An environmentally friendly air-supported membrane construction method for foundation pit operations

Abstract

This invention relates to the field of air-supported membrane construction, and more particularly to an environmentally friendly air-supported membrane construction method for foundation pit operations, comprising: acquiring the size and geological information of the construction foundation pit; performing simulation calculations of the air-supported membrane to preliminarily determine the size information of the air-supported membrane and the cable net; excavating retaining wall trenches and pouring the retaining wall and installing the cable net fixing guide rails; laying the air-supported membrane, sealing and connecting it, and installing the cable net, fan, exhaust valve, and vehicle passage; inflating the inside of the air-supported membrane to form the membrane; collecting the expansion dimensions of the sub-domain air-supported membrane and the tensile stress of each cable in the cable net within a preset time period when the internal and external pressure differences reach a stable first preset pressure difference and a second preset pressure difference; obtaining the air-supported membrane expansion characteristic value and determining whether the construction of the air-supported membrane meets the preset standards based on the air-supported membrane expansion characteristic value, thereby improving the efficiency and quality of air-supported membrane construction.

Description

Technical Field

[0001] This invention relates to the field of air-supported membrane construction, and more particularly to an environmentally friendly air-supported membrane construction method for foundation pit operations. Background Technology

[0002] Foundation pit construction mainly includes the design and construction of the foundation pit support system and earthwork excavation, and is a highly comprehensive system engineering project. The foundation pit support system is a temporary structure that is no longer needed after the underground engineering is completed. The foundation pit retaining structure system includes sheet (pile) walls, walers (capping beams), sheet-column type, column type, gravity retaining walls, combined type, as well as soil anchors, reverse construction method, caissons and other auxiliary components. The vertical part above the ground is basically unobstructed, and even if there is obstruction, it is covered by dust-proof netting.

[0003] With increasing national emphasis on environmental protection, on-site requirements include dust control, noise reduction, rain protection, and heat insulation. In recent years, air-supported membrane structures for foundation pits have been widely adopted. An air-supported membrane structure is a structure made of architectural membrane materials that can be placed over a foundation pit. It mainly consists of membrane materials, cable nets, anchors, and other components. A stable internal pressure is provided by an air supply system to inflate the membrane, maintaining its shape and bearing external loads. Traditional air-supported membrane construction methods suffer from low construction efficiency and poor safety due to a lack of corresponding simulation calculations and effective on-site verification. Summary of the Invention

[0004] Therefore, the present invention provides an environmentally friendly air-supported membrane construction method for foundation pit operations, which overcomes the problems of low construction efficiency and poor safety in the prior art due to the lack of corresponding simulation calculations and effective on-site inspections.

[0005] To achieve the above objectives, the present invention provides an environmentally friendly air-supported membrane construction method for foundation pit operations, comprising:

[0006] Obtain the size and geological information of the construction pit, including humidity and soil permeability information;

[0007] After performing simulation calculations on the air-supported membrane based on the aforementioned size information, the size information of the air-supported membrane and the cable net size information are initially determined. The cable net size information includes the cable net spacing and the cable net diameter.

[0008] After the foundation pit is laid out, the retaining wall trench is excavated and the retaining wall is poured and the cable net fixing guide rail is installed. The upper part of the retaining wall is provided with an air inlet, an air outlet and a passage door.

[0009] After clearing the foundation pit, the air membrane is laid in sequence, the edge of the air membrane is sealed to the top surface of the retaining wall, and the cable net, fan, exhaust valve and vehicle passage are installed. The fan is connected to the air inlet, the exhaust valve is connected to the exhaust outlet, and the vehicle passage is connected to the passage door.

[0010] When the wind speed is lower than the preset wind speed, the vehicle passage and the exhaust valve are closed, and each of the fans is turned on to inflate the inside of the air film to form the film.

