Soft soil foundation beaded membrane bag pressure compaction reinforcement device and reinforcement method

Abstract

This invention discloses a beaded membrane bag pressurization and compaction reinforcement device and method for soft soil foundations, relating to the field of building foundation reinforcement. It includes multiple membrane bag units connected sequentially by a chain conveyor. Each membrane bag unit includes at least one sequentially connected membrane bag, and one of the membrane bags in the multiple membrane bag units is connected to a branch pipe. Each branch pipe is equipped with a switch valve, and all branch pipes are connected to a common pressurization conduit. This invention implants the beaded membrane bag pressurization and compaction reinforcement device into the weak soil layer of the soft soil foundation to be reinforced. The surface of the site to be reinforced is then pressurized with grout to inject grout into the membrane bags at the designated depth using a pressurized grouting device. After the grout is injected into the corresponding membrane bags, the membrane bags expand, forming a compression reinforcement on the surrounding soil outside the membrane bags.

Description

Technical Field

[0001] This invention relates to the field of building foundation reinforcement, and more specifically, to a beaded membrane bag pressurization and compaction reinforcement device and method for soft soil foundations. Background Technology

[0002] Soft soil is widely distributed in my country, especially concentrated in coastal and riverine areas. The current urbanization phase, focusing on "stock optimization," has spurred numerous foundation reinforcement projects under complex conditions. This places higher demands on the protection and control of existing buildings, underground pipelines, and groundwater around the reinforcement sites. However, traditional reinforcement methods all have significant limitations.

[0003] Grouting reinforcement involves injecting grout under pressure to fill the pores and cement the soil in the foundation. It is suitable for foundations such as sandy soil and fractured rock, and is minimally invasive and flexible in construction. However, the grout has the problem of disordered diffusion in sites with complex soil pore structures, and dilution issues must be considered when it encounters groundwater, making it difficult to guarantee the quality of construction.

[0004] Deep mixing: This method uses machinery to force-mix cement and other curing agents with soft soil to form piles. It is suitable for soft foundation treatment such as silty soil, and is simple to construct, low in cost, and without vibration or noise. However, the pile strength is greatly affected by soil properties, requires a large site space, and is prone to uneven mixing in sand and gravel layers; the curing agent diffuses slowly, the construction period is long, the curing effect is poor in low-temperature environments, and it causes significant disturbance to the existing foundation soil.

[0005] Dynamic compaction foundation: This method uses a heavy hammer to impact the soil layer from a high height, achieving forced compaction and drainage consolidation. It is suitable for coarse-grained foundations such as gravelly soil and sandy soil, and features a large reinforcement depth (up to 10m or more), low cost, and short construction period. However, it generates significant vibration and noise, and is limited to areas with sensitive surrounding environments; soft clay sites are prone to forming rubbery soil, and saturated silt may liquefy; the surface layer is loose and requires a subbase, and uniformity is difficult to control.

[0006] To address the shortcomings of traditional technologies, such as "significant disturbance, difficulty in controlling the reinforcement range, and unstable quality," an expansion pile has been proposed in the market. This involves placing an expandable membrane bag over a steel casing, and creating grouting holes in the steel pipe that connect to the inside of the membrane bag. Grout is injected into the membrane bag through the steel pipe, compressing the soil and thus achieving reinforcement. However, existing membrane bags are all monolithic structures, making it impossible to adjust the compression force on soil at different depths during construction.

[0007] Therefore, a reinforcement device and method with a distributed expansion and compaction mechanism is proposed to achieve targeted treatment and layered compaction of specific weak layers with controllable quality. Summary of the Invention

[0008] The purpose of this invention is to provide a beaded membrane bag pressurization and compaction reinforcement device and method for soft soil foundations. It can not only achieve directional treatment and layered compaction of specific weak layers, but also improve material utilization and significantly improve the stability of reinforcement quality, thereby avoiding the risk of local soil compaction failure caused by uneven expansion and compaction.

[0009] To achieve the purpose of this invention, the technical solution adopted is as follows: a soft soil foundation beaded membrane bag pressurization and compaction reinforcement device, comprising multiple membrane bag units connected in sequence by a chain belt, each membrane bag unit including at least one membrane bag connected in sequence, and one of the membrane bags in the multiple membrane bag units is connected to a branch pipe, each branch pipe is equipped with a switch valve, and the multiple branch pipes are connected to a pressurization conduit individually or jointly.

