A diaphragm wall combined steel pile enclosure structure and a construction method thereof

Abstract

The application discloses a kind of underground continuous wall combined type steel pile enclosure structure and its construction method, comprising the following steps: step one: measurement is released, and pile position is fixed, and combined type steel pile is struck and set;Step two: earthwork excavation, fixed pile body high-strength bolt;Step three: prefabricated underground continuous wall is hoisted and fixed section by section, block by block section;Step four: horizontal is struck and set layered sealing grouting baffle;Step five: sectional, module high-pressure grouting joint sealing;Step six: prestressed reinforcement perforation, tension, anchoring and grouting;Step seven: repeat step two to six, until complete all prefabricated underground continuous wall site hoisting;Step eight: joint waterproofing membrane paving;Step nine: joint node stiffened rib board installation, high-pressure injection fine stone concrete surface layer.The application forms "combined type steel pile+prefabricated underground continuous wall+soil reinforcement body" combined stress system, prefabricated structure hoisting, bearing and water stop are combined, construction speed is fast, worthy of industry popularization and application.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of underground construction, and particularly relates to a combined steel pile retaining structure of underground diaphragm wall and a construction method thereof. BACKGROUND

[0002] Fabricated building is a major change to the traditional "wet operation" construction method. Fabricated building shows the advantages of low energy consumption, low pollution, low labor demand, fast construction speed, etc., which meets the needs of industry development, transformation and upgrading. Prefabricated building is a new building production method, and is a construction mode of whole industry chain such as standardized design, industrialized production, mechanized construction and intelligent management. The existing concrete building structure is mainly cast-in-situ concrete structure, and its construction process mainly includes on-site binding of reinforcement cage, on-site production of component formwork, pouring and tamping of concrete, curing and form removal, etc. The overall performance and stiffness of the structure are good, and it is suitable for buildings with high seismic fortification and overallity requirements. However, the entire construction process must be operated on site, the process is complicated, the curing time is long, the construction period is long, and a large amount of formwork is used. Underground diaphragm wall is a main technical means of foundation enclosure structure for building engineering, subway construction, etc., and can provide a relatively safe and reliable construction environment for underground structure construction. For water-rich sand layer geological conditions, the use of underground diaphragm wall enclosure structure is more remarkable. The current traditional wet operation underwater pouring of concrete has certain adverse effects on construction quality, building cost, construction progress and environmental protection. Based on this, the application discloses a combined steel pile retaining structure of underground diaphragm wall and a construction technology system, provides precast structure hoisting, combines with combined steel-pile double bearing retaining, and the combined bearing effect is better. Compared with the traditional construction method, the combined steel-pile retaining structure system of underground diaphragm wall has the advantages of fast construction speed, low comprehensive building cost and high green building level, and is worthy of popularization and application in the industry. It is planned to gradually establish a reliable new technology system in the field of underground structure construction, and to provide effective technical support for high-quality transformation and development of China's building industry. SUMMARY

[0003] The application aims to provide a combined steel pile retaining structure of underground diaphragm wall and a construction method thereof, so as to solve the problems in the background art.

[0004] To achieve the above-mentioned purpose, the application adopts the following technical solutions:

[0005] A combined steel pile retaining structure of underground diaphragm wall, comprising a combined steel pile, a prefabricated underground diaphragm wall, high-strength bolts, reinforced connecting angle steels, prestressed tendons, waterproof coiled material and stiffened ribbed slabs.

[0006] Composite steel piles are driven into the foundation soil layer and fixed to the precast diaphragm wall with high-strength bolts. The precast diaphragm wall is equipped with prestressed tendons. Waterproof membrane is laid at the connection node between the precast diaphragm wall and the composite steel piles, and stiffening ribs are provided outside the waterproof membrane. Reinforcing angle steel is also provided at the end of the connection node between the composite steel piles and the precast diaphragm wall.

[0007] The connection point between the precast diaphragm wall and the composite steel pile is grooved, and high-strength micro-expansion fine stone concrete is placed inside the groove at the connection point between the precast diaphragm wall and the composite steel pile.

[0008] The entire enclosure structure is covered with a high-pressure sprayed fine aggregate concrete surface layer.

[0009] A construction method for a combined steel pile retaining structure with a diaphragm wall includes the following steps:

[0010] Step 1: Measure and set out the stake positions, and drive in the composite steel piles;

[0011] Step 2: Excavate the earthwork and fix the composite steel piles with high-strength bolts;

[0012] Step 3: The precast diaphragm wall is hoisted and fixed section by section and block by block;

[0013] Step 4: Install layered sealing grouting baffles horizontally;

[0014] Step 5: Segmented and modular high-pressure grouting for sealing;

[0015] Step Six: Drilling, tensioning, anchoring, and grouting of prestressed tendons;

[0016] Step 7: Repeat steps 2 to 6 until all precast diaphragm walls are hoisted on site;

[0017] Step 8: Laying waterproof membrane at the seams;

[0018] Step 9: Install stiffening ribs at the joints and apply high-pressure sprayed fine aggregate concrete surface layer;

[0019] The specific steps are as follows:

[0020] Step 1: Measure and set out the stake positions, then drive in the composite steel piles.

