Method for determining outburst prevention thickness and critical water pressure of tunnel excavation on hanging wall of fault

Abstract

This invention discloses a method for determining the anti-outburst thickness and critical water pressure during tunnel excavation on the hanging wall of a fault. The invention primarily involves first calculating the geometric relationship between the dimensions of the tunnel's failure surface on the hanging wall of the fault, then calculating the external force power of the fault water pressure and the internal energy dissipation power of the surrounding rock, and finally determining the critical water pressure at which the fault experiences water inrush failure when the external force power equals the internal energy dissipation power, given the known distance between the tunnel excavation and the fault; or determining the critical anti-outburst thickness of the tunnel at the fault distance when the fault water pressure is known. This invention provides a calculation method for determining the critical water pressure and critical anti-outburst thickness at the tunnel face during water inrush failure on the hanging wall of a fault. Based on this, it is possible to evaluate whether water inrush will occur during tunnel excavation on the hanging wall of a fault, whether the anti-outburst thickness meets the requirements, and to provide a basis for remedial measures such as drainage and pressure reduction, and grouting reinforcement. For example, under high water pressure, reducing the water pressure to below the critical water pressure; or grouting to increase the strength of the surrounding rock itself, can effectively prevent water inrush. Simultaneously, the method of this invention can determine the critical anti-outburst thickness and critical water pressure for tunnel excavation on the hanging wall under different fault dip angles.

Description

Technical Field

[0001] This invention belongs to the field of tunnel inrush water and mud damage evaluation and prevention technology, specifically involving a method for determining the anti-outrush thickness and critical water pressure during tunnel excavation on the hanging wall of a fault. Background Technology

[0002] Faults are a common geological feature encountered during tunnel and underground engineering construction, especially fault fracture zones. Construction in water-rich or underwater fault fracture zones frequently results in water inrushes and mudslides, causing significant losses to the project. Therefore, research on water inrushes in tunnel faults has substantial engineering significance and scientific value.

[0003] Currently, most methods for determining the anti-outburst thickness of tunnel faults for water inrush are based on numerical simulation or empirical formulas. There is very little research on the anti-outburst thickness and critical water pressure of underwater or high-pressure water-rich tunnel faults. Existing literature and patents mostly analyze the measures taken for specific fault tunnels, but fail to provide a theoretical analytical method. Summary of the Invention

[0004] The purpose of this invention is to provide a method for determining the anti-water inrush thickness and critical water pressure during tunnel excavation on the hanging wall of a fault. This invention can determine whether a water inrush is likely to occur in a tunnel fault and whether the anti-water inrush thickness meets the requirements. It also provides a theoretical basis for remedial measures such as grouting reinforcement and water drainage to reduce pressure. For example, under high water pressure, reducing the water pressure to below the critical water pressure; or grouting to increase the strength of the surrounding rock can effectively prevent water inrush. Furthermore, the method of this invention can determine the critical anti-water inrush thickness and critical water pressure during tunnel excavation on the hanging wall under different fault dip angles.

[0005] The method for determining the anti-outburst thickness and critical water pressure during tunnel excavation on the hanging wall of a fault according to the present invention includes the following steps in sequence: (1) The geometric relationship between the dimensions of the tunnel failure surface on the hanging wall of the fault is determined as follows: ; ; ; ; ; ; ; In the formula: L OJ D is the length between points O and J; D is the tunnel excavation height. φ The internal friction angle of the surrounding rock; L KJ The length between points K and J is the anti-collision thickness. LOE This is the length between points O and E; a The fault dip angle; L JE Let J be the length between points J and E; L OF The length between points O and F; L JF The length between points J and F; L BE The length between points B and E; L AF The distance between points A and F is the length. (2) External force power of fault water pressure: ; In the formula: W is the external force power of the fault water pressure; P W This refers to the fault water pressure. v 0 represents the discontinuous velocity at the fracture surface; (3) The energy dissipation power within the surrounding rock is: ; In the formula: E D This refers to the energy dissipation power within the surrounding rock. c The cohesion of the surrounding rock; (4) According to the principle of energy conservation, the power of the fault water pressure external force is equal to the power of energy dissipation within the surrounding rock: ; ; ; (5) Critical head height: ; In the formula: H W This is the critical head height; It is the density of water.

