Method for determining construction distance between first tunnel and second tunnel in high stress soft rock tunnel

Abstract

The application provides a construction distance determination method for a pilot hole and a subsequent hole of a high-stress soft rock tunnel, belongs to the technical field of tunnel engineering construction, and solves the problem that a traditional method is difficult to determine a construction distance; the method comprises the following steps: a vibration sensor group is buried behind a pilot hole face, and a blasting vibration speed generated at different longitudinal depths is monitored during blasting; a position of a region where a peak value speed range is located is determined as an initial position of a subsequent hole face, and then a pilot hole primary support is constructed and a stress monitoring element is pre-buried; a vibration sensor group is buried behind the subsequent hole face, a blasting vibration speed is also monitored, a stress of the pilot hole primary support is monitored through the stress monitoring element, the construction distance of the subsequent hole face and the pilot hole is adjusted, and the same principle is used to adjust and confirm a position of a second lining construction of the pilot hole; the application efficiently and reasonably determines the construction distance between the pilot hole and the subsequent hole in tunnel construction, and ensures safety and construction efficiency.

Description

Technical Field

[0001] This invention belongs to the field of tunnel engineering construction technology and is applied to small-spacing twin-tunnel tunnels, specifically a method for determining the construction distance between the lead tunnel and the follow tunnel in a high-stress soft rock tunnel. Background Technology

[0002] In the construction of tunnels in soft rock with high ground stress, especially for tunnels with small gaps, the existing technology uses mining methods for excavation. The construction processes of the first tunnel and the second tunnel will affect each other, and the blasting of the second tunnel may cause structural damage to the first tunnel.

[0003] Therefore, the distance between the working faces of the pre-tunnel and the subsequent tunnel, as well as the distance between the secondary lining of the pre-tunnel and the working face of the subsequent tunnel, are crucial. Inappropriate distances can easily lead to structural instability of the pre-tunnel, seriously affecting construction safety. Currently, the industry lacks a standardized and efficient method for determining the construction distance between the pre-tunnel and the subsequent tunnel. Only after establishing a reasonable distance can factors such as the stress release effects of subsequent tunnel blasting and excavation on the pre-tunnel be considered to ensure that the pre-tunnel structure is not damaged and the rock pillar does not become unstable. Therefore, those skilled in the art have begun relevant core research to design and construct the most efficient and reasonable distance determination method. Summary of the Invention

[0004] This invention solves the problem of determining the construction distance of small-spacing tunnels in soft rock tunnels under high ground stress. It proposes a method for determining the construction distance between the lead tunnel and the follow tunnel. The key point is to deploy triaxial vibration sensors at different depths behind the face of the lead tunnel to monitor the blasting vibration velocity and further monitor and evaluate the rationality of the key positions of the lead tunnel and the follow tunnel, thereby preventing the structure of the lead tunnel from being damaged by the blasting of the follow tunnel.

[0005] The present invention employs the following technical solutions to achieve its objective:

[0006] A method for determining the construction distance between the initial tunnel and the subsequent tunnel in a high-stress soft rock tunnel, the method comprising the following steps:

[0007] S1. During the forward construction of the pilot tunnel, before the blasting of the pilot tunnel, the first vibration sensor group is buried behind the working face of the pilot tunnel.

[0008] S2. After the preliminary tunnel is blasted, the first blasting vibration velocity generated at different longitudinal depths along the preliminary tunnel is monitored by the first vibration sensor group.

[0009] S3. According to the blasting safety regulations, the location range of the area where the first peak velocity range of the first blasting vibration velocity is located is determined as the initial location range of the tunnel face in the subsequent tunnel.

[0010] S4. Construct the initial support for the pilot tunnel. Before construction, embed stress monitoring elements at the initial support location of the pilot tunnel, and then prepare for the forward construction process of the subsequent tunnel.

[0011] S5. During the forward construction of the rear tunnel, before the blasting of the rear tunnel, a second vibration sensor group is buried behind the working face of the rear tunnel.

[0012] S6. After the blasting of the subsequent tunnel, the initial support stress of the preceding tunnel and the second blasting vibration velocity generated at different longitudinal depths of the subsequent tunnel are monitored by stress monitoring elements and the second vibration sensor group, respectively.

