A treatment method for the cracking of the invert of a tunnel in a water-rich soft stratum

Abstract

The present invention discloses a treatment method for the cracking of the inverted arch of a tunnel in a water-rich soft stratum, belonging to the technical field of tunnel disease treatment. The treatment of the cracking of the inverted arch of a tunnel in a water-rich soft stratum is carried out by successively determining the water-containing influence area, burying steel supports in the inverted arch filling layer, arranging locking foot conduits, arranging grouting pipes, draining and relieving pressure, grouting and strengthening, and connecting the crushed stones of the pavement structure. The method of the present invention can be re-constructed without demolishing the existing inverted arch through the combined action of structural reinforcement and grouting reinforcement. While strengthening the soft stratum, the overall stability of the inverted arch can be enhanced, and the effective treatment of the cracking of the tunnel inverted arch can be realized; the method of the present invention has simple process operation, high construction efficiency and good safety.

Description

Technical Field

[0001] The present invention belongs to the technical field of tunnel disease treatment, and particularly relates to a treatment method for the cracking of the invert of a tunnel in a water-rich soft stratum. Background Art

[0002] When a tunnel passes through poor strata such as water-rich and soft strata, especially when passing through fully strongly weathered surrounding rock, joint fissures are developed and weakened by water, which is extremely likely to cause the cracking of the already built invert. After the invert cracks, on the one hand, it will reduce the strength of the support structure and damage the integrity of the tunnel; on the other hand, the cracks will cause the water conduction channels between the invert and the surrounding rock to be connected. Under the action of groundwater pressure, large-scale water gushing and other diseases will occur in the invert, endangering the safety of the tunnel. When treating the cracking of the invert, at present, the treatment methods of using a hydraulic breaker to chisel and blasting to demolish the invert are mostly adopted. However, when using a hydraulic breaker to chisel, the vibration is large, the duration is long, and the concrete of the primary support is likely to fall off. The instantaneous impact vibration of blasting demolition is large, and in the invert section with steel bars, it is necessary to increase the explosive charge, which has a greater impact on the already constructed lining, and there is still a risk of cracking when re-constructing the invert. Summary of the Invention

[0003] In view of the above defects, the present invention proposes a treatment method for the cracking of the invert of a tunnel in a water-rich soft stratum, which can effectively treat diseases such as cracking and subsidence of the tunnel invert in poor geological sections and the water gushing problem that may be caused by groundwater without demolishing the invert and without affecting the existing lining.

[0004] A treatment method for the cracking of the invert of a tunnel in a water-rich soft stratum comprises the following specific steps:

[0005] Step 1: Determination of the water-containing influence area

[0006] Select a number of transverse sections along the longitudinal direction of the tunnel on the invert surface. Drill a number of exploration holes on each transverse section. The number of exploration holes on each transverse section extends radially downward from the invert surface to the outside of the tunnel. The depth of each exploration hole is 8 - 10 m, and the outermost exploration hole with an angle of 45° - 60° with the vertical plane is used as the outermost boundary of the exploration area.

[0007] During the drilling of the exploration holes, record the depth at which the water gushing changes significantly. The area surrounded by the depths at which the water gushing changes significantly of all the exploration holes is the water-containing influence area. After the exploration is completed, grout the exploration holes;

[0008] Among them, the depth at which the water gushing changes significantly refers to: the position where the water gushing volume changes for the first time when each exploration hole is constructed and the position where the water gushing volume significantly decreases or there is no water gushing.

[0009] Step 2: Embedding steel supports in the invert filling layer

[0010] At the invert surface above the water-affected area, along the longitudinal direction of the tunnel, a first installation groove is opened downward every 2m - 3m. The length direction of the first installation groove is the transverse direction of the tunnel. The length of the first installation groove is the same as the width of the invert surface, the width is 35 - 50cm, and the depth is 40 - 50cm. Then, an I-beam support is buried in the first installation groove. The web of the I-beam support is perpendicular to the invert surface. The flanges of the I-beam support are respectively located on both sides of the web. The arc length of the I-beam support is determined according to the thickness of the invert filling. The distance between the upper flange of the I-beam support and the invert filling surface is at least 50mm.

