Support directly descending mobile deep foundation pit variable interval support construction method

Abstract

The application provides a support directly descending movable deep foundation pit variable interval support construction method, which comprises the following steps: A, foundation pit enclosure mechanism installation; B1, first permanent support construction; B2, temporary servo support construction; B3, permanent servo support construction; B4, temporary servo support displacement installation; repeating the steps of B3 and B4 until the distance between the last installed permanent servo support and the bottom elevation of the foundation pit is less than the set depth; B5, continuing to dig the foundation pit earthwork in the space surrounded by the foundation pit enclosure mechanism to the bottom elevation of the foundation pit, and constructing the foundation pit bottom plate; the distance between the adjacent permanent servo supports gradually decreases from top to bottom. The application has the advantages of being capable of completing support variable interval installation, and is used for solving the problem of support equidistance installation waste.

Description

Technical Field

[0001] This application relates to the field of foundation pit construction technology, and in particular to a method for constructing a deep foundation pit with a variable spacing support for direct descent and movement. Background Technology

[0002] Excavation of foundation pits is required during underground space development. The existing construction method for foundation pits is as follows: A retaining structure is built at the edge of the area containing the foundation pit. Then, the soil within the retaining structure is excavated to a predetermined depth (the depth to which the soil can be excavated in one go is called the predetermined depth; support must be provided during this excavation, otherwise the retaining structure will deform beyond its range). A permanent support is then erected. This process is repeated until the foundation pit depth reaches the bottom elevation, at which point the bottom of the pit is poured. After the foundation pit construction is completed, the permanent support is removed (permanent support refers to support that is not removed before the foundation pit construction is completed). Existing foundation pit supports are installed at equal intervals to facilitate the excavation of the foundation pit soil. (Support is necessary before the foundation pit reaches the set depth; otherwise, the deformation of the foundation pit retaining structure towards the inside of the pit will exceed the set range. Any inward or outward deformation of any part of the retaining structure must be within the set range to meet requirements. The foundation pit retaining structure acts as an elastic body within the pit, and can produce localized arching when subjected to excessive pressure.) Traditional foundation pit construction typically uses reinforced concrete supports or (prestressed) steel supports. However, traditional supports often result in excessive deformation of the retaining structure and uneven development of axial forces among the supports. Therefore, a servo support system was designed. The servo support system can monitor and adjust the axial forces of each support in real time, actively controlling the deformation of the retaining structure. However, when the excavation depth is deep, the upper servo supports maintain a consistently high axial force, often causing negative deformation of the retaining structure towards the outside of the pit. To reduce this negative deformation, the axial force of the upper supports is often set at a lower threshold during subsequent construction, resulting in high servo support consumption. If the servo supports are installed with varying spacing from top to bottom, the consumption can be reduced. The location and axial force of each servo support can be preliminarily calculated when using variable spacing. During construction, only minor adjustments to the axial force are needed to correct for errors caused by actual geological conditions and geological data obtained from testing, ensuring the axial force meets actual requirements. However, when installing variable spacing servo supports, the spacing between supports will be greater than the set depth, making variable spacing servo support installation impossible. Summary of the Invention

[0003] This invention aims to provide a construction method for a deep foundation pit variable-spacing support that allows for direct lowering and movement of supports, enabling variable-spacing installation, in order to solve the problem of wasted supports during equidistant installation.

