A tunnel floor heave middle partition-wall-anchor combined control structure and construction method

Abstract

This invention relates to a combined control structure and construction method for tunnel floor heave with a partition wall and anchorage. The structure includes a tunnel invert, a reinforced concrete partition wall, deep anchors, tunnel floor anchors, partition wall anchor cables, corner anchor cables, and drainage pipes. It divides the tunnel floor rock strata horizontally, reducing the length-to-thickness ratio of each layer of surrounding rock at the tunnel floor and enhancing the tunnel floor's resistance to compression and stability. High-strength reinforced concrete partition walls are excavated at the tunnel floor, and deep anchors are placed at the bottom below these walls to fix them to the original deep rock, ensuring the vertical stability of the partition walls. The tunnel floor anchors increase the integrity of the layered rock mass at the bottom, reducing displacement of the tunnel invert caused by high ground stress. This invention offers simple construction and better control of tunnel floor heave disasters without increasing the amount of excavation.

Description

Technical Field

[0001] This invention relates to the field of tunnel deformation control technology, specifically to a combined control structure and construction method for tunnel floor bulge partition wall-anchoring. Background Technology

[0002] With the rapid economic development in the mountainous areas of western my country, the number of transportation infrastructure projects in the region is also increasing. Highways and railways often need to pass through many tunnels, making tunnel structural safety a top priority. Tunnel excavation leads to the redistribution of stress in the surrounding rock, and tunnel floor heave disasters often occur in areas of high ground stress, mainly caused by horizontal compression of the surrounding rock at the tunnel floor.

[0003] To eliminate tunnel bottom heave hazards, previous techniques mainly relied on anchoring and excavation to dissipate stress. Patent CN110847930A, "Multi-stage yielding support structure and construction method for large deformation tunnels in soft rock with extremely high ground stress," utilizes long anchor cables and short anchor rods with timely high pre-tightening force to transfer surface rock pressure to deeper layers and expand the bearing capacity of the surrounding rock, thereby controlling rock deformation and maintaining structural stability. However, for layered rock strata, especially thin-layered rock masses, anchoring alone is insufficient to guarantee the integrity of the rock strata under high ground stress and to ensure they maintain their compressive strength. Patent CN1076... 30706A, "A Tunnel Bottom Structure and Construction Method for Eliminating Tunnel Invert Heave in High Ground Pressure Zones," describes a method that eliminates high ground stress in the surrounding rock of a tunnel by excavating multiple pressure relief holes and then backfilling them, thereby preventing invert heave. While this method is simple to construct and can reduce tunnel bottom heave caused by high ground stress, excavating multiple pressure relief holes undermines the integrity of the tunnel bottom structure. Although it may reduce the occurrence of tunnel bottom heave in the short term, the deformation of the surrounding rock is a long-term process. The multiple pressure relief holes also reduce the bearing capacity of the surrounding rock at the tunnel bottom, making the tunnel bottom more susceptible to damage when creep occurs later. Summary of the Invention

[0004] The purpose of this invention is to provide a combined control structure and construction method for tunnel floor heave with a partition wall and anchorage. Addressing the problem of tunnel floor heave, this invention proposes placing a reinforced concrete partition wall in the surrounding rock at the tunnel floor to enhance the stability of the rock strata. Multi-stage anchor bolts are placed on both sides of the reinforced concrete partition wall in the surrounding rock at the tunnel floor to strengthen the integrity of the layered rock mass. Long anchor bolts are used at the bottom of the reinforced concrete partition wall to connect it to the deep rock mass, preventing the reinforced concrete partition wall from sliding upwards under high ground stress. This invention's combined control structure for tunnel floor heave with a partition wall and anchorage alters the stress model of the tunnel floor rock mass, is simple to construct, has a small disturbance range to the surrounding rock, and has excellent application prospects.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] In a first aspect, the present invention provides a tunnel bottom arch-anchoring joint control structure, the structure comprising a tunnel invert arch, a reinforced concrete partition wall, deep anchor bolts, tunnel bottom anchor bolts, partition wall anchor cables, bottom corner anchor cables, and drainage pipes;

[0007] The compressive strength of the reinforced concrete partition wall is higher than that of the tunnel rock mass. A number of deep anchors are installed at the bottom of the reinforced concrete partition wall to fix the reinforced concrete partition wall to the bottom stable rock mass along the tunnel direction. The length of the deep anchor is greater than or equal to twice the height h of the reinforced concrete partition wall, and the upper end of the deep anchor extends into the middle of the reinforced concrete partition wall to ensure a stable connection between the reinforced concrete partition wall and the bottom stable rock mass.

