An adaptive composite lining structure applicable to large-deformation soft rock tunnels

Abstract

The present invention relates to an adaptive composite lining structure applicable to large-deformation soft rock tunnels, which is used to timely control the deformation of the surrounding rock of large-deformation soft rock tunnels and achieve adaptive support for large-deformation soft rock tunnels. The adaptive composite lining structure is composed of an early-strength primary support structure layer and a secondary lining layer arranged in sequence from outside to inside. The early-strength primary support structure layer is composed of an outer layer and an inner layer formed by integral shotcreting, and a pressure-relieving adaptive sub-structure is arranged between the outer layer and the inner layer. Compared with the prior art, the present invention has the advantages of high early support strength, being able to adapt to the deformation of the surrounding rock, high safety redundancy, wide applicability, etc.

Description

Technical Field

[0001] The present invention relates to the field of tunnel lining structures, and particularly to an adaptive composite lining structure suitable for large-deformation soft rock tunnels. Background Art

[0002] Highway tunnels are mostly located in mountainous areas and buried underground. During the construction process, various complex environments and adverse geology will inevitably be encountered, and large deformation of high in-situ stress soft surrounding rock is one of them. There are large areas of soft rock strata distributed in the western mountainous areas of our country. In the construction of mountain tunnels, complex geological conditions such as high in-situ stress levels and soft and broken surrounding rocks are often encountered. After the tunnel is excavated, the surrounding rock deforms greatly and lasts for a long time, resulting in a continuous increase in the stress on the support structure, often exceeding the bearing limits of the surrounding rock and lining. Cracking of the initial lining and deformation of the surrounding rock invading the tunnel clearance often occur, and in severe cases, major engineering disasters such as collapses occur, posing major challenges to the design and construction of soft rock tunnels. Such as Jiazhuqing Tunnel, Wushaoling Tunnel and Gansu Muzhailing Tunnel on the Nankun Line, as well as the Sichuan-Tibet Railway under planning and construction, have encountered great difficulties in design and construction.

[0003] The traditional support theory for large-deformation soft rock tunnels is early and strong support. The early and strong support theory has two meanings: one is to construct the support structure as early as possible after the tunnel is excavated; the other is to increase the stiffness of the support structure, such as using thickened shotcrete, more closely spaced high-strength steel arch frames and thicker secondary linings, etc. Although this support measure inhibits the deformation of the surrounding rock to a certain extent, controls the range of the loosened zone, and prevents tunnel collapses, when the properties of the surrounding rock are poor, after the construction of the double-layer lining structure is completed, with the gradual release of stress during the tunnel excavation process, the continuous rheology of the rock mass and the swelling characteristics shown after encountering water, etc., excessive surrounding rock pressure is induced, resulting in the support structure being in an extremely high stress state, and then causing the inner and outer linings to converge and deform, and even crack, seriously reducing the durability and waterproofness of the tunnel, etc., affecting the normal use of the tunnel. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above-mentioned defects existing in the prior art and provide an adaptive composite lining structure suitable for large-deformation soft rock tunnels.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] An adaptive composite lining structure suitable for large-deformation soft rock tunnels, used to timely control the deformation of the surrounding rock of large-deformation soft rock tunnels and achieve adaptive support for large-deformation soft rock tunnels. The adaptive composite lining structure is composed of an early-strength initial support structure layer and a secondary lining layer arranged in sequence from outside to inside. The early-strength initial support structure layer is composed of an outer layer and an inner layer formed by integral spraying, and a pressure-relieving adaptive sub-structure is arranged between the outer layer and the inner layer.

[0007] A plurality of long constant-resistance large-deformation bolt belts and short constant-resistance large-deformation bolt belts are alternately arranged along the extension direction of the tunnel axis and are parallel to each other, and the projection lines of each long constant-resistance large-deformation bolt belt and short constant-resistance large-deformation bolt belt on the tunnel bottom surface are perpendicular to the tunnel axis respectively.

[0008] A plurality of long constant-resistance large-deformation bolts are arranged at equal intervals in each long constant-resistance large-deformation bolt belt, and a plurality of short constant-resistance large-deformation bolts are arranged at equal intervals in each short constant-resistance large-deformation bolt belt, and every 3-5 short constant-resistance large-deformation bolts are fixed in series by a W-shaped steel belt.