[0004] To achieve the above-mentioned objectives, the present invention employs the following technology: a method for constructing a direct-descent, mobile, variable-spacing support for deep foundation pits, comprising: A) Installation of the foundation pit retaining structure: constructing the foundation pit retaining structure within the perimeter of the soil in the area where the foundation pit is located; B) Excavation of the foundation pit: excavating the foundation pit soil within the space enclosed by the foundation pit retaining structure and supporting the foundation pit retaining structure until the foundation pit is excavated to the bottom elevation; characterized in that the specific process of step B is as follows: B1) Permanent support construction: excavating the foundation pit soil within the space enclosed by the foundation pit retaining structure to the point where permanent support can be installed, and using a permanent support to support the upper end of the foundation pit retaining structure; B2) Temporary servo support construction: continuing to excavate the foundation pit soil to a set depth within the space enclosed by the foundation pit retaining structure, installing a temporary servo support at the lower end of the excavated foundation pit, and adjusting the axial force of the temporary servo support to meet the requirements; B3) Permanent servo support construction: constructing the foundation pit retaining structure within the space enclosed by the foundation pit retaining structure... B3. Continue excavating the foundation pit within the enclosed space until the location of the permanent servo support closest to the temporary servo support is exposed. Install a permanent servo support at the location of the permanent servo support on the foundation pit retaining structure, and adjust the axial force of the permanent servo support to meet the requirements. B4. Temporary servo support relocation and installation: Continue excavating the foundation pit to the set depth within the space enclosed by the foundation pit retaining structure, reducing the axial force of the temporary servo support until it can be removed. Transfer the temporary servo support to the lower end of the excavated foundation pit, and adjust the axial force of the temporary servo support to meet the requirements. Repeat steps B3 and B4 until the distance between the last installed permanent servo support and the bottom elevation of the foundation pit is less than the set depth. B5. Continue excavating the foundation pit within the space enclosed by the foundation pit retaining structure to the bottom elevation of the foundation pit, and construct the foundation pit bottom slab. The distance between adjacent permanent servo supports decreases sequentially from top to bottom. This achieves the construction of variable-pitch servo support installation.

[0005] Preferably, the permanent support is a reinforced concrete structure, and the foundation pit retaining structure includes a diaphragm wall and a capping beam cast on top of the diaphragm wall, with the permanent support cast together with the capping beam. This ensures that the upper part of the foundation pit retaining structure remains in a fixed position.

[0006] Preferably, when adjusting the axial force of the temporary servo support, the axial force of all permanent servo supports located above the temporary servo support is kept constant; when adjusting the axial force of the permanent servo support, the axial force of both the temporary and permanent servo supports located above the permanent servo support being adjusted is kept constant. This allows for easy adjustment of the axial force to meet requirements and maintain the deformation of the foundation pit retaining structure within the set range.

[0007] Preferably, during step B4, while reducing the axial force of the temporary servo support until it can be removed, the following inspection is performed: Check whether the deformation of the portion of the foundation pit retaining structure located between the two adjacent permanent servo supports meets the protection requirements. If it does not meet the requirements, adjust the axial force of the permanent servo support below the temporary servo support until the deformation of the portion of the foundation pit retaining structure between the two adjacent permanent servo supports meets the requirements. This ensures that the constructed foundation pit accurately meets the requirements.

[0008] Preferably, a dial indicator is provided at each end of the temporary servo support, with the tips of the two dial indicators extending in opposite directions. The temporary servo support is horizontal and perpendicular to the pit retaining structure, supporting it. When the axial force of the temporary servo support meets the requirements, the tips of both dial indicators are pressed against the pit retaining structure, the readings of both dial indicators are non-zero, and the sum of the readings is n. When the absolute value of the sum of the readings of the two dial indicators minus n is less than a set value, it indicates that the deformation of the pit retaining structure meets the requirements. The axial force of the temporary servo support is then reduced. During the process of removing the temporary servo support, the readings of both dial gauges are maintained at a non-zero value. If the sum of the two dial gauge readings minus n is greater than zero and greater than the set value, the axial force of the permanent servo support located below the temporary servo support is increased until the absolute value of the sum of the two dial gauge readings minus n is less than the set value. If the sum of the two dial gauge readings minus n is less than zero and the absolute value is greater than the set value, the axial force of the permanent servo support located below the temporary servo support is decreased until the absolute value of the sum of the two dial gauge readings minus n is less than the set value. This method allows for convenient detection of whether the deformation of the foundation pit retaining structure meets the requirements using the temporary servo support. The accuracy during detection is good. If the detection instrument is moved and repositioned during each detection, the resulting measurement error is large; this technical solution overcomes this problem.

