Horizontal partition modified reinforced abrupt slope embankment structure and design method thereof

Abstract

The invention provides a horizontal partition modified reinforced abrupt slope embankment structure and a design method thereof, and the method comprises the following steps: S1, obtaining the filling layer number of high-content cement modified soil and low-content cement modified soil according to the height of each layer of high-content cement modified soil and low-content cement modified soil after layered filling; s2, the most dangerous sliding face of the embankment is obtained, and the cement mixing amount of the high-mixing-amount cement modified soil and the cement mixing amount of the low-mixing-amount cement modified soil of all the layers in different side slope instability modes are calculated; and S3, determining the final cement mixing amount of the high-mixing-amount cement modified soil and the low-mixing-amount cement modified soil of each layer. The problems that an existing embankment structure is high in engineering cost, the cement mixing amount is not accurately controlled, and the occupied area is increased are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of slope treatment, and in particular relates to a horizontally partitioned modified reinforced steep slope embankment structure and a design method thereof. Background Art

[0002] With the rapid development of highway construction in my country, a large number of steep slope embankments are inevitable in mountainous areas and various road projects. In some mountainous and hilly areas in the south with heavy rainfall, traditional steep slope embankment structures often cannot meet the requirements of stability and bearing capacity.

[0003] The existing embankment structures generally have the following problems:

[0004] (1) Traditional fill embankment structures often undergo overall modification of the embankment during construction, lacking reasonable analysis and calculation of the stress on the embankment's different zones, which results in an increase in project costs.

[0005] (2) The friction coefficient between the wet clay and the geogrid in the existing reinforced embankment slope with wet clay as filler is too low. Although cement modification can effectively increase the friction coefficient between the geogrid and the filler, thereby improving the anchoring effect of the geogrid on the soil, no detailed design and calculation instructions are provided to accurately control the cement content.

[0006] (3) Traditional high-fill embankments usually have multi-level slope reduction. Although this can improve the overall stability of the embankment slope, it will increase the occupied area.

[0007] Therefore, it is necessary to develop a new type of steep slope embankment structure and its design method that can adapt to various complex terrain conditions. Summary of the Invention

[0008] The purpose of the embodiments of the present invention is to provide a horizontally partitioned modified reinforced steep slope embankment structure and a design method thereof, so as to solve the problems of high engineering cost, inaccurate control of cement content, and increased floor space in existing embankment structures.

[0009] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0010] The horizontally partitioned modified reinforced steep slope embankment includes geogrids, geocells, modified reinforced areas, and non-modified reinforced areas. The modified reinforced area is located 2 to 6 meters from the embankment slope surface to the inside of the embankment. The rest of the embankment is the non-modified reinforced area. In the modified reinforced area, a layer of high-cement modified soil and a layer of low-cement modified soil are alternately distributed from bottom to top. The geogrid is fixed to each layer of high-cement modified soil and is wrapped upward to the adjacent layer of high-cement modified soil. The adjacent geogrids are connected at their junctions with geogrid connecting rods.

[0011] Furthermore, the geocell is fixed to the inner side of the slope surface and is wrapped by the geogrid; the geocell is fixedly connected to the vegetation bag filled with vegetation soil; and the non-modified reinforced area is obtained by layered filling of plain fill soil.

[0012] Another technical solution adopted by the present invention is:

[0013] The design method of the horizontally partitioned modified reinforced steep slope embankment includes the following steps:

[0014] S1: Obtain the number of filling layers of high-content cement-modified soil and low-content cement-modified soil according to the height of each layer of high-content cement-modified soil and low-content cement-modified soil after layered filling;

[0015] S2: Obtain the most dangerous sliding surface of the embankment and calculate the cement content of each layer of high-content cement-modified soil and low-content cement-modified soil under different side slope instability modes;

[0016] S3: Determine the final cement content of each layer of high-content and low-content cement-modified soil.

[0017] Furthermore, in said S1,

[0018] The height of each layer of high-content cement-modified soil after layered filling is 0.15m-0.25m. From bottom to top, each layer of high-content cement-modified soil is represented as: high-content 1, high-content 2, ... high-content i ... high-content n1; where i is the sequence number of the high-content cement-modified soil, and n1 is the total number of high-content cement-modified soil layers. The geogrid is represented as: reinforcement 1, reinforcement 2, ... reinforcement i ... reinforcement n1.

[0019] The height of each layer of low-content cement-modified soil on the embankment after layered filling is 0.25m-0.35m. From bottom to top, each layer of low-content cement-modified soil is represented as: low-content 1, low-content 2,... low-content i... low-content n2; among them, i is the serial number of the low-content cement-modified soil, and n2 is the total number of filling layers of low-content cement-modified soil.

[0020] Furthermore, the S2 includes:

[0021] S21: Obtain the most dangerous sliding surface of the embankment; the first failure mode of the overall slope instability is: the soil below the embankment slope shears off the low-cement modified soil along the sliding surface, and the reinforcement slides out of the slope at the same time;

[0022] The most dangerous sliding surface is cut into n soil strips longitudinally. The first n-1 soil strips are obtained by vertically cutting the most dangerous sliding surface with equal arc lengths. The nth soil strip is obtained by vertically cutting the intersection of the most dangerous sliding surface and the low-content cement-modified soil. i is the sequence number of the soil strip. For each soil strip i, the calculation formula for the landslide thrust transmitted by soil strip i to soil strip i+1 is as follows:

[0023]

[0024] In formula (1), W i is the self-weight of soil strip i; α i F represents the angle between the tangent line of the lower arc of the i-th soil strip and the horizontal direction; s is the safety factor; P i P represents the landslide thrust transmitted from soil strip i to soil strip i+1; i-1 represents the landslide thrust transmitted from soil strip i-1 to soil strip i; Q i represents the horizontal force acting on soil strip i; l i represents the length of soil strip i; u i represents the pore stress at the bottom of soil strip i; tan is the tangent function; c i '、 Respectively represent the lateral cohesion and internal friction angle of soil strip i; 1≤i<n-1;

[0025] Transfer coefficient ψ i-1 Calculated by formula (2):

[0026]

[0027] Among them, α i-1 represents the angle between the tangent line of the lower arc of the i-1th soil strip and the horizontal direction;

[0028] Calculate the landslide thrust from strips 1 to n-1 to strips 2 to n when sliding out of the slope from low-mix 1;

[0029] S22: The anti-sliding force P of soil strip n is calculated as follows:

[0030]

[0031] In formula (3), S is the area of ​​soil strip n; γ is the density of soil, α′ is the angle between the tangent line of the lower arc of soil strip n and the horizontal direction, is the internal friction angle of cement-modified soil when the cement content is x, c′(x) is the cohesion of cement-modified soil when the cement content is x; l is the length of soil strip n, x is the cement content;

[0032] Fitting the relationship between cement content x, cohesion c′(x), and internal friction angle by static triaxial test The relationship between

[0033] c′(x)=80.23-48.34 / (1+e (x-5.06) / 1.12 ) (4)

[0034]

[0035] In formula (5), e represents the base of natural logarithm;

[0036] The sum of the anti-sliding force P of soil strip n and the allowable tensile strength T of the geogrid is greater than the landslide thrust transmitted from soil strip n-1 to soil strip n. Simultaneously, equations (3), (4), and (5) are combined to solve the cement content x1 for low cement content 1.

