Phased array type monitoring method for soil pressure behind green gabion retaining wall

Abstract

The invention belongs to the technical field of geotechnical engineering, and particularly relates to a phased array type monitoring method for soil pressure behind a green gabion retaining wall, which comprises the following steps: firstly, determining a rasterized rectangular projection surface of a monitoring section, burying soil pressure cells, and enabling the projection of the soil pressure cells in the rectangular projection surface to be located at the central position of two rows of grid units; then, a soil pressure fitting line is drawn in the column direction of measured data by adopting a least square method, interval oscillation is adopted in the row direction, and a measured phase two-dimensional distribution matrix is constructed; then, a theoretical soil pressure curve of a certain column is calculated through a horizontal stratification method, consistent expansion is kept in the row direction, and a theoretical phase two-dimensional distribution matrix is generated; then, a simulation phase two-dimensional distribution matrix is generated through numerical simulation; and finally, dynamic weight distribution is carried out on each phase through parameter weighting, and after weighting, a wall-behind soil pressure plane distribution cloud picture is output. According to the method, monitoring information of the whole section is deduced in a graphical mode through limited actually-measured soil pressure values, the construction state is captured in real time, and a basis is provided for early warning.

Description

Technical Field

[0001] The present invention belongs to the technical field of geotechnical engineering, and particularly relates to a phased array monitoring method for the earth pressure behind a green gabion retaining wall. Background Technique

[0002] In recent years, the pace of infrastructure construction in China has been changing with each passing day. In particular, gabion retaining walls composed of geogrids and multi-faceted gabion cages filled with gravel are increasingly widely used in the field of geotechnical engineering. The earth pressure behind the wall is an important load for the structural design and stability calculation of the retaining wall. Its magnitude and distribution law are closely related to the bearing mode and displacement mode of the retaining wall. Once the construction method and engineering measures are not properly handled, engineering disasters such as the instability of the retaining wall and slope collapse are likely to occur, resulting in extremely heavy casualties and economic losses. Geotextiles are laid inside the gabion retaining wall as reinforcement, enabling the gabion retaining wall to withstand tensile, compressive, and shear forces. Its stiffness is between that of flexible and rigid retaining walls, and there are various displacement modes. However, the soil mass behind the wall still moves towards the gabion retaining wall as a whole, and the earth pressure behind the wall belongs to the category of active earth pressure calculation.

[0003] Currently, the research on the earth pressure behind gabion retaining walls mainly focuses on field tests, theoretical studies, numerical simulations, and model tests. Field tests are mainly contact monitoring. Affected by various factors, sensors and transmission data lines are extremely prone to damage, resulting in monitoring blanks. Theoretical studies are often based on various assumptions. For example, in the patent application with the publication number CN102828497A, the results of this solution have a large deviation. There is a certain degree of empiricism in the selection of the constitutive relationship between the retaining wall and the soil mass in numerical simulations. The similarity relationship of model tests is generally difficult to meet. For example, in the existing patent solution with the publication number CN105113555B, the calculation results of this solution have a certain difference from the engineering reality and cannot meet the guiding requirements for the construction of gabion retaining walls. Summary of the Invention

[0004] The present invention provides a phased array monitoring method for the earth pressure behind a green gabion retaining wall, which includes the following steps:

[0005] S1. Determine the monitoring section of the backfill soil behind the retaining wall, project the monitoring section onto the same vertical rectangular plane to obtain a rectangular projection plane, rasterize the rectangular projection plane, and bury a number of earth pressure cells in the monitoring section so that the projection positions of the number of earth pressure cells in the rectangular projection plane are exactly located at the center positions of some grid cells in two columns of grid cells, forming an earth pressure cell array;

[0006] S2. Obtain the monitoring data of each earth pressure cell, use the least squares method to plot the earth pressure fitting line for the monitoring data of the earth pressure cells in the same column of grid cells, obtain the earth pressure values of all grid cells in this column, then use interval oscillation for the monitoring data of the earth pressure cells in the same row of grid cells to obtain the earth pressure values of all grid cells, and then construct the measured phase two-dimensional distribution matrix through the earth pressure values of each grid cell;

[0007] S3. Based on the structural parameters of the retaining wall, displacement mode and physical and mechanical parameters of the backfill soil, use the horizontal layer division method to calculate the theoretical earth pressure curve of a certain column of grid cells, obtain the theoretical earth pressure values of all grid cells in this column, and then expand it horizontally to maintain consistency, generating a theoretical phase two-dimensional distribution matrix with the same dimension as the measured phase two-dimensional distribution matrix;