[0011] Step Three: Install the foot-locking pipes

[0012] Use a steel pipe with a diameter of φ42mm and a length of 8 - 10m as the foot-locking pipe of the I-beam support. There are 4 foot-locking pipes at each end of the I-beam support. There are 2 foot-locking pipes with a transverse spacing of 15cm at each end on both sides of the web of the I-beam support. The 4 foot-locking pipes on the same side of the web are arranged along the length direction of the I-beam support (i.e., the transverse direction of the tunnel). The 8 foot-locking pipes are pairwise corresponding in the width direction of the I-beam support (i.e., the longitudinal direction of the tunnel). Among them, the 4 foot-locking pipes close to the ends of the I-beam support are marked as sequence I, and the remaining 4 foot-locking pipes are marked as sequence II.

[0013] All 8 foot-locking pipes pass through the upper and lower flanges of the I-beam support, and the top of the foot-locking pipe is 10cm higher than the upper flange. The foot-locking pipe is welded and fixed to the I-beam support.

[0014] The foot-locking pipe is a perforated pipe. The pipe is provided with perforations with a spacing of 10cm and a diameter of 1cm, arranged in a plum blossom pattern. A threaded steel bar is inserted into the pipe. The upper end of the threaded steel bar is flush with the foot-locking pipe, and the lower end extends beyond the foot-locking pipe by a distance of 5cm.

[0015] Step Four: Install the grouting pipes

[0016] Use a geological drill to drill grouting holes downward from the invert surface. The grouting holes include long holes and short holes. The depth of the long hole is the maximum depth of the position where the water inflow significantly decreases or there is no water inflow. The depth of the short hole is the minimum depth of the position where the water inflow first changes. Then, install grouting pipes at the grouting holes. The grouting pipe is a perforated pipe with a diameter of 42cm. The top of the pipe orifice of the grouting pipe is 15 - 20cm higher than the invert surface. The grouting pipe includes two forms: a long pipe arranged in the long hole and a short pipe arranged in the short hole. The long pipe and the short pipe are arranged in a plum blossom pattern in a staggered interval manner. The spacing of the long pipes is 2 * 2m, and the spacing of the short pipes is 1.5 * 1.5m.

[0017] Step Five: Drain and relieve pressure

[0018] Select the grouting holes at the locations with large water inflow in the water-affected area as the drainage and pressure-relief holes. Use the grouting pipes of these grouting holes as the drainage pipes. Install valves and pressure gauges at the upper ends of the drainage pipes, and wrap the lower ends with anti-filter geotextiles. When the formation around the drainage pipe is hollowed out due to excessive sediment carried by the drainage and pressure-relief holes, select the grouting pipes around the drainage and pressure-relief holes, increase the grouting pressure, and make the slurry flow into the position of the drainage pipe actively to create slurry cross-flow, so as to reinforce the formation around the drainage pipe.

[0019] Step Six: Grouting Reinforcement

[0020] Use the locking-foot pipes as grouting pipes to construct a curtain water cut-off wall. First construct the first sequence, and then construct the second sequence. Adjust the ratio of the quick-setting grouting material and the grouting pressure to control the slurry diffusion range, and form the outermost curtain water cut-off wall; for the grouting of the invert base, adopt the long-hole and short-hole sequential and skip-hole grouting reinforcement method, with the water-cement ratio of 0.5:1 - 0.8:1 and the grouting pressure of 0.2 - 0.5 MPa. Carry out skip-hole grouting for the long pipes and short pipes respectively. When carrying out skip-hole grouting, adopt the method of grouting one hole and skipping one hole for multiple cycles to complete the reinforcement.