[0009] The yielding self-adaptive sub-structure includes precast foam concrete members and a plurality of steel arch frames arranged at equal distances and parallel to each other along the tunnel axis. Each steel arch frame is composed of multiple sections of I-beams and a plurality of sliding joints connecting adjacent two sections of I-beams. And, the precast foam concrete members are arranged inside the inner layer and the positions correspond to the positions of the sliding joints of each steel arch frame, and the arrangement direction of each precast foam concrete member is parallel to the tunnel axis.

[0010] The sliding joint is a sleeve structure with an I-shaped inner cavity formed by fastening a channel steel and a steel plate with high-strength bolts applying a pre-tightening force. The end parts of adjacent two sections of I-beams are respectively inserted into the sliding joint and can slide and adjust the distance in the I-shaped inner cavity.

[0011] The long constant-resistance large-deformation bolt and the short constant-resistance large-deformation bolt have the same structure, and both are composed of an anchoring end, a rod body, a constant-resistance sleeve, a constant-resistance body and a locking device. Its anchoring end is prestressed and anchored in the surrounding rock mass of the tunnel, and the free end is anchored in the outer layer of the early-strength primary support structure layer and is welded through a steel mesh.

[0012] A plurality of PVC pipes arranged at equal intervals in the circumferential direction are also provided between the outer surface of the secondary lining layer and the inner layer of the early-strength primary support structure layer, and the arrangement direction of each PVC pipe is parallel to the tunnel axis.

[0013] The secondary lining layer is formed by spraying reinforced concrete with a strength grade of C30 or above, and a waterproof board and a non-woven fabric are provided on its outer surface.

[0014] Both the outer layer and the inner layer of the early-strength primary support structure layer are formed by spraying concrete with a strength grade of C25, and 425# ordinary Portland cement is used for the cement, and a waterproof agent and an early-strength agent are admixed.

[0015] The setting method of this self-adaptive composite lining structure is as follows:

[0016] 1) Excavate the rock mass;

[0017] 2) Initially spray 5 - 8 cm thick C25 early - strength concrete on the inner side of the excavated surrounding rock to form the outer layer of the early - strength initial support structure layer;

[0018] 3) At certain intervals on the free surface of the outer layer after initial spraying, drive constant - resistance large - deformation bolts, and conduct prestressed tension anchoring on the anchoring ends of the constant - resistance large - deformation bolts. The tension prestress is determined according to the in - situ stress and the initial surrounding - rock stress. Then lay the steel mesh;

[0019] 4) Arrange a steel arch frame at certain intervals on the inner side of the outer layer. Each steel arch frame is formed by connecting multiple I - beams through sliding joints, and make the flange of the I - beam parallel to the tunnel surface;

[0020] 5) Install precast foam - concrete components between the sliding joints of two adjacent steel arch frames. After installation, spray 30 cm thick C25 early - strength concrete to form the inner layer of the early - strength initial support structure layer. The inner surface of the precast foam - concrete component is flush with the inner surface of the inner layer;

[0021] 6) If the surrounding - rock deformation is unstable, arrange PVC pipes along the tunnel axis as a pressure - yielding self - adaptive layer. If the surrounding - rock deformation has been well controlled, the PVC pipes can be not installed and left empty. The layout density of the PVC pipes is increased or decreased according to the stability degree of the surrounding rock;

[0022] 7) Lay the waterproof board and non - woven fabric. After installation, construct 30 - 50 cm thick C30 reinforced concrete as the secondary lining layer.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] I. High early - support strength: After the excavation is completed, for the self - adaptive composite lining structure applicable to large - deformation soft - rock tunnels involved in the present invention, by applying prestress to the constant - resistance large - deformation bolts, the stress state of the surrounding rock on the excavation surface changes from tensile to tri - axial compression, restoring to the stress state before excavation, thereby realizing early strong support and playing a role in strengthening the surrounding rock at the same time.

[0025] II. Can adapt to the deformation of the surrounding rock: The self - adaptive composite lining structure applicable to large - deformation soft - rock tunnels involved in the present invention realizes the matching of the multi - level self - adaptive structure through the arrangement of the intermediate - layer PVC pipes, the installation of sliding joints and precast foam - concrete components. Cooperating with large - deformation bolts / cables, it can absorb a part of the surrounding - rock deformation, effectively control the convergence deformation of the inner lining, and avoid the cracking of the inner lining due to large surrounding - rock deformation.

[0026] III. High safety redundancy: For the self - adaptive composite lining structure applicable to large - deformation soft - rock tunnels involved in the present invention, by applying prestress to the constant - resistance large - deformation bolts, it has a high early - support force; at the same time, the pressure - yielding self - adaptive structure in the intermediate layer provides a part of unloading redundancy, making it have a high safety redundancy.

