Road slope risk assessment method and system

Abstract

The invention provides a road slope risk assessment method and system, and the method comprises the steps: firstly building a risk assessment index system which comprises risk factors, an assessment index corresponding to each risk factor, and basic score segments of different grades of each assessment index; then, investigating a to-be-evaluated road slope, and determining an importance sequence of the evaluation indexes and a basic score R of each evaluation index; then, according to importance ranking of the evaluation indexes, calculating a weight coefficient gamma of each evaluation index; the score of each evaluation index is calculated, the sum of the scores of the evaluation indexes is the slope risk F value, and the score of each evaluation index is the product of the basic score of each evaluation index and the corresponding weight coefficient; and finally, according to the size of the slope risk F value, the road slope risk grade is determined, a systematic and scientific evaluation method is formed, and the evaluation method is simple to operate and high in accuracy, and has important significance in risk pre-judgment and timely response of the in-service road slope.

Description

Technical Field

[0001] The invention relates to the technical field of slope risk assessment, and in particular to a highway slope risk assessment method and system. Background Art

[0002] Highway slopes are slopes with a certain slope on both sides of the roadbed to ensure the stability of the roadbed. Due to the influence of geological conditions, climate change, human factors and other factors, the stability of highway slopes often faces great risks. The catastrophic problem of slopes is an extremely complex, highly uncertain and dynamically changing system problem, which has not been well solved so far. Due to different sedimentary histories and congenital defects such as the development of rock joints and fissures, the parameters of the slope rock and soil mass are spatially non-uniform, anisotropic and discontinuous. Therefore, considering the influence of various uncertain factors in actual working conditions, the reliability analysis of slope stability with the help of probability analysis methods has become an important development trend in slope catastrophic analysis.

[0003] Highway slope risk assessment is an important means to ensure the safety, economy and environmental protection of highway projects, and is of great significance to the construction, operation and maintenance of highways. Through risk assessment, the potential instability and landslide risks of slopes can be identified and predicted, so that corresponding prevention and remediation measures can be taken to ensure the safe operation of highways and prevent traffic accidents caused by slope problems.

[0004] Therefore, it is of great significance to develop a scientific and systematic risk assessment method for highway slopes. Summary of the invention

[0005] The purpose of the present invention is to provide a risk assessment method and a processing method for highway slopes in view of the problems existing in the prior art.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A risk assessment method for a highway slope comprises the following steps:

[0008] Step 1: Establish a risk assessment indicator system, including risk factors, assessment indicators corresponding to each risk factor, and basic score ranges of different levels for each assessment indicator;

[0009] Step 2: Determine the importance ranking of the evaluation indicators and the basic score R of each evaluation indicator;

[0010] Step 3: Calculate the weight coefficient γ of each evaluation indicator according to the importance of the evaluation indicators;

[0011] Step 4: Calculate the scores of each evaluation index. The sum of the scores of each evaluation index is the slope risk F value.

[0012] Among them, the score of each evaluation indicator is the product of the basic score of each evaluation indicator and the corresponding weight coefficient;

[0013] Step 5: Determine the highway slope risk level according to the slope risk F value.

[0014] The invention provides a highway slope risk assessment method. First, a risk assessment index system is established, including risk factors, assessment indicators corresponding to each risk factor, and basic score segments of different levels for each assessment indicator. Then, a highway slope to be assessed is investigated to determine the importance ranking of the assessment indicators and the basic score R of each assessment indicator. After that, a weight coefficient γ of each assessment indicator is calculated according to the importance ranking of the assessment indicators. The score of each assessment indicator is calculated, and the sum of the scores of each assessment indicator is the slope risk F value, wherein the score of each assessment indicator is the product of the basic score of each assessment indicator and the corresponding weight coefficient. Finally, according to the size of the slope risk F value, the highway slope risk level is determined, and the highway slope risk is evaluated, thereby forming a systematic and scientific assessment method. The assessment method is simple to operate and highly accurate, and has important significance for risk prediction and timely response of in-service highway slopes.

[0015] Furthermore, in step 1, the risk factors are at least one of construction scale, rock type and slope combination, unfavorable structural surface combination, engineering protection, sensitive terrain or structures, deformation history and current deformation status, triggering factors and hydrogeology.

[0016] Furthermore, the evaluation indicators corresponding to the construction scale include slope height; the evaluation indicators corresponding to the rock type and slope rate combination include slope rock type and slope rate; the evaluation indicators of the unfavorable structural surface combination include slope structure combination; the evaluation indicators of engineering protection include the type of engineering protection measures; the evaluation indicators of sensitive terrain or structures include sensitive structures; the evaluation indicators of deformation history and deformation status include deformation status and deformation history; the evaluation indicators corresponding to triggering factors include rainfall and earthquake intensity; the evaluation indicators corresponding to hydrogeology include groundwater occurrence.

[0017] Furthermore,

[0018] The basic score ranges of different levels of slope height include: soil slope H≥40m, rock slope H≥60m, basic score range is 75-100; soil slope 30m≤H<40m, rock slope 40m≤H<60m, basic score range is 50-74; soil slope 20m≤H<30m, rock slope 30m≤H<40m, basic score range is 25-49; soil slope H<20m, rock slope H<30m, basic score range is 0-24;

[0019] The basic score ranges for slope lithology and slope ratio include: soil slope: slope ratio steeper than 1:1.0, basic score range is 75-100; slope ratio is 1:1.0-1:1.25, basic score range is 50-74; slope ratio is 1:1.25-1:1.50, basic score range is 25-49; slope ratio is gentler than 1:1.50, basic score range is 0-24;

[0020] Soft rock slope: The slope ratio is steeper than 1:0.75, and the basic score range is 75-100; the slope ratio is 1:0.75-1:1, and the basic score range is 50-74; the slope ratio is 1:1-1:1.25, and the basic score range is 25-49; the slope ratio is gentler than 1:1.25, and the basic score range is 0-24;

