A method for constructing a large-section underground passage for protecting access to a building / structure

Abstract

A method for constructing a large-section underground passage near a building / structure, comprising the following steps: setting a ring of a pipe shed at the passage section, setting ring and neutral column MJS piles around the outside of the pipe shed, conducting small pipe grouting to supplement stratum reinforcement in a non-MJS reinforcement area, setting a dewatering well at each of four corner positions of the excavated full section; breaking the underground continuous wall by measuring and marking the excavation contour line, and cutting off the reinforcing steel; excavating the full section of the soil, dividing the full section into at least four small sections, excavating each small section in turn until all small sections are completed; excavating the small sections while conducting excavation passage primary support structure construction to realize excavation and support simultaneously; after the primary support structure is completed, removing the steel arch frame, and then conducting waterproof layer construction; and finally conducting secondary lining structure construction. The method can ensure the stability of the soil during excavation, prevent damage to surrounding buildings / structures and underground pipelines, and provide safety assurance for construction.

Description

Technical Field

[0001] This invention relates to the field of underground passage construction technology, and in particular to a method for constructing large-section underground passages that protect adjacent buildings / structures. Background Technology

[0002] With urbanization, cities are generally densely populated with limited land, leading to the extensive use of underground engineering in municipal projects. In complex environments with numerous surrounding buildings and structures, and dense underground pipelines, traditional open-cut construction methods are becoming increasingly unsuitable, giving rise to cut-and-cover (CPC) construction techniques. However, CPC construction presents the following challenges: 1. Unstable soil conditions in the tunnel, posing safety risks; 2. The excavation process can easily cause damage to surrounding buildings, structures, and underground pipelines. Summary of the Invention

[0003] In order to solve the above-mentioned technical problems, the present invention provides a construction method for large-section underground passages that protects adjacent buildings / structures. This method can ensure the stability of the soil during the excavation process, prevent damage to surrounding buildings / structures and underground pipelines, and provide safety assurance for construction.

[0004] To achieve the above objectives, the technical solution adopted by this invention is as follows: a construction method for a large-section underground passage protecting adjacent buildings / structures is provided, comprising the following steps:

[0005] 1) Before the tunnel is excavated, a ring of pipe roofs is set up on the tunnel cross section. Ring and central column MJS piles are set up around the outside of the pipe roofs. Small pipe grouting is carried out in the non-MJS reinforcement area to supplement the stratum reinforcement. Dewatering wells are set up at the four corners of the excavation section.

[0006] 2) Mark the excavation outline by surveying and setting out, break up the diaphragm wall, and cut off the reinforcing steel.

[0007] 3) Excavate the entire cross-section of soil, dividing the entire cross-section into 4 smaller cross-sections. Excavate the 4 smaller cross-sections in sequence, and proceed to the next smaller cross-section after the previous smaller cross-section has been excavated through, until all 4 smaller cross-sections have been completed.

[0008] 4) After the full-section soil excavation is completed, the initial support structure of the excavation tunnel will be constructed.

[0009] 5) After the initial support structure of the excavated tunnel is completed, the steel arch frame is removed, and then the waterproof layer is constructed;

[0010] 6) After the waterproof layer is completed, the secondary lining structure will be constructed.

[0011] As a further improvement of the present invention, in step 1), the pipe shed adopts an advanced large pipe shed with a diameter of at least 108mm.

[0012] As a further improvement of the present invention, in step 1), an electric tunnel is provided below the channel, and a water bag is placed inside the electric tunnel to prevent the electric tunnel from floating.

[0013] As a further improvement of the present invention, in step 2), a water-cooled drill is used to break the diaphragm wall. Before breaking the diaphragm wall, the area to be broken needs to be sprayed on the wall surface with paint. Then, the water-cooled drill is used to drill the wall surface within the area to separate it.

[0014] As a further improvement of the present invention, in step 3), during the full-section soil excavation process, settlement monitoring is required for the tunnel, ground buildings and structures, underground pipelines, rainwater culverts and power tunnels, etc., to observe whether their settlement data meet the design specifications.

[0015] As a further improvement of the present invention, in step 3), before excavation, a working platform is set up in the foundation pit near the excavation section. During excavation, a construction method combining pneumatic picks, shovels and hand picks is adopted. The soil around the perimeter is excavated first, and the soil in the center is reserved as a temporary working platform. The excavated soil is removed by a combination of manual and mechanical methods and transported to the soil collection box on the ground by a hoist. The excavation depth is controlled to be 600-800mm each time.

