Deep foundation pit speed drop flash support steel support system and excavation construction method

Abstract

This invention provides a rapid descent steel support system and excavation construction method for deep foundation pits. The method includes: a. excavating the first layer of soil and constructing the first layer of conventional support; b. excavating the second layer of soil to a certain depth, assembling the rapid descent steel support under the first layer of conventional support, and connecting it to the vertical lifting system of the rapid descent steel support; the hydraulic servo system pushes it outward; c. continuing to excavate soil, the hydraulic servo system depressurizes and retracts, the vertical lifting system lowers the rapid descent steel support to the design elevation, and then applies jacking force to the diaphragm wall; constructing the current layer of conventional support; d. repeating step c to excavate the foundation pit until the last layer of soil is excavated; vertically lifting the rapid descent steel support to the design elevation of the pit bottom; constructing the foundation pit bottom slab. This invention can significantly reduce the unsupported exposure time of the foundation pit and effectively achieve the beneficial effect of controlling deformation during deep foundation pit excavation.

Description

Technical Field

[0001] This invention relates to the field of rail transit engineering, and in particular to a deep foundation pit rapid descent flash brace steel support system and excavation construction method. Background Technology

[0002] With rapid urban development, the construction difficulty of rail transit projects in my country is increasing, and the construction risks are also rising accordingly. At the same time, the requirements for controlling the impact of foundation pit excavation on the surrounding environment are becoming increasingly stringent. How to effectively control the deformation of foundation pit excavation has become an urgent problem to be solved in the new round of rail transit construction.

[0003] It generally takes more than 10 days for reinforced concrete supports to reach the design strength, from rebar binding, formwork erection, and pouring. Long-term exposure of the foundation pit without support is unavoidable.

[0004] Traditional steel supports are easy and quick to install when the foundation pit is shallow. However, as underground engineering development moves to deeper spaces and the excavation depth of the foundation pit becomes deeper, more and stronger support systems are needed, which leads to longer construction time and a significant increase in the time the foundation pit is exposed without support.

[0005] Numerous studies have shown that a large portion of the deformation during foundation pit excavation occurs during the unsupported, exposed stage of the foundation pit.

[0006] Therefore, significantly reducing the unsupported exposure time of the foundation pit has become the key to deformation control during ultra-deep foundation pit excavation. Summary of the Invention

[0007] In order to overcome the problems existing in the prior art, the present invention provides a deep foundation pit rapid descent flash bracing steel support system and excavation construction method, which can significantly reduce the time of unsupported exposure of the foundation pit.

[0008] To achieve the above objectives, a first aspect of the present invention provides a method for constructing a rapid descent and flash bracing system for steel supports in deep foundation pit excavation, comprising the following steps:

[0009] a. Excavate the first layer of earthwork and construct the first conventional support, which is equipped with cable-through holes;

[0010] b. Excavate the second layer of soil to a certain depth, and assemble the rapid-descent steel support on the horizontal plane under the first conventional support of the foundation pit. The ends of the rapid-descent steel support are equipped with a hydraulic servo system. Install the vertical lifting system of the rapid-descent steel support on the sling penetration hole, and install the lifting tool to connect it to the rapid-descent steel support through the vertical lifting system. Start the vertical lifting system to clamp the lifting tool. The hydraulic servo system pushes outward to automatically apply the jacking force to the underground continuous wall of the foundation pit according to the design value.

[0011] c. Continue excavating the second layer of soil, depressurize and retract the hydraulic servo system, and lower the rapid descent steel support using the vertical hoisting system; after the rapid descent steel support is vertically lowered to the design elevation, the hydraulic servo system pushes it outward, automatically applying jacking force to the underground continuous wall of the foundation pit according to the design value, and locking the hoisting equipment; construct the second conventional support;

[0012] d. Excavate the third layer of earthwork, unlock and extend the lifting equipment; after vertically lowering the rapid descent steel support to the design elevation in the order of step c, start the vertical lifting system to clamp the lifting equipment, and push the hydraulic servo system outward to automatically apply the jacking force to the underground continuous wall of the foundation pit according to the design value; construct the conventional support for the current layer;

[0013] e. Repeat step d to excavate the foundation pit until the last layer of soil is excavated, unlock and extend the lifting equipment; vertically lower the rapid descent steel support to the design elevation of the pit bottom in the sequence of step c, start the vertical lifting system to clamp the lifting equipment, the hydraulic servo system pushes it outward, and the rapid descent steel support replaces the conventional support to automatically apply the jacking force to the underground continuous wall of the foundation pit according to the design value; fix the rapid descent steel support, dismantle the lifting equipment and vertical lifting system, and construct the foundation pit bottom slab.

