An expansion tunnel supporting structure for collapsible mixed stratum and a construction method thereof

Abstract

The application discloses an expansion and collapsible mixed stratum tunnel supporting structure and a construction method thereof, and the tunnel is pre-supported by a rigid support, meanwhile, the surrounding rock of the tunnel is grouted and reinforced by sectional grouting anchor rods, so that the stability of the surrounding rock of the tunnel in the expansion and collapsible soil layer is ensured; then the tunnel section after grouting and reinforcement is subjected to inverted arch concrete formwork, side concrete formwork and vault concrete formwork from bottom to top in sequence, the tunnel is further supported and reinforced by the formwork structure, meanwhile, water seepage is effectively prevented, soil layer deformation and collapse are avoided, then the reinforcing anchor rods are punched into the surrounding rock on the formwork structure, so that the surrounding rock of the tunnel is secondarily reinforced, and the stability and safety of the tunnel construction are ensured.

Description

Technical Field

[0001] This invention belongs to the technical field of tunnel support, specifically relating to a tunnel support structure and construction method for a mixed expansive and collapsible strata. Background Technology

[0002] Expansive-collapse mixed strata are a type of geological structure primarily composed of moist loess and expansive soil, exhibiting both collapsibility and expansibility. When the soil layer contains a high amount of water, the collapsible loess will rapidly collapse and subside, while the expansive soil will expand upon absorbing water. This results in an extremely complex geological structure for expansive-collapse mixed strata, making soil deformation and collapse highly likely during tunnel construction. The collapsibility of loess poses a significant threat to tunnels. During construction, soil collapse can lead to rapid increases in surrounding rock deformation and even collapse, increased stress on initial supports, and even cracking. During operation, it can cause secondary lining cracking and tunnel water leakage. Therefore, special attention must be paid to preventing water infiltration when constructing tunnels in collapsible soil conditions.

[0003] During tunnel construction, tunnel support is one of the most crucial aspects. Preventing displacement, slippage, and swaying of the tunnel rock mass is paramount. Current tunnel support techniques typically involve directly driving anchor bolts into the surrounding rock, combined with internal supports or pipe roofs. However, for tunnel construction in expansive and collapsible soil layers, simply using traditional methods of directly driving anchor bolts, installing supports, and pipe roofs is insufficient to achieve stable and safe tunnel support.

[0004] Therefore, considering the characteristics of expansive collapsible soil layers, this invention discloses a tunnel support structure for expansive collapsible mixed strata and its construction method. Summary of the Invention

[0005] The purpose of this invention is to provide a support structure and construction method for tunnels in expansive and collapsible mixed strata, which can ensure the construction efficiency of tunnels in expansive and collapsible mixed strata while further ensuring the stability of the surrounding rock during tunnel construction.

[0006] This invention is achieved through the following technical solution: A tunnel support structure for expansive and collapsible mixed strata includes a rigid support that moves along the tunnel. A waterproof layer is provided between the rigid support and the inner side of the tunnel. Several segmented grouting anchors are installed on the rigid support. Each segmented grouting anchor includes an anchoring portion extending into the surrounding rock and having grouting holes. A detachable grouting portion is provided at the end of the anchoring portion near the rigid support, passing through the waterproof layer and the rigid support. On the excavated section of the rigid support away from the tunnel face, a concrete formwork for the arch is provided corresponding to the arch. Side concrete formwork is provided on the left and right sides of the arch concrete formwork, corresponding to the sidewalls of the tunnel. The top of the side concrete formwork is provided with an invert concrete formwork corresponding to the invert arch of the tunnel; a first connecting joint is provided between the invert concrete formwork and the side concrete formwork, and a first connecting piece for connecting the invert concrete formwork and the side concrete formwork is provided in the first connecting joint; a second connecting joint is provided between the side concrete formwork and the invert concrete formwork, and a second connecting piece for connecting the side concrete formwork and the invert concrete formwork is provided in the second connecting joint; reinforcing anchor rods extending into the surrounding rock are provided through the invert concrete formwork, the side concrete formwork, and the invert concrete formwork.

[0007] The surrounding rock of the tunnel is pre-reinforced with grout before excavation. After each unit distance of tunnel excavation, a waterproof layer is applied to the inner side of the excavated section. A rigid support is then installed at the end of the excavated section near the tunnel face, with its outer surface in contact with the waterproof layer for support and reinforcement. Segmented grouting anchors are then inserted into pre-drilled holes on the rigid support. Each segmented grouting anchor consists of an anchoring part and a grouting part. The anchoring part penetrates the installation holes on the rigid support and the waterproof layer, inserting into the surrounding rock to anchor it. One end of the anchoring part is connected to the grouting part extending into the tunnel interior. Before grouting reinforcement of the surrounding rock, drainage is necessary to prevent excessive water content in the strata, which could lead to coating deformation or even collapse during later concrete formwork construction. Water accumulated in the surrounding rock is drained through the grouting holes on the anchoring parts inserted into the rock and flows into the tunnel interior through the grouting parts. Drainage channels are installed on both sides of the tunnel invert, allowing water flowing into the tunnel to be quickly discharged. After drainage is completed, the grouting pipe is connected to the grouting section, and grout is injected into the anchoring section through the grouting section. The concrete grout enters the surrounding rock through the grouting holes on the anchoring section, reinforcing the surrounding rock. After grouting is completed, the grouting section is removed from the anchoring section, leaving the anchoring section inside the surrounding rock as an anchoring structure. Then the rigid support can be moved to the next working section.

