Local reinforcement parameter determination method for tunnel face

Abstract

The invention relates to the technical field of tunnel construction data calculation, in particular to a method for determining local reinforcement parameters of a tunnel face. According to the local reinforcement parameter determination method, reinforcement parameters such as the reinforcement range of the advance support are solved through theoretical analysis, advance reinforcement is carried out in the reinforcement range, the use amount of reinforcement materials can be reduced, the construction cost is reduced, and the good advance reinforcement effect of the soft stratum is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel construction data calculation, and in particular to a method for determining local reinforcement parameters of a tunnel face. Background Art

[0002] With the continuous expansion and improvement of the domestic railway operation network, the number of tunnel construction is increasing. Tunnel construction often encounters complex and changeable geological conditions. When the tunnel passes through soft strata, the surrounding rock of such strata is often loose and broken, with developed joints and fissures, poor stability, and a significant decrease in bearing capacity after encountering water. During the excavation process, engineering geological disasters such as water gushing, landslides, and mud bursts are prone to occur, which will not only slow down the construction progress and increase project investment, but also seriously threaten the safety of on-site construction personnel. Existing advance reinforcement measures usually involve a large-scale one-time reinforcement of the soil ahead of the excavation. The reinforcement range is difficult to control, the operation time is long, and the construction cost is high.

[0003] At present, the technical means of advanced reinforcement of tunnel faces include: surface grouting reinforcement, horizontal jet grouting pile advanced reinforcement, freezing method advanced reinforcement, etc. Among them, surface grouting reinforcement is the most widely used. As shown in the Chinese invention patent with application number 202110250136.8, surface grouting reinforcement includes the following steps: first determine the target grouting reinforcement area, set up monitoring points in the target grouting reinforcement area; then pour the grouting wall, implement advanced grouting and advanced pipe shed drilling operations, and then carry out advanced grouting construction and advanced pipe shed construction in sequence.

[0004] However, in the actual construction process, the existing advance reinforcement measures are affected by the construction environment and construction conditions, resulting in the inability to control the reinforcement range well when a large-scale advance reinforcement is carried out on the soil behind the face. This not only increases the construction time and the consumption of engineering materials, but also fails to guarantee the reinforcement quality. At the same time, most of the existing research is to optimize and improve the existing advance reinforcement measures to adapt to the complex and changeable construction environment, while there is little research on the method of determining the local reinforcement parameters of the tunnel face in soft strata.

[0005] Therefore, based on the fact that the current advance reinforcement measures for tunnel faces cannot effectively solve the demand for advance reinforcement of local weak surrounding rock at the face, the research on determining the local reinforcement parameters of tunnel faces has practical significance and engineering value. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for determining local reinforcement parameters of a tunnel face.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for determining local reinforcement parameters of a tunnel face, comprising the following steps: S1: Solve the ultimate support force of the tunnel face using the Horm tunnel face wedge sliding body analysis model; S2: Calculate the maximum tensile stress value of the fixed end beam model based on the results of S1 and the fixed end beam calculation model, and use the maximum tensile stress value as the reinforcement parameter; S3: Substitute the S2 calculation formula into , the calculation formula for the local advance reinforcement range is obtained: ; Where D is the height of the local reinforced rock mass, h is the height of the rock mass, B is the span of the tunnel face, l is the calculated length of the fixed end beam, γ is the weight of the rock mass, t is the range of local advance reinforcement, σ tmax is the maximum tensile stress value of the fixed-end beam model, [σ t ] is the ultimate tensile stress value of the reinforced soil.

[0008] The beneficial effect of the present invention is that the local reinforcement parameter determination method of the tunnel face of the present invention obtains the reinforcement range of the advance support through theoretical analysis, and advance reinforcement is carried out within the reinforcement range, which can reduce the amount of reinforcement materials used, reduce construction costs, and achieve a good advance reinforcement effect for soft strata. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a flow chart of a method for determining local reinforcement parameters of a tunnel face according to an embodiment of the present invention; Figure 2 A wedge-shaped body model diagram of an embodiment of the present invention; Figure 3 This is a force analysis diagram of a wedge-shaped body according to an embodiment of the present invention; Figure 4 A calculation model diagram of a fixed end beam according to an embodiment of the present invention; Figure 5 It is a schematic diagram of local advance reinforcement construction according to an embodiment of the present invention. DETAILED DESCRIPTION

[0010] In order to explain the technical content, achieved objectives and effects of the present invention in detail, the following is an explanation in combination with the implementation modes and the accompanying drawings.

