Combined steel pile enclosure structure of underground diaphragm wall and construction method of combined steel pile enclosure structure

Abstract

The invention discloses an underground diaphragm wall combined type steel pile enclosure structure and a construction method thereof. The construction method comprises the following steps that firstly, the paying-off pile fixing position is measured, and combined type steel piles are driven; secondly, earth excavation is conducted, and pile body sturdy bolts are fixed; thirdly, the prefabricated underground diaphragm wall is hoisted and fixed section by section and block by block; 4, a layered slurry sealing partition plate is arranged in the horizontal direction; step 5, performing high-pressure grouting and caulking in sections and modules; sixthly, the prestressed tendons are perforated, tensioned, anchored and grouted; seventhly, the second step to the sixth step are repeated till on-site hoisting of all the prefabricated underground diaphragm walls is completed; eighthly, waterproof coiled materials are laid at the abutted seams; and ninthly, stiffening rib plates are installed at the joint joints, and a fine aggregate concrete surface layer is sprayed at high pressure. A combined stress system of the combined steel piles, the prefabricated underground diaphragm wall and the soil layer reinforcing body is formed, hoisting, bearing and water stopping of the prefabricated structure are combined, the construction speed is high, and the prefabricated underground diaphragm wall is worthy of industrial application and popularization.

Description

Technical Field

[0001] The invention belongs to the technical field of underground construction, and in particular relates to an underground continuous wall combined steel pile enclosure structure and a construction method thereof. Background Art

[0002] Prefabricated buildings represent a significant evolution from traditional wet construction methods. They offer advantages such as low energy consumption, minimal pollution, low labor demand, rapid construction, and civilized construction, meeting the needs of industry transformation and upgrading. Prefabricated buildings are a new construction method, encompassing a comprehensive industry chain encompassing standardized design, industrialized production, mechanized construction, and intelligent management. Existing concrete building structures are mostly cast-in-place. Construction processes primarily include on-site reinforcement cage binding, on-site component formwork fabrication, concrete pouring, curing, and formwork removal. These structures offer excellent overall structural performance and stiffness, making them suitable for buildings requiring high seismic resistance and integrity. However, the entire construction process requires on-site operation, resulting in numerous steps, lengthy curing times, and a long construction period, as well as the extensive use of formwork. Underground diaphragm walls, a primary technology for retaining foundation pits in construction projects and subway construction, can provide a safer and more reliable environment for underground structure construction. The use of underground diaphragm walls is particularly effective in areas with water-rich sandstone formations. Current wet underwater concrete pouring methods have negative impacts on construction quality, cost, schedule, and environmental protection. Based on this, the present invention discloses an underground continuous wall combined steel pile retaining structure and construction technology system, which provides prefabricated structure hoisting and combines the combined steel-pile dual load-bearing retaining wall. The combined load-bearing effect of the two is better. Compared with the traditional construction method, the underground continuous wall combined steel-pile retaining structure system has the advantages of fast construction speed, low comprehensive construction cost, high level of green construction and civilized construction, and is worthy of industry promotion and application. It is planned to gradually establish a reliable new technology system in the field of underground structure construction to provide effective technical support for the high-quality transformation and development of my country's construction industry. Summary of the Invention

[0003] The object of the present invention is to provide an underground continuous wall combined steel pile enclosure structure and a construction method thereof, so as to solve the problems raised in the above-mentioned background technology.

[0004] To achieve the above object, the present invention adopts the following technical solutions: An underground continuous wall composite steel pile enclosure structure, comprising composite steel piles, a prefabricated underground continuous wall, high-strength bolts, reinforced connection angle steels, prestressed tendons, waterproof coils, and stiffening rib plates; Composite steel piles are driven into the foundation soil layer and fixed to the prefabricated underground continuous wall with high-strength bolts. Prestressed tendons are installed inside the prefabricated underground continuous wall. Waterproof membranes are laid at the connection points between the prefabricated underground continuous wall and the composite steel piles, and stiffening rib plates are installed outside the waterproof membranes. Reinforced connection angle steels are also installed at the ends of the connection points between the composite steel piles and the prefabricated underground continuous wall. The connection node between the prefabricated underground continuous wall and the composite steel is in a groove shape, and high-strength slightly expanding fine stone concrete is provided in the groove at the connection node between the prefabricated underground continuous wall and the composite steel pile.

[0005] The entire enclosure structure surface is provided with a high-pressure sprayed fine stone concrete surface layer.

