A construction method for deep foundation pit support

Abstract

The present invention relates to a construction method for supporting a deep foundation pit, and the construction method comprises: S101, excavating the first layer of earthwork of the foundation pit by excavating equipment, and setting support points distributed at intervals on two opposite pit walls of the foundation pit. S102, distributing a plurality of support devices in the foundation pit in sequence along the vertical direction, and the two ends of the support devices respectively abut against the corresponding support points. S103, excavating the next layer of earthwork of the foundation pit by excavating equipment; S104, retracting the adjacent support device and releasing the support for the pit wall, and then moving it to the support point below the bottom support device by a hoisting device. S105, moving one of the middle support devices down to the support point corresponding to the original adjacent support device, and the other middle support devices are moved down alternately; repeating steps S103-S105 until the foundation pit is excavated to a preset depth. The adjacent support device and the bottom support device alternately support the lower layer of the foundation pit, so as to avoid the foundation pit being exposed without support and improve construction safety.

Description

Technical Field

[0001] The invention relates to the technical field of excavation, and in particular to a construction method for deep foundation pit support. Background Art

[0002] In the construction of large foundation pits, it is crucial to ensure the stability and safety of the foundation pit. With the rapid development of urban infrastructure such as rail transit, the number and scale of deep foundation pit projects are increasing. The construction of these projects is difficult. If there are no appropriate support measures, it may cause the foundation pit to deform, the surrounding buildings to tilt or even collapse, causing serious consequences and huge economic losses. In order to ensure the safety of underground structures and the surrounding environment of the foundation pit, a series of measures are usually required to support the side walls of the foundation pit and the surrounding environment to prevent excessive foundation pit deformation and surface settlement.

[0003] The existing deep foundation pit construction method usually adopts the following steps: 1. Concrete wall pouring, that is, building a concrete wall to isolate the foundation pit from the surrounding environment. 2. Step-by-step layered excavation: The foundation pit construction is usually carried out in a step-by-step layered manner. After each layer of soil is excavated, support work will be carried out immediately to maintain the stability of the foundation pit. 3. Support frame installation: After each layer of soil is excavated, the support frame is lifted and placed in the designed position using large lifting equipment, and then a pre-loaded axial force is applied to enhance the support effect.

[0004] However, the existing deep foundation pit construction methods have the following problems: 1. Inaccurate support positioning of the foundation pit: The installation of the support frame usually relies on visual positioning by construction personnel, which may lead to installation deviations and require multiple debugging to reach the designed position, which consumes a lot of time. Between the excavation of each layer of soil and the installation of the support frame, the foundation pit may be exposed without support for up to 8-12 hours, which increases the technical problem of potential safety hazards. 2. Difficulty in lifting: As the excavation depth of the foundation pit increases, the difficulty of lifting the support frame will also increase significantly, so it needs to be improved. Summary of the invention

[0005] In order to overcome the problems existing in the related art, an embodiment of the present invention provides a construction method for deep foundation pit support, which is used to solve the technical problems that the foundation pit excavation is exposed for a long time and the support device is difficult to debug the pit wall support.

[0006] According to a first aspect of an embodiment of the present invention, a construction method for deep foundation pit support is provided, the construction method comprising:

[0007] S101, excavating the first depth of earthwork of the foundation pit by using an excavation device, and setting support points distributed at intervals on two opposite pit walls of the foundation pit;

[0008] S102, distributing a plurality of support devices in the foundation pit in sequence and at intervals along the vertical direction, with the two ends of the support devices respectively abutting against corresponding support points, the support devices comprising a bottom support device, an adjacent support device and a plurality of middle support devices, and the adjacent support device is located above the bottom support device;

[0009] S103, excavating the next layer of earthwork of the foundation pit by using the excavation equipment;

[0010] S104, retracting the adjacent support device and releasing the support for the pit wall, and then moving to the support point below the bottom support device through the hoisting device to form a walking downward movement;

[0011] S105, moving one of the middle support devices downward to the supporting point corresponding to the original adjacent support device, and the other middle support devices are moved downward alternately;

[0012] Steps S103 to S105 are repeated until the foundation pit is excavated to a preset depth, and the central support devices are distributed at intervals to support the foundation pit.

[0013] In one embodiment, the number of the supporting devices is set to be multiple, and the maximum spacing distance between two adjacent supporting devices is less than or equal to 6 meters.

[0014] In one embodiment, the hoisting device spans across the top of the foundation pit and slides along the length direction of the foundation pit to adjust the hoisting position, and the adjacent support device is laterally lifted away from the vertical plane where the support device is located by the hoisting device and then moves downward.

[0015] In one embodiment, the lifting device includes a vertical sling and a side-pull sling connected to the support device;

[0016] The vertical sling is extended to loosen the supporting device, and the side-pull sling is tightened to suspend the supporting device, so that the supporting device is offset laterally;

[0017] The side-pull sling drives the support device downward to the horizontal direction of the next support point;

[0018] The vertical sling is tightened while the side-pull sling is gradually extended, so that the support device is gradually reset to the vertical plane;

[0019] Both ends of the supporting device abut against corresponding supporting points.

