JP7540678B1 - System and method for backfilling narrow excess trenches in a mine with liquefied hardened soil - Google Patents

Abstract

[Problem] To provide a system and construction method for backfilling narrow excess trenches in a pit with fluidized hardening soil. [Solution] The system includes a pit excavation surrounding system, an excess trench floor slab reservation post-injection zone system, an excess trench ground reinforcement system, an excess trench piping deformation prevention support system, and a basement waterproof system. The excess trench floor slab reservation post-injection zone technology is adopted, and a temporary support steel plate is installed in the post-injection zone as a temporary support for the formwork support system, thereby ensuring the synchronous construction of the structural plates of the same floor in different sections of the foundation pit, and fluidized hardening soil is used to backfill the second excess trench, and then the work of the second floor slab waterproof system is carried out, and finally the work of the post-seal injection zone is carried out, thereby improving the construction efficiency and quality of the basement main structure, and the excess trench ground reinforcement technology is adopted, and steel pipe piles are driven in the excess trench, and fluidized hardening soil is used to backfill the excess trench in the foundation pit, thereby improving the denseness of the backfilling, solving the difficult problem that it is difficult to pour conventional concrete in a narrow space. [Selected Figure] Figure 1

Description

The present invention belongs to the field of backfilling of excess trenches in foundation pits, and in particular to a system and method for backfilling narrow excess trenches in pits with fluidized hardened soil.

The extra trench refers to the space between the foundation, the basement outer wall and the foundation support structure inner wall, providing a working surface for construction. In construction, the foundation pit excavation range is constrained by land restrictions, underground piping network, geological conditions, etc., and from the viewpoint of use function, buildings often require a larger usable area. In order to fully utilize the underground space, the width of the extra trench of the foundation pit becomes smaller and smaller, and the foundation pit becomes deeper and deeper. The narrowest part of some construction extra trenches is already less than 50 cm, which greatly increases the difficulty of backfilling the extra trench of the foundation pit. Construction agencies often focus on the main structure construction quality as the main focus, and ignore the backfill soil control of the extra trench, which leads to various pipes laid in the extra trench always forming cracks and other destruction due to uneven settlement, causing unnecessary economic losses. The selection of backfilling materials and construction quality of the extra trench are very important for the foundation safety, the normal use of the pipes, and the stability of the entire building. Due to the narrow excess trench, normal dust-like solid backfill material cannot be used as there is no tamping space available.

One of the reasons why backfilling of foundation pits is complicated is that currently, above-ground structures often use cantilever structures, and the formwork support frames are often placed on the backfill soil. If reasonable control measures are not taken, there are potential risks such as the formwork support frame foundation settling.

In recent years, construction accidents caused by excessive trench backfilling quality have often involved water, particularly in mountainous areas. When heavy rains occur or water cannot be properly drained from the ground and seeps into the excess trenches, this can not only cause the backfill soil piles to settle, but can also lead to accidents where underground structures float.

Therefore, in order to avoid safety problems such as soil subsidence, pipe bursting, and underground structure floating caused by uneven soil settlement during construction of narrow excess trenches in foundation pits, and to ensure normal construction of the entire upper structure, to prevent the backfilling of excess trenches from occupying important routes, and to avoid the impact of the reservation of the injection zone after penetration of the basement structure on the overall structure, it is necessary to research and develop a fluidized hardening soil backfilling system and construction method for narrow excess trenches.

The object of the present invention is to provide a system and method for backfilling narrow excess trenches in a pit with fluidized hardened soil to overcome the shortcomings of the prior art.

