Safety factor calculation method for loess landslide considering dominant infiltration of sinkholes

Abstract

The present invention provides a method for calculating the safety factor of a loess landslide taking into account the dominant infiltration of sinkholes, comprising: separately calculating the influence of each sinkhole on the safety factor of the loess landslide; and superimposing the influence of all the sinkholes on the safety factor of the loess landslide to obtain the safety factor of the landslide affected by the dominant infiltration of sinkholes. Since loess-mudstone type loess landslides usually develop sinkholes, which are distributed in a point-like or beaded shape, when encountering heavy rainfall, rainwater cannot infiltrate the soil in time, forming surface runoff, flowing down the slope and pouring into the sinkholes, thereby forming a dominant infiltration phenomenon. By taking into account the influence of the dominant infiltration of sinkholes on the safety factor of the loess landslide, the present invention makes the safety factor of the loess landslide more consistent with the actual situation.

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 loess landslides 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 approach was to assume that rainfall infiltrated 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 simulations 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. That is, water does not infiltrate into the sliding surface position, and therefore 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 loess landslide.

[0006] To solve the above problems, the present invention provides a method for calculating the safety factor of loess landslides taking into account the dominant infiltration of sinkholes, including:

[0007] Step S1000: Calculate the influence of each sinkhole on the safety factor of the loess landslide;

[0008] 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.

[0009] Furthermore, the step S1000 in the above-mentioned method for calculating the safety factor of loess landslide considering the dominant infiltration of sinkholes includes:

[0010] Step S1100: establishing a plurality of landslide calculation models according to the landslide type and the distribution of the sinkholes;

[0011] Step S1200: Calculating different landslide calculation parameters using the landslide calculation model to obtain critical time calculation results, and determining from the critical time calculation results 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;

[0012] 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 rate of decrease of the safety factor affected by the dominant infiltration of the sinkhole after the critical time is greater than that before the critical time.

[0013] 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.

[0014] Furthermore, the critical time calculation formula in the above-mentioned method for calculating the safety factor of loess landslide considering the dominant infiltration of sinkholes is as follows:

[0015]

[0016] 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.

[0017] Furthermore, in the above-mentioned method for calculating the safety factor of loess landslide considering the dominant infiltration of sinkholes, the safety factor affected by the dominant infiltration of sinkholes described in step S1300 is linearly negatively correlated with the calculation time.

[0018] Furthermore, the safety factor calculation formula for the influence of sinkhole dominant infiltration in the above-mentioned loess landslide safety factor calculation method considering sinkhole dominant infiltration is as follows:

[0019]

[0020] in, For the i The safety factor of the influence of the dominant infiltration of the sinkhole is For the i The width of the sinkhole, is the width of the landslide, is the rate of reduction of the safety factor due to the dominant infiltration of the sinkhole 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.

[0021] Furthermore, the step 2000 in the above-mentioned method for calculating the safety factor of loess landslide considering the dominant infiltration of sinkholes includes:

[0022] 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.

[0023] Furthermore, the calculation formula for the safety factor of a loess landslide affected by the dominant infiltration of sinkholes in the above-mentioned calculation method for the safety factor of a loess landslide considering the dominant infiltration of sinkholes is:

[0024]

[0025] in, is the safety factor of the landslide affected by the dominant infiltration of the sinkhole, is the total number of sinkholes on the slope of the landslide.

[0026] 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:

[0027]

[0028] in, is the safety factor of the loess landslide, Safety factor calculated by traditional method.

[0029] Since loess-mudstone type loess landslides usually develop sinkholes, which are distributed in point-like or bead-like shapes, when encountering heavy rainfall, rainwater cannot penetrate into the soil in time, forming surface runoff, flowing down the slope and pouring into the sinkholes, thereby forming a dominant infiltration phenomenon. The present invention considers the impact of the dominant infiltration of sinkholes on the safety factor of the loess landslide, making the safety factor of the loess landslide more in line with the actual situation. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the safety factor calculation model for loess landslide according to the embodiment of the present invention;

[0031] Figure 2 It is a schematic diagram of the process of the embodiment shown in the present invention;

[0032] Figure 3 Schematic diagram of a curve showing the change of the safety factor of a loess landslide with calculation time in the embodiment shown in the present invention;

[0033] Figure 4 Schematic diagram of the relationship between the time it takes 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 of the present invention;

[0034] Figure 5 Schematic diagram of the relationship between the time it takes for the saturated area to expand to the sliding surface and the saturated permeability coefficient in the embodiment of the present invention;

[0035] Figure 6 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;

[0036] Figure 7 Schematic diagram of the relationship between the adjustment coefficient of the safety factor reduction rate and the saturated permeability coefficient in the first stage of the embodiment of the present invention;

[0037] Figure 8 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 of the present invention;

[0038] Figure 9 Schematic diagram of the relationship between the adjustment coefficient of the safety factor reduction rate in the second stage and the saturated permeability coefficient in the embodiment shown in the present invention.