[0008] For tunnel sections that have already been grouted, the concrete formwork for the invert arch, the side concrete formwork, and the top arch concrete formwork are constructed sequentially from bottom to top. First, the invert arch concrete formwork is constructed corresponding to the tunnel's invert arch. Then, side concrete formwork is constructed at both ends of the invert arch formwork, corresponding to the tunnel's sidewalls. Finally, the arch concrete formwork is constructed between the tops of the side concrete formworks, corresponding to the tunnel's arch. The formwork forms the inner lining support, thereby supporting and reinforcing the tunnel. For each formwork location, reinforcing anchor bolts are installed to anchor the surrounding rock.

[0009] To better realize the present invention, the first connecting member further includes an elastic rubber pad, a top formwork anchor rod, a side formwork top anchor rod, and a first tension spring. The elastic rubber pad is disposed inside the first connecting joint and fills and seals the first connecting joint. The top formwork anchor rod and the side formwork top anchor rod are slidably connected to each other inside the elastic rubber pad. The end of the top formwork anchor rod away from the side formwork top anchor rod extends and is anchored to the inside of the arch concrete formwork. The end of the side formwork top anchor rod away from the top formwork anchor rod extends and is anchored to the inside of the side concrete formwork. A first tension spring is disposed between the end of the top formwork anchor rod extending into the elastic rubber pad and the end of the side formwork top anchor rod extending into the elastic rubber pad.

[0010] To better realize the present invention, the elastic rubber pad is further provided with a first connecting sleeve inside, the end of the top mold anchor rod away from the top anchor rod of the side mold extends into the inner hole of one end of the first connecting sleeve and is slidably connected to the inner hole, the end of the top anchor rod of the side mold away from the top mold anchor rod extends into the inner hole of the other end of the first connecting sleeve and is slidably connected to the inner hole; the first connecting sleeve is provided with a first tension spring for connecting the top mold anchor rod and the top anchor rod of the side mold.

[0011] To better realize the present invention, the second connecting member further includes an elastic rubber pad, an inverted arch anchor rod, a side formwork bottom anchor rod, and a second tension spring. The elastic rubber pad is disposed inside the second connecting joint and fills and seals the second connecting joint. The inverted arch anchor rod and the side formwork bottom anchor rod are slidably connected to each other inside the elastic rubber pad. The end of the inverted arch anchor rod away from the side formwork bottom anchor rod extends and is anchored to the inside of the inverted arch concrete formwork. The end of the side formwork bottom anchor rod away from the inverted arch anchor rod extends and is anchored to the inside of the side concrete formwork. A second tension spring is disposed between the end of the inverted arch anchor rod extending into the elastic rubber pad and the end of the side formwork bottom anchor rod extending into the elastic rubber pad.

[0012] To better realize the present invention, furthermore, inverted arch anchor rods are provided inside both the left and right ends of the inverted arch concrete formwork, and the inverted arch anchor rods at the left and right ends are connected by a reinforcing beam.

[0013] To better realize the present invention, the anchoring part is further provided with a central grouting cavity inside, and a plurality of grout outlets connected to the central grouting cavity are provided on the side wall of the anchoring part; a mother flange is provided at the end of the anchoring part away from the surrounding rock; a daughter flange is provided at the end of the grouting part near the anchoring part to connect with the mother flange, and a grouting pipeline connected to the central grouting cavity is provided inside the grouting part.

[0014] To better realize the present invention, the mother flange is provided with a tapered interface at one end near the grouting part, and the daughter flange is provided with a tapered boss that mates with the tapered interface at one end near the anchoring part.

