Trench foundation jet grouting and steel plate collaborative support method
Patent Information
- Application Number
- CN202611216453.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-12
- Publication Date
- 2026-09-29
AI Technical Summary
[0003]本发明的目的在于克服现有技术存在的不足，而提供一种沟槽基坑旋喷固结和钢板协同支护方法，旨在解决新开挖沟槽从既有管线上方垂直穿越时，钢板桩不连续以及支护局部支撑强度不足，引起的基坑渗漏、倾斜甚至倒塌等隐患
[0015]作为优选，所述混凝土管预制基座为整体预制，所述混凝土管预制基座的左右两侧与所述钢板支护组件相接触，所述混凝土管预制基座两端的预留钢筋与钢板桩支护组件内现浇混凝土管基座连接固定；且所述混凝土管预制基座的横截面为凸字形结构，其正中心设置有用于搁置新建管道的搁置槽，左右两侧为台阶状；通过上述结构的设置，有效减少了沟槽开挖到底部后人工在沟槽中施工的时间和混凝土养护的时间，提升了施工效率和施工安全性，同时，左右两侧为台阶状，在搁置过程中，因接触面积小，与钢板支护组件之间的贴合及对齐更为便捷，而且，当新建管道搁置完成后，土体复原并压实之后，使得土体与新建管道之间的径向力能大部分消抵在呈台阶状的左右两侧面处，降低了管道施工作业对于下方现有管道的影响。
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Figure CN122833997A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of civil engineering technology, and in particular relates to a method for combined jet grouting consolidation and steel plate support in trench foundation pits. Background Technology
[0002] With the advancement of urban construction, a large number of complex underground pipelines already exist in cities. While these pipelines do not affect the space for new pipelines, they can hinder their construction. For situations where new pipelines are to be constructed vertically above existing ones, current construction methods typically employ trenching with sheet pile support. However, in some areas above existing pipelines, sheet piles often cannot be driven deeper into the soil below the existing pipelines. Furthermore, this trenching method generally only allows sheet piles to be driven to the portion above the existing pipeline in that section, or to be connected to the sheet piles with retaining walls. Although this construction method is relatively mature, simple, and efficient, it often results in discontinuous sheet piles, insufficient local embedment depth, changes in lateral pressure in the foundation pit, and safety hazards such as pit leakage, pile tilting, cracking, and even collapse. Summary of the Invention
[0003] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a method for jet grouting consolidation and steel sheet pile co-support in trench foundation pits. This method aims to solve the hidden dangers of foundation pit leakage, tilting or even collapse caused by the discontinuity of steel sheet piles and insufficient local support strength when a newly excavated trench passes vertically above an existing pipeline.
[0004] The objective of this invention is achieved through the following technical solution: a method for combined jet grouting consolidation and steel plate support in trench foundation pits, comprising the following steps: S1. Measurement and positioning, site leveling and trenching of the new pipeline, determining the specific construction range affected by the existing pipeline, the support range of the steel plate support component is the support on both sides along the direction of the new pipeline, and the length of the support is twice the diameter d of the existing pipeline on both sides, the width of the support is D, and the steel plate support component is vertically perpendicular to the existing pipeline. S2. For the support of the steel sheet pile support components, after the site is leveled, steel sheet piles are driven into the ground outside the construction influence range of the steel sheet support components. The piles are driven to the designed depth and interlocked with each other. The steel sheet pile support components are supported on both sides along the direction of the new pipeline, and their width is consistent with the width D of the steel sheet support components. S3. Support of steel sheet support components: After the steel sheet pile construction is completed, steel sheet construction is carried out within the influence range, and the steel sheet is driven to 0.5 to 1m below the bottom of the excavated pit. S4. Determine the pile formation range of the high-pressure jet grouting pile at the intersection between the new pipeline and the existing pipeline. The pile formation range inside the steel plate is 2m deep from the bottom of the trench to the top of the existing pipeline, and the pile formation range outside the steel plate is D range outside the steel plate support components. S5. For high-pressure jet grouting pile construction, the inner side of the steel plate support assembly is constructed first, followed by the outer side of the steel plate support assembly. The bottom of the steel plate is solidified and fixed by high-pressure jet grouting piles. S6. Excavation of earthwork within the construction area of the new pipeline shall be carried out vertically in stages and sections, with steel support rods installed before excavation. S7. Installation of precast concrete pipe base: After the earthwork is excavated, the precast concrete pipe base is hoisted at an angle to the inside of the steel plate support assembly by a crane and placed on top of the bottom high-pressure jet grouting pile. Both ends are connected to the existing structure through reserved steel bars.