[0006] A construction method for an underground continuous wall combined steel pile enclosure structure comprises the following steps: Step 1: Measure and lay out the lines to determine the pile positions, and drive the composite steel piles; Step 2: Excavate the earth and fix the high-strength bolts on the top of the composite steel pile; Step 3: Hoist and fix the prefabricated underground continuous wall section by section and block by block; Step 4: Install layered sealing slurry partitions horizontally; Step 5: High-pressure grouting and sealing in sections and modules; Step 6: Prestressed tendon punching, tensioning, anchoring and grouting; Step 7: Repeat steps 2 to 6 until all prefabricated underground continuous walls are hoisted on site; Step 8: Laying waterproof membrane at the joints; Step 9: Install stiffening ribs at joints and spray fine stone concrete surface layer with high pressure; The specific steps are as follows: Step 1: Measure and lay out the lines, determine the pile positions, and drive the composite steel piles: To address complex geological conditions such as water-rich sand layers, the design incorporates an underground continuous wall composite steel pile retaining structure system. To ensure the accurate placement of the prefabricated underground continuous wall in sections, layers, and modules, measurements and layouts were first performed according to the construction drawings, accurately locating the planar positions of each pile. The composite steel piles were then driven into place using the static pile driving method. The composite steel piles consist of H-shaped steel and cross-shaped piles, which are integrated in the factory and then driven and sunk on-site. The design dimensions of the composite steel piles were determined based on a comprehensive consideration of the excavation depth, soil pressure, geological environment, and groundwater conditions, ensuring they met strength and stiffness requirements. When composite steel piles encounter complex geological soil layers that make it difficult to continue driving, first pull out the composite steel piles, then use high-pressure water jetting and drilling expansion methods to treat them. Fill the holes of the treated composite steel piles with a mixture of fine gravel and coarse sand in a ratio of 1:2.5, and then continue to sink the composite steel piles. The horizontal position error of the sunken composite steel piles shall not exceed 6mm, and the verticality deviation shall not exceed 0.5%; Step 2: Excavation and fixing the high-strength bolts on the combined steel piles: When all the composite steel piles are sunk, in order to better control the maximum displacement of the top of the foundation pit in the future, reinforced concrete piers are designed on the periphery of the foundation pit 2000mm away from the top of the composite steel piles. Prestressed steel bars are used to tie the top surface of the composite steel piles to the reinforced concrete piers. After the tying process is completed, the first layer of earthwork excavation is carried out. The excavation depth of each layer of earthwork does not exceed 3500mm. The earthwork is excavated until the composite steel piles are exposed. Then, the cross piles of the composite steel piles close to the inside of the foundation pit are cleaned manually. Work, clean the bolt holes of the composite steel pile body, then pass the high-strength bolts used to connect the composite steel pile and the prefabricated underground continuous wall from the inside of the composite steel pile through the bolt holes, and fix the high-strength bolts with nuts on the other side of the bolt holes. The high-strength bolts are evenly arranged along the composite steel pile body, with a design spacing of 600mm and double rows. The top high-strength bolt is not less than 350mm away from the top surface of the composite steel pile, and the high-strength bolts at the bottom of each construction section are not less than 350mm away from the bottom surface of the prefabricated underground continuous wall after they are in place; Step 3: Hoisting and fixing of prefabricated underground continuous wall section by section and block by block: After the high-strength bolts on the composite steel piles are fixed, the prefabricated underground continuous wall of the first floor is hoisted. Before the prefabricated underground continuous wall is hoisted, the spacing between the composite steel piles is checked, and the dimensions and reserved connection hole positions of the prefabricated underground continuous walls at various locations that have been delivered to the site are compared. If the error is large and affects the hoisting of the overall structure, a solution must be proposed and submitted to the supervising engineer for approval before implementation; The prefabricated underground continuous wall has a groove interface at the connection node with the composite steel pile. The prefabricated underground continuous wall is hoisted using the "secondary fixing method" section by section and block by block. After the prefabricated underground continuous wall is hoisted into place, the high-strength bolts of the extended composite steel pile body are calibrated. The extended high-strength bolts are inserted into the reserved holes of the prefabricated underground continuous wall body at one time with manual assistance, and nuts are used to tighten and fix them initially. After all the high-strength bolts of the prefabricated underground continuous wall are perforated, the high-strength bolts are tightened and fixed for the second time. The final setting sequence adopts the technical method of "tightening from the middle to both sides, first tightening the upper part and then the lower part"; In order to better strengthen the connection nodes between the composite steel piles and the prefabricated underground continuous wall, on the basis of direct fixation with high-strength bolts, a "secondary bolt" is provided at the connection node near the inner side of the foundation pit to strengthen the connection angle steel. One end of the strengthening connection angle steel is fixed to the composite steel pile by bolts, and the other end of the strengthening connection angle steel is tightened into the internal thread thread reserved inside the prefabricated underground continuous wall by bolts. The bolt connection diameter used for the "secondary bolt" fixation of the strengthening connection angle steel is not less than 20mm, the spacing is not more than 450mm, and the cross-sectional size of the angle steel is not less than 200mm×200mm×12mm; Step 4: Install the layered sealing partitions horizontally: The design of the grouting diaphragm is primarily to prevent leakage during subsequent high-pressure grouting of the gaps between the prefabricated underground continuous wall, composite steel piles, and the soil. After the first layer of prefabricated underground continuous wall is hoisted and constructed, to meet the requirements of the subsequent high-pressure grouting process, layered grouting diaphragms are installed horizontally at the bottom of the prefabricated underground continuous wall in the construction section. These mortaring diaphragms are driven either piece by piece or in strips, with a depth of at least 350mm into the soil and a thickness of at least 12mm. Their surface is roughened, with a roughened surface area of ​​at least 90%. When the mortar sealing partition is installed piece by piece, the length of each mortar sealing partition is 500mm; when the mortar sealing partition is installed in an integral strip, the length of each side of the mortar sealing partition exceeds the prefabricated underground continuous wall by 300mm (that is, the length of the mortar sealing partition is 600mm longer than the corresponding prefabricated underground continuous wall hoisting length). The mortar sealing partition overlap length at the intersection of the prefabricated underground continuous walls of adjacent sections shall be at least 300mm; Step 5: High-pressure grouting and sealing in sections and modules: After all prefabricated components in the construction section are hoisted and sealed with grouting partitions, high-pressure grouting is carried out through the reserved holes at the bottom of the prefabricated underground continuous wall. Only grouting holes are reserved, and no overflow holes are left. The grouting material uses low-shrinkage, high-strength, and slightly expanding grouting material. The grouting process is divided into three pressurized grouting steps, and finally the grouting material fills the gaps between the prefabricated underground continuous wall, the composite steel piles, and the soil layer. The grouting material is penetrated into the soil layer through stepped pressurization, so that the composite steel piles can be reinforced while the surrounding soil is reinforced, forming a combined stress form of "combined steel piles + prefabricated underground continuous wall + soil reinforcement body", which can ultimately play a role in resisting soil pressure and ensure the safety and reliability of the foundation pit retaining structure; Step 6: Prestressed tendon punching, tensioning, anchoring and grouting: After high-pressure grouting in the construction section, after curing for at least 72 hours, the lower earthwork excavation and the hoisting of the prefabricated underground continuous wall are carried out. For the construction section that has been hoisted and constructed, prestressed tendon channels are provided inside the prefabricated underground continuous wall. The prestressed tendon channel openings inside the prefabricated underground continuous walls in adjacent sections should be at the same position to facilitate the subsequent prestressed tendon perforation operation; during the hoisting of the prefabricated underground continuous wall, the prestressed tendon channels inside each adjacent prefabricated underground continuous wall are connected by wire rope traction method, and prestressed tendon perforation, tensioning, anchoring and grouting work are carried out on the prefabricated underground continuous wall of every 3 to 5 sections. No less than 3 prestressed tendons are designed inside each prefabricated underground continuous wall. A prestressed tendon is provided 300mm below the top and 300mm above the bottom of the first-layer prefabricated underground continuous wall. The tensioning and anchoring ends of the prestressed tendons between the upper and lower adjacent layers of prefabricated underground continuous walls should be staggered with each other, at least 1000mm; Step 7: Repeat steps 2 to 6 until all prefabricated underground continuous walls are hoisted on site: After all the above processes are completed in the first-floor prefabricated underground continuous wall construction section, repeat steps 2 to 6 until all prefabricated underground continuous walls are hoisted on site. Carry out the process acceptance of each construction section, focusing on the acceptance of concealed works such as high-pressure grouting; Step 8: Laying waterproof membrane at the joints: After the entire underground retaining structure is hoisted and constructed, SBS waterproof membrane is used for cold bonding at the joints between the combined steel piles and the prefabricated underground continuous wall and at the joints between the two adjacent prefabricated underground continuous walls. Double-layer waterproofing is applied, and the waterproof membrane is laid tightly along the joints between the combined steel piles and the prefabricated underground continuous wall. No hollowing is allowed. The horizontal joint waterproof membrane is laid on the inner side of the vertical joint waterproof membrane. The width of the waterproof membrane is not less than 600mm and each side exceeds the joint by not less than 200mm. The waterproofing of the lowest part of the retaining structure is combined with the waterproofing of the basement floor. The waterproofing membrane is laid from the basement to the vertical prefabricated underground continuous wall, and the height of the waterproof membrane is not less than 500mm. Step 9: Installation of stiffening ribs at joints and high-pressure sprayed fine stone concrete surface layer: After all the waterproof membranes are laid at the joints, stiffening rib plates are installed at the joints between the combined steel piles and the prefabricated underground continuous wall and at the joints between the two adjacent prefabricated underground continuous walls. The length of the stiffening rib plates shall not be less than 750mm, the width of the stiffening rib plates shall not be less than 90mm, and the thickness of the stiffening rib plates shall not be less than 16mm. They shall be tightened to the prefabricated underground continuous wall using internal thread self-tapping sleeves. The spacing between the stiffening rib plates shall not exceed 600mm. Both ends of the stiffening rib plates shall be connected to the prefabricated underground continuous wall, and the connection and fixing points shall not be located within the range of the laid waterproof membrane. Therefore, the membrane laying position and the embedded position of the stiffening rib plate fixing points shall be fully considered during the prefabrication production process of the prefabricated underground continuous wall in the PC factory in the early stage. After all the stiffening rib plates at the joint nodes are installed, high-pressure sprayed fine stone concrete shall be used for spraying the surface layer of the overall enclosure structure, and the overall acceptance work shall be carried out.