[0015] A construction method for a tunnel support structure in expansive and collapsible mixed strata, based on the aforementioned tunnel support structure, includes the following steps: Step 1: Install advance support, then carry out preliminary excavation and apply a waterproof layer on the inside of the tunnel, and then install rigid supports in the preliminary excavation section. Step 2: Install segmented grouting anchors along the inner contour of the tunnel on the rigid support. The anchoring part of the segmented grouting anchor is inserted into the surrounding rock. The grouting part of the segmented grouting anchor is connected to the drainage pipe. Drainage is carried out on the top of the surrounding rock through the grouting hole of the anchoring part. After the drainage operation is completed, grouting operation is carried out on the anchoring part through the grouting part. Step 3: After the grouting operation is completed, separate the anchoring part from the grouting part, so that the anchoring part remains inside the surrounding rock; then move the rigid support along the tunnel to the next excavation area. Step 4: Construct invert concrete formwork at the invert arch position of the grout-reinforced tunnel section, and install reinforcing anchor bolts extending into the surrounding rock along the outline of the invert concrete formwork; using the invert concrete formwork as a support, construct side concrete formwork at both ends of the invert concrete formwork, and install reinforcing anchor bolts extending into the surrounding rock along the outline of the tunnel sidewalls on the side concrete formwork; using the side concrete formwork on both sides as a support, construct arch concrete formwork between the tops of the side concrete formwork on both sides along the outline of the tunnel arch, and install reinforcing anchor bolts extending into the surrounding rock along the outline of the tunnel arch on the arch concrete formwork. Step 5: Install the second connector in the second connection joint between the bottom of the invert concrete formwork and the side concrete formwork, install the first connector in the first connection joint between the top of the side concrete formwork and the arch concrete formwork, and seal the first connection joint and the second connection joint with shotcrete. Step 6: Repeat steps 1-5 above until the entire tunnel excavation and support are completed.

[0016] To better realize the present invention, parallel I-beams are constructed on both sides of the top of the inverted arch concrete formwork as sliding tracks for rigid supports; after the side concrete formwork is constructed, temporary side supports are constructed between the top of the I-beams and the side concrete formwork; after the arch top concrete formwork is constructed, temporary arch top supports are constructed between the top of the I-beams and the arch top concrete formwork.

[0017] To better realize the present invention, after the overall tunnel construction is completed, the rigid support, side temporary support, and arch temporary support are removed, while the I-beams are retained. Then, a secondary lining is constructed on top of the inverted arch concrete formwork to cover the I-beams.

[0018] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) This invention pre-supports the tunnel by constructing rigid supports inside the tunnel and reinforces the surrounding rock of the tunnel by grouting anchors in sections, thereby ensuring the stability of the surrounding rock of the tunnel in the expansive collapsible soil layer; then, after grouting and reinforcing the tunnel section, the inverted arch concrete formwork, the side concrete formwork, and the arch top concrete formwork are constructed sequentially from bottom to top, and the tunnel is further supported and reinforced by the formwork structure, while effectively preventing water seepage and avoiding soil deformation and collapse. Then, by driving reinforcement anchors into the surrounding rock on the formwork structure, the surrounding rock of the tunnel is reinforced for a second time, thereby ensuring the stability and safety of the tunnel construction. (2) The present invention uses a combination of rigid support pre-support grouting reinforcement and formwork structure to progressively excavate and support the tunnel, which not only effectively ensures the efficiency of tunnel excavation, but also effectively ensures the stability and safety of tunnel support in expansive collapsible soil layers. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the formwork structure of the present invention; Figure 2 This is a schematic diagram of the installation of a rigid bracket; Figure 3 This is an axial sectional view of the tunnel; Figure 4 for Figure 1 A magnified view of part A; Figure 5 for Figure 1 A magnified view of section B; Figure 6 for Figure 2 A magnified view of a portion of point C.

[0020] Wherein: 1-rigid support; 2-waterproof layer; 3-segmented grouting anchor; 4-arch top concrete formwork; 5-side concrete formwork; 6-invert arch concrete formwork; 7-reinforcement anchor; 8-reinforcement beam; 01-first connector; 02-second connector; 111-first connecting joint; 222-second connecting joint; 31-mother flange; 32-daughter flange; 301-anchoring part; 302-grouting part; 011-top formwork anchor; 012-side formwork top anchor; 013-first tension spring; 014-first connecting sleeve; 021-invert arch anchor; 022-side formwork bottom anchor; 023-second tension spring. Detailed Implementation

[0021] Example 1: This embodiment describes a tunnel support structure for a mixed expansion and collapse strata, such as... Figures 1-3 As shown, it includes a rigid support 1 that moves along the tunnel, a waterproof layer 2 between the rigid support 1 and the inner side of the tunnel, and a number of segmented grouting anchors 3 on the rigid support 1.

[0022] like Figure 6 As shown, the segmented grouting anchor 3 includes an anchoring part 301 extending into the surrounding rock and having grouting holes. The anchoring part 301, near the rigid support 1, has a detachable grouting part 302 that passes through the waterproof layer 2 and the rigid support 1. In the excavation section on the side of the rigid support 1 away from the tunnel face, an arch-top concrete formwork 4 is provided corresponding to the arch top. Side concrete formwork 5 is provided on the left and right sides of the arch-top concrete formwork 4, corresponding to the tunnel sidewalls. Between the tops of the side concrete formwork 5 on both sides, corresponding to the tunnel's invert, an invert concrete formwork 6 is provided. A first connecting joint 111 is provided between the formwork 4 and the side concrete formwork 5, and a first connecting piece 01 for connecting the arch concrete formwork 4 and the side concrete formwork 5 is provided in the first connecting joint 111; a second connecting joint 222 is provided between the side concrete formwork 5 and the invert concrete formwork 6, and a second connecting piece 02 for connecting the side concrete formwork 5 and the invert concrete formwork 6 is provided in the second connecting joint 222; and reinforcing anchor rods 7 extending into the surrounding rock are provided through the arch concrete formwork 4, the side concrete formwork 5, and the invert concrete formwork 6.

