Slope stability assessment method based on monitoring result feedback

Abstract

The invention discloses a slope stability assessment method based on monitoring result feedback. The slope stability assessment method comprises the following steps: establishing a slope geological generalization model based on slope landform; a monitoring device used for monitoring slope drilling depth deformation and the underground water level is installed on the slope; on the basis of the monitoring device, physical and mechanical parameters are given to a slope rock-soil body, a potential slip crack surface of the slope is determined, and a slope stability evaluation model is established; and obtaining the safety coefficient of the slope based on the slope stability evaluation model, and evaluating the slope stability. The evaluation result is obtained based on the actual feedback of the monitoring result, is accurate and reliable, and is suitable for popularization.

Description

Technical Field

[0001] The invention relates to a slope stability assessment method applicable to natural slopes and artificial slopes and realized based on monitoring result feedback, belonging to the technical field of slope stability assessment. Background Art

[0002] The stability assessment problem is the fundamental problem in slope engineering research, but the complexity, ambiguity, incompleteness and uncertainty of slope engineering have brought great difficulties to slope stability assessment. Slope stability analysis is a complex system engineering, and its own uncertainty and discreteness make its analysis much more difficult. At present, the more popular slope stability analysis methods mainly include rigid body limit equilibrium method. Although it has made great achievements, it still has shortcomings. The slip mode involved in the traditional rigid body limit equilibrium method is mainly determined by the geological and stratigraphic information revealed by drilling, geophysical exploration and adits. Due to the complexity and variability of the geological environment, it relies on expert experience and analogy, and there are certain human factors. Therefore, this method can no longer meet the actual needs of the project. It can be seen that in order to analyze the slope stability more objectively, it has become a new development direction and trend to further evaluate the slope stability based on the geological and stratigraphic information revealed by drilling, geophysical exploration and adits. Summary of the invention

[0003] The purpose of the present invention is to provide a slope stability assessment method based on monitoring results feedback, the assessment result of which is obtained based on the actual feedback of monitoring results, is accurate and reliable, and is suitable for promotion.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A slope stability assessment method based on monitoring results feedback, including:

[0006] 1) Establish a generalized slope geological model based on the slope topography and geomorphology;

[0007] 2) Install monitoring devices on the slope to monitor the deformation of the slope borehole depth and the groundwater level;

[0008] 3) Based on the monitoring device, physical and mechanical parameters are assigned to the slope rock and soil, and the potential sliding surface of the slope is determined to establish a slope stability assessment model;

[0009] 4) Obtaining the safety factor of the slope based on the slope stability assessment model to evaluate the slope stability.

[0010] The advantages of the present invention are:

[0011] The present invention obtains the potential slip points of the slope by monitoring the groundwater level and deep deformation (monitoring results) of the slope and combining the topographic and geomorphic characteristics of the slope, and then determines the critical slip line and constructs the potential slip surface, and finally obtains the safety factor of the slope, thereby evaluating the stability of the slope based on the safety factor. The evaluation result is obtained through actual feedback from the monitoring results, which is accurate and reliable, providing a scientific basis and reliable data support for slope engineering research. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is an implementation flow chart of the slope stability assessment method of the present invention.

[0013] Figure 2 It is a schematic diagram of the installation of the monitoring device.

[0014] Figure 3 This is a schematic diagram for explaining how to obtain the potential slip line.

[0015] Figure 4 This is a schematic diagram of drilling on the slope.

[0016] Figure 5 It is a schematic diagram illustrating rock and soil layers and infiltration lines. DETAILED DESCRIPTION

[0017] like Figure 1 The present invention proposes a slope stability assessment method based on monitoring result feedback, including:

[0018] 1) Establish a generalized slope geological model based on the slope topography and geomorphology;

[0019] 2) Installing a monitoring device on the slope for monitoring the deformation of the slope borehole depth and the groundwater level, wherein the monitoring device includes a piezometer 10 and a flexible displacement meter 50;

[0020] 3) Based on the monitoring device, the physical and mechanical parameters of the slope rock and soil are assigned, the potential sliding surface of the slope is determined, and a slope stability assessment model is established;

[0021] 4) Based on the slope stability assessment model, the safety factor of the slope is obtained to evaluate the slope stability.

