Grouting lifting method for settlement of brick-concrete structure strip foundation on collapsible loess foundation
By setting monitoring points and grouting lifting ports in brick-concrete structures on collapsible loess foundations, and using dry drilling and quick-setting agent grouting methods, the settlement problem of brick-concrete structures on collapsible loess foundations was solved, and the safety and stability of the buildings and the soil density were improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- BEIJING HENGXIANG HONGYE FOUND REINFORCEMENT TECH CO LTD
- Filing Date
- 2025-08-01
- Publication Date
- 2026-07-24
AI Technical Summary
Uneven settlement of brick-concrete structures on collapsible loess foundations leads to local tilting, subsidence, and component cracking. Existing technologies are insufficient for effective targeted grouting and reinforcement.
The method of setting up monitoring points, setting up grouting lifting ports, and drilling grouting reinforcement was adopted. The brick-concrete structure was grouted and lifted in stages by dry drilling at low speed and reaction with quick-setting agent to form stable grout, ensuring the construction sequence and effect. The soil density was evaluated by shear wave velocity.
It effectively improves the safety and stability of brick-concrete structures, reduces the risk of foundation subsidence, ensures the safe use of buildings, and achieves a significant improvement in soil density.
Smart Images
Figure CN120592287B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of settlement treatment technology for brick-concrete structures, and specifically relates to a grouting and lifting method for the settlement of strip foundations of brick-concrete structures on collapsible loess foundations. Background Technology
[0002] Loess itself is relatively dense and, under natural moisture content, often possesses high strength and low compressibility. However, when soaked by rainwater or other liquids, its shear strength rapidly decreases, leading to soil structure damage and significant subsidence, forming collapsible loess. This causes localized tilting and subsidence of buildings, cracking of major components, and impacts functionality. This problem is particularly pronounced in brick-concrete structures, which have low stiffness and poor ductility. Brick masonry is a brittle material with weak tensile and shear strength, making it sensitive to uneven settlement. The foundation form of brick-concrete structures is generally strip foundation, which differs significantly from the raft foundations and pile foundations of shear walls, frame structures, and other structures during grouting and lifting. Therefore, targeted grouting and lifting designs are necessary for this specific situation. Summary of the Invention
[0003] This invention provides a grouting and lifting method for the settlement of strip foundations of brick-concrete structures on collapsible loess foundations, in order to solve technical problems such as monitoring, grouting, lifting and reinforcement of brick-concrete structures on collapsible loess foundations.
[0004] To achieve the above objectives, the present invention adopts the following technical solution: The brick-concrete structure includes brick masonry walls, floor slabs perpendicular to the walls, and strip foundations connected to the bottom of the walls. The strip foundations are divided into horizontal transverse and horizontal longitudinal foundations. There is collapsible loess foundation under the strip foundations and corresponding settlement occurs. The specific steps of the grouting and lifting method for settlement of strip foundations of brick-concrete structures on collapsible loess foundations are as follows: Step 1: Place monitoring points at the corners of the outer walls of the building, at the junctions of longitudinal and transverse walls, and on both sides of the settlement joints of each brick-concrete structure building unit; in the vertical direction, place monitoring points at the top of the first-floor walls; connect the placed monitoring points along the longitudinal wall direction to form an axis. Step 2: Investigate the settlement of the existing brick-concrete structure, number the transverse walls according to the grouting construction sequence, and determine at least the settlement of the four corners of the independent brick-concrete structural unit. Step 3: Set up grouting lifting ports on the outside of the brick-concrete structure. The grouting lifting ports are arranged on the longitudinal outside of the brick-concrete structure corresponding to the transverse wall axis, and the holes are drilled at an angle. Step 4: Grouting reinforcement is carried out on the shallow and deep soil layers under the strip foundations through the grouting lift ports. Grouting lift is performed on the lift zone in the middle of the shallow and deep reinforcement zones. First, the strip foundation under the transverse wall on the side with the greatest settlement is lifted. The original grouting lift port is used. The grouting lift is started from the bottom of the intersection of the transverse and longitudinal strip foundations to form the lifting force point and lift the transverse wall. Starting from the side with the greatest settlement, the transverse walls are lifted one by one in the order of the previous numbering. Step 5: After the lifting is completed, the allowable local tilt value for the brick-concrete structure is 0.003, and the allowable longitudinal overall tilt value for each unit of the brick-concrete structure is 0.005. Step 6: Test the collapsibility of the loess foundation under the strip foundation. If the shear wave velocity Vs > 300 m / s, it indicates that the compaction has been significantly improved and the reinforcement treatment has met the standard. If Vs does not meet the standard in some areas, the area needs to be reinforced by grouting.
