A method for determining shear strength parameters of unstable slope rock and soil

Abstract

The present invention discloses a method for determining the shear strength parameters of unstable slope rock and soil, comprising the following steps: S1, determining the cross-sectional dimensions of the slope before it becomes unstable; S2, determining the type, combined structure and bulk density of the rock and soil layers of the slope; S3, determining the cross-sectional shape of the slope after the landslide; S4, determining the shape of the only sliding surface when the slope becomes unstable; S5, determining the cross-sectional dimensions of the slope other than the sliding surface. t The shape of any other sliding surface j; S6. Determine the shear strength parameters of the unstable slope rock mass: cohesion C i,s And the internal friction angle #imgabs0#The present invention adopts the above-mentioned method for determining the shear strength parameters of the unstable slope rock and soil, and determines the shear strength parameters of the unstable slope rock and soil by considering the type, uniformity of the rock and soil and the shape of the sliding surface, which is more accurate.

Description

Technical Field

[0001] The invention belongs to the technical field of geotechnical engineering and geological engineering, and relates to a method for determining shear strength parameters of unstable slope rock and soil bodies. Background Art

[0002] It is known from the common knowledge in this field that the shear strength parameters of soil and rock slope rock mass will continue to decrease under the influence of rainfall, until the slope is about to reach a critical value where it will become unstable and fail. At this time, landslide geological disasters will easily occur, causing certain casualties, economic losses, traffic blockages and ecological damage.

[0003] For the recent landslide disasters, it is particularly important to determine the critical shear strength parameters of the rock and soil mass that causes the failure of the unstable slope in order to carry out the reasonable design and control of the landslide and to carry out accurate monitoring and early warning of similar slopes.

[0004] The type and uniformity of rock and soil and the shape of the sliding surface will have different degrees of influence on the size of the shear strength parameters of the rock and soil of the unstable slope. However, there is currently no method that takes these factors into consideration to determine the shear strength parameters of the rock and soil of the unstable slope.

[0005] Therefore, a method is needed to determine the shear strength parameters of unstable slope rock and soil, so as to reasonably determine the shear strength parameters of unstable slope rock and soil with different rock and soil types, rock and soil combinations and sliding surface shapes, so as to better serve the reasonable design and control of landslides and carry out accurate monitoring and early warning of similar slopes. Summary of the invention

[0006] The purpose of the present invention is to provide a method for determining the shear strength parameters of unstable slope rock and soil mass, which is used to solve the following problems:

[0007] 1. Solve the problem of determining the shear strength parameters (including cohesion C and internal friction angle φ) of unstable slope rock and soil with homogeneous rock and soil materials;

[0008] 2. Solve the problem of determining the shear strength parameters of unstable slope rock and soil with different shapes of sliding surfaces.

[0009] 3. Solve the problem of determining the shear strength parameters of unstable slope rock and soil with complex rock and soil layer combinations.

[0010] To achieve the above object, the present invention provides a method for determining the shear strength parameters of unstable slope rock and soil, comprising the following steps:

[0011] S1. Determine the cross-sectional dimensions before the slope becomes unstable

[0012] Determined by measuring the shape of adjacent un-instability slopes or consulting design drawings;

[0013] S2. Determine the type, combination structure and bulk density of the slope rock and soil layers

[0014] S20. Determine the type and combination structure of the slope rock and soil layers

[0015] Assume that there are M types of rock and soil layers to be determined;

[0016] S21. Determine bulk density γ

[0017] Under the premise of considering the influencing factors, it is determined by sampling indoor test; for any rock and soil layer i, the bulk density value when the slope is unstable is γ i,s ;

[0018] S3. Determine the cross-sectional shape of the slope after the landslide

[0019] A plurality of measuring points are set on the rear slope of the landslide and the coordinates of the measuring points are determined, and then the coordinates of adjacent measuring points are connected in sequence to form the rear slope of the landslide;

[0020] S4. Determine the unique sliding surface shape when the slope fails

[0021] The specific expression form is at least one of an arc, a polyline, and a combination of a polyline and an arc;

[0022] S5. Determine the sliding surface j t The shape of any other sliding surface j;

[0023] S6. Determine the shear strength parameters of unstable slope rock and soil: cohesion C i,s Angle of internal friction

[0024] S60, establishing a slope cross-section model before landslide;

[0025] S61, cohesion C of slope rock and soil layer i i,s , internal friction angle and bulk densityγ i,s Assign values ​​separately;

