Construction method of large-section underground passage for protecting approximate buildings / structures

Abstract

A construction method of a large-section underground passage for protecting approaching buildings / structures comprises the steps that a circle of annular pipe shed is arranged on the section of the passage, annular and middle stand column type MJS piles are arranged on the periphery of the outer side of the pipe shed, small guide pipe grouting supplement stratum reinforcement is conducted in a non-MJS reinforcement area, and dewatering wells are arranged at the four corners of the excavated full section; an excavation contour line is marked through surveying and setting-out, the underground diaphragm wall is broken, and the steel bars are cut off; the full-section soil body is excavated, the full section is divided into at least four small sections, and each small section is excavated in sequence until all the small sections are constructed; when the small section is excavated, primary support structure construction of the excavated channel is carried out, and excavation and supporting are carried out at the same time; after the primary supporting structure is completed, the steel arch is dismantled, and then waterproof layer construction is conducted; and finally, secondary lining structure construction is conducted. According to the method, the soil stability in the excavation process can be guaranteed, surrounding buildings / structures and underground pipelines are prevented from being damaged, and safety guarantee is provided for construction.

Description

Technical Field

[0001] The invention relates to the technical field of underground passage construction, and in particular to a large-section underground passage construction method for protecting adjacent buildings / structures. Background Art

[0002] With the development of urbanization, cities are generally densely populated and land is scarce, and underground projects are widely used in municipal engineering. In view of the complex environment with many surrounding buildings / structures and dense underground pipelines, the traditional full-section open excavation construction method is gradually not applicable, and the dark excavation construction technology has emerged. However, in the dark excavation construction process, there are the following problems: 1. The soil of the channel is unstable, which poses a safety risk; 2. The excavation process is likely to cause certain damage to the surrounding buildings / structures and underground pipelines. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a method for constructing a large-section underground passage close to buildings / structures, which can ensure the stability of the soil during excavation, prevent damage to surrounding buildings / structures and underground pipelines, and provide safety protection for construction.

[0004] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: providing a large-section underground passage construction method for protecting a building / structure, comprising the following steps:

[0005] 1) Before the channel is excavated, a ring of pipe sheds is set up in the channel section, and ring and neutral column MJS piles are set up around the outside of the pipe shed. Small pipe grouting is carried out in the non-MJS reinforcement area to supplement the stratum reinforcement, and precipitation wells are set up at the four corners of the excavated full section;

[0006] 2) Mark the excavation contour by measuring and setting out, break down the underground continuous wall, and remove the steel bars;

[0007] 3) Excavate the soil of the entire section, divide the entire section into 4 small sections, and excavate the 4 small sections in sequence. After the excavation of the previous small section is completed, the next small section will be excavated until all 4 small sections are completed;

[0008] 4) After the full-section soil excavation is completed, the initial support structure of the excavation channel is constructed;

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

[0010] 6) After the waterproof layer construction is completed, the secondary lining structure construction shall be carried out.

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

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

[0013] As a further improvement of the present invention, in step 2), a water-grinding drill is used to break the underground continuous wall. Before breaking the underground continuous wall, the breaking range needs to be sprayed on the wall surface with paint, and then the wall surface within the breaking range is drilled with a water-grinding drill to separate it.

[0014] As a further improvement of the present invention, in step 3), during the excavation of the full-section soil, it is necessary to monitor the settlement of the underground passages, ground structures, underground pipelines, rainwater culverts and power tunnels to observe whether their settlement data meet the design specification requirements.

[0015] As a further improvement of the present invention, in step 3), before excavation, a working platform is set up near the excavation section in the foundation pit. During excavation, a construction method combining pneumatic picks, shovels and hand picks is adopted to first excavate the surrounding soil, and reserve the central soil as a temporary working platform; the excavated debris is unearthed by a combination of manual and mechanical methods, and transported to the soil collection box on the ground through a bucket; the excavation size 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 upper right, lower right, upper left, and lower left in sequence.

