A combined cast-in-place road structure and a design method thereof

Abstract

The application discloses a combined pouring type road structure, which comprises, from bottom to top, a lower roadbed, an upper roadbed, a transition layer, a bottom base layer, a base layer and a surface layer, wherein the lower roadbed is a natural roadbed, the upper roadbed and the transition layer are formed by pouring flow-solidified soil, the base layer and the bottom base layer are formed by pouring flow-solidified slag soil, and the surface layer is an asphalt concrete or a cement concrete pavement; wherein the flow-solidified soil is composed of waste soil, clean water and a cementing agent; the flow-solidified slag soil is composed of waste slag soil containing sand and stone aggregates, clean water and a cementing agent; the application further discloses a design method of the combined pouring type road structure; and the application has the advantages of good overall performance, high utilization rate of waste slag soil resources and the like, and can be applied to new construction, reconstruction and expansion projects of roads of various grades.

Description

Technical Field

[0001] This invention relates to the field of road construction technology. More specifically, this invention relates to a composite cast-in-place road structure and its design method. Background Technology

[0002] Currently, the total length of highways in China has reached 5.2807 million kilometers. In the stage of "emphasizing both construction and maintenance," the demand for filling materials for roadbeds and base courses in road reconstruction and expansion projects is enormous. Traditional filling materials for roadbeds, subbases, and base courses are loose materials (such as backfill soil, graded gravel, graded crushed stone, cement-stabilized crushed stone, etc.). The use of stone filling is difficult to guarantee, and it consumes a large amount of high-quality natural resources, which will have irreversible impacts on resources, environment, and ecology. Moreover, in order to meet the requirements of pavement structural stability, vibratory compaction technology must be used to compact the pavement in layers to achieve the designed rebound modulus. Therefore, the requirements for the above-mentioned loose materials (such as the moisture content and organic matter content of backfill soil, the gradation and mud content of crushed stone, etc.) are quite stringent, resulting in greater difficulty in quality control during the construction process.

[0003] Furthermore, in seasonally frozen soil areas, the water stability of backfill soil used in roller-compacted roadbeds is poor. Under freeze-thaw cycles, differential settlement occurs in the roadbed, leading to pavement cracks. Repeated axle traffic from vehicles can cause pavement pumping and frost heaving, which will negatively impact various pavement evaluation indices in the long term and cause significant challenges to later highway operation and maintenance. Therefore, there is an urgent need to design a road structure to address the problems of unreliable fill material sources and poor road quality. Summary of the Invention

[0004] Another objective of this invention is to provide a combined cast-in-place road structure and its design method, which has advantages such as good overall performance and high utilization rate of waste soil resources, and can be applied to the construction, reconstruction and expansion of roads of all grades.

[0005] To achieve these objectives and other advantages according to the present invention, a composite cast-in-place road structure is provided, comprising, from bottom to top, a lower roadbed, an upper roadbed, a transition layer, a subbase, a base course, and a surface course, wherein the lower roadbed is a natural roadbed, the upper roadbed and the transition layer are cast from fluidized solidified soil, the base course and the subbase are cast from fluidized solidified slag, and the surface course is asphalt concrete or cement concrete pavement.

[0006] The fluidized solidified soil is composed of waste soil, clean water, and a binder; the fluidized solidified slag soil is composed of waste slag containing sand and gravel aggregate, clean water, and a binder.

[0007] Preferably, the binder in the fluidized solidified soil is the same as the binder in the fluidized solidified slag soil, both being geopolymer-based soft soil binders.

[0008] Preferably, both the transition layer and the base layer have multiple slits spaced apart along the length of the road, and any slit is set along the width of the road. The slits of the transition layer extend downward to the upper roadbed, and the slits of the transition layer are filled with adhesive, and the top surface is covered with polypropylene woven fabric or polypropylene braided fabric. The slits of the base layer extend downward to the subbase layer, and the slits of the base layer are filled with asphalt, and the top surface is covered with fiberglass grid.

[0009] A design method for a composite cast-in-place road structure specifically includes the following steps:

[0010] S1. Based on the service life of the road design, the cumulative number of vehicle axle loads, and the traffic load level, determine the standard value of the top surface equivalent resilient modulus of the surface layer; determine the top surface equivalent resilient modulus of the subgrade based on the site survey; based on the determined top surface equivalent resilient modulus of the subgrade, set the initial design values ​​of the resilient modulus and structural thickness of the upper subgrade, transition layer, subbase, base layer, and surface layer.

