Foundation pit support structure and construction method thereof

Abstract

The invention relates to the field of foundation pit enclosure, in particular to a foundation pit enclosure structure and a construction method thereof, the foundation pit enclosure structure adopts the technical scheme of H-shaped steel pile supporting, underground diaphragm wall enclosure, additional tie bar reinforcement, post-pouring concrete forming and anchor rod driving for reinforcement, and the construction method comprises the steps of measuring, paying off and pile fixing positions, hoisting cylindrical steel pipe pier columns and driving H-shaped steel piles; earthwork is excavated in a layered, segmented, interval-divided and module-divided mode, and residual soil on the pile side is cleaned; hoisting a reinforcement cage, adding a tie bar for perforation, and installing an anchoring plate; the profiled steel sheet is fixed, and an anchor rod sleeve is pre-embedded; correcting the additional rib plate, installing a corner profiled steel sheet and pre-burying an anchor rod sleeve; fine aggregate concrete is poured in a segmented mode, and the underground diaphragm wall is formed; strengthening maintenance, arranging anchor rods and fixing the anchor rods; and the steps are repeated until all building envelope construction is completed, and finally overall acceptance check is conducted. The structural design is innovated, and the process method is optimized.

Description

Technical Field

[0001] The invention relates to the field of foundation pit retaining, and in particular to a foundation pit retaining structure and a construction method thereof. Background Art

[0002] The research and development and application of new technologies for deep foundation pit enclosure construction have become a major issue facing the transformation and development of the construction industry, and the safe construction of foundation pit enclosure has become a key technical issue that needs to be solved urgently. The wet operation "underwater pouring of concrete" process used in traditional underground continuous walls has many problems, such as difficult operation of the process, mud pollution of the environment, large blindness of underwater construction, difficulty in acceptance of hidden projects, and poor quality of underground continuous wall forming, which ultimately leads to insufficient bearing capacity of the enclosure structure and affects construction safety. In order to solve the industry pain points in the deep foundation pit support system, such as efficient construction and bearing safety issues in the foundation pit enclosure structure, the problem of excessive deformation or failure of the support structure due to loose connection of the support system, the safety and economy of the hoisting construction of the layered and segmented enclosure structure, the bearing and water stopping issues of the enclosure structure, and the integration of the enclosure structure and the main structure, the team has studied the technical solution of the present invention. Summary of the invention

[0003] The object of the present invention is to provide a foundation pit retaining structure and a construction method thereof to solve the problems raised by the background technology.

[0004] To achieve the above object, the present invention provides the following technical solution: a foundation pit retaining structure, comprising H-shaped steel piles, steel cages, corrugated steel plates, additional tie bars, fine stone concrete, additional ribs and anchor rods,

[0005] The H-shaped steel piles are arranged along the edge of the foundation pit, the steel cage is arranged between two adjacent H-shaped steel piles, the additional tie bars are passed through the webs of the H-shaped steel piles, and anchor plates are arranged at both ends of the additional tie bars, and extend into the two steel cages respectively;

[0006] The additional ribs are formed integrally with the H-shaped steel piles at the corners of the foundation pit, and are located on the wing plates of the H-shaped steel piles close to the inner side of the foundation pit, and the additional ribs are perpendicular to the wing plates; the corrugated steel plates are fixed to the wing plates of two adjacent H-shaped steel piles close to the inner side of the foundation pit or to the additional ribs and the wing plates of two adjacent H-shaped steel piles close to the inner side of the foundation pit by bolts;

[0007] The fine stone concrete is poured between the H-shaped steel piles, the corrugated steel plates and the soil outside the foundation pit to form an underground continuous wall. Anchor rods are also driven on the underground continuous wall. One end of the anchor rod is driven into the soil layer outside the foundation pit, and the other end is anchored to the corrugated steel plate.

[0008] The present invention also provides the following technical solutions: a construction method of a foundation pit retaining structure, in order to realize the above foundation pit retaining structure, the following steps are adopted:

[0009] Step S1: measuring and setting out the lines to determine the pile positions, hoisting the cylindrical steel pipe piers, and driving the H-shaped steel piles;

[0010] Step S2: excavate the earthwork in layers, sections, intervals and modules, and clean up the remaining soil on the pile side;

[0011] Step S3: hanging the steel cage, adding reinforcement punching, and installing the anchor plate;

[0012] Step S4: fixing the corrugated steel plate and pre-embedding the anchor rod casing;

[0013] Step S5: Correct the additional ribs, install the corner corrugated steel plates and embed the anchor sleeves;

[0014] Step S6: pouring fine stone concrete in sections to form an underground continuous wall;

[0015] Step S7: Strengthen maintenance, install anchor rods and fix them;

[0016] Step S8: Repeat steps S1 to S7 until all enclosure structures are constructed;

[0017] Step S9: Overall acceptance.

