Back pressure protection way optimization design method and system for high fill slope

Abstract

The invention relates to the technical field of high fill side slopes, in particular to a back pressure protection way optimization design method and system for a high fill side slope, the optimization design method is used for an integral slip plane after filling a side slope on a foundation and carrying out back pressure treatment, and the integral slip plane after filling the side slope on the foundation and carrying out back pressure treatment has four types, the four sliding surfaces include (1) a sliding surface which is cut out from the upper part of the protective road when the interior of the filling body is damaged, (2) a sliding surface which is cut out from the upper part of the protective road by a deep arc of an original filling side slope, (3) a composite sliding surface which is connected with an arc and a straight line, and (4) a deep arc sliding surface which is reversely pressed on the protective road. By using the optimization design method, the method has the advantages that the slope is kept stable with the minimum earthwork volume, and the engineering cost is low, and the problems that in the previous engineering construction process, a reaction protection way is not economical enough and not reasonable enough, and the slope is prone to sliding due to the fact that the dead weight of the back pressure protection way is too large are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of high-filled slopes, and particularly to an optimized design method and system for a counterweight berm for high-filled slopes. Background Technique

[0002] With the rapid development of infrastructure construction in western China, during the construction of projects such as airport runways, high-speed railways, and expressways, a large number of high-filled slope projects have emerged. A large number of engineering practices have proved that during the project construction process, it is often necessary to conduct counterweight treatment on the toe of the high-filled slope to improve the slope stability, which is a cost-effective and effective method. This treatment method has been widely applied in projects such as highway embankments, airport high fills, foundation pits, and the water storage side of dams.

[0003] However, during the previous project construction process, when designing the counterweight berm of the high-filled slope, the height of the counterweight berm often was determined by experience, generally taking 1 / 3 to 1 / 2 of the slope height. However, under the condition of the same counterweight width, when the counterweight height takes 1 / 3 to 1 / 2 of the slope height, the slope stability safety factor does not necessarily increase with the increase of the counterweight height. At this time, in order to meet the slope stability requirements, it is necessary to increase the width of the counterweight berm. The counterweight berm is often neither economical nor reasonable, resulting in a large number of slope landslide problems. Therefore, we propose an optimized design method and system for a counterweight berm for high-filled slopes. Summary of the Invention

[0004] The purpose of the present invention is to provide an optimized design method and system for a counterweight berm for high-filled slopes, which have the advantages of maintaining slope stability with the least amount of earthwork and low project cost, and solve the problem that during the previous project construction process, when designing the counterweight berm of the high-filled slope, the height of the counterweight berm often was determined by experience, generally taking 1 / 3 to 1 / 2 of the slope height. However, under the condition of the same counterweight width, when the counterweight height takes 1 / 3 to 1 / 2 of the slope height, the slope stability safety factor does not necessarily increase with the increase of the counterweight height. At this time, in order to meet the slope stability requirements, it is necessary to increase the width of the counterweight berm. The counterweight berm is often neither economical nor reasonable, resulting in a large number of slope landslide problems.

[0005] To achieve the above purpose, the present invention provides the following technical solution: An optimized design method for a counterweight berm for high-filled slopes, which is used for the overall slip surface after filling a slope on the foundation and conducting counterweight treatment. There are four types of overall slip surfaces after filling a slope on the foundation and conducting counterweight treatment, namely: ① a slip surface where failure occurs in the filling body and cuts out from the upper part of the berm; ② a deep circular arc of the original filled slope cutting the berm type slip surface; ③ a circular arc connected to a straight line composite type slip surface; and ④ a deep circular arc type slip surface of the counterweight berm itself. The method includes the following steps:

[0006] S1: Assume the berm width B f is large enough. Temporarily ignore the slip surface ④, and determine the minimum height H of the surcharge berm through the slip surfaces ① and ② fmin ;

[0007] S2: Assume the berm width B f is large enough, and determine the maximum height H of the surcharge berm through the slip surface ④ fmax ;

[0008] S3: Check if H fmin ≤H fmax holds. If not, it means that this surcharge treatment method cannot meet the stability requirements of the slope, and other treatment methods should be comprehensively adopted; if it holds, proceed to S4;

[0009] S4: Take the height H of the surcharge berm as H fmin , and determine the width B of the surcharge berm with the slip surface ③ f ;

[0010] S5: Check if B fm exceeds the maximum allowable surcharge width B fmax : If B fm ≤B fmax , then H fmin , B fm are the height and width of the surcharge berm required for the final design; otherwise, proceed to S6;

[0011] S6: Take the surcharge berm width as B fmax , and determine the height H of the surcharge berm through the slip surfaces ① and ② fm ;

[0012] S7: Check if H fm ≤H fmax holds. If it holds, then H fm , B fmax are the optimal cross-sectional height and width of the surcharge berm; if not, it means that this surcharge treatment method cannot meet the stability requirements of the slope, and other treatment methods must be adopted to keep the slope stable.

