Tunnel construction method suitable for urban underground boulder area

Abstract

The invention discloses a tunnel construction method suitable for an urban underground boulder area. The tunnel construction method comprises the steps that firstly, full-section grouting reinforcement is conducted on a tunnel face soil body; secondly, an advanced pipe shed support is arranged at the position of a tunnel portal; and thirdly, boulder removing construction of the horizontal drill of the down-the-hole hammer is conducted. According to the construction method, the shallow-buried excavation method and the down-the-hole hammer horizontal drilling boulder removal are combined, the risk of manual operation existing in the shallow-buried excavation method can be avoided, horizontal drilling crushing can be conducted on a soil layer with complex geology and boulder, the content of large rock in the stratum is reduced, it is guaranteed that the pipe jacking tunneling posture is controllable, and the construction efficiency is improved. And safe and efficient construction and smooth penetration of the jacking pipe are ensured.

Description

Technical Field

[0001] The invention relates to the technical field of underground engineering, and in particular to a tunnel construction method suitable for underground boulder areas in cities. Background Art

[0002] With the rapid development of urban construction, the problem of urban traffic congestion has become increasingly prominent. Along with the development and utilization of underground space, many cities have begun to carry out tunnel construction. As the main construction methods for urban underground projects: shallow buried tunneling and jacking can avoid the interference of open construction process on the surface, and have stronger adaptability and high flexibility to complex strata than shield method.

[0003] Shallow buried tunneling is mostly used in underground projects in soft quaternary strata, where the surrounding rock has poor bearing capacity. Its design points can be summarized as pipe ahead, strict grouting, short advance, strong support, early closure, frequent measurement, and fast feedback. However, improper construction organization or poor management can easily lead to construction risk accidents, such as excessive ground settlement or collapse, damage to ground buildings (structures), and cave collapse. If these risk accidents occur, the losses and impacts caused are very large.

[0004] Pipe jacking technology is a non-excavation mechanical excavation construction method used in municipal construction. During the jacking process, the jacking speed should be dynamically adjusted according to the monitored deformation, ground settlement control should be carried out, and the posture changes of the jacking machine should be monitored at all times. If there is any change, it should be corrected immediately, and the correction amplitude should not be too large. Therefore, pipe jacking technology is suitable for soft and geologically uniform soil layers such as silty clay, clay, silty clay, and sandy soil, but not for moderately weathered rock layers and soil layers with complex geology and isolated rocks.

[0005] The shallow buried tunneling method involves manual labor and does not require high geological uniformity, but it has greater risks. The pipe jacking technology uses a mechanical excavation construction method, but it has high requirements for the jacking posture and is not suitable for soil layers with complex geology and the presence of isolated rocks.

[0006] In view of this, the inventors have improved the shallow buried tunnel construction process and proposed a tunnel construction method suitable for urban underground rock areas to reduce the risk of manual operations and improve construction safety and efficiency. Summary of the invention

[0007] The purpose of the present invention is to provide a tunnel construction method suitable for urban underground boulder areas. The method combines the two construction processes of shallow buried dark excavation and down-the-hole hammer horizontal drilling and boulder removal. It can not only solve the risk of manual operation in the shallow buried dark excavation method, but also can perform horizontal drilling and crushing on the geologically complex and boulder-containing soil layers, reduce the content of large rocks in the stratum, ensure that the jacking tunneling posture is controllable, and ensure the safe and efficient construction of the jacking pipe and smooth penetration.

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

[0009] The present invention provides a tunnel construction method suitable for an underground boulder area in an urban area, comprising the following steps:

[0010] Step 1: Perform full-section grouting reinforcement on the soil at the tunnel face;

[0011] Step 2: Set up advanced pipe support at the tunnel entrance;

[0012] Step 3: Use down-the-hole hammer to drill horizontally to remove boulders.

