A method for reinforcing and lifting buildings on collapsible loess foundation

Abstract

The present invention discloses a method for reinforcing and elevating a building on a collapsible loess foundation, comprising: drilling downwardly obliquely around the base plate of the target building to form a first curtain hole and injecting grouting to form an inclined water-retaining curtain wall; drilling vertically downwardly within the outer ring of the first curtain hole to form a second curtain hole and injecting grouting to form an enclosed vertical water-retaining curtain wall; drilling vertically downwardly based on the hole position of the first curtain hole to the bottom elevation of the raft slab of the target building to form a first reinforcement grouting hole, and injecting grouting into the first reinforcement grouting hole to form an irregular reinforcement body; drilling from the ground to the ground to form a second reinforcement grouting hole and injecting grouting to form a reinforcement body in the collapsible loess layer; drilling downwardly from the ground to form an elevation hole, and performing pressure grouting at the bottom of the elevation hole to elevate the target building to a preset height. The present invention alleviates the technical problem of conventional methods for reinforcing and elevating collapsible loess foundations, which are prone to secondary settlement and cause the building to tilt and sink.

Description

Technical Field

[0001] The invention relates to the technical field of building reinforcement and lifting, and in particular to a method for reinforcing and lifting a building on a collapsible loess foundation. Background Art

[0002] Loess itself is relatively dense, but the overall structure is unstable, with well-developed vertical joints and strong vertical permeability. Especially when soaked by liquids such as rainwater, the deep loess is in a saturated state, which will damage the soil structure and cause significant sinking, forming collapsible loess, which reduces strength and bearing capacity, causing buildings to tilt and sink, affecting functional use. Traditional methods for reinforcing and raising buildings on collapsible loess foundations are mostly single grouting reinforcement of pile foundations or composite foundations, or a combination of the two, followed by grouting and raising. Traditional grouting reinforcement and raising methods do not fully consider the impact of groundwater on the soil. When there is heavy rainfall in the summer, the large groundwater flow cannot effectively prevent water from infiltrating the soil, further damaging the integrity of the soil, causing secondary settlement of the collapsible loess foundation, causing the building to tilt and sink, affecting functional use. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for reinforcing and lifting a building on a collapsible loess foundation in order to solve at least one of the above technical problems.

[0004] In the first aspect, an embodiment of the present invention provides a method for reinforcing and lifting a building on a collapsible loess foundation, comprising: drilling holes obliquely downward around the base plate of a target building to form a first curtain hole and injecting grouting to form an inclined water-retaining curtain wall; the target building is a building on a collapsible loess foundation; drilling holes vertically downward in the outer circle of the first curtain hole to form a second curtain hole and injecting grouting to form an enclosed vertical water-retaining curtain wall; drilling holes vertically downward based on the hole position of the first curtain hole to the bottom elevation of the raft slab of the target building to form a first reinforcement grouting hole, and injecting grouting into the first reinforcement grouting hole to form a second water-retaining curtain wall. An irregular reinforcement body; drilling a hole from the ground into the underground to form a second reinforcement grouting hole, injecting cement slurry into the second reinforcement grouting hole, so that the cement slurry penetrates into the cracks in the collapsible loess layer and fills and compacts the collapsible loess to form a collapsible loess layer reinforcement body; the collapsible loess layer reinforcement body is connected to the pile foundation of the target building as a whole; drilling a hole from the ground downward to a preset depth below the collapsible loess layer reinforcement body to form a lifting hole, performing pressure grouting on the bottom of the lifting hole, pushing the collapsible loess layer reinforcement body and the pile foundation to be lifted upward together, thereby driving the target building to be lifted to a preset height.

[0005] Furthermore, first curtain holes are drilled obliquely downward around the foundation slab of the target building and grouting is performed to form an inclined water retaining curtain wall, including: drilling obliquely downward around the foundation slab of the target building to form a plurality of spaced first curtain holes; the first curtain holes extend to the top surface of the collapsible loess layer; grouting is injected into the first curtain holes so that the grouting ranges of two adjacent first curtain holes interlock and overlap with each other to form the inclined water retaining curtain wall; the inclined water retaining curtain wall forms a pyramid shape.

[0006] Furthermore, grouting into the first curtain hole includes: grouting the first curtain hole in a plurality of sections in a vertical direction in sequence using a drilling and grouting machine.