[0013] S7. Based on the initial support stress of the pilot tunnel, adjust the construction distance between the working face of the subsequent tunnel and the pilot tunnel, and confirm the position of the working face of the subsequent tunnel, based on the initial position range of the working face of the subsequent tunnel.

[0014] S8. Based on the initial support stress of the pilot tunnel and the blasting safety regulations, the location of the area where the second peak velocity of the second blasting vibration velocity is located is determined as the location for the construction of the secondary lining of the pilot tunnel.

[0015] Specifically, the blasting safety regulations used in this invention are GB6722-2014; in its relevant provisions, the permissible mass vibration velocity in traffic tunnels is 10-20 cm / s.

[0016] In summary, due to the adoption of this technical solution, the beneficial effects of this invention are as follows:

[0017] The key point of the method for determining the construction distance between the pre-exit tunnel and the subsequent tunnel proposed in this invention is to monitor the blasting vibration velocity at different radial positions by deploying triaxial vibration sensors at different longitudinal depths behind the tunnel face, thereby considering the position of the tunnel face of the subsequent tunnel, and to evaluate the rationality of the position by monitoring the stress and deformation of the initial support structure of the pre-exit tunnel after the excavation of the subsequent tunnel.

[0018] This invention also considers the construction location of the secondary lining of the preceding tunnel by monitoring the blasting vibration velocity generated at different longitudinal depths at the tunnel face during the subsequent tunnel excavation, and assesses the rationality of this location by monitoring the deformation and stress of the secondary lining structure of the preceding tunnel after the excavation of the subsequent tunnel. This invention thus solves the problem of difficult distance determination in traditional technologies in an efficient and reasonable manner, successfully preventing structural damage to the preceding tunnel structure due to improper distance caused by the subsequent tunnel blasting. Attached Figure Description

[0019] Figure 1 A flowchart illustrating the method for determining the construction distance between the preliminary tunnel and the subsequent tunnel;

[0020] Figure 2 This is a structural schematic diagram of a small-spacing tunnel in soft rock under high ground stress.

[0021] Figure 3 This is a schematic diagram showing the layout of multiple triaxial vibration sensors at different depth positions. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0023] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0024] Example

[0025] A method for determining the construction distance between the lead tunnel and the follow tunnel in a high-stress soft rock tunnel. The overall process of this method can be found in [reference needed]. Figure 1 This is a schematic diagram; this embodiment will strictly follow the execution order of the steps in the method, and will describe the details of each step in detail.

[0026] 1. Installation of vibration sensor array in the pilot tunnel

[0027] During the forward construction of the pilot tunnel, before blasting, the first set of vibration sensors is installed behind the tunnel face. (See here for reference.) Figure 3 The diagram illustrates that the first vibration sensor group consists of multiple triaxial vibration sensors. Figure 3 The symbols “•” arranged sequentially on one side of the tunnel represent triaxial vibration sensors pre-embedded at different longitudinal positions.

[0028] 2. Monitor and record the blasting vibration velocity after the preliminary tunnel blasting.

[0029] After the initial tunnel is blasted, the first blasting vibration velocity generated at different longitudinal depths along the initial tunnel can be monitored using a first vibration sensor group. In this embodiment, the first blasting vibration velocity is monitored and recorded in the form of a velocity-time graph.

[0030] 3. Determine the initial position range of the tunnel face after the tunnel is moved.

[0031] According to the relevant provisions of the Blasting Safety Regulations GB6722-2014, the permissible mass vibration velocity for traffic tunnels is 10-20 cm / s. Therefore, in this embodiment, based on the velocity-time relationship diagram of the first blasting vibration velocity, the triaxial vibration sensors corresponding to the first peak velocity range of 10-20 cm / s are determined. The distance range between the positions of these triaxial vibration sensors and the current position of the tunnel face of the preceding tunnel can be used as the distance range between the tunnel face of the subsequent tunnel and the tunnel face of the preceding tunnel.

[0032] However, based on this, as a preferred method in this embodiment, the first peak velocity is determined to be a specific value of 15cm / s, and an additional guarantee condition is added to ensure that the distance between the working face of the subsequent tunnel and the working face of the preceding tunnel is not less than the range of 4-5D, which is used as the distance between the working face of the subsequent tunnel and the working face of the preceding tunnel.

