Small-space site foundation pit supporting system and construction method thereof

Abstract

The invention discloses a small-space site foundation pit supporting system which comprises supporting walls located on the edge of a foundation pit, latticed columns vertically arranged in the foundation pit and horizontal supporting steel pipes transversely supported between the supporting walls on the opposite sides. A supporting platform used for being connected with the horizontal supporting steel pipes and vertically supporting the horizontal supporting steel pipes is arranged at the tops of the latticed columns. The invention further discloses a construction method for the small-space site foundation pit supporting system. According to the method, excavation and construction of the supporting system are carried out at the same time in a horizontal steel pipe supporting mode, so that supporting and excavation of the foundation pit are completed under the condition that existing surrounding buildings are not affected; the supporting platform is arranged on the latticed column, limiting and fixing of the horizontal steel pipe support or the inclined steel pipe support in the horizontal direction and the height direction are guaranteed, and then the supporting strength of the horizontal steel pipe support or the inclined steel pipe support is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of foundation pit support, and in particular to a foundation pit support system for a small space site. Background Art

[0002] With the development of urbanization, the scale of underground space development is getting bigger and bigger. At present, most foundation pit projects are located in urban areas with dense distribution of existing buildings, municipal roads and underground pipelines. However, the impact of foundation pit excavation on the surrounding environment is very sensitive. How to carry out reasonable foundation pit support construction in a small space has brought challenges to technical personnel and put forward new requirements for foundation pit support in the construction industry.

[0003] In the prior art, common foundation pit excavation generally adopts slope excavation, anchor retaining wall support, anti-slip pile board retaining wall and other methods. However, slope excavation generally requires a larger site space, which is difficult to implement in a small space, and it is necessary to ensure that the soil quality of the construction site is good and there are no important existing structures in the surrounding area; although the foundation pit construction with anchor retaining wall support does not require a larger site space, the anchors are easy to damage the existing structures in the surrounding area, so it is not suitable for the situation where there are important existing structures in the surrounding area; as for the foundation pit construction with anti-slip pile board retaining wall support, it usually requires a larger diameter pile foundation, and the area with poor soil quality in the retaining wall still needs to be anchored. This foundation pit support method consumes more materials, and the process is more complicated and the cost is higher.

[0004] Therefore, it is necessary to improve the existing foundation pit support system structure so that it can be suitable for small space sites with important existing buildings and structures around it. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a small space site foundation pit support system, which can improve construction efficiency, ensure construction safety, reduce the impact on the surrounding environment, and other problems by optimizing the underground structure foundation pit excavation and support system.

[0006] The present invention provides a small space site foundation pit support system, comprising a support wall located at the edge of the foundation pit, lattice columns vertically arranged in the foundation pit, and horizontal support steel pipes laterally supported between opposite side support walls, wherein the top of the lattice column is provided with a support platform for connecting to the horizontal support steel pipe and vertically supporting the horizontal support steel pipe.

[0007] Furthermore, the cross-section of the supporting wall in the height direction is a U-shaped structure and is formed by a number of supporting piles arranged at intervals, and the tops of the several supporting piles are connected by a crown beam to form a whole.

[0008] Furthermore, a hanging plate is provided at the connection between the crown beam and the horizontal supporting steel pipe, and the hanging plate is used to temporarily place the supporting end of the horizontal supporting steel pipe.

[0009] Furthermore, the support platform includes a horizontally arranged support plate, the upper surface of the support plate is provided with a clamp for fixing the horizontal support steel pipe, and the lower surface of the support plate is provided with a reinforcing structure for strengthening the connection strength between the support plate and the lattice column.

[0010] Furthermore, it also includes an arc plate arranged on the support plate to increase the contact area between the support plate and the horizontal support steel pipe.

[0011] Furthermore, a connecting rod is provided between adjacent support platforms to connect the two.

[0012] Furthermore, an inclined support steel pipe for enhancing the support strength of the foundation pit is arranged between adjacent supporting walls, and the inclined support steel pipe is arranged on the excavation side of the foundation pit.

[0013] Furthermore, the horizontal supporting steel pipe and the oblique supporting steel pipe each include a fixed end portion fixedly connected to the crown beam and a flexible end portion for adjusting the supporting strength.

[0014] Furthermore, the horizontal supporting steel pipe and the inclined supporting steel pipe are both segmented structures, and the movable end and the fixed end are fixed by a flange.