[0037] S23: Repeat S21-S22 to calculate the cement content x of low-mixed i when sliding out of the slope. i ; Until for low-mix a, the cement content is x a At this time, the landslide thrust transmitted from soil strip n-1 to soil strip n is negative. The upper soil layer of low-mixed a, that is, low-mixed a+1 to low-mixed n2, will not become unstable even without cement in the first failure mode of overall slope instability.

[0038] Furthermore, the S2 further includes:

[0039] S24: The second failure mode of the overall instability of the embankment slope is: the soil below the embankment slope shears off the low-content cement-modified soil along the sliding surface, and the reinforcement is pulled out of the slope;

[0040] The pull-out resistance of geogrid is calculated as follows:

[0041] S fi =2σ vi aLf (6)

[0042] In formula (6): S fi is the pull-out resistance of reinforcement i; σ vi is the vertical soil pressure stress, σ vi =γh i , γ is the specific gravity of high-content cement-modified soil, h i is the height from the top of the embankment to the reinforcement i; a is the width of reinforcement i; L is the total length of reinforcement i in the high-mixed soil i; f is the friction coefficient between reinforcement i and cement-modified soil, determined based on on-site pull-out tests;

[0043] The plain fill of the steep embankment was mixed with cement in different proportions, and the modified soil was subjected to on-site pull-out tests. The relationship between the friction coefficient between the reinforcement and the modified soil and the cement content was obtained, and a function was fitted.

[0044] The fitting curve function f(x) formula between the friction coefficient between reinforcement and modified soil and cement content is as follows:

[0045] f(x)=0.49x 0.24 (7)

[0046] The sum of the anti-sliding force P of soil strip n and the anti-pulling force of geogrid is greater than the landslide thrust transmitted from soil strip n-1 to soil strip n. At the same time, the inverse calculation of equations (3) to (7) is used to obtain the cement content x1, x2, ..., x2 of low-mix 1, low-mix 2, ..., low-mix a. a At this time, the upper soil layer of low-mixed a, that is, low-mixed a+1 to low-mixed n2, will not become unstable even without cement in the second failure mode of overall slope instability.

[0047] Furthermore, the S2 further includes:

[0048] S25: The third failure mode of overall slope instability is: the high-content cement-modified soil in the modified reinforced area (1) slides out of the slope between the two layers of low-content cement-modified soil above and below it;

[0049] The sum of the friction forces F between the high-content cement-modified soil and the upper and lower layers of low-content cement-modified soil is calculated as follows:

[0050] F=σ vi1 Laμ+σ vi2 Laμ (8)

[0051] In formula (8), σ vi1 is the vertical soil compressive stress on the upper surface of the high-doping i, L is the length of the high-doping i, a is the width of the high-doping i, σ vi2 is the vertical soil compressive stress under the high-addition i, μ is the friction coefficient between the high-addition i and low-addition cement modified soil;

[0052] Vertical earth pressure stress σ on the surface under high-doping i vi2 Calculate as follows:

[0053] σ vi2 =γ(h i1 +h) (9)

[0054] In formula (9), h i1 is the height from the top of the embankment to the upper surface of the high-doping i, γ represents the gravity of the high-doping i; h is the height of the high-doping i;

[0055] The horizontal earth pressure on the high-mixed i is:

[0056] E xi =σ hi ha (10)

[0057] In formula (10), σ hi is the horizontal soil stress of high-doping i; a is the width of high-doping i,

[0058] Horizontal soil stress σ hi for:

[0059] σ hi =λi γh i (11)

[0060] In formula (11), h i is the height from the top of the embankment to the center of the high-pressure embankment, λ i is the depth h in the modified reinforced area (1) i The earth pressure coefficient at is calculated according to the following formulas (12) and (13):

[0061] When h i When ≤6m, earth pressure coefficient λ i Calculate as follows:

[0062] λ i =λ0(1-h i / 6)+λ a (h i / 6) (12)

[0063] In formula (12), λ0 is the static earth pressure coefficient, is the internal friction angle of high-doping i; λ a is the active earth pressure coefficient,

[0064] When h i >6m,

[0065] λ i =λ a (13)

[0066] When F ≥ E xi When , the high-mixed soil in the modified reinforced area (1) will not slide out of the slope between the two layers of low-mixed soil above and below it. Simultaneously, equations (8) to (13) are combined to obtain inequalities (14) and (15):

[0067] When h i When ≤6m, the inequality (14) is obtained:

[0068]

[0069] When h i When >6m, the inequality (15) is obtained:

[0070]

[0071] In inequalities (14) and (15), x is the cement content of high-mixed soil; is the internal friction angle of cement-modified soil, determined by formula (5);

[0072] The cement content of each layer of high-mixed soil is obtained by inverse calculation using inequalities (14) and (15).

[0073] Furthermore, the S2 further includes:

[0074] S26: Local instability mode of embankment slope The first failure mode is: the reinforcement in the non-anchored area is pulled out of the slope from the middle of the high-content cement-modified soil; First, the rupture surface, non-anchored area, and anchored area are determined based on the 0.3H method.