[0011] When the internal and external pressure differences are stabilized at the first and second preset pressure differences, the expansion size of the subdomain air film and the tensile stress of each cable in the cable net are collected within a preset time period.

[0012] When the characteristic value of air film expansion is obtained and it is initially determined that the construction of the air film does not meet the preset standard based on the characteristic value of air film expansion, the construction of the air film is further determined based on the average tensile stress of the cable, or the reason why the construction of the air film does not meet the preset standard is determined based on the membrane stress difference.

[0013] Furthermore, the simulation calculation process for the air film includes:

[0014] Obtain design parameters;

[0015] Modeling was completed using simulation software;

[0016] Input material information and load information, wherein the load information includes dead load, live load, wind load and snow load;

[0017] The calculation outputs nonlinear reaction forces, nonlinear internal forces, and nonlinear displacements.

[0018] Verify the limit value of the steel cable stress ratio, the maximum stress on the membrane surface, the horizontal displacement of the membrane surface, and the vertical displacement of the membrane surface under various loads;

[0019] In response to the verification meeting the preset standard, the initial output of the air membrane size information and cable net size information is generated.

[0020] Furthermore, the process of initially determining that the construction of the air-supported membrane does not meet the preset standards includes:

[0021] The air film expansion characteristic value is compared with the first preset expansion characteristic threshold and the second preset expansion characteristic threshold, respectively.

[0022] If the air film expansion characteristic value is greater than or equal to a first preset expansion characteristic threshold, it is preliminarily determined that the construction of the air film does not meet the preset standard.

[0023] Under the condition that the air film expansion characteristic value is greater than or equal to the first preset expansion characteristic threshold and less than the second preset expansion characteristic threshold, the construction of the air film is further determined based on the average tensile stress of the cable to determine whether the construction meets the preset standard.

[0024] Under the condition that the air film expansion characteristic value is greater than or equal to the second preset expansion characteristic threshold, the reason why the construction of the air film does not meet the preset standard is determined based on the membrane stress difference.

[0025] Furthermore, the air film expansion characteristic value is the distance between the intersection point of the perpendicular bisector of the plane formed by the sub-domain air film along the sub-domain boundary and the sub-domain air film under the first preset pressure difference and the second preset pressure difference, wherein the air film corresponding to a single cell of the cable net is denoted as the sub-domain air film.

[0026] Furthermore, when the average tensile stress of the cables is greater than or equal to a preset stress threshold, it is further determined that the construction of the air membrane does not meet the preset standard, and the length of each extended cable is determined based on the difference between the average tensile stress of the cables and the preset stress threshold.

[0027] Furthermore, the extension length of each cable is positively correlated with the extension difference, wherein the extension difference is the difference between the average tensile stress of the cable and the preset stress threshold.

[0028] Furthermore, the reasons why the construction of the air membrane does not meet the preset standards include that the air supply flow of the fan is not up to standard, or that the cable net spacing is not up to standard;

[0029] If the air supply flow rate of the fan is not up to standard, the air supply flow rate will be increased to the corresponding value according to the ratio of the preset membrane stress difference threshold to the membrane stress difference value.

[0030] If the cable-net spacing does not meet the standard, the cable-net spacing will be reduced to the corresponding value according to the ratio between the membrane stress difference value and the preset membrane stress difference threshold value.

[0031] Furthermore, the membrane stress difference value is the average of the tensile stress difference of each sub-domain gas film under the second preset pressure difference and the first preset pressure difference.

[0032] Furthermore, several spacing reduction methods are provided for reducing the cable net spacing, and each spacing reduction method reduces the cable net spacing by a different amount.

[0033] Furthermore, when the soil permeability is less than a preset permeability threshold, the increase in the air supply flow rate is corrected, and the correction magnitude of the increase in air supply flow rate is positively correlated with the permeability difference, wherein the permeability difference is the difference between the preset permeability threshold and the soil permeability.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention uses the digital twin method to perform preliminary simulation of the construction parameters of the air membrane in the foundation pit, and preliminarily determines the size information of the air membrane and the size information of the cable net, which effectively saves construction time and improves construction efficiency.

