Double-layer two-way assembly type road structure transversely penetrating through high-fill roadbed and construction method

Abstract

The invention discloses a double-layer two-way assembly type road structure transversely penetrating through a high-fill roadbed and a construction method. According to the overall scheme, the double functions of reinforcing soil layers on the two sides of a road through cement soil stirring reinforcing sections, arranging jet grouting piles in an engaged mode, conducting central island type earthwork layered excavation, conducting vertical supporting through prefabricated shear wall plates and cast-in-place structural columns, conducting symmetrical arrangement of foundation longitudinal beams, conducting bearing through prefabricated laminated double-T-beam integrated plates and conducting enclosure supporting are followed. According to the principle that the anchor rod group improves the overall enclosure structure to carry cooperatively, internal space layout pipelines are optimized, the comprehensive function of the roadbed is improved, loads are effectively dispersed through the overall structure, and the coordination capacity of the roadbed to differential settlement is remarkably enhanced.

Description

Technical Field

[0001] This invention relates to the field of prefabricated road technology, specifically to a double-layer, two-way prefabricated road structure and construction method that crosses a high embankment subgrade. Background Technology

[0002] In the field of road construction, high embankment roads generally suffer from insufficient stability due to their large fill thickness and high soil self-weight load. The construction of traditional roads traversing high embankment subgrades faces numerous technical challenges: First, the soil layers of high embankment subgrades often contain loose soils such as sand and silt, which have weak natural bearing capacity. Furthermore, the compaction degree of the fill is difficult to control evenly, leading to uneven settlement during later use and causing cracking and damage to the road structure. Second, excavation is required when traversing high embankment subgrades, which easily disrupts the original soil balance, causing slope collapses, landslides, and other safety hazards, posing a serious threat to construction safety. Third, in traditional construction methods, the connection between excavation and support processes is complex, resulting in poor overall support structure integrity and insufficient collaborative bearing capacity, making it difficult to effectively resist the lateral pressure of the soil during excavation. Additionally, traditional road structures are mostly single-layer designs, with low space utilization, chaotic pipeline layout, and construction primarily based on on-site casting, resulting in long construction periods, significant environmental impact, long concrete curing cycles, and overall low construction efficiency, failing to meet the demands of modern road construction for safety, efficiency, and comprehensive functionality. Summary of the Invention

[0003] The purpose of this invention is to provide a double-layer, two-way prefabricated road structure and construction method that crosses a high embankment roadbed, aiming to solve technical problems such as poor stability of traditional high embankment roadbeds, easy roadbed collapse during the cross-excavation process, and difficulty in earthwork excavation and support.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a double-layer, bidirectional prefabricated road structure traversing a high embankment subgrade, comprising a cement-soil mixing and reinforcement section, jet grouting piles, anchor bolts, foundations, foundation longitudinal beams, cast-in-place structural columns, a lower road structure concrete layer, precast shear wall panels, precast composite double-T beam integrated slabs, and an upper road structure concrete layer; the high embankment subgrade soil layers on both sides of the road are provided with cement-soil mixing and reinforcement sections and interlocking jet grouting piles, and the anchor bolts are driven into the interior of the cement-soil mixing and reinforcement section through the jet grouting piles; the road crosses... A foundation is set between the two jet grouting piles. The foundation longitudinal beam is arranged along the road longitudinally between the foundation and the jet grouting piles. A cast-in-place structural column is set on the top surface of the foundation near the inner side of the jet grouting pile. The cast-in-place structural column is located on the upper side of the foundation longitudinal beam. A precast shear wall panel is also set on the upper side of the foundation longitudinal beam. The precast composite double T beam integrated slab is supported on the top of the cast-in-place structural column and the precast shear wall panel. The top of the precast composite double T beam integrated slab is provided with an upper road structure concrete layer. A lower road structure concrete layer is provided between the two precast shear wall panels in the transverse direction of the road and above the foundation.

[0005] Preferably, the depth of the cement-soil mixing reinforcement section is not less than 3.0m below the bottom elevation of the foundation; the jet grouting piles are installed on the basis of the cement-soil reinforcement section, perpendicular to the longitudinal direction of the high embankment subgrade, and the diameter of each jet grouting pile is not less than 500mm. The interlocking jet grouting piles are arranged in a "parabolic" shape to play a role in double solidification of the high embankment subgrade soil layer.

