Ultra-high performance concrete-steel arch composite structure and method for reinforcing shield tunnel lining structure

Abstract

The present invention relates to the field of tunnel engineering, and proposes an ultra-high performance concrete (UHPC)-steel arch frame combined structure and method for reinforcing the shield tunnel lining structure. The structure includes five key components: a steel arch frame (4), UHPC (2), a transverse bolt (5), a vertical chemical anchor bolt (6), and a vertical embedded reinforcement (3). The structure and method described in the present invention give full play to the advantages of UHPC, such as high strength, high rigidity, good durability, and strong interface adhesion, and reduce the risk of disasters caused by high-temperature softening of the steel arch frame; at the same time, the problem of UHPC's own shrinkage cracking is solved by applying prestress to the steel arch frame, and the disadvantage of brittle failure of the UHPC reinforced structure is overcome. The present invention has the effect of increasing the strength and rigidity of the tunnel lining structure and effectively controlling cracks. Moreover, the present invention is convenient in obtaining materials, fast in construction, safe and reliable, and has broad application prospects.

Description

Technical Field

[0001] The invention relates to the field of tunnel engineering, and in particular to an ultra-high performance concrete (UHPC)-steel arch frame combined structure and method for reinforcing a shield tunnel lining structure. Background Art

[0002] Shield tunnels have the advantages of high mechanization level, high construction safety, construction operations are not affected by climatic conditions, and have little impact on ground buildings, environment, and underground pipelines. Therefore, shield methods have been widely used in the construction of rapidly developing urban rail transit. Some shield tunnels have been in operation for decades, and the lining structures have gradually exposed problems such as water leakage, cracks, and large deformation. There are also a small number of newly built tunnels that have similar problems due to design defects, insufficient construction management, or nearby engineering activities. These diseases affect the normal operation of the tunnel and even the structural safety. At present, for shield tunnel lining structures with serious diseases, reinforcement treatment is often used to improve the stress performance of the tunnel, mainly including enhancing the structural bearing capacity, controlling structural deformation, controlling the development of cracks, preventing seepage and plugging leaks, while taking into account fire resistance, durability, and avoiding brittle failure modes of reinforced structures. Existing reinforcement methods include:

[0003] The reinforcement method of pasting carbon fiber cloth and aramid cloth uses an adhesive to paste the fiber cloth on the inner surface of the pipe segment. The advantage is that the reinforcement material is light and the construction is convenient. However, its fire resistance is extremely poor, and its effect on controlling structural deformation and preventing seepage and plugging leakage is not obvious.

[0004] The steel ring reinforcement method uses a steel ring made of multiple curved steel plates. First, the segmented steel plates are fixed with expansion bolts on the inner side of the tunnel segments, and then the steel plates are welded together to form a steel ring that is basically the same shape as the inner wall of the tunnel. Finally, epoxy resin is poured into the gap between the steel ring and the segment structure. This method effectively improves the rigidity of the structure and is conducive to controlling structural deformation; however, the installation of steel plates requires special lifting equipment, there are many welds, the welding quality fluctuates greatly, the steel structure is prone to corrosion and softening at high temperatures, and there is no obvious sign of tunnel structure damage after reinforcement, and it is brittle.

[0005] The composite component reinforcement method is to first install the composite cavity on the inner curved surface brushed with adhesive, and then inject mortar into the composite cavity. This method is convenient to construct and has obvious effects in improving structural rigidity and controlling structural deformation. However, the structure after reinforcement shows brittle failure, has extremely poor fire resistance, and does not have the function of preventing seepage and plugging leakage.

[0006] Steel arch reinforcement, this method uses bolts to connect I-beam components to support the inner surface of the tunnel, which has the advantages of fast construction and high reinforcement strength. However, the steel arch has the disadvantages of occupying a large clearance height, being easily unstable under pressure, being easily corroded, and softening at high temperatures.

[0007] The steel plate-concrete composite structure reinforcement method first installs the steel plates on the inner side of the pipe segment through chemical anchor bolts, then welds the steel plates into one piece, and finally pours fine stone concrete into the gap between the steel ring and the pipe segment. This method has all the advantages of the steel ring reinforcement method. In addition, the structure reinforced with the steel plate-concrete composite structure presents the plastic failure characteristics expected by the engineering community. However, this method uses ordinary steel plates and fails to overcome the defects of complex steel plate installation, large fluctuations in welding quality, easy corrosion and high temperature softening. The fine stone concrete has no significant effect in the tension zone, and the thickness of the composite structure affects the clearance in the tunnel.