[0011] Please refer to Figures 1 to 5 , a method for determining local reinforcement parameters of a tunnel face, comprising the following steps: S1: Solve the ultimate support force of the tunnel face using the Horm tunnel face wedge sliding body analysis model; S2: Calculate the maximum tensile stress value of the fixed end beam model based on the results of S1 and the fixed end beam calculation model, and use the maximum tensile stress value as the reinforcement parameter; S3: Substitute the S2 calculation formula into , the calculation formula for the local advance reinforcement range is obtained: ; Where D is the height of the local reinforced rock mass, h is the height of the rock mass, B is the span of the tunnel face, l is the calculated length of the fixed end beam, γ is the weight of the rock mass, t is the range of local advance reinforcement, σ tmax is the maximum tensile stress value of the fixed-end beam model, [σ t ] is the ultimate tensile stress value of the reinforced soil.

[0012] From the above description, it can be seen that the beneficial effect of the present invention is that in order to ensure the safety of tunnel construction in soft strata, it is necessary to take advance reinforcement measures on the tunnel face to ensure the stability of the soil behind the face and avoid mud and water gushing, unstable landslides and other diseases on the face. Based on the fixed end beam model, the present invention obtains the reinforcement range of the advance support through theoretical analysis, and can be combined with the local advance reinforcement method selected for the specific construction section to accurately perform advance reinforcement within the designed reinforcement range, while reducing the amount of reinforcement materials, reducing the construction cost, and achieving a good advance reinforcement effect for soft strata.

[0013] The present invention solves the reinforcement range based on the fixed end beam model, which has the following advantages: 1. The unstable rock mass behind the tunnel face in soft strata and the surrounding stable rock mass form a stable "solid end beam" advance support structure to ensure the stability of the tunnel excavation working face; 2. It can be used for advance support of tunnels in different soft strata.

[0014] Furthermore, the calculation method of the ultimate support force of the tunnel face in S1 is: ; Where q2 is the ultimate support force of the tunnel face, α is the angle of the fracture surface, B is the span of the tunnel face, D is the height of the locally reinforced rock mass, G is the deadweight of the wedge, and q1 is the weight of the overlying soil.

[0015] Furthermore, the calculation method of the wedge-shaped body's deadweight is: ; Where G is the deadweight of the wedge, γ is the weight of the rock mass, B is the span of the tunnel face, D is the height of the locally reinforced rock mass, and α is the angle of the fracture surface.

[0016] Furthermore, the calculation method of the overburden weight is: q 1 =γh ; Where q1 is the weight of the overlying soil, γ is the density of the rock mass, and h is the height of the rock mass.

[0017] Furthermore, By combining the following formulas: ; ; Among them, F x is the force in the x-axis direction, F y is the force in the y-axis direction, q2 is the ultimate support force of the tunnel face, N is the support force of the stable rock mass on the wedge-shaped sliding body, α is the angle of the fracture surface, B is the span of the tunnel face, D is the height of the locally reinforced rock mass, G is the deadweight of the wedge-shaped body, and q1 is the weight of the overlying soil.

[0018] Furthermore, the calculation method of the maximum tensile stress value of the fixed end beam model in S2 is: ; Among them, σ tmax is the maximum tensile stress value of the fixed end beam model, D is the height of the locally reinforced rock mass, h is the height of the rock mass, B is the span of the tunnel face, l is the calculated length of the fixed end beam, γ is the weight of the rock mass, and t is the range of local advance reinforcement.

