Multi-pilot tunnel excavation construction method for weak surrounding rock large-section double-arch tunnel

Abstract

The weak surrounding rock large-section double-arch tunnel multi-pilot-tunnel excavation construction method comprises the following steps that S1, a left line middle pilot tunnel and a right line middle pilot tunnel are excavated at the same time, and MJS piles on the two sides of a tunnel are constructed; s2, after MJS pile construction is completed, a left line main line side pilot tunnel and a left line ramp side pilot tunnel are excavated at the same time; s3, right line ramp side pilot tunnel excavation and right line main line side pilot tunnel excavation are conducted; s4, after the left line middle pilot tunnel and the right line middle pilot tunnel are excavated, middle partition wall construction is conducted; s5, after the middle partition wall is completed, a left line main line main hole and a right line ramp main hole are excavated; s6, a left line ramp main hole and a right line main line main hole are excavated; s7, the secondary lining is constructed along with the primary support; s8, vault sinking monitoring is carried out; and S9, convergence displacement monitoring. According to the method, the total deformation of the structure is ensured to be within a specified allowable value, and the method can be better used for guiding construction.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel construction, and in particular to a multi-guide tunnel excavation construction method for a large-section double-arch tunnel in soft surrounding rock. Background Art

[0002] Due to the complex geological structure and environment, large-section double-arch tunnels with weak surrounding rocks are prone to local surface collapse, excessive surface settlement, large displacement of surrounding rock and large convergence deformation in the tunnel during construction. Double-arch tunnels are gradually replaced by separate and small-clearance tunnels in tunnel engineering due to their large span, complex structural stress, and prominent water leakage. However, in some special areas, affected by the terrain and line selection, double-arch tunnels are the most preferred tunnel form.

[0003] The prior art lacks relevant research on the influence of improper excavation sequence on the deformation and stress performance of tunnel surrounding rock during the excavation process of double-arch tunnels. Based on this, the present invention provides a multi-guide tunnel excavation construction method for large-section double-arch tunnels with soft surrounding rock. Summary of the invention

[0004] The purpose of the present invention is to provide a multi-guide tunnel excavation construction method for a large-section double-arch tunnel in soft surrounding rock to solve the problems existing in the prior art.

[0005] To achieve the above object, the present invention provides the following solution: The present invention provides a method for excavating multiple tunnels of a double-arch tunnel with a large cross section in soft surrounding rock, comprising the following steps:

[0006] S1: excavate the left and right central guide tunnels simultaneously, and construct MJS piles on both sides of the tunnel;

[0007] S2: After the MJS pile construction on the same side is completed, the left main line side guide tunnel and the left ramp side guide tunnel are excavated at a distance of not less than 50m from the middle guide tunnel face, and the guide tunnel faces on both sides are kept synchronous;

[0008] S3: After the left main line side guide tunnel is excavated for 30m, the right line ramp side guide tunnel and the right main line side guide tunnel are excavated;

[0009] S4: After the excavation of the left and right line middle guide tunnels is completed, the middle partition wall construction is carried out respectively;

[0010] S5: After the middle partition wall is completed, the main tunnel of the left main line and the main tunnel of the right ramp are excavated respectively;

[0011] S6: After the main tunnel of the left main line and the main tunnel of the right ramp are excavated for 30m, the main tunnel of the left ramp and the main tunnel of the right main line are excavated;

[0012] S7: Secondary lining followed by initial support construction;

[0013] S8: Vault subsidence monitoring;

[0014] S9: Convergence displacement monitoring.

[0015] According to the multi-guide tunnel excavation construction method for a large-section double-arch tunnel in soft surrounding rock provided by the present invention, before excavating the left-line main tunnel, the right-line main tunnel, the left-line ramp main tunnel and the right-line ramp main tunnel, it is necessary to complete the concrete pouring construction of the middle partition wall in the left-line middle guide tunnel and the right-line middle guide tunnel to provide support points for their initial support.

[0016] According to the multi-guide tunnel excavation construction method for a large-section double-arch tunnel in soft surrounding rock provided by the present invention, the middle guide tunnel and the side wall guide tunnel are both constructed by the short step method, and initial support and temporary support are promptly applied after excavation. Locking anchor pipes are set at the foot of the initial support wall, and a temporary invert arch is set.

[0017] According to the multi-tunnel excavation construction method for a large-section double-arch tunnel in soft surrounding rock provided by the present invention, in S8, two monitoring cross sections are respectively set at the tunnel entrance and exit, and a level and a spirit level are used to monitor the surface subsidence of the tunnel entrance.