[0013] Furthermore, the full-section grouting reinforcement of the tunnel face soil described in step 1 specifically includes: the grouting is designed according to the limited soil around the consolidation pipe shed, Ф42 sleeve valve pipe grouting reinforcement is adopted, the slurry diffusion radius is not less than 0.5m, and cement slurry is adopted for grouting, and the grouting parameters are:

[0014] Cement paste water-cement mass ratio: 1:1

[0015] Grouting pressure: 0.5~0.8MPa

[0016] Final hole pressure: 2.0MPa.

[0017] Furthermore, during grouting construction, the end standard of single-hole grouting is:

[0018] (1) The grouting pressure is gradually increased until it reaches the designed final hole pressure and remains stable for 10 minutes;

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

[0020] (3) The slurry feeding speed is 1 / 4 of the initial slurry feeding speed;

[0021] All grouting holes must meet the single-hole completion conditions and there must be no leakage. After grouting, the grouting effect must be checked. If it does not meet the requirements, additional injection must be carried out.

[0022] Furthermore, the specific requirements for setting up the advanced pipe support at the tunnel portal in step 2 include:

[0023] The pipe-roof steel pipe adopts Ф245*10 hot-rolled seamless steel pipe. Hoops and steel bars are arranged inside the pipe-roof steel pipe. The parameters of the hoop are Ф10mm@500mm, and the parameters of the steel bar are 4Ф25 (4 steel bars with a diameter of 25 mm).

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

[0025] A guide pipe is provided 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, the plugging treatment shall be carried out;

[0027] The number of joints in the same longitudinal 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 pipe roof steel pipe joints are connected by threaded connections, and the thread length is 30cm.

[0029] Furthermore, the down-the-hole hammer horizontal drilling and boulder removal construction in step 3 includes:

[0030] a. The sandy soil in the jacking working well shall be backfilled in layers at one time until the drill rod of the down-the-hole hammer can horizontally drill through the highest boulder area within the jacking pipe section, and the compaction coefficient of the sandy soil shall not be less than 0.95;

[0031] b. Arrange down-the-hole hammers within the projection range of the top pipe section in the isolated rock area to perform horizontal drilling and remove the surrounding structures in the area;

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

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

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

[0035] Furthermore, the concentrated mortar is mixed with bentonite, cement, clean water, CMC adhesive and caustic soda, and the mass ratio thereof is 1:0.1:0.4:0.001:0.001.

[0036] After adopting the above scheme, the present invention has the following beneficial effects:

[0037] The construction method of the present invention combines the two construction techniques of shallow buried tunneling and down-the-hole hammer horizontal drilling and boulder removal. It can not only solve the risk of manual operation in the shallow buried tunneling, but also can perform horizontal drilling and crushing on the geologically complex and boulder-containing soil layers, reduce the content of large rocks in the stratum, ensure the controllable posture of the jacking pipe excavation, and ensure the safe and efficient construction and smooth penetration of the jacking pipe. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0039] Figure 2 It is the cross-sectional layout of the pipe shed;

[0040] Figure 3 It is a large-scale drawing of the pipe shed;

[0041] Figure 4 It is the layout diagram of down-the-hole hammer horizontal drilling;

[0042] Figure 5 This is a large-scale drawing of bentonite grouting pipe.

[0043] Description of symbols

[0044] Ground leveling elevation 100

[0045] Sleeve valve pipe 1, jacking pipe section 2, pipe rack steel pipe 3, grouting hole 31, jacking working pit 4, hot-rolled seamless steel pipe 5, hoop 6, steel bar 7, boulder area 8, grouting pipe 9, foam concrete 10. DETAILED DESCRIPTION

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

[0047] S1. Grouting reinforcement of the whole section of the tunnel face soil; this step specifically includes: grouting is designed according to the limited soil around the consolidation pipe shed, 1 Ø42 sleeve valve pipe is used for grouting reinforcement, the slurry diffusion radius is not less than 0.5m, and cement slurry is used for grouting, and the grouting parameters are:

[0048] Cement paste water-cement mass ratio: 1:1

[0049] Grouting pressure: 0.5~0.8MPa

[0050] Final hole pressure: 2.0MPa.