[0026] S62, calculate the slope along the sliding surface j t The stability coefficient K1 when the failure occurs, and the stability coefficient K when the slope fails along any other sliding surface j j ;

[0027] S63. Determine the cohesion C of any rock and soil layer i when the unstable slope fails based on the following limiting conditions: i,s Angle of internal friction The final value of is limited by:

[0028]

[0029] |K1-K jmin |≤0.03 (2)

[0030]

[0031]

[0032]

[0033]

[0034]

[0035] Where K1 is the slope along the sliding surface j t Stability coefficient when damage occurs; K jmin is the slope along the sliding surface j t The minimum stability coefficient when any other sliding surface other than the above is destroyed, and the corresponding sliding surface is jmin; is the determination coefficient, which reflects the relationship between the sliding surface jmin and the sliding surface j t The degree of overlap; SS res is the residual sum of squares; SS tot is the total sum of squares; y 1,i is the sliding surface j t The i-th observation on ; For all observations y 1,i The average value of y 2,i is the i-th observation value on the sliding surface jmin.

[0036] Preferably, in step S21, the influencing factor is rainfall.

[0037] Preferably, in step S3, the coordinates of adjacent measuring points are sequentially connected using polylines or spline curves in the drawing software.

[0038] Preferably, in step S3, the coordinates of the measuring points are determined by one of a laser rangefinder, a total station, a level or a GNSS receiver, or a combination thereof.

[0039] Preferably, in step S4, the sliding surface is determined by field investigation, measurement, drilling or geophysical exploration.

[0040] Preferably, in step S62, the slope limit equilibrium method is used to calculate the stability coefficients K1 and K j .

[0041] Preferably, the slope limit equilibrium method includes at least one of the Swedish strip method, the simplified Bishop method, the transfer coefficient method, the Spencer method, and the Morgenstern-Price method.

[0042] Preferably, in step S63, when it is determined that there are multiple cohesion C i,s Angle of internal friction When , the average of multiple values ​​is taken as the final value of the two values.

[0043] Therefore, the present invention adopts the above-mentioned method for determining the shear strength parameters of the unstable slope rock and soil, which takes into account the type and uniformity of the rock and soil and the shape of the sliding surface to determine the shear strength parameters of the unstable slope rock and soil, which is more accurate.

[0044] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a schematic diagram of the cross section of the unstable slope of the present invention;

[0046] Figure 2 is the observed value y of the present invention 1,i With y 2,i Schematic diagram of the description;

[0047] Figure 3 The actual unstable slope described in the experimental example of the present invention;

[0048] Figure 4 This is a cross-sectional view of an actual unstable slope described in the experimental example of the present invention. DETAILED DESCRIPTION

[0049] The present invention will be further described below in conjunction with the accompanying drawings. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to this embodiment.

[0050] Figure 1 FIG. 1 is a schematic diagram of the unstable slope cross section of the present invention, as shown in FIG. Figure 1 As shown, the present invention comprises the following steps:

[0051] S1. Determine the cross-sectional dimensions before the slope becomes unstable

[0052] Determined by measuring the shape of adjacent un-instability slopes or consulting design drawings;

[0053] S2. Determine the type, combination structure and bulk density of the slope rock and soil layers

[0054] S20. Determine the type and combination structure of the slope rock and soil layers

[0055] The types and combined structures of the rock and soil layers of the slope can be determined by field investigation, drilling, geophysical exploration and other methods. It is assumed that there are M types of rock and soil layers;

[0056] S21. Determine bulk density γ

[0057] Under the premise of considering the influencing factors, it is determined by sampling indoor test; for any rock and soil layer i, the bulk density value when the slope is unstable is γ i,s ;

[0058] Preferably, in step S21, the influencing factor is rainfall.

[0059] S3. Determine the cross-sectional shape of the slope after the landslide

[0060] A plurality of measuring points are set on the rear slope of the landslide and the coordinates of the measuring points are determined, and then the coordinates of adjacent measuring points are connected in sequence to form the rear slope of the landslide;

[0061] Preferably, in step S3, adjacent measuring point coordinates are sequentially connected using polylines or spline curves in a drawing software (such as AutoCAD). Preferably, in step S3, the measuring point coordinates are determined by a laser rangefinder, a total station, a level, or a GNSS receiver, or a combination thereof.

[0062] S4. Determine the shape of the unique sliding surface when the slope fails

[0063] The specific expression form is at least one of an arc, a polyline, and a combination of a polyline and an arc;

[0064] Preferably, it should be noted that, for a general landslide, its sliding surface is usually unique, and in step S4, the sliding surface is determined by field investigation, measurement, drilling or geophysical exploration.