[0005] Furthermore, in step one, the transverse walls are brick-concrete structures arranged along the short side, and the longitudinal walls are set perpendicular to the transverse walls; the longitudinal walls are arranged along the long side of the brick-concrete structure, set in stages and connected to each transverse wall.
[0006] Furthermore, the first-floor walls of brick-concrete structures bear high pressure and develop diagonal cracks under uneven settlement; monitoring points are set at the diagonal cracks on the first floor or at locations prone to diagonal cracks; these diagonal cracks are those that meet the requirements of use and functionality in brick-concrete structures, and if they exceed the design requirements or cannot meet normal use, the brick-concrete structure itself should be repaired or taken out of service.
[0007] Furthermore, in step four, starting from the side with the greatest settlement, the transverse walls are raised one by one, and construction is carried out in sequence according to the previous numbering; during the construction process, a monitoring system is used to precisely monitor the displacement changes of each monitoring point; Among them, the numbered monitoring points are set at the outer edge of the long position of the brick-concrete structure, and the grouting lifting ports of the transverse walls that are close to each other are set with the same number, and the grouting construction is carried out synchronously for those with the same number. The distance between the grouting lifting port and the outer wall shall not be less than 1.0m.
[0008] Furthermore, when drilling for grouting and lifting, dry drilling should be used in collapsible loess foundations to prevent water from the drill bit from causing further subsidence of the foundation. During drilling, the drill bit should be rotated at a low speed of ≤50 rpm to reduce vibration and disturbance to the borehole wall. For each auger drill depth of 0.5~1m, the drill bit should be lifted to remove slag and prevent blade blockage. During drilling, the grout is mixed at the grout outlet. This prevents water from entering the collapsible loess foundation and causing further subsidence when the foundation comes into contact with water. A quick-setting agent was added to the grout to accelerate the setting speed, with the setting time controlled between 5 and 30 seconds. At the same time, the quick-setting agent in the grout can also react with soluble salts in collapsible loess to form stable insoluble components, preventing collapse caused by their dissolution.
[0009] Furthermore, in step four, the shallow and deep soils under the strip foundation are reinforced by grouting through the grouting lifting port. The shallow soils are grouted through the shallow reinforcement hole, and the deep soils are grouted through the deep reinforcement hole. When shallow reinforcement grouting is performed, it acts as a buffer to transmit upward lifting force, protecting the base plate and reducing damage to the building; deep reinforcement provides support for the lifting operation of the upper soil, enabling the settlement side of the building to be lifted steadily.
[0010] Furthermore, the thickness of the shallow reinforcement layer increases with the increase of the superstructure load. When the superstructure has 1 to 2 floors, the thickness of the shallow reinforcement layer is 3m; when the superstructure has 3 to 5 floors, the thickness of the shallow reinforcement layer is 5m; when the superstructure has 6 floors or more, the thickness of the shallow reinforcement layer is 7m. At the same time, low-pressure grouting of 0.5 to 1.0 MPa is used during shallow reinforcement to focus on reinforcement and 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 points on the foundation within 6m to 10m along the longitudinal direction of the brick-concrete load-bearing structure to its distance; that is, the horizontal distance satisfies b=6~10m. Then, the ratio of the settlement displacement difference ΔS(m) to b is calculated to see if the local tilt requirement is met, that is: ΔS / b≤0.003; and the monitoring points on each axis are calculated in a cross-overlapping manner to ensure that all positions meet the local tilt calculation.
[0012] Furthermore, each unit of the brick-concrete structure is inclined longitudinally as a whole, as shown in the following formula: △S 总 / b 总 ≤0.005; △S 总 b is the difference in settlement (m) between the two longitudinal ends of the building unit. 总 The longitudinal length (m) of the building unit.
