Grouting lifting method for settlement of brick-concrete structure strip-shaped foundation on collapsible loess foundation

Abstract

The invention discloses a grouting lifting method for settlement of a strip-shaped foundation of a brick-concrete structure on a collapsible loess foundation. The brick-concrete structure comprises a brick masonry wall body, a floor slab perpendicular to the wall body and the strip-shaped foundation connected to the bottom of the wall body. A collapsible loess foundation exists below the strip-shaped foundation, and corresponding settlement exists below the strip-shaped foundation; through the transverse and longitudinal arrangement form and stress form of the wall body, the position determination and the construction sequence of the grouting lifting opening are facilitated, the determination of the lifting force generation point of grouting is facilitated, and the grouting reinforcement and lifting construction effect is greatly ensured; through utilization of the transverse wall body, the transverse wall plays a decisive role in anti-seismic performance and vertical load transmission, force is applied to multiple points of a certain transverse wall strip base at the same time for lifting, the safety of a transverse wall bearing component is better guaranteed, and the safety of the whole structure is better guaranteed; and the compactness of the lifted soil body is evaluated through the shear wave velocity, so that the reinforcement effect of the soil body is ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of brick-concrete structure settlement treatment, and particularly relates to a grouting and lifting method for settlement of a brick-concrete structure strip foundation on a collapsible loess foundation. Background Art

[0002] Loess itself is relatively dense, and at its natural moisture content, it often has high strength and low compressibility. However, after being soaked by liquids such as rainwater, its shear strength decreases rapidly, the soil structure is damaged, and significant subsidence occurs, forming collapsible loess, which causes the building to partially tilt and sink, and the main components to crack, affecting its functionality. This problem is particularly prominent in brick-concrete structures, which have low stiffness and poor ductility. Brick masonry is a brittle material with weak tensile and shear resistance, and is sensitive to uneven settlement. The foundation form of brick-concrete structures is generally strip foundation, which is very different from shear walls, raft foundations of frame structures, pile foundations, etc. when it comes to grouting and lifting. Therefore, it is necessary to carry out targeted grouting and lifting design under such conditions. Summary of the Invention

[0003] The present invention provides a grouting and lifting method for settlement of a strip foundation of a brick-concrete structure on a collapsible loess foundation, which is used to solve technical problems such as monitoring, grouting, lifting and reinforcement of the brick-concrete structure on the collapsible loess foundation.

[0004] To achieve the above object, the present invention adopts the following technical solutions: The brick-concrete structure consists of brick walls, floor slabs perpendicular to the walls, and strip foundations connected to the bottom of the walls. The strip foundations are divided into horizontal and vertical settings. Under the strip foundations lies a collapsible loess foundation with corresponding settlement. The grouting and lifting method for settlement of brick-concrete strip foundation on collapsible loess foundation has the following specific steps: Step 1: Place monitoring points at the corners of the building's outer walls, at the intersections of the longitudinal and transverse walls, and on both sides of the settlement joints of each building unit in the brick-concrete structure; in the vertical direction, the monitoring points are placed at the top of the ground floor walls; connect the arranged monitoring points along the longitudinal wall direction to form an axis; Step 2: Exploring the settlement of the existing brick-concrete structure, numbering the transverse walls according to the grouting construction sequence, and determining at least the settlement of the four corners of the independent brick-concrete structural unit; Step 3: Set a grouting lifting port on the outside of the brick-concrete structure. The grouting lifting port is arranged on the longitudinal outside of the brick-concrete structure corresponding to the horizontal wall axis, and the hole is drilled obliquely. Step 4: Grouting reinforcement is performed on the shallow soil and deep soil under the strip foundation through the grouting lifting openings respectively. Grouting and lifting are performed on the lifting area in the middle of the shallow reinforcement area and the deep reinforcement area. First, the strip foundation under the transverse wall on the side with the largest settlement is lifted. The lifting opening still uses the original grouting lifting opening. The grouting and lifting force is started from the bottom of the intersection of the transverse strip foundation and the longitudinal strip foundation to form a lifting force point to lift the transverse wall. Starting from the side with the largest settlement, the transverse walls are lifted one by one, and the construction is carried out in the order of the previous numbers. Step 5: After the lifting is completed, the allowable value of the local tilt of the brick-concrete structure is 0.003, and the allowable value of the overall longitudinal tilt of each unit of the brick-concrete structure is 0.005: Step 6: Test the collapsibility of the loess foundation below the strip foundation. If the shear wave velocity Vs is greater than 300 m / s, it indicates that the density has been significantly improved and the reinforcement treatment has met the standards. If the local Vs does not meet the standards, the area needs to continue grouting reinforcement.