[0014] Furthermore, the rapid descent steel supports are connected longitudinally and laterally into frames via cross joints.

[0015] Furthermore, the vertical lifting system includes an upper clamping mechanism and a lower clamping mechanism for clamping the lifting device. The upper clamping mechanism has a top plate at its top and a bottom plate at its bottom. An automatically retractable main top device is connected between the top plate and the bottom plate.

[0016] Furthermore, a main top displacement sensor is installed on the vertical hoisting system, and an angle sensor is installed on the rapid descent steel support;

[0017] During the process of lowering the rapid-descent steel support by the vertical lifting system, the vertical lifting system automatically reads the data from the main jacking displacement sensor and the tilt sensor, and automatically adjusts the retraction speed of the main jacking device according to the collected data, so that the rapid-descent steel support always remains in a horizontal state.

[0018] Furthermore, the steps for the vertical lifting system to lower the rapid descent steel support include:

[0019] Release the upper clamping mechanism, keep the lower clamping mechanism clamped, and extend the main top device of the vertical lifting system to the upper limit position;

[0020] The upper clamping mechanism is activated to clamp the lifting device, the lower clamping mechanism is released, the hydraulic servo system is depressurized and retracted, the main jacking device retracts to the lower limit, and the steel support is lowered into a rapid descent section.

[0021] Furthermore, after the rapid descent steel support is vertically hoisted to the design elevation, the following steps are also included:

[0022] The lower clamping mechanism is activated to clamp the lifting device, and the hydraulic servo system pushes outward, automatically applying a jacking force to the underground continuous wall of the foundation pit according to the design value.

[0023] Remove the main jacking device and upper clamping mechanism, install the outer steel pipe, and fix it to the lifting device to prevent the lifting device from falling.

[0024] Furthermore, the lifting device adopts an assembly structure.

[0025] A second aspect of the present invention provides a support system for the steel-supported rapid descent and flash bracing construction method for deep foundation pit excavation as described above, the support system comprising:

[0026] The rapid descent steel support is equipped with a hydraulic servo system at its end. By activating the hydraulic servo system, it is pushed outward to automatically apply a jacking force to the underground continuous wall of the foundation pit according to the design value.

[0027] A lifting device, the lower end of which is connected to the descent steel support;

[0028] The vertical lifting system for clamping or releasing the lifting device has sling through holes on the conventional supports. The vertical lifting system is installed on the sling through holes of the first conventional support, and the lifting device passes through the vertical lifting system and the sling through holes from top to bottom.

[0029] Furthermore, the vertical lifting system includes an upper clamping mechanism and a lower clamping mechanism for clamping the lifting device. The upper clamping mechanism has a top plate at its top and a bottom plate at its bottom. An automatically retractable main top device is connected between the top plate and the bottom plate.

[0030] Furthermore, a main top displacement sensor is installed on the vertical hoisting system, and an angle sensor is installed on the rapid descent steel support.

[0031] By adopting the above technical solution, the present invention has the following beneficial effects:

[0032] 1. After each layer of earthwork is excavated, the rapid descent steel support can be quickly hoisted to the designated height. Then, the hydraulic servo system pushes it outward to apply jacking force to the underground continuous wall of the foundation pit, thereby reducing the unsupported exposure time of the foundation pit and effectively controlling the deformation of the foundation pit.

[0033] 2. Rapid descent steel supports can serve as the last line of conventional support without requiring additional supports, offering better economic performance. Attached Figure Description

[0034] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0035] Figures 1-4 This is a flowchart of the deep foundation pit excavation steel support rapid descent and flash bracing construction method according to an embodiment of the present invention.

