Loess landslide safety coefficient calculation method considering dominant infiltration of sinkhole

Abstract

The invention provides a loess landslide safety coefficient calculation method considering dominant infiltration of sinkholes. The loess landslide safety coefficient calculation method comprises the steps that the influence of each sinkhole on the loess landslide safety coefficient is calculated; the loess-mudstone type loess landslide is characterized in that the loess-mudstone type loess landslide is generally provided with the sinkholes which are distributed in a point shape or a bead shape and the like, when heavy rainfall occurs, rainwater cannot permeate into soil in time, surface runoff is formed, and the safety coefficient of the landslide influenced by the dominant infiltration of the sinkholes is obtained by overlapping the influence of all the sinkholes on the safety coefficient of the loess landslide, so that the safety coefficient of the landslide influenced by the dominant infiltration of the sinkholes is obtained. According to the method, the influence of dominant infiltration of the sinkhole on the safety coefficient of the loess landslide is considered, so that the safety coefficient of the loess landslide is more fit with the actual condition.

Description

Technical Field

[0001] The invention relates to the technical field of loess landslide investigation, and in particular to a method for calculating the safety factor of a loess landslide taking into account the dominant infiltration of sinkholes. Background Art

[0002] Loess landslide is a common and serious geological disaster in the Loess Plateau. Rainfall is one of the main factors that trigger loess landslides. Heavy rainfall usually leads to the occurrence of a large number of loess landslides.

[0003] In the early research on the instability mechanism of rainfall-induced loess landslides, the main idea was to use the idea that rainfall infiltrates uniformly downward along the surface. According to the traditional method of calculating the safety factor of loess landslides, rainfall infiltration is usually simplified to uniform infiltration. However, through field tests, numerical simulation and other methods, it was found that the depth of rainfall infiltration uniformly downward along the surface is very limited, at most 2-3 meters, which is much smaller than the thickness of the sliding body. In other words, water does not infiltrate into the sliding surface, so it will not have much impact on the stability of the landslide. This is inconsistent with the actual situation of rainfall-induced loess landslides.

[0004] It can be seen that the existing calculation method of safety factor of loess landslide is difficult to accurately evaluate the stability of loess landslide. Summary of the invention

[0005] The invention aims to provide a method for calculating the safety factor of loess landslide taking into account the dominant infiltration of sinkholes, which can accurately evaluate the stability of the loess landslide.

[0006] In order to solve the above problems, the present invention provides a method for calculating the safety factor of loess landslide considering the dominant infiltration of sinkholes, comprising: Step S1000: Calculate the influence of each sinkhole on the safety factor of loess landslide respectively; Step S2000, superimposing the influence of all the sinkholes on the safety factor of the loess landslide, and obtaining the safety factor of the landslide affected by the dominant infiltration of the sinkholes.

[0007] Furthermore, the step S1000 in the above-mentioned method for calculating the safety factor of loess landslide considering the dominant infiltration of sinkholes includes: Step S1100: establishing a plurality of landslide calculation models according to the landslide type and the sinkhole distribution; Step S1200: using the landslide calculation model to calculate different landslide calculation parameters to obtain a critical time calculation result, and from the critical time calculation result, it is concluded that the critical time for the saturated area formed by the dominant infiltration of the sinkhole to expand to the sliding surface is correlated with the distance from the bottom of the sinkhole to the sliding surface and the vertical saturated permeability coefficient of loess; Step S1300: Utilizing the landslide calculation model to calculate different landslide calculation parameters, the safety factor calculation results before and after the critical time are obtained, and it is concluded that the safety factor affected by the dominant infiltration of the sinkhole is negatively correlated with the calculation time, and the safety factor reduction rate of the dominant infiltration of the sinkhole after the critical time is greater than that before the critical time.

[0008] Furthermore, the critical time in the above-mentioned method for calculating the safety factor of loess landslide considering the dominant infiltration of sinkholes is positively correlated with the distance from the bottom of the sinkhole to the sliding surface and the vertical saturated permeability coefficient of the loess.

[0009] Furthermore, the critical time calculation formula described in the above-mentioned method for calculating the safety factor of loess landslide considering the dominant infiltration of sinkholes is as follows: in, For the i The critical time for the saturated area formed by the dominant infiltration of the sinkholes 4 to expand to the sliding surface, For the i The distance from the bottom of the sinkhole to the sliding surface, is the vertical saturated permeability coefficient of the loess.

[0010] Furthermore, the safety factor affected by the dominant infiltration of sinkholes described in step S1300 in the above-mentioned method for calculating the safety factor of loess landslide considering the dominant infiltration of sinkholes is linearly negatively correlated with the calculation time.