[0013] Preferably, the four overall failure modes after surcharge treatment are: ① the slip surface where failure occurs in the filling body and is cut out from the upper part of the berm, ② the deep circular arc cutting the berm type slip surface of the original fill slope, ③ the circular arc connected to the straight line composite type slip surface, and ④ the deep circular arc type slip surface of the surcharge berm itself.

[0014] Preferably, the calculation method of the safety factor of the ① slip surface where failure occurs in the filling body and is cut out from the upper part of the berm includes the following steps:

[0015] a: Take the reduction factor of the strength parameter of this type of slip surface F = F (0) =1, for the fill body c, The value is reduced as follows:

[0016] cr = c / F;

[0017] Where: c r , are the cohesion and internal friction angle of the compacted mass after strength reduction;

[0018] b: According to Check the stability calculation diagram of homogeneous simple soil slope by Soviet scholar Lobasov and get the stability number N at this time (0) , and then calculate the slope stability safety factor F defined by Taylor according to the following formula s2 (0) :

[0019]

[0020] Where: Hc is the maximum height that the slope can reach to remain stable after strength reduction; H is the height of the slope formed on the upper part of the berm; γ is the bulk density of the slope soil layer;

[0021] c: If F s2 (0) >1, then increase the strength parameter reduction factor to F (1) , repeat steps a and b; if F s2 (0) <1, then reduce the strength parameter reduction factor to F (1) , repeat steps a and b until F s2 (n) = Until 1 o'clock.

[0022] Preferably, the method for calculating the safety factor of the sliding surface of the deep arc cut berm type of the original fill slope ② comprises the following steps:

[0023] a: The simplified calculation formula of the safety factor of the soil in the middle part B'BCC' is:

[0024]

[0025] In the formula: c, ——The shear strength index of relatively soft soil layer;

[0026] W——weight of soil B'BCC';

[0027] l is the length of the sliding surface on the relatively soft soil layer;

[0028] E a 、E p——active earth pressure and passive earth pressure respectively;

[0029] b: Take the reduction factor of the strength parameter of this type of slip surface F = F (0) =1, for the fill and foundation soil layer c, The values ​​are all reduced according to the formula;

[0030] c: The reduced strength parameter cr (0) , Substituting into the formula, the safety factor F of the middle part of the soil B'BC C' can be calculated s (0) ;

[0031] d: If F s (0) >1, then increase the strength parameter reduction factor to F (1) , repeat steps b and c; if F s (0) <1, then reduce the strength parameter reduction factor to F (1) , repeat steps b and c until F s (n) = Until 1 o'clock.

[0032] Preferably, the calculation method of the safety factor of the composite sliding surface of arc-to-straight line (③) includes the following contents:

[0033] a: The simplified calculation formula of the safety factor of the middle part of the soil B'BCC' can be used by the simplified calculation formula of the safety factor in step a of ② the calculation method of the safety factor of the sliding surface of the deep arc cut berm type of the original fill slope;

[0034] b: Calculate the passive earth pressure E p The influence of the berm soil outside point C' on the passive earth pressure is not considered.

[0035] Preferably, the calculation method of the safety factor of the deep arc-shaped sliding surface of the anti-pressure berm itself includes the following contents:

[0036] a: The simplified calculation formula of the safety factor of the soil B'BCC' on the right side of the berm can be calculated by the simplified calculation formula of the safety factor in step a of ② Calculation method of the safety factor of the sliding surface of the deep arc cut berm type of the original fill slope;

[0037] b: ④ The calculation steps of the stability safety factor of the deep arc-shaped sliding surface of the counter-pressure berm itself refer to the calculation steps of the stability safety factor of the deep arc-cut berm sliding surface of the original fill slope and the composite sliding surface of the arc-to-straight line.

[0038] Preferably, the safety factor of the high fill slope is 1.3.

[0039] A back pressure berm optimization system for high fill slopes, the optimization system comprising a slope data acquisition module, a slope data optimization processing module, a storage module, a performance comparison module and a data display module, wherein:

[0040] Slope data collection module, used to collect various data of high fill slope;

[0041] The slope data optimization processing module is used to calculate the most optimized solution based on the collected data;

[0042] Storage module, used to store and organize various data and generated optimization solutions;

[0043] The performance comparison module compares and verifies the obtained optimization solutions multiple times;

[0044] The data display module is used to display the generated solutions.

[0045] Preferably, the storage module includes a memory stick, a memory card and a cloud system.

[0046] Preferably, the data display module includes a computer, a mobile phone and a tablet.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] 1. The present invention can determine the most economical berm section for single-stage backpressure treatment of high fill slopes through only a small amount of calculation. This method fills the gap in the current optimization design of backpressure berms for high fill projects in mountainous areas of the southwest, and has a certain reference value for the design and construction of actual high fill projects.