[0017] As a further improvement of the present invention, in step 4), the steps of constructing the initial support structure of the excavated channel are as follows: install a steel arch frame to form a closed ring, connect the steel arch frame with high-strength bolts, provide a central column and a cross brace, form a field-shaped structure between the central column and the cross brace, lay steel mesh on the inside and outside of the steel arch frame and weld connecting ribs, pre-embed the grouting pipe and then spray concrete to form the initial support structure of the excavated channel.

[0018] As a further improvement of the present invention, in step 5), when dismantling the steel arch frame, all the cross braces of the steel arch frame are dismantled first, and then the central columns are dismantled one by one; the waterproof layer adopts 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, with the channel bottom plate being constructed first and then the side walls and top plate being cast at one time.

[0020] The beneficial effects of the present invention are as follows: in this method, the channel section is reinforced with a combined support using pipe sheds, MJS piles and small pipes, which enhances the load-bearing, reinforcement and water-stopping effects on the surrounding strata, ensures the stability of the strata during excavation, prevents damage to surrounding buildings / structures, and provides safety protection for subsequent excavation. In addition, this method uses at least 4 small sections for step-by-step excavation, which can prevent the excavation size from being too large and affecting the stability of the channel soil, and supports the excavation as it is excavated to achieve the effect of stabilizing the excavation section. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a plan view of a dark excavation passage in an embodiment of the present invention;

[0022] Figure 2 It is a vertical view of a dark excavation passage and support reinforcement in an embodiment of the present invention;

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

[0024] Figure 4 This is a schematic diagram of the first excavation section sequence 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 It is a schematic diagram of the fourth excavation section sequence in an embodiment of the present invention. DETAILED DESCRIPTION

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

[0029] The underground tunnel of this project is located between the east and west open excavation pits of the No. 1 entrance and exit, and serves as a connection. Because there is a 3500×2400mm box culvert on the top of the underground tunnel, and a 3500mm diameter power tunnel at the bottom, and one side of the underground tunnel is residential, and the other side is the existing road. The situation of above-ground and underground buildings (structures) is complicated. It is impossible to open excavate, so underground excavation is adopted. The underground excavation section is length × width × height (9.1m×8.3m×5.23m). Most of the strata of the excavation section are in powder-fine sand and medium-coarse sand, and the top and bottom of the tunnel slightly involve silty soil. In order to ensure the safety of construction and the safety of surrounding buildings / structures, the project adopts a large-section underground tunnel construction method to protect the buildings / structures.

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

[0031] 1) Before the channel is excavated, a circle of annular pipe shed 27 is set on the channel section. The reinforcement formed by grouting the pipe shed 27 is used to prevent the upper rainwater culvert 11 of the dark excavated channel from sinking, the lower power tunnel 10 from floating, and the load-bearing support during the dark excavation process. Annular and neutral column MJS piles 26 are set around the outer side of the pipe shed 27. The cross-section stratum is reinforced and water-stopped, and it plays a supporting role for the rainwater culvert 11 above. Small conduits 28 are grouted in non-MJS reinforced areas to supplement the stratum reinforcement and improve the self-stability and water-stopping effect of the stratum. This combined support method is used to ensure the safety and stability of the excavation. Four precipitation wells 16 are set at the four corners of the excavation section to reduce the groundwater to the designed depth. After the construction preparation is completed and confirmed by exploration, the construction will be officially carried out.

[0032] 2) Mark the excavation contour line by measuring and setting out, and use a water-grinding drill to break the underground continuous wall 20. The ground-connected wall 20 must be broken by spraying the range on the wall surface with spray paint in advance, and then the wall surface within the breaking range is drilled with a water-grinding drill to separate it. Finally, the separated ground-connected wall 20 is broken and chiseled little by little. The underground continuous wall 20 is broken according to the size and order of the excavation section. After the first section of the ground-connected wall 20 is broken and the ground-connected wall steel bars 21 are cut off, the soil can be excavated.

