Underwater soft soil foundation concealed tunnel and construction method thereof

Abstract

An underwater soft soil foundation concealed tunnel and a construction method thereof, the tunnel comprising: two vertical shafts arranged on the bank sides of two banks in a water area to be crossed by the tunnel, a side wall of each vertical shaft being provided with a door hole matched with a prefabricated tunnel pipe segment, and a notch being arranged at the upper or lower center or the left or right center of the inner edge of the door hole; two rows of fender piles arranged in parallel and crossing the water area to be crossed, the two ends of the fender piles corresponding to the bank sides of the vertical shafts; the distance between the two rows of fender piles being greater than the diameter of the tunnel, and the length of the fender piles being greater than the length of the tunnel in the water area to be crossed; two guide cables being respectively pulled horizontally through the notches arranged at the upper or lower center or the left or right center of the door hole of the side wall of each vertical shaft and anchored to the two vertical shafts; the tunnel being composed of a plurality of prefabricated tunnel pipe segments connected in series; a connecting ring being arranged on the upper or lower or left or right outer edge of the cross section of each prefabricated tunnel pipe segment; the connecting ring on the prefabricated tunnel pipe segment being arranged on the two guide cables; and a solidified mixture being filled between the two rows of fender piles and on the tunnel.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of tunnel engineering, in particular to a concealed tunnel in underwater soft soil foundation and a construction method thereof. BACKGROUND

[0002] The existing tunnel construction methods in soil or rock layers without groundwater include open-cut method and underground excavation method, the existing tunnel construction methods in soil layers with groundwater include shield method and pipe jacking method, and the existing underwater tunnel construction methods include pipe sinking method and steel guide cable positioning pipe jacking method.

[0003] For example, the “underwater inverted arch suspended tunnel using steel guide cable positioning and construction method” disclosed in Chinese patent application No. 201910481081.4 and the “underwater inverted arch suspended double tunnel using steel guide cable positioning and construction method” disclosed in Chinese patent application No. 201910481071.0 adopt the method of setting guide cables in water and jacking tunnel pipe sections in water.

[0004] The existing pipe sinking tunnel technology involves underwater excavation of a foundation trench before sinking the tunnel pipe sections and conventional soil backfilling of the foundation trench after sinking the tunnel pipe sections, and a small number of technologies involve conventional soil covering of the tunnel pipe sections after sinking the tunnel pipe sections. However, the soil backfilling and covering in the pipe sinking tunnel technology has low strength, and the covered soil has low strength and cannot be thick and heavy, so the protection against accidental loads from the sides and above the tunnel is weak. The connection between the tunnel pipe sections is underwater, which is technically difficult and more costly. SUMMARY

[0005] The present application aims to provide a concealed tunnel in underwater soft soil foundation and a construction method thereof, which is used for fast and economical construction of underwater tunnels in rivers, lakes and seas, and provides reliable concealment protection measures for tunnels.

[0006] To achieve the above-mentioned purpose, the technical solution of the present application is as follows:

[0007] A concealed tunnel in underwater soft soil foundation comprises:

[0008] Two vertical shafts are arranged on the shore side of the two banks in the water area to be crossed, and weakly permeable soil or impermeable soil with a length of more than 30 m is reserved between the vertical shafts and the shore side of the water area to be crossed, and the bottom of the vertical shaft is higher than the water bottom foundation; the side wall of the two vertical shafts is processed with door holes matched with the prefabricated tunnel pipe sections, and the upper and lower or left and right center of the inner edge of the door holes is provided with a notch;

[0009] Two rows of fender piles are arranged in parallel and across the water area to be crossed, and are driven into the soft soil of the water bottom foundation, and the two ends of the fender piles correspond to the shore side of the vertical shaft; the distance between the two rows of fender piles is greater than the diameter of the tunnel, and the length of the fender piles is greater than the length of the tunnel in the water area to be crossed;

[0010] Two guide cables, respectively passing through the upper and lower or left and right central gaps provided in the side wall door hole of the two shafts, and the two ends of the guide cables are anchored in the two shafts;

[0011] Tunnel, composed of a plurality of precast tunnel pipe sections connected in series; the upper and lower or left and right connecting rings are respectively provided on the outer edge of the cross section of each precast tunnel pipe section; the connecting rings provided on the upper and lower or left and right of each precast tunnel pipe section are arranged on the two guide cables; the two rows of fender piles are filled with solidified mixture.

[0012] Preferably, the fender piles are connected to each other to form a chain pile, or are connected to each other to form a chain pile by a plurality of concrete pipe piles with a lock and a matching section steel.