[0021] Rock slope: The slope ratio is steeper than 1:0.5, and the basic score range is 75-100; the slope ratio is 1:0.5-1:0.75, and the basic score range is 50-74; the slope ratio is 1:0.75-1:1, and the basic score range is 25-49; the slope ratio is gentler than 1:1, and the basic score range is 0-24;

[0022] The basic score ranges of different levels of slope structure combination include: if there are soft structural surfaces or combinations with gentle slope along the slope, the basic score is 75-100 if they are connected, and 50-74 if they are not connected; if there are hard structural surfaces or combinations with gentle slope along the slope, the basic score is 50-74 if they are connected, and 25-49 if they are not connected; if there are structural surfaces in other directions in the slope, and they are connected and developed, the basic score is 25-49; if there are structural surfaces in other directions in the slope, they are not connected and not developed, and the basic score is 0-24;

[0023] The basic score ranges of different levels of engineering protection measures include: anti-slide piles, with a basic score range of 75 to 100; anchoring engineering, with a basic score range of 50 to 74; grouting engineering, with a basic score range of 25 to 49; retaining wall engineering / slope protection engineering, with a basic score range of 0 to 24;

[0024] The basic score ranges of different levels of sensitive structures include: if there are surface buildings, underground objects, high-voltage towers, and water facilities within 0.5H beyond the top excavation line and 1.0H below the roadbed, the basic score range is 75-100; if there are surface buildings, underground objects, high-voltage towers, and water facilities within 1.0H beyond the top excavation line and 1.5H below the roadbed, the basic score range is 50-74; if there are surface buildings, underground objects, high-voltage towers, water facilities within 1.5H beyond the top excavation line and 2.0H below the roadbed, the basic score range is 25-49; if the facilities are located outside the above range, the basic score range is 0-24;

[0025] The basic score ranges of different levels of deformation status include: the current deformation state of the slope is serious: tension cracks appear on the top of the slope, the slope surface is seriously broken and the slope foot is bulging, the basic score range is 75-100; the deformation is moderate, the slope surface is deformed and partially deformed, the basic score range is 50-74; the deformation is slight, the slope surface is slightly deformed, the basic score range is 25-49; the slope surface has no deformation, the basic score range is 0-24;

[0026] The basic score ranges of different levels of deformation history include: the confirmed previous slope deformation history is serious, tension cracks appear on the top of the slope, the slope surface is seriously broken and the slope foot is uplifted, the basic score range is 75-100; the deformation history is moderate, the slope surface is deformed and partially deformed, the basic score range is 50-74; the deformation history is slight, the slope surface is slightly deformed, the basic score range is 25-49; there is no deformation history, the basic score range is 0-24;

[0027] The basic score ranges for different levels of rainfall include: when the rainfall is more than 2000mm, the basic score range is 75-100; when the rainfall is 1500-2000mm, the basic score range is 50-74; when the rainfall is 1000-1500mm, the basic score range is 25-49; when the rainfall is less than 1000mm, the basic score range is 0-24;

[0028] The basic score ranges of different levels of earthquake intensity include: earthquake intensity X~XII, the basic score range is 75~100; earthquake intensity VIII~IX, the basic score range is 50~74; earthquake intensity VI~VII, the basic score range is 25~49; earthquake intensity V and below, the basic score range is 0~24;

[0029] The basic score ranges for different levels of groundwater conditions include: karst and fissure development, good water storage space, abundant water and shallow burial, with a basic score range of 75 to 100; karst or fissure development, abundant karst water or fissure water, with a basic score range of 50 to 74; a certain amount of pore water is stored, with a basic score range of 25 to 49; groundwater is relatively scarce, with a basic score range of 0 to 24.

[0030] Furthermore, in step 2, the evaluation indicators are arranged in descending order of importance as follows: slope height, slope lithology and slope rate, slope structure combination, type of engineering protection measures, sensitive structures, deformation history, deformation status, rainfall, earthquake intensity and groundwater occurrence.

[0031] Through long-term investigation, monitoring analysis and related numerical calculations, as well as expert review, the combination of theoretical analysis, numerical simulation, expert opinions, and actual work results is more comprehensive than other methods, and a large number of work cases have confirmed the effectiveness of this assessment method. This assessment method assesses slope risk by scoring 10 fixed indicators. The method is relatively simple. Only the basic information of the slope is needed to obtain the risk level of the slope. It is suitable for promotion to slope risk assessment in large areas and provides a basis for treatment measures.

[0032] Furthermore, in step 2, the basic score is determined by the following method:

[0033] When the evaluation index is the slope height, the basic score is determined according to the following two standard methods. The first standard method: when the soil slope H≥60m and the rock slope H≥80m, the basic score is determined to be 100, and other scores are calculated by linear interpolation of height (the soil slope H≥40m and the rock slope H≥60m, the basic score range is 75-100. If the soil slope H≥60m and the rock slope H≥80m, the basic score is determined to be 100; the other scores are calculated by linear interpolation (the soil slope H≥40m and the rock slope H≥60m, the basic score range is 75-100). , the basic score for a 50m soil slope is 87.5. Others are similar); the second standard method: when the single-level slope, that is, the distance between two falling platforms, is h≥12m for soil slopes and h≥15m for rock slopes, take the larger value; when the single-level soil slope is h≤6m and the rock slope is h≤8m, take the smaller value; when the height of the single-level soil slope is h=8m and the rock slope is h=10m, take the middle value, and in other cases, calculate the value by linear interpolation according to the graded height; when the basic scores given by the two standards are different, use the larger value;

[0034] When the evaluation index is the lithology and slope rate of the slope, the basic score is determined as follows: for a rock-soil mixed slope, the score is determined based on the proportion of rock and soil; if there is a slippery or soft stratum, the score is reduced by one level; if the stratum distribution is complex, a larger value is taken; otherwise, a smaller value is taken;

[0035] When the evaluation index is a combination of slope structures, the angle between the inclination of the structural surface and its combined surface and the slope inclination is β = 0°, the basic score takes the large value, β = 45°, the basic score takes the middle value, β = 60°, the basic score takes the small value, and other values ​​are determined by linear interpolation;

[0036] When the evaluation indicator is groundwater conditions, the slope is equipped with complete waterproofing measures and the basic score is the minimum value of the score range.