[0007] The technical effects and advantages of the present invention are as follows: This invention effectively utilizes combined steel piles and prefabricated underground continuous walls for retaining and bearing, employing high-pressure grouting for installation and grouting while simultaneously reinforcing the surrounding soil, resulting in a more balanced overall structural load-bearing system. The combined load-bearing system of "combined steel piles + prefabricated underground continuous walls + soil reinforcement" created by this invention combines prefabricated structure hoisting with load-bearing and water-stopping, resulting in rapid construction and worthy of industry promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is a construction process flow chart for an underground continuous wall combined steel pile retaining structure Figure 2 It is a three-dimensional structural diagram of an underground continuous wall combined steel pile enclosure structure; Figure 3 This is a side view structural diagram of an underground continuous wall combined steel pile enclosure structure; Figure 4 This is a schematic diagram of the front structure of an underground continuous wall combined steel pile enclosure structure; Figure 5 A schematic diagram of the three-dimensional structure of an underground continuous wall combined steel pile enclosure structure from another perspective; Figure 6 This is a schematic diagram of the explosion structure of an underground continuous wall combined steel pile enclosure structure; Figure 7 A schematic diagram of the partial structure of an underground continuous wall combined steel pile enclosure structure Figure 1 ; Figure 8 A schematic diagram of the partial structure of an underground continuous wall combined steel pile enclosure structure Figure 2 ; Figure 9 A schematic diagram of the partial structure of an underground continuous wall combined steel pile enclosure structure Figure 3 ; Figure 10 A schematic diagram of the partial structure of an underground continuous wall combined steel pile enclosure structure Figure 4 .

[0009] In the figure: 1. Prefabricated underground continuous wall; 101. Groove; 2. Composite steel piles; 3. High-strength bolts; 4. Prestressed tendons; 5. Waterproof membrane; 6. Stiffening ribs; 7. Reinforced connecting angle steel; 8. High-strength slightly expansive fine stone concrete. DETAILED DESCRIPTION

[0010] The following is a combination of the embodiments of the present invention Figures 1-10 , the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. The specific embodiments described here are only used to explain the present invention and are not used to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0011] Embodiment: This embodiment provides an underground continuous wall composite steel pile enclosure structure, which is intended to connect two adjacent prefabricated underground continuous walls 1 together. The underground continuous wall composite steel pile enclosure structure includes composite steel piles 2, prefabricated underground continuous walls 1, high-strength bolts 3, reinforced connection angle steels 7, prestressed tendons 4, waterproof membranes 5, and stiffening rib plates 6; The composite steel piles 2 are driven into the foundation soil layer. The composite steel piles 2 are fixed to the prefabricated underground continuous wall 1 by high-strength bolts 3. Prestressed tendons 4 are provided inside the prefabricated underground continuous wall 1. A waterproof membrane 5 is laid at the connection node between the prefabricated underground continuous wall 1 and the composite steel piles 2. A stiffening rib plate 6 is provided outside the waterproof membrane 5. A reinforcing connecting angle steel 7 is also provided at the end of the connection node between the composite steel piles 2 and the prefabricated underground continuous wall 1. The connection node between the prefabricated underground continuous wall 1 and the combined steel pile 2 is in the shape of a groove 101. High-strength slightly expansive fine stone concrete 8 is provided in the groove 101 at the connection node between the prefabricated underground continuous wall 1 and the combined steel pile 2. Finally, all gaps between the two adjacent prefabricated underground continuous walls 1 are filled with concrete.

