Construction method for progressive excavation of small clear distance triple-arch station tunnel

Abstract

The present application discloses a construction method for a small clear distance triple-arch progressive station tunnel, including the following steps: Step 1: Excavate the arch pilot tunnels on both sides; Step 2: Expand the excavation of the arches on both sides, close the steel frames in the side arches into a ring, and form a middle wall with the steel frames and concrete between the previously excavated pilot tunnel and the subsequently excavated pilot tunnel in the side arches; Step 3: Demolish the middle walls in the arches on both sides, carry out the secondary lining construction of the inverted arch parts of the arches on both sides, and backfill the inverted arches of the side arches; Install precast intermediate rock pillar members in the arches on both sides. The precast intermediate rock pillar members are provided with perfusion cavities, and the perfusion cavities penetrate the upper surface and the lower surface of the precast intermediate rock pillar members. When the precast intermediate rock pillar members are installed, the upper edge of the precast intermediate rock pillar members close to the middle arch abuts against the inner wall of the pilot tunnel of the side arch. In the present application, no formwork needs to be set on the side of the precast intermediate rock pillar member close to the middle arch, making the secondary lining construction of the side arch more efficient.

Description

Technical Field

[0001] This application relates to the field of tunnel construction technologies, and particularly to a construction method for a small clear distance triple-arch progressive station tunnel. Background Art

[0002] In subway tunnel construction, the crossover tunnel section needs to be excavated with a large cross-section by the mining method to meet the requirement that the main line section and the parking line are in the same large cross-section tunnel. The triple-arch tunnel is a type of large cross-section tunnel, and the small clear distance triple-arch tunnel refers to a special tunnel layout form where the thickness of the middle rock pillar between the tunnels is less than the recommended value. Generally, the large cross-section excavation adopts the center diaphragm method (CD method) or the cross center diaphragm method (CRD method). The CD method is a construction method in a large-span tunnel with soft surrounding rock, where one side of the tunnel is excavated in sections first, and the middle diaphragm is constructed, and then the other side is excavated in sections. The CRD method is a construction method in a large-span tunnel with soft surrounding rock, where one side of the tunnel is excavated in sections first, the middle diaphragm and the cross diaphragm are constructed, and then the other side of the tunnel is excavated in sections and the construction of the cross diaphragm is completed, that is, the tunnel is divided into four sections for excavation.

[0003] During the cyclic progressive excavation construction process of the triple-arch tunnel, the middle arch and the side arches on both sides are usually constructed successively. The middle rock pillar between the middle arch and the side arches is usually formed in the secondary lining (referred to as the second lining) of the previously constructed tunnel. The second lining construction mainly uses a lining trolley. During the second lining construction, a template needs to be additionally set on the side of the middle rock pillar away from the lining trolley, so that this template and the template plates on the lining trolley jointly form a space adapted to the surface contour of the middle rock pillar. When the concrete of the middle rock pillar solidifies, this template needs to be removed. However, after the middle rock pillar is formed, the gap between this template and the inner wall of the previously constructed tunnel is small, and the disassembly and assembly are inconvenient, affecting the work efficiency. Summary of the Invention

[0004] In order to solve the problem that the disassembly and assembly of the template of the middle rock pillar in the triple-arch tunnel in the prior art are relatively inconvenient, this application provides a construction method for a small clear distance triple-arch progressive station tunnel.

[0005] The construction method for a small clear distance triple-arch progressive station tunnel provided by this application adopts the following technical solutions:

[0006] The construction method for a small clear distance triple-arch progressive station tunnel includes the following steps:

[0007] Step 1: Excavate the pilot tunnels on both sides, spray concrete on the inner walls of the pilot tunnels, hang a steel mesh, erect a steel frame for supporting the inner walls of the pilot tunnels, carry out anchor rod construction, and re-spray concrete;

[0008] Step 2: Expand the excavation of both side arches. Spray concrete on the inner wall of the newly excavated pilot tunnel, hang a steel mesh, erect a steel frame for supporting the inner wall of the newly excavated pilot tunnel, carry out anchor rod construction, and re-spray concrete; the steel frames in the side arches are closed into a ring to form the initial support for the side arches, and the steel frames and concrete between the previously excavated pilot tunnel and the subsequently excavated pilot tunnel in the side arches form a middle wall.