[0006] Preferably, dense anchor bolt groups are driven into the cement-soil reinforcement section on the surface of the jet grouting piles near the excavation side of the high embankment subgrade. The spacing between adjacent anchor bolts shall not exceed 450mm, and the length of each anchor bolt shall not be less than 3.0m. The top row of anchor bolts at the top of the jet grouting pile shall be at least 300mm and no more than 750mm from the top of the pile. The bottom row of anchor bolts at the bottom of the jet grouting pile shall be at least 200mm from the bottom of the foundation and located within the height range of the foundation longitudinal beam. The end of each anchor bolt shall be anchored to the outer surface of the jet grouting pile using an "anchor + steel washer" method. The steel washer shall not exceed 2.0m in length, not less than 250mm in width, and not less than 20mm in thickness.

[0007] Preferably, the design height of the foundation longitudinal beam is not less than the foundation thickness, the cross-sectional width is not less than 1000mm and the end face near the foundation extends beyond the corresponding edge of the precast shear wall panel by not less than 200mm, the foundation longitudinal beam is reinforced with not less than 8 threaded steel bars with a diameter of 16mm, and the concrete strength is not less than C35. The vertical reinforcing bars of the cast-in-place structural columns are anchored into the foundation longitudinal beams with an anchorage length of not less than 500mm. At the corresponding position in the foundation longitudinal beams at the bottom of the precast shear wall, there are extended reinforcing bars designed under the same conditions as the vertical distributed reinforcing bars of the precast shear wall. The lower part of the extended reinforcing bars is anchored into the foundation longitudinal beams for not less than 500mm, and the extended reinforcing bars extend out of the top surface of the foundation longitudinal beams for not less than 300mm. The lower part of the precast shear wall is equipped with a grouting corrugated pipe for grouting anchor lap connection. The outward reinforcing bars on the top surface of the foundation longitudinal beam are inserted into the grouting corrugated pipe and fixed by grouting through the grouting anchor lap connection of the precast shear wall. The reinforcing bars inside the cast-in-place structural column are led out from the foundation longitudinal beam, with a cross-sectional dimension of not less than 400mm×400mm. There are not less than 12 reinforcing bars with a diameter of 22mm inside, and closed stirrups of not less than Φ10@150mm are used. The stirrups are densified within a range of 1000mm at the bottom and top of the precast column. The spacing of the stirrups in the densified area does not exceed 100mm. 100% of the longitudinal reinforcing bars of the cast-in-place structural column are provided with anchor plates at the top.

[0008] Preferably, the precast composite double-T beam integrated slab is hoisted at the top of the cast-in-place structural column and the precast shear wall panel. The end of the precast part of the precast composite double-T beam integrated slab rests on the precast shear wall panel for at least 10mm. Its two ends form cast-in-place nodes with the cast-in-place structural column and the precast shear wall panel. The longitudinal reinforcing bars at both ends of the precast composite double-T beam integrated slab at the cast-in-place node are respectively anchored into the interior of the cast-in-place structural column. All the vertical distribution bars of the precast shear wall panel are anchored into the interior of the cast-in-place node. The concrete strength of the cast-in-place node is at least one grade higher than the designed strength of the cast-in-place structural column and the precast shear wall panel. The thickness of the precast composite floor slab in the precast composite double-T beam integrated slab structure is not less than 120mm, and the size and reinforcement of its precast double-T beam are determined according to the specific engineering design.

[0009] This invention also provides a construction method for a double-layer, two-way prefabricated road structure that traverses a high embankment subgrade, comprising the following steps: Step S1: Measure and set out the road location, and construct the cement-soil mixing and reinforcement section; Step S2: Verify and determine the pile position, and construct the double-interlocking jet grouting piles; Step S3: Excavation of the first layer of earthwork and surface treatment of jet grouting piles; Step S4: Install the first layer of anchor bolts and excavate the lower layer of earthwork in a central island style. Step S5: Install lower-level anchor bolts and construct foundation longitudinal beams; Step S6: Construction of cast-in-place structural columns, hoisting and temporary support of precast shear wall panels; Step S7: Hoisting of precast composite double T-beam integrated slabs and post-casting of joints; Step S8: Continue excavation of the lower central island, pour and cure the foundation concrete; Step S9: Pour the lower road structure concrete layer and fully pave the asphalt concrete surface layer.