[0005] The beneficial effects of this invention are as follows: Compared with the prior art, within the area where the new pipeline intersects with the existing pipeline, the overall stability of the foundation pit is improved through the combined support method of steel plate support components, high-pressure jet grouting piles (on the sides and bottom of the trench), and steel supports; the gravity dam of the high-pressure jet grouting piles on the sides enhances the stability of the soil around the foundation pit, and the auxiliary steel plates connect the high-pressure jet grouting piles with the outer steel sheet piles as a whole, resulting in better stress performance and avoiding the risk of foundation pit tilting and collapse caused by discontinuity of steel sheet piles; combined with the high-pressure jet grouting piles at the bottom, the groundwater channel is isolated, effectively solving the risk of foundation pit leakage and effectively protecting the existing underground pipelines; at the same time, the use of precast concrete pipe bases instead of cast-in-place concrete effectively reduces the time spent on manual construction in the trench after the trench is excavated to the bottom and the time for concrete curing, greatly improving construction efficiency and safety, and reducing the impact of pipeline construction on the existing pipelines below.
[0006] As a preferred option, in step S5, high-pressure jet grouting piles are constructed. The pile diameter is 500mm, with a 100mm overlap, using a single-pipe method. Each meter is mixed with ordinary Portland cement and chloride at a ratio of 50:1, achieving a compressive strength of not less than 1.2 MPa after 28 days. Depending on the characteristics of different geological soil layers, appropriate measures must be taken. For hard soil, clay, and deep soil layers, the lifting and rotation speeds should be appropriately slowed down, or the jet grouting pressure should be increased. Because the geological conditions of natural foundations are complex, using a single technical parameter for jet grouting will result in a consolidation body with extremely uneven diameter, leading to inconsistent jet grouting diameters and affecting bearing capacity. Therefore, appropriate measures must be taken according to the characteristics of different geological soil layers. For hard soil, clay, and deep soil layers, the lifting and rotation speeds should be appropriately slowed down, or the jet grouting pressure should be increased, significantly improving the bearing capacity of the high-pressure jet grouting piles.
[0007] As a preferred method, in step S6, the section excavation method is as follows: first excavate the soil inside the sheet pile support components, then excavate the soil inside the sheet support components, and vertically excavate to 0.5m below the center line of the horizontal brace, then construct steel support rods. The excavation thickness of each layer should not exceed 1m, leaving 0.2-0.3m at the bottom for manual excavation. By excavating the soil inside the sheet pile support components first, and then excavating the soil inside the sheet support components, the soil at the pipe intersection is less likely to collapse during the excavation process. The use of steel support rods and the stability of the sheet pile and sheet support are also better. At the same time, the excavation thickness and the manual excavation at the bottom can be adjusted according to the actual trench depth required, resulting in better accuracy.
[0008] Preferably, in step S7, the length of the precast concrete pipe base is equal to the length of the steel plate support assembly, and the reserved reinforcing bars at both ends extend out of the steel plate support assembly and into the steel sheet pile support assembly. When the concrete base is cast in place within the steel sheet pile support assembly, at the intersection of the cast-in-place concrete base and the precast concrete pipe base, the reserved reinforcing bars are embedded in the cast-in-place concrete base, and the horizontal height of the newly constructed pipeline resting on the cast-in-place concrete base is flush with the horizontal height of the precast concrete pipe base. Through the implementation of the above steps, the construction at the intersection of the new pipeline and the existing pipeline is more efficient. It is highly efficient, and the cast-in-place concrete foundation can be directly cast at the height of the precast concrete pipe foundation during the pouring process. This results in a better horizontal height of the support surface for the new pipeline. In addition, the reserved steel bars are set, and the length of the precast concrete pipe foundation is equal to the length of the steel plate support component. This reduces the risk of pit leakage in the construction area where the new pipeline intersects with the existing pipeline, improves the overall stress performance, and makes it less prone to cracking. It greatly solves the hidden dangers of pit leakage, tilting, or even collapse caused by the discontinuity of steel sheet piles and insufficient local support strength when the newly excavated trench crosses vertically above the existing pipeline.