[0075] The pull-out stability coefficient of geogrid is calculated as follows:

[0076] K i =S fi / E xi (16)

[0077] In formula (10), K i is the pull-out stability coefficient of reinforcement i, S fi is the pull-out strength of reinforcement i, E xi is the horizontal earth pressure on reinforcement i;

[0078] Pullout strength S of reinforcement i fi for:

[0079] S fi =2σ vi aL b f (17)

[0080] In formula (17), σ vi is the vertical soil pressure stress, σ vi =γh i ,γ is the density of high-mixed soil, h i is the height from the top of the embankment to the reinforcement i; a is the width of the reinforcement; L b is the effective anchorage length of the reinforcement; f is the friction coefficient between reinforcement i and cement-modified soil, determined based on on-site pull-out tests;

[0081] Horizontal earth pressure E on reinforcement i xi Calculate according to formula (18):

[0082] E xi =σ hi S x S y (18)

[0083] In formula (18), σ hi is the horizontal soil pressure stress, S x 、S y is the horizontal and vertical spacing between reinforcement i;

[0084] Combining equations (11) to (13) and (16) to (18), we can obtain the following equation:

[0085] When h i When ≤6m,

[0086] When h i ≥6m,

[0087] In formulas (19) and (20), x is the cement content, is the internal friction angle of cement-modified soil, f(x) is the friction coefficient between reinforcement and cement-modified soil when the content is x, which is obtained by formula (7);

[0088] Reinforcement pull-out stability coefficient K i ≥2, the cement content x of each layer of high-content cement-modified soil is obtained by inverse calculation.

[0089] Furthermore, the S2 further includes:

[0090] S27: The second failure mode of local instability of the embankment slope is: the high-content cement-modified soil in the non-anchored area slides out of the slope between the two layers of low-content cement-modified soil above and below it;

[0091] The sum of the friction forces F between the high-content cement-modified soil and the upper and lower layers of low-content cement-modified soil is calculated as follows:

[0092] F=σ vi1 L b aμ+σ vi2 L b aμ (21)

[0093] In formula (8), σ vi1 is the vertical soil pressure stress on the surface of high-doped i, L b is the effective anchoring length of the high-doped i, a is the width of the high-doped i, σ vi2 is the vertical soil compressive stress under the high-addition i, μ is the friction coefficient between the high-addition i and low-addition cement modified soil;

[0094] Vertical earth pressure stress σ on the surface under high-doping i vi2 Calculated by formula (9),

[0095] The horizontal earth pressure on high-mixed i is calculated by equations (10) to (13):

[0096] When F ≥ E xi When , the high-mixed soil in the modified reinforced area (1) will not slide out of the slope between the two layers of low-mixed soil above and below it. Simultaneously, equations (21), (8) to (13) are combined to obtain inequalities (22) and (23):

[0097] When h i When ≤6m, the inequality (22) is obtained:

[0098]

[0099] When h i When >6m, the inequality (23) is obtained:

[0100]

[0101] The cement content of each layer of high-mixed soil is obtained by inverse calculation using inequalities (22) and (23).

[0102] Furthermore, the S3 includes:

[0103] Compare the cement content of each layer of high-mixed soil and each layer of low-mixed soil, and take the larger value of the cement content of high-mixed soil and low-mixed soil as the final cement content of each layer of high-mixed soil and each layer of low-mixed soil.

[0104] The beneficial effects of the present invention are:

[0105] (1) The horizontally partitioned, reinforced, steep-slope embankment of the present invention is divided into a reinforced zone and a non-reinforced zone based on the embankment's stress characteristics. A steep-slope embankment structure with alternating "high-low-high" distribution of cement-modified soil is designed. The geogrid is located in the center of each layer of high-volume cement-modified soil and is wrapped around the center of the previous layer of high-volume cement-modified soil. This design is suitable for steep-slope embankments and can reduce floor space.

[0106] (2) The present invention analyzes five failure modes existing based on this embankment structure, including three failure modes of overall instability of the embankment slope and two failure modes of local instability. The cohesion and internal friction angle of the modified soil under different cement content are obtained through experiments. By performing a force analysis on each failure mode, the force balance equations under various failure modes are jointly established, and the cement content of each layer of the modified reinforced area under various failure modes is obtained by inverse calculation, thereby obtaining the cement content of each layer of the modified reinforced area under various failure modes.

[0107] (3) In the present invention, cement modification is used to increase the friction coefficient between the geogrid and the filler, thereby improving the anchoring effect of the geogrid on the soil. Based on the relationship between the cement content and the friction coefficient obtained from the on-site pull-out test, the cement content is obtained by inverse calculation under the premise of meeting the pull-out stability of the geogrid, thereby achieving precise control of the cement content, reducing the amount of cement used and thus reducing costs, and ensuring the safety and economy of the embankment structure.

[0108] (4) Based on various failure modes of the embankment, the present invention conducts reasonable analysis and calculation of the embankment slope, and only modifies the embankment slope surface to 2 to 6 meters inside the embankment. Compared with the overall modification of the traditional embankment structure, it reduces the amount of cement used and reduces the project cost.

[0109] (5) The greening system of the present invention includes: vegetation bags in geocells that are wrapped by geogrids and fixed on the inner side of the slope, and vegetation soil in the vegetation bags. The vegetation bags and the vegetation soil in the vegetation bags reinforce and protect the soil in the modified reinforced area, improve the shear strength of the soil, effectively reduce the erosion of the steep embankment slope by rainwater, and prevent soil loss; in addition, the system improves the overall stability of the steep embankment slope and has a greening effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0110] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0111] Figure 1 It is a steep slope embankment zoning diagram of the present invention.

[0112] Figure 2 It is a longitudinal sectional view of a steep slope embankment of the present invention.

[0113] Figure 3 It is a schematic diagram of the position of the longitudinal drainage ditch of the present invention.

[0114] Figure 4 It is a schematic diagram of calculating the low soil-cement content of the present invention.

[0115] Figure 5 It is a simplified diagram for calculating the residual sliding force in the present invention.

[0116] Figure 6 It is a schematic diagram of the use of the 0.3H broken line method to determine the fracture surface in the present invention.

[0117] Figure 7 It is a fitting curve diagram of cohesion and cement content of the present invention.

[0118] Figure 8 It is a fitting curve diagram of the internal friction angle and cement content of the present invention.

[0119] Figure 9 It is a fitting curve diagram of the friction coefficient and cement content of the present invention.

[0120] In the figure, 1. modified reinforced area, 2. non-modified reinforced area, 3. geocell, 4. vegetation bag, 5. drainage ditch, 6. geogrid connecting rod, 7. drainage ditch at the bottom of the slope. DETAILED DESCRIPTION

[0121] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.

[0122] This embodiment provides a horizontally partitioned modified reinforced steep slope embankment structure and a design method thereof.

[0123] like Figure 1 As shown, a horizontally partitioned modified reinforced steep slope embankment structure is shown. The embankment is divided into a modified reinforced area 1 and a non-modified reinforced area 2. The modified reinforced area 1 is located 2 to 6 meters from the embankment slope surface to the inside of the embankment, and is determined according to the stress characteristics of the embankment and the actual width and height of the embankment; the rest is the non-modified reinforced area 2.