[0016] As a further improvement of the present invention, in step 3), the excavation sequence of the four small sections is to excavate in the order of upper right, lower right, upper left, and lower left.

[0017] As a further improvement of the present invention, in step 4), the construction steps of the initial support structure of the excavation channel are as follows: install steel arch frames to form a closed ring, the steel arch frames are connected by high-strength bolts, the steel arch frames are equipped with central columns and horizontal braces, and a grid structure is formed between the central columns and horizontal braces. Steel mesh is laid on the inner and outer sides of the steel arch frames and connecting bars are welded. After the grouting pipes are pre-embedded, sprayed concrete is carried out to form the initial support structure of the excavation channel.

[0018] As a further improvement of the present invention, in step 5), when dismantling the steel arch frame, all the horizontal supports of the steel arch frame are dismantled first, and then the central column is dismantled in a way that is done one at a time; the waterproof layer is made of PVC waterproof board.

[0019] As a further improvement of the present invention, in step 6), the secondary lining structure is constructed using cast-in-place reinforced concrete. The bottom slab of the passage is constructed first, and then the side walls and top slab are poured in one go.

[0020] The beneficial effects of this invention are as follows: In this method, the cross-section of the passage is reinforced by a combination of pipe roof, MJS piles, and small guide pipes, which enhances the load-bearing capacity, strengthens the surrounding strata, and prevents water seepage, ensuring the stability of the strata during excavation, preventing damage to surrounding buildings / structures, and providing a safety guarantee for subsequent excavation. Furthermore, this method uses at least four small cross-sections for step-by-step excavation, which prevents excessively large excavation sizes from affecting the stability of the passage soil. Additionally, support is provided as excavation progresses, achieving a stable excavation cross-section. Attached Figure Description

[0021] Figure 1 This is a plan view of the tunnel excavation in an embodiment of the present invention;

[0022] Figure 2 This is an elevation view of the tunnel excavation and support reinforcement in an embodiment of the present invention;

[0023] Figure 3 This is a cross-sectional view of the tunnel excavation construction in an embodiment of the present invention;

[0024] Figure 4 This is a schematic diagram of the sequence of the first excavation section in an embodiment of the present invention;

[0025] Figure 5 This is a schematic diagram of the second excavation section sequence in an embodiment of the present invention;

[0026] Figure 6 This is a schematic diagram of the third excavation section sequence in an embodiment of the present invention;

[0027] Figure 7 This is a schematic diagram of the fourth excavation section sequence in an embodiment of the present invention. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0029] This project's cut-and-cover tunnel is located between the east and west open-cut excavation pits of Exit I, serving a connecting function. Because the cut-and-cover section has a 3500×2400mm box culvert at the top and a 3500mm diameter power tunnel at the bottom, and is bordered by residential buildings on one side and an existing road on the other, the situation is complex with above-ground and underground buildings and structures. Open-cut excavation is not feasible, therefore cut-and-cover construction is adopted. The cut-and-cover cross-section is 9.1m × 8.3m × 5.23m (length × width × height). The strata at the excavation section are mostly composed of silty-fine sand and medium-coarse sand, with slight contact with silty soil at the top and bottom of the tunnel. To ensure construction safety and the safety of surrounding buildings and structures, the project adopts a large-section underground tunnel construction method that protects adjacent buildings and structures.

[0030] like Figure 1-7 As shown, the steps of a construction method for a large-section underground passage protecting adjacent buildings / structures are as follows:

[0031] 1) Before excavation, a ring of pipe roofs 27 is installed around the tunnel cross-section. The solidified body formed by grouting in the pipe roofs 27 prevents the subsidence of the upper rainwater culvert 11 and the uplift of the lower power tunnel 10, and provides load-bearing support during the tunnel excavation process. Ring-shaped and centrally located MJS piles 26 are installed around the outside of the pipe roofs 27. This reinforces and seals the ground strata and provides support for the upper rainwater culvert 11. Small-diameter pipes 28 are used to grout the non-MJS-reinforced areas to supplement ground strata reinforcement, improving ground stability and water-stopping effect. This combined support method ensures the safety and stability of the excavation. Four dewatering wells 16 are installed at the four corners of the excavation cross-section to lower the groundwater level to the designed depth. Construction only commences after thorough preparation and exploratory confirmation.