[0020] In one embodiment, one of the middle support devices is moved down to the supporting point corresponding to the original adjacent support device, and the other middle support devices are moved down alternately, including the following steps:

[0021] S201, moving the middle support device of the upper level to the supporting point corresponding to the middle support device of the lower level by means of a hoisting device;

[0022] S202, the middle support device of the previous level gradually increases the loading force to the supporting point, and the middle support device of the next level gradually reduces the loading force until the pressure of the middle support device of the previous level reaches a preset load value;

[0023] S203, moving the middle support device of the next level to the next support point by means of the hoisting device;

[0024] S204, repeating steps S201 and S203 until all the middle support devices are moved and supported in place.

[0025] In one embodiment, in step S202, the loading force levels of the central support device are set to 2 to 10, and each level of loading force increases in proportion to the design load of the support point.

[0026] In one embodiment, in step S202, the central support device needs to remain stationary for no less than 5 minutes after each level of loading force adjustment is completed.

[0027] In one embodiment, providing support points distributed at intervals on two opposite pit walls of a foundation pit includes the following steps:

[0028] S301, determining a plurality of support areas at the pit wall along the vertical direction of the pit wall;

[0029] S302, detecting the flatness of each supporting area;

[0030] S303, when the flatness meets the design requirements, a support point is formed;

[0031] S304, when the flatness does not meet the design requirements, the support area is chiseled or a pad is installed to form a support point.

[0032] In one embodiment, determining the support state of the support device at each support point;

[0033] When the supporting state of the supporting device is in the movable abutment position, the supporting device movably abuts against the supporting point;

[0034] When the supporting state of the supporting device is in a fixed abutting position, the cable is connected to the embedded part at the pit wall, and the other end of the cable is connected to the supporting device.

[0035] In one embodiment, the support device includes a support rod assembly and an axial force servo loading assembly arranged at at least one end of the support rod assembly, the axial force servo loading assembly includes a lifting shell, a lifting system located in the lifting shell, a displacement detection system and a pressure compensation system, the support rod assembly is connected to the lifting shell, and the lifting system pushes the support rod assembly to apply loading force to the support point step by step;

[0036] The displacement detection system is used to detect the initial position of the support device when it is lifted into place, and output an electrical signal when the support point is deformed and the axial force servo loading assembly moves downward. The pressure compensation system controls the lifting system to compensate for the loading force after receiving the electrical signal output by the displacement detection system.

[0037] In one embodiment, the loading force of the supporting device on the supporting point increases with the depth of the foundation pit, and the load force on the supporting device is the sum of the gravity of the soil and the uniformly distributed load:

[0038] F = γhA + qA

[0039] Where F is the load on the support device, γ is the weight of the soil, the unit is kN / m 3 ; h is the height of the soil layer, in m; A is the cross-sectional area of ​​the support device, in m 2 ; q is the uniform load on the soil, in kN / m 2 .

[0040] In one embodiment, the lifting device includes a crown beam arranged on the top of the foundation pit and a lifting bracket installed on the crown beam, the lifting bracket is provided with a hoisting mechanism and a loading platform detachably connected to the hoisting mechanism, the hoisting mechanism is used to lift the supporting device and / or the loading platform, the hoisting mechanism is provided with a detection device, and the detection device is used to detect the lifting rotation speed and load angle to determine the lifting posture of the supporting device and / or the loading platform.

[0041] The technical solution provided by the embodiment of the present invention may include the following beneficial effects: a plurality of support devices are distributed in the foundation pit in sequence and at intervals along the vertical direction, thereby increasing the support density, and also increasing the support points, and the support effect is good. Pre-positioning the support points on the pit wall of the foundation pit can provide a reference and guide for the support part of the support device, thereby effectively improving the support adjustment efficiency and improving the foundation pit construction efficiency. The adjacent support device and the bottom support device alternately support the lower part of the foundation pit, so that support can be provided in time after the next layer of earthwork is excavated, avoiding the foundation pit from being exposed without support, thereby realizing the non-exposure construction of the foundation pit and improving the construction safety.

[0042] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0044] Figure 1The figure is a schematic diagram showing the support layout of the support device above the earthwork at the first depth according to an exemplary embodiment.

[0045] Figure 2 It is a schematic diagram of a support layout in which the support devices above the second-layer depth earthwork alternately move downward according to an exemplary embodiment.

[0046] Figure 3 is a schematic diagram showing a support device connected at a support point according to an exemplary embodiment.