[0005] Furthermore, in step one, the transverse wall is a wall arranged along the short side of the brick-concrete structure, and the longitudinal wall is arranged perpendicular to the transverse wall; the longitudinal wall is arranged along the long side of the brick-concrete structure, arranged in stages and connecting each transverse wall.

[0006] Furthermore, the first-floor walls of the brick-concrete structure are under great pressure and produce oblique cracks due to uneven settlement; monitoring points are set at the oblique cracks on the first floor or at places where oblique cracks are prone to appear; the oblique cracks here are cracks in the brick-concrete structure that meet the use and functional requirements. If they exceed the design requirements or cannot meet normal use, the brick-concrete structure itself will be repaired or shut down.

[0007] Furthermore, in step 4, starting from the side with the largest settlement, the transverse walls are lifted one by one and constructed in sequence according to the previous numbers; during the construction process, a monitoring system is used to precisely monitor the displacement changes of each monitoring point; Among them, the numbered corresponding monitoring points are set at the longitudinal position of the brick-concrete structure, and the horizontal wall grouting lifting openings with similar distances are set with the same number, and the grouting construction of the same numbered ones is carried out simultaneously; The grouting lifting port must be at least 1.0m away from the outer wall.

[0008] Furthermore, when grouting and lifting drilling, dry drilling is used in collapsible loess foundations to prevent water from coming out of the drill bit and causing further subsidence of the foundation. During the drilling process, the drill rotates at a low speed of ≤50rpm to reduce vibration disturbance to the hole wall. The auger is lifted and slag is cleared every 0.5-1m to prevent blade clogging. When drilling, the slurry is allowed to form a mixed slurry at the slurry outlet. In this way, when the slurry is discharged, no water will enter the collapsible loess foundation, causing the foundation to collapse further when it encounters water. Accelerators are added to the grouting slurry to speed up the setting process and control the setting time within 5 to 30 seconds. At the same time, the accelerators in the slurry can react with the soluble salts in the collapsible loess to form stable insoluble components, thus preventing collapse caused by their dissolution.

[0009] Furthermore, in step 4, the shallow soil and deep soil under the strip foundation are reinforced by grouting through the grouting lifting port, the shallow soil is grouted through the shallow reinforcement hole, and the deep soil is grouted through the deep reinforcement hole; When shallow reinforcement is grouting, it acts as a buffer when transmitting upward lifting force, protects the bottom plate, and reduces damage to the building; deep reinforcement provides support for the upper soil lifting operation, so that the sinking side of the building can be steadily lifted.

[0010] Furthermore, the thickness of the shallow reinforcement body increases with the increase of the upper load. When the upper brick-concrete structure is 1 to 2 stories, the thickness of the shallow reinforcement layer is 3m; when the upper structure is 3 to 5 stories, the thickness of the shallow reinforcement layer is 5m; when the upper structure is 6 stories or more, the thickness of the shallow reinforcement layer is 7m; at the same time, small pressure grouting of 0.5~1.0MPa is used for shallow reinforcement, mainly for reinforcement, to avoid ground bulging or damage to the brick-concrete structure wall during shallow grouting.