[0124] like Figure 2 As shown, in the modified reinforced area 1, the geogrid is fixed vertically from the center of each layer of high-content cement-modified soil and wraps upward to the center of the adjacent high-content cement-modified soil, connecting the geogrids at the intersection with geogrid connecting rods 6. The unmodified reinforced area 2 is formed by layering plain fill.

[0125] like Figure 2 As shown, the geocell 3 is wrapped by the geogrid and fixed on the inner side of the slope; the greening system includes the vegetation bag 4 fixed by the geocell 3 and the vegetation soil filled in the vegetation bag 4. The system reinforces and protects the soil in the modified reinforced area 1, improves the shear strength of the soil, reduces the erosion of the steep embankment slope by rainwater, prevents soil loss, and greatly improves the greening effect of the slope.

[0126] The vegetation soil filled in the vegetation bag 4 includes peat, coconut coir, perlite, slow-release fertilizer, plant seeds, etc. The various plants planted in the vegetation bag 4 not only beautify the environment, but also prevent the soil on the slope surface from being directly eroded by rainwater, thereby improving the stability of the slope.

[0127] like Figure 2 、 3 As shown, the drainage system consists of a drainage ditch 5 on the embankment slope and a drainage ditch 7 at the bottom of the slope. The drainage ditch 5 is located on the surface of the embankment slope and is arranged every 4 meters along the longitudinal direction of the embankment slope, extending from the top of the slope to the bottom of the slope.

[0128] The drainage ditch 5 on the embankment slope is 0.2m to 0.4m wide and 0.2m to 0.4m deep; the drainage ditch 7 at the bottom of the slope is set at 1.2m from the slope foot, with a width and depth of 0.6m.

[0129] This embodiment also provides a design method for a horizontally partitioned modified reinforced steep slope embankment structure, and proposes five failure modes based on this embankment structure, including three failure modes of overall instability of the embankment slope and two failure modes of local instability, and conducts detailed analysis and calculation for each failure mode.

[0130] The first failure mode for the overall instability of the embankment slope is: the soil within a certain range below the embankment slope shears off the low-cement-modified soil along the sliding surface, and the reinforcement slides out of the slope. The second failure mode is: the soil within a certain range below the embankment slope shears off the low-cement-modified soil along the sliding surface, and the reinforcement is pulled out of the slope. The third failure mode is: the high-cement-modified soil in the reinforced area of ​​the embankment slides out of the slope between the low-cement-modified soil layers above and below it.

[0131] The local instability mode of the embankment slope is analyzed based on the 0.3H method to determine the rupture surface. The first failure mode is: the non-anchored area ( Figure 6 ) of the reinforcement is pulled out from the middle of the high-content cement-modified soil slope; Among them, the second failure mode is: the non-anchored area ( Figure 6 )'s high-content cement-modified soil slid out of the slope between the two layers of low-content cement-modified soil above and below it.

[0132] S1: Given a steep embankment example, perform analysis and calculation, such as Figure 2 The specific parameters are as follows:

[0133] The embankment is 10m high, the embankment slope is 60°, the cohesion of the plain fill is 30kPa, the internal friction angle is 18°, and the target stability safety factor of the embankment slope is 1.35.

[0134] The height of each layer of high-content cement-modified soil of the embankment after layered filling is 0.15m-0.25m, and 0.2m is selected in this embodiment. The height of each layer of low-content cement-modified soil of the embankment after layered filling is 0.25m-0.35m, and 0.3m is selected in this embodiment.

[0135] The density of cement modified soil with different dosage is 20kN / m 3 .

[0136] The layers of high-content cement-modified soil in the modified reinforced area are named from the bottom to the top of the embankment: high-content cement-modified soil 1, high-content cement-modified soil 2, ... high-content cement-modified soil 20.

[0137] The layers of low-content cement-modified soil in the modified reinforced area are named from the bottom to the top of the embankment: low-content cement 1, low-content cement 2, ... low-content cement 20.

[0138] The geogrids located in the middle of each layer of high-content cement-modified soil are named from the bottom to the top of the embankment: Rebar 1, Rebar 2, ... Rebar 20.

[0139] S2: First, the GEO5 software is used to automatically search for the most dangerous sliding surface of the embankment and determine the most dangerous sliding surface from each layer of low-content cement-modified soil.

[0140] S21: For the first and second failure modes of overall slope instability, such as Figure 4 As shown in the figure, the most dangerous sliding surface is cut into 10 soil strips from top to bottom. The first 9 soil strips are obtained by vertically cutting the most dangerous sliding surface with equal arc lengths. The 10th soil strip is obtained by vertically cutting the intersection point A between the most dangerous sliding surface 3 and the low-content cement-modified soil. Each strip is simplified, and the unbalanced thrust method is used to calculate the thrust, resulting in the derivation formula (1):

[0141]

[0142] In formula (1), W i is the self-weight of soil strip i; α i F represents the angle between the tangent line of the lower arc of the i-th soil strip and the horizontal direction; s is the safety factor; P i P represents the thrust transmitted from soil strip i to soil strip i+1, i The direction of P is parallel to the bottom sliding surface of soil strip i, where the bottom sliding surface is regarded as a plane; i-1 P represents the thrust transmitted from soil strip i-1 to soil strip i, i-1 The direction is parallel to the bottom sliding surface of soil strip i-1; Q i Denote the horizontal force acting on soil strip i, calculate Q i Horizontal earthquake force and groundwater pressure need to be considered when calculating the horizontal earthquake force. However, the influence of horizontal earthquake force and groundwater pressure is not considered here. i The value is 0; l i represents the length of soil strip i; u i represents the pore stress at the bottom of soil strip i. The pore stress is mainly caused by groundwater and can be estimated by measuring the groundwater level or based on the data in the geological report. The influence of groundwater is not considered here. u i The value is 0; tan is the tangent function; c i '、 denote the lateral cohesion and internal friction angle of soil strip i respectively;

[0143] Transfer coefficient ψ i-1 Calculated by formula (2):

[0144]

[0145] The landslide thrust P of the most dangerous sliding surface of the No. 1 to No. 9 soil strips sliding out of the slope from the low-mix 1 is calculated. i, List 1 is as follows:

[0146] Table 1 Landslide thrust P of soil strips No. 1 to No. 9 on the most dangerous sliding surface when sliding out of the slope from low-mix 1 i

[0147]

[0148]

[0149] S22: Therefore, for the first failure mode of overall slope instability, the unbalanced thrust transmitted by soil strip No. 9 is offset by the anti-sliding force P provided by soil strip No. 10 and the allowable tensile strength T of the geogrid.