[0047] In the figure, there are support device 10; middle support device 11; adjacent support device 12; bottom support device 13; axial force servo loading assembly 14; support rod assembly 15; lifting device 20; lifting bracket 21; winch mechanism 22; support point 30; embedded part 31; concrete 32; sling 33. DETAILED DESCRIPTION

[0048] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on this patent; in order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0049] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "inner", "outer", etc. appear, the orientation or position relationship indicated is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as a limitation on this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0050] In the description of the present invention, unless otherwise clearly specified and limited, if the term "connection" or the like appears to indicate the connection relationship between components, the term should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two components or the interaction relationship between two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0051] like Figures 1 to 3 As shown, the present invention provides a construction method for deep foundation pit support, and the construction method comprises the following steps:

[0052] S101, excavating the first layer of earthwork of the foundation pit by excavating equipment, and setting support points 30 distributed at intervals on two opposite pit walls of the foundation pit. The support points 30 are distributed at intervals along the depth direction of the foundation pit, and are used to locate and install the support positions of the foundation pit support. The corresponding positions are pre-designed before the foundation pit construction.

[0053] S102, multiple support devices 10 are distributed in the foundation pit in sequence along the vertical direction, and the two ends of the support devices 10 are respectively against the corresponding support points 30. The support devices 10 include a bottom support device 13, an adjacent support device 12 and a plurality of middle support devices 11, and the adjacent support device 12 is located above the bottom support device 13. Each support device 10 is provided with multiple strips, and the support devices 10 are arranged in multiple rows at intervals along the length direction of the foundation pit. In the depth direction of the foundation pit, each row is provided with multiple support devices 10. The two ends of each support device 10 are respectively against the corresponding support points 30 of the pit walls on both sides of the foundation pit, thereby realizing positioning support. Multiple support devices 10 are distributed in the foundation pit corresponding to the first layer of depth, with high support density and high overall support strength. Multiple support devices 10 can be assembled to the foundation pit, thereby reducing the number of support devices 10 to be added later, and realizing continuous support of the foundation pit by moving downward. For ease of description, the bottom support device 13 is the support device 10 at the bottom layer of the current foundation pit depth, the adjacent support device 12 is the upper support device 10 closest to the bottom support device 13, and the position relationship of the corresponding support points 30 of the bottom support device 13 and the adjacent support device 12.

[0054] S103, excavating the next layer of earthwork of the foundation pit by the excavating equipment. After the multiple supporting devices 10 complete the foundation pit support of the first layer, the excavating equipment starts to dig downward again and transports the earthwork out of the foundation pit through the output device until the excavation reaches the preset depth of the next layer of the foundation pit.

[0055] S104, retract the adjacent support device 12 and release the support for the pit wall, and then move it to the support point 30 below the bottom support device 13 through the hoisting device 20. The adjacent support device 12 releases the support for the support point 30. Preferably, the distance between the adjacent support device 12 and the bottom support device 13 is small, so that the two support devices 10 have a high density of support for the bottom of the foundation pit. The adjacent support device 12 and the bottom support device 13 move downward alternately in steps, which can reduce the local deformation of the foundation pit. Further preferably, the adjacent support device 12 and the bottom support device 13 jointly support the same support point 30. The adjacent support device 12 releases the support for the support point 30 and moves to the bottom of the bottom support device 13, so that the adjacent support device 12 supports the support point 30 of the next layer of the foundation pit, thereby forming a non-exposed support for the foundation pit.

[0056] S105, one of the middle support devices 11 is moved down to the support point 30 corresponding to the original adjacent support device 12, and the other middle support devices 11 are moved down alternately. The middle support devices 11 are moved downward to support the vacant support points 30, so that the support points 30 of the foundation pit can be supported. The middle support devices 11 are moved downward one by one, so that the foundation pit walls can be evenly distributed in the foundation pit, thereby maintaining a good support effect of the foundation pit.

[0057] Repeat steps S103-S105 until the foundation pit is excavated to a preset depth, and the middle support devices 11 are distributed at intervals to support the foundation pit. Multiple support devices 10 are distributed in the foundation pit in sequence along the vertical direction, thereby increasing the support density and increasing the support points by 30, with a good support effect.

[0058] Pre-positioning the support point 30 on the pit wall of the foundation pit can provide a reference and guide for the support part of the support device 10, thereby effectively improving the support adjustment efficiency and the foundation pit construction efficiency. The adjacent support device 12 and the bottom support device 13 alternately support the lower part of the foundation pit, so that support can be provided in time after the next layer of earthwork is excavated, avoiding the exposure state of the foundation pit without support, realizing the non-exposure construction of the foundation pit, and improving the construction safety.

[0059] In one embodiment, the number of the supporting devices 10 is set to be multiple, for example, the supporting devices 10 are provided with 3, 4, 5, 6, 7, 8, 10, 12, 15, 18, 20, 24, 25. The spacing distance of the supporting devices 10 can be adjusted according to the depth of the foundation pit, and the number of the supporting devices 10 can be adjusted according to the depth of the foundation pit. Preferably, the maximum spacing distance between two adjacent supporting devices 10 is less than or equal to 6 meters. For example, the maximum spacing distance between two adjacent supporting devices 10 is set to 2.5 meters, 3 meters, 3.5 meters, 4 meters, 4.5 meters, 5 meters.