[0027] IV. Wide applicability: The self-adaptive composite lining structure applicable to large-deformation soft rock tunnels involved in the present invention can adjust the magnitude of prestress, the arrangement of bolts / cables, and the placement position and quantity of PVC pipes according to the requirements of different projects, enabling the structural system to reach the most effective support state. The design is flexible and has wide applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic structural diagram of the present invention. Among them, Fig. (1a) is a main sectional view of the structure, and Fig. (1b) is a partial enlarged view of part A in Fig. (1a).

[0029] Figure 2 It is a developed view of the structure of the present invention.

[0030] Figure 3 It is a schematic structural diagram of a constant-resistance large-deformation bolt. Among them, Fig. (3a) is a schematic structural diagram of a short constant-resistance large-deformation bolt, and Fig. (3b) is a schematic structural diagram of a long constant-resistance large-deformation bolt.

[0031] Figure 4 It is a schematic structural diagram of a steel arch frame. Among them, Fig. (4a) is a schematic installation position diagram of a sliding node, and Fig. (4b) is a schematic structural diagram of the sliding node.

[0032] Figure 5 It is a schematic diagram of self-adaptive yielding deformation. Among them, Fig. (5a) is a schematic structural diagram of self-adaptive yielding deformation, Fig. (5b) is a sectional view along a-a in Fig. (5a), and Fig. (5c) is a sectional view along b-b in Fig. (5a).

[0033] Description of the marks in the figures:

[0034] 1. Early-strength primary support structure layer, 2. Yielding self-adaptive sub-structure, 3. Secondary lining layer, 11. Outer layer, 12. Inner layer, 111. Long constant-resistance large-deformation bolt, 112. Short constant-resistance large-deformation bolt, 21. Steel arch frame, 22. Sliding node, 23. Prefabricated foam concrete member, 24. PVC pipe. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] Embodiment

[0037] As Figure 1-2 shown, the present invention provides a self-adaptive composite lining structure applicable to large-deformation soft rock tunnels, which is used to timely control the deformation of the surrounding rock of large-deformation soft rock tunnels, and at the same time achieve self-adaptive support for large-deformation soft rock tunnels and has a high safety redundancy.

[0038] This structure is arranged on the inner side of the surrounding rock after excavation. This composite lining structure mainly includes three parts: the early-strength primary support structure layer 1, the pressure-relieving self-adaptive sub-structure 2, and the secondary lining layer 3. The early-strength primary support structure layer 1 consists of prestressed constant-resistance large-deformation bolts / cables, an inner layer 12, an outer layer 11, and a W-shaped steel strip; the pressure-relieving self-adaptive sub-structure 2 consists of a steel arch 21 with a sliding node 22, a foam concrete precast member 23, and a PVC pipe 24; the secondary lining layer 3 consists of a waterproof board, a non-woven fabric, and reinforced concrete.

[0039] As Figure 3 shown, the constant-resistance large-deformation bolt / cable consists of a locking device, a bearing plate, a filling material, a rod body, a casing, a constant-resistance body, a constant-resistance head, and a guide head. When the tensile force acting on the free end is greater than or equal to the constant resistance of the constant-resistance large-deformation bolt, the constant-resistance body will slide within the casing. As long as the constant resistance is less than the elastic limit of the rod body, theoretically the deformation of the bolt can be designed to be arbitrarily long, thus achieving large deformation.

[0040] After the constant-resistance large-deformation bolt / cable is installed, prestress tensioning and anchoring are carried out on the distal end, and the prestress is determined according to the in-situ stress and the initial surrounding rock stress.

[0041] The concrete strength grade of the outer layer 11 and the inner layer 12 of the early-strength primary support structure layer 1 is C25. The cement used is 425# ordinary Portland cement, with a waterproofing agent and an early-strength agent added. The initial spraying thickness is 5 - 8 cm, and after the steel arch 21 and the foam concrete precast member 23 are installed, the re-spraying thickness is 20 - 30 cm.

[0042] As Figure 4 shown, the steel arch 21 is composed of multiple sections of I-beams / H-beams connected by sliding nodes 22, and the flanges of the I-beams are parallel to the tunnel surface. It is arranged on the inner side of the outer layer 11 at intervals of 0.3 - 1.5 m along the tunnel axis.

