A slope conversion and early warning method for highway landslide risk prediction

Abstract

The present invention discloses a slope conversion method for highway landslide risk prediction, which converts a geological slope into an engineering slope. Specifically, the method comprises: S1, taking the geological slope as the analysis object, determining the hydrological field under the critical state when the stability coefficient Fs=1 based on the original cohesion C and internal friction angle IFA of the geological slope, and obtaining the soil water content θ of the hydrological field. 临界 and pore water pressure P 临界 Parameters. This invention takes into account the changes in the mechanical parameters of rock and soil caused by external human intervention in the assessment, forecasting, and early warning of landslide susceptibility along highways. For the first time, it quantifies the extent to which human intervention improves the mechanical parameters of the original geological slopes, thereby improving the accuracy of landslide susceptibility assessment, forecasting, and early warning along highways, laying a good foundation for landslide-related work along highways.

Description

Technical Field

[0001] The present invention relates to the field of highway landslide monitoring, and in particular to a slope conversion and early warning method for highway landslide risk prediction. Background Art

[0002] Research on methods for assessing the susceptibility, forecasting, and early warning of highway landslides will help highway authorities take preventive measures and reduce landslide losses. Existing methods for highway landslide forecasting and early warning, for example, primarily rely on basic approaches for geological disaster forecasting and early warning, such as using statistical methods to analyze rainfall characteristics that triggered historical disasters, establishing rainfall thresholds, probabilistic evaluation methods, and forecast indices. These methods all have limitations. For example, geometeorological statistical methods require extensive data; probabilistic evaluation methods quantify the probabilities of various factors contributing to highway flooding, resulting in low forecast and early warning accuracy; and the selection of influencing factors and determination of correlation coefficients in forecast indices remain incomplete. The timing and extent of rainfall events significantly impact prediction accuracy. Furthermore, to address the lack of historical data, some researchers have developed forecast and early warning models based on disaster mechanisms. In slope instability simulation, grids or slope units are typically used to simulate changes in soil moisture content and pore water pressure under rainfall to assess slope stability and provide geological disaster early warning. The physical model takes a long time to run. Some researchers have tried to combine the respective advantages of the physical model and the rainfall threshold method, and use the simulation results of the physical model to construct a rainfall threshold curve that triggers geological disasters; however, the above methods do not take into account the particularity of highway disaster-bearing bodies. Summary of the Invention

[0003] To address the aforementioned issues, the present invention aims to provide a slope conversion method for highway landslide risk prediction. This method quantifies for the first time the extent to which human intervention can improve the mechanical parameters of existing geological slopes. This method can thus improve the accuracy of landslide susceptibility assessment, prediction, and early warning along highways, laying a solid foundation for landslide-related work along highways. Also disclosed is an early warning method for highway landslide risk prediction.

[0004] The present invention is achieved through the following technical solutions:

[0005] A slope conversion method for highway landslide risk prediction converts geological slopes into engineering slopes, specifically including: S1, taking the geological slope as the analysis object, based on the original cohesion C and internal friction angle IFA of the geological slope, determining the hydrological field under the critical state when the stability coefficient Fs = 1, and obtaining the soil water content θ of this hydrological field 临界 and pore water pressure P 临界 Parameters; S2, when the pore water pressure and soil moisture content are in the critical state, that is, when the soil moisture content θ 临界 and pore water pressure P临界 Under the condition of keeping the cohesion C unchanged, the range of internal friction angle value [IFA] is determined by simulation when the stability coefficient Fs changes in the range of 1.05-1.25. min ,IFA max ]; S3, under the condition that the pore water pressure and soil water content are in a critical state, the soil water content θ 临界 and pore water pressure P 临界 Under the condition of keeping the internal friction angle IFS unchanged, the range of cohesion value variation when the stability coefficient Fs changes in the range of 1.05-1.25 is determined by simulation [C min ,C max ]; S4, transform the geological slope mechanical parameter value into the engineering slope mechanical parameter value: For a geological slope unit, in [IFA min ,IFA max ] and [C min ,C max ], the Monte Carlo random search method is used to select n times, n ≥ 100, and the average value of the cohesion C and the average value of the internal friction angle IFS are obtained. That is, C 平均 and IFA 平均 The cohesion C and internal friction angle IFS of the slope unit are assigned to complete the conversion from geological slope to engineering slope. Theoretically, the larger the n value, the better, but considering the efficiency of calculation, this value is generally taken as 100.

[0006] The limit equilibrium analysis method is used to determine the hydrological field in the critical state of Fs=1 in S1.

[0007] An early warning method for highway landslide risk prediction, as described above, converts the geological slopes in the area requiring early warning into engineering slopes, and then inputs the obtained engineering slope mechanical parameters, cohesion C and internal friction angle IFS, into a highway landslide risk early warning model for early warning.

