Retaining wall with combination of buttress and relieving slab and internal force calculation method thereof

Abstract

The present application relates to the field of slope support engineering, and provides a retaining wall with a combination of a retaining plate and an unloading plate and a method for calculating internal force of the retaining wall, which comprises a bottom plate, a first vertical plate, a second vertical plate, a retaining plate and an unloading plate, all of which are reinforced concrete structures; the retaining wall structure is filled with backfill behind the structure; the first vertical plate is arranged on the bottom plate, the second vertical plate is arranged directly above the first vertical plate, and the first vertical plate, the second vertical plate and the retaining plate are overlapped; the unloading plate is arranged between the first vertical plate and the second vertical plate, and forms an unloading and decompression platform; the unloading plate is overlapped with the adjacent retaining plate, the first vertical plate and / or the second vertical plate. The combination of the retaining plate and the unloading plate effectively reduces the horizontal earth pressure acting on the retaining wall, reduces the internal force of the structure on the retaining wall, including shear force and bending moment, reduces the horizontal displacement of the retaining wall, and reduces the cross-sectional size of the retaining wall structure, thereby reducing the difficulty and cost of engineering construction.

Description

Technical Field

[0001] This invention relates to the field of slope protection engineering, and in particular to a combined retaining wall of buttress panels and unloading plates and its internal force calculation method. Background Technology

[0002] Embankment slope engineering is a crucial sub-project in building construction, railway engineering, highway engineering, and water conservancy and port engineering. Commonly used support methods for embankment slope engineering include gravity retaining walls, cantilever retaining walls, buttress retaining walls, anchored plate retaining walls, and reinforced soil retaining walls. The height of gravity retaining walls should not exceed 8m, cantilever retaining walls should not exceed 6m, buttress retaining walls should not exceed 10m, anchored plate retaining walls should not exceed 8m per level, and reinforced soil retaining walls should not exceed 10m per level. For taller embankment slopes, the earth pressure acting on the retaining structure increases exponentially, and the above retaining wall methods become somewhat insufficient in terms of structural stress, construction difficulty, and cost. Furthermore, with the soaring land costs in large and medium-sized cities in my country, construction units have increasingly higher requirements for soil usability, with most requiring that slope support structures not occupy the embankment site or affect its use. Therefore, for high embankment slope projects, the structural form that effectively reduces the earth pressure on the retaining structure—the combined retaining wall of buttress board and unloading board—is an effective solution to reduce the difficulty and cost of engineering construction.

[0003] Unloading plate retaining walls are widely used in port construction projects in my country. The railway sector has conducted a series of studies since the 1960s, concluding that unloading plates use the backfill soil on the plate as gravity (counterweight) to resist overturning moments. Simultaneously, the unloading effect of the plate reduces the horizontal earth pressure acting on the back of the wall, saving materials and lowering costs. However, current building slope engineering codes do not include relevant provisions for unloading plates. Therefore, content on the calculation methods for earth pressure and internal forces in buttress + unloading plate combined retaining walls is essential. Summary of the Invention

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] This invention provides a combined retaining wall of buttress panels and unloading plates, comprising a base slab, a first vertical slab, a second vertical slab, buttress panels, and unloading plates, all of which are reinforced concrete structures. Backfill material is placed behind the retaining wall structure. The first vertical slab is positioned on the base slab, and the second vertical slab is positioned directly above the first vertical slab, overlapping with the buttress panels. The unloading plate is positioned between the first and second vertical slabs, forming an unloading and pressure-reducing platform. The unloading plate overlaps with adjacent buttress panels and the first and / or second vertical slabs. The base slab, first vertical slab, second vertical slab, and buttress panels form a triangle. The unloading plate is embedded at approximately the middle height of the retaining wall, and the ratio of the unloading plate length to the corresponding retaining wall segment length is between 1.2 and 1.5. The number of unloading plates can be determined based on the net height of the retaining wall.