[0060] The adjacent support device 12 and the bottom support device 13 move alternately in a step-by-step manner, while the middle support device 11 moves down alternately one by one, thereby adjusting the spacing distance. Among them, the hoisting device 20 spans across the top of the foundation pit, and the hoisting device 20 slides along the length direction of the foundation pit to adjust the hoisting position. The adjacent support device 12 is laterally lifted away from the vertical plane where the support device 10 is located by the hoisting device 20 and then moves downward. The hoisting device 20 slides at intervals along the length direction of the foundation pit, so that the hoisting position of the support device 10 can be flexibly adjusted. The hoisting device 20 lifts the support device 10 and moves it laterally, thereby being able to drive the support device 10 to deviate from the original vertical plane, so that the support device 10 can move downward to the side and below the bottom support device 13 to form a step-by-step alternating support. The support device 10 adopts a step-by-step movement, which can keep the foundation pit in a supporting state at all times and can shorten the time to avoid the exposure of the foundation pit.

[0061] After the excavation of the next layer of foundation pit depth is completed, the bottom support device 13 continues to support the lowest part of the previous layer of foundation pit depth to maintain the stability of the support. Preferably, the adjacent support device 12 gradually releases pressure, and the bottom support device 13 increases pressure accordingly to prevent the foundation pit from being deformed due to the pressure relief of the adjacent support device 12. Further, the adjacent support device 12 detaches from the support point 30 and moves laterally to the lowest support point 30 of the next layer of the casing, thereby supporting the foundation pit of the next layer of depth, with high support installation efficiency and short foundation pit exposure time. Further, the bottom middle support device 11 is moved downward and supports the support point 30 of the original adjacent support device 12 to achieve support reinforcement. The bottom support device 13 moves to the next layer of foundation pit depth and abuts against the corresponding support point 30, and multiple support devices 10 support the next layer of foundation pit.

[0062] The hoisting device 20 hoists the supporting device 10 from the side so that the adjacent supporting device 12 and the bottom supporting device 13 are alternately moved down in a step-by-step manner. The hoisting device 20 includes a vertical sling 33 and a side-pull sling 33 connected to the supporting device 10 .

[0063] The lifting process includes the following steps:

[0064] Step 1: The vertical sling 33 is extended to loosen the support device 10, and the side-pull sling 33 is tightened to lift the support device 10, so that the support device 10 is offset laterally. The vertical sling 33 is connected to the support device 10 to drive the support device 10 to move up and down in a straight line in the vertical direction. The length of the side-pull sling 33 is extended so that the vertical sling 33 can drive the support device 10 to move downward. After the support device 10 moves to the next support point 30, the vertical sling 33 is gradually extended, and the side-pull sling 33 is gradually shortened until the support device 10 is tightened, so that the support device 10 moves laterally and deviates from the vertical plane where the support device 10 is originally located.

[0065] Step 2: The side-pull sling 33 drives the support device 10 downward to the horizontal direction of the next support point 30. The side-pull sling 33 is connected to the support device 10 to drive the support device 10 to move up and down in a straight line in the lateral vertical direction. The length of the side-pull sling 33 is extended so that the vertical sling 33 can drive the support device 10 to move downward to a parallel position of the next support point 30.

[0066] Step 3: The vertical sling 33 is tightened and the side sling 33 is gradually extended to gradually restore the support device 10 to the vertical plane. The vertical sling 33 and the side sling 33 are gradually extended to gradually apply lateral tension to the support device 10, so that the support device 10 is hoisted and restored to the vertical plane, thereby achieving lifting and moving.

[0067] Step 4: Both ends of the support device 10 are abutted against the corresponding support points 30. The support device 10 is extended and loaded to the support points 30 to form a support structure.

[0068] The supporting device 10 can be hoisted in a walking manner by changing the telescopic size of the vertical sling 33 and the side sling 33, which is convenient. The middle support device 11 can be lifted and lowered in a straight line, which can be completed by only adjusting the vertical sling 33, which is convenient to adjust.

[0069] The lifting, movement and loading of the support device 10 is not a simple loosening and loading, but needs to be flexibly adjusted in combination with the soil layer state and the foundation pit depth. In step S105, one of the middle support devices 11 is moved down to the support point 30 corresponding to the original adjacent support device 12, and the other middle support devices 11 are moved down alternately, including the following steps:

[0070] S201, the upper-level middle support device 11 is moved to the supporting point 30 corresponding to the lower-level middle support device 11 by the lifting device 20. The vertical sling 33 is extended to lift the unloaded middle support device 11 away from the original supporting point 30, and the middle support device 11 moves downward along the vertical plane to approach the supporting point 30 where the lower-level middle support device 11 or the bottom support device 13 is located, so that step-by-step descending and replacement can be achieved, thereby constituting alternating downward movement.

