A design method for back pressure stability control of stacked load shedding

Abstract

The present invention relates to the field of geotechnical engineering and geological engineering application technology, and provides a method for designing the stability control of load reduction and back pressure of a stacked body, comprising the following steps: dividing the stacked body, obtaining the safety factor of each typical section, and then obtaining the load reduction neutral point and back pressure neutral point of each typical section; obtaining the load reduction neutral line according to the connection of the load reduction neutral points, and obtaining the back pressure neutral line according to the connection of the back pressure neutral points, and then dividing the stacked body into load reduction partitions and back pressure partitions; designing the load reduction surface in the load reduction partition, and designing the back pressure surface in the back pressure partition; updating the typical section and re-obtaining the safety factor; judging whether the safety factor of each typical section meets the requirements, and if so, completing the design. The present invention can overcome the shortcomings of the prior art in designing the load reduction and back pressure scheme of the stacked body, which does not take into account the influence of the soil excavated for load reduction and the soil filled for back pressure on the lateral seismic force, resulting in the calculation results being unconservative and having safety hazards.

Description

Technical Field

[0001] The present invention relates to the field of geotechnical engineering and geological engineering application technology, and in particular to a stacking body load reduction back pressure stability control design method. Background Art

[0002] Load reduction and counterpressure refers to excavating and removing some of the sliding mass at the rear edge of the pile (i.e., the uphill side of the pile), and then filling the soil at the front edge (i.e., the downhill side of the pile). This reduces the downward force of the pile and increases its anti-slip resistance. This measure can quickly suppress deformation of the pile. For pile management, it is both an emergency rescue measure and the most stable long-term method among many pile management measures.

[0003] At present, the design method of the load-reducing and back-pressure prevention pile is mainly based on the classic load-reducing and back-pressure analysis method. This method first takes multiple typical sections along the sliding direction of the pile and divides the cross-section of the pile. It is assumed that load reduction or back-pressure will not only cause changes in the gravity of the soil strip, but also cause changes in the pore water pressure (related to the pore pressure coefficient). Since the test of the pore pressure coefficient is very difficult, this method assumes that a point at the bottom of the sliding surface is the back-pressure neutral point, and the pore pressure coefficient at this point is equal to 1; it is assumed that a point at the sliding surface is the load-reducing neutral point, and the angle between the tangent line at this point and the horizontal line is in represents the effective friction angle of the sliding surface where the bottom edge of the bar is located, F0 represents the safety factor of the typical section, and the pore pressure coefficient is equal to 0. The load-reducing neutral point of each typical section is connected to obtain the load-reducing neutral line, and the back-pressure neutral point of each stacking body section is connected to obtain the back-pressure neutral line, thereby determining the load-reducing zone and the back-pressure zone.

[0004] However, this method has certain limitations. In actual practice, it was found that although this method takes into account the impact of soil excavation and filling on pore water pressure and introduces a pore pressure coefficient, in reality, during the load-reducing and back-pressure construction process, the soil is slowly excavated and filled, which does not cause a cumulative change in pore water pressure. When the load-reducing and back-pressure construction is completed, the excess pore water pressure has basically dissipated, and there is no significant change in the pore water pressure compared to the original pile. On the other hand, this method ignores the impact of the soil excavated by load reduction and the soil filled by back-pressure on the lateral seismic force. After the soil is filled, the seismic force on the soil strip increases, which reduces the anti-sliding force of the soil strip, increases the sliding force, and reduces the stability of the slope. Therefore, the original calculation method will lead to an overestimation of the pile stability calculation results, which is not conservative and is not suitable for actual engineering design. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art in which the load-reducing and counter-pressure schemes for stacking bodies are designed without taking into account the influence of the soil excavated for load reduction and the soil filled for counter-pressure on the lateral seismic force, resulting in unconservative calculation results and potential safety hazards, and to provide a design method for the stability control of load-reducing and counter-pressure stacking bodies.

[0006] In a first aspect, the present invention provides a method for designing a back pressure stability control system for a stacked body, comprising the following steps:

[0007] S1. Obtaining characteristics and geological information of the deposit; dividing the deposit according to the characteristics and geological information of the deposit to obtain multiple typical sections, each of which contains multiple strips;

[0008] S2. Obtain the safety factor of each typical section, and obtain the load-shedding neutral point of each typical section based on the safety factor of each typical section; obtain the back-pressure neutral point of each typical section;

[0009] S3. Obtain a load-reducing neutral line based on a line connecting the load-reducing neutral points of multiple typical sections, and obtain a reverse-pressure neutral line based on a line connecting the reverse-pressure neutral points of multiple typical sections; and divide the stack into load-reducing zones and reverse-pressure zones based on the load-reducing neutral line and the reverse-pressure neutral line.

[0010] S4. Design the load-reducing surface within the load-reducing zone and the back-pressure surface within the back-pressure zone; update each typical section and re-divide the strips and blocks based on the load-reducing surface and the back-pressure surface, and re-obtain the safety factor of each typical section;

[0011] S5. Determine whether the safety factor of each typical section meets the design requirements. If not, return to step S4 and modify the design of the load-reducing surface and / or the back-pressure surface; if so, complete the design.

[0012] The load-reducing and back-pressure stability control design method of the stacking body of the present invention considers the influence of the load-reducing soil at the rear edge of the stacking body and the back-pressure soil at the front edge of the stacking body on the gravity and seismic force acting on the soil of the stacking body, and ignores the influence on the pore water pressure, and proposes an improved load-reducing neutral point and back-pressure neutral point calculation method. On this basis, it clarifies the load-reducing neutral line and back-pressure neutral line determination method of the stacking body and the load-reducing zoning and back-pressure zoning of the stacking body, and further proposes a stability calculation method and design analysis process for the load-reducing and back-pressure prevention stacking body, thereby improving the current problem that the classical load-reducing and back-pressure prevention stacking body design method considers the change of pore water pressure but ignores the influence of seismic force, resulting in the calculation results being too large and tending to be unsafe. Moreover, compared with the classical method, the parameters of the present invention are relatively simple, easy to understand, and quick to calculate, which is convenient for promotion and application.

