Air film environment-friendly construction method for foundation pit operation

Abstract

The invention relates to the field of gas film construction, in particular to a gas film environment-friendly construction method for foundation pit operation, which comprises the following steps: acquiring size information and geological information of a constructed foundation pit; preliminarily determining size information of the gas film and size information of the cable net after simulation calculation of the gas film; a retaining wall groove is excavated, a retaining wall is poured, and a cable net fixing guide rail is installed; laying an air film, performing sealed connection, and mounting a cable net, a fan, an exhaust valve and a vehicle channel; inflating the interior of the gas film to take the film; respectively inflating until the internal and external pressure difference is stabilized at a first preset pressure difference and a second preset pressure difference, and acquiring the subdomain gas film expansion size and the tensile stress of each cable in the cable net within a preset time length; the gas film expansion characteristic value is obtained, whether gas film construction meets the preset standard or not is judged according to the gas film expansion characteristic value, and the efficiency and quality of gas film construction are improved.

Description

Technical Field

[0001] The present invention relates to the field of air film construction, and in particular to an air film environmentally friendly construction method for foundation pit operations. Background Art

[0002] Excavation works primarily involve the design and construction of the excavation support system and excavation, and are a highly comprehensive system. The excavation support system is a temporary structure that is no longer needed after the underground construction is completed. The excavation retaining structure includes slab (pile) walls, purlins (crown beams), slab-column, column-column, gravity retaining walls, combined structures, soil anchors, reverse construction, caissons, and other ancillary components. The vertical portion of the structure, which faces upward from the ground, is essentially unobstructed. Even if obstructed, it is covered with a dust-proof net canopy.

[0003] With the increasing emphasis on environmental protection, on-site requirements for dust prevention, noise reduction, rain protection, and thermal insulation have been adopted. In recent years, foundation pit air membranes have been widely used. These structures, constructed from architectural membrane materials, can be placed over foundation pits. They primarily consist of membrane materials, cable nets, and anchors. Air is inflated through an air supply system to provide a stable internal pressure, maintaining the membrane's surface shape and withstanding external loads. However, traditional air membrane construction methods, lacking simulations and effective on-site testing, result in low efficiency and poor safety. Summary of the Invention

[0004] To this end, the present invention provides an air film environmental protection construction method for foundation pit operations, which is used to overcome the problems of low efficiency and poor safety of air film construction in the prior art due to the lack of corresponding simulation calculations and effective on-site inspections.

[0005] To achieve the above-mentioned object, the present invention provides an air film environmental protection construction method for foundation pit operation, comprising: Acquiring size information and geological information of the construction pit, wherein the geological information includes moisture information and soil permeability information; After performing simulation calculation of the air film based on the size information, the size information of the air film and the size information of the cable net are preliminarily determined, wherein the size information of the cable net includes the cable net spacing and the cable net diameter; After the foundation pit is laid out, a retaining wall trench is excavated and the retaining wall is poured and the cable net fixing rail is installed, wherein the upper portion of the retaining wall is provided with an air inlet, an air outlet and a passage door; After cleaning the foundation pit, the air film is laid in sequence, the edge of the air film is sealed and connected to the top surface of the retaining wall, and the cable net, fan, exhaust valve and vehicle passage are installed, wherein the fan is connected to the air inlet, the exhaust valve is connected to the exhaust port, and the vehicle passage is connected to the passage door; When the wind speed is less than the preset wind speed, the vehicle passage and the exhaust valve are closed, and the fans are turned on to inflate the interior of the air film to form the film; Inflate the air film until the internal and external pressure differences are stable at the first preset pressure difference and the second preset pressure difference, respectively, and collect the expansion size of the sub-domain air film and the tensile stress of each cable in the cable net within a preset time period; When the air film expansion characteristic value is obtained and it is preliminarily determined that the construction of the air film does not meet the preset standard based on the air film expansion characteristic value, the construction of the air film is additionally determined whether it meets the preset standard based on the average value of the cable tensile stress, or the reason why the construction of the air film does not meet the preset standard is determined based on the membrane stress difference.