[0009] Preferably, the new pipeline is constructed with bottom high-pressure jet grouting piles below it and side high-pressure jet grouting piles on both sides. Both the bottom and side high-pressure jet grouting piles are located above the existing pipeline. The steel sheet pile support assembly is located on both sides of the new pipeline along its length and is fixed between the bottom and side high-pressure jet grouting piles. The steel sheet pile support assembly is connected to both sides of the steel sheet pile support assembly and extends along the length of the new pipeline. With the above structure, steel sheet piles cannot be constructed above the existing pipeline and within the protection area of the existing pipeline. A high-pressure jet grouting pile gravity dam is used instead of steel sheet pile support. To increase the safety and stability of the foundation pit, a 2m thick high-pressure jet grouting pile is installed at the bottom of the foundation pit for reinforcement. At the same time, steel plate reinforcement is added on both sides of the trench to connect the jet grouting piles and the external steel sheet pile support into a whole.
[0010] Preferably, the bottom of the bottom high-pressure jet grouting pile and the bottom of the side high-pressure jet grouting pile are both on the same plane. The top of the side high-pressure jet grouting pile is at the same height as the steel sheet support assembly, and the bottom of the steel sheet support assembly is located below the bottom plane of the bottom high-pressure jet grouting pile and the side high-pressure jet grouting pile and above the existing pipeline. The bottom of the steel sheet pile support assembly is lower than the bottom of the existing pipeline. With the above structure, the high-pressure jet grouting pile and the steel sheet pile support assembly are connected into a whole by the steel sheet support assembly, resulting in better stress performance. In the construction area where the new pipeline intersects with the existing pipeline, not only is the risk of pit tilting and collapse caused by discontinuity of steel sheet piles avoided, but the risk of pit leakage is also effectively solved.
[0011] Preferably, the length of the high-pressure jet grouting pile is twice the width of the steel plate support assembly extending to both sides in the width direction, and the width of the high-pressure jet grouting pile is twice the width of the existing pipeline extending to both sides in the width direction, and the length of the steel plate support assembly is equal to the width of the high-pressure jet grouting pile; through the above structural arrangement, the foundation pit at the intersection of the existing pipeline and the new pipeline has better stability and better stress performance.
[0012] Preferably, the steel plate support assembly consists of three steel plates and three steel support rods. The steel plate located in the center is positioned directly above the existing pipeline, while the bottoms of the other two steel plates are lower than the bottom of the existing pipeline. The three steel support rods are each supported on one of the three corresponding steel plates. By setting up the above structure and ensuring that the bottoms of the two steel plates are lower than the bottom of the existing pipeline, the risk of leakage in the foundation pit is greatly reduced. At the same time, it also ensures the straightness between the steel plates and sheet piles in the connecting section within and outside the influence area of the foundation pit, resulting in better overall stress distribution.
[0013] Preferably, the steel plate is provided with latches on both sides, and the latches are arranged along the height direction of the steel plate. Adjacent steel plates are fixed together by the latches. The above structure improves the stability between adjacent steel plates, makes disassembly and assembly convenient, and improves the overall stress performance.
[0014] Preferably, the sheet pile support assembly consists of several sheet piles, and the sheet piles are fixed to the sheet piles by means of a connecting buckle on one side of the sheet pile and a locking buckle. Adjacent sheet piles are fixed to each other by means of their respective connecting buckles. The above structure makes the stability between adjacent sheet piles better and the disassembly and assembly more convenient.