[0022] In actual implementation, step 1) specifically includes: selecting representative locations on the slope to carry out drilling, using the geological information revealed by the drill core and the drill television images to obtain the distribution of the rock-soil interface and the stratigraphic structure line of each borehole, so as to establish a geological generalization model that can reflect the topographic and geomorphic characteristics of the slope, wherein all the boreholes on the slope are arranged in multiple rows along the up and down directions of the slope, and the rows are parallel or approximately parallel.

[0023] In actual implementation, step 2) specifically includes:

[0024] 2-1) A piezometer 10 is buried at the bottom of the drilled hole 60, and the piezometer 10 is used to monitor the groundwater level of the slope;

[0025] 2-2) Placing a plastic pipe 30 in the borehole 60, and vertically installing a flexible displacement meter 50 in the plastic pipe 30, the flexible displacement meter 50 is used to monitor the deformation at different depths of the same hole;

[0026] 2-3) The cables leading out of the piezometer 10 and the flexible displacement meter 50 are extended to the surface of the slope 20 and then connected to a collection device (not shown in the figure);

[0027] 2-4) Backfill the borehole 60 with medium-coarse sand (particle size 2mm-5mm) to 2 meters from the borehole 60 opening, and then continue to backfill mortar to the opening;

[0028] 2-5) Construct a concrete pier 40 at the opening of the drill hole 60 to seal and protect the piezometer 10 and the flexible displacement meter 50.

[0029] In the present invention, the flexible displacement meter 50 and the piezometer 10 are both existing devices in the art, and can be reasonably installed on the slope according to the drill holes. The drill holes 60 opened on the slope 20 should be reasonably designed according to the shape of the slope, but when looking down from the top of the slope 20, all the drill holes should be arranged in multiple straight lines or multiple rows along the up and down direction of the slope, and the spacing between adjacent drill holes in each row can be the same or different. Figure 4 , the figure shows that all the drill holes on the slope are arranged in 3 rows, the rows are parallel or nearly parallel, and the layout of the drill holes in each row is different. However, from the up and down direction of the slope, the drill holes in each row are arranged in a straight line.

[0030] Figure 2 The installation and layout of the monitoring device on the slope are schematically shown. Figure 2 shows the horizontal direction, vertical Figure 2 The direction of the paper is upstream and downstream. Figure 2 A borehole 60 is drilled on the slope, a piezometer 10 is set at the bottom of the borehole 60, a plastic pipe 30 is placed in the borehole 60, and a flexible displacement meter 50 is vertically installed in the plastic pipe 30. After the borehole 60 is backfilled with medium-coarse sand and mortar is poured to the hole mouth, a concrete pier 40 is constructed to block the hole mouth, and the cables led out of the piezometer 10 and the flexible displacement meter 50 are connected to the collection device on the surface of the slope 20. The collection device is a well-known electronic device with signal receiving, processing and storage functions.

[0031] In the present invention, the slope 20 generally includes a slope top 201 and a slope surface 202. In the art, a slope generally includes a slope top, a slope surface and a slope bottom. The monitoring device involved in the present invention is generally installed on the slope top 201 and the slope surface 202, not on the slope bottom. The drilling depth carried out on the slope should be reasonably designed according to the slope shape and is not limited.

[0032] In actual implementation, step 3) specifically includes:

[0033] 3-1) Drawing the distribution of the piezometer 10 and the flexible displacement meter 50 on the generalized geological model of the slope;

[0034] 3-2) According to the buried depth of the groundwater level measured by the piezometer 10 in each borehole and in combination with the water level outside the slope, the distribution of the infiltration line of the slope is obtained by interpolation and extrapolation method;

[0035] 3-3) Considering that rock and soil generally softens when exposed to water, the corresponding physical and mechanical parameters are assigned to the rock and soil in each rock and soil layer according to the distribution of the slope infiltration line, where the rock and soil below the infiltration line is assigned the friction angle, cohesion and saturated bulk density of the rock and soil layer in a saturated state, and the rock and soil above the infiltration line is assigned the friction angle, cohesion and natural bulk density of the rock and soil layer in a natural state;