[0036] Figure 5 This is a plan view of the installation of the deep foundation pit rapid descent steel support according to an embodiment of the present invention.

[0037] Figures 6-10 This is a flowchart illustrating the workflow of the vertical hoisting system for rapid descent steel supports in deep foundation pits, according to an embodiment of the present invention.

[0038] The labels in the diagram are explained as follows:

[0039] 11-First layer of earthwork; 12-Second layer of earthwork; 13-Third layer of earthwork; 21-First conventional support; 22-Second conventional support; 23-Third conventional support; 3-Rapid descent steel support; 4-Hydraulic servo system; 5-Diaphragm wall of foundation pit; 6-Sling penetration hole; 7-Vertical lifting system; 71-Main jacking device; 72-Upper clamping mechanism; 73-Lower clamping mechanism; 74-Main jacking displacement sensor; 75-Outer steel pipe; 8-Lifting tool; 9-Tilting sensor. Detailed Implementation

[0040] The objects and functions of the present invention, as well as the methods for achieving these objects and functions, will be clarified by referring to exemplary embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings; in the drawings, the same reference numerals denote the same or similar steps.

[0041] See Figures 1-10 As shown in the figure, this invention provides a method for constructing a rapid descent and flash bracing system for steel supports in deep foundation pit excavation, comprising the following steps:

[0042] (a) Excavate the first layer of earthwork 11 and construct the first conventional support 21, with a cable through hole 6 on the support.

[0043] (b) Excavate the second layer of soil 12 downwards to a certain depth (the depth should meet the space requirements for assembling the rapid descent steel support 3). Assemble the rapid descent steel support 3 under the first conventional support 21 in the foundation pit. The rapid descent steel support 3 is connected longitudinally and laterally through cross joints 31 to form a rapid descent steel support system. The longitudinal and transverse ends of the rapid descent steel support 3 are equipped with hydraulic servo systems 4. Install the vertical lifting system 7 of the rapid descent steel support on the sling through hole 6. Install the lifting device 8 to connect it to the complete rapid descent steel support 3 through the vertical lifting system 7, keeping the complete rapid descent steel support 3 horizontal. The lifting device 8 can be quickly assembled from internally threaded steel pipes. Activate the upper clamping mechanism 72 and the lower clamping mechanism 73 of the vertical lifting system 7 to clamp the lifting device 8. The hydraulic servo system 4 pushes outwards, automatically applying a jacking force to the underground continuous wall 5 of the foundation pit according to the design value.

[0044] The vertical lifting system 7 mainly includes an upper clamping mechanism 72, a lower clamping mechanism 73, and an automatically retractable main top device 71. The upper clamping mechanism 72 and lower clamping mechanism 73 are used to clamp the lifting device 8. Specifically, the upper clamping mechanism 72 and lower clamping mechanism 73 can be composed of several unit blocks similar to a clamping hoop structure. When clamping, the unit blocks move inward to clamp the lifting device 8; when releasing, the unit blocks spread outward to loosen the clamping device 8. The lifting device 8 vertically passes through the upper clamping mechanism 72 and lower clamping mechanism 73. The upper clamping mechanism 72 can be installed below a top plate via several connectors, with a central opening in the top plate for the lifting device 8 to pass through. Similarly, the lower clamping mechanism 73 can be installed above a bottom plate via connectors, with a central opening in the bottom plate for the lifting device 8 to pass through. Figures 6-8 As shown. The main lifting device 71 can be several small electric push rods or small hydraulic push rods, with the upper end connected and fixed to the top plate and the lower end connected and fixed to the bottom plate. The extension and retraction of the main lifting device 71 can change the relative distance between the top plate and the bottom plate, that is, change the relative distance between the upper clamping mechanism 72 and the lower clamping mechanism 73. Preferably, the several main lifting devices 71 are evenly distributed around the upper clamping mechanism 72 and the lower clamping mechanism 73, so that the relative movement of the upper clamping mechanism 72 and the lower clamping mechanism 73 is more stable.

[0045] Furthermore, the vertical hoisting system 7 is equipped with a main top displacement sensor 74 and an inclination sensor 9 on the truss rapid descent steel support 3.

