A construction method for underground cavern intersections

Abstract

A construction method for an underground cavern intersection involves adjusting the height of the arch of the preceding cavern (1) in advance to be higher than that of the following cavern (2); then proceeding with normal excavation until the preceding cavern (1) completely penetrates the cross-section of the following cavern (2); reinforcing the surrounding rock near the intersection and reserving the outline of the following cavern (2); and finally excavating into the following cavern (2) in stages. This method reduces the large-scale demolition of the preceding cavern structure, minimizes disturbance to the surrounding rock, improves the construction efficiency of the intersection, shortens the construction period, reduces construction costs, and enhances the safety and controllability of the intersection construction.

Description

Technical Field

[0001] This invention relates to the field of underground engineering construction technology, specifically to a construction method for underground cavern intersections. Background Technology

[0002] The construction of long tunnels is often constrained by factors such as terrain, topography, and construction period. To shorten the construction period, new working faces are often created during construction through inclined shafts, ventilation ducts, or cross passages, resulting in various structural forms of intersections. Common intersections include "T-shaped intersections" and "cross-shaped intersections." Due to the complex geological conditions and high variation rate of surrounding rock in long tunnels, there are high risks during intersection construction. At the same time, the stress at the intersection is complex, leading to great construction difficulties.

[0003] One common construction method for "T-shaped intersections" is the cantilever method. This method involves starting construction from the initial tunnel chamber and gradually adjusting the height of the smaller tunnel chambers until they cross the cross-section of the subsequent tunnel chambers.

[0004] Another method is the top-lifting method, which involves turning the small cavern cross-section and gradually expanding it until it reaches the cross-section of the subsequent cavern. Then, the gradually expanding arch frame is removed to complete the construction of the intersection.

[0005] The cantilever method involves adjusting the height of the roof along an arc, and it also involves a gradual expansion of the space. Both methods require cross-sectional adjustments before dismantling the arch frame, which presents several problems:

[0006] 1. Conventional construction methods require continuous adjustment of the cross-section of the pilot tunnel. After the adjustment is completed, the structure of the pilot tunnel is dismantled and replaced. The whole process causes multiple disturbances to the surrounding rock at the intersection, increasing the number of uncontrollable factors in construction safety.

[0007] 2. Conventional construction methods are complex, and the increased number of steps leads to slow construction progress, high construction costs, and a waste of a lot of raw materials and human resources.

[0008] In view of the above, there is an urgent need for a construction method for underground cavern intersections that minimizes surrounding rock disturbance, is simple in process, safe in construction, and low in construction cost. Summary of the Invention

[0009] This invention provides a construction method for underground cavern intersections to solve the technical problems in existing underground cavern intersection construction, such as large-scale demolition of the prior cavern structure, large disturbance to the surrounding rock, poor construction safety, low construction efficiency, high construction cost, and poor construction controllability.

[0010] According to the construction method for underground cavern intersections of the present invention, the height of the arch of the preceding cavern is adjusted in advance to be higher than that of the following cavern; then, normal excavation is carried out until the preceding cavern completely passes through the cross section of the following cavern; then, the surrounding rock near the intersection is reinforced, and the outline of the following cavern is reserved; finally, the following cavern is excavated in stages to enter the following cavern.

[0011] According to the construction method of the underground cavern intersection of the present invention, the height of the arch of the preceding cavern is adjusted in advance so that it is higher than the arch of the following cavern at the intersection by a certain distance, so as to facilitate the pre-reinforcement and excavation of the top of the following cavern.

[0012] According to the construction method of underground cavern intersection of the present invention, the reserved outline of the subsequent cavern is reserved in advance through the cross section of the subsequent cavern during the construction of the preceding cavern. No shotcrete construction is carried out within the reserved area to facilitate subsequent construction.

[0013] According to the construction method for underground cavern intersections of the present invention, when reinforcing the surrounding rock near the intersection, different types of surrounding rock can be reinforced by one or more means such as pipe roof, radial grouting, and double-layer initial support.

[0014] In the above-mentioned construction method for underground cavern intersections, when the surrounding rock is poor and the initial support of the completed preliminary cavern is deformed or converged, a second layer of initial support is constructed at the same location in that section to strengthen the structure of the preliminary cavern and ensure the stability of the cavern body.

