A method for dividing dangerous areas of excavation in high and steep jointed slopes

Abstract

The invention discloses a method for dividing dangerous areas of excavation of a high-steep jointed slope, comprising: A. establishing a geological generalization model of the slope; B. using a continuous medium mechanics analysis method to establish a numerical model of the slope, analyzing the dynamic stability of the slope under the action of step-by-step excavation, and if instability occurs, stopping the excavation and turning to step C, otherwise turning to step F; C. judging and obtaining the potential sliding surface of the slope according to the distribution of plastic zones of the slope and the settlement of displacement cloud maps; D. using a discontinuous medium mechanics analysis method to establish a numerical model of the slope according to the potential sliding surface of the slope obtained in step C, and analyzing the potential instability process of the slope; E. performing dangerous area division on the slope according to the accumulation range of the rock mass after the slope becomes unstable; F: ending the dangerous area division; the method avoids the interference of subjective factors, the area division result is more accurate, and provides a method and technical support for the dangerous area division of the high-steep slope under the action of excavation.

Description

Technical Field

[0001] The invention belongs to the technical field of geotechnical engineering such as water conservancy, hydropower, open-pit mines, etc., and specifically relates to a method for dividing dangerous areas of high and steep jointed slope excavation, which is particularly suitable for dangerous areas of high and steep slopes under step-by-step excavation. Background Art

[0002] With the development and utilization of resources and the improvement of energy structure, a large number of high and steep slopes have appeared in the fields of water conservancy, hydropower, open-pit mines, etc. High and steep slopes generally have the characteristics of complex geological environment, large ground stress, large excavation volume, long excavation cycle, frequent external disturbance, etc. At the same time, their prevention and control schemes are more complicated than those of general slopes. Therefore, the stability of high and steep slopes throughout their life cycle has an important impact on the construction and operation of the project, and the hazard zoning of high and steep slopes is conducive to the reasonable arrangement of project construction.

[0003] The traditional hazard zoning method is mainly the engineering analogy method, that is, the new project is zoned according to the hazard zoning of similar projects. This method is highly subjective and relies heavily on the engineering experience of engineers. The zoning results may be too conservative, resulting in a large number of constructible areas not being constructed, delaying the progress of the project; or too optimistic, resulting in construction work in dangerous areas, causing safety accidents. Therefore, developing a reasonable, objective and accurate high and steep slope hazard zoning method is the key and difficulty of slope engineering disaster prevention and control. Summary of the invention

[0004] In order to address the deficiencies in the prior art, the present invention aims to solve the problem that the traditional hazard zoning method is highly subjective and highly dependent on the engineering experience of engineers. The zoning results may be too conservative, resulting in a large number of constructible areas not being constructed, delaying the progress of the project; or they may be too optimistic, resulting in construction work being carried out in dangerous areas, causing safety accidents.

[0005] In order to achieve the above object, the present invention relates to: a method for dividing dangerous areas of high and steep jointed slope excavation, comprising the following steps:

[0006] A. Determine the physical and mechanical parameters of the rock and soil mass and the distribution of the structural surface through engineering geological surveys, and establish a geological generalization model of the slope;

[0007] B. Based on the generalized geological model of the slope, a numerical model of the slope is established using the continuous medium mechanics analysis method to analyze the dynamic stability of the slope under the step-by-step excavation. If instability occurs, stop excavation and turn to step C, otherwise turn to step F;

[0008] C. Determine and obtain the potential sliding surface of the slope based on the distribution of the plastic zone of the slope and the settlement of the displacement cloud map;

[0009] D. Based on the potential sliding surface of the slope obtained in step C, a numerical model of the slope is established using a discontinuous medium mechanics analysis method to analyze the potential instability process of the slope;

[0010] E. Draw dangerous areas on the slope according to the accumulation range of rock mass after the slope becomes unstable;

[0011] F: End the dangerous zone.

[0012] Furthermore, the method of establishing the slope numerical model by using the continuum mechanics analysis method is to establish the slope numerical model by using the joint finite element method.

[0013] Furthermore, in step (B), the dynamic stability of the slope under the step-by-step excavation is analyzed; the specific criteria for judging the dynamic stability are:

[0014] The stability during excavation is determined based on whether the plastic zone is continuous, the displacement cloud map settlement, and whether the safety factor is less than 1. If a continuous plastic zone, an obvious displacement cloud map interface, or a safety factor less than 1 is formed, the slope is considered to be unstable.