[0046] Furthermore, the hydraulic servo system 4 is existing technology, which is a closed-loop control system composed of a hydraulic power mechanism and a feedback mechanism. The hydraulic power mechanism can be a small hydraulic jack, and the feedback mechanism connects and controls the extension and retraction of the small hydraulic jack.

[0047] (c) Continue excavating the second layer of earthwork 12 (over-excavating to a certain depth), loosen the upper clamping mechanism 72, and keep the lower clamping mechanism 73 clamped. The main jacking device 71 of the vertical lifting system 7 extends to its upper limit. Activate the upper clamping mechanism 72 to clamp the lifting device 8, loosen the lower clamping mechanism 73, depressurize and retract the hydraulic servo system 4, and retract the main jacking device 71 to its lower limit, lowering the truss-shaped rapid-descent steel support 3. During the lifting process, the vertical lifting system automatically reads data from the main jacking displacement sensor 74 and the tilt sensor 9 installed on the truss-shaped rapid-descent steel support 3, and automatically adjusts the retraction speed of each main jacking device 71 based on the collected data to keep the truss-shaped rapid-descent steel support 3 horizontal at all times. After the truss-shaped rapid-descent steel support 3 is vertically lowered to the design elevation, activate the lower clamping mechanism 73 to clamp the lifting device 8, and push the hydraulic servo system 4 outward, automatically applying jacking force to the underground continuous wall 5 of the foundation pit according to the design value. Remove the main jacking device 71 and the upper clamping mechanism 72. Install the outer steel pipe 75 and fix it to the lifting device 8 to prevent the lifting device 8 from falling. Construct the second conventional support 22.

[0048] (d) Excavate the third layer of earthwork 13 (over-excavating to a certain depth), remove the outer steel pipe 75, install the main jacking device 71 and the upper clamping mechanism 72, and extend the lifting device 8. After hoisting the rapid-descent steel support 3 to the design elevation in the sequence of step (c), activate the lower clamping mechanism 73 to clamp the lifting device 8, and the hydraulic servo system 4 pushes outward, automatically applying jacking force to the underground continuous wall 5 of the foundation pit according to the design value. Remove the main jacking device 71 and the upper clamping mechanism 72. Install the outer steel pipe 75 and fix it to the lifting device 8 to prevent the lifting device 8 from falling. Construct the third conventional support 23.

[0049] (e) Repeat step (d) to excavate the foundation pit until the last layer of soil 14 is excavated. Remove the outer steel pipe 75, install the main jacking device 71 and the upper clamping mechanism 72, and extend the lifting device 8. Vertically lower the rapid-descent steel support 3 to the design elevation of the pit bottom in the sequence of step (c). Activate the lower clamping mechanism 73 to clamp the lifting device 8, and the hydraulic servo system 4 pushes it outward. The rapid-descent steel support 3 replaces the conventional support and automatically applies jacking force to the underground continuous wall 5 of the foundation pit according to the design value. Fix the rapid-descent steel support 3, remove the lifting device 8 and the vertical lifting system 7, and construct the foundation pit bottom slab.

[0050] This invention provides a method for constructing rapid-descent steel supports in deep foundation pit excavation. Through a vertical hoisting system and lifting equipment, the rapid-descent steel supports can be quickly lowered into the foundation pit. A hydraulic servo system is installed at the end of the rapid-descent steel support. This system can extend outwards, automatically applying a jacking force to the diaphragm wall of the foundation pit according to design values, thereby fixing the rapid-descent steel support. When the hydraulic servo system retracts, the rapid-descent steel support can be lowered. The operation is convenient, and the rapid-descent steel support can also serve as a final conventional support. Therefore, this invention can significantly reduce the unsupported exposure time of the foundation pit, effectively achieving the beneficial effect of deformation control in deep foundation pit excavation.

[0051] Furthermore, the present invention also provides a support system for implementing the deep foundation pit excavation steel support rapid descent and flash bracing construction method of the above embodiments, which mainly includes:

[0052] Rapid descent steel support 3 is connected longitudinally and laterally via cross joints 31 to form a rapid descent steel support system. Hydraulic servo systems 4 are installed at the longitudinal and transverse ends of the rapid descent steel support 3. By activating these hydraulic servo systems 4, the support is pushed outwards, automatically applying a jacking force to the underground continuous wall of the foundation pit according to the design value.