[0011] Furthermore, in step five, local tilt refers to the ratio of the settlement difference between two foundation points of the brick-concrete load-bearing structure within 6m~10m in the longitudinal direction to their distance; that is, the horizontal distance satisfies b=6~10m, and then the ratio of its settlement displacement difference △S(m) and b is calculated to see whether it meets the local tilt requirement, that is: △S / b≤0.003; and the monitoring points on each axis are cross-overlapped and calculated to ensure that all positions meet the local tilt calculation.

[0012] Furthermore, each unit of the brick-concrete structure is tilted longitudinally as a whole, as shown in the following formula: △S 总 / b 总 ≤0.005; △S 总 is the settlement difference between the two longitudinal end points of the building unit (m), b 总 is the longitudinal length of the building unit (m).

[0013] Furthermore, surface wave exploration is used to explore the foundation. By analyzing the dispersion characteristics of Rayleigh surface waves on the surface, the shear wave velocity (Vs) profile of the underground soil layer is inverted to quantify the changes in soil density. During on-site data collection: geophones were linearly arranged with 1m intervals around the perimeter of the brick-concrete structure and between the two strip foundations. Surface wave signals were monitored in real time and collected at multiple offsets. Dispersion curves were extracted from the collected data and the shear modulus Vs was inverted. The shear wave velocity Vs was used to evaluate soil density and reinforcement effectiveness. Among them, when Vs>300 m / s, the collapsible risk level corresponds to no risk and the corresponding physical state is dense; between 240≤Vs≤300 m / s, the collapsible risk level corresponds to low risk and the corresponding physical state is slightly dense; between 220≤Vs<240 m / s, the collapsible risk level corresponds to medium risk and the corresponding physical state is loose; and Vs<220 m / s, the collapsible risk level corresponds to high risk and the corresponding physical state is extremely loose. After grouting reinforcement and lifting, the shear wave velocity Vs>300 m / s, indicating that the density has been significantly improved and the reinforcement treatment has met the standards; if the local Vs does not meet the standards, the area needs to continue grouting reinforcement.

[0014] The beneficial effects of the present invention are embodied in: 1) The present invention facilitates the determination of the location and construction sequence of the grouting lifting openings through the horizontal and vertical layout and force forms of the wall, and facilitates the determination of the lifting force points of the grouting, thereby greatly ensuring the construction effect of grouting reinforcement and lifting; 2) The present invention utilizes transverse walls, which play a decisive role in seismic performance and vertical load transfer. By simultaneously applying force to multiple points on a transverse wall strip foundation, the present invention better ensures the safety of the transverse wall's load-bearing components, thereby better guaranteeing the safety of the entire structure. 3) Taking advantage of the fact that the first-floor walls of brick-concrete structures are prone to cracking, the present invention arranges monitoring points on the first-floor walls, densely distributed at the intersection of the horizontal and vertical walls. The local tilt values ​​of the two monitoring points and the tilt value of the entire unit are cross-overlapped and calculated. This allows the local tilt of each wall to be determined, thereby better ensuring the effect and safety after lifting. The soil density after lifting is evaluated by shear wave velocity, which helps to ensure the soil reinforcement effect. 4) The drilling method of the present invention adopts dry drilling and low-speed rotary drilling, which reduces the disturbance to the collapsible loess during the drilling process and avoids the problem of water entering the collapsible loess foundation during the drilling process and further collapse of the foundation due to water.

[0015] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or may be understood by practicing the present invention; the main purpose and other advantages of the present invention can be realized and obtained through the solutions particularly pointed out in the description. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a vertical schematic diagram of the monitoring point layout; Figure 2 It is a plan diagram of the monitoring point layout; Figure 3 It is a schematic diagram of the layout of the grouting lifting port; Figure 4 It is a schematic diagram of grouting in shallow reinforcement area and deep reinforcement area; Figure 5 It is a schematic diagram of grouting in the lifting area; Figure 6 This is a schematic diagram of the detector arrangement.