[0018] Preferably, step S1: measuring and laying out the lines to determine the pile positions, hoisting the cylindrical steel pipe piers, and driving the H-shaped steel piles:

[0019] Clean up the site and use the "secondary positioning method" to locate the H-shaped steel piles: use the theodolite to measure and lay out the specific positions of each H-shaped steel pile around the foundation pit, and preliminarily locate the positions of the H-shaped steel piles for the first time; hang cylindrical steel pipe piers on the soil layer where the H-shaped steel piles are first located, accurately check the plane position of the cylindrical steel pipe piers, ensure that the center line of the cylindrical steel pipe piers coincides with the center line of the H-shaped steel piles to be placed, and calibrate and locate the positions of the H-shaped steel piles for the second time;

[0020] Steel chisels are driven into the reserved holes around the cylindrical steel pipe pier one by one for temporary fixation. After the cylindrical steel pipe pier is fixed, the H-shaped steel pile is sunk by static pile pressure method: the crane first lifts the H-shaped steel pile and inserts it into the cavity inside the cylindrical steel pipe pier, adjusts the verticality of the H-shaped steel pile, and guides it with the cylindrical steel pipe pier, and then sinks the pile;

[0021] After the H-shaped steel pile is sunk into place, the steel chisel is immediately pulled out, and the cylindrical steel pipe pier is rotated to the next pile position, and the above operation process is repeated to complete the sunk work of all H-shaped steel piles;

[0022] Step S2: excavate the earthwork in layers, sections, intervals and modules, and clean up the remaining soil on the pile side:

[0023] After the overall H-shaped steel piles are sunk, the first layer of earthwork excavation can be carried out. The earthwork excavation is carried out in layers, sections, intervals and modules. The earthwork excavation depth is strictly determined according to the design height of the H-shaped steel piles and each layer of corrugated steel plates in the technical plan. The depth of each layer of earthwork excavation shall not exceed 3m. The earthwork should not be exposed for too long after excavation. The earthwork on the side of the H-shaped steel piles should be cleaned in time, and the bolt holes on the wing plates of the H-shaped steel piles close to the inner side of the foundation pit should be cleaned;

[0024] Step S3: Hang the steel cage, add additional reinforcement holes, and install the anchor plate:

[0025] Before hanging the steel cage, a T-shaped water-stop steel beam is used as a node to connect the upper and lower underground continuous wall concrete pouring connections. First, the T-shaped water-stop steel beam is installed at the bottom of the excavated earthwork on the first floor, that is, the top of the next layer of earthwork. More than half of the height of the T-shaped water-stop steel beam is pressed into the lower layer of earthwork, and the remaining part extends into the bottom or inside of the first-floor steel cage position;

[0026] The two ends of the T-shaped water-stop steel beam are welded or bolted to the web of the H-shaped steel pile. The top wing plate of the T-shaped water-stop steel beam is used as the connection node and the slurry blocking plate, and the lower web is used as the node connection and the water-stop steel plate. When the excavation depth of the foundation pit exceeds 7m, anchor holes are reserved on the web of the T-shaped water-stop steel beam, and the anchor layout is increased.

[0027] The steel cage is manufactured in layers, sections and modules and hoisted on site. Both ends of the steel cage extend into the H-shaped steel pile. During the installation of the steel cage, the additional reinforcements are punched and fixed one by one along the reserved holes on the web of the H-shaped steel pile, and anchor plates are installed at both ends of the additional reinforcements. Both ends of the additional reinforcements extend into the steel cage, and 100% of the additional reinforcements are anchored.

[0028] Step S4: Fix the corrugated steel plate and embed the anchor rod sleeve:

[0029] After the steel cage is installed, clean the bolt holes on the wing plate of the H-shaped steel pile near the inner side of the foundation pit again, and then fix each layer of corrugated steel plate with bolts: each bolt is passed from the inside of the bolt hole on the wing plate of the H-shaped steel pile to the outside, and the inner end of the bolt is fixed and screwed on the outer surface of the corrugated steel plate;

[0030] A waterproof coiled material strip is provided between the corrugated steel plate and the H-shaped steel pile at the connection bolts;

[0031] Pass the anchor sleeve through the anchor hole on the corrugated steel plate, adjust the angle and drive it into the soil outside the foundation pit, while paying attention to avoid affecting the installed steel cage;

[0032] Step S5: Correct the additional ribs, install the corner corrugated steel plates and embed the anchor sleeves:

[0033] Additional ribs are only installed on the wing plates on the inner side of the foundation pit near the H-shaped steel piles at the corners. After the steel cages at the corner sections are installed, the additional ribs on the H-shaped steel piles at the corners are cleaned, and the corrugated steel plates at the corners are installed with bolts in conjunction with the wing plates on the inner side of the foundation pit near the adjacent H-shaped steel piles. The anchor rods on them are constructed in the same way as other sections.

[0034] Step S6: pouring fine stone concrete in sections to form an underground continuous wall:

[0035] After the installation of the enclosure structures of each section and module is completed, high-pressure grouting method is used to pour fine stone concrete to form an underground continuous wall. High-pressure grouting is carried out at the grouting hole 150mm above the bottom of the corrugated steel plate. The strength of fine stone concrete is not less than C30. Micro-expansion fine stone concrete is added with early strength agent. The coarse aggregate in the fine stone concrete is mainly pebbles.

