A construction method for high and low-amplitude diaphragm walls on stepped terrain

Abstract

The present invention discloses a method for constructing high and low-amplitude ground diaphragm walls on stepped terrain, which is mainly suitable for the construction of deep foundation pit retaining structures. The construction process includes the optimized construction of multi-elevation ground diaphragm walls on stepped terrain and the connection construction of high and low-amplitude ground diaphragm walls. In view of the difficulties in construction operations on stepped sites and the connection construction of sudden changes in high and low-amplitude ground diaphragm walls, the construction process is reasonably divided into three construction stages: the first stage completes the construction of low-elevation ground diaphragm walls, the second stage completes the construction of high-elevation ground diaphragm walls, and the third stage backfills the soil on the basis of the first stage to increase the high-field leveling section trenching machine's high working surface to construct transition sections with different elevations; the problem of misaligned connection is solved by backfilling at the connection, setting up blocking templates, arranging crawler crane hoisting and other multi-link coordination. This method effectively solves the problem of complex ground diaphragm wall construction caused by inconsistent site leveling elevations, ensures the smooth progress of the project, and improves construction quality and efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of deep foundation pit enclosure construction, and in particular to a method for constructing a high-low-amplitude ground-connected wall on stepped terrain. Background Art

[0002] In subway station construction, underground diaphragm walls are often used as retaining structures for deep foundation pit construction. Stations are often built on municipal roads, with flat sites, uniform ground-connected wall elevations, and an excellent working environment. However, in some station construction scenarios outside of urban main roads, the station foundation pit is partially adjacent to high-slope embankments or mountains. To reduce the impact of eccentric pressure from embankment fill and mountains on foundation pit excavation, the design typically adopts a ground layout with a different elevation difference between the eccentric area and the rest of the section, forming a high-low span ground-connected wall structure. This lacks an effective working surface for trenching and steel cage hoisting, significantly increasing the construction difficulty and requiring repeated equipment deployment and high-support formwork construction for local ground-connected walls. This poses severe challenges and safety risks to the construction of the entire subway station's retaining structure.

[0003] The current standard construction practice involves deploying a trenching machine and crawler crane on the elevated flat section to handle construction. For localized diaphragm walls above ground, a two-step construction process is employed: 1. Conventional underwater construction techniques are used to construct the subsurface portion, followed by the protruding portion above ground using high-support formwork and piling. 2. For diaphragm wall construction on sloping sites, a supplementary backfill method is employed to create a high-step platform to provide a working surface for diaphragm wall trenching and slurry wall protection. This construction process is complex and unsafe.

[0004] In summary, there are many problems in the construction of conventional diaphragm walls on stepped terrain and with high and low amplitudes. There is an urgent need for a safe, convenient and scientific diaphragm wall construction method suitable for stepped terrain and with high and low amplitudes. Summary of the Invention

[0005] The purpose of the present invention is to address the problems existing in the prior art and provide a method for constructing high-low-amplitude diaphragm walls on stepped terrain, so as to solve the problems of unreasonable construction sequence on stepped terrain, complex construction procedures for sudden changes in the connection sections of high-low-amplitude diaphragm walls, and low safety in traditional construction methods, thereby meeting the needs of safe construction of underground projects such as track construction and station excavation.

[0006] The present invention is achieved by adopting the following technical solutions:

[0007] A method for constructing a high-low-amplitude diaphragm wall on a stepped terrain includes optimizing the construction process of the multi-elevation diaphragm wall on the stepped terrain and connecting the high-low-amplitude diaphragm wall. The construction steps are as follows:

[0008] Step 1: Divide the construction area into three parts: low-level area, high-level area and site slope area. Divide the regional ground-connected wall into three stages of construction: the first stage is to construct the ground-connected wall at the low-level area, the second stage is to construct the ground-connected wall at the high-level area, and the third stage is to connect and construct the ground-connected wall at the high-low amplitude sudden change section. Backfill the soil on the basis of the first stage to increase the high-level flat section trenching machine's high working surface and construct transition sections at different elevations. The optimized construction process of the multi-elevation ground-connected wall on the stepped terrain comprehensively considers the lifting capacity of the crawler crane and the safety operation requirements of the trenching machine's edge before construction, and plans two site step slope positions. The first slope is to complete the lifting of all the ground-connected walls on the high step. The second backfill slope is to ensure that the trenching machine has sufficient edge working width in the site slope connection section to complete the trenching construction, thereby avoiding the crawler crane from climbing back and forth.