[0006] Compared with existing technologies and research methods, this invention has the following advantages: Currently, most methods for determining the anti-outburst thickness of tunnel faults for water inrush are based on numerical simulation or empirical formulas. There is very little research on the anti-outburst thickness and critical water pressure of underwater or high-pressure water-rich tunnel faults. Existing literature and patents mostly analyze the measures taken for specific fault tunnels, but fail to provide a theoretical analytical method.

[0007] This method is applicable to fault dip angles. a With anti-penetration thickness L KJ Given the given information, the critical fault water pressure P at which a tunnel on the hanging wall of the fault fails due to water inrush can be calculated.W and its corresponding critical head height H W ; or at fault water pressure P W With fault dip angle a Given the information, the critical anti-outburst thickness for tunnel failure due to water inrush on the hanging wall of the fault can be calculated. L KJ And it can determine different fault dip angles. a The critical anti-outburst thickness and critical water pressure of the upper tunnel excavation.

[0008] This invention provides a calculation method for determining the anti-water inrush thickness and critical water pressure during tunnel excavation on the hanging wall of a fault. Based on this method, it is possible to determine whether a tunnel will experience water inrush and whether the anti-water inrush thickness meets the requirements. It also provides a theoretical basis for remedial measures such as water drainage and pressure reduction, and grouting reinforcement. For example, under high water pressure, reducing the water pressure to below the critical water pressure, or grouting to increase the strength of the surrounding rock, can effectively prevent water inrush. Furthermore, the method of this invention can determine the critical anti-water inrush thickness and critical water pressure during tunnel excavation on the hanging wall under different fault dip angles.

[0009] The method of this invention can also be applied to determining whether water will burst at water-rich faults in underground structures such as mining roadways and hydraulic tunnels, as well as determining the critical water pressure and critical anti-burst thickness. Attached Figure Description

[0010] Figure 1 This is a schematic diagram illustrating the principle of the method of the present invention.

[0011] Figure 2 This is a graph showing the relationship between different anti-surge thicknesses and critical water pressure and critical head height in an embodiment of the present invention.

[0012] Figure 3 This is a graph showing the relationship between the anti-outburst thickness and the critical head height under different fault dip angles in embodiments of the present invention.

[0013] Figure 4 This is a graph showing the relationship between the fault dip angle and the critical head height when the anti-outburst thickness is 5m according to an embodiment of the present invention.

[0014] Figure 5 This is a graph showing the relationship between the fault dip angle and the critical anti-outburst thickness when the water head height is 30m in an embodiment of the present invention.

[0015] In the diagram, D represents the tunnel excavation height; H represents the tunnel burial depth. φ H is the internal friction angle of the surrounding rock; W This is the critical head height; P W This refers to the fault water pressure. a The fault dip angle; v 0 represents the intermittent velocity on the fracture surface. Implementation

[0016] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0017] See Figure 1 This is a schematic diagram illustrating the principle of the method for determining the anti-outburst thickness and critical water pressure during tunnel excavation on the hanging wall of a fault according to the present invention.

[0018] First, based on the tunnel project overview, surrounding rock grade, fault occurrence, and water level, relevant parameters are obtained, such as the surrounding rock cohesion c and the internal friction angle of the surrounding rock mentioned above. φ Tunnel excavation height D, fault dip angle a Anti-protrusion thickness L KJ wait.