[0015] Preferably, the precast concrete pipe base is integrally precast. The left and right sides of the precast concrete pipe base are in contact with the steel plate support assembly. The reserved reinforcing bars at both ends of the precast concrete pipe base are connected and fixed to the cast-in-place concrete pipe base inside the steel sheet pile support assembly. The cross-section of the precast concrete pipe base is a convex structure with a support groove for supporting the new pipeline at its center and stepped sides. The above structure effectively reduces the time for manual construction in the trench after the trench is excavated to the bottom and the time for concrete curing, improving construction efficiency and safety. At the same time, the stepped sides make it easier to fit and align with the steel plate support assembly during the support process due to the small contact area. Moreover, after the new pipeline is supported and the soil is restored and compacted, most of the radial force between the soil and the new pipeline can be offset at the stepped left and right sides, reducing the impact of pipeline construction on the existing pipeline below. Attached Figure Description
[0016] Figure 1 This is a schematic diagram of the main structure of the support device of the present invention.
[0017] Figure 2 This is a top view schematic diagram of the support device of the present invention.
[0018] Figure 3 This is a schematic diagram of the structure between the steel plate and the steel sheet pile of the present invention.
[0019] Figure 4 This is a schematic diagram of the structure between the steel plates of the present invention.
[0020] Figure 5 This is a front view schematic diagram of the precast concrete pipe base structure of the present invention.
[0021] Figure 6 This is a top view schematic diagram of the precast concrete pipe base structure of the present invention.
[0022] The labels in the attached diagram are as follows: 1. High-pressure jet grouting pile; 2. Steel sheet support assembly; 3. Steel sheet pile support assembly; 4. New pipeline; 5. Existing pipeline; 6. Precast concrete pipe base; 11. Bottom high-pressure jet grouting pile; 12. Side high-pressure jet grouting pile; 21. Steel plate; 22. Steel support rod; 23. Locking buckle; 31. Steel sheet pile; 32. Connecting buckle; 61. Reserved reinforcing steel. Detailed Implementation
[0023] The invention will now be described in detail with reference to the accompanying drawings: as shown in the drawings Figures 1 to 6 As shown, the support method of the present invention includes the following steps: S1. Measurement and positioning, site leveling and layout of the trench and foundation pit for the new pipeline 4, determining the specific construction range affected by the existing pipeline 5 when excavating the trench and foundation pit. The support range of the steel plate support component 2 is the support on both sides along the direction of the new pipeline 4, and the length of the support is twice the diameter d of the existing pipeline 5 on both sides. The width of the support is D, and the steel plate support component 2 is vertically perpendicular to the existing pipeline 5. The load-bearing range at the intersection between the new pipeline 4 and the existing pipeline 5 is twice the width on both sides of the intersection. This makes the load-bearing capacity at the intersection between the new pipeline 4 and the existing pipeline 5 more stable. When excavating the trench at the intersection, the load-bearing range is larger, and the load-bearing capacity is guaranteed on all sides, while the seepage prevention is better. S2, the support of the steel sheet pile support component 3: after the site is leveled, the steel sheet piles are driven into the ground outside the construction influence range of the steel sheet support component 2, driven to the design depth and interlocked with each other. The steel sheet pile support component 3 supports both sides along the direction of the new pipeline 4, and its width is consistent with the width D of the steel sheet support component 2. S3. For the support of steel sheet support component 2, after the steel sheet pile construction is completed, steel plates are installed within the affected area and driven to 0.5-1m below the bottom of the excavated pit. Specifically, the steel plates in contact with the existing pipeline 5 are driven above the existing pipeline 5, and the remaining steel plates are driven to 0.5-1m below the bottom of the excavated pit. This not only makes the support more stable, but also makes the connection between the steel sheet pile and the support more stable, thus making the overall trench pit retaining stability better. S4. The pile formation range of the high-pressure jet grouting piles is determined at the intersection between the newly built pipeline 4 and the existing pipeline 5. The pile formation range inside the steel plate is 2m deep from the bottom of the trench to the top of the existing pipeline, and the pile formation range outside the steel plate is the area D outside the steel plate support component 2. The effect is that steel sheet piles cannot be constructed above the existing pipeline and within the protection area of the existing pipeline, so the high-pressure jet grouting pile gravity dam is used to replace the steel sheet pile support. In order to increase the safety and stability of the foundation pit, a 2m thick high-pressure jet grouting pile is set at the bottom of the foundation pit for bottom reinforcement. At the same time, steel plate reinforcement is added on both sides of the trench to connect the jet grouting piles with the external steel sheet pile support into a whole. Combined with the high-pressure jet grouting piles at the bottom of the newly built pipeline at the intersection, the groundwater channel is isolated, effectively solving the risk of foundation pit leakage and effectively protecting the existing underground pipelines. S5. For the construction of high-pressure jet grouting pile 1, the inner side of the steel plate support component 2 is constructed first, and then the outer side of the steel plate support component 2 is constructed. The bottom of the steel plate is fixed by high-pressure jet grouting pile 1. S6. Excavation of earthwork within the construction area of the new pipeline 4 shall be carried out vertically in stages and sections, with steel support rods installed before excavation. S7. Installation of precast concrete pipe base 6: After the earthwork is excavated, the precast concrete pipe base 6 is hoisted at an angle to the inside of the steel plate support component 2 by a crane and placed above the bottom high-pressure jet grouting pile 11. Both ends are connected to the existing structure through reserved steel bars 61.
