Novel supporting structure suitable for river-adjacent tunnel portal section and construction method

Abstract

The invention belongs to the technical field of tunnel portal section construction, and provides a novel supporting structure suitable for a river-adjacent tunnel portal section and a construction method to solve the technical problems that when the river-adjacent tunnel portal section is constructed at present, the stability of an adopted protection structure cannot be guaranteed, and the collapse risk exists. Comprising a continuous supporting unit, two rows of first anti-slide piles, an extended open cut tunnel and a protection unit, the continuous supporting unit is arranged on the side, close to a river, of a tunnel portal section, the two rows of first anti-slide piles are arranged on the side, close to a slope body, of the tunnel portal section, the extended open cut tunnel is arranged between an opposite tunnel and the river, and the protection unit is arranged on the outer side of the extended open cut tunnel. Through the design that the two rows of double-pipe jet grouting piles are meshed in all directions, river water can be effectively isolated, and the influence of the river on a tunnel foundation is reduced; and a continuous whole is formed by the second anti-slide piles and the waterproof curtain, so that the stability of a tunnel slope can be effectively improved, and the strength of a tunnel foundation is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel portal construction, and in particular relates to a novel support structure and a construction method suitable for a riverside tunnel portal. Background Art

[0002] The construction of the tunnel portal section is often a difficult and important point in tunnel construction because of obstacles at the portal or the fact that it is close to the river cliff and cannot meet the construction requirements. The construction of the tunnel portal section combines unfavorable factors such as shallow burial depth, poor surrounding rock, and complex force structure. If not handled properly, landslides are very likely to occur. The terrain of the tunnel portal is complex, the side slopes are steep, and there are a large number of dangerous rocks and rocks on the top of the portal. The tunnel is close to the river, and the surrounding rock of the tunnel is greatly affected by the water quality and water level of the river. It often does not meet the basic construction requirements, resulting in difficulties in the construction of the tunnel portal section. In order to ensure the safe construction of the tunnel and the subsequent safe operation of the tunnel, it is necessary to support the dangerous construction environment of the tunnel portal section near the river.

[0003] At present, the tunnel entrance protection structure mostly adopts simple support of sprayed concrete. For dangerous slopes near rivers and affected by river erosion, this simple support often fails to meet safety standards. A large number of cracks often appear on the surface of the concrete support, which seriously affects the construction process of the tunnel entrance section. At the same time, the bedrock below the tunnel entrance section has been affected by river erosion for a long time, and its stability cannot be guaranteed, with the risk of collapse. Therefore, it is necessary to design a new support structure and construction method for the tunnel entrance section near the river to solve the existing tunnel entrance safety problems and potential safety hazards during operation. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide a new type of support structure and construction method suitable for the tunnel portal section of a river.

[0005] The first object of the present invention is to provide a new type of support structure suitable for the tunnel entrance section near a river, including a continuous support unit, two rows of first anti-slip piles, an extended open hole and a protection unit. The continuous support unit is arranged on the side of the tunnel entrance section close to the river, the two rows of first anti-slip piles are arranged on the side of the tunnel entrance section close to the slope, the extended open hole is arranged between the opposite tunnel and the river, and the protection unit is arranged on the outside of the extended open hole.

[0006] Preferably, the continuous support unit comprises a water-stop curtain and a row of second anti-slip piles, the water-stop curtain is arranged between the second anti-slip piles and the river, the anti-slip piles and the water-stop curtain are engaged with each other, and concrete is poured between two adjacent second anti-slip piles.

[0007] Preferably, the water-stop curtain comprises two rows of double-tube jet grouting piles, adjacent double-tube jet grouting piles are interlocked with each other, and the second anti-slip piles are interlocked with a row of double-tube jet grouting piles adjacent to each other.

[0008] Preferably, the center distance between two adjacent second anti-slip piles is 1.1 m, and the length of the second anti-slip pile is 17 m;

[0009] The center distance between two adjacent first anti-slip piles in each row is 5.2 m, and the two rows of first anti-slip piles are staggered with each other. The length of the first anti-slip piles is 6.5 m.

[0010] Preferably, the protection unit includes a concrete side wall, an open hole backfill layer, a concrete protective layer and an intercepting ditch. The concrete side wall is arranged on the side of the extended open hole outer surface close to the river, the open hole backfill layer is arranged on the extended open hole outer surface, the concrete protective layer is arranged on the top of the open hole backfill layer, the intercepting ditch is opened on the side of the top of the concrete protective layer close to the extended open hole entrance, and the bottom of the intercepting ditch extends to the open hole backfill layer.

[0011] The second object of the present invention is to provide a construction method for a novel support structure suitable for a tunnel portal section along a river, comprising the following steps:

[0012] S1. Continuous support unit construction is carried out on the side of the tunnel portal close to the river;

[0013] S2. After the construction of the continuous support unit is completed, two rows of first anti-slide piles are constructed on the side of the tunnel entrance section close to the slope;

[0014] S3, using the continuous support unit and two rows of first anti-slide piles as pile foundation, and carrying out extended open hole construction between the opposite tunnel and the underlying river;

[0015] S4. After the construction of the extended open tunnel is completed, the protection unit construction will be carried out on the outside of the extended open tunnel to complete the support construction of the Linhe Tunnel entrance section.