[0021] For complex geological conditions such as water-rich sand layers, a combined steel pile retaining structure system for diaphragm walls was designed. To ensure accurate placement of the prefabricated diaphragm walls in sections, layers, and modules, the first step was to measure and lay out the lines according to the construction drawings to precisely locate the planar position of each pile. Then, the combined steel piles were driven into place using the static pile driving method. The combined steel piles consist of H-beams and cross-shaped piles, which are integrally formed in the factory and driven into place as a whole on site. The design dimensions of the combined steel piles should be comprehensively considered based on the excavation depth, earth pressure, geological environment, and groundwater conditions to meet the strength and stiffness requirements. When composite steel piles encounter complex geological soil layers and cannot be driven further, the composite steel piles are first extracted. Then, high-pressure water jetting and drilling enlargement methods are used for treatment. After treatment, the pile holes of the composite steel piles are filled with a mixture of fine gravel and coarse sand in a ratio of 1:2.5, and the composite steel piles are driven again. The horizontal position error of the driven composite steel piles shall not exceed 6mm, and the verticality deviation shall not exceed 0.5%.

[0022] Step Two: Earthwork excavation and fixing of composite steel piles with high-strength bolts:

[0023] After all the composite steel piles have been driven in, to better control the maximum displacement at the top of the foundation pit, reinforced concrete piers are designed around the perimeter of the foundation pit, 2000mm from the top of the composite steel piles. Prestressed steel bars are used to connect the top surface of the composite steel piles to the reinforced concrete piers. After the connection process is completed, the first layer of earthwork excavation begins. The excavation depth of each layer does not exceed 3500mm, and the earthwork is excavated until the composite steel piles are exposed. Then, the cross-shaped piles on the side of the composite steel piles closest to the inside of the foundation pit are manually cleaned. The work involves cleaning the bolt holes of the composite steel piles, then passing the high-strength bolts used to connect the composite steel piles and the precast diaphragm wall through the bolt holes from the inside of the composite steel piles outwards. On the other side of the bolt holes, the high-strength bolts are fixed with nuts. The high-strength bolts are evenly distributed along the composite steel pile body, with a design spacing of 600mm and arranged in double rows. The distance between the top high-strength bolts and the top surface of the composite steel pile is not less than 350mm, and the distance between the bottom high-strength bolts of each construction section and the bottom surface of the precast diaphragm wall after it is in place is not less than 350mm.

[0024] Step 3: Precast diaphragm wall segment by segment and block by block hoisting and fixing:

[0025] After the high-strength bolts of the composite steel piles are fixed, the precast underground continuous wall of the first floor will be hoisted. Before hoisting the precast underground continuous wall, the spacing between each composite steel pile will be checked, and the dimensions and reserved connection hole positions of the precast underground continuous walls that have been brought to the site will be compared. For cases with large errors that affect the hoisting of the overall structure, a solution must be provided and submitted to the supervising engineer for approval before implementation.

[0026] The precast diaphragm wall has a grooved interface at the connection point with the composite steel piles. The precast diaphragm wall is hoisted using a segment-by-segment, block-by-block "secondary fixing method." After hoisting the precast diaphragm wall to its position, the high-strength bolts of the protruding composite steel piles are aligned. With manual assistance, the protruding high-strength bolts are inserted into the pre-drilled holes in the precast diaphragm wall body in one go, and initially tightened with nuts. After all the high-strength bolts of the precast diaphragm wall block are drilled, a second tightening is performed. The final setting sequence adopts the technique of "tightening sequentially from the middle to both sides, tightening the upper part first and then the lower part." To better strengthen and fix the connection nodes of the composite steel piles and precast diaphragm walls, in addition to direct fixing with high-strength bolts, a secondary bolt fixing of reinforcing angle steel is installed at the connection node near the inner side of the foundation pit. One end of the reinforcing angle steel is fixed to the composite steel pile with bolts, and the other end of the reinforcing angle steel is tightened into the internal thread reserved inside the precast diaphragm wall with bolts. The bolt diameter used for fixing the secondary bolts of the reinforcing angle steel is not less than 20mm, the spacing is not more than 450mm, and the cross-sectional dimensions of the angle steel are not less than 200mm×200mm×12mm.

[0027] Step 4: Install layered grouting baffles horizontally:

[0028] The design of the grout sealing diaphragm is primarily to prevent grout leakage during high-pressure grouting of the gaps between the precast diaphragm wall, composite steel piles, and soil layers. After the first layer of precast diaphragm wall is hoisted and constructed, in order to meet the requirements of the subsequent high-pressure grouting process, layered grout sealing diaphragms are installed horizontally at the bottom of the precast diaphragm wall in the construction section. The grout sealing diaphragms are installed piece by piece or as a whole strip, with a depth of not less than 350mm into the soil layer, a thickness of not less than 12mm, and a roughened surface treatment with a roughened surface area of ​​not less than 90%.

[0029] When the sealing diaphragm is installed piece by piece, the length of each sealing diaphragm is 500mm; when the sealing diaphragm is installed as an integral strip, the length of each side of the sealing diaphragm exceeds the length of the precast diaphragm wall by 300mm (i.e., the length of the sealing diaphragm is 600mm longer than the hoisting length of the corresponding precast diaphragm wall), and the overlap length of the sealing diaphragm at the junction of adjacent precast diaphragm walls is at least 300mm.

[0030] Step 5: Segmented and modular high-pressure grouting for sealing:

[0031] After all precast components in the construction section are hoisted and the sealing grouting baffles are installed, high-pressure grouting is carried out through the reserved holes at the bottom of the precast diaphragm wall. Only grouting holes are reserved, and no overflow holes are left. The grouting material is low-shrinkage, high-strength, and micro-expansion grouting material. The grouting process is carried out in three pressurized injection stages. In the end, the grouting material fills the gaps between the precast diaphragm wall, the composite steel piles, and the soil layer. Through stepped pressurization, the grouting material can penetrate into the soil layer. This allows the composite steel piles to retain soil while the surrounding soil is reinforced, forming a combined force-bearing structure of "composite steel piles + precast diaphragm wall + soil reinforcement". Ultimately, this structure can resist soil pressure and ensure the safety and reliability of the foundation pit retaining structure.