[0023] Before tunnel excavation, the tunnel is first pre-grouted for support. Grouting pipes are pre-installed at the tunnel arch and sidewall locations, and grouting reinforcement is carried out. After grouting reinforcement, the tunnel is excavated in progressive units of 5m-10m. Excavation proceeds sequentially as upper, middle, and lower layers, reserving central soil when excavating the upper soil. After excavating the upper soil layer, a waterproof layer 2 is applied at the tunnel arch location, followed by the installation of a top support for the arch, and temporary support for the top support. Then, the upper central soil and middle soil layers are excavated. After excavating the middle soil layer, a waterproof layer is applied at the tunnel sidewall locations, followed by the installation of side supports for the tunnel sidewalls, and temporary support for the side supports. Then, the lower soil layer is excavated. After excavating the lower soil layer, a waterproof layer is applied to the tunnel invert, and then the side supports are connected to the top support, with a sliding section at the bottom of the side supports to form a rigid support 1.

[0024] After the rigid support 1 is constructed, segmented grouting anchors 3 are installed along the tunnel outline. The anchoring part 301 of the segmented grouting anchor 3 extends through the installation holes on the rigid support 1 into the surrounding rock around the tunnel. The end of the anchoring part 301 near the tunnel interior is connected to the grouting part 302. Grout is injected into the anchoring part 301 through the grouting part 302, thereby reinforcing the surrounding rock around the tunnel. After the grouting reinforcement is completed, the grouting part 302 can be extended beyond one end of the anchoring part 301, leaving the anchoring part 301 inside the surrounding rock as a support structure. At this point, tunnel excavation can continue, and the rigid support 1 can be moved to the next tunnel working section.

[0025] For the tunnel section that has been grouted and reinforced after the rigid support 1 has been removed, firstly, an invert concrete formwork 6 is constructed for the invert section. Reinforcing steel mesh is pre-embedded inside the invert concrete formwork 6. Anchor holes are reserved during the construction of the invert concrete formwork 6. After the invert concrete formwork 6 is completed, reinforcing anchor rods 7 are driven into the surrounding rock through the anchor holes for reinforcement. Then, side concrete formwork 5 is constructed on the left and right sides of the invert concrete formwork 6, corresponding to the tunnel sidewalls. A second connecting joint 222 is provided between the bottom of the side concrete formwork 5 and the end of the invert concrete formwork 6 as an expansion and contraction adjustment gap. Simultaneously, a second connector 02 is installed in the second connecting joint 222 to elastically connect the bottom of the side concrete formwork 5 and the end of the invert concrete formwork 6, allowing for a certain amount of elastic adjustment margin between the side concrete formwork 5 and the invert concrete formwork 6. Anchor holes are reserved during the construction of the side concrete formwork 5. After the side concrete formwork 5 is completed, reinforcing anchor rods 7 are driven into the surrounding rock through the anchor holes. Then, an arch concrete formwork 4 is constructed between the tops of the side concrete formwork 5 on both sides, corresponding to the tunnel arch. A first connecting joint 111 is provided between the top of the side concrete formwork 5 and the end of the arch concrete formwork 4 as an expansion and contraction adjustment gap. A first connector 01 is installed inside the first connecting joint 111 to elastically connect the top of the side concrete formwork 5 and the end of the arch concrete formwork 4, so that there is a certain elastic adjustment margin between the side concrete formwork 5 and the arch concrete formwork 4. Anchor holes are reserved in the arch concrete formwork 4. After the arch concrete formwork 4 is constructed, reinforcing anchor rods 7 are driven into the surrounding rock through the anchor holes for reinforcement.

[0026] The tunnel was supported and reinforced by a formwork structure, and drainage and grouting were carried out on the ungrouted tunnel sections by a rigid support 1, which improved construction efficiency while ensuring the stability of the tunnel.

[0027] Example 2: This embodiment is a further optimization based on Embodiment 1 described above, such as... Figure 1 and Figure 4 As shown, the first connecting member 01 includes an elastic rubber pad, a top formwork anchor rod 011, a side formwork top anchor rod 012, and a first tension spring 013. The elastic rubber pad is disposed inside the first connecting joint 111 and fills and seals the first connecting joint 111. The top formwork anchor rod 011 and the side formwork top anchor rod 012 are slidably connected to each other inside the elastic rubber pad. The end of the top formwork anchor rod 011 away from the side formwork top anchor rod 012 extends and is anchored to the interior of the arch concrete formwork 4. The end of the side formwork top anchor rod 012 away from the top formwork anchor rod 011 extends and is anchored to the interior of the side concrete formwork 5. A first tension spring 013 is disposed between the end of the top formwork anchor rod 011 extending into the elastic rubber pad and the end of the side formwork top anchor rod 012 extending into the elastic rubber pad.

