A tunnel construction method suitable for urban underground boulder areas

Abstract

This invention discloses a tunnel construction method suitable for urban underground boulder areas, comprising: Step 1, full-section grouting reinforcement of the tunnel face soil; Step 2, installation of advanced pipe roof support at the tunnel portal; Step 3, horizontal drilling with a down-the-hole hammer to remove boulders. This construction method combines shallow-buried tunneling and horizontal drilling with a down-the-hole hammer for boulder removal. It not only solves the risks of manual labor inherent in shallow-buried tunneling but also allows for horizontal drilling and fracturing in complex geological conditions with boulder layers, reducing the content of large rocks in the strata, ensuring controllable tunneling posture, and guaranteeing safe, efficient, and successful tunneling.

Description

Technical Field

[0001] This invention relates to the field of underground engineering technology, and specifically to a tunnel construction method suitable for urban underground boulder areas. Background Technology

[0002] With the rapid development of urban construction, urban traffic congestion has become increasingly prominent. Along with the development and utilization of underground space, many cities have begun to construct tunnel projects. As the main construction methods for urban underground engineering, shallow-buried tunneling and pipe jacking methods can avoid the interference of open-cut construction on the surface, while having stronger adaptability and high flexibility to complex strata compared to shield tunneling.

[0003] Shallow-buried tunneling is mostly used in underground engineering projects in Quaternary soft strata where the surrounding rock has very poor bearing capacity. Its design principles can be summarized as: advanced pipe installation, rigorous grouting, short excavation lengths, strong support, early closure, frequent measurements, and rapid feedback. However, improper construction organization or poor management can easily lead to construction risks and accidents, such as excessive ground settlement or collapse, damage to surface buildings and structures, and tunnel collapses. The losses and impacts caused by these accidents are substantial.

[0004] Pipe jacking is a trenchless mechanical tunneling construction method used in municipal construction. During the jacking process, the jacking speed should be dynamically adjusted based on monitored deformation to control ground settlement. The attitude of the pipe jacking machine must be constantly monitored, and any changes should be corrected immediately, but the correction should not be too large. Therefore, pipe jacking is suitable for relatively soft and homogeneous soil layers such as silty clay, clay, silty clay, and sand, but not for moderately weathered rock layers or complex geological layers containing isolated boulders.

[0005] Shallow buried tunneling involves manual labor and does not require high uniformity of the geology, but it carries significant risks. Pipe jacking technology employs mechanical tunneling, but it requires precise jacking posture and is not suitable for complex geological conditions or soil layers containing boulders.

[0006] In view of this, the inventors have improved the shallow buried tunneling method and proposed a tunnel construction method suitable for urban underground boulder areas to reduce the risks of manual labor and improve construction safety and efficiency. Summary of the Invention

[0007] The purpose of this invention is to provide a tunnel construction method suitable for urban underground boulder areas. This method combines two construction techniques: shallow buried tunneling and down-the-hole hammer horizontal drilling for boulder removal. It not only solves the risks of manual operation in shallow buried tunneling, but also enables horizontal drilling to break up complex geological layers containing boulder, reducing the content of large rocks in the strata, ensuring controllable tunneling posture, and ensuring safe and efficient tunneling and successful breakthrough.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] This invention provides a tunnel construction method suitable for urban underground boulder areas, comprising the following steps:

[0010] Step 1: Reinforce the soil at the tunnel face with full-section grouting;

[0011] Step 2: Install advanced pipe roof support at the tunnel entrance;

[0012] Step 3: Horizontal drilling with down-the-hole hammer to remove isolated boulders.

[0013] Furthermore, the full-section grouting reinforcement of the tunnel face soil described in step one specifically includes: grouting is designed according to the limited soil mass around the consolidated pipe roof, using Ф42 sleeve valve pipes for grouting reinforcement, with a grout diffusion radius of not less than 0.5m, and cement grout is used. Grouting parameters are as follows:

[0014] Cement grout water-cement ratio: 1:1

[0015] Grouting pressure: 0.5~0.8MPa

[0016] Final pressure: 2.0 MPa.

[0017] Furthermore, during grouting construction, the standard for completing grouting in a single hole is as follows:

[0018] (1) Gradually increase the grouting pressure until it reaches the designed final hole pressure and stabilizes for 10 minutes;

[0019] (2) The grouting volume shall not be less than 80% of the designed grouting volume;

[0020] (3) The feed rate is 1 / 4 of the initial feed rate;

[0021] All grouting holes must meet the single-hole termination conditions and there must be no missed grouting. After grouting, the grouting effect should be checked. If the requirements are not met, supplementary grouting should be carried out.