[0013] Preferably, the solidified mixture includes: sand and / or gravel, which accounts for more than 60% of the volume ratio; inorganic coagulation material, which accounts for less than 40% of the volume ratio; wherein the particle size of the sand and / or gravel is 0.3-15mm.

[0014] Preferably, the inorganic coagulation material includes blast furnace slag or steel slag, the particle size of the blast furnace slag is 0.3-5mm, and the particle size of the steel slag is 3-15mm.

[0015] The construction method of the underwater soft soil foundation covered tunnel of the application comprises the following steps:

[0016] 1) Two shafts are made as driving shaft and receiving shaft respectively, a side wall of the driving shaft and the receiving shaft is processed with a door hole matched with the precast tunnel pipe section, a gap is provided in the upper and lower or left and right center of the door hole, and a temporary sealing structure is provided for the door hole and the gap;

[0017] 2) The driving shaft and the receiving shaft are respectively arranged on the shore side of the two banks in the water area to be crossed by the tunnel, and a weak water permeable soil or impermeable soil with a length of more than 30m is reserved between the shaft and the shore of the water area to be crossed, and the bottom of the shaft is higher than the water bottom bed; two rows of fender piles are sunk in the soft soil foundation along the axial direction of the tunnel to be made; the soil layer between the two rows of fender piles is removed, and the tunnel bed surface is leveled; the top of the two rows of fender piles is 5-20m higher than the surface of the tunnel bed;

[0018] 3) The gap in the door hole of the driving shaft and the receiving shaft is opened, two guide cables with connectors are respectively arranged in the gap of the door hole of the driving shaft and the receiving shaft, and directional drilling is performed to cross the weak water permeable soil or impermeable soil layer of the two banks to the middle of the water area to be crossed, and the two guide cables of the driving shaft and the receiving shaft are connected into one; the two guide cables are tensioned, and the two guide cables are arranged in parallel on the upper and lower or left and right of the door hole of the driving shaft and the receiving shaft, and the two ends of the guide cables are anchored in the two shafts;

[0019] 4) send the first section of prefabricated tunnel pipe into the driving well, the prefabricated tunnel pipe is steel pipe or steel pipe concrete pipe, which is half ring body of installation connection ring on the cross section up and down or left and right; send the first section of prefabricated tunnel pipe to the door hole, and connect the other half ring body of connection ring with the half ring body of connection ring on the prefabricated tunnel pipe to form a circular ring after hanging the other half ring body of connection ring on the guide cable; move the first section of prefabricated tunnel pipe to the receiving well direction through the door hole by pushing the first section of prefabricated tunnel pipe through the jacking device, and reserve part of the first section of prefabricated tunnel pipe in the driving well; the front end of the first section of prefabricated tunnel pipe is provided with a closed end plate;

[0020] 5) send the second section of prefabricated tunnel pipe into the driving well, connect the other half ring body of connection ring with the half ring body of connection ring on the second prefabricated tunnel pipe to form a circular ring after hanging the other half ring body of connection ring on the guide cable; the front end of the second section of prefabricated tunnel pipe is connected with the first section of prefabricated tunnel pipe as a whole, and the second section of prefabricated tunnel pipe is pushed through the door hole to the receiving well direction by pushing the second section of prefabricated tunnel pipe through the jacking device, and part of the second section of prefabricated tunnel pipe is reserved in the driving well;

[0021] 6) repeat step 5) to send N sections of prefabricated tunnel pipe into the driving well in turn, connect the previous section of prefabricated tunnel pipe and push through the door hole until the first section of prefabricated tunnel pipe reaches the receiving well and passes through the receiving well door hole; all the prefabricated tunnel pipes connected through are sunk between the two rows of support piles, and the top surface of the prefabricated tunnel pipe is lower than the top of the two rows of support piles; remove the closed end plate at the head of the first section of prefabricated tunnel pipe and connect with the receiving well;

[0022] 7) blow the solidified mixture between the two rows of support piles and the tunnel, the top surface of the solidified mixture corresponds to the top of the double-row chain piles, and is higher than the top surface of the tunnel, and after the solidified mixture is solidified, an underground soft soil foundation is formed to build a buried tunnel.

[0023] Preferably, the diameter or maximum side length of the concrete pipe pile is ≥800mm, and the maximum side length of the steel pile section is ≥800mm.

[0024] Preferably, the horizontal distance between the two rows of support piles is 2-20m, the top ends of the support piles have the same elevation and are higher than the tunnel bed surface by ≥5m.

[0025] Preferably, the diameter of the guide cable is 100-1000mm.