[0028] Anchor holes are pre-drilled at the top of the side concrete formwork 5, and top anchor rods 012 of the side formwork are anchored in the anchor holes. The anchoring end of the top anchor rod 012 extends into the anchor hole, and the connecting end of the top anchor rod 012 extends into the elastic rubber pad in the first connecting joint 111. Anchor holes are pre-drilled at the ends of the arch concrete formwork 4, and top formwork anchor rods 011 are anchored in the anchor holes. The anchoring end of the top anchor rod 011 extends into the anchor hole, and the connecting end of the top anchor rod 011 extends into the elastic rubber pad in the first connecting joint 111. The connecting ends of the top anchor rods 012 and 011 of the side formwork are slidably connected, allowing the top anchor rods 012 and 011 to move closer or further apart relative to each other. A first tension spring 013 is provided between the connecting ends of the top anchor rods 012 and 011 of the side formwork for buffering, thereby compensating for the amount of edge deformation during concrete solidification. After the arch concrete formwork 4 and the side concrete formwork 5 have solidified to the required standard, concrete can be sprayed into the first connection joint 111 to achieve a complete connection between the arch concrete formwork 4 and the side concrete formwork 5.

[0029] The other parts of this embodiment are the same as those in Embodiment 1, so they will not be described again.

[0030] Example 3: This embodiment is a further optimization based on the above embodiment 1 or 2, such as... Figure 4 As shown, the elastic rubber pad is provided with a first connecting sleeve 014 inside. The end of the top mold anchor rod 011 away from the side mold top anchor rod 012 extends into the inner hole of one end of the first connecting sleeve 014 and is slidably connected to the inner hole. The end of the side mold top anchor rod 012 away from the top mold anchor rod 011 extends into the inner hole of the other end of the first connecting sleeve 014 and is slidably connected to the inner hole. The first connecting sleeve 014 is provided with a first tension spring 013 for connecting the top mold anchor rod 011 and the side mold top anchor rod 012.

[0031] A first connecting sleeve 014 is pre-embedded inside the elastic rubber pad, and connecting holes are respectively provided at both ends of the first connecting sleeve 014. The connecting end of the top mold anchor rod 011 extends into the connecting hole at one end of the first connecting sleeve 014 and is slidably connected to the connecting hole. Similarly, the connecting end of the side mold top anchor rod 012 extends into the connecting hole at the other end of the first connecting sleeve 014 and is slidably connected to the connecting hole. A first tension spring 013 is provided inside the first connecting sleeve 014, and the two ends of the first tension spring 013 are respectively connected to the connecting ends of the side mold top anchor rod 012 and the top mold anchor rod 011, thereby providing elastic buffering when the top mold anchor rod 011 and the side mold top anchor rod 012 move relative to each other.

[0032] The other parts of this embodiment are the same as those in Embodiment 1 or 2 above, so they will not be described again.

[0033] Example 4: This embodiment is a further optimization based on any one of embodiments 1-3 above, such as... Figure 1 and Figure 5 As shown, the second connector 02 includes an elastic rubber pad, an inverted arch anchor rod 021, a side formwork bottom anchor rod 022, and a second tension spring 023. The elastic rubber pad is disposed inside the second connecting joint 222 and fills and seals the second connecting joint 222. The inverted arch anchor rod 021 and the side formwork bottom anchor rod 022 are slidably connected to each other inside the elastic rubber pad. The end of the inverted arch anchor rod 021 away from the side formwork bottom anchor rod 022 extends and is anchored to the inside of the inverted arch concrete formwork 6. The end of the side formwork bottom anchor rod 022 away from the inverted arch anchor rod 021 extends and is anchored to the inside of the side concrete formwork 5. A second tension spring 023 is disposed between the end of the inverted arch anchor rod 021 extending into the elastic rubber pad and the end of the side formwork bottom anchor rod 022 extending into the elastic rubber pad.

[0034] The elastic rubber pad has a connecting hole inside. The connecting end of the invert arch anchor 021 extends into one end of the connecting hole and slides into it. The connecting end of the side formwork bottom anchor 022 extends into the other end of the connecting hole and slides into it. A second tension spring 023 is installed inside the connecting hole. The two ends of the second tension spring 023 are connected to the connecting ends of the invert arch anchor 021 and the side formwork bottom anchor 022, respectively, so as to provide elastic buffering when the invert arch anchor 021 and the side formwork bottom anchor 022 move relative to each other.

[0035] The other parts of this embodiment are the same as any one of the embodiments 1-3 above, so they will not be described again.

[0036] Example 5: This embodiment is a further optimization based on any one of embodiments 1-4 above, such as... Figure 1 As shown, the interior of both the left and right ends of the inverted arch concrete formwork 6 is provided with inverted arch anchor rods 021, and the inverted arch anchor rods 021 at the left and right ends are connected by a reinforcing beam 8.