[0049] 2. The present invention proposes a complete set of optimization design methods for single-stage backpressure treatment of slopes, and also proposes a simplified algorithm for the safety factors of three typical sliding surfaces involved in the optimization design. It has been verified that the relative error of the safety factor of each sliding surface does not exceed 12%; the relative error of the optimization design of the backpressure protection section does not exceed 20%, among which the relative error of the safety factors of the second and third types of sliding surfaces calculated by the simplified algorithm does not exceed 5%; for the more common engineering geological conditions such as the presence of a hard crust layer, the relative error of the safety factors of the second and third types of sliding surfaces calculated by the simplified algorithm does not exceed 2%, and the accuracy is higher.

[0050] 3. Among the various simplified calculation methods of the present invention, the depth of the horizontal section of the three-fold slip surface that minimizes the relative error is related to factors such as the friction angle of the relatively weak layer. Under the soil layer parameters and other various conditions, after verification, the simplified algorithm has the highest accuracy when the depth of the horizontal section of the three-fold slip surface is taken as the bottom of the relatively weak layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a schematic diagram of the slope failure mode when the single-stage back pressure slope foot is applied to the present invention;

[0052] Figure 2 It is a structural flow chart of the present invention;

[0053] Figure 3 It is the stability calculation diagram of homogeneous simple soil slope of the present invention;

[0054] Figure 4 This is a simplified schematic diagram of the second type of slip surface of the present invention;

[0055] Figure 5 This is a simplified schematic diagram of the third type of slip surface of the present invention;

[0056] Figure 6 This is a simplified schematic diagram of the fourth type of slip surface of the present invention;

[0057] Figure 7 A schematic diagram of a three-fold sliding surface of the present invention;

[0058] Figure 8 This is a schematic diagram of high fill slope calculation in the present invention;

[0059] Figure 9 For the present invention B f H f / H 2 With the back pressure height ratio H f / H change curve diagram;

[0060] Figure 10 This is a system block diagram of the present invention. DETAILED DESCRIPTION

[0061] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0062] See also Figures 1-10 As shown, the present invention provides a technical solution: a method and system for optimizing the design of a back-pressure berm for a high fill slope, the optimization design method is used for the overall slip surface of the fill slope on the foundation and after the back-pressure treatment, the overall slip surface of the fill slope on the foundation and after the back-pressure treatment has four types, ① the fill body is damaged and sheared out from the upper part of the berm type slip surface, ② the original fill slope deep arc cutting berm type slip surface, ③ arc connecting straight line composite slip surface and ④ the back-pressure berm itself deep arc type slip surface four kinds of slip surfaces, including the following steps:

[0063] This technical solution adopts the typical engineering geological conditions of the southwestern mountainous area. Figure 1 There are two types shown: one is a soft soil layer with an average depth of about 10m on the bedrock Figure 1 (a); The second is that there are soft layers and hard shell layers of a certain depth from the top of the bedrock upwards. Figure 1 (b) In actual engineering, the latter is often more common. After the slope is filled on this foundation and the back pressure is treated, the overall failure mode can be divided into four categories, such as Figure 1 Slip surfaces ①, ②, ③, and ④ are shown as follows: Slip surface ① is a "slip surface that is sheared out from the upper part of the berm due to damage in the fill"; Slip surface ② is a "deep arc-cutting berm slip surface of the original fill slope"; Slip surface ③ is a "composite arc-connected straight line slip surface"; Slip surface ④ is a "deep arc slip surface of the counter-pressure berm itself". In view of the above typical engineering geological conditions and four failure modes, this paper analyzes and proposes that when the single-stage counter-pressure slope foot method is used to improve the slope stability, it can be Figure 2 The process shown determines Figure 1 Cross section of the medium back-pressure berm.

[0064] It is understandable that: Figure 2 and elsewhere in this section, B fmax It is the maximum back pressure width actually allowed.

[0065] S1: Assumed berm width B f Large enough, without considering the sliding surface ④, the minimum height H of the back pressure berm is determined by the sliding surfaces ① and ② fmin ;

[0066] It is understandable that: that is, increasing H f , in order to satisfy the calculation of the slope safety factor according to the sliding surfaces ① and ②, which is exactly equal to 1.3. At this time, H f That is H fmin The basis of this step is that the safety factors corresponding to sliding surfaces ① and ② obviously increase with the increase of the height of the back-pressure berm.

[0067] S2: Assumed berm width B f Large enough, the maximum height H of the back pressure berm is determined by the sliding surface ④ fmax ;

[0068] It can be understood that: that is, increasing H f , so that the safety factor calculated according to the slip surface ④ gradually decreases to just equal to 1.3.

[0069] S3: Verify H fmin ≤H fmax Is it established? If not established, it means that this back pressure treatment method cannot make the slope meet the stability requirements, and other treatment methods should be adopted in combination; if established, enter S4;

[0070] S4: Take the height of the back pressure guardway H = H fmin , the width B of the back pressure berm is determined by the sliding surface ③ f ;

[0071] It is understandable that: that is, increasing B f To B fm , so that the safety factor of sliding surface ③ is exactly equal to 1.3.