The fluidized hardening soil backfill system of the narrow extra trench in such a pit includes a pit excavation surrounding system in the pit, an extra trench floor slab reservation post-injection zone system, an extra trench ground reinforcement system, an extra trench piping deformation prevention support system, and a basement waterproof system;
The excavation surrounding system in the pit includes a first foundation pit, a second foundation pit, a first support pile, a second support pile, and a jetted concrete layer, the first foundation pit adopts the first support pile as the surrounding structure, and a cushion layer is laid at the bottom of the pit, the second foundation pit adopts the second support pile and the jetted concrete layer after slope excavation as the surrounding structure, and a cushion layer is laid at the bottom of the pit, and a bottom plate is provided at the bottom of the second foundation pit;
The overfill groove floor slab reservation post-injection zone system includes a first overfill groove, a second overfill groove, a first floor slab, a second floor slab, a post-injection zone, and a temporary support steel plate, a first outer wall is provided between an end of the first floor slab and an end of the second floor slab, a second outer wall is provided between an end of the second floor slab and an end of the bottom plate, the first overfill groove is located between the first outer wall and the first support pile, the second overfill groove is located between the second outer wall, the second support pile and the jetted concrete layer, the post-injection zone is installed on the second floor slab above the second overfill groove, and the temporary support steel plate is laid on both ends of the post-injection zone.

Preferably, a formwork support system for constructing a first floor slab in the first foundation pit is further provided, and the formwork support system supports the second floor slab on the temporary support steel plate.

Preferably, a first reserved rebar and a second reserved rebar are provided at both ends of the post-injection zone, and a first reserved waterproof coil material and a second reserved waterproof coil material are provided below, respectively.

Preferably, the extra trench ground reinforcement system includes a first steel pipe pile, a second steel pipe pile, a third steel pipe pile, and fluidized hardening backfill soil, the first steel pipe pile is buried in the bottom of the first extra trench and has a top at the same elevation as the outdoor floor surface, the second steel pipe pile is buried in the bottom of the second extra trench and has a corbel at its top that is supported below the temporary support steel plate, the lower end of the third steel pipe pile is inserted into the second support pile by a reserved cup mouth and has a corbel at its top that is supported below the temporary support steel plate, and the fluidized hardening backfill soil is injected into the first extra trench and the second extra trench.

Preferably, the extra trench piping deformation prevention support system includes a pipeline, a flexible support plate, a support frame, and a flange band, the pipeline passes through the second support pile, the second extra trench, and the second outer wall in that order, and the flexible support plate is installed below the pipeline and fixed to the second steel pipe pile body by the support frame and flange band.

Preferably, the basement waterproofing system includes a protective layer, a waterproof coil material, a leveling layer, a first water-impermeable layer, and a second water-impermeable layer, and the protective layer, waterproof coil material, and leveling layer are provided in this order below the bottom plate, and the leveling layer is bonded to the cushion layer, the first water-impermeable layer is located above the cushion layer in the first extra groove and is fixed to the first support pile by the first reinforcement, the second water-impermeable layer is located above the cushion layer in the second extra groove and is fixed to the second support pile by the second reinforcement, and the protective layer, waterproof coil material, and leveling layer in the basement waterproofing system extend from below the bottom plate to the second exterior wall, the second floor slab, and the outside of the first exterior wall in this order.

The construction method for backfilling the narrow excess trench of such a pit with liquefied hardened soil is as follows:
Step 1: Construction of the first support pile, excavation of the first foundation pit, construction of the second support pile, slope construction of the injection concrete layer and excavation of the second foundation pit, construction of the bottom plate and the second exterior wall, construction of the second floor slab, construction of the reservation post-injection zone and the first exterior wall in that order;
Step 2: driving a second steel pipe pile in the second extra trench, penetrating a flexible support plate therethrough, installing a support frame and a flange band under the flexible support plate and fixing it to the second steel pipe pile body, driving a third steel pipe pile, and inserting it into the reserved cup mouth of the second support pile;
Step 3 includes installing a temporary support steel plate, laying a formwork support system, and constructing a first floor slab;
Step 4: remove the formwork support system, the temporary support steel plate, the corbels of the second steel pipe pile and the third steel pipe pile in order, then pour anti-permeable concrete into the bottom of the second extra trench to form a second water impermeable layer, fill and inject fluidized hardening backfill soil into the inside, and construct the basement waterproof system;
and step 5 of driving a first steel pipe pile into the first extra trench, pouring anti-permeation concrete into the bottom to form a first water barrier layer, filling and injecting fluidized hardening backfill soil into the inside, and leveling the first extra trench to match the elevation of the outdoor floor surface.

Preferably, step 3 further includes attaching stopper bolts to both sides of the temporary support steel plate.