[0019] Furthermore, Obtained by the following formula: ; ; ; Among them, q is the uniformly distributed load acting on the fixed end beam, B is the span of the tunnel face, q2 is the ultimate support force of the tunnel face, l is the calculated length of the fixed end beam, M + max is the maximum positive bending moment in the fixed end beam, M - max is the maximum negative bending moment in the fixed end beam, σ cmax is the maximum compressive stress value of the fixed-end beam model, σ tmax is the maximum tensile stress value of the fixed-end beam model, M max is the maximum bending moment in the fixed end beam, y max is the position of the fixed end beam farthest from the neutral axis, I z is the moment of inertia of the cross section of the fixed end beam, t is the range of local advance reinforcement, h is the height of the rock mass, and γ is the weight of the rock mass.

[0020] Furthermore, [σ t ]Confirmed through geotechnical tests and literature research.

[0021] Furthermore, [σ t ]Confirmed by geotechnical tests or literature research.

[0022] Furthermore, the calculation method of the height of the locally reinforced rock mass is: ; Where D is the height of the locally reinforced rock mass, S tunnel section is the cross-sectional area of ​​the tunnel; B is the span of the tunnel face, and its value is the same as the width of the locally reinforced rock mass.

[0023] Please refer to Figures 1 to 5 , Embodiment 1 of the present invention is: a method for determining local reinforcement parameters of a tunnel face, the steps are as follows: S1: The Horm wedge sliding body analysis model is used to solve the ultimate support force q2 of the tunnel face.

[0024] S11: Consider the fractured rock mass as a wedge-shaped body ABIJCD, such as Figure 2 The size of rectangle ABCD in the wedge-shaped model is determined according to the height and span of the tunnel section and the area equivalence principle: the width B of rectangle ABCD is the span of the tunnel section, and the height D is determined by dividing the tunnel section area by the width of the rectangle, that is: ; Among them, D is the height of the locally reinforced rock mass, S tunnel section is the cross-sectional area of ​​the tunnel; B is the span of the tunnel face, and its value is the same as the width of the locally reinforced rock mass.

[0025] S12: The wedge ABIJCD is subjected to a force analysis. It is subjected to the vertical pressure of the upper sinking soil, gravity, the support force of the inclined plane CDJI, and friction resistance. Figure 3 ; To ensure construction safety, when solving the ultimate bearing capacity of the tunnel face according to the static equilibrium condition, a conservative approach is adopted and the frictional resistance of the inclined plane CDJI to the wedge is not considered; thus, the static equilibrium equations in the x and y directions are listed as follows: ; ; Among them, F x is the force in the x-axis direction, F y is the force in the y-axis direction, q2 is the ultimate support force of the tunnel face, N is the support force of the stable rock mass on the wedge-shaped sliding body, α is the angle of the fracture surface, B is the span of the tunnel face, D is the height of the locally reinforced rock mass, G is the deadweight of the wedge-shaped body, and q1 is the weight of the overlying soil.

[0026] S13: By combining the static equilibrium equations in S12, we obtain: ; q2 is the ultimate support force of the tunnel face, α is the angle of the fracture surface, B is the span of the tunnel face, D is the height of the local reinforced rock mass, G is the deadweight of the wedge, and q1 is the weight of the overlying soil; The calculation method of the wedge's deadweight is: ; G is the deadweight of the wedge, γ is the weight of the rock mass, B is the span of the tunnel face, D is the height of the local reinforced rock mass, and α is the angle of the fracture surface; The calculation method of overlying soil weight is: q 1 =γh ; q1 is the weight of the overlying soil, γ is the density of the rock mass, and h is the height of the rock mass.