[0011] Furthermore, the safety factor calculation formula for the influence of the dominant infiltration of sinkholes in the above-mentioned method for calculating the safety factor of loess landslide considering the dominant infiltration of sinkholes is as follows:

[0012] in, For the i The safety factor of the sinkhole advantage infiltration is For the i The width of the sinkhole, is the width of the landslide, is the safety factor reduction rate of the sinkhole dominant infiltration before the critical time, is the rate of reduction of the safety factor due to the dominant infiltration of the sinkhole after the critical time, is the calculation time.

[0013] Furthermore, the step 2000 in the above-mentioned method for calculating the safety factor of loess landslide considering the dominant infiltration of sinkholes includes: Step S2100: Accumulate the safety factor of each sinkhole affected by the dominant infiltration to obtain the safety factor of the landslide affected by the dominant infiltration of the sinkhole.

[0014] Furthermore, the calculation formula for the safety factor of the loess landslide affected by the dominant infiltration of sinkholes in the above-mentioned calculation method of the safety factor of the loess landslide considering the dominant infiltration of sinkholes is: in, is the safety factor of the landslide affected by the dominant infiltration of the sinkhole, It is the total number of sinkholes on the slope of the landslide.

[0015] Furthermore, in the above-mentioned method for calculating the safety factor of loess landslide considering the dominant infiltration of sinkholes, the safety factor of the loess landslide is obtained according to the safety factor of the landslide affected by the dominant infiltration of the sinkholes. The specific calculation formula is:

[0016] in, is the safety factor of the loess landslide, Safety factor calculated by traditional method.

[0017] Since loess-mudstone type loess landslides usually develop sinkholes distributed in point or bead shapes, when encountering heavy rainfall, rainwater cannot penetrate into the soil in time, forming surface runoff, flowing downward along the slope and pouring into the sinkholes, thereby forming a dominant infiltration phenomenon. The present invention makes the safety factor of the loess landslide more in line with the actual situation by considering the influence of the dominant infiltration of sinkholes on the safety factor of the loess landslide. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the safety factor calculation model of loess landslide in the embodiment of the present invention; Figure 2 It is a schematic diagram of the process of the embodiment shown in the present invention; Figure 3 Schematic diagram of a curve showing a change in the safety factor of a loess landslide with calculation time in the embodiment shown in the present invention; Figure 4 It is a schematic diagram of the relationship between the time for the saturated area to expand to the sliding surface and the distance from the bottom of the sinkhole to the sliding surface in the embodiment shown in the present invention; Figure 5 is a schematic diagram of the relationship between the time for the saturated area to expand to the sliding surface and the saturated permeability coefficient in the embodiment of the present invention; Figure 6 It is a schematic diagram of the relationship between the safety factor reduction rate in the first stage and the distance from the bottom of the sinkhole to the sliding surface in the embodiment shown in the present invention; Figure 7 It is a schematic diagram of the relationship between the adjustment coefficient of the safety factor reduction rate in the first stage of the embodiment shown in the present invention and the saturated permeability coefficient; Figure 8 It is a schematic diagram of the relationship between the safety factor reduction rate in the second stage and the distance from the bottom of the sinkhole to the sliding surface in the embodiment shown in the present invention; Fig. 9 It is a schematic diagram of the relationship between the adjustment coefficient of the safety factor reduction rate in the second stage of the embodiment shown in the present invention and the saturated permeability coefficient.

[0019] Reference numerals: 1: loess; 2: mudstone; 3: slip surface; 4: sinkhole. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0021] Due to the material composition, structure, etc. of loess and the influence of water, sinkholes are usually developed in loess. The sinkholes are distributed on the slope in the form of dots or beads. When encountering heavy rainfall, rainwater cannot penetrate into the soil in time, and it will form surface runoff, flow down the slope and pour into the sinkholes, forming a dominant infiltration phenomenon. A water column of a certain height formed in the sinkhole will form a pressurized infiltration inside the sliding body. Water continues to penetrate downward and around the slope, greatly accelerating the infiltration speed, greatly affecting the stability of loess landslides, especially for shallow loess landslides, such as shallow loess-mudstone landslides. It can be seen that the existing loess landslide safety factor calculation method is difficult to accurately evaluate the stability of loess landslides. The main reason is that it only considers the uniform infiltration of rainfall along the surface without considering the influence of the dominant infiltration of rainfall, and does not consider the dominant infiltration channels such as sinkholes, cracks, and fissures that usually exist in loess.