[0071] S202, the upper-level middle support device 11 gradually increases the loading force to the support point 30, and the lower-level middle support device 11 gradually reduces the loading force until the pressure of the upper-level middle support device 11 reaches the preset load value. After the upper-level middle support device 11 is hoisted and moved to the corresponding support point 30, the upper-level middle support device 11 approaches the lower-level middle support device 11, and the upper-level middle support device 11 is loaded with load force, and correspondingly, the lower-level middle support device 11 is depressurized to reduce the load force.

[0072] In this step S202, the loading force loading level of the middle support device 11 is set to 2 to 10 levels, and the design load of the middle support device 11 is loaded in multiple levels so that the load force on the support point 30 is gradually increased, thereby improving the smooth transition of the bearing effect, and the design load is the load value of the corresponding support point when it is fully loaded. The loading force of each level is increased according to the design load ratio of the support point 30. For example, the loading force loading level of the middle support device 11 is set to 5 levels. Accordingly, the middle support device 11 of the previous level is loaded with 20% of the load of the support point 30 at each level, and the middle support device 11 of the next level is depressurized to reduce the load of the support point 30 by 20%. Through 5 levels of loading, the middle support device 11 of the previous level is loaded step by step until it is loaded to the full load state of the support point 30, and the middle support device 11 of the previous level is depressurized step by step until the middle support device 11 is completely unloaded and suspended by the vertical sling 33. For example, the middle support device 11 No. 1 is loaded with 20%, the middle support device 11 No. 2 is unloaded with 20%, the middle support device 11 No. 3 is loaded with 20%, the middle support device 11 No. 4 is unloaded with 20%, the middle support device 11 No. 5 is loaded with 20%, the middle support device 11 No. 6 is unloaded with 20%, the middle support device 11 No. 7 is loaded with 20%, the middle support device 11 No. 8 is unloaded with 20%, the middle support device 11 No. 9 is loaded with 20%, and the middle support device No. 10 is unloaded with 20%, and the ten middle support devices 11 are alternated in sequence.

[0073] S203 , moving the middle support device 11 of the next stage to the next support point 30 by means of the hoisting device 20 , so as to support the middle support device 11 at the next support point 30 .

[0074] S204, repeating steps S201 and S203 until all the middle support devices 11 are moved to support in place.

[0075] The middle support devices 11 are adjusted one by one to gradually increase the spacing distance between adjacent middle support devices 11, and the adjustment between the middle support devices 11 is a gradual replacement rather than a one-time pressure relief and suspension, so that the load of the support point 30 can be smoothly transitioned, the support change to the pit wall is small, and the stability of the support can be maintained.

[0076] Further, in step S202, after each level of loading force adjustment of the middle support device 11 is completed, it needs to be stationary for a corresponding period of time to avoid excessive load changes and affect load stability. Among them, the stationary time is not less than 5 minutes to maintain the alternating and smooth transition of each level of the middle support device 11, reduce the large fluctuation of the foundation pit stress, and thus avoid local collapse due to excessive support force changes. For example, after each level of loading force adjustment of the middle support device 11 is completed, it needs to be stationary for 5 minutes, 8 minutes, 10 minutes, 20 minutes, etc.

[0077] Before excavating the foundation pit, it is necessary to construct a concrete wall, which is located on both sides of the foundation pit. The concrete wall is located at the pit wall of the foundation pit. The concrete wall includes an internal embedded part 31 and an externally wrapped concrete 32. The support point 30 is set on the concrete wall to form the support position of the support device 10 on the pit wall of the foundation pit.

[0078] The method of setting spaced support points 30 on two opposite pit walls of the foundation pit includes the following steps:

[0079] S301, determine multiple support areas on the pit wall along the vertical direction of the pit wall. The support area corresponds to the support position of the support device 10 on the pit wall, and the area of ​​the support area is greater than or equal to the area of ​​the support point to improve the abutment requirement of the support device 10.

[0080] S302, detecting the flatness of each supporting area. To ensure the effectiveness of the load application of the supporting device 10, the plane where the supporting device 10 applies the load in the supporting area needs to be flat to keep the load force vertically supported and avoid eccentric loading.

[0081] S303, when the flatness meets the design requirements, a support point is formed.

[0082] S304, when the flatness does not meet the design requirements, the support area is chiseled or a pad is installed to form a support point.

[0083] The support point is a part of the support area, and its position is determined when the foundation pit is designed. Due to the construction design point of the concrete wall, the effective support of the foundation pit can be maintained. For example, the concrete wall at the pit wall is chiseled flat to form a support point 30. The support point 30 is a support point pre-arranged during the foundation pit design process, which can ensure the reliability of the foundation pit support. The earth in the foundation pit is excavated in layers. After each layer of earth is excavated, the support point 30 at the designed position needs to be trimmed and chiseled flat so that the support device 10 can be evenly abutted against the support point 30.