[0051] As a further preferred embodiment, during the grouting construction, the single hole grouting end standard is set as:

[0052] (1) The grouting pressure is gradually increased until it reaches the designed final hole pressure and remains stable for 10 minutes;

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

[0054] (3) The slurry feeding speed is 1 / 4 of the initial slurry feeding speed;

[0055] All grouting holes must meet the single-hole completion conditions and there must be no leakage. After grouting, the grouting effect must be checked. If it does not meet the requirements, additional injection must be carried out.

[0056] S2. Set up advanced pipe support at the tunnel entrance; see Figure 2 Pipe shed cross-section layout, Figure 3 The pipe shed drawing includes:

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

[0058] The inclination angle of the pipe-roof steel pipe 3 is set to be 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 arranged at the tunnel portal support, and the guide pipe is made of Ф299*10 hot-rolled seamless steel pipe;

[0060] After the pipe shed construction is completed, the plugging treatment shall be carried out;

[0061] The number of joints in the same longitudinal cross 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 pipe-roof steel pipe 3 are connected by threaded connection, and the thread length is 30 cm.

[0063] S3, down-the-hole hammer horizontal drilling and boulder removal construction, this step specifically includes:

[0064] a. See Figure 4 DTH hammer horizontal drilling arrangement diagram, the sandy soil in the jacking working well 4 is backfilled in layers at one time until the DTH hammer drill rod can horizontally drill through the highest rock area 8 within the jacking pipe section 2. The one-time backfill height is as follows Figure 4 As shown in the height of the middle P position, the compaction coefficient of sandy soil is not less than 0.95;

[0065] b. Arrange a down-the-hole hammer to drill horizontal holes in the projection range of the top pipe section 2 according to the isolated rock area 8, remove the surrounding structure in this area, and take measures to ensure the stability of the soil in the rest of the tunnel entrance, such as using soil reinforcement methods such as vibration compaction and grouting;

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

[0067] d. After drilling horizontally with a down-the-hole hammer, clean the hole and then connect a 50 PVC grouting pipe 9 (see Figure 5 Bentonite grouting pipe drawing), specifically, a grouting hole is opened at the center of the Ф200 foam concrete 10 to install a 50pvc grouting pipe. Each grouting pipe 9 is provided with a control gate valve to control the grouting pressure, and the concentrated cement is injected. 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 is completed, use micro-expansive concrete for secondary sealing.

[0069] Furthermore, the raw materials of the thick clay are mainly bentonite, and also include cement, clean water, CMC adhesive, and caustic soda. The proportion (mass ratio) of the thick clay is 1:0.1:0.4:0.001:0.001, see Table 1.

[0070] Table 1 Ratio of concentrated clay

[0071] Material Ordinary bentonite cement Shimizu CMC Caustic Soda Normal section 1 0.1 0.4 0.001 0.001

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

[0073] 1) Combined with the shallow buried tunneling method, the advanced pipe and strict grouting construction technology, the full-section grouting reinforcement is carried out on the face soil, and an advanced pipe shed support is set at the tunnel portal to prevent the face soil from becoming unstable and the road surface from settling during the subsequent down-the-hole hammer horizontal drilling and boulders removal and pipe jacking construction.

[0074] 2) During the construction of removing boulders by horizontal drilling with a down-the-hole hammer, thick clay is injected after the hole is drilled horizontally by the down-the-hole hammer to seal it, and then micro-expansive concrete is used for secondary sealing to reduce the loss of strata during the process of removing boulders and cause road subsidence.

[0075] 3) Combined with the down-the-hole hammer horizontal drilling and boulder removal construction technology, horizontal drilling and crushing can be carried out on the soil layer with complex geology and boulder existence, reducing the content of large rocks in the stratum, ensuring the controllable posture of the jacking tunneling, and ensuring the safe and efficient construction and smooth penetration of the jacking tunnel.