[0007] Furthermore, second curtain holes are drilled vertically downward in the outer circle of the first curtain holes and grouting is performed to form an enclosed vertical water retaining curtain wall, including: drilling holes vertically downward in the outer circle of the first curtain holes to form a plurality of spaced second curtain holes; the bottoms of the second curtain holes extend below the collapsible loess layer reinforcement body; grouting is performed into the second curtain holes so that the grouting ranges of two adjacent second curtain holes interlock and overlap with each other to form an enclosed vertical water retaining curtain wall.

[0008] Furthermore, grouting into the second curtain hole includes: grouting the second curtain hole in a plurality of sections in a vertical direction in sequence using a drilling and grouting machine.

[0009] Furthermore, grouting is performed into the first reinforcement grouting hole to form an irregular reinforcement body, including: grouting is performed in the first reinforcement grouting hole to reinforce the soil around and above the raft slab by grouting, and the voids in the soil within the range are filled and compacted to form the irregular reinforcement body.

[0010] Furthermore, the irregular reinforcement body, the inclined water retaining curtain wall and the raft slab are interconnected and serve as mutual supporting structures.

[0011] Furthermore, the bottom of the second reinforcement grouting hole extends into the collapsible loess layer.

[0012] Furthermore, pressure grouting is performed on the bottom of the lifting hole, including: performing pressure grouting on the bottom of the lifting hole 12-24 hours after the reinforcement of the collapsible loess layer is completed.

[0013] Furthermore, pressure grouting is performed on the bottom of the lifting hole, including: performing a segmented backward grouting and lifting operation on the bottom of the lifting hole based on a drilling and grouting machine.

[0014] The present invention provides a method for reinforcing and lifting a building on a collapsible loess foundation. By arranging an inclined water-retaining curtain wall and a vertical water-retaining curtain wall, the influence of groundwater on the foundation is prevented; the reinforcement body of the collapsible loess layer is connected to the pile foundation as a whole, which can effectively prevent the secondary settlement of the building; at the same time, the curtain wall isolates the foundation soil below the raft slab from the foundation soil outside the raft slab, providing a closed environment for grouting of the reinforcement body and lifting grouting, avoiding interference from the external environment, preventing the loss of grouting liquid, and saving grouting materials; and the reinforcement body can play a buffering role when transmitting the upward lifting force, protecting the bottom plate of the building, and reducing damage to the building. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the implementation methods of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the specific implementation methods or the description of the prior art. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0016] Figure 1 A flow chart of a method for reinforcing and lifting a building on a collapsible loess foundation provided by an embodiment of the present invention;

[0017] Figure 2 A schematic diagram of a building structure on a collapsible loess foundation provided by an embodiment of the present invention;

[0018] Figure 3 A schematic diagram of a building foundation structure reinforcement on a collapsible loess foundation provided by an embodiment of the present invention;

[0019] Figure 4 A schematic diagram of the partial structure of a building on a collapsible loess foundation provided by an embodiment of the present invention;

[0020] Figure 5 A top view of a first curtain hole and a second curtain hole provided in an embodiment of the present invention;

[0021] Figure 6 A schematic diagram of the overall structure of a curtain wall and a building provided by an embodiment of the present invention;

[0022] Figure 7 A schematic plan view of a reinforced grouting hole provided in an embodiment of the present invention.

[0023] In the figure: 1. First curtain hole, 2. Second curtain hole, 3. First reinforcement grouting hole, 4. Second reinforcement grouting hole, 5. Lifting hole, 10. Target building, 20. Raft slab, 21. Inclined water retaining curtain wall, 22. Vertical water retaining curtain wall, 23. Irregular reinforcement body, 24. Reinforcement body of collapsible loess layer, 30. Pile foundation, 40. Collapsible loess layer. DETAILED DESCRIPTION

[0024] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0025] Figure 1 This is a flow chart of a method for reinforcing and lifting a building on a collapsible loess foundation provided according to an embodiment of the present invention. Figure 2 Schematic diagram of a building structure on a collapsible loess foundation provided by an embodiment of the present invention. Figure 1 Shown and Figure 2 As shown, the method specifically includes the following steps:

[0026] Step S102 : Drill downwardly oblique holes around the foundation slab of the target building 10 to form first curtain holes 1 and inject grout to form an inclined water retaining curtain wall 21 ; wherein the target building 10 is a building on a foundation of collapsible loess layer 40 .

[0027] In step S104 , a second curtain hole 2 is formed by vertically drilling downwards in the outer circle of the first curtain hole 1 and grouting is performed to form an enclosed vertical water retaining curtain wall 22 .