[0015] In the above-mentioned construction method for the intersection of underground caverns, when the surrounding rock is extremely poor, the double-layer support of the preceding cavern can be constructed first and then the corresponding part of the following cavern can be removed to form a composite lining for cavern reinforcement.

[0016] The above-mentioned construction method for underground cavern intersections can strengthen the support of the intersections and, within the reserved outline of the subsequent caverns, implement pre-reinforcement measures such as advanced pipe roofs to ensure the smooth progress of subsequent cavern construction.

[0017] The construction method for underground cavern intersections according to the present invention comprises the following specific steps:

[0018] Step 1: Adjust the height of the upper step arch of the pilot cavern. In the raised area, adjust the height of the top surface of the pilot cavern to be about 1m higher than the height of the top surface of the subsequent cavern. The starting point of the raised area should be 10-15m away from the subsequent cavern.

[0019] Step 2: Continue excavating the raised area of ​​the initial cavern until it surpasses the subsequent cavern. If there is space, reinforcement measures can be carried out simultaneously, and pipe sheds can be constructed along the outline of the subsequent cavern.

[0020] Step 3: The construction of the first tunnel proceeds down the steps until the initial support construction of the first tunnel is completed; no shotcrete construction is carried out in the reserved positions of the subsequent tunnel section; the reinforcement construction of the intersection is completed.

[0021] Step 4: Install double-layer support for the initial tunnel. The double-layer support should be installed in the same position to ensure that the double-layer support effectively supports the initial support of the initial tunnel. The reserved position in the cross-section of the subsequent tunnel does not need to be constructed with double-layer support. It can be removed according to the outline of the subsequent tunnel when the subsequent tunnel is constructed.

[0022] Step four should be used selectively depending on the surrounding rock conditions. If the surrounding rock at the intersection is poor and there are phenomena such as deformation and convergence, then step four is required; if the surrounding rock at the intersection is good, then step four can be omitted.

[0023] Step 5: Backfill the intersection of the pre-excavation chamber and the subsequent chamber until the step height is suitable for excavating the subsequent chamber; if double-layer support exists, cut off the double-layer support and the arch frame of the pre-excavation chamber at the reserved position of the subsequent chamber; if double-layer support does not exist, only cut off the arch frame of the pre-excavation chamber.

[0024] Step 6: Excavate the tunnel on one side (either at a large or small mileage) in stages until the initial support excavation of the tunnel is completed. Reinforce the tunnel as needed during the excavation process.

[0025] Step 7: Excavate the other side (the opposite direction of Step 6, at a small or large mileage) in stages until the initial support excavation of the tunnel is completed. During the excavation process, the tunnel may be reinforced as needed.

[0026] According to the above-mentioned construction method for the intersection of underground caverns, in step two, pipe roof 3 uses φ108 steel pipes with a length of 15m-20m, a circumferential spacing of 60cm, and is installed within a circumferential angle range of 120°, with an installation angle of 3.5°.

[0027] Furthermore, before constructing the pipe shed 3, the construction of the locking foot at the intersection of the pilot tunnel and its front and rear sections will be carried out. The locking foot will use φ76 self-advancing anchor rods with a length of 9m, which will be installed within 3m before and after the intersection section of the tunnel, with an installation angle of 35°.

[0028] The beneficial effects of this invention are:

[0029] The underground cavern intersection construction method of the present invention, by adjusting the height of the arch of the preceding cavern in advance to be higher than that of the subsequent cavern before normal excavation, reduces the time required for multi-cycle, step-by-step construction in traditional construction techniques, thus shortening the construction period. Simultaneously, this method avoids large-scale demolition of the preceding cavern structure, reduces the number of disturbances to the surrounding rock, improves intersection construction efficiency, reduces construction costs, and enhances the safety and controllability of intersection construction. Therefore, this construction method can meet the needs of the vast majority of intersection construction in the current tunnel industry, possessing significant advantages and broad application value. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of step one in the construction method for underground cavern intersections of the present invention.

[0031] Figure 2 This is a schematic diagram of step two in the construction method for underground cavern intersections of the present invention.

[0032] Figure 3 This is a schematic diagram of step three in the construction method for underground cavern intersections of the present invention.

[0033] Figure 4 This is a schematic diagram of step five in the construction method for underground cavern intersections of the present invention.