[0036] The high-pressure grouting process allows the early-strength micro-expansion fine stone concrete to be filled from the bottom of each section of the underground continuous wall upwards. The high-pressure grouting construction method of inserting a conduit from the top can also be used. Ensure the quality of concrete pouring in each section, do a good job of process acceptance and record, and do not pour concrete when the daily average temperature is below 5 degrees Celsius;

[0037] Step S7: Strengthen maintenance, install anchor rods and fix them:

[0038] When the concrete strength reaches 85% or more of the design strength, the anchor holes can be drilled. When the concrete strength reaches 100% of the design strength, the anchor rods can be threaded, grouted, tensioned and anchored.

[0039] The anchor rods are anchored to the outer surface of the corrugated steel sheet, and the anchoring ends are set in the concave area of ​​the corrugated steel sheet; if steel mesh and shotcrete surface layer are used for subsequent construction, the steel mesh can be fixed to the anchoring ends of each anchor rod, and the protruding parts of the anchoring ends of the anchor rods do not need to be cut off;

[0040] Step S8: Repeat steps S1 to S7 until all enclosure structures are constructed:

[0041] After all the above processes are completed, repeat steps 1 to 7 in a continuous process until all the enclosure structures are constructed;

[0042] Step S9: Overall acceptance:

[0043] After all the above-mentioned construction processes are completed, the acceptance work of the entire retaining structure and real-time monitoring of the foundation pit will be carried out; after qualified acceptance, the concrete cushion layer of the foundation pit will be poured immediately, and it must not be exposed for too long. Preventive work such as quicksand and pipe bursts will be done, and the whole process of groundwater precipitation will be coordinated. After ensuring that all links are correct, the underground structure engineering will be constructed. Before backfilling the underground engineering, the foundation pit retaining structure will be fully monitored, early warning values ​​will be set, and emergency plans will be prepared to ensure the smooth completion of the project.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] 1. The present invention adopts the enclosure structure of "H-shaped steel pile support, underground continuous wall enclosure, additional reinforcement, post-cast concrete molding, and anchor reinforcement" as a whole to strengthen the connection of various components of the enclosure structure and improve its bearing effect.

[0046] 2. The present invention divides the structure into sections and modules, and piles and walls are jointly stressed, and the assembly construction is combined with partial cast-in-place, which better guarantees the construction quality of each construction section, thereby ensuring the bearing capacity and water-stopping effect of the entire foundation pit retaining structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 is a top view of the foundation pit retaining structure of the present invention;

[0048] Figure 2 It is a construction process flow chart of the construction method of the present invention;

[0049] Figure 3 It is a schematic diagram of the cylindrical steel pipe pier structure in the construction method of the present invention;

[0050] Figure 4 It is a schematic diagram of the structure of a T-shaped water-stop steel beam in the construction method of the present invention. DETAILED DESCRIPTION

[0051] The embodiment of the present invention discloses a foundation pit retaining structure and a construction method thereof. Figure 1 As shown, it includes H-shaped steel piles 1, steel cages 2, corrugated steel plates 33, additional tie bars 44 and fine stone concrete. The H-shaped steel piles 1 are arranged along the edge of the foundation pit, and a steel cage 2 is arranged between two adjacent H-shaped steel piles 1. The corrugated steel plates 3 are fixed to the wing plates of the two adjacent H-shaped steel piles 2 close to the inner side of the foundation pit by bolts 5. Additional tie bars 4 are passed through the webs of the H-shaped steel piles 1, and anchor plates 6 are arranged at both ends of the additional tie bars 4. Fine stone concrete is poured into the cavity after the overall structure is installed to form an underground continuous wall.

[0052] Specifically:

[0053] The web of the H-shaped steel pile 1 is provided with reserved holes, the diameter of the reserved holes is not less than 20mm, the reserved holes are arranged along the web, the hole spacing is 500mm, the reserved hole spacing within 600mm above and below the layered part of the underground continuous wall is 350mm, and the H-shaped steel pile 1 is also provided with bolt holes on the wing plate close to the inner side of the foundation pit, and the bolt hole spacing is not more than 450mm.

[0054] The steel cage 2 is arranged between adjacent H-shaped steel piles 1. The steel cage 2 is arranged in layers and sections along with the earthwork. Both ends extend into the interior of the H-shaped steel pile 1 and are 20mm away from the web. The steel cage 2 is arranged in double layers and two directions. The diameter of the steel bar is not less than 10mm, and the spacing between the distributed steel bars is not more than 150mm. It is arranged in layers and sections and in modules between two adjacent H-shaped steel piles 1. Tight-type tie bars are used to firmly support the upper and lower layers of the steel cage 2.

[0055] In order to realize that the underground retaining structure also serves as the underground main structure wall, the thickness of the corrugated steel plate 3 provided between two adjacent H-shaped steel piles 1 is not less than 5 mm. The corrugated steel plate 3 is installed in place in layers, sections and modules as the earthwork is excavated, and is fixed to the wing plate of the H-shaped steel pile 1 with bolts 5. As one of the important components of the underground continuous wall construction, the corrugated steel plate 3 also serves as a permanent grouting template during the construction process. Grouting holes are also provided at the bottom of each section of the corrugated steel plate 3, and one grouting hole is provided on each layer and module section.