[0150] The anti-sliding force of soil strip No. 10 is calculated as follows:

[0151]

[0152] In formula (3), S is the area of ​​the No. 10 soil strip; γ is the density of the soil, which is 20 kN / m 3 , α′ is the angle between the tangent line of the lower arc of soil strip No. 10 and the horizontal direction, is the internal friction angle of cement-modified soil, c′(x) is the cohesion of cement-modified soil; l is the length of the No. 10 soil strip, and x is the dosage.

[0153] The side of the No. 10 soil strip is a low-content cement-modified soil mixed with cement. Through the test, the relationship between cement content and cohesion and internal friction angle can be obtained. The anti-sliding force P of the No. 10 soil strip and the allowable tensile strength T of the geogrid are combined to balance the unbalanced thrust transmitted by the No. 9 soil strip, and then the cohesion c' and internal friction angle of each soil layer after modification are obtained by inverse calculation. The corresponding cement content is obtained, thereby obtaining the corresponding cement content x of the low-content cement-modified soil layer.

[0154] The plain fill soil sampled on site from the steep embankment structure was mixed with cement in different proportions, specifically 0%, 2%, 4%, and 8%. Static triaxial tests were performed on the prepared samples to obtain the cohesion c' and internal friction angle of the modified soil. The relationship between them and the dosage is calculated respectively, and the corresponding function is fitted by the data analysis software, such as Figure 7 、 8 shown.

[0155] Cohesion c′ and internal friction angle of modified soil The fitting curve functions between them and the dosage are as follows:

[0156] c′=g(x)=80.23-48.34 / (1+e (x-5.06) / 1.12) (4)

[0157]

[0158] Where c′ is the cohesion of the modified soil, is the internal friction angle of the modified soil, and x is the cement content.

[0159] When P+T≥85.48kN, the first failure mode of overall slope instability will not occur.

[0160] By combining equations (3), (4) and (5), we can solve the cement content x1 of low cement content.

[0161] Similarly, the landslide thrust P of the soil strips No. 1 to No. 9 that slide out of the most dangerous sliding surface of the slope from low-mix 2 is i , List 2 is as follows:

[0162] Table 2 Landslide thrust P of soil strips No. 1 to 9 on the most dangerous sliding surface when sliding out of the slope from low-mix 2 i

[0163]

[0164] The landslide thrust P of soil strips No. 1 to No. 9 that slide out of the most dangerous sliding surface of the slope from low-mix 3 i , List 3 is as follows:

[0165] Table 3 Landslide thrust P of soil strips No. 1 to 9 on the most dangerous sliding surface when sliding out of the slope from low-mix 3 i

[0166]

[0167] The landslide thrust P of soil strips No. 1 to No. 9 that slide out of the most dangerous sliding surface of the slope from low-mix 4 i , List 4 is as follows:

[0168] Table 4 Landslide thrust P of soil strips No. 1 to 9 on the most dangerous sliding surface when sliding out of the slope from low-mix 4 i

[0169]

[0170]

[0171] S23: Similarly, referring to the cement content x1 obtained by inverse calculation from low-mix 1, the corresponding cement content x2, x3, and x4 from low-mix 2, low-mix 3, and low-mix 4 can be inversely calculated in sequence.

[0172] Calculations show that the soil layer above low-mix 4, that is, low-mix 5 to low-mix 20 in the modified reinforced area, has a negative landslide thrust of the last soil strip, that is, soil strip No. 9, calculated by the unbalanced thrust transfer coefficient method. This indicates that there is no residual sliding force, that is, it can be in a stable state without adding cement and will not become unstable. The residual sliding force can be resisted by relying on the strength of the plain fill itself, that is, the upper soil layer (low-mix 5 to low-mix 20) will not become unstable under the first failure mode.

[0173] S24: The second failure mode for the overall instability of the slope, relying on the anti-sliding force P of the No. 10 soil strip (Eq. (3)) and the anti-pulling force S of the geogrid fi (Equation (6)) is used to balance the unbalanced thrust transmitted by the No. 9 soil block.

[0174] The anti-sliding force of the No. 10 soil strip is calculated by formula (3), and the landslide thrust transmitted by the No. 9 soil strip has been calculated by the above table.

[0175] The pull-out resistance of geogrid is calculated based on the pull-out resistance generated by the upper and lower surfaces of the geogrid, as follows:

[0176] S fi =2σ vi aLf (6)

[0177] In formula (6): S fi is the pull-out resistance of reinforcement i; σ vi is the vertical soil pressure stress, σ vi =γh i , γ is the specific gravity of high-content cement-modified soil, h i is the height from the top surface of the embankment to the reinforcement i; a is the width of the reinforcement i; L is the full length of the reinforcement i in the high-mix soil; f is the friction coefficient between the reinforcement i and the cement-modified soil, which is determined based on the on-site pull-out test.

[0178] The plain fill of the steep embankment was mixed with cement in different proportions, specifically 0%, 2%, 4%, and 8%. On-site pull-out tests were conducted on the modified soil to obtain the relationship between the friction coefficient of the reinforcement and the modified soil and the dosage. The corresponding function was fitted by data analysis software, as shown in the following example: Figure 9 .

[0179] The fitting curve function between the friction coefficient of reinforcement and modified soil and the dosage is as follows:

[0180] y(x)=0.49x 0.24 (7)

[0181] The combined equations (3) to (7) can be used to inversely calculate the corresponding cement content x1, x2, x3, and x4 for low-mix 1, low-mix 2, low-mix 3, and low-mix 4.

[0182] Since the soil layer above low-mixture 4 can rely on the strength of the plain fill to resist the remaining sliding force, the upper soil layer (low-mixture 5 to low-mixture 20) will not become unstable in the second failure mode.

[0183] S25: The third failure mode for the overall instability of the slope relies on the friction between the high-mixed soil and the upper and lower layers of low-mixed soil to balance the horizontal earth pressure on the high-mixed soil, thereby ensuring that the high-mixed soil in the modified and reinforced area of ​​the embankment will not slide out of the slope between the upper and lower layers of low-mixed soil.