[0009] Preferably, the temporary servo support includes a temporary servo support body, with temporary servo support jacks at both ends of the temporary servo support body; the permanent servo support includes a permanent servo support body, with permanent servo support jacks at both ends of the permanent servo support body.

[0010] Preferably, the temporary servo support body has a cylindrical section for the temporary servo support, and the permanent servo support body has a cylindrical section for the permanent servo support. A first connecting ring is fitted onto the cylindrical section of the temporary servo support. The first connecting ring is connected to a second connecting ring via a telescopic structure. The second connecting ring is an openable and closable ring. The specific process of transferring the temporary servo support to the lower end of the excavated pit in step B4 is as follows: The distance between the first and second connecting rings is adjusted using the telescopic structure until the second connecting ring can connect to the permanent servo support located below the temporary servo support. The second connecting ring is fitted onto the cylindrical section of the permanent servo support, detaching the temporary servo support from the pit retaining structure. The temporary servo support is rotated about the cylindrical section of the permanent servo support until it is located below the permanent servo support connected to the second connecting ring. The vertical position of the temporary servo support is adjusted using the telescopic structure until it aligns with the installation location of the temporary servo support on the pit retaining structure. The temporary servo support is then installed. Moving the temporary servo support is convenient, labor-saving, and safe.

[0011] Preferably, the telescopic structure is a hydraulic cylinder.

[0012] Preferably, the second connecting ring includes two half-rings, one end of which is hinged to a telescopic structure via a hinge pin; a locking bolt passing through the other end of each half-ring; and a locking nut threaded onto the locking bolt. In use, the locking nut and bolt are removed, the two half-rings are separated, and then moved radially along the permanent servo support to be mounted on the cylindrical section of the permanent servo support. The locking nut, in conjunction with the locking bolt, connects the two half-rings together, thus fitting them onto the cylindrical section of the permanent servo support. Connecting and removing the second connecting ring to the cylindrical section of the permanent servo support is convenient and provides reliable connection.

[0013] Preferably, a hanging ring is connected to the first connecting ring. The specific process of rotating the temporary servo support around the cylindrical section of the permanent servo support is as follows: the hoist is fixed to the permanent servo support or the permanent support located above the temporary servo support. The hook of the hoist's chain is hooked onto the hanging ring, causing the hoist to push against the temporary servo support, causing the temporary servo support to lose its balance. The rotation speed of the temporary servo support is controlled by controlling the extension speed of the hoist's chain. This improves the safety and convenience when moving the temporary servo support.

[0014] The present invention has the following advantages: the variable pitch setting of the support can reduce the number of supports and make full use of the load capacity of the supports; the accuracy of detecting the deformation of the foundation pit retaining structure is good and convenient; and the servo support displacement is safe and convenient. Attached Figure Description

[0015] Figure 1This is a schematic diagram showing the permanent and temporary servo supports during the construction of the foundation pit;

[0016] Figure 2 This is a schematic diagram of the first permanent servo support after the foundation pit construction is completed;

[0017] Figure 3 This is a diagram showing the temporary support being moved below the first permanent servo support.

[0018] Figure 4 This is a schematic diagram showing the second permanent servo support after the foundation pit construction is completed;

[0019] Figure 5 This is a diagram showing the temporary support being moved below the second permanent servo support.

[0020] Figure 6 This is a diagram showing the completion of all permanent servo support installations;

[0021] Figure 7 This is a cross-sectional schematic diagram of the connection point between the temporary servo support and the permanent servo support connected to the temporary servo support.