[0056] The diameter of the bolt 5 used to fix the H-shaped steel pile 1 and the corrugated steel plate 3 shall not be less than 20 mm, and the diameter of the bolt 5 shall be 2 mm to 3 mm smaller than the bolt hole diameter on the wing plate of the H-shaped steel pile 1. The bolt holes on the H-shaped steel pile 1 and the bolt holes on the corrugated steel plate 3 shall be accurately aligned, and the single hole error shall not exceed 1 mm to ensure accurate perforation connection during on-site construction.

[0057] In order to strengthen the node connection strength between the H-shaped steel pile 1 and each segmented underground continuous wall and improve the overall enclosure bearing capacity, the diameter of the additional tie bar 4 penetrated on the web of the H-shaped steel pile 1 is not less than 20mm, and is 2mm to 3mm smaller than the diameter of the reserved hole on the web of the H-shaped steel pile 1. The cutting length of the additional tie bar 4 is not less than 1200mm, and after perforation, the two ends extend into the steel cage 2 of the underground continuous wall on the left and right sides by not less than 600mm. The layout spacing of the additional tie bar 4 is the same as the reserved hole spacing on the web of the H-shaped steel pile 1. An anchor plate 6 is screwed on the end of each additional tie bar 4, and the anchor plate 6 is 100% set on each additional tie bar 4.

[0058] After all components are installed, fine stone concrete is poured in the cavity between the H-shaped steel pile 1, the corrugated steel plate 3 and the soil outside the foundation pit. Micro-expansion fine stone concrete is used, and the strength is not less than C30. In order to ensure the pouring of fine stone concrete between each layered section and each module, and solve the water-stopping problem between the upper and lower underground continuous walls, after the earthwork is excavated to each layered position, a water-stop steel plate is pressed into the lower soil, and the upper part of the water-stop steel plate extends into the steel cage 2. The concrete pouring adopts the "secondary grouting method", that is, after the first pouring of fine stone concrete, high-pressure grouting is performed from the grouting holes 200mm at the bottom of each section of the corrugated steel plate 3.

[0059] In order to further optimize the enclosure structure and reduce consumables, additional ribs 7 are provided on the wing plates of the H-shaped steel piles 1 at the corners of the foundation pit, which are close to the inner side of the foundation pit. The additional ribs 7 are integrated with the H-shaped steel piles 1 in the factory, and bolt holes are also provided on the additional ribs 7, which are mainly used for the installation of the corrugated steel plates 3 at the corners of the foundation pit. The size of the additional ribs 7 and the design requirements of the reserved holes thereon are consistent with those on the wing plates of the H-shaped steel piles 1.

[0060] In order to further improve the bearing effect of the overall enclosure structure, anchor rods 8 are also driven on each section of the underground continuous wall to reinforce the enclosure structure and the soil outside the foundation pit. One end of the anchor rod 8 is driven into the soil layer, and the other end is anchored on the corrugated steel plate 3. The length of the anchor rod 8 is not less than 1500mm, and the diameter is not less than 25mm. There are no less than 6 anchor rods 8 on each layer, each section, and each module enclosure structure. The spacing between adjacent anchor rods 8 does not exceed 900mm. The end anchor rod 8 near the H-shaped steel pile 1 is no more than 300mm away from the H-shaped steel pile 1, and the spacing between the upper and lower anchor rods 8 should be appropriately increased.

[0061] In order to realize the above technical solution, the present invention provides a construction method of the foundation pit retaining structure. Figure 2 ,

[0062] Step S1: measure and lay out the lines to determine the pile positions, hoist the cylindrical steel pipe piers, and drive the H-shaped steel piles. The specific technologies include the following:

[0063] According to the technical plan, the entire site was first cleaned up, and the "secondary positioning method" was used to position the H-shaped steel piles: the specific positions of each H-shaped steel pile around the foundation pit were measured and laid out using a theodolite, and the positions of the H-shaped steel piles were initially positioned for the first time. The on-site H-shaped steel pile sinking adopted the "cylindrical steel pipe pier guidance, internal static pile pressure" technical method, that is, the cylindrical steel pipe pier was suspended on the soil layer where the H-shaped steel pile was first positioned, and the plane position of the cylindrical steel pipe pier was accurately checked to ensure that the center line of the cylindrical steel pipe pier coincided with the center line of the H-shaped steel pile to be placed, which was the second calibration to locate the position of the H-shaped steel pile.

[0064] Then, steel chisels are drilled into the reserved holes around the cylindrical steel pipe pier for temporary fixation. Figure 3As shown, the cylindrical steel pipe pier 9 is hollow as a whole, with a partially enlarged base at the bottom. A reserved hole is provided on the base. A steel drill 10 is driven through the reserved hole and drilled into the ground to fix the cylindrical steel pipe pier 9. The length of the steel drill 10 is not less than 1000mm and the diameter is not less than 30mm. To facilitate the drilling of the steel drill, a 150mm thick steel base is provided at the bottom of the prefabricated cylindrical steel pipe pier. Reserved holes are evenly provided in the middle of the base. The diameter of the reserved holes is 2mm to 3mm larger than the designed steel drill diameter. The number of steel drills 10 provided on each cylindrical steel pipe pier is not less than 6. The height of the cylindrical steel pipe pier 9 is not less than 1200mm. A lifting ring 11 is provided on the upper part. The number of the lifting rings 11 is not less than 3, which is mainly used to realize the on-site lifting of the cylindrical steel pipe pier 9. The lifting ring 11 is not less than 120mm from the top surface of the cylindrical steel pipe pier 9. The wall thickness of the cylindrical steel pipe pier 9 is not less than 100 mm, and the base size is 500 mm larger than the outer diameter of the cylindrical steel pipe pier 9.

