A drainage device and method suitable for bench excavation of a tunnel in a water-rich soft rock formation

Abstract

The application relates to a drainage device and method suitable for tunnel bench excavation in water-rich soft rock stratum, which comprises a drainage ditch and a drainage pipe; the drainage ditch is arranged at a lower bench, the drainage pipe is arranged in the lower bench along the horizontal direction, the drainage pipe is arranged on both sides of the drainage ditch and is communicated with the drainage ditch, the drainage pipe is provided with a water inlet hole to collect the accumulated water in the lower bench, and the accumulated water in the drainage pipe is converged through the drainage ditch to facilitate water discharge. When the tunnel is excavated by the upper and lower bench method, the stratum at the lower bench can be drained, the surface rock and soil of the lower bench is prevented from softening due to underground water accumulation, the initial support of the tunnel is prevented from collapsing due to instability, and secondary lining of the tunnel is facilitated.

Description

A drainage device and method suitable for bench excavation of tunnels in water-rich soft rock strata. Technical Field

[0001] This invention belongs to the field of tunnel construction technology, specifically relating to a drainage device and method suitable for bench excavation of tunnels in water-rich soft rock strata. Background Technology

[0002] Water-rich, low-strength soft rock geology is mostly composed of silty mudstone, strongly weathered rock layers, which are extremely soft, have very low compressive strength, poor cohesion, and are highly unstable. Furthermore, their strength decreases significantly upon contact with water. Therefore, the excavation of water-rich, low-strength soft rock strata often employs the step-excavation method to reduce deformation of the surrounding rock in tunnels.

[0003] The inventors learned that after the upper step was excavated, groundwater often seeped into the lower step and accumulated on the surface of the lower step, which worsened the construction environment. When steel arch lining was carried out to support the arch top, the arch foot was soaked by groundwater, which softened the soil and rock, making it easy for the initial support to become unstable and collapse. Moreover, the soil in the water-rich, low-strength soft rock strata was weak, and the fine particles lost could easily clog the drainage pipes, resulting in poor long-term drainage. Summary of the Invention

[0004] To address the aforementioned issues, this invention proposes a drainage device and method suitable for bench excavation of tunnels in water-rich soft rock strata. This device utilizes a prefabricated drainage structure during the bench excavation process, enabling efficient drainage of the strata at the lower bench. This prevents groundwater accumulation that could soften the upper surface of the lower bench, thus avoiding instability and collapse of the initial tunnel support. It also provides structural support and construction convenience for both the upper bench support and the lower bench excavation.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a drainage device suitable for bench excavation of tunnels in water-rich soft rock strata, comprising: a drainage ditch and a drainage pipe; the drainage ditch is disposed at the lower bench, the drainage pipe is disposed horizontally in the lower bench, the drainage pipe is disposed on both sides of the drainage ditch and communicates with the drainage ditch, the drainage pipe is provided with a water inlet hole to collect the accumulated water in the lower bench and to collect the accumulated water in the drainage pipe through the drainage ditch.

[0007] The drainage device provided by this invention is suitable for the bench excavation of tunnels in water-rich soft rock strata. It can achieve drainage of the strata at the lower bench when excavating tunnels using the bench method, avoid groundwater accumulation that causes softening of the upper surface of the lower bench, prevent instability and collapse of the tunnel's initial support, and facilitate the secondary lining of the tunnel.

[0008] As an alternative implementation, the upper end of the drainage ditch extends through the upper surface of the lower step, and the bottom surface is flush with the bottom surface of the lower step.

[0009] As an alternative implementation, the side wall of the drain pipe is provided with a plurality of water inlet holes, and a filter screen is provided at each water inlet hole.

[0010] As an alternative implementation, the drainage ditch extends in the same direction as the tunnel.

[0011] As an alternative implementation, the vertical symmetry plane of the drainage ditch coincides with the center plane of the tunnel.

[0012] As an alternative implementation, the drainage ditch is connected to a water collection tank, which is located at the bottom of the tunnel.

[0013] As an alternative implementation, the drainage ditch is provided with a support structure for supporting the inner surface of the drainage ditch.

[0014] As an alternative implementation, the support structure includes a side support plate supporting the sidewall of the drainage ditch and a bottom plate supporting the bottom wall of the drainage ditch; a cover plate is provided above the side support plate, and the side support plate, the bottom plate, and the cover plate together form a drainage channel.

[0015] As an alternative implementation, the drainage ditch has an inverted trapezoidal structure, and the sidewalls of the drainage ditch form a set angle with the vertical plane.

[0016] Secondly, the present invention provides a construction method for a drainage device suitable for bench excavation of tunnels in water-rich soft rock strata, comprising:

[0017] After completing the predetermined advance on the steps, level the steps.