[0018] According to the multi-tunnel excavation construction method for a large-section double-arch tunnel in soft surrounding rock provided by the present invention, in S8, two monitoring cross sections are respectively set at the tunnel entrance and exit, and a level and a spirit level are used to monitor the surface subsidence of the tunnel entrance.

[0019] According to the multi-pilot excavation construction method for a large-section double-arch tunnel in soft surrounding rock provided by the present invention, in S9, the measuring points are arranged according to the double-side wall pilot pit method, and the tail end of the convergence hook is welded to the steel support surface at each measuring point, and the welding direction is perpendicular to the excavation direction. The convergence hook is used in conjunction with a convergence meter to observe the change pattern of the distance between two points on the tunnel wall.

[0020] According to the multi-pilot excavation construction method for a large-section double-arch tunnel in soft surrounding rock provided by the present invention, a control section is taken every 5-10 m in the surrounding rock section, and 16 measuring points are arranged on each left and right line.

[0021] According to the construction method for excavating multiple pilot tunnels of a large-section double-arch tunnel in soft surrounding rock provided by the present invention, the left-line and right-line tunnel pilot tunnels are excavated successively according to the principle of left-line first and right-line following in due time.

[0022] The present invention discloses the following technical effects:

[0023] 1. The present invention excavates the left and right line middle guide tunnels first, and then excavates the left and right line side guide tunnels after staggering at least 50m from the middle guide tunnel face. After the middle partition wall construction is completed, the left and right line main tunnels are excavated, and the subsequent secondary lining construction is completed. This is beneficial to reducing the group tunnel effect, and at the same time, it is beneficial to reduce the disturbance of the surrounding rock and ensure the stability of the surrounding rock.

[0024] 2. The present invention can verify the accuracy of the parameters used in the engineering design through the monitoring data of the surface subsidence at the tunnel entrance and the convergence displacement in the tunnel, facilitate timely adjustment of the parameters, and provide a measured basis for the safety and rationality of the engineering construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 It is a flow chart of the multi-pilot excavation construction method of a large-section double-arch tunnel in soft surrounding rock according to the present invention;

[0027] Figure 2 This is a schematic diagram of the distribution of control points for the surface subsidence of the tunnel entrance;

[0028] Figure 3 This is a schematic diagram of the arrangement of measurement points for convergence displacement monitoring in the left tunnel;

[0029] Figure 4 Schematic diagram of the layout of the measurement points for convergence displacement monitoring in the right-line tunnel.

[0030] Among them, 1. The middle guide tunnel of the left line; 2. The middle guide tunnel of the right line; 3. The side guide tunnel of the left line main line; 4. The side guide tunnel of the left line ramp; 5. The side guide tunnel of the right line ramp; 6. The side guide tunnel of the right line main line; 7. The main tunnel of the left line main line; 8. The main tunnel of the right line ramp; 9. The main tunnel of the left line ramp; 10. The main tunnel of the right line main line; 11. Measuring point. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] Reference Figure 1-Figure 4 The present invention provides a multi-pipe excavation construction method for a large-section double-arch tunnel in soft surrounding rock, comprising the following steps:

[0034] S1: excavate the left-line central guide tunnel 1 and the right-line central guide tunnel 2 simultaneously, and construct MJS piles on both sides of the tunnel;

[0035] S2: After the MJS pile construction on the same side is completed, the left main line side guide tunnel 3 and the left ramp side guide tunnel 4 are excavated simultaneously at a distance of not less than 50m from the middle guide tunnel face, and the guide tunnel faces on both sides are kept synchronous;

[0036] S3: After the left main line side guide tunnel 3 is excavated for 30m, the right line ramp side guide tunnel 5 and the right main line side guide tunnel 6 are excavated;

[0037] S4: After the excavation of the left line middle guide tunnel 1 and the right line middle guide tunnel 2 is completed, the middle partition wall construction is carried out respectively;

[0038] S5: After the middle partition wall is completed, the left main line main tunnel 7 and the right ramp main tunnel 8 are excavated respectively;

[0039] S6: After excavating the left-line main tunnel 7 and the right-line ramp main tunnel 8 for 30m, excavate the left-line ramp main tunnel 9 and the right-line main tunnel 10;

[0040] S7: Secondary lining followed by initial support construction;

[0041] S8: Vault subsidence monitoring;

[0042] S9: Convergence displacement monitoring.