[0053] The lifting device 8 is fixedly connected to the quick-descent steel support 3 at its lower end. The lifting device 8 can be quickly assembled from internally threaded steel pipes.

[0054] The vertical lifting system 7 used to clamp or release the lifting device 8 has sling through holes 6 on each of the conventional supports. The vertical lifting system 7 is installed on the sling through holes 6 on the first conventional support 21. The lifting device 8 passes through the vertical lifting system 7 and all the sling through holes from top to bottom.

[0055] The vertical lifting system 7 mainly includes an upper clamping mechanism 72, a lower clamping mechanism 73, and an automatically retractable main top device 71. The upper clamping mechanism 72 and lower clamping mechanism 73 are used to clamp the lifting device 8. Specifically, the upper clamping mechanism 72 and lower clamping mechanism 73 can be composed of several unit blocks similar to a clamp structure. When clamping, the unit blocks move inward to clamp the lifting device 8; when releasing, the unit blocks spread outward to release the clamp 8. The lifting device 8 vertically passes through the upper clamping mechanism 72 and lower clamping mechanism 73. The upper clamping mechanism 72 can be installed below a top plate via several connectors, with a central opening in the top plate for the lifting device 8 to pass through. Similarly, the lower clamping mechanism 73 can be installed above a bottom plate via connectors, with a central opening in the bottom plate for the lifting device 8 to pass through. Figures 6-8 As shown. The main lifting device 71 can be several small electric push rods or small hydraulic push rods, with the upper end connected and fixed to the top plate and the lower end connected and fixed to the bottom plate. The extension and retraction of the main lifting device 71 can change the relative distance between the top plate and the bottom plate, that is, change the relative distance between the upper clamping mechanism 72 and the lower clamping mechanism 73. Preferably, the several main lifting devices 71 are evenly distributed around the upper clamping mechanism 72 and the lower clamping mechanism 73, so that the relative movement of the upper clamping mechanism 72 and the lower clamping mechanism 73 is more stable.

[0056] Furthermore, the vertical hoisting system 7 is equipped with a main top displacement sensor 74 and an inclination sensor 9 on the truss rapid descent steel support 3.

[0057] Furthermore, the hydraulic servo system 4 is existing technology, which is a closed-loop control system composed of a hydraulic power mechanism and a feedback mechanism. The hydraulic power mechanism can be a small hydraulic jack, and the feedback mechanism connects and controls the extension and retraction of the small hydraulic jack.

[0058] Although embodiments of the present invention have been shown and described, these specific embodiments are merely explanations of the invention and are not intended to limit it. The specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. After reading this specification, those skilled in the art may make modifications, substitutions, and variations to the embodiments as needed without departing from the principles and spirit of the invention, but such modifications, substitutions, and variations are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A method for constructing a rapid descent and flash bracing system using steel supports during deep foundation pit excavation, characterized in that... Includes the following steps: a. Excavate the first layer of earthwork and construct the first conventional support, which is equipped with cable-through holes; b. Excavate the second layer of soil to a certain depth, and assemble the rapid-descent steel support on the horizontal plane under the first conventional support of the foundation pit. The ends of the rapid-descent steel support are equipped with a hydraulic servo system. Install the vertical lifting system of the rapid-descent steel support on the sling penetration hole, and install the lifting tool to connect it to the rapid-descent steel support through the vertical lifting system. Start the vertical lifting system to clamp the lifting tool. The hydraulic servo system pushes outward to automatically apply the jacking force to the underground continuous wall of the foundation pit according to the design value. c. Continue excavating the second layer of soil, depressurize and retract the hydraulic servo system, and lower the rapid descent steel support using the vertical hoisting system; after the rapid descent steel support is vertically lowered to the design elevation, the hydraulic servo system pushes it outward, automatically applying jacking force to the underground continuous wall of the foundation pit according to the design value, and locking the hoisting equipment; construct the second conventional support. d. Excavate the third layer of earthwork, unlock and extend the lifting equipment; after vertically lowering the rapid descent steel support to the design elevation in the order of step c, start the vertical lifting system to clamp the lifting equipment, and push the hydraulic servo system outward to automatically apply the jacking force to the underground continuous wall of the foundation pit according to the design value; construct the conventional support for the current layer; e. Repeat step d to excavate the foundation pit until the last layer of soil is excavated, unlock and extend the lifting equipment; vertically lower the rapid-descent steel support to the design elevation of the pit bottom in the sequence of step c, start the vertical lifting system to clamp the lifting equipment, the hydraulic servo system pushes it outward, and the rapid-descent steel support replaces the conventional support to automatically apply the jacking force to the underground continuous wall of the foundation pit according to the design value; fix the rapid-descent steel support, dismantle the lifting equipment and vertical lifting system, and construct the foundation pit bottom slab.

