Foundation pit support structure for pipe connecting point construction and construction method of foundation pit support structure

Abstract

The invention discloses a foundation pit support structure for pipe connecting point construction and a construction method thereof.The foundation pit support structure comprises four arc-shaped steel plates which are symmetrically arranged around an existing pipeline and a proposed pipeline with the pipe connecting point as the center, and the arc-shaped steel plates keep a certain distance from the existing pipeline and the proposed pipeline; every two adjacent arc-shaped steel plates are connected through a plurality of rectangular steel plates, and the arc-shaped steel plates and the rectangular steel plates form a rectangle with four arc angles on a plane graph. The vertical connectors are arranged at the two ends of the arc-shaped steel plate, the rectangular steel plates are vertically embedded into the vertical connectors, the horizontal connectors are arranged at the tops of the rectangular steel plates, the rectangular steel plates are vertically connected through the horizontal connectors, and a force transmission structure formed by the vertical connectors and the horizontal connectors can effectively transmit bending moment, axial force and shearing force and has waterproof performance. A space stress structure similar to a cylinder is formed, effective supporting can be formed on soil bodies below pipelines which cannot be supported by the cylinder, and the structure is suitable for construction of pipe connecting point foundation pits with different pipe diameters and burial depths.

Description

Technical Field

[0001] The present invention belongs to the technical field of pipeline connection point enclosure structures, and in particular relates to a foundation pit enclosure structure for connection point construction and a construction method thereof. Background Art

[0002] In the urban infrastructure system, the interconnection of municipal pipelines such as water supply, rainwater, and sewage can effectively improve the safety and risk resistance of the municipal pipeline network system. Therefore, newly built municipal pipelines need to be connected to existing pipelines at the connection point, that is, the local pipelines at the existing municipal pipelines are replaced with T-shaped or cross-shaped pipe joints to connect with the newly built pipelines. Large-diameter municipal pipelines are often buried deep, and in urban areas, the construction conditions for slope excavation are often not available. Therefore, the construction of the connection point requires vertical foundation pit support, and it is required to minimize the construction land, construction period, and disturbance to the surrounding environment. Depending on the burial depth of the existing pipeline and the environmental protection requirements of the surrounding foundation pit, conventional foundation pit retaining forms at the connection point include steel sheet piles, SMW piles, bored piles, steel casing caissons, etc. Among the above-mentioned foundation pit retaining structures, the steel sheet pile structure has a lower construction cost, but its overall rigidity is low, its water-stopping ability is poor, and its construction disturbance to existing pipelines is relatively large; the SMW method pile uses three-axis mixing piles as a water-stop curtain, and its support system rigidity is relatively large, but its construction cost is high and the construction period is long; bored cast-in-place piles need to be supplemented with a water-stop curtain (generally using rotary jet piles or mixing piles), and its support system rigidity is the largest, but the construction cost is the highest and the construction period is the longest. In addition, the above-mentioned foundation pit retaining piles are all vertical load-bearing components, and the horizontal connection between the retaining piles is weak, requiring the support of an internal support system to increase the horizontal rigidity, which leads to the vertical space for pipeline connection operations in the foundation pit being limited, and also increases the overall construction period and construction cost. Steel casing caissons (or riding caissons) use large-diameter circular steel cylinders, which sink from the ground. During the sinking process, excavation is carried out simultaneously in the well. This construction method is to meet the requirements of internal excavation. The steel cylinder has a large diameter and a heavy weight, and the construction area is large and the construction is difficult. At the same time, there are problems such as sinking difficulties and deviations are easy to occur during the sinking process. The steel cylinder can only sink to the top of the existing pipeline, resulting in the steel cylinder being unable to form effective support for the soil below the pipeline, and it cannot fit with the existing pipeline, with a large gap, and the construction safety is poor. Summary of the Invention

[0003] In view of this, the object of the present invention is to provide a foundation pit retaining structure for pipe connection point construction and a construction method thereof, so as to solve the deficiencies in the prior art.