[0032] Step Six: Prestressed Tendon Drilling, Tensioning, Anchoring, and Grouting:

[0033] After high-pressure grouting in the construction section, and curing for at least 72 hours, the lower layer of earthwork excavation and hoisting of the precast diaphragm wall will be carried out. For the construction section that has been hoisted and completed, prestressed tendon ducts are provided inside the precast diaphragm wall. The prestressed tendon duct openings inside the precast diaphragm walls in adjacent sections should be in the same position to facilitate subsequent prestressed tendon drilling operations. During the hoisting of the precast diaphragm wall, the prestressed tendon ducts inside each adjacent precast diaphragm wall are connected by the wire rope traction method. Prestressed tendon drilling, tensioning, anchoring and grouting work is carried out on every 3 to 5 sections of the precast diaphragm wall. Each precast diaphragm wall is designed with no less than 3 prestressed tendons. One prestressed tendon is set 300mm below the top and 300mm above the bottom of the first layer of precast diaphragm wall. The tensioning and anchoring ends of the prestressed tendons between two adjacent layers of precast diaphragm walls should be staggered by at least 1000mm.

[0034] Step 7: Repeat steps 2 to 6 until all precast diaphragm walls are hoisted on-site.

[0035] After all the above-mentioned processes are completed in the first-floor precast diaphragm wall construction section, repeat steps two to six until all precast diaphragm walls are hoisted on site. Perform process acceptance work for each construction section, with a focus on the acceptance work of concealed works such as high-pressure grouting.

[0036] Step 8: Laying waterproof membrane at the seams:

[0037] After the entire underground retaining structure is hoisted and constructed, SBS waterproof membrane is cold-applied and laid at the joints of the combined steel piles and precast underground continuous walls, as well as at the joints of two adjacent precast underground continuous walls. Double-layer waterproofing is carried out. The waterproof membrane is laid tightly along the joints of the combined steel piles and precast underground continuous walls, without any hollow areas. The waterproof membrane for the horizontal joints is laid on the inside of the waterproof membrane for the vertical joints. The width of the waterproof membrane is not less than 600mm and extends beyond the joint by not less than 200mm on each side. The waterproofing of the lowest part of the retaining structure is combined with the waterproofing of the basement floor slab. The waterproof membrane is laid from the basement to the vertical precast underground continuous walls, and the waterproof membrane is covered with a layer of not less than 500mm above the wall.

[0038] Step Nine: Install stiffening ribs at the joints, and apply high-pressure sprayed fine aggregate concrete surface layer.

[0039] After all the waterproof membrane at the joints is laid, stiffening ribs are installed at the joints connecting the combined steel piles and the precast diaphragm wall, as well as at the joints between adjacent precast diaphragm walls. The stiffening ribs should be at least 750mm long, 90mm wide, and 16mm thick, and tightened onto the precast diaphragm wall using internal thread self-tapping screws. The spacing between stiffening ribs should not exceed 600mm. Both ends of the stiffening ribs are connected to the precast diaphragm wall, and the connection points must not be located within the area where the waterproof membrane has already been laid. Therefore, the membrane laying position and the pre-embedded position of the stiffening rib fixing points must be fully considered during the initial precast production process at the PC factory. After all the stiffening ribs at the joints are installed, high-pressure sprayed fine aggregate concrete is used to coat the surface layer of the overall enclosure structure, and overall acceptance is carried out.

[0040] The technical effects and advantages of this invention are as follows:

[0041] This invention effectively utilizes a combination of composite steel piles and precast diaphragm walls for retaining and bearing loads. High-pressure grouting is used for hoisting and joint filling while simultaneously reinforcing the surrounding soil, resulting in a more rational overall structural stress distribution. The combined load-bearing system of "composite steel piles + precast diaphragm walls + soil reinforcement" formed by this invention, with its precast structure hoisting, combines load-bearing and water-stopping functions, enabling rapid construction and making it worthy of widespread application in the industry. Attached Figure Description

[0042] Figure 1 A construction process flow diagram for a combined steel pile retaining structure for underground continuous wall;

[0043] Figure 2 A three-dimensional structural diagram of a combined steel pile retaining structure for underground continuous wall;

[0044] Figure 3 This is a side view schematic diagram of a combined steel pile retaining structure for underground continuous wall;

[0045] Figure 4 This is a front view schematic diagram of a combined steel pile retaining structure for underground continuous wall;

[0046] Figure 5 This is a three-dimensional structural diagram of a combined steel pile retaining structure for underground continuous wall from another perspective.

[0047] Figure 6 This is an exploded structural diagram of a combined steel pile retaining structure for underground continuous wall;

[0048] Figure 7 A partial structural diagram of a combined steel pile retaining structure for underground continuous wall. Figure 1 ;

[0049] Figure 8 A partial structural diagram of a combined steel pile retaining structure for underground continuous wall. Figure 2 ;

[0050] Figure 9 A partial structural diagram of a combined steel pile retaining structure for underground continuous wall. Figure 3 ;

[0051] Figure 10 A partial structural diagram of a combined steel pile retaining structure for underground continuous wall. Figure 4 .

[0052] In the diagram: 1. Precast diaphragm wall; 101. Groove; 2. Composite steel pile; 3. High-strength bolt; 4. Prestressed tendon; 5. Waterproof membrane; 6. Stiffening rib plate; 7. Reinforcing connecting angle steel; 8. High-strength micro-expansion fine aggregate concrete. Detailed Implementation

[0053] The following will refer to the appendices in the embodiments of the present invention. Figures 1-10 The technical solutions in the embodiments of the present invention are clearly and completely described herein. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0054] Example: This example provides a combined steel pile retaining structure for underground continuous wall, which aims to connect two adjacent precast underground continuous walls 1 together. The combined steel pile retaining structure for underground continuous wall includes combined steel piles 2, precast underground continuous wall 1, high-strength bolts 3, reinforcing connecting angle steel 7, prestressed tendons 4, waterproof membrane 5, and stiffening rib plates 6.