[0006] Furthermore, the simulation calculation process of the air film includes: Get design parameters; Modeling is done using simulation software; Inputting material information and load information, wherein the load information includes dead load, live load, wind load and snow load; Calculate to output nonlinear reaction force, nonlinear internal force and nonlinear displacement; Verify the cable stress ratio limit, membrane surface maximum stress, membrane surface horizontal displacement and membrane surface vertical displacement under various loads; In response to the verification satisfying the preset standard, the size information of the air film and the size information of the cable net are preliminarily outputted.

[0007] Furthermore, the process of preliminarily determining that the construction of the air membrane does not meet the preset standards includes: Comparing the air film expansion characteristic value with the first preset expansion characteristic threshold and the second preset expansion characteristic threshold respectively, Under the condition that 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, wherein, Under the condition that the air film expansion characteristic value is greater than or equal to a first preset expansion characteristic threshold value and less than a second preset expansion characteristic threshold value, additionally determining whether the construction of the air film meets the preset standard based on the average value of the cable tensile stress; Under the condition that the air film expansion characteristic value is greater than or equal to a second preset expansion characteristic threshold, the reason why the construction of the air film does not meet the preset standard is determined according to the membrane stress difference.

[0008] Furthermore, the air film expansion characteristic value is the distance between the perpendicular bisector of the plane formed by each subdomain air film along the subdomain boundary and the intersection of the subdomain 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 recorded as a subdomain air film.

[0009] Furthermore, when the average tensile stress of the cable is greater than or equal to a preset stress threshold, it is additionally determined that the construction of the air film does not meet the preset standard, and the length of each extended cable is determined according to the difference between the average tensile stress of the cable and the preset stress threshold.

[0010] 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.

[0011] Further, it is determined 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 does not meet the standards, or the cable net spacing does not meet the standards; Under the condition that the air supply flow rate of the fan does not meet the standard, increasing the air supply flow rate to a corresponding value according to the ratio of a preset membrane stress difference threshold value to the membrane stress difference value; When the cable net spacing does not meet the standard, the cable net spacing is reduced to a corresponding value according to the ratio between the membrane stress difference value and a preset membrane stress difference threshold value.

[0012] Furthermore, the membrane stress difference is an average value of the tensile stress difference of the air film in each of the sub-domains under the second preset pressure difference and the first preset pressure difference.

[0013] Furthermore, several spacing reduction methods are provided for reducing the cable net spacing, and each spacing reduction method has a different reduction range for the cable net spacing.

[0014] Furthermore, under the condition that the soil permeability is less than a preset permeability threshold, the increase in the air supply flow rate is corrected, and the correction amplitude of the increase in the 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.

[0015] Compared with the existing technology, the beneficial effect of the present invention is that: the present invention uses the digital twin method to preliminarily simulate the construction parameters of the foundation pit air film, preliminarily determines the size information of the air film and the size information of the cable net, effectively saving construction time and improving construction efficiency.

[0016] Furthermore, after the initial completion of the construction, the present invention obtains the expansion size of the sub-domain air film and the tensile stress of each cable line in the cable net in the film-forming stage, thereby determining the air film expansion characteristic value and preliminarily judging whether the construction of the air film meets the standards based on the air film expansion characteristic value, thereby optimizing the design parameters in a targeted manner when it does not meet the standards, optimizing the construction parameters quickly and accurately, and ensuring the construction quality of the air film. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a flow chart of an air film environmental protection construction method for foundation pit operations according to an embodiment of the present invention; Figure 2 This is the maximum stress cloud diagram of the membrane surface under the condition of 0° wind in the embodiment of the present invention; Figure 3A This is a cloud diagram of the horizontal displacement of the membrane surface under the condition of 0° wind in the embodiment of the present invention; Figure 3B This is a cloud diagram of the vertical displacement of the membrane surface under the condition of 0° wind in the embodiment of the present invention; Figure 4 This is a flow chart of an embodiment of the present invention for determining whether the construction of the air film meets the preset standards. DETAILED DESCRIPTION

[0018] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are merely used to explain the present invention and are not intended to limit the present invention.

