Construction method of pile cap foundation pit water stop support based on assembly type steel formwork

Abstract

The invention discloses a construction method of a pile cap foundation pit water stop support based on an assembly type steel formwork. The construction method comprises the steps that pile cap earthwork is excavated, a pile cap assembly type steel formwork is installed, an anti-deformation supporting structure is installed, gap earthwork between the outer portion of the pile cap assembly type steel formwork and a pile cap foundation pit is backfilled, concrete cushion layers of the bottom and the peripheral area of the pile cap are poured, steel bars in the pile cap are bound, and concrete of the pile cap area is poured. And finishing the construction of the pile cap structure. According to the construction method, the prefabricated steel formwork serves as a formwork structure of the pile cap foundation pit, internal water stopping can be conducted quickly, the box body can safely bear lateral pressure of external water, quicksand and backfill soil, and a safe and stable construction environment is created for follow-up operation procedures such as steel bar binding and concrete construction of the pile cap.

Description

Technical Field

[0001] This invention relates to the field of building construction technology, and in particular to a construction method for water-stopping support of pile cap foundation pits. Background Technology

[0002] In underground construction projects, wooden formwork or brick walls are typically used as structural formwork for the construction of pile caps, sump pits, and elevator shaft pits. Wooden formwork is widely available, flexible in assembly, and has a certain applicability in construction scenarios. However, existing formwork structures have the following shortcomings during construction:

[0003] 1) Wooden formwork has low structural strength and cannot withstand large external forces, so it is only suitable for foundations with relatively gentle angles. In addition, wood does not have water-blocking properties, and it is easy for the formwork to leak in environments with groundwater seepage, which affects the construction quality. At the same time, wooden formwork needs to be reused after dismantling. During construction, additional auxiliary measures such as well point dewatering and steel sheet pile support are required, which not only increases the construction cost, but also makes it easy for quicksand piping to occur due to incomplete dewatering or deformation of the support structure, which may lead to the risk of foundation pit collapse.

[0004] 2) When wooden formwork cannot meet construction requirements, the industry usually chooses brick walls as an alternative formwork. However, in some special construction environments, brick walls also face severe challenges: First, in areas with poor geological conditions, there is often a problem of abundant groundwater and high content of quicksand. Under such adverse geological conditions, the excavation depth of pile caps and elevator shaft foundation pits is usually large. The overall stability of brick walls is weak, making it difficult to resist the seepage pressure of groundwater and the lateral squeezing effect of quicksand. This can easily lead to safety hazards such as wall cracking and collapse, seriously threatening construction safety. Second, in southern and coastal areas, typhoons are frequent and rainfall is abundant. During the construction of the bottom structure in the underground stage, strong winds and heavy rainfall can easily exacerbate the instability of the soil around the foundation pit, further weakening the overturning resistance of the brick walls. This can not only cause damage to the formwork structure but also delay the construction progress, bringing great difficulties to the construction of the bottom structure in the underground stage.

[0005] 3) Traditional wooden formwork requires on-site cutting and assembly, which is complicated and relies on manual operation. After the formwork is installed, it is necessary to wait for external support or rainwater stabilization before subsequent work can be carried out. In addition, wooden formwork is easily deformed by the lateral pressure of external soil during construction, requiring frequent adjustment and reinforcement, which further prolongs the construction period.

[0006] 4) In traditional construction, after the pile cap formwork is installed, sufficient working space needs to be reserved for rebar tying and concrete pouring. Furthermore, the area around the foundation pit cannot be backfilled before the formwork is removed, which causes the construction in this area to conflict with other processes (such as basement structure construction), occupying on-site construction space and affecting the overall construction progress.

[0007] 5) Traditional formwork needs to be removed after construction. The removal process can easily damage the surface of the pile cap structure. Some formwork is difficult to reuse due to poor size adaptability. If it is not removed in time, it is easy to be soaked in groundwater and corroded, increasing construction risks. Summary of the Invention

[0008] In view of this, in order to solve the technical problems existing in the prior art, the present invention provides a construction method that uses prefabricated and assembled prefabricated steel formwork as the formwork structure for pile cap foundation pits under such adverse geological conditions. This method can quickly stop internal water, and the box body can safely bear the lateral pressure of external water, quicksand, and backfill soil. It creates a safe and stable construction environment for subsequent operations such as pile cap reinforcement binding and concrete construction. This method can effectively solve the impact of excessive and rapid groundwater and quicksand on pile cap foundation pit construction, improve construction safety and efficiency, shorten the construction cycle, and accelerate the construction progress.

[0009] The present invention solves the above-mentioned technical problems through the following technical solutions:

[0010] A construction method for water-stopping support of pile cap foundation pit based on prefabricated steel formwork, the construction method comprising the following steps:

[0011] Step 1) Excavate the soil for the pile cap;

[0012] Step 2) Install prefabricated steel formwork for pile caps: This specifically includes:

[0013] Step 21) Prefabrication of formwork: The first support steel plate, formwork unit, first connection structure, second connection structure, and anti-deformation support structure are prefabricated in the factory;

[0014] Step 22) Assemble the second support steel plate: Connect and fix the two template units into a second support steel plate through the first connecting structure, and repeat the above operation to assemble the second support steel plate;

[0015] Step 23) Assemble into a box-type prefabricated steel formwork: Use a crane to lift the two first support steel plates and the two second support steel plates assembled in step 22) into the foundation pit, arrange them according to the design outline of the pile cap, with the first support steel plate corresponding to the short side of the pile cap and the second support steel plate corresponding to the long side of the pile cap. The two first support steel plates and the two second support steel plates are assembled into a box-type prefabricated steel formwork through the second connecting structure.