[0184] The sum of the friction forces F between the high-mixed soil and the upper and lower layers of low-mixed soil is calculated as follows:

[0185] F=σ vi1 Laμ+σ vi2 Laμ (8)

[0186] In formula (8), σ vi1 is the vertical earth pressure stress on the upper surface of the high-mixed soil, L is the length of the high-mixed soil in the modified reinforced area, a is the width of the high-mixed soil, here the unit width is 1m, σ vi2 is the vertical soil compressive stress on the lower surface of the high-mixed soil, μ is the friction coefficient between the high-mixed soil and the low-mixed soil, which is taken as 0.3 here.

[0187] Since the height of each layer of high-mixed soil is 0.2m, the vertical soil pressure stress σ on the lower surface of the high-mixed soil is vi2 Calculate as follows:

[0188] σ vi2 =γ(h i1 +0.2) (9)

[0189] In formula (9), h i1 is the height from the top of the embankment to the upper surface of the high-doping i, where γ represents the severity of the high-doping i;

[0190] The horizontal earth pressure on the high-mixed soil is:

[0191] E xi =σ hi ha (10)

[0192] In formula (10), σ hi is the horizontal soil stress of the high-mixed soil; h is the thickness of the high-mixed soil, which is 0.2m here; a is the width of the high-mixed soil, which is 1m in unit width here.

[0193] The horizontal soil stress is:

[0194] σ hi =λ i γh i (11)

[0195] In formula (11), γ is the density of high-doped i, which is 20kN / m 3 , h i is the height from the top of the embankment to the center of the high-pressure embankment, λ i h for reinforced earth embankment i The earth pressure coefficient at depth is calculated according to the following formulas (12) and (13):

[0196] When h i When the height is ≤6m, the earth pressure coefficient is calculated as follows:

[0197] λ i =λ0(1-h i / 6)+λ a (h i / 6) (12)

[0198] In formula (12), λ0 is the static earth pressure coefficient, The internal friction angle of high-doped i can be obtained through experiments; λ a is the active earth pressure coefficient,

[0199] When h i ≥6m,

[0200] λ i =λ a (13)

[0201] Therefore, when F ≥ E xi When , the high-mixed soil in the modified reinforced area of ​​the embankment will not slide out of the slope between the two layers of low-mixed soil above and below it. Combining equations (8) to (13), we can obtain inequalities (14) and (15):

[0202] When h i When ≤6m, the inequality (14) is obtained:

[0203]

[0204] When h i When ≥6m, the inequality (15) is obtained:

[0205]

[0206] In inequalities (14) and (15), x is the cement content of high-mixed soil; is the internal friction angle of cement-modified soil, determined by formula (5);

[0207] Therefore, the cement content of each layer of high-mixed soil can be inversely calculated from inequalities (14) and (15).

[0208] S26: For the first failure mode of local instability of the slope, according to the "Code for Design of Railway Roadbed Support Structures" (TB10025-2019), when the pull-out stability coefficient of the geogrid is greater than or equal to 2, the geogrid will not be pulled out of the slope.

[0209] The pull-out stability coefficient of geogrid is calculated as follows:

[0210] K i =S fi / E xi (16)

[0211] In formula (10), K i is the pull-out stability coefficient of reinforcement i, S fi is the pull-out strength of reinforcement i, E xi is the horizontal earth pressure borne by reinforcement i.

[0212] See also Figure 6 , the pull-out strength S of reinforcement i fi for:

[0213] S fi =2σ vi aL b f (17)

[0214] In formula (17), σ vi is the vertical soil pressure stress, σ vi =γh i ,γ is the density of high-mixed soil, h i is the height from the top of the embankment to the reinforcement i; a is the width of the reinforcement; L b is the effective anchorage length of the reinforcement; f is the friction coefficient between reinforcement i and cement-modified soil, which is determined based on on-site pull-out tests.

[0215] Horizontal earth pressure E borne by reinforcement i xi Calculate according to formula (18):

[0216] E xi =σ hi S x S y (18)

[0217] In formula (18), σ hi is the horizontal soil pressure stress, S x 、S y is the horizontal and vertical spacing between reinforcements (m). When geogrid is used, S y =0.5m, S x =1m.

[0218] Combining equations (11) to (13) and (16) to (18), we can obtain the following equation:

[0219] When h i When ≤6m,

[0220] When h i ≥6m,

[0221] In formulas (19) and (20), x is the cement content, a is the width of the reinforcement, and L is b is the effective anchorage length of the reinforcement, is the internal friction angle of cement-modified soil, and f(x) is the friction coefficient between reinforcement and cement-modified soil when the dosage is x, which is obtained through on-site pull-out test.

[0222] Combined reinforcement pull-out stability coefficient K i ≥2, the cement content x of each layer of high-content cement-modified soil can be obtained by inverse calculation.

[0223] S27: See Figure 6 For the second failure mode of local instability of the slope, the design and calculation method is similar to the third failure mode of overall instability of the slope. The only difference is that the effective anchorage length of the high-mixed soil is L b , L b is the length of the anchorage area to the right of the 0.3H dividing line. Similarly, the cement content of each layer of high-mixed soil can also be obtained by inverse calculation.

[0224] Due to the high soil-admixture effective anchoring length L b It is smaller than the total length L of the high-mixed soil in the modified reinforced area. Therefore, the second failure mode of local instability of the slope is compared with the third mode of overall instability of the slope. The mixing amount of the high-mixed soil is greater than that of the third mode of overall instability of the slope.

[0225] Under the five aforementioned failure modes, the cement content of each layer of high-mixed soil and each layer of low-mixed soil is compared, and the larger value of the cement content of high-mixed soil and low-mixed soil is taken as the final cement content of each layer of high-mixed soil and each layer of low-mixed soil. This can ensure that the embankment slope remains stable both overall and locally.

[0226] Comparison of the method of the present invention with the existing method:

[0227] While existing embankment structures use 25% to 30% cement, the present invention uses only 12% to 15%, a reduction of 10% to 18%. Furthermore, calculations show that the amount of high- and low-admixture cement decreases vertically from bottom to top in the modified reinforced area. This maximizes the use of material properties, significantly reduces material waste, cement usage, and project costs.

[0228] Each embodiment in this specification is described in a related manner. Similar parts between the various embodiments can be referred to in conjunction with each other. Each embodiment focuses on the differences between the other embodiments. In particular, the system embodiment is generally similar to the method embodiment, so the description is relatively simple. For related parts, refer to the description of the method embodiment.

[0229] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention are included in the scope of protection of the present invention.