[0009] Step 3: Demolish the middle wall in both side arches, carry out the secondary lining construction of the inverted arch part of both side arches, and backfill the inverted arch of the side arches; install precast middle rock pillar members in both side arches. The precast middle rock pillar members are provided with perfusion cavities, and the perfusion cavities penetrate the upper surface and the lower surface of the precast middle rock pillar members. When the precast middle rock pillar members are installed, the upper edge of the precast middle rock pillar members close to the middle arch side abuts against the inner wall of the pilot tunnel of the side arches; carry out the secondary lining construction of the arch wall part of the side arches, and the center of the contour of the inner wall of the arch wall formed by the secondary lining construction deviates towards the side of the side arch far from the middle arch.

[0010] Step 4: Carry out the excavation of the middle arch, spray concrete on the inner wall of the middle arch, hang a steel mesh, erect a steel frame for supporting the inner wall of the middle arch, carry out anchor rod construction, and re-spray concrete.

[0011] By adopting the above technical solutions, during the construction process of the triple-arch tunnel, when carrying out the secondary lining construction of both side arches, first construct the inverted arch, then install the precast middle rock pillar members on the side of both side arches close to the middle arch, and then use the lining trolley to carry out the secondary lining construction of the arch wall part. During the secondary lining construction of the arch wall part, the concrete enters the perfusion cavity of the precast middle rock pillar member. When the concrete solidifies, the precast middle rock pillar member is connected with the concrete to form an integral body, making the middle rock pillar become a part of the arch wall; during the above construction process, no formwork needs to be set at the position where the precast middle rock pillar member is located, making the secondary lining construction of the side arches more efficient.

[0012] Optionally, a steel reinforcement cage is arranged in the perfusion cavity of the precast middle rock pillar member. During the secondary lining construction of the arch wall part of the side arches in Step 3, first carry out lining reinforcement, and then carry out secondary lining concrete pouring. When carrying out lining reinforcement, the steel bars for lining reinforcement are connected with the steel reinforcement cage.

[0013] By adopting the above technical solutions, the steel bars for lining reinforcement in the secondary lining construction of both side arches are connected with the steel reinforcement cage in the perfusion cavity, strengthening the connection between the middle rock pillar and the remaining parts of the secondary lining construction, so as to improve the integrity of the secondary lining structure of the side arches.

[0014] Optionally, the two inner walls of the perfusion cavity corresponding to the two cross-sections of the precast middle rock pillar member are respectively set as a first inner wall and a second inner wall, and the first inner wall and the second inner wall of the perfusion cavity gradually incline towards each other from top to bottom.

[0015] By adopting the above technical solution, when the second lining construction of the arch wall part is carried out on the side arch, the concrete in the second lining construction is injected into the perfusion cavity. Since the first inner wall and the second inner wall of the perfusion cavity gradually incline downward and approach the center of the perfusion cavity, the unhardened concrete in the perfusion cavity forms a downward acting force on the precast intermediate rock pillar through the first inner wall and the second inner wall, so that the lower surface of the precast intermediate rock pillar is closely attached to the inverted arch of the side arch, and the concrete in the perfusion cavity is not easy to leak outwards.

[0016] Optionally, the inclination angle of the first inner wall is greater than that of the second inner wall. When the precast intermediate rock pillar is installed, the first inner wall of the perfusion cavity is close to another precast intermediate rock pillar installed earlier.