[0065] After the cylindrical steel pipe pier is fixed, the static pile pressure method is used to sink the H-shaped steel pile. The inner diameter of the cylindrical steel pipe pier is designed to be 10mm larger than the maximum nominal diameter of the outer contour of the H-shaped steel pile. When the H-shaped steel pile is hoisted on site, the cylindrical steel pipe pier is used as a guide device for the H-shaped steel pile to be placed and sunk. The crane first lifts the H-shaped steel pile and inserts it into the cavity inside the cylindrical steel pipe pier. The verticality of the H-shaped steel pile is adjusted, and the cylindrical steel pipe pier guides it, and then the pile is sunk, and the error is controllable. Finally, the depth of each pile in the field is accurately determined.

[0066] For complex geological conditions such as sandy soil, silt and abundant groundwater, the soil layer can be reinforced by mixing cement soil, and then the H-shaped steel piles can be sunk.

[0067] After the H-shaped steel piles are sunk into place, the steel chisel is immediately pulled out, and the cylindrical steel pipe pier is rotated to the next pile position. The above-mentioned operation process is repeated to complete the sinking of all H-shaped steel piles. During the process, error verification and adjustment are carried out, and acceptance is filed.

[0068] Step S2: excavate the earthwork in layers, sections, intervals and modules, and clean up the remaining soil on the pile side. The specific technologies include:

[0069] After the overall H-shaped steel piles are sunk, the first layer of earthwork excavation can be carried out. The earthwork excavation is carried out in layers, sections, intervals and modules. The earthwork excavation depth is strictly determined according to the design height of the H-shaped steel piles and each layer of corrugated steel plates in the technical plan. The depth of each layer of earthwork excavation does not exceed 3m. The earthwork should not be exposed for too long after excavation. The earthwork on the side of the H-shaped steel piles should be cleaned in time, and the bolt holes on the wing plates of the H-shaped steel piles close to the inside of the foundation pit should be cleaned. Considering the influence of factors such as the engineering environment, the nature of the earthwork, the excavation depth and other special working conditions, the H-shaped steel piles and the soil between the piles must not be disturbed during the earthwork excavation process, and the process acceptance work must be done well.

[0070] Step S3: Hang the steel cage, add additional reinforcement holes, and install the anchor plate. The specific technologies include:

[0071] The connection between the construction sections of each floor and the prevention and control of groundwater have become the key to solving the problem. Before hanging the steel cage, a T-shaped water-stop steel beam is used as a node to connect the upper and lower underground continuous wall concrete pouring connections. The T-shaped water-stop steel beam is first installed at the bottom of the excavated earth on the first floor (the top of the next layer of earth). More than half of the height of the T-shaped water-stop steel beam is pressed into the lower layer of earth, and the remaining part extends into the bottom or inside of the first-floor steel cage.

[0072] like Figure 4 As shown, the T-shaped water-stop steel beam 12 mainly includes a wing plate, a web plate, a top additional steel plate 13 and a bottom rib plate 14. The thickness of the wing plate is not less than 30 mm, and the width of the wing plate is 80 to 120 mm greater than the thickness of the prefabricated underground continuous wall; the thickness of the web plate is not less than 30 mm, and the height is not less than 200 mm. The top additional steel plate 13 is not less than 60 mm high and not less than 20 mm thick. The additional steel plate 13 also serves as a water-stop steel plate. The bottom rib plate 14 is not less than 50 mm wide and not less than 25 mm thick. The T-shaped water-stop steel beam is designed to be welded at both ends or end plates are bolted to the web of the H-shaped steel pile. It can also be used as a frame structure member that supports the entire enclosure structure. The top wing plate serves as a connection node and a slurry blocking plate, and the lower web serves as a node connection and a water-stop steel plate.

[0073] When the excavation depth of the foundation pit exceeds 7m, a T-shaped water-stop steel beam can be designed to be combined with anchor rods, that is, anchor rod holes are also left on the web of the T-shaped water-stop steel beam to increase the density of anchor rods and strengthen node design to ensure the safety of the construction of the foundation pit retaining structure.

[0074] The steel cage used in the on-site construction of the underground continuous wall is manufactured in layers, sections and modules and hoisted into place on site. The length of the two ends of the steel cage extending into the H-shaped steel pile should meet the design requirements. Additional steel bars can be set at both ends of the steel cage and fixed to the H-shaped steel pile by welding.