[0028] Step S106 : drilling vertically downwards based on the hole position of the first curtain hole 1 until reaching the bottom elevation of the raft 20 of the target building 10 to form a first reinforcement grouting hole 3 , and injecting grout into the first reinforcement grouting hole 3 to form an irregular reinforcement body 23 .

[0029] Figure 3 Schematic diagram of a building foundation structure reinforcement on a collapsible loess foundation provided by an embodiment of the present invention. Figure 3 As shown:

[0030] Step S108, drilling a hole from the ground into the underground to form a second reinforcement grouting hole 4, and injecting cement slurry into the second reinforcement grouting hole 4, so that the cement slurry penetrates into the cracks in the collapsible loess layer 40 and fills and compacts the collapsible loess to form a collapsible loess layer reinforcement body 24; wherein, the collapsible loess layer reinforcement body 24 is connected to the pile foundation 30 of the target building 10 as a whole.

[0031] Step S110: Drill a hole downward from the ground to a preset depth below the collapsible loess layer reinforcement body 24 to form a lifting hole 5, and perform pressure grouting on the bottom of the lifting hole 5 to push the collapsible loess layer reinforcement body 24 and the pile foundation 30 upward together, thereby driving the target building 10 to be lifted to a preset height.

[0032] Preferably, 12-24 hours after the completion of the collapsible loess layer reinforcement body 24, pressure grouting is performed on the bottom of the lifting hole 5. Specifically, a segmented backward grouting and lifting operation is performed on the bottom of the lifting hole 5 based on the drilling and grouting integrated machine.

[0033] The embodiment of the present invention provides a method for reinforcing and lifting a building on a collapsible loess foundation. The arrangement of the inclined water retaining curtain wall and the vertical water retaining curtain wall further prevents the influence of groundwater on the foundation. The cement slurry penetrates into the cracks in the collapsible loess layer, fills and compacts the collapsible loess, and bonds with it to form a collapsible loess layer reinforcement body. The reinforcement body is connected to the pile as a whole and will not cause secondary settlement of the building. Pressure grouting is performed at the bottom of the lifting hole. As the slurry in the curtain wall continues to increase and solidifies rapidly, the foundation soil in the curtain wall is filled and squeezed, and the curtain wall The constraints form an upward lifting force and act on the reinforcement body; the lifting force pushes the reinforcement body to move upward and drives the building above it to lift upward synchronously, and finally the building is gradually lifted to the set lifting height; at the same time, the curtain wall isolates the foundation soil below the raft slab from the foundation soil outside the raft slab, providing a closed environment for the reinforcement body grouting and lifting grouting, avoiding interference from the external environment, preventing the loss of grouting liquid, and saving grouting materials; the reinforcement body plays a buffering role when transmitting the upward lifting force, protects the bottom plate, and reduces damage to the building.

[0034] Specifically, step S102 includes the following steps:

[0035] Step S1021 : Drill holes obliquely downward around the foundation bottom plate of the target building 10 to form a plurality of first curtain holes 1 spaced apart from each other; wherein the first curtain holes 1 extend to the top surface of the collapsible loess layer 40 .

[0036] Optionally, Figure 4 This is a schematic diagram of the partial structure of a building on a collapsible loess foundation provided by an embodiment of the present invention. Figure 4 As shown, the first curtain hole 1 is at an angle of 30° to the vertical, which can provide workers with enough space for drilling operations and facilitate construction.

[0037] Step S1022 , grouting is injected into the first curtain holes 1 so that the grouting ranges of two adjacent first curtain holes 1 overlap with each other to form an inclined water retaining curtain wall 21 .

[0038] Preferably, the first curtain hole 1 is vertically divided into multiple sections and grouting is sequentially performed based on a drilling and grouting machine.

[0039] Figure 5 1 is a top view of a first curtain hole and a second curtain hole provided according to an embodiment of the present invention. Figure 5 As shown, the first curtain holes 1 are located approximately 2.0-2.7 meters above ground level from the exterior wall of the target building 10, with a spacing of 2.0 meters between holes. The first curtain holes 1 are constructed using the skip-hole method, with grouting injected into the first curtain holes 1 using a drilling and grouting machine. Grouting areas of two adjacent first curtain holes 1 overlap, forming an inclined water-retaining curtain wall 21 with an effective thickness of 3 meters. The grouting pressure within the first curtain holes 1 is determined based on the designed thickness of the curtain wall and the stratum, and is generally 0.3-0.5 MPa.