[0012] The entire enclosure structure surface is provided with a high-pressure sprayed fine stone concrete surface layer.

[0013] It should be noted that the composite steel piles 2 are a combination of H-shaped steel piles and cross-shaped piles. The composite steel piles 2 are integrated with the prefabricated underground continuous wall 1 in the PC factory. The specific design dimensions should be determined based on a comprehensive consideration of the excavation depth of the foundation pit, the geological conditions of the soil layer, the groundwater conditions, and the surrounding environment. The design length of each section of the composite steel piles 2 is 4500mm to 6000mm, and the piles are connected by welding. The composite steel piles 2 and the prefabricated underground continuous wall 1 are hoisted and connected on-site during the layered excavation process. At the connection node between the composite steel piles 2 and the prefabricated underground continuous wall 1, a "different structural design, long-path water-stopping" effect is formed, and the dual design effect of water-stopping is taken into account while completing the bearing process of the underground continuous wall retaining structure.

[0014] A high-strength bolt 3 connection hole is provided on the web of the cross steel pile on the side of the composite steel pile 2 close to the foundation pit. The diameter of the high-strength bolt 3 connection hole is 2mm~3mm larger than the designed diameter of the high-strength bolt 3. During the hoisting process of the prefabricated underground continuous wall 1 on site, the composite steel pile 2 and the prefabricated underground continuous wall 1 are connected by the high-strength bolt 3. Before connecting the composite steel pile 2 and the prefabricated underground continuous wall 1, one end of the high-strength bolt 3 is first fixed to the web of the cross steel pile. A double-row design is used. The high-strength bolts 3 at the upper and lower ends of the connection node between the composite steel pile 2 and the prefabricated underground continuous wall 1 should be designed to be denser. A 4-row design can be adopted with appropriately denser spacing. The design length of the high-strength bolt 3 should be able to ensure that the end of the high-strength bolt 3 can extend 30mm out of the surface of the prefabricated underground continuous wall 1 after installation, thereby improving the installation quality of the on-site retaining structure.

[0015] The three holes for high-strength bolts on the cross-shaped steel piles should accurately correspond to the reserved holes inside the underground continuous wall. The embedded bolt holes on the prefabricated underground continuous wall 1 are designed with externally threaded steel sleeves. The three holes for embedded high-strength bolts are integrally manufactured and formed with the prefabricated underground continuous wall 1 at the PC factory. The position error of a single embedded high-strength bolt 3 does not exceed 3mm, and the embedded position error of adjacent high-strength bolts 3 on the same prefabricated underground continuous wall 1 does not exceed 2mm. When the excavation depth of the foundation pit exceeds 10m, or the number of high-strength bolts 3 connected on a single composite steel pile 2 exceeds 80, or other complex geological conditions exist, the design of the composite steel pile 2 and prefabricated underground continuous wall 1 can use BIM technology to simulate construction and design verification, and formulate a special plan for the in-depth design of the composite steel pile 2 and prefabricated underground continuous wall 1.

[0016] In order to strengthen the connection node strength of the combined steel piles 2 and the prefabricated underground continuous wall 1 during the segmented and modular construction process, transverse prestressed tendons 4 are added inside the prefabricated underground continuous wall 1. The prestressed tendons 4 inside the prefabricated underground continuous wall 1 are arranged by the bonding post-tensioning method. Tensioning is carried out once every three underground continuous walls in the same direction or every 12 meters. The tensioning and anchoring positions of the prestressed tendons 4 at the longitudinal connection nodes of the upper and lower layers of prefabricated underground continuous walls 1 should be staggered by at least one module segment. The prestressed tendons 4 are punched during the hoisting process of the prefabricated underground continuous wall 1. After the prestressed tendons 4 are punched, they are first anchored at one end of the prefabricated underground continuous wall 1, and the other end is tensioned and anchored according to the technical plan after the prefabricated underground continuous wall 1 is hoisted into place in transverse sections. The prestressed tendons 4 are tensioned by 1.05σcon, tensioned at one end, and staggered and staggered anchored.

[0017] The design principle of the underground continuous wall enclosure structure also serves as the outer wall of the underground structure. After the underground continuous wall is fully hoisted into place, a double-layer waterproof membrane 5 is added to the outer surface of the underground continuous wall. That is, the first layer of waterproof membrane 5 is laid on the surface of the underground continuous wall by hot melt method. The overlap of the first layer of waterproof membrane 5 is also provided with stiffening rib plates 6. The stiffening rib plates 6 are used to press the overlap seams of the waterproof membrane 5. Then, on the basis of the first layer of waterproof membrane 5, the second layer of waterproof membrane 5 is fully or partially laid by cold bonding method to enhance the waterproof effect of the overall enclosure structure. The hot melt and cold bonding double-layer waterproof design can not only realize the waterproofing of the underground structure during the earth excavation process, but also take into account the structural waterproofing problems during the later use of the underground structure.