[0021] Step Seven: Aggregate Connection of Road Surface Structure

[0022] A second installation groove is opened longitudinally along the tunnel on the invert surface. The second installation groove is communicated with the first installation groove. The second installation groove is provided with steel pipe with holes. The steel pipe with holes passes through the web of the I-beam support and is welded to the adjacent I-beam support, so that the steel pipe with holes and the I-beam are connected into a whole.

[0023] Then, use the steel pipe with holes as the grouting pipe, and spread the slurry to the graded aggregate through the holes in the pipe, so that the aggregate becomes a concrete structure, strengthening the integrity and strength. After the grouting is completed, backfill the first installation groove and the second installation groove with concrete.

[0024] The beneficial effects of the present invention are as follows: Aiming at the problem of invert cracking in tunnels in water-rich soft strata, through the combined action of structural reinforcement and grouting reinforcement, it can be re-constructed without demolishing the existing invert. While strengthening the soft strata, it can enhance the overall stability of the invert and effectively control the invert cracking of the tunnel. Among them, the present invention is reinforced by the structure of the criss-cross steel pipe with holes and I-beam, which has good spatial integrity. The steel pipe with holes and I-beam in two directions jointly bear the forces acting on the tunnel invert, making the force on the invert surface relatively uniform at the reinforcement position, so that it is not easy to generate deformation at the cracking position; since cracks are more likely to occur in soft strata, and the present invention grouts and reinforces the water-rich area, making the overall stiffness of the area between the tunnel invert and the groundwater increase under the action of grouting, thus reducing the possibility of tunnel invert cracking. In addition, the process of the present invention is simple in operation, high in construction efficiency and good in safety. Description of the Drawings

[0025] Figure 1 Schematic diagram for determining the water-containing influence area of a transverse section in Example 1;

[0026] Figure 2 Position relationship diagram of the foot-locking conduit and the I-beam support described in Example 1;

[0027] Figure 3 In Example 1, from Figure 2 Schematic diagram of the position relationship between the foot-locking conduit and the I-beam support obtained from the left-side view;

[0028] Figure 4 Schematic diagram of the distribution of the grouting holes described in Example 1;

[0029] Figure 5 Schematic diagram of the overall structure of the crushed stone connection of the pavement structure described in Example 1. Detailed implementation method

[0030] The terms used in the present invention generally have the meanings commonly understood by those of ordinary skill in the art unless otherwise specified.

[0031] The present invention will be further described in detail below with reference to specific examples and data. The following examples are only for illustrating the present invention and do not limit the scope of the present invention in any way.

[0032] In the present invention, the longitudinal direction of the tunnel is the driving direction in the tunnel, and the transverse direction perpendicular to the driving direction is the transverse direction of the tunnel.

[0033] Example 1

[0034] A treatment method for the cracking of the invert of a tunnel in a water-rich soft stratum, the specific steps are as follows:

[0035] Step 1: Determination of the water-containing influence area

[0036] As Figure 1 shown, several transverse sections are selected along the longitudinal direction of the tunnel on the invert surface 1, and several exploration holes 2 are drilled on each transverse section. The several exploration holes 2 on each transverse section extend radially downward from the invert surface 1 towards the outside of the tunnel. The depth of each exploration hole 2 is 8 - 10 m (through actual construction experience, the water inrush beyond a depth of 10 m has little impact on the cracking of the tunnel invert). The outermost exploration hole 2 with an angle β of 45° - 60° with the vertical plane is used as the outermost boundary of the exploration area.

[0037] During the drilling process of the exploration hole 2, the depth at which the water inrush changes significantly is recorded. The area surrounded by the depths at which the water inrush changes significantly of all the exploration holes 2 is the water-containing influence area. After the exploration is completed, the exploration holes 2 are grouted.

[0038] Among them, the depth where the water inrush significantly changes specifically refers to two depth positions: the position a where the water inrush volume first changes when each exploration hole 2 is constructed, and the position b where the water inrush volume significantly decreases or there is no water inrush (when there is still water inrush when drilling to 8 - 10 m, the end point of drilling is b).