[0033] D is the diameter of the tunnel entrance. The range of this guarantee condition can be selected based on the actual conditions such as the surrounding rock characteristics and tunnel indicators at the tunnel construction site. This value is based on existing tunnel engineering cases. If the working faces of the tunnel entrance and the tunnel exit are too close, not only will the construction disturbance be large, but the effect of "geological prediction" will not be achieved. Therefore, a reasonable value must be limited on the basis of the peak speed.

[0034] In this embodiment, when determining the initial position of the tunnel face, the distance between the triaxial vibration sensor corresponding to the first peak velocity of 15 cm / s and the tunnel face of the preceding tunnel is prioritized. (See also...) Figure 2 , Figure 2 The distance L1 is the distance between the working face of the subsequent tunnel and the working face of the preceding tunnel.

[0035] 4. Monitoring of the initial support of the pilot tunnel and preparation for the construction of the subsequent tunnel.

[0036] Part 3 only defines the initial position of the tunnel face for the subsequent tunnel. Adjustments to this position will depend on the monitoring of the initial support of the preceding tunnel. After the preceding tunnel is blasted and excavated, initial support must be constructed promptly, and the structural deformation of the initial support must be monitored using a total station. During construction, the initial support arch frame is first erected. After the arch frame is erected, rock pressure cells, steel stress gauges, and concrete strain gauges are pre-embedded at the arch crown, arch waist, and arch foot of the preceding tunnel as stress monitoring elements to continuously monitor the structural stress of the initial support of the preceding tunnel. Subsequently, preparations can be made for the forward construction of the subsequent tunnel.

[0037] 5. Installation of vibration sensor array in the tunnel

[0038] Similar to Part 1, during the forward construction of the rear tunnel, a second vibration sensor group, consisting of multiple triaxial vibration sensors, is first installed behind the tunnel face before the blasting of the rear tunnel. The installation method can also be found in [reference needed]. Figure 3 The illustration.

[0039] 6. Monitor and record the blasting vibration velocity after the subsequent blasting of the tunnel and the initial support stress of the preceding tunnel.

[0040] After the subsequent tunnel blasting, the second vibration sensor group can monitor the second blasting vibration velocity generated at different longitudinal depths along the subsequent tunnel. In this embodiment, the second blasting vibration velocity is also monitored and recorded in the form of a velocity-time graph. In this part, based on the stress monitoring elements pre-embedded at the initial support location of the preceding tunnel, the distance between the tunnel face and the preceding tunnel face needs to be checked and adjusted first to ensure safety.

[0041] 7. Determine the final position of the tunnel face after the tunnel is moved.

[0042] During the blasting and excavation of the subsequent tunnel, by monitoring the initial support stress of the preceding tunnel, if the initial support of the preceding tunnel experiences encroachment or the initial support stress exceeds the structural design load of the initial support, it indicates that the initial support of the preceding tunnel is not stable. At this time, it is necessary to adjust the position of the tunnel face of the subsequent tunnel and increase the construction distance between the tunnel face of the subsequent tunnel and the preceding tunnel until the aforementioned encroachment or exceeding of the design load no longer occurs.

[0043] Similarly, if, during the subsequent blasting and excavation of the rear tunnel, the initial support of the preceding tunnel does not exhibit any encroachment phenomenon, and the stress of the initial support of the preceding tunnel does not exceed the structural design load of the initial support, it indicates that the initial support of the preceding tunnel has stabilized. There is no need to adjust the construction distance between the tunnel face of the rear tunnel and the preceding tunnel, and the position of the current tunnel face of the rear tunnel can be directly confirmed. Subsequently, the location of the secondary lining of the preceding tunnel can be determined.

[0044] 8. Determine the location for the secondary lining of the pilot tunnel.

[0045] Based on the second blasting vibration velocity monitored and recorded in Part 6, and also in accordance with the Blasting Safety Regulations GB6722-2014, in the velocity-time relationship graph of the second blasting vibration velocity, the distance between the triaxial vibration sensor position corresponding to the second peak velocity of 10 cm / s and the position of the tunnel face at that time is taken as the distance between the secondary lining construction position of the preceding tunnel and the tunnel face of the following tunnel. This distance can be referenced. Figure 2 The L2 distance is illustrated in the diagram. The safety of the secondary lining structure of the pilot tunnel needs to be further guaranteed; therefore, stricter standards must be adopted. In this embodiment, a peak velocity of 10 cm / s is used as the basis for the distance.