[0018] A construction method for an underground continuous wall combined steel pile enclosure structure comprises the following steps: Step 1: Measure and lay out the lines to determine the pile position, and drive the composite steel pile 2; Step 2: Excavate the earthwork and fix the combined steel pile 2 with high-strength bolts 3; Step 3: Hoist and fix the prefabricated underground continuous wall 1 section by section and block by block; Step 4: Install layered sealing slurry partitions horizontally; Step 5: High-pressure grouting and sealing in sections and modules; Step 6: Punching, tensioning, anchoring and grouting of prestressed tendons 4; Step 7: Repeat steps 2 to 6 until all prefabricated underground continuous walls 1 are hoisted on site; Step 8: Lay waterproof membrane 5 at the joints; Step 9: Install the stiffening rib plate 6 at the joint and spray the surface layer of fine stone concrete with high pressure; The specific steps are as follows: Step 1: Measure and lay out the lines to determine the pile position and drive the composite steel piles 2: To address complex geological conditions such as water-rich sand layers, the design incorporates a 2-component retaining structure system for underground continuous walls with composite steel piles. To ensure the accurate placement of the prefabricated underground continuous wall 1 in sections, layers, and modules, measurements and layouts were first performed according to the construction drawings, accurately locating the planar positions of each pile. The composite steel piles 2 were then driven into place using the static pile driving method. The composite steel piles 2 consist of H-shaped steel and cross-shaped piles, which are integrated in the factory and then driven and sunk on-site. The design dimensions of the composite steel piles 2 were designed based on a comprehensive consideration of the excavation depth, soil pressure, geological environment, and groundwater conditions to meet strength and stiffness requirements. When the composite steel pile 2 encounters a complex geological soil layer that makes it difficult to continue driving, the composite steel pile 2 is first pulled out, and then treated by high-pressure water jetting and drilling expansion and flushing methods. The pile hole of the treated composite steel pile 2 is filled with a mixture of fine gravel and coarse sand in a ratio of 1:2.5, and then the composite steel pile 2 is continued to be sunk. The horizontal position error of the composite steel pile 2 does not exceed 6mm, and the verticality deviation does not exceed 0.5%; Step 2: Excavation, fix the combined steel pile 2 with high strength bolts 3: When all the composite steel piles 2 are sunk, in order to better control the maximum displacement of the foundation pit top in the future, reinforced concrete piers are designed on the periphery of the foundation pit 2000mm away from the top of the composite steel piles 2, and prestressed steel bars are used to tie the top surface of the composite steel piles 2 to the reinforced concrete piers. After the tying process is completed, the first layer of earth excavation is carried out. The depth of each layer of earth excavation does not exceed 3500mm. The earth excavation is carried out until the composite steel piles 2 are exposed. Then, the cross piles of the composite steel piles 2 close to the inside of the foundation pit are cleaned manually. The bolt holes of the combined steel pile 2 are cleaned, and then the high-strength bolts 3 used to connect the combined steel pile 2 and the prefabricated underground continuous wall 1 are passed through the bolt holes from the inside of the combined steel pile 2 to the outside. The high-strength bolts 3 are fixed with nuts on the other side of the bolt holes. The high-strength bolts 3 are evenly arranged along the combined steel pile 2. The design spacing of the high-strength bolts 3 is 600mm, and they are arranged in double rows. The top high-strength bolts 3 are not less than 350mm away from the top surface of the combined steel pile 2, and the high-strength bolts 3 at the bottom of each construction section are not less than 350mm away from the bottom surface of the prefabricated underground continuous wall 1 after they are in place. Step 3: Hoisting and fixing of prefabricated underground continuous wall 1 section by section and block by block: After the high-strength bolts 3 on the top of the composite steel piles 2 are fixed, the first-floor prefabricated underground continuous wall 1 is hoisted. Before the prefabricated underground continuous wall 1 is hoisted, the spacing between the composite steel piles 2 is checked, and the sizes and reserved connection hole positions of the prefabricated underground continuous walls 1 at various locations that have been delivered to the site are compared. If the error is large and affects the hoisting of the overall structure, a solution must be provided and submitted to the supervising engineer for approval before implementation; The prefabricated underground continuous wall 1 has a groove 101 interface at the connection node with the combined steel pile 2. The prefabricated underground continuous wall 1 is hoisted using the "secondary fixing method" section by section and block by block. After the prefabricated underground continuous wall 1 is hoisted into place, the high-strength bolts 3 of the extended combined steel pile 2 are calibrated. The extended high-strength bolts 3 are inserted into the reserved holes of the prefabricated underground continuous wall 1 at one time with manual assistance, and are initially tightened and fixed with nuts. After all the high-strength bolts 3 of the prefabricated underground continuous wall 1 are perforated, the high-strength bolts 3 are tightened and fixed again. The final setting sequence adopts the technical method of "tightening from the middle to both sides, first tightening the upper part and then the lower part". ; In order to better strengthen the fixation of the connection node between the composite steel pile 2 and the prefabricated underground continuous wall 1, on the basis of direct fixation by high-strength bolts 3, a "secondary bolt" is provided at the connection node near the inner side of the foundation pit to fix the reinforced connection angle steel 7. One end of the reinforced connection angle steel 7 is fixed to the composite steel pile 2 by bolts, and the other end of the reinforced connection angle steel 7 is tightened by bolts into the internal thread sleeve reserved inside the prefabricated underground continuous wall 1. The bolt connection diameter used for the "secondary bolt" fixation of the reinforced connection angle steel 7 is not less than 20mm, the spacing is not more than 450mm, and the cross-sectional size of the angle steel is not less than 200mm×200mm×12mm; Step 4: Install the layered sealing partitions horizontally: The grout sealing diaphragms are designed primarily to prevent leakage during subsequent high-pressure grouting of the gaps