[0017] Figure numbers: 1-wall, 2-floor, 3-strip foundation, 4-monitoring point, 5-grouting lifting port, 6-shallow reinforcement hole, 7-deep reinforcement hole, 8-shallow reinforcement area, 9-deep reinforcement area, 10-lifting hole, 11-lifting area, 12-lifting force point. DETAILED DESCRIPTION

[0018] For example, a residential building project has seven floors above ground, no basement, two staircase units, and an expansion joint in between. The building is 41.8m long and 10.8m wide, with a roof structure elevation of 20.75m. The ±0.000 elevation of the building corresponds to absolute elevations of 291.62m and 290.39m. The first floor of the building is used for commercial purposes, while the first floor above is residential. The building structure is brick-concrete with a strip foundation. The foundation bottom elevations are -1.35m and -0.12m, respectively, and the foundation depth is -1.35m. The foundation soil is primarily collapsible loess. Heavy rains have caused the foundation to soak, resulting in subsidence and uneven settlement. Therefore, the building foundation needs to be reinforced and elevated to further control the tilting and cracking of the walls caused by uneven settlement within the area.

[0019] Combine Figures 1 to 6 As shown, the brick-concrete structure includes a brick wall 1, a floor slab 2 arranged perpendicular to the wall 1, and a strip foundation 3 connected to the bottom of the wall 1; the strip foundation 3 is divided into a horizontal transverse setting and a horizontal longitudinal setting. There is a collapsible loess foundation under the strip foundation 3 and corresponding settlement occurs.

[0020] Combine Figures 1 to 2 Further explanation: the grouting and lifting method for the settlement of brick-concrete strip foundation on collapsible loess foundation has the following specific steps: Step 1: Place monitoring points 4 at the corners of the building's outer wall 1, the junction of the longitudinal wall 1 and the transverse wall 1, and on both sides of the settlement joints of each building unit of the brick-concrete structure; in the vertical direction, the monitoring points 4 are arranged at the top of the first-floor wall 1; connect the arranged monitoring points 4 along the direction of the longitudinal wall 1 to form an axis.

[0021] For step one, the transverse wall 1 is a wall 1 arranged on the short side of the brick-concrete structure, and the longitudinal wall 1 is arranged perpendicular to the transverse wall 1; the longitudinal wall 1 is arranged along the long side of the brick-concrete structure, arranged in stages and connecting each transverse wall 1.

[0022] The first-floor wall 1 of the brick-concrete structure is under great pressure and produces oblique cracks due to uneven settlement; monitoring points 4 are set at the oblique cracks on the first floor or at places where oblique cracks are likely to appear; the oblique cracks here are cracks in the brick-concrete structure that meet the use and functional requirements. If they exceed the design requirements or cannot meet normal use, the brick-concrete structure itself will be repaired or shut down.

[0023] Step 2: Exploring the settlement of the existing brick-concrete structure, numbering the transverse walls 1 according to the grouting construction sequence, and determining at least the settlement of the four corners of the independent brick-concrete structure unit. Figure 2 As shown, the settlement at point A1 is -22mm, at point C1 is -31mm, at point A6 is -70mm, at point C6 is -83mm, at point A7 is -81mm, at point C7 is -92mm, at point A12 is -232mm, and at point C13 is -241mm. Among them, the settlement on the right side is the largest.

[0024] Step 3: Set a grouting lifting port 5 on the outside of the brick-concrete structure. The grouting lifting port 5 is arranged on the longitudinal outside of the brick-concrete structure corresponding to the axis position of the transverse wall 1, and is drilled obliquely.