[0024] In step S5, the high-pressure jet grouting pile 1 is constructed. The high-pressure jet grouting pile 1 has a diameter of 500mm and an overlap of 100mm. It is constructed using the single-pipe method. Ordinary Portland cement and chloride are mixed in a 50:1 ratio per meter. The compressive strength after 28 days is not less than 1.2MPa. Depending on the characteristics of different geological soil layers, corresponding measures should be taken. For hard soil, clay, and deep soil layers, the lifting speed and rotation speed should be appropriately slowed down or the jet grouting pressure should be increased.
[0025] In step S6, the method of excavating soil in sections is as follows: first excavate the soil inside the steel sheet pile support component 3, then excavate the soil inside the steel sheet support component 2, and excavate vertically to 0.5m below the center line of the horizontal brace, and construct steel support rods 22. The excavation thickness of each layer is no more than 1m, and leave 0.2-0.3m at the bottom for manual excavation.
[0026] In step S7, the length of the precast concrete pipe base 6 is equal to the length of the steel plate support component 2, and the reserved reinforcing bars 61 at both ends extend out of the steel plate support component 2 and into the steel sheet pile support component 3. When the concrete base is cast in place in the steel sheet pile support component 3, at the intersection of the cast-in-place concrete base and the precast concrete pipe base 6, the reserved reinforcing bars 61 are embedded in the cast-in-place concrete base, and the horizontal height of the newly built pipe 4 placed on the cast-in-place concrete base is the same as the horizontal height of the precast concrete pipe base 6.
[0027] The new pipeline 4 is piled with a bottom high-pressure jet grouting pile 11 below it, and piled with a side high-pressure jet grouting pile 12 on both sides of the new pipeline 4. The bottom high-pressure jet grouting pile 11 and the side high-pressure jet grouting pile 12 are both located above the existing pipeline 5. The steel plate support assembly 2 is located on both sides of the length direction of the new pipeline 4 and is fixed between the bottom high-pressure jet grouting pile 11 and the side high-pressure jet grouting pile 12. The steel sheet pile support assembly 3 is connected to both sides of the steel sheet support assembly 2 and extends along the length direction of the new pipeline 4.
[0028] The bottom of the bottom high-pressure jet grouting pile 11 and the bottom of the side high-pressure jet grouting pile 12 are both on the same plane. The top of the side high-pressure jet grouting pile 12 is at the same height as the steel plate support component 2. The bottom of the steel plate support component 2 is located below the bottom plane of the bottom high-pressure jet grouting pile 11 and the side high-pressure jet grouting pile 12 and above the existing pipeline 5. The bottom of the steel sheet pile support component 3 is lower than the bottom of the existing pipeline 5.
[0029] The length of the high-pressure jet grouting pile 1 is twice the width of the steel plate support component 2 extending to both sides in the width direction. The width of the high-pressure jet grouting pile 1 is twice the width of the existing pipeline 5 extending to both sides in the width direction. The length of the steel plate support component 2 is equal to the width of the high-pressure jet grouting pile 1.
[0030] The steel plate support assembly 2 consists of three steel plates 21 and three steel support rods 22. The steel plate 21 located in the center is directly above the existing pipeline 5, while the bottoms of the other two steel plates 21 are lower than the bottom of the existing pipeline 5. The three steel support rods 22 are supported on the three opposite steel plates 21 respectively.