[0026] Preferably, the guide cable is a composite cable composed of a chemical fiber inner core and a steel cable rope wound outside, and the average mass density of the composite cable differs from the mass density of water by not more than ±5%.

[0027] Preferably, counterweights are arranged in the prefabricated tunnel pipe section that has been penetrated to maintain the buoyancy less than the gravity, and after the solidification of the solidification mixture, the prefabricated tunnel pipe section is built into the underwater soft soil foundation to form a buried tunnel, and then the counterweights arranged in the tunnel are gradually removed to construct the facilities in the tunnel and maintain the buoyancy less than the gravity.

[0028] Preferably, the particle size of the solidification mixture is 3-15 mm; wherein the particle size of the sand and / or gravel is 0.3-15 mm, and the volume ratio is greater than 60%; the particle size of the inorganic coagulation material blast furnace slag is 0.3-5 mm, and the particle size of the steel slag is 3-15 mm, and the volume ratio is less than 40%.

[0029] Preferably, the maximum lateral deviation of the guide cable in the water area is less than 2 times the diameter of the guide cable, and the maximum lateral deviation of the guide cable in the soil area of the shore is less than 0.5 times the diameter of the guide cable.

[0030] Preferably, in step 5), the prefabricated tunnel pipe section is pushed through the door hole to the receiving well direction by the jacking device, and at the same time, the expansion sealing material is injected into the soil layer of the shore within one tunnel radius range outside the prefabricated tunnel pipe section at 2-5 times the hydrostatic pressure value to prevent water seepage to the driving well.

[0031] Preferably, the expansion sealing material comprises polyurethane foam material.

[0032] The beneficial effects of the present application are as follows:

[0033] Compared with the "underwater inverted arch-shaped suspended tunnel using steel guide cable positioning and construction method" disclosed in Chinese patent application No. 201910481081.4 and the "underwater inverted arch-shaped suspended double tunnel using steel guide cable positioning and construction method" disclosed in Chinese patent application No. 201910481071.0, the present application adopts the directional jacking and connecting technology of simultaneously arranging guide cables in the soft soil layer and the water to accurately position the tunnel in the soft soil layer and the water; adopts the waterproof leakage prevention technology of simultaneously jacking the tunnel pipe section in the soft soil layer and the water to implement the water-free operation in the shore side caisson under the water surface; adopts the two-side interlocking row piles and the blowing of the solidification mixture with certain late strength between the two-side interlocking row piles and the tunnel to provide shielding protection to the tunnel against external mechanical loads and actions, and in addition, the control of the weak alkaline material of the solidification mixture has the corrosion protection effect on the shielded tunnel steel.

[0034] The existing immersed tunnel technology does not involve two-side chained row piles protection, the backfill and covered soil has low strength, the covered soil has low strength and cannot be thick and heavy, and therefore the protection against unexpected load from the two sides and above the tunnel is weak. The application adopts the two-side chained row piles and the dredged and solidified mixture between the two-side chained row piles and the tunnel, and the control of the solidified mixture with certain strength to mask and protect the tunnel. In addition, the solidified mixture uses the weak alkaline inorganic binder such as blast furnace slag and steel slag, which has the corrosion protection effect on the masked tunnel steel.

[0035] The existing pipe jacking tunnel technology only jacks the tunnel pipe section in the soft soil layer. The application adopts the directional jacking and connecting technology of setting the guide cable in the soft soil layer and water, and can implement the jacking of the tunnel pipe section in the soft soil layer and water. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 It is a structural schematic diagram of the embodiment of the application;

[0037] Figure 2 It is a sectional view of the embodiment of the application;

[0038] Figure 3 It is a sectional view of the shaft in the embodiment of the application;

[0039] Figure 4 It is Figure 3 the enlarged schematic diagram of A part;

[0040] Figure 5 It is the schematic diagram of the temporary closure of the shaft door in the embodiment of the application. DETAILED DESCRIPTION

[0041] Referring to Figures 1-4 , the underwater soft soil foundation masked tunnel comprises:

[0042] Two shafts 1 are respectively arranged on the bank side of the two banks in the water area 100 to be crossed, and the weak water permeable soil or impermeable soil 200 with a length greater than 30m is reserved between the shaft and the bank of the water area 100 to be crossed, and the bottom of the shaft 1 is higher than the water bottom bed; the side wall of the two shafts 1 for the precast tunnel pipe section to pass through is processed with the door hole 101 matched with the precast tunnel pipe section, and the upper and lower or left and right center of the inner edge of the door hole 101 (taking the shaft 1 as an example, the same below) is provided with the notch 102;

