Full-life-cycle combined yielding supporting structure and construction method thereof

Abstract

The invention discloses a full-life-cycle combined yielding supporting structure and a construction method thereof. The full-life-cycle combined yielding supporting structure comprises a plurality of energy absorption anchor rods, a deformable primary support, a buffer layer and a secondary lining which are sequentially arranged from outside to inside in the radial direction of a tunnel. One end of each energy-absorbing anchor rod is connected with the deformable primary support, the energy-absorbing anchor rods are distributed at intervals, contractible steel arch frames and compressible components are arranged in the deformable primary support, the contractible steel arch frames are of a sectional structure, the compressible components are connected between the adjacent contractible steel arch frames, and the compressible components are connected between the adjacent contractible steel arch frames. And the buffer layer is fixed on the deformable primary support. The supporting system is suitable for tunnel engineering under soft rock, high ground stress and complex geological conditions, coordinated deformation of the whole supporting structure system is achieved by optimizing the multi-layer structure of the supporting system, the long-term stability and construction safety of a tunnel are improved, the service life of the tunnel is prolonged, and the maintenance cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel and underground engineering, and in particular to a full-life cycle combined pressure-yielding support structure and a construction method thereof. Background Art

[0002] Due to the unique geological conditions of ultra-deep soft rock tunnels, such as high geostress environment, significant rheological properties of soft rock, and low strength characteristics of surrounding rock, the construction process and support measures face huge challenges. High geostress not only means that the stress redistribution process of the surrounding rock after tunnel excavation is more complex and violent, but may also cause abnormally significant immediate and long-term deformation of the surrounding rock. The rheological properties of soft rock further aggravate this problem, causing the deformation of the surrounding rock to continue to increase over time, making it difficult to predict and control. In addition, the surrounding rock itself has low strength and is more susceptible to construction disturbances, which increases the burden on the support structure.

[0003] Traditional support methods, such as shotcrete support and the New Austrian Tunneling Method (NATM), perform well in tunnel construction under conventional geological conditions. However, in soft rock tunnels, shotcrete support may fail due to continuous deformation of the surrounding rock, and the New Austrian Tunneling Method (NATM) may cause cracking of the initial support due to insufficient initial support strength or mismatched stiffness, and cannot effectively limit the deformation of the surrounding rock. At the same time, the secondary lining may also be damaged due to long-term deformation of the surrounding rock, making it difficult to effectively control large deformation of the surrounding rock, affecting its bearing capacity and durability.

[0004] Long-term deformation of the surrounding rock not only directly threatens the safety of the support structure, but also imposes additional loads on the support structure. This additional load may cause the support structure to crack or yield early before reaching its design life, seriously affecting the safety and service life of the tunnel. In addition, due to high ground stress and complex geological environment during construction, the risk of surrounding rock collapse and support failure increases significantly, and the support structure may lose stability during construction, posing a serious threat to construction safety. Therefore, in view of the special geological conditions of ultra-deep soft rock tunnels, it is urgent to develop a combined support system and design method that can adapt to large deformation of the surrounding rock and coordinate the deformation characteristics of the entire life cycle, so as to improve the adaptability and durability of tunnel support. Summary of the invention

[0005] The purpose of the present invention is to provide a full-life cycle combined pressure-yielding support structure and a construction method thereof, so as to solve the problem that the prior art cannot adapt to large deformation of surrounding rock and thus leads to support failure.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A full-life cycle combined pressure-yielding support structure, comprising a plurality of energy-absorbing anchors, a deformable initial support, a buffer layer and a secondary lining arranged in sequence from the outside to the inside along the tunnel radial direction; One end of the energy absorbing anchor is connected to a deformable initial support, and a plurality of the energy absorbing anchors are distributed at intervals. A retractable steel arch frame and a compressible component are arranged in the deformable initial support. The retractable steel arch frame is a segmented structure. The compressible component is connected between adjacent retractable steel arch frames, and the buffer layer is fixed on the deformable initial support.

[0007] Furthermore, a telescopic sleeve is sleeved on the middle part of the energy absorbing anchor rod, and the other end of the energy absorbing anchor rod is inserted into a borehole in the surrounding rock.

[0008] Furthermore, the retractable steel arches are connected by sliding joints, the compressible components are connected to the sliding joints by epoxy resin coatings, polytetrafluoroethylene films are adhered to the compressible components, and the number of the sliding joints is equal to the number of the compressible components.