[0043] To further optimize the plan, before excavating the left-line main tunnel 7, the right-line main tunnel 10, the left-line ramp main tunnel 9 and the right-line ramp main tunnel 8, the concrete pouring construction of the middle partition wall in the left-line central guide tunnel 1 and the right-line central guide tunnel 2 must be completed to provide support points for their initial support.

[0044] To further optimize the plan, the middle guide tunnel and the side wall guide tunnel were constructed using the short step method. Initial support and temporary support were carried out in a timely manner after excavation. Locking anchor pipes were installed at the foot of the initial support wall, and a temporary invert arch was set.

[0045] The short step method is adopted for the construction of the middle guide tunnel and the side wall guide tunnel. The construction process is drilling and blasting, slag removal, frame erection, concrete spraying, tunnel bottom excavation and support. The drilling and blasting adopts smooth blasting technology. When drilling, the upper and lower steps are carried out simultaneously. After the drilling is completed, the explosives are loaded at the same time. When detonating, the lower step is detonated first, and then the excavator repairs the ramp. The loader drags the excavation platform to a safe position on the lower step and detonates the upper step. After the blasting operation is completed, ventilation and smoke exhaust are carried out immediately. The loader and slag removal truck are in place in advance. The slag is removed from the lower step first. The loader is used to load the slag and the dump truck is used to remove the slag. When the slag of the lower step is basically removed, the excavator is used to scrape the slag from the upper step to the lower step. After the slag removal is completed, The excavator stops at the upper step, and the dump truck continues to discharge slag; while the excavator is repairing the upper step ramp, the arch frame, connecting bars, mesh, anchor rods, advance small pipes and other materials outside the tunnel are transported to the site by the loader. In order to reduce the time of the erection process, the upper and lower step steel frames are installed at the same time, and the advance small pipes, locking anchor rods, etc. are installed. When erecting the frame, the steel frame should be installed according to the designed position, and the steel frame and the closed concrete should be as close as possible; during the erection process, the shotcrete team will prepare the wet spraying machinery, quick setting agent, wind, water and electricity at the same time. After the arch frame is installed, the shotcrete operation is carried out immediately. The shotcrete uses two wet spraying machines to operate on the upper and lower steps at the same time, which shortens the shotcrete operation time; the tunnel bottom excavation and support are carried out according to the safety step distance and excavation advance requirements. The short step method construction, the upper and lower steps follow closely, and the invert is closed into a ring earlier, which solves the long-standing problem of excessive safety step distance that has been difficult to solve, and greatly eliminates the safety hazards caused by excessive safety step distance.

[0046] To further optimize the plan, in S8, two monitoring cross sections are set at the tunnel entrance and exit, and a level and a spirit level are used to monitor the surface subsidence of the tunnel entrance.

[0047] To further optimize the plan, in S8, two monitoring cross sections are set at the tunnel entrance and exit, and a level and a spirit level are used to monitor the surface subsidence of the tunnel entrance.

[0048] To further optimize the plan, in S9, the measuring point 11 is arranged according to the double-side wall pilot pit method. At each measuring point 11, the tail end of the convergence hook is welded to the steel support surface. The welding direction is perpendicular to the excavation direction. The convergence hook is used in conjunction with the convergence meter to observe the change pattern of the distance between two points on the tunnel wall.

[0049] To further optimize the scheme, a control section was taken every 5-10 m in the surrounding rock section, and 16 measuring points were arranged on the left and right lines respectively11.

[0050] A total of 32 monitoring and measuring points 11 are set up in the left and right double-arch tunnels. The measuring points 11 are arranged according to the double-side wall pilot method. At each measuring point 11, the convergence tail is welded to the steel support surface. The welding direction is perpendicular to the excavation direction. The convergence hook is used in conjunction with the convergence meter to observe the change law of the distance between two points on the tunnel wall. Peripheral displacement convergence monitoring is an important project for tunnel construction monitoring. The convergence value is the most basic measurement data. By observing the horizontal clearance convergence amount and speed around the surrounding rock, the deformation law of the surrounding rock over time is mastered, so as to judge the stability of the surrounding rock and provide a basis for determining the time of secondary support, ensure that the total deformation of the structure is within the prescribed allowable value, and better guide the construction.

[0051] To further optimize the plan, the left and right tunnel guide tunnels will be excavated successively according to the principle of left line first and right line following in due course.