[0010] This invention also provides a construction method for a double-layer, two-way prefabricated road structure that traverses a high embankment subgrade, comprising the following steps: Step S1: Surveying and setting out the road location, construction of the cement-soil mixing and reinforcement section: First, excavate the earthwork within the designed road area on the top of the high embankment and within a range of no less than 15m on both sides, and compact the earthwork within the excavation area to provide sufficient working face for subsequent processes. Use a total station to determine the specific locations of the earthwork excavation area, jet grouting piles, and cement-soil mixing reinforcement section, and use lime powder to clearly mark the boundaries of each area. Then, starting from the design road edge line and moving outwards, use deep mixing machinery to forcibly mix cement and high embankment soil in situ, with a cement content of no less than 15%, to achieve the purpose of reinforcing the high embankment soil layer. After the cement-soil reinforcement section is completed, use a combination of wire mesh and high-pressure shotcrete to reinforce the surface of the high embankment top and slope within the cement-soil reinforcement section. If encountering complex working conditions such as sandy soil, silty soil, rainy season, or long-term vibration, use a combination of wire mesh, high-pressure shotcrete, and anchor bolts to reinforce the surface of the high embankment top and slope within the cement-soil reinforcement section. Ensure proper process acceptance and record-keeping. Step S2: Verify and determine pile positions, and construct double-interlocking jet grouting piles: After the cement-soil mixing and reinforcement section is completed, high-pressure equipment is used to continuously construct jet grouting piles at the high embankment subgrade. The jet grouting pile construction adopts the scheme of "double-interlocking arrangement of jet grouting piles with H-shaped steel piles inserted inside". The bottom of the jet grouting piles is at least 2000mm below the bottom elevation of the cushion layer. The total width of the double-row jet grouting piles is not less than 1200mm. After all the jet grouting piles are completed, before the cement slurry finally sets, H-shaped steel piles of the same length as the jet grouting piles are statically driven one by one. The cross-sectional dimensions of the H-shaped steel piles inserted inside the jet grouting piles are not less than 600mm×800mm×30mm. The spacing between the H-shaped steel piles does not exceed 900mm. Static curing is carried out for at least 2 days to avoid large vibrations or large machinery operations on the top of the high embankment subgrade during the curing period. Process acceptance and recording are carried out. Step S3: First layer excavation, jet grouting pile surface treatment: After the double-interlocking jet grouting piles are completed, the high embankment subgrade outside the planned road area will be hardened. The first layer of soil will be excavated in layers to 200mm-300mm below the bottom elevation of the upper road structure concrete layer. Then, the surface of the first layer of double-interlocking jet grouting piles will be cleaned, and loose soil will be removed. A total station will be used to check the positional relationship of the first layer of double-interlocking jet grouting piles after their formation, and the error will be calibrated. The error handling plan for the first layer of double-interlocking jet grouting piles will be revised to ensure that the positional relationship of the first layer of road retaining structure after construction meets the design requirements. In order to meet the technical requirements of full-process construction monitoring, Beidou / GNSS foundation pit monitoring technology will be used to dynamically monitor and warn of indicators throughout the entire process of high embankment subgrade excavation, retaining, and construction, and process acceptance and monitoring data collection will be carried out. Step S4: Install the first layer of anchor bolts, and excavate the lower layer of earthwork in a central island style: After the first layer of earthwork is excavated to the design elevation and the surface of the first layer of double-interlocking jet grouting piles is cleaned, a distribution diagram of the anchor bolt group for the first layer retaining structure is first drawn. The specific location of each anchor bolt is then marked on the surface of the jet grouting piles according to this diagram. Next, drilling is performed on each anchor bolt location using appropriate equipment to install the first layer of anchor bolts. Finally, a steel mesh is installed on the surface of the first layer of double-interlocking jet grouting piles with the installed anchor bolts. A bidirectional steel mesh with a diameter of not less than 6mm and a spacing of not more than 150mm is used. Taking into account the errors in the retaining