[0013] Furthermore, surface wave exploration was used to explore the foundation. By analyzing the dispersion characteristics of Rayleigh surface waves on the ground, the shear wave velocity (Vs) profile of the underground soil layers was inverted to quantify the changes in soil density. During on-site data acquisition: geophones were linearly arranged on the 1m ring around the outer perimeter of the brick-concrete structure and in the middle of the two strip foundations, with a geophone interval of 1m, to check the surface wave signal in real time and acquire data signals at multiple offsets; the dispersion curve was extracted from the acquired data and the shear modulus Vs was inverted; the soil compaction and reinforcement effect were evaluated based on the magnitude of the shear wave velocity Vs. Specifically, when Vs > 300 m / s, the risk level of subsidence is no risk, and the corresponding physical state is dense; when Vs ≤ 300 m / s, the risk level of subsidence is low risk, and the corresponding physical state is slightly dense; when Vs < 240 m / s, the risk level of subsidence is medium risk, and the corresponding physical state is loose; when Vs < 220 m / s, the risk level of subsidence is high risk, and the corresponding physical state is extremely loose. After grouting reinforcement and lifting, if the shear wave velocity Vs > 300 m / s, it indicates that the density has been significantly improved and the reinforcement treatment has met the standard. If the Vs in a local area does not meet the standard, the area needs to be further reinforced by grouting.
[0014] The beneficial effects of this invention are reflected in: 1) The present invention, through the horizontal and vertical arrangement and stress form of the wall, facilitates the determination of the location of the grouting lifting port and the construction sequence, and also facilitates the determination of the lifting force point of grouting, which greatly ensures the construction effect of grouting reinforcement and lifting. 2) By utilizing the transverse wall, the transverse wall plays a decisive role in seismic performance and vertical load transfer. By simultaneously applying force to lift multiple points of a transverse wall strip foundation, the safety of the transverse wall load-bearing components is better guaranteed, thus providing better assurance for the safety of the entire structure. 3) This invention takes advantage of the characteristic that the first-floor walls of brick-concrete structures are prone to cracking. Monitoring points are arranged on the first-floor walls, densely distributed at the intersections of horizontal and vertical walls. The local tilt values of two monitoring points and the tilt value of the entire unit are calculated by cross-overlapping. This allows for the local tilt of the wall at each location, thereby better ensuring the effect and safety after the lifting. Furthermore, the soil compaction after lifting is evaluated by using shear wave velocity, which helps to ensure the soil reinforcement effect. 4) The drilling method in this 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, causing the foundation to collapse further when it encounters water.
[0015] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention; the main objects and other advantages of the invention may be realized and obtained by means of the embodiments particularly pointed out in the description. Attached Figure Description
[0016] Figure 1 This is a vertical schematic diagram of the monitoring point layout; Figure 2 This is a schematic diagram of the monitoring point layout; Figure 3 This is a schematic diagram of the layout of the grouting lifting ports; Figure 4 This is a schematic diagram of grouting in the shallow and deep reinforcement zones; Figure 5 This is a schematic diagram of grouting in the uplift zone; Figure 6 This is a schematic diagram of the detector arrangement.
[0017] Attached diagram labels: 1-wall, 2-floor slab, 3-strip foundation, 4-monitoring point, 5-grouting and lifting port, 6-shallow reinforcement hole, 7-deep reinforcement hole, 8-shallow reinforcement zone, 9-deep reinforcement zone, 10-lifting hole, 11-lifting zone, 12-lifting force application point. Detailed Implementation
[0018] Taking a residential building project as an example, the building has 7 floors above ground, no basement, two stairwell units, and an expansion joint in the middle. The building is 41.8m long and 10.8m wide, with a roof structure elevation of 20.75m. The building's ±0.000 elevation corresponds to absolute elevations of 291.62m and 290.39m. The first floor is commercial space, and the upper floors are residential. The building structure is brick-concrete with strip foundations. The foundation bottom elevations are -1.35m and -0.12m, with a foundation depth of -1.35m. The foundation soil is mainly collapsible loess. Heavy rain caused water to seep into the foundation, resulting in subsidence and uneven settlement. Therefore, foundation reinforcement and lifting are necessary to further control the uneven settlement in the area, which could lead to wall tilting and cracking.