[0037] Anchor holes are pre-drilled at both ends of the invert concrete formwork 6, and the interior of the anchor holes connects to the anchor ends of the invert anchor rods 021. A transverse reinforcement section is provided between the anchor ends and the connecting ends of the invert anchor rods 021. This transverse reinforcement section passes through the invert concrete formwork 6 along the cross-section of the tunnel and extends to the outside of the invert concrete formwork 6. The transverse reinforcement sections of the invert anchor rods 021 on both sides are connected by a reinforcing beam 8, the bottom of which is connected to the steel bars pre-embedded inside the invert concrete formwork 6. This forms a transverse reinforcement structure to support and reinforce the load-bearing invert.

[0038] Example 6: This embodiment is a further optimization based on any one of embodiments 1-5 above, such as... Figure 6 As shown, the anchoring part 301 has a central grouting cavity inside, and the side wall of the anchoring part 301 has several grout outlets connected to the central grouting cavity; the end of the anchoring part 301 away from the surrounding rock is provided with a mother flange 31; the end of the grouting part 302 near the anchoring part 301 is provided with a daughter flange 32 that connects to the mother flange 31, and the interior of the grouting part 302 is provided with a grouting pipeline connected to the central grouting cavity.

[0039] Some grout outlets are inclined upwards, while others are inclined downwards. The downward-inclined grout outlets are used as drainage holes before grouting. Water accumulated inside the surrounding rock quickly enters the central grouting cavity inside the anchoring part 301 through the downward-inclined grouting outlets, and then flows to the inside of the tunnel through the grouting pipes inside the grouting part 302.

[0040] The anchoring part 301 and the grouting part 302 are connected by the mating of the mother flange 31 and the daughter flange 32. After the mother flange 31 and the daughter flange 32 are mated, they are connected and reinforced by connecting bolts.

[0041] Furthermore, the female flange 31 has a tapered interface at one end near the grouting part 302, and the female flange 32 has a tapered boss at one end near the anchoring part 301 that mates with the tapered interface. The tapered boss and the tapered structure work together to guide the female flange 31 and the female flange 32, allowing for quick and accurate docking.

[0042] The other parts of this embodiment are the same as any one of the embodiments 1-5 above, so they will not be described again.

[0043] Example 7: A construction method for a tunnel support structure in expansive and collapsible mixed strata, based on the aforementioned tunnel support structure, includes the following steps: Step 1: Install advanced support, then conduct preliminary excavation and apply a waterproof layer 2 to the inner side of the tunnel. Next, install rigid supports 1 in the preliminary excavation section. For the tunnel arch and the surrounding rock on the outer sidewalls, install advanced support pipes and reinforce the surrounding rock around the arch and sidewalls with grouting. For the advanced support pipes arranged in a fan shape on the tunnel arch, the central angle of the corresponding circle should be less than or equal to 120°. For the advanced support pipes installed on the tunnel sidewalls, the pipes are staggered from top to bottom. After grouting reinforcement is completed, tunnel excavation can begin.

[0044] Tunnel excavation includes the following steps: (1) First, the upper soil is excavated and the central soil is reserved. Then, a waterproof layer 2 is applied to the tunnel arch. Then, a top support is applied to the corresponding arch position. The arch is temporarily supported by the top support, and segmented grouting anchors 3 are driven into the arch surrounding rock through the anchor holes reserved on the top support.

[0045] (2) Excavate the middle layer of soil, then apply a waterproof layer 2 to the tunnel sidewall, then install a side support at the corresponding position of the sidewall, and temporarily support the tunnel sidewall directly through the side, and drive segmented grouting anchor rods 3 into the surrounding rock of the sidewall through the anchor holes reserved on the side support.

[0046] (3) Excavate the lower soil layer, then apply a waterproof layer 2 to the tunnel arch, then connect the top support and the side support to form a rigid support 1, and set a sliding structure at the bottom of the rigid support 1.

[0047] Step 2: Install segmented grouting anchors 3 along the inner contour of the tunnel on the rigid support 1. The anchoring part 301 of the segmented grouting anchor 3 is inserted into the surrounding rock, and the grouting part 302 of the segmented grouting anchor 3 is connected to the drainage pipe. Drainage is carried out on the top of the surrounding rock through the grouting hole of the anchoring part 301. After the drainage operation is completed, grouting operation is carried out on the anchoring part 301 through the grouting part 302. Step 3: After the grouting operation is completed, the anchoring part 301 and the grouting part 302 are separated, so that the anchoring part 301 remains inside the surrounding rock; then the rigid support 1 is moved along the tunnel to the next excavation area. Step 4: Construct an invert concrete formwork 6 at the invert position of the grout-reinforced tunnel section, and install reinforcing anchor bolts 7 extending into the surrounding rock along the outline of the invert concrete formwork 6; based on the invert concrete formwork 6, construct side concrete formwork 5 at the left and right ends of the invert concrete formwork 6, and install reinforcing anchor bolts 7 extending into the surrounding rock along the outline of the tunnel sidewall on the side concrete formwork 5; based on the side concrete formwork 5 on the left and right sides, construct an arch concrete formwork 4 along the outline of the tunnel arch between the tops of the side concrete formwork 5 on the left and right sides, and install reinforcing anchor bolts 7 extending into the surrounding rock along the outline of the tunnel arch on the arch concrete formwork 4. Step 5: Install the second connector 02 in the second connecting joint 222 between the bottom of the invert concrete formwork 6 and the side concrete formwork 5, install the first connector 01 in the first connecting joint 111 between the top of the side concrete formwork 5 and the arch concrete formwork 4, and seal the first connecting joint 111 and the second connecting joint 222 with shotcrete. Step 6: Repeat steps 1-5 above until the entire tunnel excavation and support are completed.