between the prefabricated underground continuous wall 1, the composite steel piles 2, and the soil. After the first layer of prefabricated underground continuous wall 1 is hoisted and installed, to meet the requirements of the subsequent high-pressure grouting process, layered grout sealing diaphragms are installed horizontally at the bottom of the prefabricated underground continuous wall 1 in the construction section. These mortar sealing diaphragms are driven either piece by piece or in strips, with a depth of at least 350mm into the soil and a thickness of at least 12mm. Their surfaces are roughened to a surface area of ​​at least 90%. When the mortar sealing partition is laid out piece by piece, the length of each mortar sealing partition is 500mm; when the mortar sealing partition is laid out in an integral strip, the length of each side of the mortar sealing partition exceeds the prefabricated underground continuous wall 1 by 300mm (that is, the length of the mortar sealing partition is 600mm longer than the corresponding hoisting length of the prefabricated underground continuous wall 1), and the overlap length of the mortar sealing partition at the intersection of the prefabricated underground continuous wall 1 of adjacent sections shall be at least 300mm; Step 5: High-pressure grouting and sealing in sections and modules: After all prefabricated components in the construction section are hoisted and sealed with grouting partitions, high-pressure grouting is carried out through the reserved holes at the bottom of the prefabricated underground continuous wall 1. Only grouting holes are reserved, and no overflow holes are left. The grouting material uses low-shrinkage, high-strength, and slightly expanding grouting material. The grouting process is divided into three pressurized grouting steps, and finally the grouting material fills the gaps between the prefabricated underground continuous wall 1, the composite steel piles 2, and the soil layer. The grouting material is penetrated into the soil layer through stepped pressurization, so that the composite steel piles 2 can be used to retain the soil while the soil around them is reinforced, forming a joint stress form of "combined steel piles 2 + prefabricated underground continuous wall 1 + soil reinforcement body", which can finally play a role in resisting soil pressure and ensure the safety and reliability of the foundation pit retaining structure; Step 6: Perforation, tensioning, anchoring and grouting of prestressed tendon 4: After high-pressure grouting in the construction section, after curing for at least 72 hours, the lower earthwork excavation and the hoisting of the precast underground continuous wall 1 are carried out. For the construction section that has been hoisted and constructed, a prestressed tendon 4 channel is provided inside the precast underground continuous wall 1. The prestressed tendon 4 channel openings inside the precast underground continuous wall 1 in adjacent sections should be at the same position to facilitate the subsequent prestressed tendon 4 perforation operation; during the hoisting process of the precast underground continuous wall 1, the prestressed tendon 4 channels inside each adjacent precast underground continuous wall 1 are connected by wire rope traction method, and the prestressed tendon 4 perforation, tensioning, anchoring and grouting work are carried out on the precast underground continuous wall 1 in every 3 to 5 sections. No less than 3 prestressed tendons 4 are designed inside each precast underground continuous wall 1. A prestressed tendon 4 is provided 300mm below the top and 300mm above the bottom of the first-layer precast underground continuous wall 1. The tensioning and anchoring ends of the prestressed tendons 4 between the upper and lower adjacent layers of precast underground continuous walls 1 should be staggered with each other, at least 1000mm; Step 7: Repeat steps 2 to 6 until all prefabricated underground continuous walls 1 are hoisted on site: After all the above processes are completed in the construction section of the first-floor prefabricated underground continuous wall 1, repeat steps 2 to 6 until the on-site hoisting of the entire prefabricated underground continuous wall 1 is completed. Carry out the process acceptance work of each construction section, focusing on the acceptance work of concealed works such as high-pressure grouting; Step 8: Laying waterproof membrane 5 at the joints: After the entire underground retaining structure is hoisted and constructed, SBS waterproof membrane 5 is used for cold bonding at the joints of the combined steel piles 2 and the prefabricated underground continuous wall 1 and at the joints of the two adjacent prefabricated underground continuous walls 1. Double-layer waterproofing is carried out. The waterproof membrane 5 is laid along the joints of the combined steel piles 2 and the prefabricated underground continuous wall 1. No hollowing is allowed. The horizontal joint waterproof membrane 5 is laid on the inner side of the vertical joint waterproof membrane 5. The width of the waterproof membrane 5 is not less than 600mm and each side exceeds the joint by not less than 200mm. The waterproofing of the lowest part of the retaining structure is combined with the waterproofing of the basement floor. The waterproofing membrane 5 of the basement is laid to the vertical prefabricated underground continuous wall 1. The laying height of the waterproof membrane 5 is not less than 500mm. Step 9: Install the stiffening rib plate 6 at the joint and spray the surface layer of high-pressure fine stone concrete: After all the waterproof membrane 5 is laid at the joints, stiffening rib plates 6 are set at the joints of the combined steel piles 2 and the prefabricated underground continuous wall 1 and the joints of the two adjacent prefabricated underground continuous walls 1. The length of the stiffening rib plates 6 shall not be less than 750mm, the width of the stiffening rib plates 6 shall not be less than 90mm, and the thickness of the stiffening rib plates 6 shall not be less than 16mm. They shall be tightened on the prefabricated underground continuous wall 1 using internal thread self-drilling sleeves. The spacing between the stiffening rib plates 6 shall not exceed 600mm. Both ends of the stiffening rib plates 6 shall be connected to the prefabricated underground continuous wall 1, and the connection and fixing points shall not be set within the range of the laid waterproof membrane 5. Therefore, in the early prefabrication production process of the prefabricated underground continuous wall 1 in the PC factory, the membrane laying position and the embedded position of the stiffening rib plates 6 fixing points shall be fully considered; after all the stiffening rib plates 6 at the joint nodes are installed, high-pressure sprayed fine stone concrete shall be used to spray the surface layer of the overall enclosure structure, and the overall acceptance work shall be carried out.