[0017] By adopting the above technical solution, the concrete has a horizontal component force on the first inner wall and the second inner wall. Since the slope of the first inner wall is greater than that of the second inner wall, the acting force of the concrete on the first inner wall is greater than that on the second inner wall, so that the horizontal component force received by the first inner wall is greater than the horizontal component force of the second inner wall, making the whole precast intermediate rock pillar have a moving tendency from the second inner wall towards the direction close to the first inner wall. By making the first inner wall of the perfusion cavity close to the precast intermediate rock pillar installed earlier when the precast intermediate rock pillar is installed, it is beneficial to make the precast intermediate rock pillar installed later close to the precast intermediate rock pillar installed earlier, so that the adjacent precast intermediate rock pillars are arranged more closely.

[0018] Optionally, the circumferential contour shape of the steel reinforcement cage is adapted to the shape of the inner peripheral wall of the perfusion cavity.

[0019] By adopting the above technical solution, the circumferential contour shape of the steel reinforcement cage is adapted to the shape of the inner wall of the perfusion cavity. Since the first inner wall and the second inner wall of the perfusion cavity gradually incline towards each other downward, the steel reinforcement cage is tightly pressed against the inner wall of the perfusion cavity as much as possible under the action of its own gravity and the concrete pressure, so that the cooperation between the steel reinforcement cage and the concrete precast member is closer. On the other hand, the first inner wall and the second inner wall of the perfusion cavity can form a common supporting effect on the steel reinforcement cage, so that the precast intermediate rock pillar and the steel reinforcement cage can be transported in a set without worrying about the problem of the steel reinforcement cage falling out of the precast intermediate rock pillar, which is more convenient.

[0020] Optionally, embedded positioning parts are provided on both sides of the inverted arch of the side arch close to the middle arch in step 3, and the embedded positioning parts are used to partially extend into the perfusion cavity; when the embedded positioning parts are located in the perfusion cavity, a gap is reserved between the circumferential side of the embedded positioning parts and the inner peripheral wall of the perfusion cavity.

[0021] By adopting the above technical solution, the embedded positioning member partially extends into the pouring cavity of the middle rock pillar precast member. After the concrete in the pouring cavity solidifies, the embedded positioning member and the solidified concrete in the pouring cavity form an interlaced relationship along the vertical direction, which can position the middle rock pillar horizontally, thereby making the position of the middle rock pillar more stable. By reserving a gap between the peripheral side of the embedded positioning member and the inner peripheral wall of the pouring cavity, a large adjustment space is provided for the installation of the middle rock pillar precast member in all horizontal directions.

[0022] Optionally, the embedded positioning member is an I-beam, the length direction of the I-beam is arranged along the length direction of the middle rock pillar precast member, and the two flanges of the I-beam are respectively located inside the invert and inside the middle rock pillar precast member.

[0023] By adopting the above technical solution, after the concrete in the pouring cavity solidifies, the two flanges of the I-beam are respectively wrapped in the invert of the side arch and the concrete in the pouring cavity, so that the arch wall and the invert of the side arch are connected by the I-beam. Compared with the lining steel bars, the connection strength between the arch wall and the invert of the side arch can be greatly improved by the I-beam.

[0024] Optionally, a plurality of clamping rods are inserted through the web of the I-beam. The clamping rods are used to clamp the inner wall of the pouring cavity. The clamping rods are arranged in sequence along the length direction of the I-beam. The two ends of each clamping rod are respectively bent to form guiding sections, and the two guiding sections are in a downward-opening state. The dimension between the ends of the two guiding sections is greater than or equal to the dimension of the pouring cavity along the thickness direction of the middle rock pillar precast member.

[0025] By adopting the above technical solution, when the I-beam is located in the pouring cavity, the clamping rods clamp the two inner side walls of the pouring cavity. When the concrete in the pouring cavity solidifies, the concrete wraps the clamping rods, so that the clamping rods strengthen the concrete on both sides of the web of the I-beam; the two guiding sections of the clamping rods have a guiding effect on the inner wall of the pouring cavity of the middle rock pillar precast member. When the middle rock pillar precast member is placed in place, the two ends of the clamping rods respectively abut against the two inner side walls of the pouring cavity, so that the cooperation between the clamping rods and the middle rock pillar precast member is relatively stable.

