Grouting reinforcement method suitable for shallow-buried excavation tunnel stratum

Abstract

The invention discloses a grouting reinforcement method suitable for a shallow-buried excavation tunnel stratum. A reinforcement area radiates towards the periphery with a tunnel vault as a base line. The grouting reinforcement method comprises the following steps that 1, in the horizontal projection range of a reinforcement area, a plurality of grouting hole channels are drilled downwards from the ground to the designed height; 2, grouting pipes are installed in the grouting hole channels; at least one grout outlet is formed in the bottom or the side wall of the grouting pipe; 3, fine stone is filled to a first height from the bottom of the grouting hole channel; 4, a clay layer and an isolation layer are arranged above the fine stone, and the grouting hole channel in the range from the first height to the ground height is blocked; and 5, after plugging is completed, grouting equipment is adopted, and reinforcing grout is injected into the unplugged part of the grouting hole channel through the grouting pipe. According to the grouting reinforcement method, the high plasticity of the fine stone and the clay is utilized, the grouting hole channel is flexibly and effectively blocked, and the adverse effect caused by hole reaming is avoided through simple and convenient operation.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel stratum grouting reinforcement, and in particular to a grouting reinforcement method suitable for shallow buried and dark-excavated tunnel strata. Background Art

[0002] For shallow buried tunnel projects, the bearing capacity of the soil and rock layer between the tunnel vault and the ground surface plays an important role in the safety of tunnel construction and ground road safety. For example, in the mountain-penetrating project between Xiamen University Baicheng Station and Zengcuoan Station on the southern extension line of Xiamen Metro Line 3, the tunnel passes through a soft, water-rich soil layer, and the soil layer above the tunnel vault needs to be grouting reinforced. The tunnel project adopts the CRD method, that is, the cross-middle partition wall method for excavation. The excavation face is divided into four parallel pilot tunnels, and the space of each pilot tunnel is limited. Therefore, grouting reinforcement of the upper soil layer in the tunnel not only limits the operation of equipment and affects the excavation efficiency, but also poses great challenges in terms of water and grouting. Therefore, for this type of engineering situation, it is usually necessary to drill holes from the surface for grouting reinforcement.

[0003] Chinese patent CN108505512A discloses a method for reinforcing the vault of a weak soil layer in an urban tunnel. The method reinforces the rock and soil overlying the vault of a shallow urban tunnel by drilling and grouting from the surface. However, the method has the following problems that have not yet been solved: the method uses a grouting plug to isolate the upper part of the grouting hole to prevent the upper sealing slurry from seeping in. In view of the easy-to-occur hole expansion phenomenon, the grouting plug cannot fit the hole wall to completely seal the grouting hole, so the grouting problem still exists. Therefore, a flexible and stable grouting reinforcement method is urgently needed to fundamentally solve this problem. Summary of the Invention

[0004] The main technical problem to be solved by the present invention is to provide a grouting reinforcement method suitable for shallow buried tunnel strata, so as to avoid the defect that traditional grouting plugs cannot completely seal the grouting holes when the hole is expanded, thereby safely and stably grouting the soil layer above the tunnel.

[0005] In order to solve the above technical problems, the present invention provides a grouting reinforcement method suitable for shallow buried tunnel strata, wherein the reinforcement area radiates from the tunnel vault as the baseline to the surrounding areas; the grouting reinforcement method comprises the following steps:

[0006] Step 1: Drill several grouting channels from the ground downward to the designed height within the horizontal projection range of the reinforcement area;

[0007] Step 2: installing a grouting pipe in the grouting channel; the grouting pipe is provided with at least one slurry outlet on the bottom or side wall;

[0008] Step 3: Filling the grouting channel with fine stones from the bottom to a first height;

[0009] Step 4: blocking the grouting channel within the range from the first height to the ground height;

[0010] Step 5: After the plugging is completed, a grouting device is used to inject a reinforcement slurry into the unplugged portion of the grouting channel through the grouting pipe.

[0011] In a preferred embodiment: in the step 2, within the second height range of the grouting channel from the bottom, the grouting pipe is provided with a plurality of slurry outlets spaced apart along the height direction on the side wall; the second height is not higher than the first height.