[0008] Two parallel partition wall anchor cables are installed on the rock mass on both sides of the reinforced concrete partition wall to ensure the vertical stability of the rock mass on both sides of the reinforced concrete partition wall and to prevent the rock mass at the bottom of the tunnel from sliding upward on both sides of the reinforced concrete partition wall. The angle α between the partition wall anchor cable and the horizontal direction is 45° to 60°. The lower end of the two parallel partition wall anchor cables is fixed to the reinforced concrete partition wall and the upper end is fixed to the tunnel floor.

[0009] The tunnel bottom anchor bolts are distributed in multiple levels, with multiple levels of support anchor bolts. The length of each level of support anchor bolt is different. The length of the first-level support anchor bolt is consistent with the height of the reinforced concrete partition wall, and the length of the largest-level support anchor bolt is twice the height h of the reinforced concrete partition wall.

[0010] The multi-level support anchors are arranged in an alternating manner, and the direction of the support anchors is perpendicular to the tangent direction of the tunnel floor.

[0011] Corner anchor cables perpendicular to the direction of the maximum principal stress of the surrounding rock are installed at the bottom corner of the tunnel;

[0012] Drainage pipes are installed between the reinforced concrete partition wall and the tunnel invert.

[0013] Furthermore, the lower ends of the two parallel partition wall anchor cables on one side of the rock mass are respectively fixed at the three equal division points of the height h of the reinforced concrete partition wall.

[0014] Furthermore, depending on the specific engineering practice, the number of reinforced concrete partition walls can be arranged in a single row, double row, or multiple rows. When multiple rows are arranged, multiple reinforced concrete partition walls are arranged at the points where the cross-section perpendicular to the tunnel direction is equally divided, and multi-level tunnel bottom anchor bolts are also arranged between two adjacent reinforced concrete partition walls.

[0015] Furthermore, the tunnel floor anchor bolts include primary support anchor bolts and secondary support anchor bolts. The length of the primary support anchor bolts is consistent with the height of the reinforced concrete partition wall, and the length of the secondary support anchor bolts is twice the length of the primary support anchor bolts. The primary and secondary support anchor bolts are arranged alternately, and the direction of the support anchor bolts is perpendicular to the tangent direction of the tunnel floor slab.

[0016] Furthermore, the tunnel bottom anchors are evenly arranged in multiple rows along the tunnel direction, with a spacing of d between adjacent rows. The partition wall anchors are arranged in the middle of adjacent rows of tunnel bottom anchors, with a distance of 0.5d from the adjacent row of tunnel bottom anchors. All graded support anchors in each row of tunnel bottom anchors are in the same plane. Multiple sets of bottom corner anchors are also arranged along the tunnel direction, with two bottom corner anchors in each set, located on both sides of the tunnel floor.

[0017] Furthermore, the drainage pipe is located above the reinforced concrete partition wall, and a leak-proof plate is installed above the drainage pipe.

[0018] Secondly, the present invention provides a construction method for a tunnel floor bulge diaphragm-anchorage combined control structure, comprising the following steps:

[0019] Step 1: After the tunnel excavation is completed, determine the number and height h of the reinforced concrete partition walls according to the design structural dimensions. Excavate a backfill area with a width of b downwards along the tunnel bottom at the equal division points. The depth of the backfill area is the sum of the height of the reinforced concrete partition walls and the height of the drainage pipes.