[0025] Step 4: Grouting reinforcement is performed on the shallow soil and deep soil under the strip foundation 3 through the grouting lifting port 5 respectively, and the lifting area 11 in the middle of the shallow reinforcement area 8 and the deep reinforcement area 9 is grouting and lifted. First, the strip foundation 3 under the transverse wall 1 on the side with the largest settlement is lifted; the lifting port still uses the original grouting lifting port 5, and the grouting lifting is started from the bottom of the intersection of the transverse strip foundation 3 and the longitudinal strip foundation 3 to form a lifting force point 12 to lift the transverse wall 1; starting from the side with the largest settlement, the transverse walls 1 are lifted one by one, and the construction is carried out in sequence according to the previous numbering.

[0026] For step 4, starting from the side with the largest settlement, the transverse walls 1 are lifted one by one and constructed in sequence according to the previous numbers; during the construction process, the monitoring system is used to accurately monitor the displacement changes of each monitoring point 4; Figure 3 The numbers shown are 1-9; among them, the numbered corresponding monitoring point 4 is set at the outward extension of the lengthwise position of the brick-concrete structure, and the grouting lifting openings 5 ​​of the transverse wall 1 with a similar distance are set with the same number, and the grouting construction of the same number is carried out simultaneously; the grouting lifting opening 5 is not less than 1.0m away from the outer wall 1.

[0027] In step 4, the shallow soil and deep soil under the strip foundation 3 are reinforced by grouting through the grouting lifting port 5, the shallow soil is grouted through the shallow reinforcement hole 6, and the deep soil is grouted through the deep reinforcement hole 7; When shallow reinforcement is grouting, it acts as a buffer when transmitting upward lifting force, protects the bottom plate, and reduces damage to the building; deep reinforcement provides support for the upper soil lifting operation, so that the sinking side of the building can be steadily lifted.

[0028] In this embodiment, when grouting and lifting drilling, dry drilling is used for drilling in collapsible loess foundation to prevent water from coming out of the drill bit and causing further collapse of the foundation. During the drilling process, the drill rotates at a low speed of ≤50rpm to reduce vibration disturbance to the hole wall. Every time the spiral drill drills 0.5~1m deep, the drill is lifted and slag is cleared to prevent blade blockage.

[0029] In this embodiment, when drilling, the slurry is allowed to form a mixed slurry at the slurry outlet. In this way, when the slurry is discharged, no water will enter the collapsible loess foundation, causing the foundation to further collapse when it encounters water.

[0030] Accelerators are added to the grouting slurry to speed up the setting process and control the setting time within 5 to 30 seconds. At the same time, the accelerators in the slurry can react with the soluble salts in the collapsible loess to form stable insoluble components, thus preventing collapse caused by their dissolution.

[0031] In this embodiment, the thickness of the shallow reinforcement body increases with the increase of the upper load. When the upper brick-concrete structure is 1 to 2 floors, the thickness of the shallow reinforcement layer is 3m; when the upper structure is 3 to 5 floors, the thickness of the shallow reinforcement layer is 5m; when the upper structure is 6 floors or more, the thickness of the shallow reinforcement layer is 7m; at the same time, small pressure grouting of 0.5~1.0MPa is used for shallow reinforcement, mainly for reinforcement, to avoid ground bulging or damage to the brick-concrete structure wall 1 during shallow grouting.

[0032] Step 5. After the lifting is completed, the allowable value of the local tilt of the brick-concrete structure is 0.003, and the allowable value of the overall longitudinal tilt of each unit of the brick-concrete structure is 0.005.

[0033] For step five, local tilt refers to the ratio of the settlement difference between two foundation points of the brick-concrete load-bearing structure within 6m~10m in the longitudinal direction to their distance; that is, the horizontal distance satisfies b=6~10m, and then the ratio of its settlement displacement difference △S(m) and b is calculated to see whether it meets the local tilt requirement, that is: △S / b≤0.003; and the monitoring point 4 on each axis is cross-overlapped and calculated to ensure that all positions meet the local tilt calculation.

[0034] In this embodiment, each unit of the brick-concrete structure is tilted longitudinally as a whole, as shown in the following formula: △S 总 / b 总 ≤0.005; △S 总 is the settlement difference between the two longitudinal end points of the building unit, m, b 总 is the longitudinal length of the building unit in m.