[0011] S2. Based on the initial design values ​​of the resilient modulus and structural thickness of each structural layer set in S1, the equivalent resilient modulus of the top surface of the surface layer is calculated.

[0012] S3. Based on the calculated value of the equivalent resilient modulus of the top surface of the surface layer in S2, adjust the structural thickness of each structural layer until the calculated value of the equivalent resilient modulus of the top surface of the surface layer is not less than the standard value, and take the adjusted structural thickness of each structural layer as the final design value of the structural thickness of each structural layer.

[0013] S4. Based on the initial design value of the resilient modulus of each structural layer, design the mix proportions of the fluidized solidified soil or fluidized solidified slag soil corresponding to the subgrade, transition layer, subbase and base course.

[0014] S5. Lay the upper subgrade, transition layer, subbase, base course and surface course in sequence from bottom to top, and the design is complete.

[0015] Preferably, step S2 specifically includes:

[0016] S21. Using the subgrade, transition layer, subbase, base course, and surface course as calculation layers in sequence, the equivalent resilient modulus of the top surface course is finally calculated. The calculation formula is as follows:

[0017]

[0018]

[0019]

[0020] In the formula: E i —Calculate the resilient modulus of the layer; hi —Calculation layer thickness; a, b —Regression coefficients of the equivalent resilient modulus of the top surface; E0 —Equivalent resilient modulus of the top surface of the layer below the calculation layer; E t —Calculate the equivalent resilient modulus of the top surface of the layer.

[0021] Preferably, step S4 specifically includes:

[0022] S41. Based on the initial design value of the resilient modulus of each structural layer, the unconfined compressive strength of each structural layer is calculated using the following formula;

[0023] E1 = 165.98 × q u1 (4)

[0024] E2 = 241.36 × q u2 (5)

[0025] In the formula, qu1 is the unconfined compressive strength of the structural layer formed by pouring solidified soil; qu2 is the unconfined compressive strength of the structural layer formed by pouring solidified slag soil; E1 and E2 are the initial design values ​​of the resilient modulus of the structural layer.

[0026] S42. Based on the workability of the selected waste soil and waste slag, set the water-solid ratio of the subgrade, transition layer, subbase, and base course; based on the unconfined compressive strength and corresponding water-solid ratio of each structural layer, calculate the amount of binder for each structural layer, as follows:

[0027] k = 0.35 × ln(t) - 0.20 (7)

[0028]

[0029] Where: m c —Agglomerate dosage, kg / m 3 λ—water-to-solid ratio; m c0 —Minimum dosage of adhesive for molding, kg / m 3 t—Maintenance age; k—Maintenance age coefficient; qu i —Unconfined compressive strength;

[0030] S43. Based on the selected waste soil and waste slag, the specific gravity of soil particles, the specific gravity of water, and the initial moisture content of the soil were obtained through experiments, as were the specific gravity of slag particles, the specific gravity of water, and the initial moisture content of the slag. Based on the selected binder, the specific gravity of binder particles and the water-cement ratio of the binder slurry were obtained through experiments. Based on the binder dosage and water-solid ratio of each structural layer, the wet weight of the soil or slag in each structural layer and the corresponding weight of water to be added were calculated. Finally, the mix proportions of the fluidized solidified soil or fluidized solidified slag corresponding to each structural layer were obtained, and the calculation formulas are as follows:

[0031]

[0032] m0 = m s ×(1+ω0) (10)

[0033] m w =λ·(m s +m c )-m s ·ω0-m c ·(ω / c) (11)

[0034] Where: m c —Amount of adhesive used, kg / m 3 λ—water-to-solid ratio; γ0—specific gravity of soil or slag particles, kg / m³ 3 γ1—Specific gravity of binder particles, kg / m³ 3 ;γ w —Specific gravity of water, kg / m³ 3 m s —Dry weight of soil or slag, kg; m0 —Wet weight of soil or slag, kg; m0 w —Weight of added water, kg; w0 —Initial moisture content of soil or slag; w / c —Water-cement ratio of binder slurry.

[0035] Preferably, step S5 specifically includes:

[0036] S51. Based on the final design value of the structural thickness of each structural layer and the corresponding mix ratio of the fluidized solidified soil or fluidized solidified slag, the upper subgrade, transition layer, subbase, and base course are poured in sequence.