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

[0005] On the one hand, a foundation pit retaining structure for the construction of a takeover point is provided, which includes four arc-shaped steel plates symmetrically arranged around the existing pipeline and the planned pipeline with the takeover point as the center. The arc-shaped steel plates maintain a certain distance from the existing pipeline and the planned pipeline. Two adjacent arc-shaped steel plates are connected by multiple rectangular steel plates. The arc-shaped steel plates and the rectangular steel plates form a rectangle with four arc corners in a plan view.

[0006] As described in the foundation pit retaining structure for takeover point construction, vertical joints are respectively provided at the left and right ends of the arc-shaped steel plate, and a plurality of rectangular steel plates are vertically embedded in the vertical joints between two arc-shaped steel plates in sequence.

[0007] As described in the foundation pit retaining structure for taking over point construction, wherein the vertical joint includes a vertical Y-shaped groove and a first waterproof felt arranged in the vertical Y-shaped groove, and vertical mortises are respectively provided in the vertical Y-shaped groove and at both ends of the rectangular steel plate.

[0008] As described in the foundation pit retaining structure for takeover point construction, a horizontal joint is provided on the top of the rectangular steel plate, and the bottom of each rectangular steel plate is embedded in the horizontal joint located below at the top of the rectangular steel plate.

[0009] As described in the foundation pit retaining structure for takeover point construction, wherein the horizontal joint includes a horizontal Y-shaped groove and a second waterproof felt arranged in the horizontal Y-shaped groove, a fixing ring is provided at the top of the horizontal Y-shaped groove, and a circular hole is opened at the bottom of the rectangular steel plate, through which an insert rod is inserted into the circular hole and the fixing ring of the rectangular steel plate.

[0010] As described in the foundation pit retaining structure for takeover point construction, wherein the inner side of the arc-shaped steel plate is provided with a matching positioning rod and sleeve, and the top of the positioning rod is connected to form a gate-shaped structure.

[0011] On the other hand, a method for constructing a foundation pit retaining structure for connecting a connection point is provided, comprising the following steps:

[0012] S1: At the location of the planned connection point of the existing pipeline, four curved steel plates are pressed from the ground. The four curved steel plates are symmetrically arranged with the connection point as the center;

[0013] S2: rectangular steel plate pressed into the ground;

[0014] S3: Carry out pit dewatering and earth excavation. After excavating to the bottom of the pit, remove the existing local pipelines at the connection points and install pipe joints.

[0015] S4: Pull out the rectangular steel plates at the proposed pipeline from the ground one by one until the distance between the bottom of the lowest rectangular steel plate and the top of the proposed pipeline is greater than the safety protection distance of the pipeline. Under the support of the rectangular steel plate above the proposed pipeline, carry out the pipe connection operation to connect the proposed pipeline with the installed pipeline joint;

[0016] S5: After the pipeline pressure test is completed, backfill the foundation pit at the connection point and remove the remaining rectangular steel plates;

[0017] S6: Pull out the curved steel plate. During the removal process, the positioning rod is used to synchronously inject grout to fill the soil voids caused by the removal of the curved steel plate. After that, the positioning rod is pulled out and secondary grouting is performed to fill the soil voids caused by the removal of the positioning rod.

[0018] As described in the foundation pit retaining structure construction method for connecting point construction, step S1 includes:

[0019] S11: Layout and locate the curved steel plates and positioning rods on the ground. The net distance between the vertical joints of the curved steel plates is the pipe diameter + 2 times the safety distance. The vertical joints are oriented perpendicular to the pipe.

[0020] S12: Press the positioning rod into the soil, ensuring that the verticality meets the requirements during the pressing process;

[0021] S13: Press the arc-shaped steel plate into the soil along the positioning rod, and make the positioning rod enter the sleeve to ensure that the verticality of the arc-shaped steel plate meets the requirements.