[0084] The support devices 10 move in a step-by-step and alternating manner to form an interval-distributed support pit. In the process of the support devices 10 moving, the support devices 10 near one end of the pit opening preferentially reach the designated support point position, while the remaining support devices 10 gradually move to the corresponding support points through step-by-step and alternating movements.

[0085] Furthermore, the supporting device 10 needs to adopt corresponding pre-processing methods at different supporting points.

[0086] Among them, the supporting state of the supporting device at each supporting point is determined; the supporting state of the supporting device is different at different foundation pit depths.

[0087] When the supporting state of the supporting device is in the active abutment position, the supporting device abuts against the supporting point. The active abutment position is a temporary supporting point for the supporting device to move down alternately or step by step. Accordingly, both ends of the supporting device abut against the plane of the supporting point to facilitate loading, unloading and movement.

[0088] When the supporting state of the supporting device is in the fixed abutment position, the cable is connected to the embedded part at the pit wall, and the other end of the cable is connected to the supporting device. The movable abutment position is that the supporting device does not move after reaching the designated supporting point, and accordingly, both ends of the supporting device abut on the plane of the supporting point to facilitate loading, unloading and movement.

[0089] A partially exposed embedded part 31 is provided at the support point 30. The embedded part 31 is partially exposed, which can be easily welded to assist in fixing the support device 10, improve the support stability of the support device 10, and especially prevent the support device 10 from sliding down when the foundation pit wall is deformed.

[0090] For example, at least one cable is connected to the embedded part 31, and the cable is used to connect the support device 10 and the support point 30 in an oblique manner. One end of the cable is fixed to the embedded part 31, and the other end is connected to the support device 10, so that one end of the support device 10 can be connected to the embedded part 31. Preferably, two to four cables are provided to improve the connection strength. The pit wall of the foundation pit undergoes dimensional deformation as the earth is excavated. Taking the vertical plane as the reference plane, the pit wall may protrude positively from the protruding reference plane, or may be negatively depressed from the concave reference plane. Preferably, the cable obliquely connects the support device 10 and the embedded part 31 to form an oblique connection. Preferably, the cable is welded and fixed to the embedded part 31, and the connection strength is high.

[0091] In one embodiment, the support device 10 includes a strut assembly 15 and an axial force servo loading assembly 14 disposed at at least one end of the strut assembly 15. The loading force of the axial force servo loading assembly 14 is controllable, so as to facilitate the control of the loading force at each level. Among them, the loading range of the axial force servo loading assembly 14 is 20t to 1000t. For example, the loading force of the axial force servo loading assembly 14 at each level is 50t, and the total loading force is 250t. Optionally, the axial force servo loading assembly 14 is installed at one end of the strut assembly 15 to load the load force on one side. Preferably, the axial force servo loading assembly 14 is installed at both ends of the strut assembly 15 to load the load force on both sides and to make the load application more balanced.

[0092] Among them, the axial force servo loading assembly 14 includes a jacking shell, a jacking system located in the jacking shell, a displacement detection system and a pressure compensation system. The strut assembly 15 is connected to the jacking shell, and the jacking system pushes the strut assembly 15 to apply loading force to the support point step by step. The jacking shell is a shell structure, and the output end of the jacking system extends out of the jacking shell and abuts against the support point 30. The jacking shell is abutted and connected with the end of the strut assembly 15. The jacking system can be set as a hydraulic mechanism to achieve pressure output. The pressure compensation system can relieve or pressurize the jacking system, so that the jacking system can always maintain an appropriate load force. In particular, when the pit wall is deformed, it is necessary to flexibly adjust the load force according to the deformation amount of the foundation pit.

[0093] The displacement detection system is used to detect the initial position of the support device 10 when it is lifted into place, and outputs an electrical signal when the support point 30 is deformed and the axial force servo loading assembly 14 moves downward. The pressure compensation system controls the lifting system to compensate for the loading force after receiving the electrical signal output by the displacement detection system. The support device 10 abuts the support point 30, and the displacement detection system is used to detect the displacement of the support device 10 and the pressure value of the support device 10. The displacement detection system will detect the parameter change and output an electrical signal. The pressure compensation system receives the electrical signal and controls the lifting system to pressurize or release the pressure based on the electrical signal to achieve self-adjusting balance of the lifting system.

[0094] Optionally, the working principle of the axial force servo loading assembly 14 can refer to the content of the public document CN109896483A. However, the load adjustment process and loading process of the axial force servo loading assembly 14 can be adaptively adjusted in accordance with the different depths of the foundation pit in the deep foundation pit non-exposure construction, and different loading forces can be adaptively adjusted according to the different depths of the foundation pit excavation. The loading range is large and the loading flexibility is high, and the number of connected and adjusted pipelines is small. In particular, the axial force servo loading assembly 14 does not require external pipelines, and can cooperate with the support device 10 to realize the step-by-step adjustment of the support point 30, and the adjustment effect is good.

