Soil landslide matrix suction test method and system based on soil conductivity performance

Abstract

The present invention relates to a soil landslide matrix suction test method and system based on soil conductivity performance, and the method comprises the following steps: 1) establishing a calculation formula for a method for measuring matrix suction of unsaturated residual soil based on soil conductivity performance; 2) obtaining measured data of unsaturated soil conductivity-water content curve measured by an indoor soil slope rainfall experiment; 3) obtaining measured data of unsaturated soil water content-matrix suction curve measured by an indoor soil slope rainfall experiment; 4) substituting the measured unsaturated soil conductivity data and unsaturated soil matrix suction data into the calculation formula for fitting, and obtaining a saturation index and fitting parameters; 5) substituting the obtained saturation index and fitting parameters into the calculation formula, and obtaining a conductivity-matrix suction model of the soil; for unsaturated soil, substituting its conductivity into the conductivity-matrix suction model, that is, obtaining the soil matrix suction. The method and system are conducive to conveniently and effectively measuring soil matrix suction.

Description

Technical Field

[0001] The invention belongs to the technical field of rock, soil and geological engineering, and particularly relates to a soil landslide matrix suction testing method and system based on soil conductivity performance. Background Art

[0002] Rainfall is the most important and common environmental factor that affects slope stability and causes slope instability. One factor that cannot be ignored in the influence of water infiltration on landslide stability is the change in soil matrix suction. With the infiltration of water, the matrix suction of the unsaturated zone of the slope decreases, which greatly reduces the shear strength of the weak interlayer of the soil or rock mass, thereby reducing the stability of the slope. Matrix suction is an important variable to characterize the properties of unsaturated soil. As a component of soil cohesion, it can improve the shear strength of the soil and contribute to slope stability. The soil-water characteristic curve shows that matrix suction is extremely water-sensitive. With the increase of water content, matrix suction decreases rapidly. In actual engineering, most slopes are in an unsaturated state or a partially saturated state. Under the action of rainfall, with the infiltration of rainwater, the soil matrix suction decreases rapidly, the cohesion decreases, and the stability of the slope decreases. Therefore, matrix suction is an important monitoring indicator in landslide early warning, but the large-scale monitoring methods of matrix suction are still not diverse and convenient enough.

[0003] Soil conductivity is an important physical property of soil, and its size is related to soil moisture content, soil particle size, etc. Because it is easy, fast and cheap to test, it has also been applied in slope research. Experimental studies have shown that the conductivity of the slope and the matrix suction have certain similarities in overall distribution, and there is a strong correlation between the two. As an effective indicator reflecting the state of water in the medium, and thanks to the more diverse and convenient detection methods of conductivity, for natural slopes with complex and changeable water distribution characteristics and migration laws, using the slope medium conductivity to feedback the distribution characteristics of its water content, matrix suction and other related parameters is an effective method. Summary of the invention

[0004] The object of the present invention is to provide a soil landslide matrix suction testing method and system based on soil conductivity performance, which method and system are conducive to conveniently and effectively measuring soil matrix suction.

[0005] To achieve the above object, the technical solution adopted by the present invention is: a soil landslide matrix suction test method based on soil conductivity performance, comprising the following steps:

[0006] 1) Establish a method for measuring the matrix suction of unsaturated residual soil based on the electrical conductivity of the soil:

[0007]

[0008] In the formula, σ is the soil conductivity, σ s is the saturated soil conductivity, ψ is the matrix suction, α and β are fitting parameters, and p is the saturation index;

[0009] 2) Obtain the measured data of the unsaturated soil conductivity-water content curve measured by indoor soil slope rainfall experiment;

[0010] 3) Obtain the measured data of the unsaturated soil moisture content-matrix suction curve measured by indoor soil slope rainfall experiment;

[0011] 4) Substituting the unsaturated soil conductivity data measured in step 2) and the unsaturated soil matrix suction data measured in step 3) into equation (1) for fitting, and obtaining the saturation index p and fitting parameters α, β;

[0012] 5) Substitute the obtained saturation index p and fitting parameters α and β into formula (1) to obtain the conductivity-matrix suction model of the soil; for unsaturated soil, substitute its conductivity into the conductivity-matrix suction model to calculate the soil matrix suction.