[0035] When calculating the local tilt by performing front-to-back cross-overlap calculation on monitoring point 4 on each axis: Figure 2 In the test, the corresponding △S and b of (A1, A3), (A2, A4), (A3, A5), (A4, A6), (A7, A9), (A8, A10), (A9, A11), (A10, A12), (B1, B 3), (B 2, B4), (B 3, B 5), (B 4, B 6), (B 7, B 9), (B 8, B 10), (B 9, B 11), (B 10, B 12), (C1, C 3), (C 2, C 4), (C 3, C 5), (C 4, C 6), (C 5, C 7), (C 8, C 10), (C 9, C 11), (C 10, C 12), and (C11, C 13) are cross-checked to ensure that the ratio is ≤0.003.

[0036] The overall longitudinal tilt verification is to Figure 2 The △S corresponding to (A1, A6), (A7, A12), (B1, B7), (B8, B13), (C1, C7) and (C8, C13) respectively 总 and b 总 Verify that the ratio is ≤0.005.

[0037] Step 6: Test the collapsibility of the loess foundation below strip foundation 3. The shear wave velocity Vs>300 m / s, indicating that the density has been significantly improved and the reinforcement treatment has met the standards. If the local Vs does not meet the standards, the area needs to continue grouting reinforcement.

[0038] Use surface wave exploration to explore the foundation. By analyzing the dispersion characteristics of Rayleigh surface waves on the surface, the shear wave velocity Vs profile of the underground soil layer is inverted to quantify the change in soil density. During on-site data collection, geophones 13 were linearly arranged in a 1m ring around the periphery of the brick-concrete structure and between the two strip foundations 3, with the geophones 13 spaced 1m apart. Surface wave signals were monitored in real time, and data signals were collected at multiple offsets. Dispersion curves were extracted from the collected data and the shear modulus Vs was inverted. The soil density and reinforcement effect were evaluated based on the shear wave velocity Vs. Among them, when Vs>300 m / s, the collapsible risk level corresponds to no risk and the corresponding physical state is dense; between 240≤Vs≤300 m / s, the collapsible risk level corresponds to low risk and the corresponding physical state is slightly dense; between 220≤Vs<240 m / s, the collapsible risk level corresponds to medium risk and the corresponding physical state is loose; and Vs<220 m / s, the collapsible risk level corresponds to high risk and the corresponding physical state is extremely loose. After grouting reinforcement and lifting, the shear wave velocity Vs>300 m / s, indicating that the density has been significantly improved and the reinforcement treatment has met the standards; if the local Vs does not meet the standards, the area needs to continue grouting reinforcement.

[0039] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that a person skilled in the art can conceive within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention.