[0010] Furthermore, the membrane bag located away from the inlet end of the pressurized conduit also has a traction ring for inserting tools.

[0011] Furthermore, the pressurized conduit is a flexible tube.

[0012] The method for reinforcing soft soil foundations using beaded membrane bags under pressure includes the following steps:

[0013] S1. Collect the depth range, soil strength, void ratio, and moisture content of the soft soil foundation to be reinforced as site parameters.

[0014] S2. Select or customize a beaded membrane bag pressurization and compaction reinforcement device according to site parameters. Based on the self-weight stress range of the foundation soil, the strength of the foundation soil, the void ratio, the water content, the void ratio of the foundation soil corresponding to the foundation bearing capacity to be achieved after reinforcement, and the expansion amount achieved by each membrane bag unit in the selected beaded membrane bag pressurization and compaction reinforcement device, determine the number, arrangement form, arrangement spacing, and arrangement location of the beaded membrane bag pressurization and compaction reinforcement device to be implanted within the scope of the soft soil foundation to be reinforced.

[0015] S3. Based on the distribution range of lateral earth pressure on the side of the membrane bag at different depths within the soft soil treatment depth range of the soft soil foundation to be reinforced, determine whether each membrane bag unit needs to be interconnected or partially connected, and control the expansion and compaction at different depths under different grouting and pressurization conditions according to the different pressure ranges of the soft soil foundation to be reinforced.

[0016] S4. Install the beaded membrane bag pressurization and compaction reinforcement device according to the structure, quantity and arrangement position determined in step S2. Determine the grouting and pressurization control for each membrane bag unit according to the strength and depth of the foundation soil to be reinforced, and pressurize and grout each membrane bag unit according to the expansion amount reached by each membrane bag unit in step S2.

[0017] Furthermore, in step S2, when selecting or customizing the beaded membrane bag pressure compaction and reinforcement device, it is necessary to determine the arrangement depth, arrangement quantity, number of membrane bag units, and the volume range that the membrane bag material can expand under pressure grouting.

[0018] Furthermore, in step S2, the expansion amount of each membrane bag unit is controlled according to the volume of grout material injected during pressurized grouting of that membrane bag unit. During pressurized grouting, the maximum pressurized expansion pressure exerted by the membrane bag on the soil satisfies the following condition:

[0019]

[0020] in, The pressure control for the membrane bag unit; The pressure required for the membrane bag (2) to expand to a predetermined volume without considering the soil resistance on the outside of the membrane bag (2); It is the sum of the vertical self-weight pressure of the overlying soil and the vertical additional pressure. The cohesion of the foundation soil outside the membrane bag; The internal friction angle is the angle of friction between the soil on the outer side of the membrane bag and the foundation soil.

[0021] Furthermore, the formula for calculating the sum of the vertical self-weight pressure of the overlying soil and the vertical additional pressure is as follows:

[0022]

[0023] in, The unit weight of the i-th soil layer from the surface to the center of the corresponding membrane bag unit; Let be the thickness of the i-th soil layer; This refers to the vertical additional stress at the depth of the membrane bag.

[0024] The beneficial effects of this invention are:

[0025] 1. This invention adopts a flexible modular structure of "independent sealed membrane bag unit + pressurized conduit" to replace the traditional grouting mode of "open injection through steel pipe side hole". Each membrane bag unit is connected to the ground pressurization system through branch pipelines and pressurized conduits. This invention can be flexibly designed to be independently controlled or modularly connected (such as 3-4 membrane bags forming a membrane bag unit) according to the soil depth and lateral resistance difference of the soft soil foundation to be reinforced. It realizes a closed grouting reinforcement mechanism of "directional accumulation and expansion of grouting material in the membrane bag → compression of the outer soil". This invention achieves "targeted compaction", which not only improves the utilization rate of the invention, but also significantly improves the reinforcement quality and stability. It solves the pain points of disordered diffusion, loss and dilution of grout in loose soil layers and groundwater in traditional steel pipe grouting.

