Green gabion retaining wall back soil pressure phased array monitoring method

Abstract

The present application belongs to the technical field of geotechnical engineering, and particularly relates to a green gabion retaining wall back soil pressure phased array type monitoring method. First, the rectangular projection plane of the monitoring section grid is determined, and the soil pressure cell is buried, so that the projection of the soil pressure cell in the rectangular projection plane is located at the center position of the two column grid units. Then, the least square method is used to draw the soil pressure fitting line in the column direction, and the interval oscillation is used in the row direction to construct the measured phase two-dimensional distribution matrix. After that, the horizontal layer method is used to calculate the theoretical soil pressure curve of a column, the row direction is kept consistent, and the theoretical phase two-dimensional distribution matrix is generated. Then, the simulation phase two-dimensional distribution matrix is generated through numerical simulation. Finally, the dynamic weight distribution of each phase is allocated through parameter weighting, and the weighted wall back soil pressure plane distribution cloud chart is output. Through the limited measured soil pressure value, the monitoring information of the whole section is deduced graphically, and the construction state is captured in real time, thereby providing a basis for early warning.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of geotechnical engineering, and particularly relates to a green gabion retaining wall backfill soil pressure phased array monitoring method. BACKGROUND

[0002] In recent years, the pace of infrastructure construction in China is changing with each passing day, especially the gabion retaining wall wrapped with geogrid, polyhedral gabion net cage and gravel is more and more widely used in the field of geotechnical engineering. The soil pressure behind the wall is an important load for the design and stability calculation of the retaining wall structure, and its size and distribution law is closely related to the bearing mode and displacement mode of the retaining wall. If the construction method and engineering measures are not handled properly, the retaining wall instability and slope collapse and other engineering disasters will easily occur, causing heavy casualties and economic losses. The internal geogrid of the gabion retaining wall is laid as a reinforcement, so that the gabion retaining wall can withstand tensile, compressive and shear effects, and the stiffness is between flexible and rigid retaining walls, and there are multiple displacement modes, but the overall soil body behind the wall still moves towards the gabion retaining wall, and the soil pressure behind the wall belongs to the category of active earth pressure calculation.

[0003] At present, the research on the soil pressure behind the gabion retaining wall is mainly based on field test, theoretical research, numerical simulation and model test. The field test is mainly contact monitoring, and the sensor and data transmission line are easily damaged and cause monitoring blank due to the influence of various factors. The theoretical research is often based on various assumptions, such as the patent application with publication number CN102828497A. The result of this scheme has large deviation. The numerical simulation has certain experience in the selection of the constitutive relationship of the retaining wall and the soil body. The similarity relationship of the model test is generally difficult to meet, such as the existing patent scheme with announcement number CN105113555B. The calculation result of this scheme has certain difference with the actual engineering, and cannot meet the guiding needs of the gabion retaining wall engineering construction. SUMMARY

[0004] The present application provides a green gabion retaining wall backfill soil pressure phased array monitoring method, which comprises the following steps:

[0005] S1, determining the monitoring section of the backfill soil of the retaining wall, projecting the monitoring section into the same vertical rectangular plane to obtain a rectangular projection plane, and gridding the rectangular projection plane, and burying a plurality of soil pressure cells in the monitoring section, so that the projection positions of the plurality of soil pressure cells in the rectangular projection plane are located at the center positions of part of the grid cells in two columns of grid cells, forming a soil pressure cell array;

[0006] S2, obtaining monitoring data of each earth pressure cell, drawing an earth pressure fitting line of the monitoring data of the earth pressure cells in the same column grid unit by using the least square method to obtain the earth pressure values of all grid units in the column, and obtaining the earth pressure values of all grid units in the same row grid unit by using interval oscillation to the monitoring data of the earth pressure cells in the same row grid unit, and then constructing a measured phase two-dimensional distribution matrix through the earth pressure values of each grid unit;

[0007] S3, based on the structural parameters, displacement mode and physical and mechanical parameters of the backfill soil of the retaining wall, the theoretical earth pressure curve of a column grid unit is calculated by using the horizontal layer division method to obtain the theoretical earth pressure values of all grid units in the column, and then the consistency is maintained in the horizontal direction to generate a theoretical phase two-dimensional distribution matrix with the same dimension as the measured phase two-dimensional distribution matrix;

[0008] S4, a numerical model with the same proportion as the entity engineering is established in the simulation software, the grid division parameters are kept consistent, the distribution data of the earth pressure behind the wall are obtained through numerical simulation, and a simulation phase two-dimensional distribution matrix with the same dimension as the measured phase two-dimensional distribution matrix is generated;

[0009] S5, the corresponding earth pressure data of each grid unit in the measured phase two-dimensional distribution matrix, the theoretical phase two-dimensional distribution matrix and the simulation phase two-dimensional distribution matrix are extracted, the dynamic weight distribution is performed through parameter weighting, the data fusion is performed by using the weighted average algorithm, the corrected grid unit pressure characteristic value is generated, the pressure characteristic values of all corrected grid units are subjected to spatial interpolation, and finally the monitoring section earth pressure distribution cloud picture is output.