[0034] Figure 5 This is a schematic diagram of step six in the construction method for underground cavern intersections of the present invention.

[0035] The attached figures are labeled as follows:

[0036] 1-Preliminary cavern, 11-Upper step of the preliminary cavern, 12-Lower step of the preliminary cavern, 13-Elevated area; 2-Subsequent cavern, 20-Upper step of the subsequent cavern, 21-Middle step of the subsequent cavern, 22-Lower step of the subsequent cavern, 23-Outline of the subsequent cavern; 3-Pipe shed. Detailed Implementation

[0037] The following is in conjunction with the appendix Figure 1-5 The present invention will be described in detail, but this is not intended to limit the invention in any way.

[0038] A construction method for an underground cavern intersection includes the following steps:

[0039] Step 1: Adjust the height of the arch of the upper step 11 of the pilot cavern. In the raised area 13, adjust the cross-sectional height of the pilot cavern 1 to be approximately 1 meter higher than the cross-sectional height of the subsequent cavern 2. Figure 1 As shown, the end of the raised area 13 is 10-15m away from the rear cavern.

[0040] Step 2, as follows Figure 2As shown, continue excavating the upper step 11 of the preliminary cavern until it surpasses the subsequent cavern 2. If there is space, reinforcement measures can be carried out simultaneously. Pipe roof 3 is constructed along the outline 23 of the subsequent cavern. Pipe roof 3 uses φ108 steel pipes, and the length can be adjusted, generally 15m-20m. The circumferential spacing is about 60cm, and it is installed within a circumferential angle of 120°, with an external insertion angle of 3.5°.

[0041] Before constructing the pipe shed, the construction of the reinforcing anchors at the intersection and the sections before and after the tunnel is carried out. The anchors are made of φ76 self-advancing anchors, 9m in length, and are installed within 3m before and after the intersection at an angle of 35°.

[0042] Step 3, as follows Figure 3 As shown, the construction proceeds from step 12 down to the first tunnel until the initial support of the first tunnel 1 is completed; no shotcrete construction is carried out at the reserved position on the cross-section of the subsequent tunnel 2; the reinforcement construction at the intersection is completed.

[0043] Step 4: Install double-layer support for the first tunnel 1. The double-layer support is installed in the same position to ensure that the double-layer support effectively supports the initial support of the first tunnel 1. The reserved position in the cross-section of the second tunnel 2 does not need to be constructed with double-layer support. It will be removed according to the outline of the second tunnel when the second tunnel is constructed.

[0044] Step four is a step that can be added or removed depending on the surrounding rock conditions. If the surrounding rock at the intersection is poor and there are phenomena such as deformation and convergence, then step four is required; if the surrounding rock at the intersection is good, then step four can be omitted.

[0045] Step 5, as follows Figure 4 As shown, backfill the lower part of the preliminary cavern 1 until it is suitable for the step height of the subsequent cavern 2; when there is double support, cut off the double support and the arch frame of the preliminary cavern at the reserved position of the subsequent cavern 2; when there is no double support, only cut off the arch frame of the preliminary cavern.

[0046] Step Six, as Figure 5 As shown, after the construction of one side of the tunnel is carried out in stages, the initial support excavation of the tunnel is completed. During the excavation process, the tunnel is reinforced as needed.

[0047] Step 7: Excavate the other side of the tunnel 2 in stages until the initial support excavation of tunnel 2 is completed. During the excavation process, the tunnel may be reinforced as needed.

[0048] In the construction of the intersections of the East Tianshan Tunnel, the traditional step-and-jacking method would have taken up to 30 days. However, this project successfully completed the construction of one "T-shaped intersection" and two "T-shaped intersections" within 10-13 days using the aforementioned method. These projects demonstrate the superior effectiveness of this method.