[0022] Reference below Figure 1 The loess landslide targeted by the present invention is mainly a loess-mudstone type landslide, that is, the first layer below the surface is loess 1, below the loess 1 is mudstone 2, the sliding surface is the contact surface between the loess 1 and the mudstone 2, and there are sinkholes 4 distributed on the landslide. Since the permeability coefficient of the mudstone 2 is small, it is not easy for water to penetrate into the mudstone 2. After the saturated area formed by the dominant infiltration of the sinkholes expands to the sliding surface, the saturated area continues to expand along the sliding surface, thus having a great impact on the safety factor of the loess landslide.

[0023] refer to Figure 2Next, the implementation method of the method for calculating the safety factor of loess landslide considering the dominant infiltration of sinkholes of the present invention is shown, which specifically includes: Step S1000: Calculate the influence of each sinkhole 4 on the safety factor of the loess landslide.

[0024] The dominant infiltration of the sinkhole gradually forms a saturated area around the sinkhole 4 and continuously expands to the sliding surface 3. Before the saturated area expands to the sliding surface 3, the impact on the safety factor of the loess landslide is small. After the saturated area expands to the sliding surface 3, it will have a greater impact on the safety factor of the loess landslide, and the safety factor of the loess landslide will be significantly reduced at this time. Therefore, the impact of the dominant infiltration of the sinkhole on the safety factor of the loess landslide is divided into two stages. The first stage is before the saturated area formed by the dominant infiltration of the sinkhole expands to the sliding surface 3, and the sinkhole 4 has little impact on the safety factor of the loess landslide; the second stage is after the saturated area formed by the dominant infiltration of the sinkhole expands to the sliding surface 3. At this time, the sinkhole 4 has a significant impact on the safety factor of the loess landslide. Therefore, it is necessary to first calculate the critical time for the saturated area formed by the dominant infiltration of the sinkhole to expand to the sliding surface 3.

[0025] Therefore, step S1000 specifically includes: Step S1100: establishing a number of landslide calculation models according to the landslide type and the distribution of sinkholes 4; Step S1200: Utilize the landslide calculation model to calculate different landslide calculation parameters to obtain the critical time calculation result. From the critical time calculation result, it is concluded that the critical time for the saturated area formed by the dominant infiltration of the sinkhole to expand to the sliding surface 3 is correlated with the distance from the bottom of the sinkhole 4 to the sliding surface 3 and the vertical saturated permeability coefficient of the loess.

[0026] Specifically, by fitting the calculation results of the critical time, it is found that the critical time is positively correlated with the distance from the bottom of the sinkhole 4 to the sliding surface 3 and the vertical saturated permeability coefficient of loess.

[0027] The landslide calculation model is used to calculate the seepage and stability of different landslide calculation parameters (such as different sliding body thickness, slope, sinkhole width and depth, etc.). When the loess thickness is 10 meters, Figure 3 As shown, from Figure 3 It can be seen that the safety factor of loess landslide is reduced by the influence of the dominant infiltration of sinkholes and has a good regularity with the calculation time. It can be divided into two stages, and the dividing point of the two stages is the critical time.

[0028] The landslide calculation model is used to calculate different landslide calculation parameters (such as different sliding body thickness, slope, sinkhole width and depth, etc.), and the time for the saturated area formed by the sinkhole to expand to the sliding surface 3 and the distance from the bottom of the sinkhole to the sliding surface are obtained. Vertical saturated permeability coefficient of loess The fitting calculation results of the critical time for the saturated area formed by the dominant infiltration of the sinkhole to expand to the sliding surface 3 are shown in Tables 1 and 2, respectively. The fitting curves are shown in Figure 4 and Figure 5 shown.

[0029] Table 1

[0030] Table 2

[0031] like Figure 4 and Figure 5 As shown in the figure, the critical time calculation formula for the expansion of the saturated area formed by the dominant infiltration of the sinkhole to the sliding surface 3 is as follows: (1) in, For the i The critical time for the saturated area formed by the dominant infiltration of the sinkhole 4 to expand to the sliding surface 3, For the i The distance from the bottom of the sinkhole 4 to the sliding surface 3, is the vertical saturated permeability coefficient of loess.

[0032] Step S1300: Calculate the safety factor calculation results before and after the critical time using the landslide calculation model for different landslide calculation parameters. It is found that the safety factor affected by the dominant infiltration of the sinkhole is negatively correlated with the calculation time, and the rate of reduction of the safety factor affected by the dominant infiltration of the sinkhole after the critical time is greater than that before the critical time. The rate of reduction of the safety factor of the loess landslide in the first stage is mainly related to the distance from the bottom of the sinkhole to the sliding surface. The safety factor calculation results before and after the critical time are shown in Table 3, and the calculation results and fitting curves are shown in Table 3, respectively. Figure 6 shown.