Claims

1. Horizontally partitioned modified reinforced steep slope embankment structure, including: The geogrid and geocell (3) are characterized in that they also include: a modified reinforced area (1) and a non-modified reinforced area (2); the modified reinforced area (1) is located 2 to 6 m from the surface of the embankment slope to the inside of the embankment; the rest of the embankment is the non-modified reinforced area (2); in the modified reinforced area (1), a layer of high-cement modified soil and a layer of low-cement modified soil are alternately distributed from bottom to top; the geogrid is fixed to each layer of high-cement modified soil and is wrapped upward to the adjacent layer of high-cement modified soil, and the adjacent geogrids are connected at the junction with a geogrid connecting rod (6).

2. The horizontal partition modified reinforced steep slope embankment structure according to claim 1 is characterized in that: The geocell (3) is fixed to the inner side of the slope surface and is wrapped by the geogrid; the geocell (3) is fixedly connected to a vegetation bag (4) filled with vegetation soil; and the non-modified reinforced area (2) is obtained by layering plain fill soil.

3. The design method of the horizontal partition modified reinforced steep slope embankment structure according to claim 1 or 2 is characterized in that: The following steps are involved: S1: According to the height of each layer of high-mixed cement modified soil and low-mixed cement modified soil after layered filling, the number of filling layers of high-mixed cement modified soil and low-mixed cement modified soil is obtained; S2: Obtain the most dangerous sliding surface of the embankment and calculate the cement content of each layer of high-content cement-modified soil and low-content cement-modified soil under different side slope instability modes; S3: Determine the cement content of each final layer of high-content and low-content cement-modified soil.

4. The design method of the horizontal partition modified reinforced steep slope embankment structure according to claim 3 is characterized in that: In S1, The height of each layer of high-mix cement modified soil after layered filling is 0.15m-0.25m. From bottom to top, each layer of high-mix cement modified soil is represented as: high-mix 1, high-mix 2, ... high-mix i ... high-mix n1; where i is the sequence number of high-mix cement modified soil, and n1 is the total number of filling layers of high-mix cement modified soil; geogrids are represented as: reinforcement 1, reinforcement 2, ... reinforcement i ... reinforcement n1; The height of each layer of low-content cement-modified soil on the embankment after layered filling is 0.25m-0.35m. From bottom to top, each layer of low-content cement-modified soil is represented as: low-content 1, low-content 2, ... low-content i... low-content n2; among which, i is the serial number of the low-content cement-modified soil, and n2 is the total number of filling layers of the low-content cement-modified soil.

5. The design method of the horizontal partition modified reinforced steep slope embankment structure according to claim 3 is characterized in that: The S2 includes: S21: Obtain the most dangerous sliding surface of the embankment; the first failure mode of the overall instability of the slope is: the soil below the embankment slope shears off the low-cement modified soil along the sliding surface, and the reinforcement slides out of the slope; The most dangerous sliding surface is cut into n soil strips longitudinally, among which the first n-1 soil strips are obtained by vertical cutting of the most dangerous sliding surface with equal arc length, and the nth soil strip is obtained by vertical cutting of the intersection of the most dangerous sliding surface and the low-content cement modified soil. i is the sequence number of the soil strip. For each soil strip i, the calculation formula of the landslide thrust transmitted by soil strip i to soil strip i+1 is as follows: In formula (1), W i is the self-weight of soil strip i; α i represents the angle between the tangent line of the lower arc of the i-th soil strip and the horizontal direction; F s is the safety factor; P i P represents the landslide thrust transmitted from soil strip i to soil strip i+1; i-1 represents the landslide thrust transmitted from soil strip i-1 to soil strip i; Q i represents the horizontal force acting on soil strip i; l i represents the length of soil strip i; u i represents the pore stress at the bottom of soil strip i; tan is the tangent function; c i '、 Respectively represent the lateral cohesion and internal friction angle of soil strip i; 1≤i<n-1; Transmission coefficient ψ i-1 Calculated by formula (2): Among them, α i-1 represents the angle between the tangent line of the lower arc of the i-1th soil strip and the horizontal direction; Calculate the landslide thrust from soil strips 1 to soil strips n-1 to soil strips 2 to soil strips n when sliding out of the slope from low-mix 1; S22: The anti-sliding force P of soil strip n is calculated as follows: In formula (3), S is the area of ​​soil strip n; γ is the density of soil, α′ is the angle between the tangent line of the lower arc of soil strip n and the horizontal direction, is the internal friction angle of cement-modified soil when the cement content is x, c′(x) is the cohesion of cement-modified soil when the cement content is x; l is the length of soil strip n, x is the cement content; Fitting the relationship between cement content x, cohesion c′(x), and internal friction angle through static triaxial test The relationship between c′(x)=80.23-48.34 / (1+e (x-5.06) / 1.12 ) (4) In formula (5), e represents the base of natural logarithm; The sum of the anti-sliding force P of soil strip n and the allowable tensile strength T of the geogrid is greater than the landslide thrust transmitted from soil strip n-1 to soil strip n. Simultaneously, equations (3), (4), and (5) are combined to solve the cement content x1 of low-mix 1. S23: Repeat S21-S22 to calculate the cement content x of low-mixed i when sliding out of the slope from low-mixed i. i ; until for low-mix a, the cement content is x a At this time, the landslide thrust transmitted from soil strip n-1 to soil strip n is a negative value. The upper soil layer with low admixture a, i.e., low admixture a+1 to low admixture n2, will not become unstable even without cement under the first failure mode of overall slope instability.

6. The design method of the horizontal partition modified reinforced steep slope embankment structure according to claim 5 is characterized in that: The S2 further includes: S24: The second failure mode of overall instability of the embankment slope is: the soil below the embankment slope shears off the low-cement modified soil along the sliding surface, and the reinforcement is pulled out of the slope; The pull-out resistance of geogrid is calculated as follows: S fi =2σ vi aLf (6) In formula (6): S fi is the pull-out resistance of reinforcement i; vi is the vertical soil pressure stress, σ vi =γh i , γ is the specific gravity of high-content cement-modified soil, h i is the height from the top of the embankment to the reinforcement i; a is the width of reinforcement i; L is the total length of reinforcement i in the high-mixed soil i; f is the friction coefficient between reinforcement i and cement-modified soil, which is determined based on on-site pull-out tests; The plain fill of the steep embankment was mixed with cement in different proportions, and the modified soil was subjected to on-site pull-out tests. The relationship between the friction coefficient of the reinforcement and the modified soil and the cement content was obtained, and a function was fitted. The fitting curve function f(x) formula between the friction coefficient between the reinforcement and the modified soil and the cement content is as follows: f(x)=0.49x 0.24 (7) The sum of the anti-sliding force P of soil strip n and the anti-pulling force of the geogrid is greater than the landslide thrust transmitted from soil strip n-1 to soil strip n. At the same time, by combining equations (3) to (7), the cement content x1, x2, ..., x2 of low-mix 1, low-mix 2, ..., low-mix a is obtained by inverse calculation. a At this time, the upper soil layer with low admixture a, that is, low admixture a+1 to low admixture n2, will not become unstable even without cement under the second failure mode of overall slope instability.