[0039] Step 2: Embed steel supports in the inverted arch filling layer

[0040] As Figure 2 and Figure 3 shown, on the inverted arch surface 1 above the water-bearing influence area, a first installation groove 3 is opened downward every 2 m - 3 m along the longitudinal direction of the tunnel. The length direction of the first installation groove 3 is the transverse direction of the tunnel. The length of the first installation groove 3 is the same as the width of the inverted arch surface 1, the width is 35 - 50 cm, and the depth is 40 - 50 cm. Then, an I-beam support 4 is embedded in the first installation groove 3. The web of the I-beam support 4 is perpendicular to the inverted arch surface 1. The flanges of the I-beam support 4 are respectively located on both sides of the web. The arc length of the I-beam support 4 is determined according to the thickness of the inverted arch filling. The distance between the upper flange of the I-beam support 4 and the inverted arch filling surface is at least 50 mm. The "up" and "down" directions in this paragraph correspond to the "up" and "down" directions in Figure 2 and Figure 3 .

[0041] Step 3: Install locking foot conduits

[0042] As Figure 2 shown, a steel pipe with a diameter of φ42 mm and a length of 8 - 10 m is used as the locking foot conduit 5 of the I-beam support 4. As Figure 5 shown, 4 locking foot conduits 5 are provided at each end of the I-beam support 4. 2 locking foot conduits 5 with a transverse spacing of 15 cm are provided at each end on both sides of the web of the I-beam support 4. The 4 locking foot conduits 5 on the same side of the web are arranged along the length direction of the I-beam support 4 (i.e., the transverse direction of the tunnel). The 8 locking foot conduits 5 are pairwise corresponding in the width direction of the I-beam support 4 (i.e., the longitudinal direction of the tunnel). Among them, the 4 locking foot conduits 5 close to the end of the I-beam support 4 are denoted as the first order, and the remaining 4 locking foot conduits 5 are denoted as the second order.

[0043] As Figure 3 shown, all 8 locking foot conduits 5 pass through the upper and lower flanges of the I-beam support 4, and the top of the locking foot conduit 5 is 10 cm higher than the upper flange. The locking foot conduit 5 is welded and fixed to the I-beam support 4.

[0044] The locking foot conduit 5 is a perforated pipe. The pipe is provided with perforations arranged in a plum blossom pattern with a spacing of 10 cm and a diameter of 1 cm. A threaded steel bar 7 is inserted into the pipe. The upper end of the threaded steel bar 7 is flush with the locking foot conduit 5, and the lower end extends beyond the locking foot conduit 5 by a distance of 5 cm.

[0045] Step 4: Install grouting pipes

[0046] Use a geological drill to drill grouting holes downward from the invert surface 1. The grouting holes include long holes and short holes. The depth of the long holes is the maximum depth at position b, and the depth of the short holes is the minimum depth at position a. Then, arrange grouting pipes at the grouting holes. The grouting pipes are perforated pipes with a diameter of 42 cm, and the top of the pipe orifice is 15 - 20 cm higher than the invert surface 1. As Figure 4 shown, the grouting pipes include two forms: long pipes 8 arranged in the long holes and short pipes 9 arranged in the short holes. The long pipes 8 and the short pipes 9 are arranged in a plum blossom pattern in a staggered interval manner. The spacing of the long pipes 8 is 2 * 2 m, and the spacing of the short pipes 9 is 1.5 * 1.5 m.

[0047] Step Five: Drainage and pressure relief

[0048] Select the grouting holes at the locations with large water inflow in the water - affected area as the drainage and pressure relief holes. Use the grouting pipes of these grouting holes as drainage pipes. Install a valve and a pressure gauge at the upper end of the drainage pipe, and wrap an anti - filtering geotextile at the lower end. When the formation around the drainage pipe is hollowed out due to excessive sediment carried by the drainage and pressure relief holes, select the grouting pipes around the drainage and pressure relief holes, increase the grouting pressure, and make the slurry flow into the position of the drainage pipe actively to create slurry cross - flow, thereby strengthening the formation around the drainage pipe.