[0006] Preferably, the buttress panel is a right-angled triangle.

[0007] Preferably, the backfill soil is permeable sand and gravel soil to prevent water from failing to drain behind the wall and causing instability of the retaining wall.

[0008] Furthermore, when the concrete strength of the first vertical slab and buttress slab reaches 75% or more of the design strength, backfill soil in layers and compact it to the design elevation of the bottom of the unloading slab; after leveling the plain concrete cushion layer, tie the unloading slab reinforcement, erect formwork, and pour concrete; complete the reinforcement binding and concrete pouring of the remaining vertical slabs and buttress slabs, backfill with sand and compact it to the design elevation of the backfill at the top of the wall.

[0009] This invention also provides a method for calculating the internal forces of a retaining wall composed of buttress panels and unloading plates.

[0010] The retaining wall composed of buttress panels and unloading plates includes a main structure and an auxiliary structure. The main structure is a buttress retaining wall, which includes a base plate, vertical plates, and buttress panels. The vertical plates include a first vertical plate and a second vertical plate, with the second vertical plate positioned directly above the first vertical plate. The auxiliary structure is an unloading plate.

[0011] The internal force calculation method includes:

[0012] (1) Calculate the horizontal earth pressure σ above the bottom of the unloading plate. a ;

[0013] (2) Calculate the horizontal earth pressure value in the unloading zone at the bottom of the unloading plate;

[0014] (3) Calculate the horizontal earth pressure unloading value ΔE per meter in the unloading zone. aX ;

[0015] (4) Calculate the horizontal earth pressure values ​​at the remaining locations;

[0016] Calculated according to Equation 1, σ a =γzKa Formula 1

[0017] (5) Determine the distribution diagram of horizontal earth pressure on the back of the composite retaining wall;

[0018] (6) Calculate the standard value of shear force V of the main structure. kz and the standard value of bending moment M kz ;

[0019] (7) Calculate the internal forces of the auxiliary structure; the unloading plate of the auxiliary structure is simplified to the first rectangular plate element with three fixed ends and one free end. The upper part is subjected to the weight of the soil and its own weight. The calculation can be carried out in accordance with the relevant content of the "Handbook of Static Calculation of Building Structures" (Second Edition).

[0020] Furthermore, in step (1), the horizontal earth pressure value σ above the bottom of the unloading plate a The specific expression is:

[0021] The horizontal earth pressure intensity σ acting on the back of the wall above the unloading plate a The expression is:

[0022] σ a =γzK a Formula 1

[0023] When considering the horizontality of the backfill surface behind the wall, the Coulomb active earth pressure coefficient K a The formula is:

[0024]

[0025] Where z represents the vertical distance from the top of the wall;

[0026] γ represents the natural unit weight of the backfill soil.

[0027] δ is the internal friction angle of the backfill soil, α is the external friction angle between the backfill soil and the wall backing material, and α is the angle between the imaginary wall backing behind the retaining wall and the vertical plane.

[0028] Furthermore, the specific calculation process for step (2) is as follows:

[0029] Let point D be a point on the horizontal edge of the unloading plate. Then the formula for the horizontal earth pressure strength at point D is:

[0030] σ ad =γh1K a Formula 3

[0031] Where h1 represents the length of the second vertical plate;

[0032] Let point A be the junction between the bottom of the unloading slab and the buttress slab. Since the backfill above the unloading slab is entirely borne by the unloading slab, the formula for the horizontal earth pressure intensity at point A is σ. aa =0 Equation 4;

[0033] Draw a line from point D on the bottom edge of the unloading plate at an angle to the horizontal line of the bottom of the unloading plate. The straight lines θ and θ intersect the vertical plate at points B and C, respectively. θ is the internal friction angle of the backfill soil, and θ is the fracture angle of the backfill soil;

[0034] The formula for the horizontal earth pressure strength at intersection B is:

[0035] Where l represents the length of the unloading plate;

[0036] The formula for the horizontal earth pressure intensity at intersection C, without considering the unloading effect of the unloading plate, is: σ ac =γ(h1+ltanθ)K a Formula 6;

[0037] Furthermore, let point E be the intersection of the base plate and the vertical plate. Does the intersection point C, determined by ltanθ, exceed point E?