[0015] A construction method for a foundation pit support system for a small space site is also provided, using the foundation pit support system for a small space site as described above, comprising the following steps:

[0016] S1. Complete the construction of support piles and crown beams according to the size of the site edge, and complete the construction of lattice columns inside the site;

[0017] S2. Excavate the foundation pit to the first design height and clean the lattice columns;

[0018] S3. A support platform is set on the top of the lattice column, and the horizontal support steel pipe is passed through the support platform and supported on the support wall on the opposite side, or the inclined support steel pipe is passed through the support platform and supported on the support wall on the adjacent side;

[0019] S4. Adjust the flexible ends of the horizontal support steel pipe and the inclined support steel pipe, and apply prestress step by step until the horizontal support steel pipe and the inclined support steel pipe are supported on the supporting wall with a preset support strength;

[0020] S5. Complete foundation pit excavation to the target design height.

[0021] The beneficial effects of the present invention are as follows: the small space site foundation pit support system of the present invention determines the support system of the foundation pit for excavation of the underground structure according to the site environment overview, the foundation structure type and the characteristics of the underground structure, and adopts the horizontal steel pipe support method to carry out the construction of the support system while excavating, so as to complete the support and excavation of the foundation pit without affecting the surrounding existing buildings and structures; wherein by arranging a support platform on the lattice column, the horizontal and height directions of the horizontal steel pipe support or the inclined steel pipe support are limited and fixed, thereby ensuring the support strength of the horizontal steel pipe support or the inclined steel pipe support; and the hanging plate arranged on the crown beam for temporarily placing the end of the horizontal steel pipe support helps the construction site to adjust the support strength according to the actual situation, thereby greatly improving the construction efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0023] Figure 1 It is a structural schematic diagram of the foundation pit support system for small and medium space sites of the present invention;

[0024] Figure 2 It is a top view of the connection between the support platform and the horizontal support steel pipe in the present invention;

[0025] Figure 3 It is a front view of the connection between the support platform and the horizontal support steel pipe in the present invention;

[0026] Figure 4 It is a schematic diagram of the connection between the horizontal supporting steel pipe and the hanging plate in the present invention;

[0027] Figure 5 It is a structural schematic diagram of the hanging plate in the present invention;

[0028] Explanation of the reference numerals: 1-support pile; 2-crown beam; 3-lattice column; 4-horizontal support steel pipe; 5-inclined support steel pipe; 6-connecting rod; 7-hoop; 8-arc plate; 9-support plate; 10-reinforcement structure; 11-hanging plate; 12-flange connection; 13-fixed end; 14-flexible end. DETAILED DESCRIPTION

[0029] As shown in the figure, the present invention provides a small space site foundation pit support system, including a supporting wall located at the edge of the foundation pit, a lattice column 3 vertically arranged in the foundation pit and a horizontal support steel pipe 4 laterally supported between the opposite side support walls, and the top of the lattice column 3 is provided with a support platform for connecting with the horizontal support steel pipe 4 and vertically supporting the horizontal support steel pipe 4; by adopting a support system in which the supporting wall, the lattice column 3 and the horizontal support steel pipe 4 cooperate with each other, the support system is constructed while excavating, so as to complete the support and excavation of the foundation pit of the small space site without affecting the surrounding existing structures; and by arranging a support platform on the lattice column 3, the horizontal and height limit fixation of the horizontal steel pipe support is guaranteed, thereby ensuring the support strength of the horizontal steel pipe support.

[0030] In this embodiment, the cross section of the support wall in the height direction is a U-shaped structure and is formed by a number of support piles 1 arranged at intervals, and the tops of the several support piles 1 are connected by a crown beam 2 to form a whole; Figure 1 As shown, the supporting wall is formed by a plurality of supporting piles 1 arranged at intervals. In this scheme, since there are existing important structures on the opposite side of the excavation port, the supporting wall is constructed with supporting piles 1 on the excavation port side and on the adjacent two sides of the excavation port, and finally a supporting wall with a U-shaped cross-section is formed, and the tops of the supporting piles 1 are connected by a crown beam 2 to form a whole.

[0031] In this embodiment, the crown beam 2 is provided with a hanging plate 11 at the connection with the horizontal supporting steel pipe 4, and the hanging plate 11 is used to temporarily place the supporting end of the horizontal supporting steel pipe 4; Figure 4 and Figure 5 As shown, according to the elevation and positioning of the connection point between the horizontal supporting steel pipe 4 and the crown beam 2, a hanging plate 11 is provided on the crown beam 2 at the side close to the connection with the horizontal supporting steel pipe 4. The hanging plate 11 is mainly used to temporarily place the hanging plate 11 at the end of the horizontal steel pipe support, which helps the construction site to adjust the support strength according to actual conditions and greatly improves the construction efficiency; and the overall structure of the hanging plate 11 is Z-shaped, and the hanging plate 11 is hung on the inner side of the crown beam 2 and round steel embedded reinforcement is used to fix the hanging plate 11 and the crown beam 2 together.