[0026] Optionally, a protrusion is provided on the cross section of one side of the middle rock pillar precast member, and a groove adapted to the protrusion is provided on the other cross section of the middle rock pillar precast member. The outward protrusion height of the protrusion is less than or equal to the inward concave depth of the groove.

[0027] By adopting the above technical solution, the cooperation between the protrusion and the groove between two adjacent middle rock pillar precast members is beneficial to increasing the connection strength between the two adjacent middle rock pillar precast members. The outer convex height of the protrusion is less than or equal to the inner concave depth of the groove. When the protrusion of one middle rock pillar precast member cooperates with the groove of another middle rock pillar precast member, it is beneficial to making the edge areas of the mating parts of the two adjacent middle rock pillar precast members fit as closely as possible, so that the overall middle rock pillar is flatter.

[0028] Optionally, when constructing the anchor bolts of the middle arch in step 4, the anchor bolts of the middle arch and the anchor bolts of the two side arches are arranged in longitudinal dislocation along the tunnel. The longitudinal position setting between the anchor bolts of the middle arch and the side arches uses the middle rock pillar as a common reference.

[0029] By adopting the above technical solution, the anchor bolts of the middle arch and the two side arches are arranged in longitudinal dislocation along the tunnel, which helps to avoid the situation of damaging the previously constructed anchor bolts in the side arches during the construction of the anchor bolts of the middle arch. The longitudinal position setting between the anchor bolts of the middle arch and the side arches uses the middle rock pillar as a common reference. Thus, when constructing the anchor bolts of the middle arch, it is convenient to effectively avoid the anchor bolts of the side arches, so that the anchor bolts of the middle arch and the anchor bolts of the side arches form a dislocation along the tunnel longitudinal direction.

[0030] In summary, the present application includes at least one of the following beneficial technical effects:

[0031] 1. During the construction of the triple-arch tunnel, concrete enters the perfusion cavity of the middle rock pillar precast member. After the concrete solidifies, the middle rock pillar precast member is integrated with the concrete, making the middle rock pillar become a part of the arch wall. During the above construction process, no formwork needs to be set at the position where the middle rock pillar precast member is located, making the construction of the secondary lining of the side arch more efficient;

[0032] 2. By setting the embedded positioning parts, part of the embedded positioning parts extends into the perfusion cavity of the rock pillar precast member. After the concrete entering the perfusion cavity solidifies, the embedded positioning parts and the solidified concrete in the perfusion cavity form an interlaced relationship along the vertical direction, which can play a positioning role in the horizontal direction for the middle rock pillar, thus making the position of the middle rock pillar more stable;

[0033] 3. The longitudinal position setting between the anchor bolts of the middle arch and the side arches uses the middle rock pillar as a common reference. Thus, when constructing the anchor bolts of the middle arch, it is convenient to effectively avoid the anchor bolts of the side arches, so that the anchor bolts of the middle arch and the anchor bolts of the side arches form a dislocation along the tunnel longitudinal direction. Description of the Drawings

[0034] Figure 1 is the flow chart of the construction method of the small clear distance triple-arch progressive station tunnel.

[0035] Figure 2 is the schematic diagram of the construction state of step 1.

[0036] Figure 3 It is a schematic diagram of the construction state in Step 2.

[0037] Figure 4 It is a schematic diagram of the construction state in Step 3.

[0038] Figure 5 It is a schematic diagram of the construction state in Step 4.

[0039] Figure 6 It is a schematic diagram of the construction state in Step 5.

[0040] Figure 7 It is a schematic diagram of the structure of the middle rock pillar precast member in this embodiment.

[0041] Figure 8 It is a schematic diagram for reflecting the positional relationship between the middle rock pillar precast member and the steel reinforcement cage and the embedded positioning member respectively in this embodiment.

[0042] Figure 9 It is a schematic diagram for reflecting the connection relationship between the middle rock pillar precast member and the embedded positioning member in this embodiment.