[0013] At the same time, the present invention reduces the anti-slip moment in the stability calculation of the stacked body and increases the sliding moment by considering the influence of the unloaded soil and the counter-pressure soil on the seismic force, making the stability calculation result conservative and effectively improving the accuracy of the stacked body stability analysis.

[0014] Preferably, in step S4, the load-reducing surface and the back-pressure surface are designed according to the following steps:

[0015] Draw the slope load shedding line in the area enclosed by the load shedding neutral line and the perimeter and close to the uphill side; draw the sliding surface load shedding line in the area enclosed by the slope load shedding line and the perimeter and close to the uphill side. The area enclosed by the slope load shedding line, the sliding surface load shedding line and the perimeter is the load shedding surface;

[0016] A slope surface counter-pressure line is drawn in the area enclosed by the counter-pressure neutral line and the perimeter and close to the downslope side. An outer slope counter-pressure line is drawn outside the area enclosed by the perimeter and close to the downslope side. The area enclosed by the slope surface counter-pressure line and the outer slope counter-pressure line is the counter-pressure surface.

[0017] For the unloading neutral point, if soil excavation is carried out in the area above the unloading neutral point, that is, on the side of the unloading neutral point close to the uphill direction, that is, unloading, it will help to improve the safety factor of the confrontation; for the counter-pressure neutral point, if soil ballasting is carried out in the area below the counter-pressure neutral point, that is, on the side of the counter-pressure neutral point close to the downhill direction, that is, counter-pressure, it will also help to improve the safety factor of the confrontation; based on this, this scheme sets the unloading surface on the unloading neutral line, that is, the area where the line connecting the unloading neutral points is close to the uphill side, and sets the counter-pressure surface on the counter-pressure neutral line, that is, the area where the line connecting the counter-pressure neutral points is close to the downhill side; unloading within the unloading surface and counter-pressure within the counter-pressure surface can improve the safety factor of the stacking body.

[0018] Preferably, in step S4, each typical section is updated according to the following steps:

[0019] Project the intersection of the slope unloading line and the typical section onto the slope to obtain the corresponding slope unloading point; project the intersection of the sliding surface unloading line and the typical section onto the sliding surface to obtain the corresponding sliding surface unloading point; connect the slope projection point and the sliding surface projection point to obtain the corresponding typical section unloading line;

[0020] Projecting the intersection of the slope surface counter-pressure line and the typical section onto the slope surface to obtain the corresponding slope surface counter-pressure point; projecting the intersection of the slope outer counter-pressure line and the typical section onto the slope surface to obtain the corresponding slope outer counter-pressure point; obtaining the counter-pressure line corresponding to the typical section; connecting the slope surface counter-pressure point and the slope outer counter-pressure point with an arc, with the center of the arc located between the slope surface counter-pressure point and the slope outer counter-pressure point along the longitudinal slope direction and the center of the arc located below the slope surface counter-pressure point and the slope outer counter-pressure point along the plumb bob direction, to obtain the counter-pressure line corresponding to the typical section;

[0021] Extend the downslope end of the sliding surface to the inside of the counter-pressure line to obtain the extended sliding surface;

[0022] The area enclosed by the unloading line, counter-pressure line, extended sliding surface and slope surface is used as the updated typical section.

[0023] It should be noted that projection onto the slope surface refers to projection along the plumb bob direction.

[0024] This solution provides a specific operation method for updating the typical cross-section, which can make the shape of the typical cross-section of the stacking body more consistent with the cross-section shape after load reduction and back pressure, so that subsequent calculations are more consistent with actual conditions.

[0025] Preferably, the following steps are further included after step S5:

[0026] S6. Repeat steps S4 to S5 to obtain multiple alternative plans and corresponding safety factors, where the load reduction surface and / or backpressure surface of each alternative plan are designed differently; and obtain the excavation volume and backfill volume of each alternative plan;

[0027] S7. Select the best option from among the alternative options based on their safety factor, excavation volume and backfill volume.

[0028] The present invention obtains multiple load-reducing and counter-pressure alternative schemes and corresponding safety factors of the stacking body, excavation volume and backfill volume by multiple cycles of steps S3 to S5, and obtains the alternative scheme with the highest cost-effectiveness as the optimal scheme through comprehensive comparison. For example, the alternative scheme with the least excavation volume and backfill volume is selected to reduce construction costs, or the alternative scheme with the highest safety factor is selected to ensure construction safety, thereby ensuring the economy and safety of construction; at the same time, multiple cycles of selection can also make the load-reducing surface and counter-pressure surface obtained by the present invention more reliable.

[0029] Preferably, when obtaining the unloading neutral point of each typical section in step S2, the influence of the average height of the strips on the slope stability is ignored.

[0030] When obtaining the unloading neutral point of each typical section, it is necessary to calculate the slope stability, but the slope stability equation is very difficult to solve. The inventors of the present invention have found that if the average height of the bars in the slope stability equation is omitted, not only will the slope stability be easier to solve, but it will also cause the calculated results of the slope stability to be reduced, thereby making the calculation of the safety factor more conservative, that is, more on the safe side. Therefore, this solution chooses to ignore the average height of the bars, which can both simplify the calculation and ensure the safety of the calculation results.

[0031] Preferably, in step S2, the load shedding neutral point of each typical section is obtained according to the following formula:

[0032]

[0033] Where, α n It represents the angle between the tangent line at a point on the sliding surface corresponding to the unloaded neutral point and the horizontal line; represents the effective friction angle of the sliding surface where the bottom edge of the block numbered i is located; K s represents the earthquake influence coefficient; F0 represents the safety factor of the corresponding typical section; i represents the number of the block, i = 1, 2, 3...