[0020] Step 2: Deploy deep anchor bolts with a length of ≥2h from the bottom of the backfill area described in Step 1 into the depth of the tunnel bottom, with the top of the deep anchor bolts 0.5h higher than the bottom of the backfill area, so that the reinforced concrete partition wall remains stable with the deep surrounding rock through the deep anchor bolts;

[0021] Step 3: Install two parallel partition wall anchor cables on both sides of the backfill area. The bottom ends of the two parallel partition wall anchor cables are located at a distance from the bottom of the backfill area. At this point, the angle α between the two parallel partition wall anchor cables and the horizontal direction is 45° to 60°.

[0022] Step 4: Arrange the steel cage from bottom to top at the bottom of the backfill area, and then pour concrete to form a reinforced concrete partition wall with a height of h. Reserve a drainage pipe 7 above the reinforced concrete partition wall 2.

[0023] Step 5: Arrange graded support anchors downward on the tunnel floor slab on both sides of the backfill area. The graded support anchors of different lengths are arranged alternately in the direction of the tunnel cross section.

[0024] Step 6: Install corner anchor cables at the bottom corner of the tunnel, perpendicular to the direction of the maximum principal stress of the surrounding rock;

[0025] Step 7: Lay a leak-proof board with a width of ≥2b above the drainage pipe;

[0026] Step 8: Arrange the invert arch reinforcement cage, reserve channels for bottom corner anchor cables on both sides, and pour the tunnel invert arch;

[0027] Step 9: After the reinforced concrete of the tunnel invert has hardened, the bottom corner anchor cables are tensioned and locked, and the construction is completed.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] This invention involves arranging at least one reinforced concrete partition wall in the surrounding rock at the tunnel floor, reducing the width of the tunnel floor slab and preventing the rock mass from fracturing under horizontal compressive force, thus enhancing the horizontal stability of the rock strata. This invention has a small excavation area, minimal disturbance to the surrounding rock, and does not increase the area of ​​the excavation disturbance zone. The backfilled reinforced concrete partition wall has a strength higher than the surrounding rock strength and is anchored to the stable surrounding rock zone via deep anchor bolts, restricting the vertical displacement of the reinforced concrete partition wall. Two parallel partition wall anchor cables on both sides of the reinforced concrete partition wall restrict the movement of the tunnel floor slab on both sides, ensuring the overall vertical stability. The tunnel floor is anchored using graded anchor bolts. The first-level short anchor bolts primarily enhance the integrity of the layered surrounding rock, forming a unified rock mass on both sides of the reinforced concrete partition wall. The second-level long anchor bolts connect the rock mass on both sides of the reinforced concrete partition wall to the deep stable surrounding rock, enhancing the connection stability and further restricting the vertical displacement of the tunnel floor slab, increasing the stability and integrity of the tunnel floor slab.

[0030] The length and distribution of the graded anchor bolts in this application are related to the height of the reinforced concrete partition wall. The length of the first-level short anchor bolts is the same as the height h of the reinforced concrete partition wall, and the length of the second-level long anchor bolts is ≥2h. The partition wall-anchoring combined control structure in this application is an integrated control system. The reinforced concrete partition wall is designed to have a strength higher than that of the rock mass, and the reinforced concrete partition wall is connected and fixed to the deep stable rock mass with anchor bolts. The partition wall anchor cables on both sides of the reinforced concrete partition wall connect the reinforced concrete partition wall to the rock mass on both sides into a whole, without compromising its integrity or causing stress concentration. Under the premise of long-term effectiveness, the overall strength is enhanced by connecting the whole to resist deformation and effectively mitigate the phenomenon of tunnel floor heave. Attached Figure Description

[0031] Figure 1 This is a three-dimensional structural schematic diagram of the tunnel floor drum partition wall-anchoring combined control structure of the present invention;

[0032] Figure 2 for Figure 1 Section 1-1 (tunnel section at the location of the partition wall anchor cable);

[0033] Figure 3 for Figure 1 Section 1-2 (a tunnel section showing the location of a set of tunnel bottom anchor bolts);

[0034] Figure 4 This is a three-dimensional structural schematic diagram of Embodiment 2 of the tunnel floor drum partition wall-anchoring combined control structure of the present invention;

[0035] Figure 5 for Figure 4Section 2-1 (tunnel section at the location of the partition wall anchor cable);

[0036] Figure 6 for Figure 4 Section 2-2 (a tunnel section showing the location of a set of tunnel bottom anchor bolts);

[0037] Among them, 1—tunnel invert arch, 2—reinforced concrete partition wall, 3—deep anchor bolt, 4—tunnel bottom anchor bolt, 5—bottom corner anchor cable, 6—partition wall anchor cable, and 7—drainage pipe. Detailed Implementation

[0038] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments, but this is not intended to limit the scope of protection of this application.