[0072] S5: Verify B fm Whether it exceeds the maximum allowable back pressure width B fmax :If B fm ≤B fmax , then H fmin , B fm The height and width of the back pressure berm required for the final design; otherwise, enter S6;

[0073] It should be noted that since the airport high fill slope discussed in this article is built in a barren mountain and slope area, there are almost no other important buildings and facilities nearby, so the actual maximum allowable back pressure width B fmax It is often much larger than the B calculated in this step. fm Therefore, in most cases, the optimization design can be completed in this step.

[0074] S6: Take the width of the back pressure berm as B fmax , determine the back pressure berm height H through sliding surfaces ① and ② fm ;

[0075] S7: Verify H fm ≤H fmax Is it true: If true, then H fm , B fmax is the optimal cross-sectional height and width of the back-pressure berm; if it is not true, it means that this back-pressure treatment method cannot make the slope meet the stability requirements, and other treatment methods must be used to keep the slope stable.

[0076] Specifically, there are four types of overall failure modes after back pressure treatment: ① a shear-type slip surface that occurs in the fill and cuts out from the upper part of the berm, ② a deep arc slip surface of the original fill slope cutting the berm, ③ a composite slip surface of arc connecting to a straight line, and ④ a deep arc slip surface of the back pressure berm itself.

[0077] Specifically, ① the calculation method of the safety factor of the sliding surface of the type that is damaged in the fill and sheared out from the upper part of the berm includes the following steps:

[0078] a: Take the reduction factor of the strength parameter of this type of slip surface F = F (0) =1, for the fill body c, The value is reduced as follows:

[0079] cr = c / F;

[0080] Where: c r , are the cohesion and internal friction angle of the compacted mass after strength reduction;

[0081] b: According to Look up the calculation diagram of homogeneous simple soil slope stability by Soviet scholar Lobasov, such as Figure 3 As shown, the stable number N is obtained at this time (0) , and then calculate the slope stability safety factor F defined by Taylor according to the following formula s2 (0) :

[0082]

[0083] Where: Hc is the maximum height that the slope can reach to remain stable after strength reduction; H is the height of the slope formed on the upper part of the berm; γ is the bulk density of the slope soil layer;

[0084] It should be noted that the slope safety factor F defined by Taylor is s2 It is different from the safety factor defined by the conventional method, but when the slope is in the critical state of failure, F s2 The slope stability safety factor is the same as that defined by the conventional method, which is equal to 1.

[0085] c: If F s2 (0) >1, then increase the strength parameter reduction factor to F (1) , repeat steps a and b; if F s2 (0) <1, then reduce the strength parameter reduction factor to F (1) , repeat steps a and b until F s2 (n) = Until 1 o'clock.

[0086] It can be understood that the corresponding strength parameter reduction factor F (n) It is the stability safety factor of the slope sliding along the first type of slip surface.

[0087] Specifically, the calculation method of the safety factor of the sliding surface of the deep arc cut berm type of the original fill slope includes the following steps:

[0088] In this technical solution, taking the engineering geological conditions with a hard crust as an example, the second type of slip surface can be simplified as follows: Figure 4 The shown slip surface is a broken line.

[0089] a: The simplified calculation formula of the safety factor of the soil in the middle part B'BCC' is:

[0090]

[0091] In the formula: c, ——The shear strength index of relatively soft soil layer;

[0092] W——weight of soil B'BCC';

[0093] l is the length of the sliding surface on the relatively soft soil layer;

[0094] E a 、E p ——active earth pressure and passive earth pressure respectively;

[0095] Understandably, When the slope height is 0, according to analysis, the difference between the slope height and the berm height is greater than 4c / γ (γ is the bulk density of the fill and the back pressure berm). When the depth of the horizontal section of the three-fold sliding surface is taken as the bottom of the weak layer and the top of the soft layer, the active earth pressure E a The increment is greater than the passive earth pressure E on the right side p The increment of . Since the left slope height of the middle part of the soil B'BCC' is much greater than the height of the right berm, it can be seen from the formula: when the horizontal section is taken at the bottom of the layer, the safety factor is smaller and closer to the minimum safety factor. The larger the value, the deeper the horizontal section of the three-fold slip surface is taken as the bottom of the weak layer and the top of the soft layer, and E p The more the term increases, the more E a The smaller the term increases, the smaller the safety factor is and the closer it is to the accurate value when it is large enough. Since the value relative to the soft layer is generally small, all simplified algorithms proposed in this paper take the horizontal segment of the three-fold slip surface at the bottom of the soft layer.

[0096] b: Take the reduction factor of the strength parameter of this type of slip surface F = F (0) =1, for the fill and foundation soil layer c, The values ​​are all reduced according to the formula;

[0097] c: The reduced strength parameter cr (0) , Substituting into the formula, the safety factor F of the middle part of the soil B'BC C' can be calculated s (0) ;

[0098] d: If F s (0) >1, then increase the strength parameter reduction factor to F (1) , repeat steps b and c; if F s (0) <1, then reduce the strength parameter reduction factor to F (1) , repeat steps b and c until Fs (n) = Until 1 o'clock.