[0019] The specific calculation steps are as follows: Step 1: Determine the geometric relationship between the dimensions of the tunnel failure surface on the hanging wall of the fault as follows: ; ; ; ; ; ; ; In the formula: L OJ D is the length between points O and J; D is the tunnel excavation height. φ The internal friction angle of the surrounding rock; L KJ The length between points K and J is the anti-collision thickness. L OE This is the length between points O and E; a The fault dip angle; L JE Let J be the length between points J and E; L OF The length between points O and F; L JF The length between points J and F; L BE The length between points B and E; L AF The distance between points A and F is the length. Step 2: External force power of fault water pressure: ; In the formula: W is the external force power of the fault water pressure;P W The fault water pressure; v 0 represents the discontinuous velocity at the fracture surface; Step 3: The energy dissipation power within the surrounding rock is: ; In the formula: E D This refers to the energy dissipation power within the surrounding rock. c For the cohesion of the surrounding rock; Step 4: Based on the principle of energy conservation, the power of the external force of fault water pressure is equal to the power of energy dissipation within the surrounding rock. ; ; ; Step 5: Critical head height: ; Where: H W This is the critical head height; It is the density of water.

[0020] The above equation is an explicit equation, which is relevant to the cohesion of the surrounding rock. c The internal friction angle of the surrounding rock is 100 kPa. φ The angle is 25º, the tunnel excavation height D is 7m, and the fault dip angle is... a The specific gravity of water is 60º. 10kN / m 3 Based on the above steps, the critical water pressure and critical head height for different anti-outburst thicknesses can be obtained, such as... Figure 2 As shown. Further calculations can be made to determine the anti-outburst thickness and critical water head height at different fault dip angles, such as... Figure 3 As shown. Further, the relationship between the fault dip angle and the critical hydraulic head height when the anti-outburst thickness is 5m can be obtained, as shown below. Figure 4 As shown. Further, the relationship between the fault dip angle and the critical anti-outburst thickness when the water head is 30m can be obtained, as follows: Figure 5 As shown in the figure, it can be seen that as the thickness of the anti-outburst layer increases, both the critical water pressure and the critical head height increase, and the gradient becomes larger and larger; at a certain head height, as the fault dip angle increases, the critical anti-outburst thickness gradually decreases; at a certain anti-outburst thickness, as the fault dip angle increases, the critical head height gradually increases.

Claims

1. A method for determining the anti-outburst thickness and critical water pressure during tunnel excavation on the hanging wall of a fault, characterized in that... The steps include the following sequence: (1) The geometric relationship between the dimensions of the tunnel failure surface on the hanging wall of the fault is determined as follows: ； ； ； ； ； ； ； In the formula: L OJ D is the length between points O and J; D is the tunnel excavation height. φ The internal friction angle of the surrounding rock; L KJ The length between points K and J is the anti-collision thickness. L OE This is the length between points O and E; a The fault dip angle; L JE Let J be the length between points J and E; L OF The length between points O and F; L JF The length between points J and F; L BE The length between points B and E; L AF The distance between points A and F is the length. (2) External force power of fault water pressure: ； In the formula: W is the external force power of the fault water pressure; P W This refers to the fault water pressure. v 0 represents the discontinuous velocity at the fracture surface; (3) The energy dissipation power within the surrounding rock is: ； In the formula: E D This refers to the energy dissipation power within the surrounding rock. c The cohesion of the surrounding rock; (4) According to the principle of energy conservation, the power of the fault water pressure external force is equal to the power of energy dissipation within the surrounding rock: ； ； ； (5) Critical head height: ； In the formula: H W This is the critical head height; The specific gravity of water; At the fault dip angle a With anti-penetration thickness L KJ Given the given information, the critical fault water pressure P at which a tunnel on the hanging wall of the fault fails due to water inrush can be calculated. W and its corresponding critical head height H W ; or at fault water pressure P W With fault dip angle a Given the information, the critical anti-outburst thickness for tunnel failure due to water inrush on the hanging wall of the fault can be calculated. L KJ， And it can determine different fault dip angles a The critical anti-outburst thickness and critical water pressure of the upper tunnel excavation.

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