[0037] S52. Based on the final design value of the surface layer thickness, pour the surface layer;

[0038] Among them, after the solidified soil of the upper roadbed and transition layer is poured and cured, the top surface of the transition layer is cut at intervals along the length of the road, the cuts are filled with adhesive, and the top surface of the cuts is covered with polypropylene woven fabric or polypropylene braided fabric.

[0039] After the subbase and base course are formed and cured by pouring and solidifying the slag, the top surface of the base course is cut at intervals along the length of the road. The cuts are filled with asphalt and fiberglass grids are laid on the top surface of the cuts.

[0040] The present invention has at least the following beneficial effects:

[0041] 1. The road structure filling materials of this invention include pumpable solidified soil and solidified slag, which have good integrity after being cast and molded, can effectively transfer the load borne by the road surface, avoid differential settlement of the roadbed, and reduce the occurrence of reflective cracks; the solidified soil and solidified slag are water-stable materials with low permeability coefficients, which can effectively prevent rainwater and groundwater from eroding the roadbed, effectively prevent the occurrence of freeze-thaw disease, and increase the service life of the road.

[0042] 2. The main component of the fluidized solidified soil of the present invention is waste soil, and the main component of the fluidized solidified slag soil is waste slag. Therefore, during filling, waste soil and waste slag within the route range can be used as raw materials for preparation, reducing the consumption of natural resources and effectively reducing the cost of construction materials.

[0043] 3. The fluidized solidified soil and fluidized solidified slag of the present invention can be flexibly adjusted through mix design to achieve the unconfined compressive strength, resilient modulus and other indicators of each structural layer. Compared with the traditional method of achieving the designed resilient modulus through vibration compaction, the road structure of the present invention has smoother connection between each layer and more stable road structure.

[0044] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0045] Figure 1 This is a side view schematic diagram of a combined cast-in-place road structure according to an embodiment of the present invention;

[0046] Figure 2 This is a schematic diagram of the cross-sectional structure of the combined cast-in-place road structure described in the above embodiments;

[0047] Explanation of reference numerals on the accompanying drawings:

[0048] 1. Surface layer; 2. Base layer; 3. Subbase layer; 4. Transition layer; 5. Upper subgrade; 6. Fiberglass grid; 7. Cut seam; 8. Polypropylene woven fabric or polypropylene braided fabric. Detailed Implementation

[0049] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0050] It should be noted that in the description of this invention, the terms "lateral", "longitudinal", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0051] like Figure 1 As shown, the present invention provides a combined cast-in-place road structure, comprising a lower roadbed, an upper roadbed, a transition layer, a subbase, a base layer and a surface layer arranged sequentially from bottom to top. The lower roadbed is a natural roadbed, the upper roadbed and the transition layer are cast from fluidized solidified soil, the base layer and the subbase are cast from fluidized solidified slag, and the surface layer is an asphalt concrete or cement concrete pavement.

[0052] The fluidized solidified soil is composed of waste soil, clean water, and a binder; the fluidized solidified slag soil is composed of waste slag containing sand and gravel aggregate, clean water, and a binder.

[0053] In the above technical solution, both the fluidized solidified soil and the fluidized solidified slag are pumpable mixed materials. After casting, they have good integrity. When used as filling materials in road structures, they can effectively transfer the load borne by the pavement, avoid differential settlement of the subgrade, and reduce the occurrence of reflective cracks. Specifically, the subgrade is the existing subgrade structure in the construction area. The asphalt concrete or cement concrete surface layer has high stiffness, with a larger stiffness span compared to the subgrade of the natural subgrade. Since the upper subgrade and transition layer are located in contact with the lower subgrade, they are less affected by the vehicle load on the road surface. Fluidized solidified soil without added aggregate is used for casting. The base course and subbase course are in contact with the pavement, and fluidized solidified slag with added aggregate is used to form a solidified structure. The load is distributed in a coordinated manner, transferring vehicle loads layer by layer from top to bottom to avoid reflective cracking of the road surface. The mobile solidified soil and mobile solidified slag are water-stable materials with low permeability, effectively preventing erosion of the roadbed by rainwater and groundwater, preventing freeze-thaw damage, and increasing the service life of the road. The waste soil for mobile solidified soil is excavated soil or silt from old roads, while the waste slag for mobile solidified slag is milled material from old roads or a mixture of waste slag and waste soil. Both waste soil and waste slag can be obtained from within the construction route, reducing the consumption of natural resources, effectively lowering construction material costs, and simultaneously solving the problem of safe disposal of large quantities of waste soil and waste slag and the source of large-volume filling materials for road engineering.