7. The design method of the horizontal partition modified reinforced steep slope embankment structure according to claim 3 is characterized in that: The S2 further includes: S25: The third failure mode of overall slope instability is: the high-cement modified soil in the modified reinforced area (1) slides out of the slope between the two layers of low-cement modified soil above and below it; The sum of the friction F between the high-content cement-modified soil and the upper and lower layers of low-content cement-modified soil is calculated as follows: F=σ vi1 Lam+s vi2 Lam (8) In formula (8), σ vi1 is the vertical soil pressure stress on the surface of high-doping i, L is the length of high-doping i, a is the width of high-doping i, σ vi2 is the vertical soil compressive stress on the surface under high-mixed i, μ is the friction coefficient between high-mixed i and low-mixed cement modified soil; Vertical earth pressure stress σ on the surface under high doping i vi2 Calculate as follows: s vi2 =γ(h i1 +h) (9) In formula (9), h i1 is the height from the top of the embankment to the upper surface of the high-doping i, γ represents the severity of the high-doping i; h is the height of the high-doping i; The horizontal earth pressure on the high-mixture i is: AND xi =σ hi has (10) In formula (10), σ hi is the horizontal soil stress on high-doping i; a is the width of high-doping i, Horizontal soil stressσ hi for: s hi =λ i c h i (11) In formula (11), h i is the height from the top of the embankment to the center of the high-doping i, λ i is the depth h in the modified reinforced zone (1) i The earth pressure coefficient at is calculated according to the following formulas (12) and (13): When h i When ≤6m, earth pressure coefficient λ i Calculate as follows: λ i =λ0(1-h i / 6)+λ a (h i / 6) (12) In formula (12), λ0 is the static earth pressure coefficient, is the internal friction angle of high-doping i; a is the active earth pressure coefficient, When h i >6m, l i =λ a (13) When F ≥ E xi When , the high-mixed soil in the modified reinforced area (1) will not slide out of the slope between the two layers of low-mixed soil above and below it. At the same time, by combining equations (8) to (13), we can obtain inequalities (14) and (15): When h i When ≤6m, the inequality (14) is calculated as follows: When h i When >6m, the inequality (15) is obtained: In inequalities (14) and (15), x is the cement content of high-soil blending; is the internal friction angle of cement-modified soil, determined by formula (5); The cement content of each layer of high-mixed soil is calculated by inverse calculation using inequalities (14) and (15).

8. The design method of the horizontal partition modified reinforced steep slope embankment structure according to claim 3 or 7 is characterized in that: The S2 further includes: S26: Local instability mode of embankment slope The first failure mode is: the reinforcement in the non-anchored area is pulled out of the slope from the middle of the high-cement modified soil; first, the rupture surface, non-anchored area, and anchored area are determined based on the 0.3H method. The pull-out stability coefficient of geogrid is calculated as follows: K i =S fi / E xi (16) In formula (10), K i is the pull-out stability coefficient of reinforcement i, S fi is the pull-out resistance of reinforcement i, E xi is the horizontal earth pressure on reinforcement i; Pullout resistance S of reinforcement i fi for: S fi =2σ vi aL b f (17) In formula (17), σ vi is the vertical soil pressure stress, σ vi =γh i , γ is the density of high-mixed soil, h i is the height from the top of the embankment to the reinforcement i; a is the width of the reinforcement; L b is the effective anchorage length of the reinforcement; f is the friction coefficient between reinforcement i and cement-modified soil, which is determined based on the on-site pull-out test; Horizontal earth pressure E on reinforcement i xi Calculate according to formula (18): AND xi =σ hi S x S y (18) In formula (18), σ hi is the horizontal soil compressive stress, S x , S y is the horizontal and vertical spacing between reinforcement i; Combining equations (11) to (13) and (16) to (18), we can obtain the following equation: When h i When ≤6m, When h i ≥6m, In formula (19) and (20), x is the cement content, is the internal friction angle of cement modified soil, f(x) is the friction coefficient between the reinforcement and cement modified soil when the dosage is x, which is obtained by formula (7); Reinforcement pull-out stability factor K i ≥2, the cement content x of each layer of high-content cement-modified soil is obtained by inverse calculation.

9. The design method of the horizontal partition modified reinforced steep slope embankment structure according to claim 3 or 7 is characterized in that: The S2 further includes: S27: The second failure mode of local instability of embankment slope is: the high-cement modified soil in the non-anchored area slides out of the slope between the two layers of low-cement modified soil above and below it; The sum of the friction F between the high-content cement-modified soil and the upper and lower layers of low-content cement-modified soil is calculated as follows: F=σ vi1 50 b aμ+σ vi2 50 b aμ (21) In formula (8), σ vi1 is the vertical soil pressure stress on the surface of high-doped i, L b is the effective anchoring length of high-doped i, a is the width of high-doped i, σ vi2 is the vertical soil compressive stress on the surface under high-mixed i, μ is the friction coefficient between high-mixed i and low-mixed cement modified soil; Vertical earth pressure stress σ on the surface under high doping i vi2 Calculated by formula (9), The horizontal earth pressure on high-mixed i is calculated by equations (10) to (13): When F ≥ E xi When , the high-mixed soil in the modified reinforced area (1) will not slide out of the slope between the two layers of low-mixed soil above and below it. At the same time, by combining equations (21), (8) to (13), we can obtain inequalities (22) and (23): When h i When ≤6m, the inequality (22) is calculated as follows: When h i When >6m, the inequality (23) is obtained: The cement content of each layer of high-mixed soil is obtained by inverse calculation using inequalities (22) and (23).

10. The design method of the horizontal partition modified reinforced steep slope embankment structure according to claim 3 is characterized in that: The S3 includes: Compare the cement content of each layer of high-mixed soil and each layer of low-mixed soil, and take the larger value of the cement content of high-mixed soil and low-mixed soil as the final cement content of each layer of high-mixed soil and each layer of low-mixed soil.

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