Deep foundation pit assembled steel truss internal support system and construction process

Abstract

This invention discloses a prefabricated steel truss internal support system and construction technology for deep foundation pits, relating to the field of engineering foundation pit support technology. This internal support system introduces a sidewall auxiliary support system, which includes fixed support columns, a first load-bearing component, a second load-bearing component, a load-bearing purlin, a corbel load-bearing component, a load-bearing rib, a hydraulic jack mounting base, and a hydraulic jack. When the original support needs to be removed for continued construction in the deep foundation pit, one end of the load-bearing rib is connected to the connection point of the second load-bearing component, and the other end passes through the output end of the hydraulic jack and is anchored. The hydraulic jack is then driven to tighten the load-bearing rib, transferring the vertical downward gravity of the sidewall support structure borne by the original support to the sidewall auxiliary support system. This achieves a smooth transfer of the original support system in the stress zone. After the support replacement is completed, the original support structure affecting the construction of the main structure is removed, providing an operating plane for subsequent operations. The support replacement ensures that the stress state of the foundation pit does not change abruptly during the removal process.

Description

Technical Field

[0001] This invention relates to the field of engineering foundation pit support technology, and in particular to a prefabricated steel truss internal support system and construction process for deep foundation pits. Background Technology

[0002] As urban underground space development moves towards greater depth and area, the choice of internal support system for deep foundation pits directly affects project safety, construction period, and environmental benefits. Currently, the mainstream internal support technologies in engineering projects mainly include cast-in-place concrete supports, traditional steel pipe / H-beam supports, and early-generation prefabricated steel supports, but all of these technologies have significant limitations. Firstly, there is cast-in-place concrete support, which is one of the most widely used forms in deep foundation pit engineering. Its advantages are high overall rigidity and strong deformation control. However, its inherent defects are also very prominent. The support structure needs to be demolished by blasting or machinery after the underground structure construction is completed, generating a large amount of construction waste, which does not conform to the concept of green construction. Moreover, the demolition cycle is long and the noise and dust pollution is serious. At the same time, it requires on-site binding of steel bars, formwork, pouring and curing, which occupies the critical construction period and cannot achieve rapid support. Although traditional steel supports (such as φ609 steel pipes and double H-beams) have the potential for recycling, they have the problem of "low degree of assembly" in practical applications. They rely heavily on on-site welding or steel wedge-type movable joints. The welding quality is greatly affected by the working conditions and is difficult to reuse. For deep foundation pits with large spans, the rigidity of traditional single steel pipes or steel sections is limited, and they are prone to excessive deflection, making it difficult to meet the strict deformation control requirements.

[0003] Furthermore, during the transition phase of "support replacement" between support removal and main structure construction, existing technologies often require overall or large-scale unloading, leading to sudden changes in the stress state of the foundation pit, making it difficult to control the displacement of the retaining structure, posing significant safety risks. Moreover, the support replacement process is lengthy, impacting the overall construction progress. This is especially true in the humid, rainy, and geologically complex regions of southern China, where the longer the foundation pit is exposed, the higher the risk.

[0004] Based on the above, there is an urgent need to design a prefabricated steel truss internal support system for deep foundation pits. This support system can smoothly transfer the original support system of the corresponding stress zone to the auxiliary replacement support system according to the construction of the main structure. Then, the support structure that affects the construction of the main structure can be removed to provide an operating plane for subsequent operations. The "replacement support" ensures that the stress state of the foundation pit will not change suddenly during the removal process. Summary of the Invention

[0005] To address the above shortcomings, this invention provides a prefabricated steel truss internal support system and construction process for deep foundation pits. This system overcomes the technical defects of existing technologies by smoothly transferring the original support system to the corresponding stress zone during the construction of the main structure, achieving "support replacement" during construction. Afterwards, the support structures affecting the construction of the main structure are removed, providing an operating plane for subsequent operations. "Support replacement" ensures that the dismantling process does not cause a sudden change in the stress state of the foundation pit. The specific technical solution is as follows:

[0006] A prefabricated steel truss internal support system for deep foundation pits includes:

[0007] A vertical fixed support system is set along the circumference of the deep foundation pit to support the sidewalls of the deep foundation pit and prevent the soil in the foundation pit from collapsing.

[0008] The sidewall auxiliary support system is a construction work platform located outside the top edge of the deep foundation pit. The sidewall auxiliary support system includes a fixed support column, a first load-bearing component, a second load-bearing component, a bearing purlin, a corbel bearing component, a load-bearing reinforcement, a hydraulic jack mounting base, and a hydraulic jack. The fixed support column is installed on the construction work platform, the first load-bearing component is fixed to the construction work platform, the corbel bearing component is installed on the vertical fixed support system, the second load-bearing component is installed on the corbel bearing component, the hydraulic jack mounting base is installed on the fixed support column, and the hydraulic jack is installed on the hydraulic jack mounting base.