[0032] In this embodiment, the support platform includes a horizontally arranged support plate 9, the upper surface of the support plate 9 is provided with a clamp 7 for fixing the horizontal support steel pipe 4, and the lower surface of the support plate 9 is provided with a reinforcing structure 10 for strengthening the connection strength between the support plate 9 and the lattice column 3; and also includes an arc plate 8 arranged on the support plate 9 for increasing the contact area between the support plate 9 and the horizontal support steel pipe 4; combined Figure 2 and Figure 3 As shown, the reinforcement structure 10 is an oblique reinforcement rod arranged between the support plate 9 and the lattice column 3, and the oblique reinforcement rod is made of channel steel.

[0033] In this embodiment, a connecting rod 6 is provided between adjacent support platforms to connect the two. The connecting rod 6 is made of I-beams and is mainly used to increase the connection strength between the support platforms to ensure the overall connection strength of the support system.

[0034] In this embodiment, an inclined support steel pipe 5 for strengthening the foundation pit support strength is arranged between adjacent supporting walls, and the inclined support steel pipe 5 is arranged on the excavation side of the foundation pit; Figure 1 As shown, since there are only a few horizontal support steel pipes 4 arranged in the foundation pit, and the excavation side of the foundation pit is often passed by equipment, vehicles, etc., which can easily damage the overall structural strength of the support system, inclined support steel pipes 5 are arranged between adjacent support walls to strengthen the foundation pit support strength, and lattice columns 3 and support platforms are also arranged below the inclined support steel pipes 5.

[0035] In this embodiment, the horizontal support steel pipe 4 and the oblique support steel pipe 5 both include a fixed end 13 fixedly connected to the crown beam 2 and a movable end 14 for adjusting the support strength; the horizontal support steel pipe 4 and the oblique support steel pipe 5 are both segmented structures, and the movable end is fixed to the fixed end 13 by a flange; Figure 4 As shown, the horizontal supporting steel pipe 4 and the inclined supporting steel pipe 5 usually have a fixed end 13 at one end and a flexible end 14 with prestress applied at the other end, and the fixed end 13 and the flexible end 14 are connected by bolts at the flange. This is the prior art and will not be described here.

[0036] This embodiment also provides a construction method for a foundation pit support system for a small space site, using the small space site foundation pit support system as described above, including the following steps:

[0037] S1. Complete the construction of support piles 1 and crown beams 2 according to the size of the site edge, and complete the construction of lattice columns 3 inside the site;

[0038] S2. Excavate the foundation pit to the first design height position, and clean the lattice column 3; the lattice column 3 is set during the pile foundation construction. After the earthwork is excavated to the first design height position, the lattice column 3 is cleaned first. The surveying personnel strictly release the center point of the horizontal support steel pipe 4 on the crown beam 2 and the lattice column 3 according to the coordinates of the drawing. In order to facilitate the construction, the surveying team needs to use spray paint to draw a line in the horizontal and vertical directions at the center of the horizontal support steel pipe 4, so as to facilitate the calibration of the steel support position after the steel support is installed;

[0039] S3. Set a support platform on the top of the lattice column 3, and pass the horizontal support steel pipe 4 through the support platform to support the supporting wall on the opposite side, or pass the inclined support steel pipe 5 through the support platform to support the supporting wall on the adjacent side; then set the support platform on the column and connect it by welding. After the hanging plate 11 on the crown beam 2 and the support platform of the lattice column 3 are installed, use a tape measure to measure the actual length between the center points of the horizontal support steel pipe 4, and cut and assemble the steel pipe according to the actual length. One end of each horizontal support steel pipe 4 is a fixed end, and the other end is a flexible end 14. If conditions permit, the horizontal support steel pipe 4 is pre-assembled on the ground with a crane and manual labor to the corresponding splicing length. The total length of each pipe (when the movable section is retracted) is 10 to 30 cm smaller than the net distance of the enclosure structure. Each connection is connected with high-strength bolts staggered in adjacent holes to tighten the horizontal support steel pipe 4. The exposed bolts must not be less than two teeth. Since the horizontal support steel pipe 4 is relatively long, two-point lifting is adopted during lifting, and a cable wind rope is tied to ensure safe, stable and accurate lifting. When the horizontal support steel pipe 4 is hoisted into place, do not loosen the hook immediately. The fixed end is first hung on the supporting temporary hanging plate 11, and the middle is placed on the supporting platform of the lattice column 3. The other end is hung on the supporting embedded part by adjusting the length of the active end 14. Then weld the clamp 7 and the I-shaped connecting rod 6 to prevent the horizontal support steel pipe 4 from sliding horizontally. The horizontal support steel pipe 4 needs to be installed with an axial force meter, and cooperate with the monitoring unit to install the axial force meter.