[0022] Furthermore, the specific requirements for setting up advanced pipe roof support at the tunnel entrance in step two include:

[0023] The steel pipe for the pipe shed is made of Ф245*10 hot-rolled seamless steel pipe. The steel pipe for the pipe shed is equipped with hoops and reinforcing bars. The hoop parameters are Ф10mm@500mm, and the reinforcing bar parameters are 4Ф25 (4 reinforcing bars with a diameter of 25 mm).

[0024] The inclination angle of the steel pipes in the pipe shed is the same as the longitudinal slope of the route, and the direction is parallel to the centerline of the road;

[0025] A guide pipe is installed at the tunnel portal support, and the guide pipe is made of Ф299*10 hot-rolled seamless steel pipe;

[0026] After the pipe shed construction is completed, a sealing treatment should be carried out.

[0027] The number of joints in the same cross section of the pipe roof steel pipe shall not exceed 50%, and the joints of adjacent pipe roof steel pipes shall be staggered by at least 1m.

[0028] The steel pipe joints for the pipe shed are connected by threaded connections, with each thread being 30cm long.

[0029] Furthermore, step three, the horizontal drilling operation for removing boulders with a down-the-hole hammer, includes:

[0030] a. The sandy soil in the jacking working shaft is backfilled in layers in one go to the highest point of the isolated rock area within the range where the down-the-hole hammer drill rod can be drilled horizontally through the jacking pipe section, and the compaction coefficient of the sandy soil is not less than 0.95;

[0031] b. Based on the isolated rock area, arrange down-the-hole hammers within the projection range of the jacking pipe section to perform horizontal drilling and remove the retaining structure in this area.

[0032] c. The longitudinal and transverse errors of the down-the-hole hammer horizontal drill shall not exceed ±50mm, and the elevation error shall be strictly controlled to exceed the burial depth of large stones. After each row of pretreatment is completed, the down-the-hole hammer equipment shall be hoisted to the ground, a layer shall be excavated and compacted.

[0033] d. After drilling a hole horizontally with a down-the-hole hammer, clean the hole and then connect a 50 PVC grouting pipe to the hole. Each grouting pipe is equipped with a control gate valve. Pressurize the thick mortar with a grouting pressure of not less than 2 MPa.

[0034] e. Seal the grouting holes. Use a one-way ball valve that matches the reserved grouting holes to seal the grouting holes. After sealing, use micro-expansion concrete for secondary sealing.

[0035] Furthermore, the concentrated mortar is composed of bentonite, cement, water, CMC binder, and caustic soda, with a mass ratio of 1:0.1:0.4:0.001:0.001.

[0036] By adopting the above solution, the present invention has the following beneficial effects:

[0037] The construction method of this invention combines two construction techniques: shallow buried tunneling and horizontal drilling with down-the-hole hammer to remove boulders. It not only solves the risks of manual operation in shallow buried tunneling, but also enables horizontal drilling to break up soil layers with complex geology and boulders, reducing the content of large rocks in the strata, ensuring controllable tunneling posture, and ensuring safe and efficient construction and successful tunneling. Attached Figure Description

[0038] Figure 1 This is a cross-sectional layout diagram of the grouting holes in the sleeve valve pipe;

[0039] Figure 2 This is a cross-sectional layout diagram of the pipe shed;

[0040] Figure 3 This is a detailed drawing of the pipe shed;

[0041] Figure 4 This is a layout diagram of a down-the-hole hammer horizontal drill.

[0042] Figure 5 This is a detailed drawing of a bentonite grouting pipe.

[0043] Label Explanation

[0044] Ground leveling elevation 100

[0045] 1. Sleeve valve pipe, 2. Pipe section of jacking pipe, 3. Pipe roof steel pipe, 31. Grouting hole, 4. Jacking working well, 5. Hot-rolled seamless steel pipe, 6. Ring hoop, 7. Reinforcing bar, 8. Boulder area, 9. Grouting pipe, 10. Foamed concrete. Detailed Implementation

[0046] like Figure 1-5 As shown, this invention discloses a tunnel construction method suitable for urban underground boulder areas, the steps of which are as follows:

[0047] S1. Full-section grouting reinforcement of the soil at the tunnel face; this step specifically includes: grouting is designed according to the limited soil mass around the consolidated pipe shed, using Ф42 sleeve valve pipe 1 for grouting reinforcement, the grout diffusion radius is not less than 0.5m, and cement grout is used for grouting. Grouting parameters:

[0048] Cement grout water-cement ratio: 1:1

[0049] Grouting pressure: 0.5~0.8MPa

[0050] Final pressure: 2.0 MPa.