[0009] A temporary load-bearing steel frame is installed inside the deep foundation pit;

[0010] A steel truss support structure includes walers, corner bracing structures, sidewall bracing structures, and top bracing structures. The walers are installed on the corbel bearing members. The corner bracing structures are installed on the external corner areas of the deep foundation pit and are supported by the walers. The sidewall bracing structures are installed near the upper end of the inner sidewall of the deep foundation pit. Second load-bearing members are provided at both opposite ends of the sidewall bracing structures. A plurality of bearing walers are arranged between two second load-bearing members to support the sidewall bracing structures. The temporary load-bearing steel frame... The rib is positioned below the bearing purlin to support the bearing purlin, thereby indirectly supporting the side wall support structure. When the deep foundation pit needs to be dismantled and the temporary load-bearing steel frame is removed to continue construction, one end of the load-bearing rib is connected to the connection point of the second load-bearing member, and the other end passes through the output end of the hydraulic jack and is anchored to the fixed support column. The hydraulic jack is then driven to tighten the load-bearing rib, so that the vertical downward gravity of the side wall support structure originally supported by the temporary load-bearing steel frame is transferred to the side wall auxiliary support system.

[0011] The top support pile is installed in the deep foundation pit and located between the two sections of the top support structure to support the top support structure. One end of the top support structure is abutted to the inner wall of the deep foundation pit, and the other end is abutted to the top support pile.

[0012] Preferably, the vertical fixed support system includes an outer closed pile row and an inner closed pile row, the outer closed pile row being located outside the inner closed pile row, and both the outer closed pile row and the inner closed pile row being composed of several spaced support piles.

[0013] Preferably, the first force-bearing component includes a stable triangular frame, a force-transmitting rotating shaft, and force-transmitting anti-slip ridges. The stable triangular frame is fixedly installed on the construction platform by connecting bolts. Several force-transmitting anti-slip ridges are provided on the bottom surface of the stable triangular frame. The force-transmitting rotating shaft is rotatably installed at the top of the stable triangular frame.

[0014] Preferably, the second force-bearing component is a triangular component.

[0015] Preferably, the corner support structure includes a triangular connector and a corner brace truss unit, with both ends of the corner brace truss unit being installed onto the waler via the triangular connector.

[0016] Preferably, the sidewall support structure includes an upper chord, a lower chord, web members, and end connectors. The upper chord is installed on the waler. The web members include several H-beams of different lengths. The two ends of the web members are connected to the upper chord and the lower chord respectively through node connecting plates. Several web members are installed on the upper chord. The end connectors are disposed at both ends of the upper chord and are used to anchor the lower chord and apply prestress.

[0017] Preferably, the lower chord is made of high-strength steel strand.

[0018] Preferably, the top support pile includes a main pile body and a foot support. The main pile body is installed in the deep foundation pit, and one end of the foot support is connected to the main pile body, and the other end is connected to the bottom of the deep foundation pit.

[0019] Preferably, the top support structure includes a hinged head, a steel support, a hydraulic propulsion device, and a flange mounting plate. The hinged head is installed on the vertical fixed support system via a waist beam. The steel support is slidably mounted on the hinged head. The other end of the steel support is installed on the main pile column via the flange mounting plate. The hydraulic propulsion device is installed at the hinged head, and its output end is connected to the steel support.

[0020] A construction process for a prefabricated steel truss internal support system for deep foundation pits, comprising the following steps:

[0021] S1: Define the boundary of the target construction area;

[0022] S2: The flatness of the ground surface in the target construction area;

[0023] S3: Construction of retaining piles;

[0024] S3.1: Using rotary drilling rigs and percussion drilling rigs, multiple first pile holes are laid out circumferentially around the boundary of the defined target construction area to form an outer closed pile row;

[0025] S3.2: Multiple second pile holes are arranged at intervals along the inner circumference of the outer closed pile row to form an inner closed pile row, wherein the outer closed pile row surrounds the inner closed pile row in a plane;

[0026] S3.3: Suspend steel cages into the first pile hole and the second pile hole, and pour concrete to form support piles;

[0027] S4: Construction of the water-stop curtain;

[0028] S4.1: A water-stop curtain construction axis is set along the circumferential direction of the boundary of the target construction area. The water-stop curtain construction axis is located between the outer closed pile row and the inner closed pile row, and is parallel to both of them.

[0029] S4.2: Multiple sets of cement-soil mixing piles are constructed sequentially along the construction axis of the water-stop curtain using a three-axis mixing pile machine. Adjacent sets of cement mixing piles are connected by a splicing and overlapping method to form a continuous wall.