[0026] 2. By adopting a flexible modular structure of "independently sealed membrane bag unit + pressurized conduit", a quantitative control logic of "grouting volume → membrane bag expansion volume → soil compaction volume" is established during the reinforcement of soft soil foundation. By adjusting the grouting volume of the membrane bag unit, the expansion volume can be precisely controlled, achieving layered and directional compaction of specific soft soil layers. That is, this invention transforms the traditional "experience-dependent" reinforcement into a "parameter-controllable" project. The grouting pressure of each membrane bag unit can be independently set according to the soil layer depth (lateral earth pressure difference) (the maximum control pressure is calculated based on the Mohr-Coulomb theory), avoiding the risk of uneven expansion and compaction and local soil compaction failure.

[0027] 3. Because this invention is a flexible, elongated structure, and each component can be prefabricated in the factory and assembled on the construction site, the number of membrane bags can be flexibly adjusted according to the thickness of the soft soil layer when reinforcing soft soil foundations, thus adapting to confined working spaces. At the same time, this invention can be implanted using a low-disturbance implantation method, effectively avoiding secondary impacts on surrounding buildings and underground pipelines. It successfully solves the reinforcement problems in "space-constrained and environment-sensitive" scenarios such as urban renewal, ancient building protection, and precision factory renovation. Compared with traditional technologies, it reduces disturbance to surrounding structures and expands the application scope of soft soil foundation reinforcement technology. Attached Figure Description

[0028] The accompanying drawings illustrate exemplary embodiments of the invention and, together with the description thereof, serve to explain the principles of the invention. These drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification.

[0029] Figure 1 This is a front view of the soft soil foundation beaded membrane bag pressurization compaction reinforcement device before pressurized grouting;

[0030] Figure 2 This is a side view of the soft soil foundation beaded membrane bag pressurization compaction reinforcement device before pressurized grouting;

[0031] Figure 3 This is a front view of the soft soil foundation after pressure grouting using a beaded membrane bag pressure compaction and reinforcement device.

[0032] The attached diagram shows the markings and corresponding component names:

[0033] 1. Chain belt, 2. Membrane bag, 3. Traction ring, 4. Pressure tube. Detailed Implementation

[0034] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be noted that, for ease of description, only the parts relevant to the present invention are shown in the accompanying drawings.

[0035] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other. The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0036] like Figure 1 , Figure 2 , Figure 3 As shown, the present invention provides a soft soil foundation beaded membrane bag pressurization and compaction reinforcement device, comprising multiple membrane bag units connected in sequence by a chain belt 1. The chain belt 1 is a flexible belt, specifically, the chain belt 1 can be a metal chain or a flexible rope, such as nylon rope, plastic rope, etc. The chain belt 1 and the membrane bag units are connected in a detachable manner, for example, the chain belt 1 and the membrane bag units are connected by a chain buckle, so that the number of membrane bag units can be selected as needed when using the present invention.

[0037] In this invention, there is at least one membrane bag 2 in the membrane bag unit, and the membrane bag unit is also composed of multiple membrane bags 2 connected in series. When there are multiple membrane bags 2 in the membrane bag unit, the connection method between two adjacent membrane bags 2 can be the same as the connection method between two adjacent membrane bag units. This connection method allows for the disassembly of two adjacent membrane bags 2 in the membrane bag unit. In this case, a flexible tube is needed to connect two adjacent membrane bags 2 in the membrane bag unit. However, in order to ensure both communication and easy disassembly between two adjacent membrane bags 2, a plug-in connection is used between the flexible tube and the membrane bag 2. Furthermore, to prevent the flexible tube from breaking off when the invention is implanted in the foundation, a locking connector can be used to connect the flexible tube and the membrane bag 2. Of course, two adjacent membrane bags 2 in the membrane bag unit can also be directly connected through a flexible tube, and then the flexible tube and the membrane bag 2 can be connected using a locking connector.

[0038] In this invention, the number of membrane bag units and the number of membrane bags 2 within each unit can be determined based on the height of each membrane bag 2 and the thickness of the soft soil layer in the soft soil foundation to be reinforced. For example, if each membrane bag unit contains 3-4 membrane bags and each membrane bag 2 is 0.5m long, then the length of each membrane bag unit is 1.5m-2.5m. In actual use, modules are assembled according to the burial depth and thickness of the soft soil layer in the soft soil foundation to be reinforced. For example, if the burial depth of the soft soil layer is 6m and the thickness is 5m, then 3-4 membrane bag units can be used, and the pressurization control pressure of each membrane bag unit is determined according to different depths. If the pressure difference between multiple membrane bag units is not large, multiple membrane bag units can be connected simultaneously; if the pressure difference between multiple membrane bag units is large, each membrane bag unit is pressurized separately. Alternatively, multiple membrane bag units can be grouped according to pressurization requirements, with one or more membrane bag units in the same group, and each group of membrane bag units corresponding to a pressurization pressure.