[0034] This scheme provides a specific calculation formula for the angle between the tangent line and the horizontal line at a point on the sliding surface corresponding to the load-shedding neutral point, ignoring the average height of the bars, which is used to accurately determine the position of the load-shedding neutral point.

[0035] Preferably, in step S2, the back pressure neutral point of each typical section is obtained according to the following steps:

[0036] A point on the sliding surface along the horizontal direction of the tangent is selected as the neutral point of the back pressure.

[0037] If the unloading neutral point is loaded below it, that is, on the downhill side of the unloading neutral point, the safety factor will continue to increase. Recalculating the unloading neutral point based on this safety factor will reveal that it has shifted downward. Theoretically, when the safety factor approaches infinity, the unloading neutral point will move to the lowest point on the sliding surface, where the tangent line to a point on the sliding surface is horizontal. Therefore, this solution selects a point on the sliding surface where the tangent line is horizontal as the counterpressure neutral point to increase the efficiency of counterpressure in improving the safety factor.

[0038] Preferably, in step S1, the stack is divided according to the following steps:

[0039] A number of typical sections are divided on the stacked body along the transverse slope, and the typical sections are all parallel to the longitudinal slope and the plumb bob direction; the typical sections are divided into a number of strips along the longitudinal slope, and the dividing lines between two adjacent strips are all along the plumb bob direction.

[0040] This solution provides a specific method for dividing the stacking body.

[0041] Preferably, in step S1, the characteristics and geological information of the pile body include the perimeter, sliding surface and shear outlet of the pile body, the internal friction angle, cohesion, and natural density of the pile body and the surrounding rock and soil, the effective internal friction angle and effective cohesion of the sliding surface of the pile body, and the distribution of infiltration lines within the pile body.

[0042] This solution provides the specific deposit characteristics and geological information that should be collected in step S1.

[0043] Preferably, in step S1, the safety factor of each typical section is obtained according to the following steps:

[0044] According to the characteristics of the strips and blocks and the infiltration line, the body force, seismic force, pore water pressure at the bottom of the strips, and the angle between the bottom of the strips and the horizontal plane of each strip are obtained; according to the body force, seismic force, pore water pressure at the bottom of the strips, the angle between the bottom of the strips and the horizontal plane and the effective internal friction angle and effective cohesion of the sliding surface, the sum of the anti-slip moments of the corresponding typical section is obtained, and then the safety factor of the corresponding typical section is obtained.

[0045] This solution provides the calculation process of the safety factor of a typical section.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] The present invention provides a design method for load-reducing and back-pressure stability control of a stacked body. By considering the influence of the load-reducing soil at the rear edge of the stacked body and the back-pressure soil at the front edge of the stacked body on the gravity and seismic force acting on the soil of the stacked body, and ignoring the influence on the pore water pressure, an improved load-reducing neutral point and back-pressure neutral point calculation method is proposed. On this basis, the load-reducing neutral line and back-pressure neutral line determination method of the stacked body and the load-reducing zoning and back-pressure zoning of the stacked body are clarified, and a stability calculation method and design analysis process of the load-reducing and back-pressure prevention stacked body are further proposed, thereby improving the current problem that the classical load-reducing and back-pressure prevention stacked body design method considers the change in pore water pressure but ignores the influence of seismic force, resulting in a large calculation result that tends to be unsafe. Compared with the classical method, the parameters of the present invention are relatively simple, easy to understand, and quick to calculate, which is convenient for promotion and application.

[0048] At the same time, the present invention reduces the anti-slip moment in the stability calculation of the stacked body and increases the sliding moment by considering the influence of the unloaded soil and the counter-pressure soil on the seismic force, making the stability calculation result conservative and effectively improving the accuracy of the stacked body stability analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a flow chart of a stacking body load reduction back pressure stability control design method of the present invention;

[0050] Figure 2 is a characteristic schematic diagram of the stacking body in Example 1;

[0051] Figure 3 is a schematic diagram of the infiltration line of the stacked body in Example 1;

[0052] Figure 4 This is a schematic diagram of a typical cross section of the stacked body in Example 1;

[0053] Figure 5Schematic diagram of the division of the stacked body into strips and blocks, as well as the geometric dimensions and force of the strips in Example 1;

[0054] Figure 6 Schematic diagram of the geometric dimensions of the blocks in the stack in Example 1;

[0055] Figure 7 Schematic diagram of the forces acting on the bars in the stack in Example 1;

[0056] Figure 8 Schematic diagram of the load-reducing neutral point and the reverse-pressure neutral point of the stack in Example 1;

[0057] Figure 9 Schematic diagram of the load-shedding neutral line and the reverse-pressure neutral line of the stack in Example 1;

[0058] Figure 10 is a schematic cross-sectional view of the stacked body in Example 1 after updating the typical cross-section and re-dividing the strips;

[0059] Figure 11 Schematic diagram of the corresponding relationship between the unloading surface and the back pressure surface of the stacking body in Example 1 and the unloading line and the back pressure line in the typical cross section; DETAILED DESCRIPTION

[0060] The present invention will be further described in detail below in conjunction with test examples and specific embodiments. However, this should not be understood as limiting the scope of the present invention to the following embodiments, and all technologies implemented based on the present invention fall within the scope of the present invention.

[0061] Unless otherwise specified, in the description of the specific embodiments of the present invention, the terms indicating orientation or positional relationships such as "upper," "lower," "left," "right," "center," "inside," and "outside" are based on the orientation or positional relationships shown in the accompanying drawings, or are the orientation or positional relationships in which the inventive product / device / apparatus is typically placed when in use. These terms indicating orientation or positional relationships are merely for the purpose of facilitating the description of the present invention or simplifying the description of the specific embodiments to facilitate a quick understanding of the solutions by technicians. They do not indicate or imply that a particular device / component / element must have a specific orientation or be constructed and operated in a specific positional relationship, and therefore should not be construed as limiting the present invention.