[0037] Furthermore, in step 3, the weight coefficient γ of each evaluation index is calculated by the following formula: Among them, γ is the weight coefficient of the evaluation index, n is the number of evaluation indicators, m is the importance ranking number, and the sum of the weight coefficients of each evaluation indicator is 1.

[0038] Furthermore, in step 5, when the slope risk F value is greater than 70, the risk level is IV, extremely high risk; when 50﹤F≤70, the risk level is III, high risk; when 30﹤F≤50, the risk level is II, moderate risk; when F≤30, the risk level is I, low risk.

[0039] Another object of the present invention is to provide a risk assessment system for highway slopes.

[0040] A highway slope risk assessment system comprises at least one processor and a memory in communication with the at least one processor; the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can implement the above-mentioned risk assessment method.

[0041] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0042] The invention provides a highway slope risk assessment method. First, a risk assessment index system is established, including risk factors, assessment indicators corresponding to each risk factor, and basic score segments of different levels for each assessment indicator. Then, a highway slope to be assessed is investigated to determine the importance ranking of the assessment indicators and the basic score R of each assessment indicator. After that, a weight coefficient γ of each assessment indicator is calculated according to the importance ranking of the assessment indicators. The score of each assessment indicator is calculated, and the sum of the scores of each assessment indicator is the slope risk F value, wherein the score of each assessment indicator is the product of the basic score of each assessment indicator and the corresponding weight coefficient. Finally, according to the size of the slope risk F value, the highway slope risk level is determined, and the highway slope risk is evaluated, thereby forming a systematic and scientific assessment method. The assessment method is simple to operate and highly accurate, and has important significance for risk prediction and timely response of in-service highway slopes. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a diagram of the disease situation during the on-site investigation in Example 1.

[0044] Figure 2 This is the design diagram for the monitoring equipment layout in Example 1.

[0045] Figure 3 This is the slope displacement diagram at measuring point S1 in Example 1.

[0046] Figure 4 This is the slope displacement diagram at measuring point S2 in Example 1.

[0047] Figure 5 This is the on-site slope landslide map in Example 2.

[0048] Figure 6 This is a distribution diagram of the monitoring equipment in Example 2.

[0049] Figure 7 This is the deep layer oblique displacement map in Example 2.

[0050] Figure 8 This is the deep-layer incline displacement diagram of the DB3 surface displacement in Example 2.

[0051] Fig. 9 This is a diagram of the on-site investigation in Example 3.

[0052] Fig.10 This is the layout diagram of the monitoring station in Example 3.

[0053] Fig.11 This is the horizontal cumulative displacement-time curve of the DB monitoring point.

[0054] Fig.12 This is a graph of the cumulative displacement of the sliding surface in the sliding direction of the CX measuring point in Example 3 versus time.

[0055] Fig.13 This is an operational flow chart of the risk assessment method for highway slopes provided by the present invention. DETAILED DESCRIPTION

[0056] The present invention will be described in detail below in conjunction with the accompanying drawings.

[0057] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0058] Example 1

[0059] like Fig.13 As shown, the present invention provides a risk assessment method for a highway slope, comprising the following steps:

[0060] Step 1: Establish a risk assessment indicator system, including risk factors, assessment indicators corresponding to each risk factor, and basic score ranges of different levels for each assessment indicator;

[0061] Step 2: Investigate the road slope to be evaluated, determine the importance ranking of the evaluation indicators and the basic score R of each evaluation indicator;

[0062] Step 3: Calculate the weight coefficient γ of each evaluation indicator according to the importance of the evaluation indicators;

[0063] Step 4: Calculate the scores of each evaluation index. The sum of the scores of each evaluation index is the slope risk F value.

[0064] Among them, the score of each evaluation indicator is the product of the basic score of each evaluation indicator and the corresponding weight coefficient;

[0065] Step 5: Determine the highway slope risk level according to the slope risk F value.

[0066] Specifically, in step 3, the weight coefficient γ of each evaluation index is calculated by the following formula: Among them, γ is the weight coefficient of the evaluation index, n is the number of evaluation indicators, m is the importance ranking number, and the sum of the weight coefficients of each evaluation indicator is 1.

[0067] The weight coefficient table of the indicator system importance ranking method is shown in Table 0-1.

[0068] Table 0-1

[0069]

[0070] Specifically, the overall risk assessment index system for slope construction safety is shown in Table 0-2.

[0071] Table 0-2

[0072]

[0073]

[0074]

[0075]

[0076] Residual slope soil slope

[0077] The left side slope of GW Expressway ZM section K195+100~K196+060 was selected as a case study of residual slope accumulation type soil slope engineering.

[0078] (1) Project Overview

[0079] 1. Overview

[0080] The section K195+100 to K196+060 of the GW Expressway is located on a hillside somewhere in Guangxi. During the rainy seasons of 2006 and 2007, landslides occurred due to the action of rainwater and were treated. During 2018 to 2019, maintenance inspectors found signs of the development of slope diseases.

[0081] 2. Engineering geological conditions

[0082] ① Topography

[0083] The landslide site at K195+100~K196+850 is located in low mountain and hilly terrain, on the river bank slope between mountains. After artificial excavation and filling, the slope was covered with vegetation and the slope shape and gradient changed.