[0022] In the diagram: 1. Foundation pit support structure; 2. Soil in the foundation pit area; 3. Diaphragm wall; 4. Crown beam; 5. Permanent support; 6. Temporary servo support; 7. Main body of temporary servo support; 8. Jack of temporary servo support; 9. Dial indicator; 10. Top of dial indicator; 11. First connecting ring; 12. Telescopic structure; 13. Second connecting ring; 14. Hinge shaft; 15. Half ring; 16. Locking bolt; 17. Locking nut; 18. Hanging ring; 19. Permanent servo support; 20. Main body of permanent servo support; 21. Jack of permanent servo support; 22. Foundation pit bottom plate. Detailed Implementation

[0023] The present invention will now be described in conjunction with the accompanying drawings and specific embodiments, wherein the anchor rod is inclined with one end higher than the other end, which is connected to the inner retaining wall, and the lower end of the anchor rod is lower than the bottom of the inner pit.

[0024] See Figures 1 to 7 A method for constructing a direct-descending, mobile, variable-spacing support system for deep foundation pits.

[0025] See Figure 1 and combined Figure 7The process includes: A) Installation of the foundation pit retaining structure: Constructing the foundation pit retaining structure 1 to the perimeter of the soil 2 in the area where the foundation pit is located; the foundation pit retaining structure includes a diaphragm wall 3 and a capping beam 4 cast on top of the diaphragm wall. B) Excavation of the foundation pit: Excavating the foundation pit soil within the space enclosed by the foundation pit retaining structure and supporting the foundation pit retaining structure until the foundation pit is excavated to the bottom elevation; The specific process of step B is as follows: B1) Construction of permanent support: Excavating the foundation pit soil within the space enclosed by the foundation pit retaining structure to the point where permanent support 5 can be installed, using a permanent support to support the upper end of the foundation pit retaining structure. The permanent support is a reinforced concrete structure and is cast together with the capping beam. B2) Construction of temporary servo support: Continuing to excavate the foundation pit soil to the set depth within the space enclosed by the foundation pit retaining structure, installing a temporary servo support 6 at the lower end of the excavated foundation pit, and adjusting the axial force of the temporary servo support to meet the requirements. The temporary servo support includes a main body 7 and temporary servo support jacks 8 at both ends. The axial force is changed by adjusting the extension length of the jacks. A cylindrical section of the temporary servo support is provided on the main body (in this embodiment, the entire temporary support body is cylindrical, thus having a cylindrical section of the temporary servo support). A dial indicator 9 is provided at each end of the temporary servo support, with the tips 10 of the two dial indicators extending in opposite directions. The temporary servo support is horizontal and perpendicular to the foundation pit retaining structure, supporting the foundation pit retaining structure. When the axial force of the temporary servo support meets the requirements, the tips of both dial indicators are on the foundation pit retaining structure, and the readings of both dial indicators are non-zero. The sum of the readings of the two dial indicators is n. When the absolute value of the sum of the readings of the two dial indicators minus n is less than the set value, it indicates that the deformation of the foundation pit retaining structure meets the requirements. A first connecting ring 11 is fitted onto the cylindrical section of the temporary servo support. The first connecting ring is connected to a second connecting ring 13 via a telescopic structure 12. The second connecting ring is an openable and closable ring. The telescopic structure is a hydraulic cylinder. The second connecting ring includes two half-rings 15, one end of which is hinged to the telescopic structure via a hinge pin 14; a locking bolt 16 passing through the other end of the two half-rings; and a locking nut 17 threaded onto the locking bolt. A hanging ring 18 is connected to the first connecting ring.

[0026] See Figure 2B3. Construction of Permanent Servo Support: Within the space enclosed by the foundation pit retaining structure, continue excavating the foundation pit until the location of the permanent servo support closest to the temporary servo support is exposed. Install a permanent servo support at the designated permanent servo support location on the foundation pit retaining structure, and adjust the axial force of the permanent servo support to meet requirements. The permanent servo support includes a main body 20, with permanent servo support jacks 21 at both ends; the main body has a cylindrical section, which in this embodiment is cylindrical.