[0010] In a specific embodiment, the retaining wall is a multi-stage gabion retaining wall, each stage of gabion retaining wall is stacked from bottom to top with a certain slope by using gabion stone cages, the slopes of the gabion retaining walls are consistent, the top of each gabion retaining wall is provided with a height adjustment concrete block, a bunching grid is laid between the adjacent two layers of gabion stone cages, the monitoring section is defined as a ladder surface parallel to the back surface of each gabion stone cage and with equal distance, the earth pressure cell is buried in the ladder surface by using the bag suspension method, and the earth pressure cell is connected with the comprehensive acquisition instrument through a cable.

[0011] In a specific embodiment, the specific operation of drawing an earth pressure fitting line of the monitoring data of the earth pressure cells in the same column grid unit by using the least square method is as follows: a coordinate system is established with one bottom edge corner point of the bottommost grid unit in the column grid unit as a coordinate origin, the measured pressure values x i , the height values y i of each earth pressure cell and the number n of earth pressure cells are obtained, and the expression of the unconstrained least square method is constructed as wherein

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

[0013] In a specific embodiment, the multi-level gabion retaining wall has three displacement modes of translation, rotation around the wall bottom and rotation around the wall top, and the horizontal layer division method is used to construct the micro-unit balance equation by comprehensively considering the soil arching effect and the interlayer shear stress, and the theoretical soil pressure curve of each column of grid units under any displacement mode is obtained by 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 application has the following beneficial effects: the present application can graphically deduce the entire plane monitoring information through a limited number of measured soil pressure values, obtain the green gabion retaining wall back soil pressure response data in real time, capture the construction state, and provide a basis for early warning. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The flowchart of the embodiment of the present application.

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

[0019] Figure 3 The structure diagram of the rectangular projection surface of the grid in the embodiment of the present application.

[0020] Figure 4 The measured soil pressure distribution nephogram obtained in the embodiment of the present application.

[0021] Figure 5 The theoretical soil pressure distribution nephogram obtained in the embodiment of the present application.

[0022] Figure 6 The simulated soil pressure distribution nephogram obtained in the embodiment of the present application.

[0023] Figure 7 The monitoring section soil pressure distribution nephogram finally output in the embodiment of the present application.

[0024] The figure mark: gabion 1, elevation adjustment concrete block 2, cluster grid 3, backfill soil 4, soil pressure cell 5. DETAILED DESCRIPTION

[0025] In order to make the technical solutions of the present application more convenient to understand, the following will take a certain gabion retaining wall project as an example, and further illustrate the embodiments of the present application in combination with the drawings.

[0026] Please refer to Figure 1 and Figure 2 The gabion retaining wall is a galvanized gabion retaining wall covered with a high-wear organic coating, which is divided into three levels from bottom to top. The design height of the three-level gabion retaining wall is 7m, 10m and 10m from bottom to top, respectively. Each level of gabion retaining wall is stacked with gabion baskets 1 from bottom to top with a slope of 1:0.2. Among them, the first level of gabion retaining wall is stacked with gabion baskets 1 with a length, height and width size of 3m×0.5m×0.8m. The second and third levels of gabion retaining wall are stacked with gabion baskets 1 with a length, height and width size of 3m×0.5m×0.8m in the lower half, and stacked with gabion baskets 1 with a length, height and width size of 3m×1m×1m 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 a level adjustment concrete block 2 made of C30 ordinary portland cement concrete. A bunch of grating 3 is laid between the adjacent two layers of gabion baskets 1. The design structure of this three-level gabion retaining wall is more stable.

[0027] A monitoring section of the backfill soil 4 behind the gabion retaining wall is determined. The monitoring section is the stepped surface formed by the back of each gabion basket 1. Projecting the monitoring section onto the same vertical rectangular plane obtains a rectangular projection plane with a height of 27m and a width of 18m as shown in Figure 3 The rectangular projection plane is gridded. The miscellaneous fill soil is backfilled behind the gabion retaining wall. The comprehensive density of the miscellaneous fill soil is 18.5kg / m 3 , the internal friction angle is 12°, and the cohesion is 9.7kPa. According to the construction sequence, a plurality of JMZX-5020Am vibrating wire soil pressure cells 5 are sequentially buried in the monitoring section by using the bag suspension method, so that the projection positions of the plurality of soil pressure cells 5 in the rectangular projection plane are located at the center positions of part of the grid cells in columns A and B, forming an array of soil pressure cells 5. The soil pressure cells 5 are connected to a comprehensive acquisition instrument through a cable. The comprehensive range of the soil pressure cells 5 is 2MPa, and the sensitivity is 0.001MPa. It should be noted that the monitoring section can be any stepped surface parallel to the back of each gabion basket 1 and with equal distance.