[0054] In another technical solution, the binder in the fluidized solidified soil is the same as the binder in the fluidized solidified slag soil, both being geopolymer-based soft soil binders.

[0055] In this technical solution, the binder selected is a geopolymer-based soft soil binder with application number "201710171392.1", which has a better consolidation effect.

[0056] In another technical solution, multiple slits are spaced apart along the length of the road on both the transition layer and the base layer, and any slit is set along the width of the road. The slits of the transition layer extend downward to the upper subgrade, and the slits of the transition layer are filled with adhesive, and the top surface is covered with polypropylene woven fabric or polypropylene braided fabric; the slits of the base layer extend downward to the subbase layer, and the slits of the base layer are filled with asphalt, and the top surface is covered with fiberglass grid.

[0057] In this technical solution, such as Figure 2 As shown, in order to prevent the occurrence of reflective cracks in the pavement due to cracking of the upper subgrade, transition layer, subbase and base course, after the transition layer and upper subgrade are cast and grouted, the top surface of the transition layer and the top surface of the base course are cut and grouted. The cuts on the transition layer extend vertically to the upper subgrade, and the cuts on the base course extend vertically to the subbase course.

[0058] A design method for a composite cast-in-place road structure specifically includes the following steps:

[0059] S1. Based on the service life of the road design, the cumulative number of vehicle axle loads, and the traffic load level, determine the standard value of the top surface equivalent resilient modulus of the surface layer; determine the top surface equivalent resilient modulus of the subgrade based on the site survey; based on the determined top surface equivalent resilient modulus of the subgrade, set the initial design values ​​of the resilient modulus and structural thickness of the upper subgrade, transition layer, subbase, base layer, and surface layer.

[0060] S2. Based on the initial design values ​​of the resilient modulus and structural thickness of each structural layer set in S1, the equivalent resilient modulus of the top surface of the surface layer is calculated.

[0061] S21. Using the subgrade, transition layer, subbase, base course, and surface course as calculation layers in sequence, the equivalent resilient modulus of the top surface course is finally calculated. The calculation formula is as follows:

[0062]

[0063]

[0064]

[0065] In the formula: E i —Calculate the resilient modulus of the layer; h i—Calculation layer thickness; a, b —Regression coefficients of the equivalent resilient modulus of the top surface; E0 —Equivalent resilient modulus of the top surface of the layer below the calculation layer; E t —Calculate the equivalent resilient modulus of the top surface of the layer;

[0066] S3. Based on the calculated value of the equivalent resilient modulus of the top surface of the surface layer in S2, adjust the structural thickness of each structural layer until the calculated value of the equivalent resilient modulus of the top surface of the surface layer is not less than the standard value, and take the adjusted structural thickness of each structural layer as the final design value of the structural thickness of each structural layer.

[0067] S4. Based on the initial design value of the resilient modulus of each structural layer, design the mix proportions of the fluidized solidified soil or fluidized solidified slag soil corresponding to the subgrade, transition layer, subbase and base course.

[0068] S41. Based on the initial design value of the resilient modulus of each structural layer, the unconfined compressive strength of each structural layer is calculated using the following formula;

[0069] E1 = 165.98 × q u1 (4)

[0070] E2 = 241.36 × q u2 (5)

[0071] In the formula, qu1 is the unconfined compressive strength of the structural layer formed by pouring solidified soil; qu2 is the unconfined compressive strength of the structural layer formed by pouring solidified slag soil; E1 and E2 are the initial design values ​​of the resilient modulus of the structural layer.