[0055] Composite steel piles 2 are driven into the foundation soil layer. Composite steel piles 2 are fixed to precast diaphragm wall 1 by high-strength bolts 3. Prestressed tendons 4 are provided inside the precast diaphragm wall 1. Waterproof membrane 5 is laid at the connection node between precast diaphragm wall 1 and composite steel piles 2. Reinforcing ribs 6 are provided outside the waterproof membrane 5. Reinforcing angle steel 7 is also provided at the end of the connection node between composite steel piles 2 and precast diaphragm wall 1.

[0056] The connection node between the precast diaphragm wall 1 and the composite steel pile 2 is shaped like a groove 101. High-strength micro-expansion fine stone concrete 8 is placed in the groove 101 at the connection node between the precast diaphragm wall 1 and the composite steel pile 2. Finally, all gaps between two adjacent precast diaphragm walls 1 are filled with concrete.

[0057] The entire enclosure structure is covered with a high-pressure sprayed fine aggregate concrete surface layer.

[0058] It should be noted that the composite steel pile 2 is composed of H-shaped steel piles and cross-shaped piles. The composite steel pile 2 and the precast diaphragm wall 1 are integrally formed in the PC factory. The specific design dimensions should be determined based on a comprehensive consideration of the excavation depth, soil geological conditions, groundwater conditions, and surrounding environment. The design length of each composite steel pile 2 segment is 4500mm to 6000mm. The piles are connected by welding. The composite steel pile 2 and the precast diaphragm wall 1 are hoisted and connected on site during the layered excavation of the earthwork. At the connection node between the composite steel pile 2 and the precast diaphragm wall 1, a "heterogeneous structure design and long-path water-stopping" effect is formed, which takes into account the dual design effect of water-stopping while completing the load-bearing of the diaphragm wall retaining structure.

[0059] The composite steel pile 2 has high-strength bolt 3 connection holes on the web of the cross-shaped steel pile on the side closest to the foundation pit. The diameter of the high-strength bolt 3 connection hole is 2mm to 3mm larger than the designed diameter of the high-strength bolt 3. During the hoisting of the precast diaphragm wall 1 on site, the composite steel pile 2 and the precast diaphragm wall 1 are connected by high-strength bolt 3. Before connecting the composite steel pile 2 and the precast diaphragm wall 1, one end of the high-strength bolt 3 is fixed to the web of the cross-shaped steel pile. The high-strength bolt 3 should be densely designed at the upper and lower ends of the connection node between the composite steel pile 2 and the precast diaphragm wall 1. A 4-row design can be adopted with appropriate spacing. The design length of the high-strength bolt 3 should ensure that the end of the high-strength bolt 3 can extend 30mm beyond the surface of the precast diaphragm wall 1 after installation, thereby improving the installation quality of the on-site retaining structure.

[0060] The high-strength bolt holes on the cross-shaped steel piles should accurately correspond to the reserved holes inside the diaphragm wall. The pre-embedded bolt holes on the precast diaphragm wall 1 adopt a design with externally threaded steel sleeves. The pre-embedded high-strength bolt holes are integrally formed with the precast diaphragm wall 1 in the PC factory. The positional error of a single pre-embedded high-strength bolt 3 should not exceed 3mm, and the positional error of adjacent high-strength bolts 3 on the same precast diaphragm wall 1 should 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 are encountered, the design of the composite steel pile 2 and the precast diaphragm wall 1 can use BIM technology to simulate construction and design verification, and develop a special detailed design scheme for the composite steel pile 2 and the precast diaphragm wall 1.

[0061] To enhance the strength of the connection between the combined steel piles 2 and the precast diaphragm wall 1 during segmented and modular construction, transverse prestressing tendons 4 are added inside the precast diaphragm wall 1. The prestressing tendons 4 inside the precast diaphragm wall 1 are laid out using a bonded post-tensioning method. Tensioning is performed once every three diaphragm walls or every 12m in the same direction. The tensioning and anchoring positions of the prestressing tendons 4 at the longitudinal connection nodes of the upper and lower layers of precast diaphragm walls 1 should be staggered by at least one module segment. The prestressing tendons 4 are drilled during the hoisting of the precast diaphragm wall 1. After drilling, the prestressing tendons 4 are first anchored at one end of the precast diaphragm wall 1. The other end is tensioned and anchored according to the technical plan after the precast diaphragm wall 1 is horizontally segmented and in place. The prestressing tendons 4 are over-tensioned using 1.05σcon, tensioned at one end, and anchored in staggered layers and positions.

[0062] The design principle of using the diaphragm wall retaining structure as the exterior wall of the underground structure is as follows: after all the diaphragm walls are hoisted into place, a double-layer waterproof membrane 5 is added to the outer surface of the diaphragm wall. The first layer of waterproof membrane 5 is laid on the surface of the diaphragm wall using the hot-melt method. The overlap of the first layer of waterproof membrane 5 is also equipped with stiffening ribs 6, which are used to press the overlap of the waterproof membrane 5 tightly. Then, on the basis of the first layer of waterproof membrane 5, the second layer of waterproof membrane 5 is laid entirely or partially using the cold-adhesion method. This enhances the waterproof effect of the overall retaining structure. The hot-melt and cold-adhesion double-layer waterproof design can not only achieve waterproofing of the underground structure during the earthwork excavation process, but also take into account the structural waterproofing problem during the later use of the underground structure.