[0035] Furthermore, after the initial construction is completed, the present invention obtains the expansion dimensions of the sub-domain air-supported membrane and the tensile stress of each cable in the cable net during the membrane-forming stage, thereby determining the characteristic value of the air-supported membrane expansion and making a preliminary judgment on whether the construction of the air-supported membrane meets the standards based on the characteristic value of the air-supported membrane expansion. If the standards are not met, the design parameters are optimized in a targeted manner, and the construction parameters are optimized quickly and accurately to ensure the construction quality of the air-supported membrane. Attached Figure Description

[0036] Figure 1 This is a flowchart of an air-supported membrane environmentally friendly construction method for foundation pit operations according to an embodiment of the present invention;

[0037] Figure 2 This is a cloud diagram showing the maximum stress on the membrane surface under 0° oncoming wind conditions according to an embodiment of the present invention.

[0038] Figure 3A This is a cloud map showing the horizontal displacement of the membrane surface under 0° oncoming wind conditions according to an embodiment of the present invention.

[0039] Figure 3B This is a cloud map showing the vertical displacement of the membrane surface under 0° oncoming wind conditions according to an embodiment of the present invention.

[0040] Figure 4 This is a flowchart for determining whether the construction of the air-supported membrane meets the preset standards in an embodiment of the present invention. Detailed Implementation

[0041] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0042] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0043] Please see Figure 1 , Figure 2 , Figure 3A , Figure 3B and Figure 4The diagrams shown are, respectively, a flowchart of an air-supported membrane environmental protection construction method for foundation pit operations according to an embodiment of the present invention; a cloud diagram of the maximum stress on the membrane surface under 0° wind conditions according to an embodiment of the present invention; a cloud diagram of the horizontal displacement of the membrane surface under 0° wind conditions according to an embodiment of the present invention; a cloud diagram of the vertical displacement of the membrane surface under 0° wind conditions according to an embodiment of the present invention; and a flowchart for determining whether the construction of the air-supported membrane meets the preset standards according to an embodiment of the present invention.

[0044] An embodiment of the present invention provides an environmentally friendly air-supported membrane construction method for foundation pit operations, comprising:

[0045] Step S1: Obtain the size information and geological information of the construction pit, wherein the geological information includes humidity information and soil permeability information;

[0046] Step S2: After performing simulation calculations on the air film based on the size information, the size information of the air film and the size information of the cable net are initially determined, wherein the size information of the cable net includes the cable net spacing and the cable net diameter;

[0047] Step S3: After laying out the foundation pit, excavate the retaining wall trench and pour the retaining wall and install the cable net fixing guide rail. The upper part of the retaining wall is provided with an air inlet, an air outlet and a passage door.

[0048] Step S4: After cleaning the foundation pit, the air membrane is laid in sequence, the edge of the air membrane is sealed to the top surface of the retaining wall, and the cable net, fan, exhaust valve and vehicle passage are installed. The fan is connected to the air inlet, the exhaust valve is connected to the exhaust outlet, and the vehicle passage is connected to the passage door.

[0049] Step S5: When the wind speed is less than the preset wind speed of 6m / s, close the vehicle passage and the exhaust valve, and turn on each of the fans to inflate the inside of the air film to form the film.

[0050] Step S6: When the internal and external pressure difference is stabilized at the first preset pressure difference and the second preset pressure difference, the expansion size of the subdomain air film and the tensile stress of each cable in the cable net are collected within a preset time period. The first preset pressure difference is set to 80 Pa and the second preset pressure difference is set to 250 Pa.

[0051] Step S7: Obtain the characteristic value of air film expansion and preliminarily determine whether the construction of the air film meets the preset standard based on the characteristic value of air film expansion. If it is determined that the construction of the air film does not meet the preset standard, further determine whether the construction of the air film meets the preset standard based on the average tensile stress of the cable, or determine the reason why the construction of the air film does not meet the preset standard based on the membrane stress difference.