[0072] S42. Based on the workability of the selected waste soil and waste slag, set the water-solid ratio of the subgrade, transition layer, subbase, and base course; based on the unconfined compressive strength and corresponding water-solid ratio of each structural layer, calculate the amount of binder for each structural layer, as follows:

[0073] k = 0.35 × ln(t) - 0.20 (7)

[0074]

[0075] Where: m c —Agglomerate dosage, kg / m 3 λ—water-to-solid ratio; m c0 —Minimum dosage of adhesive for molding, kg / m 3 t—Maintenance age; k—Maintenance age coefficient; qu i —Unconfined compressive strength;

[0076] S43. Based on the selected waste soil and waste slag, the specific gravity of soil particles, the specific gravity of water, and the initial moisture content of the soil were obtained through experiments, as were the specific gravity of slag particles, the specific gravity of water, and the initial moisture content of the slag. Based on the selected binder, the specific gravity of binder particles and the water-cement ratio of the binder slurry were obtained through experiments. Based on the binder dosage and water-solid ratio of each structural layer, the wet weight of the soil or slag in each structural layer and the corresponding weight of water to be added were calculated. Finally, the mix proportions of the fluidized solidified soil or fluidized solidified slag corresponding to each structural layer were obtained, and the calculation formulas are as follows:

[0077]

[0078] m0 = m s ×(1+ω0) (10)

[0079] m w =λ·(m s +m c )-m s ·ω0-m c ·(ω / c) (11)

[0080] Where: m c —Amount of adhesive used, kg / m 3 λ—water-to-solid ratio; γ0—specific gravity of soil or slag particles, kg / m³ 3 γ1—Specific gravity of binder particles, kg / m³ 3 ;γ w —Specific gravity of water, kg / m³ 3 m s —Dry weight of soil or slag, kg; m0 —Wet weight of soil or slag, kg; m0 w —Weight of added water, kg; w0 —Initial moisture content of soil or slag; w / c —Water-cement ratio of binder slurry;

[0081] Wherein, the wet weight of the soil is the weight of the waste soil designed in the fluidized solidified soil, and the wet weight of the slag is the weight of the waste slag designed in the fluidized solidified slag; based on the amount of binder for each structural layer calculated in step S42, the wet weight of the waste soil or waste slag for each structural layer calculated in step S43, and the corresponding weight of water to be added, the mix proportion of the fluidized solidified soil or fluidized solidified slag for each structural layer can be obtained.

[0082] S5. Lay the upper subgrade, transition layer, subbase, base course and surface course in sequence from bottom to top, and the design is complete;

[0083] S51. Based on the final design value of the structural thickness of each structural layer and the corresponding mix ratio of the fluidized solidified soil or fluidized solidified slag, the upper subgrade, transition layer, subbase, and base course are poured in sequence.

[0084] S52. Based on the final design value of the surface layer thickness, pour the surface layer;

[0085] Among them, after the solidified soil of the upper subgrade and transition layer is poured and cured, horizontal cuts are made at intervals of 8 to 12m along the width of the road on the top surface of the transition layer, and 10 to 20cm of vertical cuts are left uncut. The cut width is 2 to 4mm, the cut is filled with adhesive, and a 0.5 to 1.0m wide polypropylene woven fabric or polypropylene braided fabric is laid on the top surface of the cut.

[0086] After the solidified slag of the subbase and base course is poured and cured, horizontal cuts are made at intervals of 15-25m along the width of the road on the top surface of the base course, and 10-20cm vertical cuts are left uncut. The cuts are 2-4mm wide and filled with asphalt. A 0.5-1m wide fiberglass grid is laid on the top surface of the cuts.

[0087] Based on the differences in casting materials, structural thickness, and resilient modulus of each structural layer, the width of the cuts and the filling materials of each structural layer are limited, which can better release the expansion and contraction stress of each structural layer and prevent cracking. The upper subgrade and the lower base course are both left uncut with a vertical 10-20cm section, which can prevent water from the underlying layer from entering the cuts and thus affecting the expansion and contraction stress.

[0088] In the above technical solution, the present invention first determines the equivalent resilient modulus of the top surface of the surface layer according to road design standards, and then adjusts the structural thickness of each structural layer based on the equivalent resilient modulus of the top surface to obtain the actual thickness required for each structural layer during construction, thereby achieving the accuracy of design data. The mix ratio of the fluidized solidified soil or fluidized solidified slag used in each structural layer is adjusted according to the designed equivalent resilient modulus of each structural layer, so that the resilient modulus of each structural layer after the road structure is laid can meet the design specifications. Compared with the traditional method of achieving the designed resilient modulus through vibratory compaction, the present invention achieves the unconfined compressive strength, resilient modulus, and other indicators of each structural layer through flexible adjustment of the mix ratio design. The connection between different layers of the road structure is smoother, the road structure is more stable, and the quality of the construction process is controllable.