[0043] Two rows of fender piles 2 are arranged in parallel and cross the water area 100 to be crossed, and are driven into the soft soil of the water bottom bed 300, and the two ends of the fender piles 2 correspond to the bank side of the shaft; the distance between the two rows of fender piles 2 is greater than the diameter of the tunnel, and the length of the fender piles 2 is greater than the length of the tunnel in the water area 100 to be crossed;

[0044] Two guide cables 3 are respectively passed through the notches 102 set at the upper and lower or left and right center of the door openings 101 on one side wall of the two vertical shafts 1, and the two ends of the guide cables 3 are respectively anchored to the two vertical shafts 1;

[0045] The tunnel 4 is composed of several prefabricated tunnel pipe sections 41 connected in series; connecting rings 5 ​​are respectively provided on the upper and lower or left and right outer edges of the cross section of each prefabricated tunnel pipe section 41; the connecting rings 5 ​​provided on the upper and lower or left and right of each prefabricated tunnel pipe section 41 are passed through the two guide cables 3; and the space between the two rows of retaining piles 2 and the tunnel 4 are filled with solidified mixture 6.

[0046] Preferably, the retaining piles 2 are chain piles formed by steel sheet piles with locking buckles that are interlocked and connected to each other, or chain piles formed by several concrete pipe piles with locking buckles and matching steel sections that are connected to each other.

[0047] Preferably, the solidified mixture 6 comprises: sand and / or gravel, which accounts for more than 60% by volume; and inorganic coagulant material, which accounts for less than 40% by volume; wherein the particle size of the sand and / or gravel is 0.3-15 mm.

[0048] Preferably, the inorganic coagulant material includes blast furnace slag or steel slag, the particle size of the blast furnace slag is 0.3 to 5 mm, and the particle size of the steel slag is 3 to 15 mm.

[0049] The method for constructing a shielded tunnel on an underwater soft soil foundation according to the present invention comprises the following steps:

[0050] 1) Make two vertical shafts, one as the driving shaft and the other as the receiving shaft. The side walls of the driving shaft and the receiving shaft for the prefabricated tunnel pipe section to pass through are machined with door openings that match the prefabricated tunnel pipe section. Notches are set at the top and bottom or left and right center of the door openings, and temporary closing structures are made for the above-mentioned door openings and notches. Figure 5 ;

[0051] 2) The driving shaft and receiving shaft are respectively set up on the banks of the water area to be crossed by the tunnel; a weakly permeable or impermeable soil of more than 30m is retained between the vertical shaft and the bank of the water area to be crossed, and the bottom of the vertical shaft is higher than the underwater subgrade; two rows of parallel retaining piles are sunk into the soft soil foundation along the axis of the tunnel to be constructed; the overburden between the two rows of retaining piles is removed to form a smooth tunnel subgrade; the tops of the two rows of retaining piles are 5m to 20m higher than the surface of the tunnel subgrade;

[0052] 3) opening the gap on the door hole of the driving well and the receiving well, respectively threading each two jointed guide cables through the gap on the door hole of the driving well and the receiving well, and directional drilling through the weak water-permeable soil or impermeable soil on both sides of the bank to the middle of the water area to be crossed, connecting the two guide cables on the driving well and the receiving well into one; tensioning the two guide cables to make them parallel to each other on the upper and lower or left and right of the door hole of the driving well and the receiving well, and anchoring the two ends of the guide cables to the two vertical wells respectively;

[0053] 4) sending the first segment of the prefabricated tunnel pipe into the driving well, the prefabricated tunnel pipe being a steel pipe or a steel pipe concrete pipe, and the cross section being a half ring body of the installation connection ring in 180 degrees on the upper and lower or left and right; sending the first segment of the prefabricated tunnel pipe to the door hole, hanging the other half ring body of the connection ring on the guide cable to connect with the half ring body of the connection ring on the prefabricated tunnel pipe to form a circular ring; pushing the first segment of the prefabricated tunnel pipe through the door hole to the receiving well direction by the jacking device, and reserving part of the first segment of the prefabricated tunnel pipe in the driving well; the front end of the first segment of the prefabricated tunnel pipe is provided with a closed end plate;

[0054] 5) sending the second segment of the prefabricated tunnel pipe into the driving well, hanging the other half ring body of the connection ring on the guide cable to connect with the half ring body of the connection ring on the second prefabricated tunnel pipe to form a circular ring; the front end of the second segment of the prefabricated tunnel pipe is connected with the first segment of the prefabricated tunnel pipe into one, and the second segment of the prefabricated tunnel pipe is pushed through the door hole to the receiving well direction by the jacking device, and part of the second segment of the prefabricated tunnel pipe is reserved in the driving well;