[0019] This invention effectively utilizes two combined steel piles and a prefabricated underground continuous wall for retaining and bearing, employing high-pressure grouting for installation and grouting while simultaneously reinforcing the surrounding soil, resulting in a more rational overall structural load-bearing system. The invention forms a combined load-bearing system of "two combined steel piles + one prefabricated underground continuous wall + soil reinforcement," enabling prefabricated structure hoisting, combining load-bearing and water-stopping, and expedited construction, making it worthy of industry promotion and application.

[0020] Finally, it should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent replacements for some of the technical features therein. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An underground continuous wall combined steel pile enclosure structure, characterized in that: It includes a composite steel pile (2), a prefabricated underground continuous wall (1), high-strength bolts (3), a reinforced connection angle steel (7), prestressed tendons (4), a waterproof coil (5) and a stiffening rib plate (6); The combined steel pile (2) is driven into the foundation soil layer, the combined steel pile (2) and the prefabricated underground continuous wall (1) are fixed by high-strength bolts (3), prestressed tendons (4) are provided inside the prefabricated underground continuous wall (1), a waterproof roll (5) is laid at the connection node between the prefabricated underground continuous wall (1) and the combined steel pile (2), and a stiffening rib plate (6) is provided outside the waterproof roll (5); and a reinforcing connecting angle steel (7) is also provided at the end of the connection node between the combined steel pile (2) and the prefabricated underground continuous wall (1).

2. The underground continuous wall combined steel pile enclosure structure according to claim 1, characterized in that: The connection node between the prefabricated underground continuous wall (1) and the combined steel pile (2) is in the shape of a groove (101), and high-strength slightly expansive fine stone concrete (8) is provided in the groove (101) at the connection node between the prefabricated underground continuous wall (1) and the combined steel pile (2).

3. The underground continuous wall combined steel pile enclosure structure according to claim 1, characterized in that: The entire enclosure structure surface is provided with a high-pressure sprayed fine stone concrete surface layer.