[0040] Figure 6 1 is a schematic diagram of the overall structure of a curtain wall and a building provided according to an embodiment of the present invention. Figure 6 As shown, the inclined water retaining curtain wall 21 is formed in a pyramid shape.

[0041] Through the above technical solution, the inclined water-retaining curtain wall 21 has a certain slope. Under extreme rainfall conditions in the rainy season (heavy rainfall in a short period of time), after the liquid such as rainfall on the ground penetrates, it diffuses at a certain angle to a range far away from the foundation of the building, thereby avoiding the rainwater from directly and quickly penetrating into the collapsible loess foundation of the building and its surrounding areas, providing a larger stable area for the foundation of the building and reducing the settlement and deformation of the foundation.

[0042] Specifically, step S104 further includes the following steps:

[0043] In step S1041 , holes are drilled vertically downward in the outer area of ​​the first curtain hole 1 to form a plurality of spaced second curtain holes 2 ; the bottoms of the second curtain holes 2 are set below the collapsible loess layer reinforcement 24 .

[0044] like Figure 5 As shown, the second curtain hole 2 is located within a certain range of the outer circle of the first curtain hole 1, with a hole spacing of 2.0m. The drilling depth is drilled below the collapsible loess layer according to geological survey data. Optionally, the second curtain hole 2 is constructed using the skip hole method.

[0045] Step S1042: Grouting is performed into the second curtain holes 2, so that the grouting areas of two adjacent second curtain holes 2 overlap, forming a closed vertical water-retaining curtain wall 22. Optionally, grouting is performed sequentially in multiple vertical sections using a drilling and grouting machine. Optionally, the effective thickness of the vertical water-retaining curtain wall 22 is 3 meters.

[0046] Specifically, the vertical retaining curtain wall 22 is constructed using a drilling and grouting machine. Grouting is performed in multiple vertical sections. After being ejected from the grouting pipe, the slurry is pressed into the surrounding soil and solidifies within 30-60 seconds. This method is highly efficient, and the slurry solidifies quickly, minimizing the softening effect on the soil and preventing secondary settlement of the building.

[0047] Optionally, the grouting pressure in the second curtain hole 2 is determined according to the designed thickness of the curtain wall and the stratum, and is generally 0.3-0.5 MPa.

[0048] like Figure 1 and Figure 6 As shown, the top end of the vertical water retaining curtain wall 22 is connected to the bottom end of the inclined water retaining curtain wall 21.

[0049] Through the above technical solution, firstly, the vertical water retaining curtain wall 22 can prevent the horizontal diffusion of the slurry of the lifting grouting, thereby saving grouting materials; secondly, the vertical water retaining curtain wall 22 is provided in the entire depth of the collapsible loess layer and below, and forms an enclosed space, which generates an extrusion pressure on the soil within the range. Since the soil is constrained by the curtain wall, the extrusion pressure is converted into vertical upward and downward forces, and the upward force forms a lifting force, which lifts the reinforced body of the collapsible loess layer and the pile foundation together.

[0050] Specifically, grouting is performed in the first reinforcement grouting hole 3 to form the irregular reinforcement body 23 , including: grouting is performed in the first reinforcement grouting hole 3 , the soil around and above the raft 20 is reinforced by grouting, and the voids in the soil within the range are filled and compacted to form the irregular reinforcement body 23 .

[0051] The first reinforcement grouting hole 3 is constructed using a skip hole method, and a drilling and grouting machine is used to inject grout into the first reinforcement grouting hole 3.

[0052] In this embodiment of the present invention, pressure grouting at the bottom of the lifting hole 5 is performed using a drilling and grouting machine, with grouting and lifting performed in stages and in reverse. This prevents the grout from splitting the foundation and creating leaking channels due to continuous grouting at the same point or increased grouting pressure. Multiple reverse grouting ensures that the grout applies a more uniform pressure to the surrounding soil, resulting in a more even lifting effect.

[0053] like Figure 1 As shown, the irregular reinforcement 23 is interconnected with the inclined water-retaining curtain wall 21 and the raft 20, forming a mutually supporting structure. This effectively prevents rainwater from flowing into the loess foundation through the gap between the building and the inclined water-retaining curtain wall, thereby preventing further deformation of the loess foundation due to wetting. It also helps to limit the lateral displacement of the raft foundation.