[0027] S2: Calculate the maximum tensile stress value of the fixed end beam model based on the results of S1 and the fixed end beam calculation model, and use the maximum tensile stress value as the reinforcement parameter; S21: Since the tensile strength of soil is much smaller than its compressive strength, the soil is more prone to tensile cracking. Therefore, the reinforced soil is considered approximated by the elastic model. The reinforced soil is simulated by the fixed-end beam model. The uniformly distributed load q acting on the beam is determined according to the ultimate support force q2 of the tunnel face. The size of the fixed-end beam model is determined according to the size of the wedge model. The result is: ; ; ; Among them, q is the uniformly distributed load acting on the fixed end beam, B is the span of the tunnel face, q2 is the ultimate support force of the tunnel face; l is the calculated length of the fixed end beam, which is the larger value of the width B and height D of the rectangle ABCD; S22: Based on the fixed end beam calculation model, see Figure 4 , substitute the uniformly distributed load q and the size of the fixed-end beam model, and calculate the maximum bending moment and the corresponding maximum tensile stress value of the fixed-end beam model: ; ; Among them, M + max is the maximum positive bending moment in the fixed end beam, M - max is the maximum negative bending moment in the fixed end beam, σ cmax is the maximum compressive stress value of the fixed-end beam model, σ tmax is the maximum tensile stress value of the fixed-end beam model, M max is the maximum bending moment in the fixed end beam, y max is the position of the fixed end beam farthest from the neutral axis, I zis the moment of inertia of the cross section of the fixed end beam, q is the uniformly distributed load acting on the fixed end beam, l is the calculated length of the fixed end beam, t is the range of local advance reinforcement, D is the height of the local reinforced rock mass, h is the height of the rock mass, B is the span of the tunnel face, l is the calculated length of the fixed end beam, and γ is the weight of the rock mass. S3: To ensure that the tunnel face is not unstable, the fixed end beam model does not exceed its ultimate strength when subjected to the ultimate support force of the tunnel face; that is, the maximum stress value calculated by the fixed end beam model should be less than the ultimate strength of the reinforced soil: ; ; Among them, σ cmax is the maximum compressive stress value of the fixed-end beam model, σ tmax is the maximum tensile stress value of the fixed-end beam model, [σ c ] is the ultimate compressive stress value of the reinforced soil, [σ t ] is the ultimate tensile stress value of the reinforced soil.

[0028] For general rock and soil, ; Therefore, the local advance reinforcement range and the ultimate strength of the reinforced soil must satisfy the following relationship: ; Where D is the height of the local reinforced rock mass, h is the height of the rock mass, B is the span of the tunnel face, l is the calculated length of the fixed end beam, γ is the weight of the rock mass, t is the range of local advance reinforcement, σ tmax is the maximum tensile stress value of the fixed-end beam model, [σ t ] is the ultimate tensile stress value of the reinforced soil.

[0029] S4: From S3, we can get the strength σ (t) that the rock mass should have after reinforcement. max The following relationship should be satisfied with the local advance reinforcement range t: ; Among them, σ(t) max is the maximum tensile stress value under a certain t value.

[0030] S5: According to the specific local advance reinforcement method, determine the ultimate tensile stress value [σ t ], and then combine the following two formulas to determine the final reinforcement parameters, and carry out local advance reinforcement of the soil to be reinforced to ensure construction safety. The reinforcement diagram is shown in Figure 5 ; The local advance reinforcement method adopts surface grouting or freezing method; ; .

[0031] In summary, the method for determining the local reinforcement parameters of the tunnel face provided by the present invention and the method for local advance reinforcement of the tunnel face based on the fixed end beam model determine the local reinforcement parameters in multiple steps through theoretical calculations combined with geotechnical tests or literature research, and form a stable "fixed end beam" advance support structure with the unstable rock mass behind the tunnel face in soft strata and the surrounding stable rock mass, providing a new technical idea for the advance support construction of the tunnel face in soft strata. Through theoretical analysis, the advance support reinforcement parameters of the tunnel face in soft strata are obtained, including the scope of local advance reinforcement and the strength that the rock mass should have after reinforcement. Combined with geotechnical tests or literature research, the reinforcement parameters are accurately determined in multiple steps to reduce the operation time of advance support while reducing engineering expenditures. In combination with the specific construction section, the appropriate local reinforcement method is selected from the two advance reinforcement measures of surface grouting and freezing method. Before the excavation of the tunnel face in soft strata, a stable "solid end beam" advance support structure is formed, which has a good displacement and deformation constraint effect on the unstable rock mass behind the face.