[0008] S4. Establish a numerical model proportional to the physical project in the simulation software, keep the grid division parameters consistent, obtain the distribution data of the earth pressure behind the wall through numerical simulation, and generate a simulation phase two-dimensional distribution matrix with the same dimension as the measured phase two-dimensional distribution matrix;

[0009] S5. Extract the corresponding earth pressure data of each grid cell in the measured phase two-dimensional distribution matrix, theoretical phase two-dimensional distribution matrix and simulation phase two-dimensional distribution matrix, perform dynamic weight distribution through parameter weighting, use the weighted average algorithm for data fusion, generate the corrected pressure characterization value of the grid cell, and perform spatial interpolation on the corrected pressure characterization values of all grid cells, and finally output the earth pressure distribution cloud map of the monitoring section.

[0010] In a specific embodiment, the retaining wall is a multi-level gabion retaining wall, and each level of gabion retaining wall is stacked from bottom to top with a certain slope using gabion cages. The slopes of each level of gabion retaining wall are the same. A elevation adjustment concrete block is provided at the top of each level of gabion retaining wall. A bundled grille is laid between adjacent two layers of gabion cages. The monitoring section is defined as a stepped surface parallel to the back of each gabion cage and at an equal distance. The earth pressure cell is buried in the stepped surface using the hanging bag method, and the earth pressure cell is connected to the comprehensive acquisition instrument through a cable.

[0011] In a specific embodiment, the specific operation of using the least squares method to plot the earth pressure fitting line for the monitoring data of the earth pressure cells in the same column of grid cells is as follows: Establish a coordinate system with a bottom corner point of the bottommost grid cell in this column of grid cells as the coordinate origin, and obtain the measured pressure value x of each earth pressure cell in this column of grid cells i 、the height value y of each earth pressure cell i and the number n of earth pressure cells, and construct the expression of the unconstrained least squares method as where

[0012] L i(x)(i = 1, 2,... n) is the residual function, which can be a linear function or a non-linear function, and w i is the optimal parameter to be determined.

[0013] In a specific embodiment, there are three displacement modes for the multi-level gabion retaining wall, namely translation, rotation around the bottom of the wall, and rotation around the top of the wall. Considering the soil arch effect and the shear stress between soil layers comprehensively, the horizontal layer division method is used to construct the equilibrium equation of the micro element, and the theoretical earth pressure curve of each grid unit in any displacement mode is obtained by cumulative summation.

[0014] In a specific embodiment, the simulation software is three-dimensional finite element analysis software or discrete element software.

[0015] In a specific embodiment, the weighting coefficient values of the corresponding data in the measured phase two-dimensional distribution matrix, the theoretical phase two-dimensional distribution matrix, and the simulated phase two-dimensional distribution matrix are 0.6, 0.2, and 0.2 respectively.

[0016] The present invention has the following beneficial effects: The present invention can graphically deduce the monitoring information of the entire plane through a finite number of measured earth pressure values, obtain the earth pressure response data behind the green gabion retaining wall in real time, capture the construction state, and provide a basis for early warning. Description of the Drawings

[0017] Figure 1 is the flow chart of the embodiment of the present invention.

[0018] Figure 2 is the longitudinal section structure diagram of the gabion retaining wall in the embodiment of the present invention.

[0019] Figure 3 is the structure diagram of the rasterized rectangular projection plane in the embodiment of the present invention.

[0020] Figure 4 is the measured earth pressure distribution nephogram obtained in the embodiment of the present invention.

[0021] Figure 5 is the theoretical earth pressure distribution nephogram obtained in the embodiment of the present invention.

[0022] Figure 6 is the simulated earth pressure distribution nephogram obtained in the embodiment of the present invention.

[0023] Figure 7 is the monitored cross-section earth pressure distribution nephogram finally output in the embodiment of the present invention.

[0024] Reference Signs: Gabion 1, Elevation-adjusting Concrete Block 2, Cluster Grating 3, Backfill Soil 4, Earth Pressure Cell 5. Detailed Embodiments

[0025] To facilitate a better understanding of the technical solution of the present invention, the following takes a gabion retaining wall project as an example and further illustrates the embodiments of the present invention in conjunction with the accompanying drawings.