[0013] Furthermore, step 1) specifically includes the following steps:

[0014] 1a) Extend the Archie model to unsaturated soil and establish the relationship between soil saturation and resistivity:

[0015] ρ=aρ w n -m S r -p (2)

[0016] Where ρ is the soil resistivity, ρ w is the pore water resistivity, a is the soil property parameter, m is the soil property parameter, n is the soil porosity, S r is the saturation, p is the saturation index;

[0017] 1b) The electrical conductivity of soil is the inverse of its resistivity:

[0018]

[0019] 1c) Combining equations (2) and (3), we can obtain the soil saturation-conductivity relationship:

[0020]

[0021] In the formula, σ is the soil conductivity, σ w is the pore water conductivity;

[0022] 1d) The conversion relationship between soil volume moisture content and soil saturation is as follows:

[0023]

[0024] Where θ is the volumetric water content, V W is the pore water volume, V is the total volume of the soil sample, w is the water content, γ d is the dry weight of soil, γ W is the pore water density;

[0025] 1e) Combine equations (4) and (5), substitute the soil volume moisture content and soil density conversion relationship into the relationship between soil saturation and moisture content, and obtain the soil conductivity-moisture content model:

[0026]

[0027] 1f) In unsaturated soil, the relationship curve between soil suction and volumetric water content is called the soil-water characteristic curve, which is expressed by the Van Genuchten model as follows:

[0028]

[0029] Where: θ s and θ r are saturated volume moisture content and residual volume moisture content respectively;

[0030] Without considering the influence of residual moisture content, the VG model is modified as follows:

[0031]

[0032] 1g) Replace the volumetric water content parameter in the Van Genuchten model parameters with the conductivity in the conductivity-volume water content formula, and combine equations (6) and (8) to obtain the mathematical model between matrix suction and conductivity as follows:

[0033]

[0034] Furthermore, in step 4), the fitting method of the saturation index p and the fitting parameters α and β is specifically as follows: based on the measured unsaturated soil conductivity data and unsaturated soil matrix suction data, a scatter plot is drawn with conductivity as the horizontal coordinate and matrix suction as the vertical coordinate, and then a nonlinear fitting is performed to obtain the saturation index p and the fitting parameters α and β.

[0035] The present invention provides a soil landslide matrix suction testing system based on soil electrical conductivity, comprising a memory, a processor and computer program instructions stored in the memory and capable of being executed by the processor. When the processor executes the computer program instructions, the above method steps can be implemented.

[0036] Compared with the prior art, the present invention has the following beneficial effects: the present invention uses soil conductivity performance parameters to measure soil matrix suction, which adds a new option for soil matrix suction measurement, and benefits from more diverse and convenient detection methods for soil conductivity, such as resistivity tomography (ERT), etc., which solves the problem that large-scale monitoring methods for matrix suction are still not diverse and convenient enough. Matrix suction, as a component of soil cohesion, can improve soil shear strength and contribute to slope stability. Therefore, measuring matrix suction through soil conductivity has important theoretical and practical significance for slope stability analysis and monitoring and early warning. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a flow chart of a method implementation of an embodiment of the present invention;

[0038] Figure 2 is a cross-sectional diagram of the instrument arrangement of the indoor soil slope rainfall experiment in an embodiment of the present invention;

[0039] Figure 3 1. is a plan view of the instrument layout of the indoor soil slope rainfall experiment in the embodiment of the present invention;

[0040] Figure 4 It is a fitting diagram of residual soil conductivity-matrix suction curve in an embodiment of the present invention. DETAILED DESCRIPTION

[0041] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0042] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0043] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0044] like Figure 1 As shown, this embodiment provides a soil landslide matrix suction test method based on soil conductivity performance, comprising the following steps:

[0045] 1) Establish a method for measuring the matrix suction of unsaturated residual soil based on the electrical conductivity of the soil:

[0046]

[0047] In the formula, σ is the soil conductivity, σ s is the saturated soil conductivity, ψ is the matrix suction, α and β are fitting parameters, and p is the saturation index.