[0055] 6) repeating step 5) to send N segments of the prefabricated tunnel pipe into the driving well in turn, connect the previous segment of the prefabricated tunnel pipe and push through the door hole until the first segment of the prefabricated tunnel pipe reaches the receiving well and passes through the door hole of the receiving well; all the prefabricated tunnel pipes connected through are sunk between the two rows of supporting piles, and the top surface of the prefabricated tunnel pipe is lower than the top of the two rows of supporting piles; the closed end plate of the first segment of the prefabricated tunnel pipe is removed and connected with the receiving well;

[0056] 7) blowing and filling the coagulation mixture between the two rows of supporting piles and the tunnel, the top surface of the coagulation mixture corresponding to the top of the double-row interlocking piles and higher than the top surface of the tunnel, and the underwater soft soil foundation is built into a buried tunnel after the coagulation mixture is coagulated.

[0057] Preferably, the diameter or maximum side length of the concrete pipe pile is ≥800mm, and the maximum side length of the steel pile cross section is ≥800mm.

[0058] Preferably, the horizontal distance between the two rows of supporting piles is 2-20m, the top ends of the supporting piles are at the same height and higher than the surface of the tunnel bed by ≥5m.

[0059] Preferably, the diameter of the guide cable is 100-1000mm.

[0060] Preferably, the guide cable is a composite cable consisting of a synthetic fiber inner core and an outer steel cable, and the average mass density of the composite cable differs from the mass density of water by no more than ±5%.

[0061] Preferably, weights are arranged in the prefabricated tunnel pipe section that has been penetrated to maintain the buoyancy less than the gravity, and after the solidification of the solidification mixture, the prefabricated tunnel pipe section is built into the buried tunnel in the soft soil foundation, and then the weights arranged in the tunnel are gradually removed to construct the facilities in the tunnel and maintain the buoyancy less than the gravity.

[0062] Preferably, the particle size of the solidification mixture is 3-15 mm, the particle size of the sand and / or gravel is 0.3-15 mm, the volume ratio of the sand and / or gravel is greater than 60%, the particle size of the inorganic coagulation material blast furnace slag is 0.3-5 mm, the particle size of the steel slag is 3-15 mm, and the volume ratio of the steel slag is less than 40%.

[0063] Preferably, the maximum lateral deviation of the guide cable in the water area is less than 2 times the diameter of the guide cable, and the maximum lateral deviation of the guide cable in the soil area of the shore is less than 0.5 times the diameter of the guide cable.

[0064] Preferably, in step 5), the prefabricated tunnel pipe section is pushed through the door hole by the jacking device to move towards the receiving well, and the expansion sealing material is injected into the soil layer of the shore within a range of one tunnel radius outside the prefabricated tunnel pipe section at a value of 2-5 times the hydrostatic pressure to prevent water seepage towards the driving well.

[0065] Preferably, the expansion sealing material includes polyurethane foam material.

[0066] Embodiment

[0067] A method for constructing a buried tunnel in a soft soil foundation, comprising the following steps:

[0068] 1) From the driving well shore side to the receiving well shore side of the water area to be crossed, two rows of parallel surrounding piles are sunk into the soft soil foundation by a four-tower crawling pile driving platform, which are composed of interlocked concrete pipe piles with lock and steel piles with H-shaped cross section interlocking with each other; the length of the concrete pipe pile is 40 m, the length of the steel pile is 32 m, the cross-sectional diameter of the concrete pipe pile is 1200 mm, the web length of the H-shaped cross section of the steel pile is 2000 mm, and the flange plate length is 200 mm; the concrete pipe piles or steel piles are initially driven into the soft soil foundation by the double towers of the pile driving platform close to the receiving well shore side and the pile hammers hung thereon, and the pile top is 5 m above the average water level, corresponding to the height of the platform bottom; the concrete pipe piles or steel piles are re-driven to the required depth by the double towers of the pile driving platform close to the driving well shore side and the pile hammers and pile delivery rods hung thereon; four crawling feet are arranged on each side of the pile driving platform, a total of eight crawling feet; the eight crawling feet are temporarily fixed above the initially driven concrete pipe piles and steel piles during pile driving, and move away from the driving well shore side during pile driving interval; the horizontal distance between the two surrounding pile axes is 16 m; the top ends of the concrete pipe piles or steel piles are at the same elevation, all 15 m below the average water level, and 7 m above the mud surface;

[0069] 2) The 6 m thick overburden layer is removed between the two rows of surrounding piles to arrange the tunnel bed; the tunnel bed elevation is 28 m below the average water level, 13 m below the top of the double rows of surrounding piles;