[0019] Combination Figures 1 to 6 As shown, the brick-concrete structure includes a brick masonry wall 1, a floor slab 2 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 horizontal and vertical settings. There is a collapsible loess foundation under the strip foundation 3 and corresponding settlement exists.
[0020] Combination Figures 1 to 2 To further explain, the grouting and lifting method for settlement of strip foundations of brick-concrete structures on collapsible loess foundations involves the following specific steps: Step 1: Place 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 brick-concrete structure unit; in the vertical direction, place monitoring points 4 at the top of the first floor wall 1; connect the placed monitoring points 4 along the longitudinal wall 1 to form an axis.
[0021] In step one, the transverse wall 1 is a wall 1 arranged along the short side of the brick-concrete structure, and the longitudinal wall 1 is set perpendicular to the transverse wall 1; the longitudinal wall 1 is arranged along the long side of the brick-concrete structure, and is set in stages and connected to each transverse wall 1.
[0022] The first-floor wall 1 of the brick-concrete structure bears a large pressure and develops diagonal cracks under uneven settlement; monitoring point 4 is set at the diagonal cracks on the first floor or at places where diagonal cracks are likely to occur; the diagonal cracks here are cracks in the brick-concrete structure that meet the requirements of use and functionality. If they exceed the design requirements or cannot meet normal use, the brick-concrete structure itself should be repaired or taken out of service.
[0023] Step 2: Investigate the settlement of the existing brick-concrete structure. Number the transverse walls 1 according to the grouting construction sequence, and determine at least the settlement at the four corners of each independent brick-concrete structural unit. In this embodiment, as shown... Figure 2 As shown, the settlement at point A1 is -22 mm, at point C1 it is -31 mm, at point A6 it is -70 mm, at point C6 it is -83 mm, at point A7 it is -81 mm, at point C7 it is -92 mm, at point A12 it is -232 mm, and at point C13 it is -241 mm. The settlement on the right side is the largest.
[0024] Step 3: Set up 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 of the transverse wall 1, and the hole is drilled at an angle.
[0025] Step 4: Grouting reinforcement is carried out on the shallow and deep soil under the strip foundation 3 through the grouting lifting port 5. Grouting lifting is carried out on the lifting zone 11 in the middle of the shallow reinforcement zone 8 and the deep reinforcement zone 9. First, the strip foundation 3 under the transverse wall 1 on the side with the largest settlement is lifted. The lifting port is still the original grouting lifting port 5. The grouting lifting starts from the bottom of the intersection of the transverse strip foundation 3 and the longitudinal strip foundation 3 to form the lifting force point 12, which lifts 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 numbering.
[0026] In step four, starting from the side with the greatest settlement, the transverse wall 1 is raised one by one, following the previously numbered sequence; during construction, a monitoring system is used to precisely monitor the displacement changes of each monitoring point 4; such as Figure 3 The numbers shown are 1-9; among them, the number corresponds to the monitoring point 4, which is set on the outer side of the brick-concrete structure along the longitudinal direction, and the grouting lifting port 5 of the transverse wall 1 with close distance is set with the same number, and the grouting construction of the same number is carried out synchronously; the distance between the grouting lifting port 5 and the outer wall 1 is not less than 1.0m.
[0027] In step four, the shallow 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 grouting is performed, it acts as a buffer to transmit upward lifting force, protecting the base plate and reducing damage to the building; deep reinforcement provides support for the lifting operation of the upper soil, enabling the settlement side of the building to be lifted steadily.
[0028] In this embodiment, when drilling for grouting and lifting, dry drilling is used in collapsible loess foundations to prevent water from the drill bit from causing further subsidence of the foundation. During drilling, the drill bit rotates at a low speed of ≤50rpm to reduce vibration and disturbance to the borehole wall. The auger is lifted to remove slag every 0.5~1m of drilling depth to prevent blade blockage.