[0016] Preferably, step S1 comprises the following steps:

[0017] S11. Drill holes at the planned positions on the side of the tunnel entrance section close to the river to obtain two rows of lead holes;

[0018] S12, inserting a jet grouting pipe into a lead hole, and then performing high-pressure jet grouting. After the high-pressure jet grouting is completed, the jet grouting pipe is pulled out to complete the construction of a double-tube jet grouting pile;

[0019] S13, move the rotary jet pipe to the next lead hole, repeat step S12, complete the next double-tube rotary jet pile, until the two rows of double-tube rotary jet piles are completed, after the two rows of double-tube rotary jet piles are completed, the adjacent double-tube rotary jet piles are mutually engaged, and the pile overlap thickness between the adjacent double-tube rotary jet piles is not less than 25cm, to obtain a water-stop curtain;

[0020] S14, arranging a row of pile holes at a planned position on one side of the tunnel entrance section close to the river, and then constructing second anti-sliding piles in each row of pile holes. After the construction of the second anti-sliding piles in the row is completed, the second anti-sliding piles in the row are interlocked with the adjacent row of double-tube jet grouting piles.

[0021] S15. Pour concrete filler between two adjacent second anti-slide piles to form a whole between the double-tube rotary jet grouting piles, the second anti-slide piles and the concrete filler to obtain a continuous support unit.

[0022] Preferably, in step S12, the construction control parameters of high-pressure rotary jet grouting are set to: water pressure: 28-35 MPa, water supply: 80-120 L / min; air pressure: 0.7-0.8 MPa, air supply: 1-2 m3 / min; slurry pressure: 1-2 MPa, liquid supply: 80-120 L / min; lifting speed 0.08-0.1 m / min; rotation speed 5-8 r / min.

[0023] Preferably, step S3 comprises the following steps:

[0024] S31, using the continuous support unit and the two rows of first anti-slide piles as pile foundations, installing an invert formwork between the opposite tunnel and the underlying river, and pouring invert concrete to obtain an invert;

[0025] S32. After the invert construction is completed, a lining formwork is installed above the invert, and lining concrete is poured to complete the lining construction;

[0026] S33. A waterproof layer is constructed on the lining surface. After the waterproof layer is constructed, an extended open hole is formed.

[0027] Preferably, step S4 comprises the following steps:

[0028] S41. Build a concrete side wall on the side of the extended outer surface of the Mingdong near the river;

[0029] S42, use blocky pebbles and sand to backfill and counter-press the outer side of the extended open hole, between the concrete side wall and the slope to form an open hole backfill layer;

[0030] S43, install a steel mesh at the edge and upper side of the open hole backfill layer, and then spray concrete evenly onto the steel mesh to form a concrete protective layer;

[0031] S44. Build a drainage ditch on the top of the concrete protective layer near the extended open tunnel entrance, and extend the bottom of the drainage ditch to the open tunnel backfill layer to complete the construction of the protection unit, that is, complete the support construction of the Linhe Tunnel entrance section.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) The novel support structure provided by the present invention can ensure good sealing effect in all directions by means of two rows of double-tube jet grouting piles interlocking with each other in the upper, lower, left and right directions to form an outermost water-stopping curtain design, thereby effectively isolating river water and reducing the impact of the river on the tunnel foundation;

[0034] (2) The present invention interlocks a row of second anti-slip piles with the water-stop curtain and pours concrete between the second anti-slip piles, so that the second anti-slip piles and the water-stop curtain form a continuous whole. The second anti-slip piles and the water-stop curtain are jointly stressed, which can effectively improve the stability of the tunnel slope and the strength of the tunnel foundation. For complex geological conditions, it can better adapt to changes in the strata and improve the safety and reliability of the project.

[0035] (3) The present invention can effectively increase the stability of the slope by arranging two rows of staggered first anti-slip piles on the near-slope side. Specifically, the staggered layout can more evenly distribute the pressure from the slope, thereby reducing the load borne by a single first anti-slip pile. Moreover, the staggered arrangement makes the mutual support between the first anti-slip piles stronger, further enhancing the protection capability of the entire support structure and preventing the slope from sliding or collapsing.

[0036] (4) The present invention uses continuous support units and two rows of first anti-sliding piles as pile foundations, and combines extended open holes and backfill back pressure to perform comprehensive support design, which can not only reduce the impact of slope disasters such as rockfall, but also improve slope stability and ensure the safety of tunnel construction;

[0037] (5) The present invention provides the entire supporting structure with good waterproof and anti-seepage properties through the design of the concrete protective layer;

[0038] (6) The present invention ensures smooth drainage during the flood season and the safe operation of the tunnel through the design of the intercepting ditch, while also reducing the impact of rainwater on the surrounding environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a pile layout diagram of the continuous support unit in an embodiment of the present invention.

[0040] Figure 2 Schematic diagram of the structure of the anti-sliding pile reinforcement in an embodiment of the present invention;

[0041] Figure 3 for Figure 2 Middle BB section view;

[0042] Figure 4 for Figure 2 Middle AA section view;

[0043] Figure 5Schematic diagram of the structure of the spiral stirrup in the embodiment of the present invention;

[0044] Figure 6 It is a schematic diagram of the structure of the positioning bracket steel bar in an embodiment of the present invention;

[0045] Figure 7 A plan view of a novel support structure provided by an embodiment of the present invention;

[0046] Figure 8 It is a schematic cross-section diagram of the extended open hole and backfill in an embodiment of the present invention;

[0047] Fig. 9 It is a schematic diagram of the longitudinal section of the extended open tunnel and the backfilled river side in an embodiment of the present invention;

[0048] Fig.10 It is a schematic diagram of the longitudinal section of the extended open tunnel and the backfilled near-slope side in an embodiment of the present invention;

[0049] Fig.11 A schematic diagram of a construction method according to Embodiment 2 of the present invention;