[0027] See Figures 2 to 7B4. Temporary servo support relocation and installation: Continue excavating the foundation pit to a set depth within the space enclosed by the foundation pit retaining structure, reducing the axial force of the temporary servo support until it can be removed. Transfer the temporary servo support to the lower end of the excavated foundation pit and adjust its axial force to meet the requirements. Repeat steps B3 and B4 until the distance between the last installed permanent servo support and the bottom elevation of the foundation pit is less than the set depth. B5. Continue excavating the foundation pit to the bottom elevation within the space enclosed by the foundation pit retaining structure, and construct the foundation pit bottom slab 22. The distance between adjacent permanent servo supports decreases sequentially from top to bottom. When adjusting the axial force of the temporary servo support, maintain a constant axial force for all permanent servo supports located above the temporary servo support; when adjusting the axial force of the permanent servo support, maintain a constant axial force for both the temporary and permanent servo supports located above the permanent servo support being adjusted. In step B4, during the process of reducing the axial force of the temporary servo support until it can be removed, the following testing is performed: Check whether the deformation of the portion of the pit retaining structure located between the two adjacent permanent servo supports meets the protection requirements. If it does not meet the requirements, adjust the axial force of the permanent servo support below the temporary servo support until the deformation of the portion of the pit retaining structure between the two adjacent permanent servo supports meets the requirements. During the process of reducing the axial force of the temporary servo support until it can be removed, always maintain the readings of both dial gauges non-zero. If the sum of the two dial gauge readings minus n is greater than zero and greater than the set value, increase the axial force of the permanent servo support below the temporary servo support until the absolute value of the sum of the two dial gauge readings minus n is less than the set value. If the sum of the two dial gauge readings minus n is less than zero and the absolute value is greater than the set value, reduce the axial force of the permanent servo support below the temporary servo support until the absolute value of the sum of the two dial gauge readings minus n is less than the set value. The specific process of transferring the temporary servo support to the lower end of the excavated pit in step B4 is as follows: Adjust the distance between the first and second connecting rings using a telescopic structure until the second connecting ring can connect to the permanent servo support located below the temporary servo support. Fit the second connecting ring onto the cylindrical section of the permanent servo support, disengaging the temporary servo support from the pit retaining structure. Rotate the temporary servo support around the cylindrical section of the permanent servo support until it is located below the permanent servo support connected to the second connecting ring. Adjust the vertical position of the temporary servo support using the telescopic structure until it aligns with the installation location of the temporary servo support on the pit retaining structure. Install the temporary servo support.The specific process of rotating the temporary servo support around the cylindrical section of the permanent servo support is as follows: the hoist is fixed on the permanent servo support or the permanent support located above the temporary servo support, the hook of the hoist chain is hooked on the hanging ring, so that the hoist pushes the temporary servo support, causing the temporary servo support to lose balance, and the rotation speed of the temporary servo support is controlled by controlling the extension speed of the hoist chain.

Claims

1. A method for constructing a direct-descending, movable, variable-spacing support system for deep foundation pits, comprising: A) Installation of the foundation pit support structure: constructing the foundation pit support structure within the perimeter of the soil in the area where the foundation pit is located; B) Excavation of the foundation pit: excavating the foundation pit soil within the space enclosed by the foundation pit support structure and supporting the foundation pit support structure until the foundation pit is excavated to the bottom elevation; characterized in that... The specific process of B step is: B1, permanent support construction: excavate the foundation pit soil in the space surrounded by the foundation pit enclosure mechanism to the position where the permanent support can be installed, and support the upper end of the foundation pit enclosure mechanism with a permanent support; B2, temporary servo support construction: continue to excavate the foundation pit soil of a set depth in the space surrounded by the foundation pit enclosure mechanism, install a temporary servo support at the lower end of the excavated foundation pit, and adjust the axial force of the temporary servo support to meet the requirements; B3, permanent servo support construction: continue to excavate the foundation pit soil in the space surrounded by the foundation pit enclosure mechanism to the position where the permanent servo support can be installed, expose the position where the permanent servo support can be installed, install a permanent servo support at the position where the permanent servo support can be installed, and adjust the axial force of the permanent servo support to meet the requirements; B4, temporary servo support displacement installation: continue to excavate the foundation pit soil of the set depth in the space surrounded by the foundation pit enclosure mechanism, reduce the axial force of the temporary servo support to the position where the temporary servo support can be removed, move the temporary servo support to the lower end of the excavated foundation pit, and adjust the axial force of the temporary servo support to meet the requirements; repeat steps B3 and B4 until the distance between the last installed permanent servo support and the bottom of the foundation pit is less than the set depth; B5, continue to excavate the foundation pit soil in the space surrounded by the foundation pit enclosure mechanism to the bottom of the foundation pit, and construct the foundation pit bottom plate; the distance between adjacent permanent servo supports decreases from top to bottom.