[0075] During the installation of the steel cage, the additional reinforcements are pierced and fixed one by one along the reserved holes on the web of the H-shaped steel pile, and anchor plates are installed at both ends of the additional reinforcements to strengthen the integrity between adjacent sections of the enclosure structure and improve the bearing capacity. The length of the additional reinforcements extending into the steel cage should also meet the design requirements. Anchor plates are set at 100% of the two ends of the additional reinforcements without omission. The acceptance records are kept during the process, otherwise the next step of construction cannot be entered.

[0076] Step S4: fix the corrugated steel plate and embed the anchor rod casing. The specific technologies include:

[0077] During on-site construction, the corrugated steel plate used is one of the components of the foundation pit retaining structure, and it also serves as a permanent formwork for the underground continuous wall concrete pouring construction, thus serving a dual purpose.

[0078] After the steel cage is installed, clean the bolt holes on the wing plate on the inner side of the H-shaped steel pile near the foundation pit again, and then fix each layer of corrugated steel plate with bolts. The positions of the connection holes, anchor holes, and grouting holes reserved on each fixed corrugated steel plate must be accurate, and no design or production reasons should affect the efficient installation on site.

[0079] In order to facilitate the installation of the corrugated steel sheet on site and reduce the difficulty of construction, each bolt is passed from the inside of the bolt hole on the wing plate of the H-shaped steel pile to the outside, and the inner end of the bolt is fixed and screwed on the outer surface of the corrugated steel sheet.

[0080] In order to prevent leakage of concrete pouring in subsequent processes, a waterproof membrane strip with a width of not less than 160mm is provided between the corrugated steel plate and the H-shaped steel pile at the connecting bolts, which effectively solves the leakage problem of concrete pouring of the underground continuous wall retaining body of the combined structure and optimizes the construction process on the basis of innovating the overall foundation pit retaining structure.

[0081] In order to provide specific driving positions and angle guidance for on-site anchor construction, before pouring the underground continuous wall concrete, a steel casing with a length of not less than 500mm is used to pass through the anchor holes on the corrugated steel plate as the anchor casing, and the angle is adjusted to drive it into the soil outside the foundation pit. When the anchor sleeve collides with the internal steel cage during the process of driving into the soil layer, it cannot be driven in force to avoid affecting the position of the installed steel cage. The direction can be adjusted appropriately to gently pass through the steel cage, and finally driven into the soil layer, and the process acceptance record should be kept.

[0082] Step S5: Correct the additional ribs, install the corner corrugated steel plates and embed the anchor sleeves. The specific technologies include:

[0083] Additional ribs are only set on the H-shaped steel piles at the corners near the inner wing plates of the foundation pit. Their main function is to solve the corner problem of the foundation pit retaining structure installation. Each corrugated steel plate requires 2 H-shaped steel piles as support. The ingenious design of the additional ribs can save 1 H-shaped steel pile. After the middle corrugated steel plate is fixed, the design of additional ribs needs to be considered for the installation of the retaining structure at the corner. After the steel cage at the corner section is installed, the additional ribs on the corner H-shaped steel piles are cleaned, and the corrugated steel plate at the corner can be installed. The anchor construction on it is the same as the construction operation process of other sections.

[0084] Step S6: pouring fine stone concrete in sections to form an underground continuous wall. The specific techniques include:

[0085] After the installation of the enclosure structures of each section and each module is completed, the underground continuous wall concrete can be poured. The high-pressure grouting method is used for the on-site fine stone concrete pouring. High-pressure grouting is carried out from the bottom of the corrugated steel plate to the grouting hole 150mm above. The strength of fine stone concrete is not less than C30. The micro-expansion fine stone concrete is added with an early strength agent. The coarse aggregate in the fine stone concrete is mainly pebbles. The high-pressure grouting process makes the early-strength micro-expansion fine stone concrete fill from the bottom of the underground continuous wall of each section upward. The high-pressure grouting construction method of inserting the conduit from the top can also be used to ensure the quality of concrete pouring in each section. The process acceptance and record are done well. Concrete shall not be poured when the daily average temperature is below 5 degrees Celsius. A special person shall be assigned to supervise the entire concrete pouring process. The quality of hidden engineering construction shall not be affected. The acceptance records of each construction section shall be done well.

[0086] Step S7: Strengthen maintenance, install anchor rods and fix them. The specific technologies include the following:

[0087] After the pouring of fine stone concrete in each section is completed, maintenance work should be strengthened. When the concrete strength reaches more than 85% of the design strength, the anchor holes can be drilled. When the concrete strength reaches 100% of the design strength, the anchor rods can be threaded, grouting, tensioning and anchoring can be carried out.

[0088] During on-site construction, each anchor rod is finally anchored to the outer surface of the corrugated steel plate, and the anchor end is set in the concave area of ​​the corrugated steel plate, and must not be set in the protruding area of ​​the corrugated steel plate, so as not to affect the appearance quality of the retaining structure construction and subsequent construction safety issues. If the foundation pit retaining structure is subsequently used as the outer wall of the underground main structure, the steel mesh + shotcrete surface layer is used for construction, and the steel mesh can be fixed to the anchor end of each anchor rod. Therefore, the protruding part of the anchor end of the anchor rod does not need to be cut off later.

[0089] Step S8: Repeat steps 1 to 7 until all enclosure structures are constructed. The following techniques are included:

[0090] After all the above processes are completed, repeat steps 1 to 7 in a flow-line manner until all the enclosure structure construction is completed.