[0018] Start digging a drainage ditch at the center of the lower step, and dig to the bottom of the lower step.

[0019] Lay a base plate at the bottom of the drainage ditch and lay side support plates on both sides of the slope;

[0020] Drill a hole in the step below the side support plate to the set depth, and insert the drain pipe into the hole;

[0021] Support the side support plate and cover it with the cover plate.

[0022] This invention provides a construction method for a drainage device suitable for bench excavation of tunnels in water-rich soft rock strata. It guides the construction of drainage structures at the lower bench and uses prefabricated drainage structures to achieve short-term and efficient drainage of the lower bench while the upper bench is being excavated, greatly shortening the construction cycle and providing corresponding structural support and construction convenience for the upper bench support and the lower bench excavation.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] (1) A method of collecting groundwater by installing drainage pipes in the stratum where the lower step is located is adopted. Multiple drainage pipes and water inlets on the drainage pipes can form a network for collecting groundwater. Without compromising the support strength of the lower step, the groundwater is collected in the drainage ditch and finally discharged from the drainage ditch. The combination of drainage ditch and drainage pipe can reduce groundwater accumulation in the entire lower step, thereby reducing the occurrence of soil and rock layer softening and collapse caused by groundwater accumulation on the upper surface of the lower step; and the drainage effect is obvious, which is conducive to the subsequent construction of the secondary lining of the upper step and enhances the safety factor of the project.

[0025] (2) A support structure is set in the drainage ditch to prevent the drainage ditch from collapsing or deforming under the pressure of the stratum at the lower step; the bottom surface of the drainage ditch is flush with the bottom surface of the lower step to ensure that the drainage ditch can accumulate groundwater at any height in the lower step.

[0026] (3) The drainage structure is temporary, with connecting grooves on the prefabricated base plate and cover plate. The two side support plates have "L"-shaped protrusions on their upper and lower edges, which can be directly inserted into the connecting grooves, forming a nested arrangement between the side support plates and the base plate and cover plate. The use of prefabricated, nested drainage devices ensures the sealing of the drainage system. The installation and dismantling of the devices are simple and easy to operate, improving labor efficiency, reducing the workload of drainage structure construction, and greatly shortening the construction cycle.

[0027] (4) By using side support plates, bottom plates and cover plates to form a drainage channel, the groundwater flowing out of the drainage pipe can be prevented from directly contacting the soil and rock in the drainage ditch, and the groundwater can be prevented from re-contacting the soil and rock to form a slurry state, which facilitates the groundwater to flow out from the drainage ditch.

[0028] (5) The construction method of the drainage structure has low environmental requirements. The drainage ditch and drainage pipe can be excavated during the excavation of the upper step, which has little impact on the construction progress. At the same time, the construction of the drainage pipe can also serve as a preparatory step for subsequent construction. For example, the holes drilled during the drainage process can be used as explosive holes for the subsequent excavation, which facilitates the excavation and support of the lower step.

[0029] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0030] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0031] Figure 1 is a schematic diagram of the tunnel cross section when the step excavation method is used in an embodiment of the present invention;

[0032] Figure 2 is a schematic diagram of the structure of the drainage pipe in an embodiment of the present invention;

[0033] Figure 3 is a schematic diagram of the support structure at the drainage ditch in an embodiment of the present invention;

[0034] Figure 4 is a cross-sectional schematic diagram of the drainage ditch in an embodiment of the present invention;

[0035] Figure 5 is a schematic diagram of the side support plate in an embodiment of the present invention;

[0036] Figure 6 is a three-dimensional schematic diagram of the side support plate in an embodiment of the present invention;

[0037] Figure 7 is a schematic diagram of the structure of the base plate in an embodiment of the present invention;

[0038] In the diagram: 1. Arch frame; 2. Drainage ditch; 3. Drainage pipe; 4. Upper step; 5. Tunnel center face; 6. Water collection pool; 7. Lower step; 8. Side support plate; 9. Bottom plate; 10. Connecting groove; 11. Through hole; 12. Support hole; 13. Water inlet hole; 14. Cover plate; 15. Support rod. Detailed Implementation

[0039] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0040] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0041] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. Furthermore, it should be understood that the terms “comprising” and “having”, and any variations thereof, are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0042] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0043] As shown in Figure 1, after the upper bench 4 has been excavated to a certain extent, the surface of the lower bench 7 needs to be used for support. The arch frame 1 is used to support the tunnel arch, and the arch foot of the arch frame 1 is in direct contact with the upper surface of the lower bench 7. However, after the upper bench is excavated, groundwater seeps into the lower bench and accumulates on its surface. When steel arch frames are installed to support the arch, the arch foot is soaked by groundwater, causing the soil and rock to soften and easily leading to instability and collapse of the initial support.