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

[0029] Depth of burial Z / m Soil pressure for group A / kPa Soil pressure for 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 same column grid unit is plotted into an earth pressure fitting line by using the least square method. Specifically, a coordinate system is established with a bottom corner point of a bottom grid unit in the column grid unit as a coordinate origin, the measured pressure values x of the earth pressure cells 5 in the column grid unit are obtained i , the height values y of the earth pressure cells 5 i , and the number n of the earth pressure cells 5, and an expression of the unconstrained least square method is constructed as follows:

[0032] wherein

[0033] L i (x)(i = 1, 2,..., n) is a residual function, which is a linear function or a nonlinear function, w i is an optimal undetermined parameter.

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

[0035]

[0036] Then, the value of b in the equation y = bx + a is calculated:

[0037]

[0038] Then, the value of a is calculated by using the following formula:

[0039]

[0040] Then, the correlation coefficient is calculated by using the following formula:

[0041]

[0042] wherein, 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 square method can obtain a continuous pressure line in the height direction of group A according to the discrete values of the measured earth pressure in the height direction, and then the center pressure values of all the grid units in column A are obtained. The calculation method of the fitting curve equation of group B is the same as that of group A, and will not be described herein.

[0044] The monitoring data of the earth pressure cell 5 in the same row grid unit is adopted interval oscillation, the principle is that in the measured values of group A and group B, two pressure values at the same height form a data interval, such as the data interval [8.31, 6.94], in other grid units at the same height, a value is randomly generated within the data interval radius based on Mason rotation algorithm or linear congruential algorithm, and then the pressure values of all grids of the grid rectangular projection plane are obtained, and the measured two-dimensional distribution matrix is constructed by the earth pressure values of each grid unit.

[0045] The earth pressure values of the measured two-dimensional distribution matrix are color filled according to the size of the force, and the measured earth pressure distribution nephogram is obtained as shown in Figure 4 .

[0046] The rigidity of the gabion retaining wall is between the flexible and rigid retaining wall, there are three displacement modes of translation, rotation around the wall bottom and rotation around the wall top, 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 mode and physical and mechanical parameters of the backfill soil, considering the soil arching effect and soil layer shear stress, the micro unit balance equation of one column grid unit is constructed by horizontal layer division method, and the theoretical earth pressure curve of the column grid unit under any displacement mode is obtained by summation, such as σ 理 = 12.13Z-15.71 (0≤Z≤27), the theoretical earth pressure values of all grid units in the column are obtained, wherein the micro unit balance equation of the column grid unit constructed by horizontal layer division method is the existing calculation method, and the specific calculation process is not described here. The consistency is maintained in the horizontal direction, that is, the earth pressure values of the grid units at the same height are set to be consistent, and the theoretical two-dimensional distribution matrix with the same dimension as the measured two-dimensional distribution matrix is generated. The earth pressure values of the theoretical two-dimensional distribution matrix are color filled according to the size of the force, and the theoretical earth pressure distribution nephogram is obtained as shown in Figure 5 .

[0047] Then, a three-dimensional calculation model with the same proportion as the entity engineering 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, the grid division parameters are kept consistent, the distribution data of the soil pressure behind the wall are 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. Figure 6

[0048] Finally, the corresponding soil 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 0.6, 0.2 and 0.2 of the corresponding data in the measured two-dimensional distribution matrix, the theoretical two-dimensional distribution matrix and the simulation two-dimensional distribution matrix are respectively dynamically weighted and distributed, and then the weighted average algorithm is used for data fusion to generate a corrected grid unit pressure characteristic value, the pressure characteristic values of all the corrected grid units are subjected to spatial interpolation, and finally a monitoring section soil pressure distribution cloud diagram as shown in Figure 7

[0049] The present application has the following beneficial effects: the present application can obtain the green gabion retaining wall soil pressure response data in real time by a limited number of measured soil pressure values, graphical deduction of the entire plane monitoring information, capture of the construction state, and provision of a basis for early warning.