[0038] When intersection point C does not exceed the length of the vertical plate, the earth pressure distribution points under the unloading plate are in the order of ABCE, and the horizontal earth pressure intensity at point E is: σ ae =γ(h1+h2)K a Formula 7;

[0039] When the intersection point C exceeds the length range of the vertical plate, the earth pressure distribution points under the unloading plate are in the order ABE. The horizontal earth pressure intensity value at point E is obtained using the finite difference method.

[0040] Specifically, the horizontal earth pressure intensity value at point C calculated by Equation 6 and the horizontal earth pressure intensity value at point B calculated by Equation 5 are used to obtain the horizontal earth pressure intensity value σ at point E. ae Specifically:

[0041]

[0042] Furthermore, in step (3), the unloading value ΔE of the horizontal earth pressure per meter in the unloading zone. ax The specific expression is:

[0043]

[0044] Where l represents the length of the unloading plate;

[0045] Furthermore, in step (5), the earth pressure intensity values ​​of the control points (i.e., the earth pressure distribution points under the unloading plate) and their corresponding heights are plotted and connected in sequence to form a horizontal earth pressure distribution diagram of the combined retaining wall.

[0046] Furthermore, the specific calculation process for step (6) is as follows:

[0047] The main structure is simplified to a cantilevered variable cross-section T-beam, and the load acting on it is the earth pressure determined in step (5);

[0048] Standard value of shear force V acting on the section at a distance z from the top of the wall of the main structure kz for:

[0049] The standard value of the bending moment M acting on the section at a distance z from the top of the wall of the main structure kz for:

[0050] Where, σ ay The value is the earth pressure value corresponding to the upper y direction in the earth pressure distribution diagram in step (5).

[0051] Furthermore, the first upright plate, the second upright plate, and the buttress plate overlap, and the base plate, the first upright plate, the second upright plate, and the buttress plate form a triangle, wherein the lower end of the first upright plate, the upper end of the second upright plate, and the lower end of the buttress plate constitute the three vertices of the triangle.

[0052] Before calculating the internal forces, the retaining wall needs to be simplified. The simplification includes:

[0053] The unloading plate in the retaining wall is simplified as a first rectangular plate unit with three fixed ends and one free end. The three fixed ends include the upper end of the first vertical plate, the lower end of the second vertical plate, and the corresponding buttress plate end.

[0054] The toe plate of the inner bottom slab of the retaining wall is simplified to a cantilever beam unit fixed to the main body of the retaining wall; the heel plate of the bottom slab is simplified to a second rectangular plate unit with three ends fixed and one end free.

[0055] The first upright plate is simplified into a third rectangular plate unit with three ends fixed and one end free.

[0056] The second upright plate is simplified into a fourth rectangular plate unit with four fixed ends;

[0057] The buttress panel is simplified as a variable cross-section T-shaped cantilever beam unit fixed on the base plate;

[0058] In this unit, the flange plates of the variable cross-section T-shaped cantilever beam are the first vertical plate and the second vertical plate, and the web plate of the variable cross-section T-shaped cantilever beam is the buttress plate.

[0059] The present invention has the following beneficial effects:

[0060] This invention effectively reduces the horizontal earth pressure acting on the retaining wall by combining buttress panels and unloading plates, thereby reducing the internal forces on the retaining wall structure, including shear force and bending moment; reducing the horizontal displacement of the retaining wall; reducing the cross-sectional dimensions of the retaining wall structure; reducing the amount of concrete and steel reinforcement used; and reducing the difficulty and cost of engineering construction. It is also applicable to high embankment slope engineering. Attached Figure Description

[0061] Figure 1 This is a cross-sectional view of the combined retaining wall of the present invention.