Preferably, steps 4 and 5 further include filling and injecting fluidized hardening backfill soil into the first steel pipe pile, the second steel pipe pile and the third steel pipe pile.

Preferably, in step 1, the second reinforcement is attached to the bottom pile body of the second support pile, a flexible support plate is installed below the pipeline, a leveling layer, a waterproof coil material and a protective layer are constructed as a waterproof system, and a first reserved waterproof coil material is installed; the first reinforcement is attached to the bottom pile body of the first support pile, a leveling layer, a waterproof coil material and a protective layer are constructed as a waterproof system, and a second reserved waterproof coil material is installed; the first reserved rebar and the second reserved rebar are installed at both ends of the post-injection zone; and in step 4, the specific method of constructing the basement waterproof system is to, after the fluidized hardened backfill soil in the second extra trench has hardened, sequentially install the post-injection zone position. A leveling layer is applied to the position, the first reserved waterproof coil material and the second reserved waterproof coil material are welded together, a protective layer is applied, and post-injection band concrete is poured to form a complete second floor slab and its waterproof system. When welding the first reserved waterproof coil material and the second reserved waterproof coil material, multiple hot melt gaskets are evenly positioned in the lap area between the two using an infrared laser positioning device, the hot melt gaskets are heated by an ultrasonic welding machine to weld and fix the first reserved waterproof coil material and the second reserved waterproof coil material, and a running welding machine is used to double-slit weld and seal the gap between the boundaries of the two.

The beneficial effects of the present invention are as follows:

1) This invention adopts the extra groove floor slab reservation post-injection zone technology, and installs a temporary support steel plate in the post-injection zone as a temporary support for the formwork support system, thereby ensuring the synchronous construction of structural plates on the same floor in different sections of the foundation pit, and also adopts fluidized hardening soil to backfill the second extra groove, and then works on the second floor slab waterproofing system, and finally works on the post-seal injection zone, improving the construction efficiency and quality of the basement main structure.

2) This invention employs an extra trench ground strengthening technology, drives steel pipe piles into the extra trench, and backfills it with fluidized hardened soil, improving the backfill density of the extra trench in the foundation pit and solving the difficult problem of it being difficult to pour conventional concrete in narrow spaces.

3) The present invention adopts support technology to prevent excess trench piping deformation, and by installing flexible support plates, support frames and flange bands below the pipeline, and combining such measures as reinforcing steel pipe piles and backfilling with fluidized hardening soil, it achieves a triple reinforcement deformation prevention effect, and can effectively prevent piping deformation caused by uneven settlement of excess trench ground soil.

4) The present invention adopts basement exterior wall waterproofing technology, installs a protective layer, waterproof coil material and leveling layer on the outside of the structure, strengthens the floor slab by welding the reserved waterproof coil material for injection, and installs braces and water-proof layers on the support structure at the bottom of the extra trench in different sections, thereby improving the anti-seepage properties of the entire basement structure and avoiding the impact of the groundwater level on the extra trench area.

FIG. 13 is a schematic diagram of the construction before backfilling of the narrow excess trench in the pit. FIG. 13 is a schematic diagram of the construction after backfilling of the narrow excess trench in the pit. This is a schematic diagram of the support system to prevent deformation of the extra trench piping in the mine. A schematic diagram of the injection zone system after the extra trench floor slab reservation before backfilling. A schematic diagram of the injection zone system after the excess trench floor slab reservation after backfilling. FIG. 1 is a schematic diagram of a second extra trench in a basement waterproofing system. FIG. 1 is a schematic diagram of a first extra trench in a basement waterproofing system.

Example 1
As one example, the fluidized hardened soil backfill system for the narrow extra trench in such a tunnel includes a tunnel excavation surrounding system in the tunnel, an extra trench floor slab reservation post-injection zone system, an extra trench ground reinforcement system, an extra trench piping deformation prevention support system, and a basement waterproofing system.