4. A construction method for an underground continuous wall combined steel pile enclosure structure, characterized in that: The following steps are involved: Step 1: Measure and lay out the lines to determine the pile positions and drive the composite steel piles (2); Step 2: excavation, fixing the composite steel pile (2) with high-strength bolts (3); Step 3: Prefabricated underground continuous wall (1) is hoisted and fixed section by section and block by block; Step 4: Install layered sealing slurry partitions horizontally; Step 5: High-pressure grouting and sealing in sections and modules; Step 6: Prestressed tendons (4) are punched, tensioned, anchored and grouted; Step 7: Repeat steps 2 to 6 until all prefabricated underground continuous walls (1) are hoisted on site; Step 8: Lay the waterproof membrane (5) at the joints; Step 9: Install the stiffening rib plate (6) at the joints and spray the surface layer with high-pressure fine stone concrete; The specific steps are as follows: Step 1: Measure and lay out the lines, determine the pile positions, and drive the composite steel piles (2): First, the construction drawings are used to measure and lay out the lines, and the plane positions of the pile bodies are accurately located. Then, the combined steel piles (2) are driven into place by the static pile-pressing method. The combined steel piles (2) include H-shaped steel and cross-shaped piles. The H-shaped steel and cross-shaped piles are formed as a whole in the factory and are driven and sunk on site. When the combined steel piles (2) encounter a complex geological layer and are difficult to continue to be driven, the combined steel piles (2) are first pulled out, and then treated by high-pressure water jetting and drilling expansion methods. The pile holes of the treated combined steel piles (2) are filled with a mixture of fine gravel and coarse sand in a ratio of 1:2.5, and then the combined steel piles (2) are continued to be sunk. The horizontal position error of the sunken combined steel piles (2) does not exceed 6 mm, and the verticality deviation does not exceed 0.5%; Step 2: Excavation, fix the composite steel pile (2) and the pile high-strength bolts (3): After all the combined steel piles (2) have been sunk, in order to better control the maximum displacement of the top of the foundation pit, a reinforced concrete pier is designed on the periphery of the foundation pit 2000mm away from the top of the combined steel pile (2), and the top surface of the combined steel pile (2) is tied to the reinforced concrete pier by using prestressed steel bars. After the tying process is completed, the first layer of earthwork excavation is carried out. The depth of each layer of earthwork excavation does not exceed 3500mm. The earthwork is excavated until the combined steel pile (2) is exposed. Then, the cross pile of the combined steel pile (2) close to the inside of the foundation pit is cleaned manually to clean the combined steel pile (2). The bolt holes of the pile body are cleaned, and then the high-strength bolts (3) used to connect the composite steel pile (2) and the prefabricated underground continuous wall (1) are passed through the bolt holes from the inside of the composite steel pile (2) to the outside, and the high-strength bolts (3) are fixed with nuts on the other side of the bolt holes. The high-strength bolts (3) are evenly arranged along the pile body of the composite steel pile (2). The design spacing of the high-strength bolts (3) is 600mm, and they are arranged in double rows. The top high-strength bolts (3) are not less than 350mm away from the top surface of the composite steel pile (2), and the high-strength bolts (3) at the bottom of each construction section are not less than 350mm away from the bottom surface of the prefabricated underground continuous wall (1) after being in place. Step 3: Prefabricated underground continuous wall (1) Hoisting and fixing section by section and block by block: After the high-strength bolts (3) on the piles of the composite steel piles (2) are fixed, the first-floor prefabricated underground continuous wall (1) is hoisted and installed. Before the prefabricated underground continuous wall (1) is hoisted, the spacing between the composite steel piles (2) is checked, and the sizes and reserved connection hole positions of the prefabricated underground continuous walls (1) at various locations that have been brought into the site are compared; The prefabricated underground continuous wall (1) has a groove (101) interface at the connection node with the combined steel pile (2). The prefabricated underground continuous wall (1) is hoisted using the "secondary fixing method" of each section and each block. After the prefabricated underground continuous wall (1) is hoisted to the position, the high-strength bolts (3) of the extended combined steel pile (2) are calibrated. The extended high-strength bolts (3) are inserted into the reserved holes of the prefabricated underground continuous wall (1) at one time by means of manual assistance, and are initially tightened and fixed using nuts. After all the high-strength bolts (3) of the prefabricated underground continuous wall (1) are perforated, the high-strength bolts (3) are tightened and fixed again. The final setting sequence adopts the technique of "tightening from the middle to both sides, first tightening the upper part and then the lower part". Technical method: In order to better strengthen the connection node of the combined steel pile (2) and the prefabricated underground continuous wall (1), on the basis of direct fixation by high-strength bolts (3), a "secondary bolt" fixing of a strengthening connection angle steel (7) is provided at the connection node near the inner side of the foundation pit, one end of the strengthening connection angle steel (7) is fixed to the combined steel pile (2) by bolts, and the other end of the strengthening connection angle steel (7) is tightened into the internal threaded sleeve reserved inside the prefabricated underground continuous wall (1) by bolts, the bolt connection diameter used for the "secondary bolt" fixing of the strengthening connection angle steel (7) is not less than 20mm, the spacing is not more than 450mm, and the cross-sectional size of the angle steel is not less than 200mm×200mm×12mm; Step 4: Install the layered sealing partitions horizontally: After the first layer of prefabricated underground continuous wall (1) is hoisted and installed, in order to meet the requirements of the subsequent high-pressure grouting process, a layered mortar sealing partition is horizontally installed at the bottom of the prefabricated underground continuous wall (1) in the construction section. The mortar sealing partition is installed piece by piece or in an overall strip shape. The depth of the mortar sealing partition is not less than 350mm and the thickness of the mortar sealing partition is not less than 12mm. The surface is roughened and the rough surface area is not less than 90%; When the sealing diaphragm is made piece by piece, the length of each sealing diaphragm is 500mm; when the sealing diaphragm is made in an integral strip shape, the length of each side of the sealing diaphragm exceeds the prefabricated underground continuous wall (1) by 300mm, and the overlapping length of the sealing diaphragm at the junction of the prefabricated underground continuous wall (1) of adjacent sections is at least 300mm; Step 5: High-pressure grouting and sealing in sections and modules: After all prefabricated components in the construction section are hoisted and sealed with grouting partitions, high-pressure grouting is carried out through the reserved holes at the bottom of the prefabricated underground continuous wall (1). Only grouting holes are reserved, and no overflow holes are left. The grouting material uses low-shrinkage, high-strength, and slightly expanding grouting material. The grouting process is divided into three pressure grouting steps, so that the grouting material finally fills the gaps between the prefabricated underground continuous wall (1), the combined steel piles (2), and the soil layer, and the grouting material can penetrate into the soil layer through stepped pressure increase, so that the combined steel piles (2) can be reinforced while the soil around them is reinforced, forming a "combined steel piles (2) + prefabricated underground continuous wall (1) + soil reinforcement body" joint stress form, which can finally play a role in resisting soil pressure and ensure the safety and reliability of the foundation pit retaining structure; Step 6: Prestressed tendons (4) perforation, tensioning, anchoring and grouting: After high-pressure grouting in the construction section, curing for at least 72 hours, the lower earthwork excavation and the hoisting of the prefabricated underground continuous wall (1) are carried out. For the construction section that has been hoisted and constructed, a prestressed tendon (4) hole is provided inside the prefabricated underground continuous wall (1). The prestressed tendon (4) hole openings inside the prefabricated underground continuous wall (1) in adjacent sections should be at the same position to facilitate the subsequent prestressed tendon (4) perforation operation; during the hoisting process of the prefabricated underground continuous wall (1), the interior of each adjacent prefabricated underground continuous wall (1) is pulled by a wire rope. The prestressed tendon (4) holes are connected, and the prestressed tendon (4) perforation, tensioning, anchoring and grouting work are carried out on the prefabricated underground continuous wall (1) of every 3 to 5 sections. No less than 3 prestressed tendons (4) are designed inside each prefabricated underground continuous wall (1). A prestressed tendon (4) is set 300mm below the top and 300mm above the bottom of the first prefabricated underground continuous wall (1). The tensioning and anchoring ends of the prestressed tendons (4) between the upper and lower adjacent prefabricated underground continuous walls (1) should be staggered with each other, at least 1000mm; Step 7: Repeat steps 2 to 6 until all prefabricated underground continuous walls (1) are hoisted on site: After all the above processes are completed in the construction section of the first-floor prefabricated underground continuous wall (1), repeat steps 2 to 6 until the on-site hoisting of all prefabricated underground continuous walls (1) is completed, and the process acceptance work of each construction section is carried out, with a focus on the acceptance work of concealed works such as high-pressure grouting; Step 8: Laying waterproof membrane (5) at the joints: After the entire underground retaining structure is hoisted and constructed, SBS waterproof membrane (5) is used for cold bonding at the joints of the combined steel pile (2) and the prefabricated underground continuous wall (1) and the joints of the two adjacent prefabricated underground continuous walls (1). Double-layer waterproofing is constructed. The waterproof membrane (5) is laid along the joints of the combined steel pile (2) and the prefabricated underground continuous wall (1). The horizontal joint waterproof membrane (5) is laid on the inner side of the vertical joint waterproof membrane (5). The width of the waterproof membrane (5) is not less than 600mm and each side exceeds the joint by not less than 200mm. The waterproofing of the lowest part of the retaining structure is combined with the waterproofing of the basement floor. The basement waterproof membrane (5) is laid to the vertical prefabricated underground continuous wall (1). The upper package height of the waterproof membrane (5) is not less than 500mm. Step 9: Installation of stiffening rib plates (6) at joints and high-pressure sprayed fine stone concrete surface layer: After all the waterproof membranes (5) are laid at the joints of the combined steel piles (2) and the prefabricated underground continuous wall (1) and the joints of the adjacent two prefabricated underground continuous walls (1), the stiffening rib plates (6) are set. The length of the stiffening rib plates (6) is not less than 750mm, the width of the stiffening rib plates (6) is not less than 90mm, and the thickness of the stiffening rib plates (6) is not less than 16mm. The stiffening rib plates (6) are tightened on the prefabricated underground continuous wall (1) using internal thread self-drilling sleeves. The spacing between the stiffening rib plates (6) does not exceed 600mm. The two ends of the stiffening rib plates (6) are connected to the prefabricated underground continuous wall (1), and the connection and fixing points shall not be set within the range of the waterproof membrane (5) that has been laid. After all the stiffening rib plates (6) at the joints are installed, the high-pressure sprayed fine stone concrete is used to spray the surface layer of the overall enclosure structure, and the overall acceptance work is done well.

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