[0016] Step 24) Install anti-deformation support structure: Install anti-deformation support structure inside the box-type prefabricated steel formwork;

[0017] Step 3) Backfill the gap between the prefabricated steel formwork of the pile cap and the pile cap foundation pit.

[0018] Step 4) Pour the concrete cushion layer at the bottom and around the pile cap;

[0019] Step 5) Tie the internal reinforcement bars of the pile cap;

[0020] Step 6) Pour concrete in the pile cap area to complete the pile cap structure construction.

[0021] Further, the prefabricated steel formwork described in step 2) includes two first support steel plates, two second support steel plates, a second connecting structure, and anti-deformation supports. The two first support steel plates are arranged in parallel relative to each other, and the two second support steel plates are arranged in parallel relative to each other. The two first support steel plates and the two second support steel plates are assembled into a box-type prefabricated steel formwork through the second connecting structure.

[0022] Furthermore, the first support steel plate has a plurality of first lifting holes, and the second support steel plate has a plurality of second lifting holes. The plurality of first lifting holes are distributed at intervals on the upper end of the first support steel plate, and the plurality of second lifting holes are distributed at intervals on the upper end of the second support steel plate.

[0023] Further, in step 23), the second connection structure includes a second angle steel connecting plate and a second connecting bolt. The second angle steel connecting plate has a second long adjustment hole, and the first support steel plate has a first connecting hole that mates with the second connecting bolt. The first support steel plate and the second support steel plate have a first bolt hole and a second bolt hole that mate with the second connecting bolt, respectively. The second angle steel connecting plate is located at the junction of the first support steel plate and the second support steel plate. The second connecting bolt passes through the second long adjustment hole of the second angle steel connecting plate, the first bolt hole of the first support steel plate, and the second bolt hole of the second support steel plate and is then locked to fix the first support steel plate and the second support steel plate together.

[0024] Furthermore, the back of the first support steel plate is provided with a plurality of first vertical reinforcement members arranged at equal intervals along the vertical direction of the first support steel plate, and the back of the first support steel plate is provided with a plurality of first transverse reinforcement members arranged at intervals along the horizontal direction of the first support steel plate. The plurality of first transverse reinforcement members are evenly spaced along the vertical direction of the first vertical reinforcement members. The first transverse reinforcement members are arranged parallel to each other on the back of the first support steel plate and intersect perpendicularly with the adjacent first vertical reinforcement members and are welded together.

[0025] Further, in step 23), each second support steel plate is formed by connecting and fixing two template units through a first connecting structure. The first connecting structure includes a first connecting steel plate and several first connecting bolts. The two template units are arranged side by side and connected to each other. A first long adjustment hole is provided on the first connecting steel plate. A third bolt hole that cooperates with several first connecting bolts is provided on the two template units. The first connecting steel plate is set at the joint of the two template units and locked and fixed by several first connecting bolts.

[0026] Furthermore, each template unit has several second vertical reinforcement members arranged at equal intervals along the vertical direction of the template unit on its back, and several second transverse reinforcement members arranged at intervals along the horizontal direction of the template unit on its back. The several second transverse reinforcement members are evenly spaced along the vertical direction of the second vertical reinforcement members. The second transverse reinforcement members are arranged parallel to each other on the back of the template unit and intersect perpendicularly with the adjacent second vertical reinforcement members and are welded together.

[0027] Further, the anti-deformation support structure described in step 24) includes several anti-deformation support rods, movable bolts, and fixing nuts. The several anti-deformation support rods are spaced apart between the two second support steel plates. Each second support steel plate is provided with fixing holes that cooperate with the movable bolts. The fixing holes extend from the second support steel plate to the second vertical reinforcement of the second support steel plate. The fixing nuts of the anti-deformation support structure are welded to the second vertical reinforcement of the second support steel plate and aligned with the fixing holes. The two ends of the anti-deformation support rods are respectively aligned with the fixing nuts on the second vertical reinforcement of the second support steel plate. The movable bolts are inserted into the fixing nuts on the second vertical reinforcement of one of the second support steel plates and one end of the anti-deformation support rod, and then tightened to fix one end of the anti-deformation support rod to one of the second support steel plates. At the same time, the other end of the anti-deformation support rod is connected to the corresponding fixing hole of the other second support steel plate through the movable bolts and locked with the fixing nuts.

[0028] Furthermore, the box-type prefabricated steel formwork assembled in step 23) is embedded in the concrete of the pile cap area as a permanent water-stopping support structure.