[0048] In this embodiment, step 1) specifically includes the following steps:

[0049] 1a) Extend the Archie model to unsaturated soil and establish the relationship between soil saturation and resistivity:

[0050] ρ=aρ w n -m S r -p (2)

[0051] Where ρ is the soil resistivity, ρ w is the pore water resistivity, a is the soil property parameter, m is the soil property parameter, n is the soil porosity, S r is the saturation, and p is the saturation index.

[0052] 1b) The electrical conductivity of soil is the inverse of its resistivity:

[0053]

[0054] 1c) Combining equations (2) and (3), we can obtain the soil saturation-conductivity relationship:

[0055]

[0056] In the formula, σ is the soil conductivity, σ w is the pore water conductivity.

[0057] 1d) The conversion relationship between soil volume moisture content and soil saturation is as follows:

[0058]

[0059] Where θ is the volumetric water content, V W is the pore water volume, V is the total volume of the soil sample, w is the water content, γ d is the dry weight of soil, γ W is the pore water density.

[0060] 1e) Combine equations (4) and (5), substitute the soil volume moisture content and soil density conversion relationship into the relationship between soil saturation and moisture content, and obtain the soil conductivity-moisture content model:

[0061]

[0062] 1f) In unsaturated soil, the relationship curve between soil suction and volumetric water content is called soil-water characteristic curve (SWCC), which is related to the permeability function and shear strength index of the soil. Common models include Van Genuchten model and Fredlund-Xing model. In this embodiment, the Van Genuchten model is used to express as follows:

[0063]

[0064] Where: θ s and θ r are the saturated volume moisture content and the residual volume moisture content, respectively.

[0065] Since it is difficult to determine the residual moisture content of residual soil, the influence of the residual moisture content is not considered in this embodiment, and the VG model is modified as follows:

[0066]

[0067] 1g) Replace the volumetric water content parameter in the Van Genuchten model parameters with the conductivity in the conductivity-volume water content formula (Keller correction formula), and combine equations (6) and (8) to obtain the mathematical model between matrix suction and conductivity as follows:

[0068]

[0069] 2) Obtain the measured data of the unsaturated soil conductivity-moisture content curve measured through indoor soil slope rainfall experiments.

[0070] 3) Obtain the measured data of unsaturated soil moisture content-matrix suction curve obtained through indoor soil slope rainfall experiment.

[0071] 4) Substitute the unsaturated soil conductivity data measured in step 2) and the unsaturated soil matrix suction data measured in step 3) into equation (1) for fitting to obtain the saturation index p and fitting parameters α and β.

[0072] In this embodiment, the fitting method of the saturation index p and the fitting parameters α and β is specifically as follows: based on the measured unsaturated soil conductivity data and unsaturated soil matrix suction data, a scatter plot is drawn with conductivity as the horizontal coordinate and matrix suction as the vertical coordinate, and then a nonlinear fitting is performed to obtain the saturation index p and the fitting parameters α and β.

[0073] 5) Substitute the obtained saturation index p and fitting parameters α and β into formula (1) to obtain the conductivity-matrix suction model of the soil; for unsaturated soil, substitute its conductivity into the conductivity-matrix suction model to calculate the soil matrix suction.

[0074] This embodiment also provides a soil landslide matrix suction testing system based on soil electrical conductivity, including a memory, a processor, and computer program instructions stored in the memory and capable of being executed by the processor. When the processor executes the computer program instructions, the above method steps can be implemented.

[0075] The present invention will be further described below in conjunction with specific examples:

[0076] The soil sample used in this embodiment is unsaturated residual soil in Fuzhou, Fujian. First, according to the indoor soil landslide rainfall experiment, by burying soil conductivity moisture content sensor and matrix suction sensor in the indoor soil slope (the indoor soil slope model and the sensor buried cross-section and plan view are shown in Figure 2). Figure 2 , 3 As shown in the figure, the matrix suction values ​​under different conductivity of the soil are obtained, and a scatter plot is drawn with soil conductivity as the horizontal axis and matrix suction as the vertical axis. The data is then substituted into the matrix suction measurement model based on soil conductivity, that is, formula (1), and nonlinear fitting is performed to obtain the saturation index p and fitting parameters α and β. The fitting results of the residual soil used in the experiment are α = 0.03, β = 1.64, and p = 1.31. The residual soil matrix suction prediction model based on soil conductivity is: ψ = 33.33 [(σ s / σ) 1.95 -1] 0.61 , R 2 =0.84, the fitting curve is as follows Figure 4 Some points are randomly selected from the measured data, substituted into the fitting formula for verification, and the measured values ​​are compared with the fitted values. The error range is reasonable and relatively accurate, as shown in Table 1.