[0048] Example 8: This embodiment is a further optimization based on the above embodiment 7. Parallel I-beams are constructed on both sides of the top of the inverted arch concrete formwork 6 as sliding tracks for the rigid support 1. The bottom of the rigid support 1 is slidably connected to the I-beams through sliding supports with rollers. The rigid support 1 can move along the tunnel by sliding along the I-beams through the sliding supports. After the side concrete formwork 5 is completed, temporary side supports are installed between the top of the I-beam and the side concrete formwork 5; after the arch concrete formwork 4 is completed, temporary arch supports are installed between the top of the I-beam and the arch concrete formwork 4. The temporary supports ensure the stability of the side concrete formwork 5 and the arch concrete formwork 4 before they are fixedly connected to form an integral structure.

[0049] Furthermore, after the overall tunnel construction is completed, the rigid support 1, the side temporary support, and the arch temporary support are removed, while the I-beams are retained. Then, a secondary lining is constructed on top of the inverted arch concrete formwork 6 to cover the I-beams.

[0050] The other parts of this embodiment are the same as those in Embodiment 7 above, so they will not be described again.

[0051] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A construction method for a tunnel support structure in a mixed expansive and collapsible stratum, characterized in that, The tunnel support structure for the expansion-collapse mixed strata includes a rigid support (1) that moves along the tunnel. A waterproof layer (2) is provided between the rigid support (1) and the inner side of the tunnel. Several segmented grouting anchors (3) are provided on the rigid support (1). Each segmented grouting anchor (3) includes an anchoring part (301) that extends into the surrounding rock and has grouting holes. The end of the anchoring part (301) near the rigid support (1) is detachably provided with a grouting part (302) that passes through the waterproof layer (2) and the rigid support (1). An arch concrete is provided at the arch crown in the excavation section on the side of the rigid support (1) away from the tunnel face. The arch concrete formwork (4) is provided with side concrete formwork (5) on the left and right sides corresponding to the side walls of the tunnel, and an invert concrete formwork (6) is provided between the tops of the side concrete formwork (5) corresponding to the invert of the tunnel; a first connecting joint (111) is provided between the arch concrete formwork (4) and the side concrete formwork (5), and a first connector (01) for connecting the arch concrete formwork (4) and the side concrete formwork (5) is provided in the first connecting joint (111); a second connecting joint (6) is provided between the side concrete formwork (5) and the invert concrete formwork (6). 222), the second connecting joint (222) is provided with a second connecting member (02) for connecting the side concrete formwork (5) and the invert concrete formwork (6); the arch top concrete formwork (4), the side concrete formwork (5) and the invert concrete formwork (6) are all provided with reinforcing anchor rods (7) extending into the surrounding rock; the first connecting member (01) includes an elastic rubber pad, a top formwork anchor rod (011), a side formwork top anchor rod (012) and a first tension spring (013), the elastic rubber pad is provided inside the first connecting joint (111) and fills and seals the first connecting joint (111), the elastic The rubber pad is equipped with a top formwork anchor rod (011) and a side formwork top anchor rod (012) that are slidably connected to each other. The end of the top formwork anchor rod (011) away from the side formwork top anchor rod (012) extends and is anchored to the interior of the arch concrete formwork (4). The end of the side formwork top anchor rod (012) away from the top formwork anchor rod (011) extends and is anchored to the interior of the side concrete formwork (5). A first tension spring (013) is provided between the end of the top formwork anchor rod (011) extending into the elastic rubber pad and the end of the side formwork top anchor rod (012) extending into the elastic rubber pad. The specific construction method includes the following steps: Step 1: Install advance support, then carry out preliminary excavation and apply a waterproof layer on the inside of the tunnel (2), and then install rigid supports in the preliminary excavation section (1). Step 2: Install segmented grouting anchors (3) along the inner contour of the tunnel on the rigid support (1). The anchoring part (301) of the segmented grouting anchor (3) is inserted into the surrounding rock. The grouting part (302) of the segmented grouting anchor (3) is connected to the drainage pipe. Drainage is carried out on the top of the surrounding rock through the grouting hole of the anchoring part (301). After the drainage operation is completed, grouting operation is carried out on the anchoring part (301) through the grouting part (302). Step 3: After the grouting operation is completed, the anchoring part (301) and the grouting part (302) are separated, so that the anchoring part (301) remains inside the surrounding rock; then the rigid support (1) is moved along the tunnel to the next excavation area; Step 4: Construct an invert concrete formwork (6) at the invert position of the tunnel section that has been grouted and reinforced, and install reinforcing anchor rods (7) extending into the surrounding rock along the outline of the invert concrete formwork (6); based on the invert concrete formwork (6), construct side concrete formwork (5) at the left and right ends of the invert concrete formwork (6), and install reinforcing anchor rods (7) extending into the surrounding rock along the outline of the tunnel sidewall on the side concrete formwork (5); based on the side concrete formwork (5) on the left and right sides, construct an arch concrete formwork (4) between the tops of the side concrete formwork (5) on the left and right sides, and install reinforcing anchor rods (7) extending into the surrounding rock along the outline of the tunnel arch on the arch concrete formwork (4). Step 5: Install the second connector (02) in the second connecting joint (222) between the bottom of the invert concrete formwork (6) and the side concrete formwork (5), install the first connector (01) in the first connecting joint (111) between the top of the side concrete formwork (5) and the arch concrete formwork (4), and seal the first connecting joint (111) and the second connecting joint (222) with shotcrete. Step 6: Repeat steps 1-5 above until the entire tunnel excavation and support are completed.