[0029] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects:

[0030] 1) The construction method of this invention includes excavating the pile cap soil, installing prefabricated steel formwork for the pile cap, installing anti-deformation support structure, backfilling the gap between the prefabricated steel formwork and the pile cap foundation pit, pouring concrete cushion layer at the bottom and surrounding area of ​​the pile cap, tying internal reinforcement bars of the pile cap, and pouring concrete in the pile cap area to complete the pile cap structure construction. This construction method uses prefabricated, assembled steel formwork as the water-stopping support formwork structure for the pile cap foundation pit. It can quickly stop internal water flow and safely withstand the lateral pressure of external water, quicksand, and backfill soil. It provides a safe and stable construction environment for subsequent operations such as reinforcement tying and concrete construction of the pile cap, effectively solving the impact of excessive and rapid groundwater and quicksand on the pile cap foundation pit construction, improving construction safety and efficiency, shortening the construction cycle, and accelerating the construction progress.

[0031] 2) The prefabricated steel formwork of the present invention adopts two first support steel plates and two second support steel plates spliced ​​together to form a box-shaped integrated prefabricated steel formwork structure. The steel formwork is welded to the vertical and horizontal reinforcements on the back, resulting in excellent overall rigidity and sealing performance. After the box-shaped prefabricated steel formwork structure is formed, it can quickly achieve internal water stoppage and can safely bear the lateral pressure of external water, quicksand and backfill soil. The box-shaped prefabricated steel formwork is equipped with an anti-deformation support structure inside to further resist lateral pressure and effectively avoid the risk of quicksand inflow and foundation pit collapse.

[0032] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, the following detailed description is provided in conjunction with preferred embodiments and accompanying drawings. Attached Figure Description

[0033] Figure 1 This is a flowchart of the construction method of the present invention;

[0034] Figure 2 This is a schematic diagram of the excavation of the pile cap soil according to the present invention;

[0035] Figure 3 This is a schematic diagram of the prefabricated steel formwork for installing pile caps according to the present invention;

[0036] Figure 4 This is a schematic diagram of the earthwork between the exterior of the prefabricated steel formwork for the backfill pile cap and the pile cap foundation pit according to the present invention.

[0037] Figure 5 This is a schematic diagram of the concrete cushion layer at the bottom and surrounding area of ​​the pile cap according to the present invention.

[0038] Figure 6 This is a schematic diagram of the internal reinforcement of the pile cap of the present invention;

[0039] Figure 7 This is a schematic diagram of the concrete pouring process for the pile cap area according to the present invention.

[0040] Figure 8 This is a schematic diagram of the prefabricated steel formwork of the present invention;

[0041] Figure 9 This is a schematic diagram of the structure of the first support steel plate of the present invention;

[0042] Figure 10 This is a structural schematic diagram of the first support steel plate of the present invention from another angle;

[0043] Figure 11 This is a schematic diagram of the structure of the second support steel plate of the present invention;

[0044] Figure 12 This is a structural schematic diagram of the second support steel plate of the present invention from another angle;

[0045] Figure 13 This is an exploded view of the second support steel plate of the present invention;

[0046] Figure 14 This is a schematic diagram showing the relationship between the first support steel plate, the first connecting structure, and the second support steel plate of the present invention.

[0047] Figure 15 This is a detailed schematic diagram showing the connection between the anti-deformation support structure of the present invention and the template unit in the second support steel plate.

[0048] In the diagram: 1. Prefabricated steel formwork; 11. First support steel plate; 11. First hoisting hole; 111. First vertical reinforcement; 112. First horizontal reinforcement; 113. First bolt hole; 114. Second support steel plate; 12. Second hoisting hole; 121. Formwork unit; 122. Third bolt hole; 1221. First connecting structure; 123. First connecting steel plate; 1231. First connecting bolt; 1232. Second vertical reinforcement; 124. Second horizontal reinforcement; 125. Fixing hole; 126. Second bolt hole; 127. Second connecting structure; 13. Second angle steel connecting plate; 131. Second connecting bolt; 132. Anti-deformation support structure; 14. Anti-deformation support rod; 141. Movable bolt; 142. Fixing nut; 143. Pile cap; 2. Concrete cushion layer; 3. Backfill soil; 4. Internal reinforcement; 5. Concrete structure; 6. Detailed Implementation

[0049] The present invention will now be described in detail with reference to the accompanying drawings, which form part of this specification. The principles of the invention are illustrated by means of embodiments, and other aspects, features, and advantages of the invention will become apparent from this detailed description. In the accompanying drawings, the same or similar parts in different figures are indicated by the same reference numerals.

[0050] like Figures 1-7 As shown, the present invention provides a construction method for water-stopping support of the pile cap 2 foundation pit based on prefabricated steel formwork 1. The construction method includes the following steps:

[0051] Step 1) Excavation of pile cap 2: According to the design dimensions of pile cap 2 (3000mm long × 2000mm wide × 1500mm deep), an excavator is used to excavate the foundation pit. During the excavation, the slope is set at 1:0.5 to prevent the slope from collapsing.

[0052] Step 2) Install the prefabricated steel formwork 1 for the pile cap 2, specifically including:

[0053] Step 21) Prefabrication of templates: The first support steel plate 11, template unit 122, first connecting structure 123, second connecting structure 13, and anti-deformation support structure 14 are prefabricated in the factory. The template unit 122 has the same structure as the first support steel plate 11.