[0077] Table 1 Calculation results of conductivity-matrix suction prediction model

[0078]

[0079]

[0080] The currently published models for measuring the matrix suction of unsaturated soil do not use the soil conductivity performance parameters as measurement indicators. The present invention uses the soil conductivity performance parameters to measure the soil matrix suction, which adds a new option for the measurement of soil matrix suction. In addition, thanks to the more diverse and convenient detection methods of conductivity, such as electrical resistivity tomography (ERT), the problem that the large-scale monitoring methods of matrix suction are still not diverse and convenient enough is solved, which has important theoretical and practical significance for soil slope stability analysis and monitoring and early warning.

[0081] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0082] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0083] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0084] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0085] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A soil landslide matrix suction test method based on soil conductivity, characterized in that: The following steps are involved: 1) Establish a method for measuring the matrix suction of unsaturated residual soil based on the electrical conductivity of the soil: In the formula, σ is the soil conductivity, σ s is the saturated soil conductivity, ψ is the matrix suction, α and β are fitting parameters, and p is the saturation index; 2) Obtain the measured data of the unsaturated soil conductivity-water content curve measured by indoor soil slope rainfall experiment; 3) Obtain the measured data of the unsaturated soil moisture content-matrix suction curve measured by indoor soil slope rainfall experiment; 4) Substituting the unsaturated soil conductivity data measured in step 2) and the unsaturated soil matrix suction data measured in step 3) into equation (1) for fitting, and obtaining the saturation index p and fitting parameters α, β; 5) Substituting the obtained saturation index p and fitting parameters α and β into formula (1), the conductivity-matrix suction model of the soil is obtained; for unsaturated soil, its conductivity is substituted into the conductivity-matrix suction model to obtain the soil matrix suction; Step 1) specifically includes the following steps: 1a) Extend the Archie model to unsaturated soil and establish the relationship between soil saturation and resistivity: p = ap w n -m S r -p (2) Where ρ is the soil resistivity, ρ w is the pore water resistivity, a is the soil property parameter, m is the soil property parameter, n is the soil porosity, S r is the saturation, p is the saturation index; 1b) The electrical conductivity of soil is the inverse of its resistivity: 1c) Combining equations (2) and (3), we can obtain the soil saturation-conductivity relationship: In the formula, σ is the soil conductivity, σ w is the pore water conductivity; 1d) The conversion relationship between soil volume moisture content and soil saturation is as follows: Where θ is the volumetric water content, V W is the pore water volume, V is the total volume of the soil sample, w is the water content, γ d is the dry weight of soil, γ W is the pore water density; 1e) Combine equations (4) and (5), substitute the soil volume moisture content and soil density conversion relationship into the relationship between soil saturation and moisture content, and obtain the soil conductivity-moisture content model: 1f) In unsaturated soil, the relationship curve between soil suction and volumetric water content is called the soil-water characteristic curve, which is expressed by the Van Genuchten model as follows: Where: θ s and θ r are saturated volume moisture content and residual volume moisture content respectively; Without considering the influence of residual moisture content, the VG model is modified as follows: 1g) Replace the volumetric water content parameter in the Van Genuchten model parameters with the conductivity in the conductivity-volume water content formula, and combine equations (6) and (8) to obtain the mathematical model between matrix suction and conductivity as follows: In step 4), the fitting method of the saturation index p and the fitting parameters α and β is as follows: based on the measured unsaturated soil conductivity data and unsaturated soil matrix suction data, a scatter plot is drawn with conductivity as the horizontal coordinate and matrix suction as the vertical coordinate, and then a nonlinear fitting is performed to obtain the saturation index p and the fitting parameters α and β.

2. A soil landslide matrix suction test system based on soil conductivity, characterized in that: The method comprises a memory, a processor and computer program instructions stored in the memory and capable of being executed by the processor. When the processor executes the computer program instructions, the method steps as claimed in claim 1 can be implemented.

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