[0043] The sliding node 22 consists of a channel steel, a steel plate, and high-strength bolts. The channel steel and the steel plate are connected by high-strength bolts, and a certain pre-tightening force is applied to the high-strength bolts. The maximum static friction force achieved by the pre-tightening force should ensure that the steel plate at the node and the steel arch do not slide before yielding.

[0044] The foam concrete precast member 23 is a precast component with a relatively large porosity and is easily deformed under pressure. The inner surface of the foam concrete precast member should be flush with the inner surface of the sprayed concrete inner layer 12.

[0045] The PVC pipe 24 is arranged between the early-strength primary support structure layer 1 and the secondary lining layer 3 at certain intervals along the tunnel axis. It is easily buckled under radial pressure to achieve self-adaptive deformation of the structure.

[0046] The secondary lining layer 3 includes a waterproof board, a non-woven fabric, and reinforced concrete. The reinforced concrete is C30, and its thickness is 30 - 50 cm.

[0047] As Figure 5 shown, in the initial stage of compression, as the pressure gradually increases, when the tangential pressure of the steel arch is greater than the frictional force brought by the pre-tightening force of the high-strength bolts, the end of the I-beam / H-beam starts to slide in the inner cavity of the I-beam. Part of the pressure begins to transfer to the concrete. Since the pores of the precast foam concrete components at the joints are relatively large and are prone to deformation under pressure, the precast foam concrete components start to compress as the joints of the steel arch slide, achieving mutual matching. The sliding of the joints of the steel arch and the compression of the precast foam concrete components can absorb part of the deformation of the surrounding rock, effectively reduce the stress level of the surrounding rock, and avoid the structure being in a high stress state. Applying a certain pre-tightening force to the high-strength bolts can ensure that the steel plate at the joint and the steel arch do not slide before yielding, that is, they can slide under compression and do not fail under bending and shear, ensuring the safety at the joint.

[0048] The specific installation method of the present invention is as follows:

[0049] 1. Use construction methods such as drill and blast method or new idea method to excavate the rock mass;

[0050] 2. Initially spray 5 - 8 cm of C25 early-strength concrete on the inner side of the excavated surrounding rock;

[0051] 3. Drive constant-resistance large-deformation anchor cables at certain intervals on the free surface after the initial spraying, and prestress and anchor the far ends of the constant-resistance large-deformation anchor cables. The prestress tension is determined according to the in-situ stress and the initial stress of the surrounding rock. Then lay the steel mesh; for example Figure 1 shown, two types of anchor cables with different lengths can be used. The spacing of the 4300 mm anchor cables is 1000×1200 mm, and every 3 - 5 anchor cables are connected in series with a W-shaped steel strip, mainly playing the role of strengthening the rock mass; the 10300 mm anchor cables do not use a W-shaped steel strip, and the spacing is 2000×1200 mm, mainly playing the role of anchoring. The steel mesh can be welded with Φ8 mm steel bars, and the mesh size is 100×100 mm;

[0052] 4. Arrange a steel arch every 0.3 - 1.0 m on the inner side of the sprayed concrete. The steel arch is composed of multiple sections of HW200b steel sections connected by sliding joints, and the flange of the I-beam is parallel to the tunnel surface;

[0053] 5. Install precast foam concrete components between the sliding joints of two steel arches. After installation, spray 30 cm thick C25 early-strength concrete. The inner surface of the precast foam concrete components should be flush with the inner surface of the sprayed concrete;

[0054] 6. If the surrounding rock deformation is unstable, PVC pipes with an inner diameter of 200 mm are arranged along the tunnel axis as a pressure-relieving adaptive layer; if the surrounding rock deformation has been well controlled, the PVC pipes may not be installed and left empty. The arrangement of PVC pipes can be appropriately densified or reduced according to the stability of the surrounding rock.

[0055] 7. Lay the waterproof board and non-woven fabric, and construct 30 - 50 cm thick C30 reinforced concrete as the secondary lining after installation.