[0052] Specifically, the simulation calculation process for the air film includes:

[0053] Step S201: Obtain design parameters, including total number of nodes 6265, total number of supports 224, total number of elements 923, number of membrane elements 12304, material type 1, section type 1, load case 6, structural importance coefficient 1.000, and critical support angle: 15.000°.

[0054] Step S202: Complete the modeling using the simulation software 3D3S Design 2024.0;

[0055] Step S203: Input material information and load information. The material information is: steel strand 1270, size φ20mm, elastic modulus 190.000kN / mm². 2 The coefficient of linear expansion is 1.36e. -05 Load information includes dead load, live load, wind load, and snow load.

[0056] Step S204: Calculate and output nonlinear reaction force, nonlinear internal force, and nonlinear displacement;

[0057] Step S205: Verify the limit value of the steel cable stress ratio, the maximum stress on the membrane surface, the horizontal displacement and the vertical displacement of the membrane surface under each load. The limit value of the steel cable stress ratio is shown in Table 1, the maximum stress on the membrane surface is shown in Table 2, and the horizontal displacement and vertical displacement of the membrane surface are shown in Table 3.

[0058] Step S206: In response to the verification meeting the preset standard, the size information of the air membrane and the size information of the cable net are initially output.

[0059] Table 1. Limits of cable stress ratio under various loads

[0060] ,

[0061] Table 2 Maximum stress on the membrane surface under various loads

[0062] ,

[0063] Table 3. Horizontal and vertical displacements of the membrane surface under various loads.

[0064] ,

[0065] Specifically, in step S7, the process of initially determining whether the construction of the air film meets the preset standards based on the air film expansion characteristic value includes:

[0066] The air film expansion characteristic value is compared with the first preset expansion characteristic threshold of 75.00 mm and the second preset expansion characteristic threshold of 125.00 mm, respectively.

[0067] If the air film expansion characteristic value is less than a first preset expansion characteristic threshold, it is preliminarily determined that the construction of the air film meets the preset standard.

[0068] If the air film expansion characteristic value is greater than or equal to a first preset expansion characteristic threshold, it is preliminarily determined that the construction of the air film does not meet the preset standard.

[0069] Under the condition that the air film expansion characteristic value is greater than or equal to the first preset expansion characteristic threshold and less than the second preset expansion characteristic threshold, the construction of the air film is further determined based on the average tensile stress of the cable to determine whether the construction meets the preset standard.

[0070] Under the condition that the air film expansion characteristic value is greater than or equal to the second preset expansion characteristic threshold, the reason why the construction of the air film does not meet the preset standard is determined based on the membrane stress difference.

[0071] Specifically, the air film expansion characteristic value is the distance between the intersection point of the perpendicular bisector of the plane formed by the sub-domain air film along the sub-domain boundary and the sub-domain air film under the first preset pressure difference and the second preset pressure difference, wherein the air film corresponding to a single cell of the cable net is denoted as the sub-domain air film.

[0072] Specifically, the construction of the air-supported membrane is judged to meet the preset standards based on the average tensile stress of the cables.

[0073] If the average tensile stress of the cable is less than the preset stress threshold of 493 MPa, then it is further determined that the construction of the air membrane meets the preset standard.

[0074] If the average tensile stress of the cable is greater than or equal to the preset stress threshold, it is further determined that the construction of the air membrane does not meet the preset standard, and the length of each cable after extension is determined according to the difference between the average tensile stress of the cable and the preset stress threshold.

[0075] Specifically, the extension length of each cable is positively correlated with the extension difference, where the extension difference is the difference between the average tensile stress of the cable and the preset stress threshold. The positive correlation can be linear or nonlinear, and there is no specific limitation. It can be understood that the larger the extension difference, the larger the extension length of each cable.