[0040] S4. Adjust the flexible ends of the horizontal support steel pipe 4 and the inclined support steel pipe 5, and apply prestress step by step until the horizontal support steel pipe 4 and the inclined support steel pipe 5 are supported on the supporting wall with the preset support strength; after the installation of the horizontal support steel pipe 4 is completed, the connection status of each node should be checked in time, and the prestress (150kN) can be applied only after confirming that the elevation, plane position, disturbance, and axis deviation meet the requirements; put two 100T hydraulic jacks into the top pressure position of the flexible end 14, and pay attention to keep the jacks moving in unison. After the prestress is applied in place, the gasket is wedge-tightened in the flexible end 14 and fixed firmly. After 2 to 5 minutes, the oil can be returned to loosen the jack, untie the lifting wire rope, and complete the installation of the support. Before prestressing construction, the oil pump and jack must be calibrated and records must be kept. During the application of prestress, the prestress must be applied step by step in strict accordance with the design requirements. The first prestress is 30% of the total prestress. After checking the bolts and nuts and finding no abnormalities, the second prestress is 50% of the total prestress. After checking the bolts and nuts and finding no abnormalities, the third prestress of 150KN is applied to meet the design requirements. When applying prestress to the support, the stress loss during operation should be taken into account. Therefore, the applied prestress value should be 15% higher than the designed axial force, and the prestress value should be recorded for future reference.

[0041] S5. Complete foundation pit excavation to the target design height.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A foundation pit support system for a small space, characterized by: It includes a supporting wall located at the edge of a foundation pit, lattice columns vertically arranged in the foundation pit, and horizontal supporting steel pipes laterally supported between the supporting walls on opposite sides. The top of the lattice column is provided with a supporting platform for connecting with the horizontal supporting steel pipe and vertically supporting the horizontal supporting steel pipe.

2. The small space foundation pit support system according to claim 1 is characterized by: The cross section of the supporting wall in the height direction is a U-shaped structure and is formed by a plurality of supporting piles arranged at intervals, and the tops of the plurality of supporting piles are connected by a crown beam to form a whole.

3. The small space foundation pit support system according to claim 2 is characterized in that: The crown beam is provided with a hanging plate at the connection with the horizontal supporting steel pipe, and the hanging plate is used for temporarily placing the supporting end of the horizontal supporting steel pipe.

4. The small space foundation pit support system according to claim 1 is characterized by: The support platform includes a horizontally arranged support plate, the upper surface of the support plate is provided with a clamp for fixing the horizontal support steel pipe, and the lower surface of the support plate is provided with a reinforcing structure for strengthening the connection strength between the support plate and the lattice column.

5. The small space foundation pit support system according to claim 4 is characterized in that: It also includes an arc plate arranged on the support plate for increasing the contact area between the support plate and the horizontal support steel pipe.

6. The small space foundation pit support system according to claim 4 is characterized by: A connecting rod is arranged between adjacent support platforms to connect the two.

7. The small space foundation pit support system according to claim 2 is characterized by: An inclined support steel pipe for reinforcing the foundation pit support strength is arranged between adjacent support walls, and the inclined support steel pipe is arranged on the excavation side of the foundation pit.

8. The small space foundation pit support system according to claim 7 is characterized by: The horizontal support steel pipe and the oblique support steel pipe both include a fixed end portion fixedly connected to the crown beam and a flexible end portion for adjusting the support strength.

9. The small space foundation pit support system according to claim 8 is characterized by: The horizontal supporting steel pipe and the inclined supporting steel pipe are both segmented structures, and the movable end and the fixed end are fixed by a flange.

10. A construction method for a foundation pit support system in a small space, characterized in that: Using the small space site foundation pit support system as described in any one of claims 1 to 9 comprises the following steps: S1. Complete the construction of support piles and crown beams according to the size of the site edge, and complete the construction of lattice columns inside the site; S2. Excavate the foundation pit to the first design height and clean the lattice columns; S3. A support platform is set on the top of the lattice column, and the horizontal support steel pipe is passed through the support platform and supported on the support wall on the opposite side, or the inclined support steel pipe is passed through the support platform and supported on the support wall on the adjacent side. S4. Adjust the flexible ends of the horizontal support steel pipe and the inclined support steel pipe, and apply prestress step by step until the horizontal support steel pipe and the inclined support steel pipe are supported on the supporting wall with a preset support strength; S5. Complete foundation pit excavation to the target design height.

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