[0008] The ultra-high performance concrete (UHPC) reinforcement method, that is, applying a layer of UHPC on the inner surface of the segment through cast-in-place or spraying technology, can effectively improve the bearing capacity of the shield tunnel lining structure, control structural deformation, crack development, and meet the requirements of corrosion resistance and fire resistance. However, cast-in-place UHPC requires a template, and spraying UPHC will cause material waste due to rebound, and the ductility of the UHPC reinforced structure is limited. In addition, UHPC itself shrinks greatly and is prone to shrinkage damage cracks. Summary of the invention

[0009] In view of the above technical defects and adverse effects during application, the purpose of the present invention is to provide an ultra-high performance concrete (UHPC)-steel arch frame combined structure and method for reinforcing the shield tunnel lining structure. The present invention has the effect of increasing the strength and rigidity of the lining structure and effectively controlling cracks, and can also increase the ductility of the reinforced structure damage.

[0010] The technical solution of the present invention is as follows:

[0011] An ultra-high performance concrete (UHPC)-steel arch frame composite structure for reinforcing a shield tunnel lining structure, characterized in that it comprises five key components: a steel arch frame (4), UHPC (2), transverse bolts (5), vertical chemical anchor bolts (6), and vertical embedded steel bars (3).

[0012] The UHPC (2) and the steel arch frame (4) are arranged at intervals along the axial direction of the tunnel segment.

[0013] The UHPC (2) and the steel arch frame (4) are connected via bolts (5) welded to the web of the steel arch frame.

[0014] The UHPC (2) and the tunnel segment (1) are connected via vertical chemical anchor bolts (6) and embedded reinforcement bars (3).

[0015] A reinforcement method for an ultra-high performance concrete (UHPC)-steel arch composite structure for reinforcing a shield tunnel lining structure, characterized in that the specific implementation comprises the following steps:

[0016] (A) The inner surface of the tunnel segment is roughened;

[0017] (B) Drill holes on the inner arc surface and implant rebars and chemical anchors;

[0018] (C) Remove the debris and dust generated in the above two steps;

[0019] (D) Welding studs on the web of the steel arch;

[0020] (E) Steel arches are erected inside the tunnel segments and axial compressive prestress is applied;

[0021] (F) Casting UHPC;

[0022] (G) Curing at room temperature and pressure for 28 days. During this process, the prestressing of the steel arch frame is released according to the monitored UHPC shrinkage strain, so that the tensile strain of UHPC is close to zero.

[0023] The roughening treatment in step (A) is to make the bond between the ultra-high performance concrete and the original reinforced concrete segment more firmly. A roughening machine is used, and the roughening depth is required to be 5-10mm, the spacing is 30mm, and the roughening rate is not less than 90%.

[0024] Wherein, in step (B), holes are drilled on the inner surface of the tunnel segment, rebar glue is applied to the holes and rebars are implanted, the drilling depth is about 1 / 3-1 / 2 of the segment thickness, the drilling positions are arranged in a grid, and the spacing is about 0.3-1.0 times the segment thickness. Drill holes on the inner surface of the tunnel segment, rebar glue is applied to the holes and chemical anchors are implanted, the drilling depth is 1 / 3-1 / 2 of the segment thickness, the drilling positions are arranged in a grid, the spacing is 1.0-1.5 times the segment thickness, and the rebar arrangement is staggered in the segment width direction and circumferential direction. When some holes are located at the segment bolt hand holes, these holes should be abandoned. When some holes encounter the original segment circumferential reinforcement during drilling, they should be re-drilled within 5 cm of the vicinity, and the holes encountering the original segment reinforcement should be sealed with rebar glue.

[0025] Among them, the end of the embedded reinforcement extending out of the original tunnel segment in step (B) is provided with an L-shaped hook, and the bending direction is consistent with the circumferential direction of the segment.

[0026] Among them, the cleaning of the inner surface of the pipe segment and the surface of the rebar in step (C) must be carried out after the rebar glue is cured. The cleaning range includes the inner surface of the pipe segment after roughening and the exposed part of the rebar. The cleaning methods include broom sweeping and water washing to remove dust.

[0027] Wherein, in step (D), studs are welded on the web of the steel arch frame, and the stud welding spacing is 3-5 times the web height.