[0036] 3-4) Based on the different depth deformation data monitored by each flexible displacement meter 50 at different times, the depth deformation curve of each borehole of the slope is drawn, and the depth deformation curve of each borehole reflects the evolution law of the deformation amount of the borehole at different depths;

[0037] 3-5) Based on the depth deformation curve, the depth of each borehole where the deformation mutation occurs is obtained, and the position of this depth is recorded as a potential slip point, wherein the potential slip point corresponding to each row of boreholes arranged on the slope constitutes a potential slip line, and the position of the above depth may be the monitoring point of the flexible displacement meter 50, or may not be the monitoring point of the flexible displacement meter 50;

[0038] 3-6) According to the obtained potential slip points, multiple groups of shear-in points and shear-out points of potential slip lines are obtained, and based on the determination of the minimum anti-sliding stability safety factor F, the critical slip line is preferably obtained, thereby obtaining the potential slip surface of the slope;

[0039] 3-7) Complete the establishment of slope stability assessment model.

[0040] In the present invention, obtaining the infiltration line distribution by interpolation and extrapolation based on the groundwater level and the groundwater level is a well-known technique in the art and will not be described here. The interpolation and extrapolation method is a well-known method. The infiltration line is the intersection of the seepage water flow surface and the cross section of the earth dam. The rock and soil below it is in a saturated state, and the particle weight is the effective weight. At the same time, it is affected by the penetration force of the seepage water. Therefore, the height and shape of the infiltration line in the dam body have a great influence on the stress of the dam body, the shear strength of the soil material, the stability of the dam slope and the penetration stability of the soil material. The slope is composed of multiple rock and soil layers, and each rock and soil layer is composed of rock and soil. The physical and mechanical parameters of the rock and soil above and below the infiltration line are different.

[0041] like Figure 5 The figure schematically shows a situation where the slope is composed of three rock and soil layers 70. In actual implementation, according to the buried depth of the groundwater level measured by the piezometer 10 in each borehole and the water level outside the slope, the infiltration line 80 on a certain longitudinal section of the slope is obtained by interpolation and extrapolation method. Figure 5 As shown, according to the distribution of the infiltration line 80, the rock mass of each rock layer 70 is assigned corresponding physical and mechanical parameters. Specifically, the rock mass below the infiltration line 80 is assigned the friction angle, cohesion and saturated bulk density of the rock layer where the rock mass is located in a saturated state, and the rock mass above the infiltration line 80 is assigned the friction angle, cohesion and natural bulk density of the rock layer where the rock mass is located in a natural state.

[0042] In step 3-5), the position of the sudden change depth of deformation obtained based on the depth deformation curve of the borehole may be the monitoring point of the flexible displacement meter 50, or may not be the monitoring point of the flexible displacement meter 50. Figure 2 As shown, it is assumed that the flexible displacement meter 50 in a certain borehole monitors deformation at seven monitoring points ag at seven different depths. By drawing the depth deformation curve, it is found that the monitoring point d has a sudden deformation change, so the depth position of the monitoring point d is recorded as a potential slip point. Of course, in actual implementation, it is also possible to draw the depth deformation curve to find the depth where the sudden deformation occurs, such as between the monitoring point d and the monitoring point e, and then record this depth position as a potential slip point.

[0043] In actual implementation, steps 3-6) specifically include:

[0044] A) According to the maximum value α3, angle α1 and angle α2 of the shearing section, the angle variation range [α min , α max ]:

[0045] α min =max[α1,α2] 1)

[0046] αmax =α3 2)

[0047] In equations 1) and 2), angle α1 is the acute angle between the sliding segment at the lowest position of the slope (i.e., the line connecting two adjacent potential sliding points at the lowest position of the slope) and the horizontal direction, and angle α2 is the acute angle between the line connecting the potential sliding point at the lowest position of the slope and the end point of the shear side of the slope and the horizontal direction. The end point of the shear side of the slope is defined by the generalized geological model of the slope.

[0048] B) According to the shear segment angle, the maximum value β3, angle β1 and angle β2 are set, and the angle variation range [β min , β max ]:

[0049] β min =max[β1,β2] 3)

[0050] β max =β3 4)

[0051] In equations 3) and 4), angle β1 is the acute angle between the sliding segment at the highest position of the slope (i.e., the line connecting two adjacent potential sliding points at the highest position of the slope) and the horizontal direction, and angle β2 is the acute angle between the line connecting the potential sliding point at the highest position of the slope and the end point of the shear side of the slope and the horizontal direction. The end point of the shear side of the slope is defined by the generalized geological model of the slope.