[0062] Figure 2 This is a flowchart of the internal force calculation process of the present invention.

[0063] Figure 3 This is a cross-sectional view of the combined retaining wall of the present invention with annotations.

[0064] Figure 4 This is a cross-sectional view of the combined retaining wall in an embodiment.

[0065] Figure 5 This is a diagram showing the earth pressure distribution in the embodiment.

[0066] Figure 6 This is a line graph showing the standard shear force of a 4m wide retaining wall in the embodiment.

[0067] Figure 7 This is a line graph showing the standard bending moment value of the 4m wide retaining wall in the embodiment. Detailed Implementation

[0068] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the embodiments are only specific illustrations of the invention and should not be regarded as limitations on the invention. The purpose of the embodiments is to enable those skilled in the art to better understand and reproduce the technical solution of the present invention. The scope of protection of the present invention should still be determined by the scope defined in the claims.

[0069] like Figure 1 As shown, the present invention provides a retaining wall composed of buttress panels and unloading plates, including a base slab 1, a first vertical plate 2, a second vertical plate 3, a buttress panel 4, and an unloading plate 5, all of which are reinforced concrete structures; backfill material 6 is filled behind the retaining wall structure; the first vertical plate 2 is disposed on the base slab 1, and the second vertical plate 3 is disposed directly above the first vertical plate 2, with the second vertical plate 3 overlapping the buttress panel 4; the unloading plate 5 is disposed between the first vertical plate 2 and the second vertical plate 3, forming an unloading and pressure-reducing platform; the unloading plate 5 overlaps with adjacent buttress panels and the first vertical plate 2 and / or the second vertical plate 3; the base slab 1, the first vertical plate 2, the second vertical plate 3, and the buttress panel 4 form a triangle.

[0070] Preferably, the buttress panel 4 is a right-angled triangle.

[0071] Preferably, the backfill soil 6 is permeable sand and gravel soil to prevent water from failing to drain behind the wall and causing instability of the retaining wall.

[0072] In some preferred schemes, the retaining wall is constructed in sections from bottom to top. The first section is constructed up to the bottom of the unloading slab. When the concrete strength of the vertical slab and buttress reaches 75% or more of the design value, sand is backfilled in layers to the design elevation of the bottom of the unloading slab. After leveling with plain concrete, the reinforcement of the unloading slab is tied, formwork is erected, and concrete is poured. The above construction procedures are repeated to complete the construction of the upper unloading slab, and finally the entire structure construction and backfilling work behind the wall are completed.

[0073] This invention also provides a method for calculating the internal forces of a retaining wall composed of buttress panels and unloading plates.

[0074] The retaining wall composed of buttress plate and unloading plate includes a main structure and an auxiliary structure. The main structure is a buttress retaining wall, which includes a base plate 1, vertical plates and buttress plates 4. The vertical plates include a first vertical plate 2 and a second vertical plate 3, with the second vertical plate 3 located directly above the first vertical plate 2. The auxiliary structure is an unloading plate 5.

[0075] like Figure 2 As shown, the internal force calculation method includes:

[0076] S1, Calculate the horizontal earth pressure σ above the bottom of the unloading plate. a ;

[0077] The horizontal earth pressure intensity σ acting on the back of the wall above the unloading plate a The expression is:

[0078] σ a =γzK a Formula 1

[0079] When considering the horizontality of the backfill surface behind the wall, the Coulomb active earth pressure coefficient K a The formula is:

[0080]

[0081] Where z represents the vertical distance from the top of the wall;

[0082] γ represents the natural unit weight of the backfill soil.

[0083] δ is the internal friction angle of the backfill soil, α is the external friction angle between the backfill soil and the wall backing material, and α is the angle between the imaginary wall backing behind the retaining wall and the vertical plane.