[0009] Step 2: Slope the site side slope according to the construction area division to ensure that the slope foot does not affect the construction of the low-field flat ground connecting wall, and then complete the construction of the low-field flat ground connecting wall.

[0010] Step 3: Arrange crawler crane at low elevation site, calculate whether the lifting height is met based on the length of steel cage, length of hoisting device, site elevation and working range of crawler crane, and hoist the steel cage of high-level ground connected wall that can be hoisted from low elevation site; for some steel cages of high-level ground connected wall that cannot be hoisted from low elevation site, hoist them directly at high elevation site.

[0011] Step 4. In order to complete the construction of the ground-connected wall in the section with sudden changes in height, the high ground will be leveled and filled with soil to widen it to form a filling platform. The filling platform needs to ensure that the edge line of the trenching machine is at a safe distance of more than 3m from the top of the slope when constructing the trenching of the ground-connected wall in the section with sudden changes in height; during the filling process of the filling platform, attention should be paid to ensuring the combination of the new and old roadbeds, and at the same time ensuring that the filling compaction degree is not less than 91% to provide safe working conditions for the trenching machine and crawler crane; by backfilling the soil, widening the high-field leveling construction platform, and backfilling the high-step platform, a working surface for the transition-width ground-connected wall trenching and mud wall protection is provided.

[0012] Step 5: A trenching machine was used to trench the ground diaphragm wall at the sudden change in height. A crawler crane was deployed at the lower elevation, with lifting points and slings selected based on cage weight and length. The two cranes coordinated effectively during the lifting operation. The main crane lowered the steel cage and poured concrete, completing all ground diaphragm wall construction. Once the cage was in place, sandbags were promptly backfilled into the over-grip areas behind the anti-circulation steel plates to reduce concrete bypass during the pouring process. The ground diaphragm wall at the lower elevation was constructed first to ensure connection with subsequent processes, followed by work on the ground diaphragm wall at the higher elevation. Finally, soil was backfilled to create a stable platform for construction of the transition section and soil stabilization. The coordinated implementation of multiple steps, including the installation of anti-circulation steel plates at the junction of the high and low amplitude ground diaphragm walls, backfilling of sandbags behind the steel plates at the over-excavated trench sections, and deployment of crawler cranes, effectively resolved the problem of misaligned connections, ensuring smooth construction, structural stability, and improving both efficiency and quality.

[0013] Further preferred: the anti-circulation steel plate is welded to the prefabricated ground-connected wall reinforcement cage, and its width is smaller than the width of the excavated ground-connected wall groove section to prevent the concrete from overflowing from the gap during the pouring process.

[0014] Further preferably, anti-circulation iron sheets are welded on both sides of the anti-circulation steel plate to enhance the anti-circulation capability of the concrete.

[0015] The bottom surface position of the welded installation of the anti-circulation steel plate is consistent with the top surface height of the low-level concrete that has been constructed, ensuring that the gap between the bottom surface of the anti-circulation steel plate and the top of the low-width ground-connected wall is small after the steel cage is hoisted and lowered, and the concrete cannot overflow and circumvent. The steel cage structure of the high-low width ground-connected wall connection section is the last closed width of construction. When forming the groove, the blade part of the groove forming machine grab has a certain width and shape. In order to ensure the grabbing effect, the blade may exceed the designed wall width during the opening and closing process. When the high-low connection width ground-connected wall steel cage is manufactured, effective measures are taken to prevent concrete circumvention for the high-width ground-connected wall steel cage: Under the premise of ensuring the thickness of the protective layer on the side of the low-width ground-connected wall, a section of U-shaped anti-circulation steel plate is welded to the steel cage as a blocking template during the concrete pouring process. It is necessary to ensure that the bottom surface of the anti-circulation steel plate is consistent with the top elevation of the low-width ground-connected wall after the steel cage is hoisted and lowered.