[0032] 2) Mark the excavation outline by surveying and setting out. Use a water-jet drill to break down the diaphragm wall 20. Before breaking down the diaphragm wall 20, spray paint the area on the wall surface, then use the water-jet drill to drill into the wall within the breaking area to separate it. Finally, break down the separated diaphragm wall 20 little by little. The diaphragm wall 20 is broken down according to the excavation cross-sectional dimensions and sequence. After the first section of the diaphragm wall 20 is broken down and the diaphragm wall reinforcement 21 is cut off, the soil can be excavated.

[0033] 3) The entire cross-section of the soil will be excavated, divided into four smaller sections. After the first smaller section is completed, the second section will be excavated, and so on, until all four sections are completed. Throughout the construction process, settlement monitoring will be conducted on the tunnel, surface buildings (structures), underground pipelines, rainwater culverts (box culverts), and power tunnel (electric tunnel), to ensure the settlement data meets design specifications. During excavation, a working platform will be erected near the excavation section within the western foundation pit (pit 13). After the continuous wall (diaphragm wall 20) is broken, the soil at the section will be excavated using a combination of pneumatic picks, shovels, and hand picks. The surrounding soil will be excavated first, reserving the central soil as a temporary working platform to facilitate the erection of the steel arch frame (frame 25). This platform will also provide some support to the soil at the section, preventing collapse. The excavated soil was removed using a combination of manual and mechanical methods and transported to a soil collection box at ground level 12 via a hoist. Each excavation depth was controlled to be between 600 and 800 mm.

[0034] 4) While carrying out the excavation of the small cross-section, the construction of the primary support structure of the excavation passage is carried out to achieve support while excavating. Specifically, after the tunneling is completed, the steel arch frame 25 is installed in time to form a closed loop. The steel arch frame 25 is connected by high-strength bolts 33. The steel mesh is laid on the inner and outer sides of the steel arch frame 25 and the connecting bars 24 are welded. After the grouting pipes 29 are预埋, shotcrete can be carried out to form the primary support structure of the excavation passage. The construction is carried out step by step in this way to form a loop and complete the construction of the entire cross-section.

[0035] 5) After the primary support is completed, first remove all the cross braces 34 of the steel arch frame 25, and remove the middle columns 35 in the way of removing one every other. When carrying out the waterproof layer construction, the waterproof layer uses PVC waterproof board.

[0036] 6) After the waterproof layer construction is completed. The construction of the secondary lining structure 15 is carried out, using cast-in-place reinforced concrete. First, the construction of the channel floor is carried out, and the side walls and the top plate are poured一次性.

[0037] The combined support of multiple structural forms such as MJS piles 26 + pipe sheds 27 + small ducts 28 is adopted to adapt to different engineering conditions and construction requirements. A stable support system can be formed to effectively improve the stability.

[0038] The circumferential and middle column MJS piles 26 are constructed on the periphery of the excavation cross-section to reinforce and stop water for the cross-section stratum, support the upper rainwater culvert 11, and press the lower power tunnel 10 to prevent floating.

[0039] An advance large pipe shed 27 with a diameter of 108 mm is arranged in a circle in the circumferential direction of the excavation cross-section to support and bear the weight of the soil body of the excavation cross-section, preventing the settlement or floating of the surrounding buildings, rainwater culvert 11 and power tunnel 10 of the mined tunnel. The construction of the advance large pipe shed 27 uses the I25a directional steel frame 23 and the guide pipe 22 with a diameter of 127 mm to ensure the construction quality.

[0040] The steel arch frame 25 is provided with temporary middle columns 25 and cross braces 24 to form a "field" shape. To ensure the stability during the excavation of 4 cross-sections, when each cross-section advances a distance of one bay, the steel arch frame 25 is installed in a loop to form a reliable support body, and the connecting bars 24 and the steel mesh are welded in time, and then shotcrete is carried out to form the primary support structure. After the excavation of 4 cross-sections is completed and the primary support structure is completed, the cross braces 24 and some of the middle columns 25 can be removed. After the waterproof layer and the secondary lining structure 15 are constructed, all the middle columns 25 are removed.

[0041] The entire large cross-section of the mined tunnel is divided into 4 small cross-sections, and the construction sequence is upper right 1-1, lower right 1-2, upper left 1-3, lower left 1-4. After the excavation and primary support of each small cross-section are completed and connected, the excavation of the next small cross-section is carried out. Until the construction of all cross-sections is completed in sequence. It should be noted that the "一次性" in the translation of item 6 should be adjusted according to the actual context, perhaps it should be "at one time" or something more appropriate. And there may be some inaccuracies in the translation due to the lack of some clear context information, but it is translated as accurately as possible according to the requirements.