[0050] The above is a further detailed description of the present application in combination with a specific preferred embodiment, and the specific implementation of the present application cannot be limited to these descriptions. For ordinary skilled persons in the technical field to which the present application belongs, a number of simple deductions and replacements can be made without departing from the concept of the present application, and all of them should be regarded as falling within the protection scope of the present application.​​

Claims

1. A method for monitoring the earth pressure behind a green gabion retaining wall, characterized in that, The method comprises the following steps: S1, determining a monitoring section of backfill soil of a retaining wall, projecting the monitoring section into the same vertical rectangular plane to obtain a rectangular projection plane, rasterizing the rectangular projection plane, and burying a plurality of earth pressure cells in the monitoring section so that the projection positions of the plurality of earth pressure cells in the rectangular projection plane are located at the center positions of part of the grid cells in two columns of grid cells, forming an earth pressure cell array; S2, obtaining monitoring data of each earth pressure cell, using the least square method to draw an earth pressure fitting line for the monitoring data of the earth pressure cells in the same column of grid cells to obtain the earth pressure values of all grid cells in the column, using interval oscillation to obtain the earth pressure values of all grid cells in the same row of grid cells, and constructing a measured phase two-dimensional distribution matrix through the earth pressure values of each grid cell; the principle of interval oscillation is that two pressure values at the same height form a data interval, a value is randomly generated in the data interval radius of other grid cells at the same height based on the Mason rotation algorithm or the linear congruential algorithm, and then the pressure values of all grids of the rasterized rectangular projection plane are obtained, and a measured phase two-dimensional distribution matrix is constructed through the earth pressure values of each grid cell; S3, based on the structural parameters, displacement mode and physical and mechanical parameters of the backfill soil body of the retaining wall, the theoretical earth pressure curve of a column of grid cells is calculated by using the horizontal layer division method to obtain the theoretical earth pressure values of all grid cells in the column, and the same dimension theoretical phase two-dimensional distribution matrix as the measured phase two-dimensional distribution matrix is generated by keeping consistency in the horizontal direction; S4, a numerical model with the same proportion as the entity engineering is established in the simulation software, the grid division parameters are kept consistent, the distribution data of the earth pressure behind the wall is obtained through numerical simulation, and the same dimension simulation phase two-dimensional distribution matrix as the measured phase two-dimensional distribution matrix is generated; S5, the corresponding earth pressure data of each grid cell in the measured phase two-dimensional distribution matrix, the theoretical phase two-dimensional distribution matrix and the simulation phase two-dimensional distribution matrix are extracted, dynamic weight distribution is performed through parameter weighting, data fusion is performed by using the weighted average algorithm, the corrected grid cell pressure characteristic value is generated, the pressure characteristic values of all corrected grid cells are subjected to spatial interpolation, and finally the soil pressure distribution cloud map of the monitoring section is output.

2. The green gabion retaining wall back-soil pressure phased array monitoring method according to claim 1, characterized in that, In step S1, the retaining wall is a multi-stage gabion retaining wall, each stage of gabion retaining wall is stacked from bottom to top with a certain slope by using gabion stone cages, the slopes of the gabion retaining walls are consistent, the top of each gabion retaining wall is provided with a height adjustment concrete block, and a bunching grid is laid between adjacent two layers of gabion stone cages; the monitoring section is defined as a stepped surface parallel to the back surface of each gabion stone cage and having an equal distance; the earth pressure cell is buried in the stepped surface by using the bag suspension method; and the earth pressure cell is connected with the comprehensive acquisition instrument through a cable.

3. The green gabion retaining wall back-soil pressure phased array monitoring method according to claim 2, characterized in that, In step S2, the specific operation of drawing the soil pressure fitting line by using the least square method for the monitoring data of the soil pressure cell in the same column grid unit is as follows: taking one bottom corner point of the bottom grid unit in the column grid unit as the coordinate origin to establish a coordinate system, obtaining the measured pressure value x of each soil pressure cell in the column grid unit i , the height value y of each soil pressure cell i , and the number n of soil pressure cells, and constructing the expression of the unconstrained least square method as where Li(x) (i = 1, 2,... n) is a residual function, which is a linear function or a non-linear function, W i is an optimal parameter to be determined.

4. The method for monitoring the earth pressure behind the green gabion retaining wall according to claim 2, characterized in that, In step S3, the multi-stage gabion retaining wall has three displacement modes of translation, rotation around the wall bottom and rotation around the wall top, the horizontal layer division method is used to construct the micro unit balance equation by comprehensively considering the soil arching effect and the shear stress between soil layers, and the theoretical earth pressure curve of each column of grid cells under any displacement mode is obtained by summation.

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

6. The method for monitoring the earth pressure behind the green gabion retaining wall according to claim 1, wherein, 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 respectively 0.6, 0.2 and 0.2.

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