[0009] Furthermore, the compressible component is foamed concrete, and the yield load is 8-10 MPa.

[0010] Furthermore, reflective sheets are installed at the arch top and the waist of the deformable initial support, strain gauges are installed on the compressible member, and the surface of the deformable initial support is provided with sprayed concrete.

[0011] Furthermore, the material of the buffer layer is polyethylene material, and the buffer layer is fixed to the inner side of the deformable initial support by expansion bolts.

[0012] Furthermore, the secondary lining is made of cast-in-place reinforced concrete, and a waterproof layer is laid in the formwork of the cast-in-place reinforced concrete.

[0013] Furthermore, the allowable displacement of the energy-absorbing anchor rod is determined by the maximum slippage of each sliding joint on the retractable steel arch frame and the ultimate compression of the buffer layer, and the maximum slippage of each sliding joint is determined by the ultimate compression of the compressible member.

[0014] Furthermore, a locking anchor rod is connected to the bottom of the deformable initial support.

[0015] A construction method of the full life cycle combined yielding support structure comprises: Insert the energy-absorbing anchor into the drilled hole of the surrounding rock, inject cement-water glass slurry, ensure that the slurry fills the pores and forms a close bond with the surrounding rock. After the grouting solidifies, apply prestress to enhance the anchoring effect; Connect the retractable steel arches of the segmented structure, check the centering of the retractable steel arches, connect the compressible members between adjacent retractable steel arches, spray the shotcrete, and complete the setting of the deformable initial support; Clean the inner surface of the retractable steel arch frame. When the retractable steel arch frame reaches the maximum slippage and the compressible component reaches the limit strain, fix the buffer layer on the inner side of the deformable initial support. After completion, press lightly to ensure that the buffer layer fits tightly with the deformable initial support. Install the steel formwork and fix it in the center to ensure that the steel formwork is tightly spliced ​​and firmly supported, then pour the concrete. After pouring, vibrate the concrete to ensure that there are no voids or segregation, and complete the setting of the secondary lining.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a full-life cycle combined pressure-yielding support structure, which sequentially arranges a plurality of energy-absorbing anchors, a deformable initial support, a buffer layer and a secondary lining along the radial direction of the tunnel from the outside to the inside, connects one end of the energy-absorbing anchor to the deformable initial support, and the plurality of energy-absorbing anchors are distributed at intervals, and the energy-absorbing anchor reinforces the surrounding rock from the inside of the surrounding rock, enhances the stability of the surrounding rock, and has the ability to coordinate deformation with the surrounding rock. A retractable steel arch frame and a compressible member are arranged in the deformable initial support, and the retractable steel arch frame is arranged as a segmented structure, and the compressible member is connected between adjacent retractable steel arch frames. The deformable initial support is composed of a retractable steel arch frame and a shotcrete lining containing a compressible member. Under a certain surrounding rock pressure, the retractable steel arch frame slides through a joint, and the shotcrete lining containing a compressible member allows the deformable initial support to produce a considerable cross-sectional contraction through the compression of the compressible member, which is mainly used to release the early aging large deformation of the surrounding rock during the construction stage. The buffer layer is then fixed on the deformable initial support, and the compression of the buffer layer is used to absorb the long-term deformation of the surrounding rock during the service stage of the tunnel, thereby reducing the pressure on the secondary lining structure, improving the long-term stability of the secondary lining structure, and jointly forming a full-life cycle joint pressure-yielding support structure. The present invention is suitable for tunnel projects with soft rocks, high ground stress and complex geological conditions. By optimizing the multi-layer structure of the support system, the coordinated deformation of the entire support structure system is achieved, the long-term stability and construction safety of the tunnel are improved, the service life of the tunnel is extended, and the maintenance cost is reduced. At the same time, it meets environmental protection requirements, reduces the impact of construction on the environment, and has broad application prospects and significant economic benefits.

[0017] Furthermore, in the combined pressure-yielding support structure, the allowable displacement of the energy-absorbing anchor is determined by the maximum slip of each sliding joint on the retractable steel arch and the ultimate compression of the buffer layer. The maximum slip of each sliding joint is determined by the ultimate compression of the compressible component, and the number of sliding joints is equal to the number of compressible components. By accurately calculating the slip of the sliding joints and the compression of the buffer layer, the pressure borne by the support structure can be more effectively absorbed and dispersed, and the stress performance and deformation performance of the support structure can be optimized. When the support structure is subjected to stress, it can deform according to certain rules and expectations, thereby achieving coordinated deformation of the entire support structure system, thereby avoiding structural damage caused by uneven deformation, and better adapting to various situations with complex geological conditions or restricted construction conditions, ensuring construction safety and project quality.