[0089] <Example 1>

[0090] The basic information of a secondary highway with a design speed of 60km / h is as follows: the average daily traffic volume of large passenger cars and freight cars in the initial design lane is 2106 vehicles / day; the design service life is 10 years; and the road surface design traffic load level is heavy traffic load level.

[0091] A1. Based on the relevant basic information of road design and the survey of natural roadbed, the standard value of the top surface equivalent resilient modulus of the surface layer is determined to be 629.0 MPa, and the top surface equivalent resilient modulus of the subgrade is 45.0 MPa. The initial design values ​​of the resilient modulus and structural thickness of the upper subgrade, transition layer, subbase, base layer and surface layer are set, and the calculated value of the top surface equivalent resilient modulus of the surface layer is obtained according to formulas (1) to (3). The structural thickness of each structural layer is adjusted according to the calculated value as the final design value. The specific data are shown in Table 1.

[0092] Table 1

[0093]

[0094] A2: Based on the resilient modulus of each structural layer in Table 1, the unconfined compressive strength of each structural layer as shown in Table 2 is calculated according to formulas (4) to (5). Among them, the base layer and subbase layer are the 7-day unconfined compressive strength of the solidified slag, and the transition layer and upper subgrade are the 28-day unconfined compressive strength of the solidified soil.

[0095] A3. Use the excavated soil from the old road as the waste soil material. The waste slag is a mixture of old road milling material and waste soil material = 3:1. According to formula (7) to (11), design the mix ratio of the flow solidified soil or flow solidified slag for each structural layer. The design results are shown in Table 2.

[0096] Table 2

[0097]

[0098] A4. Pour the upper subgrade, transition layer, subbase, and base course in sequence;

[0099] After the solidified soil of the subgrade and transition layer is poured and formed, after 7 days of curing, horizontal cuts are made at intervals of 8m on the top surface of the transition layer, leaving 20cm of uncut vertically. The cuts are 4mm wide and filled with binder grout. A 1.0m wide polypropylene woven fabric is laid on the top surface. After the solidified slag of the subgrade and base course is poured and formed as a whole, horizontal cuts are made at intervals of 20m on the top surface after 3 days of curing. The cuts are 2mm wide and 15cm of uncut vertically. Asphalt is used for filling the cuts, and a 1.0m wide geogrid is laid on the top surface.

[0100] A5. Construction pavement, the design of the combined cast-in-place road structure is completed.

[0101] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A design method for a composite cast-in-place road structure, the road structure comprising, from bottom to top, a subgrade, an upper subgrade, a transition layer, a subbase, a base course, and a surface course, characterized in that, The lower subgrade is a natural roadbed, the upper subgrade and transition layer are formed by pouring solidified soil, the base course and subbase course are formed by pouring solidified slag, and the surface course is asphalt concrete or cement concrete pavement. The fluidized solidified soil is composed of waste soil, clean water, and a binder; the fluidized solidified slag soil is composed of waste slag containing sand and gravel aggregate, clean water, and a binder. The design method for composite cast-in-place road structures includes the following steps: S1. Based on the service life of the road design, the cumulative number of vehicle axle loads, and the traffic load level, determine the standard value of the top surface equivalent resilient modulus of the surface layer; determine the top surface equivalent resilient modulus of the subgrade based on the site survey; based on the determined top surface equivalent resilient modulus of the subgrade, set the initial design values ​​of the resilient modulus and structural thickness of the upper subgrade, transition layer, subbase, base layer, and surface layer. S2. Based on the initial design values ​​of the resilient modulus and structural thickness of each structural layer set in S1, the equivalent resilient modulus of the top surface of the surface layer is calculated. S3. Based on the calculated value of the equivalent resilient modulus of the top surface of the surface layer in S2, adjust the structural thickness of each structural layer until the calculated value of the equivalent resilient modulus of the top surface of the surface layer is not less than the standard value, and take the adjusted structural thickness of each structural layer as the final design value of the structural thickness of each structural layer. S4. Based on the initial design value of the resilient modulus of each structural layer, design the mix proportions of the fluidized solidified soil or fluidized solidified slag soil corresponding to the subgrade, transition layer, subbase and base course. S5. Lay the upper subgrade, transition layer, subbase, base course and surface course in sequence from bottom to top, and the design is complete; Step S2 specifically includes: taking the subgrade, transition layer, subbase, base course, and surface course as calculation layers in sequence, and finally calculating the equivalent resilient modulus of the top surface course. The calculation formula is as follows: （1） （2） （3） In the formula: E i —Calculate the resilient modulus of the layer; h i —Calculation layer thickness; a, b —Regression coefficients of the equivalent resilient modulus of the top surface; E0 —Equivalent resilient modulus of the top surface of the layer below the calculation layer; E t —Calculate the equivalent resilient modulus of the top surface of the layer.