[0022] In the foundation pit retaining structure construction method for connecting point construction, step S2 includes:

[0023] S21: inserting the rectangular steel plate into the vertical Y-shaped notches of the vertical joints at both ends of the curved steel plate, and pressing the first rectangular steel plate into place;

[0024] S22: Insert the second rectangular steel plate into the vertical Y-shaped notches at both ends of the curved steel plate, and insert the bottom of the second rectangular steel plate into the horizontal Y-shaped notch at the top of the first rectangular steel plate, and fix the upper and lower rectangular steel plates with a rod;

[0025] S23: Continue to press the second rectangular steel plate into the ground;

[0026] S24: Repeat steps S22 to S23 above the existing pipeline until the distance between the bottom of the lowest rectangular steel plate and the top of the existing pipeline is greater than or equal to the safety protection distance of the pipeline; repeat steps S22 to S23 at the proposed pipeline until the bottom of the lowest rectangular steel plate is flush with the bottom of the curved steel plate.

[0027] The beneficial effects of the technical solution of the present invention are:

[0028] 1. The entire enclosure system forms a cylindrical spatial force-bearing structure. The enclosure structure itself has large horizontal and vertical stiffness, so there is no need to set up an additional horizontal support system inside. It does not occupy the internal space of the foundation pit, leaving enough space for the construction of the pipe connection point in the foundation pit;

[0029] 2. Compared with traditional steel casing structures, the foundation pit retaining structure of the present invention can minimize the gap between the retaining structure and the existing pipeline, and also effectively support the soil below the existing pipeline. At the same time, the foundation pit retaining structure of the present invention is small and lightweight. The single-piece structure is light in weight and small in size, so the construction difficulty of transportation, lifting, sinking, and extraction is low, the required machinery and equipment are small, the construction area is smaller, and the impact on the surrounding environment is smaller;

[0030] 3. When carrying out pipe joints and pipe connection operations for planned pipelines, a specified number of rectangular steel plates at the planned pipeline can be pulled out, and the rectangular steel plates above the planned pipeline can be retained as support structures, thereby shortening the time when the soil below the planned pipeline is unsupported and maintaining the integrity of the entire foundation pit retaining structure during the connection operation;

[0031] 4. The present invention adopts a combined structure of arc-shaped steel plates and rectangular steel plates above the pipeline. By adjusting the length of the rectangular steel plates, it can be applied to the foundation pit structure of the connection point for pipelines of different diameters; by adjusting the vertical height of the rectangular steel plates, it can be applied to the foundation pit structure of the connection point for pipelines of different burial depths;

[0032] 5. The method of first constructing the positioning rod and then pressing the curved steel plate into place improves the verticality of the curved steel plate, ensuring that the rectangular steel plate can be smoothly inserted into the vertical joint of the curved steel plate. At the same time, the positioning rod and its sleeve structure can be used to increase the vertical rigidity of the curved steel plate and reduce the structural deformation of the curved steel plate. The positioning rod is made of steel flower tube, which also serves as the synchronous grouting pipe when the curved steel plate is pulled out, promptly filling the soil voids caused by the steel plate pulling out and preventing ground subsidence. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] To further illustrate the above-mentioned objectives, structural features and effects of the present invention, the present invention will be described in detail below with reference to the accompanying drawings.

[0034] Figure 1 This is a plan layout diagram of the construction stage S1 of a preferred embodiment of the present invention;

[0035] Figure 2 for Figure 1 Elevation view along direction A;

[0036] Figure 3 This is a plan layout diagram of the construction stage S2 of a preferred embodiment of the present invention;

[0037] Figure 4 for Figure 3 Section view along 1-1;

[0038] Figure 5 This is a plan layout diagram of the construction stages S3 to S4 of a preferred embodiment of the present invention;

[0039] Figure 6a This is the elevation view along direction B during construction stage S3;

[0040] Figure 6b This is the elevation view along direction B during construction stage S4;

[0041] Figure 7a This is the section view along 2-2 during construction stage S3;

[0042] Figure 7b This is the section view along 2-2 during construction stage S4;