[0026] Please refer to Figure 1 and Figure 2 , the gabion retaining wall is a gabion retaining wall made of galvanized material and coated with a highly wear-resistant organic coating. It is divided into three levels from bottom to top. The designed heights of the three-level gabion retaining walls are 7m, 10m, and 10m respectively from bottom to top. Each level of gabion retaining wall is stacked by gabion cages 1 with a slope of 1:0.2 from bottom to top. Among them, the first-level gabion retaining wall is stacked by gabion cages 1 with dimensions of 3m×0.5m×0.8m in length, height, and width. The second-level gabion retaining wall and the third-level gabion retaining wall are stacked by gabion cages 1 with dimensions of 3m×0.5m×0.8m in length, height, and width in the lower half, and are stacked by gabion cages 1 with dimensions of 3m×1m×1m in length, height, and width in the upper half. The step width of each level of gabion retaining wall is 2m. The top of each level of gabion retaining wall is provided with elevation-adjusting concrete blocks 2 made of C30 ordinary portland cement concrete. A bundled grille 3 is laid between adjacent two layers of gabion cages 1. The design structure of this three-level gabion retaining wall is more stable.

[0027] Determine the monitoring section of the backfill soil 4 behind the gabion retaining wall. This monitoring section is the stepped surface formed by the back of each gabion cage 1. Project this monitoring section onto the same vertical rectangular plane to obtain a rectangular projection plane with a height of 27m and a width of 18m as shown in Figure 3 . Grid the rectangular projection plane. Backfill miscellaneous soil behind the gabion retaining wall. The comprehensive density of the miscellaneous soil is 18.5 kg / m 3 , the internal friction angle is 12°, and the cohesion is 9.7 kPa. According to the construction sequence, a number of vibrating wire earth pressure cells 5 of model JMZX-5020Am are successively buried in the monitoring section by the hanging bag method, so that the projection positions of the earth pressure cells 5 in the rectangular projection plane are exactly at the center positions of some grid cells in column A and column B of the grid cells, forming an array of earth pressure cells 5, and connecting the earth pressure cells 5 to the comprehensive acquisition instrument through cables. The comprehensive range of the earth pressure cells 5 is 2 MPa, and the sensitivity is 0.001 MPa. It should be noted that the monitoring section can be any stepped surface parallel to and at an equal distance from the back of each gabion cage 1.

[0028] Then, obtain the earth pressure values monitored by the earth pressure cells 5 in column A and column B and the depth values corresponding to the burial of each earth pressure cell 5 as shown in Table 1:

[0029] Burial depth Z / m Earth pressure of Group A / kPa Earth pressure of Group B / kPa 0 0 0 2 8.31 6.94 4 30.98 35.12 6 51.12 58.42 8 74.59 76.68 10 110.2 105.91 12 127.8 126.54 14 161.11 144.63 16 177.14 179.55 18 199.87 210.39 20 218.99 217.52 21 226.78 224.78 23 259.57 268.11 25 280.62 284.76 27 305.17 316.72

[0030] Table 1

[0031] The monitoring data of the earth pressure cells 5 in the grid cells of the same column are used to draw the earth pressure fitting line by the least squares method. The specific operation is as follows: A coordinate system is established with a bottom corner point of the bottommost grid cell in this column of grid cells as the coordinate origin, and the measured pressure values x of each earth pressure cell 5 in this column of grid cells are obtained. i , the height values y of each earth pressure cell 5 i and the number n of the earth pressure cells 5, and the expression of the unconstrained least squares method is constructed as:

[0032] where

[0033] L i (x)(i = 1, 2,...n) is the residual function, and this residual function is a linear function or a non - linear function, and w i is the optimal parameter to be determined.

[0034] Taking the earth pressure values measured by the earth pressure cells in Group A in Table 1 as an example, first calculate the average depth of the earth pressure cells in Group A and the average pressure value of the measured earth pressure:

[0035]

[0036] Then calculate the value of b in the equation of the form y = bx + a:

[0037]

[0038] Then substitute it into the following formula to calculate the value of a:

[0039]

[0040] Then calculate the correlation coefficient using the following formula:

[0041]

[0042] where the residual value is

[0043] Finally, the fitting curve equation of Group A is obtained as σ = 11.67Z - 11.46(0 ≤ Z ≤ 27), and the fitting correlation coefficient is The least squares method can obtain a continuous pressure line of Group A in the height direction based on the discrete values of the measured earth pressure in the height direction, and then obtain the central pressure values of all grid cells in Column A. The calculation method of the fitting curve equation of Group B is the same as that of Group A, which will not be elaborated here.