[0030] S5: Area division and construction;

[0031] S5.1: Divide the target construction area into excavation area A, excavation area B, excavation area C and excavation area D;

[0032] S5.2: Several dewatering well points shall be excavated in the areas of excavation zone A, excavation zone B, excavation zone C and excavation zone D respectively;

[0033] S5.3: Lower a water pump into the dewatering well point to pump out the water from the well point;

[0034] S6: Layered excavation and installation of the waist beam

[0035] S6.1: After drainage is completed, the excavated areas A, B, C and D shall be excavated in layers;

[0036] S6.2: After excavating to the first depth below the design elevation of the support, use a drilling rig to drill a hole at the vertical fixed support system in an inclined downward manner, then grout after the lower anchor rod, and install the waist beam. The waist beam is locked to the vertical fixed support system by the anchor rod.

[0037] S6.3: Repeat step S6.2, excavate several layers, and complete the installation of several layers of wainscoting to complete the excavation of the deep foundation pit;

[0038] S7: Installation of the sidewall auxiliary support system;

[0039] S7.1: Install the corbel bearing member onto the waist beam;

[0040] S7.2: Several grouting holes are arranged on the construction platform, lattice columns are placed into the grouting holes and concrete is poured to form the fixed support columns, the hydraulic jack mounting base is installed on the fixed support columns, and the hydraulic jack is installed on the hydraulic jack mounting base.

[0041] S7.3: Install the first load-bearing component onto the construction platform using connecting bolts;

[0042] S7.4: Install the second load-bearing member on the corbel bearing member, and make its right-angled edge fit against the surface of the waist beam, and fix it on the waist beam with bolts;

[0043] S7.5: Install a plurality of the aforementioned bearing purlins between the two second load-bearing members;

[0044] S7.6: A temporary load-bearing steel frame is installed below the load-bearing purlin to support the load-bearing purlin;

[0045] S8: Installation of steel truss support structure;

[0046] S8.1: The waler is hoisted onto the corbel bearing member, and the corner support structure is installed on the external corner area of ​​the deep foundation pit and supported by the waler;

[0047] S8.2: Hoist and install the sidewall support structure onto the load-bearing purlin;

[0048] S9: Installation of the top support structure;

[0049] S9.1: Excavate a top support grouting hole in the deep foundation pit, put a steel cage into the top support grouting hole and pour concrete to form the top support pile;

[0050] S9.2: Weld foot bracing near the bottom end of the main pile of the top support pile to reinforce the main pile;

[0051] S9.3: Install the hinge head on the waist beam, attach the steel support to the hinge head, and install the other end of the steel support to the main pile body of the top support pile through the flange mounting plate;

[0052] S9.4: Install the hydraulic propulsion device at the movable head, with its output end connected to the steel support, and use the hydraulic propulsion device to indirectly support the two opposing inner walls of the deep foundation pit;

[0053] S10: Construction and support replacement;

[0054] S10.1: When the temporary load-bearing steel frame needs to be removed from the deep foundation pit for continued construction, one end of the load-bearing rib is connected to the connection point of the second load-bearing component, and the other end is passed through the output end of the hydraulic jack and anchored to the fixed support column. The hydraulic jack is then driven to tighten the load-bearing rib so that the vertical downward gravity of the side wall support structure originally borne by the temporary load-bearing steel frame is transferred to be borne by the side wall auxiliary support system.

[0055] Compared with the prior art, the beneficial effects of the present invention are:

[0056] 1. The present invention provides a sidewall auxiliary support system in the internal support system of a prefabricated steel truss for deep foundation pits. When the original support of the deep foundation pit needs to be removed for continued construction, the vertical downward gravity of the sidewall support structure borne by the original support is transferred to the sidewall auxiliary support system, realizing the smooth transfer of the original support system in the stress zone. After the support replacement is completed, the original support structure that affects the construction of the main structure is removed, providing an operating plane for subsequent operations. The support replacement ensures that the stress state of the foundation pit will not change suddenly during the removal process.

[0057] 2. The top support structure in this invention "cuts off" the original top support steel support into two sections. The top support piles serve as both load-bearing and force-transmitting components. This design overcomes the technical problem that traditional single steel pipe or steel section supports have limited stiffness and are prone to excessive deflection in deep foundation pits with large spans. By "cutting off" it into two sections, i.e. dividing it into two parts, the possibility of excessive deflection of the top support component due to the large span of the top support is effectively reduced, ensuring the stability of the top support. Attached Figure Description

[0058] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0059] Figure 1 This is a layout diagram of the overall support system of the present invention.

[0060] Figure 2 This is a schematic diagram of the initial target construction area in this invention.

[0061] Figure 3 This is a schematic diagram of the sidewall support structure in this invention.

[0062] Figure 4 This is a schematic diagram of the installation of the top support structure in this invention.

[0063] Figure 5 This is a schematic diagram illustrating the application principle of the sidewall-assisted support system in this invention.

