Method for obtaining reinforcement parameters of glass fiber bars for soft soil tunnel face

Abstract

The present invention discloses a method for obtaining the reinforcement parameters of glass fiber bars for the face of a soft soil tunnel, including: constructing a three-dimensional model of the tunnel and its surrounding rock in the natural state; conducting simulated excavation and calculating the reinforcement parameter I of the glass fiber bars required when the safety factor of the face reaches a set value; conducting on-site tests to monitor the maximum extrusion deformation and the deformation influence depth at the center position of the tunnel face caused by each excavation cycle; back-calculating the mechanical parameter II of the surrounding rock from the maximum extrusion deformation of the face measured in each excavation cycle in the test section, keeping the length of the glass fiber bars unchanged, and recalculating the reinforcement parameter II of the glass fiber bars required when the safety factor of the face reaches the set value; conducting simulated excavation and calculating the maximum extrusion displacement and the safety factor of the face corresponding to the glass fiber bars with different remaining lengths on the face in each excavation cycle during the excavation process; determining the optimal lap length of the glass fiber bars during the construction process, and considering both safety and economy in the design of the reinforcement parameters.

Description

Technical Field

[0001] The present invention belongs to the technical field of soft soil tunnel construction, and more specifically, the present invention relates to a method for obtaining glass fiber reinforcement parameters of a soft soil tunnel face. Background Art

[0002] At present, most of the tunnels in my country are constructed using the New Austrian Tunneling Method (NATM), which is mainly based on the flexible support system of anchor shotcrete, emphasizing timely support after excavation to give full play to the self-bearing capacity of the surrounding rock. However, the New Austrian Tunneling Method (NATM) ignores the control effect of the tunnel's advanced core soil on tunnel deformation, so the New Austrian Tunneling Method is often difficult to construct in soft soil. The rock and soil deformation control method (New Method) emphasizes maintaining the stability of the tunnel face by improving and reinforcing the advanced core soil of the tunnel face, and then excavating a large section to improve construction efficiency.

[0003] However, when reinforcing the face, if a large number of glass fiber bars are used, the investment cost will increase and the construction efficiency will be reduced. If the glass fiber used is short and the number is small, it will be detrimental to construction safety. At present, the cost of pre-reinforcement of the face in the industry is at a relatively high level, and the time spent on face reinforcement is relatively long, the construction efficiency is relatively low, and it is not conducive to resource conservation and environmental protection. Summary of the invention

[0004] The present invention provides a method for obtaining parameters of reinforced glass fiber bars for a soft soil tunnel face, aiming to improve the above-mentioned problem.

[0005] The present invention is implemented as follows: a method for obtaining glass fiber reinforcement parameters of a soft soil tunnel face, the method specifically comprising the following steps:

[0006] S1. Construct a three-dimensional model of the tunnel and its surrounding rock in its natural state;

[0007] S2. Conduct simulated excavation and calculate the reinforcement parameter I of the glass fiber reinforcement required when the safety factor F1 of the tunnel face reaches the set value;

[0008] S3. Field tests were conducted based on the reinforcement parameters of glass fiber reinforcement I. Multiple excavation cycles were tested to monitor the maximum extrusion deformation d at the center of the tunnel face caused by each excavation cycle. i And deformation influence depth D i ;

[0009] S4. The maximum extrusion deformation of the tunnel face measured in each excavation cycle in the test section is d i Inverse the mechanical parameters of the surrounding rock II, keep the length L1 of the glass fiber reinforcement unchanged, and recalculate the reinforcement parameters II of the glass fiber reinforcement required when the safety factor of the tunnel face reaches the set value based on the mechanical parameters of the surrounding rock II;

[0010] S5. Conduct simulated excavation based on the reinforcement parameter Ⅱ of glass fiber bars, and calculate the maximum extrusion displacement and safety factor of the tunnel face corresponding to the glass fiber bars with different remaining lengths in each excavation cycle during the excavation process based on the mechanical parameters Ⅱ of the surrounding rock.

[0011] S6. Determine the optimal lap length of the glass fiber bars during the construction process based on the relationship curve between the maximum extrusion deformation amount and the safety factor corresponding to different remaining lengths, and determine the length L2 of the glass fiber bars, that is, determine the reinforcement parameters of the glass fiber bars.