[0070] 3) The driving well and the receiving well with rectangular cross section are respectively arranged on the two banks of the water area to be crossed, and the distance between them is 399 m, and the length of the impermeable clay body between them is 49.5 m;

[0071] The driving well is 32.4 m high, 25.5 m long and 16 m wide; the left and right side walls, the inner side wall and the bottom plate are reinforced concrete structures with a thickness of 0.5 m, and the outer side wall is a reinforced concrete structure with a thickness of 1.0 m; the bottom plate elevation is 28.4 m below the average water level, and a circular door hole with a radius of 5.05 m is opened at a height of 5.95 m above the surface of the bottom plate in the center of the inner side wall; a notch is opened directly below the circular door hole, the lower half of the notch is a semicircle with a diameter of 0.52 m, and the upper half is a rectangle with a width of 0.52 m and a height of 0.21 m, and the notch is connected with the door hole; a notch is opened directly above the circular door hole, the upper half of the notch is a semicircle with a diameter of 0.52 m, and the lower half is a rectangle with a width of 0.52 m and a height of 0.21 m, and the notch is connected with the door hole; the notch and the door hole are temporarily closed;

[0072] The receiving well is 32.4 mm high, 16 m long and 16 m wide; the left and right side walls, the inner side wall and the bottom plate are made of reinforced concrete with a thickness of 0.5 m, and the outer side wall is made of reinforced concrete with a thickness of 1.0 m; the bottom plate is at an elevation of 28.4 m below the average water level, and a circular door hole 23 with a radius of 5.05 m is formed in the center of the inner side wall at a height of 5.95 m above the surface of the bottom plate; a notch is formed directly below the circular door hole, the lower half of the notch is a semicircle with a diameter of 0.52 m, the upper half is a rectangle with a width of 0.52 m and a height of 0.21 m, and the notch is in communication with the circular door hole; a notch is formed directly above the circular door hole, the upper half of the notch is a semicircle with a diameter of 0.52 m, and the lower half is a rectangle with a width of 0.52 m and a height of 0.21 m, and the notch is in communication with the circular door hole; the notch and the door hole are temporarily closed;

[0073] 4) Open the notches above and below the door hole of the driving well, respectively push out two guide cables with joints towards the receiving well, and pass through the notches and the impermeable clay body;

[0074] Open the notches above and below the door hole of the receiving well, respectively push out two guide cables with joints towards the driving well, and pass through the notches and the impermeable clay body;

[0075] Connect the joints of the guide cables with joints from the driving well and the receiving well in the water area to form an integral structure; stretch the two guide cables horizontally and then anchor them in the two vertical wells; the diameter of the guide cable is 0.4 m;

[0076] 5) The prefabricated tunnel pipe section is a steel pipe or a steel pipe-concrete pipe, the central axis of each pipe section is a straight line, the outer diameter of the cross section of each pipe section is 10 m, and the length of the central axis of each pipe section is 20 m;

[0077] 6) Place the first prefabricated tunnel pipe section in the driving well, and fix one half of the two connecting rings on the upper and lower parts of the prefabricated tunnel pipe section;

[0078] 7) Set a head closing end plate at the end of the first prefabricated tunnel pipe section close to the receiving well, then use the tunnel jacking device in the driving well to push the first prefabricated tunnel pipe section through the door hole of the driving well and move it towards the receiving well, the connecting ring passes through the notch of the door hole accordingly, and counterweights are arranged in the first prefabricated tunnel pipe section to maintain a buoyancy slightly smaller than the gravity;

[0079] 8) Put the second prefabricated tunnel pipe section in the driving well, and fix the connecting ring on the upper and lower part of the second prefabricated tunnel pipe section; use bolt connection or welding method to connect the second prefabricated tunnel pipe section with the first prefabricated tunnel pipe section adjacent to the receiving well, and then use the jacking device in the driving well to push the second prefabricated tunnel pipe section to move to the receiving well direction; set counterweight in the first prefabricated tunnel pipe section to maintain the buoyancy slightly less than the gravity; at the same time, inject polyurethane foam expansion sealing material into the soil layer of the bank within one tunnel radius outside the prefabricated tunnel pipe section at 4 times the hydrostatic pressure value;

[0080] 9) Repeat the above steps 6) to 8), and install the twentieth prefabricated tunnel pipe section, and push all the connected prefabricated tunnel pipe sections to the predetermined position, wherein the head of the first prefabricated tunnel pipe section reaches the receiving well and passes through the receiving well door; all the connected prefabricated tunnel pipe sections are between the two rows of support piles that have been sunk, and the height is lower than the top height of the two rows of support piles;