[0064] 100 - Vertical fixed support system; 110 - Outer closed pile row; 120 - Inner closed pile row; 130 - Support pile column; 140 - Waist beam; 200 - Deep foundation pit; 300 - Side wall auxiliary support system; 310 - Fixed support column; 320 - Primary load-bearing component; 321 - Stabilizing triangular frame; 322 - Load-bearing transmission shaft; 323 - Load-bearing anti-slip convex strip; 324 - Connecting bolt; 330 - Secondary load-bearing component; 340 - Bearing purlin; 350 - Corbel bearing component; 360 - Load-bearing reinforcement; 370 - Hydraulic jack mounting base; 380 - Hydraulic jack Top, 400-Temporary load-bearing steel frame, 500-Steel truss support structure, 510-Walter, 520-Angle support structure, 521-Triangular connector, 522-Angle brace truss unit, 530-Side wall support structure, 531-Upper chord, 532-Lower chord, 533-Web member, 534-End connector, 535-Node connection plate, 540-Top support structure, 541-Handle head, 542-Steel support, 543-Hydraulic propulsion equipment, 544-Flange mounting plate, 600-Top support pile, 610-Main pile, 620-Foot brace. Detailed Implementation

[0065] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0066] In the description of this invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0067] In the description of this invention, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. Where the terms "first," "second," and "third" are used for descriptive purposes and to distinguish technical features, they should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the sequential relationship of the indicated technical features.

[0068] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Furthermore, the technical features involved in the different embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0069] Example

[0070] like Figures 1 to 5 As shown, the present invention provides a prefabricated steel truss internal support system for deep foundation pits, specifically including a vertical fixed support system 100, a side wall auxiliary support system 300, a temporary load-bearing steel frame 400, a steel truss support structure 500, and a top support pile 600.

[0071] Preferably, the vertical fixed support system 100 is arranged circumferentially along the deep foundation pit 200 to support the sidewalls of the deep foundation pit 200 and prevent the foundation pit soil from collapsing; the sidewall auxiliary support system 300 is arranged on the construction work platform outside the top edge line of the deep foundation pit 200. The sidewall auxiliary support system 300 includes a fixed support column 310, a first load-bearing member 320, a second load-bearing member 330, a bearing purlin 340, a corbel bearing member 350, a load-bearing reinforcement 360, a hydraulic jack mounting base 370, and a hydraulic jack 380. The fixed support column 310 is installed on the construction work platform, the first load-bearing member 320 is fixed to the construction work platform, and the corbel bearing member 350 is fixed to the construction work platform. Component 350 is installed on the vertical fixed support system 100, the second load-bearing component 330 is installed on the corbel bearing component 350, the hydraulic jack mounting base 370 is installed on the fixed support column 310, and the hydraulic jack 380 is installed on the hydraulic jack mounting base 370; the temporary load-bearing steel frame 400 is located within the deep foundation pit 200; the steel truss support structure 500 includes a waler 510, a corner support structure 520, a side wall support structure 530, and a top support structure 540. The waler 510 is installed on the corbel bearing component 350, and the corner support structure 520 is installed in the external corner area of ​​the deep foundation pit 200, and is supported by the... The waler 510 provides support. The sidewall support structure 530 is installed near the upper end of the inner sidewall of the deep foundation pit 200. Second load-bearing members 330 are provided at both opposite ends of the sidewall support structure 530. A plurality of bearing walers 340 are arranged between the two second load-bearing members 330 to support the sidewall support structure 530. The temporary load-bearing steel frame 400 is arranged below the load-bearing walers 340 to support the load-bearing walers 340, thereby indirectly supporting the sidewall support structure 530. When the temporary load-bearing steel frame 400 needs to be removed from the deep foundation pit 200 for continued construction, one end of the load-bearing reinforcement 360 is connected to the connection point of the second load-bearing member 330, and the other end passes through… The hydraulic jack 380 is anchored to the fixed support column 310 at its output end. The hydraulic jack 380 is driven to push the stressed rib 360 to tighten it. This transfers the downward vertical weight of the side wall support structure 530, originally supported by the temporary load-bearing steel frame 400, to the side wall auxiliary support system 300. By setting up the side wall auxiliary support system 300, the original support system in the stress zone is smoothly transferred. After the "support replacement" is completed, the support structure (i.e., the original support) that affects the construction of the main structure is removed, providing an operating plane for subsequent operations. The "support replacement" ensures that the stress state of the foundation pit will not change suddenly during the demolition process.The top support pile 600 is installed within the deep foundation pit 200 and located between the two sections of the top support structure 540. It supports the top support structure 540, with one end abutting against the inner wall of the deep foundation pit 200 and the other end abutting against the top support pile 600. The function of the top support structure 540 is to "cut" the original top support steel support into two sections. The top support pile 600 acts as both a load-bearing and force-transmitting component. This design overcomes the technical problem of limited stiffness and excessive deflection of traditional single steel pipe or section steel supports for large-span deep foundation pits 200. By "cutting" it into two sections, the possibility of excessive deflection of the top support component due to the large span of the top support is effectively reduced.