[0065] S5. Determine the sliding surface j t The shape of any other sliding surface j;

[0066] The slope along the sliding surface t When failure occurs, the slope stability coefficient should be equal to 1 in theory. t When any other sliding surface j is destroyed, the slope stability coefficient may be greater than, equal to, or less than 1. Therefore, it is necessary to determine t The shape of any other sliding surface j other than the above can be used to facilitate the subsequent slope stability calculation and analysis.

[0067] It should be noted that, in addition to the sliding surface t The shapes of other arbitrary sliding surfaces j can be determined through field investigation, exploration, geophysical exploration or even artificial assumptions, and the number should be as large as possible.

[0068] S6. Determine the shear strength parameters of unstable slope rock and soil: cohesion C i,s Angle of internal friction

[0069] S60, establish the slope section model before the landslide (including M types of rock and soil layer combination structure, known sliding surface j t , any other sliding surface j);

[0070] S61, cohesion C of slope rock and soil layer i i,s , internal friction angle and bulk densityγ i,s Assign values ​​separately (the first two can be assigned values ​​arbitrarily, while the latter remains constant);

[0071] S62, calculate the slope along the sliding surface j t The stability coefficient K1 when the failure occurs, and the stability coefficient K when the slope fails along any other sliding surface j j ;

[0072] Preferably, in step S62, the slope limit equilibrium method is used to calculate the stability coefficients K1 and K j Preferably, the slope limit equilibrium method includes at least one of the Swedish strip method, the simplified Bishop method, the transfer coefficient method, the Spencer method, and the Morgenstern-Price method, which are existing technologies and will not be described in detail here.

[0073] S63. Determine the cohesion C of any rock and soil layer i when the unstable slope fails based on the following limiting conditions: i,s Angle of internal friction The final value of is limited by:

[0074]

[0075] |K1-K jmin |≤0.03 (2)

[0076]

[0077]

[0078]

[0079]

[0080]

[0081] Where K1 is the slope along the sliding surface j t Stability coefficient when damage occurs; K jmin is the slope along the sliding surface j t The minimum stability coefficient when any other sliding surface other than the above is destroyed, and the corresponding sliding surface is jmin; is the determination coefficient, which reflects the relationship between the sliding surface jmin and the sliding surface jt The degree of overlap; SS res is the residual sum of squares; SS tot is the total sum of squares; y 1,i is the sliding surface j t The i-th observation on ; For all observations y 1,i The average value of y 2,i is the i-th observation value on the sliding surface jmin.

[0082] In the above limiting conditions, formula (1) ensures that the slope reaches the critical condition of instability and moves along the sliding surface j t Formula (2) ensures that the possibility of slope failure along any other sliding surface j is no greater than that along sliding surface j t The possibility of damage is too great; Formula (3) ensures that even if the slope is along the sliding surface j t When any other sliding surface of the j The corresponding sliding surface jmin and sliding surface j t It also has a higher degree of overlap.

[0083] Preferably, in step S63, when it is determined that there are multiple cohesion C i,s Angle of internal friction When , the average of multiple values ​​is taken as the final value of the two values.

[0084] Figure 2 is the observed value y of the present invention 1,i With y 2,i Schematic diagram of the description, such as Figure 2 As shown, the observed value y in step S63 1,i With y 2,i Determined by: sliding surface jmin and sliding surface j t They are and Set the origin of the coordinate system to O in the figure. Assume that the coordinates of points A, B, C, and D are (x A ,y A )、(x B ,y B )、(x C ,y C ) and (x D ,y D ). Take x A 、x B 、x C 、x D The points corresponding to the second and third largest values ​​in are taken as the starting points of the analysis interval (such as Figure 2 A in the middle) and the end point (such as Figure 2The horizontal length S of the analysis interval is equal to the abscissa of the end point minus the abscissa of the start point, that is, S = x B -x A , divide the analysis interval into (n-1) equal parts along the horizontal axis direction (n is an integer and should not be less than 10), draw vertical dotted lines at the starting point, each equalization point and the end point, respectively, connected to the sliding surface jmin and the sliding surface j t Assume that the vertical dashed line i intersects with the sliding surface jmin and the sliding surface j t The coordinates of the intersection points are (x i ,y 2,i ) and (x i ,y 1,i ), where y 1,i The sliding surface j t The i-th observation on y 2,i It is the i-th observation value on the sliding surface jmin.