[0076] The above description is only an implementation 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 in the protection scope of the present invention.

Claims

1. A tunnel construction method suitable for urban underground rock areas, characterized in that , including the following steps: Step 1: Perform full-section grouting reinforcement on the soil at the tunnel face; Step 2: Set up advanced pipe support at the tunnel entrance; Step 3: Use down-the-hole hammer to drill horizontally to remove boulders.

2. A tunnel construction method suitable for urban underground boulder areas as claimed in claim 1, characterized in that: The full-section grouting reinforcement of the tunnel face soil described in step 1 specifically includes: the grouting is designed according to the limited soil around the consolidation pipe shed, Ф42 sleeve valve pipe grouting reinforcement is adopted, the slurry diffusion radius is not less than 0.5m, and cement slurry is adopted for grouting, and the grouting parameters are as follows: Cement paste water-cement mass ratio: 1:1 Grouting pressure: 0.5~0.8MPa Final hole pressure: 2.0MPa.

3. A tunnel construction method suitable for urban underground boulder areas as claimed in claim 2, characterized in that: During grouting construction, the standard for the end of single-hole grouting is: (1) The grouting pressure is gradually increased until it reaches the designed final hole pressure and remains stable for 10 minutes; (2) The grouting volume shall not be less than 80% of the designed grouting volume; (3) The slurry feeding speed is 1 / 4 of the initial slurry feeding speed; All grouting holes must meet the single-hole completion conditions and there must be no leakage. The grouting effect must be checked after grouting. If it does not meet the requirements, additional injection must be carried out.

4. A tunnel construction method suitable for urban underground boulder areas as claimed in claim 1, characterized in that: The specific requirements for setting up advanced pipe support at the tunnel portal in step 2 include: The pipe-roof steel pipe adopts Ф245*10 hot-rolled seamless steel pipe. Hoops and steel bars are arranged inside the pipe-roof steel pipe. The parameters of the hoop are Ф10mm@500mm, and the parameters of the steel bar are 4Ф25. The inclination angle of the steel pipes of the pipe shed is set to be the same as the longitudinal slope of the route, and the direction is parallel to the center line of the road; A guide pipe is provided 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, the plugging treatment shall be carried out; The number of joints in the same longitudinal 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 pipe roof steel pipe joints are connected by threaded connections, and the thread length is 30cm.

5. A tunnel construction method suitable for urban underground boulder areas as claimed in claim 1, characterized in that: Step 3: Down-the-hole hammer horizontal drilling and boulder removal construction includes: a. The sandy soil in the jacking working well shall be backfilled in layers at one time until the drill rod of the down-the-hole hammer can horizontally drill through the highest boulder area within the jacking pipe section, and the compaction coefficient of the sandy soil shall not be less than 0.95; b. Arrange down-the-hole hammers within the projection range of the top pipe section in the isolated rock area to perform horizontal drilling and remove the surrounding structures in the area; c. The vertical and horizontal errors of down-the-hole hammer horizontal drilling shall not exceed ±50mm, and the elevation error shall be strictly controlled to exceed the burial depth of large rocks. After each row of pretreatment is completed, the down-the-hole hammer equipment shall be hoisted to the ground, and a layer shall be excavated and compacted; d. After drilling horizontally with a down-the-hole hammer, clean the hole and then connect a 50pvc grouting pipe to the hole. Each grouting pipe is equipped with a control gate valve to inject thick cement. The grouting pressure is not less than 2MPa. e. Seal the grouting holes. Use a one-way ball valve that matches the reserved grouting holes to seal the grouting holes. After the sealing is completed, use micro-expansive concrete for secondary sealing.

6. A tunnel construction method suitable for urban underground boulder areas as claimed in claim 5, characterized in that: The concentrated glue is prepared by mixing bentonite, cement, clean water, CMC adhesive and caustic soda, and the mass ratio thereof is 1:0.1:0.4:0.001:0.001.

Images