[0043] Description of reference numerals: 1, side arch; 2, middle arch; 3, pilot tunnel; 4, steel frame; 5, anchor bolt; 6, middle partition wall; 7, invert; 8, arch wall; 9, middle rock pillar precast member; 91, protrusion; 92, groove; 93, pouring cavity; 931, first inner wall; 932, second inner wall; 94, steel reinforcement cage; 10, embedded positioning member; 101, clamping rod; 102, guiding section. Detailed implementation manners

[0044] The following further describes the present application in detail Figures 1-9 in conjunction with the attached drawings.

[0045] The embodiment of the present application discloses a construction method for a small clear distance triple-arch progressive station tunnel. Referring to Figures 1-6 , the construction method for a small clear distance triple-arch progressive station tunnel includes the following steps:

[0046] Step 1: Excavate the pilot tunnels 3 on both sides of the arch 1, spray concrete on the inner wall of the pilot tunnel 3, hang a steel mesh, erect a steel frame 4 for supporting the inner wall of the pilot tunnel 3, carry out the construction of anchor bolts 5, and re-spray concrete;

[0047] Step 2: Widen the excavation of the arch 1 on both sides, spray concrete on the inner wall of the newly excavated pilot tunnel 3, hang a steel mesh, erect a steel frame 4 for supporting the inner wall of the newly excavated pilot tunnel 3, carry out the construction of anchor bolts 5, and re-spray concrete; The steel frames 4 inside the side arch 1 are closed into a ring to form the initial support for the side arch 1, and the steel frames 4 and concrete between the previously excavated pilot tunnel 3 and the subsequently excavated pilot tunnel 3 inside the side arch 1 form the middle partition wall 6;

[0048] Step 3: Demolish the middle partition wall 6 inside the two side arches 1, carry out the secondary lining construction of the inverted arch 7 part of the two side arches 1, and backfill the inverted arch 7 of the side arches 1; Install the middle rock pillar precast member 9 inside the two side arches 1. When installing the middle rock pillar precast member 9, the upper edge of the middle rock pillar precast member 9 close to the middle arch 2 abuts against the inner wall of the pilot tunnel 3 of the side arch 1; Carry out the secondary lining construction of the arch wall 8 part of the side arch 1, and the center of the contour of the inner wall of the arch wall 8 formed by the secondary lining construction deviates towards the side of the side arch 1 far from the middle arch 2;

[0049] Step 4: Carry out the excavation of the middle arch 2, spray concrete on the inner wall of the middle arch 2, hang a steel mesh, erect a steel frame 4 for supporting the inner wall of the middle arch 2, carry out the construction of the anchor bolts 5. The anchor bolts 5 of the middle arch 2 and the anchor bolts 5 of the two side arches 1 are arranged longitudinally staggered along the tunnel. The longitudinal position between the anchor bolts 5 of the middle arch 2 and the side arches 1 is set with the middle rock pillar as a common reference. After the construction of the anchor bolts 5 of the middle arch 2, re-spray concrete; The designed excavation size specification of the middle arch 2 is the same as that of the side arch 1, and part of the middle arch 2 and the side arch 1 overlap alternately;

[0050] Step 5: Demolish the steel frame 4 in the overlapping area between the middle arch 2 and the side arch 1 in the initial support of the side arch 1, carry out the secondary lining construction of the inverted arch 7 part of the middle arch 2, backfill the inverted arch 7 of the middle arch 2, and carry out the secondary lining construction of the arch wall 8 part of the middle arch 2; The secondary lining construction of the inverted arch 7 and the arch wall 8 parts of the side arch 1 both include the processes of lining reinforcement and concrete pouring.

[0051] Through the above steps, the end face size of the two side arches 1 finally constructed of the triple-arch tunnel is smaller than the cross-section size of the middle arch 2; During the construction of the triple-arch tunnel, the middle rock pillars between the middle arch 2 and the two side arches 1 are formed during the secondary lining construction of the two side arches 1; When carrying out the secondary lining construction of the two side arches 1, first construct the inverted arch 7, then install the middle rock pillar precast member 9 on the side of the two side arches 1 close to the middle arch 2, and then construct the arch wall 8 of the side arch 1 to connect the arch wall 8 and the middle rock pillar precast member 9 into a whole. During this period, no formwork needs to be set on the side of the middle rock pillar precast member 9 close to the middle arch 2, making the secondary lining construction of the side arch 1 more efficient.