[0072] In some preferred embodiments, the vertical fixed support system 100 includes an outer closed pile row 110 and an inner closed pile row 120. The outer closed pile row 110 is located outside the inner closed pile row 120. Both the outer closed pile row 110 and the inner closed pile row 120 are composed of a number of spaced support piles 130.

[0073] In some preferred embodiments, the first force-bearing component 320 includes a stabilizing triangular frame 321, a force-transmitting rotating shaft 322, and force-transmitting anti-slip ribs 323. The stabilizing triangular frame 321 is fixedly installed on the construction platform by connecting bolts 324. A plurality of force-transmitting anti-slip ribs 323 are provided on the bottom surface of the stabilizing triangular frame 321. The force-transmitting rotating shaft 322 is rotatably installed at the top of the stabilizing triangular frame 321. The force-bearing rib 360 bypasses the force-transmitting rotating shaft 322 and passes through the output end of the hydraulic jack 380, anchoring to the fixed support column 310. Pushing tightens the force-bearing rib 360. Since the force-bearing rib 360 is supported by the axial surface of the force-transmitting shaft 322, and this support is curved, it effectively prevents the force-bearing rib 360 from wearing down and breaking during tightening. The force-transmitting shaft 322 also effectively reduces friction between the force-bearing rib 360 and the shaft. When tightening the force-bearing rib 360, it acts on the first force-bearing component 320, and the resultant force is downward, transmitted to the construction platform through the force-transmitting anti-slip protrusion 323, further stabilizing the first force-bearing component 320. It is worth noting that, utilizing the principle of triangle stability, the second force-bearing component 330 is also a triangular component.

[0074] In some preferred embodiments, the corner support structure 520 includes a triangular connector 521 and a corner brace truss unit 522. The corner brace truss unit 522 is formed by splicing several standardized H-beam steel segments with high-strength bolts, and its two ends are respectively installed to the waler 510 through the triangular connector 521.

[0075] In some preferred embodiments, the sidewall support structure 530 includes an upper chord 531, a lower chord 532, a web member 533, and end connectors 534. The upper chord 531 is installed on the waler 510. The web member 533 includes several H-beams of different lengths. The two ends of the web member 533 are connected to the upper chord 531 and the lower chord 532 respectively through node connecting plates 535. The H-beams of different lengths are installed on the upper chord 531 in a structurally symmetrical manner. The end connectors 534 are disposed at both ends of the upper chord 531 (specifically, anchored into the vertical fixed support system 100). The end connectors 534 are used to anchor the lower chord 532 and apply prestress. It is worth mentioning that the lower chord 532 is a high-strength steel strand. The lower chord 532 is connected to the ends of several web members 533, and its connection outline is fish-belly shaped. The sidewall support structure 530 adopts prefabricated prestressed fish belly beam steel structure support technology, which is an existing technology, and its specific principle will not be elaborated.

[0076] In some preferred embodiments, the top support pile 600 includes a main pile 610 and a foot support 620. The main pile 610 is installed in the deep foundation pit 200. One end of the foot support 620 is connected to the main pile 610, and the other end is connected to the bottom of the deep foundation pit 200. The foot support 620 reinforces the installation of the main pile 610.

[0077] In some preferred embodiments, the top support structure 540 includes a hinge head 541, a steel support 542, a hydraulic propulsion device 543, and a flange mounting plate 544. The hinge head 541 is installed on the vertical fixed support system 100 via a waist beam 140. The steel support 542 is slidably disposed on the hinge head 541. The other end of the steel support 542 is installed on the main pile column 610 via the flange mounting plate 544. The hydraulic propulsion device 543 is installed at the hinge head 541, and its output end is connected to the steel support 542.

[0078] A construction process for a prefabricated steel truss internal support system for deep foundation pits, comprising the following steps:

[0079] S1: Define the boundary of the target construction area;

[0080] S2: The flatness of the ground surface in the target construction area;

[0081] S3: Construction of retaining piles;

[0082] S3.1: Using rotary drilling rigs and percussion drilling rigs, multiple first pile holes are laid out circumferentially around the boundary of the determined target construction area to form an outer closed pile row 110;

[0083] S3.2: Multiple second pile holes are arranged at intervals along the inner circumference of the outer closed pile row 110 to form an inner closed pile row 120, wherein the outer closed pile row 110 surrounds the inner closed pile row 120 in a plane.

