A three-step approximation method for determining the optimal tunnel overbreak and underbreak control contour

Abstract

The present invention relates to a three-step approximation method for determining the optimal tunnel over-excavation and under-excavation control contour line, including determining the final contour line by a three-step approximation method based on a theoretical minimum contour line geometric characteristic value R, through different weight combinations of four deformation amounts of surrounding rock, the deformation amounts are respectively the average value A of the survey deformation amount, the theoretical total reserved amount B, the average value C of the basic stable deformation amount and the average value D of the final stable deformation amount; the geometric shape and position of contour line I are calculated by formula R+0.8A+0.2B; the geometric shape and position of contour line II are calculated by formula R+0.5B+0.5C; the geometric shape and position of contour line III are calculated by formula R+0.1A+0.1B+0.8D, that is, contour line III can be used as the actual construction contour line of the section. The advantages of the present invention are that the excavation section contour line is scientifically and reasonably optimized, and the over-excavation and under-excavation are controlled more accurately. The present invention is applicable to tunnels excavated by the step method and tunnels excavated by the full section.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel blasting over-break and under-break, in particular to a three-step approximation method for determining an optimal tunnel over-break and under-break control contour line. Background Art

[0002] At present, most rock tunnels are still excavated by drilling and blasting or mechanical methods. During excavation, if the excavation contour is not set reasonably, it often causes over-excavation and under-excavation, which is the main factor affecting construction costs.

[0003] At present, the main way to reduce over-break and under-break during tunnel construction is to optimize the layout of blastholes and charging methods and other precise control blasting methods. However, due to the complex and changeable geological conditions, blasting according to theoretical design will inevitably lead to a large amount of over-break and under-break during the entire tunnel excavation process. Only by analyzing the actual geological conditions of the construction site and designing a blasting plan based on the scientific determination of the boundaries of the blasthole layout can the project cost be reduced and the waste of construction costs be reduced. Summary of the invention

[0004] The purpose of the present invention is to solve the problems of frequent over-break and under-break in existing tunnel construction, unreasonable blasthole layout and high construction cost. A three-step approximation method for determining the optimal tunnel over-break and under-break control contour line is provided, which can reduce the range of blasthole layout, reduce the occurrence of over-break and under-break, and save construction costs.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A three-step approximation method for determining the optimal tunnel overbreak and underbreak control contour line includes using the three-step approximation method to calculate the geometric shape and position of the final contour line based on the theoretical minimum contour line geometric characteristic value R. The specific steps are as follows:

[0007] (1) Determine four deformations: The average deformation value A of the survey deformation is defined as the average deformation of the tunnel surrounding rock under the same surrounding rock and cross-section conditions obtained by the literature survey method; the theoretical total reserved deformation B is defined as the design reserved deformation + construction error + breakthrough error; the average basic stable deformation value C is defined as the deformation value when the deformation rate of four consecutive sections is in a basically stable state when the measurement and monitoring sections are set up during tunneling in the same group of strata; the average final stable deformation value D is defined as the deformation value when the deformation rate of four consecutive sections is in a final stable state when the deformation of the surrounding rock is measured by a multi-point measurement method;

[0008] (2) Calculate the geometric shape and position of contour line I: Use the literature survey method to obtain the average deformation of the tunnel surrounding rock under similar surrounding rock and cross-section conditions, that is, the average deformation value A. The number of survey samples is not less than 3. The geometric shape and position of contour line I are calculated using the formula R+0.8A+0.2B.

[0009] (3) Calculate the geometric shape and position of contour line II: set up measurement and monitoring sections during excavation of surrounding rock in the same stratum. When the deformation rate of no less than four sections is in a basically stable state, that is, the average value of the basically stable deformation amount C, the geometric shape and position of contour line II is calculated using the formula R+0.5B+0.5C;

[0010] (4) Determination of the actual excavation contour line: The deformation of the surrounding rock of the tunnel section is obtained by a multi-point measurement method. When the deformation of four consecutive sections is in a stable state, that is, the final stable deformation average value D, the geometric shape and position of contour line III is calculated using the formula R+0.1A+0.1B+0.8D. That is, contour line III can be used as the actual construction excavation contour line of the section.

[0011] Furthermore, in step (2), the deformation of tunnel surrounding rock under similar surrounding rock and cross-section conditions is obtained by using a literature research method. When researching scientific research papers, the journal level should generally be constrained to be CSCD or above, and the number of research papers should be preferably 10 to 20.

[0012] Furthermore, in step (2), at least 4 surrounding rock deformation values ​​whose geological conditions are close to those of the construction site are selected from 10 to 20 documents. The closer the surrounding rock deformation values ​​are to the on-site geological conditions, the greater the weight of the surrounding rock deformation values ​​described in the documents when calculating the average. The weight of the closest deformation values ​​when calculating the average is at least 0.3.