2. The construction method of a tunnel support structure for expansive and collapsible mixed strata according to claim 1, characterized in that, The elastic rubber pad is provided with a first connecting sleeve (014). The end of the top mold anchor rod (011) away from the side mold top anchor rod (012) extends into the inner hole of one end of the first connecting sleeve (014) and is slidably connected to the inner hole. The end of the side mold top anchor rod (012) away from the top mold anchor rod (011) extends into the inner hole of the other end of the first connecting sleeve (014) and is slidably connected to the inner hole. The first connecting sleeve (014) is provided with a first tension spring (013) for connecting the top mold anchor rod (011) and the side mold top anchor rod (012).

3. The construction method of a tunnel support structure for a mixed expansive and collapsible stratum according to claim 1, characterized in that, The second connector (02) includes an elastic rubber pad, an inverted arch anchor rod (021), a side formwork bottom anchor rod (022), and a second tension spring (023). The elastic rubber pad is disposed inside the second connecting joint (222) and fills and seals the second connecting joint (222). The inverted arch anchor rod (021) and the side formwork bottom anchor rod (022) are slidably connected inside the elastic rubber pad. The end of the inverted arch anchor rod (021) away from the side formwork bottom anchor rod (022) extends and is anchored to the inside of the inverted arch concrete formwork (6). The end of the side formwork bottom anchor rod (022) away from the inverted arch anchor rod (021) extends and is anchored to the inside of the side concrete formwork (5). A second tension spring (023) is disposed between the end of the inverted arch anchor rod (021) extending into the elastic rubber pad and the end of the side formwork bottom anchor rod (022) extending into the elastic rubber pad.

4. The construction method of a tunnel support structure for a mixed expansive and collapsible stratum according to claim 3, characterized in that, The inverted arch concrete formwork (6) is provided with inverted arch anchor rods (021) at both ends, and the inverted arch anchor rods (021) at both ends are connected by a reinforcing beam (8).

5. A construction method for a tunnel support structure in an expansion-collapse mixed stratum according to any one of claims 1-4, characterized in that, The anchoring part has a central grouting cavity inside, and the side wall of the anchoring part has several grout outlets connected to the central grouting cavity; the end of the anchoring part away from the surrounding rock is provided with a mother flange (31); the end of the grouting part near the anchoring part is provided with a daughter flange (32) that connects to the mother flange (31), and the grouting part has a grouting pipeline connected to the central grouting cavity inside.

6. The construction method of a tunnel support structure for a mixed expansive and collapsible stratum according to claim 5, characterized in that, The mother flange (31) is provided with a tapered interface at one end near the grouting part, and the daughter flange (32) is provided with a tapered boss that mates with the tapered interface at one end near the anchoring part.

7. The construction method of a tunnel support structure for a mixed expansive and collapsible stratum according to claim 1, characterized in that, Parallel I-beams are constructed on both sides of the top of the inverted arch concrete formwork (6) as sliding tracks for the rigid support (1); after the side concrete formwork (5) is constructed, temporary side support is constructed between the top of the I-beams and the side concrete formwork (5); after the arch top concrete formwork (4) is constructed, temporary arch top support is constructed between the top of the I-beams and the arch top concrete formwork (4).

8. The construction method of a tunnel support structure for a mixed expansive and collapsible stratum according to claim 1, characterized in that, After the overall tunnel construction is completed, the rigid support (1), the side temporary support, and the arch temporary support are removed, and the I-beams are retained. Then, a secondary lining is constructed on top of the inverted arch concrete formwork (6) to cover the I-beams.

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