[0099] It can be understood that the corresponding strength parameter reduction factor F (n) It is the stability safety factor of the slope sliding along the second type of slip surface.

[0100] Specifically, the calculation method of the safety factor of the arc-to-straight line composite sliding surface includes the following contents:

[0101] In this technical solution, taking the engineering geological conditions with a hard crust as an example, the third type of slip surface can be simplified as follows: Figure 5 The shown slip surface is a broken line.

[0102] a: The simplified calculation formula of the safety factor of the middle part of the soil B'BCC' can be used by the simplified calculation formula of the safety factor in step a of ② the calculation method of the safety factor of the sliding surface of the deep arc cut berm type of the original fill slope;

[0103] b: Calculate the passive earth pressure E p The influence of the berm soil outside point C' on the passive earth pressure is not considered.

[0104] Specifically, the calculation method of the safety factor of the deep arc-shaped sliding surface of the counterpressure berm itself includes the following contents:

[0105] In this technical solution, since the slope ratio of the airport high fill slope and the berm is usually no more than 1:2, and the strength of the fill (or berm) soil layer is higher than the strength of the foundation soil layer above the bedrock, when the berm itself fails, its failure mode is generally the bottom of the slope. At this time, taking the engineering geological conditions with a hard crust as an example, the fourth type of slip surface can be simplified as Figure 6 The shown slip surface is a broken line.

[0106] a: The simplified calculation formula of the safety factor of the soil B'BCC' on the right side of the berm can be calculated by the simplified calculation formula of the safety factor in step a of ② Calculation method of the safety factor of the sliding surface of the deep arc cut berm type of the original fill slope;

[0107] b: ④ The calculation steps of the stability safety factor of the deep arc-shaped sliding surface of the counter-pressure berm itself refer to the calculation steps of the stability safety factor of the deep arc-cut berm sliding surface of the original fill slope and the composite sliding surface of the arc-to-straight line.

[0108] Specifically, the safety factor of the high fill slope is 1.3.

[0109] A back pressure berm optimization system for high fill slopes, the optimization system comprising a slope data acquisition module, a slope data optimization processing module, a storage module, a performance comparison module and a data display module, wherein:

[0110] Slope data collection module, used to collect various data of high fill slope;

[0111] The slope data optimization processing module is used to calculate the most optimized solution based on the collected data;

[0112] Storage module, used to store and organize various data and generated optimization solutions;

[0113] The performance comparison module compares and verifies the obtained optimization solutions multiple times;

[0114] The data display module is used to display the generated solutions.

[0115] Specifically, the storage module includes a memory stick, a memory card and a cloud system.

[0116] Specifically, the data display module includes a computer, a mobile phone and a tablet.

[0117] A brief proof of the optimality of the solution

[0118] It can be proved that when the back pressure berm height H f In H fmin With H fmax The maximum back pressure width B is actually allowed. fmax is large enough, that is, the most dangerous sliding surface of the slope is Figure 1 When the third type of slip surface is used, under the condition of increasing the same amount of counter-pressure berm earthwork, increasing only the berm width is more effective than increasing only the berm height in terms of improving the slope stability safety factor. In other words, the counter-pressure berm height is H fmin ≤H f ≤H fmax , and the maximum back pressure width actually allowed is B fmax Under sufficiently large conditions, the slope stability safety factor F = F 3 =1.3 in all the back pressure berms, the berm height H f =H fmin The solution uses the least amount of earthwork. The proof process is as follows:

[0119] Taking the engineering geological conditions with hard crust as an example, according to the simplified broken line slip surface proposed above, Figure 7 As shown in Figure 3, the stability safety factor of the middle soil B'BCC' can still be calculated using Formula 3:

[0120] From formula 3, we can get:

[0121]

[0122] The increment of the back pressure berm area can be calculated as follows:

[0123] △A=△(Bf H f ).....Formula 5

[0124] The following two cases are used to calculate the increment of safety factor when the unit area of ​​the back pressure protection road is increased.

[0125] (1) Only increase the back pressure width B f :

[0126]

[0127] (2) Only increase the back pressure height H f :

[0128]

[0129] Formula 6-Formula 7, we can get

[0130]

[0131] Obviously, B f -n 2 H f >0(i.e. Figure 7 The projection of point C' on the horizontal plane is outside the original slope foot), that is, formula 8 is always greater than 0, which means that increasing the back pressure width is more effective than increasing the back pressure height. Figure 7 The safety factor of the broken line slip surface is more effective. Therefore, the height of the back pressure berm is taken as H fmin ≤H f ≤H fmax , B f -n 2 H f >0, and the maximum back pressure width B actually allowed fmax Under sufficiently large conditions, the slope stability safety factor F = F 3 =1.3 in all the back-pressure berms, the back-pressure berm height H is H fmin The amount of earthwork used is the least, that is, the back-pressure berm section determined by the method introduced in this section is the optimal single-stage back-pressure berm solution.