[0043] Figure 8 This is a plan layout diagram of the construction stage S5 of a preferred embodiment of the present invention;

[0044] Figure 9 This is a plan layout diagram of the construction stage S6 of a preferred embodiment of the present invention;

[0045] Figure 10 This is a plan view of the vertical joint and the horizontal joint in a preferred embodiment of the present invention;

[0046] Figure 11 This is a cross-sectional view of a horizontal joint in a preferred embodiment of the present invention;

[0047] In the figure: 1. Existing pipeline; 2. Proposed pipeline; 3. Curved steel plate; 4. Rectangular steel plate; 5. Vertical joint; 6. Horizontal joint; 5a. Vertical Y-shaped notch; 5b. First waterproof felt; 5c. Vertical tenon; 6a. Horizontal Y-shaped notch; 6b. Second waterproof felt; 7a. Positioning rod; 7b. Sleeve; 8a. Pipe joint; 8b. Flange joint; 9. Insert rod; 10. Fixing ring. DETAILED DESCRIPTION

[0048] The terms "invention," "present invention," and "the present invention" as used in this specification are intended to refer broadly to all subject matter of this specification and any patent claims that follow. Statements containing these terms should not be construed to limit the subject matter described herein or to limit the meaning or scope of any patent claim that follows. Furthermore, this specification does not attempt to describe or limit the subject matter covered by any claim of any particular component, paragraph, statement, or figure of this application. The subject matter should be understood with reference to the entire specification, all drawings, and any claims that follow. The invention may have other embodiments and be practiced or implemented in other ways. Furthermore, it should be understood that the phraseology and terminology employed herein are for illustrative purposes only and should not be considered limiting.

[0049] The details of the present invention will now be discussed with reference to the accompanying drawings which illustrate the present invention by way of example only. In the accompanying drawings, similar features or components may be marked with the same reference numerals.

[0050] The use of "including," "having," and "comprising" and variations thereof herein is intended to encompass the items listed thereafter and equivalents thereof and additional items. Although reference may be made to directions such as above, below, upward, downward, rearward, bottom, top, front, and rear in describing the drawings, for convenience, reference is made relative to the drawings. These directions are not intended to literally define or limit the present invention in any manner. Furthermore, terms such as "first," "second," and "third" are used herein for descriptive purposes and are not intended to indicate or imply importance or significance.

[0051] See Figures 1 to 11 As shown, the foundation pit retaining structure for the construction of the connection point of the present invention includes four arc-shaped steel plates 3 symmetrically arranged around the existing pipeline 1 and the planned pipeline 2 with the connection point as the center. The arc-shaped steel plates 3 maintain a certain safety distance from the existing pipeline 1 and the planned pipeline 2. Two adjacent arc-shaped steel plates 3 are connected by multiple rectangular steel plates 4. The arc-shaped steel plates 3 and the rectangular steel plates 4 form a rectangle with four arc corners in the plan view.

[0052] The left and right ends of the curved steel plates 3 are respectively provided with vertical joints 5, and multiple rectangular steel plates 4 are vertically embedded in the vertical joints 5 between the two curved steel plates 3. The inner side of the curved steel plates 3 is provided with matching positioning rods 7a and sleeves 7b, and the tops of the positioning rods 7a are connected to form a gate-shaped structure.

[0053] Furthermore, the vertical joint 5 includes a vertical Y-shaped notch 5a and a first waterproof felt 5b arranged in the vertical Y-shaped notch 5a. Vertical mortises 5c are respectively provided in the vertical Y-shaped notch 5a and at both ends of the rectangular steel plate 4.

[0054] A horizontal joint 6 is provided on the top of the rectangular steel plate 4 , and the bottom of each rectangular steel plate 4 is embedded in the horizontal joint 6 located on the top of the rectangular steel plate 4 below.