The excavation enclosure system for the above-mentioned pit includes a first foundation pit 1, a second foundation pit 2, a first support pile 3, a second support pile 4, and a jetted concrete layer 5. The first foundation pit 1 uses the first support pile 3 as an enclosure structure, and a cushion layer 6 is laid at the bottom of the pit, while the second foundation pit 2 uses the second support pile 4 and the jetted concrete layer 5 after slope excavation as an enclosure structure, and a cushion layer 6 is laid at the bottom of the pit.

A formwork support system 34 is further provided in the first foundation pit 1 for constructing the first floor slab 9, and the formwork support system 34 supports the second floor slab 10 and the temporary support steel plate 12 that have already been cast.

The excess groove floor slab reservation post-injection zone system includes a first excess groove 7, a second excess groove 8, a first floor slab 9, a second floor slab 10, a post-injection zone 11, and a temporary support steel plate 12. The first excess groove 7 is located between the first exterior wall 13 and the first support pile 3, the second excess groove 8 is located between the second exterior wall 14, the second support pile 4, and the jetted concrete layer 5, the post-injection zone 11 is installed on the second floor slab 10 above the second excess groove 8, and the temporary support steel plate 12 is laid on both ends of the post-injection zone 11. A first reserved rebar 35 and a second reserved rebar 36 are provided at both ends of the post-injection zone 11, respectively, and a first reserved waterproof coil material 37 and a second reserved waterproof coil material 38 are provided below, respectively.

The extra trench ground reinforcement system includes a first steel pipe pile 15, a second steel pipe pile 16, a third steel pipe pile 17, and fluidized hardening backfill soil 18. The first steel pipe pile 15 is buried in the bottom of the first extra trench 7, and the top is at the same elevation as the outdoor floor surface 19. The second steel pipe pile 16 is buried in the bottom of the second extra trench 8, and the top is provided with a corbel 20 supported below the temporary support steel plate 12. The lower end of the third steel pipe pile 17 is inserted into the second support pile 4 by a reservation cup mouth 21, and the top is provided with a corbel 20 supported below the temporary support steel plate 12. The fluidized hardening backfill soil 18 is injected into the first extra trench 7 and the second extra trench 8.

The excess groove piping deformation prevention support system includes a pipeline 22, a flexible support plate 23, a support frame 24, and a flange band 25. The pipeline 22 passes through the second support pile 4, the second excess groove 8, and the second outer wall 14 in order, and the flexible support plate 23 is installed below the pipeline 22 and is fixed to the pile body of the second steel pipe pile 16 by the support frame 24 and the flange band 25.

The basement waterproofing system includes a bottom plate 26, a first exterior wall 13, a second exterior wall 14, a protective layer 27, a waterproof coil material 28, a leveling layer 29, a first water-impermeable layer 30, and a second water-impermeable layer 31. The bottom plate 26 is provided at the bottom of the second foundation pit 2, and the protective layer 27, the waterproof coil material 28, and the leveling layer 29 are installed in order below the bottom plate 26, and the leveling layer 29 is attached to the cushion layer 6, and the first water-impermeable layer 30 is located above the cushion layer 6 of the first extra groove 7 and fixed to the first support pile 3 by the first reinforcement 32, and the second water-impermeable layer 31 is located above the cushion layer 6 of the second extra groove 8 and fixed to the second support pile 4 by the second reinforcement 33. The protective layer 27, waterproof coil material 28 and leveling layer 29 in the basement waterproofing system extend from below the bottom plate 26 to the outside of the second exterior wall 14, the second floor slab 10 and the first exterior wall 13 in that order.

Example 2
As another example, a method for constructing a fluidized hardened soil backfill system for narrow excess trenches in such a well includes the following steps:

As shown in Figure 1, the first support pile 3 is constructed, the first foundation pit 1 is excavated to the designed elevation, the second support pile 4 is constructed, a reservation cup mouth 21 is installed at the top of the pile, the slope is excavated to a certain depth, the sprayed concrete layer 5 is then worked on, and the second foundation pit 2 is excavated to the designed elevation.