[0012] Furthermore, the method for obtaining the reinforcement parameter Ⅰ of the glass fiber bars is specifically as follows:

[0013] S21. Set the initial reinforcement parameters of the glass fiber bars on the tunnel face. The length of the initial reinforcement parameters is L0, and the circumferential spacing is R0.

[0014] S22. Calculate the safety factor F1 of the tunnel face based on the initial reinforcement parameters of the glass fiber bars.

[0015] S23. If the safety factor F1 of the tunnel face is greater than the set value, increase the circumferential spacing R2 of the glass fiber bars and execute step S22. If the safety factor F1 of the tunnel face is less than the set value, decrease the circumferential spacing R2 of the glass fiber bars and execute step S22 until the reinforcement parameters of the glass fiber bars required when the safety factor F1 of the tunnel face reaches the set value are the reinforcement parameter Ⅰ.

[0016] Furthermore, the method for obtaining the optimal lap length S of the glass fiber bars is specifically as follows:

[0017] In the simulation conditions, take the remaining length l0 of the glass fiber bars on the tunnel face as the dividing line, and each increase or decrease of △l is a simulation condition, forming fewer simulation conditions than the set number.

[0018] Establish a relationship curve with different remaining lengths as the abscissa and the corresponding maximum extrusion deformation amount and safety factor of the tunnel face as the ordinate.

[0019] Obtain the point s with the largest change rate of the maximum extrusion deformation amount of the tunnel face when the safety factor is between 1.5 and 2. The remaining length of the glass fiber bars corresponding to the point s is the optimal lap length.

[0020] Furthermore, the length L2 of the glass fiber bars = n(max{D i}+S);

[0021] max{D i} is the maximum value of the influence depth D i of the tunnel face deformation caused by all excavation cycles in the field test. The value range of n should be 2 - 4.

[0022] Furthermore, the diameter Φ of the glass fiber bars is 25 mm.

[0023] Furthermore, the set value range of the face safety factor F1 is 1.5 - 2.

[0024] The present invention preliminarily determines the design parameters for face reinforcement through numerical simulation to ensure the construction safety of the test section, then inversely corrects the surrounding rock parameters through the test section to ensure the accuracy and reliability of the calculation results, corrects the face reinforcement parameters with the face safety factor as the index, and optimizes the lap length through multi-condition simulation. When designing the reinforcement parameters, safety is considered while taking economy into account. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a flow chart of the method for obtaining the parameters of the glass fiber bars for reinforcing the face of a soft soil tunnel provided by the present invention;

[0026] Figure 2 It is a schematic diagram of tunnel face reinforcement based on glass fiber bars provided by an embodiment of the present invention;

[0027] Figure 3 It is a schematic diagram of the distribution of glass fiber bars on the tunnel face provided by an embodiment of the present invention;

[0028] Figure 4 It is a schematic diagram of the method for determining the optimal lap length provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The following further details the specific embodiments of the present invention with reference to the accompanying drawings and descriptions of the embodiments to help those skilled in the art have a more complete, accurate, and in-depth understanding of the inventive concept and technical solution of the present invention.

[0030] Figure 1 It is a flow chart of the method for obtaining the parameters of the glass fiber bars for reinforcing the face of a soft soil tunnel provided by the present invention, and the method specifically includes the following steps:

[0031] S1. Construct a three-dimensional model of the tunnel and its surrounding rock based on the finite difference calculation software FLAC3D, input the mechanical parameters Ⅰ of the surrounding rock in the geological exploration report into the three-dimensional model, and the three-dimensional model inversely calculates the initial site conditions of the surrounding rock;

[0032] The initial site conditions include: the in-situ stress field and the seepage field. If there is no seepage influence or the seepage influence is small in the site, the seepage field may not need to be inversely calculated. After the inversion is completed, the displacement and velocity of the initial in-situ stress field are set to zero.