[0132] When the maximum back pressure width B fmax is not large enough, and the B calculated in step 3 of the above optimization design process fm >B fmax ,It is easy to conclude from the above proof process that the fourth step of the above design process is reasonable.

[0133] Verification of the optimization design method

[0134] In order to verify the simplified calculation methods of various slip surfaces proposed above, Figure 8The slope shown in the figure has a temporary slope height of 40m and a slope ratio of 1:5. At this time, the slope is stable. Considering that a new slope with a slope ratio of 1:2 is formed on the original slope, the slope stability does not meet the requirements. It is necessary to add a back pressure berm in front of the slope to enhance its stability. The slope ratio of the back pressure berm is 1:2 and the width is B. f Five cases of 0, 10, 20, 30 and 50 m are considered respectively, and the materials used are the same as those of the fill. The parameters of each soil layer and fill material are shown in Table 1.

[0135] Table 1 shows the soil material parameter values.

[0136]

[0137] According to whether the foundation soil layer has a hard crust layer (referring to the hard layer above the plastic red clay layer, see Figure 8 (b)) The following two cases are discussed separately:

[0138] (1) No hard crust layer: The relatively soft soil layer is the plastic red clay at the Kunming Xiaoshao Airport site, with an average depth of 10 m, and below it is a medium-weathered rock layer. At this time, the back pressure berm height H f is 7m.

[0139] (2) There is a hard shell layer: The hard shell layer is hard plastic red clay, 5m deep, and the relatively weak layer is a plastic red clay layer, 5m deep. Below this soil layer is a medium-weathered rock layer. At this time, the back pressure berm height H f is 6m.

[0140] The strength reduction finite element method is more perfect in theory and can take into account complex geological conditions. A large number of previous literatures have shown that its calculation results are very close to the exact solution [57,140], so it can be considered that the calculation results of the strength reduction finite element method are more accurate. Therefore, this paper uses the strength reduction finite element method (using the Moore-Coulomb failure criterion) to verify the simplified algorithm. The simplified algorithm proposed in this paper is used to calculate the safety factor of the slope under the following two conditions, and the comparison with the slope stability safety factor calculated by finite element under the same conditions is shown in Table 2.

[0141] Table 2 shows the verification of safety factors of various sliding surfaces.

[0142]

[0143]

[0144] From Table 2, we can see that:

[0145] (1) The difference between the safety factors of various sliding surfaces calculated by the simplified algorithm proposed in this paper and the strength reduction finite element method is small, and the maximum relative error is only 11.5%. Among them, the relative error of the safety factor of the second type of sliding surface does not exceed 2.5%, and the relative error of the safety factor of the third type of sliding surface (without considering B fand H f The relative error of the second and third types of slip surfaces (without considering B f and H f The calculation method of the safety factor has a fairly high accuracy.

[0146] (2) There is a hard shell layer or a back pressure berm (in Table 2, B f and H f When both are not 0), the safety factor calculated by the simplified algorithm has a relatively small error. When there is a hard crust layer, the safety factor F calculated by the simplified algorithm in various slip surfaces 简 The maximum relative error is 8.4%; there is a back pressure berm (Table 2, B f and H f When both are not 0, F 简 The maximum relative error is 4.6%; when there is both a hard shell layer and a back pressure berm, F 简 The maximum relative error is only 1.9%.

[0147] (3) For the third type of slip surface, the larger the back pressure width, the smaller the relative error.

[0148] (4) For the fourth type of slip surface, when verifying the stability of the berm itself (or the slope without berm), F 简 The relative error increases with the increase of the berm height (or the height of the slope without berm).

[0149] Verification of optimal earthwork quantity

[0150] Verification Example 1: Figure 8 The slope with a hard crust layer on the foundation shown actually corresponds to an actual section of a certain project in the T8 section of the Kunming New Airport. In order to facilitate comparative analysis, the optimal backpressure earthwork volume of the slope without a hard crust layer under the same conditions was also verified.

[0151] Figure 8 In the figure, the original slopes with and without a hard crust layer are newly filled to form a slope with a height of 40m and a slope ratio of 1:2. The fill and soil layers are the same as those in the above figure. At this time, the slope stability does not meet the requirements. It is necessary to adopt a single-stage backpressure berm to enhance the slope stability (assuming that the maximum backpressure width B is actually allowed). fmax large enough).

[0152] The finite element method can be used to verify the optimization design method of the back pressure berm size proposed in this paper. After analysis, this paper uses the finite element method for optimization design as follows:

[0153] (1) Assuming that the width of the back pressure berm is large enough and the berm height varies within the range of 0 to H, the H determined by the second type of slip surface can be calculated. fmin2 and H determined by the fourth type of slip surface fmax ;

[0154] (2) Let the back pressure guard height H f In H fmin ~H fmax (for slope height) range, for each berm height H f , the width of the back pressure berm B required to maintain the slope stability can be calculated f , and then the required earthwork volume for different berm heights can be calculated, and the berm section size corresponding to the minimum earthwork volume is the final optimized design result.