After flattening the bottom of the second foundation pit 2, a cushion layer 6 is laid, and the second reinforcement 33 is attached to the bottom pile body of the second support pile 4 by chemical reinforcement or other methods, and a leveling layer 29, waterproof coil material 28 and protective layer 27 are installed as the waterproof system of the bottom plate. The basement bottom plate 26 is then constructed by processes such as support, rebar fastening and concrete pouring, and then the second exterior wall 14 is constructed, and the leveling layer 29, waterproof coil material 28 and protective layer 27 are installed on the outside as the waterproof system of the second exterior wall, and the first reserved waterproof coil material 37 is installed on the top of the wall, and during this period a flexible support plate 23 is installed below the pipeline 22, and it is temporarily fixed between the second support pile 4 and the second exterior wall 14 to support them against each other.

A cushion layer 6 is laid at the bottom of the first foundation pit 1, and the first reinforcement 32, construction leveling layer 29, waterproof coil material 28 and protective layer 27 are attached to the bottom pile body of the first support pile 3 as a waterproof system for the second floor slab, and the second reserved waterproof coil material 38 is installed. Then, the second floor slab 10 and the first exterior wall 13 are constructed, and here, a post-injection zone 11 is reserved for the second floor slab 10 above the second excess groove 8, and the first reserved rebar 35 and the second reserved rebar 36 are installed at both ends of the post-injection zone 11 when the rebar of the second floor slab 10 is fastened.

The second steel pipe pile 16 is driven into the second extra groove 8, the flexible support plate 23 is inserted therethrough, the support frame 24 and the flange band 25 are attached below the flexible support plate 23, and the flange band 25 bolts are tightened to fix the flexible support plate 23 to the pile body of the second steel pipe pile 16, as shown in FIG. 3. Then, the third steel pipe pile 17 is driven into the reserved cup mouth 21 of the second support pile 4, and the top ends of the second steel pipe pile 16 and the third steel pipe pile 17 are ensured to be flush with the top surface of the second floor slab 10.

As shown in Figures 1 and 4, flat steel plates are laid on both ends of the post-injection zone 11 as temporary support steel plates 12. To prevent offsetting of the temporary support steel plates 12, stopper bolts 41 may be embedded on both sides to restrict it. After that, footholds are placed in the first foundation pit 1 as a formwork support system 34 for constructing the first floor slab 9, and the first floor slab 9 is poured to complete the construction, ensuring the synchronous construction of structural plates on the same floor in different sections of the foundation pit.

As shown in Fig. 2, the formwork support system 34 and the temporary support steel plate 12 are removed in order, the corbels 20 of the second steel pipe pile 16 and the third steel pipe pile 17 are cut, and after cutting, the top ends of the second steel pipe pile 16 and the third steel pipe pile 17 are ensured to be flush with the cushion layer 6 of the first foundation pit 1. As shown in Fig. 6, the bottom of the second extra trench 8 is then poured with anti-seepage concrete to form a second water impermeable layer 31, and the second steel pipe pile 16, the third steel pipe pile 17 and the second extra trench 8 are filled with fluidized hardening backfill soil.
As shown in FIG. 5, after the fluidized hardened backfill soil 18 in the second excess trench 8 has hardened, a leveling layer 29 is applied in sequence at the post-injection zone 11 position, the first reserved waterproof coil material 37 and the second reserved waterproof coil material 38 are welded, a protective layer 27 is applied, and concrete is poured in the post-injection zone 11 to form a complete second floor slab 10 and its waterproof system. Here, when the first reserved waterproof coil material 37 and the second reserved waterproof coil material 38 are welded together, a plurality of hot melt gaskets 39 are uniformly positioned in the lap area of both materials by an infrared laser positioning device, and the hot melt gaskets 39 are heated by an ultrasonic welding machine to weld and fix the first reserved waterproof coil material 37 and the second reserved waterproof coil material 38, and a running welding machine 40 is used to perform double slit welding and sealing at the gap between the boundaries of both materials.

As shown in Figures 2 and 7, the first steel pipe pile 15 is driven into the first extra trench 7, anti-seepage concrete is poured into the bottom to form the first water-impermeable layer 30, and fluidized hardening backfill is used to fill the first steel pipe pile 15 and the first extra trench 7, so that the first extra trench 7 after being backfilled and leveled matches the elevation of the outdoor floor surface 19.

Finally, once all the foundation pits have been constructed and completed, work on the superstructure will commence.