[0055] Furthermore, the horizontal joint 6 includes a horizontal Y-shaped slot 6a and a second waterproof felt 6b arranged in the horizontal Y-shaped slot 6a. A fixing ring 10 is provided at the top of the horizontal Y-shaped slot 6a, and a circular hole is opened at the bottom of the rectangular steel plate 4. An insert rod 9 is inserted into the circular hole and the fixing ring 10 of the rectangular steel plate 4.

[0056] Waterproof felt is provided in both the vertical joint 5 and the horizontal joint 6, which enhances the waterproof performance of the joint and the enclosure system.

[0057] See Figure 2As shown, during the construction of the curved steel plate 3, the positioning rod 7a is first pressed into the soil, and it is ensured that the verticality of the positioning rod 7a meets the requirements. The tops of the positioning rods 7a on the inner side of the same curved steel plate 3 are connected to form a gate-shaped structure to enhance the vertical stiffness and overall stability of the curved steel plate 3; then the curved steel plate 3 is pressed into the soil along the positioning rod 7a, and the positioning rod 7a is made to enter the sleeve 7b to ensure that the verticality of the curved steel plate 3 meets the requirements.

[0058] See Figure 4 As shown, multiple rectangular steel plates 4 are vertically embedded in the vertical joint 5 between the two arc-shaped steel plates 3 in sequence, and vertical concave and convex tenons 5c are provided in the vertical Y-shaped groove 5a and at both ends of the rectangular steel plates 4 to fix the rectangular steel plates 4.

[0059] The length of the rectangular steel plate 4 located above the existing pipeline 1 is the diameter of the existing pipeline 1 + 2 times the safety distance. The length of the rectangular steel plate 4 located above the proposed pipeline 2 is the diameter of the proposed pipeline 2 + 2 times the safety distance. The net distance between the curved steel plate 3 and the vertical joint 5 is consistent with the length of the rectangular steel plate 4.

[0060] See Figure 6a 、 Figure 6b 、 Figure 7a and Figure 7b As shown, after the excavation of the foundation pit for the pipeline is completed, a cross-shaped pipe joint 8a is constructed within the foundation pit. When the proposed pipeline 2 is constructed to the connection point and the conditions for connection are met, the rectangular steel plate 4 above the proposed pipeline 2 is pulled out from the ground until the distance between the bottom of the lowest rectangular steel plate 4 and the top of the newly constructed pipeline is greater than or equal to the pipeline's safety protection distance. Then, with the support of the rectangular steel plate 4 above the proposed pipeline 2, the connection operation between the proposed pipeline 2 and the pipe joint 8a is carried out.

[0061] See Figure 10 As shown, the vertical joints 5 at both ends of the curved steel plate 3 consist of vertical Y-shaped notches 5a and a first waterproof felt 5b disposed within the notches. The force transmission structure formed by the rectangular steel plate 4 inserted into the vertical Y-shaped notches 5a effectively transmits horizontal bending moments, axial forces, and shear forces, thereby increasing the horizontal stiffness between the curved steel plate 3 and the rectangular steel plate 4.

[0062] See Figure 11As shown, a horizontal joint 6 is provided at the top of the rectangular steel plate 4, comprising a horizontal Y-shaped notch 6a and a second waterproof felt 6b disposed within the notch. A fixing ring 10 is provided at the top of the notch, and a rod 9 is used to connect the fixing ring 10 and the reserved circular hole at the bottom of the upper rectangular steel plate 4, forming a vertical force transmission structure between the upper and lower rectangular steel plates 4. This allows the lower rectangular steel plate 4 to be smoothly pulled out during the steel plate extraction and recovery phase, and can also be quickly removed after being pulled out of the ground. The bottom of the rectangular steel plate 4 is embedded in the horizontal joint 6 at the top of the rectangular steel plate 4 below it, forming a force transmission structure that can effectively transmit vertical bending moment, axial force, and shear force, thereby improving the vertical stiffness between the upper and lower rectangular steel plates 4.

[0063] Figure 1 、 Figure 3 、 Figure 5 、 Figure 8 and Figure 9 Shown are the plan layouts of various construction stages of the preferred embodiments of the present invention.