[0084] S3.3: Suspend steel cages into the first pile hole and the second pile hole, and pour concrete to form support piles 130;

[0085] S4: Construction of the water-stop curtain;

[0086] S4.1: A water-stop curtain construction axis is set along the circumferential direction of the boundary of the target construction area. The water-stop curtain construction axis is located between the outer closed pile row and the inner closed pile row, and is parallel to both of them.

[0087] S4.2: Multiple sets of cement-soil mixing piles are constructed sequentially along the construction axis of the water-stop curtain using a three-axis mixing pile machine. Adjacent sets of cement mixing piles are connected by a splicing and overlapping method to form a continuous wall.

[0088] S5: Area division and construction;

[0089] S5.1: Divide the target construction area into excavation area A, excavation area B, excavation area C and excavation area D;

[0090] S5.2: Several dewatering well points shall be excavated in the areas of excavation zone A, excavation zone B, excavation zone C and excavation zone D respectively;

[0091] S5.3: Lower a water pump into the dewatering well point to pump out the water from the well point;

[0092] S6: Layered excavation and installation of the waist beam

[0093] S6.1: After drainage is completed, the excavated areas A, B, C and D shall be excavated in layers;

[0094] S6.2: After excavating to the first depth below the support design elevation, use a drilling rig to drill a hole at the vertical fixed support system 100 in an inclined downward manner, then grout after the lower anchor rod, and install the waist beam 140. The waist beam 140 is locked to the vertical fixed support system 100 by the anchor rod.

[0095] S6.3: Repeat steps S6.2, excavate several layers, and complete the installation of several layers of 140mm wainscoting, and complete the excavation of the 200mm deep foundation pit;

[0096] S7: Installation of the 300-meter sidewall auxiliary support system;

[0097] S7.1: Install the corbel bearing member 350 on the waist beam 140;

[0098] S7.2: A number of grouting holes are arranged on the construction platform, lattice columns are placed into the grouting holes and concrete is poured to form the fixed support column 310, the hydraulic jack mounting base 370 is installed on the fixed support column 310, and the hydraulic jack 380 is installed on the hydraulic jack mounting base 370.

[0099] S7.3: Install the first load-bearing component 320 onto the construction platform using connecting bolts 324;

[0100] S7.4: Install the second force-bearing member 330 on the corbel bearing member 350, and make its right-angled edge fit against the surface of the waist beam, and at the same time fix it on the waist beam 140 by bolts;

[0101] S7.5: Install a plurality of the bearing purlins 340 between the two second force-bearing members 330;

[0102] S7.6: A temporary load-bearing steel frame 400 is installed below the load-bearing purlin 340 to support the load-bearing purlin 340;

[0103] S8: Installation of the 500 steel truss support structure;

[0104] S8.1: The waler 510 is hoisted onto the corbel bearing member 350, and the corner support structure 520 is installed on the external corner area of ​​the deep foundation pit 200 and supported by the waler 510;

[0105] S8.2: Hoist the sidewall support structure 530 and install it onto the bearing purlin 340;

[0106] S9: Installation of the top support structure 540;

[0107] S9.1: Excavate a top support grouting hole in the deep foundation pit 200, put a steel cage into the top support grouting hole and pour concrete to form the top support pile 600.

[0108] S9.2: Weld a foot brace 620 near the bottom end of the main pile column 610 of the top support pile column 600 to reinforce the main pile column 610;

[0109] S9.3: Install the hinge head 541 on the waist beam 140, attach the steel support 542 to the hinge head 541, and install the other end of the steel support 542 to the main pile body 610 of the top support pile 600 through the flange mounting end plate 544.

[0110] S9.4: The hydraulic propulsion device 543 is installed at the movable head 541, and its output end is connected to the steel support 542. The hydraulic propulsion device 543 is used to indirectly support the two opposing inner walls of the deep pit 200.

[0111] S10: Construction and support replacement;

[0112] S10.1: When the deep foundation pit 200 needs to dismantle the temporary load-bearing steel frame 400 to continue construction, one end of the load-bearing rib 360 is connected to the connection point of the second load-bearing member 330, and the other end is connected to the output end of the hydraulic jack 380. The hydraulic jack 380 is driven to tighten the load-bearing rib 360 so that the vertical downward gravity of the side wall support structure 530 originally borne by the temporary load-bearing steel frame 400 is transferred to be borne by the side wall auxiliary support system 300.

