A method for controlling micro-deformation of foundation pit in soft soil area

Abstract

The invention discloses a method for controlling micro-deformation of foundation pits in soft soil areas, which belongs to the technical field of foundation pit support and comprises the following steps: after constructing underground continuous walls and column piles on the protection side of the foundation pit, constructing a first concrete support at the upper pit mouth of the foundation pit, and the side of the first concrete is simultaneously extended to the underground continuous wall to support it, and the column piles close to one side of the underground continuous wall and the underground continuous wall are separated to form a pit edge soil retention area on the protection side of the foundation pit; constructing cast-in-place concrete on the lower side of the first concrete; excavating the pit edge soil retention area, and excavating the pit edge soil retention area by one layer until it is flush with the foundation pit; constructing a prefabricated internal support servo system with cast-in-place concrete as support; repeating the above steps until all prefabricated internal supports of the foundation pit are completed; the method of the invention can be constructed quickly under the condition of ensuring that the internal supports have greater rigidity, and solves the defects that the concrete internal support force transmission system is slowly formed and is not conducive to controlling the deformation of the foundation pit, thereby better controlling the micro-deformation of the foundation pit.

Description

Technical Field

[0001] The invention belongs to the technical field of foundation pit support, and in particular relates to a method for controlling micro-deformation of a foundation pit in a soft soil area. Background Art

[0002] At present, with the continuous advancement of urban construction, the status of foundation pit engineering in cities is becoming increasingly important. There are a series of safety hazards in the construction of foundation pit engineering. During the construction of the foundation pit, after the side wall of the foundation pit is excavated, the stress field of the original earthwork balance is destroyed, and rebound is prone to occur. There are problems such as the slow formation of the support axial force transmission system in the cast-in-place internal support, and the time and space effect of the deformation of the foundation pit in the soft soil area cannot be well utilized to reduce the deformation of the foundation pit. For example, it takes 2 to 3 days to apply the axial force of the concrete internal support. The axial force can only be applied after the strength of the cast-in-place concrete is increased. During this period, the foundation pit has undergone a large deformation. Summary of the invention

[0003] In view of this, the purpose of the present invention is to provide a method for controlling micro-deformation of foundation pits in soft soil areas, which can be constructed quickly while ensuring that the internal support has a large rigidity, and solve the defects of slow formation of the force transmission system of the concrete internal support and being unfavorable for controlling the deformation of the foundation pit, thereby better controlling the micro-deformation of the foundation pit, and at the same time shortening the construction period and reducing the project cost.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] The present invention discloses a method for controlling micro-deformation of foundation pit in soft soil area, comprising the following steps:

[0006] a. The first concrete support: after the underground continuous wall and column piles are constructed on the protection side of the foundation pit, the first concrete support is constructed at the upper pit mouth of the foundation pit. The side of the first concrete is extended to the underground continuous wall to support it. The column piles close to the underground continuous wall are separated from the underground continuous wall to form a pit edge soil retention area on the protection side of the foundation pit;

[0007] b. Excavation of foundation pit: excavate one layer from the central basin to the soil retention area at the pit edge on the protection side of the foundation pit;

[0008] c. Cast-in-place concrete construction: Cast-in-place concrete is constructed on the lower side of the first concrete layer, and cast-in-place concrete is used for construction on the column piles;

[0009] d. Excavation of the soil retaining area at the edge of the pit, excavate the soil retaining area at the edge of the pit one layer until it is flush with the foundation pit;

[0010] e. Use cast-in-place concrete as support to construct a prefabricated internal support servo system;

[0011] f. Repeat steps b~e until all prefabricated internal supports of the foundation pit are completed.

[0012] Furthermore, the prefabricated internal support servo system includes a servo jack, a first articulated seat, a prefabricated support beam, a second articulated seat and an angle adjustment support seat, and the first articulated seat and the second articulated seat are respectively arranged at both ends of the prefabricated support beam; when installing the prefabricated internal support servo system, the angle adjustment support seat is first installed on the column pile, and the position of the angle adjustment support seat corresponds to the position of the cast-in-place concrete. A makeshift hole for the angle adjustment support seat is opened on the cast-in-place concrete, and the angle adjustment support seat is connected to one end of the prefabricated support beam through the second articulated seat, and the other end of the prefabricated support beam is connected to the servo jack through the first articulated seat. After the prefabricated support beam is horizontally supported, the servo jack is started to lift it toward the side to support the underground continuous wall.