[0064] Construction phase S1 specifically includes the following steps:

[0065] S11: Layout and position the arc-shaped steel plate 3 and the positioning rod 7a on the ground. The net distance between the arc-shaped steel plate 3 and the vertical joint 5 = the pipe diameter + 2 times the safety distance. The direction of the vertical joint 5 is perpendicular to the existing pipe 1.

[0066] S12: Press the positioning rod 7a into the soil, ensuring that the verticality meets the requirements during the pressing process;

[0067] S13: Press the arc-shaped steel plate 3 into the soil along the positioning rod 7a, and make the positioning rod 7a enter the sleeve 7b to ensure that the verticality of the arc-shaped steel plate 3 meets the requirements.

[0068] Construction phase S2 specifically includes the following steps:

[0069] S21: Insert the rectangular steel plate 4 into the vertical Y-shaped notches 5a of the vertical joints 5 at both ends of the arc-shaped steel plate 3, and press the first rectangular steel plate 4 into place;

[0070] S22: Embed the second rectangular steel plate 4 into the vertical Y-shaped slots 5a of the vertical joints 5 at both ends of the arc-shaped steel plate 3, and embed its bottom into the horizontal Y-shaped slot 6a of the horizontal joint 6 at the top of the first rectangular steel plate 4, and insert the insertion rod 9 into the circular holes and the fixing ring 10 of the upper and lower rectangular steel plates 4 to realize the connection between the upper and lower rectangular steel plates 4.

[0071] S23: Continue to press the second rectangular steel plate 4 into the ground.

[0072] S24: Repeat steps S22 to S23 above the existing pipeline 1 until the distance between the bottom of the lowest rectangular steel plate 4 and the top of the existing pipeline 1 is greater than or equal to the safety protection distance of the pipeline; repeat steps S22 to S23 at the planned pipeline 2 on both sides of the existing pipeline until the bottom of the lowest rectangular steel plate 4 is flush with the bottom of the curved steel plate 3.

[0073] In the construction phase S3, dewatering and earth excavation are carried out in the pit. After excavation to the bottom of the pit, the existing pipeline 1 at the connection point is partially removed, and a cross-shaped pipe joint 8a and a flange joint 8b are installed.

[0074] In construction phase S4, the rectangular steel plates 4 at the proposed pipeline 2 are sequentially pulled out of the ground until the distance between the bottom of the lowest rectangular steel plate 4 and the top of the proposed pipeline 2 meets the pipeline's safety protection distance. With the support of the rectangular steel plates 4 above the proposed pipeline 2, the proposed pipeline 2 is connected to the installed pipe joint 8a.

[0075] In the construction stage S5, after the pipeline pressure test is completed, the foundation pit of the connection point is backfilled and the remaining rectangular steel plate 4 is removed.

[0076] In construction stage S6, the curved steel plate 3 is removed. During the removal process, the positioning rod 7a is used to synchronously inject grout to fill the soil voids created by the removal of the curved steel plate 3. After that, the positioning rod 7a is removed and secondary grouting is performed to fill the soil voids created by the removal of the positioning rod 7a.

[0077] The above are only preferred embodiments of the present invention and do not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A foundation pit retaining structure for pipe connection point construction, characterized in that: It includes four arc-shaped steel plates symmetrically arranged around the existing pipeline and the planned pipeline with the connection point as the center. The arc-shaped steel plates maintain a certain distance from the existing pipeline and the planned pipeline. Two adjacent arc-shaped steel plates are connected by multiple rectangular steel plates. The arc-shaped steel plates and the rectangular steel plates form a rectangle with four arc corners in the plan view.

2. The foundation pit retaining structure for pipe connection point construction according to claim 1, characterized in that: The left and right ends of the arc-shaped steel plate are respectively provided with vertical joints, and a plurality of rectangular steel plates are vertically embedded in the vertical joints between two arc-shaped steel plates in sequence.