2. The design method for combined cast-in-place road structures as described in claim 1, characterized in that, The binder in the fluidized solidified soil is the same as that in the fluidized solidified slag soil; both are geopolymer-based soft soil binders.

3. The design method for combined cast-in-place road structures as described in claim 1, characterized in that, Both the transition layer and the base layer have multiple slits spaced apart along the length of the road, and any slit is set along the width of the road. The slits of the transition layer extend downward to the upper roadbed, and the slits of the transition layer are filled with adhesive, and the top surface is covered with polypropylene woven fabric or polypropylene braided fabric; the slits of the base layer extend downward to the subbase layer, and the slits of the base layer are filled with asphalt, and the top surface is covered with fiberglass grid.

4. The design method for combined cast-in-place road structures as described in claim 1, characterized in that, Step S4 specifically includes: S41. Based on the initial design value of the resilient modulus of each structural layer, the unconfined compressive strength of each structural layer is calculated using the following formula; （4） （5） In the formula, qu1 is the unconfined compressive strength of the structural layer formed by pouring solidified soil; qu2 is the unconfined compressive strength of the structural layer formed by pouring solidified slag soil; E1 and E2 are the initial design values ​​of the resilient modulus of the structural layer. S42. Based on the workability of the selected waste soil and waste slag, set the water-solid ratio of the subgrade, transition layer, subbase, and base course; based on the unconfined compressive strength and corresponding water-solid ratio of each structural layer, calculate the amount of binder for each structural layer, as follows: （7） （8） Where: m c —Agglomerate dosage, kg / m 3 λ — water-to-solid ratio; m c0 —Minimum dosage of adhesive for molding, kg / m 3 t — maintenance age; k — maintenance age coefficient; qu i —Unconfined compressive strength; S43. Based on the selected waste soil and waste slag, the specific gravity of soil particles, the specific gravity of water, and the initial moisture content of the soil were obtained through experiments, as were the specific gravity of slag particles, the specific gravity of water, and the initial moisture content of the slag. Based on the selected binder, the specific gravity of binder particles and the water-cement ratio of the binder slurry were obtained through experiments. Based on the binder dosage and water-solid ratio of each structural layer, the wet weight of the soil or slag in each structural layer and the corresponding weight of water to be added were calculated. Finally, the mix proportions of the fluidized solidified soil or fluidized solidified slag corresponding to each structural layer were obtained, and the calculation formulas are as follows: （9） （10） （11） Where: m c —Amount of adhesive used, kg / m 3 λ—water-to-solid ratio; γ0—specific gravity of soil or slag particles, kg / m³ 3 γ1—Specific gravity of binder particles, kg / m³ 3 ;γ w —Specific gravity of water, kg / m³ 3 m s —Dry weight of soil or slag, kg; m0 —Wet weight of soil or slag, kg; m0 w —Weight of added water, kg; w0 —Initial moisture content of soil or slag; w / c —Water-cement ratio of binder slurry.

5. The design method for combined cast-in-place road structures as described in claim 1, characterized in that, Step S5 specifically includes: S51. Based on the final design value of the structural thickness of each structural layer and the corresponding mix ratio of the fluidized solidified soil or fluidized solidified slag, the upper subgrade, transition layer, subbase, and base course are poured in sequence. S52. Based on the final design value of the surface layer thickness, pour the surface layer; Among them, after the solidified soil of the upper roadbed and transition layer is poured and cured, the top surface of the transition layer is cut at intervals along the length of the road, the cuts are filled with adhesive, and the top surface of the cuts is covered with polypropylene woven fabric or polypropylene braided fabric. After the subbase and base course are formed and cured by pouring and solidifying the slag, the top surface of the base course is cut at intervals along the length of the road. The cuts are filled with asphalt and fiberglass grids are laid on the top surface of the cuts.

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