[0062] In addition, if the terms "horizontal", "vertical", "overhanging", "parallel" and the like appear, it does not mean that the corresponding devices / components / elements are required to be absolutely horizontal or vertical or overhanging or parallel, but may be slightly tilted or have deviations. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but may be slightly tilted. Alternatively, it can be simply understood that the corresponding devices / components / elements are set in directions such as "horizontal", "vertical", "overhanging", and "parallel", and can have an error / deviation of ±10% relative to the corresponding direction setting, more preferably an error / deviation within ±8%, more preferably an error / deviation within ±6%, more preferably an error / deviation within ±5%, and more preferably an error / deviation within ±4%. As long as the corresponding device / component / element is within the error / deviation range, it can still achieve its role in the solution of the present invention.

[0063] In addition, in the description of the embodiments of the present invention, "several," "plurality," and "a number" represent at least two. It can also be any number such as two, three, four, five, six, seven, eight, nine, or even more than nine.

[0064] Example 1

[0065] like Figure 1 As shown, a design method for stack load reduction back pressure stability control includes the following steps:

[0066] S1. Obtaining characteristics and geological information of the deposit; dividing the deposit according to the characteristics and geological information of the deposit to obtain multiple typical sections, each of which contains multiple strips;

[0067] S2. Obtain the safety factor of each typical section, and obtain the load-shedding neutral point of each typical section based on the safety factor of each typical section; obtain the back-pressure neutral point of each typical section;

[0068] S3. Obtain a load-reducing neutral line based on a line connecting the load-reducing neutral points of multiple typical sections, and obtain a reverse-pressure neutral line based on a line connecting the reverse-pressure neutral points of multiple typical sections; and divide the stack into load-reducing zones and reverse-pressure zones based on the load-reducing neutral line and the reverse-pressure neutral line.

[0069] S4. Design the load-reducing surface within the load-reducing zone and the back-pressure surface within the back-pressure zone; update each typical section and re-divide the strips and blocks based on the load-reducing surface and the back-pressure surface, and re-obtain the safety factor of each typical section;

[0070] S5. Determine whether the safety factor of each typical section meets the design requirements. If not, return to step S4 and modify the design of the load-reducing surface and / or the back-pressure surface; if so, complete the design.

[0071] In an optional implementation, in step S1, in order to ensure the reliability of the calculation results and the prevention and control design of the pile body, it is necessary to obtain the key parameters related to the stability of the pile body as accurately as possible. Therefore, the characteristics of the pile body at least include the perimeter of the pile body, the sliding surface, the shear outlet, the pile body wall, and the pile body bed; the geological information of the pile body at least includes the rock and soil properties of each stratum, such as the internal friction angle, cohesion, and natural density of the pile body and the surrounding rock and soil; and the mechanical parameters of the sliding surface of the pile body, such as the effective internal friction angle and effective cohesion of the sliding surface, and the distribution of infiltration lines in the pile body also need to be collected. The meaning of the characteristics of the pile body is as follows: Figure 2 and Figure 3 shown.

[0072] In an optional embodiment, step S1 includes:

[0073] S1A. Obtain the perimeter, sliding surface, shear opening, and other features of the stockpile; acquisition methods include on-site investigation, stockpile displacement monitoring, core drilling, and other technical means.

[0074] S1B. Obtain formation information such as the internal friction angle, cohesion, and natural density of the pile and surrounding rock and soil. For example, first obtain soil or rock samples of the pile and surrounding rock and soil through coring, and then conduct direct shear tests or triaxial tests.

[0075] S1C. Obtain the effective internal friction angle and effective cohesion of the sliding surface; for example, obtain soil or rock samples from the sliding surface by coring through drilling holes, and then conduct direct shear tests or triaxial tests.

[0076] S1D, obtain the infiltration line in the stack; for example, Figure 3 As shown, water level sensors are arranged in the cored holes, and the water levels of the holes in the same typical section are connected to form an infiltration line.

[0077] It should be noted that there is no fixed order among S1A, S1B, S1C, and S1D. They can be performed in sequence of S1A, S1B, S1C, and S1D, or simultaneously, or the order of some steps can be swapped.

[0078] In an optional embodiment, when dividing the stockpile according to the characteristics of the stockpile and geological information in step S1, dividing the stockpile based on the Swedish striping method includes the following steps:

[0079] S11. Multiple typical sections are divided at intervals along the transverse slope on the pile body. The typical sections are all parallel to the longitudinal slope (i.e., the main sliding direction) and the plumb bob direction. Considering that when performing stability analysis and calculation, the safety factor of some typical sections may be less than the target safety factor, while some may be greater than the target safety factor. Therefore, the number of typical sections is generally not less than 3, and the typical sections should not be too close to the two sides of the pile body perimeter. For example, Figure 4 As shown, in this embodiment, three typical sections are selected from the stacking body and are labeled as I, II, and III respectively.

[0080] S12. Divide the typical section into multiple strips of equal width along the longitudinal slope, with the dividing lines between adjacent strips along the plumb bob direction (parallel to the direction of gravity). The number of strips can be selected arbitrarily, but is generally required to be greater than or equal to 10 and less than or equal to 100, because when the number of strips is too small, the accuracy of the calculation results is lower; when the number of strips is too large, the calculation time increases significantly, and the improvement in the accuracy of the calculation results is limited.

[0081] In an optional embodiment, when obtaining the safety factor for each typical section in step S2, the sum of the sliding moment and the sum of the anti-slip moment of each bar in each typical section are calculated, and finally the safety factor for the corresponding typical section is calculated. This method assumes that the resultant force between the bars is parallel to the bottom edge of the bar and does not affect the reaction force at the bottom of the bar. When calculating the safety factor, only the balance of the moment of the sliding force and the moment of the anti-slip force is considered. The method includes the following steps:

[0082] S21. Obtain the body force, seismic force, pore water pressure at the bottom of the block, and the angle between the bottom of the block and the horizontal plane of each block based on the block characteristics and infiltration line; the meanings of body force, seismic force, pore water pressure at the bottom of the block, and the angle between the bottom of the block and the horizontal plane are as follows: Figures 5 to 7 As shown, in addition, S i Indicates the anti-sliding force of the soil strip; where:

[0083] The formula for physical strength can be expressed as:

[0084]

[0085] Where i represents the number of the bar, i = 1, 2, 3...; W i represents the physical strength of the bar numbered i; γ si Indicates the natural density of the bar numbered i; a i It represents the area of ​​the strip numbered i. The unit can be international units, such as W i Take kN / m, γ si Take kN / m 3 , a i Take m 2 .