[0008] Through careful consideration in practice, the inventors believe that it is inappropriate to treat highway slopes as ordinary, untouched geological slopes when conducting landslide susceptibility assessment, forecasting, and early warning work along highways. This is because during highway construction, construction workers have already treated high-risk landslides through excavation, reinforcement, and slope protection, which has led to earth-shaking changes in the hydrological conditions and internal mechanical parameters of the original geological slopes. The ultimate result is that the anti-slip capacity of the slopes along the highway has been significantly improved, thereby enhancing the ability of the slopes along the highway to withstand extreme rainfall weather. The inventors further considered from the perspective of geotechnical mechanics that the current human intervention phenomenon must have improved the mechanical parameters of the original slopes, which can enhance the current highway's anti-slip capacity. In other words, before carrying out the above landslide disaster prevention work, a most critical technical problem needs to be solved: when faced with the numerous slope problems distributed along highways, how to quantify the extent to which human intervention has improved the mechanical parameters of the original geological slopes, thereby improving the accuracy of landslide susceptibility assessment, forecasting, and early warning work along highways. Therefore, the technical solution of the present invention is to quantitatively improve the mechanical parameters of the original geological slope through artificial intervention based on the inventor's discovery of the current technical problem, thereby achieving the transformation of the geological slope into an engineering slope. Of course, drilling and sampling every slope along the highway and combining it with indoor testing is an effective means of obtaining the mechanical parameters of the reinforced slope, but this method cannot cope with the large number of slopes along the highway. Therefore, the technical solution of the present invention is also a new quantitative method that can cope with the numerous slopes along the highway.

[0009] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0010] The present invention takes into account the changes in the mechanical parameters of rock and soil caused by external human intervention in the work of landslide susceptibility assessment, forecasting and early warning along highways. For the first time, it quantifies the extent to which human intervention improves the mechanical parameters of the original geological slopes, thereby improving the accuracy of landslide susceptibility assessment, forecasting and early warning along highways, laying a good foundation for landslide-related work along highways. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0012] Figure 1 This is a sampling point distribution data diagram for Fengjie County in the present invention.

[0013] Figure 2 The distribution diagram of mechanical parameters of engineering slope of the present invention;

[0014] Figure 3 This is the distribution diagram of geological slope mechanical parameters of the present invention. DETAILED DESCRIPTION

[0015] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with examples and drawings. The exemplary embodiments of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention.

[0016] Example 1

[0017] Soil mechanics parameters mainly include soil cohesion and internal friction angle. In fact, it is difficult to obtain accurate soil mechanics parameters of each grid unit on a regional scale. There are currently three main methods, including field sampling, soil type inversion method, and manual method. As for the first method, the direct shear test of field samples can be used to obtain soil cohesion and internal friction angle, and then the soil mechanics parameters of each grid point in the area are obtained with the help of the spatial difference method. Therefore, the number of field samples needs to be sufficient to ensure the reliability of this method. In 2017, in order to carry out landslide early warning work in Fengjie County, the inventor obtained a total of 312 samples ( Figure 1 ).

[0018] Direct shear tests were conducted on these 312 samples in the laboratory, and their soil cohesion and internal friction angle values ​​were obtained. Based on these 312 sets of soil mechanical parameters, the Kriging interpolation method in the ArcGIS Spatial Analysis module was used to obtain distribution maps of soil cohesion and internal friction angle that were consistent with the DEM accuracy.

[0019] It should be pointed out that: Figure 1 In the 2016 study, slopes intersecting highways and expressways are no longer simply geological slopes. This is because transportation authorities have implemented surface anti-seepage and reinforcement measures along these roads, including surface waterproofing, retaining walls, and anchor cables, to enhance the slopes' ability to resist sliding. However, current models for assessing and predicting geological hazard susceptibility are unable to account for changes in geotechnical parameters caused by this external human intervention.

[0020] In order to realize the transformation of geological slope into engineering slope, the present invention is based on the original geological slope mechanical parameters and combines the technical standards and specifications of highway slope reinforcement to carry out the transformation. The specific implementation plan is as follows:

[0021] ◆ Taking the geological slope as the analysis object: Under the input conditions of the original cohesion C and the internal friction angle IFA, the limit equilibrium analysis method is used to determine the hydrological field under the critical state of Fs=1, and determine the soil water content θ at this time cr and pore water pressure P cr and other parameters;

[0022] ◆ Under the conditions of θ critical and P critical: keep the cohesion C unchanged, simulate and determine the value range of the internal friction angle under the conditions of Fs=1.05-1.25 [IFA min ,IFA max ];

[0023] ◆ Under the conditions of θ critical and P critical: keep the internal friction angle IFS unchanged, and simulate to determine the value range of the internal friction angle under the conditions of Fs=1.05-1.25 [C min ,C max ];

[0024] ◆Use Monte Carlo random search to obtain the mechanical parameter values ​​of engineering slopes: For a geological slope unit, in [IFA min ,IFA max ] and [C min ,C max ] The Monte Carlo random search method is used to select 100 times, and the average value of n times is obtained. The C average amplitude and the IFA average amplitude are given to the slope unit, thereby improving the anti-slip performance of the slope unit and transforming it into an engineering slope.