[0012] In a preferred embodiment: Step 4 includes:

[0013] Step 41: laying a clay layer at the first height;

[0014] Step 42: pouring plugging slurry on the upper part of the clay layer to the ground level.

[0015] In a preferred embodiment, step 42 includes:

[0016] Step 421: pouring a layer of plugging slurry on the upper portion of the clay layer and allowing it to stand to form an isolation layer;

[0017] Step 422: Continue pouring the plugging slurry above the isolation layer to ground level.

[0018] In a preferred embodiment: the step 1 further includes: during the process of drilling the grouting channel, pouring wall protection slurry on the side wall of the grouting channel to prevent the hole from collapsing.

[0019] In a preferred embodiment, there is an intermediate step between step 3 and step 4:

[0020] The side wall of the grouting channel is flushed by high-pressure water jet through the grouting pipe to make the wall-protecting slurry fall off.

[0021] In a preferred embodiment: the grouting equipment includes a pressure gauge, and the pressure gauge is used to feedback the real-time grouting pressure;

[0022] In step 5, during the grouting process, when the grouting pressure value displayed by the pressure gauge becomes stable after climbing, the grouting is stopped immediately.

[0023] In a preferred embodiment, the particle size of the fine stone is 5 to 15 mm.

[0024] In a preferred embodiment: in step 1, the grouting channels are arranged in a plum blossom shape in the horizontal direction.

[0025] In a preferred embodiment: in step 2, the grouting pipe is supported at the bottom of the grouting channel, or is fixed at the top to be suspended in the grouting channel.

[0026] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0027] The grouting reinforcement method provided by the present invention is to fill the grouting section of the grouting channel with fine stones, and set a clay layer and an isolation layer on top of the fine stones. By taking advantage of the high plasticity of the fine stones and clay materials, the grouting channel after the hole is expanded can be flexibly and effectively blocked, and the adverse effects caused by the expansion are avoided with simple operation. At the same time, the filled fine stones provide stable lateral support for the side walls of the grouting channel, getting rid of the traditional method's reliance on wall-protecting mud or wall-protecting steel mesh. Furthermore, in terms of construction cost, filling the grouting section of the grouting channel with fine stones is more economical than filling the grouting section of the grouting channel with cement slurry. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the cross section of grouting reinforcement according to a preferred embodiment of the present invention;

[0029] Figure 2 A plan view of the grouting channel layout according to a preferred embodiment of the present invention;

[0030] Figure 3 A schematic diagram of drilling a grouting channel according to a preferred embodiment of the present invention;

[0031] Figure 4 A schematic diagram of installing a grouting pipe according to a preferred embodiment of the present invention;

[0032] Figure 5 A schematic diagram of filling fine stones in a preferred embodiment of the present invention;

[0033] Figure 6 This is a schematic diagram of blocking the upper portion of a grouting pipe according to a preferred embodiment of the present invention;

[0034] Figure 7 This is a schematic diagram of grouting reinforcement according to a preferred embodiment of the present invention.

[0035] Markings in the figure are: 1-tunnel, 2-reinforcement area, 3-grouting channel, 4-geological drilling rig, 5-wall protection slurry, 6-grouting pipe, 61-slurry outlet, 7-fine stone, 8-clay layer, 9-sealing slurry, 91-isolation layer, 10-small diameter grouting pipe, 11-reinforcement slurry; H1-first height, H2-second height. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0037] In the description of the present invention, it should be noted that the terms "upper," "lower," "inner," "outer," "top / bottom," and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0038] In the description of the present invention, it should be noted that, unless otherwise clearly stipulated and limited, the terms "installed", "provided with", "set / connected", "connected", etc. should be understood in a broad sense. For example, "connection" can be a wall-mounted connection, a detachable connection, or an integral connection. It can be a mechanical connection or an electrical connection. It can be a direct connection or an indirect connection through an intermediate medium. It can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0039] like Figures 1 to 7 The embodiment of the present invention provides a grouting reinforcement method applicable to shallow buried tunnel strata, comprising the following steps:

[0040] Step 1: Within the horizontal projection range of the reinforcement area 2, drill a grouting channel 3 from the ground downward to the designed height.