[0052] C) The range of the angle between the cut-out section from the slip line and the free surface direction [α min , α max ] and the range of the angle between the shearing section of the slip line and the mountain direction [β min , β max ] are randomly selected to form a group, recorded as (α, β), α represents the angle between the shear-out segment of the slip line and the direction of the free surface, β represents the angle between the shear-in segment of the slip line and the direction of the mountain;

[0053] D) Based on the value group (α, β), the intersection points of the shear-in segment of the slip line, the shear-out segment of the slip line and the slope surface are calculated and recorded as the shear-in point and shear-out point of the potential slip line, that is, the shear-in point is the point where the shear-in side of the slope intersects with the slope surface, and the shear-out point is the point where the shear-out side of the slope intersects with the slope surface;

[0054] E) Obtain the potential sliding fracture line of the slope;

[0055] F) Based on the physical and mechanical parameters of the rock and soil bodies of each rock and soil layer, the anti-sliding stability safety factor F of the potential slip line is calculated according to the Morgenstern-Price method (a limit equilibrium method for slope stability analysis proposed by Morgenstern and Price) which takes into account the force and moment equilibrium conditions in slope stability analysis;

[0056] G) Repeat steps C)-F) N times (N is a natural number greater than 2) to find the minimum value F of the anti-sliding stability safety factor F min The corresponding potential slip line is recorded as the critical slip line, that is, by using the optimization method, the shear entry point and shear exit point positions of the potential slip line are changed by changing the value of (α, β), and many potential slip lines are constructed. Finally, the potential slip line with the smallest anti-sliding stability safety factor F is searched from all potential slip lines as the final critical slip line;

[0057] H) Based on all the determined critical slip lines, the potential slip surface is obtained.

[0058] Here, the above-mentioned angles α1, α2, α3, β1, β2, and β3 are all acute angles. Figure 3 The horizontal direction is shown, where: in the horizontal direction, the direction from the bottom of the slope to the top of the slope is the mountain direction, and the opposite is the air surface direction.

[0059] For example:

[0060] like Figure 3 , Figure 3 The figure shows a typical slope geological generalization model M, where E and F are the slope shear-out side endpoint and slope shear-in side endpoint of the slope in the model, i.e., the left and right endpoints E and F of the slope surface in the figure, where A1, A2, ..., A n are the potential slip points obtained based on the depth deformation curve. In the horizontal direction, the direction from the bottom of the slope to the top is the mountain direction, and the opposite direction is the free surface direction, such as Figure 3 , set the range of the included angle (acute angle) between the shearing section of the slip line and the free surface direction to [α min , α max ], the range of the angle between the shearing section of the slip line and the direction of the mountain (acute angle) is [β min , β max ], wherein the slip line cut-out section is usually lower than the slip line cut-in section. In other words, the slip line cut-in section is at a higher position, and the slip line cut-out section is at a lower position.

[0061] The range of the angle between the shear section of the slip line and the free surface direction [α min , α max The determination process of ] is:

[0062] 1. Calculate the angle between the sliding segment A2A1 and the free surface direction, denoted as α1;

[0063] 2. Calculate the angle between the line A1E and the horizontal direction, recorded as α2;

[0064] 3. The angle between the cut-out section of the slip line and the horizontal direction is generally not greater than 70°, that is, the maximum angle of the cut-out section is set to 70°, recorded as α3;

[0065] So, α min =max(α1, α2), that is, take the larger one from α1 and α2,

[0066] α max =α3.

[0067] Similarly, the range of the angle between the shearing section of the slip line and the mountain direction [β min , β max The determination process of ] is:

[0068] 1. Calculate the sliding segment A n-1 A n The angle with the mountain direction is denoted as β1;

[0069] 2. Calculate connection A n The angle between F and the horizontal direction is denoted as β2;

[0070] 3. The angle between the shear section of the slip line and the horizontal direction is generally not greater than 70°, that is, the maximum value of the shear section angle is set to 70°, recorded as β3;

[0071] So, β min =max(β1, β2), that is, take the larger one from β1 and β2,

[0072] β max =β3.