[0039] Example 1:

[0040] like Figure 1 The tunnel bottom drum-anchoring combined control structure of the present invention includes a tunnel invert arch 1, a reinforced concrete partition wall 2, a deep anchor 3, a tunnel bottom anchor 4, a bottom corner anchor cable 5, a partition wall anchor cable 6, and a drainage pipe 7.

[0041] The compressive strength of the reinforced concrete partition wall 2 should be higher than that of the rock mass. A deep anchor 3 is installed at the bottom of the reinforced concrete partition wall 2 to fix the reinforced concrete partition wall 2 to the stable rock mass at the bottom. The length of the deep anchor 3 is greater than or equal to twice the height h of the reinforced concrete partition wall 2, and the upper end of the deep anchor 3 should extend into the middle of the reinforced concrete partition wall 2 to ensure a stable connection between the reinforced concrete partition wall 2 and the stable rock mass at the bottom.

[0042] like Figure 2 As shown, two parallel wall anchors 6 are symmetrically installed on both sides of the reinforced concrete partition wall 2 to ensure the vertical stability of the rock mass on both sides of the reinforced concrete partition wall and to prevent the rock mass at the bottom of the tunnel from sliding upward on both sides of the reinforced concrete partition wall. The angle α between the wall anchors 6 and the horizontal direction is 45° to 60°. The lower ends of the two parallel wall anchors on one side of the rock mass are fixed at the three equal division points of the height h of the reinforced concrete partition wall.

[0043] like Figure 3 As shown, the tunnel bottom anchor bolts 4 are arranged in a multi-level distribution. In this embodiment, they are arranged in a two-level distribution, including primary support anchor bolts and secondary support anchor bolts. The length of the primary support anchor bolts is consistent with the height of the reinforced concrete partition wall 2, and the length of the secondary support anchor bolts is twice the length of the primary support anchor bolts. The primary and secondary support anchor bolts are distributed alternately on one side of the reinforced concrete partition wall 2, and the direction of the anchor bolts is perpendicular to the tangent direction of the tunnel bottom slab.

[0044] The tunnel bottom anchor bolts 4 are evenly arranged in multiple rows along the tunnel direction, with a spacing of d between adjacent rows. The partition wall anchor cable 6 is located in the middle of two adjacent rows of tunnel bottom anchor bolts 4, and the distance from the adjacent row of tunnel bottom anchor bolts is 0.5d. Each row of tunnel bottom anchor bolts consists of graded support anchor bolts of varying lengths arranged in an alternating pattern, and all graded support anchor bolts in each row of tunnel bottom anchor bolts are in the same plane.

[0045] The bottom corner anchor cable 5 is perpendicular to the direction of the maximum principal stress of the rock mass at the bottom corner position (the area between the side wall and the tunnel floor). Multiple sets of bottom corner anchor cables are also arranged along the tunnel direction, with two bottom corner anchor cables in each set, located on both sides of the tunnel floor.

[0046] The drainage pipe 7 is located above the reinforced concrete partition wall 2.

[0047] The construction method of the tunnel floor bulge partition wall-anchorage combined control structure includes the following steps:

[0048] Step 1: After the tunnel excavation is completed, according to the designed structural dimensions, a backfill area with a width of b is excavated downwards along the middle of the tunnel bottom. The depth of the backfill area is the sum of the design height h of the reinforced concrete partition wall 2 and the height of the drainage pipe 7.