[0044] The monitoring data of the earth pressure cells 5 in the same-row grid cells are subjected to interval oscillation. The principle is that in the measured values of Group A and Group B, two pressure values at the same height are used to form a data interval, such as the data interval of [8.31, 6.94]. For other grid cells at the same height, based on the Mersenne Twister algorithm or the linear congruential algorithm, a value is randomly generated within the radius of the data interval, and then the pressure values of all grid cells on the rasterized rectangular projection plane are obtained. The measured two-dimensional distribution matrix is constructed through the earth pressure values of each grid cell.

[0045] Color-fill the grid cells according to the magnitude of the earth pressure values in the measured two-dimensional distribution matrix to obtain the measured earth pressure distribution cloud diagram as Figure 4 shown.

[0046] The stiffness of this gabion retaining wall is between that of flexible and rigid retaining walls, and there are three displacement modes: translation, rotation around the bottom of the wall, and rotation around the top of the wall. The earth pressure behind the wall belongs to the category of active earth pressure calculation. Based on the structural parameters of the retaining wall, displacement modes, and physical and mechanical parameters of the backfill soil, considering the soil arch effect and shear stress between soil layers, the micro-element equilibrium equations of one column of grid cells are constructed using the horizontal layer division method, and the theoretical earth pressure curve of this column of grid cells under any displacement mode is obtained by cumulative summation, such as σ 理 = 12.13Z - 15.71 (0 ≤ Z ≤ 27), and the theoretical earth pressure values of all grid cells in this column are obtained. Among them, constructing the micro-element equilibrium equations of the column grid cells using the horizontal layer division method is an existing calculation method, and the specific calculation process will not be elaborated here. Then, it is extended horizontally to maintain consistency, that is, the earth pressure values of grid cells at the same height are set to be the same, and a theoretical two-dimensional distribution matrix with the same dimension as the measured two-dimensional distribution matrix is generated. Color-fill the grid cells according to the magnitude of the earth pressure values in the theoretical two-dimensional distribution matrix to obtain the theoretical earth pressure distribution cloud diagram as Figure 5 shown.

[0047] Then, a three-dimensional calculation model proportional to the physical project is established in a three-dimensional finite element analysis software. Then, the three-dimensional calculation model is reduced in dimension to generate a two-dimensional numerical graph, while keeping the grid division parameters consistent. The distribution data of the earth pressure behind the wall is obtained through three-dimensional finite element analysis numerical simulation, and a simulation two-dimensional distribution matrix with the same dimension as the measured two-dimensional distribution matrix is generated. Of course, in other embodiments, the simulation software can also use discrete element software, which adopts the particle flow mode. The particles, such as those of different sizes and shapes, are encapsulated into a whole like the stones in a gabion retaining wall, and the numerical calculation is carried out considering the bond relationship between particles, the crushing criterion, etc. It should be noted that using three-dimensional finite element analysis software and discrete element software to simulate and generate the distribution data of the earth pressure behind the wall are both existing methods, and the specific simulation steps will not be elaborated here. The earth pressure values in the simulation two-dimensional distribution matrix are used to fill the colors of the grids according to the magnitude of the force, and the simulated earth pressure distribution nephogram is obtained as shown in Figure 6 shown.

[0048] Finally, the corresponding earth pressure data of each grid unit in the measured two-dimensional distribution matrix, the theoretical two-dimensional distribution matrix, and the simulation two-dimensional distribution matrix are extracted. The weighting coefficients of 0.6, 0.2, and 0.2 are assigned to the corresponding data in the measured two-dimensional distribution matrix, the theoretical two-dimensional distribution matrix, and the simulation two-dimensional distribution matrix respectively for dynamic weight distribution. Then, the weighted average algorithm is used for data fusion to generate the corrected pressure characterization value of the grid unit. The pressure characterization values of all the corrected grid units are subjected to spatial interpolation, and finally the monitored cross-section earth pressure distribution nephogram as shown in Figure 7 is output.

[0049] The present invention has the following beneficial effects: The present invention can graphically deduce the monitoring information of the entire plane through a finite number of measured earth pressure values, obtain the earth pressure response data behind the green gabion retaining wall in real time, capture the construction state, and provide a basis for early warning.

[0050] The above content is a further detailed description of the present invention in combination with specific preferred implementation manners, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions and substitutions can still be made, and all should be regarded as belonging to the protection scope of the present invention.