[0031] Both sides of the steel plate 21 are provided with latches 23, and the latches 23 are set along the height direction of the steel plate 21. Adjacent steel plates 21 are fixed together by latches 23.
[0032] The sheet pile support assembly 3 is composed of several sheet piles 31. The sheet piles 31 and the sheet 21 are fastened together by a connecting buckle 32 and a locking buckle 23 on one side of the sheet pile 31. Adjacent sheet piles 31 are fastened together by their respective connecting buckles 32.
[0033] The precast concrete pipe base 6 is precast as a whole. The left and right sides of the precast concrete pipe base 6 are in contact with the steel plate support component 2. The reserved steel bars 61 at both ends of the precast concrete pipe base 6 are connected and fixed to the cast-in-place concrete pipe base in the steel sheet pile support component 3. The cross-section of the precast concrete pipe base 6 is a convex structure, with a support groove for supporting the newly built pipe 4 set in the center, and the left and right sides are stepped.
[0034] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.
Claims
1. A method for combined jet grouting consolidation and steel plate support in trench foundation pits, characterized in that: This support method includes the following steps: S1. Measurement and positioning, site leveling and trenching of the new pipeline (4), determine the specific construction range affected by the existing pipeline (5) in the excavation of the trench and foundation pit, the support range of the steel plate support component (2) is the support on both sides along the direction of the new pipeline (4), and the length of the support is twice the diameter d of the existing pipeline (5) on both sides, the width of the support is D, and the steel plate support component (2) is vertically perpendicular to the existing pipeline (5); S2, the support of the steel sheet pile support component (3), after the site is leveled, the steel sheet piles are driven outside the construction influence range of the steel sheet support component (2), driven to the design depth and interlocked with each other, and the steel sheet pile support component (3) is supported on both sides along the direction of the new pipeline (4), and its width is consistent with the width D of the steel sheet support component (2). S3, support of steel sheet support components (2), after the steel sheet pile construction is completed, steel sheet construction is carried out within the influence range, and the steel sheet is driven to 0.5 to 1m below the bottom of the excavated pit; S4. Determine the pile range of the high-pressure jet grouting pile at the intersection between the new pipeline (4) and the existing pipeline (5). The pile range inside the steel plate is 2m deep from the bottom of the trench to the top of the existing pipeline, and the pile range outside the steel plate is D range outside the steel plate support component (2). S5. For the construction of high-pressure jet grouting piles (1), first construct the inner side of the steel plate support assembly (2), then construct the outer side of the steel plate support assembly (2). The bottom of the steel plate is solidified and fixed by high-pressure jet grouting piles (1). S6. Excavation of earthwork within the construction scope of the new pipeline (4) shall be carried out vertically in stages and sections, and steel support rods shall be installed before earthwork is excavated. S7. Installation of precast concrete pipe base (6): After the earthwork is excavated, the precast concrete pipe base (6) is hoisted obliquely to the inside of the steel plate support assembly (2) by a crane and placed on the bottom high-pressure jet grouting pile (11). Both ends are connected to the existing structure through reserved steel bars (61).
2. The method for combined jet grouting consolidation and steel plate support in trench foundation pits according to claim 1, characterized in that: In step S5, the high-pressure jet grouting pile (1) is constructed. The high-pressure jet grouting pile (1) has a pile diameter of 500mm and an overlap of 100mm. It is constructed using the single-pipe method. Ordinary silicate cement and chloride are mixed in a ratio of 50:1 per meter. The compressive strength after 28 days is not less than 1.2MP. In addition, appropriate measures should be taken according to the characteristics of different geological soil layers. For hard soil, clay and deep soil layers, the lifting speed and rotation speed should be appropriately slowed down or the jet grouting pressure should be increased.
3. The method for combined jet grouting consolidation and steel plate support in trench foundation pits according to claim 1, characterized in that: In step S6, the method of excavating soil in sections is as follows: first excavate the soil inside the steel sheet pile support component (3), then excavate the soil inside the steel sheet support component (2), and in the vertical excavation to 0.5m below the center line of the horizontal support, construct the steel support rod (22), the excavation thickness of each layer is not greater than 1m, and leave 0.2-0.3m at the bottom for manual excavation.