[0052] Refer to Figure 7 and Figure 8 , the middle rock pillar precast member in Step 3 is provided with a perfusion cavity 93. The perfusion cavity 93 penetrates the upper surface and the lower surface of the middle rock pillar precast member 9. A steel reinforcement cage 94 is arranged in the perfusion cavity 93 of the middle rock pillar precast member 9. The peripheral contour shape of the steel reinforcement cage 94 is adapted to the inner peripheral wall shape of the perfusion cavity 93. During the secondary lining construction of the arch wall 8 part of the side arch 1, the steel bars for lining reinforcement are tied and connected with the steel reinforcement cage 94. During the construction of the arch wall 8 of the secondary lining of the side arch 1, the concrete enters the perfusion cavity 93 of the middle rock pillar precast member 9. When the concrete solidifies, the middle rock pillar precast member 9 is integrated with the concrete, making the middle rock pillar become a part of the arch wall 8.

[0053] Refer toFigure 8 For Figure 8 , the two inner walls of the perfusion cavity 93 corresponding to the two cross-sections of the middle rock pillar precast member 9 are respectively set as the first inner wall 931 and the second inner wall 932. The first inner wall 931 and the second inner wall 932 of the perfusion cavity 93 gradually approach each other obliquely from top to bottom. Thus, after the concrete for the secondary lining construction of the arch wall 8 of the side arch 1 enters the perfusion cavity 93, the unfixed concrete generates a downward acting force on the middle rock pillar precast member 9 through the first inner wall 931 and the second inner wall 932, making it difficult for the unfixed concrete to leak out of the perfusion cavity 93.

[0054] On the other hand, the first inner wall 931 and the second inner wall 932 approach each other obliquely, enabling the first inner wall 931 and the second inner wall 932 to jointly form a supporting effect on the steel reinforcement cage 94, facilitating the integrated transportation of the middle rock pillar precast member 9 and the steel reinforcement cage 94.

[0055] Refer to Figure 8 As shown in Figure 8 , the inclination angle of the first inner wall 931 is greater than that of the second inner wall 932. When the middle rock pillar precast member 9 is installed, the first inner wall 931 of the perfusion cavity 93 is close to another previously installed middle rock pillar precast member 9. The concrete entering the perfusion cavity 93 has a horizontal component force on the first inner wall 931 and the second inner wall 932. Since the slope of the first inner wall 931 is greater than that of the second inner wall 932, the acting force of the concrete on the first inner wall 931 is greater than its acting force on the second inner wall 932, causing the overall middle rock pillar precast member 9 to have a moving tendency from the second inner wall 932 towards the direction close to the first inner wall 931. By making the first inner wall 931 of the perfusion cavity 93 close to the previously installed middle rock pillar precast member 9, it is beneficial for the subsequently installed middle rock pillar precast member 9 to be close to the previously installed middle rock pillar precast member 9, thereby making the arrangement of adjacent middle rock pillar precast members 9 more compact.

[0056] Refer to Figure 7 As shown in Figure 7 , a protrusion 91 is provided on one cross-section of the middle rock pillar precast member 9, and a groove 92 adapted to the protrusion 91 is provided on the other cross-section of the middle rock pillar precast member 9. The groove 92 penetrates the upper surface of the middle rock pillar precast member 9, and the outward convex height of the protrusion 91 is less than or equal to the inward concave depth of the groove 92. The connection between adjacent two middle rock pillar precast members 9 is strengthened through the cooperation of the protrusion 91 and the groove 92.