[0085] Experimental example:

[0086] Figure 3 The actual unstable slope described in the experimental example of the present invention; Figure 4 is a cross-sectional view of an actual unstable slope described in the experimental example of the present invention, as shown in Figure 3 and Figure 4 The type of rock and soil of the unstable slope shown is loess containing calcareous nodules. The shear strength parameters of the loess of the unstable slope are determined according to the following steps:

[0087] S1. Determine the cross-sectional dimensions of the loess slope before it becomes unstable

[0088] By measuring the morphological parameters (slope and slope length) of the adjacent uninstability slope, the cross-sectional dimensions of the loess slope before instability were determined.

[0089] S2. Determine the type, combination structure and bulk density of the slope rock and soil layers

[0090] Through on-site investigation, it is believed that the slope rock and soil type is loess containing calcareous nodules, and the slope rock and soil can be approximately regarded as homogeneous loess. Considering the possible rainfall infiltration effect, the bulk density γ value of loess is taken as 19.5kN / m 3 .

[0091] S3. Determine the cross-sectional shape of the slope after the landslide

[0092] Laser displacement meter Figure 3 The dotted line set on the unstable slope surface is used for multi-point testing, and then the coordinates of these measuring points are determined through geometric relationships. In the drawing software AutoCAD, the cross-sectional shape of the slope surface after the landslide can be determined by connecting adjacent measuring points in sequence with spline curves.

[0093] S4. Determine the shape of the unique sliding surface when the slope fails

[0094] Through on-site investigation and measurement, it was found that the cross-section of the back wall of the landslide was in the shape of an arc, the slide exit was located at the foot of the slope, and the sliding surface intersected with the top of the slope at point A. Therefore, it can be approximately considered that the only sliding surface when the slope is unstable is in the shape of an arc. Take a measuring point on the cross-section of the back wall of the landslide, and the only sliding surface j passing through points O and A can be determined through this measuring point. t .

[0095] S5. Determine the sliding surface j t The shape of any other sliding surface j

[0096] In addition to the sliding surface t Any other sliding surface j can be considered to be in the shape of an arc. t Any other sliding surface j other than can be automatically searched in the slope stability calculation software with built-in limit equilibrium method (it should be noted that the number of sliding surfaces j is assumed to be multiple here).

[0097] S6. Determine the shear strength parameters of the unstable slope loess

[0098] Table 1 is x i ,y 1,i With y 2,i Correspondence table

[0099] i <![CDATA[x i ]]> <![CDATA[y 1,i ]]> <![CDATA[y 2,i ]]> 1 0.000 0.0000 0.0000 2 1.625 0.7100 0.9083 3 3.250 1.5418 1.9099 4 4.875 2.5077 3.0127 5 6.500 3.6241 4.2265 6 8.125 4.9136 5.5632 7 9.750 6.4081 7.0385 8 11.375 8.1556 8.6728 9 13.000 10.2338 10.4935 10 14.625 12.7841 12.5397 11 16.25 16.135 14.8758

[0100] Figure 4 is a cross-sectional view of an actual unstable slope according to an experimental example of the present invention, Figure 4 Combined with Table 1, it can be seen that in the figure, the foot of the original slope is set as the coordinate origin O, and the sliding surface jmin is t They are and The starting and ending points of the analysis interval are Figure 4 The horizontal length S of the analysis interval is equal to the horizontal coordinate of the end point minus the horizontal coordinate of the starting point, that is, S = xA-xO = 16.135. Divide the analysis interval into 10 equal parts along the horizontal coordinate direction, and draw vertical dotted lines at the starting point, each equal point and the end point, respectively, which are connected to the sliding surface jmin and the sliding surface j t The total number of vertical dashed lines set is 11. Assume that the i-th vertical dashed line intersects with the sliding surface jmin and the sliding surface j t The coordinates of the intersection points are (x i ,y 2,i ) and (x i ,y 1,i ). Here y 1,i The sliding surface j tThe i-th observation on y 2,i It is the i-th observation value on the sliding surface jmin.

[0101] according to Figure 4 Establish the slope section model before landslide (including one loess layer and known sliding surface t ), the bulk density of the loess layer is assigned to be 19.5 kN / m 3 , the cohesion C of the loess layer s , internal friction angle The slope stability calculation software SlopeLE with the simplified Bishop method (one of the limit equilibrium methods) is used to calculate the slope along the sliding surface j. t The stability coefficient K1 when the failure occurs. On the other hand, the stability coefficient K when the slope fails along any other sliding surface j is calculated. j According to the requirements of the limiting conditions (1)-(8), the cohesion C of the loess layer s , internal friction angle A series of trial calculations were performed to determine the cohesion C of the loess layer when the unstable slope was destroyed. s Angle of internal friction Take 5kPa and 33.5° respectively.