[0051] As a further preferred embodiment, during grouting construction, the criterion for ending grouting in a single hole is set as follows:

[0052] (1) Gradually increase the grouting pressure until it reaches the designed final hole pressure and stabilizes for 10 minutes;

[0053] (2) The grouting volume shall not be less than 80% of the designed grouting volume;

[0054] (3) The feed rate is 1 / 4 of the initial feed rate;

[0055] All grouting holes must meet the single-hole termination conditions and there must be no missed grouting. After grouting, the grouting effect should be checked. If the requirements are not met, supplementary grouting should be carried out.

[0056] S2. Advanced pipe roof support is installed at the tunnel entrance; please refer to [link / reference]. Figure 2 Pipe shed cross-sectional layout diagram Figure 3 The detailed drawing of the pipe shed, this step specifically includes:

[0057] The steel pipe 3 of the pipe shed is made of Ф245*10 hot-rolled seamless steel pipe (outer diameter 245MM, wall thickness 10MM, inner diameter 225MM). The steel pipe 3 of the pipe shed is equipped with a hoop 6 and a reinforcing bar 7. The hoop parameter is Ф10mm@500mm, and the reinforcing bar parameter is 4Ф25 (4 reinforcing bars with a diameter of 25 mm).

[0058] The inclination angle of the steel pipe 3 in the pipe shed is the same as the longitudinal slope of the route, and the direction is parallel to the center line of the road;

[0059] A guide pipe (not shown in the figure) is installed at the tunnel portal support. The guide pipe is made of Ф299*10 hot-rolled seamless steel pipe.

[0060] After the pipe shed construction is completed, a sealing treatment should be carried out.

[0061] The number of joints in the same cross section of the longitudinal section of the pipe roof steel pipe 3 shall not exceed 50%, and the joints of adjacent pipe roof steel pipes 3 shall be staggered by at least 1m.

[0062] The joints of the steel pipe 3 in the pipe shed are connected by threaded connections, with each thread being 30cm long.

[0063] S3. Down-the-hole hammer horizontal drilling for boulder removal. This step specifically includes:

[0064] a. See Figure 4 Layout diagram of down-the-hole hammer horizontal drill. Sandy soil in the jacking shaft 4 is backfilled in layers until the drill rod can horizontally drill through to the highest point of the isolated boulder area 8 within the jacking pipe section 2. The backfill height is as follows: Figure 4 As shown at the height of position P, the compaction coefficient of sandy soil is not less than 0.95;

[0065] b. Based on the isolated rock area 8, a down-the-hole hammer is arranged within the projection range of the jacking pipe section 2 to perform horizontal drilling, and the retaining structure in this area is removed. At the same time, measures are taken to ensure the stability of the soil in the remaining area at the tunnel entrance, such as using soil reinforcement methods such as compaction and grouting.

[0066] c. The longitudinal and transverse errors of the down-the-hole hammer horizontal drill shall not exceed ±50mm, and the elevation error shall be strictly controlled to exceed the burial depth of large stones. After each row of pretreatment is completed, the down-the-hole hammer equipment shall be hoisted to the ground, a layer shall be excavated and compacted.

[0067] d. After drilling a hole horizontally with a down-the-hole hammer and cleaning the hole, connect a 50mm PVC grouting pipe (see [link]) at the hole. Figure 5 (Detailed drawing of bentonite grouting pipe), specifically, a grouting hole is opened at the center of Ф200 foamed concrete 10 and a 50pvc grouting pipe is installed. Each grouting pipe 9 is equipped with a control gate valve to control the grouting pressure. Thick mortar is injected and the grouting pressure is not less than 2MPa.

[0068] e. Seal the grouting holes. Use a one-way ball valve that matches the reserved grouting holes to seal the grouting holes to prevent mud loss. After sealing, use micro-expansion concrete for secondary sealing.

[0069] Furthermore, the main raw material for the concentrated mortar is bentonite, and it also includes cement, water, CMC binder, and caustic soda. The proportion (by mass) of the concentrated mortar is 1:0.1:0.4:0.001:0.001, as shown in Table 1.

[0070] Table 1. Proportions for Thick Clay

[0071] Material Ordinary bentonite cement Clear water CMC Caustic soda ordinary section 1 0.1 0.4 0.001 0.001

[0072] The construction method of this invention has the following advantages:

[0073] 1) Combining the shallow buried tunneling method with advanced and strict grouting construction technology, the soil at the tunnel face is reinforced by full-section grouting, and advanced pipe shed support is set at the tunnel portal to prevent soil instability and road settlement during the later removal of boulders by down-the-hole hammer horizontal drilling and pipe jacking construction.