[0019] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0020] See also Figure 1 、 Figure 2 、 Figure 3A 、 Figure 3B and Figure 4 As shown, they are respectively a flow chart of the environmentally friendly air film 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 a 0° wind direction according to an embodiment of the present invention; a cloud diagram of the horizontal displacement of the membrane surface under a 0° wind direction according to an embodiment of the present invention; a cloud diagram of the vertical displacement of the membrane surface under a 0° wind direction according to an embodiment of the present invention; and a flow chart of determining whether the construction of the air film meets preset standards according to an embodiment of the present invention.

[0021] An embodiment of the present invention provides an air film environmentally friendly construction method for foundation pit operations, comprising: Step S1, obtaining size information and geological information of the construction pit, wherein the geological information includes humidity information and soil permeability information; Step S2, preliminarily determining the size information of the air film and the size information of the cable net after performing simulation calculation of the air film based on the size information, wherein the size information of the cable net includes the cable net spacing and the cable net diameter; Step S3, after staking out the foundation pit, excavating a retaining wall trench, casting the retaining wall, and installing the cable net fixing rails, wherein the upper portion of the retaining wall is provided with an air inlet, an air outlet, and a passage door; Step S4, after cleaning the foundation pit, sequentially laying the air film, sealing the edge of the air film with the top surface of the retaining wall, installing the cable net, fan, exhaust valve and vehicle passage, wherein the fan is connected to the air inlet, the exhaust valve is connected to the exhaust port, and the vehicle passage is connected to the passage door; Step S5: When the wind speed is less than a preset wind speed of 6 m / s, the vehicle passage and the exhaust valve are closed, and the fans are turned on to inflate the interior of the air film to form the film; Step S6, respectively inflating until the internal and external pressure differences stabilize at a first preset pressure difference and a second preset pressure difference, collecting the subdomain air film expansion size and the tensile stress of each cable in the cable net within a preset time period, wherein the first preset pressure difference is set to 80Pa and the second preset pressure difference is set to 250Pa; Step S7, obtaining the air film expansion characteristic value and preliminarily determining whether the construction of the air film meets the preset standard based on the air film expansion characteristic value; and when it is determined that it does not meet the preset standard, additionally determining whether the construction of the air film meets the preset standard based on the average value of the cable tensile stress, or determining the reason why the construction of the air film does not meet the preset standard based on the membrane stress difference.

[0022] Specifically, the simulation calculation process of the air film includes: Step S201, obtaining design parameters, including the total number of nodes: 6265, the total number of supports: 224, the total number of elements: 923, the number of membrane elements: 12304, the material type: 1, the cross-section type: 1, the load case: 6, the structural importance coefficient: 1.000, and the support critical angle: 15.000°; Step S202, using simulation software 3D3S Design 2024.0 to complete modeling; Step S203: Input material information and load information. The material information is: steel strand 1270, size φ20mm, elastic modulus 190.000kN / mm 2 , linear expansion coefficient 1.36e -05 ; Load information includes dead load, live load, wind load and snow load; Step S204, performing calculations to output nonlinear reaction force, nonlinear internal force and nonlinear displacement; Step S205: Verify the cable stress ratio limit, membrane surface maximum stress, membrane surface horizontal displacement, and membrane surface vertical displacement under various loads. The cable stress ratio limit is shown in Table 1, the membrane surface maximum stress is shown in Table 2, and the membrane surface horizontal displacement and membrane surface vertical displacement are shown in Table 3. Step S206 : In response to the verification meeting the preset standard, preliminarily outputting the size information of the air film and the size information of the cable net.

[0023] Table 1 Cable stress ratio limits under various loads , Table 2 Maximum stress on membrane surface under various loads , Table 3 Horizontal displacement and vertical displacement of membrane surface under various loads , Specifically, in step S7, the process of preliminarily determining whether the construction of the air film meets the preset standard according to the air film expansion characteristic value includes: The air film expansion characteristic value is compared with the first preset expansion characteristic threshold value of 75.00 mm and the second preset expansion characteristic threshold value of 125.00 mm respectively. Under the condition that 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. Under the condition that 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, wherein, Under the condition that the air film expansion characteristic value is greater than or equal to a first preset expansion characteristic threshold value and less than a second preset expansion characteristic threshold value, additionally determining whether the construction of the air film meets the preset standard based on the average value of the cable tensile stress; Under the condition that the air film expansion characteristic value is greater than or equal to a second preset expansion characteristic threshold, the reason why the construction of the air film does not meet the preset standard is determined according to the membrane stress difference.