[0049] Step Six: Grouting reinforcement

[0050] Use the locking foot pipe 5 as the grouting pipe to construct a curtain water - intercepting wall. First, construct the first sequence, and then construct the second sequence. Adjust the ratio of the quick - setting grouting material and the grouting pressure to control the slurry diffusion range to form the outermost curtain water - intercepting wall. For the invert base grouting, use the long - hole and short - hole sequential and staggered - hole grouting reinforcement method. The water - cement ratio is 0.5:1 - 0.8:1, and the grouting pressure is 0.2 - 0.5 MPa. Perform staggered - hole grouting on the long pipes 8 and the short pipes 9 respectively. When performing staggered - hole grouting, adopt the method of grouting every other hole and skipping one hole for multiple cycles to complete the grouting reinforcement.

[0051] Step Seven: Connection of the road surface structure with crushed stones

[0052] As Figure 5 shown, a second installation groove 10 is opened longitudinally along the tunnel on the invert surface 1. The second installation groove 10 is communicated with the first installation groove 3. The second installation groove 10 is provided with perforated steel pipes 11. The perforated steel pipes 11 pass through the web of the I - beam support 4 and are welded to the adjacent I - beam support 4, so that the perforated steel pipes 11 and the I - beam 4 are connected into a whole.

[0053] Then, use the perforated steel pipes 11 as grouting pipes, and diffuse the slurry to the graded crushed stones through the holes, so that the crushed stones become a concrete structure, strengthening the structural integrity and strength. After the grouting is completed, backfill the first installation groove 3 and the second installation groove 10 with concrete.

[0054] Example 2

[0055] On the basis of Embodiment 1, taking the invert cracking of Jiangxi Lianhua Tunnel as an example for illustration.

[0056] Step 1: Determination of the water-bearing influence area

[0057] As Figure 1 shown, several transverse sections are selected along the longitudinal direction of the tunnel, the spacing between several transverse sections is 40 - 50 cm, and several exploration holes 2 are drilled on each transverse section. The spacing between adjacent two exploration holes 2 on the invert surface 1 is 40 - 50 cm; several exploration holes 2 are drilled on each transverse section in a radial direction downward from the invert surface 1 using a φ89 mm drill bit, the depth of the exploration holes 2 is 10 m, and the outermost exploration hole 2 with an angle of 45° with the vertical plane is used as the outer boundary of the exploration area. When each exploration hole 2 is constructed, the position a where the water inflow rate first changes is recorded, and when drilling continues to the position b where the water inflow rate significantly decreases or there is no water inflow, a second record is made. After all the exploration holes 2 are constructed according to this step, the area surrounded by the positions a and positions b of all the exploration holes 2 is the water-bearing influence area. In the present invention, the minimum distance of the position a is 2.5 m, and the maximum distance of the position b is 8 m. After the exploration is completed, all the exploration holes 2 are grouted.

[0058] Step 2: Embedding steel supports in the invert filling layer

[0059] As Figure 2 shown, at the invert surface 1 above the water-bearing influence area, a first installation groove 3 is opened downward every 2 m along the longitudinal direction of the tunnel. The length direction of the first installation groove 3 is the transverse direction of the tunnel, the length of the first installation groove 3 is the same as the width of the invert surface 1, the depth is 40 cm, and the width is 50 cm; then an I20a steel beam support 4 is embedded in the first installation groove 3. The flanges of the steel beam support 4 are located on the upper and lower sides, and the web is perpendicular to the invert surface 1 (as Figure 3 ), the arc length of the steel beam support 4 is 772.6 cm, and the thickness of the upper flange of the steel beam and the invert filling surface is 200 mm. The "up" and "down" directions in this paragraph correspond to the "up" and "down" directions in Figure 2 and Figure 3 .