[0084] ② Stratigraphic lithology

[0085] According to ground investigation and drilling, the strata in the landslide area of ​​GW Expressway K195+100~K196+850 are mainly composed of Quaternary (Q) and Devonian (D), which are briefly described as follows:

[0086] Quaternary

[0087] According to the type of genesis, it can be divided into alluvial layer (Qal), collapse accumulation layer (Qc) and landslide accumulation layer (Odel).

[0088] a) Alluvial layer (Qal)

[0089] It is composed of grayish yellow sub-clay and clay, mainly distributed in the front edge of the landslide area K195+100~K196+060. The depth of the sub-clay on the left side of the landslide is less than 2m. The right side is deeper but discontinuous, and contains a small amount of angular gravel in some places, with a particle size of 2mm~10mm, angular shape, and the composition is strongly weathered muddy siltstone.

[0090] b) Collapse deposit layer (Qc)

[0091] The landslide slope of the GW Expressway K195+100~K196+850 section is mainly composed of collapsed deposits, the main component of which is gravel soil, with a gravel content of 50%~80%. The composition is strongly weathered muddy siltstone and quartz sandstone. In some sections, the sandstone blocks are severely weathered and appear sandy. The soil-to-rock ratio is greatly disparate and irregular.

[0092] b. The Lower Devonian Lianhuashan Formation (Dll) and Nagaoling Formation (Dln)

[0093] The Nagaoling Formation (Dln) is mainly composed of purple-red mud siltstone, mudstone, shale and blue-gray medium-thick siliceous cemented limestone. The former is thin-layered, soft rock, easily weathered, while the latter is harder rock with relatively stable rock properties. It is shallowly exposed in the K195+100~K195+600 section, and the rest is buried deeper.

[0094] The Lianhuashan Formation (D11) is composed of fine sandstone, siltstone, muddy siltstone, and intercalated muddy shale, with medium to thick layers. It is a relatively hard rock, with a thin thickness of 3m to 5m after strong weathering. The terrain is high and steep. The north-south ridge on the east side of the landslide area and the mountainous terrain on the south are composed of rock groups.

[0095] 3. Site survey

[0096] Slope photos see Figure 1 The local masonry gravity retaining wall of the landslide body No. 5 deformed body moved sideways at the toe of the slope, squeezing the road ditch. The top platform of the anti-slide pile was uplifted, with the maximum uplift height of about 1.0m. The slope surface was constantly creeping, cracking and sinking, with a length of more than 80 meters and a maximum collapse height of about 1.8 meters. A small part of the retaining wall and anti-slide piles was broken.

[0097] (2) Slope classification

[0098] (1) Establishing a risk factor set

[0099] Based on the project profile of the slope, the risk factor set of the slope is established as {slope construction scale (slope height), slope lithology and slope rate, unfavorable structural surface combination, protection structure type, sensitive terrain or structure, deformation status, deformation history, rainfall, earthquake intensity), hydrogeology}.

[0100] (2) Slope risk assessment

[0101] After consulting experts, the risk factors in the slope were ranked, and the ranking results and weight coefficients are shown in Table 1.

[0102] Table 1 K195+100~K196+060 right slope importance index ranking and weight coefficient table

[0103] Importance Evaluation Metrics Weight 1 Slope height 0.19 2 Slope lithology and slope 0.17 3 Slope structure surface combination 0.15 4 Types of engineering protection measures 0.13 5 Sensitive structures 0.11 6 Deformation History 0.09 7 Deformation status 0.07 8 Rainfall 0.05 9 earthquake intensity 0.03 10 Groundwater storage 0.01

[0104] According to the evaluation indexes and weight coefficients determined in Table 1, the evaluation scores of each index of the slope section are determined, see Table 2 for details.

[0105] Table 2 Slope importance index evaluation score table

[0106]

[0107]

[0108] According to the importance index and evaluation score of the slope section determined in Table 2, the risk F value of the high slope of the road cutting is calculated by substituting it into the formula:

[0109] F=∑X ij =56.8;

[0110] According to Table 3, the overall risk level of slope safety from K195+100 to K196+060 determined by the index system method is: Level III (high risk), which requires risk monitoring of the slope, formulation of corresponding monitoring plans, and increased monitoring frequency.

[0111] Table 3 Overall risk classification standard for slopes of operating highways

[0112]

[0113]

[0114] (3) Monitoring program design and implementation

[0115] According to the relevant specifications, the landslide was divided into three sections. On each section, surface displacement points were set up on the retaining wall at the top, middle, and bottom of the slope boundary line. In the three sections in the middle, groundwater monitoring was added. Considering the collapse and cracking phenomena in the three sections, deep horizontal displacement monitoring and surface crack monitoring were added near the original surface monitoring points to facilitate mutual verification of the observation results of various instruments, thereby ensuring the reliability of the observation results.

[0116] Displacement monitoring points are also set up on the anti-slide piles at the bottom of the landslide, and surveying robots are used for regular monitoring, so that the slope can achieve a monitoring technology that combines conventional and long-distance monitoring, mechanical methods and electrical measurements, and surface and underground monitoring, forming a three-dimensional monitoring network and alarm system of points, lines, and surfaces.

[0117] According to national standards and relevant design drawings, the slope is divided into three sections. The number and layout of monitoring points are shown in Table 4 and Figure 2 As shown in the figure, the layout location of specific monitoring points can be adjusted according to the actual situation on site.

[0118] Table 4 Monitoring equipment and quantity

[0119]

[0120]

[0121] (4) Data analysis and evaluation

[0122] Figure 3 and Figure 4 This is the surface displacement data of the slope measured by GNSS from 2019-12-05 to 2020-9-05. The measuring points S1 and S2 are located at different slope heights. As can be seen from the figure, the slope underwent a large slope displacement deformation in April 2020, and then the deformation stabilized. It is necessary to assign personnel to conduct special exploration of the slope. If the slope has a certain degree of deformation and damage, reasonable reinforcement measures should be taken; if the slope is in good condition, the previous monitoring frequency can be maintained for slope monitoring.