[0155] Different berm height ratio H f / H, the required back pressure earthwork volume B for slope stability is obtained by the finite element method mentioned above. f H f / H 2 like Figure 9 As shown. Figure 9 It can be seen that among all the cross-sectional dimensions of the berm that can make the slope stable, H f The smaller it is, the less earthwork is required, which is consistent with the optimization design method proposed and demonstrated in this paper.

[0156] The optimal design method of slope backpressure berm proposed in this paper and the optimal design cross-sectional size H of the backpressure berm determined by the finite element method fmin2 , H fmax , B f The comparison is shown in Table 3.

[0157] Table 3 is the verification of the optimization design results of the back pressure berm section

[0158]

[0159] In Table 3, for a homogeneous soil slope whose filling material is slightly weathered material from a steep slope temple, after dividing its shear strength parameter by the reduction factor 1.3, the cohesion and internal friction angle of the filling body are: r =18.31kPa, According to the slope angle α=atan(1 / 2)=26.57°, the internal friction angle check Figure 3 The stability number N = 0.02;

[0160] From formula 2, it can be calculated that the maximum height of the homogeneous soil slope of slightly weathered material in this Doupo Temple group to maintain stability is H c =c r / (γN)=18.31 / (20.1×0.02)=45.5m. This shows that when the slope height is less than 45.5m, no back pressure is needed to prevent the slope from being damaged in the form of the first type of slip surface. Therefore, when the slope height is 40m, the slope ratio is 1:2, and the filling material is slightly weathered material in the Doupo Temple Formation, the minimum height H of the back pressure berm determined by the first type of slip surface is fmin1 =0.

[0161] It can be seen from Table 3 that the minimum back pressure height H of the berm calculated by the optimization design method proposed in this paper is fmin2 Too small, maximum back pressure height H fmax The relative error is not more than 20%; the optimal back pressure width B is calculated. fm The relative error is less than 10%. This shows that the optimization design method proposed in this paper is feasible. In actual engineering design and construction, the allowable value of the safety factor of various sliding surfaces or the H fmin With B f , appropriately reduce H fmax The results of the optimization design can be directly applied to the optimization design of the cross-sectional dimensions of the high slope back-pressure protection road.

[0162] Verification Example 2: The slope height of another section of Kunming New Airport T8 section is 38m, the plastic red clay foundation depth is 12m, and the other conditions are the same as Figure 8 (a) and Figure 8 (b) is the same as the slope shown in Figure 2. Due to space limitations, only the cross-sectional dimensions H of the slope backpressure berm optimization design method proposed in this paper and the backpressure berm optimization design cross-sectional dimensions H determined by the strength reduction finite element method are presented. fmin2 , H fmax , B f The comparison results are given in Table 4.

[0163] Table 4 is the verification of the optimization design results of the back pressure berm section

[0164]

[0165] Obviously, in this example, the relative error between the cross-sectional dimensions of the berm determined by the optimization method proposed in this paper and the cross-sectional dimensions determined by the strength reduction finite element method does not exceed 20%, which is similar to the conclusion of Example 1.

[0166] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for optimizing the design of a backpressure berm for a high fill slope, characterized in that: The optimization design method is used for the overall sliding surface after the back pressure treatment of the back slope on the foundation. The overall sliding surface after the back pressure treatment of the back slope on the foundation has four types, namely, ① the shear-out type sliding surface caused by damage in the backfill and from the upper part of the berm, ② the deep arc cutting berm type sliding surface of the original backfill slope, ③ the arc-to-straight line composite sliding surface and ④ the deep arc sliding surface of the back pressure berm itself, including the following steps: S1: Assumed berm width B f Large enough, without considering the sliding surface ④, the minimum height H of the back pressure berm is determined by the sliding surfaces ① and ② fmin ; S2: Assumed berm width B f Large enough, the maximum height H of the back pressure berm is determined by the sliding surface ④ fmax ; S3: Verify H fmin ≤H fmax Is it established? If not established, it means that this back pressure treatment method cannot make the slope meet the stability requirements, and other treatment methods should be adopted in combination; if established, enter S4; S4: Take the height of the back pressure guardway H = H fmin , the width B of the back pressure berm is determined by the sliding surface ③ f ; S5: Verify B fm Whether it exceeds the maximum allowable back pressure width B fmax :If B fm ≤B fmax , then H fmin , B fm The height and width of the back pressure berm required for the final design; otherwise, enter S6; S6: Take the width of the back pressure berm as B fmax , determine the back pressure berm height H through sliding surfaces ① and ② fm ; S7: Verify H fm ≤H fmax Is it true: If true, then H fm , B fmax is the optimal cross-sectional height and width of the back-pressure berm; if it is not true, it means that this back-pressure treatment method cannot make the slope meet the stability requirements, and other treatment methods must be used to keep the slope stable.