[0029] In this embodiment, during drilling, the slurry is mixed at the slurry outlet, so that when the slurry is discharged, water will not enter the collapsible loess foundation, causing the foundation to collapse further when it encounters water.
[0030] A quick-setting agent was added to the grout to accelerate the setting speed, with the setting time controlled between 5 and 30 seconds. At the same time, the quick-setting agent in the grout can also react with soluble salts in collapsible loess to form stable insoluble components, preventing collapse caused by their dissolution.
[0031] In this embodiment, the thickness of the shallow reinforcement layer increases with the increase of the upper load. When the upper brick-concrete structure has 1 to 2 layers, the thickness of the shallow reinforcement layer is 3m; when the upper structure has 3 to 5 layers, the thickness of the shallow reinforcement layer is 5m; when the upper structure has 6 layers or more, the thickness of the shallow reinforcement layer is 7m. At the same time, low-pressure grouting of 0.5 to 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 local tilt value of the brick-concrete structure is 0.003, and the allowable longitudinal overall tilt value of each unit of the brick-concrete structure is 0.005.
[0033] In step five, local tilt refers to the ratio of the settlement difference between two points on the foundation within 6m to 10m along the longitudinal direction of the brick-concrete load-bearing structure to its distance; that is, the horizontal distance must be b=6~10m. Then, calculate the ratio of the settlement displacement difference ΔS(m) to b to see if it meets the local tilt requirement, that is: ΔS / b≤0.003; and perform cross-over calculations on monitoring points 4 on each axis to ensure that all positions meet the local tilt calculation.
[0034] In this embodiment, each unit of the brick-concrete structure is inclined longitudinally as a whole, as shown in the following formula: △S 总 / b 总 ≤0.005; △S 总 Let m and b be the settlement difference between the two longitudinal ends of the building unit. 总 Let m be the longitudinal length of the building unit.
[0035] When calculating the local tilt by performing front-to-back overlap calculations for monitoring point 4 on each axis: Figure 2 Cross-check the ΔS and b corresponding to (A1, A3), (A2, A4), (A3, A5), (A4, A6), (A7, A9), (A8, A10), (A9, A11), (A10, A12), (B1, B3), (B2, B4), (B3, B5), (B4, B6), (B7, B9), (B8, B10), (B9, B11), (B10, B12), (C1, C3), (C2, C4), (C3, C5), (C4, C6), (C5, C7), (C8, C10), (C9, C11), (C10, C12), and (C11, C13) to ensure that their ratio is ≤0.003.
[0036] The longitudinal overall tilt check is to calculate the tilt of the entire system. Figure 2 Let (A1, A6), (A7, A12), (B1, B7), (B8, B13), (C1, C7), and (C8, C13) correspond to △S respectively. 总 and b 总 Perform a verification to ensure that the ratio is ≤0.005.
[0037] Step 6: Test the collapsibility of the loess foundation under strip foundation 3. If the shear wave velocity Vs > 300 m / s, it indicates that the compaction has been significantly improved and the reinforcement treatment has met the standard. If Vs does not meet the standard in some areas, the area needs to be reinforced by grouting.
[0038] The foundation was explored using surface wave exploration techniques. By analyzing the dispersion characteristics of Rayleigh surface waves at the surface, the shear wave velocity Vs profile of the underground soil layers was inverted, and the changes in soil density were quantified. During on-site data acquisition: geophones 13 are linearly arranged on the 1m ring around the brick-concrete structure and in the middle of the two strip foundations 3, with geophones 13 spaced 1m apart, to check the surface wave signal in real time and acquire data signals at multiple offsets; the dispersion curve is extracted from the acquired data and the shear modulus Vs is inverted; the soil compaction and reinforcement effect are evaluated based on the magnitude of the shear wave velocity Vs. Specifically, when Vs > 300 m / s, the risk level of subsidence is no risk, and the corresponding physical state is dense; when Vs ≤ 300 m / s, the risk level of subsidence is low risk, and the corresponding physical state is slightly dense; when Vs < 240 m / s, the risk level of subsidence is medium risk, and the corresponding physical state is loose; when Vs < 220 m / s, the risk level of subsidence is high risk, and the corresponding physical state is extremely loose. After grouting reinforcement and lifting, if the shear wave velocity Vs > 300 m / s, it indicates that the density has been significantly improved and the reinforcement treatment has met the standard. If the Vs in a local area does not meet the standard, the area needs to be further reinforced by grouting.