[0033] 3) Excavate the soil of the entire section, and divide the entire section into 4 small sections for excavation. After the first small section is completed, the second section is excavated. After the second section is penetrated, the third section is constructed, and so on, until all 4 sections are completed. During the entire construction process, settlement monitoring is required for the dark excavation passage, ground 12 buildings (structures), underground pipelines, rainwater culverts 11 and power tunnels 10, etc., to observe whether their settlement data meet the requirements of the design specifications. During the excavation process, an operating platform is set up near the excavation section in the west foundation pit 13. After the continuous wall 20 is broken, the soil of the section is excavated. A construction method combining pneumatic picks, shovels and hand picks is used. The surrounding soil is excavated first, and the central soil is reserved as a temporary operating platform to facilitate the construction of the steel arch frame 25. It can also exert a certain force on the soil of the section to prevent the collapse of the soil of the section. The excavated soil is excavated by a combination of manual and mechanical methods and transported to a soil collection box on the ground 12 by a bucket. The excavation size is controlled at 600 to 800 mm each time.

[0034] 4) While carrying out small-section excavation, construct the primary support structure of the excavation passage to achieve support as excavation progresses. Specifically, immediately install the steel arch 25 to form a closed loop after tunneling is completed. The steel arch 25 is connected by high-strength bolts 33. Lay the steel mesh on the inner and outer sides of the steel arch 25 and weld the connecting bars 24. After pre-burying the grouting pipes 29, shotcrete can be carried out to form the primary support structure of the excavation passage. Construct in a loop step by step according to this method to complete the construction of the entire section.

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

[0036] 6) After the waterproof layer construction is completed, carry out the construction of the secondary lining structure 15, using cast-in-place reinforced concrete. First, carry out the construction of the channel floor, and the side walls and roof are poured at one time.

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

[0038] Construct circumferential and middle column MJS piles 26 on the periphery of the excavation section to reinforce and waterproof the section stratum, support the upper rainwater culvert 11, and counterweight the lower power tunnel 10 to prevent floating.

[0039] Arrange a circle of advanced large-diameter pipe roofs 27 with a diameter of 108 mm circumferentially in the excavation section to support and bear the weight of the excavation section soil, preventing the settlement or floating of the surrounding buildings, rainwater culvert 11 and power tunnel 10 of the mined tunnel. The construction of the advanced large-diameter pipe roof 27 uses I25a directional steel frames 23 and guide pipes 22 with a diameter of 127 mm to ensure the construction quality.

[0040] Temporary middle columns 25 and cross braces 24 are set on the steel arch 25 to form a "field" shape to ensure the stability during the excavation of 4 sections. For each section, when tunneling a distance of one bay, the steel arch 25 is installed to form a closed loop to form a reliable support body, and the connecting bars 24 and steel mesh are welded in time, and then shotcrete is carried out to form the primary support structure. After the excavation of 4 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] Divide the entire large section of the mined tunnel into 4 small 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 section are completed and connected, then carry out the excavation of the next small section. Until the construction of all sections is completed in sequence.

[0042] During the tunnel excavation process, water bags are set in the lower power tunnel 10, and the water bags are placed at the corresponding positions of the dark excavated tunnel. The water bags apply a certain pressure to the power tunnel 10 to prevent the tunnel from floating up. Settlement observations are also carried out regularly.

[0043] A water-grinding drill is used to continuously drill holes in the ground-connected wall 20 outside the excavated section, and the drilling depth reaches the position of the surface of the inner layer of steel bars 21 of the ground-connected wall 20. The order of opening and breaking the continuous wall 20 is the same as the order of section excavation, and it is broken in 4 parts. The opening position is carried out from the right angle to both sides. After the opening is completed, a pneumatic pick is used to manually break the ground-connected wall 20 structure. Finally, the inner layer of steel bars 21 of the ground-connected wall 20 are cut off.

[0044] The above embodiments are only used to illustrate the present invention and are not intended to limit the present invention in any form. Any person with ordinary knowledge in the technical field may make partial changes or modifications to the technical contents disclosed in the present invention without departing from the scope of the technical features of the present invention, and the equivalent embodiments without departing from the technical features of the present invention are still within the scope of the technical features of the present invention.