[0076] Specifically, the reasons why the construction of the air-supported membrane does not meet the preset standards are determined based on the membrane stress difference value, wherein,

[0077] If the membrane stress difference is less than the preset membrane stress difference threshold of 3.20 MPa, it is determined that the construction of the air membrane does not meet the preset standard because the air supply flow of the fan is not up to standard, and the air supply flow of the fan is increased to the corresponding value according to the ratio of the preset membrane stress difference threshold to the membrane stress difference.

[0078] If the membrane stress difference is greater than or equal to the preset membrane stress difference threshold, it is determined that the construction of the air membrane does not meet the preset standard because the cable net spacing is not up to standard, and the cable net spacing is reduced to the corresponding value according to the ratio between the membrane stress difference and the preset membrane stress difference threshold.

[0079] Specifically, the membrane stress difference is the average of the tensile stress difference between each of the sub-domain gas films under the second preset pressure difference and the first preset pressure difference.

[0080] Specifically, several spacing reduction methods are provided for reducing the spacing of the cable nets, among which,

[0081] If the ratio between the membrane stress difference and the preset membrane stress difference threshold is less than the first preset ratio of 1.15, then the reduced cable net spacing is determined by multiplying the first preset spacing adjustment coefficient of 0.98 with the cable net spacing.

[0082] If the ratio between the membrane stress difference and the preset membrane stress difference threshold is greater than or equal to the first preset ratio and less than the second preset ratio of 1.33, then the reduced cable net spacing is determined by multiplying the second preset spacing adjustment coefficient of 0.95 with the cable net spacing.

[0083] If the ratio between the membrane stress difference and the preset membrane stress difference threshold is greater than or equal to the second preset ratio, then the reduced cable net spacing is determined by multiplying the third preset spacing adjustment coefficient 0.92 with the cable net spacing.

[0084] Specifically, when the soil permeability is less than a preset permeability threshold, the increase in the air supply volume of the fan is corrected, and the correction magnitude of the increase in air supply volume is positively correlated with the permeability difference. The permeability difference is the difference between the preset permeability threshold and the soil permeability. Soil permeability can be characterized by porosity, air diffusivity, air conductivity, and permeability coefficient, and is not specifically limited. In this invention, porosity is used for determination. The preset permeability threshold is set to 33%. It is understood that soil permeability affects the decompression rate of the air film. By increasing the air supply volume, the influence of soil permeability can be eliminated.

[0085] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

[0086] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An environmentally friendly air-supported membrane construction method for foundation pit operations, characterized in that, include: Obtain the size and geological information of the construction pit, including humidity and soil permeability information; After performing simulation calculations on the air-supported membrane based on the aforementioned size information, the size information of the air-supported membrane and the cable net size information are initially determined. The cable net size information includes the cable net spacing and the cable net diameter. After the foundation pit is laid out, the retaining wall trench is excavated and the retaining wall is poured and the cable net fixing guide rail is installed. The upper part of the retaining wall is provided with an air inlet, an air outlet and a passage door. After clearing the foundation pit, the air membrane is laid in sequence, the edge of the air membrane is sealed to the top surface of the retaining wall, and the cable net, fan, exhaust valve and vehicle passage are installed. The fan is connected to the air inlet, the exhaust valve is connected to the exhaust outlet, and the vehicle passage is connected to the passage door. When the wind speed is lower than the preset wind speed, the vehicle passage and the exhaust valve are closed, and each of the fans is turned on to inflate the inside of the air film to form the film. When the internal and external pressure differences are stabilized at the first and second preset pressure differences, the expansion size of the subdomain air film and the tensile stress of each cable in the cable net are collected within a preset time period. When the characteristic value of air film expansion is obtained and it is initially determined that the construction of the air film does not meet the preset standard based on the characteristic value of air film expansion, the construction of the air film is further determined based on the average tensile stress of the cable, or the reason why the construction of the air film does not meet the preset standard is determined based on the membrane stress difference. The process of initially determining that the construction of the air-supported membrane does not meet the preset standards includes: The air film expansion characteristic value is compared with the first preset expansion characteristic threshold and the second preset expansion characteristic threshold, respectively. If the air film expansion characteristic value is greater than or equal to a first preset expansion characteristic threshold, it is preliminarily determined that the construction of the air film does not meet the preset standard. Under the condition that the air film expansion characteristic value is greater than or equal to the first preset expansion characteristic threshold and less than the second preset expansion characteristic threshold, the construction of the air film is further determined based on the average tensile stress of the cable to determine whether the construction meets the preset standard. Under the condition that the air film expansion characteristic value is greater than or equal to the second preset expansion characteristic threshold, the reason why the construction of the air film does not meet the preset standard is determined based on the membrane stress difference. The air film expansion characteristic value is the distance between the intersection point of the perpendicular bisector of the plane formed by the sub-domain air film along the sub-domain boundary and the sub-domain air film under the first preset pressure difference and the second preset pressure difference, wherein the air film corresponding to a single cell of the cable net is denoted as the sub-domain air film.