[0057] Refer to Figure 9, on both sides of the invert 7 of the side arch 1, embedded positioning members 10 are provided on the side close to the middle arch 2. The embedded positioning members 10 are specifically I-beams, and the length direction of the I-beams is arranged along the length direction of the middle rock pillar precast member 9. The two flanges of the I-beam are respectively located in the invert 7 of the side arch 1 and the pouring cavity 93. When concrete is injected into the pouring cavity 93, the concrete solidifies and wraps the flange of the I-beam located in the pouring cavity 93, and a gap is reserved between the flange of the I-beam in the pouring cavity 93 and the inner peripheral wall of the pouring cavity 93. Compared with the lining reinforcement, the connection between the invert 7 of the side arch 1 and the arch wall 8 through the I-beam can enhance the connection between the invert 7 of the side arch 1 and the arch wall 8.

[0058] In another embodiment, the I-beam can be replaced with an H-beam or a channel steel, etc.

[0059] Refer to Figure 8 and Figure 9 , a plurality of clamping rods 101 are inserted through the web of the I-beam. The web of the I-beam is provided with through holes for the clamping rods 101 to pass through. There is a clearance fit between the clamping rods 101 and the through holes. The clamping rods 101 are used to clamp the inner wall of the pouring cavity 93. The clamping rods 101 are arranged equidistantly along the length direction of the I-beam. Both ends of the clamping rods 101 are bent to form guiding sections 102. The two guiding sections 102 are in a downward-opening state, and the dimension between the ends of the two guiding sections 102 is greater than or equal to the dimension of the pouring cavity 93 along the thickness direction of the middle rock pillar precast member 9.

[0060] The clamping rods 101 are used to clamp the two inner side walls of the pouring cavity 93. When the concrete entering the pouring cavity 93 solidifies, the concrete wraps the clamping rods 101, so that the clamping rods 101 strengthen the concrete on both sides of the web of the I-beam; the two guiding sections 102 of the clamping rods 101 have a guiding effect on the inner wall of the pouring cavity 93 of the middle rock pillar precast member 9. When the middle rock pillar precast member 9 is placed in place, both ends of the clamping rods 101 respectively abut against the two inner side walls of the pouring cavity 93, making the cooperation between the clamping rods 101 and the middle rock pillar precast member 9 relatively stable.

[0061] The above are all the preferred embodiments of this application. The protection scope of this application is not limited by this. Therefore, all equivalent changes made according to the structure, shape, and principle of this application should be covered within the protection scope of this application.

Claims

1. Construction method for a small clear distance triple-arch progressive station tunnel, characterized in that: It includes the following steps: Step 1: Excavate the pilot tunnels (3) on both sides of the arch (1). Spray concrete on the inner wall of the pilot tunnel (3), hang a steel mesh, erect a steel frame (4) for supporting the inner wall of the pilot tunnel (3), construct rock bolts (5), and re-spray concrete. Step 2: Expand the excavation of both sides of the arch (1). Spray concrete on the inner wall of the newly excavated pilot tunnel (3), hang a steel mesh, erect a steel frame (4) for supporting the inner wall of the newly excavated pilot tunnel (3), construct rock bolts (5), and re-spray concrete. The steel frames (4) inside the side arches (1) are closed into a ring to form the initial support for the side arches (1). The steel frames (4) and concrete between the previously excavated pilot tunnel (3) and the subsequently excavated pilot tunnel (3) inside the side arches (1) form a middle wall (6). Step 3: Demolish the middle wall (6) inside both sides of the arch (1), perform the secondary lining construction of the inverted arch (7) part of both sides of the arch (1), and backfill the inverted arch (7) of the side arches (1). Install a middle rock pillar precast member (9) inside both sides of the arch (1). The middle rock pillar precast member (9) is provided with a perfusion cavity (93), and the perfusion cavity (93) penetrates the upper surface and the lower surface of the middle rock pillar precast member (9). When the middle rock pillar precast member (9) is installed, the upper edge of the middle rock pillar precast member (9) close to the middle arch (2) abuts against the inner wall of the pilot tunnel (3) of the side arch (1). Perform the secondary lining construction of the arch wall (8) part of the side arch (1), and the center of the contour of the inner wall of the arch wall (8) formed by the secondary lining construction deviates towards the side of the side arch (1) away from the middle arch (2). Step 4: Excavate the middle arch (2), spray concrete on the inner wall of the middle arch (2), hang a steel mesh, erect a steel frame (4) for supporting the inner wall of the middle arch (2), construct rock bolts (5), and re-spray concrete.