[0028] In step (E), the steel arch frame is erected along the inner arc surface of the tunnel segment, and three rows are evenly arranged in the ring width direction of the segment, and axial compressive prestress is applied to it, wherein the prestress is about 40%-50% of the strength of the steel arch frame material.

[0029] Among them, the UHPC is cast using an inner template and a lateral template in step (F), the inner template is composed of multiple steel templates (12) and a pouring port (13) is reserved, the single steel template is fixed to the steel arch frame by an electromagnetic adsorption device (14), the lateral template is played by the steel arch frame, and the UHPC is embedded with a strain sensor; the UHPC is mainly composed of cement, silica fume, quartz powder, quartz sand, steel fiber, water reducer and water, and the 28-day compressive strength is not less than 130MPa, and the tensile strength is not less than 10MPa. The casting process is from bottom to top according to the position of the pouring port reserved in the inner template, and a layered casting method is adopted. After the casting surface reaches the pouring port, the current pouring port is blocked, and then pouring is continued from the pouring port at a higher position until the entire ring is cast. After pouring the UHPC for 24 hours, the power is turned off and the inner template is removed.

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] The advantages of UHPC, such as high strength, high rigidity, good durability and strong interface adhesion, are fully utilized, and the risk of disaster caused by high temperature softening of steel arch frames is reduced; at the same time, the shrinkage cracking problem of UHPC itself is solved by applying prestress to the steel arch frames, and the disadvantage of brittle failure of UHPC reinforced structures is overcome. The present invention has the effect of increasing the strength and rigidity of the tunnel lining structure and effectively controlling cracks, and can increase the ductility of the reinforced structure failure; moreover, the present invention is convenient to obtain materials, fast in construction, safe and reliable, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic diagram of the structural cross section of a shield tunnel reinforced by the method of the present invention;

[0033] Figure 2 for Figure 1 AA section view;

[0034] Figure 3 The present invention is a schematic diagram of the installation of a casting formwork according to the method of the present invention.

[0035] Description of reference numerals:

[0036] 1- Tunnel segment; 2- Ultra-high performance concrete (UHPC);

[0037] 3-Rebar planting; 4-Steel arch frame;

[0038] 5-bolt; 6-chemical anchor bolt;

[0039] 7-Joint; 8-Trackbed;

[0040] 9-bolt hand hole; 10-prestressing device;

[0041] 11- original segment circumferential reinforcement; 12- steel formwork;

[0042] 13-casting port; 14-electromagnetic adsorption device. DETAILED DESCRIPTION

[0043] The embodiments of the present invention are further described below in conjunction with the accompanying drawings.

[0044] Example:

[0045] refer to Figure 1-3 , an ultra-high performance concrete (UHPC)-steel arch composite structure for reinforcing a shield tunnel lining structure, comprising five key components: a steel arch (4), UHPC (2), transverse bolts (5), vertical chemical anchor bolts (6), and vertical embedded reinforcement (3).

[0046] The implementation method comprises the following steps:

[0047] Step (A) The inner surface of the tunnel segment (1) is roughened using a roughening machine, with a roughening depth of 5 mm, a spacing of 30 mm, and a roughening rate of 90%.

[0048] Step (B) Drill holes on the inner surface of the tunnel segment (1) and implant rebars (3). The drilling depth is about 1 / 3 of the segment thickness. The drilling positions are arranged in a grid pattern with a spacing of 150 mm. Use rebar glue to implant rebars on the holes. When some holes are located at the segment bolt hand holes (9) or joints (7), these holes should be abandoned. When certain holes encounter steel bars in the tunnel segment (such as the original segment annular steel bars) during drilling, they should be re-drilled within 5 cm of the vicinity, and the holes encountering the steel bars of the tunnel segment should be sealed with rebar glue. Among them, an L-shaped hook is provided at one end of the rebar extending out of the tunnel segment (1), and the rebar (3) uses HRB400 steel bars with a diameter of 10 mm. The chemical anchor bolts (6) are spaced 350 mm apart and use M10 bolts.

[0049] Figure 3 The present invention is a schematic diagram of the installation of a casting formwork according to the method of the present invention.

[0050] Step (C) After the anchoring glue is cured, the inner surface of the original reinforced concrete segment (1) and the surface of the anchoring (3) are cleaned by sweeping with a broom and washing with water to remove dust.