[0050] In the figure: 1. continuous support unit; 2. second anti-sliding pile; 3. concrete filling; 4. first anti-sliding pile; 5. anti-sliding pile reinforcement; 5-1. longitudinal reinforcement; 5-2. spiral stirrups; 5-3. bottom reinforcement; 5-4. structural reinforcement; 5-5. positioning bracket reinforcement; 6. concrete layer; 7. lining; 8. extended open hole opening; 9. open hole backfill layer; 10. opposite tunnel; 11. river; 12. longitudinal section line near the river side; 13. longitudinal section line near the slope side; 14. pile top crown beam; 15. open hole concrete side wall; 16. concrete protective layer; 17. intercepting ditch; 18. double-tube rotary jet pile. DETAILED DESCRIPTION

[0051] The following is a description of the embodiments of the present invention. Figures 1 to 11 , the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] Example 1

[0053] The embodiment of the present invention provides a new type of support structure suitable for the tunnel entrance section near the river, including a continuous support unit 1, two rows of first anti-slip piles 4, an extended open hole and a protection unit. The continuous support unit 1 is arranged on the side of the tunnel entrance section close to the river, the two rows of first anti-slip piles 4 are arranged on the side of the tunnel entrance section close to the slope, the extended open hole is arranged between the opposite tunnel 10 and the river 11, and the protection unit is arranged on the outside of the extended open hole. In the embodiment of the present invention, the continuous support unit 1 and the two rows of first anti-slip piles 4 are used as pile foundations, and an extended open hole is built above the two. During the specific construction, the extended open hole covers the two rows of first anti-slip piles 4, and the continuous support unit 1 partially exceeds the extended open hole and is not completely covered by the extended open hole. The embodiment of the present invention covers the two rows of first anti-slip piles 4 by extending the open hole to provide additional physical protection, and at the same time, the first anti-slip piles 4 are used to strengthen the overall stability of the tunnel entrance section, which helps to resist the pressure from the hillside direction and the potential threat of falling rocks. At the same time, the reason why the embodiment of the present invention arranges the continuous support unit 1 to partially extend beyond the extended open tunnel is to optimize the drainage system, ensure that rainwater and other surface water can be effectively guided to a location away from the tunnel, and reduce the impact of moisture on the tunnel structure.

[0054] In an embodiment of the present invention, the continuous support unit 1 includes a water-stop curtain and a row of second anti-slip piles 2. The water-stop curtain is arranged between the second anti-slip piles 2 and the river 11, and the second anti-slip piles 2 and the water-stop curtain are engaged with each other. Concrete filler 3 is poured between two adjacent second anti-slip piles 2.

[0055] In an embodiment of the present invention, the water-stop curtain includes two rows of double-tube rotary jet piles 18, and the adjacent double-tube rotary jet piles 18 are interlocked with each other, specifically in the upper, lower, left and right directions, and the second anti-slip pile 2 is interlocked with a row of adjacent double-tube rotary jet piles 18. The double-tube rotary jet piles 18 in the embodiment of the present invention adopt Ф800@550 double-tube rotary jet piles, and the overlap thickness between two adjacent double-tube rotary jet piles 18 is not less than 25cm, and the pile length of the double-tube rotary jet pile 18 is required to enter the relatively impermeable layer 2m. In this embodiment, the second anti-slip pile 2 is interlocked with the water-stop curtain, and the second anti-slip piles 2 are connected by concrete fillers 3, and the three form a continuous structure and are subjected to force together. The second anti-slip pile 2 can be flexibly arranged as needed and is suitable for various terrains and geological conditions.

[0056] At the same time, the double-tube jet grouting pile 18 in the embodiment of the present invention is prepared by mixing PO42.5R ordinary silicate cement slurry with triethanolamine, and the specific density of the cement slurry is 1.3-1.5 g / cm 3 The water-cement ratio is 1:1, the cement consumption per meter of double-tube rotary jet pile 18 is not less than 400kg, and the amount of triethanolamine added is 1% of the cement slurry.

[0057] In the embodiment of the present invention, the center distance between two adjacent second anti-slip piles 2 is 1.1m, and the length of the second anti-slip piles 4 is 17m; the center distance between two adjacent first anti-slip piles 4 in each row of first anti-slip piles 4 is 5.2m, and the two rows of first anti-slip piles 4 are staggered, and the length of the first anti-slip piles 4 is 6.5m. The present invention can effectively increase the stability of the slope by arranging two rows of staggered first anti-slip piles 4 on the near slope side. Specifically, this staggered layout can more evenly distribute the pressure from the slope, thereby reducing the load borne by a single first anti-slip pile 4, and the staggered arrangement makes the mutual support between the first anti-slip piles 4 stronger, further enhancing the protection ability of the entire support structure, and preventing the slope from sliding or collapsing. Since the second anti-slip piles 2 arranged on the river side usually need to be embedded deeper to resist water erosion and groundwater pressure, the length of the second anti-slip piles 2 is set to 17m to improve stability; while the first anti-slip piles 4 arranged on the near slope side may be more concerned with resisting the pressure from the hillside and preventing landslides, so their length is set to 6.5m. At the same time, the spacing between the second anti-slide piles 2 on the river side is smaller (1.1m) in order to better prevent river water infiltration and provide stronger support for the foundation; the spacing between the first anti-slide piles 4 on the slope side is larger (5.2m) based on cost-benefit analysis and the bearing capacity required in the area, while also taking into account the construction difficulty and material utilization efficiency.