[0102] Verification: When the cohesion C of the loess layer s Angle of internal friction When the pressure is 5 kPa and the temperature is 33.5°, equations (1), (2) and (3) can satisfy the following conditions:

[0103]

[0104] |K1-K jmin |=|0.974-0.956|=0.018≤0.03;

[0105]

[0106] Therefore, the present invention adopts the above-mentioned method for determining the shear strength parameters of the unstable slope rock and soil, which takes into account the type and uniformity of the rock and soil and the shape of the sliding surface to determine the shear strength parameters of the unstable slope rock and soil, which is more accurate.

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for determining the shear strength parameters of unstable slope rock and soil, characterized by: The following steps are involved: S1. Determine the cross-sectional dimensions before the slope becomes unstable Determined by measuring the shape of adjacent un-instability slopes or consulting design drawings; S2. Determine the type, combination structure and bulk density of the slope rock and soil layers S20. Determine the type and combination structure of the slope rock and soil layers Assume that there are M types of rock and soil layers to be determined; S21. Determine bulk density γ Under the premise of considering the influencing factors, it is determined by sampling indoor test; for any rock and soil layer i, the bulk density value when the slope is unstable is γ i,s ; S3. Determine the cross-sectional shape of the slope after the landslide A plurality of measuring points are set on the rear slope of the landslide and the coordinates of the measuring points are determined, and then the coordinates of adjacent measuring points are connected in sequence to form the rear slope of the landslide; S4. Determine the shape of the unique sliding surface when the slope fails The specific expression form is at least one of an arc, a polyline, and a combination of a polyline and an arc; S5. Determine the sliding surface j t The shape of any other sliding surface j; S6. Determine the shear strength parameters of unstable slope rock and soil: cohesion C i,s Angle of internal friction S60, establishing a slope cross-section model before landslide; S61, cohesion C of slope rock and soil layer i i,s , internal friction angle and bulk densityγ i,s Assign values ​​separately; S62, calculate the slope along the sliding surface j t The stability coefficient K1 when the failure occurs, and the stability coefficient K when the slope fails along any other sliding surface j j ; S63. Determine the cohesion C of any rock and soil layer i when the unstable slope fails based on the following limiting conditions: i,s Angle of internal friction The final value of is limited by: |K1-K jmin |≤0.03 (2) Where K1 is the slope along the sliding surface j t Stability coefficient when damage occurs; K jmin is the slope along the sliding surface j t The minimum stability coefficient when any other sliding surface other than the above is destroyed, and the corresponding sliding surface is jmin; is the determination coefficient, which reflects the relationship between the sliding surface jmin and the sliding surface j t The degree of overlap; SS res is the residual sum of squares; SS tot is the total sum of squares; y 1,i is the sliding surface j t The i-th observation on ; For all observations y 1,i The average value of y 2,i is the i-th observation value on the sliding surface jmin.

2. The method for determining the shear strength parameters of unstable slope rock and soil according to claim 1, characterized in that: In step S21, the influencing factor is rainfall.

3. A method for determining shear strength parameters of unstable slope rock and soil according to claim 2, characterized in that: In step S3, the coordinates of adjacent measuring points are sequentially connected using polylines or spline curves in the drawing software.

4. The method for determining the shear strength parameters of unstable slope rock and soil according to claim 3, characterized in that: In step S3 , the coordinates of the measuring points are determined by using one of a laser rangefinder, a total station, a level, or a GNSS receiver, or a combination thereof.

5. The method for determining the shear strength parameters of unstable slope rock and soil according to claim 4, characterized in that: In step S4, the sliding surface is determined by field investigation, measurement, drilling or geophysical exploration.

6. A method for determining shear strength parameters of unstable slope rock and soil according to claim 5, characterized in that: In step S62, the slope limit equilibrium method is used to calculate the stability coefficients K1 and K j .

7. The method for determining the shear strength parameters of unstable slope rock and soil according to claim 6, characterized in that: The slope limit equilibrium method includes at least one of the Swedish strip method, simplified Bishop method, transfer coefficient method, Spencer method, and Morgenstern-Price method.

8. The method for determining the shear strength parameters of unstable slope rock and soil according to claim 7, characterized in that: In step S63, when it is determined that there are multiple cohesion C i,s Angle of internal friction When , the average of multiple values ​​is taken as the final value of the two values.

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