[0054] Step 22) Assemble the second support steel plate 12: Hoist the two prefabricated template units 122 (same as the first support steel plate 11) to the flat area at the edge of the foundation pit, align them according to the design position (joint gap ≤ 2mm), and assemble them using the first connecting structure 123. Attach the first connecting steel plate 1231 of the first connecting structure 123 to the outside of the joint of the two template units 122, aligning the first long adjustment hole on the first connecting steel plate 1231 with the pre-set third bolt hole of the template unit 122. The third bolt hole on 22 is prefabricated in the factory. The hole spacing matches the first long adjustment hole of the first connecting steel plate 1231. After the first connecting bolt 1232 of the first connecting structure 123 is inserted, the nut is tightened. The position of the template unit 122 is finely adjusted through the first long adjustment hole to ensure that the overall verticality of the spliced ​​second support steel plate 12 is ≤1‰. After checking with a level, the first connecting bolt 1232 is tightened to complete the assembly of one second support steel plate 12. The above operation is repeated to assemble the second second support steel plate 12.

[0055] Step 23) Assemble into box-type prefabricated steel formwork 1: Use a crane to lift two first support steel plates 11 and two assembled second support steel plates 12 into the pile cap 2 foundation pit. Arrange the first support steel plates 11 to correspond to the short side of the pile cap 2 and the second support steel plates 12 to correspond to the long side of the pile cap 2 according to the design outline of the pile cap 2, forming box-type prefabricated steel formwork 1. Specifically, first place the first support steel plates 11 upright on both sides of the short side of the foundation pit, adjust their position to make the first support steel plates 11 fit tightly with the bottom of the foundation pit (gap ≤ 5mm), check the verticality of the first support steel plates 11 with a level, and use temporary supports (wooden) (Fang) Fix; then place the second support steel plate 12 upright on both sides of the long side of the foundation pit, so that the end of the second support steel plate 12 is in contact with the side of the first support steel plate 11, with a joint gap of ≤2mm. Use the second angle steel connecting plate 131 to connect. Place the second angle steel connecting plate 131 in contact with the junction of the first support steel plate 11 and the second support steel plate 12, so that the second long adjustment hole on the second angle steel connecting plate 131 is aligned with the first bolt hole 114 of the first support steel plate 11 and the second bolt hole 127 of the second support steel plate 12. Then insert the second connecting bolt 132 and tighten it to complete the assembly of the box-type prefabricated steel formwork 1.

[0056] Step 24) Install the anti-deformation support structure 14: Based on the lateral pressure of the soil in the foundation pit (calculated as 15 kPa in this embodiment), install the anti-deformation support structure 14 inside the box-type prefabricated steel formwork 1. Align the two ends of the anti-deformation support rod 141 of the anti-deformation support structure 14 with the fixing holes 126 on the second support steel plate 12 (prefabricated in the factory). The two second support steel plates 12 are provided with fixing holes 126 that cooperate with the movable bolts 142. The fixing holes 126 extend from the second support steel plate 12 to the second vertical reinforcement 124 of the second support steel plate 12. Weld the fixing nuts 143 of the anti-deformation support structure 14 to the second vertical reinforcement 124 of the second support steel plate 12 and align them with the fixing holes 126. Align the two ends of the anti-deformation support rod 141 with the fixing nuts 143 on the second vertical reinforcement 124 of the second support steel plate 12. Insert the movable bolts 142 into the second vertical reinforcement of one of the second support steel plates 12. After initially tightening the fixing nut 143 on 124 and one end of the anti-deformation support rod 141, adjust the levelness of the anti-deformation support rod 141. Use a level to check that the horizontal deviation is ≤2mm / m to ensure that the anti-deformation support rod 141 is perpendicular to the second support steel plate 12. Then, tighten the movable bolt 142 completely to fix one end of the anti-deformation support rod 141 to one of the second support steel plates 12. At the same time, connect the other end of the anti-deformation support rod 141 to the corresponding fixing hole 126 of the other second support steel plate 12 (the hole position is prefabricated in the factory) through the movable bolt 142, and lock it with the fixing nut 143 to prevent the anti-deformation support rod 141 from shifting. In this embodiment, multiple anti-deformation support rods 141 are installed on the outer side of each second support steel plate 12 along the height direction, with a spacing of 800mm. Each anti-deformation support rod 141 is close to both sides of the second support steel plate 12 to ensure that the box formwork can resist the lateral pressure of external water, quicksand and backfill soil 4.

[0057] Step 3) Backfilling the gap between the prefabricated steel formwork 1 and the foundation pit of pile cap 2: After the prefabricated steel formwork 1 is installed and accepted, the gap between the prefabricated steel formwork 1 and the slope of the foundation pit, with a gap width of about 200~300mm, is backfilled. Plain soil is used for layered backfilling, with each layer having a thickness of ≤200mm. A small compactor (vibration force ≥20kN) is used to compact each layer, with a compaction degree ≥93%.