Claims

1. A grouting and lifting method for settlement of brick-concrete strip foundation on collapsible loess foundation, characterized in that: The brick-concrete structure comprises a brick wall (1), a floor slab (2) arranged perpendicular to the wall (1), and a strip foundation (3) connected to the bottom of the wall (1); the strip foundation (3) is divided into a horizontal transverse setting and a horizontal longitudinal setting, and there is a collapsible loess foundation under the strip foundation (3) and corresponding settlement occurs; The grouting and lifting method for settlement of brick-concrete strip foundation on collapsible loess foundation has the following specific steps: Step 1: arranging monitoring points (4) at the corners of the outer wall (1) of the building, at the junction of the longitudinal wall (1) and the transverse wall (1), and on both sides of the settlement joints of each building unit of the brick-concrete structure; in the vertical direction, the monitoring points (4) are arranged at the top of the first-floor wall (1); the arranged monitoring points (4) are connected along the longitudinal wall (1) to form an axis; Step 2: Exploring the settlement of the existing brick-concrete structure, numbering the transverse walls (1) according to the grouting construction sequence, and determining at least the settlement of the four corners of the independent brick-concrete structure unit; Step 3: setting a grouting lifting port (5) on the outside of the brick-concrete structure. The grouting lifting port (5) is arranged on the longitudinal outside of the brick-concrete structure corresponding to the axis position of the transverse wall (1), and the hole is drilled obliquely; Step 4: Grouting reinforcement is performed on the shallow soil and deep soil under the strip foundation (3) through the grouting lifting port (5), and the lifting area (11) in the middle of the shallow reinforcement area (8) and the deep reinforcement area (9) is grouting and lifting. First, the strip foundation (3) under the transverse wall (1) on the side with the largest settlement is lifted; the lifting port still uses the original grouting lifting port (5), and the grouting lifting is started from the bottom of the intersection of the transverse strip foundation (3) and the longitudinal strip foundation (3) to form a lifting force point (12) to lift the transverse wall (1); starting from the side with the largest settlement, the transverse walls (1) are lifted one by one, and the construction is carried out in the order of the previous numbers; Step 5: After the lifting is completed, the allowable value of the local tilt of the brick-concrete structure is 0.003, and the allowable value of the overall longitudinal tilt of each unit of the brick-concrete structure is 0.005: Step 6: Test the collapsibility of the loess foundation below the strip foundation (3). If the shear wave velocity Vs is greater than 300 m / s, it indicates that the density has been significantly improved and the reinforcement treatment has met the standards. If the local Vs does not meet the standards, the area needs to be further reinforced by grouting.

2. The grouting and lifting method for settlement of a brick-concrete strip foundation on a collapsible loess foundation according to claim 1, characterized in that: In step 1, the transverse wall (1) is a wall (1) arranged along the short side of the brick-concrete structure, and the longitudinal wall (1) is arranged perpendicular to the transverse wall (1); the longitudinal wall (1) is arranged along the long side of the brick-concrete structure, and is arranged in stages and connects each transverse wall (1).

3. The grouting and lifting method for settlement of a brick-concrete strip foundation on a collapsible loess foundation according to claim 2, characterized in that: The first-floor wall (1) of the brick-concrete structure is subjected to great pressure and produces oblique cracks under uneven settlement; the monitoring point (4) is set at the oblique cracks on the first floor or at the place where oblique cracks are likely to appear; the oblique cracks here are cracks in the brick-concrete structure that meet the use and functional requirements. If they exceed the design requirements or cannot meet normal use, the brick-concrete structure itself will be repaired or shut down.

4. The grouting and lifting method for settlement of a brick-concrete strip foundation on a collapsible loess foundation according to claim 3, characterized in that: In step 4, starting from the side with the largest settlement, the transverse walls (1) are lifted one by one and constructed in sequence according to the previous numbers; during the construction process, the displacement changes of each monitoring point (4) are precisely monitored using a monitoring system; The numbered corresponding monitoring points (4) are set at the longitudinal position of the brick-concrete structure, and the grouting lifting openings (5) of the transverse wall (1) with similar distances are set with the same number, and the grouting construction is carried out synchronously with the same number; The distance between the grouting lifting opening (5) and the outer wall (1) is not less than 1.0m.

5. The grouting and lifting method for settlement of a brick-concrete strip foundation on a collapsible loess foundation according to claim 4, characterized in that: When grouting and lifting drilling, dry drilling is used in collapsible loess foundations to prevent water from coming out of the drill bit and causing further subsidence of the foundation. During drilling, the drill is rotated at a low speed of ≤50rpm to reduce vibration disturbance to the hole wall. The auger is lifted and slag is cleared every 0.5-1m to prevent blade clogging. When drilling, the slurry is allowed to form a mixed slurry at the slurry outlet. In this way, when the slurry is discharged, no water will enter the collapsible loess foundation, causing the foundation to collapse further when it encounters water. Accelerators are added to the grouting slurry to speed up the setting process and control the setting time within 5 to 30 seconds. At the same time, the accelerators in the slurry can react with the soluble salts in the collapsible loess to form stable insoluble components, thus preventing collapse caused by their dissolution.