[0056] The above embodiments are only illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. An adaptive composite lining structure applicable to large-deformation soft rock tunnels, which is used to timely control the deformation of surrounding rocks in large-deformation soft rock tunnels and achieve adaptive support for large-deformation soft rock tunnels. It is characterized in that The adaptive composite lining structure is composed of an early-strength primary support structure layer (1) and a secondary lining layer (3) arranged in sequence from outside to inside. The early-strength primary support structure layer (1) is composed of an outer layer (11) and an inner layer (12) formed by integral shotcreting. A pressure-relieving adaptive sub-structure (2) is provided between the outer layer (11) and the inner layer (12); The outer layer is provided with multiple long constant-resistance large-deformation bolt belts and short constant-resistance large-deformation bolt belts that are alternately arranged and parallel to each other along the extension direction of the tunnel axis. The projection lines of each long constant-resistance large-deformation bolt belt and short constant-resistance large-deformation bolt belt on the tunnel bottom surface are respectively perpendicular to the tunnel axis; Multiple long constant-resistance large-deformation bolts (111) are evenly distributed at equal intervals in each long constant-resistance large-deformation bolt belt, and multiple short constant-resistance large-deformation bolts (112) are evenly distributed at equal intervals in each short constant-resistance large-deformation bolt belt. And every 3-5 short constant-resistance large-deformation bolts (112) are fixed in series by a W-shaped steel belt; The setting method of this adaptive composite lining structure is as follows: 1) Excavate the rock mass; 2) Shotcrete 5-8 cm of C25 early-strength concrete on the inner side of the excavated surrounding rock to form the outer layer of the early-strength primary support structure layer; 3) Drive constant-resistance large-deformation bolts at certain intervals on the free surface of the outer layer after initial shotcreting, and prestress and anchor the anchoring ends of the constant-resistance large-deformation bolts. The prestress is determined according to the in-situ stress and the initial surrounding rock stress, and then a steel mesh is laid; 4) Arrange a steel arch frame at certain intervals on the inner side of the outer layer. Each steel arch frame is formed by connecting multiple I-beams through sliding joints, and the flange of the I-beam is parallel to the tunnel surface; 5) Install precast foam concrete components between the sliding joints of adjacent two steel arch frames. After installation, shotcrete 30 cm thick C25 early-strength concrete to form the inner layer of the early-strength primary support structure layer. The inner surface of the precast foam concrete component is flush with the inner surface of the inner layer; 6) If the surrounding rock deformation is unstable, arrange PVC pipes along the tunnel axis as the pressure-relieving adaptive layer. If the surrounding rock deformation has been well controlled, the PVC pipes can not be installed and left empty. The arrangement density of the PVC pipes is increased or decreased according to the stability degree of the surrounding rock; 7) Lay a waterproof board and non-woven fabric. After installation, construct 30-50 cm thick C30 reinforced concrete as the secondary lining layer; The pressure-relieving adaptive sub-structure (2) includes precast foam concrete components (23) and multiple steel arch frames (21) arranged at equal distances and parallel to each other along the tunnel axis. Each steel arch frame (21) is composed of multiple sections of I-beams and multiple sliding joints (22) connecting adjacent two sections of I-beams. And the precast foam concrete components (23) are arranged in the inner layer (12) and the positions correspond to the positions of the sliding joints (22) of each steel arch frame (21). The setting direction of each precast foam concrete component (23) is parallel to the tunnel axis; The sliding joint (22) is a sleeve structure with an I-shaped inner cavity formed by fastening a channel steel and a steel plate with high-strength bolts applying a pre-tightening force. The end parts of adjacent two sections of I-beams are respectively inserted into the sliding joint and can slide and adjust the distance in the I-shaped inner cavity; The long constant-resistance and large-deformation bolt (111) and the short constant-resistance and large-deformation bolt (112) have the same structure, both consisting of an anchorage end, a rod body, a constant-resistance sleeve, a constant-resistance body and a locking device. The anchorage end is prestressed and anchored in the surrounding rock mass of the tunnel, and the free end is anchored in the outer layer (11) of the early-strength initial support structure layer (1) and welded through a steel mesh.

2. The adaptive composite lining structure for large-deformation soft rock tunnels according to claim 1, characterized in that, A plurality of PVC pipes (24) arranged at equal intervals along the circumference are further provided between the outer surface of the secondary lining layer (3) and the inner layer (12) of the early-strength initial support structure layer (1), and the arrangement direction of each PVC pipe (24) is parallel to the tunnel axis.

3. An adaptive composite lining structure applicable to large-deformation soft rock tunnels according to claim 1, characterized in that, The secondary lining layer (3) is formed by spraying reinforced concrete with a strength grade of C30 or above, and a waterproof board and a non-woven fabric are provided on its outer surface.

4. An adaptive composite lining structure applicable to large-deformation soft rock tunnels according to claim 1, characterized in that, Both the outer layer (11) and the inner layer (12) of the early-strength initial support structure layer (1) are formed by spraying concrete with a strength grade of C25, and 425# ordinary portland cement is used for the cement, with a waterproof agent and an early-strength agent admixed.

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