[0058] Step 4) Pouring the concrete cushion layer 3 at the bottom and around the pile cap 2: Specifically including:

[0059] Step 41) Arrangement of foundation reinforcement: According to the design drawings, HRB400E steel mesh is laid on the bottom surface of the foundation pit inside the box-type prefabricated steel formwork 1 and around the outer perimeter of the prefabricated formwork, with a height of 300mm. Spacers with a thickness of 50mm are set between the steel mesh and the prefabricated formwork to ensure that the thickness of the steel reinforcement protective layer meets the design requirements (bottom surface ≥ 50mm, side surface ≥ 40mm).

[0060] Step 42) Concrete pouring: C15 concrete is used to pour the foundation layer. The pouring sequence is as follows: first pour the bottom foundation layer with a thickness of 100mm, then pour the surrounding foundation layer with a height of 300mm, and pour it as a whole with the bottom foundation layer. During the pouring process, an immersion vibrator with a diameter of 50mm is used to compact the concrete. The vibration spacing is ≤300mm to avoid missed vibration or over-vibration. After pouring, a membrane is used for curing. The curing time is ≥7 days to ensure that the concrete strength of the foundation layer reaches more than 70% of the design strength.

[0061] Step 5) Binding the internal reinforcement 5 of pile cap 2: After the concrete of the foundation layer has been cured and qualified, bind the internal reinforcement 5 according to the design drawings of pile cap 2.

[0062] Step 6) Pour concrete in the pile cap 2 area to complete the construction of the pile cap 2 structure: C30 commercial concrete is used to pour the pile cap 2 in layers, with each layer having a thickness of ≤500mm. An immersion vibrator is used to compact the concrete until there are no air bubbles and the surface of the concrete structure 6 is covered with slurry. The prefabricated steel formwork 1 is then permanently embedded in the concrete structure 6. After pouring, the concrete is covered with a membrane and geotextile for curing within 12 hours. After the concrete strength reaches 100% of the design strength, the pile cap 2 structure is inspected and accepted. After the inspection is passed, the construction of the pile cap 2 structure is completed.

[0063] like Figures 8-15 As shown, in specific implementation, the prefabricated steel formwork 1 described in step 2) includes two first support steel plates 11, two second support steel plates 12, a second connecting structure 13, and anti-deformation supports. The two first support steel plates 11 are arranged in parallel relative to each other, and the two second support steel plates 12 are arranged in parallel relative to each other. The two first support steel plates 11 and the two second support steel plates 12 are assembled into a box-type prefabricated steel formwork 1 through the second connecting structure 13. The box-type prefabricated steel formwork 1 formed by the specific connecting structure and steel formwork assembly method can effectively resist the lateral pressure of external water, quicksand, and backfill soil 4. This invention utilizes the advantages of prefabricated steel formwork 1 to solve the impact of groundwater and quicksand on construction under adverse geological conditions, improve construction safety and efficiency, shorten the construction cycle, and the assembled prefabricated steel formwork 1 can remain permanently in the pile cap 2 structure without affecting the project quality.

[0064] A plurality of first lifting holes 111 are provided at the upper end of the first support steel plate 11, and a plurality of second lifting holes 121 are provided at the upper end of the second support steel plate 12. The plurality of first lifting holes 111 are spaced apart from each other at the upper end of the first support steel plate 11, and the plurality of second lifting holes 121 are spaced apart from each other at the upper end of the second support steel plate 12. In specific implementation, the size of the first lifting holes 111 and the second lifting holes 121 is 30mm in diameter. The provision of the first lifting holes 111 and the second lifting holes 121 facilitates the hoisting of the assembled box-type prefabricated steel formwork 1 onto the pile cap 2.

[0065] In a specific implementation of this embodiment, the second connecting structure 13 in step 23) includes a second angle steel connecting plate 131 and a second connecting bolt 132. The second angle steel connecting plate 131 has a second long adjustment hole. The first support steel plate 11 has a first connecting hole that mates with the second connecting bolt 132. The first support steel plate 11 and the second support steel plate 12 have a first bolt hole 114 and a second bolt hole 127 that mate with the second connecting bolt 132, respectively. The second angle steel connecting plate 131 is located at the junction of the first support steel plate 11 and the second support steel plate 12. The second connecting bolt 132 passes through the second long adjustment hole of the second angle steel connecting plate 131, the first bolt hole 114 of the first support steel plate 11, and the second bolt hole 127 of the second support steel plate 12 and is then locked to fix the first support steel plate 11 and the second support steel plate 12 together. The second angle steel connecting plate 131 is made of L-shaped angle steel with a specification of L100mm x 16mm and a length of 2000mm. The second connecting bolt 132 is an M12 bolt with a strength grade of 8.8. The second long adjustment hole on the second angle steel connecting plate 131 has a size of 14mm x 34mm. The second connecting bolt 132 passes through the second long adjustment hole of the second angle steel connecting plate 131, the first bolt hole 114 of the first support steel plate 11, and the second bolt hole 127 of the second support steel plate 12 and is then locked and fixed, thereby realizing the connection and fixation between the first support steel plate 11 and the second support steel plate 12. The second connecting structure 13 is connected by the second connecting bolt 132 to ensure that the pile cap 2 structural template can achieve the effect of rapid installation and forming.