[0049] The above description is merely a specific embodiment of the present invention, and the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for construction of underground cavern intersection, characterized in that: the vault height of the leading cavern (1) is adjusted in advance to be higher than that of the following cavern (2); then the leading cavern (1) is excavated normally until it completely crosses the section of the following cavern (2); then the surrounding rock near the intersection is reinforced to reserve the profile of the following cavern (2); finally the following cavern (2) is excavated step by step; the construction steps are as follows: Step one, adjust the vault height of the upper step (11) of the leading cavern, in the raised area (13), the height of the section of the leading cavern (1) is adjusted to be about 1m higher than that of the following cavern (2), and the start of the raised area (13) is 10-15m away from the following cavern (2); Step two, continue to excavate the raised area (13) of the leading cavern until it exceeds the following cavern (2), and there is space to carry out reinforcement measures simultaneously, and a pipe shed (3) is constructed along the profile line (23) of the following cavern; Step three, the lower step (12) of the leading cavern is constructed until the initial support construction of the leading cavern (1) is completed; the reserved position of the section of the following cavern (2) is not sprayed with concrete; the intersection reinforcement construction is completed; Step four, double-layer support is constructed for the leading cavern (1), the double-layer support is installed in the same position to ensure that the double-layer support effectively supports the initial support of the leading cavern (1); the reserved position of the section of the following cavern (2) is not constructed with double-layer support, and the double-layer support is removed according to the profile of the following cavern (2) when the following cavern (2) is constructed; Step four should be used selectively according to the surrounding rock conditions, if the surrounding rock at the intersection is poor and there is deformation and convergence, step four needs to be used; if the surrounding rock at the intersection is good, step four can be omitted; Step five, the intersection part of the leading cavern (1) and the following cavern (2) is backfilled until the step height suitable for excavating the following cavern (2) is reached; when there is double-layer support, the double-layer support on the part of the reserved position of the following cavern (2) and the arch of the leading cavern are cut off; when there is no double-layer support, only the arch of the leading cavern is cut off; Step six, the following cavern (2) is excavated step by step on one side, which is the large or small mileage side, until the initial support excavation of the following cavern (2) is completed, and the cavern is reinforced as needed during the excavation process; Step seven, the following cavern (2) is excavated step by step on the other side, which is the opposite direction of step six, and is the small or large mileage side, until the initial support excavation of the following cavern (2) is completed, and the cavern is reinforced as needed during the excavation process. 2.The method for construction of underground cavern intersection according to claim 1, characterized in that: the vault height of the leading cavern (1) is adjusted in advance by adjusting the vault height of the auxiliary passage or inclined shaft to be a certain distance higher than that of the following cavern (2) at the intersection, so as to smoothly complete the top excavation of the following cavern (2). 3.The method for construction of underground cavern intersection according to claim 2, characterized in that: the step of reserving the profile of the following cavern (2) is that during the construction of the leading cavern (1), the profile of the following cavern (2) is reserved in advance through part of the following cavern (2), and the reserved range is not sprayed with concrete, so as to facilitate subsequent construction. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 4. The underground cavern intersection construction method according to claim 3, characterized in that: When reinforcing the surrounding rock near the intersection, different surrounding rocks are reinforced by one or more of the following means: pipe shed, radial grouting, and double-layer initial support.

5. The underground cavern intersection construction method according to claim 4, characterized in that: When the surrounding rock is poor, the initial support of the completed preceding cavern (1) deforms or converges, a second layer of initial support is constructed at the same position in the section to strengthen the structure of the preceding cavern (1) and ensure the stability of the cavern.

6. The underground cavern intersection construction method according to claim 5, characterized in that: When the surrounding rock is extremely poor, the preceding cavern (1) is first constructed with double-layer support, and then the corresponding part of the following cavern (2) is removed to form a composite lining cavern opening for reinforcement.

7. The underground cavern intersection construction method according to any one of claims 1-6, characterized in that: The intersection support is strengthened, and within the reserved contour of the following cavern, advanced pipe shed pre-reinforcement measures are taken for the following cavern to ensure the smooth development of the subsequent construction of the following cavern.

8. The underground cavern intersection construction method according to claim 7, characterized in that: In step two, the pipe shed (3) uses φ108 steel pipes with a length of 15m-20m, a ring spacing of 60cm, and a ring angle within the range of 120°, and the setting angle is 3.5°.

9. The underground cavern intersection construction method according to claim 8, characterized in that: Before setting the pipe shed (3), the intersection of the preceding cavern and the sections before and after it are reinforced by setting the lock feet, and the lock feet use φ76 self-advancing anchor rods with a length of 9m, which are set within a range of 3m before and after the intersection section, and the setting angle is 35°.

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