[0086] The reaction force at the bottom of the bar can be expressed as:

[0087] N i =W i cosα i -K s W i sinα i +Q i cos(α i -θ i )

[0088] Where N i Represents the reaction force at the bottom of the bar numbered i; αi 表 K represents the angle between the lower boundary of the block numbered i and the horizontal plane; s It represents the earthquake influence coefficient, which is a dimensionless parameter and can be determined according to the relevant provisions of the Code for Seismic Design of Buildings; Q i represents the external load of the bar numbered i; θ i Indicates Q i The angle between the normal line of the upper boundary of the block numbered i and the unit can be international units, such as N i and Q i Take kN / m, θ i Take °.

[0089] The pore water pressure at the bottom of the strip can be expressed as:

[0090]

[0091] Where U i represents the pore water pressure at the bottom of the strip numbered i; γ w Indicates the weight of water; h wi Indicates the water level of the boundary of the block numbered i close to the uphill side; h wi+1 It represents the water level at the boundary of the bar numbered i on the downhill side; b represents the width of the bar; the unit can be an international unit, such as U i Take kN / m, γ w Take kN / m 3 , h wi and h wi+1 Take m.

[0092] S22. Obtain the total anti-sliding moment of the corresponding typical section based on the body force of each strip, seismic force, pore water pressure at the bottom of the strip, angle between the bottom of the strip and the horizontal plane, and effective internal friction angle and effective cohesion of the sliding surface, and then obtain the safety factor of the corresponding typical section. Where:

[0093] The total anti-slip torque can be expressed as:

[0094]

[0095] Where M r represents the total anti-slip moment; R represents the radius of the arc-shaped sliding surface; n represents the total number of bars in the corresponding typical section; c` i represents the effective cohesion of the sliding surface where the bottom edge of the bar numbered i is located; l i Indicates the length of the bottom side of the bar numbered i; It represents the effective friction angle of the sliding surface where the bottom edge of the block numbered i is located; the units can be international units, such as R and l i Take m, Take °, c` i Take kPa, M r Take kN.

[0096] The total sliding torque can be expressed as:

[0097]

[0098] Where, X i Y represents the horizontal distance from the center of gravity of the bar numbered i to the center of the sliding surface; i represents the longitudinal distance from the center of gravity of the bar numbered i to the center of the sliding surface; X qi Y represents the lateral distance between the center point of the top of the block numbered i and the center of the sliding surface when the external load acts on it; qi It represents the longitudinal distance between the center point of the top of the bar numbered i and the center of the sliding surface. The unit can be international units, such as X i , Y i , X qi , Y qi Take m, M s Take kN.

[0099] The safety factor corresponding to a typical section can be expressed as the ratio of the total anti-slip moment to the total slip moment:

[0100]

[0101] Where F0 represents the safety factor corresponding to the typical section and is a dimensionless parameter.

[0102] Substitute M r and M s The expression of , we can get:

[0103]

[0104] or

[0105]

[0106] S23. Calculate the corresponding safety factors for all typical sections according to the steps from S21 to S22 to obtain the safety factors of each typical section and add corresponding subscripts. For example, the safety factors of the typical sections numbered Ⅰ, Ⅱ, and Ⅲ are recorded as F 0Ⅰ 、F 0Ⅱ 、F 0Ⅲ …

[0107] Correspondingly, when the safety factor of the typical section needs to be re-obtained in step S4, the calculation can also be performed according to steps S21 to S23.

[0108] In an optional implementation, the use of load shedding and counter-pressure to prevent and control the pile is actually to excavate and reduce the rock and soil at the rear edge of the pile, and to pile up the rock and soil at the front edge of the pile, thereby reducing the sliding force and increasing the anti-sliding force, thereby improving the stability of the pile. For load shedding and counter-pressure, there are two neutral points, that is, at which load shedding or excavation will not affect the stability of the pile, and they are respectively defined as the load shedding neutral point and the counter-pressure neutral point, such as Figure 8 As shown, N C That is, it represents the load-shedding neutral point, N L It represents the neutral point of the reverse pressure; for different typical sections, in N C and N L Then add the corresponding subscript to distinguish them, for example Figure 9 As shown, N CⅠ , N CⅡ , N CⅢ Respectively represent the load-shedding neutral points of typical sections numbered Ⅰ, Ⅱ, and Ⅲ, N LⅠ , N LⅡ , N LⅢ Respectively represent the respective back-pressure neutral points of the typical sections numbered Ⅰ, Ⅱ, and Ⅲ; correspondingly, in step S2, when obtaining the load-reducing neutral point of each typical section and obtaining the back-pressure neutral point of each typical section according to the safety factor of each typical section, the following steps are included:

[0109] S24. Obtain the unloaded neutral point of each typical section based on the safety factor of each typical section. The derivation process can be referred to as follows:

[0110] When unloading or counter-pressing the pile, the weight of the soil changes, which is denoted by ΔW. During the unloading phase, ΔW is negative, while during the counter-pressing phase, ΔW is positive. Considering the moment balance, the stability of the slope after unloading and counter-pressing at a certain block numbered i in the pile can be expressed as:

[0111]

[0112] Where F1 represents the stability of the slope, which is a dimensionless parameter; h i Indicates the average height of the bar numbered i; the unit can be an international unit, such as h i Take m.