[0095] In one embodiment, the lifting load range of the lifting system is 20t to 1000t, and the load loading range of the lifting system is large. Optionally, each level of the lifting system can be set to 1t, 2t, 5t, 10t, 20t, 30t, 50t, 100t.

[0096] As the excavation depth of the foundation pit changes, the loading force corresponding to each support point 30 increases to maintain the stability of the pit wall support. However, the change in the foundation pit needs to be within a controllable range to avoid collapse. Among them, the maximum cumulative deformation of the support point is less than 30mm. The maximum cumulative deformation is the deformation of multiple support points, and the displacement detection system monitors the deformation of the pit wall in real time to monitor the deformation of the pit wall.

[0097] The support device 10 supports the pit wall, and the support point changes with the deformation of the foundation pit depth. The support device 10 can provide support and adjust the load force when the support point is deformed. Preferably, the pressure compensation system automatically adjusts the loading force based on the deformation of the support point and the change in the lifting load of the lifting system.

[0098] In one embodiment, the loading force of the support device 10 on the support point 30 increases as the depth of the foundation pit increases, wherein the load force on the support device 10 is the sum of the gravity of the soil and the uniformly distributed load:

[0099] F = γhA + qA

[0100] Where F is the load on the support device, γ is the weight of the soil, the unit is kN / m 3 ; h is the height of the soil layer, in m; A is the cross-sectional area of ​​the support device, in m 2 ; q is the uniform load on the soil, in kN / m 2 The supporting device 10 can calculate a stable load force based on the supporting points at each depth and soil parameters. The load force changes based on the depth of the foundation pit, and the axial force servo loading component 14 is designed to increase step by step based on the load force, with high control accuracy.

[0101] In the above embodiment, the lifting device includes a crown beam arranged at the top of the foundation pit and a lifting bracket 21 installed on the crown beam. The lifting bracket 21 is provided with a hoisting mechanism 22 and a loading platform detachably connected to the hoisting mechanism 22. The hoisting mechanism 22 is used to lift the support device 10 and / or the loading platform. The hoisting mechanism 22 is provided with a detection device, and the detection device is used to detect the lifting rotation speed and load angle to determine the lifting posture of the support device 10 and / or the loading platform. The crown beam is arranged along the length direction of the foundation pit, and the lifting bracket 21 moves along the crown beam to perform lifting operations on the support device 10 and the loading platform at different positions. Preferably, the lifting bracket 21 has a lifting function, and its structure and function can be referred to the public document CN 109898513A, which will not be repeated here.

[0102] In this embodiment, based on the walking hoisting of the support device 10 and the alternating downward hoisting of the middle support device, the hoisting mechanism 22 needs to control the moving angle, moving direction and moving speed of the support device 10 accordingly. For example, the hoisting mechanism 22 controls the telescopic movement of the vertical sling 33 and the side pull sling 33 to achieve the translation, downward movement and inclination movement of the support device 10, which can improve the rapid sliding down of the support device 10 to support the construction of the foundation pit without exposure time.

[0103] Preferably, the loading platform can carry goods or people to the corresponding construction location, such as processing the support point area, the support device 10 connects the vertical sling 33 and the side pull sling 33 for construction and other lifting and lifting operations.

[0104] The detection device is used to detect the lifting speed and load angle, so as to adjust the elongation speed and elongation length of the rope by the winch mechanism 22 accordingly, so as to realize accurate control of the lifting. The detection device can realize the walking type lifting and the alternating downward lifting of the middle support device by detecting parameters, especially in the process of walking type lifting, the lifting position and lifting angle can be controlled by the eccentric load force, which is not available in conventional lifting equipment.

[0105] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and practicing the disclosure disclosed herein. This application is intended to cover any variations, uses or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art that are not disclosed by the present invention. The description and examples are to be considered exemplary only, and the true scope and spirit of the present invention are indicated by the following claims.

[0106] It should be understood that the present invention is not limited to the exact construction that has been described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A construction method for deep foundation pit support, characterized in that: Construction methods include: S101, excavating the first depth of earthwork of the foundation pit by using an excavation device, and setting support points distributed at intervals on two opposite pit walls of the foundation pit; S102, multiple support devices are distributed in the foundation pit in sequence and at intervals along the vertical direction, and the two ends of the support devices are respectively against the corresponding support points, and the support devices include a bottom support device, an adjacent support device and a plurality of middle support devices, and the adjacent support device is located above the bottom support device; the bottom support device is the support device at the bottom layer of the current foundation pit depth, and the adjacent support device is the upper support device closest to the bottom support device; S103, excavating the next layer of earthwork of the foundation pit by using the excavation equipment; S104, retracting the adjacent support device and releasing the support for the pit wall, and then moving to the support point below the bottom support device through the hoisting device to form a walking downward movement; S105, moving one of the middle support devices downward to the supporting point corresponding to the original adjacent support device, and the other middle support devices are moved downward alternately; Repeat steps S103 to S105 until the foundation pit is excavated to a preset depth, and the middle support devices are distributed at intervals to support the foundation pit, wherein the adjacent support devices and the bottom support devices are alternately moved downward in steps.