[0084] S2, calculate the horizontal earth pressure value in the unloading zone at the bottom of the unloading plate;

[0085] like Figure 3As shown, let point D be a point on the horizontal edge of the unloading plate. Then the formula for the horizontal earth pressure strength at point D is: σ ad =γh1K a Formula 3

[0086] Let point A be the junction between the bottom of the unloading slab and the buttress slab. Since the backfill above the unloading slab is entirely borne by the unloading slab, the formula for the horizontal earth pressure intensity at point A is σ. aa =0 Equation 4;

[0087] Draw a line from point D on the bottom edge of the unloading plate at an angle to the horizontal line of the bottom of the unloading plate. The straight lines θ and θ intersect the vertical plate at points B and C, respectively. θ is the internal friction angle of the backfill soil, and θ is the fracture angle of the backfill soil;

[0088] The formula for the horizontal earth pressure strength at intersection B is:

[0089] The formula for the horizontal earth pressure intensity at intersection C, without considering the unloading effect of the unloading plate, is: σ ac =γ(h1+ltanθ)K a Formula 6;

[0090] Let point E be the intersection of the base plate and the vertical plate. Does the intersection point C, determined by ltanθ, exceed point E?

[0091] When intersection point C does not exceed the length of the vertical plate, the earth pressure distribution points under the unloading plate are in the order of ABCE, and the horizontal earth pressure intensity at point E is: σ ae =γ(h1+h2)K a Formula 7;

[0092] When the intersection point C exceeds the length range of the vertical plate, the earth pressure distribution points under the unloading plate are in the order ABE. The horizontal earth pressure intensity value at point E is obtained using the finite difference method.

[0093] Specifically, the horizontal earth pressure intensity value at point C calculated by Equation 6 and the horizontal earth pressure intensity value at point B calculated by Equation 5 are used to obtain the horizontal earth pressure intensity value σ at point E. ae Specifically:

[0094]

[0095] S3, calculate the horizontal earth pressure unloading value ΔE per meter in the unloading zone. aX (i.e., the shaded area);

[0096]

[0097] Where l represents the length of the unloading plate;

[0098] h1 represents the length of the second vertical plate;

[0099] h2 represents the length of the first vertical plate;

[0100] S4, calculate the horizontal earth pressure values ​​at the remaining locations;

[0101] The strength value is calculated using the Coulomb active earth pressure method without considering the unloading effect of the unloading plate, i.e., according to Equation 1, σ a =γzK a Formula 1;

[0102] S5, determine the horizontal earth pressure distribution diagram on the back of the composite retaining wall; by drawing the earth pressure intensity values ​​of the control points and their corresponding heights, and connecting them in order, the horizontal earth pressure distribution diagram of the composite retaining wall is formed.

[0103] S6, Calculate the standard value of the shear force V of the main structure. kz and the standard value of bending moment M kz ;

[0104] The main structure is simplified to a cantilevered variable cross-section T-beam, on which the load is the earth pressure determined according to step S5;

[0105] Standard value of shear force V acting on the section at a distance z from the top of the wall of the main structure kz for:

[0106] The standard value of the bending moment M acting on the section at a distance z from the top of the wall of the main structure kz for:

[0107] Where, σ ay The value is the earth pressure value corresponding to the upper y-direction in the earth pressure distribution diagram in step S5.

[0108] (7) Calculate the internal forces of the auxiliary structure; the unloading plate of the auxiliary structure is simplified to the first rectangular plate element with three fixed ends and one free end. The upper part is subjected to the weight of the soil and its own weight. The calculation can be carried out in accordance with the relevant content of the "Handbook of Static Calculation of Building Structures" (Second Edition).

[0109] In some preferred embodiments, the second upright plate 3 overlaps with the buttress plate 4, and the base plate 1, the first upright plate 2, the second upright plate 3 and the buttress plate 4 form a triangle, wherein the lower end of the first upright plate 2, the upper end of the second upright plate 3 and the lower end of the buttress plate 4 constitute the three vertices of the triangle.