[0016] The beneficial effects of the present invention are:

[0017] During construction, the construction method and process were precisely implemented, first properly completing the low-elevation ground diaphragm wall construction to reserve a high-quality working surface for subsequent processes. The high-elevation ground diaphragm wall construction was then completed using the crawler crane's capabilities. Finally, backfilling formed a stable platform for the ground diaphragm wall at the connecting elevation. To address the challenges of constructing the high-low section ground diaphragm wall, a reinforced cage structure was proposed for the high-low ground diaphragm wall connecting section. This reduced concrete bypass during construction and the subsequent removal of excess concrete from the ground diaphragm wall during excavation. Close coordination among all links during the process effectively resolved the high-low ground diaphragm wall construction challenges, ensuring project quality and progress, and demonstrating the broad application prospects of this construction method in the construction of ground diaphragm walls in complex terrain, similar to rail transit projects.

[0018] 2. It effectively solved the problem of complex ground-anchored wall construction caused by inconsistent site elevations, ensured the smooth progress of the project, improved construction quality and efficiency, and improved the construction quality of the sudden connection sections of high and low-amplitude ground-anchored walls. At the same time, it has important reference and reference significance for ground-anchored wall construction under similar complex site conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a plan view of the working conditions of stepped terrain and high and low amplitude diaphragm walls;

[0020] Figure 2 This is a schematic diagram of the longitudinal section of the working conditions of the stepped terrain and high and low amplitude diaphragm wall;

[0021] Figure 3 It is a detailed zoning map of stepped terrain and high and low-width ground-connected walls;

[0022] Figure 4 It is the detailed longitudinal section zoning diagram of the stepped terrain, high and low amplitude ground connection wall;

[0023] Figure 5 This is a schematic diagram of the construction of the low-field flat ground connecting wall;

[0024] Figure 6 This is a schematic diagram of the construction of the high-ground flat wall;

[0025] Figure 7 This is a schematic diagram of the high-ground level filling and widening platform;

[0026] Figure 8 It is a steel cage structure for the connection section of high and low amplitude ground-connected walls;

[0027] Figure 9 for Figure 8 Schematic top view of

[0028] Figure 10 This is a construction diagram of the lowering of the steel cage structure at the connection section of the high and low amplitude ground diaphragm wall;

[0029] Figure 11 for Figure 10 Schematic top view of

[0030] Figure 12 This is a schematic diagram of the construction of the ground-connected wall at the sudden change of height;

[0031] The component names corresponding to the serial numbers in the figure are:

[0032] 1. Low-field flat ground ditch wall, 2. High-field flat ground ditch wall, 3. Site slope, 4. Ground ditch wall at high-low amplitude change section, 5. Crawler crane, 6. Filling platform, 7. Steel cage, 8. Anti-circulation steel plate, 9. Filling sandbags, 10. High-field flat, 11. Low-field flat, 12. Embankment slope line, 13. High-field flat ground, 14. Low-field flat ground, 15. Boundary line of high and low amplitude ground ditch walls, 16. Slope top line, 17. Slope toe line, 18. Original slope, 19. Backfill slope, 20. High-elevation field flat section of the completed trough, 21. Low-elevation field flat section of the completed trough, 22. Trough forming machine. DETAILED DESCRIPTION

[0033] The technical solutions of the invention are clearly and completely described below in conjunction with the embodiments. The described embodiments are only a part of the present invention, rather than all the embodiments. Example

[0034] A method for constructing a high-low-amplitude diaphragm wall on a stepped terrain includes optimizing the construction process of the multi-elevation diaphragm wall on the stepped terrain and connecting the high-low-amplitude diaphragm wall. The construction steps are as follows:

[0035] Step 1: Figures 1-4 As shown, the construction area is divided into three parts: low-level area 11, high-level area 10, and site slope area 3. The regional ground diaphragm wall is divided into three stages of construction: the first stage is the construction of the low-level ground diaphragm wall 1, the second stage is the construction of the high-level ground diaphragm wall 2, and the third stage is the construction of the ground diaphragm wall 4 in the transition section with a sudden change in height. On the basis of the first stage, backfill soil is added to increase the high-level trenching machine's high working surface to construct transition sections at different elevations. The optimized construction process of the multi-elevation ground diaphragm wall on stepped terrain comprehensively considers the lifting capacity of the crawler crane and the safe operation requirements of the trenching machine's edge before construction. Two site step slope positions are planned. The first slope is to complete the lifting of all ground diaphragm walls on the high step. The second backfill slope is to ensure that the trenching machine has sufficient edge working width to complete the trenching construction in the transition section, thus avoiding the need for crawler cranes to climb back and forth.