2. The method according to claim 1, wherein, The permanent support is a reinforced concrete structure, and the foundation pit enclosure mechanism comprises a underground continuous wall and a corbel poured on the top of the underground continuous wall.

3. The construction method of claim 1 or 2, wherein, When adjusting the axial force of the temporary servo support, the axial forces of all the permanent servo supports located above the temporary servo support are maintained constant; when adjusting the axial force of the permanent servo support, the axial forces of all the temporary servo supports and permanent servo supports located above the permanent servo support being adjusted are maintained constant.

4. The construction method of supporting directly descending mobile deep foundation pit variable spacing support according to claim 1 or 2, characterized in that, In the process of reducing the axial force of the temporary servo support to the position where the temporary servo support can be removed in step B4, the following detection operation is performed: whether the deformation of the part of the foundation pit enclosure mechanism located between the two permanent servo supports adjacent to the temporary servo support meets the requirements, and if not, the axial force of the permanent servo support located below the temporary servo support is adjusted to make the deformation of the part of the foundation pit enclosure mechanism located between the two permanent servo supports adjacent to the temporary servo support meet the requirements.

5. The construction method of supporting directly descending mobile deep foundation pit variable spacing support according to claim 1 or 2, characterized in that, The temporary servo support comprises a temporary servo support part body, and temporary servo support part jacks are arranged at the two ends of the temporary servo support part body; the permanent servo support comprises a permanent servo support part body, and permanent servo support part jacks are arranged at the two ends of the permanent servo support part body.

6. The construction method of claim 5, wherein, The temporary servo support part body is provided with a temporary servo support part cylinder segment, the permanent servo support part body is provided with a permanent servo support part cylinder segment, the temporary servo support part cylinder segment is sleeved with a first connecting ring, the first connecting ring is connected with a second connecting ring through an extension structure, and the second connecting ring is an openable and closable ring; the specific process of transferring the temporary servo support to the lower end of the excavated foundation pit in B4 is as follows: the distance between the first connecting ring and the second connecting ring is adjusted to the distance at which the second connecting ring can be connected to the permanent servo support located below the temporary servo support through the extension structure, the second connecting ring is sleeved on the permanent servo support part cylinder segment, the temporary servo support is separated from the foundation pit enclosure mechanism, the temporary servo support is rotated around the permanent servo support part cylinder segment to be located below the permanent servo support connected with the second connecting ring, the up-and-down position of the temporary servo support is adjusted to the position at which the temporary servo support is aligned with the part of the foundation pit enclosure mechanism on which the temporary servo support is installed through the extension structure, and the temporary servo support is installed.

7. The construction method of claim 6, wherein, The extension structure is an oil cylinder.

8. The method according to claim 6, wherein, The second connecting ring comprises two half rings hinged together with the extension structure through a hinge shaft, locking bolts penetrating the other ends of the two half rings, and locking nuts threadedly connected with the locking bolts.

9. The method according to claim 6, wherein, The first connecting ring is connected with a hanging ring, and the specific process of rotating the temporary servo support around the permanent servo support part cylinder segment is as follows: the gourd is fixed on the permanent servo support or the permanent support located above the temporary servo support, the hook of the gourd zipper is hooked on the hanging ring, the gourd pulls the temporary servo support, the temporary servo support is pushed to lose balance, and the speed of rotating the temporary servo support is controlled by controlling the elongation speed of the gourd chain.

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