[0041] Specifically, if Figure 1 As shown, with the arch of tunnel 1 as the baseline, the soil layer with a thickness of about 5.0m radiating outward is the reinforcement area 2 of this embodiment. Figure 2 As shown, within the horizontal projection range of the reinforcement area 2, a geological drill rig 4 is used to drill several grouting channels 3 vertically downward from the ground to the designed height. The diameter of the grouting channels 3 is 110 mm. Figure 3 As shown, in the horizontal direction, the grouting channels 3 are arranged in a plum blossom shape, and the axial distance between two adjacent grouting channels 3 is 1500mm. In this embodiment, the geological drilling rig 4 used is model XY-1A, with a maximum drilling depth of 180m and a drilling diameter of 75-220mm.

[0042] During the drilling process, the grouting channel 3 is prone to collapse due to lateral groundwater pressure and lateral soil pressure. This phenomenon is particularly common in soft, water-rich soil layers. Therefore, the grouting channel 3 needs to be treated with a wall protection treatment. Specifically, the wall protection treatment method used in this embodiment is to pour a wall protection mud 5 on the sidewalls of the grouting channel 3. The wall protection mud 5 is made of bentonite, admixture, and water in a certain ratio. Before pouring, it needs to be fully stirred and allowed to stand to ensure that the wall protection mud 5 has good uniformity and viscosity.

[0043] As an equivalent alternative to this embodiment, in other embodiments, a cylindrical steel mesh may be laid on the side wall of the grouting channel 3 to perform wall protection.

[0044] Step 2: Install a grouting pipe 6 in the grouting channel 3.

[0045] Specifically, if Figure 4 As shown, after the wall protection construction of the grouting channel 3 is completed, the grouting pipe 6 is supported at the bottom of the grouting channel 3, or the top of the grouting pipe 6 is fixed to be suspended in the grouting channel 3. In this embodiment, the grouting pipe 6 is made of PVC-U pipe with an inner diameter of 25 mm, a wall thickness of 2 mm, and a pressure rating of PN1.6 MPa.

[0046] Within the second height H2 of the grouting channel 3 from the bottom, the grouting pipe 6 is provided with 4mm diameter grouting openings 61 on the sidewall every 150mm in the height direction. The second height H2 is not higher than the top elevation of the reinforced area 2.

[0047] Step 3: Starting from the bottom of the grouting channel 3, fill the fine stones 7 to a first height H1.

[0048] Specifically, if Figure 5 As shown, fine stones 7 are filled into the area between the grouting channel 3 and the grouting pipe 6 to a first height H1. The first height H1 is not lower than the second height H2. In this embodiment, the particle size of the fine stones 7 is 5 to 15 mm. Furthermore, while filling the fine stones 7, a hard pipe or stick is inserted into the grouting channel 3 to stir the fine stones up and down. This not only ensures that the fine stones 7 are densely packed, but also allows the fine stones 7 to scrape off the wall slurry 5 when being stirred.

[0049] Intermediate Step: After the fine stone 7 is filled, connect a water pump or water gun to the top of the grouting pipe 6. Use a high-pressure water jet through the slurry outlet 61 on the side wall of the grouting pipe 6 to flush the sidewall of the grouting channel 3 to remove the wall-protecting slurry 5. The flushing water pressure is controlled at 0.3-0.5 MPa, ensuring that the high-pressure water jet still has a strong impact on the wall-protecting slurry 5 after passing through the fine stone 7. The flushing time is controlled to be 10-20 minutes.

[0050] In this way, the retaining wall slurry 5 below the first height H1 is scraped off by the fine stones 7 and flushed by the high-pressure water jet, providing a smooth infiltration surface for the subsequent reinforcement slurry 11 to enter the soil layer from the side walls of the grouting channel 3. At this time, the densely packed fine stones 7 replace the retaining wall slurry 5, providing stable lateral support for the side walls of the grouting channel 3.

[0051] Step 4: Seal the grouting channel 3 within the range from the first height H1 to the ground height.