[0013] Furthermore, in step (2), among the selected 10 to 20 documents, the four deformations closest to the geological conditions of the construction site are ranked A1, A2, A3 and A4 according to the degree of proximity, and the average value of the surveyed deformation A=(A1×0.4+A2×0.3+A3×0.2+A4×0.1) / 4.

[0014] Furthermore, according to the actual geological conditions, when the left and right convergence of the tunnel surrounding rock is not synchronized, multi-point measurement of the absolute deformation of the surrounding rock is carried out, and asymmetric contour lines are set. At this time, the size of the steel arch frame also needs to be adjusted accordingly.

[0015] Furthermore, the over-excavation contour line of the tunnel construction is greater than the theoretical minimum contour line, and the maximum deviation between the two vertices is d, the distance between contour line I and the theoretical minimum contour line is c, the distance between contour line II and the theoretical minimum contour line is b, and the distance between contour line III and the theoretical minimum contour line is a, then d>c>b>a.

[0016] Compared with the prior art, the advantages of the technical solution of the present invention are:

[0017] (1) Based on the theoretical minimum geometric characteristic value R of the contour line, the present invention uses a three-step approximation method to determine the contour line that is more conducive to overbreak and underbreak control by combining different weights of the four deformation quantities of the surrounding rock. The setting range of the blasting holes can be calculated more accurately, thereby reducing the occurrence of tunnel overbreak and underbreak and reducing construction costs.

[0018] (2) The working method of the present invention is simple, scientific and reasonable. Technical personnel at the construction site can quickly determine the reasonable layout range of the blastholes, thereby improving work efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the tunnel excavation section contour line determination process of the present invention. DETAILED DESCRIPTION Example 1

[0020] To make the present invention more clear, a three-step approximation method for determining the optimal tunnel over- and under-break control contour of the present invention is further described below in conjunction with the accompanying drawings. The specific embodiments described here are only used to explain the present invention and are not used to limit the present invention.

[0021] In this embodiment, a three-step approximation method for determining the optimal tunnel over-break and under-break control contour line is provided. The tunnel contour line is as follows: Figure 1 As shown in the figure, the main parameters involved in this method include the theoretical minimum contour line geometric characteristic value R; the average survey deformation value A, which is defined as the average deformation of the tunnel surrounding rock under the same surrounding rock and section conditions obtained by the literature survey method; the theoretical total reserved deformation value B, which is defined as the design reserved deformation value + construction error value + breakthrough error value; the average basic stable deformation value C, which is defined as the deformation value when the deformation rate of four consecutive sections is in a basically stable state when the measurement and monitoring section is set during tunnel excavation in the same group of strata; the average final stable deformation value D, which is defined as the deformation of the surrounding rock measured by a multi-point measurement method when the deformation rate of four consecutive sections is in a final stable state.

[0022] In practice, the excavation contour line of tunnel construction is usually larger than the theoretical minimum contour line. Assume that the maximum offset distance d between the two is 13 cm.

[0023] When the method of the present invention is used to calculate the excavation contour line, first, the deformation of the tunnel surrounding rock under the same surrounding rock and cross-section conditions is obtained by using the literature research method. When conducting research on scientific research papers, the journal level should generally be constrained to be CSCD or above, and the number of research papers should be 10 to 20. Assuming that the four deformations closest to the geological conditions of the construction site in these 10 to 20 documents are ranked A1, A2, A3 and A4 according to the degree of proximity, the average value of the research deformation A=(A1×0.4+A2×0.3+A3×0.2+A4×0.1) / 4, and then the formula 0.8A+0.2B is used to calculate the offset distance c between the contour line I and the theoretical minimum contour line. c must be less than d, assuming c is 9cm.

[0024] Then, during the excavation of the surrounding rock in the same group of strata, measurement and monitoring sections are set up. When the deformation rate of no less than 4 sections is in a basically stable state, the formula 0.5B+0.5C is used to calculate the offset distance b between contour line II and the theoretical minimum contour line. b must be less than c. Assume that b is 7.5 cm.

[0025] Finally, the deformation of the surrounding rock was obtained by a multi-point measurement method. When the deformation of four consecutive sections was in the final stable state, the formula 0.1A+0.1B+0.8D was used to calculate the offset distance a between contour line III and the theoretical minimum contour line. a must be smaller than b. Assuming a is 6 cm, contour line III can be used as the actual construction excavation contour line of the section. Example 2

[0026] This embodiment provides a three-step approximation method for determining the optimal tunnel over-excavation and under-excavation control contour line, and its working method is basically the same as that of Embodiment 1; the only difference is that under different geological environments, the surrounding rock deformation values ​​​​researched in the literature, the surrounding rock deformation values ​​​​measured by the multi-point measurement method, the calculated offset distances a, b, c, and the offset distance d between the theoretical minimum contour line finally calculated and the actual construction contour line III are different.