[0046] This section contains the same additional guarantee condition, namely, ensuring that the distance between the secondary lining construction position of the preliminary tunnel and the working face of the subsequent tunnel is not less than 4-5D, where D is the diameter of the opening of the preliminary tunnel.

[0047] In this embodiment, also as a preferred method for the secondary lining structure of the preliminary tunnel, stress monitoring elements are pre-embedded at the location of the secondary lining construction before the secondary lining construction is carried out, and the stress of the secondary lining is continuously monitored during the subsequent engineering construction process after the secondary lining construction is completed.

[0048] During the next round of blasting in the secondary tunnel, based on the monitoring results of the stress of the secondary lining of the primary tunnel, if the stress of the secondary lining of the primary tunnel is greater than or equal to the preset safety threshold, it means that the distance between the construction position of the secondary lining of the primary tunnel and the working face of the secondary tunnel cannot guarantee safety, so the distance between the construction position of the secondary lining of the primary tunnel and the working face of the secondary tunnel is increased; if the stress of the secondary lining of the primary tunnel is less than the preset safety threshold, it means that the secondary lining structure of the primary tunnel has stabilized, so the current construction position of the secondary lining of the primary tunnel is taken as the final determined position.

Claims

1. A method for determining the construction distance between the initial tunnel and the subsequent tunnel in a high-stress soft rock tunnel, characterized in that, The method includes the following steps: S1. During the forward construction of the pilot tunnel, before the blasting of the pilot tunnel, a first vibration sensor group is installed behind the working face of the pilot tunnel. The first vibration sensor group includes multiple triaxial vibration sensors, which are installed at different longitudinal positions behind the working face of the pilot tunnel. S2. After the preliminary tunnel is blasted, the first vibration sensor group is used to monitor and record the first blasting vibration velocity generated at different longitudinal depths along the preliminary tunnel in the form of a velocity-time relationship graph. S3. According to the blasting safety regulations, the location range of the area where the first peak velocity range of the first blasting vibration velocity is located is determined as the initial location range of the tunnel face in the subsequent tunnel. S4. Construct the initial support for the pilot tunnel. Before construction, embed stress monitoring elements at the initial support location of the pilot tunnel, and then prepare for the forward construction process of the subsequent tunnel. S5. During the forward construction of the rear tunnel, before the blasting of the rear tunnel, a second vibration sensor group is installed behind the working face of the rear tunnel. The second vibration sensor group includes multiple triaxial vibration sensors, which are installed at different longitudinal positions behind the working face of the rear tunnel. S6. After the blasting of the subsequent tunnel, the initial support stress of the preceding tunnel and the second blasting vibration velocity generated at different longitudinal depths of the subsequent tunnel are monitored by stress monitoring elements and the second vibration sensor group, respectively. S7. Based on the initial support stress of the pilot tunnel, adjust the construction distance between the working face of the subsequent tunnel and the pilot tunnel, and confirm the position of the working face of the subsequent tunnel, based on the initial position range of the working face of the subsequent tunnel. S8. Based on the initial support stress of the pilot tunnel and the blasting safety regulations, the location of the area where the second peak velocity in the second blasting vibration velocity is located is determined as the construction location of the secondary lining of the pilot tunnel. In steps S1 and S5, the triaxial vibration sensor is used to monitor and record the specific value of the blasting vibration velocity transmitted to its buried location due to construction blasting. In step S3, based on the velocity-time relationship graph of the first blasting vibration velocity, the triaxial vibration sensor corresponding to the first peak velocity range of 10-20cm / s is determined. The distance range between the position of the triaxial vibration sensor and the position of the tunnel face at this time is taken as the distance range between the tunnel face of the subsequent tunnel and the tunnel face of the preceding tunnel, thereby determining the initial position range of the tunnel face of the subsequent tunnel. In step S3, after ensuring that the distance between the face of the subsequent tunnel and the face of the preceding tunnel is not less than 4-5D, the triaxial vibration sensor corresponding to the first peak velocity of 15cm / s is determined according to the velocity-time relationship diagram of the first blasting vibration velocity. The distance between the position of the triaxial vibration sensor and the position of the face of the preceding tunnel at this time is taken as the distance between the face of the subsequent tunnel and the face of the preceding tunnel, and the initial position of the face of the subsequent tunnel is determined; where D is the diameter of the opening of the preceding tunnel.