[0052] The purpose of blocking the grouting channel 3 is to form a closed space below the first height H1 of the grouting channel 3, so that in the subsequent grouting reinforcement process, the reinforcement slurry 11 overflows from the side wall of the grouting channel 3 and penetrates into the soil layer after being compressed by the confined space. Figure 6 As shown, step 4 includes the following steps:

[0053] Step 41: Lay a clay layer 8 at the first height H1, i.e., on top of the fine stone 7. Clay has good compactness and acts as an isolation interface, preventing the subsequent plugging slurry 9 from seeping into the fine stone 7 below and solidifying, which would affect the penetration and diffusion of the reinforcement slurry 11 during the subsequent grouting reinforcement process. The thickness of the clay layer 8 depends on the specific height of the plugging section of the grouting channel 3 and should not be less than 100 mm.

[0054] Step 42: Pour the plugging slurry 9 on the upper part of the clay layer 8 to the ground level. In order to achieve a better plugging effect, in this embodiment, the plugging slurry 9 is first used to set an isolation layer 91 on the upper part of the clay layer 8. Specifically, a small-diameter grouting pipe 6 is inserted into the grouting channel 3. The small-diameter grouting pipe 6 is a PVC pipe with an inner diameter of 25 mm, and the bottom pipe mouth is 0.5 to 1.0 m above the clay layer 8. Use a water pump to extract the plugging slurry 9, inject it into the grouting channel 3 through the small-diameter grouting pipe 6, and then let it stand for 30 minutes to form the isolation layer 91. In this embodiment, the height of the isolation layer 91 is 0.2 to 0.5 m. The specific height can be adjusted according to the specific project conditions, and the present invention does not limit this. After the isolation layer 91 is formed by standing, continue to pour the plugging slurry 9 to the ground level to complete the plugging. In this embodiment, the plugging slurry 9 is cement slurry with a water-cement ratio in the range of 0.6 to 1; the water pump is a small sewage pump with a model number of 50WQ20-7-0.75.

[0055] Step 5: After the plugging is completed, a grouting device is used to inject the reinforcement slurry 11 into the unplugged portion of the grouting channel 3 through the grouting pipe 6 .

[0056] Specifically, if Figure 7 As shown, grouting equipment is used to inject the reinforcement slurry 11 into the unblocked part of the grouting channel 3 through the grouting pipe 6 at a certain initial pressure. It can be understood that the unblocked part is the part below the first height H1. In this embodiment, the grouting equipment uses a double-liquid grouting machine of model ZKSY90-125, with a slurry discharge volume of 7m 3 / h, the grouting pressure is 0-16MPa; the reinforcement slurry 11 uses cement slurry with a water-cement ratio in the range of 0.6-1, and the cement uses No. 42.5 ordinary Portland cement.

[0057] The dual-liquid grouting machine includes a pressure gauge to provide real-time feedback on the grouting pressure. During the grouting process, as the reinforcement slurry 11 gradually fills the grouting channel 3, the grouting pressure gradually increases. Grouting is then continued, allowing the reinforcement slurry 11 to penetrate into the surrounding soil layer under the pressure of the confined space. When the grouting pressure reported by the pressure gauge stabilizes after increasing, the dual-liquid grouting machine can be turned off, and grouting can be stopped.

[0058] After the reinforcement grouting is completed, the working equipment is closed and removed, the grouting pipe 6 is left in the grouting channel 3, and the top of the grouting channel 3 is filled and modified.

[0059] The grouting reinforcement method provided in the embodiment of the present invention creatively fills the lower half of the grouting channel 3 with fine stones 7, and arranges a clay layer 8 and an isolation layer 91 on top of the fine stones 7 to act as an isolation interface, which has many advantages:

[0060] (1) Due to the influence of construction level and soil conditions, the grouting channel 3 is prone to hole enlargement during the drilling process. Traditional grouting plugs used to isolate the upper and lower interfaces are usually prepared before construction in pursuit of construction efficiency. Therefore, they cannot ensure that they match the actual aperture of the grouting channel 3, resulting in the subsequent slurry used for plugging to seep down from the edge of the grouting plug and solidify, affecting the effect of grouting reinforcement. At the same time, on-site adjustment of the grouting plug according to the hole enlargement situation obviously reduces the construction efficiency. In this embodiment, the fine stone 7 filled on-site and the clay layer 8 laid have high plasticity, which can flexibly and effectively seal the grouting channel 3 after hole enlargement, and avoid the adverse effects caused by hole enlargement with simple operation.