[0039] Reference numerals:

[0040] 1: Loess; 2: Mudstone; 3: Slide surface; 4: Sinkhole. DETAILED DESCRIPTION

[0041] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention will be 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 merely exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present invention.

[0042] Due to the composition and structure of loess, as well as the influence of water, sinkholes often develop in loess. These sinkholes are distributed across the slope in a dotted or beaded pattern. During heavy rainfall, rainwater cannot penetrate the soil immediately, resulting in surface runoff that flows down the slope and into the sinkholes, creating a phenomenon of preferential infiltration. A water column of a certain height forms in the sinkhole, causing pressurized infiltration within the sliding mass. Water continues to penetrate downward and around the slope, significantly accelerating the infiltration rate and significantly affecting the stability of loess landslides, especially for shallow loess landslides, such as shallow loess-mudstone landslides. Existing methods for calculating the safety factor of loess landslides are incapable of accurately assessing their stability. This is primarily due to the fact that they only consider uniform rainfall infiltration along the surface, ignoring the impact of preferential rainfall infiltration and the common presence of sinkholes, cracks, and fissures within loess.

[0043] Reference below Figure 1 The loess landslides targeted by this invention are primarily loess-mudstone landslides, where the first layer below the surface is loess 1, and below that is mudstone 2. The sliding surface is the interface between loess 1 and mudstone 2, and sinkholes 4 are distributed along the landslide. Because the mudstone 2 has a low permeability coefficient, water does not easily penetrate it. Once the saturated area formed by the sinkholes reaches the sliding surface, the saturated area continues to expand along the sliding surface, significantly affecting the safety factor of the loess landslide.

[0044] refer to Figure 2 Next, an implementation method of the present invention for calculating the safety factor of loess landslide considering the dominant infiltration of sinkholes is shown, which specifically includes:

[0045] Step S1000: Calculate the influence of each sinkhole 4 on the safety factor of the loess landslide.

[0046] 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.

[0047] Therefore, step S1000 specifically includes:

[0048] Step S1100: establishing several landslide calculation models according to the landslide type and the distribution of sinkholes 4;

[0049] Step S1200: Calculate the critical time using the landslide calculation model for different landslide calculation parameters. From the critical time calculation results, 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.

[0050] Specifically, by fitting the calculation results of the critical time, it was found that the critical time was 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.

[0051] 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 between the two stages is the critical time.

[0052] 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 it takes for the saturated area formed by the dominant infiltration of 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 Table 1 and Table 2 respectively. The fitting curves are shown in Table 1 and Table 2 respectively. Figure 4 and Figure 5 shown.

[0053] Table 1

[0054]

[0055] Table 2

[0056]

[0057] 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 obtained by fitting as follows:

[0058] (1)

[0059] in, For the iThe 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.

[0060] Step S1300: Calculate the safety factor 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 decrease in 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 decrease in 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.

[0061] Table 3

[0062]

[0063] 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:

[0064] (2)

[0065] in, is the rate of reduction of safety factor of loess landslide, It is the distance from the bottom of the sinkhole 4 to the sliding surface 3.

[0066] 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 modify 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.

[0067] Table 4

[0068]

[0069] 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:

[0070] (3)

[0071] in, is the adjustment coefficient for the reduction rate of the safety factor of loess landslide, is the permeability coefficient.

[0072] 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 landslide width is used as the reduction factor, which is: sinkhole width / landslide width. Therefore, according to formulas (2) and (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:

[0073] (4)

[0074] in, is the safety factor reduction rate of the first stage sinkhole dominant infiltration effect, 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.

[0075] The fitting calculation results of the reduction rate of the safety factor of the 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.