[0113] If the load reduction counter pressure is applied at the position corresponding to the load reduction neutral point, the safety factor remains unchanged, that is, So it can be expressed as:

[0114]

[0115] By simplifying, the above formula can be expressed as:

[0116]

[0117] For this formula, due to the existence of h i This makes the equation difficult to solve, so in an optional embodiment, h i Ignore, make The denominator in the formula increases, that is, F1 decreases. The safety factor F1 obtained in this way is relatively safe and easier to calculate. Ignoring h i After that, the above formula can be simplified to:

[0118]

[0119] The angle between the tangent line and the horizontal line at a point on the sliding surface corresponding to the unloaded neutral point can be expressed as:

[0120]

[0121] Where, α n It represents the angle between the tangent line at a point on the sliding surface corresponding to the unloaded neutral point and the horizontal line.

[0122] It can be seen that when the earthquake influence coefficient K s When α is equal to 0, n equal As the earthquake influence coefficient K s The increase of α n Gradually decreases, that is, the neutral point of load reduction gradually moves downward; for this neutral point of load reduction, excavation of rock and soil in the area above it, that is, "load reduction" will help to improve the safety factor of the pile, that is, improve the stability of the pile, so that this point can be used as the neutral point of load reduction.

[0123] S25. Obtain the back pressure neutral point of each typical section:

[0124] If the unloading neutral point is loaded below it, that is, on the downhill side of the unloading neutral point, the safety factor will continue to increase. Recalculating the unloading neutral point based on this safety factor will reveal that it has shifted downward. Theoretically, when the safety factor approaches infinity, the unloading neutral point will move to the lowest point on the sliding surface, where the tangent line to a point on the sliding surface is horizontal. Therefore, this solution selects a point on the sliding surface where the tangent line is horizontal as the counterpressure neutral point to increase the efficiency of counterpressure in improving the safety factor.

[0125] In an optional implementation, step S3 includes the following steps:

[0126] S31. Obtain the load-reducing neutral line based on the connection line of the load-reducing neutral points of multiple typical sections, and obtain the reverse pressure neutral line based on the connection line of the reverse pressure neutral points of multiple typical sections; since the load-reducing neutral point and the reverse pressure neutral point are fixed points on the typical section of the stacked body, Figure 9 As shown, by connecting the load-shedding neutral point and the reverse-pressure neutral point in each typical section, the load-shedding neutral line and the reverse-pressure neutral line can be obtained; the specific form of the connection includes but is not limited to a broken line and a curve.

[0127] S32, dividing the stack into load shedding zones and back pressure zones according to the load shedding neutral line and the back pressure neutral line; Figure 9 As shown, the two ends of the load-reducing neutral line and the counter-pressure neutral line obtained by connecting the load-reducing neutral point and the counter-pressure neutral point respectively are extended so that they intersect with the opposite perimeter. The area enclosed by the perimeter can be divided into three areas, which are the load-reducing zone, the middle zone and the counter-pressure zone from uphill to downhill. During subsequent construction, load reduction should be carried out in the load-reducing zone and counter-pressure should be carried out in the counter-pressure zone. Load reduction or counter-pressure in the middle zone has little effect on the safety factor, so no engineering measures are required in the middle zone.

[0128] It should be noted that the form of the load-reducing neutral line and the reverse pressure neutral line is related to factors such as the sliding surface and does not necessarily appear as follows. Figure 9 The saddle shape shown may even cause the load-shedding neutral line and the counter-pressure neutral line to be parallel. Therefore, the neutral line needs to be drawn and partitioned according to the specific neutral point calculation results.

[0129] In an optional embodiment, step S4 includes:

[0130] S4A. Draw the slope load shedding line, i.e., the excavation line of the stockpile surface, in the area enclosed by the load shedding neutral line and the perimeter and close to the uphill side; draw the sliding surface load shedding line, i.e., the rear edge limit of the sliding surface excavation, in the area enclosed by the slope load shedding line and the perimeter and close to the uphill side; the area enclosed by the slope load shedding line, the sliding surface load shedding line, and the perimeter is the load shedding surface; if Figure 10As shown, the slope surface load relief line and the sliding surface load relief line can be drawn on the top view of the stacking body with the load relief neutral line.

[0131] S4B. Draw the slope surface counter-pressure line in the area enclosed by the counter-pressure neutral line and the perimeter and close to the downslope side, i.e., the counter-pressure boundary line of the pile surface; draw the slope outer counter-pressure line outside the area enclosed by the perimeter and close to the downslope side, i.e., the outer edge limit of the counter-pressure soil body; the area enclosed by the slope surface counter-pressure line and the slope outer counter-pressure line is the counter-pressure surface; if Figure 10 As shown, the slope surface back pressure line and the off-slope back pressure line can be drawn on the top view of the stacking body with the back pressure neutral line.

[0132] This embodiment can control the safety factor of the stacking body by controlling the unloading surface and the back pressure surface on the stacking body. When the unloading surface and the back pressure surface are selected appropriately, only a small amount of earthwork can be unloaded and back pressured to achieve a significant improvement in the safety factor of the stacking body.

[0133] It should be noted that there is no fixed order between S4A and S4B. They can be performed sequentially according to S4A and S4B, or simultaneously, or the order of some steps can be swapped.

[0134] In an optional embodiment, in step S4, each typical section is updated according to the following steps:

[0135] S41. Project the intersection of the slope unloading line and the typical section onto the slope to obtain the corresponding slope unloading point; project the intersection of the sliding surface unloading line and the typical section onto the sliding surface to obtain the corresponding sliding surface unloading point; connect the slope projection point and the sliding surface projection point to obtain the unloading line of the corresponding typical section.

[0136] S42. Project the intersection of the slope surface back pressure line and the typical section onto the slope surface to obtain the corresponding slope surface back pressure point; project the intersection of the slope outer back pressure line and the typical section onto the slope surface to obtain the corresponding slope outer back pressure point; according to the fill side slope slope of 1:1.5 and the backfill top surface slope of 1:25, connect the slope surface back pressure point and the slope outer back pressure point with a polyline to obtain the back pressure line of the corresponding typical section.