[0091] Step S9: Overall acceptance. Specifically including the following technologies:

[0092] After all the above-mentioned processes are completed, the acceptance of the entire retaining structure and real-time monitoring of the foundation pit will be carried out. After the acceptance is qualified, the concrete cushion layer of the foundation pit will be poured immediately, and it must not be exposed for too long. Preventive work such as quicksand and pipe bursts will be done well, and the whole process of groundwater precipitation will be coordinated. After ensuring that all links are correct, the underground structure engineering will be constructed. Before the underground engineering backfills the soil, the retaining structure of the foundation pit will be fully monitored, the early warning value will be set, and the emergency plan will be prepared to ensure the smooth completion of the project.

[0093] The foundation pit retaining structure of the present invention adopts the technical scheme of "H-shaped steel pile support, underground continuous wall enclosure, additional reinforcement, high-pressure grouting molding, and anchor rod reinforcement", which is divided into sections and modules, pile-wall joint force, assembly construction and partial cast-in-place, which better guarantees the construction quality of each construction section, thereby ensuring the bearing capacity and water-stopping effect of the entire foundation pit retaining structure.

[0094] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A foundation pit retaining structure, characterized in that: It includes H-shaped steel piles, steel cages, corrugated steel plates, additional tie bars, fine stone concrete, additional ribs and anchor rods. The H-shaped steel piles are arranged along the edge of the foundation pit, the steel cage is arranged between two adjacent H-shaped steel piles, the additional tie bars are passed through the webs of the H-shaped steel piles, and anchor plates are arranged at both ends of the additional tie bars, and extend into the two steel cages respectively; The additional ribs are formed integrally with the H-shaped steel piles at the corners of the foundation pit, and are located on the wing plates of the H-shaped steel piles close to the inner side of the foundation pit, and the additional ribs are perpendicular to the wing plates; the corrugated steel plates are fixed to the wing plates of two adjacent H-shaped steel piles close to the inner side of the foundation pit or to the additional ribs and the wing plates of two adjacent H-shaped steel piles close to the inner side of the foundation pit by bolts; The fine stone concrete is poured between the H-shaped steel piles, the corrugated steel plates and the soil outside the foundation pit to form an underground continuous wall. Anchor rods are also driven on the underground continuous wall. One end of the anchor rod is driven into the soil layer outside the foundation pit, and the other end is anchored to the corrugated steel plate.

2. A construction method for a foundation pit retaining structure, characterized in that: To realize the foundation pit retaining structure described in claim 1, the following steps are adopted: Step S1: measuring and setting out the lines to determine the pile positions, hoisting the cylindrical steel pipe piers, and driving the H-shaped steel piles; Step S2: excavate the earthwork in layers, sections, intervals and modules, and clean up the remaining soil on the pile side; Step S3: hanging the steel cage, adding reinforcement punching, and installing the anchor plate; Step S4: fixing the corrugated steel plate and pre-embedding the anchor rod casing; Step S5: Correct the additional ribs, install the corner corrugated steel plates and embed the anchor sleeves; Step S6: pouring fine stone concrete in sections to form an underground continuous wall; Step S7: Strengthen maintenance, install anchor rods and fix them; Step S8: Repeat steps S1 to S7 until all enclosure structures are constructed; Step S9: Overall acceptance.