[0123] Example 2

[0124] Soil-rock binary translation landslide

[0125] (1) Project Overview

[0126] 1. Overview

[0127] The left side slope of the LB Expressway K93+686~K93+880 section is mainly soft rock that becomes soft when soaked in water. There are weak interlayers or mud interlayers and interlayer dislocation zones in the rock strata. The slope is 56.2m high and the slope protection is carried out by prestressed anchor rods, anchor frame lattice beams + spraying grass and other methods.

[0128] 2. Engineering geological conditions

[0129] ① Topography

[0130] The slope is located in the transition zone from the Yunnan-Guizhou Plateau to the Baise Valley. The overall terrain is high in the northwest and low in the southeast. The area along the route is mainly mountainous, with strong erosion and cutting, and steep mountains.

[0131] ② Stratigraphic lithology

[0132] The surface of the survey area is covered by Quaternary residual strata, with relatively developed surface vegetation and relatively stable natural slopes. According to geological surveys and drilling, the strata in the survey area are mainly composed of Quaternary strata, mainly Quaternary artificial fill, Holocene alluvial and diluvial layers, colluvial deposits, and slope residual soils. The underlying bedrock is mainly composed of Permian Lower System (P1) limestone and Triassic Middle System (T2) sandstone and siltstone.

[0133] Among them, the residual slope deposit layer is widely distributed and is divided into three sublayers.

[0134] a. Silty clay layer of slope accumulation: It is brownish yellow or brownish red, mainly composed of clay powder particles, containing a small amount of gravel or crushed stone, and is plastic to hard plastic. It has good engineering performance and is distributed on the surface of hillside sections. Its thickness is generally in the range of 0.5 to 2.0 m, and in some sections it reaches 3.0 m.

[0135] b. Slope deposit gravel layer: It is brownish yellow or grayish yellow, with gravel accounting for 50-60%, with local intercalation of blocks, and is mainly composed of medium-weathered sandstone and siltstone, filled with clay and silt particles. It has good engineering performance and is distributed on the surface of hillsides. Its thickness is generally in the range of 0.5 to 3.0 m, and reaches 5.0 m in some areas.

[0136] c. Residual layer residual clay soil: weathering residues of sandstone and siltstone: brown-yellow, brown-red, can be hard plastic, mainly clay-silt particles, some containing 10-20% medium and fine sand particles, this layer is distributed along the hillside, with a thickness of 1-3m and a burial depth of 2.5-5.5m.

[0137] 3. Site survey

[0138] Slope photos see Figure 5At 15:47 on October 1, 2020, a landslide occurred on the downline ZK2041+600 (construction pile number ZK93+800) of LB Road, with a landslide area of ​​about 1,500m2. It caused traffic congestion, but no casualties occurred.

[0139] (2) Slope classification

[0140] 1. Establish a risk factor set

[0141] Based on the project profile of the slope, the risk factor set of the slope is established as {slope construction scale (slope height), slope lithology and slope rate, unfavorable structural surface combination, engineering protection, deformation history and current deformation status, triggering factors (rainfall, earthquake intensity), and hydrological status}.

[0142] 2. Slope risk assessment

[0143] The risk factors in the slope are ranked, and the ranking results and weight coefficients are shown in Table 5.

[0144] Table 5 K93+686~K93+880 left slope importance index ranking and weight coefficient table

[0145] Importance Evaluation Metrics Weight 1 Slope height 0.19 2 Slope lithology and slope 0.17 3 Slope structure surface combination 0.15 4 Types of engineering protection measures 0.13 5 Sensitive structures 0.11 6 Deformation History 0.09 7 Deformation status 0.07 8 Rainfall 0.05 9 earthquake intensity 0.03 10 Groundwater storage 0.01

[0146] According to the evaluation indicators and weight coefficients determined in the above table, the evaluation scores of each indicator of the slope section are determined, see Table 6 for details.

[0147] Table 6 Slope importance index evaluation score table

[0148]

[0149]

[0150] According to the importance index and evaluation score of the slope section determined in Table 6, the overall risk F value of the construction safety of the high slope of the road cutting is calculated by substituting it into the formula:

[0151] F=∑X ij =57.443;

[0152] The overall risk level of slope safety at K93+686~K93+880 determined by the indicator system method is: Level III (high risk). It is necessary to monitor the slope risks, formulate corresponding monitoring plans, and increase the monitoring frequency.

[0153] (3) Monitoring program design and implementation

[0154] In view of the engineering geological characteristics and structural form of the slope of this section, combined with the existing diseases found in the on-site investigation, GNSS, deep inclinometer, laser total station and other equipment are used to monitor the surface deformation and deep displacement of the slope of this section. The monitoring equipment and quantity are shown in Table 7. Figure 6 As shown, the sampling frequency of automated monitoring is once per hour, and the frequency of periodic observation is twice per month.

[0155] Table 7 Monitoring equipment and quantity

[0156]

[0157]

[0158] (4) Data analysis and evaluation

[0159] The deep displacement distribution of the slope is shown in Figure 7 As shown in the figure, although the deep displacement monitoring hole is not completely located directly above the landslide body, it can still be seen that the deformation of the main sliding direction of the JCK1 hole is significantly higher than that of the JCK2 hole. On October 1, when the landslide occurred, the maximum displacement was close to 80mm, while the maximum deformation of the lower JCK02 hole was 4.3mm, which was relatively stable. Combined with the survey data, it can be judged that the slope does not have a complete through sliding surface, and the landslide body is mainly the upper residual slope accumulation layer.