[0074] 2) In the process of removing boulders using a down-the-hole hammer horizontal drilling, after drilling the hole with the down-the-hole hammer, thick mortar is injected to seal it, and then micro-expansion concrete is used for secondary sealing to reduce the loss of soil layers during the removal of boulders and thus reduce road surface settlement.

[0075] 3) Combining the horizontal drilling technology of down-the-hole hammer to remove boulders, horizontal drilling can be used to break up soil layers with complex geology and boulders, reducing the content of large rocks in the strata, ensuring that the tunneling posture is controllable, and ensuring safe and efficient construction and smooth breakthrough of the tunnel.

[0076] The above description is merely an example of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A tunnel construction method suitable for urban underground boulder areas, characterized in that... This includes the following steps: Step 1: Perform full-section grouting reinforcement on the soil at the tunnel face; Step one, the full-section grouting reinforcement of the tunnel face soil, specifically includes: grouting designed according to the limited soil mass around the consolidated pipe roof, using Ф42 sleeve valve pipes for grouting reinforcement, with a grout diffusion radius of not less than 0.5m, and using cement grout. Grouting parameters: Cement grout water-cement ratio: 1:1 Grouting pressure: 0.5~0.8MPa Final borehole pressure: 2.0 MPa; Step 2: Install advanced pipe roof support at the tunnel entrance; The specific requirements for setting up advanced pipe roof support at the tunnel portal in step two include: The steel pipe for the pipe shed is made of Ф245*10 hot-rolled seamless steel pipe. The steel pipe for the pipe shed is equipped with hoops and reinforcing bars. The hoop parameters are Ф10mm@500mm and the reinforcing bar parameters are 4Ф25. The inclination angle of the steel pipes in the pipe shed is the same as the longitudinal slope of the route, and the direction is parallel to the centerline of the road; A guide pipe is installed at the tunnel portal support, and the guide pipe is made of Ф299*10 hot-rolled seamless steel pipe; After the pipe shed construction is completed, a sealing treatment should be carried out. The number of joints in the same cross section of the pipe roof steel pipe shall not exceed 50%, and the joints of adjacent pipe roof steel pipes shall be staggered by at least 1m. The steel pipe joints for the pipe shed are threaded connections, with each thread being 30cm long. Step 3: Removal of isolated boulders using a down-the-hole hammer horizontal drilling method; Step three, the horizontal drilling operation for removing boulders with a down-the-hole hammer, includes: a. The sandy soil in the jacking working shaft is backfilled in layers in one go to the highest point of the isolated rock area within the range where the down-the-hole hammer drill rod can be drilled horizontally through the jacking pipe section, and the compaction coefficient of the sandy soil is not less than 0.95; b. Based on the isolated rock area, arrange down-the-hole hammers within the projection range of the jacking pipe section to perform horizontal drilling and remove the retaining structure in this area. c. The longitudinal and transverse errors of the down-the-hole hammer horizontal drill shall not exceed ±50mm, and the elevation error shall be strictly controlled to exceed the burial depth of large stones. After each row of pretreatment is completed, the down-the-hole hammer equipment shall be hoisted to the ground, a layer shall be excavated and compacted. d. After drilling a hole horizontally with a down-the-hole hammer, clean the hole and then connect a 50 PVC grouting pipe to the hole. Each grouting pipe is equipped with a control gate valve. Pressurize the thick mortar with a grouting pressure of not less than 2 MPa. e. Seal the grouting holes. Use a one-way ball valve that matches the reserved grouting holes to seal the grouting holes. After sealing, use micro-expansion concrete for secondary sealing.

2. The tunnel construction method applicable to urban underground boulder areas as described in claim 1, characterized in that: During grouting construction, the standard for completing grouting in a single hole is: (1) Gradually increase the grouting pressure until it reaches the designed final hole pressure and stabilizes for 10 minutes; (2) The grouting volume shall not be less than 80% of the designed grouting volume; (3) The feed rate is 1 / 4 of the initial feed rate; All grouting holes must meet the single-hole termination conditions and there must be no missed grouting. After grouting, the grouting effect should be checked. If the requirements are not met, supplementary grouting should be carried out.

3. The tunnel construction method applicable to urban underground boulder areas as described in claim 1, characterized in that: The thick mortar is made of bentonite, cement, water, CMC binder and caustic soda, and its mass ratio is 1:0.1:0.4:0.001:0.001.

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