[0033] S2. Simulate excavation based on the construction method and calculate the reinforcement parameter I of the glass fiber reinforcement required when the safety factor F1 of the tunnel face reaches 1.5. The length of the glass fiber reinforcement in the reinforcement parameter I is L1, the annular spacing is R1 and the number is N1. The annular spacing R1 is as follows: Figure 3 The schematic diagram of the tunnel face reinforcement based on glass fiber reinforcement is shown in Figure 2 As shown;

[0034] In the embodiment of the present invention, the method for obtaining the reinforcement parameter I of the glass fiber reinforcement is specifically as follows:

[0035] S21, setting the initial reinforcement parameters of the glass fiber reinforcement at the tunnel face, wherein the initial reinforcement parameters are length L0=20m, circumferential spacing R0=1.5m, and the number N0 of the glass fiber reinforcement can be determined based on the tunnel face area;

[0036] S22, based on the initial reinforcement parameters of the glass fiber reinforcement at the tunnel face, the strength reduction method is used to calculate the safety factor F1 of the tunnel face;

[0037] S23. If the safety factor F1 of the tunnel face is greater than 1.5, the circumferential spacing R2 of the glass fiber reinforcement is increased, and step S22 is executed. If the safety factor F1 of the tunnel face is less than 1.5, the circumferential spacing R2 of the glass fiber reinforcement is reduced, and step S22 is executed. The reinforcement parameter of the glass fiber reinforcement required when the safety factor F1 of the tunnel face reaches 1.5 is obtained, which is reinforcement parameter I.

[0038] S3. Conduct field tests on the test section. The excavation length of the test section is 0.4L1. The tunnel face is reinforced using the preliminary reinforcement parameters of glass fiber reinforcement. A deep soil horizontal displacement monitoring device is embedded to monitor the maximum extrusion deformation d at the center of the tunnel face caused by each excavation cycle. i And deformation influence depth D i ;

[0039] S4. Excavate based on the construction method for multiple cycles. After each cycle of excavation, when the deformation is stable, read the maximum extrusion deformation d of the tunnel face in the current cycle. i And deformation influence depth D i ;

[0040] S5. The maximum extrusion deformation of the tunnel face measured after each excavation cycle in the test section is d i Inverse the mechanical parameters of the surrounding rock II, keep the length of the glass fiber reinforcement L1 unchanged, and recalculate the reinforcement parameters II of the glass fiber reinforcement when the safety factor of the tunnel face reaches 1.5 based on the mechanical parameters of the surrounding rock II. The length of the glass fiber reinforcement in the reinforcement parameters II is L1, the annular spacing is R2, and the number is N2;

[0041] S6. Perform simulated excavation with the reinforcement parameters of the circumferential spacing R2, quantity N2, and length L1 of the glass fiber bars. Based on the mechanical parameters Ⅱ of the surrounding rock, calculate the maximum extrusion deformation amount and safety factor of the tunnel face corresponding to the glass fiber bars with different remaining lengths in each excavation cycle during the excavation process. Determine the optimal lap length S of the glass fiber bars during the construction process based on the relationship curve between the maximum extrusion deformation amount of the tunnel face and the safety factor corresponding to different remaining lengths.

[0042] In the embodiment of the present invention, the method for obtaining the optimal lap length S of the glass fiber bars is specifically as follows:

[0043] In the simulation conditions, take the remaining length of 6m of the glass fiber bars at the tunnel face as the dividing line, and increase or decrease by 0.5m for each simulation condition to form less than 10 simulation conditions.

[0044] Take different remaining lengths as the abscissa, and the corresponding maximum extrusion deformation amount of the tunnel face and the safety factor as the ordinate to establish a relationship curve.

[0045] Determine the point s with the largest change rate of the maximum extrusion deformation amount of the tunnel face when the safety factor is between 1.5 and 2. The remaining length of the glass fiber bars corresponding to the point s is the optimal lap length S, as Figure 4 shown.

[0046] S7. The minimum one-time construction length L2 of the glass fiber bars = n(max{D i}+S).

[0047] max{D i} is the maximum value of the influence depth of the tunnel face deformation caused by all excavation cycles in the on-site test. The value range of n should be 2 - 4. The value of n considers the maximum one-time construction length and efficiency of the construction equipment for the glass fiber bars. The minimum one-time construction length L2 of the glass fiber bars should not be less than 20m.