[0063] A construction method for a combined steel pile retaining structure with a diaphragm wall includes the following steps:

[0064] Step 1: Measure and set out the stake positions, and drive 2 composite steel piles;

[0065] Step 2: Excavate the earthwork and fix 2 composite steel piles and 3 high-strength bolts;

[0066] Step 3: Precast diaphragm wall 1 is hoisted and fixed section by section and block by block;

[0067] Step 4: Install layered sealing grouting baffles horizontally;

[0068] Step 5: Segmented and modular high-pressure grouting for sealing;

[0069] Step Six: Drilling, tensioning, anchoring, and grouting of prestressed tendons 4;

[0070] Step 7: Repeat steps 2 to 6 until all precast diaphragm walls 1 are hoisted on site;

[0071] Step 8: Lay the waterproof membrane at the seams;

[0072] Step 9: Install stiffening rib plates 6 at the joint nodes, and apply high-pressure sprayed fine aggregate concrete surface layer;

[0073] The specific steps are as follows:

[0074] Step 1: Measure and lay out the stake positions, then drive in the composite steel piles 2.

[0075] For complex geological conditions such as water-rich sand layers, a combined underground continuous wall and steel pile 2 retaining structure system was designed. To ensure accurate placement of the prefabricated underground continuous wall 1 in sections, layers, and modules, the first step was to measure and lay out the lines according to the construction drawings to accurately locate the planar position of each pile. Then, the combined steel pile 2 was driven into place using the static pile driving method. The combined steel pile 2 consists of H-beams and cross-shaped piles, which are integrally formed in the factory and driven into place as a whole on site. The design dimensions of the combined steel pile 2 should be comprehensively considered based on the excavation depth, earth pressure, geological environment, and groundwater conditions to meet the strength and stiffness requirements. When the composite steel pile 2 encounters complex geological soil layers and is difficult to continue driving, it should first be pulled out. Then, high-pressure water jetting and drilling enlargement methods should be used for treatment. After treatment, the pile hole of the composite steel pile 2 should be filled with a mixture of fine gravel and coarse sand in a ratio of 1:2.5, and the composite steel pile 2 should continue to be driven. The horizontal position error of the driven composite steel pile 2 should not exceed 6mm, and the verticality deviation should not exceed 0.5%.

[0076] Step 2: Earthwork excavation, fixing 2 composite steel piles and 3 high-strength bolts:

[0077] After all the composite steel piles 2 were driven in, to better control the maximum displacement of the top of the foundation pit, reinforced concrete piers were designed around the perimeter of the foundation pit, 2000mm from the top of the composite steel piles 2. Prestressed steel bars were used to connect the top surface of the composite steel piles 2 to the reinforced concrete piers. After the connection process was completed, the first layer of earthwork excavation was carried out. The excavation depth of each layer did not exceed 3500mm, and the earthwork was excavated until the composite steel piles 2 were exposed. Then, the cross-shaped piles on the side of the composite steel piles 2 closest to the inside of the foundation pit were cleaned manually. The bolt holes of the composite steel pile 2 are cleaned, and then the high-strength bolts 3 used to connect the composite steel pile 2 and the precast underground continuous wall 1 are passed through the bolt holes from the inside of the composite 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 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 distance between the top high-strength bolts 3 and the top surface of the composite steel pile 2 is not less than 350mm. The distance between the bottom high-strength bolts 3 and the bottom surface of the precast underground continuous wall 1 after placement is not less than 350mm.

[0078] Step 3: Precast diaphragm wall 1: Sectional and block-by-block hoisting and fixing:

[0079] After the high-strength bolts 3 of the combined steel piles 2 are fixed, the first-floor precast diaphragm wall 1 is hoisted. Before hoisting the precast diaphragm wall 1, the spacing between each combined steel pile 2 is checked, and the dimensions and reserved connection hole positions of the precast diaphragm wall 1 at each location that has been brought to the site are compared. For cases with large errors that affect the hoisting of the overall structure, a solution must be provided and submitted to the supervising engineer for approval before implementation.

[0080] The precast diaphragm wall 1 has a groove 101 interface at the connection node with the composite steel pile 2. The precast diaphragm wall 1 is hoisted using a segment-by-segment, block-by-block "secondary fixing method". After the precast diaphragm wall 1 is hoisted to the position, the high-strength bolts 3 of the protruding composite steel pile 2 are aligned. The protruding high-strength bolts 3 are then manually inserted into the reserved holes in the wall body of the precast diaphragm wall 1 in one go, and the nuts are initially tightened to fix it. After all the high-strength bolts 3 of the precast diaphragm wall 1 have been drilled, the high-strength bolts 3 are tightened again for a second time. The final setting sequence adopts the technical method of "tightening from the middle to both sides, tightening the upper part first and then the lower part". To better strengthen and fix the connection node between the composite steel pile 2 and the precast underground continuous wall 1, in addition to direct fixing with high-strength bolts 3, a secondary bolt fixing with reinforcing connecting angle steel 7 is provided at the connection node near the inner side of the foundation pit. One end of the reinforcing connecting angle steel 7 is fixed to the composite steel pile 2 with bolts, and the other end of the reinforcing connecting angle steel 7 is tightened into the internal thread reserved inside the precast underground continuous wall 1 with bolts. The bolt connection diameter used for fixing the secondary bolt of the reinforcing connecting angle steel 7 is not less than 20mm, the spacing is not more than 450mm, and the cross-sectional dimensions of the angle steel are not less than 200mm×200mm×12mm.