[0042] During the tunnel excavation, water bags were placed inside the lower power tunnel 10, positioned at the corresponding location of the mined tunnel. The water bags applied pressure to the power tunnel 10 to prevent it from floating. Settlement was monitored regularly.

[0043] A water-cooled drill was used to continuously drill holes in the diaphragm wall 20 outside the excavated section, reaching the surface of the inner layer of reinforcing steel 21. The drilling and breaking sequence of the diaphragm wall 20 was consistent with the excavation sequence, divided into four sections for breaking. The drilling positions were from the right angle outwards to both sides. After drilling was completed, a pneumatic pick was used to manually break the diaphragm wall 20 structure. Finally, the inner layer of reinforcing steel 21 of the diaphragm wall 20 was cut off.

[0044] The above-described embodiments are merely illustrative of the present invention and are not intended to limit the present invention in any way. Any person skilled in the art who makes partial modifications or alterations to the technical content disclosed in the present invention without departing from the scope of the technical features of the present invention shall still fall within the scope of the technical features of the present invention.

Claims

1. A method of constructing a large cross-section underground passage for protecting access to a building / structure, characterized in that The method comprises the following steps: 1) Before the excavation of the passage, a ring of pipe roof is arranged on the passage section, ring and central column type MJS piles are arranged around the outside of the pipe roof, small pipe grouting is carried out in the non-MJS reinforced area to supplement the stratum reinforcement, and a dewatering well is arranged at the position of the four corners of the full section excavation; 2) The excavation contour line is marked by measurement and line laying, the underground continuous wall is broken, and the steel bars are cut off; 3) The full section soil is excavated, the full section is divided into at least four small sections, each small section is excavated in turn, the next small section is excavated after the excavation of the previous small section is completed, and the construction of all small sections is completed; 4) While the small section is excavated, the excavation passage primary support structure construction is carried out to realize the excavation and support simultaneously; 5) After the completion of the excavation passage primary support structure, the steel arch is removed, and then the waterproof layer is constructed; 6) After the completion of the waterproof layer construction, the secondary lining structure construction is carried out; In step 1), the pipe roof adopts an advanced large pipe roof with a diameter of at least 108 mm; the power tunnel is arranged below the passage, and water bags are arranged in the power tunnel to prevent the power tunnel from floating; In step 3), the small section is divided into four, and the excavation sequence of the four small sections is right upper, right lower, left upper and left lower in turn; In step 4), the steps of the excavation passage primary support structure construction are as follows: the steel arch is installed to form a ring, the steel arch is connected by high-strength bolts, the steel arch is provided with central columns and cross braces, the central columns and cross braces form a T-shaped structure, the steel mesh is laid on the inner and outer sides of the steel arch and welded to the connecting bars, the grouting pipe is embedded, and then the shotcrete is sprayed to form the excavation passage primary support structure.

2. A method of constructing a large cross-section underground passage for protecting access to a building / structure according to claim 1, characterized in that: In step 2), the underground continuous wall is broken by water drilling, and the wall surface in the breaking range is drilled by water drilling before the underground continuous wall is broken, so that it is separated.

3. A method of constructing a large cross-section underground passage for protecting access to a building / structure according to claim 1, characterized in that: In step 3), during the excavation of the full section soil, the settlement of the underground excavation passage, ground building structures, underground pipelines, rainwater box culverts and power tunnels is monitored to observe whether the settlement data meets the design specification requirements.

4. A method of constructing a large cross-section underground passage for protecting access to a building / structure according to claim 1, characterized in that: In step 3), before excavation, an operation platform is erected near the excavation section in the foundation pit, during excavation, the construction method of combining wind pick, shovel and hand pick is used, the soil around the central soil is excavated first, and the central soil is reserved as a temporary operation platform; the excavated soil is removed by combining manual and mechanical methods, and is transported to the soil collection box on the ground by a bucket; the excavation penetration size is controlled to be 600-800 mm each time.

5. A method of constructing a large cross-section underground passage for protecting access to a building / structure according to claim 1, characterized in that: In step 5), when the steel arch is removed, all the cross braces of the steel arch are removed first, and then the central columns are removed by the method of removing one every other; the waterproof layer adopts PVC waterproof board.

6. A method of constructing a large cross-section underground passage for protecting access to a building / structure according to claim 1, characterized in that: In step 6), the secondary lining structure construction adopts cast-in-place reinforced concrete, the passage bottom plate is constructed first, and then the side wall and the roof are poured at one time.

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