[0052] During the construction of the left and right double-arch tunnels, since the clear distance between the guide tunnels is small, considering the group tunnel effect, the construction of the left and right tunnels should be prioritized. The present invention is constructed in the order of "left line first, right line following in due time", and the excavation sequence is that the right line lags behind the left line by at least 30m in excavation span, wherein the left line middle guide tunnel 1 and the right line middle guide tunnel 2 are excavated first, the left line ramp side guide tunnel 4 and the left line main line side guide tunnel 3 lag behind the left line middle guide tunnel 1 and the right line middle guide tunnel 2 by at least 50m, and the right line main line side guide tunnel 6 and the right line ramp side guide tunnel 5 lag behind the left line ramp side guide tunnel 4 and the left line main line side guide tunnel 3 by at least 30m.

[0053] The embodiment of the present invention can further improve the safety of construction by setting the side guide pit on the side away from the middle partition wall. First, after excavating the side guide pit of the tunnel and applying support, the main tunnel of the tunnel is supported by the support structure of the side guide pit on one side and by the constructed middle partition wall on the other side, thereby achieving support on both sides by the left and right side support structures, greatly improving the construction safety and stability of the main tunnel, thereby meeting the excavation of ultra-large section double-arch tunnels in soft strata.

[0054] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0055] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for excavating multiple tunnels of a large-section double-arch tunnel in soft surrounding rock, characterized in that: The steps include: S1: excavate the left-line central guide tunnel (1) and the right-line central guide tunnel (2) simultaneously, and construct MJS piles on both sides of the tunnel; S2: After the MJS piles on the same side are constructed, the left main line side guide tunnel (3) and the left ramp side guide tunnel (4) are excavated simultaneously at a distance of not less than 50m from the middle guide tunnel face, and the guide tunnel faces on both sides are kept synchronous; S3: After the left main line side guide tunnel (3) is excavated for 30m, the right line ramp side guide tunnel (5) and the right main line side guide tunnel (6) are excavated; S4: After the excavation of the left line middle guide tunnel (1) and the right line middle guide tunnel (2) is completed, the middle partition wall construction is carried out respectively; S5: After the middle partition wall is completed, the left main line tunnel (7) and the right ramp tunnel (8) are excavated respectively; S6: After the left-line main tunnel (7) and the right-line ramp main tunnel (8) are excavated for 30 m, the left-line ramp main tunnel (9) and the right-line main tunnel (10) are excavated; S7: Secondary lining followed by initial support construction; S8: Vault subsidence monitoring; S9: Convergence displacement monitoring.

2. The method for excavating multiple tunnels of a double-arch tunnel with a large cross section in soft surrounding rock according to claim 1, characterized in that: Before excavating the left line main tunnel (7), the right line main tunnel (10), the left line ramp main tunnel (9) and the right line ramp main tunnel (8), the concrete pouring construction of the middle partition wall in the left line middle guide tunnel (1) and the right line middle guide tunnel (2) must be completed to provide support points for their initial support.

3. The method for excavating multiple tunnels of a double-arch tunnel with a large cross section in soft surrounding rock according to claim 1, characterized in that: The center guide tunnel and the side wall guide tunnel are constructed using the short step method. Initial support and temporary support are carried out in a timely manner after excavation. Locking anchor pipes are installed at the foot of the initial support wall, and a temporary invert arch is installed.

4. The method for excavating multiple tunnels of a double-arch tunnel with a large cross section in soft surrounding rock according to claim 1, characterized in that: In S8, two monitoring cross sections are set at the tunnel entrance and exit, and a level and a spirit level are used to monitor the surface subsidence of the tunnel entrance.

5. The method for excavating multiple tunnels of a double-arch tunnel with a large cross section in soft surrounding rock according to claim 4, characterized in that: In S8, two monitoring cross sections are set at the tunnel entrance and exit, and a level and a spirit level are used to monitor the surface subsidence of the tunnel entrance.

6. The method for excavating multiple tunnels of a double-arch tunnel with a large cross section in soft surrounding rock according to claim 1, characterized in that: In S9, the measuring point (11) is arranged according to the double-side wall pilot method. At each measuring point (11), the tail end of the convergence hook is welded to the steel support surface. The welding direction is perpendicular to the excavation direction. The convergence hook is used in conjunction with the convergence meter to observe the change pattern of the distance between two points on the tunnel wall.

7. The method for excavating multiple tunnels of a double-arch tunnel with a large cross section in soft surrounding rock according to claim 6, characterized in that: A control section is taken every 5-10 m in the surrounding rock section, and 16 measurement points are arranged on the left and right lines respectively (11).

8. The method for excavating multiple tunnels of a double-arch tunnel with a large cross section in soft surrounding rock according to claim 1, characterized in that: The left and right tunnel guide tunnels are excavated successively according to the principle of left line first and right line following in due time.

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