[0113] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A prefabricated steel truss internal support system for deep foundation pits, characterized in that, include: A vertical fixed support system (100) is provided around the deep foundation pit (200) to support the sidewalls of the deep foundation pit (200) and prevent the foundation pit soil from collapsing. A sidewall auxiliary support system (300) is a construction platform located outside the top edge of the deep foundation pit (200). The sidewall auxiliary support system (300) includes a fixed support column (310), a first load-bearing component (320), a second load-bearing component (330), a load-bearing purlin (340), a corbel load-bearing component (350), a load-bearing reinforcement (360), a hydraulic jack mounting base (370), and a hydraulic jack (380). The fixed support column (310) The first load-bearing component (320) is fixed to the construction work platform, the corbel bearing component (350) is installed on the vertical fixed support system (100), the second load-bearing component (330) is installed on the corbel bearing component (350), the hydraulic jack mounting base (370) is installed on the fixed support column (310), and the hydraulic jack (380) is installed on the hydraulic jack mounting base (370). A temporary load-bearing steel frame (400) is installed inside the deep foundation pit (200); A steel truss support structure (500) includes a waler (510), a corner support structure (520), a side wall support structure (530), and a top support structure (540). The waler (510) is installed on the corbel bearing member (350). The corner support structure (520) is installed on the external corner area of ​​the deep foundation pit (200) and is supported by the waler (510). The side wall support structure (530) is installed near the upper end of the inner side wall of the deep foundation pit (200). Second load-bearing members (330) are provided at both ends of the side wall support structure (530). Several bearing walers (340) are arranged between the two second load-bearing members (330) to support the side wall support structure (530). The temporary load-bearing steel frame (400) is set below the load-bearing purlin (340) to support the load-bearing purlin (340), thereby indirectly supporting the side wall support structure (530). When the deep foundation pit (200) needs to dismantle the temporary load-bearing steel frame (400) to continue construction, one end of the stress-bearing rib (360) is connected to the connection point of the second stress-bearing member (330), and the other end passes through the output end of the hydraulic jack (380) and is anchored to the fixed support column (310). The hydraulic jack (380) is driven to tighten the stress-bearing rib (360) so that the vertical downward gravity of the side wall support structure (530) originally supported by the temporary load-bearing steel frame (400) is transferred to be supported by the side wall auxiliary support system (300). The top support pile (600) is installed in the deep foundation pit (200) and located between the two sections of the top support structure (540) to support the top support structure (540). One end of the top support structure (540) is abutted to the inner wall of the deep foundation pit (200), and the other end is abutted to the top support pile (600).

2. The prefabricated steel truss internal support system for deep foundation pits according to claim 1, characterized in that, The vertical fixed support system (100) includes an outer closed pile row (110) and an inner closed pile row (120). The outer closed pile row (110) is located outside the inner closed pile row (120). Both the outer closed pile row (110) and the inner closed pile row (120) are composed of several spaced support piles (130).

3. The prefabricated steel truss internal support system for deep foundation pits according to claim 2, characterized in that, The first force-bearing component (320) includes a stable triangular frame (321), a force-bearing transmission shaft (322), and a force-transmitting anti-slip ridge (323). The stable triangular frame (321) is fixedly installed on the construction work platform by connecting bolts (324). Several force-transmitting anti-slip ridges (323) are provided on the bottom surface of the stable triangular frame (321). The force-bearing transmission shaft (322) is rotatably installed at the top of the stable triangular frame (321).

4. The prefabricated steel truss internal support system for deep foundation pits according to claim 3, characterized in that, The second force-bearing component (330) is a triangular component.

5. The prefabricated steel truss internal support system for deep foundation pits according to claim 1, characterized in that, The corner support structure (520) includes a triangular connector (521) and a corner truss unit (522). The two ends of the corner truss unit (522) are respectively installed on the waler (510) through the triangular connector (521).

6. The prefabricated steel truss internal support system for deep foundation pits according to claim 1, characterized in that, The sidewall support structure (530) includes an upper chord (531), a lower chord (532), a web member (533), and an end connector (534). The upper chord (531) is installed on the waler (510). The web member (533) includes several H-beams of different lengths. The two ends of the web member (533) are connected to the upper chord (531) and the lower chord (532) respectively through node connecting plates (535). Several web members (533) are installed on the upper chord (531). The end connector (534) is provided at both ends of the upper chord (531) for anchoring the lower chord (532) and applying prestress.

7. The prefabricated steel truss internal support system for deep foundation pits according to claim 6, characterized in that, The lower chord (532) is a high-strength steel strand.

8. The prefabricated steel truss internal support system for deep foundation pits according to claim 1, characterized in that, The top support pile (600) includes a main pile body (610) and a foot support (620). The main pile body (610) is installed in the deep foundation pit (200). One end of the foot support (620) is connected to the main pile body (610), and the other end is connected to the bottom of the deep foundation pit (200).

9. The prefabricated steel truss internal support system for deep foundation pits according to claim 8, characterized in that, The top support structure (540) includes a hinged head (541), a steel support (542), a hydraulic propulsion device (543), and a flange mounting plate (544). The hinged head (541) is installed on the vertical fixed support system (100) via a waist beam (140). The steel support (542) is slidably mounted on the hinged head (541). The other end of the steel support (542) is installed on the main pile column (610) via the flange mounting plate (544). The hydraulic propulsion device (543) is installed at the hinged head (541), and its output end is connected to the steel support (542).