[0039] To individually control the expansion of each membrane bag unit, a branch pipe can be fixedly connected to one of the membrane bags 2 in each membrane bag unit, and a switch valve can be installed on each branch pipe. To facilitate grouting into each membrane bag unit through the branch pipes, the inlet ends of multiple branch pipes are respectively connected to pressurized conduits 4, and the inlet ends of the pressurized conduits 4 are connected to the grouting equipment. In this invention, to simplify the piping system, the inlet ends of multiple branch pipes can also be simultaneously connected to a single pressurized conduit 4.

[0040] In this invention, since each branch pipeline is equipped with a switch valve, during use, the pressurizing conduit 4 can be connected to the membrane bag 2 in only one membrane bag unit, or the pressurizing conduit 4 can be connected to the membrane bag 2 in multiple membrane bag units at the same time. The number of membrane bag units connected to the pressurizing conduit 4 can be determined according to the difference in resistance required to overcome the lateral expansion of the soft soil layer at different depths in the soft soil foundation to be reinforced, so as to achieve independent control during compaction.

[0041] In this invention, the pressurized conduit 4 and the branch pipes are all made of flexible pipes, such as fiber braided hoses or spiral composite material hoses.

[0042] In this invention, to facilitate the implantation of the beaded membrane bag pressurization and compaction reinforcement device into the soft soil foundation, a traction ring 3 for tool insertion is provided on the membrane bag 2 located away from the inlet end of the pressurization conduit 4. The traction ring 3 can be detachably connected to the membrane bag 2 via a chain belt 1, and the diameter of the traction ring 3 is larger than the diameter of the tip of the implantation tube or implantation rod, while the diameter of the traction ring 3 is smaller than the diameter of the implantation tube or implantation rod. When the beaded membrane bag pressurization and compaction reinforcement device needs to be implanted into the foundation, the traction ring 3 can be fitted onto the lower end of the implantation tube or implantation rod. As the implantation tube or implantation rod is inserted into the foundation, it simultaneously drives the membrane bag 2 on the beaded membrane bag pressurization and compaction reinforcement device into the foundation. Then, the implantation tube or implantation rod can be pulled out from the soft soil foundation.

[0043] When using the beaded membrane bag pressure compaction and reinforcement device of the present invention, it is inserted into the foundation through an implantation tube or implantation rod, and then the implantation tube or implantation rod is pulled out from the soft foundation. At the same time, in the present invention, the implantation tube or implantation rod can be driven by mechanical equipment when inserted into the soft foundation to ensure that the implantation tube or implantation rod can drive the beaded membrane bag pressure compaction and reinforcement device to be implanted to a fixed depth in the soft foundation.

[0044] In this invention, to avoid affecting the expansion of the membrane bag 2 which is far from the inlet end of the pressurized conduit 4, the traction ring 3 can also be directly fixed to the membrane bag 2.

[0045] Based on the above-mentioned beaded membrane bag pressure compaction and reinforcement device for soft soil foundations, the present invention also provides a method for pressure compaction and reinforcement of soft soil foundations using beaded membrane bags, comprising the following steps:

[0046] S1. Based on the site geotechnical engineering investigation report or other data, collect the depth range of the soft soil layer, foundation soil strength, void ratio, water content and other parameters of the soft soil foundation to be reinforced as site parameters.

[0047] S2. Based on the parameters of the soft soil foundation to be reinforced collected in step S1, select or customize a beaded membrane bag pressure compaction reinforcement device, and determine the number of membrane bag units in the beaded membrane bag pressure compaction reinforcement device, the number of membrane bags 2 in each membrane bag unit, the arrangement depth of the beaded membrane bag pressure compaction reinforcement device, the arrangement quantity of the beaded membrane bag pressure compaction reinforcement device, and the volume range that the material of the membrane bag 2 can expand under pressure grouting; at the same time, based on the self-weight stress range of the foundation soil in the soft soil foundation to be reinforced, the foundation soil strength, void ratio, water content, and the void ratio of the foundation soil corresponding to the foundation bearing capacity to be achieved after the foundation soil treatment in the soft soil foundation to be reinforced, and the expansion amount that the membrane bag 2 in the selected beaded membrane bag pressure compaction reinforcement device can achieve, determine the number, arrangement form, and arrangement spacing of the beaded membrane bag pressure compaction reinforcement devices to be implanted in the area of ​​the soft soil foundation to be reinforced;