2. The method for rapid descent and flash bracing of steel supports in deep foundation pit excavation according to claim 1, characterized in that, The rapid descent steel supports are connected longitudinally and laterally into frames via cross joints.

3. The method for rapid descent and flash bracing of steel supports in deep foundation pit excavation according to claim 1, characterized in that, The vertical lifting system includes an upper clamping mechanism and a lower clamping mechanism for clamping the lifting device. The upper clamping mechanism has a top plate at its top and a bottom plate at its bottom. An automatically retractable main top device is connected between the top plate and the bottom plate.

4. The method for rapid descent and flash bracing of steel supports in deep foundation pit excavation according to claim 3, characterized in that, The vertical hoisting system is equipped with a main top displacement sensor, and the rapid descent steel support is equipped with an tilt sensor. During the process of lowering the rapid-descent steel support by the vertical lifting system, the vertical lifting system automatically reads the data from the main jacking displacement sensor and the tilt sensor, and automatically adjusts the retraction speed of the main jacking device according to the collected data, so that the rapid-descent steel support always remains in a horizontal state.

5. The method for rapid descent and flash bracing of steel supports in deep foundation pit excavation according to claim 3, characterized in that, The steps for lowering a rapid-descent steel support using a vertical hoisting system include: Release the upper clamping mechanism, keep the lower clamping mechanism clamped, and extend the main top device of the vertical lifting system to the upper limit position; The upper clamping mechanism is activated to clamp the lifting device, the lower clamping mechanism is released, the hydraulic servo system is depressurized and retracted, the main jacking device retracts to the lower limit, and the steel support is lowered into a rapid descent section.

6. The method for rapid descent and flash bracing of steel supports in deep foundation pit excavation according to claim 5, characterized in that, After the rapid descent steel support is vertically hoisted to the design elevation, the following steps are also included: The lower clamping mechanism is activated to clamp the lifting device, and the hydraulic servo system pushes outward, automatically applying a jacking force to the underground continuous wall of the foundation pit according to the design value. Remove the main jacking device and upper clamping mechanism, install the outer steel pipe, and fix it to the lifting device to prevent the lifting device from falling.

7. The method for rapid descent and flash bracing of steel supports in deep foundation pit excavation according to claim 1, characterized in that, The lifting device adopts an assembly structure.

8. A support system for the deep foundation pit excavation steel support rapid descent and flash bracing construction method as described in any one of claims 1 to 7, characterized in that, The support system includes: The rapid descent steel support is equipped with a hydraulic servo system at its end. By activating the hydraulic servo system, it is pushed outward to automatically apply a jacking force to the underground continuous wall of the foundation pit according to the design value. A lifting device, the lower end of which is connected to the descent steel support; The vertical lifting system for clamping or releasing the lifting device has sling through holes on the conventional supports. The vertical lifting system is installed on the sling through holes of the first conventional support, and the lifting device passes through the vertical lifting system and the sling through holes from top to bottom.

9. The support system according to claim 8, characterized in that, The vertical lifting system includes an upper clamping mechanism and a lower clamping mechanism for clamping the lifting device. The upper clamping mechanism has a top plate at its top and a bottom plate at its bottom. An automatically retractable main top device is connected between the top plate and the bottom plate.

10. The support system according to claim 9, characterized in that, The vertical hoisting system is equipped with a main top displacement sensor, and the rapid descent steel support is equipped with an tilt sensor.

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