2. The method for optimizing the design of a back-pressure berm for a high fill slope according to claim 1 is characterized in that: The four types of overall failure modes after back pressure treatment are: ① a shear-type slip surface that occurs in the fill and is sheared out from the upper part of the berm, ② a deep arc slip surface of the original fill slope cutting the berm, ③ a composite slip surface of an arc connecting a straight line, and ④ a deep arc slip surface of the back pressure berm itself.

3. The method for optimizing the design of a back-pressure berm for a high fill slope according to claim 1, characterized in that: The calculation method of the safety factor of the sliding surface of the shear type that occurs when the fill body is damaged and shears out from the upper part of the berm is as follows: The following steps are involved: a: Take the reduction factor of the strength parameter of this type of slip surface F = F (0) =1, for the fill body c, The value is reduced as follows: Where: c r , are the cohesion and internal friction angle of the compacted mass after strength reduction; b: According to Check the stability calculation diagram of homogeneous simple soil slope by Soviet scholar Lobasov and get the stability number N at this time (0) , and then calculate the slope stability safety factor F defined by Taylor according to the following formula s2 (0) : Where: Hc is the maximum height that the slope can reach to remain stable after strength reduction; H is the height of the slope formed on the upper part of the berm; γ is the bulk density of the slope soil layer; c: If F s2 (0) >1, then increase the strength parameter reduction factor to F (1) , repeat steps a and b; if F s2 (0) <1, then reduce the strength parameter reduction factor to F (1) , repeat steps a and b until F s2 (n) = Until 1 o'clock.

4. The method for optimizing the design of a back-pressure berm for a high fill slope according to claim 1, characterized in that: The method for calculating the safety factor of the sliding surface of the deep arc cut berm type of the original fill slope ② comprises the following steps: a: The simplified calculation formula of the safety factor of the soil in the middle part B'BCC' is: Where: c, ——The shear strength index of relatively soft soil layer; W——weight of soil B'BCC'; l is the length of the sliding surface on the relatively soft soil layer; E a 、E p ——active earth pressure and passive earth pressure respectively; b: Take the reduction factor of the strength parameter of this type of slip surface F = F (0) =1, for the fill and foundation soil layer c, The values ​​are all reduced according to the formula; c: The reduced strength parameter cr (0) , Substituting into the formula, the safety factor F of the middle part of the soil B'BC C' can be calculated s (0) ; d: If F s (0) >1, then increase the strength parameter reduction factor to F (1) , repeat steps b and c; if F s (0) <1, then reduce the strength parameter reduction factor to F (1) , repeat steps b and c until F s (n) = Until 1 o'clock.

5. The method for optimizing the design of a backpressure berm for a high fill slope according to claim 1, characterized in that: The calculation method of the safety factor of the composite sliding surface of arc-to-straight line (③) includes the following contents: a: The simplified calculation formula of the safety factor of the middle part of the soil B'BCC' can be used by the simplified calculation formula of the safety factor in step a of ② the calculation method of the safety factor of the sliding surface of the deep arc cut berm type of the original fill slope; b: Calculate the passive earth pressure E p The influence of the berm soil outside point C' on the passive earth pressure is not considered.

6. The method for optimizing the design of a backpressure berm for a high fill slope according to claim 1, characterized in that: The calculation method of the safety factor of the deep arc-shaped sliding surface of the anti-pressure berm itself includes the following contents: a: The simplified calculation formula of the safety factor of the soil B'BCC' on the right side of the berm can be calculated by the simplified calculation formula of the safety factor in step a of ② Calculation method of the safety factor of the sliding surface of the deep arc cut berm type of the original fill slope; b: ④ The calculation steps of the stability safety factor of the deep arc-shaped sliding surface of the counter-pressure berm itself refer to the calculation steps of the stability safety factor of the deep arc-cut berm sliding surface of the original fill slope and the composite sliding surface of the arc-to-straight line.

7. The method for optimizing the design of a backpressure berm for a high fill slope according to claim 1 is characterized in that: The safety factor of the high fill slope is 1.

3.

8. A system for optimizing backpressure berms for high fill slopes, the system for optimizing backpressure berms for high fill slopes being used to execute the optimization design method for backpressure berms for high fill slopes as claimed in any one of claims 1 to 7, characterized in that: The optimization system includes a slope data acquisition module, a slope data optimization processing module, a storage module, a performance comparison module and a data display module, wherein: Slope data collection module, used to collect various data of high fill slope; The slope data optimization processing module is used to calculate the most optimized solution based on the collected data; Storage module, used to store and organize various data and generated optimization solutions; The performance comparison module compares and verifies the obtained optimization solutions multiple times; The data display module is used to display the generated solutions.

9. The back pressure berm optimization system for high fill slope according to claim 8, characterized in that: The storage module includes a memory stick, a memory card and a cloud system.

10. The back pressure berm optimization system for high fill slope according to claim 8, characterized in that: The data display module includes a computer, a mobile phone and a tablet.

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