[0048] In the embodiment of the present invention, the diameter of the glass fiber bars all adopts the standard value Φ25mm.

[0049] The present invention has been described exemplarily. Obviously, the specific implementation of the present invention is not limited by the above methods. As long as various non-substantive improvements are made by adopting the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A method for obtaining the reinforcement parameters of glass fiber bars for the heading face of a soft soil tunnel, characterized in that, The method specifically includes the following steps: S1. Construct a three-dimensional model of the tunnel and its surrounding rock in the natural state; S2. Conduct simulated excavation and calculate the reinforcement parameter I of the glass fiber bars required when the safety factor of the tunnel face reaches the set value; S3. Based on the reinforcement parameter I of the glass fiber bars, conduct on-site tests and monitor the maximum extrusion deformation and deformation influence depth at the center position of the tunnel face caused by each excavation cycle; S4. Invert the mechanical parameter II of the surrounding rock with the maximum extrusion deformation of the tunnel face measured in each excavation cycle in the test section. Keep the length of the glass fiber bars unchanged and recalculate the reinforcement parameter II of the glass fiber bars required when the safety factor of the tunnel face reaches the set value based on the mechanical parameter II of the surrounding rock; S5. Based on the reinforcement parameter II of the glass fiber bars, conduct simulated excavation and calculate the maximum extrusion displacement and safety factor of the tunnel face corresponding to the glass fiber bars with different remaining lengths around the tunnel face during each excavation cycle based on the mechanical parameter II of the surrounding rock; S6. Determine the optimal lap length of the glass fiber bars during the construction process based on the relationship curve between the maximum extrusion deformation and the safety factor corresponding to different remaining lengths, and determine the final length L2 of the glass fiber bars.

2. The method for obtaining the reinforcement parameters of glass fiber bars for the soft soil tunnel face as described in claim 1, characterized in that, The method for obtaining the reinforcement parameter I of the glass fiber bars is specifically as follows: S21. Set the initial reinforcement parameters of the glass fiber bars on the tunnel face. The length of the initial reinforcement parameter is L0, and the circumferential spacing is R0; S22. Calculate the safety factor F1 of the tunnel face based on the initial reinforcement parameters of the glass fiber bars; S23. If the safety factor F1 of the tunnel face is greater than the set value, increase the circumferential spacing R2 of the glass fiber bars and execute step S22. If the safety factor F1 of the tunnel face is less than the set value, decrease the circumferential spacing R2 of the glass fiber bars and execute step S22 until the reinforcement parameters of the glass fiber bars required when the safety factor F1 of the tunnel face reaches the set value are obtained as the reinforcement parameter I.

3. The method for obtaining the glass fiber reinforced plastic bar reinforcement parameters of the soft soil tunnel face according to claim 1, characterized in that, The method for obtaining the optimal lap length S of the glass fiber bars is specifically as follows: In the simulation conditions, take the remaining length l0 of the glass fiber bars on the tunnel face as the dividing line, and each increase or decrease of △l is a simulation condition, forming fewer simulation conditions than the set number; Establish a relationship curve with different remaining lengths as the abscissa and the corresponding maximum extrusion deformation and safety factor of the tunnel face as the ordinate; Obtain the point s with the largest change rate of the maximum extrusion deformation of the tunnel face when the safety factor is between 1.5 and 2. The remaining length of the glass fiber bars corresponding to the point s is the optimal lap length.

4. The method for obtaining the reinforcement parameters of glass fiber bars for the soft soil tunnel face as described in claim 1, characterized in that, The length L2 of the glass fiber bars = n(max{D i}+S), where S is the optimal lap length of the glass fiber bars, and max{D i} is the influence depth D i of the face deformation caused by all excavation cycles in the in-situ test. The maximum value of n ranges from 2 to 4.

5. The method for obtaining the reinforcement parameters of glass fiber bars for the face of a soft soil tunnel according to claim 1, characterized in that, The diameter Φ of the glass fiber bars is 25 mm.

6. The method for obtaining the reinforcement parameters of glass fiber bars for the soft soil tunnel face according to claim 1, characterized in that The set value range of the safety factor F1 of the tunnel face is 1.5 - 2.

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