3. The foundation pit retaining structure for pipe connection point construction according to claim 2, characterized in that: The vertical joint includes a vertical Y-shaped notch and a first waterproof felt arranged in the vertical Y-shaped notch. Vertical concave and convex tenons are respectively provided in the vertical Y-shaped notch and at both ends of the rectangular steel plate.

4. The foundation pit retaining structure for pipe connection point construction according to claim 1, characterized in that: A horizontal joint is provided on the top of the rectangular steel plate, and the bottom of each rectangular steel plate is embedded in the horizontal joint located on the top of the rectangular steel plate.

5. The foundation pit retaining structure for pipe connection point construction according to claim 4, characterized in that: The horizontal joint includes a horizontal Y-shaped slot and a second waterproof felt arranged in the horizontal Y-shaped slot. A fixing ring is provided at the top of the horizontal Y-shaped slot, and a circular hole is opened at the bottom of the rectangular steel plate. A rod is inserted into the circular hole and the fixing ring of the rectangular steel plate.

6. The foundation pit retaining structure for pipe connection point construction according to claim 1, characterized in that: The inner side of the arc-shaped steel plate is provided with a matching positioning rod and a sleeve, and the tops of the positioning rods are connected to form a door-shaped structure.

7. A construction method for a foundation pit retaining structure for pipe connection point construction, characterized in that: The following steps are involved: S1: At the location of the planned connection point of the existing pipeline, four curved steel plates are pressed from the ground. The four curved steel plates are symmetrically arranged with the connection point as the center; S2: rectangular steel plate pressed into the ground; S3: Carry out pit dewatering and earth excavation. After excavating to the bottom of the pit, remove the existing local pipelines at the connection points and install pipe joints. S4: Pull out the rectangular steel plates at the proposed pipeline from the ground one by one until the distance between the bottom of the lowest rectangular steel plate and the top of the proposed pipeline is greater than the safety protection distance of the pipeline. Under the support of the rectangular steel plate above the proposed pipeline, carry out the pipe connection operation to connect the proposed pipeline with the installed pipeline joint; S5: After the pipeline pressure test is completed, backfill the foundation pit at the connection point and remove the remaining rectangular steel plates; S6: Pull out the curved steel plate. During the removal process, the positioning rod is used to synchronously inject grout to fill the soil voids caused by the removal of the curved steel plate. After that, the positioning rod is pulled out and secondary grouting is performed to fill the soil voids caused by the removal of the positioning rod.

8. The method for constructing a foundation pit retaining structure for connecting a connection point as claimed in claim 7, wherein: Step S1 includes: S11: Layout and locate the curved steel plates and positioning rods on the ground. The net distance between the vertical joints of the curved steel plates is the pipe diameter + 2 times the safety distance. The vertical joints are oriented perpendicular to the pipe. S12: Press the positioning rod into the soil, ensuring that the verticality meets the requirements during the pressing process; S13: Press the arc-shaped steel plate into the soil along the positioning rod, and make the positioning rod enter the sleeve to ensure that the verticality of the arc-shaped steel plate meets the requirements.

9. The method for constructing a foundation pit retaining structure for connecting point construction according to claim 7, wherein: Step S2 includes: S21: inserting the rectangular steel plate into the vertical Y-shaped notches of the vertical joints at both ends of the curved steel plate, and pressing the first rectangular steel plate into place; S22: Insert the second rectangular steel plate into the vertical Y-shaped notches at both ends of the curved steel plate, and insert the bottom of the second rectangular steel plate into the horizontal Y-shaped notch at the top of the first rectangular steel plate, and fix the upper and lower rectangular steel plates with a rod; S23: Continue to press the second rectangular steel plate into the ground; S24: Repeat steps S22 to S23 above the existing pipeline until the distance between the bottom of the lowest rectangular steel plate and the top of the existing pipeline is greater than or equal to the safety protection distance of the pipeline; repeat steps S22 to S23 at the proposed pipeline until the bottom of the lowest rectangular steel plate is flush with the bottom of the curved steel plate.

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