LIST OF SYMBOLS 1 First foundation pit 2 Second foundation pit 3 First support pile 4 Second support pile 5 Injected concrete layer 6 Cushion layer 7 First extra groove 8 Second extra groove 9 First floor slab 10 Second floor slab 11 Post-injection zone 12 Temporary support steel plate 13 First exterior wall 14 Second exterior wall 15 First steel pipe pile 16 Second steel pipe pile 17 Third steel pipe pile 18 Fluidized hardened backfill soil 19 Outdoor floor surface 20 Corbel 21 Reserved cup mouth 22 Pipe 23 Flexible support plate 24 Support frame 25 Flange band 26 Bottom plate 27 Protective layer 28 Waterproof coil material 29 Leveling layer 30 First water-impermeable layer 31 Second water-impermeable layer 32 First reinforcement 33 Second reinforcement 34 Formwork support system 35 First reserved reinforcing bar 36 Second reserved reinforcing bar 37 First reserved waterproof coil material 38 Second reserved waterproof coil material 39 Hot melt gasket 40 Running welding machine 41 Stopper bolt

Claims (10)

A system for backfilling a narrow extra trench in a pit with fluidized hardened soil , the system includes: a pit excavation surrounding structure in the pit, an extra trench floor slab reservation post-injection zone structure , an extra trench ground reinforcement structure , an extra trench piping deformation prevention support structure , and a basement waterproof structure ;
The excavation surrounding structure in the pit includes a first foundation pit, a second foundation pit, a first support pile, a second support pile, and a jetted concrete layer, the first foundation pit adopts the first support pile as the surrounding structure, and a cushion layer is laid at the bottom of the pit, the second foundation pit adopts the second support pile and the jetted concrete layer after slope excavation as the surrounding structure, and a cushion layer is laid at the bottom of the pit, and a bottom plate is provided at the bottom of the second foundation pit;
The system for backfilling narrow overfill trenches in a pit with fluidized hardened soil, characterized in that the overfill trench floor slab reservation post-injection zone structure includes a first overfill trench, a second overfill trench, a first floor slab, a second floor slab, a post-injection zone, and a temporary support steel plate, a first outer wall is provided between an end of the first floor slab and an end of the second floor slab, a second outer wall is provided between an end of the second floor slab and an end of the bottom plate, the first overfill trench is located between the first outer wall and the first support pile, the second overfill trench is located between the second outer wall, the second support pile and the jetted concrete layer, the post-injection zone is installed on the second floor slab above the second overfill trench, and the temporary support steel plate is laid on both ends of the post-injection zone. The system for backfilling a narrow excess trench of a pit with fluidized hardened soil as described in claim 1, further comprising a formwork support structure for constructing a first floor slab in the first foundation pit, the formwork support structure supporting the second floor slab on a temporary support steel plate. A system for backfilling narrow excess trenches in a pit with fluidized hardened soil as described in claim 1, characterized in that a first reserved rebar and a second reserved rebar are provided at both ends of the post-injection zone, respectively, and a first reserved waterproof coil material and a second reserved waterproof coil material are provided below, respectively. The system for backfilling the narrow extra trench with fluidized hardening soil in the pit as described in claim 1, characterized in that the extra trench ground reinforcement structure includes a first steel pipe pile, a second steel pipe pile, a third steel pipe pile, and fluidized hardening backfill soil, the first steel pipe pile is buried in the bottom of the first extra trench, and the top is provided with a corbel supported below the temporary support steel plate at the top, the lower end of the third steel pipe pile is inserted into the second support pile by a reserved cup mouth, and the top is provided with a corbel supported below the temporary support steel plate at the bottom, and the fluidized hardening backfill soil is injected into the first extra trench and the second extra trench. The system for backfilling a narrow extra trench in a pit with fluidized hardened soil as described in claim 1, characterized in that the extra trench piping deformation prevention support structure includes a pipeline, a flexible support plate, a support frame, and a flange band, the pipeline passes through a second support pile, a second extra trench, and a second outer wall in sequence, and the flexible support plate is installed below the pipeline and fixed to the second steel pipe pile body by the support frame and the flange band. The basement waterproof structure includes a protective layer, a waterproof coil material, a leveling layer, a first water-proof layer, and a second water-proof layer, and the protective layer, the waterproof coil