[0013] Furthermore, before the servo jack is lifted, the center lines of the servo jack, the prefabricated support beam and the angle adjustment support seat are adjusted to the same height, and then the relative positions between the servo jack and the prefabricated support beam, and between the prefabricated support beam and the angle adjustment support seat are locked respectively.

[0014] Furthermore, the angle adjustment support seat includes an L-shaped base, a side pressure plate and an end pressure plate, one side of the L-shaped base is provided with a hinge plate that cooperates with the second hinge seat, and the bottom of the side pressure plate is fixed with a first sliding rod. During installation, the inner corner of the L-shaped base is clamped on one side of the column pile, and the first sliding rod is slidably set in a sliding groove opened on one side of the L-shaped base and fixed by a locking piece; second sliding rods are fixed at both ends of the end pressure plate, and the second sliding rods at both ends are respectively slidably set in the sliding grooves opened on the side pressure plate and the L-shaped base and fixed by a locking piece.

[0015] Furthermore, before installing the next prefabricated internal support servo system, a narrow groove for installing the next prefabricated internal support servo system is first excavated in the soil area at the edge of the pit. Before the next concrete support, the next prefabricated internal support servo system is connected to the prefabricated support beam of the previous prefabricated internal support servo system to pre-support the underground shear wall.

[0016] Furthermore, an articulated shaft is installed on the side of the L-shaped base away from the articulated plate. When the rear prefabricated internal support servo system is connected to the prefabricated support beam of the previous prefabricated internal support servo system, the angle adjustment support seat of the rear prefabricated internal support servo system is sleeved on the outside of the prefabricated support beam of the previous prefabricated internal support servo system, and is connected to the second articulated seat through the articulated shaft on the angle adjustment support seat. After adjusting the angle, the articulated shaft and the second articulated seat are fixed, and the servo jack of a prefabricated internal support servo system is started to lift it toward the side to pre-support the underground continuous wall.

[0017] The beneficial effects of the present invention are:

[0018] In a method for controlling micro-deformation of foundation pit in soft soil area disclosed by the present invention,

[0019] 1. After the excavation of the protection side is completed, the prefabricated internal support servo system with servo jack is assembled, which can ensure that the force transmission system of the foundation pit is quickly formed in a short time. Unlike traditional concrete internal support, it is necessary to wait for the strength of the concrete to increase before forming the force transmission system of the foundation pit, thereby reducing the micro-deformation of the foundation pit.

[0020] 2. This method can better control the deformation of the foundation pit, reduce the number of sub-pits of the foundation pit, and greatly save the construction period and project cost of the foundation pit.

[0021] 3. The prefabricated internal support servo system has the advantages of convenient assembly and construction, reusability, etc., which is conducive to green, low-carbon and environmental protection.

[0022] Other advantages, objectives and features of the present invention will be described in the following description and will be apparent to those skilled in the art to some extent, or those skilled in the art may be taught from the practice of the present invention. The objectives and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to make the purpose, technical solution and beneficial effects of the present invention clearer, the present invention provides the following drawings for illustration:

[0024] Figure 1 It is a construction flow chart of the control method of the present invention;

[0025] Figure 2 This is a schematic diagram of the construction of the first concrete layer of the present invention;

[0026] Figure 3 This is a schematic diagram of the first layer of basin excavation;

[0027] Figure 4 This is the construction diagram of the first cast-in-place concrete;

[0028] Figure 5 This is a schematic diagram of the excavation of the first layer of soil retention area around the pit;

[0029] Figure 6 It is a support schematic diagram of the prefabricated internal support servo system;

[0030] Figure 7 is a schematic diagram of a narrow slot;

[0031] Figure 8 It is a pre-support schematic diagram of the latter prefabricated internal support servo system;

[0032] Fig. 9 This is a schematic diagram of the second-level basin excavation;

[0033] Fig.10This is the construction diagram of the second cast-in-place concrete;

[0034] Fig.11 This is a schematic diagram of the excavation of the second layer of soil retention area at the pit edge;

[0035] Fig.12 This is a schematic diagram of the construction plan;

[0036] Fig.13 It is a structural schematic diagram of the prefabricated internal support servo system;

[0037] Fig.14 It is a structural schematic diagram of the angle adjustment support seat.