[0036] Step 2: Figure 5 ,According to the construction area division, the site slope 3 is graded to ensure that the slope foot does not affect the construction of the low-field flat ground connecting wall 1, and then the construction of the low-field flat ground connecting wall 1 is completed.

[0037] Step 3: Figure 6 , arrange the crawler crane 5 at the low-elevation site, calculate whether the lifting height is met based on the length of the steel cage, the length of the hoisting device, the site elevation and the working range of the crawler crane, and hoist the steel cage 7 of the high-field flat ground connecting wall 2 that can be hoisted from the low-elevation site; for the steel cage 7 of the high-field flat ground connecting wall 2 that cannot be hoisted from the low-elevation site, hoist it directly at the high-elevation site.

[0038] Step 4: Figure 7 In order to complete the construction of the ground-connecting wall 4 at the sudden change in height, the high field level 10 is filled and widened to form a filling platform 6. The filling platform 6 needs to ensure that the edge line of the trenching machine 22 is at least 3 meters away from the top of the slope when constructing the trenching of the ground-connecting wall 4 at the sudden change in height; during the filling process of the filling platform 6, attention should be paid to ensuring the combination of the new and old roadbeds, and at the same time ensuring that the filling compaction degree is not less than 91%, so as to provide safe working conditions for the trenching machine 22 and the crawler crane 5; by backfilling the soil, widening the high field level elevation construction platform, and backfilling the high step platform, a working surface for the transition width ground-connecting wall trenching and mud wall protection is provided.

[0039] Step 5: Figure 10-12, a trenching machine 22 is used to trench the ground diaphragm wall 4 at the sudden change in height. A crawler crane 5 is arranged at the low-elevation site. The lifting point and lifting equipment are selected according to the weight and length of the cage. The two machines cooperate in an orderly manner when lifting. The main crane lowers the steel cage 7, pours concrete, and completes the construction of all ground diaphragm walls. After the steel cage 7 is lowered into place, the over-grasping area on the back of the anti-circulation steel plate 8 is promptly backfilled with sandbags 9 to reduce the amount of concrete bypass during the pouring process. The ground diaphragm wall at the low elevation is constructed first to ensure the connection of subsequent processes, and then the related operations of the ground diaphragm wall at the high elevation are carried out. Finally, the soil is backfilled to form a stable platform for the construction of the transition section and to stabilize the soil. The anti-circulation steel plate is set on the steel cage structure at the connection section of the high-low amplitude ground diaphragm wall, sandbags are backfilled on the back of the steel plate at the over-excavation of the trench section, and crawler cranes are arranged for lifting. The problem of misaligned connection is effectively solved, which ensures smooth construction, structural stability, and improves construction efficiency and quality.

[0040] The anti-circulation steel plate 8 is welded to the prefabricated ground-connected wall reinforcement cage, and its width is smaller than the width of the excavated ground-connected wall groove section to prevent concrete from overflowing from the gap during the pouring process.

[0041] The anti-circulation iron sheets are welded on both sides of the anti-circulation steel plate 8 to enhance the anti-circulation capability of the concrete.

[0042] The bottom surface position of the welded installation of the anti-circulation steel plate 8 is consistent with the top surface height of the low-level concrete constructed, ensuring that the gap between the bottom surface of the anti-circulation steel plate and the top of the low-width ground-connected wall is small after the steel cage is hoisted and lowered, and the concrete cannot overflow and circumvent.

[0043] The steel cage structure of the high and low amplitude ground-connected wall connection section is the last closed width of the construction. When the trench is formed, the blade of the trenching machine grab has a certain width and shape. In order to ensure the grabbing effect, the blade may exceed the designed wall width during the opening and closing process; Figure 8 When making the steel cage of the high-low connecting ground-connected wall, effective measures should be taken to prevent concrete bypass for the steel cage of the high-width ground-connected wall: on the premise of ensuring the thickness of the protective layer on the side of the low-width ground-connected wall, a section of U-shaped anti-bypass steel plate is welded to the steel cage as a sealing template during the concrete pouring process. It is necessary to ensure that the bottom surface of the anti-bypass steel plate is consistent with the top elevation of the low-width ground-connected wall after the steel cage is hoisted and lowered.