Claims

1. A phased array monitoring method for earth pressure behind a green gabion retaining wall, characterized in that It includes the following steps: S1. Determine the monitoring section of the backfill soil behind the retaining wall, project the monitoring section onto the same vertical rectangular plane to obtain a rectangular projection plane, rasterize the rectangular projection plane, and bury a number of earth pressure cells in the monitoring section so that the projection positions of the number of earth pressure cells in the rectangular projection plane are exactly located at the center positions of some grid cells in two columns of grid cells, forming an earth pressure cell array; S2. Obtain the monitoring data of each earth pressure cell, use the least squares method to draw an earth pressure fitting line for the monitoring data of the earth pressure cells in the same column of grid cells, obtain the earth pressure values of all grid cells in this column, then use interval oscillation for the monitoring data of the earth pressure cells in the same row of grid cells to obtain the earth pressure values of all grid cells, and then construct a measured phase two-dimensional distribution matrix through the earth pressure values of each grid cell; S3. Based on the structural parameters of the retaining wall, displacement mode and physical and mechanical parameters of the backfill soil, use the horizontal layer division method to calculate the theoretical earth pressure curve of a certain column of grid cells, obtain the theoretical earth pressure values of all grid cells in this column, and then expand it in the horizontal direction to maintain consistency, generating a theoretical phase two-dimensional distribution matrix with the same dimension as the measured phase two-dimensional distribution matrix; S4. Establish a numerical model in the simulation software that is proportional to the physical project, keep the grid division parameters consistent, obtain the distribution data of the earth pressure behind the wall through numerical simulation, and generate a simulation phase two-dimensional distribution matrix with the same dimension as the measured phase two-dimensional distribution matrix; S5. Extract the corresponding earth pressure data of each grid cell in the measured phase two-dimensional distribution matrix, theoretical phase two-dimensional distribution matrix and simulation phase two-dimensional distribution matrix, perform dynamic weight distribution through parameter weighting, use the weighted average algorithm for data fusion, generate a corrected pressure characterization value for the grid cell, perform spatial interpolation on the corrected pressure characterization values of all grid cells, and finally output the earth pressure distribution cloud map of the monitoring section.

2. The phased array monitoring method for the earth pressure behind the green gabion retaining wall according to claim 1, characterized in that, In step S1, the retaining wall is a multi-level gabion retaining wall. Each level of gabion retaining wall is stacked from bottom to top with a certain slope using gabion cages. The slopes of each level of gabion retaining wall are the same. A elevation adjustment concrete block is provided at the top of each level of gabion retaining wall. A bundled grille is laid between adjacent two layers of gabion cages. The monitoring section is defined as a stepped surface parallel to the back of each gabion cage and at an equal distance. The earth pressure cell is buried in the stepped surface using the hanging bag method. The earth pressure cell is connected to the comprehensive acquisition instrument through a cable.

3. The phased array monitoring method for the earth pressure behind the green gabion retaining wall according to claim 2, characterized in that In step S2, the specific operation of using the least squares method to draw an earth pressure fitting line for the monitoring data of the earth pressure cells in the same column of grid cells is as follows: Establish a coordinate system with a bottom corner point of the bottommost grid cell in this column of grid cells as the coordinate origin, n, and construct an expression for the unconstrained least squares method as where L i (x)(i = 1, 2,... n) is the residual function, which can be a linear function or a non-linear function, and w i is the optimal parameter to be determined.

4. The phased array monitoring method for the earth pressure behind the green gabion retaining wall according to claim 2, characterized in that, In step S3, the multi-level gabion retaining wall has three displacement modes: translation, rotation around the bottom of the wall, and rotation around the top of the wall. Considering the soil arch effect and shear stress between soil layers comprehensively, use the horizontal layer division method to construct a micro-element balance equation, and accumulate and sum to obtain the theoretical earth pressure curve of each column of grid cells under any displacement mode.

5. The phased array monitoring method for the earth pressure behind the green gabion retaining wall according to claim 1, characterized in that In step S4, the simulation software is a three-dimensional finite element analysis software or a discrete element software.

6. The phased array monitoring method for the earth pressure behind the green gabion retaining wall according to claim 1, characterized in that, In step S5, the weighting coefficient values of the corresponding data in the measured phase two-dimensional distribution matrix, the theoretical phase two-dimensional distribution matrix, and the simulated phase two-dimensional distribution matrix are 0.6, 0.2, and 0.2 respectively.

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