[0110] Before calculating the internal forces, the retaining wall needs to be simplified. The simplification includes:

[0111] The unloading plate 5 in the retaining wall is simplified as a first rectangular plate unit with three ends fixed and one end free. The three fixed ends include the upper end of the first vertical plate, the lower end of the second vertical plate, and the corresponding buttress plate end.

[0112] The toe plate of the inner bottom plate 1 of the retaining wall is simplified to a cantilever beam unit fixed on the main body of the retaining wall; the heel plate of the bottom plate is simplified to a second rectangular plate unit with three ends fixed and one end free.

[0113] The first upright plate 2 is simplified into a third rectangular plate unit with three ends fixed and one end free.

[0114] The second upright plate 3 is simplified into a fourth rectangular plate unit with four fixed ends;

[0115] Buttress panel 4 is simplified as a variable cross-section T-shaped cantilever beam unit fixed on the base plate;

[0116] In this unit, the flange plates of the variable cross-section T-shaped cantilever beam are the first vertical plate and the second vertical plate, and the web plate of the variable cross-section T-shaped cantilever beam is the buttress plate.

[0117] Example

[0118] The fill height of a certain project is approximately 18.5m. The foundation is moderately weathered slate. The backfill soil behind the wall is well-graded sand and gravel with a unit weight γ of 19kN / m3, a cohesion c of 0kPa, and an internal friction angle of... The angle is 30°, and the overload at the top of the wall is considered as an equivalent uniformly distributed load, with q = 20 kPa. The retaining wall adopts a combination of buttress slabs and unloading slabs, such as... Figure 4 As shown.

[0119] The retaining wall has a total height of 20.5m, a base slab thickness of 2m, a vertical slab height of 18.5m, a buttress spacing of 4m, and a buttress thickness of 0.6m. Various combinations of load-bearing plate embedment depth and length were created. Analysis revealed the optimal combination for load-bearing effect: the embedment depth of the load-bearing plates is approximately at the midpoint of the retaining wall, and the ratio of the load-bearing plate length to the corresponding retaining wall section length is between 1.2 and 1.5. Considering the net height of the retaining wall is 18.5m, two load-bearing plates are installed, located 5.5m and 11.5m below the top of the wall, with lengths of 4m and 4.5m respectively.

[0120] The retaining wall composed of buttress plate and unloading plate includes a main structure and an auxiliary structure. The main structure is a buttress retaining wall, which includes a base plate 1, a vertical plate 20 and a buttress plate 4. The vertical plate 20 includes at least one first vertical plate 2 and a second vertical plate 3, with the second vertical plate 3 located directly above the first vertical plate 2. The auxiliary structure is an unloading plate 5.

[0121] The main load-bearing component of the composite retaining wall is the buttress retaining wall, which can be regarded as a cantilevered variable cross-section T-beam fixed on the base plate 1, and its calculation unit width is 4m.

[0122] Calculation of unloading range and earth pressure at the bottom of the first unloading plate:

[0123] The line connecting the bottom edge of the unloading plate forms The distance from the wall point to the bottom of the unloading plate is Its corresponding horizontal earth pressure value is

[0124] The distance from the bottom edge of the unloading plate to the wall point at an angle θ is ltanθ = 6.93m. Since 6.93m exceeds the height of the second wall section by 6m, the earth pressure intensity at this location needs to be calculated by taking the earth pressure intensity at the 6.93m position and then using the difference method to obtain the specific value of 64.78kPa.

[0125] The unloading value of the first unloading plate is ΔE. ax =183.32 kPa / m.

[0126] Calculation of unloading range and earth pressure at the bottom of the second unloading plate:

[0127] The line connecting the bottom edge of the unloading plate forms The distance from the wall point to the bottom of the unloading plate is Its corresponding horizontal earth pressure value is

[0128] The distance from the bottom edge of the unloading plate to the wall point at an angle θ is ltanθ = 7.79m. Since 7.79m exceeds the height of the third wall section by 7m, the earth pressure intensity at this location needs to be calculated by taking the earth pressure intensity at the 7.79m position and then using the difference method to obtain the specific value of 123.50kPa.