[0033] Table 3

[0034] according to Figure 6 After fitting, the calculation formula for the reduction rate of the safety factor of loess landslide in the first stage and the distance from the bottom of the sinkhole to the sliding surface can be obtained: (2) in, is the reduction rate of safety factor of loess landslide, It is the distance from the bottom of the sinkhole 4 to the sliding surface 3.

[0035] Since the saturated permeability coefficient of loess affects the speed of infiltration, and the saturated permeability coefficient of loess in different regions is different, it is necessary to correct formula (2). The fitting calculation results of the adjustment coefficient of the reduction rate of the safety factor of loess landslide in the first stage and the saturated permeability coefficient are shown in Table 4. The fitting curve is shown in Figure 7 shown.

[0036] Table 4

[0037] according to Figure 7 The curve shown in the figure is fitted to obtain the relationship between the adjustment coefficient of the reduction rate of the safety factor of loess landslide in the first stage and the saturated permeability coefficient: (3) in, is the adjustment coefficient of the reduction rate of the safety factor of loess landslide, is the permeability coefficient.

[0038] Since the safety factor affected by the dominant infiltration of sinkholes is calculated for each linear meter of landslide strips, and sinkhole 4 is distributed individually on the landslide and does not extend to the entire landslide width, it is necessary to consider the lateral reduction of the landslide, that is, the ratio of the width of sinkhole 4 to the width of the landslide is used as the reduction factor, and the reduction factor is: sinkhole width / landslide width. Therefore, according to formula (2) and formula (3), the calculation formula for the reduction rate of the safety factor affected by the dominant infiltration of a single sinkhole in the first stage can be obtained: (4) in, is the safety factor reduction rate of the first stage sinkhole dominant infiltration, For the i The distance from the bottom of the sinkhole 4 to the sliding surface 3, is the width of the landslide, For the i The width of the sinkhole 4, is the vertical saturated permeability coefficient of loess.

[0039] The fitting calculation results of the reduction rate of the safety factor of loess landslide in the second stage and the distance from the bottom of the sinkhole to the sliding surface are shown in Table 5. The fitting curve is shown in Figure 8 shown.

[0040] Table 5

[0041] Using the same method, according to Figure 8 After fitting, the calculation formula for the reduction rate of the safety factor of loess landslide in the second stage and the distance from the bottom of the sinkhole to the sliding surface can be obtained: (5) The fitting calculation results of the relationship between the adjustment coefficient of the safety factor reduction rate of loess landslide in the second stage and the saturated permeability coefficient are shown in Table 6. The fitting curve is shown in Fig. 9 shown.

[0042] Table 6

[0043] like Fig. 9 As shown in the figure, after fitting, the relationship between the adjustment coefficient of the reduction rate of the safety factor of loess landslide in the second stage and the saturated permeability coefficient is obtained: (6) Then, the calculation formula for the safety factor reduction rate affected by the dominant infiltration of a single sinkhole in the second stage can be obtained from formula (5) and formula (6): (7) in, It is the safety factor reduction rate affected by the dominant infiltration of sinkholes in the second stage.

[0044] Specifically, by fitting the safety factor calculation results, it is found that the safety factor of the sinkhole's dominant infiltration is linearly negatively correlated with the calculation time. Therefore, the calculation formula for the safety factor of each sinkhole's dominant infiltration is: (8) in, For the i The safety factor affected by the dominant infiltration of a sinkhole is For the i The width of the sinkhole 4, is the width of the landslide, is the safety factor reduction rate of the sinkhole dominant infiltration before the critical time, is the rate of reduction of the safety factor due to the dominant infiltration of the sinkhole after the critical time, and is the calculation time.

[0045] Step S2000, superimposing the influence of all sinkholes 4 on the safety factor of loess landslide, and obtaining the safety factor of landslide affected by the dominant infiltration of sinkholes.

[0046] In the actual landslide process, the distance between the sinkholes 4 is relatively far, and the superior infiltration of each sinkhole will not produce superposition phenomenon. Therefore, the safety factor of the landslide affected by the superior infiltration of the sinkholes can be obtained by summing up the safety factors affected by the superior infiltration of each sinkhole.

[0047] Step S2100: Accumulate the safety factor of each sinkhole's dominant infiltration to obtain the safety factor of the landslide affected by the sinkhole's dominant infiltration. The calculation formula is as follows: (9) in, is the safety factor of the landslide affected by the dominant infiltration of the sinkhole, is the total number of sinkholes 4 on the landslide slope.