[0058] like Figures 2 to 6As shown, the first anti-sliding pile 4 and the second anti-sliding pile 2 in the embodiment of the present invention are both composed of anti-sliding pile reinforcement bars 5. The anti-sliding pile reinforcement bars 5 include 40 φ25 longitudinal reinforcement bars 5-1, 1 φ10 spiral stirrup 5-2, 2 φ25 bottom reinforcement bars 5-3, 4 φ25 structural stirrups 5-4 and 4 groups of φ12 positioning bracket reinforcement bars 5-5. The 40 φ25 longitudinal reinforcement bars 5-1 are arranged in a circle along the circumferential direction, and the spacing between each longitudinal reinforcement bar 5-1 is 8 cm. Two adjacent longitudinal reinforcement bars 5-1 are connected and fixed by steel wire ropes to form a cylindrical pile body. The spiral stirrup 5-2 is sleeved on the outside of the cylindrical pile body to limit the cylindrical pile body on the outside. The pitch of the spiral stirrup 5-2 is 10 cm. The 4 structural stirrups 5-4 are arranged along the cylindrical pile body. The structural stirrups 5-4 are evenly spaced in the length direction and are sleeved on the inner side of the cylindrical pile body. The spacing between each structural stirrup 5-4 is 2m. The structural stirrups 5-4 limit the inner side of the cylindrical pile body. Two bottom steel bars 5-3 are orthogonally arranged inside the cylindrical pile body, and the end of the bottom steel bar 5-3 is connected to the structural stirrup 5-4 arranged at the bottom. Four groups of positioning support steel bars 5-5 are evenly spaced along the circumferential direction on the outer side of the spiral stirrup 5-2, and each group of positioning support steel bars 5-5 includes multiple positioning support steel bars 5-5. Multiple positioning support steel bars 5-5 are evenly spaced along the length direction of the cylindrical pile body on the outer side of the spiral stirrup 5-2. Each positioning support steel bar 5-5 is convex. The concrete layer 6 is filled in the gap between the anti-sliding pile steel bar 5 and the hole where the anti-sliding pile is located.

[0059] The protection unit includes a concrete side wall 15, an open hole backfill layer 9, a concrete protective layer 16 and an intercepting ditch 17. The concrete side wall 15 is arranged on the side of the extended open hole outer surface close to the river 11, the open hole backfill layer 9 is arranged on the extended open hole outer surface, the concrete protective layer 16 is arranged on the top of the open hole backfill layer 9, and the intercepting ditch 17 is opened on the side of the top of the concrete protective layer 16 close to the extended open hole entrance, and the bottom of the intercepting ditch 17 extends to the open hole backfill layer 9.

[0060] Example 2

[0061] like Fig.11 As shown, the embodiment of the present invention provides a construction method of a new type of support structure applicable to the portal section of a Linhe tunnel as described in Embodiment 1, comprising the following steps:

[0062] S1. The continuous support unit 1 is constructed on the side of the tunnel portal section close to the river 11, which specifically includes the following steps:

[0063] S11, drilling holes at the planned positions on the side of the tunnel entrance section close to the river 11 to obtain two rows of lead holes;

[0064] When the present invention is implemented, according to Figure 1The double-tube jet-jet pile 18 is arranged at the position shown, and holes are drilled at the arranged position. The drill rig is moved according to the on-site layout so that the drill rod head is aligned with the center of the hole. At the same time, in order to ensure that the drilling rig reaches the verticality required by the design, the drilling rig must be horizontally corrected after it is in place so that the axis of the drill rod is vertically aligned with the center of the borehole to ensure that the verticality of the borehole does not exceed 1.5%. During the straightening and correction inspection, a plumb bob (height not less than 2 meters) is used to check from two vertical directions. If deflection is found, a thin wooden block is added under the machine base for adjustment. After drilling, two rows of guide holes are obtained. The diameter of the guide holes is φ110mm. The holes are drilled strictly according to the determined pile positions. The plane position deviation shall not be greater than 50mm, and the original soil is used to make slurry to protect the wall.

[0065] S12, inserting a jet grouting pipe into a lead hole, and then performing high-pressure jet grouting. After the high-pressure jet grouting is completed, the jet grouting pipe is pulled out to complete the construction of a double-tube jet grouting pile 18;

[0066] (1) Intubation and test spray

[0067] After the lead hole is drilled, the invention inserts the rotary spray pipe to conduct test spraying to determine the construction technical parameters. The grouting material is 42.5R ordinary silicate cement, and the cement is prepared into cement slurry for grouting.

[0068] The water-cement ratio of cement slurry (single liquid) is 1:1, and the cement dosage of double-tube jet grouting pile 18 per meter is not less than 400kg. When using, triethanolamine is added to the cement slurry, and the amount of triethanolamine added is 1‰ of the cement dosage. The control parameters of the test spraying are set as:

[0069] The gas pressure is 0.7-0.8 MPa, the gas volume is 1000-2000 L per minute, the slurry density is 1.5 kg / L, the slurry volume is 60-70 L / min, the lifting speed is 8-10 cm / min, the nozzle diameter is 2.1 mm, and the slurry density is 1.2 g / cm 3 .

[0070] (2) High-pressure jet grouting

[0071] Before jet grouting, check the high-pressure equipment and pipeline system. The pressure and flow must meet the design requirements. There must be no debris in the grouting pipe and nozzle, and the sealing ring of the grouting pipe joint must be in good condition. When the grouting pipe penetrates the soil and the nozzle reaches the design elevation, the grouting can be sprayed according to the determined construction parameters. When spraying, the predetermined injection pressure should be reached first. After the volume is normal, the grouting pipe should be gradually lifted, and the grouting should be jetted from bottom to top. Each time the jet is jetted, the grouting should be sprayed first, then rotated and lifted to prevent the slurry pipe from twisting off. When lifted to a depth of 1.0m below the designed pile top, slow down the lifting speed to the designed elevation. After the jetting operation is completed, the slurry that emerges should be re-injected into the hole until it stops sinking.