[0018] The present invention also provides a construction method for a combined yielding support structure for the entire life cycle, which is to immediately apply energy-absorbing anchors after tunnel excavation, then install a retractable steel arch frame, and then install a compressible component at the sliding joint, and spray concrete to form a deformable initial support. When the sliding joint of the retractable steel arch frame reaches the limit slippage and the compressible component reaches the limit compression, a buffer layer is installed, and finally cast concrete to form a secondary lining. The present invention combines the evolution law of tunnel deformation and support pressure during the entire life cycle, and through dynamic construction and real-time feedback control, ensures the adaptability and safety of the support structure system during the construction and service stages. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 It is a schematic diagram of the full life cycle combined pressure-yielding support structure of the present invention.

[0021] Figure 2 It is a schematic diagram of the deformable initial support structure of the present invention.

[0022] Among them: 1-energy-absorbing anchor rod, 2-telescopic sleeve, 3-deformable initial support, 4-compressible component, 5-buffer layer, 6-expansion bolt, 7-secondary lining, 8-locking anchor rod, 9-retractable steel arch frame, 10-sliding joint, 11-sprayed concrete. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0024] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. 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.

[0025] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0026] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does 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 cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0027] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0028] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] The present invention is further described in detail below in conjunction with the accompanying drawings: See also Figure 1The present invention provides a full-life cycle combined pressure-yielding support structure, including a plurality of energy-absorbing anchor rods 1, a telescopic sleeve 2, a deformable initial support 3, a buffer layer 5, an expansion bolt 6, a secondary lining 7 and a locking anchor rod 8, wherein the plurality of energy-absorbing anchor rods 1, the deformable initial support 3, the buffer layer 5 and the secondary lining 7 are arranged in sequence from the outside to the inside along the radial direction of the tunnel.

[0030] The energy-absorbing anchor rod 1 is a high-strength, high-ductility anchor rod, which is used for releasing deformation of surrounding rocks during tunnel construction and service. A telescopic sleeve 2 is sleeved in the middle of the energy-absorbing anchor rod 1, one end of the energy-absorbing anchor rod 1 is inserted into the drill hole of the surrounding rock, and the other end is connected to the deformable initial support 3. Several energy-absorbing anchor rods 1 are distributed at intervals, which are used to reinforce the surrounding rock during the entire construction and service stage, enhance the stability of the surrounding rock, and have the ability to coordinate deformation with the surrounding rock.

[0031] like Figure 2 As shown, the deformable initial support 3 includes a retractable steel arch frame 9 and a shotcrete lining containing a compressible member 4, which is used to release the early-stage large deformation of the surrounding rock during the tunnel construction stage. Among them, the retractable steel arch frame 9 adopts a segmented structure, including multiple sections of prefabricated steel arch frames, and adjacent steel arch frames are connected by sliding joints 10. The compressible member 4 adopts foam concrete, and the yield load is designed to be 8~10MPa. The compressible member 4 is connected between adjacent retractable steel arch frames 9, and the compressible member 4 is connected by epoxy resin coating at the sliding joints 10 of two adjacent sections of steel arch frames, and then a polytetrafluoroethylene film is pasted, and the bonding effect is enhanced by pressurization and fixing. At the same time, reflective sheets are installed at the arch top and arch waist of the steel arch frame, and strain gauges are installed at the compressible member 4 for deformation monitoring. Finally, shotcrete 11 is set on the surface of the steel arch frame, and the aging hardening characteristics of the shotcrete 11 are considered to form a deformable initial support 3, which is used to release the early-stage large deformation of the surrounding rock during the tunnel construction stage. In addition, a locking anchor rod 8 is connected to the bottom of the deformable initial support 3. Fixing the other end of the locking anchor rod 8 in a stable rock layer or soil can increase the stability of the support structure and further enhance the anti-overturning ability of the support structure.