[0054] like Figure 4As shown, the bottom of the second reinforcement grouting hole 4 extends into the collapsible loess layer 40.

[0055] Figure 7 Schematic diagram of a reinforced grouting hole according to an embodiment of the present invention. Figure 3 and Figure 7 As shown, a plurality of vertical second reinforcement grouting holes 4 are opened on the indoor raft 20 of the target building 10, and the second reinforcement grouting holes 4 are arranged in a plum blossom shape of 3.0×2.8m. The outdoor second reinforcement grouting holes 4 are formed by extending the first reinforcement grouting holes 3 downward, and the bottoms of the second reinforcement grouting holes 4 extend into the collapsible loess layer 40; cement slurry is injected into the second reinforcement grouting holes 4, and the cement slurry penetrates into the cracks in the collapsible loess layer 40, fills and compacts the collapsible loess, and bonds with it, thereby forming a collapsible loess layer reinforcement body 24, and connected to the pile foundation 30 as a whole.

[0056] Preferably, the piles of the pile foundation 30 are concrete bored piles. The peripheral surface of the bored pile is an uneven rough surface, and the collapsible loess layer reinforcement body 24 formed by grouting can well form a mutual bite with the bored pile. The collapsible loess layer reinforcement body 24 acts as a buffer zone during the lifting operation, making the lifting force more uniform. The grouting of the collapsible loess layer reinforcement body 24 is carried out by a drilling and grouting machine, and forward grouting is adopted. Grouting is carried out in multiple sections vertically. After the slurry is ejected from the grouting pipe mouth, it solidifies within 30-60 seconds, and the depth of each forward movement can be 30-50 cm.

[0057] like Figure 3 As shown, 12 to 24 hours after the construction of the collapsible loess layer reinforcement body 24 in step S108 is completed, holes are arranged on the settlement side of the target building 10 and drilled downward to form lifting holes 5. The lifting holes 5 are drilled from the ground to 3-5 meters below the collapsible loess layer reinforcement body 24. The drilling angle is such that the bottom of the hole extends to just below the load-bearing wall or structural column of the target building 10. The bottom of the lifting hole 5 is higher than the bottom of the vertical water retaining curtain wall 22. The drilling and grouting of the lifting hole 5 are carried out using a drilling and grouting machine. During the drilling process, reinforced concrete structures such as raft foundations are avoided to prevent the drill from getting stuck.

[0058] Then, a staged backward grouting method is used for lifting. Specifically, after drilling to a set depth, pressure grouting is performed at the bottom of the lifting hole 5. As the grout in the vertical water retaining curtain wall 22 continues to increase, the injected grout quickly solidifies and continuously fills and compacts the soil layer in the vertical water retaining curtain wall 22. As the pressure increases and the density increases, a lifting force is generated, slowly lifting the target building 10.

[0059] After grouting for a certain period of time, under the same pressure, the injection speed of the slurry continues to slow down. At this time, the grouting pipe is retreated 10-30cm and pressure grouting is continued. After multiple retreats, the slurry is continuously injected into the vertical retaining curtain wall 22, filling and compacting the soil within the range, so that the target building 10 is continuously lifted to the set lifting height. In order to make the slurry outlet of the grouting pipe retreat to the bottom of the collapsible loess layer reinforcement body 24 before lifting the target building 10 to the set lifting height, the bottom of the lifting hole 5 is generally extended to 3-5m below the bottom of the collapsible loess layer reinforcement body 24. The distance of each retreat can also be adjusted according to actual conditions. The principle of setting the grouting pressure during the pressure grouting process is: the base pressure is equal to the gravity of the target building 10 / the area of ​​the raft 20, and the grouting pressure should be greater than the base pressure and less than 1.8 times the base pressure.

[0060] From the above description, it can be seen that the present invention provides a method for reinforcing and lifting a building on a collapsible loess foundation, which has the following beneficial effects compared with the prior art:

[0061] (1) The setting of the inclined water retaining curtain wall prevents rainwater from directly and rapidly infiltrating into the collapsible loess foundation of the building and its surrounding areas under extreme rainfall conditions, providing a larger stable area for the building foundation and reducing the settlement and deformation of the foundation; the vertical water retaining curtain wall forms an enclosed space, exerting a squeezing force on the soil within the range, making the lifting force more concentrated and effective, and the lifting speed more uniform and controllable. At the same time, the vertical water retaining curtain wall can prevent the slurry of the lifting grouting from spreading horizontally, saving grouting materials and improving construction efficiency.