[0081] Step 4: Install layered grouting baffles horizontally:

[0082] The design of the grout sealing diaphragm is mainly to prevent grout leakage during high-pressure grouting of the gap between the precast diaphragm wall 1, the composite steel piles 2, and the soil layer. After the first-layer precast diaphragm wall 1 is hoisted and constructed, in order to meet the requirements of the subsequent high-pressure grouting process, layered grout sealing diaphragms are installed horizontally at the bottom of the precast diaphragm wall 1 in the construction section in the early stage. The grout sealing diaphragms are installed piece by piece or as a whole strip, with a depth of not less than 350mm into the soil layer, a thickness of not less than 12mm, and a rough surface treatment with a rough surface area of ​​not less than 90%.

[0083] When the sealing diaphragm is installed piece by piece, the length of each sealing diaphragm is 500mm; when the sealing diaphragm is installed as an integral strip, the length of each side of the sealing diaphragm exceeds the length of the precast diaphragm wall 1 by 300mm (i.e., the length of the sealing diaphragm is 600mm longer than the hoisting length of the corresponding precast diaphragm wall 1), and the overlap length of the sealing diaphragm at the junction of adjacent sections of the precast diaphragm wall 1 is at least 300mm.

[0084] Step 5: Segmented and modular high-pressure grouting for sealing:

[0085] After all precast components in the construction section are hoisted and the sealing slabs are installed, high-pressure grouting is carried out through the reserved holes at the bottom of the precast diaphragm wall 1. Only grouting holes are reserved, and no overflow holes are left. The grouting material is low-shrinkage, high-strength, and micro-expansion grouting material. The grouting process is carried out in three pressurized grouting stages. Finally, the grouting material fills the gaps between the precast diaphragm wall 1, the composite steel pile 2, and the soil layer. Through stepped pressurization, the grouting material can penetrate into the soil layer. This allows the composite steel pile 2 to retain soil while the surrounding soil is reinforced, forming a combined force-bearing structure of "composite steel pile 2 + precast diaphragm wall 1 + soil reinforcement". Ultimately, this structure can resist soil pressure and ensure the safety and reliability of the foundation pit retaining structure.

[0086] Step Six: Drilling, tensioning, anchoring, and grouting of prestressed tendons 4:

[0087] After high-pressure grouting in the construction section, and after curing for at least 72 hours, the lower layer of earthwork excavation and the hoisting of the precast diaphragm wall 1 will be carried out. For the construction section that has been hoisted and completed, prestressed tendon 4 ducts are provided inside the precast diaphragm wall 1. The openings of the prestressed tendon 4 ducts inside the precast diaphragm wall 1 in adjacent sections should be in the same position to facilitate the subsequent prestressed tendon 4 drilling operation. During the hoisting of the precast diaphragm wall 1, the prestressed tendon 4 ducts inside each adjacent precast diaphragm wall 1 are connected by the wire rope traction method. The prestressed tendon 4 drilling, tensioning, anchoring and grouting work is carried out on every 3 to 5 sections of the precast diaphragm wall 1. Each precast diaphragm wall 1 is designed with no less than 3 prestressed tendons 4. One prestressed tendon 4 is set 300mm below the top and 300mm above the bottom of the first layer of precast diaphragm wall 1. The tensioning and anchoring ends of the prestressed tendons 4 between two adjacent layers of precast diaphragm wall 1 should be staggered by at least 1000mm.

[0088] Step 7: Repeat steps 2 to 6 until all precast diaphragm walls are hoisted on-site.

[0089] After all the above-mentioned processes are completed in the first-floor precast diaphragm wall 1 construction section, repeat steps two to six until all precast diaphragm walls 1 are hoisted on site. Perform process acceptance work for each construction section, with a focus on the acceptance work of concealed works such as high-pressure grouting.

[0090] Step 8: Laying the waterproof membrane at the seams (5 steps)

[0091] After the entire underground retaining structure is hoisted and constructed, SBS waterproof membrane 5 is cold-applied and laid at the joints of the combined steel pile 2 and the precast underground continuous wall 1, as well as at the joints of two adjacent precast underground continuous walls 1. Double-layer waterproofing is carried out. The waterproof membrane 5 is laid tightly along the joints of the combined steel pile 2 and the precast underground continuous wall 1, without any hollow areas. The waterproof membrane 5 at the horizontal joints is laid on the inside of the waterproof membrane 5 at the vertical joints. The width of the waterproof membrane 5 is not less than 600mm and extends beyond the joint by not less than 200mm on each side. The waterproofing at the bottom of the retaining structure is combined with the waterproofing of the basement floor slab. The waterproof membrane 5 is laid from the basement to the vertical precast underground continuous wall 1, and the waterproof membrane 5 is wrapped with a height of not less than 500mm.

[0092] Step Nine: Install stiffening rib plates 6 at the joint nodes, and apply high-pressure sprayed fine aggregate concrete surface layer:

[0093] After all the waterproof membrane 5 at the joints is laid, stiffening ribs 6 are installed at the joints connecting the combined steel piles 2 and the precast diaphragm wall 1, and at the joints between two adjacent precast diaphragm walls 1. The stiffening ribs 6 are at least 750mm long, 90mm wide, and 16mm thick. They are tightened onto the precast diaphragm wall 1 using internal thread self-tapping threads. The spacing between the stiffening ribs 6 is no more than 600mm. Both ends of the stiffening ribs 6 are connected to the precast diaphragm wall 1, and the connection and fixing points must not be located within the area where the waterproof membrane 5 has been laid. Therefore, the membrane laying position and the pre-embedded position of the fixing points of the stiffening ribs 6 should be fully considered during the precast production of the precast diaphragm wall 1 in the PC factory. After all the stiffening ribs 6 at the joints are installed, high-pressure sprayed fine stone concrete is used to spray the surface layer of the overall enclosure structure, and the overall acceptance work is carried out.