[0032] The buffer layer 5 is used to release the deformation of the surrounding rock during the service stage of the tunnel. It is located between the deformable initial support 3 and the secondary lining 7. The material is polyethylene material with a density of 0.91~0.96g / cm³ and high energy absorption capacity. The buffer layer 5 is installed when the retractable steel arch 9 reaches the maximum slip and the compressible member 4 reaches the limit strain. During installation, the polyethylene sheet is cut to a suitable size, hoisted to a suitable position, and the four corners of the sheet are fixed to the inner side of the deformable initial support 3 with expansion bolts 6 to ensure that the buffer layer 5 is closely attached to the deformable initial support 3 to avoid gaps affecting the support effect. It is used to absorb the long-term deformation of the surrounding rock during the service stage of the tunnel, thereby reducing the pressure acting on the secondary lining 7 structure.

[0033] The secondary lining 7 is arranged inside the buffer layer 5 and is made of cast reinforced concrete to enhance the stability of the entire structure. A waterproof layer is laid inside the formwork of the cast reinforced concrete to prevent the penetration of moisture or other harmful substances and protect the internal structure from damage.

[0034] After the excavation of the ultra-deep soft rock tunnel, the problems existing in the prior art can be effectively solved by combining the energy-absorbing anchor rod 1, the deformable initial support 3, the buffer layer 5 and the secondary lining 7. At the same time, to achieve the coordinated deformation of the entire support structure system, the allowable displacement of the energy-absorbing anchor rod 1 can be determined by the maximum slip of each sliding joint 10 on the retractable steel arch frame 9 and the ultimate compression of the buffer layer 5, and the maximum slip of each sliding joint 10 can be determined by the ultimate compression of the compressible member 4. The allowable displacement of the energy-absorbing anchor rod should be equal to the maximum slip of each sliding joint 10 of the retractable steel arch frame 9 multiplied by the number of sliding joints 10, divided by 2π and the sum of the ultimate compression of the buffer layer 5. In addition, the maximum slip of each sliding joint 10 of the retractable steel arch frame 9 should be equal to the ultimate compression of each compressible member 4, and the number of sliding joints 10 is equal to the number of compressible members 4.

[0035] In a specific embodiment of the present invention, the length of the energy absorbing anchor rod 1 is 5-10 m, the arrangement interval is 1.5-2 m, the thickness of the buffer layer 5 is 10-15 cm, and the thickness of the secondary lining 7 is 40-50 cm.

[0036] The construction method of the full life cycle combined yielding support structure of the present invention comprises the following steps: Step 1: After tunnel excavation, sprayed concrete 11 is used to cover the tunnel face and surrounding rock in a timely manner to reinforce the surface of the surrounding rock and prevent the surrounding rock from becoming unstable or collapsing.

[0037] Step 2: Insert the energy-absorbing anchor rod 1 with the telescopic sleeve 2 into the drilled hole of the surrounding rock, and use high-pressure grouting equipment to inject cement-water glass slurry to ensure that the slurry fills the pores and forms a close bond with the surrounding rock. After the grouting solidifies, use tensioning equipment to apply prestress to the design value to enhance the anchoring effect.

[0038] Step 3: hoist the retractable steel arch frame 9 of the segmented structure to the designed position, connect the adjacent steel arch frames through sliding joints 10, check the centration of the steel arch frames, use epoxy resin coating to connect the compressible components 4 at the sliding joints 10 of the two adjacent sections of the steel arch frames, then paste the polytetrafluoroethylene film, and enhance the bonding effect by pressurizing and fixing, at the same time, install reflective sheets at the arch top and arch waist of the steel arch frame, install strain gauges at the compressible components 4 for deformation monitoring, and finally set sprayed concrete 11 on the surface of the steel arch frame.

[0039] Step 4: Clean the inner surface of the steel arch frame. When the retractable steel arch frame 9 reaches the maximum slippage and the compressible component 4 reaches the limit strain, cut the polyethylene sheet to a suitable size, hoist it to a suitable position, and use expansion bolts 6 to fix the four corners of the sheet to the inner side of the deformable initial support 3. After laying, press lightly to ensure that the buffer layer 5 fits tightly against the deformable initial support 3.

[0040] Step 5: Install the steel formwork and fix it in the center, ensure that the steel formwork is tightly spliced ​​and firmly supported, and lay a waterproof layer on the inside of the steel formwork to improve the anti-seepage performance of the secondary lining 7. Use pumping equipment to pour concrete. The concrete strength grade is C40, mixed with high-strength fiber and water reducing agent, and constructed in sections. The length of each section does not exceed 6m. After pouring, use a vibrating rod to compact the concrete to ensure that there are no voids or segregation.