[0060] Step 3: Arrangement of the foot-locking conduits

[0061] A steel pipe with a diameter of φ42 mm and a length of 10 m is used as the foot-locking conduit 5 of the steel beam support 4, as Figure 5As shown in the figure, 4 locking feet conduits 5 are arranged at each end of the I-beam support 4. 2 locking feet conduits 5 with a transverse spacing of 15 cm are arranged at each end on both sides of the web of the I-beam support 4. The 4 locking feet conduits 5 on the same side of the web are arranged along the length direction of the I-beam support 4 (i.e., the transverse direction of the tunnel), and the 8 locking feet conduits 5 are pairwise corresponding in the width direction of the I-beam support 4 (i.e., the longitudinal direction of the tunnel). Among them, the 4 locking feet conduits 5 close to the end of the I-beam support 4 are denoted as the first sequence, and the remaining 4 locking feet conduits 5 are denoted as the second sequence.

[0062] During installation, as Figure 3 shown in the figure, round holes are drilled on the upper and lower flanges on the left and right sides of the web of the I-beam support 4. The size of the round holes matches the diameter of the locking feet conduit 5. After passing the locking feet conduit 5 through the round hole and being 10 cm higher than the upper edge, it is welded to the I-beam support 4. The locking feet conduit 5 is provided with perforations. Among them, the perforations are arranged in a plum blossom pattern with a spacing of 10 cm and a diameter of 1 cm. 1 threaded steel bar 7 with a diameter of 25 mm of HRB400 is inserted into the locking feet conduit 5. The upper end of the threaded steel bar 7 is flush with the locking feet conduit 5, and the lower end exceeds the locking feet conduit 5 by a distance of 5 cm.

[0063] Step 4: Layout of grouting pipes

[0064] Ordinary grouting holes in the middle part are drilled with a geological drill. Here, the middle part refers to the part between two I-beam supports 4. A 50 mm drill bit is used. During the drilling process, the water pressure is adjusted to balance the water pressure and the soil pressure, and the drillings are respectively carried out to 8 m and 2.5 m from the invert surface 1 downward; then grouting pipes are laid at the grouting holes. The grouting pipes are perforated pipes with a diameter of 42 mm. The top end of the grouting pipe is 15 - 20 cm higher than the invert surface 1; as Figure 4 shown in the figure, the grouting pipes include two forms: long pipes 8 and short pipes 9. The long pipes 8 and the short pipes 9 are arranged in a plum blossom pattern in a staggered interval manner. Among them, the spacing of the long pipes 8 is 2 * 2 m, and the spacing of the short pipes 9 is 1.5 * 1.5 m.

[0065] Step 5: Drainage and pressure relief

[0066] Select the grouting hole at the location with a large water inflow in the water-bearing influence area as the drainage and pressure relief hole. Use the grouting pipe of this grouting hole as the drainage pipe. Install a valve and a pressure gauge at the upper end of the drainage pipe, and wrap an anti-filter geotextile at the lower end. When the drainage and pressure relief hole causes the phenomenon of stratum hollowing around the drainage pipe due to excessive sediment carrying capacity, select the grouting pipes around the drainage and pressure relief hole, increase the grouting pressure, and make the slurry flow into the position of the drainage pipe actively to create slurry cross-flow, so as to reinforce the stratum around the drainage pipe.

[0067] Step 6: Grouting reinforcement

[0068] Using the locking-foot pipe 5 as the grouting pipe, construct the curtain water cut-off wall. First, construct the first sequence, and then construct the second sequence. By adjusting the proportion of the quick-setting grouting material and the grouting pressure, control the diffusion range of the slurry to form the outermost curtain water cut-off wall.