[0094] This invention effectively utilizes a combination of 2 composite steel piles and 1 precast diaphragm wall for soil retention and load-bearing. High-pressure grouting is used for hoisting and joint filling while simultaneously reinforcing the surrounding soil, resulting in a more rational overall structural stress distribution. The combined load-bearing system of "2 composite steel piles + 1 precast diaphragm wall + soil reinforcement" formed by this invention, with its precast structure hoisting, combines load-bearing and water-stopping functions, enabling rapid construction and making it worthy of widespread application in the industry.

[0095] Finally, it should be noted that the above are merely 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 foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A construction method for a combined steel pile retaining structure for underground continuous wall, characterized in that, It includes composite steel piles (2), precast underground continuous wall (1), high-strength bolts (3), reinforcing connecting angle steel (7), prestressed tendons (4), waterproof membrane (5) and stiffening rib plate (6); The composite steel pile (2) is driven into the foundation soil layer. The composite steel pile (2) is fixed to the precast underground continuous wall (1) by high-strength bolts (3). The precast underground continuous wall (1) is provided with prestressed tendons (4). Waterproof membrane (5) is laid at the connection node between the precast underground continuous wall (1) and the composite steel pile (2). Reinforcing ribs (6) are provided outside the waterproof membrane (5). Reinforcing connecting angle steel (7) is also provided at the end of the connection node between the composite steel pile (2) and the precast underground continuous wall (1). The connection node between the precast underground continuous wall (1) and the combined steel pile (2) is a groove (101), and high-strength micro-expansion fine stone concrete (8) is provided in the groove (101) at the connection node between the precast underground continuous wall (1) and the combined steel pile (2). The entire enclosure structure surface is covered with a high-pressure sprayed fine aggregate concrete surface layer; Includes the following steps: Step 1: Measure and set out the stake positions, and drive in the composite steel piles (2). Step 2: Excavation of earthwork, fixing of composite steel piles (2) and high-strength bolts (3); Step 3: Precast underground continuous wall (1) Sectional hoisting and fixing of the precast underground continuous wall; Step 4: Install layered sealing grouting baffles horizontally; Step 5: Segmented and modular high-pressure grouting for sealing; Step 6: Drilling, tensioning, anchoring and grouting of prestressed tendons (4); Step 7: Repeat steps 2 to 6 until all precast underground continuous walls are installed on site (1); Step 8: Laying the waterproof membrane (5) at the seams; Step 9: Install stiffening ribs (6) at the joint nodes, and apply high-pressure sprayed fine aggregate concrete surface layer; The specific steps are as follows: Step 1: Measure and set out the stake positions, and drive in the composite steel piles (2): First, according to the construction drawings, the survey and layout are carried out to accurately locate the plane position of each pile. Then, the composite steel pile (2) is driven into place using the static pile driving method. The composite steel pile (2) includes H-beams and cross-shaped piles. The H-beams and cross-shaped piles are integrally formed in the factory and driven into place on site. When the composite steel pile (2) encounters complex geological soil layers and is difficult to continue driving, the composite steel pile (2) is first pulled out. Then, it is treated by high-pressure water jetting and drilling expansion method. After treatment, the pile hole of the composite steel pile (2) is filled with a mixture of fine stones and coarse sand in a ratio of 1:2.5 and the composite steel pile (2) is driven into place. The horizontal position error of the driven composite steel pile (2) does not exceed 6mm and the verticality deviation does not exceed 0.5%. Step 2: Earthwork excavation, fixing of composite steel piles (2) and high-strength bolts (3): After all the composite steel piles (2) have been driven in, in order to better control the maximum displacement of the top of the foundation pit, reinforced concrete piers are designed around the foundation pit 2000mm away from the top of the composite steel piles (2). 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 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 (2) are exposed. Then, the cross-shaped piles on the side of the composite steel piles (2) closest to the inside of the foundation pit are cleaned by manual means. 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 precast underground continuous wall (1) are passed through the bolt holes from the inside of the composite 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 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 distance between the top high-strength bolts (3) and the top surface of the composite steel pile (2) is not less than 350mm. The distance between the bottom high-strength bolts (3) of each construction section and the bottom surface of the precast underground continuous wall (1) after it is in place is not less than 350mm. Step 3: Precast diaphragm wall (1) Segmental and block-by-block hoisting and fixing: After the high-strength bolts (3) of the composite steel piles (2) are fixed, the first-floor precast underground continuous wall (1) is hoisted. Before hoisting the precast underground continuous wall (1), the spacing between each composite steel pile (2) is checked, and the size and reserved connection hole position of each precast underground continuous wall (1) that has been brought to the site are compared. The precast diaphragm wall (1) has a groove (101) interface at the connection node with the composite steel pile (2). The precast diaphragm wall (1) is hoisted by a segment-by-segment, block-by-block "secondary fixing method". After the precast diaphragm wall (1) is hoisted to the position, the high-strength bolts (3) of the extended composite steel pile (2) are calibrated. The extended high-strength bolts (3) are inserted into the reserved holes of the precast diaphragm wall (1) in one go with manual assistance, and the nuts are initially tightened. After all the high-strength bolts (3) of the precast diaphragm wall (1) are through the holes, the high-strength bolts (3) are tightened again. The final setting sequence adopts the technique of "tightening from the middle to both sides, tightening the upper part first and then the lower part". Technical method; In order to better strengthen and fix the connection node between the composite steel pile (2) and the precast underground continuous wall (1), on the basis of direct fixing by high-strength bolts (3), a secondary bolt fixing of a reinforcing connecting angle steel (7) is provided at the connection node near the inner side of the foundation pit. One end of the reinforcing connecting angle steel (7) is fixed to the composite steel pile (2) by bolts, and the other end of the reinforcing connecting angle steel (7) is tightened into the internal thread reserved inside the precast underground continuous wall (1) by bolts. The bolt connection diameter used for fixing the secondary bolt of the reinforcing connecting 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 layered grouting baffles horizontally: After the first-floor precast underground continuous wall (1) is hoisted and constructed, in order to meet the requirements of subsequent high-pressure grouting process, layered grouting diaphragms are installed horizontally at the bottom of the precast underground continuous wall (1) in the construction section in the early stage. The grouting diaphragms are installed by means of individual blocks or by means of integral strips. The depth of the grouting diaphragms into the soil layer is not less than 350mm, the thickness of the grouting diaphragms is not less than 12mm, and the surface is roughened with a rough surface area of ​​not less than 90%. When the sealing partition is installed piece by piece, the length of each sealing partition is 500mm; when the sealing partition is installed as an integral strip, the length of each side of the sealing partition exceeds the precast underground continuous wall (1) by 300mm, and the overlap length of the sealing partition at the junction of the precast underground continuous wall (1) in adjacent sections is at least 300mm. Step 5: Segmented and modular high-pressure grouting for sealing: After all the precast components in the construction section are hoisted and the sealing slab is installed, high-pressure grouting is carried out through the reserved holes at the bottom of the precast underground continuous wall (1). Only grouting holes are reserved, and no overflow holes are reserved. The grouting material is low-shrinkage, high-strength, and micro-expansion grouting material. The grouting process is carried out in three pressurized grouting stages. Finally, the grouting material fills the gap between the precast underground continuous wall (1), the combined steel pile (2), and the soil layer. The grouting material can penetrate into the soil layer through the step-by-step pressurization. This allows the combined steel pile (2) to retain soil while the surrounding soil is reinforced, forming a combined force-bearing form of "combined steel pile (2) + precast underground continuous wall (1) + soil layer reinforcement". This can ultimately resist soil pressure and ensure the safety and reliability of the foundation pit retaining structure. Step Six: Drilling, tensioning, anchoring and grouting of prestressed tendons (4): After high-pressure grouting in the construction section, and curing for at least 72 hours, the lower layer of earthwork excavation and hoisting of the precast diaphragm wall (1) are carried out. For the construction section that has been hoisted and completed, prestressed tendon (4) ducts are provided inside the precast diaphragm wall (1). The prestressed tendon (4) ducts inside the precast diaphragm wall (1) in adjacent sections should be in the same position to facilitate subsequent prestressed tendon (4) drilling operations. During the hoisting process of the precast diaphragm wall (1), the ducts inside each adjacent precast diaphragm wall (1) are hoisted using the wire rope traction method. The prestressing tendons (4) ducts are connected. The prestressing tendons (4) are perforated, tensioned, anchored and grouted on the precast underground continuous wall (1) in every 3 to 5 sections. Each precast underground continuous wall (1) has no less than 3 prestressing tendons (4) inside. A prestressing tendon (4) is set 300mm below the top and 300mm above the bottom of the first-floor precast underground continuous wall (1). The tensioning and anchoring ends of the prestressing tendons (4) between two adjacent precast underground continuous walls (1) should be staggered by at least 1000mm. Step 7: Repeat steps 2 to 6 until all precast diaphragm walls are completed. (1) On-site hoisting: After all the process construction in the first-floor precast underground continuous wall (1) construction section is completed, repeat steps two to six until all the precast underground continuous walls (1) are hoisted on site. Do a good job of process acceptance of each construction section, and focus on the acceptance of high-pressure grouting concealed works. Step 8: Laying the waterproof membrane (5) at the seams: After the entire underground retaining structure is hoisted and constructed, SBS waterproof membrane (5) is cold-bonded at the joint of the combined steel pile (2) and the precast underground continuous wall (1) and at the joint of the two adjacent precast underground continuous walls (1). Double-layer waterproof construction is carried out. The waterproof membrane (5) is laid along the joint of the combined steel pile (2) and the precast underground continuous wall (1) with a tight and concave-convex pattern. The waterproof membrane (5) of the horizontal joint is laid on the inside of the waterproof membrane (5) of the vertical joint. The width of the waterproof membrane (5) is not less than 600mm and each side extends beyond the joint by not less than 200mm. The waterproofing of the bottom part of the retaining structure is combined with the waterproofing of the basement floor slab. The waterproof membrane (5) of the basement is laid towards the vertical precast underground continuous wall (1). The waterproof membrane (5) is wrapped with a laying height of not less than 500mm. Step 9: Install stiffening ribs (6) at the joints, and apply high-pressure sprayed fine aggregate concrete surface layer: After all the waterproof membrane (5) at the joints is laid, stiffening ribs (6) are installed at the joints of the combined steel piles (2) and the precast underground continuous wall (1) and at the joints of the two adjacent precast underground continuous walls (1). The stiffening ribs (6) are not less than 750mm long, not less than 90mm wide, and not less than 16mm thick. They are tightened onto the precast underground continuous wall (1) using internal thread self-tapping thread. The spacing of the stiffening ribs (6) is not more than 600mm. The two ends of the stiffening ribs (6) are connected to the precast underground continuous wall (1), and the connection and fixing points are not located within the area of ​​the waterproof membrane (5) that has been laid. After all the stiffening ribs (6) at the joints are installed, high-pressure sprayed fine stone concrete is used to spray the surface layer of the overall enclosure structure and complete the overall acceptance work.

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