[0081] 10) Remove the head of the first prefabricated tunnel pipe section and connect it with the receiving well; remove the jacking device of the driving well, and connect the twentieth prefabricated tunnel pipe section close to the driving well direction with the driving well; in this way, the connected tunnel is connected with the driving well and the receiving well at both ends to form two parallel through bodies;

[0082] 11) Blow fill the mixed material composed of sand and condensed particles such as blast furnace slag and steel slag between the two rows of support piles composed of concrete pipe piles with lock or steel piles with interlocking sections and the tunnel; the top elevation of the mixed material corresponds to the top of the double-row support piles, and is higher than the top of the tunnel; after the mixed material is solidified, it is built into a buried tunnel in the underwater soft soil foundation; then gradually remove the counterweight set in the tunnel, construct the tunnel facilities, and maintain the buoyancy slightly less than the gravity.

Claims

1. A shielded tunnel on an underwater soft soil foundation, characterized in that: include: Two vertical shafts are respectively set up on the banks of the water area to be crossed by the tunnel, with weakly permeable soil or impermeable soil of more than 30m left between the vertical shafts and the banks of the water area to be crossed, and the bottoms of the vertical shafts are higher than the bottom bed; one side wall of the two vertical shafts for the prefabricated tunnel segments to pass through is machined with a door opening that matches the prefabricated tunnel segments, and a notch is set at the upper and lower or left and right center of the inner edge of the door opening; Two rows of retaining piles are arranged in parallel, spanning the water area to be traversed, and driven into the soft soil of the underwater base bed, with the ends of the retaining piles corresponding to the banks of the vertical shaft; the spacing between the two rows of retaining piles is greater than the diameter of the tunnel, and the length of the two rows of retaining piles is greater than the length of the tunnel in the water area to be traversed; the retaining piles are chain piles formed by interlocking steel sheet piles with locking buckles, or chain piles formed by connecting a number of concrete pipe piles with locking buckles and matching steel sections; Two guide cables are respectively passed through the notches at the upper and lower or left and right centers of the door openings on one side of the two vertical shafts and stretched horizontally, and the two ends of the guide cables are respectively anchored to the two vertical shafts; The tunnel is composed of several sections of prefabricated tunnel pipe segments connected in series; connecting rings are respectively provided on the upper and lower or left and right outer edges of the cross section of each prefabricated tunnel pipe segment; the connecting rings provided on the upper and lower or left and right of each prefabricated tunnel pipe segment are passed through the two guide cables; and solidified mixture is filled between the two rows of retaining piles and on the tunnel.

2. The shielded tunnel on underwater soft soil foundation according to claim 1, characterized in that: The solidified mixture comprises: sand and / or gravel, which accounts for more than 60% by volume; and inorganic coagulant material, which accounts for less than 40% by volume; wherein the particle size of the sand and / or gravel is 0.3-15 mm.

3. The shielded tunnel on underwater soft soil foundation according to claim 2, characterized in that: The inorganic coagulant material includes blast furnace slag or steel slag, the particle size of the blast furnace slag is 0.3-5 mm, and the particle size of the steel slag is 3-15 mm.