[0160] From the perspective of time, before the slope collapsed, the deep displacement had been in a slow growth stage. Due to the long-term rainfall in the area in September, the displacement rate began to increase, and there was a significant mutation before and after the landslide, with the displacement rate reaching 20 mm. After the first landslide occurred on one side of the monitoring point, the displacement rate growth trend declined, but it was still in a rapid growth state, with a displacement rate of about 10 mm·d-1 and a displacement direction of 300°. The second landslide occurred in early November.

[0161] The GNSS (DB3) monitoring data were selected for surface displacement analysis, such as Figure 8As shown in the figure: (1) As September entered the rainy season, the horizontal and vertical displacements of the various measuring points represented by DB3 increased rapidly from September 15 to 30. The cumulative horizontal displacement increased from 10 mm to 20 mm, and was significantly higher than the vertical displacement. The analysis shows that the slope deformation is not holistic and the deformation should be concentrated in the upper gravel clay layer; (2) The displacement of the measuring point suddenly increased around October 1, with the horizontal displacement surging by 20 mm. The average daily displacement was roughly equivalent to the deep inclinometric data. Combining the data of the two, it is believed that the residual slope accumulation layer landslide has a high degree of suddenness. Its early displacement was 1 mm·d-1. Although the daily average increase is not high, if there is a continuous increase for more than 5 days, we should be particularly vigilant. (3) After the initial landslide occurred on October 1, the landslide at the measuring point continued to grow from October 1 to October 20. Although it converged later, a second landslide still occurred in early November. Analysis shows that the residual slope accumulation layer has the characteristics of a "chain reaction" and special attention should be paid to it during the actual road dredging and slope treatment process.

[0162] Example 3

[0163] (1) Project Overview

[0164] 1. Overview

[0165] The left side slope of XLN Expressway K157+300~K157+600 is located about 3.1 kilometers south of a certain county. The original landform of the slope is an erosional hilly landform. After artificial excavation, the original vegetation cover landform changed and the slope shape and gradient changed.

[0166] 2. Engineering geological conditions

[0167] The slope is affected by the Shizhai Fault, and the overall engineering geology of the slope is relatively complex. The rock joints and fissures are extremely developed, and the slope is extremely broken. The northern part of the fault is composed of residual slope accumulated gravel and soil from top to bottom, and brown-yellow fully to strongly weathered muddy siltstone downwards. The rock is relatively soft and relatively stable in nature; the southern part of the fault is composed of residual slope accumulated gravel and soil from top to bottom, and gray-white strongly weathered quartz sandstone downwards, and brown-yellow fully to strongly weathered muddy siltstone downwards.

[0168] 3. Site survey

[0169] During the early construction of the slope, sliding tension cracks and platform misalignment occurred. For details of the survey results, see Fig. 9 The preliminary design was changed to add anti-slide piles at the foot of the slope. After the anti-slide piles were constructed, cracks and misalignment appeared on the slope. The anti-slide piles were misaligned, so the secondary design was changed to reduce the load and use slope cutting, slope mesh spraying and other treatment measures.

[0170] Slope scale and protection form: slope length 360 meters, 10-level slope, slope height 99 meters, level 1 slope rate 1:1.25, level 2-10 slope rate 1:1.5; protection form is anti-slip piles + gabion retaining wall + mesh spraying concrete.

[0171] (2) Slope risk assessment

[0172] 1. Establish a risk factor set

[0173] Based on the project profile of the slope, the risk factor set of the slope is established as {slope construction scale (slope height), slope lithology and slope rate, unfavorable structural surface combination, engineering protection, deformation history and current deformation status, triggering factors (rainfall, earthquake intensity), and hydrological status}.

[0174] 2. Slope risk rating

[0175] According to the evaluation index and weight coefficient of the importance ranking method in the table, the evaluation score of each index of the slope section is determined, see Table 8 for details.

[0176] Table 8 Importance index ranking and weight coefficient table

[0177] Importance Evaluation Metrics Weight 1 Slope height 0.19 2 Slope lithology and slope 0.17 3 Slope structure surface combination 0.15 4 Types of engineering protection measures 0.13 5 Sensitive structures 0.11 6 Deformation History 0.09 7 Deformation status 0.07 8 Rainfall 0.05 9 earthquake intensity 0.03 10 Groundwater storage 0.01

[0178] Table 9 Slope importance index evaluation score table

[0179]

[0180]

[0181] According to the importance index and evaluation score of the slope section determined in Table 9, the overall risk F value of the high slope construction safety of the road cut is calculated by substituting it into the formula:

[0182] F=∑X ij =62.19.

[0183] The indicator system method determines the overall risk level of slope safety as Level III (high risk). It is necessary to establish a complete and comprehensive monitoring and early warning plan for the slope and conduct automated monitoring and early warning.

[0184] (3) Monitoring program design and implementation

[0185] The automatic monitoring system mainly includes two types: surface displacement monitoring and deep displacement monitoring. The monitoring network consists of 8 sensing stations (1 base station and 3 monitoring stations for surface displacement and 3 monitoring stations for deep displacement). The base stations are built in stable areas near the slope. The monitoring stations are comprehensively arranged based on on-site investigations and historical deformation conditions. The specific locations are as follows: Fig.10 shown.

[0186] (4) Monitoring data analysis

[0187] The cumulative horizontal displacement-time curve of the surface monitoring points is as follows: Fig.11 As shown, the stability of the slope can be determined by the cumulative displacement-time change. Since the equipment was installed in June 2021, the measuring point has been continuously displaced. From July 1 to November 30, the slope was in a slow deformation stage due to rainfall, and it was in an unstable state. From December 1 to January 31, it was in the dry season, and it was basically stable overall. From February 1 to April 30, it was affected by rainy weather, and the overall displacement of the slope first accelerated and then tended to a uniform speed. The slope was in an unstable state, and the monitoring party issued a yellow warning. During this stage, obvious cracks appeared in the slope, the retaining structure cracked, and it was in a continuous development. Strengthened inspections and certain treatment measures were taken on site.