[0038] The markings in the attached drawings are as follows: the first concrete line 1, the underground continuous wall 2, the column piles 3, the soil retained area at the edge of the pit 4, the cast-in-place concrete 5, the prefabricated internal support servo system 6, the servo jack 7, the first articulated seat 8, the prefabricated support beam 9, the second articulated seat 10, the angle adjustment support seat 11, the L-shaped base 12, the side pressure plate 13, the end pressure plate 14, the articulated plate 15, the first sliding bar 16, the slide groove 17, the second sliding bar 18, the narrow groove 19, and the articulated shaft 20. DETAILED DESCRIPTION

[0039] like Figures 1 to 12 As shown, the present invention discloses a method for controlling micro-deformation of foundation pit in soft soil area, comprising the following steps:

[0040] a. The first concrete 1 supports the underground continuous wall 2, which is located on the protection side of the foundation pit and extends downward. After the underground continuous wall 2 and the column piles 3 are constructed on the protection side of the foundation pit, the first concrete 1 is constructed at the upper pit mouth of the foundation pit. The overall scale of the first concrete 1 is adapted to the pit mouth diameter of the foundation pit. Unlike the other following concretes, the side of the first concrete 1 directly extends to the underground continuous wall 2 to support it. The column piles 3 are used to support the first concrete 1. The column piles 3 close to the underground continuous wall 2 are separated from the underground continuous wall 2 to form a pit edge soil retention area 4 on the protection side of the foundation pit;

[0041] In an embodiment of the present invention, the first concrete layer 1 includes a longitudinal beam perpendicular to the underground continuous wall 2 and a plurality of transverse beams arranged perpendicular to the longitudinal beam. The outer side of the first concrete layer 1 is surrounded by the outer side beams to form a rectangle, and the corners are connected by diagonal bracing beams, which can increase the overall strength of the structure.

[0042] b. Excavation of foundation pit: excavate one layer from the central basin to the pit edge soil retention area 4 on the protection side of the foundation pit, and reserve installation position for cast-in-place concrete 5. At the same time, it will not exceed the pit edge soil retention area 4 to reduce micro-deformation of the foundation pit during construction;

[0043] c. Cast-in-place concrete 5 is constructed on the lower side of the first concrete 1, and cast-in-place concrete is used for construction on the column pile 3;

[0044] d. Excavation of the soil area 4 at the edge of the pit, excavation of a layer of soil area 4 at the edge of the pit to the same level as the foundation pit, to facilitate the installation of the prefabricated internal support servo system 6;

[0045] e. With cast-in-place concrete 5 as support, the prefabricated internal support servo system 6 is constructed. The sides of the prefabricated internal support servo system 6 are also supported by cast-in-place concrete 5, which can reduce the force on the column pile 3 and reduce the force deformation of the column pile 3;

[0046] f. Similar to the above construction process, repeat steps b~e until all prefabricated internal supports of the foundation pit are completed. Each concrete layer corresponds to a prefabricated internal support servo system 6, which can be understood by those skilled in the art.

[0047] In the foundation pit micro-deformation control method disclosed in the present invention, after the excavation of the protection side is completed, by assembling the prefabricated internal support servo system 6 with the servo jack 7, compared with the use of all concrete internal supports, it can ensure that the force transmission system of the foundation pit is quickly formed in a short time. Unlike traditional concrete internal supports, it is unnecessary to wait for the strength of the concrete to increase before forming the force transmission system of the foundation pit, which saves construction time and can support the inner wall of the foundation pit in time, thereby reducing the micro-deformation of the foundation pit.

[0048] In this embodiment, Figures 13 and 14 As shown, the prefabricated internal support servo system 6 includes a servo jack 7, a first articulated seat 8, a prefabricated support beam 9, a second articulated seat 10 and an angle adjustment support seat 11. The prefabricated support beam 9 is made of prefabricated steel concrete or prefabricated steel, and the length is prefabricated according to the needs. The first articulated seat 8 and the second articulated seat 10 are respectively arranged at the two ends of the prefabricated support beam 9; the servo jack 7 is installed at one end of the prefabricated support beam 9 through the first articulated seat 8, and the angle of the articulation between the two can be changed. After the angle is adjusted, the positions of the two can be locked by a nut. Similarly, the angle adjustment support seat 11 is installed at the other end of the prefabricated support beam 9 through the second articulated seat 10, and the positions of the two can be locked by a nut.

[0049] Among them, when installing the prefabricated internal support servo system 6, the angle adjustment support seat 11 is first installed on the column pile 3. The position of the angle adjustment support seat 11 corresponds to the position of the cast-in-place concrete 5. A clearance hole for the angle adjustment support seat 11 is opened on the cast-in-place concrete 5 to avoid interference. The angle adjustment support seat 11 is connected to one end of the prefabricated support beam 9 through the second hinge seat 10, and the other end of the prefabricated support beam 9 is connected to the servo jack 7 through the first hinge seat 8. After the prefabricated support beam 9 is supported horizontally, the servo jack 7 is started to lift it toward the side to apply axial force to support the underground continuous wall 2.