[0015] Furthermore, in the step (C), the potential sliding surface of the slope is determined according to the distribution of the plastic zone of the slope and the settlement of the displacement cloud map; the specific criteria for determining the potential sliding surface are:

[0016] The specific criteria for judging the potential sliding surface are:

[0017] (1) If a continuous plastic zone is formed, the continuous plastic zone is regarded as a potential sliding surface. The method for determining whether a continuous plastic zone is formed is as follows: The plastic zone penetration rate is defined as:

[0018]

[0019] Where V pl represents the volume of the plastic zone, V total represents the volume along the sliding zone;

[0020] When α<1, it means that the plastic zone is not connected, and when α=1, it means that the plastic zone is connected;

[0021] (2) If a displacement-settlement interface appears, and the rock mass below the interface does not undergo displacement or settlement, but the rock mass above the interface undergoes overall displacement or settlement, then the displacement-settlement interface is considered a potential sliding surface;

[0022] The specific method for determining the displacement settlement interface is to draw a vertical line from the slope surface to the inside of the slope and record the settlement of each unit along the vertical line.

[0023] Define displacement settlement increments:

[0024]

[0025] where x i+1 represents the displacement settlement of the i+1th unit, x i represents the displacement and settlement of the ith unit; l i+1 represents the distance between the i+1th unit and the slope surface, l i represents the distance between the ith unit and the slope surface;

[0026] When β = 0, it means that the displacement settlement no longer changes (i.e., the rock mass does not experience relative displacement settlement). That is, the unit at β = 0 is the displacement settlement interface, and the displacement settlement x of the unit here is i Indicates the displacement and settlement of the entire project;

[0027] It suffices if either of the above conditions (1) or (2) is satisfied.

[0028] Furthermore, the specific method of step (D) is:

[0029] A slope block system model is established according to the potential sliding surface of the slope. By setting multiple groups of shear strength parameters of the potential sliding surface, the potential instability and failure process of the slope under different mechanical parameter conditions is simulated.

[0030] Furthermore, the method of setting multiple sets of shear strength parameters for the potential sliding surface is as follows: setting three sets of shear strength parameters for the potential sliding surface, high, medium and low, according to the internal friction angle of the rock in the area where the potential sliding surface of the slope is located. Determine the high, medium and low shear strength parameters on the potential sliding surface, where the high shear strength parameter Middle group shear strength parameters Low group shear strength parameters The above parameters are all in angle.

[0031] Furthermore, in step (E), the slope is divided into dangerous zones according to the accumulation range of the rock mass after the slope becomes unstable; the specific zoning basis is:

[0032] Prohibited operation area: refers to the area where unstable rock mass can accumulate after the slope fails under high shear strength conditions. This area has a high safety hazard;

[0033] High-risk area: refers to the area where collapsed rock mass can accumulate after the slope becomes unstable under medium shear strength conditions. This area also has high safety hazards;

[0034] Medium risk area: refers to the area where collapsed rock mass can accumulate after the slope becomes unstable under the condition of low shear strength. This area still has certain safety hazards;

[0035] Low risk area: refers to the area where collapsed rock mass cannot accumulate after the slope becomes unstable, but risks such as collapse and rockfall still need to be paid attention to;

[0036] Safety zone: The area 90m-110m away from the farthest end of the rock accumulation area under low shear strength conditions. This area is relatively safe and industrial production can be carried out according to actual conditions.

[0037] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0038] (1) The method for dividing the dangerous zoning of high and steep jointed slope excavation of the present invention uses a continuous-discontinuous analysis method to divide the dangerous zoning of high and steep slopes after determining the physical and mechanical parameters of the rock and soil mass and the distribution form of the structural surface through engineering geological survey. It has the advantages of simple operation, objectivity and fairness, high calculation accuracy, and strong engineering applicability;

[0039] (2) The method for dividing the dangerous areas of high and steep jointed slopes under excavation in the present invention avoids the interference of subjective factors, and the zoning results are more accurate, providing a method and technical support for the dangerous areas of high and steep slopes under excavation. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 A flowchart of the implementation of the hazard zoning of a preferred embodiment of the present invention;

[0041] Figure 2 A schematic diagram of a slope finite element model of a preferred embodiment of the present invention;

[0042] Figure 3 This is a schematic diagram of the relationship between the slope safety factor and the number of excavation steps in a preferred embodiment of the present invention;

[0043] Figure 4 A schematic diagram of a potential sliding surface of a slope according to a preferred embodiment of the present invention;