[0066] The prefabricated steel formwork 1 uses prefabricated steel formwork (first support steel plate 11, second support steel plate 12) in the factory. On-site assembly is achieved through the first connecting structure 123 (first connecting steel plate 1231, first connecting bolt 1232) and the second connecting structure 13 (second angle steel connecting plate 131, second connecting bolt 132). The first connecting steel plate 1231 is equipped with a first long adjustment hole, which can flexibly adjust the construction error without on-site cutting and processing. Compared with the traditional method, the formwork assembly efficiency is improved. After the steel formwork is hoisted and formed, the external gap soil can be backfilled directly without waiting for external support or dewatering to stabilize, effectively reducing the process interval and shortening the overall construction cycle.

[0067] In a specific implementation, a plurality of first vertical reinforcement members 112 are provided on the back of the first support steel plate 11 at equal intervals along the vertical direction of the first support steel plate 11. A plurality of first transverse reinforcement members 113 are provided on the back of the first support steel plate 11 at intervals along the horizontal direction of the first support steel plate 11. The plurality of first transverse reinforcement members 113 are evenly spaced along the vertical direction of the first vertical reinforcement members 112. The first transverse reinforcement members 113 are arranged parallel to each other on the back of the first support steel plate 11 and intersect perpendicularly with the adjacent first vertical reinforcement members 112 and are welded into one piece. The first support steel plate 11 of this invention is made of steel plate and has a thickness of 6mm; the first vertical reinforcement 112 is made of 6.5# channel steel, and the web surface of the first vertical reinforcement 112 is welded and fixed to the back surface of the first support steel plate 11; the first horizontal reinforcement 113 is made of steel plate and has a thickness of 6mm; the first horizontal reinforcement 113 is fixedly connected to the back surface of the first support steel plate 11 and the first vertical reinforcement 112, and the three are integrated into a structure by welding; the welding method of the first vertical reinforcement 112 and the first support steel plate 11 is full welding, and the height of the welded part is not less than 5mm; the welding method of the first horizontal reinforcement 113 to the template panel and the first vertical reinforcement 112 is also full welding, and the height of each welded part is not less than 5mm.

[0068] In step 23), each second support steel plate 12 is formed by connecting and fixing two template units 122 through a first connecting structure 123. The first connecting structure 123 includes a first connecting steel plate 1231 and several first connecting bolts 1232. The two template units 122 are arranged side-by-side and interlocked. The first connecting steel plate 1231 has a first long adjustment hole, and the two template units 122 have third bolt holes that mate with the several first connecting bolts 1232. The first connecting steel plate 1231 is positioned at the joint of the two template units 122 and is locked and fixed by the several first connecting bolts 1232. The first connecting steel plate 1231 in this invention has a thickness of 16mm and a length of 2000mm. The first long adjustment hole on the first connecting steel plate 1231 has a size of 14mm x 34mm, and the first connecting bolts 1232 are M12, 8.8 grade strength bolts.

[0069] Each template unit 122 has a plurality of second vertical reinforcement members 124 evenly spaced along the vertical direction of the template unit 122 on its back. Each template unit 122 also has a plurality of second transverse reinforcement members 125 spaced apart along the horizontal direction of the template unit 122. The second transverse reinforcement members 125 are evenly spaced along the vertical direction of the second vertical reinforcement members 124. The second transverse reinforcement members 125 are parallel to each other on the back of the template unit 122 and intersect perpendicularly with adjacent second vertical reinforcement members 124 and are welded together. Specifically, each template unit 122 has a third bolt hole that mates with the first connecting bolt 1232. The first connecting bolt 1232 passes through the first long adjustment hole of the connecting steel plate and the third bolt holes of the two template units 122 and is then locked in place, thereby achieving the connection and fixation between the two template units 122.

[0070] In this embodiment of the invention, the template unit 122 is made of steel plate and has a thickness of 6mm; the second vertical reinforcement 124 is made of 6.5# channel steel, and the web surface of the second vertical reinforcement 124 is welded and fixed to the back of the template unit 122; the second horizontal reinforcement 125 is made of steel plate and has a thickness of 6mm; the second horizontal reinforcement 125 is fixedly connected to the back of the template unit 122 and the second vertical reinforcement 124, and the three are integrated into a structure by welding; the welding method of the second vertical reinforcement 124 and the template unit 122 is full welding, and the height of the welded part is not less than 5mm; the welding method of the second horizontal reinforcement 125 to the template panel and the second vertical reinforcement 124 is also full welding, and the height of each welded part is not less than 5mm.

[0071] The prefabricated steel formwork 1 is constructed by splicing two first support steel plates 11 and two second support steel plates 12 to form a box-shaped prefabricated steel formwork 1 structure. The steel formwork is welded to the vertical and horizontal reinforcements on the back, resulting in excellent overall rigidity and sealing. After the box-shaped prefabricated steel formwork 1 structure is formed, it can quickly achieve internal water stoppage and can safely withstand the lateral pressure of external water, quicksand, and backfill soil 4. The box-shaped prefabricated steel formwork 1 is equipped with an anti-deformation support structure 14 inside to further resist lateral pressure, effectively avoid the risk of quicksand inflow and foundation pit collapse, and create a safe and stable working environment for subsequent processes such as rebar tying and concrete pouring.