[0188] The cumulative displacement-time curve of the sliding surface in the sliding direction of the deep monitoring point is as follows Fig.12 As shown, it can be seen from the cumulative displacement of the sliding surface over time:

[0189] From August 1, 2021 to November 15, 2021, the CX1 measuring point was in a slow creep state, and the deep layer of the slope was in an unstable state; from November 16, 2021 to February 15, 2022, the displacement showed a downward change due to the change in the direction of soil movement. From February 16, 2022 to May 5, 2022, the deep slope again creeped in stages.

[0190] From August 1, 2021 to November 15, 2021, the CX3 measuring point was in a slow creep state, and the deep layer of the slope was in an unstable state; from November 16, 2021 to January 30, 2022, the displacement deformation showed a stage-by-stage stable state, and from February 1, 2022 to May 5, 2022, the displacement deformation of the deep slope first accelerated and then tended to a uniform speed, and the slope was in an unstable state.

[0191] Comprehensive analysis of the survey and monitoring data shows that there is a mid-depth sliding surface on the slope as shown in Table 10. The sliding deformation of the rear edge and middle part of the slope is staged. The soil movement at the front edge of the slope changes in different directions due to the support of anti-sliding piles. The sliding surface is located in the strongly weathered weak interlayer.

[0192] Table 10 Overview of inclination holes

[0193] Measuring point number Measuring hole depth (m) Determination of sliding surface depth (m) Deformation state CX1 24.2 10.2 Deformation CX2 28.0 No obvious slip surface Undeformed CX3 41.6 21.6 Deformation

[0194] The invention provides a highway slope risk assessment method. First, a risk assessment index system is established, including risk factors, assessment indicators corresponding to each risk factor, and basic score segments of different levels for each assessment indicator. Then, a highway slope to be assessed is investigated to determine the importance ranking of the assessment indicators and the basic score R of each assessment indicator. After that, a weight coefficient γ of each assessment indicator is calculated according to the importance ranking of the assessment indicators. The score of each assessment indicator is calculated, and the sum of the scores of each assessment indicator is the slope risk F value, wherein the score of each assessment indicator is the product of the basic score of each assessment indicator and the corresponding weight coefficient. Finally, according to the size of the slope risk F value, the highway slope risk level is determined, and the highway slope risk is evaluated, thereby forming a systematic and scientific assessment method. The assessment method is simple to operate and highly accurate, and has important significance for risk prediction and timely response of in-service highway slopes.

[0195] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A risk assessment method for highway slopes, characterized in that: The following steps are involved: Step 1: Establish a risk assessment indicator system, including risk factors, assessment indicators corresponding to each risk factor, and basic score ranges of different levels for each assessment indicator; Step 2: Determine the importance ranking of the evaluation indicators and the basic score R of each evaluation indicator; Step 3: Calculate the weight coefficient γ of each evaluation indicator according to the importance of the evaluation indicators; Step 4: Calculate the scores of each evaluation index. The sum of the scores of each evaluation index is the slope risk F value. Among them, the score of each evaluation indicator is the product of the basic score of each evaluation indicator and the corresponding weight coefficient; Step 5: Determine the highway slope risk level according to the slope risk F value.

2. The risk assessment method for highway slope according to claim 1, characterized in that: In step 1, the risk factors are at least one of construction scale, lithology and slope combination, unfavorable structural surface combination, engineering protection, sensitive terrain or structures, deformation history and deformation status, triggering factors and hydrogeology.

3. The risk assessment method for highway slope according to claim 2 is characterized in that: The evaluation indicators corresponding to the construction scale include slope height; the evaluation indicators corresponding to the rock type and slope rate combination include slope rock type and slope rate; the evaluation indicators of unfavorable structural surface combination include slope structure combination; the evaluation indicators of engineering protection include the type of engineering protection measures; the evaluation indicators of sensitive terrain or structures include sensitive structures; the evaluation indicators of deformation history and deformation status include deformation status and deformation history; the evaluation indicators corresponding to triggering factors include rainfall and earthquake intensity; the evaluation indicators corresponding to hydrogeology include groundwater occurrence.

4. The risk assessment method for highway slope according to claim 3 is characterized in that: The basic score ranges of different levels of slope height include: soil slope H≥40m, rock slope H≥60m, basic score range is 75-100; soil slope 30m≤H<40m, rock slope 40m≤H<60m, basic score range is 50-74; soil slope 20m≤H<30m, rock slope 30m≤H<40m, basic score range is 25-49; soil slope H<20m, rock slope H<30m, basic score range is 0-24; The basic score ranges for slope lithology and slope ratio include: soil slope: slope ratio steeper than 1:1.0, basic score range is 75-100; slope ratio is 1:1.0-1:1.25, basic score range is 50-74; slope ratio is 1:1.25-1:1.50, basic score range is 25-49; slope ratio is gentler than 1:1.50, basic score range is 0-24; Soft rock slope: The slope ratio is steeper than 1:0.75, and the basic score range is 75-100; the slope ratio is 1:0.75-1:1, and the basic score range is 50-74; the slope ratio is 1:1-1:1.25, and the basic score range is 25-49; the slope ratio is gentler than 1:1.25, and the basic score range is 0-24; Rock slope: The slope ratio is steeper than 1:0.5, and the basic score range is 75-100; the slope ratio is 1:0.5-1:0.75, and the basic score range is 50-74; the slope ratio is 1:0.75-1:1, and the basic score range is 25-49; the slope ratio is gentler than 1:1, and the basic score range is 0-24; The basic score ranges of different levels of slope structure combination include: if there are soft structural surfaces or combinations with gentle slope along the slope, the basic score is 75-100 if they are connected, and 50-74 if they are not connected; if there are hard structural surfaces or combinations with gentle slope along the slope, the basic score is 50-74 if they are connected, and 25-49 if they are not connected; if there are structural surfaces in other directions in the slope, and they are connected and developed, the basic score is 25-49; if there are structural surfaces in other directions in the slope, they are not connected and not developed, and the basic score is 0-24; The basic score ranges of different levels of engineering protection measures include: anti-slide piles, with a basic score range of 75 to 100; anchoring engineering, with a basic score range of 50 to 74; grouting engineering, with a basic score range of 25 to 49; retaining wall engineering / slope protection engineering, with a basic score range of 0 to 24; The basic score ranges for different levels of sensitive structures include: there are surface buildings, underground objects, high-voltage towers, and water facilities within 0.5H beyond the top excavation line of the slope and 1.0H below the roadbed, with a basic score range of 75 to 100; there are surface buildings, underground objects, high-voltage towers, and water facilities within 1.0H beyond the top excavation line of the slope and 1.5H below the roadbed, with a basic score range of 50 to 74; there are surface buildings, underground objects, high-voltage towers, water facilities within 1.5H beyond the top excavation line of the slope and 2.0H below the roadbed, with a basic score range of 25 to 49; if the facilities are located outside the above range, the basic score range is 0 to 24.