4. The method for constructing a shielded tunnel on an underwater soft soil foundation according to any one of claims 1 to 3, wherein: The steps include: 1) Two vertical shafts are constructed, serving as the driving shaft and the receiving shaft respectively. Door openings matching the prefabricated tunnel segments are machined on one side wall of the driving shaft and the receiving shaft for the prefabricated tunnel segments to pass through. Notches are set at the top and bottom or left and right center of the door openings, and temporary sealing structures are constructed for the above-mentioned door openings and notches. 2) The driving shaft and receiving shaft are respectively located on the banks of the water area to be crossed by the tunnel, and a weakly permeable or impermeable soil mass of more than 30m is retained between the shaft and the bank of the water area to be crossed, and the bottom of the shaft is higher than the bottom bed; Sink two parallel rows of retaining piles into the soft soil of the underwater subgrade along the axial direction of the tunnel to be constructed; remove the overburden between the two rows of retaining piles to create a smooth tunnel subgrade; the tops of the two rows of retaining piles should be 5m to 20m above the tunnel subgrade surface; 3) Open the gaps in the doorways of the driving well and the receiving well, pass two guide cables with joints through the gaps in the doorways of the driving well and the receiving well, and directional drill through the weakly permeable soil or impermeable soil layer on both sides of the bank to the middle of the water area to be crossed, and connect the two guide cables on the driving well and the receiving well into one; tension the two guide cables so that they are arranged parallel to the upper and lower or left and right of the doorways of the driving well and the receiving well, and anchor the two ends of the guide cables to the two vertical shafts respectively; 4) Deliver the first prefabricated tunnel segment into the drive shaft. The prefabricated tunnel segment is a steel tube or steel-concrete tube with a cross-section that is 180 degrees vertically or horizontally. Install half of the connecting ring. Deliver the first prefabricated tunnel segment to the portal. Hang the other half of the connecting ring on the guide cable and connect it to the other half of the connecting ring on the prefabricated tunnel segment to form a circular ring. Use the jacking device to push the first prefabricated tunnel segment through the portal toward the receiving shaft, leaving a portion of the first prefabricated tunnel segment in the drive shaft. Install a closed end plate at the front end of the first prefabricated tunnel segment. 5) The second prefabricated tunnel segment is placed into the driving shaft. The other half of the connecting ring is hung on the guide cable and connected to the other half of the connecting ring on the second prefabricated tunnel segment to form a circular ring. The front end of the second prefabricated tunnel segment is connected to the first prefabricated tunnel segment as a whole. The second prefabricated tunnel segment is pushed through the doorway toward the receiving shaft by the jacking device, and a portion of the second prefabricated tunnel segment is left in the driving shaft. 6) Repeat step 5) to sequentially feed N precast tunnel segments into the drive shaft, connect them to the previous precast tunnel segment, and then push them through the portal until the first precast tunnel segment reaches the receiving shaft and passes through the portal. All precast tunnel segments that are connected through the shaft are sunk between the two rows of retaining piles, and the top surface of the precast tunnel segment is lower than the top of the two rows of retaining piles. Remove the head sealing end plate of the first section of prefabricated tunnel pipe segment and connect it to the receiving shaft; 7) Fill the gap between the two rows of retaining piles and the tunnel with a solidifying mixture. The top elevation of the solidifying mixture corresponds to the top of the double-row interlocking piles and is higher than the top surface of the tunnel. Once the solidifying mixture solidifies, a shielded tunnel in an underwater soft soil foundation is constructed.

5. The method for constructing a shielded tunnel on an underwater soft soil foundation according to claim 4, wherein: The diameter or maximum side length of the concrete pipe pile is ≥800mm, and the maximum side length of the steel pile section is ≥800mm.

6. The method for constructing a shielded tunnel on an underwater soft soil foundation according to claim 4, wherein: The horizontal spacing between two rows of retaining piles is 2~20m, and the top elevations of the retaining piles are consistent and ≥5m above the tunnel bed surface.

7. The method for constructing a shielded tunnel on an underwater soft soil foundation according to claim 4, wherein: The guide cable has a diameter of 100-1000 mm.

8. The method for constructing a shielded tunnel on an underwater soft soil foundation according to claim 4, wherein: The guide cable is a composite cable consisting of a chemical fiber inner core and a steel cable wrapped around the outer side, and the average mass density thereof differs from the mass density of water by no more than ±5%.

9. The method for constructing a shielded tunnel on an underwater soft soil foundation according to claim 4, wherein: Counterweights are set in the prefabricated tunnel sections that have been penetrated to maintain the buoyancy less than the gravity. After the setting mixture solidifies, a shielded tunnel is built in the underwater soft soil foundation. The counterweights set in the tunnel are then gradually removed, and the facilities in the tunnel are constructed, while maintaining the buoyancy less than the gravity.

10. The method for constructing a shielded tunnel on an underwater soft soil foundation according to claim 4, wherein: The particle size of the solidified mixture is 0.3~15mm; among them, the particle size of sand and / or gravel is 0.3~15mm, and the volume ratio is greater than 60%; the particle size of the inorganic coagulant blast furnace slag is 0.3~5mm, and the particle size of the steel slag is 3~15mm, which accounts for less than 40% of the volume ratio.

11. The method for constructing a shielded tunnel on an underwater soft soil foundation according to claim 4, wherein: The maximum lateral deviation of the guide cable in the controlled water area is less than 2 times the diameter of the guide cable, and the maximum lateral deviation of the guide cable in the shore soil area is less than 0.5 times the diameter of the guide cable.

12. The method for constructing a shielded tunnel on an underwater soft soil foundation according to claim 4, wherein: In step 5), the prefabricated tunnel pipe segment is pushed through the portal toward the receiving well by a jacking device, and at the same time, an expansion sealing material is injected into the bank soil layer within a radius of one times the tunnel outside the prefabricated tunnel pipe segment at a value of 2-5 times the hydrostatic pressure.

13. The method for constructing a shielded tunnel on an underwater soft soil foundation according to claim 12, wherein: The expanding sealing material includes polyurethane foam.

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