[0072] The construction control parameters of high-pressure rotary jet grouting are set as: water pressure: 28~35MPa, water supply: 80~120L / min; air pressure: 0.7~0.8MPa, air supply: 1~2m3 / min; slurry pressure: 1~2MPa, liquid supply: 80~120L / min; lifting speed 0.08~0.1m / min; rotation speed 5~8r / min.

[0073] (3) Waste slurry treatment

[0074] During the jet grouting construction, a lot of waste slurry will be generated. In order to ensure the cleanliness of the site and smooth construction, a mud pool is planned to be set up on the site before construction. The mud will be pumped into the mud pool during construction and transported out for treatment after the mud solidifies.

[0075] (4) Flushing equipment

[0076] When the high-pressure jet grouting is completed, the grouting pipe should be pulled out quickly and the grouting pipe and grouting pump should be thoroughly cleaned to prevent blockage by solidified slurry.

[0077] (5) Move the jet grouting machine to the next hole position. After completing the construction of one pile, move the pile driver to the next pile position and repeat the above steps to construct the next pile.

[0078] S13, move the rotary jet pipe to the next lead hole, repeat step S12, complete the construction of the next double-tube rotary jet pile 18, until the two rows of double-tube rotary jet piles 18 are completed, after the two rows of double-tube rotary jet piles 18 are completed, the adjacent double-tube rotary jet piles 18 are mutually engaged, and the pile overlap thickness between the adjacent double-tube rotary jet piles 18 is not less than 25cm, so as to obtain a water-stop curtain;

[0079] S14, a row of pile holes is arranged at the planned position on one side of the tunnel entrance section near the river 11, and then the second anti-slip piles 2 are constructed in each row of pile holes. After the construction of the second anti-slip piles 2 in a row is completed, the second anti-slip piles 2 in a row are interlocked with the adjacent row of double-tube jet-jet piles 18. The specific construction process of the second anti-slip piles 2 is as follows:

[0080] (1) Preliminary preparation

[0081] At the entrance section of Linhe Tunnel, firstly, all obstacles in the construction area were cleared and the site was leveled to ensure the safe passage of construction machinery and personnel. According to the design drawings, the position, direction and elevation of the anti-slide piles were accurately measured and released, and control points and reference lines were set to provide accurate positioning for subsequent drilling. At the same time, steel bars (φ25 longitudinal steel bars 5-1, φ10 spiral stirrups 5-2, φ25 bottom steel bars 5-3, φ25 structural stirrups 5-4, φ12 positioning bracket steel bars 5-5) and concrete and other materials that met the design requirements were prepared, and necessary inspections and tests were carried out to ensure the quality of the materials.

[0082] (2) Drilling and cleaning of hole slag

[0083] For the second anti-slip pile 2, a single row arrangement with a spacing of 1.1m is used, and the arrangement range is from the starting point of the extended open hole to the hole entrance section. Use a drilling rig with a guide system to accurately place the drilling rig at the predetermined position, adjust the verticality of the drill rod, and ensure that no deviation occurs during the drilling process. Use guided drilling technology to monitor the drilling trajectory in real time to ensure the straightness and accuracy of the drilling, reduce drilling deviation, and improve construction quality. After drilling to the designed depth, use hole cleaning equipment to thoroughly remove the sediment at the bottom of the hole to ensure that the bottom of the hole is clean and free of debris, and use a measuring rope or special tools to check the actual depth of the hole to ensure that the design requirements are met.

[0084] (3) Placement of steel cage

[0085] according to Figure 2-Figure 6 The structural schematic diagram of the anti-sliding pile reinforcement 5 shown is a prefabricated reinforcement cage. The anti-sliding pile reinforcement 5 includes 40 φ25 longitudinal reinforcements 5-1, 1 φ10 spiral stirrup 5-2, 2 φ25 bottom reinforcements 5-3, 4 φ25 structural stirrups 5-4 and 4 groups of φ12 positioning bracket reinforcements 5-5. The 40 φ25 longitudinal reinforcements 5-1 are arranged in a circle along the circumferential direction, and the spacing between each longitudinal reinforcement 5-1 is 8 cm. Two adjacent longitudinal reinforcements 5-1 are connected and fixed by steel wire ropes to form a cylindrical pile body. The spiral stirrup 5-2 is sleeved on the outside of the cylindrical pile body to limit the cylindrical pile body on the outside. The pitch of the spiral stirrup 5-2 is 10 cm. The 4 structural stirrups The reinforcement 5-4 is evenly spaced and sleeved on the inner side of the cylindrical pile body along the length direction of the cylindrical pile body, and the spacing between each structural stirrup 5-4 is 2m. The structural stirrup 5-4 limits the inner side of the cylindrical pile body. Two bottom steel bars 5-3 are orthogonally arranged inside the cylindrical pile body, and the end of the bottom steel bar 5-3 is connected to the structural stirrup 5-4 arranged at the bottom. Four groups of positioning bracket steel bars 5-5 are evenly spaced along the circumferential direction on the outer side of the spiral stirrup 5-2, and each group of positioning bracket steel bars 5-5 includes multiple positioning bracket steel bars 5-5. Multiple positioning bracket steel bars 5-5 are evenly spaced along the length direction of the cylindrical pile body on the outer side of the spiral stirrup 5-2. Each positioning bracket steel bar 5-5 is convex. Ensure that the size, shape and welding quality of the steel cage meet the standards. Use special lifting equipment to transport the steel cage smoothly to the construction site to avoid deformation, and then slowly place the steel cage into the pre-drilled hole of the anti-slip pile, ensuring that the steel cage is centered, the bottom is in good contact with the bottom of the hole, and the top is a certain height above the ground for fixation.