5. The risk assessment method for highway slope according to claim 4 is characterized in that: The basic score ranges of different levels of deformation status include: the current deformation state of the slope is serious: tension cracks appear on the top of the slope, the slope surface is seriously broken and the slope foot is bulging, the basic score range is 75-100; the deformation is moderate, the slope surface is deformed and partially deformed, the basic score range is 50-74; the deformation is slight, the slope surface is slightly deformed, the basic score range is 25-49; the slope surface has no deformation, the basic score range is 0-24; The basic score ranges of different levels of deformation history include: the confirmed previous slope deformation history is serious, tension cracks appear on the top of the slope, the slope surface is seriously broken and the slope foot is uplifted, the basic score range is 75-100; the deformation history is moderate, the slope surface is deformed and partially deformed, the basic score range is 50-74; the deformation history is slight, the slope surface is slightly deformed, the basic score range is 25-49; there is no deformation history, the basic score range is 0-24; The basic score ranges for different levels of rainfall include: when the rainfall is more than 2000mm, the basic score range is 75-100; when the rainfall is 1500-2000mm, the basic score range is 50-74; when the rainfall is 1000-1500mm, the basic score range is 25-49; when the rainfall is less than 1000mm, the basic score range is 0-24; The basic score ranges of different levels of earthquake intensity include: earthquake intensity X~XII, the basic score range is 75~100; earthquake intensity VIII~IX, the basic score range is 50~74; earthquake intensity VI~VII, the basic score range is 25~49; earthquake intensity V and below, the basic score range is 0~24; The basic score ranges for different levels of groundwater conditions include: karst and fissure development, good water storage space, abundant water and shallow burial, with a basic score range of 75 to 100; karst or fissure development, abundant karst water or fissure water, with a basic score range of 50 to 74; a certain amount of pore water is stored, with a basic score range of 25 to 49; groundwater is relatively scarce, with a basic score range of 0 to 24.

6. The risk assessment method for highway slope according to any one of claims 1 to 5, characterized in that: In step 2, the evaluation indicators are arranged in descending order of importance as follows: slope height, slope lithology and slope rate, slope structure combination, type of engineering protection measures, sensitive structures, deformation history, deformation status, rainfall, earthquake intensity and groundwater occurrence.

7. The risk assessment method for highway slope according to any one of claims 1 to 5, characterized in that: In step 2, the basic score is determined by the following method: When the evaluation index is the slope height, the basic score is determined according to the following two standard methods: the first standard method: when the soil slope H≥60m and the rock slope H≥80m, the basic score is determined to be 100, and the other scores are calculated by linear interpolation of the height; the second standard method: when the single-level slope, that is, the distance between the two falling platforms, the soil slope h≥12m and the rock slope h≥15m, take the larger value; when the single-level soil slope h≤6m and the rock slope h≤8m, take the smaller value; when the height of the single-level soil slope h=8m and the rock slope h=10m, take the middle value, and in other cases, take the value by linear interpolation of the graded height; when the basic scores given by the two standards are different, use the larger value; When the evaluation index is the lithology and slope rate of the slope, the basic score is determined as follows: for a rock-soil mixed slope, the score is determined based on the proportion of rock and soil; if there is a slippery or soft stratum, the score is reduced by one level; if the stratum distribution is complex, a larger value is taken; otherwise, a smaller value is taken; When the evaluation index is the combination of slope structures, the angle between the inclination of the structural surface and its combined surface and the slope inclination β=0°, the basic score takes the larger value, β=45°, the basic score takes the middle value, β=60°, the basic score takes the smaller value, and other values ​​are determined by linear interpolation; when the evaluation index is the groundwater occurrence, the slope is equipped with complete waterproofing measures, and the basic score takes the minimum value of the score segment.

8. The risk assessment method for highway slope according to claim 1, characterized in that: In step 3, the weight coefficient γ of each evaluation index is calculated by the following formula: Among them, γ is the weight coefficient of the evaluation index, n is the number of evaluation indicators, m is the importance ranking number, and the sum of the weight coefficients of each evaluation index is 1.

9. The risk assessment method for highway slope according to claim 1, characterized in that: In step 5, when the slope risk F value is greater than 70, the risk level is IV, extremely high risk; when 50﹤F≤70, the risk level is III, high risk; when 30﹤F≤50, the risk level is II, moderate risk; when F≤30, the risk level is I, low risk.

10. A highway slope risk assessment system, characterized in that: It includes at least one processor and a memory communicatively connected to the at least one processor; the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can implement the risk assessment method described in any one of claims 1 to 9.

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