[0073] Therefore, from the angle variation range [α min , α max ] and [β min , β max ] are randomly selected, and the shear-in point and shear-out point of the potential sliding line are calculated for each group (α, β), and then multiple potential sliding lines of the slope are obtained, and then the anti-sliding stability safety factor F of each potential sliding line is calculated. Figure 3 The cut-in point D and the cut-out point C calculated by a certain value set (α, β) are shown.

[0074] Then, based on all the calculated anti-sliding stability safety factors F, find the minimum value F min The corresponding potential slip line is taken as the critical slip line, and the potential slip surface is obtained by constructing all the obtained critical slip lines.

[0075] In actual implementation, step 4) specifically includes:

[0076] The safety factor F of the anti-sliding stability of each critical slip line is weightedly calculated (well-known calculation) to obtain the safety factor F' of the slope. The stability of the slope is evaluated by checking the numerical range of the level of the safety factor F'.

[0077] For example, Table 1 below gives four levels for evaluating slope stability, where level 1 (green) is safe, level 2 (blue) is relatively safe, level 3 (orange) is relatively dangerous, and level 4 (red) is dangerous.

[0078] Table 1

[0079] grade Slope safety factor F' 1 (green) 2.8～3.7 2 (blue) 1.9～2.8 3 (Orange) 1.5～1.9 4 (red) 0～1.5

[0080] For example, by weighted calculation of the anti-sliding stability safety factor F of each critical sliding line through step 4), the obtained safety factor F' is 1.6. Then, by checking the above table, it can be known that the slope is at level 3, which is relatively dangerous.

[0081] The advantages of the present invention are:

[0082] The present invention obtains the potential slip points of the slope by monitoring the groundwater level and deep deformation (monitoring results) of the slope and combining the topographic and geomorphic characteristics of the slope, and then determines the critical slip line and constructs the potential slip surface, and finally obtains the safety factor of the slope, thereby evaluating the stability of the slope based on the safety factor. The evaluation result is obtained through actual feedback from the monitoring results, which is accurate and reliable, providing a scientific basis and reliable data support for slope engineering research.

[0083] The above are preferred embodiments of the present invention and the technical principles used therein. For those skilled in the art, any obvious changes such as equivalent transformations, simple replacements, etc. based on the technical solution of the present invention, without departing from the spirit and scope of the present invention, are within the scope of protection of the present invention.

Claims

1. A slope stability assessment method based on monitoring results feedback, characterized in that: include: 1) Establish a generalized slope geological model based on the slope topography and geomorphology; 2) Install monitoring devices on the slope to monitor the deformation of the slope borehole depth and the groundwater level; 3) Based on the monitoring device, physical and mechanical parameters are assigned to the slope rock and soil, and the potential sliding surface of the slope is determined to establish a slope stability assessment model; 4) Obtaining the safety factor of the slope based on the slope stability assessment model to evaluate the slope stability.

2. The slope stability assessment method based on monitoring result feedback according to claim 1 is characterized in that: The step 1) specifically includes: selecting representative locations on the slope to carry out drilling, using the geological information revealed by the drilling core and drilling television images to obtain the distribution of the rock-soil interface and stratigraphic structural lines of each borehole, thereby establishing a geological generalization model that can reflect the topographic and geomorphic characteristics of the slope, wherein all the boreholes on the slope are arranged in multiple rows along the up and down directions of the slope.

3. The slope stability assessment method based on monitoring result feedback according to claim 1 is characterized in that: The step 2) specifically includes: 2-1) burying a piezometer at the bottom of the drilled hole, the piezometer being used to monitor the groundwater level of the slope; 2-2) placing a plastic pipe in the borehole, and vertically installing a flexible displacement meter in the plastic pipe, wherein the flexible displacement meter is used to monitor deformation at different depths of the same hole; 2-3) The cables leading out of the piezometer and the flexible displacement meter are extended to the slope surface and then connected to a collection device; 2-4) backfilling the borehole with medium-coarse sand to a distance of 2 meters from the borehole opening, and then continuing to backfill mortar to the hole opening; 2-5) A concrete pier is constructed at the borehole opening to seal and protect the piezometer and the flexible displacement meter.