6. The grouting and lifting method for settlement of a brick-concrete strip foundation on collapsible loess foundation according to claim 5, characterized in that: In step 4, the shallow soil and deep soil under the strip foundation (3) are reinforced by grouting through the grouting lifting port (5), the shallow soil is grouted through the shallow reinforcement hole (6), and the deep soil is grouted through the deep reinforcement hole (7); When shallow reinforcement is grouting, it acts as a buffer when transmitting upward lifting force, protects the bottom plate, and reduces damage to the building; deep reinforcement provides support for the upper soil lifting operation, so that the sinking side of the building can be steadily lifted.

7. The grouting and lifting method for settlement of a brick-concrete strip foundation on a collapsible loess foundation according to claim 6, characterized in that: The thickness of the shallow reinforcement body increases with the increase of the upper load. When the upper brick-concrete structure is 1 to 2 stories, the thickness of the shallow reinforcement layer is 3m; when the upper structure is 3 to 5 stories, the thickness of the shallow reinforcement layer is 5m; when the upper structure is 6 stories or more, the thickness of the shallow reinforcement layer is 7m. At the same time, small pressure grouting of 0.5 to 1.0 MPa is used for shallow reinforcement, mainly for reinforcement, to avoid ground bulging or damage to the brick-concrete structure wall (1) during shallow grouting.

8. The grouting and lifting method for settlement of a brick-concrete strip foundation on collapsible loess foundation according to claim 7, characterized in that: In step 5, local tilt refers to the ratio of the settlement difference between two points on the foundation of the brick-concrete load-bearing structure within 6m~10m in the longitudinal direction to their distance; that is, the horizontal distance satisfies b=6~10m, and then the ratio of the settlement displacement difference △S (m) and b is calculated to see whether it meets the local tilt requirement, that is: △S / b≤0.003; and the monitoring points (4) on each axis are cross-overlapped and calculated to ensure that all positions meet the local tilt calculation requirements.

9. The grouting and lifting method for settlement of a brick-concrete strip foundation on a collapsible loess foundation according to claim 8, characterized in that: Each unit of the brick-concrete structure is tilted longitudinally as a whole, as shown in the following formula: △S 总 / b 总 ≤0.005; △S 总 is the settlement difference between the two longitudinal end points of the building unit (m), b 总 is the longitudinal length of the building unit (m).

10. The grouting and lifting method for settlement of a brick-concrete strip foundation on collapsible loess foundation according to claim 9, characterized in that: Surface wave exploration is used to explore the foundation. By analyzing the dispersion characteristics of Rayleigh surface waves on the surface, the shear wave velocity (Vs) profile of the underground soil layer is inverted to quantify the changes in soil density. During on-site data collection: geophones (13) are linearly arranged on a 1m ring around the periphery of the brick-concrete structure and in the middle of the two strip foundations (3). The geophones (13) are spaced 1m apart to check the surface wave signal in real time and collect data signals at multiple offsets. The dispersion curve is extracted based on the collected data and the shear modulus Vs is inverted. The soil density and reinforcement effect are evaluated based on the shear wave velocity Vs. Among them, when Vs>300 m / s, the collapsible risk level corresponds to no risk and the corresponding physical state is dense; between 240≤Vs≤300 m / s, the collapsible risk level corresponds to low risk and the corresponding physical state is slightly dense; between 220≤Vs<240 m / s, the collapsible risk level corresponds to medium risk and the corresponding physical state is loose; and Vs<220 m / s, the collapsible risk level corresponds to high risk and the corresponding physical state is extremely loose. After grouting reinforcement and lifting, the shear wave velocity Vs>300 m / s, indicating that the density has been significantly improved and the reinforcement treatment has met the standards; if the local Vs does not meet the standards, the area needs to continue grouting reinforcement.

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