[0069] For the grouting of the invert base, adopt the long and short hole sequential and skip-hole grouting reinforcement method. Use the single-fluid cement slurry with a water-cement ratio of 0.8:1 and the double-fluid cement-sodium silicate slurry with a volume ratio of 2:1 - 3:1 for grouting. The grouting pressure is 0.2 - 0.5 Mpa, and perform skip-hole grouting on the long pipe 8 and the short pipe 9 respectively; when performing skip-hole grouting, adopt the method of grouting every other hole and skipping one hole for multiple cycles of grouting. Figure 5 Taking [example] as an example, when the 1st grouting hole leaks, switch to the 3rd hole for grouting, and at the same time block the 1st hole; when the 3rd grouting hole leaks, switch to the 5th hole for grouting, and at the same time block the 3rd hole, and so on, to complete the grouting reinforcement.

[0070] Step Seven: Connect the road surface structure gravel

[0071] As Figure 5 shown, on the invert surface 1, a second installation groove 10 is opened longitudinally along the tunnel. The second installation groove 10 communicates with the first installation groove 3. The second installation groove 10 is provided with a steel flower pipe 11 with a diameter of 15 cm. The steel flower pipe 11 passes through the web of the I-beam support 4 and is welded to the adjacent I-beam support 4, so that the steel flower pipe 11 and the I-beam 4 are connected into a whole. At the same time, using the steel flower pipe 11 as the grouting pipe, the slurry is diffused to the graded gravel through the flower holes, so that the gravel becomes a concrete structure, strengthening the integrity and strength. After the grouting is completed, backfill the first installation groove 3 and the second installation groove 10 with concrete.

[0072] The above are only the preferred embodiments of the present invention, and it is not a limitation of the present invention in other forms. Any person skilled in the art may use the disclosed technical content to make changes or modifications into equivalent embodiments with equivalent changes. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the technical solution content of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A treatment method for the cracking of the invert of a tunnel in a water-rich soft stratum, characterized in that, The specific steps are as follows: Step 1: Determine the water-bearing influence area At a certain interval, exploration holes (2) are evenly constructed on the invert surface (1). Record the depth at which the water inflow changes significantly during the drilling process of the exploration holes (2). The area surrounded by the depths at which the water inflow changes significantly in all the exploration holes (2) is the water-bearing influence area. After the exploration, grouting is carried out on the exploration holes (2); the depths at which the water inflow changes significantly in each exploration hole (2) include the position where the water inflow first changes and the position where the water inflow significantly decreases or there is no water inflow; Step 2: Install steel supports in the invert filling layer At the invert surface (1) above the water-bearing influence area, a first installation groove (3) is opened downward every 2 - 3 m along the longitudinal direction of the tunnel. An I-beam support (4) is installed in the first installation groove (3); the length direction of the first installation groove (3) is the transverse direction of the tunnel, and the web of the I-beam support (4) is perpendicular to the invert surface (1), and the flanges are located on both sides of the web; Step 3: Install locking feet conduits A number of locking feet conduits (5) are provided at both ends of the I-beam support (4). A number of locking feet conduits (5) all pass through the upper and lower flanges of the I-beam support (4) and are welded and fixed to it; A threaded steel bar (7) is inserted into the locking feet conduit (5). The upper end of the threaded steel bar (7) is flush with the locking feet conduit (5), and the lower end extends beyond the locking feet conduit (5); Step 4: Install grouting pipes According to the depth values at the depths where the water inflow changes significantly, grouting holes with different depths are drilled downward from the invert surface (1), and long pipes (8) and short pipes (9) with different lengths are arranged in a staggered interval manner in the grouting holes as grouting pipes; The specific process of Step 4 is: taking the maximum depth of the position where the water inflow significantly decreases or there is no water inflow as the length of the long pipe (8), and the minimum depth of the position where the water inflow first changes as the length of the short pipe (9). Grouting pipes are arranged at the grouting holes. The long pipes (8) and the short pipes (9) are arranged in a staggered interval in a plum blossom shape. The spacing between the long pipes (8) is 2×2 m, and the spacing between the short pipes (9) is 1.5×1.5 m; Step 5: Drain and relieve pressure Select the grouting hole at the position with a large water inflow in the water-bearing influence area as the drain and pressure relief hole. Take the grouting pipe of this grouting hole as the drain pipe. A valve and a pressure gauge are installed at the upper end of the drain pipe, and an anti-filter geotextile is wrapped at the lower end; When the drain and pressure relief hole causes the phenomenon of formation hollowing around the drain pipe due to excessive sediment-carrying capacity, select the grouting pipes around the drain and pressure relief hole, increase the grouting pressure, and make the slurry flow into the position of the drain pipe actively to create slurry cross-flow, so as to reinforce the formation around the drain pipe; Step 6: Grouting reinforcement Using the locking feet conduit (5) as the grouting pipe to grout to form a curtain water cutoff wall; For the grouting of the invert base, the long-hole and short-hole sequential skip-hole grouting reinforcement method is adopted, and skip-hole grouting is carried out on the long pipes (8) and the short pipes (9) respectively; Step 7: Connect the crushed stones of the pavement structure The invert surface (1) is longitudinally provided with a second installation groove (10) communicating with the first installation groove (3). A steel pipe with holes (11) is arranged in the second installation groove (10). The steel pipe with holes (11) passes through the web of the I-beam support (4) and is welded to the adjacent I-beam support (4), so that the steel pipe with holes (11) and the I-beam (4) are connected into a whole. Grout is injected into the steel pipe with holes (11). After the grouting is completed, the first installation groove (3) and the second installation groove (10) are backfilled with concrete.