4. The slope stability assessment method based on monitoring result feedback according to claim 1 is characterized in that: The step 3) specifically includes: 3-1) drawing the distribution of the piezometer and the flexible displacement meter on the generalized geological model of the slope; 3-2) According to the underground water level depth measured by the piezometer in each borehole and in combination with the water level outside the slope, the distribution of the infiltration line of the slope is obtained by interpolation and extrapolation method; 3-3) According to the obtained distribution of the infiltration line of the slope, the corresponding physical and mechanical parameters are assigned to the rock and soil bodies of each rock and soil layer, wherein: the rock and soil bodies below the infiltration line are assigned the friction angle, cohesion and saturated bulk density of the rock and soil layer where the rock and soil bodies are located in a saturated state, and the rock and soil bodies above the infiltration line are assigned the friction angle, cohesion and natural bulk density of the rock and soil layer where the rock and soil bodies are located in a natural state; 3-4) based on the deformation data of different depths monitored by each of the flexible displacement meters at different times, a depth deformation curve of each borehole of the slope is drawn, wherein the depth deformation curve of each borehole reflects the evolution law of the deformation of the borehole at different depths; 3-5) Based on the depth deformation curve, the depth of each borehole where a sudden deformation occurs is obtained, and the position of this depth is recorded as a potential slip point, wherein the potential slip points corresponding to each row of boreholes arranged on the slope constitute a potential slip line; 3-6) According to the obtained potential slip points, multiple groups of shear-in points and shear-out points of potential slip lines are obtained, and based on the determination of the minimum anti-sliding stability safety factor, the critical slip line is preferably obtained, thereby obtaining the potential slip surface of the slope; 3-7) Complete the establishment of the slope stability assessment model.

5. The slope stability assessment method based on monitoring result feedback as claimed in claim 4 is characterized in that: The steps 3-6) specifically include: A) According to the maximum value α3, angle α1 and angle α2 of the shearing section, the angle variation range [α min , α max ]: a min =max[α1,α2] 1) α max ＝α3 2) In formulas 1) and 2), angle α1 is the acute angle between the sliding segment at the lowest position of the slope and the horizontal direction, angle α2 is the acute angle between the line connecting the potential sliding point at the lowest position of the slope and the end point of the slope shearing side and the horizontal direction, and the end point of the slope shearing side is defined by the slope geological generalization model; B) According to the shear segment angle, the maximum value β3, angle β1 and angle β2 are set, and the angle variation range [β min , β max ]: b min =max[β1, β2] 3) β max ＝β3 4) In formulas 3) and 4), angle β1 is the acute angle between the sliding segment at the highest position of the slope and the horizontal direction, angle β2 is the acute angle between the line connecting the potential sliding point at the highest position of the slope and the end point of the slope shearing side and the horizontal direction, and the end point of the slope shearing side is defined by the slope geological generalization model; C) The range of the angle between the cut-out section from the slip line and the free surface direction [α min , α max ] and the range of the angle between the shearing section of the slip line and the mountain direction [β min , β max ] are randomly selected to form a group, recorded as (α, β), α represents the angle between the shear-out segment of the slip line and the direction of the free surface, β represents the angle between the shear-in segment of the slip line and the direction of the mountain; D) based on the value group (α, β), the intersection points of the shear-in section of the slip line, the shear-out section of the slip line and the slope surface are calculated and recorded as the shear-in point and shear-out point of the potential slip line; E) Obtain the potential sliding fracture line of the slope; F) calculating the anti-sliding stability safety factor of the potential slip line according to the Morgenstem-Price method based on the physical and mechanical parameters of the rock and soil bodies of each rock and soil layer; G) Repeat steps C)-F) N times to find the potential slip line corresponding to the minimum anti-sliding stability safety factor, which is recorded as the critical slip line; H) Based on all the determined critical slip lines, the potential slip surface is obtained.

6. The slope stability assessment method based on monitoring result feedback as claimed in claim 5 is characterized in that: The step 4) specifically includes: The anti-sliding stability safety factor of each critical slip line is weightedly calculated to obtain the safety factor of the slope, and the slope stability is evaluated by checking the numerical range of the level of the safety factor.

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