2. The construction method of the small clear distance triple-arch progressive station tunnel according to claim 1, characterized in that: A steel reinforcement cage (94) is provided in the perfusion cavity (93) of the middle rock pillar precast member (9). During the secondary lining construction of the arch wall (8) part of the side arch (1) in Step 3, first perform the lining reinforcement and then pour the secondary lining concrete. When performing the lining reinforcement, the reinforcement of the lining reinforcement is connected to the steel reinforcement cage (94).

3. The construction method of the small clear distance triple-arch progressive station tunnel according to claim 2, characterized in that: The two inner walls of the perfusion cavity (93) corresponding to the two cross-sections of the middle rock pillar precast member (9) are respectively set as a first inner wall (931) and a second inner wall (932), and the first inner wall (931) and the second inner wall (932) of the perfusion cavity (93) gradually incline towards each other from top to bottom.

4. The construction method of the small clear distance triple-arch progressive station tunnel according to claim 3, characterized in that: The inclination angle of the first inner wall (931) is greater than the inclination angle of the second inner wall (932). When the middle rock pillar precast member (9) is installed, the first inner wall (931) of the perfusion cavity (93) is close to another previously installed middle rock pillar precast member (9).

5. The construction method of the small clear distance triple-arch progressive station tunnel according to claim 3, characterized in that: The peripheral contour shape of the steel reinforcement cage (94) is adapted to the inner peripheral wall shape of the perfusion cavity (93).

6. The construction method of the small clear distance triple-arch progressive station tunnel according to claim 1, characterized in that: In Step 3, embedded positioning members (10) are provided on both sides of the inverted arch (7) of both sides of the arch (1) close to the middle arch (2). The embedded positioning members (10) are used to partially extend into the perfusion cavity (93). When the embedded positioning member (10) is located in the perfusion cavity (93), a gap is reserved between the peripheral side of the embedded positioning member (10) and the inner peripheral wall of the perfusion cavity (93).

7. The construction method of the small clear distance triple-arch progressive station tunnel according to claim 6, characterized in that: The embedded positioning member (10) is an I-beam, and the length direction of the I-beam is arranged along the length direction of the middle rock pillar precast member (9). The two flanges of the I-beam are respectively located inside the inverted arch (7) and the inner side of the middle rock pillar precast member (9).

8. The construction method of the small clear distance triple-arch progressive station tunnel according to claim 7, characterized in that: A plurality of clamping rods (101) are penetrated through the web of the I-beam. Each of the clamping rods (101) is arranged in sequence along the length direction of the I-beam. Both ends of the clamping rod (101) are respectively bent to form guiding sections (102). A downward-opening state is formed between the two guiding sections (102). The dimension between the ends of the two guiding sections (102) is greater than or equal to the dimension of the perfusion cavity (93) along the thickness direction of the middle rock pillar precast member (9).

9. The construction method of the small clear distance triple-arch progressive station tunnel according to claim 1, characterized in that: A protrusion (91) is provided on one cross section of the middle rock pillar precast member (9), and a groove (92) adapted to the protrusion (91) is provided on the other cross section of the middle rock pillar precast member (9). The outward convex height of the protrusion (91) is less than or equal to the inward concave depth of the groove (92).

10. The construction method of the small clear distance triple-arch progressive station tunnel according to claim 1, characterized in that: When the anchor bolts (5) of the middle arch (2) are constructed in step 4, the anchor bolts (5) of the middle arch (2) are arranged longitudinally offset from the anchor bolts (5) of the two side arches (1). The longitudinal position setting between the anchor bolts (5) of the middle arch (2) and the side arches (1) takes the middle rock pillar as a common reference.

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