[0137] S43, extending the end of the sliding surface close to the downslope to the inside of the counter-pressure line to obtain an extended sliding surface; Figure 11 As shown, the sliding surface is an arc shape. By extending it toward the counter-pressure line until it intersects with the counter-pressure line, the sliding surface extension line can be obtained. The sum of the original sliding surface and the sliding surface extension line is the extended sliding surface.

[0138] S44, the area enclosed by the load reduction line, counter pressure line, extended sliding surface, and slope surface is used as the updated typical section. Figure 11 As shown in the figure, when the safety factor of the typical section is subsequently obtained again, the updated typical section should be divided into strips and blocks and the safety factor should be calculated.

[0139] In an optional embodiment, since the load-reducing and back-pressure-preventing measures need to consider not only the safety factor of the stack itself but also issues such as engineering economics and construction difficulty, and when the safety factor of a typical section is much greater than the target safety factor, there is a problem that the load-reducing surface and the back-pressure surface may be too conservative, which may also result in excessive earth excavation or backfilling, thereby leading to excessively high project costs; therefore, the following steps are further included after step S5:

[0140] S6. Repeat steps S4 to S5 to obtain multiple alternative plans and corresponding safety factors, where the load reduction surface and / or backpressure surface of each alternative plan are designed differently; obtain the excavation volume and backfill volume of each alternative plan; wherein:

[0141] The excavation volume and backfill volume can be expressed as:

[0142]

[0143] Where G c Indicates the amount of excavated earth; G L represents the backfill volume; j represents the number of the typical section, m represents the total number of typical sections; A Cj Indicates the load reduction area; A Lj Indicates the back pressure area; the unit can be international units, such as G c and G L Take m 3 , A Cj and A Lj Take m 2 .

[0144] S7. Select the best option from among the alternative options based on their safety factor, excavation volume, and backfill volume. For example, select the option with the least excavation volume and backfill volume to reduce construction costs, or select the option with the highest safety factor to ensure construction safety, thereby ensuring the economy and safety of the construction.

[0145] Example 2

[0146] Based on Example 1, this example provides a calculation example containing specific data, including the following steps:

[0147] S1. Obtain the characteristics and geological information of the deposit. Through on-site geological surveys, determine the deposit's perimeter, sliding surface, shear opening, and other characteristics. Core sampling of the deposit and surrounding rock and soil, followed by direct shear tests, revealed that the internal friction angle of the soil within the deposit was 23.5°, the cohesion was 6.5 kPa, and the natural density was 14.8 kN / m³. The friction angle of the soil outside the deposit was 25.8°, the cohesion was 8.2 kPa, and the natural density was 15.2 kN / m³. Direct shear tests determined that the effective internal friction angle of the soil on the sliding surface was 16.7° and the effective cohesion was 2.4 kPa. The distribution curve of the infiltration line within the slope was obtained by measuring the groundwater level.

[0148] The deposit body is divided according to its characteristics and geological information to obtain multiple typical sections, each of which contains multiple strips. Three typical sections are selected on the deposit body parallel to the sliding direction, and the section numbered I is divided into 17 strips, the section numbered II is divided into 22 strips, and the section numbered III is divided into 19 strips.

[0149] S2, obtain the safety factor of each typical section; calculate the safety factor of each typical section numbered Ⅰ, Ⅱ, Ⅲ according to steps S21 to S23 in Example 1 and record them as F 0Ⅰ 、F 0Ⅱ 、F 0Ⅲ ; Among them, the earthquake influence coefficient K s According to the Code for Seismic Design of Buildings, take 0.16 and calculate F 0Ⅰ =1.09, F 0Ⅱ =1.03, F 0Ⅲ =1.07.

[0150] Obtain the load-reducing neutral point of each typical section according to the safety factor of each typical section; according to the formula in step S24 Calculation shows that the load-shedding neutral point N of section No. Ⅰ is CⅠ α n =6.29°, the unloaded neutral point N of the section numbered Ⅱ CⅡ α n =7.15°, the unloaded neutral point N of section number Ⅲ CⅢ α n =6.57°.

[0151] Obtain the back pressure neutral point of each typical section; according to step S25, the decompression neutral point of each typical section is the point along the horizontal direction of the tangent line on the corresponding sliding surface, that is, the lowest point.

[0152] S3. Obtain a load-reducing neutral line based on the connection of the load-reducing neutral points of multiple typical sections, and obtain a reverse-pressure neutral line based on the connection of the reverse-pressure neutral points of multiple typical sections; divide the stacking body into load-reducing partitions and reverse-pressure partitions based on the load-reducing neutral line and the reverse-pressure neutral line.

[0153] S4. Design the load-reducing surface within the load-reducing zone and the back-pressure surface within the back-pressure zone.

[0154] Update each typical section according to the unloading surface and the back pressure surface and re-divide the strips and blocks to re-obtain the safety factor of each typical section; when re-obtaining the safety factor of each typical section, still follow the steps S21 to S23 to calculate the updated F 0Ⅰ =1.28, F 0Ⅱ =1.23, F 0Ⅲ =1.29.

[0155] S5. Determine whether the safety factor of each typical section is greater than or equal to the target safety factor. In this embodiment, the target safety factor is 1.3. Therefore, it is necessary to return to S4 and modify the design of the unloading surface and / or the back pressure surface until the safety factor of each typical section is greater than or equal to the target safety factor. The design is completed and this solution can be used as an alternative solution.

[0156] S6. Repeat steps S4 to S5 to obtain multiple alternative solutions and corresponding safety factors. The load reduction surface and / or backpressure surface design of each alternative solution is different; obtain the excavation volume and backfill volume of each alternative solution. In this embodiment, steps S4 to S5 are repeated until at least five different alternative solutions exist. The safety factor and total volume (the sum of the excavation volume and the backfill volume) of each alternative solution are shown in the following table:

[0157] Table 1. Alternative solutions for load shedding and back pressure

[0158]

[0159] S7. Based on the safety factor, excavation volume and backfill volume of each alternative plan, the best plan is selected from the alternative plans as Plan 3, which has the least volume of earthwork when the safety factor meets the target safety factor of 1.3.