[0044] To solve the drainage problem, this embodiment provides a drainage device suitable for bench excavation of tunnels in water-rich, low-strength soft rock strata, including: a drainage ditch 2 and a drainage pipe 3; the drainage ditch 2 is set at the lower bench 7, and the drainage pipe 3 is set in the lower bench 7 in a horizontal direction. The drainage pipe 3 is set on both sides of the drainage ditch 2 and communicates with the drainage ditch 2. The drainage pipe 3 is provided with a water inlet hole 13 to collect the water accumulated in the lower bench 7 and to collect the water in the drainage pipe 3 through the drainage ditch 2.

[0045] In some embodiments, the drainage ditch 2 extends in the same direction as the tunnel.

[0046] The upper end of the drainage ditch 2 penetrates the upper surface of the lower step 7, and the bottom surface of the drainage ditch 2 is flush with the bottom surface of the lower step 7.

[0047] The drainage ditch 2 is connected to the water collection pool 6, which is located at the bottom of the tunnel.

[0048] In some implementations, the vertical symmetry plane of the drainage ditch 2 coincides with the center plane 5 of the tunnel in order to facilitate the excavation of the drainage ditch 2 and the water collection of the drainage pipe 3. However, in actual construction, it is difficult for the vertical symmetry plane of the drainage ditch 2 to coincide with the center plane 5 of the tunnel. Therefore, it is sufficient to ensure that the deviation between the symmetry plane of the drainage ditch 2 and the center plane 5 of the tunnel is kept within the set range.

[0049] In some embodiments, as shown in FIG2, the side wall of the drain pipe 3 is provided with a plurality of water inlet holes 13, and a filter screen is provided at the water inlet holes 13. The drain pipe 3 can collect the water accumulated in the lower step 7 through the permeation effect at the filter screen, and the water in the drain pipe 3 is collected through the drainage ditch 2 so as to facilitate the discharge of the water.

[0050] Specifically, multiple water inlet holes 13 on the side wall of the drainage pipe 3 are arranged in a plum blossom pattern, and geotextile is wrapped around the entire outer wall of the drainage pipe 3, forming a filter mesh structure at the water inlet holes 13.

[0051] In some embodiments, holes are drilled in the lower step 7 to facilitate the insertion of the drain pipe 3 so that the drain pipe 3 can be arranged in the lower step 7.

[0052] In some implementations, since the length of the drain pipe 3 is greater than the width of the drain ditch 2, the drain pipe 3 can be made of flexible material, or the drain pipe 3 can be made of multiple sections spliced ​​together.

[0053] In some embodiments, the drainage ditch 2 is provided with a support structure that can support the inner surface of the drainage ditch 2.

[0054] Specifically, as shown in Figure 3, the support structure includes a side support plate 8 supporting the side wall of the drainage ditch 2 and a bottom plate 9 supporting the bottom wall of the drainage ditch 2; a cover plate 14 is provided above the side support plate 8, and the side support plate 8, the bottom plate 9, and the cover plate 14 can be enclosed to form a drainage channel, as shown in Figure 4.

[0055] Specifically, as shown in Figures 5-6, support holes 12 and through holes 11 are provided on the side support plate 8. The through holes 11 are used to install the drain pipe 3 so that the drain pipe 3 can communicate with the inner cavity of the drainage ditch 2.

[0056] The through holes 11 are arranged in a multi-layer structure on the side support plate 8, and the support holes 12 are arranged opposite to each other between the two side support plates 8 so that the two ends of the horizontally arranged support rod 15 can be inserted into the support holes 12 respectively to complete the support between the two side support plates 8.

[0057] The side support plate 8 has "L"-shaped protrusions on its upper and lower sides, which can be directly inserted into the connecting groove to form a nested structure between the side support plate, the bottom plate, and the cover plate, thus forming a prefabricated and nested drainage device. The construction process is simple, the operation is convenient, and the construction cycle is shortened.

[0058] Specifically, as shown in Figure 7, a connecting groove 10 is provided on the base plate 9. The connecting groove 10 is used to insert the side support plate 8 to ensure that the water flowing into the drainage channel will not flow out from the gap between the side support plate 8 and the base plate 9.

[0059] The sidewall of the drainage ditch 2 forms a set angle with the vertical plane, and the drainage ditch 2 has an inverted trapezoidal structure.

[0060] Example 2

[0061] This embodiment provides a construction method for a drainage device suitable for bench excavation of tunnels in water-rich, low-strength soft rock strata, including the following steps:

[0062] Step 1: After the upper step 4 has been excavated to the predetermined depth, level the upper step 4;

[0063] Step 2: Begin digging drainage ditch 2 at the center of the lower step 7, and dig to the bottom of the lower step 7;

[0064] Step 3: Level the slope and bottom of drainage ditch 2, lay the bottom plate 9 at the bottom of drainage ditch 2, and then lay the side support plates 8 on both sides of the slope; after completing the leveling and support of drainage ditch 2, dig a water collection pool 6 at the bottom of the tunnel near the end of drainage ditch 2. The water collection pool 6 can collect the water discharged from drainage ditch 2.