[0025] According to the above method, taking the slope unit numbered 1 as an example, the mechanical parameters under its geological slope properties are: cohesion C = 21.3 kPa, internal friction angle The slope value β is 22.4°.

[0026] According to the limit equilibrium principle, the slope unit stability calculation formula is constructed as follows:

[0027]

[0028] r t is the dry density of soil, which is 1800kg / m3, r w P is the density of water, which is 1000kg / cm3. cr is the pore water pressure, which can be further expressed as P cr =r w *g*h cr , Hs is the depth of the soil layer. The thickness of the soil layer in Fengjie County is between 2-5m. After the thickness distribution map is superimposed with the slope unit, the soil thickness of the slope can be obtained. The thickness of the slope unit is 1, Hs = 5m.

[0029] According to formula (1), when Fs = 1, h can be obtained cr =1.98m, so the critical water content θ cr =1.98 / 5=0.397, the corresponding P cr =r w *g*hcr=19.9kPa.

[0030] (2) h cr ,θ cr , P cr Substitute Fs = 1.05 into Formula 1, keep C at its initial value, and obtain Faimin = 15.6; cr ,θ cr , P cr Substituting Fs=1.25 into Formula 1, keeping C at its initial value, we obtain Faimmax=19.9.

[0031] (3) h cr ,θ cr , P cr Substitute Fs = 1.05 into Formula 1, keep Fai as the initial value, and obtain Cmin = 21.5kPa; cr ,θ cr , P cr Substituting Fs=1.25 into Formula 1, keeping Fai at the initial value, we obtain Cmin=22.3kPa.

[0032] (4) The cohesion and internal friction angle of the locking engineering slope vary in the range of c~[21.5, 22.3] and Fai~[15.6, 19.9] respectively.

[0033] The above process shows the slope transformation process of one slope unit. After the slope transformation method of the above slope unit is used to transform the entire slope surface of Fengjie County, the parameter distribution diagram of the entire slope surface transformed into the engineering slope is obtained. Figure 2 The cohesion distribution of the engineering slope after transformation is as follows: the maximum value is 35.78 and the minimum value is 11.24; the internal friction distribution is as follows: the maximum value is 29.93 and the minimum value is 5.46. Figure 3 As shown, it is obvious Figure 2 The parameter data is higher than Figure 3 The mechanical parameter data shown. Figure 2 and Figure 3 From the comparison, the present invention takes into account the changes in the mechanical parameters of rock and soil caused by external artificial intervention, that is, the increase in mechanical parameters reflects the transformation of geological slopes into engineering slopes, and quantifies the extent to which artificial intervention improves the mechanical parameters of the original geological slopes.

[0034] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A slope conversion method for highway landslide prediction, characterized in that: The geological slope is transformed into an engineering slope, specifically including: S1. Taking the geological slope as the analysis object, based on the original cohesion C and internal friction angle IFA of the geological slope, determine the hydrological field under the critical state when the stability coefficient Fs = 1, and obtain the soil water content θ of this hydrological field. 临界 and pore water pressure P 临界 Parameters; S2, under the critical conditions of pore water pressure and soil moisture content, keep the cohesion C unchanged, and simulate and determine the range of internal friction angle when the stability coefficient Fs changes in the range of 1.05-1.25 [IFA min ,IFA max ]; S3, under the critical conditions of pore water pressure and soil moisture content, keep the internal friction angle IFS unchanged, and simulate and determine the range of cohesion value when the stability coefficient Fs changes in the range of 1.05-1.25 [C min ,C max ]; S4, transform the geological slope mechanical parameter value into the engineering slope mechanical parameter value: For a geological slope unit, in [IFA min ,IFA max ] and [C min ,C max ], the Monte Carlo random search method is used to select n times, n ≥ 100, and the average value of the cohesion C and the average value of the internal friction angle IFS are obtained respectively. 平均 and IFA 平均 The cohesion C and internal friction angle IFS are assigned to the slope unit respectively to complete the conversion from geological slope to engineering slope.

2. The method for slope conversion for highway landslide prediction according to claim 1, characterized in that: The limit equilibrium analysis method is used to determine the hydrological field in the critical state of Fs=1 in S1.

3. A warning method for highway landslide risk prediction, characterized in that: According to the method of claim 1 or 2, the geological slope in the area requiring early warning is converted into an engineering slope, and the obtained engineering slope mechanical parameters, cohesion C and internal friction angle IFS, are input into a highway landslide risk early warning model for early warning.

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