[0076] Table 5

[0077]

[0078] 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:

[0079] (5)

[0080] The fitting calculation results of 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 are shown in Table 6. The fitting curve is shown in Figure 9 shown.

[0081] Table 6

[0082]

[0083] like Figure 9 As shown in the figure, 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 after fitting:

[0084] (6)

[0085] 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):

[0086] (7)

[0087] in, The safety factor reduction rate affected by the dominant infiltration of sinkholes in the second stage.

[0088] Specifically, by fitting the safety factor calculation results, it is found that the safety factor of the influence of the dominant infiltration of the sinkhole is linearly negatively correlated with the calculation time. Therefore, the calculation formula of the safety factor of the dominant infiltration of each sinkhole is:

[0089] (8)

[0090] in, For the i Safety factor affected by the dominant infiltration of a sinkhole, For the i The width of the sinkhole 4, is the width of the landslide, is the rate of reduction of the safety factor due to the dominant infiltration of the sinkhole before the critical time, is the rate of reduction of the safety factor due to the dominant infiltration of sinkholes after the critical time, and is the calculation time.

[0091] Step S2000 , superimposing the influence of all sinkholes 4 on the safety factor of the loess landslide, and obtaining the safety factor of the landslide affected by the dominant infiltration of the sinkholes.

[0092] In the actual landslide process, the distance between the sinkholes 4 is relatively far, and the dominant infiltration of each sinkhole will not produce a superposition phenomenon. Therefore, the safety factor of the landslide affected by the dominant infiltration of the sinkholes can be obtained by summing up the safety factors affected by the dominant infiltration of each sinkhole.

[0093] 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:

[0094] (9)

[0095] in, is the safety factor of the landslide affected by the dominant infiltration of sinkholes, is the total number of sinkholes 4 on the landslide slope.

[0096] Step S3000: The safety factor of the loess landslide is obtained based on the safety factor of the landslide affected by the dominant infiltration of sinkholes. The specific calculation formula is:

[0097] (10)

[0098] in, is the safety factor of loess landslide, Safety factor calculated by traditional method.

[0099] In practice, when it is necessary to calculate the stability of loess landslides, it is only necessary to collect materials such as exploration reports, or obtain the calculation parameters of loess landslides through investigation and testing, and then the calculation of the safety factor of loess landslides can be completed through formulas (8) to (10).

[0100] It should be understood that the above-described specific embodiments of the present invention are merely illustrative or illustrative of the principles of the present invention and do not constitute limitations 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 within the scope of protection of the present invention. In addition, the appended claims are intended to cover all variations and modifications that fall within the scope and metes and bounds of the appended claims, or equivalents thereof.

Claims

1. A method for calculating the safety factor of loess landslide considering the dominant infiltration of sinkholes, characterized in that: include: Step S100 0: Calculate the influence of each sinkhole on the safety factor of loess landslide separately; The step S1000 includes: Step S1100: establishing several landslide calculation models according to the landslide type and the distribution of the sinkholes; Step S1200: Calculating different landslide calculation parameters using the landslide calculation model to obtain critical time calculation results, and determining from the critical time calculation results 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; 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 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; Step S1300: Calculating the safety factor before and after the critical time using the landslide calculation model for different landslide calculation parameters, and finding that the safety factor affected by the sinkhole's dominant infiltration is negatively correlated with the calculation time, and that the rate of decrease in the safety factor after the critical time is greater than that before the critical time. 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 influence of the dominant infiltration of the sinkhole is For the i The width of the sinkhole, is the width of the landslide, is the rate of reduction of the safety factor due to the dominant infiltration of the sinkhole 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; 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 by: 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.

3. The method for calculating the safety factor of loess landslide considering the dominant infiltration of sinkholes according to claim 2 is characterized by: The safety factor of the impact of the sinkhole's dominant infiltration in step S1300 is linearly negatively correlated with the calculation time.

4. The method for calculating the safety factor of loess landslide considering the dominant infiltration of sinkholes according to claim 3 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.

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 calculation formula for the safety factor of the landslide affected by the dominant infiltration of sinkholes is: ， in, is the safety factor of the landslide affected by the dominant infiltration of the sinkhole, is the total number of sinkholes on the slope of the landslide.

6. The method for calculating the safety factor of loess landslide considering the dominant infiltration of sinkholes according to claim 5 is characterized by: The safety factor of the loess landslide is obtained based on 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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