[0044] The above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Any changes, modifications, additions or substitutions made by ordinary technicians in this technical field within the essential scope of the present invention should fall within the scope of protection of the present invention.

Claims

1. A method for constructing a high-low-amplitude diaphragm wall on stepped terrain, characterized by: It includes the optimized construction process of multi-elevation diaphragm walls on stepped terrain and the connection construction of high and low amplitude diaphragm walls. The construction steps are as follows: Step 1: Divide the construction area into three parts: low-level area (11), high-level area (10) and site slope area (3). Divide the regional ground-connected wall into three stages of construction: the first stage is to construct the ground-connected wall at the low-level area (1), the second stage is to construct the ground-connected wall at the high-level area (2), and the third stage is to connect and construct the ground-connected wall at the high-low amplitude sudden change area (4); Step 2: Slope the site side slope (3) according to the construction area division, ensuring that the slope foot does not affect the construction of the low-field flat ground connecting wall (1), and then complete the construction of the low-field flat ground connecting wall (1); Step 3: Arrange a crawler crane (5) at a low-elevation site, calculate whether the lifting height is met based on the length of the steel cage, the length of the hoisting device, the site elevation, and the working range of the crawler crane, and hoist the steel cage (7) of the high-field flat ground connecting wall (2) that can be hoisted from the low-elevation site; hoist the steel cage (7) of the high-field flat ground connecting wall (2) that cannot be hoisted from the low-elevation site directly at the high-elevation site; Step 4: In order to complete the construction of the ground-connecting wall (4) at the sudden change of height, the high field level (10) is filled and widened to form a filling platform (6). The filling platform (6) needs to ensure that the side line of the trenching machine (22) is at least 3 meters away from the top of the slope during the trenching construction of the ground-connecting wall (4) at the sudden change of height; during the filling process of the filling platform (6), attention should be paid to ensuring the combination of the new and old roadbeds, and at the same time ensuring that the filling compaction degree is not less than 91%, so as to provide safe working conditions for the trenching machine (22) and the crawler crane (5); Step 5: Use a slotting machine (22) to slot the ground-connected wall (4) at the sudden change of height. Arrange a crawler crane (5) at a low elevation site. Select the lifting point and lifting equipment according to the weight and length of the cage. The two cranes work together in an orderly manner when lifting. The main crane lowers the steel cage (7) and pours concrete to complete the construction of all ground-connected walls. After the steel cage (7) is lowered into place, the back of the anti-circulation steel plate (8) is promptly backfilled with sandbags (9) to reduce the amount of concrete bypass during the pouring process.

2. The method for constructing a stepped terrain high and low-amplitude diaphragm wall according to claim 1, characterized in that: The anti-circulation steel plate (8) is welded to the prefabricated ground-connected wall reinforcement cage, and its width is smaller than the width of the excavated ground-connected wall groove section, so as to prevent the concrete from overflowing from the gap and flowing around during the pouring process.

3. The method for constructing a stepped terrain high and low-amplitude diaphragm wall according to claim 2, characterized in that: The anti-circulation iron sheets welded on both sides of the anti-circulation steel plate (8) enhance the anti-circulation capability of the concrete.

4. The method for constructing a stepped wall according to claim 2, characterized in that: The bottom surface position of the anti-circulation steel plate (8) welded and installed is consistent with the top surface height of the low-field flat concrete that has been constructed, ensuring that the gap between the bottom surface of the anti-circulation steel plate and the top of the low-width ground-connected wall is small after the steel cage is hoisted and lowered, and concrete cannot overflow and circulate.

5. The method for constructing a stepped terrain diaphragm wall according to claim 1, characterized in that: The optimized construction process of the multi-elevation ground tethered wall on the stepped terrain comprehensively considers the lifting capacity of the crawler crane and the safety requirements for the edge operation of the trenching machine before construction, and plans two step slope positions on the site. The first slope is to complete the lifting of all the ground tethered walls on the high step. The second backfill slope is to ensure that the trenching machine has sufficient edge operating width in the slope connection section of the site to complete the trenching construction, thereby avoiding the crawler crane from climbing back and forth.

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