[0129] The unloading value of the second unloading plate is ΔE. ax = 343.32 kPa / m.

[0130] By plotting the earth pressure intensity values ​​of control points against their corresponding heights and connecting them in sequence, a horizontal earth pressure distribution diagram of the combined retaining wall is formed. The distribution of horizontal earth pressure acting on the back of the retaining wall is shown in the figure. Figure 5 As shown, it is compared with a buttress retaining wall of the same height.

[0131] Integrate based on the horizontal earth pressure distribution diagram.

[0132] Standard value of shear force V acting on the section at a distance z from the top of the wall of the main structure kz for:

[0133] The standard value of the bending moment M acting on the section at a distance z from the top of the wall of the main structure kz for:

[0134] Calculate the standard value V of the action on the retaining wall. kz like Figure 6 As shown.

[0135] The standard value of the bending moment M on the retaining wall was calculated. kz like Figure 7 As shown.

[0136] from Figure 6-7 As can be seen, the earth pressure of the composite retaining wall is much smaller than that of the buttress retaining wall. The maximum shear force of the composite retaining wall with unloading plate is only 71.46% of that of the buttress retaining wall, and the maximum bending moment of the composite retaining wall is only 73.99% of that of the buttress retaining wall.

[0137] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0138] It should be noted that any technical features not described in detail in this invention can be implemented using any existing technology.

Claims

1. A method for calculating the internal forces of a retaining wall composed of buttress panels and unloading plates, characterized in that, The combined retaining wall of buttress and unloading plate includes a main structure and an auxiliary structure. The main structure is a buttress retaining wall, which includes a base slab, a first vertical slab, a second vertical slab, and a buttress, all of which are reinforced concrete. The auxiliary structure is an unloading plate. Backfill material is placed behind the retaining wall structure. The first vertical slab is placed on the base slab, and the second vertical slab is placed directly above the first vertical slab. The first and second vertical slabs overlap with the buttress. The unloading plate is placed between the first and second vertical slabs, forming an unloading and pressure-reducing platform. The unloading plate overlaps with adjacent buttresses, as well as the first and / or second vertical slabs. The base plate, the first upright plate, the second upright plate, and the buttress plate form a triangle; The internal force calculation method includes: (1) Calculate the horizontal earth pressure above the bottom of the unloading plate. ; Horizontal earth pressure intensity The expression is: Formula 1 When considering the horizontality of the backfill surface behind the wall, the Coulomb active earth pressure coefficient The formula is: Formula 2 in, Indicates the vertical distance from the top of the wall; The natural density of the backfill soil. The internal friction angle of the backfill soil. The external friction angle between the backfill soil and the wall backing material. The angle between the imaginary back of the retaining wall and the vertical plane; (2) Calculate the horizontal earth pressure value in the unloading zone at the bottom of the unloading plate; The specific calculation process is as follows: Let point D be a point on the horizontal edge of the unloading plate. Then the formula for the horizontal earth pressure intensity at point D is: Formula 3 in, Indicates the length of the second upright plate; Let point A be the junction between the bottom of the unloading slab and the buttress slab. Since the backfill above the unloading slab is entirely borne by the unloading slab, the formula for the horizontal earth pressure strength at point A is: Equation 4; Draw a line from point D on the bottom edge of the unloading plate at an angle to the horizontal line of the bottom of the unloading plate. and The straight lines intersect the vertical plate at points B and C, respectively. The internal friction angle of the backfill soil. For the crack angle of the backfill soil; The formula for the horizontal earth pressure strength at intersection B is: Formula 5; in, Indicates the length of the unloading plate; The formula for the horizontal earth pressure intensity at intersection C, without considering the unloading effect of the unloading plate, is as follows: Formula 6; Let point E be the junction of the base plate and the vertical plate. Does the determined intersection point C extend beyond point E? When intersection point C does not exceed the length of the vertical plate, the earth pressure distribution points under the unloading plate are in the order of ABCE, and the horizontal earth pressure intensity value at point E is: Formula 7; in, Indicates the length of the first upright plate; When the intersection point C exceeds the length range of the vertical plate, the earth pressure distribution points under the unloading plate are in the order ABE. The horizontal earth pressure intensity value at point E is obtained using the finite difference method. Specifically, the horizontal earth pressure intensity value at point C calculated by Equation 6 and the horizontal earth pressure intensity value at point B calculated by Equation 5 are used to obtain the horizontal earth pressure intensity value at point E. Specifically: Formula 8; in, Indicates the length of the unloading plate; (3) Calculate the unloading value of horizontal earth pressure per meter in the unloading zone. ; (4) Calculate the horizontal earth pressure values ​​at the remaining locations; (5) Determine the distribution diagram of horizontal earth pressure on the back of the composite retaining wall; (6) Calculate the standard value of shear force of the main structure. and standard value of bending moment ; (7) Calculate the internal forces of the auxiliary structure.