[0044] Figure 5 A schematic diagram of a slope block model of a preferred embodiment of the present invention;

[0045] Figure 6-Figure 8 Schematic diagram of rock mass accumulation range under different shear strength parameters in a preferred embodiment of the present invention ( Figure 6-Figure 8 The shear strength parameters of the sliding surface are 15°, 20° and 25° respectively);

[0046] Fig. 9 A schematic diagram of slope hazard zoning according to a preferred embodiment of the present invention;

[0047] Fig.10 A schematic diagram of determining the formation of a through plastic zone according to a preferred embodiment of the present invention;

[0048] Table 1: Physical and mechanical parameters of rock and soil mass;

[0049] Table 2: Structural surface distribution form and parameter table. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solutions 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 intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0051] The present invention will be further described below in conjunction with the accompanying drawings:

[0052] Please refer to Figure 1 The present invention relates to a method for dividing dangerous areas of high and steep jointed slope excavation, comprising the following steps:

[0053] A. Determine the physical and mechanical parameters of the rock and soil mass and the distribution of the structural surface through engineering geological surveys, and establish a geological generalization model of the slope;

[0054] B. Based on the generalized geological model of the slope, a numerical model of the slope is established by using the continuous medium mechanics analysis method (for example, a numerical model of the slope is established by using the joint finite element method), and the dynamic stability of the slope under the action of step-by-step excavation is analyzed. If instability occurs, the excavation is stopped and the process is turned to step C, otherwise, the process is turned to step F; the specific criteria for judging the dynamic stability are:

[0055] The stability during excavation is determined based on whether the plastic zone is continuous, the displacement cloud map settlement, and whether the safety factor is less than 1. If a continuous plastic zone, an obvious displacement cloud map interface, or a safety factor less than 1 is formed, the slope is considered to be unstable.

[0056] C. Determine the potential sliding surface of the slope based on the distribution of the plastic zone of the slope and the settlement of the displacement cloud map; the specific criteria for determining the potential sliding surface are:

[0057] (1) Fig.10 If a continuous plastic zone is formed, the continuous plastic zone is regarded as a potential sliding surface. The method for judging the formation of a continuous plastic zone is as follows: Define the plastic zone penetration rate:

[0058]

[0059] Where V pl represents the volume of the plastic zone, V total represents the volume along the sliding zone;

[0060] When α<1, it means that the plastic zone is not connected, and when α=1, it means that the plastic zone is connected;

[0061] (2) If a displacement-settlement interface appears, and the rock mass below the interface does not undergo displacement or settlement, but the rock mass above the interface undergoes overall displacement or settlement, then the displacement-settlement interface is considered a potential sliding surface;

[0062] The specific method for determining the displacement settlement interface is to draw a vertical line from the slope surface to the inside of the slope and record the settlement of each unit along the vertical line.

[0063] Define displacement settlement increments:

[0064]

[0065] where x i+1 represents the displacement settlement of the i+1th unit, x i represents the displacement and settlement of the ith unit; l i+1 represents the distance between the i+1th unit and the slope surface, l i represents the distance between the ith unit and the slope surface;

[0066] When β = 0, it means that the displacement settlement no longer changes (i.e., the rock mass does not experience relative displacement settlement). That is, the unit at β = 0 is the displacement settlement interface, and the displacement settlement x of the unit here is i Indicates the displacement and settlement of the entire project;

[0067] It suffices if either of the above conditions (1) or (2) is satisfied.

[0068] D. Based on the potential sliding surface of the slope obtained in step C, a numerical model of the slope is established using the discontinuous medium mechanics analysis method to analyze the potential instability process of the slope. The specific method is as follows:

[0069] A slope block system model is established according to the potential sliding surface of the slope. By setting multiple groups of shear strength parameters of the potential sliding surface, the potential instability and failure process of the slope under different mechanical parameter conditions is simulated.

[0070] The method of setting multiple groups of shear strength parameters of the potential sliding surface is as follows: setting three groups of shear strength parameters of the potential sliding surface, high, medium and low, according to the internal friction angle of the rock in the area where the potential sliding surface of the slope is located. Determine the high, medium and low shear strength parameters on the potential sliding surface, where the high shear strength parameter Middle group shear strength parameters Low group shear strength parameters The above parameters are all in angle.

[0071] When performing discontinuous medium mechanics analysis, it is necessary to set a potential sliding surface. The potential sliding surface is obtained through the results of continuous medium mechanics analysis, and the style of the potential sliding surface is used in the modeling process of discontinuous medium mechanics analysis. That is, the potential sliding surface is a bridge for transition from continuous medium mechanics analysis to discontinuous medium mechanics analysis. This is the process of combining the two.