[0041] The present invention, through the above-mentioned support system and construction method, sets up a combined support structure system of energy-absorbing anchor rods 1, deformable initial support 3, buffer layer 5 and secondary lining 7, and proposes a design and construction method for achieving coordinated deformation of the entire support structure system. It follows the support principle of "giving way while resisting, and combining resistance and giving way", is suitable for ultra-deep soft rock tunnels, fully realizes the synergistic effect of the support system and surrounding rock deformation, and improves the long-term stability and construction safety of the tunnel.

[0042] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A full life cycle combined pressure-yielding support structure, characterized in that: It comprises a plurality of energy absorbing anchor rods (1), a deformable initial support (3), a buffer layer (5) and a secondary lining (7) which are arranged in sequence from the outside to the inside along the radial direction of the tunnel; One end of the energy absorbing anchor rod (1) is connected to a deformable initial support (3), a plurality of the energy absorbing anchor rods (1) are distributed at intervals, a retractable steel arch frame (9) and a compressible component (4) are arranged in the deformable initial support (3), the retractable steel arch frame (9) is a segmented structure, the compressible component (4) is connected between adjacent retractable steel arch frames (9), and the buffer layer (5) is fixed on the deformable initial support (3).

2. A full life cycle combined pressure-yielding support structure according to claim 1, characterized in that: A telescopic sleeve (2) is sleeved on the middle part of the energy absorbing anchor rod (1), and the other end of the energy absorbing anchor rod (1) is inserted into a borehole in the surrounding rock.

3. The full life cycle combined pressure-yielding support structure according to claim 1 is characterized in that: The retractable steel arches (9) are connected via sliding joints (10), the compressible components (4) are connected to the sliding joints (10) via epoxy resin coatings, a polytetrafluoroethylene film is adhered to the compressible components (4), and the number of the sliding joints (10) is equal to the number of the compressible components (4).

4. The full life cycle combined pressure-yielding support structure according to claim 1 is characterized in that: The compressible component (4) is foamed concrete, and the yield load is 8-10 MPa.

5. The full life cycle combined pressure-yielding support structure according to claim 1 is characterized in that: Reflective sheets are installed at the arch top and the arch waist of the deformable initial support (3), a strain gauge is installed on the compressible component (4), and the surface of the deformable initial support (3) is provided with sprayed concrete (11).

6. The full life cycle combined pressure-yielding support structure according to claim 1 is characterized in that: The material of the buffer layer (5) is polyethylene material, and the buffer layer (5) is fixed to the inner side of the deformable initial support (3) by means of expansion bolts (6).

7. The full life cycle combined pressure-yielding support structure according to claim 1 is characterized in that: The secondary lining (7) is made of cast-in-place reinforced concrete, and a waterproof layer is laid in the formwork of the cast-in-place reinforced concrete.

8. The full life cycle combined pressure-yielding support structure according to claim 1 is characterized in that: The allowable displacement of the energy-absorbing anchor rod (1) is determined by the maximum slippage of each sliding joint (10) on the retractable steel arch frame (9) and the ultimate compression of the buffer layer (5), and the maximum slippage of each sliding joint (10) is determined by the ultimate compression of the compressible member (4).

9. The full life cycle combined pressure-yielding support structure according to claim 1 is characterized in that: The bottom of the deformable initial support (3) is connected to a foot-locking anchor rod (8).

10. A construction method for the full life cycle combined pressure-yielding support structure according to any one of claims 1 to 9, characterized in that: include: Insert the energy-absorbing anchor rod (1) into the drilled hole of the surrounding rock, inject cement-water glass grout, ensure that the grout fills the pores and forms a close bond with the surrounding rock, and apply prestress after the grout solidifies to enhance the anchoring effect; Connecting the retractable steel arch frames (9) of the segmented structure, checking the centering of the retractable steel arch frames (9), connecting the compressible member (4) between adjacent retractable steel arch frames (9), spraying the shotcrete (11), and completing the setting of the deformable initial support (3); Clean the inner surface of the retractable steel arch frame (9), and when the retractable steel arch frame (9) reaches the maximum slippage and the compressible member (4) reaches the limit strain, fix the buffer layer (5) on the inner side of the deformable initial support (3), and after completion, lightly press to ensure that the buffer layer (5) and the deformable initial support (3) are tightly fitted; Install the steel formwork and align and fix it to ensure that the steel formwork is tightly spliced ​​and firmly supported. Then pour the concrete. After pouring, vibrate the concrete to ensure that there are no voids or segregation. Complete the setting of the secondary lining (7).

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