[0072] In this embodiment of the invention, the anti-deformation support structure 14 in step 24) includes a plurality of anti-deformation support rods 141, movable bolts 142, and fixing nuts 143. The plurality of anti-deformation support rods 141 are spaced apart between two second support steel plates 12. Each second support steel plate 12 is provided with fixing holes 126 that cooperate with the movable bolts 142. The fixing holes 126 extend from the second support steel plate 12 to the second vertical reinforcement 124 of the second support steel plate 12. The fixing nuts 143 of the anti-deformation support structure 14 are welded to the second vertical reinforcement 124 of the second support steel plate 12 and are fixed. With holes 126 aligned, align both ends of the anti-deformation support rod 141 with the fixing nuts 143 on the second vertical reinforcement 124 of the second support steel plate 12, respectively. Insert the movable bolt 142 into the fixing nuts 143 and one end of the anti-deformation support rod 141 on the second vertical reinforcement 124 of one of the second support steel plates 12 and tighten it to fix one end of the anti-deformation support rod 141 to one of the second support steel plates 12. At the same time, connect the other end of the anti-deformation support rod 141 to the corresponding fixing hole 126 of the other second support steel plate 12 through the movable bolt 142 and lock it with the fixing nut 143. The anti-deformation support rod 141 is fixed to the second support steel plate 12 by the movable bolt 142 to prevent the anti-deformation support rod 141 from shifting. Each second support steel plate 12 is provided with a fixing hole 126 that mates with the movable bolt 142. The fixing hole 126 has a diameter of 20mm. The anti-deformation support rod 141 is a round steel pipe with an outer diameter of 48mm, a thickness of 3mm, and a length of 1490mm. The movable bolt 142 is an M12, 8.8 grade strength bolt. The fixing nut 143 is an M12 nut, which is fixed to the second vertical reinforcement member 124 corresponding to the second support steel plate 12.

[0073] The box-type prefabricated steel formwork 1 assembled in step 23) is embedded in the concrete of the pile cap 2 area as a permanent water-stopping support structure. The prefabricated steel formwork 1 installed in this invention is part of the pile cap 2 structure and does not need to be removed after construction. During long-term use, if the prefabricated steel formwork 1 experiences slight corrosion, due to the extremely small size of the steel, the gaps caused by the corrosion of the steel plate can be naturally filled by the external soil, without affecting the structural stability and bearing capacity of the pile cap 2. If subsequent projects require reinforcement or modification of the pile cap 2, part of the formwork unit 122 can be cut and removed, and after modification, it can be reassembled and reinforced. The prefabricated steel formwork 1 can be reused.

[0074] Compared with the prior art, the technical solution disclosed in the above embodiments has the following beneficial effects:

[0075] In the above embodiments, the present invention uses prefabricated steel formwork 1 as the water-stopping support structure for the foundation pit of pile cap 2. The prefabricated steel formwork 1, after assembling the first support steel plate 11 and the second support steel plate 12 into a box structure, is hoisted to the pile cap 2, enabling rapid internal water stoppage. The box structure can safely withstand the lateral pressure of external water, quicksand, and backfill soil 4, creating a safe and stable construction environment for subsequent processes such as rebar tying and concrete construction. This fully leverages the advantages of prefabricated steel formwork 1—good assembly, structural stability, and strong load-bearing capacity—effectively solving the impact of excessive and rapid groundwater and quicksand on the construction project. On the pile cap 2... After the prefabricated steel formwork 1 is hoisted and formed, it can be backfilled with 4 cubic meters of soil directly according to the engineering process without affecting other construction processes, without occupying construction space, and improving the utilization rate of the construction site. The steel formwork used for assembling the prefabricated steel formwork 1 is prefabricated in the factory. On-site, the two first support steel plates 11 and the second support steel plates 12 are assembled and constructed through the second connecting structure 13 to realize the rapid assembly and fixing of the steel formwork. An anti-deformation support structure 14 is installed inside the box-type prefabricated steel formwork 1, which can effectively resist the lateral pressure of external soil, quicksand and water accumulation on the formwork, and improve the adaptability and safety of the box-type steel formwork structure.

[0076] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A construction method for water-stopping support of pile cap foundation pit based on prefabricated steel formwork, characterized in that: The construction method includes the following steps: Step 1) Excavate the soil for the pile cap; Step 2) Install prefabricated steel formwork for pile caps: This specifically includes: Step 21) Prefabrication of formwork: The first support steel plate, formwork unit, first connection structure, second connection structure, and anti-deformation support structure are prefabricated in the factory; Step 22) Assemble the second support steel plate: Connect and fix the two template units into a second support steel plate through the first connecting structure, and repeat the above operation to assemble the second support steel plate; Step 23) Assemble into a box-type prefabricated steel formwork: Use a crane to lift the two first support steel plates and the two second support steel plates assembled in step 22) into the foundation pit, arrange them according to the design outline of the pile cap, with the first support steel plate corresponding to the short side of the pile cap and the second support steel plate corresponding to the long side of the pile cap. The two first support steel plates and the two second support steel plates are assembled into a box-type prefabricated steel formwork through the second connecting structure. Step 24) Install anti-deformation support structure: Install anti-deformation support structure inside the box-type prefabricated steel formwork; Step 3) Backfill the gap between the prefabricated steel formwork of the pile cap and the pile cap foundation pit. Step 4) Pour the concrete cushion layer at the bottom and around the pile cap; Step 5) Tie the internal reinforcement bars of the pile cap; Step 6) Pour concrete in the pile cap area to complete the pile cap structure construction.