[0051] In step (D), the steel arch frame (4) is made of H-shaped steel with a flange width of 60 mm, a height of 60 mm, a flange plate thickness of 8 mm, and a web thickness of 6 mm. Transverse studs (5) are welded on the web with a spacing of 20 cm.

[0052] Three rows of steel arch frames (4) are evenly arranged in the ring width direction of the pipe segment, and axial compressive prestress is applied by a prestress applying device (10), and the prestress magnitude is about 120 MPa.

[0053] In step (F), the inner formwork is formed by splicing a plurality of steel formworks (12), a single steel plate and a steel arch frame are fixed by an electromagnetic adsorption device (14), a UHPC pre-embedded strain sensor is used, and a layered pouring method is adopted from bottom to top according to the position of the pouring port (13) reserved by the inner steel formwork (12). After the pouring surface reaches the pouring port, the current pouring port is blocked, and then pouring is continued from a pouring port at a higher position until the entire ring is poured.

[0054] Step (G) After pouring the UHPC for 24 hours, the inner steel formwork (12) is removed by power off, and then cured at room temperature and pressure for 28 days. During the process, the prestress of the steel arch frame (4) is adjusted according to the monitored UHPC shrinkage strain, so that the tensile strain of the UHPC (2) is zero. The UHPC2 is mainly prepared from cement, silica fume, quartz powder, quartz sand, steel fiber, water reducer and water. After 28 days of testing, the compressive strength is not less than 130MPa and the tensile strength is not less than 10MPa.

[0055] The above description of the embodiment is to facilitate the understanding and use of the invention by ordinary technicians in the technical field. In the embodiment, the outer diameter of the tunnel segment is 6200mm, the thickness of the tunnel segment (1) is 350mm, and the axial length is 1200mm; the tunnel segment is assembled by 6 reinforced concrete segments (1) through seams, and the joints (6) are at 8°, 73°, 138°, 222°, 287°, and 352° respectively; when the above reinforcement method is adopted, the thickness of UHPC (2) is 6cm, the height of the steel arch frame (4) is 6cm, the diameter of the embedded steel bar (3) is HRB400 steel bar with a diameter of 10mm, and the diameter of the chemical anchor bolt (6) is M10 bolt. At present, the shield tunnel lining structure with an outer diameter of 6-15m commonly used in the engineering field can be reinforced using the method provided by the present invention. During implementation, the size of UHPC and steel arch frame, as well as the diameter and spacing of embedded steel bar, chemical anchor bolt and bolt are adjusted according to actual needs.

[0056] The present invention proposes an ultra-high performance concrete (UHPC)-steel arch composite structure and method for reinforcing the shield tunnel lining structure. The advantages of UHPC, such as high strength, high rigidity, good durability and strong interface adhesion, are fully utilized, and the risk of high temperature softening of the steel arch is reduced; the shrinkage cracking problem of UHPC itself is solved, and the disadvantage of brittle failure of the UHPC reinforced structure is overcome; the strength and rigidity of the lining structure and the ductility of failure are increased, which has a good effect on the crack control of the structure. During the implementation, the electromagnetic adsorption of the steel arch and the block steel plate provide convenience for the template erection of the UHPC casting.

[0057] It is obvious that a person skilled in the art can easily make various modifications to this embodiment and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above-mentioned embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. An ultra-high performance concrete-steel arch composite structure for reinforcing a shield tunnel lining structure, characterized in that: It includes a steel arch frame (4), UHPC (2), a transverse bolt (5), a vertical chemical anchor bolt (6), and a vertical embedded steel bar (3); The UHPC (2) and the steel arch frame (4) are arranged at intervals along the axial direction of the tunnel segment (1); the steel arch frame (4) and the tunnel segment (1) are in direct contact to transmit force, thereby increasing the strength of the tunnel lining structure; the tunnel segment (1) provides a restraining force for the steel arch frame (4) to apply axial compressive prestress; the UHPC (2) and the steel arch frame (4) are connected by transverse bolts (5) welded to the web of the steel arch frame; the UHPC (2) and the tunnel segment (1) are connected by vertical chemical anchor bolts (6) and vertical embedded steel bars (3), thereby realizing load transfer between the UHPC (2) and the tunnel segment (1); The reinforcement method for the ultra-high performance concrete-steel arch composite structure used to reinforce the shield tunnel lining structure includes the following steps: (A) The inner surface of the tunnel segment (1) is roughened; (B) drilling holes on the inner surface of the tunnel segment (1) and implanting vertical rebars (3) and vertical chemical anchor bolts (6); (C) Remove the debris and dust generated in the above two steps; (D) Welding transverse studs (5) to the web of the steel arch (4); (E) A steel arch is installed inside the tunnel segment (1) and axial compressive prestress is applied; (F) Casting of UHPC; (G) Curing at room temperature and pressure for 28 days, during which the prestress of the steel arch frame is released according to the monitored UHPC shrinkage strain, so that the tensile strain of the UHPC is close to zero; In the step (F), the UHPC is cast using an inner formwork and a lateral formwork, the inner formwork is formed by splicing a plurality of steel formworks (12) and having a reserved casting port (13), the single steel formwork is fixed to the steel arch frame by an electromagnetic adsorption device (14), the lateral formwork is served by the steel arch frame, and the UHPC is pre-embedded with a strain sensor.