[0072] E. According to the accumulation range of rock mass after the slope becomes unstable, the slope is divided into dangerous areas; the specific zoning basis is:

[0073] Prohibited operation area: refers to the area where unstable rock mass can accumulate after the slope fails under high shear strength conditions. This area has a high safety hazard;

[0074] High-risk area: refers to the area where collapsed rock mass can accumulate after the slope becomes unstable under medium shear strength conditions. This area also has high safety hazards;

[0075] Medium risk area: refers to the area where collapsed rock mass can accumulate after the slope becomes unstable under the condition of low shear strength. This area still has certain safety hazards;

[0076] Low risk area: refers to the area where collapsed rock mass cannot accumulate after the slope becomes unstable, but risks such as collapse and rockfall still need to be paid attention to;

[0077] Safety zone: The area 90m-110m away from the farthest end of the rock accumulation area under low shear strength conditions. This area is relatively safe and industrial production can be carried out according to actual conditions.

[0078] F: End the dangerous zone.

[0079] Specific calculation example:

[0080] A method for dividing dangerous areas of high and steep jointed slope excavation, the implementation process is as follows: Figure 1 As shown, the specific implementation steps are:

[0081] A. Through engineering geological survey, the physical and mechanical parameters of the rock and soil mass are determined as shown in Table 1, the distribution form and parameters of the structural surface are shown in Table 2, and the geological generalization model of the slope is established;

[0082] Table 1 Physical and mechanical parameters of rock and soil

[0083]

[0084] Table 2 Structural surface distribution form and parameters

[0085]

[0086] B. According to the generalized model of slope geology, the numerical model of slope is established by using finite element software phase2, such as Figure 2 As shown in the figure, the relationship between the safety factor of the slope under step-by-step excavation and the number of excavation steps is analyzed, as shown in the figure. Figure 3 As shown by Figure 3 It can be seen that the safety factor of the slope is 1.01 when excavating to step 11, which is in a critical equilibrium state. The safety factor is 0.98 when excavating to step 12, at which time instability occurs and turns to step (C);

[0087] C. Determine the potential sliding surface when the slope is unstable, based on the displacement settlement interface after excavation. The potential sliding surface is as follows: Figure 4 As shown;

[0088] D. According to the potential sliding surface of the slope, the discontinuous medium mechanics analysis method (DDA) is used to establish the slope block model, such as Figure 5 As shown, the potential sliding surface is located in the area of ​​two-mica quartz schist, and the internal friction angle of the rock is 34.4°, so the high group shear strength parameter of the potential sliding surface is 34.4°-10°=24.4° (rounded to 25°); the middle group shear strength parameter is 34.4°-15°=19.4° (rounded to 20°); the low group shear strength parameter is 34.4°-20°=14.4° (rounded to 15°); therefore, the shear strength parameters of the potential sliding surface are set to three levels of 25°, 20° and 15°, respectively, and the potential instability process of the slope under different shear strength parameter conditions is analyzed;

[0089] E. The accumulation range of unstable blocks in slope under different shear strength parameters is as follows: Figure 6-Figure 8 As shown in Figure 2, the slope is divided into dangerous areas according to the accumulation range of rock mass after the slope becomes unstable, such as Fig. 9 As shown. The prohibited operation area refers to the area where the unstable rock mass can still accumulate after the slope becomes unstable under the condition of a friction angle of 25°, and this area has a high safety hazard; the high-risk area refers to the area where the collapsed rock mass can accumulate after the slope becomes unstable under the condition of a friction angle of 20°, and this area also has a high safety hazard; the medium-risk area refers to the area where the collapsed rock mass can accumulate after the slope becomes unstable under the condition of a friction angle of 15°, and this area still has certain safety hazards; the low-risk area refers to the area where the collapsed rock mass cannot accumulate after the slope becomes unstable, but it is still necessary to pay attention to risks such as collapse and falling rocks; the safe area is about 100m away from the accumulated rock mass area. This area is relatively safe and industrial production can be carried out according to actual conditions;