2. The treatment method for the invert cracking of tunnels in water-rich soft strata according to claim 1, characterized in that, In step one, the specific process of constructing the exploration holes (2) is as follows: several transverse sections are selected longitudinally along the tunnel. A number of exploration holes (2) are drilled on each transverse section. The several exploration holes (2) on each transverse section extend radially downward from the invert surface (1) to the outside of the tunnel. The outermost exploration hole (2) with an angle of 45°-60° with the vertical plane is the outermost boundary of the exploration area. The depth of each exploration hole (2) is 8-10m.

3. The treatment method for the invert cracking of tunnels in water-rich soft strata according to claim 1, characterized in that, The length of the first installation groove (3) is the same as the width of the invert surface (1), the width is 35-50cm, and the depth is 40-50cm.

4. The treatment method for the invert cracking of a tunnel in a water-rich soft stratum according to claim 1, characterized in that, The I-beam support (4) is an arc-shaped I-beam.

5. The treatment method for the invert cracking of tunnels in water-rich soft strata according to claim 1, characterized in that, In step three, the specific layout process of the foot-locking pipes (5) is as follows: 4 foot-locking pipes (5) are arranged at each end of the I-beam support (4). 2 foot-locking pipes (5) with a transverse spacing of 15cm are arranged at each end on both sides of the web of the I-beam support (4). The 4 foot-locking pipes (5) on the same side of the web are arranged horizontally along the tunnel. The 8 foot-locking pipes (5) correspond to each other in pairs longitudinally in the tunnel. The length of the foot-locking pipe (5) is 8-10m.

6. The treatment method for the invert cracking of tunnels in water-rich soft strata according to claim 5, characterized in that, In step six, the specific process of grouting the foot-locking pipes (5) is as follows: first, grout the foot-locking pipe 5 close to the end of the I-beam support (4), and then grout the remaining foot-locking pipes (5). By adjusting the proportion of the quick-setting grouting material and the grouting pressure, the diffusion range of the grout is controlled to form the outermost curtain water cut-off wall.

7. The treatment method for the invert cracking of tunnels in water-rich soft strata according to claim 1, characterized in that, The skip-hole grouting is to adopt the method of grouting in a skip-one-and-grout-one manner for multiple cycles.

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