[0048] S3. Based on the distribution range of lateral earth pressure on the side of membrane bag 2 at different depths within the soft soil treatment depth range of the soft soil foundation to be reinforced, determine whether each membrane bag unit needs to be interconnected or partially interconnected, so that when each membrane bag unit is grouted and pressurized, the expansion and compaction control at different depths under different grouting and pressurization conditions can be controlled according to the different pressure ranges of the soft soil foundation to be reinforced.

[0049] When the lateral earth pressure overcome by the pressure expansion of each membrane bag unit in the beaded membrane bag pressurization and compaction reinforcement device is not much different in different depth ranges, the switch valves on each branch pipeline open and close at the same time, so that the expansion amount of membrane bag 2 in each membrane bag unit is the same.

[0050] When the lateral earth pressure overcome by the pressure expansion of each membrane bag unit in the beaded membrane bag compaction reinforcement device varies greatly at different depths, in order to achieve the expected expansion amount of membrane bag 2 in membrane bag units at different depths in the soft soil foundation to be reinforced, multiple membrane bag units can be grouped according to the relative magnitude of the lateral earth pressure on the side of membrane bag 2 in different depth intervals in the soft soil foundation to be reinforced. This can be done by grouping one membrane bag unit or multiple membrane bag units together, and the switch valves on the branch pipelines of each membrane bag unit in the same group can be opened or closed simultaneously.

[0051] S4. Based on the number of membrane bag units in the beaded membrane bag pressurization and compaction reinforcement device, the number of membrane bags 2 in each membrane bag unit, the arrangement depth of the beaded membrane bag pressurization and compaction reinforcement device, and the arrangement quantity of the beaded membrane bag pressurization and compaction reinforcement device determined in step S2, the beaded membrane bag pressurization and compaction reinforcement device is implanted into the soft soil foundation to be reinforced; the pressurization grouting sequence and pressurization grouting method of each group of membrane bag units in step S3 are designed according to the strength and depth of the foundation soil in the soft soil foundation to be reinforced, and pressurization grouting is performed according to the designed pressurization grouting sequence, pressurization grouting method and the expansion amount of membrane bags 2 in each group of membrane bag units.

[0052] In this invention, the pressurization grouting method for each group of membrane bag units in step S3 is to increase the pressure in stages, so that each group of membrane bag units expands slowly, effectively preventing the membrane bag 2 in each group of membrane bag units from damaging the soil due to excessive pressure.

[0053] Meanwhile, in order to prevent the maximum lateral compressive force exerted by the membrane bag 2 on the soil from being too large and damaging the soil during the expansion of the membrane bag 2 during pressurized grouting, the maximum pressurized expansion pressure exerted by the membrane bag 2 on the soil during pressurized grouting should be controlled. The maximum pressurized expansion pressure exerted by the membrane bag 2 on the soil during pressurized grouting should meet the following conditions:

[0054] Based on the Mohr-Coulomb failure theory of soil and the limit equilibrium condition of soil, the sum of the vertical self-weight stress and the vertical additional stress of the soil is taken as the limit equilibrium state of soil. Therefore, the pressure control pressure of the membrane bag unit at the corresponding depth position should not exceed the corresponding... ,Right now:

[0055]

[0056] in, The pressure control for the membrane bag unit; The pressure required for membrane bag 2 to expand to a predetermined volume, without considering the soil resistance on the outside of membrane bag 2; It is the sum of the vertical self-weight pressure of the overlying soil and the vertical additional pressure. The cohesion of the foundation soil outside membrane bag 2; The internal friction angle is the angle of friction of the foundation soil outside the membrane bag 2.

[0057] The sum of the vertical self-weight pressure of the overlying soil and the vertical additional pressure The calculation formula is as follows:

[0058]

[0059] in, The unit weight of the i-th soil layer from the surface to the center of the corresponding membrane bag unit; Let be the thickness of the i-th soil layer; The vertical additional stress at depth 2 of the membrane bag.