[0062] (2) Grouting is performed in the collapsible loess layer. The cement slurry penetrates into the collapsible loess layer, forming a collapsible loess reinforcement body that is connected to the pile foundation as a whole. Under the action of lifting grouting, the collapsible loess reinforcement body is lifted together with the pile foundation, thereby lifting and correcting the deviation of the building, and preventing secondary settlement of the building.

[0063] (3) Pressure grouting is performed at the bottom of the lifting hole. As the slurry in the curtain wall continues to increase and solidifies rapidly, the foundation soil in the curtain wall is filled and squeezed. In addition, the curtain wall is constrained, forming an upward lifting force that acts on the reinforcement body. The lifting force pushes the reinforcement body upward and drives the building above it to rise synchronously. Finally, the building is gradually lifted to the set lifting height.

[0064] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0065] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for reinforcing and lifting a building on a collapsible loess foundation, characterized in that: include: Drill holes obliquely downward around the foundation slab of the target building to form the first curtain hole and inject grout to form an inclined water retaining curtain wall; The target building is a building on a collapsible loess foundation; Drilling holes vertically downward in the outer circle of the first curtain hole to form a second curtain hole and injecting grout into the hole to form a closed vertical water retaining curtain wall; Based on the hole position of the first curtain hole, vertically drill downward to the bottom elevation of the raft slab of the target building to form a first reinforcement grouting hole, and inject grout into the first reinforcement grouting hole to form an irregular reinforcement body; Drilling a second reinforcement grouting hole from the ground into the underground, injecting cement slurry into the second reinforcement grouting hole, so that the cement slurry penetrates into the cracks in the collapsible loess layer and fills and compacts the collapsible loess to form a collapsible loess layer reinforcement body; the collapsible loess layer reinforcement body is connected to the pile foundation of the target building as a whole; Drilling a hole from the ground to a preset depth below the collapsible loess layer reinforcement body to form a lifting hole, performing pressure grouting at the bottom of the lifting hole to push the collapsible loess layer reinforcement body and the pile foundation upward together, driving the target building to be lifted to a preset height; Drill holes downwardly around the foundation slab of the target building to form the first curtain hole and inject grout to form an inclined water retaining curtain wall, including: Drilling holes obliquely downward around the foundation slab of the target building to form a plurality of first curtain holes spaced apart; the first curtain holes extend to the top surface of the collapsible loess layer; Grouting is injected into the first curtain holes so that the grouting ranges of two adjacent first curtain holes overlap with each other to form the inclined water retaining curtain wall; the inclined water retaining curtain wall is formed in a pyramid shape.

2. The method according to claim 1, wherein: Drilling holes vertically downward in the outer circle of the first curtain hole to form a second curtain hole and injecting grout to form an enclosed vertical water retaining curtain wall, including: Drilling holes vertically downward in the outer circle of the first curtain holes to form a plurality of spaced second curtain holes; the bottoms of the second curtain holes extend below the reinforced body of the collapsible loess layer; Grouting is injected into the second curtain holes so that the grouting ranges of two adjacent second curtain holes overlap with each other to form an enclosed vertical water retaining curtain wall.

3. The method according to claim 2, wherein: Grouting into the second curtain hole includes: grouting the second curtain hole in a plurality of sections in a vertical direction in sequence using a drilling and grouting machine.

4. The method according to claim 1, wherein: The top end of the vertical water retaining curtain wall is connected to the bottom end of the inclined water retaining curtain wall.

5. The method according to claim 1, wherein: Grouting into the first reinforcement grouting hole to form an irregular reinforcement body includes: grouting in the first reinforcement grouting hole, grouting and reinforcing the soil around and above the raft slab, and filling the voids in the soil within the range to form the irregular reinforcement body.

6. The method according to claim 1, wherein: The irregular reinforcement body, the inclined water retaining curtain wall and the raft slab are connected to each other and serve as mutual supporting structures.

7. The method according to claim 1, wherein: The bottom of the second reinforcement grouting hole extends into the collapsible loess layer.

8. The method according to claim 1, wherein: Performing pressure grouting on the bottom of the lifting hole includes: performing pressure grouting on the bottom of the lifting hole 12-24 hours after the reinforcement of the collapsible loess layer is completed.

9. The method according to claim 1, wherein: The pressure grouting is performed on the bottom of the lifting hole, comprising: performing a segmented backward grouting and lifting operation on the bottom of the lifting hole based on a drilling and grouting machine.

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