[0090] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the structural relationship and principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for dividing dangerous areas of high and steep jointed slope excavation, characterized in that The following steps are involved: A. Determine the physical and mechanical parameters of the rock and soil mass and the distribution of the structural surface through engineering geological surveys, and establish a geological generalization model of the slope; B. Based on the generalized geological model of the slope, a numerical model of the slope is established using the continuous medium mechanics analysis method to analyze the dynamic stability of the slope under the step-by-step excavation. If instability occurs, stop excavation and turn to step C, otherwise turn to step F; C. Determine and obtain the potential sliding surface of the slope based on the distribution of the plastic zone of the slope and the settlement of the displacement cloud map; In the step (C), the potential sliding surface of the slope is determined according to the distribution of the plastic zone of the slope and the settlement of the displacement cloud map; The specific criteria for judging the potential sliding surface are: (1) If a continuous plastic zone is formed, the continuous plastic zone is regarded as a potential sliding surface. The method for determining whether a continuous plastic zone is formed is as follows: The plastic zone penetration rate is defined as: in represents the volume of the plastic zone, represents the volume along the sliding zone; when When When , it indicates that the plastic zone is connected; (2) If a displacement-settlement interface appears, and the rock mass below the interface does not undergo displacement or settlement, but the rock mass above the interface undergoes overall displacement or settlement, then the displacement-settlement interface is considered a potential sliding surface; The specific method for determining the displacement settlement interface is to draw a vertical line from the slope surface to the inside of the slope and record the settlement of each unit along the vertical line. Define displacement settlement increments: in Indicates The displacement and settlement of each unit, Indicates Displacement and settlement of each unit; Indicates The distance from the unit to the slope, Indicates The distance of each unit from the slope surface; when When , it means that the displacement settlement no longer changes, that is, The unit at this location is the displacement-settlement interface, and the displacement-settlement of the unit at this location is Indicates the displacement and settlement of the entire project; Any of the above conditions (1) and (2) shall be met; D. Based on the potential sliding surface of the slope obtained in step C, a numerical model of the slope is established using a discontinuous medium mechanics analysis method to analyze the potential instability process of the slope; E. Draw dangerous areas on the slope according to the accumulation range of rock mass after the slope becomes unstable; F: End the dangerous zone.

2. A method for dividing dangerous areas for excavation of high and steep jointed slopes according to claim 1, characterized in that: The method of establishing the slope numerical model by using the continuous medium mechanics analysis method is to establish the slope numerical model by using the joint finite element method.

3. The method for dividing dangerous areas of high and steep jointed slope excavation according to claim 1 is characterized by: In step (B), the dynamic stability of the slope under the action of step-by-step excavation is analyzed; the specific criteria for judging the dynamic stability are: The stability during excavation is determined based on whether the plastic zone is connected, the displacement cloud map settlement, and whether the safety factor is less than 1. If a connected plastic zone is formed, a displacement cloud map interface is generated, or the safety factor is less than 1, the slope is considered to be unstable.

4. The method for dividing dangerous areas of high and steep jointed slope excavation according to claim 1 is characterized by: The specific method of step (D) is: A slope block system model is established according to the potential sliding surface of the slope. By setting multiple groups of shear strength parameters of the potential sliding surface, the potential instability and failure process of the slope under different mechanical parameter conditions is simulated.

5. The method for dividing dangerous areas of high and steep jointed slope excavation according to claim 4 is characterized by: The method of setting multiple groups of shear strength parameters of the potential sliding surface is as follows: setting three groups of shear strength parameters of the potential sliding surface, high, medium and low, according to the internal friction angle of the rock in the area where the potential sliding surface of the slope is located. Determine the high, medium and low shear strength parameters on the potential sliding surface, where the high shear strength parameter ; Middle group shear strength parameters ; Low group shear strength parameters ; The above parameters are all in angle.

6. The method for dividing dangerous areas of high and steep jointed slope excavation according to claim 1 is characterized by: The step (E) divides the slope into dangerous zones according to the accumulation range of the rock mass after the slope becomes unstable; the specific zoning basis is: Prohibited operation area: refers to the area where unstable rock mass can accumulate after the slope fails under high shear strength conditions. This area has a high safety hazard; High-risk area: refers to the area where collapsed rock mass can accumulate after the slope becomes unstable under medium shear strength conditions. This area also has high safety hazards; Medium risk area: refers to the area where collapsed rock mass can accumulate after the slope becomes unstable under the condition of low shear strength. This area still has certain safety hazards; Low risk area: refers to the area where collapsed rock mass cannot accumulate after the slope becomes unstable, but the risk of collapse and rockfall still needs to be paid attention to; Safety zone: The area 90m-110m away from the farthest end of the rock accumulation area under low shear strength conditions. This area is relatively safe and industrial production can be carried out according to actual conditions.

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