[0050] In some other embodiments, the servo jack 7 and the angle adjustment support seat 11 are directly fixed on both ends of the prefabricated support beam 9, and the hinge angle cannot be adjusted. The center lines of the three are located on the same straight line. In this way, when the subsequent prefabricated internal support servo system 6 is horizontally installed, it is necessary to connect the column pile 3 to provide reaction force support. However, due to the lack of support from the subsequent cast-in-place concrete 5, the column pile 3 is easily deformed, and the supporting effect is limited.

[0051] In this embodiment, before the servo jack 7 is lifted, the relative positions of the servo jack 7, the prefabricated support beam 9 and the angle adjustment support seat 11 are adjusted so that the force directions of the three are located on the same straight line, and the relative positions between the servo jack 7 and the prefabricated support beam 9, and between the prefabricated support beam 9 and the angle adjustment support seat 11 are locked respectively. That is, the prefabricated inner support servo system 6 is composed of Fig.10 The status becomes Fig.11 status.

[0052] In this embodiment, the angle adjustment support seat 11 includes an L-shaped base 12, a side pressure plate 13 and an end pressure plate 14. The cross section of the L-shaped base 12 is L-shaped and is formed by two vertically connected plates. Two sets of slide grooves 17 are opened on the outside of each plate, and the slide grooves 17 extend to the outside of the plate. A hinge plate 15 that cooperates with the second hinge seat 10 is provided on one side of the L-shaped base 12. The hinge plate 15 is perpendicular to the installation plane of the L-shaped base 12. The hinge plate 15 can be connected to the second hinge seat 10, and the angle can be changed by rotation, and then fixed by a locking member.

[0053] A first slide bar 16 is fixed to the bottom of the side pressure plate 13, and the diameter of the first slide bar 16 corresponds to the width of the slide groove 17. When installing, the inner corner of the L-shaped base 12 is tightly clamped on one side of the column pile 3, and the first slide bar 16 is slidably set in the slide groove 17 opened on one side of the L-shaped base 12 and then fixed by a locking member. The locking member adopts a nut and is threadedly connected with the first slide bar 16; the two ends of the end pressure plate 14 are fixed with a second slide bar 18, and the second slide bars 18 at both ends are respectively slidably set in the slide grooves 17 opened on the side pressure plate 13 and the L-shaped base 12 and fixed by a locking member. When in use, the side pressure plate 13 is first installed and fixed to the side of the column pile 3, and then the end pressure plate 14 is installed and fixed to the other side of the column pile 3, so that the angle adjustment support seat 11 and the column pile 3 are fastened and installed.

[0054] In this embodiment, before installing the next prefabricated internal support servo system 6, a narrow groove 19 for installing the next prefabricated internal support servo system 6 is first excavated in the soil-retaining area 4 at the edge of the pit, so as to facilitate the installation of the next prefabricated internal support servo system 6. Before supporting the next cast-in-place concrete 5, the next prefabricated internal support servo system 6 is connected to the prefabricated support beam 9 of the previous prefabricated internal support servo system 6 to pre-support the underground shear wall. During pre-support, the prefabricated support beam 9 of the next prefabricated internal support servo system 6 is arranged at an angle to form an oblique brace. By pre-supporting the underground continuous wall 2 in advance without waiting for the installation of the concrete to be completed, the problem of micro-deformation caused by the loss of support of the soil on the protection side of the foundation pit during basin-type excavation can be avoided.

[0055] In this embodiment, an articulated shaft 20 is installed on the side of the L-shaped base 12 away from the articulated plate 15. When the rear prefabricated internal support servo system 6 is connected to the prefabricated support beam 9 of the previous prefabricated internal support servo system 6, the angle adjustment support seat 11 of the rear prefabricated internal support servo system 6 is sleeved on the outer side of the prefabricated support beam 9 of the previous prefabricated internal support servo system 6, and is connected to the second articulated seat 10 through the articulated shaft 20 on the angle adjustment support seat 11. After adjusting the angle, the articulated shaft 20 is fixed to the second articulated seat 10, and the servo jack 7 of a prefabricated internal support servo system 6 is started to lift it toward the side to pre-support the underground continuous wall 2.