[0032] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention's specification and drawings, or directly or indirectly applied in related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for determining local reinforcement parameters of a tunnel face, characterized in that: The following steps are involved: S1: Solve the ultimate support force of the tunnel face using the Horm tunnel face wedge sliding body analysis model; S2: Calculate the maximum tensile stress value of the fixed end beam model based on the results of S1 and the fixed end beam calculation model, and use the maximum tensile stress value as the reinforcement parameter; S3: Substitute the S2 calculation formula into , the calculation formula for the local advance reinforcement range is obtained: ； Where D is the height of the local reinforced rock mass, h is the height of the rock mass, B is the span of the tunnel face, l is the calculated length of the fixed end beam, γ is the weight of the rock mass, t is the range of local advance reinforcement, σ tmax is the maximum tensile stress value of the fixed-end beam model, [σ t ] is the ultimate tensile stress value of the reinforced soil.

2. The method for determining local reinforcement parameters of a tunnel face according to claim 1, characterized in that: The calculation method of the ultimate support force of the tunnel face in S1 is: ； Where q2 is the ultimate support force of the tunnel face, α is the angle of the fracture surface, B is the span of the tunnel face, D is the height of the locally reinforced rock mass, G is the deadweight of the wedge, and q1 is the weight of the overlying soil.

3. The method for determining local reinforcement parameters of a tunnel face according to claim 2, characterized in that: The calculation method of the deadweight of the wedge is: ； Where G is the deadweight of the wedge, γ is the weight of the rock mass, B is the span of the tunnel face, D is the height of the locally reinforced rock mass, and α is the angle of the fracture surface.

4. The method for determining local reinforcement parameters of a tunnel face according to claim 2, characterized in that: The calculation method of the overburden weight is: q 1 =γh ； Where q1 is the weight of the overlying soil, γ is the density of the rock mass, and h is the height of the rock mass.

5. The method for determining local reinforcement parameters of a tunnel face according to claim 2, characterized in that: By combining the following formulas: ； ； Among them, F x is the force in the x-axis direction, F y is the force in the y-axis direction, q2 is the ultimate support force of the tunnel face, N is the support force of the stable rock mass on the wedge-shaped sliding body, α is the angle of the fracture surface, B is the span of the tunnel face, D is the height of the locally reinforced rock mass, G is the deadweight of the wedge-shaped body, and q1 is the weight of the overlying soil.

6. The method for determining local reinforcement parameters of a tunnel face according to claim 1, characterized in that: The calculation method of the maximum tensile stress value of the fixed end beam model in S2 is: ； Among them, σ tmax is the maximum tensile stress value of the fixed end beam model, D is the height of the locally reinforced rock mass, h is the height of the rock mass, B is the span of the tunnel face, l is the calculated length of the fixed end beam, γ is the weight of the rock mass, and t is the range of local advance reinforcement.

7. The method for determining local reinforcement parameters of a tunnel face according to claim 6, characterized in that: Obtained by the following formula: ; ； ； Among them, q is the uniformly distributed load acting on the fixed end beam, B is the span of the tunnel face, q2 is the ultimate support force of the tunnel face, l is the calculated length of the fixed end beam, M + max is the maximum positive bending moment in the fixed end beam, M - max is the maximum negative bending moment in the fixed end beam, σ cmax is the maximum compressive stress value of the fixed-end beam model, σ tmax is the maximum tensile stress value of the fixed-end beam model, M max is the maximum bending moment in the fixed end beam, y max is the position of the fixed end beam farthest from the neutral axis, I z is the moment of inertia of the cross section of the fixed end beam, t is the range of local advance reinforcement, h is the height of the rock mass, and γ is the weight of the rock mass.

8. The method for determining local reinforcement parameters of a tunnel face according to claim 1, characterized in that: The t ]Confirmed through geotechnical tests and literature research.

9. The method for determining local reinforcement parameters of a tunnel face according to claim 1, characterized in that: The t ]Confirmed by geotechnical tests or literature research.

10. The method for determining local reinforcement parameters of a tunnel face according to claim 1, characterized in that: The calculation method of the height of the locally reinforced rock mass is: ； Where D is the height of the locally reinforced rock mass, S tunnel section is the cross-sectional area of ​​the tunnel; B is the span of the tunnel face, and its value is the same as the width of the locally reinforced rock mass.

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