[0049] Step 2: Deploy deep anchor bolts 3 with a length of ≥2h from the bottom of the backfill area described in Step 1 to the depth of the tunnel bottom, and the top of the deep anchor bolts 3 should be 0.5h higher than the bottom of the backfill area, so that the reinforced concrete partition wall 2 remains stable with the deep surrounding rock through the deep anchor bolts 3;

[0050] Step 3: Install two parallel partition wall anchor cables 6 on both sides of the backfill area. The bottom ends of the two parallel partition wall anchor cables 6 are located at a distance from the bottom of the backfill area. At this location, the angle α between the two parallel partition wall anchor cables 6 and the horizontal direction is 45° to 60°.

[0051] Step 4: Arrange the steel cage from bottom to top at the bottom of the backfill area, and then pour concrete to form a reinforced concrete partition wall with a height of h. Reserve a drainage pipe 7 above the reinforced concrete partition wall 2.

[0052] Step 5: Arrange two levels of support anchors downward on the tunnel floor on both sides of the backfill area. The length of the first-level support anchor is h, and the length of the second-level support anchor is ≥2h. The two types of support anchors are arranged alternately in the tunnel cross section direction (the cross section perpendicular to the tunnel direction).

[0053] Step 6: Install corner anchor cables 5 at the bottom corner of the tunnel, which are perpendicular to the direction of the maximum principal stress of the surrounding rock at the bottom corner;

[0054] Step 7: Lay a leak-proof board with a width of ≥2b above the drainage pipe 7;

[0055] Step 8: Arrange the invert arch reinforcement cage, reserve the bottom corner anchor cable 5 channels on both sides, and pour the tunnel invert arch 1;

[0056] Step 9: After the reinforced concrete of the tunnel invert arch 1 has hardened, the bottom corner anchor cable 5 is tensioned and locked, and the construction is completed.

[0057] Example 2:

[0058] Depending on the actual engineering requirements, when the tunnel span is large or the rock strata are thin, in order to ensure the stability of the surrounding rock at the tunnel bottom, such as... Figure 4 and Figure 5 As shown, in Embodiment 2, two reinforced concrete partition walls 2 are installed, dividing the tunnel into three equal parts along the vertical direction of the tunnel. Drainage pipes 7 are installed above both reinforced concrete partition walls 2, and two parallel partition wall anchor cables 6 are installed on both sides of the two reinforced concrete partition walls at an angle of 45° to 60° with the horizontal direction. The two parallel partition wall anchor cables 6 are fixed at the three division points of the height h of the reinforced concrete partition walls 2, respectively. The tunnel bottom anchor bolts 4 between the two reinforced concrete partition walls 2 are also graded support anchor bolts.

[0059] This invention segments the tunnel floor rock strata horizontally, reducing the length-to-thickness ratio of each rock layer and enhancing the tunnel floor's resistance to compression and stability. High-strength reinforced concrete partitions are excavated at the tunnel floor, and deep anchor bolts are installed below these partitions to fix them to the underlying rock, ensuring their vertical stability. The anchor bolts at the tunnel floor increase the integrity of the layered rock mass at the bottom, reducing the displacement of the tunnel invert arch caused by high ground stress. This invention features a simple construction structure and can better control tunnel floor heave disasters without increasing the amount of excavation.