2. The construction method for water-stopping support of pile cap foundation pit based on prefabricated steel formwork according to claim 1, characterized in that: The prefabricated steel formwork described in step 2) includes two first support steel plates, two second support steel plates, a second connecting structure, and anti-deformation supports. The two first support steel plates are arranged in parallel relative to each other, and the two second support steel plates are arranged in parallel relative to each other. The second connecting structure is located between each adjacent first support steel plate and each second support steel plate. The two first support steel plates and the two second support steel plates are assembled into a box-type prefabricated steel formwork through the second connecting structure.

3. The construction method for water-stopping support of pile cap foundation pit based on prefabricated steel formwork according to claim 2, characterized in that: The first support steel plate has a plurality of first lifting holes, and the second support steel plate has a plurality of second lifting holes. The plurality of first lifting holes are distributed at intervals on the upper end of the first support steel plate, and the plurality of second lifting holes are distributed at intervals on the upper end of the second support steel plate.

4. The construction method for water-stopping support of pile cap foundation pit based on prefabricated steel formwork according to claim 2, characterized in that: In step 23), the second connection structure includes a second angle steel connecting plate and a second connecting bolt. The second angle steel connecting plate has a second long adjustment hole, and the first support steel plate has a first connecting hole that mates with the second connecting bolt. The first support steel plate and the second support steel plate have a first bolt hole and a second bolt hole that mate with the second connecting bolt, respectively. The second angle steel connecting plate is located at the junction of the first support steel plate and the second support steel plate. The second connecting bolt passes through the second long adjustment hole of the second angle steel connecting plate, the first bolt hole of the first support steel plate, and the second bolt hole of the second support steel plate and is then locked to fix the first support steel plate and the second support steel plate together.

5. The construction method for water-stopping support of pile cap foundation pit based on prefabricated steel formwork according to claim 4, characterized in that: The back of the first support steel plate is provided with a plurality of first vertical reinforcement members arranged at equal intervals along the vertical direction of the first support steel plate. The back of the first support steel plate is provided with a plurality of first transverse reinforcement members arranged at intervals along the horizontal direction of the first support steel plate. The plurality of first transverse reinforcement members are evenly spaced along the vertical direction of the first vertical reinforcement members. The first transverse reinforcement members are arranged parallel to each other on the back of the first support steel plate and intersect perpendicularly with the adjacent first vertical reinforcement members and are welded into one piece.

6. The construction method for water-stopping support of pile cap foundation pit based on prefabricated steel formwork according to claim 1, characterized in that: Each second support steel plate described in step 23) is formed by connecting and fixing two template units through a first connecting structure. The first connecting structure includes a first connecting steel plate and several first connecting bolts. The two template units are arranged side by side and connected to each other. A first long adjustment hole is provided on the first connecting steel plate. A third bolt hole that cooperates with several first connecting bolts is provided on the two template units. The first connecting steel plate is set at the joint of the two template units and locked and fixed by several first connecting bolts.

7. The construction method for water-stopping support of pile cap foundation pit based on prefabricated steel formwork according to claim 6, characterized in that: Each template unit has several second vertical reinforcement members arranged at equal intervals along the vertical direction of the template unit on its back. Each template unit also has several second horizontal reinforcement members arranged at intervals along the horizontal direction of the template unit on its back. The second horizontal reinforcement members are evenly spaced along the vertical direction of the second vertical reinforcement members. The second horizontal reinforcement members are arranged parallel to each other on the back of the template unit and intersect perpendicularly with the adjacent second vertical reinforcement members and are welded together.

8. The construction method for water-stopping support of pile cap foundation pit based on prefabricated steel formwork according to claim 1, characterized in that: The anti-deformation support structure described in step 24) includes several anti-deformation support rods, movable bolts, and fixing nuts. The several anti-deformation support rods are spaced apart between two second support steel plates. Each second support steel plate has a fixing hole that mates with the movable bolt. The fixing hole extends from the second support steel plate to the second vertical reinforcement of the second support steel plate. The fixing nut of the anti-deformation support structure is welded to the second vertical reinforcement of the second support steel plate and aligned with the fixing hole. The two ends of the anti-deformation support rod are aligned with the fixing nuts on the second vertical reinforcement of the second support steel plate. The movable bolt is inserted into the fixing nut on the second vertical reinforcement of one of the second support steel plates and into one end of the anti-deformation support rod, and then tightened to fix one end of the anti-deformation support rod to one of the second support steel plates. At the same time, the other end of the anti-deformation support rod is connected to the corresponding fixing hole of the other second support steel plate through the movable bolt and locked by the fixing nut.

9. The construction method for water-stopping support of pile cap foundation pit based on prefabricated steel formwork according to claim 1, characterized in that: The box-type prefabricated steel formwork assembled in step 23) is embedded in the concrete of the pile cap area as a permanent water-stopping support structure.

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