3. The construction method according to claim 2, characterized in that: Step S1: Measure and lay out the lines, determine the pile positions, hoist the cylindrical steel pipe piers, and drive the H-shaped steel piles: Clean the site and use the "secondary positioning method" to locate the H-shaped steel piles: use the theodolite to measure and lay out the specific positions of each H-shaped steel pile around the foundation pit, and preliminarily locate the positions of the H-shaped steel piles for the first time; hang cylindrical steel pipe piers on the soil layer where the H-shaped steel piles are first located, accurately check the plane position of the cylindrical steel pipe piers, ensure that the center line of the cylindrical steel pipe piers coincides with the center line of the H-shaped steel piles to be placed, and calibrate and locate the positions of the H-shaped steel piles for the second time; Steel chisels are driven into the reserved holes around the cylindrical steel pipe pier one by one for temporary fixation. After the cylindrical steel pipe pier is fixed, the H-shaped steel pile is sunk by static pile pressure method: the crane first lifts the H-shaped steel pile and inserts it into the cavity inside the cylindrical steel pipe pier, adjusts the verticality of the H-shaped steel pile, and guides it with the cylindrical steel pipe pier, and then sinks the pile; After the H-shaped steel pile is sunk into place, the steel chisel is immediately pulled out, and the cylindrical steel pipe pier is rotated to the next pile position, and the above operation process is repeated to complete the sunk work of all H-shaped steel piles; Step S2: excavate the earthwork in layers, sections, intervals and modules, and clean up the remaining soil on the pile side: After the overall H-shaped steel piles are sunk, the first layer of earthwork excavation can be carried out. The earthwork excavation is carried out in layers, sections, intervals and modules. The earthwork excavation depth is strictly determined according to the design height of the H-shaped steel piles and each layer of corrugated steel plates in the technical plan. The earthwork excavation depth of each layer shall not exceed 3m. The earthwork should not be exposed for too long after excavation. The earthwork on the side of the H-shaped steel piles should be cleaned in time, and the bolt holes on the wing plates of the H-shaped steel piles close to the inner side of the foundation pit should be cleaned; Step S3: Hang the steel cage, add additional reinforcement holes, and install the anchor plate: Before hanging the steel cage, a T-shaped water-stop steel beam is used as a node to connect the upper and lower underground continuous wall concrete pouring connections. First, the T-shaped water-stop steel beam is installed at the bottom of the excavated earthwork on the first floor, that is, the top of the next layer of earthwork. More than half of the height of the T-shaped water-stop steel beam is pressed into the lower layer of earthwork, and the remaining part extends into the bottom or inside of the first-floor steel cage position; The two ends of the T-shaped water-stop steel beam are welded or bolted to the web of the H-shaped steel pile. The top wing plate of the T-shaped water-stop steel beam is used as the connection node and the slurry blocking plate, and the lower web is used as the node connection and the water-stop steel plate. When the excavation depth of the foundation pit exceeds 7m, anchor holes are reserved on the web of the T-shaped water-stop steel beam, and the anchor layout is increased. The steel cage is manufactured in layers, sections and modules and hoisted on site. Both ends of the steel cage extend into the H-shaped steel pile. During the installation of the steel cage, the additional reinforcements are punched and fixed one by one along the reserved holes on the web of the H-shaped steel pile, and anchor plates are installed at both ends of the additional reinforcements. Both ends of the additional reinforcements extend into the steel cage, and 100% of the additional reinforcements are anchored. Step S4: Fix the corrugated steel plate and embed the anchor rod sleeve: After the steel cage is installed, clean the bolt holes on the wing plate of the H-shaped steel pile near the inner side of the foundation pit again, and then fix each layer of corrugated steel plate with bolts: each bolt is passed from the inside of the bolt hole on the wing plate of the H-shaped steel pile to the outside, and the inner end of the bolt is fixed and screwed on the outer surface of the corrugated steel plate; A waterproof coiled material strip is provided between the corrugated steel plate and the H-shaped steel pile at the connection bolts; Pass the anchor sleeve through the anchor hole on the corrugated steel plate, adjust the angle and drive it into the soil outside the foundation pit, while paying attention to avoid affecting the installed steel cage; Step S5: Correct the additional ribs, install the corner corrugated steel plates and embed the anchor sleeves: Additional ribs are only installed on the wing plates on the inner side of the foundation pit near the H-shaped steel piles at the corners. After the steel cages at the corner sections are installed, the additional ribs on the H-shaped steel piles at the corners are cleaned, and the corrugated steel plates at the corners are installed with bolts in conjunction with the wing plates on the inner side of the foundation pit near the adjacent H-shaped steel piles. The anchor rods on them are constructed in the same way as other sections. Step S6: pouring fine stone concrete in sections to form an underground continuous wall: After the installation of the enclosure structures of each section and module is completed, high-pressure grouting method is used to pour fine stone concrete to form an underground continuous wall. High-pressure grouting is carried out at the grouting hole 150mm above the bottom of the corrugated steel plate. The strength of fine stone concrete is not less than C30. Micro-expansion fine stone concrete is added with early strength agent. The coarse aggregate in the fine stone concrete is mainly pebbles. The high-pressure grouting process allows the early-strength micro-expansion fine stone concrete to be filled from the bottom of each section of the underground continuous wall upwards. The high-pressure grouting construction method of inserting a conduit from the top can also be used. Ensure the quality of concrete pouring in each section, do a good job of process acceptance and record, and do not pour concrete when the daily average temperature is below 5 degrees Celsius; Step S7: Strengthen maintenance, install anchor rods and fix them: When the concrete strength reaches 85% or more of the design strength, the anchor holes can be drilled. When the concrete strength reaches 100% of the design strength, the anchor rods can be threaded, grouted, tensioned and anchored. The anchor rods are anchored to the outer surface of the corrugated steel sheet, and the anchoring ends are set in the concave area of ​​the corrugated steel sheet; if steel mesh and shotcrete surface layer are used for subsequent construction, the steel mesh can be fixed to the anchoring ends of each anchor rod, and the protruding parts of the anchoring ends of the anchor rods do not need to be cut off; Step S8: Repeat steps S1 to S7 until all enclosure structures are constructed: After all the above processes are completed, repeat steps 1 to 7 in a continuous process until all the enclosure structures are constructed; Step S9: Overall acceptance: After all the above-mentioned construction processes are completed, the acceptance work of the entire retaining structure and real-time monitoring of the foundation pit will be carried out; after qualified acceptance, the concrete cushion layer of the foundation pit will be poured immediately, and it must not be exposed for too long. Preventive work such as quicksand and pipe bursts will be done, and the whole process of groundwater precipitation will be coordinated. After ensuring that all links are correct, the underground structure engineering will be constructed. Before backfilling the underground engineering, the foundation pit retaining structure will be fully monitored, early warning values ​​will be set, and emergency plans will be prepared to ensure the smooth completion of the project.

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