[0061] (2) Although the existing grouting reinforcement method has performed a wall protection treatment on the side wall of the grouting channel 3, the hollow structure of the grouting channel 3 still cannot completely avoid the risk of hole collapse. In this embodiment, the grouting channel 3 is filled with fine stones 7, which provides a stable lateral support for the side wall of the grouting channel 3. Furthermore, with the support of the fine stones 7, the wall protection mud 5 can be washed, providing a smooth penetration surface for the reinforcement slurry 11 to enter the soil layer.

[0062] (3) In terms of construction cost, the same volume of fine stone 7 is cheaper than cement slurry. Compared with filling the lower half of the grouting channel 3 with cement slurry, filling the fine stone 7 is a more economical process. In addition, the fine stone 7 has better permeability and strength. It will not affect the penetration of the reinforcement slurry 11 into the soil layer, but also ensure the overall strength of the filling in the grouting channel 3.

[0063] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any technical equivalent transformation made using the contents of the present invention specification shall fall within the protection scope of the present invention.

Claims

1. A grouting reinforcement method suitable for shallow buried tunnel strata, characterized in that: The reinforcement area radiates from the tunnel vault as the baseline; The grouting reinforcement method comprises the following steps: Step 1: Drilling a plurality of grouting channels from the ground downward to a designed height within the horizontal projection range of the reinforcement area; Step 2: installing a grouting pipe in the grouting channel; The grouting pipe is provided with at least one grout outlet on the bottom or side wall; Step 3: Filling fine stones from the bottom of the grouting channel to a first height; Step 4: blocking the grouting channel within the range from the first height to the ground height; Step 5: After the plugging is completed, a grouting device is used to inject a reinforcing slurry into the unplugged part of the grouting channel through the grouting pipe.

2. The grouting reinforcement method according to claim 1, characterized in that: In the step 2, within a second height range from the bottom of the grouting channel, the grouting pipe is provided with a plurality of slurry outlets spaced apart along the height direction on the side wall; the second height is not higher than the first height.

3. The grouting reinforcement method according to any one of claims 1 or 2, characterized in that: The step 4 comprises: Step 41: laying a clay layer at the first height; Step 42: pouring plugging slurry on the upper part of the clay layer to the ground level.

4. The grouting reinforcement method according to claim 3, characterized in that: The step 42 comprises: Step 421: pouring a layer of plugging slurry on the upper part of the clay layer and letting it stand to form an isolation layer; Step 422: Continue pouring the plugging slurry above the isolation layer to ground level.

5. The grouting reinforcement method according to any one of claims 1 to 4, characterized in that: The step 1 also includes: during the process of drilling the grouting hole, pouring wall protection slurry on the side wall of the grouting hole to prevent hole collapse.

6. The grouting reinforcement method according to claim 5, characterized in that: There are intermediate steps between step 3 and step 4: The side wall of the grouting channel is flushed by high-pressure water jet through the grouting pipe to make the wall protection mud fall off.

7. The grouting reinforcement method according to any one of claims 1 to 6, characterized in that: The grouting equipment includes a pressure gauge, and the pressure gauge is used to feedback the real-time grouting pressure; In step 5, during the grouting process, when the grouting pressure value displayed by the pressure gauge becomes stable after climbing, the grouting is stopped immediately.

8. The grouting reinforcement method according to claim 1, characterized in that: The particle size of the fine stone is 5 to 15 mm.

9. The grouting reinforcement method according to claim 1, characterized in that: In step 1, the grouting channels are arranged in a plum blossom shape in the horizontal direction.

10. The grouting reinforcement method according to claim 1, characterized in that: In step 2, the grouting pipe is supported at the bottom of the grouting channel, or is fixed at the top to be suspended in the grouting channel.

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