[0060] This invention involves implanting a beaded membrane bag pressurization and compaction reinforcement device into the weak soil layer of the soft soil foundation to be reinforced, and then using a pressurized grouting device to pressurize and inject grout into the membrane bag 2 at a specified depth on the surface of the soft soil foundation. After the grout is injected into the corresponding membrane bag 2, the membrane bag 2 expands, thereby compressing and reinforcing the soil around the outside of the membrane bag 2.

[0061] Those skilled in the art should understand that the above embodiments are merely for illustrating the present invention and are not intended to limit the scope of the invention. Those skilled in the art can make other changes or modifications based on the above disclosure, and these changes or modifications still fall within the scope of the present invention.

Claims

1. A method for reinforcing a soft soil foundation using a beaded membrane bag pressurization and compaction device, characterized in that, The soft soil foundation beaded membrane bag pressurization and compaction reinforcement device includes multiple membrane bag units connected in sequence by a chain belt (1). Each membrane bag unit includes at least one membrane bag (2) connected in sequence. One of the membrane bags (2) in the multiple membrane bag units is connected to a branch pipe. Each branch pipe is equipped with a switch valve. Each branch pipe is connected to a pressurization conduit (4) separately or together. It also includes the following steps: S1. Collect the depth range, soil strength, void ratio, and moisture content of the soft soil foundation to be reinforced as site parameters. S2. Select or customize a beaded membrane bag pressurization and compaction reinforcement device according to site parameters. Based on the self-weight stress range of the foundation soil, the strength of the foundation soil, the void ratio, the water content, the void ratio of the foundation soil corresponding to the foundation bearing capacity to be achieved after reinforcement, and the expansion amount achieved by each membrane bag unit in the selected beaded membrane bag pressurization and compaction reinforcement device, determine the number, arrangement form, arrangement spacing, and arrangement location of the beaded membrane bag pressurization and compaction reinforcement device to be implanted within the scope of the soft soil foundation to be reinforced. S3. Based on the distribution range of lateral earth pressure on the side of the membrane bag (2) at different depths within the soft soil treatment depth range of the soft soil foundation to be reinforced, determine whether each membrane bag unit needs to be interconnected or partially interconnected, and control the expansion and compaction at different depths under different grouting and pressurization conditions according to the different pressure ranges of the soft soil foundation to be reinforced. S4. Install the beaded membrane bag pressurization and compaction reinforcement device according to the structure, quantity and arrangement position determined in step S2. Determine the grouting and pressurization control for each membrane bag unit according to the strength and depth of the foundation soil to be reinforced, and pressurize and grout each membrane bag unit according to the expansion amount reached by each membrane bag unit in step S2.

2. The reinforcement method according to claim 1, characterized in that, The membrane bag (2) located away from the inlet end of the pressurized conduit (4) also has a traction ring (3) for inserting tools.

3. The reinforcement method according to claim 1, characterized in that, The pressurized conduit (4) is a flexible tube.

4. The reinforcement method according to claim 1, characterized in that, In step S2, when selecting or customizing the beaded membrane bag pressure compaction and reinforcement device, it is necessary to determine the arrangement depth, arrangement quantity, and number of membrane bag units, as well as the volume range that the membrane bag (2) material can expand under pressure grouting.

5. The reinforcement method according to claim 1, characterized in that, In step S2, the expansion amount of each membrane bag unit is controlled according to the volume of grout material injected during pressurized grouting of the membrane bag unit. During pressurized grouting, the maximum pressurized expansion pressure of the membrane bag (2) acting on the soil satisfies the following conditions: ； in, The pressure control for the membrane bag unit; The pressure required for the membrane bag (2) to expand to a predetermined volume without considering the soil resistance on the outside of the membrane bag (2); It is the sum of the vertical self-weight pressure of the overlying soil and the vertical additional pressure; The cohesion of the foundation soil outside the membrane bag (2); The internal friction angle of the foundation soil outside the membrane bag (2).

6. The reinforcement method according to claim 5, characterized in that, Formula for calculating the sum of the vertical self-weight pressure of the overlying soil and the vertical additional pressure: ； in, The unit weight of the i-th soil layer from the surface to the center of the corresponding membrane bag unit; Let be the thickness of the i-th soil layer; The vertical additional stress at the depth position of the membrane bag (2).

Images