2. The air-supported membrane environmentally friendly construction method for foundation pit operations according to claim 1, characterized in that, The simulation calculation process for the air film includes: Obtain design parameters; Modeling was completed using simulation software; Input material information and load information, wherein the load information includes dead load, live load, wind load and snow load; The calculation outputs nonlinear reaction forces, nonlinear internal forces, and nonlinear displacements. Verify the limit value of the steel cable stress ratio, the maximum stress on the membrane surface, the horizontal displacement of the membrane surface, and the vertical displacement of the membrane surface under various loads; In response to the verification meeting the preset standard, the initial output of the air membrane size information and cable net size information is generated.

3. The air-supported membrane environmentally friendly construction method for foundation pit operations according to claim 2, characterized in that, If the average tensile stress of the cable is greater than or equal to a preset stress threshold, it is further determined that the construction of the air membrane does not meet the preset standard, and the length of each cable after extension is determined based on the difference between the average tensile stress of the cable and the preset stress threshold.

4. The air-supported membrane environmentally friendly construction method for foundation pit operations according to claim 3, characterized in that, The extension length of each cable is positively correlated with the extension difference, wherein the extension difference is the difference between the average tensile stress of the cable and the preset stress threshold.

5. The air-supported membrane environmentally friendly construction method for foundation pit operations according to claim 4, characterized in that, The reasons why the construction of the air membrane does not meet the preset standards include that the air supply flow of the fan is not up to standard, or that the cable net spacing is not up to standard; If the air supply flow rate of the fan is not up to standard, the air supply flow rate will be increased to the corresponding value according to the ratio of the preset membrane stress difference threshold to the membrane stress difference value. If the cable-net spacing does not meet the standard, the cable-net spacing will be reduced to the corresponding value according to the ratio between the membrane stress difference value and the preset membrane stress difference threshold value.

6. The air-supported membrane environmentally friendly construction method for foundation pit operations according to claim 5, characterized in that, The membrane stress difference is the average of the tensile stress difference between each of the sub-domain air films under the second preset pressure difference and the first preset pressure difference.

7. The air-supported membrane environmentally friendly construction method for foundation pit operations according to claim 6, characterized in that, Several spacing reduction methods are provided for reducing the cable net spacing, and each spacing reduction method reduces the cable net spacing by a different amount.

8. The air-supported membrane environmentally friendly construction method for foundation pit operations according to claim 7, characterized in that, When the soil permeability is less than a preset permeability threshold, the increase in the air supply flow rate is corrected, and the correction magnitude of the increase in air supply flow rate is positively correlated with the permeability difference, wherein the permeability difference is the difference between the preset permeability threshold and the soil permeability.

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