4. The method for combined jet grouting consolidation and steel plate support in trench foundation pits according to claim 1, characterized in that: In step S7, the length of the precast concrete pipe base (6) is equal to the length of the steel plate support assembly (2), and the reserved steel bars (61) at both ends extend out of the steel plate support assembly (2) and into the steel sheet pile support assembly (3). When the concrete base is cast in place in the steel sheet pile support assembly (3), at the intersection of the cast-in-place concrete base and the precast concrete pipe base (6), the reserved steel bars (61) are embedded in the cast-in-place concrete base, and the horizontal height of the newly built pipe (4) on the cast-in-place concrete base is the same as the horizontal height of the precast concrete pipe base (6).
5. The method for combined jet grouting consolidation and steel plate support in trench foundation pits according to claim 1, characterized in that: The newly constructed pipeline (4) has a bottom high-pressure jet grouting pile (11) piled below it, and a side high-pressure jet grouting pile (12) piled on both sides of the newly constructed pipeline (4). The bottom high-pressure jet grouting pile (11) and the side high-pressure jet grouting pile (12) are both located above the existing pipeline (5). The steel plate support assembly (2) is located on both sides of the length direction of the newly constructed pipeline (4) and fixed between the bottom high-pressure jet grouting pile (11) and the side high-pressure jet grouting pile (12). The steel sheet pile support assembly (3) is connected to both sides of the steel plate support assembly (2) and extends along the length direction of the newly constructed pipeline (4).
6. The method for combined jet grouting consolidation and steel plate support in trench foundation pits according to claim 5, characterized in that: The bottom of the bottom high-pressure jet grouting pile (11) and the bottom of the side high-pressure jet grouting pile (12) are both on the same plane. The top of the side high-pressure jet grouting pile (12) is at the same height as the steel plate support assembly (2). The bottom of the steel plate support assembly (2) is below the bottom plane of the bottom high-pressure jet grouting pile (11) and the side high-pressure jet grouting pile (12) and above the existing pipeline (5). The bottom of the steel sheet pile support assembly (3) is lower than the bottom of the existing pipeline (5).
7. The method for combined jet grouting consolidation and steel plate support in trench foundation pits according to claim 5, characterized in that: The length of the high-pressure jet grouting pile (1) is twice the width of the steel plate support assembly (2) extending to both sides in the width direction. The width of the high-pressure jet grouting pile (1) is twice the width of the existing pipeline (5) extending to both sides in the width direction. The length of the steel plate support assembly (2) is equal to the width of the high-pressure jet grouting pile (1).
8. The method for combined jet grouting consolidation and steel plate support in trench foundation pits according to claim 1, characterized in that: The steel plate support assembly (2) consists of three steel plates (21) and three steel support rods (22). The steel plate (21) located in the center is located directly above the existing pipe (5). The bottoms of the other two steel plates (21) are lower than the bottom of the existing pipe (5). The three steel support rods (22) are supported on the three opposite steel plates (21). The steel plates (21) are provided with buckles (23) on both sides, and the buckles (23) are set along the height direction of the steel plates (21). Adjacent steel plates (21) are locked together by the buckles (23).
9. The method for combined jet grouting consolidation and steel plate support in trench foundation pits according to claim 8, characterized in that: The sheet pile support assembly (3) is composed of several sheet piles (31). The sheet piles (31) and the steel plates (21) are fastened together by the connecting buckle (32) on one side of the sheet pile (31) and the locking buckle (23). Adjacent sheet piles (31) are fastened together by their respective connecting buckles (32).
10. The method for combined jet grouting consolidation and steel plate support in trench foundation pits according to claim 1, characterized in that: The precast concrete pipe base (6) is precast as a whole. The left and right sides of the precast concrete pipe base (6) are in contact with the steel plate support assembly (2). The reserved steel bars (61) at both ends of the precast concrete pipe base (6) are connected and fixed to the cast-in-place concrete pipe base in the steel sheet pile support assembly (3). The cross-section of the precast concrete pipe base (6) is a convex structure, and a support groove for supporting the newly built pipe (4) is provided in the center. The left and right sides are stepped.