[0039] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.
Claims
1. A grouting and lifting method for settlement of strip foundations of brick-concrete structures on collapsible loess foundations, characterized in that, The brick-concrete structure includes brick masonry walls (1), floor slabs (2) set perpendicular to the walls (1), and strip foundations (3) connected to the bottom of the walls (1); the strip foundations (3) are divided into horizontal transverse and horizontal longitudinal settings, and there is collapsible loess foundation under the strip foundations (3) and corresponding settlement exists; The specific steps of the grouting and lifting method for settlement of strip foundations of brick-concrete structures on collapsible loess foundations are as follows: Step 1: Place monitoring points (4) at the corners of the outer walls (1) of the building, at the junctions of the longitudinal walls (1) and the transverse walls (1), and on both sides of the settlement joints of each building unit in the brick-concrete structure; in the vertical direction, place the monitoring points (4) at the top of the first-floor walls (1); connect the placed monitoring points (4) along the longitudinal wall (1) to form an axis. Step 2: Explore the settlement of the existing brick-concrete structure, number the transverse walls (1) according to the grouting construction sequence, and determine at least the settlement of the four corners of the independent brick-concrete structural unit. Step 3: Set up 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 of the transverse wall (1), and the hole is drilled at an angle. Step 4: Grouting reinforcement is carried out on the shallow and deep soil under the strip foundation (3) through the grouting lifting port (5). Grouting lifting is carried out on the lifting area (11) in the middle of the shallow reinforcement area (8) and the deep reinforcement area (9). First, the strip foundation (3) under the transverse wall (1) on the side with the largest settlement is lifted. The lifting port is still the original grouting lifting port (5). The grouting lifting starts from the bottom of the intersection of the transverse strip foundation (3) and the longitudinal strip foundation (3) to form the lifting force point (12) and 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. Step 5: After the lifting is completed, the allowable local tilt value for the brick-concrete structure is 0.003, and the allowable longitudinal overall tilt value for each unit of the brick-concrete structure is 0.
005. Step 6: Test the collapsibility of the loess foundation under the strip foundation (3). If the shear wave velocity Vs > 300 m / s, it indicates that the density has been significantly improved and the reinforcement treatment meets the standard. If the Vs in a local area does not meet the standard, the area needs to be reinforced by grouting.
2. The grouting and lifting method for settlement of strip foundations of brick-concrete structures on collapsible loess foundations as described in claim 1, characterized in that, In step one, the transverse wall (1) is a wall (1) arranged along the short side of the brick-concrete structure, and the longitudinal wall (1) is set perpendicular to the transverse wall (1); the longitudinal wall (1) is arranged along the long side of the brick-concrete structure, and is set in stages and connected to each transverse wall (1).
3. The grouting and lifting method for settlement of strip foundations of brick-concrete structures on collapsible loess foundations as described in claim 2, characterized in that, The first-floor wall (1) of the brick-concrete structure bears a large pressure and produces diagonal cracks under uneven settlement; the monitoring point (4) is set at the diagonal crack of the first floor or at the place where diagonal cracks are likely to occur; the diagonal cracks here are the cracks of the brick-concrete structure that meet the requirements of use and functionality. If they exceed the design requirements or cannot meet the normal use, the brick-concrete structure body shall be repaired or taken out of service.
4. The grouting and lifting method for settlement of strip foundations of brick-concrete structures on collapsible loess foundations as described in claim 3, characterized in that, In step four, starting from the side with the greatest settlement, the transverse wall (1) is raised one by one and constructed in sequence according to the previous numbering; during the construction process, a monitoring system is used to precisely monitor the displacement changes of each monitoring point (4); Among them, the number corresponding to the monitoring point (4) is set at the outer extension of the brick-concrete structure along the length, and the grouting lifting port (5) of the horizontal wall (1) with similar distance is set with the same number, and the grouting construction of the same number is carried out simultaneously. The distance between the grouting lifting port (5) and the outer wall (1) shall not be less than 1.0m.