2. The method for determining the construction distance between the initial tunnel and the subsequent tunnel in a high-stress soft rock tunnel according to claim 1, characterized in that: In step S4, during the initial support of the pilot tunnel, the structural deformation of the initial support is monitored using a total station. During the construction process, the initial support arch frame is first set up. After the arch frame is set up, rock pressure cells, steel stress gauges and concrete strain gauges are pre-embedded at the arch top, arch waist and arch foot of the pilot tunnel as stress monitoring elements to continuously monitor the structural stress of the initial support of the pilot tunnel.

3. The method for determining the construction distance between the initial tunnel and the subsequent tunnel in a high-stress soft rock tunnel according to claim 1, characterized in that: In step S6, the second blasting vibration velocity is monitored and recorded in the form of a velocity-time relationship graph; in step S7, based on the initial support stress of the pilot tunnel monitored by the stress monitoring element, if the initial support of the pilot tunnel experiences encroachment, or if the initial support stress of the pilot tunnel exceeds the structural design load of the initial support, it indicates that the initial support of the pilot tunnel is not stable. In this case, the construction distance between the working face of the subsequent tunnel and the pilot tunnel is increased, and the position of the working face of the subsequent tunnel is confirmed.

4. The method for determining the construction distance between the initial tunnel and the subsequent tunnel in a high-stress soft rock tunnel according to claim 3, characterized in that: In step S7, based on the initial support stress of the pilot tunnel monitored by the stress monitoring element, if the initial support of the pilot tunnel does not exhibit any encroachment phenomenon and the initial support stress of the pilot tunnel does not exceed the structural design load of the initial support, it indicates that the initial support of the pilot tunnel has stabilized. There is no need to adjust the construction distance between the tunnel face and the pilot tunnel, and the position confirmation of the current tunnel face is completed directly. Subsequently, the location of the secondary lining of the pilot tunnel is determined.

5. The method for determining the construction distance between the initial tunnel and the subsequent tunnel in a high-stress soft rock tunnel according to claim 4, characterized in that: In step S8, after ensuring that the distance between the construction position of the secondary lining of the preliminary tunnel and the working face of the subsequent tunnel is not less than 4-5D, the triaxial vibration sensor corresponding to the second peak velocity of 10cm / s is determined according to the velocity-time relationship diagram of the second blasting vibration velocity. The distance between the position of the triaxial vibration sensor and the position of the working face of the subsequent tunnel at this time is taken as the distance between the construction position of the secondary lining of the preliminary tunnel and the working face of the subsequent tunnel, thereby determining the construction position of the secondary lining of the preliminary tunnel; where D is the diameter of the opening of the preliminary tunnel.

6. The method for determining the construction distance between the initial tunnel and the subsequent tunnel in a high-stress soft rock tunnel according to claim 5, characterized in that: Before the construction of the secondary lining of the pilot tunnel, stress monitoring elements are pre-embedded at the construction location of the secondary lining of the pilot tunnel. After the construction of the secondary lining of the pilot tunnel is completed, the stress of the secondary lining of the pilot tunnel is continuously monitored during the subsequent construction process. During the new round of blasting of the subsequent tunnel, the distance between the construction location of the secondary lining of the pilot tunnel and the working face of the subsequent tunnel is adjusted based on the monitoring results of the stress of the secondary lining of the pilot tunnel.

7. The method for determining the construction distance between the initial tunnel and the subsequent tunnel in a high-stress soft rock tunnel according to claim 6, characterized in that: During a new round of blasting of the subsequent tunnel, if the stress of the secondary lining of the preceding tunnel is greater than or equal to the preset safety threshold, it means that the distance between the construction position of the secondary lining of the preceding tunnel and the working face of the subsequent tunnel is still not safe. In this case, the distance between the construction position of the secondary lining of the preceding tunnel and the working face of the subsequent tunnel will be increased. If the stress of the secondary lining of the preceding tunnel is less than the preset safety threshold, it means that the secondary lining structure of the preceding tunnel has been stabilized. In this case, the current construction position of the secondary lining of the preceding tunnel will be the final determined position.

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