2. The ultra-high performance concrete-steel arch composite structure for reinforcing the shield tunnel lining structure according to claim 1, characterized in that: In the step (A), the roughening process is performed by a roughening machine, and the roughening depth is required to be 5-10 mm, the spacing is 30 mm, and the roughening rate is not less than 90%.

3. The ultra-high performance concrete-steel arch composite structure for reinforcing the shield tunnel lining structure according to claim 1, characterized in that: In the step (B), holes are drilled on the inner surface of the tunnel segment (1), and rebar glue is applied to the holes and vertical rebars (3) are implanted. The drilling depth is 1 / 3-1 / 2 of the segment thickness. The drilling positions are arranged in a grid pattern with a spacing of 0.3-1.0 times the segment thickness. Holes are drilled on the inner surface of the tunnel segment (1), and rebar glue is applied to the holes and vertical chemical anchor bolts (6) are implanted. The drilling depth is 1 / 3-1 / 2 of the segment thickness. The drilling positions are arranged in a grid pattern with a spacing of 1.0-1.5 times the segment thickness. The vertical rebars (3) are arranged in a staggered manner in the segment width direction and in the circumferential direction. When some holes are located at the segment bolt hand holes, these holes are abandoned. When some holes encounter the original segment circumferential reinforcement during drilling, they are re-drilled within a 5 cm range nearby, and the holes encountering the original segment reinforcement are sealed with rebar glue.

4. The ultra-high performance concrete-steel arch composite structure for reinforcing a shield tunnel lining structure according to claim 1, characterized in that: In the step (B), one end of the vertical embedded reinforcement (3) extending out of the original tunnel segment is provided with an L-shaped hook, and the bending direction is consistent with the circumferential direction of the segment.

5. The ultra-high performance concrete-steel arch composite structure for reinforcing the shield tunnel lining structure according to claim 1, characterized in that: In the step (C), cleaning of the inner surface of the pipe segment and the surface of the vertical rebar (3) must be performed after the rebar glue has solidified. The cleaning range includes the roughened inner surface of the pipe segment and the exposed portion of the vertical rebar (3). The cleaning methods include sweeping with a broom and dust removal by washing with water.

6. The ultra-high performance concrete-steel arch composite structure for reinforcing the shield tunnel lining structure according to claim 1, characterized in that: In the step (D), transverse bolts (5) are welded on the web of the steel arch frame, and the welding spacing of the transverse bolts (5) is 3-5 times the height of the web.

7. The ultra-high performance concrete-steel arch composite structure for reinforcing the shield tunnel lining structure according to claim 1, characterized in that: In the step (E), the steel arch is erected along the inner arc surface of the tunnel segment (1), three rows are evenly arranged in the segment width direction, and axial compressive prestress is applied thereto, wherein the prestress is 40%-50% of the strength of the steel arch material.

8. The ultra-high performance concrete-steel arch composite structure for reinforcing a shield tunnel lining structure according to claim 1, characterized in that: In the step (F), the UHPC is mainly prepared from cement, silica fume, quartz powder, quartz sand, steel fiber, water reducing agent and water, and has a 28-day compressive strength of not less than 130 MPa and a tensile strength of not less than 10 MPa; the pouring process is carried out from bottom to top according to the position of the pouring port reserved by the inner template, and a layered pouring method is adopted. After the pouring surface reaches the pouring port, the current pouring port is blocked, and then pouring is continued from a higher pouring port until the entire ring is poured; after pouring the UHPC for 24 hours, the inner template is removed by power off.

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