material, and the leveling layer are provided in that order below the bottom plate, and the leveling layer is bonded to a cushion layer, and the first water-proof layer is located above the cushion layer of the first extra groove and fixed to the first support pile by a first reinforcement, and the second water-proof layer is located above the cushion layer of the second extra groove and fixed to the second support pile by a second reinforcement, and the protective layer, the waterproof coil material, and the leveling layer in the basement waterproof structure extend from below the bottom plate to the second outer wall, the second floor slab, and the outside of the first outer wall in that order. A system for backfilling a narrow extra groove in a tunnel with fluidized hardened soil as described in claim 1. A method for constructing a system for backfilling narrow excess trenches of a pit according to any one of claims 1 to 6, comprising:
Step 1: Construction of the first support pile, excavation of the first foundation pit, construction of the second support pile, slope construction of the injection concrete layer and excavation of the second foundation pit, construction of the bottom plate and the second exterior wall, construction of the second floor slab, construction of the reservation post-injection zone and the first exterior wall in that order;
Step 2: driving a second steel pipe pile in the second extra trench, penetrating a flexible support plate therethrough, installing a support frame and a flange band under the flexible support plate and fixing it to the second steel pipe pile body, driving a third steel pipe pile, and inserting it into the reserved cup mouth of the second support pile;
Step 3 includes installing a temporary support steel plate, laying a formwork support structure , and constructing a first floor slab;
Step 4: remove the formwork support structure , the temporary support steel plate, the corbels of the second steel pipe pile and the third steel pipe pile in order, then pour anti-permeable concrete into the bottom of the second extra trench to form a second water impermeable layer, fill and inject fluidized hardening backfill soil into the inside, and construct a basement waterproof structure ;
A construction method for a system for backfilling narrow excess trenches in a pit with fluidized hardening soil, comprising: a step 5 of driving a first steel pipe pile into the first excess trench, pouring anti-permeable concrete at the bottom to form a first water-proof layer, filling and injecting fluidized hardening backfill soil into the inside, and leveling and then matching the elevation of the outdoor floor surface. The construction method of a system for backfilling narrow excess trenches of a pit with fluidized hardened soil as described in claim 7, characterized in that in step 3, it further includes installing stopper bolts on both sides of the temporary support steel plate. The construction method of the system for backfilling narrow excess trenches of a pit with fluidized hardening soil as described in claim 7, characterized in that in step 4 and step 5, the construction method further includes filling and injecting fluidized hardening backfill soil into the first steel pipe pile, the second steel pipe pile and the third steel pipe pile. In step 1, the second reinforcement is attached to the bottom pile body of the second support pile, a flexible support plate is installed under the pipeline, a leveling layer, a waterproof coil material and a protective layer are constructed as a waterproof structure , and a first reserved waterproof coil material is installed; the first reinforcement is attached to the bottom pile body of the first support pile, a leveling layer, a waterproof coil material and a protective layer are constructed as a waterproof structure , and a second reserved waterproof coil material is installed; the first reserved rebar and the second reserved rebar are installed at both ends of the post-injection zone; in step 4, the specific method of constructing the basement waterproof structure is to sequentially construct a leveling layer at the post-injection zone position after the fluidized hardened backfill soil in the second excess trench hardens, and the first reserved waterproof coil material and the second reserved The construction method of a system for backfilling narrow excess trenches in tunnels with fluidized hardening soil, as described in claim 7, characterized in that when welding the first reserved waterproof coil material, constructing a protective layer, and pouring post-injection band concrete to form a complete second floor slab and its waterproof structure , and when welding the first reserved waterproof coil material and the second reserved waterproof coil material, a plurality of hot melt gaskets are evenly positioned in the lap area of both by an infrared laser positioning device, the hot melt gaskets are heated by an ultrasonic welding machine to weld and fix the first reserved waterproof coil material and the second reserved waterproof coil material, and a running welding machine is used to perform double slit welding and sealing in the gap at the boundary between the two.