[0024] Specifically, the air film expansion characteristic value is the distance between the perpendicular bisector of the plane formed by each subdomain air film along the subdomain boundary and the intersection of the subdomain 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 recorded as a subdomain air film.

[0025] Specifically, it is determined whether the construction of the air film meets the preset standard based on the average value of the tensile stress of the cable line, wherein: If the average tensile stress of the cable is less than the preset stress threshold of 493 MPa, it is additionally determined that the construction of the air film meets the preset standard; If the average tensile stress of the cable is greater than or equal to the preset stress threshold, it is additionally determined that the construction of the air membrane does not meet the preset standard, and the length of each extended cable is determined according to the difference between the average tensile stress of the cable and the preset stress threshold.

[0026] Specifically, the extended 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, wherein the positive correlation can be a linear positive correlation and a nonlinear positive correlation, and is not specifically limited. It can be understood that the greater the extension difference, the greater the extended length of each cable.

[0027] Specifically, the reason why the construction of the air film does not meet the preset standard is determined based on the membrane stress difference, wherein: If the membrane stress difference is less than a preset membrane stress difference threshold of 3.20 MPa, it is determined that the reason why the construction of the air film does not meet the preset standard is that the air supply flow rate of the fan does not meet the standard, and the air supply flow rate of the fan is increased to a corresponding value according to the ratio of the preset membrane stress difference threshold to the membrane stress difference; If the membrane stress difference is greater than or equal to a preset membrane stress difference threshold, it is determined that the reason why the construction of the air membrane does not meet the preset standard is that the cable net spacing does not meet the standard, and the cable net spacing is reduced to a corresponding value according to the ratio between the membrane stress difference and the preset membrane stress difference threshold.

[0028] Specifically, the membrane stress difference is an average value of the tensile stress difference of the air film in each of the sub-domains under the second preset pressure difference and the first preset pressure difference.

[0029] Specifically, there are several spacing reduction methods for reducing the cable net spacing, among which: If the ratio between the membrane stress difference and the preset membrane stress difference threshold is less than a first preset ratio of 1.15, the reduced cable net spacing is determined by multiplying a first preset spacing adjustment coefficient of 0.98 by the cable net spacing; If the ratio between the membrane stress difference and the preset membrane stress difference threshold is greater than or equal to a first preset ratio and less than a second preset ratio of 1.33, the reduced cable net spacing is determined by multiplying a second preset spacing adjustment coefficient of 0.95 by the cable net spacing; If the ratio of the membrane stress difference to the preset membrane stress difference threshold is greater than or equal to a second preset ratio, the reduced cable net spacing is determined by multiplying a third preset spacing adjustment coefficient of 0.92 by the cable net spacing.

[0030] Specifically, when the soil permeability is less than a preset permeability threshold, the increase in the air supply flow rate of the fan is corrected, and the correction amplitude of the increase in the 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, wherein the soil permeability can be characterized by porosity, air diffusivity, air conductivity and permeability coefficient, which are not specifically limited. In the present invention, porosity is used for determination, wherein the preset permeability threshold is set to 33%. It can be understood that the permeability of the soil will affect the pressure relief rate of the air membrane. By increasing the correction of the air supply, the influence of soil permeability can be eliminated.

[0031] Thus far, the technical solutions of the present invention have been described in conjunction with 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 may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present invention.