[0060] The above description is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A combined control structure of a partition-anchor in tunnel floor heave, characterized in that, The structure comprises a tunnel inverted arch, a reinforced concrete partition wall, deep anchor rods, tunnel bottom anchor rods, partition wall anchor cables, bottom corner anchor cables and drainage pipes; The reinforced concrete partition wall has a higher compressive strength than the compressive strength of the tunnel rock mass, and a plurality of deep anchor rods are arranged at the bottom of the reinforced concrete partition wall to fix the reinforced concrete partition wall to the stable rock mass at the bottom along the tunnel direction, the length of the deep anchor rods is greater than twice the height h of the reinforced concrete partition wall, and the upper ends of the deep anchor rods extend into the middle of the reinforced concrete partition wall; Two parallel partition wall anchor cables are arranged at the rock mass on both sides of the reinforced concrete partition wall, the angle a between the partition wall anchor cables and the horizontal direction is 45°-60°, and the lower ends of the two parallel partition wall anchor cables are fixed to the reinforced concrete partition wall and the upper ends are fixed to the tunnel bottom plate; The tunnel bottom anchor rods are distributed in multiple levels and have multiple support anchor rods, the lengths of the support anchor rods in each level are different, the length of the support anchor rods in the first level is consistent with the height of the reinforced concrete partition wall, and the length of the support anchor rods in the largest level is twice the height h of the reinforced concrete partition wall; The multiple support anchor rods are arranged in a staggered manner, and the directions of the support anchor rods are perpendicular to the tangential direction of the tunnel bottom plate; The bottom corner anchor cables are arranged at the bottom corners of the tunnel and are perpendicular to the direction of the maximum principal stress of the surrounding rock mass; The drainage pipes are arranged between the reinforced concrete partition wall and the tunnel inverted arch; The lower ends of two parallel partition wall anchor cables of one side rock mass are fixed to the height of the reinforced concrete partition wall respectively h The trisection point; According to the actual situation of a specific project, the number of the reinforced concrete partition walls is arranged as a single row, a double row or multiple rows, when arranged as multiple rows, a plurality of reinforced concrete partition walls are arranged at the equal division points of the section perpendicular to the tunnel direction, and multiple distributed tunnel bottom anchor rods are arranged between the adjacent two reinforced concrete partition walls; The tunnel bottom anchor rods comprise first level support anchor rods and second level support anchor rods, the length of the first level support anchor rods is consistent with the height of the reinforced concrete partition wall, and the length of the second level support anchor rods is twice the length of the first level support anchor rods.

2. The combined control structure of the tunnel floor heave partition-anchoring according to claim 1, characterized in that, The tunnel bottom anchor rods are uniformly arranged in multiple rows along the tunnel direction, and the distance between the adjacent two rows is 0.5 d The distance between the adjacent two rows is 0.5 d The distance between the adjacent two rows is 0.5 ; all the hierarchical support anchor rods in each row of the tunnel bottom anchor rods are in the same plane; the bottom corner anchor cables are also arranged in multiple groups along the tunnel direction, and two bottom corner anchor cables are arranged in each group and located on the two sides of the tunnel bottom plate.

3. The combined control structure of the tunnel floor heave partition-anchoring according to claim 1, characterized in that, The drainage pipes are located above the reinforced concrete partition wall, and a leakage-proof plate is arranged above the drainage pipes.

4. A method for constructing the combined control structure of the separation wall and anchor for the tunnel floor heave according to claim 1, characterized in that: The construction method comprises the following steps: Step one: after the tunnel excavation is completed, the number and height h of the reinforced concrete partition wall are determined according to the designed structure size, a backfill area with a width of b is excavated along the equal division points of the tunnel bottom, and the depth of the backfill area is the sum of the height of the reinforced concrete partition wall and the height of the drainage pipes; Step two: deep anchor rods with a length greater than 2h are arranged at the deep part of the tunnel bottom at the bottom of the backfill area, and the top ends of the deep anchor rods are higher than the bottom of the backfill area by 0.5h, so that the reinforced concrete partition wall is kept stable with the deep surrounding rock mass through the deep anchor rods; Step three: two parallel partition anchor cables are arranged on both sides of the backfill area, the bottom ends of the two parallel partition anchor cables are respectively located at a distance of 0.5H from the bottom of the backfill area , , and the included angle between the two parallel partition anchor cables and the horizontal direction is 45°~60°; α . Step four: a steel cage is arranged from bottom to top at the bottom of the backfill area, and then concrete is poured to form a reinforced concrete partition wall with a height of h, and the drainage pipes are reserved above the reinforced concrete partition wall; Step five: the backfill area is arranged with a plurality of support anchor rods with different lengths arranged in a staggered manner in the direction of the tunnel section; Step six: the bottom corner anchor cables are arranged at the bottom corners of the tunnel and are perpendicular to the direction of the maximum principal stress of the surrounding rock mass; Step seven: a leakage-proof plate with a width greater than 2b is laid above the drainage pipes; Step eight: an inverted arch steel cage is arranged, the passage of the bottom corner anchor cables is reserved on both sides, and the tunnel inverted arch is poured; Step nine: after the reinforced concrete of the tunnel inverted arch is hardened, the bottom corner anchor cables are tensioned and locked, and the construction is completed.

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