determine its influence upon the factor of safety. In the present paper, the element safety factor Fe is introduced to estimate the micro-stability of rock mass; the equation for the element safety factor is deduced by the theoretical analysis, and the influential factors to the element safety factor is studied.

scholarly journals Study of the mechanism of water inrush in karst tunnel based on transparent rock mass physical model test

2021 ◽  
Vol 861 (5) ◽  
pp. 052091
Author(s):  
Lijun Wang ◽  
Peng Huang ◽  
Luoyi Chen ◽  
Jian Wang ◽  
Zhilong Zheng ◽  
...  
Keyword(s):  
Rock Mass ◽  
Physical Model ◽  
Model Test ◽  
Water Inrush ◽  
Physical Model Test ◽  
Karst Tunnel
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