[0086] (4) Pouring concrete

[0087] Mix the concrete strictly according to the mix ratio to ensure that its strength, fluidity and other performance indicators fully meet the requirements of the project. Then pour concrete into the pre-drilled hole of the anti-sliding pile. The concrete gradually fills the gap between the anti-sliding pile reinforcement 5 and the pre-drilled hole of the anti-sliding pile. During the concrete pouring process, use a vacuum pump to extract the air in the conduit to form a negative pressure environment to ensure that the concrete is dense and free of bubbles, thereby improving the strength and durability of the concrete. At the same time, mechanical vibration is carried out in a timely manner to further eliminate possible residual bubbles and ensure that the concrete is uniform and dense. After the concrete is initially solidified to form a concrete layer 6, use professional tools to cut off the excess pile head that exceeds the design elevation, so that the pile top is flat and accurately reaches the predetermined height, and the pile top after cutting is carefully polished to remove the uneven and rough parts of the surface, so that the pile top surface is smooth and tidy, providing good basic conditions for subsequent construction.

[0088] (5) Arrangement of the second anti-slide pile 2

[0089] Figure 7 The longitudinal section line 12 near the river and the longitudinal section line 13 near the slope correspond to Fig. 9 and Fig.10 The section line in the longitudinal section view shown. Figure 7 As shown, the second anti-sliding piles 2 are arranged in a single row, and the spacing between each second anti-sliding pile 2 is 1.1m. In actual engineering, the arrangement of piles should be based on geology and arranged according to the on-site drilling conditions. Ensure that the length of the embedded section of the pile is not less than 3 times the pile diameter.

[0090] S15, pouring concrete filler 3 between two adjacent second anti-slide piles 2, so that the double-tube rotary jet pile 18, the second anti-slide pile 2 and the concrete filler 3 form a whole, and obtaining a continuous support unit 1.

[0091] like Figure 1 , Figure 7 and Fig. 9 As shown, in the present invention, each second anti-slide pile 2 is connected by a concrete filler 3, and the arrangement range is from the starting point of the extended open tunnel to the tunnel entrance section. The arrangement length of the second anti-slide pile 2 in the extended direction of the open tunnel is 17m. The double-tube jet grouting pile 1, the second anti-slide pile 2 and the concrete filler 3 form a continuous support unit 1.

[0092] S2. After the construction of the continuous support unit 1 is completed, two rows of first anti-slide piles 4 are constructed on the side of the tunnel entrance section close to the slope;

[0093] Combination Figure 7 and Fig.10As shown, two rows of first anti-slide piles 4 are arranged on the side of the tunnel entrance section close to the slope. Among them, the first anti-slide piles 4 on the outer side of the slope side are close to the extended open tunnel, with a spacing of 5.2m, and the arrangement range is the backfill counter-pressure part; the first anti-slide piles 4 on the inner side of the slope side are closer to the high slope, with a spacing of 5.2m, and the range is the backfill part, and two first anti-slide piles 4 are arranged at the edge. The two rows of first anti-slide piles 4 are staggered. The construction is carried out according to the same steps of drilling, making and placing steel cages, pouring concrete, and repairing the pile top as the second anti-slide piles 2 to ensure the quality and stability of each anti-slide pile.

[0094] Combination Fig.10 As shown, the pile tops of the second anti-sliding pile 2 and the first anti-sliding pile 4 are both provided with pile top crown beams 14. After the construction of the second anti-sliding pile 2 and the first anti-sliding pile 4 is completed, the pile top crown beam 14 is immediately constructed. First, the crown beam formwork is installed to ensure the flatness and stability of the formwork. Then, the crown beam steel bars are tied, and the steel bar spacing and protective layer thickness are strictly controlled to ensure the safety and durability of the structure. Finally, the crown beam concrete is poured, and the concrete is compacted by vibration, and then necessary maintenance is carried out until the concrete reaches the design strength, providing additional connection and support for the anti-sliding piles.

[0095] After the construction is completed, the waste residues and waste materials generated during the construction process will be cleaned up to restore the site to a clean and tidy state. At the same time, the construction equipment will be evacuated from the site in an orderly manner and the equipment maintenance work will be done well.

[0096] S3, using the continuous support unit 1 and two rows of first anti-slide piles 4 as pile foundations, and carrying out extended open tunnel construction between the opposite tunnel 10 and the underlying river 11, specifically comprising the following steps:

[0097] S31, using the continuous support unit 1 and the two rows of first anti-slide piles 4 as pile foundations, installing an invert formwork between the opposite tunnel 10 and the underlying river 11, and pouring invert concrete to obtain an invert;

[0098] In specific implementation, according to Figure 8 As shown, the extended open-cut section is located between the opposite tunnel 10 and the adjacent river 11. The second anti-slide pile 2 and the first anti-slide pile 4 are both arranged vertically on the lower side of the open-cut opening 8 and serve as biased open-cut pile foundations. First, the invert formwork is accurately installed according to the design dimensions to ensure the flatness and stability of the formwork and provide good support for subsequent concrete pouring. Next, the invert reinforcement is tied according to the design requirements, and the spacing between the reinforcements and the thickness of the protective layer are strictly controlled to ensure the safety and durability of the structure. Finally, the pouring of the invert concrete begins, and vibrating equipment is used to ensure that the concrete is dense and free of bubbles, and proper maintenance is carried out until the concrete reaches the design strength to obtain the invert;

[0099] After the construction of S32 and the inverted arch is completed, a lining template is installed above the inverted arch, and lining concrete is poured to complete the construction of lining 7;

[0100] After the invert construction is completed, the lining 7 construction will be carried out immediately. First, the lining formwork is installed, and the flatness and stability of the formwork must also be ensured to form a regular lining surface. Then, the lining steel bars are tied according to the design requirements to ensure that the steel bar spacing and the thickness of the protective layer meet the standards to enhance the overall stability of the lining structure. Next, the lining concrete is poured and compacted by vibration, and then necessary maintenance is carried out until the concrete reaches the design strength to provide a solid protective barrier for the open hole.