[0032] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. An air film environmental protection construction method for foundation pit operation, characterized in that: include: Acquiring size information and geological information of the construction pit, wherein the geological information includes moisture information and soil permeability information; After performing simulation calculation of the air film based on the size information, the size information of the air film and the size information of the cable net are preliminarily determined, wherein the size information of the cable net includes the cable net spacing and the cable net diameter; After the foundation pit is laid out, a retaining wall trench is excavated and the retaining wall is poured and the cable net fixing rail is installed, wherein the upper portion of the retaining wall is provided with an air inlet, an air outlet and a passage door; After cleaning the foundation pit, the air film is laid in sequence, the edge of the air film is sealed and connected to the top surface of the retaining wall, and the cable net, fan, exhaust valve and vehicle passage are installed, wherein the fan is connected to the air inlet, the exhaust valve is connected to the exhaust port, and the vehicle passage is connected to the passage door; When the wind speed is less than the preset wind speed, the vehicle passage and the exhaust valve are closed, and the fans are turned on to inflate the interior of the air film to form the film; Inflate the air film until the internal and external pressure differences are stable at the first preset pressure difference and the second preset pressure difference, respectively, and collect the expansion size of the sub-domain air film and the tensile stress of each cable in the cable net within a preset time period; When the air film expansion characteristic value is obtained and it is preliminarily determined that the construction of the air film does not meet the preset standard based on the air film expansion characteristic value, the construction of the air film is additionally determined whether it meets the preset standard based on the average value of the cable tensile stress, or the reason why the construction of the air film does not meet the preset standard is determined based on the membrane stress difference.

2. The air film environmental protection construction method for foundation pit operation according to claim 1 is characterized in that: The simulation calculation process of the air film includes: Get design parameters; Modeling is done using simulation software; Inputting material information and load information, wherein the load information includes dead load, live load, wind load and snow load; Calculate to output nonlinear reaction force, nonlinear internal force and nonlinear displacement; Verify the cable stress ratio limit, membrane surface maximum stress, membrane surface horizontal displacement and membrane surface vertical displacement under various loads; In response to the verification satisfying the preset standard, the size information of the air film and the size information of the cable net are preliminarily outputted.

3. The air film environmental protection construction method for foundation pit operation according to claim 1, characterized in that: The process of initially determining that the construction of the air membrane does not meet the preset standards includes: Comparing the air film expansion characteristic value with the first preset expansion characteristic threshold and the second preset expansion characteristic threshold respectively, Under the condition that 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, wherein, Under the condition that the air film expansion characteristic value is greater than or equal to a first preset expansion characteristic threshold value and less than a second preset expansion characteristic threshold value, additionally determining whether the construction of the air film meets the preset standard based on the average value of the cable tensile stress; Under the condition that the air film expansion characteristic value is greater than or equal to a second preset expansion characteristic threshold, the reason why the construction of the air film does not meet the preset standard is determined according to the membrane stress difference.

4. The air film environmental protection construction method for foundation pit operation according to claim 3 is characterized in that: The air film expansion characteristic value is the distance between the perpendicular bisector of the plane formed by each subdomain air film along the subdomain boundary and the intersection of the subdomain 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 recorded as a subdomain air film.

5. The air film environmental protection construction method for foundation pit operation according to claim 3 is characterized in that: When the average tensile stress of the cable lines is greater than or equal to a preset stress threshold, it is additionally determined that the construction of the air film does not meet the preset standard, and the length of each extended cable line is determined according to the difference between the average tensile stress of the cable lines and the preset stress threshold.

6. The air film environmental protection construction method for foundation pit operation according to claim 5, 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.

7. The air film environmental protection construction method for foundation pit operation according to claim 3 is characterized in that: The reasons for determining that the construction of the air film does not meet the preset standards include that the air supply flow of the fan does not meet the standards, or the cable net spacing does not meet the standards; Under the condition that the air supply flow rate of the fan does not meet the standard, increasing the air supply flow rate to a corresponding value according to the ratio of a preset membrane stress difference threshold value to the membrane stress difference value; When the cable net spacing does not meet the standard, the cable net spacing is reduced to a corresponding value according to the ratio between the membrane stress difference value and a preset membrane stress difference threshold value.

8. The air film environmental protection construction method for foundation pit operation according to claim 7, characterized in that: The membrane stress difference value is an average value of the tensile stress difference of the air film in each of the sub-domains under the second preset pressure difference and the first preset pressure difference.

9. The air film environmental protection construction method for foundation pit operation according to claim 8, characterized in that: There are several spacing reduction methods for reducing the cable net spacing, and each spacing reduction method has a different reduction range for the cable net spacing.

10. The air film environmental protection construction method for foundation pit operation according to claim 9, characterized in that: Under the condition that the soil permeability is less than a preset permeability threshold, the increase in the air supply flow rate is corrected, and the correction amplitude of the increase in the 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.

Images