[0048] Step S3000: The safety factor of the loess landslide is obtained according to the safety factor of the landslide affected by the dominant infiltration of the sinkhole. The specific calculation formula is: (10) in, is the safety factor of loess landslide, Safety factor calculated by traditional method.

[0049] In practice, when it is necessary to calculate the stability of loess landslides, we only need to collect materials such as exploration reports, or obtain the calculation parameters of loess landslides through investigation and experiments. The safety factor of loess landslides can be calculated using formulas (8) to (10).

[0050] It should be understood that the above specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, and do not constitute a limitation of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. In addition, the appended claims of the present invention are intended to cover all changes and modifications that fall within the scope and boundaries of the appended claims, or the equivalent forms of such scope and boundaries.

Claims

1. A method for calculating the safety factor of loess landslide considering the dominant infiltration of sinkholes, characterized in that: include: Step S1000: Calculate the influence of each sinkhole on the safety factor of loess landslide respectively; Step S2000, superimposing the influence of all the sinkholes on the safety factor of the loess landslide, and obtaining the safety factor of the landslide affected by the dominant infiltration of the sinkholes.

2. The method for calculating the safety factor of loess landslide considering the dominant infiltration of sinkholes according to claim 1 is characterized in that: The step S1000 includes: Step S1100: establishing a plurality of landslide calculation models according to the landslide type and the distribution of the sinkholes; Step S1200: using the landslide calculation model to calculate different landslide calculation parameters to obtain a critical time calculation result, and from the critical time calculation result, it is concluded that the critical time for the saturated area formed by the dominant infiltration of the sinkhole to expand to the sliding surface is correlated with the distance from the bottom of the sinkhole to the sliding surface and the vertical saturated permeability coefficient of loess; Step S1300: Utilizing the landslide calculation model to calculate different landslide calculation parameters, the safety factor calculation results before and after the critical time are obtained, and it is concluded that the safety factor affected by the dominant infiltration of the sinkhole is negatively correlated with the calculation time, and the safety factor reduction rate of the dominant infiltration of the sinkhole after the critical time is greater than that before the critical time.

3. The method for calculating the safety factor of loess landslide considering the dominant infiltration of sinkholes according to claim 2 is characterized in that: The critical time is positively correlated with the distance from the bottom of the sinkhole to the sliding surface and the vertical saturated permeability coefficient of the loess.

4. The method for calculating the safety factor of loess landslide considering the dominant infiltration of sinkholes according to claim 3 is characterized in that: The critical time calculation formula is as follows: ， in, For the i The critical time for the saturated area formed by the dominant infiltration of the sinkholes 4 to expand to the sliding surface, For the i The distance from the bottom of the sinkhole to the sliding surface, is the vertical saturated permeability coefficient of the loess.

5. The method for calculating the safety factor of loess landslide considering the dominant infiltration of sinkholes according to claim 4 is characterized in that: The safety factor of the sinkhole dominant infiltration effect in step S1300 is linearly negatively correlated with the calculation time.

6. The method for calculating the safety factor of loess landslide considering the dominant infiltration of sinkholes according to claim 5 is characterized in that: The safety factor calculation formula for the influence of the sinkhole's dominant infiltration is as follows: ， in, For the i The safety factor of the sinkhole advantage infiltration is For the i The width of the sinkhole, is the width of the landslide, is the safety factor reduction rate of the sinkhole dominant infiltration before the critical time, is the rate of reduction of the safety factor due to the dominant infiltration of the sinkhole after the critical time, is the calculation time.

7. The method for calculating the safety factor of loess landslide considering the dominant infiltration of sinkholes according to claim 6 is characterized by: The step 2000 includes: Step S2100: Accumulate the safety factor of each sinkhole affected by the dominant infiltration to obtain the safety factor of the landslide affected by the dominant infiltration of the sinkhole.

8. The method for calculating the safety factor of loess landslide considering the dominant infiltration of sinkholes according to claim 7 is characterized by: The calculation formula of the safety factor of the landslide affected by the dominant infiltration of the sinkhole is: ， in, is the safety factor of the landslide affected by the dominant infiltration of the sinkhole, It is the total number of sinkholes on the slope of the landslide.

9. The method for calculating the safety factor of loess landslide considering the dominant infiltration of sinkholes according to claim 8 is characterized in that: The safety factor of the loess landslide is obtained according to the safety factor of the landslide affected by the dominant infiltration of the sinkhole. The specific calculation formula is: ， in, is the safety factor of the loess landslide, Safety factor calculated by traditional method.

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