[0101] S33. A waterproof layer is constructed on the surface of the lining 8. After the waterproof layer is constructed, an extended open hole is formed.

[0102] In order to ensure the waterproof performance of the extended hole, after the construction of lining 7 is completed, the surface of lining 7 needs to be carefully cleaned to remove all impurities such as oil, dust, etc., to ensure that the base is dry and clean. Subsequently, a layer of fine sand cushion is laid, which not only helps the waterproof material to fit closely with the base, but also reduces the occurrence of hollowing. Next, high-performance waterproof coating is evenly applied to form the first waterproof barrier to further improve the waterproof effect. Finally, the waterproof board is laid and covered with a layer of fine sand to ensure that the waterproof board is closely combined with the base to avoid any hollowing, thus building a complete waterproof system.

[0103] S4. After the construction of the extended open tunnel is completed, the protection unit construction will be carried out on the outside of the extended open tunnel to complete the support construction of the Linhe Tunnel entrance section.

[0104] like Figure 4 As shown, the protection unit in the embodiment of the present invention includes a concrete side wall 15, an open hole backfill layer 9, a concrete protective layer 16 and an intercepting ditch 17. The concrete side wall 15 is arranged on the side of the extended open hole outer surface close to the river 11, the open hole backfill layer 9 is arranged on the extended open hole outer surface, the concrete protective layer 16 is arranged on the top of the open hole backfill layer 9, and the intercepting ditch 17 is opened on the side of the top of the concrete protective layer 16 close to the extended open hole entrance, and the bottom of the intercepting ditch 17 extends to the open hole backfill layer 9.

[0105] Step S4 of the present invention specifically comprises the following steps:

[0106] S41, build a concrete side wall 15 on the side of the extended outer surface of the Mingdong near the river 11;

[0107] S42. Use block pebbles and sand to backfill and counter-press between the outer side of the extended open hole, the concrete side wall 15 and the slope to form an open hole backfill layer 9. In this embodiment, suitable backfill materials are selected, such as large block pebbles and sand. These materials have good water permeability and stability, and can effectively prevent water accumulation and maintain slope stability. Use layered backfill compaction technology, with each layer of backfill thickness not exceeding 30cm, and use a vibrating roller for compaction to ensure the density and flatness of the backfill material and minimize the risk of settlement. At the same time, strictly control the backfill slope to 18% to ensure that the slope is relatively gentle after backfilling, so that the slope is stable and will not slip due to rain erosion or deadweight. The slope is relatively gentle after backfilling.

[0108] S43. Install steel mesh at the edge and upper side of the open hole backfill layer 9, and then spray concrete evenly onto the steel mesh to form a concrete protective layer 16; in order to further strengthen the extended open hole structure, after the top backfill work is completed, it is necessary to install steel mesh at the backfill edge and upper side to ensure that the steel mesh is firmly fixed to enhance the stability of the slope. Then, use the spraying concrete equipment to spray concrete evenly onto the steel mesh to form a concrete protective layer 16. During the construction process, strictly control the thickness of the sprayed concrete to ensure that it is uniform and smooth, providing additional protection and support for the entire extended open hole structure.

[0109] S44, build a drainage ditch 17 on the top of the concrete protective layer 16 near the extended open tunnel entrance, and extend the bottom of the drainage ditch 17 to the open tunnel backfill layer 9, completing the construction of the protective unit, that is, completing the support construction of the Linhe Tunnel entrance section.

[0110] like Fig. 9 As shown, a drainage ditch 17 is built in the front section of the extended open tunnel to collect and guide rainwater and prevent water flow from directly impacting the extended open tunnel structure. The drainage ditch 17 is excavated according to the design requirements to ensure that the size and slope of the drainage ditch 17 meet the standards so as to effectively collect and guide rainwater. The drainage ditch 17 is lined with materials with excellent anti-seepage performance to ensure the durability and anti-seepage effect of the drainage ditch 17. The drainage ditch 17 is connected to the surrounding drainage system to ensure smooth drainage during the flood season, ensure the safe operation of the tunnel, and also reduce the impact of rainwater on the surrounding environment.

[0111] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A new type of support structure suitable for the tunnel portal section of a river, characterized in that: The invention comprises a continuous support unit (1), two rows of first anti-sliding piles (4), an extended open hole and a protection unit, wherein the continuous support unit (1) is arranged on a side of the tunnel opening section close to the river, the two rows of first anti-sliding piles (4) are arranged on a side of the tunnel opening section close to the slope, the extended open hole is arranged between the opposite tunnel (10) and the river (11), and the protection unit is arranged on the outside of the extended open hole.

2. A new type of support structure suitable for the tunnel portal section of Linhe River according to claim 1, characterized in that: The continuous support unit (1) comprises a water-stop curtain and a row of second anti-slip piles (2); the water-stop curtain is arranged between the second anti-slip piles (2) and the river (11); the second anti-slip piles (2) and the water-stop curtain are engaged with each other; and a concrete filler (3) is poured between two adjacent second anti-slip piles (2).