Claims

1. A method for constructing a large-section underground passageway to protect a building or structure, characterized in that The following steps are involved: 1) Before the channel is excavated, a ring of pipe sheds is set up in the channel section, and ring and neutral column MJS piles are set up around the outside of the pipe shed. Small pipe grouting is carried out in the non-MJS reinforcement area to supplement the stratum reinforcement, and precipitation wells are set up at the four corners of the excavated full section; 2) Mark the excavation contour by measuring and setting out, break down the underground continuous wall, and remove the steel bars; 3) Excavate the soil of the entire section, divide the entire section into at least 4 small sections, and excavate each small section in turn. After the previous small section is excavated through, the next small section will be excavated until all small sections are completed; 4) While excavating the small section, carry out the initial support structure construction of the excavated channel to achieve support as excavation progresses; 5) After the initial support structure of the excavated channel is completed, the steel arch frame is removed and then the waterproof layer is constructed; 6) After the waterproof layer construction is completed, the secondary lining structure construction shall be carried out.

2. A method for constructing a large-section underground passage for protecting a building or structure according to claim 1, characterized in that: In step 1), the pipe rack uses an advanced large pipe rack with a diameter of at least 108 mm.

3. A method for constructing a large-section underground passage for protecting a building or structure according to claim 1, characterized in that: In step 1), an electric power tunnel is arranged below the channel, and a water bag is arranged in the electric power tunnel to prevent the electric power tunnel from floating up.

4. A method for constructing a large-section underground passage for protecting a building or structure according to claim 1, characterized in that: In step 2), a water-grinding drill is used to break the underground continuous wall. Before breaking the underground continuous wall, the breaking range needs to be sprayed on the wall surface with spray paint, and then the wall surface within the breaking range is drilled with a water-grinding drill to separate it.

5. A method for constructing a large-section underground passage for protecting a building or structure according to claim 1, characterized in that: In step 3), during the excavation of the full-section soil, settlement monitoring is required for the underground passages, ground structures, underground pipelines, rainwater culverts and power tunnels to observe whether their settlement data meet the design specification requirements.

6. A method for constructing a large-section underground passage for protecting a building or structure according to claim 1, characterized in that: In step 3), before excavation, a working platform is set up near the excavation section in the foundation pit. During excavation, a construction method combining pneumatic picks, shovels and hand picks is adopted. The surrounding soil is excavated first, and the central soil is reserved as a temporary working platform; the excavated slag is excavated by a combination of manual and mechanical methods, and transported to the soil collection box on the ground through a bucket; the excavation size of each time is controlled to be 600-800mm.

7. A method for constructing a large-section underground passage for protecting a building or structure according to claim 1, characterized in that: In step 3), there are 4 small sections, and the excavation sequence of the 4 small sections is upper right, lower right, upper left, and lower left.

8. A method for constructing a large-section underground passage for protecting a building or structure according to claim 1, characterized in that: In step 4), the steps of constructing the primary support structure of the excavated channel are as follows: install a steel arch frame to form a closed ring, connect the steel arch frame with high-strength bolts, set a central column and a cross brace on the steel arch frame, form a field-shaped structure between the central column and the cross brace, lay steel mesh on the inside and outside of the steel arch frame and weld connecting bars, pre-embed the grouting pipe and then spray concrete to form the primary support structure of the excavated channel.

9. A method for constructing a large-section underground passage for protecting a building or structure according to claim 8, characterized in that: In step 5), when dismantling the steel arch frame, first dismantle all the cross braces of the steel arch frame, and then dismantle the central columns one by one; the waterproof layer adopts PVC waterproof board.

10. A method for constructing a large-section underground passage for protecting a building or structure according to claim 1, characterized in that: In step 6), the secondary lining structure is constructed using cast-in-place reinforced concrete, with the channel bottom plate being constructed first, and then the side walls and top plate being cast at one time.

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