[0027] During construction, based on actual geological conditions, when the left and right surrounding rock of the tunnel converge asynchronously, the absolute deformation of the surrounding rock between points 1 and 4 on the actual construction contour line III can be measured at multiple points, and the shape of the excavation contour line between points 1 and 4 can be slightly changed inward or outward according to the deformation amount.

[0028] The method for determining the contour line for controlling the over-excavation and under-excavation of tunnel blasting of the present invention can scientifically, reasonably and conveniently calculate the minimum offset distance between the actual construction contour line and the theoretically calculated minimum contour line, thereby reducing the occurrence of over-excavation and under-excavation phenomena during blasting excavation, thereby reducing construction costs, avoiding waste of materials, and not affecting the safety of the tunnel. The present invention is applicable to both step-excavated tunnels and full-section excavated tunnels under the process of drilling and blasting excavation or mechanical excavation.

[0029] In addition to the above embodiments, the present invention may also have other implementation modes. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present invention.

Claims

1. A three-step approximation method for determining the optimal tunnel over-break and under-break control contour line, comprising: using the three-step approximation method to calculate the final contour line based on the theoretical minimum contour line geometric characteristic value R, characterized in that: (1) Determine four deformations: The average deformation value A of the survey deformation is defined as the average deformation of the tunnel surrounding rock under the same surrounding rock and cross-section conditions obtained by the literature survey method; the theoretical total reserved deformation B is defined as the design reserved deformation + construction error + breakthrough error; the average basic stable deformation value C is defined as the deformation value when the deformation rate of four consecutive sections is in a basically stable state when the measurement and monitoring sections are set up during tunneling in the same group of strata; the average final stable deformation value D is defined as the deformation value when the deformation rate of four consecutive sections is in a final stable state when the deformation of the surrounding rock is measured by a multi-point measurement method; (2) Calculate the geometric shape and position of contour line I: Use the literature survey method to obtain the average deformation of the tunnel surrounding rock under similar surrounding rock and cross-section conditions, that is, the average deformation value A. The number of survey samples is not less than 3. The geometric shape and position of contour line I are calculated using the formula R+0.8A+0.2B. (3) Calculate the geometric shape and position of contour line II: set up measurement and monitoring sections during excavation of surrounding rock in the same stratum. When the deformation rate of no less than four sections is in a basically stable state, that is, the average value of the basically stable deformation amount C, the geometric shape and position of contour line II is calculated using the formula R+0.5B+0.5C; (4) Determination of the actual excavation contour line: The deformation of the surrounding rock of the tunnel section is obtained by a multi-point measurement method. When the deformation of four consecutive sections is in the final stable state, that is, the average value of the final stable deformation amount D, the geometric shape and position of contour line III is calculated using the formula R+0.1A+0.1B+0.8D. That is, contour line III can be used as the actual construction excavation contour line of the section.

2. The three-step approximation method for determining the optimal tunnel overbreak and underbreak control contour according to claim 1 is characterized in that: In step (2), a literature survey method is used to obtain the deformation of the tunnel surrounding rock under similar surrounding rock and cross-section conditions. When conducting a research on scientific research papers, the number of research papers is 10 to 20.

3. The three-step approximation method for determining the optimal tunnel overbreak and underbreak control contour according to claim 2 is characterized in that: In step (2), at least 4 surrounding rock deformation values ​​whose geological conditions are close to those of the construction site are selected from 10 to 20 documents. The closer the surrounding rock deformation values ​​are to the on-site geological conditions, the greater the weight of the surrounding rock deformation values ​​described in the documents when calculating the average. The weight of the closest deformation values ​​when calculating the average is at least 0.

3.

4. The three-step approximation method for determining the optimal tunnel overbreak and underbreak control contour according to claim 3 is characterized in that: In step (2), among the selected 10 to 20 documents, the four deformations closest to the geological conditions of the construction site are ranked A1, A2, A3 and A4 according to the degree of proximity, and the average value of the surveyed deformation A=(A1×0.4+A2×0.3+A3×0.2+A4×0.1) / 4.

5. The three-step approximation method for determining the optimal tunnel overbreak and underbreak control contour according to any one of claims 1 to 4 is characterized in that: According to the actual geological conditions, when the left and right convergence of the tunnel surrounding rock is not synchronized, multi-point measurement of the absolute deformation of the surrounding rock is carried out and asymmetric contour lines are set. At this time, the size of the steel arch frame also needs to be adjusted accordingly.

6. The three-step approximation method for determining the optimal tunnel overbreak and underbreak control contour according to any one of claims 1 to 4, wherein: The over-excavation contour line of tunnel construction is greater than the theoretical minimum contour line, and the maximum deviation between the two vertices is d, the distance between contour line I and the theoretical minimum contour line is c, the distance between contour line II and the theoretical minimum contour line is b, and the distance between contour line III and the theoretical minimum contour line is a, then d>c>b>a.

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