[0065] Step 4: Use a drilling machine to drill a hole in the lower step 7 along the through hole 11 in the side support plate 8 to the set depth;

[0066] Step 5: Clean the drill hole and insert the drain pipe 3 into the drill hole;

[0067] Step 6: Use support components to complete the support of the side support plate 8 to prevent the side support plate 8 from being deformed by the stratum pressure, and cover it with the cover plate 14.

[0068] Step 7: Once the upper step 4 has been excavated and supported stably and the drainage volume of the lower step 7 is low, remove the prefabricated drainage structure of the lower step, namely the side support plate 8, floor 9 and cover plate 14, excavate the lower step 7, use the through hole 11 as an explosive hole, add an appropriate amount of explosive to the already buried drainage pipe 3, and complete the excavation and blasting of the lower step.

[0069] Step 8: Clear the soil and broken rocks excavated from the lower step 7, and use the water collection pool 6 as a long-term drainage ditch for the tunnel to facilitate drainage in the later stages of the tunnel.

[0070] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A drainage device suitable for bench excavation of tunnels in water-rich soft rock strata, characterized in that, include: A drainage ditch and drainage pipes are provided. The drainage ditch is located at a lower step, and a drainage pipe is installed horizontally along the lower step. The drainage pipes are located on both sides of the drainage ditch and are connected to it. The drainage pipes have inlet holes to collect water accumulated in the lower step and to collect the water in the drainage pipes through the drainage ditch. A support structure is provided in the drainage ditch to support the inner surface of the drainage ditch and prevent it from collapsing or deforming under the pressure of the strata at the lower step. The support structure includes side support plates supporting the side walls of the drainage ditch and a bottom plate supporting the bottom wall of the drainage ditch. A cover plate is provided above the side support plates, and the side support plates, bottom plate, and cover plate together form a drainage channel. Support holes and through holes are provided on the side support plates. The through holes are used to install the drainage pipes so that the drainage pipes are connected to the inner cavity of the drainage ditch. The through holes are located on the side support plates. The structure features a multi-layered layout with support holes positioned opposite each other between two side support plates. This allows the ends of horizontally arranged support rods to be inserted into the support holes, completing the support between the two side support plates. Each side support plate has an "L"-shaped protrusion on its upper and lower edges for inserting connecting grooves, forming a nested arrangement of the side support plates, bottom plate, and cover plate, creating a prefabricated, nested drainage device. The drainage channel is formed by the side support plates, bottom plate, and cover plate, preventing groundwater flowing from the drainage pipe from directly contacting the soil and rock in the drainage ditch and avoiding the groundwater from re-contacting the soil and rock to form a slurry state, thus facilitating the flow and discharge of groundwater from the drainage ditch. The vertical symmetry plane of the drainage ditch coincides with the center plane of the tunnel, and the upper end of the drainage ditch penetrates the upper surface of the lower step, while the bottom surface is flush with the bottom surface of the lower step, ensuring that the drainage ditch can accumulate groundwater at any height within the lower step.

2. The drainage device for bench excavation of tunnels in water-rich soft rock strata as described in claim 1, characterized in that, The side wall of the drain pipe is provided with multiple water inlet holes, and a filter screen is provided at each water inlet hole.

3. A drainage device suitable for bench excavation of tunnels in water-rich soft rock strata as described in claim 1, characterized in that, The drainage ditch extends in the same direction as the tunnel.

4. A drainage device suitable for bench excavation of tunnels in water-rich soft rock strata as described in claim 1, characterized in that, The drainage ditch is connected to the water collection pool, which is located at the bottom of the tunnel.

5. A drainage device suitable for bench excavation of tunnels in water-rich soft rock strata as described in claim 1, characterized in that, The drainage ditch has an inverted trapezoidal structure, and the sidewalls of the drainage ditch form a set angle with the vertical plane.

6. A construction method for a drainage device as described in any one of claims 1-5, suitable for bench excavation of tunnels in water-rich soft rock strata, characterized in that, include: After the upper step has been advanced to the predetermined depth, level it. Start digging a drainage ditch at the center of the lower step, to the bottom of the lower step. Lay a base plate at the bottom of the drainage ditch and lay side support plates on both sides of the slope. Drill holes in the lower step to the set depth through the through holes in the side support plates and insert the drainage pipes into the holes. Support the side support plates and cover them with a cover plate.

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