5. The grouting and lifting method for settlement of strip foundations of brick-concrete structures on collapsible loess foundations as described in claim 4, characterized in that, When drilling for grouting and lifting, dry drilling should be used in collapsible loess foundations to prevent water from the drill bit from causing further subsidence of the foundation. During drilling, the drill bit should be rotated at a low speed of ≤50rpm to reduce vibration and disturbance to the borehole wall. For auger drills, the drill bit should be lifted and the slag removed after each 0.5~1m of drilling depth to prevent blade blockage. During drilling, the grout is mixed at the grout outlet. This prevents water from entering the collapsible loess foundation and causing further subsidence when the foundation comes into contact with water. A quick-setting agent was added to the grout to accelerate the setting speed, with the setting time controlled between 5 and 30 seconds. At the same time, the quick-setting agent in the grout can also react with soluble salts in collapsible loess to form stable insoluble components, preventing collapse caused by their dissolution.
6. The grouting and lifting method for settlement of strip foundations of brick-concrete structures on collapsible loess foundations as described in claim 5, characterized in that, In step four, 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 grouting is performed, it acts as a buffer to transmit upward lifting force, protecting the base plate and reducing damage to the building; deep reinforcement provides support for the lifting operation of the upper soil, enabling the settlement side of the building to be lifted steadily.
7. The grouting and lifting method for settlement of strip foundations of brick-concrete structures on collapsible loess foundations as described in claim 6, characterized in that, The thickness of the shallow reinforcement layer 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, when the shallow reinforcement is carried out, a small pressure grouting of 0.5 to 1.0MPa is used to reinforce the structure and avoid the ground from bulging or causing damage to the brick-concrete structure wall (1) during shallow grouting.
8. The grouting and lifting method for settlement of strip foundations of brick-concrete structures on collapsible loess foundations as described in claim 7, characterized in that, In step five, local tilt refers to the ratio of the settlement difference between two points on the foundation within 6m to 10m along the longitudinal direction of the brick-concrete load-bearing structure to its distance; that is, the horizontal distance satisfies b=6~10m. Then, calculate the ratio of the settlement displacement difference ΔS(m) to b to see if it meets the local tilt requirement, that is: ΔS / b≤0.003; and perform front and rear cross-overlap calculations on the monitoring points (4) on each axis to ensure that all positions meet the local tilt calculation.
9. The grouting and lifting method for settlement of strip foundations of brick-concrete structures on collapsible loess foundations as described in claim 8, characterized in that, Each unit of the brick-concrete structure is inclined longitudinally as a whole, as shown in the following formula: △S 总 / b 总 ≤0.005; △S 总 b is the difference in settlement (m) between the two longitudinal ends of the building unit. 总 The longitudinal length (m) of the building unit.
10. The grouting and lifting method for settlement of strip foundations of brick-concrete structures on collapsible loess foundations as described in claim 9, characterized in that, Surface wave exploration was used to explore the foundation. By analyzing the dispersion characteristics of Rayleigh surface waves on the ground, the shear wave velocity (Vs) profile of the underground soil layers was inverted, and the change in soil density was quantified. During on-site data collection: On the 1m ring around the brick-concrete structure, in the middle of the two strip foundations (3), a geophone (13) is arranged linearly with a 1m interval between the geophones (13) 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 compaction and reinforcement effect are evaluated based on the magnitude of the shear wave velocity Vs. Specifically, when Vs > 300 m / s, the risk level of subsidence is no risk, and the corresponding physical state is dense; when Vs ≤ 300 m / s, the risk level of subsidence is low risk, and the corresponding physical state is slightly dense; when Vs < 240 m / s, the risk level of subsidence is medium risk, and the corresponding physical state is loose; when Vs < 220 m / s, the risk level of subsidence is high risk, and the corresponding physical state is extremely loose. After grouting reinforcement and lifting, if the shear wave velocity Vs > 300 m / s, it indicates that the density has been significantly improved and the reinforcement treatment has met the standard. If the Vs in a local area does not meet the standard, the area needs to be further reinforced by grouting.