[0160] The above are only preferred embodiments of the present invention and are 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 scope of protection of the present invention.

Claims

1. A design method for stacking body load reduction back pressure stability control, characterized in that: The following steps are included: S1. Obtaining characteristics and geological information of the deposit; dividing the deposit according to the characteristics and geological information of the deposit to obtain multiple typical sections, each of which contains multiple strips; S2. Obtain the safety factor of each typical section, and obtain the load-shedding neutral point of each typical section based on the safety factor of each typical section; obtain the back-pressure neutral point of each typical section; S3. Obtain a load-reducing neutral line based on a line connecting the load-reducing neutral points of multiple typical sections, and obtain a reverse-pressure neutral line based on a line connecting the reverse-pressure neutral points of multiple typical sections; and divide the stack into load-reducing zones and reverse-pressure zones based on the load-reducing neutral line and the reverse-pressure neutral line. S4. Design the load-reducing surface within the load-reducing zone and the back-pressure surface within the back-pressure zone; update each typical section and re-divide the strips and blocks based on the load-reducing surface and the back-pressure surface, and re-obtain the safety factor of each typical section; S5. Determine whether the safety factor of each typical section meets the design requirements. If not, return to step S4 and modify the design of the load-reducing surface and / or the back-pressure surface. If so, complete the design. In step S1, the stacking body is divided according to the following steps: a plurality of typical sections are divided on the stacking body along the transverse slope, wherein the typical sections are parallel to the longitudinal slope and the plumb bob direction; a plurality of strips are divided along the longitudinal slope, wherein the dividing lines between two adjacent strips are along the plumb bob direction; When obtaining the unloading neutral point of each typical section in step S2, the influence of the average height of the strips on the slope stability is ignored; In step S2, the load shedding neutral point of each typical section is obtained according to the following formula: Where, It represents the angle between the tangent line at a point on the sliding surface corresponding to the unloaded neutral point and the horizontal line; Indicates the number The effective friction angle of the sliding surface where the bottom edge of the bar is located; represents the earthquake influence coefficient; Indicates the safety factor corresponding to the typical section; Indicates the number of the bar, =1, 2, 3...; In step S2, the back pressure neutral point of each typical section is obtained according to the following steps: a point on the sliding surface along the horizontal direction of the tangent line is selected as the back pressure neutral point; In step S4, the load reduction surface and the back pressure surface are designed according to the following steps: a slope load reduction line is drawn in an area surrounded by the load reduction neutral line and the perimeter and close to the uphill side; a sliding surface load reduction line is drawn in an area surrounded by the slope load reduction line and the perimeter and close to the uphill side; the area surrounded by the slope load reduction line, the sliding surface load reduction line, and the perimeter is the load reduction surface; a slope back pressure line is drawn in an area surrounded by the back pressure neutral line and the perimeter and close to the downhill side; an outer slope back pressure line is drawn outside the area surrounded by the perimeter and close to the downhill side; the area surrounded by the slope back pressure line and the outer slope back pressure line is the back pressure surface; In step S4, each typical section is updated according to the following steps: projecting the intersection of the slope unloading line and the typical section onto the slope to obtain the corresponding slope unloading point; projecting the intersection of the sliding surface unloading line and the typical section onto the sliding surface to obtain the corresponding sliding surface unloading point; connecting the slope projection point and the sliding surface projection point to obtain the unloading line of the corresponding typical section; projecting the intersection of the slope counter-pressure line and the typical section onto the slope to obtain the corresponding slope counter-pressure point; projecting the intersection of the slope outer counter-pressure line and the typical section onto the slope to obtain the corresponding slope outer counter-pressure point; obtaining the counter-pressure line of the corresponding typical section; using an arc to connect the slope counter-pressure point and the slope outer counter-pressure point, the center of the arc is located between the slope counter-pressure point and the slope outer counter-pressure point along the longitudinal slope direction, and the center of the arc is located below the slope counter-pressure point and the slope outer counter-pressure point along the plumb bob direction to obtain the counter-pressure line of the corresponding typical section; extending the end of the sliding surface close to the downslope to the inside of the counter-pressure line to obtain the extended sliding surface; The area enclosed by the unloading line, counter-pressure line, extended sliding surface and slope surface is used as the updated typical section.

2. A stacking body load reduction back pressure stability control design method according to claim 1, characterized in that: After step S5, the following steps are further included: S6. Repeat steps S4 to S5 to obtain multiple alternative plans and corresponding safety factors, where the load reduction surface and / or backpressure surface of each alternative plan are designed differently; and obtain the excavation volume and backfill volume of each alternative plan; S7. Select the best option from among the alternative options based on their safety factor, excavation volume and backfill volume.

3. A stacking body load reduction back pressure stability control design method according to any one of claims 1 to 2, characterized in that: In step S1, the characteristics and geological information of the pile include the perimeter, sliding surface and shear outlet of the pile, the internal friction angle, cohesion and natural density of the pile and the surrounding rock and soil, the effective internal friction angle and effective cohesion of the sliding surface of the pile, and the distribution of infiltration lines within the pile.

4. A stacking body load reduction back pressure stability control design method according to claim 3, characterized in that: In step S1, the safety factor of each typical section is obtained according to the following steps: According to the characteristics of the strips and blocks and the infiltration line, the body force, seismic force, pore water pressure at the bottom of the strips, and the angle between the bottom of the strips and the horizontal plane of each strip are obtained; according to the body force, seismic force, pore water pressure at the bottom of the strips, the angle between the bottom of the strips and the horizontal plane and the effective internal friction angle and effective cohesion of the sliding surface, the sum of the anti-slip moments of the corresponding typical section is obtained, and then the safety factor of the corresponding typical section is obtained.

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