[0056] In the method disclosed in the present invention, by installing the hinge shaft 20 on the side of the L-shaped base 12, when the second hinge seat 10 of the next prefabricated internal support servo system 6 is connected and matched with it, the projections of the two prefabricated internal support servo systems 6 in the vertical direction can be staggered with each other, thereby reducing the difficulty of excavating the narrow groove 19, thereby improving the construction efficiency of the narrow groove 19. At the same time, the angle adjustment support seat 11 of the next prefabricated internal support servo system 6 is sleeved on the outside of the prefabricated support beam 9 of the previous prefabricated internal support servo system 6, and the reaction force support can be provided by the previous prefabricated internal support servo system 6, so that a stable temporary triangular pre-support structure can be formed, and there is no need to excavate around the column pile 3, which increases the stability of the soil area 4 on the side of the pit protection side of the foundation pit, thereby reducing the risk of micro-deformation of the foundation pit. When the next prefabricated internal support servo system 6 is specifically installed later, the angle adjustment support seat 11 can be removed and then installed on the outside of the column pile 3. The device structure is simple, the method construction is reliable, the construction efficiency can be improved, and the control requirements of micro-deformation of the foundation pit can be met.

[0057] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A method for controlling micro-deformation of foundation pit in soft soil area, characterized by: The following steps are involved: a. The first concrete support: after the underground continuous wall and column piles are constructed on the protection side of the foundation pit, the first concrete support is constructed at the upper pit mouth of the foundation pit. The side of the first concrete is extended to the underground continuous wall to support it. The column piles close to the underground continuous wall are separated from the underground continuous wall to form a pit edge soil retention area on the protection side of the foundation pit; b. Excavation of foundation pit: excavate one layer from the central basin to the soil retention area at the pit edge on the protection side of the foundation pit; c. Cast-in-place concrete construction: Cast-in-place concrete is constructed on the lower side of the first concrete layer, and cast-in-place concrete is used for construction on the column piles; d. Excavation of the soil retaining area at the edge of the pit, excavate the soil retaining area at the edge of the pit one layer until it is flush with the foundation pit; e. Use cast-in-place concrete as support to construct a prefabricated internal support servo system; f. Repeat steps b to e until all prefabricated internal supports of the foundation pit are completed; the prefabricated internal support servo system includes a servo jack, a first articulated seat, a prefabricated support beam, a second articulated seat and an angle adjustment support seat, and the first articulated seat and the second articulated seat are respectively arranged at both ends of the prefabricated support beam; when installing the prefabricated internal support servo system, first install the angle adjustment support seat on the column pile, the position of the angle adjustment support seat corresponds to the position of the cast-in-place concrete, and a clearance hole for the angle adjustment support seat is provided on the cast-in-place concrete. The angle adjustment support seat is connected to one end of the prefabricated support beam through the second articulated seat, and the other end of the prefabricated support beam is connected to the servo jack through the first articulated seat. After the prefabricated support beam is horizontally supported, the servo jack is started to lift toward the side to support the underground continuous wall; The angle adjustment support seat comprises an L-shaped base, a side pressure plate and an end pressure plate, one side of the L-shaped base is provided with a hinge plate matched with the second hinge seat, and the bottom of the side pressure plate is fixed with a first slide bar, when installing, the inner corner of the L-shaped base is clamped on one side of the column pile, the first slide bar is slidably set in the slide groove opened on one side of the L-shaped base and fixed by a locking piece; the two ends of the end pressure plate are fixed with a second slide bar, and the second slide bars at the two ends are respectively slidably set in the slide grooves opened on the side pressure plate and the L-shaped base and fixed by a locking piece; Before installing the next prefabricated internal support servo system, first dig a narrow groove for installing the next prefabricated internal support servo system in the soil-retained area at the pit edge, and before the next concrete support, connect the next prefabricated internal support servo system with the prefabricated support beam of the previous prefabricated internal support servo system to pre-support the underground shear wall; An articulated shaft is installed on the side of the L-shaped base away from the articulated plate. When the rear prefabricated internal support servo system is connected to the prefabricated support beam of the previous prefabricated internal support servo system, the angle adjustment support seat of the rear prefabricated internal support servo system is sleeved on the outside of the prefabricated support beam of the previous prefabricated internal support servo system, and the angle adjustment support seat is connected to the second articulated seat through the articulated shaft on the angle adjustment support seat. After adjusting the angle, the articulated shaft and the second articulated seat are fixed, and the servo jack of a prefabricated internal support servo system is started to lift it toward the side to pre-support the underground continuous wall.

2. The method for controlling micro-deformation of foundation pit in soft soil area according to claim 1, characterized in that: Before the servo jack is lifted, adjust the center lines of the servo jack, the prefabricated support beam and the angle adjustment support seat to the same height, and then lock the relative positions between the servo jack and the prefabricated support beam, and between the prefabricated support beam and the angle adjustment support seat.

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