10. A construction process for a prefabricated steel truss internal support system for deep foundation pits, applied to the prefabricated steel truss internal support system for deep foundation pits as described in any one of claims 1 to 9, characterized in that, Its construction steps include: S1: Define the boundary of the target construction area; S2: The flatness of the ground surface in the target construction area; S3: Construction of retaining piles; S3.1: Using rotary drilling rigs and percussion drilling rigs, multiple first pile holes are laid out circumferentially around the boundary of the determined target construction area to form an outer closed pile row (110). S3.2: Multiple second pile holes are arranged at intervals along the inner circumference of the outer closed pile row (110) to form an inner closed pile row (120), and the outer closed pile row (110) surrounds the inner closed pile row (120) in the plane. S3.3: Suspend steel cages into the first pile hole and the second pile hole, and pour concrete to form support piles (130). S4: Construction of the water-stop curtain; S4.1: A water-stop curtain construction axis is set along the circumferential direction of the boundary of the target construction area. The water-stop curtain construction axis is located between the outer closed pile row and the inner closed pile row, and is parallel to both of them. S4.2: Multiple sets of cement-soil mixing piles are constructed sequentially along the construction axis of the water-stop curtain using a three-axis mixing pile machine. Adjacent sets of cement mixing piles are connected by a splicing and overlapping method to form a continuous wall. S5: Area division and construction; S5.1: Divide the target construction area into excavation area A, excavation area B, excavation area C and excavation area D; S5.2: Several dewatering well points shall be excavated in the areas of excavation zone A, excavation zone B, excavation zone C and excavation zone D respectively; S5.3: Lower a water pump into the dewatering well point to pump out the water from the well point; S6: Layered excavation and installation of the waist beam S6.1: After drainage is completed, the excavated areas A, B, C and D shall be excavated in layers; S6.2: After excavating to the first depth below the support design elevation, use a drilling rig to drill a hole at the vertical fixed support system (100) in an inclined downward manner, grout after the lower anchor rod, and install the waist beam (140). The waist beam (140) is locked to the vertical fixed support system (100) by the anchor rod. S6.3: Repeat step S6.2, excavate several layers, and complete the installation of several layers of waist beams (140), and complete the excavation of the deep foundation pit (200); S7: Installation of the sidewall auxiliary support system (300); S7.1: Install the corbel bearing member (350) on the waist beam (140); S7.2: Several grouting holes are arranged on the construction operation platform, lattice columns are placed into the grouting holes and concrete is poured to form the fixed support column (310), the hydraulic jack mounting base (370) is installed on the fixed support column (310), and the hydraulic jack (380) is installed on the hydraulic jack mounting base (370). S7.3: Install the first load-bearing component (320) onto the construction platform using connecting bolts (324); S7.4: Install the second load-bearing member (330) on the corbel bearing member (350) and make its right-angled edge fit against the surface of the waist beam, and fix it on the waist beam (140) with bolts; S7.5: Install a plurality of the bearing purlins (340) between the two second force-bearing members (330); S7.6: A temporary load-bearing steel frame (400) is installed below the load-bearing purlin (340) to support the load-bearing purlin (340). S8: Installation of the steel truss support structure (500); S8.1: The waler (510) is hoisted onto the corbel bearing member (350), and the corner support structure (520) is installed on the external corner area of ​​the deep foundation pit (200) and supported by the waler (510); S8.2: Hoist the side wall support structure (530) and install it onto the load-bearing purlin (340); S9: Installation of the top support structure (540); S9.1: Excavate a top support grouting hole in the deep foundation pit (200), put a steel cage into the top support grouting hole and pour concrete to form the top support pile (600). S9.2: Weld a foot brace (620) to the bottom end of the main pile body (610) of the top support pile (600) to reinforce the main pile body (610). S9.3: Install the hinge head (541) on the waist beam (140), attach the steel support (542) to the hinge head (541), and install the other end of the steel support (542) onto the main pile body (610) of the top support pile (600) through the flange mounting plate (544); S9.4: Install the hydraulic propulsion device (543) at the movable head (541), with its output end connected to the steel support (542), and use the hydraulic propulsion device (543) to indirectly support the two opposing inner walls of the deep pit (200); S10: Construction and support replacement; S10.1: When the deep foundation pit (200) needs to dismantle the temporary load-bearing steel frame (400) to continue construction, one end of the load-bearing rib (360) is connected to the connection point of the second load-bearing component (330), and the other end is anchored to the fixed support column (310) through the output end of the hydraulic jack (380). The hydraulic jack (380) is driven to tighten the load-bearing rib (360) so that the vertical downward gravity of the side wall support structure (530) originally supported by the temporary load-bearing steel frame (400) is transferred to be supported by the side wall auxiliary support system (300).

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