2. The method for calculating the internal forces of a retaining wall composed of buttress panels and unloading plates according to claim 1, characterized in that, When the concrete strength of the first upright slab and buttress slab reaches more than 75% of the design strength, backfill soil in layers and compact it to the design elevation of the bottom of the unloading slab.

3. The method for calculating the internal forces of a retaining wall composed of buttress panels and unloading plates according to claim 1, characterized in that, Step (3) Unloading value of horizontal earth pressure per meter in the unloading zone The specific expression is: Formula 9.

4. The method for calculating the internal forces of a retaining wall composed of buttress panels and unloading plates according to claim 1, characterized in that, Step (5) involves drawing the earth pressure intensity values ​​of the control points and their corresponding heights, and connecting them in sequence to form a horizontal earth pressure distribution diagram of the combined retaining wall.

5. The method for calculating the internal forces of a retaining wall composed of buttress panels and unloading plates according to claim 1, characterized in that, The specific calculation process for step (6) is as follows: The main structure is simplified to a cantilevered variable cross-section T-beam, and the load acting on it is the earth pressure determined in step (5); Standard value of shear force acting on the section at a distance z from the top of the wall of the main structure for: Formula 10; Standard value of bending moment acting on the section at z-distance from the top of the wall of the main structure for: Formula 11; in, The value of earth pressure at the y-direction in the earth pressure distribution diagram in step (5) is the earth pressure value.

6. The method for calculating the internal forces of a retaining wall composed of buttress panels and unloading plates according to claim 1, characterized in that, The first upright plate, the second upright plate, and the buttress plate overlap, and the base plate, the first upright plate, the second upright plate, and the buttress plate form a triangle, wherein the lower end of the first upright plate, the upper end of the second upright plate, and the lower end of the buttress plate constitute the three vertices of the triangle. Before calculating the internal forces, the retaining wall needs to be simplified. The simplification includes: The unloading plate in the retaining wall is simplified as a first rectangular plate unit with three fixed ends and one free end. The three fixed ends include the upper end of the first vertical plate, the lower end of the second vertical plate, and the corresponding buttress plate end. The toe plate of the inner bottom slab of the retaining wall is simplified to a cantilever beam unit fixed to the main body of the retaining wall; the heel plate of the bottom slab is simplified to a second rectangular plate unit with three ends fixed and one end free. The first upright plate is simplified into a third rectangular plate unit with three ends fixed and one end free. The second upright plate is simplified into a fourth rectangular plate unit with four fixed ends; The buttress panel is simplified as a variable cross-section T-shaped cantilever beam unit fixed on the base plate; In this unit, the flange plates of the variable cross-section T-shaped cantilever beam are the first vertical plate and the second vertical plate, and the web plate of the variable cross-section T-shaped cantilever beam is the buttress plate.

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