2. The construction method for deep foundation pit support according to claim 1, characterized in that: The number of the supporting devices is set to be multiple, and the maximum spacing distance between two adjacent supporting devices is less than or equal to 6 meters.

3. The construction method for deep foundation pit support according to claim 1, characterized in that: The hoisting device spans across the top of the foundation pit and slides along the length direction of the foundation pit to adjust the hoisting position. The adjacent support device is laterally lifted away from the vertical plane where the support device is located by the hoisting device and then moves downward.

4. The construction method for deep foundation pit support according to claim 3, characterized in that: The lifting device includes a vertical sling and a side-pull sling connected to the supporting device; The vertical sling is extended to loosen the supporting device, and the side-pull sling is tightened to suspend the supporting device, so that the supporting device is offset laterally; The side-pull sling drives the support device downward to the horizontal direction of the next support point; The vertical sling is tightened while the side-pull sling is gradually extended, so that the support device is gradually reset to the vertical plane; Both ends of the supporting device abut against corresponding supporting points.

5. The construction method for deep foundation pit support according to claim 1, characterized in that: One of the middle support devices is moved down to the supporting point corresponding to the original adjacent support device, and the other middle support devices are moved down alternately, including the following steps: S201, moving the middle support device of the upper level to the supporting point corresponding to the middle support device of the lower level by means of a hoisting device; S202, the middle support device of the previous level gradually increases the loading force to the supporting point, and the middle support device of the next level gradually reduces the loading force until the pressure of the middle support device of the previous level reaches a preset load value; S203, moving the middle support device of the next level to the next support point by means of the hoisting device; S204, repeating steps S201 and S203 until all the middle support devices are moved and supported in place.

6. The construction method for deep foundation pit support according to claim 5, characterized in that: In step S202, the loading force level of the central support device is set to 2 to 10, and each level of loading force is increased in proportion to the design load of the support point.

7. The construction method for deep foundation pit support according to claim 5, characterized in that: In step S202, the central support device needs to remain stationary for no less than 5 minutes after each level of loading force adjustment is completed.

8. The construction method for deep foundation pit support according to claim 1, characterized in that: The method comprises the following steps: setting support points distributed at intervals on two opposite pit walls of a foundation pit; S301, determining a plurality of support areas at the pit wall along the vertical direction of the pit wall; S302, detecting the flatness of each supporting area; S303, when the flatness meets the design requirements, a support point is formed; S304, when the flatness does not meet the design requirements, the support area is chiseled or a pad is installed to form a support point.

9. The construction method for deep foundation pit support according to claim 1, characterized in that: Determine the supporting state of the supporting device at each supporting point; When the supporting state of the supporting device is in the movable abutment position, the supporting device movably abuts against the supporting point; When the supporting state of the supporting device is in a fixed abutting position, the cable is connected to the embedded part at the pit wall, and the other end of the cable is connected to the supporting device.

10. The construction method for deep foundation pit support according to claim 1, characterized in that: The support device includes a support rod assembly and an axial force servo loading assembly arranged at at least one end of the support rod assembly, the axial force servo loading assembly includes a jacking shell, a jacking system located in the jacking shell, a displacement detection system and a pressure compensation system, the support rod assembly is connected to the jacking shell, and the jacking system pushes the support rod assembly to apply loading force to the support point step by step; The displacement detection system is used to detect the initial position of the support device when it is lifted into place, and output an electrical signal when the support point is deformed and the axial force servo loading assembly moves downward. The pressure compensation system controls the lifting system to compensate for the loading force after receiving the electrical signal output by the displacement detection system.

11. The construction method for deep foundation pit support according to claim 1, characterized in that: The loading force of the supporting device on the supporting point increases with the depth of the foundation pit. The loading force on the supporting device is the sum of the gravity of the soil and the uniformly distributed load: F = γhA + qA Where F is the load on the support device, γ is the weight of the soil, the unit is kN / m 3 ; h is the height of the soil layer, in m; A is the cross-sectional area of ​​the support device, in m 2 ; q is the uniform load on the soil, in kN / m 2 .

12. The construction method for deep foundation pit support according to claim 1, characterized in that: The lifting device includes a crown beam arranged on the top of the foundation pit and a lifting bracket installed on the crown beam, the lifting bracket is provided with a hoisting mechanism and a loading platform detachably connected to the hoisting mechanism, the hoisting mechanism is used to lift the supporting device and / or the loading platform, the hoisting mechanism is provided with a detection device, and the detection device is used to detect the lifting rotation speed and load angle to determine the lifting posture of the supporting device and / or the loading platform.

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