3. A new type of supporting structure suitable for the tunnel portal section along the river according to claim 2, characterized in that: The water-stop curtain comprises two rows of double-tube jet grouting piles (18), the adjacent double-tube jet grouting piles (18) are interlocked with each other, and the second anti-slip pile (2) is interlocked with a row of double-tube jet grouting piles (18) adjacent to each other.

4. A new type of supporting structure suitable for the tunnel portal section along the river according to claim 2, characterized in that: The center distance between two adjacent second anti-slip piles (2) is 1.1 m, and the length of the second anti-slip pile (4) is 17 m; The center distance between two adjacent first anti-slip piles (4) in each row of first anti-slip piles (4) is 5.2 m, and the two rows of first anti-slip piles (4) are arranged alternately, and the length of the first anti-slip piles (4) is 6.5 m.

5. The novel support structure suitable for the tunnel portal section along the river according to claim 1 is characterized in that: The protection unit comprises a concrete side wall (15), an open hole backfill layer (9), a concrete protective layer (16) and an intercepting ditch (17); the concrete side wall (15) is arranged on the side of the extended open hole outer surface close to the river (11); the open hole backfill layer (9) is arranged on the extended open hole outer surface; the concrete protective layer (16) is arranged on the top of the open hole backfill layer (9); the intercepting ditch (17) is opened on the side of the top of the concrete protective layer (16) close to the extended open hole opening, and the bottom of the intercepting ditch (17) extends to the open hole backfill layer (9).

6. A construction method for a new type of support structure suitable for a tunnel portal section along a river according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1, constructing a continuous support unit (1) on the side of the tunnel portal section close to the river (11); S2. After the construction of the continuous support unit (1) is completed, two rows of first anti-sliding piles (4) are constructed on the side of the tunnel entrance section close to the slope; S3, using the continuous support unit (1) and two rows of first anti-sliding piles (4) as pile foundations, and carrying out extended open tunnel construction between the opposite tunnel (10) and the adjacent river (11); S4. After the construction of the extended open tunnel is completed, the protection unit construction will be carried out on the outside of the extended open tunnel to complete the support construction of the Linhe Tunnel entrance section.

7. The construction method of a new type of supporting structure suitable for the tunnel portal section of Linhe Tunnel according to claim 6 is characterized in that: Step S1 comprises the following steps: S11, drilling holes at the planned positions on the side of the tunnel entrance section close to the river (11) to obtain two rows of lead holes; S12, inserting a jet grouting pipe into a lead hole, and then performing high-pressure jet grouting. After the high-pressure jet grouting is completed, the jet grouting pipe is pulled out to complete the construction of a double-tube jet grouting pile (18); S13, the rotary jet pipe is moved to the next lead hole, and step S12 is repeated to complete the construction of the next double-tube rotary jet pile (18), until the two rows of double-tube rotary jet piles (18) are all completed, after the two rows of double-tube rotary jet piles (18) are all completed, the adjacent double-tube rotary jet piles (18) are mutually engaged, and the pile overlap thickness between the adjacent double-tube rotary jet piles (18) is not less than 25cm, so as to obtain a water-stop curtain; S14, arranging a row of pile holes at a planned position on one side of the tunnel entrance section close to the river (11), and then constructing second anti-sliding piles (2) in each of the pile holes. After the construction of the row of second anti-sliding piles (2) is completed, the row of second anti-sliding piles (2) are interlocked with the adjacent row of double-tube jet grouting piles (18); S15, pouring concrete filler (3) between two adjacent second anti-slip piles (2), so that the double-tube jet grouting piles (18), the second anti-slip piles (2) and the concrete filler (3) form a whole, thereby obtaining a continuous support unit (1).

8. The construction method of a new type of support structure suitable for the tunnel portal section of Linhe River according to claim 7 is characterized in that: In step S12, the construction control parameters of high-pressure rotary jet grouting are set as follows: water pressure: 28-35 MPa, water supply: 80-120 L / min; air pressure: 0.7-0.8 MPa, air supply: 1-2 m3 / min; slurry pressure: 1-2 MPa, liquid supply: 80-120 L / min; Lifting speed: 0.08~0.1m / min; rotation speed: 5~8r / min.

9. The construction method of a new type of supporting structure suitable for the tunnel portal section of Linhe Tunnel according to claim 6 is characterized in that: Step S3 includes the following steps: S31, using the continuous support unit (1) and the two rows of first anti-sliding piles (4) as pile foundations, installing an invert formwork between the opposite tunnel (10) and the underlying river (11), and pouring invert concrete to obtain an invert; S32, after the invert construction is completed, a lining formwork is installed above the invert, and lining concrete is poured to complete the lining construction (8); S33, constructing a waterproof layer on the surface of the lining (8). After the waterproof layer is constructed, an extended open hole is formed.

10. The construction method of a new type of supporting structure applicable to the tunnel portal section of Linhe River according to claim 6, characterized in that: Step S4 comprises the following steps: S41, construct a concrete side wall (15) on the side of the extended outer surface of the open hole close to the river (11); S42, using blocky pebbles and sand to backfill and counter-press the outer side of the extended open hole, the concrete side wall (15) and the slope to form an open hole backfill layer (9); S43, installing a steel mesh at the edge and upper side of the open hole backfill layer (9), and then spraying concrete evenly onto the steel mesh to form a concrete protective layer (16); S44, construct a drainage ditch (17) on the top of the concrete protective layer (16) near the extended open tunnel entrance, and extend the bottom of the drainage ditch (17) to the open tunnel backfill layer (9), completing the construction of the protective unit, that is, completing the support construction of the Linhe Tunnel entrance section.

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