structure described above, a high-pressure... High-strength mortar is sprayed onto the surface of the first-layer double-interlocking jet grouting piles using a spray gun. After spraying, the surface is smoothed and polished. Once the first-layer anchor group is installed and the high-pressure spraying is completed, the excavation of the lower-layer soil can begin. The lower-layer soil excavation adopts the central island excavation method. The top of the central island retains its original elevation, and its bottom is retained to 300mm~500mm inside the foundation longitudinal beam. This means that all the soil above the foundation longitudinal beam area is excavated first, and the soil in the central island area is temporarily retained to provide a favorable working surface and support conditions for the subsequent hoisting of the foundation longitudinal beam, precast shear wall panel, and precast composite double T-beam integrated slab. Step S5: Install lower-level anchor bolts and construct foundation longitudinal beams: After the lower layer of soil is excavated using the central island method, the surface of the lower layer double-interlocking jet grouting piles is cleaned. The lower layer anchor group is then fully constructed and treated using the same technical means as in step S3 above. For the construction of the foundation longitudinal beam under the jet grouting piles, the soil at the foundation longitudinal beam is first excavated manually to the design bottom elevation of the cushion layer. The cushion layer on both sides of the central island soil layer is poured in one go using fine stone concrete of not less than C25, and then cured. The foundation longitudinal beam reinforcement cage is then hoisted on the top surface of the poured cushion layer. Water-stop steel plates, longitudinal reinforcement of cast-in-place structural columns, and vertical reinforcement at the positions of precast shear wall panels are pre-embedded. After the formwork is erected, the foundation longitudinal beam concrete is poured. It should be noted that the foundation longitudinal beam formwork only needs to be erected on the side formwork near the inside of the foundation pit. The concrete strength of the foundation longitudinal beam should not be less than C35. The concealed works acceptance and record should be done well. Step S6: Construction of cast-in-place structural columns, hoisting and temporary support of precast shear wall panels: After the concrete of the foundation longitudinal beam has cured to 75% of its design strength, the longitudinal reinforcement of the cast-in-place structural column is connected at the top of the foundation longitudinal beam. All the reinforcement of the cast-in-place structural column is tied. The formwork support system of the cast-in-place structural column is quickly assembled using aluminum formwork. Fine aggregate concrete is poured from the top of the cast-in-place structural column in one go without leaving construction joints. Vibration and curing are strengthened. After the concrete of the cast-in-place structural column has cured to its design strength, the precast shear wall panels are constructed using hoisting machinery. The vertical reinforcement reserved on the top surface of the foundation longitudinal beam is inserted one by one into the grouting sleeve of the reinforcement at the bottom of the precast shear wall panel. Micro-expansion high-strength low-shrinkage grouting material is used to grout each of the precast shear walls that have been placed. Multiple horizontal adjustable steel supports are used for temporary support between the cast-in-place structural column and the fixed precast shear wall panels. The positional relationship and verticality of the precast shear wall panels after placement are checked, and the concealed works are inspected and recorded. Step S7: Hoisting of precast composite double-T beam integrated slab, post-casting treatment of joints: Since the excavation of the lower high embankment subgrade adopts the central island excavation method, before the hoisting of the precast composite double T beam integrated slab, the top of the central island soil is first manually trimmed to the bottom elevation of the precast composite double T beam integrated slab. The central island soil is fully utilized to assist in the hoisting and positioning of the precast composite double T beam integrated slab. Then, hoisting machinery is used to hoist the precast composite double T beam integrated slab to the top of the central island soil. All the reinforcing bars at the ends of the precast composite double T beam integrated slab are anchored into the cast-in-place joint at the top of the cast-in-place structural column. At the same time, the reinforcing bars at the top of the precast shear wall slab that has been hoisted into place are also anchored into the cast-in-place joint. Finally, the formwork at the cast-in-place joint is erected, and fine stone concrete of a grade one higher than that of the precast composite double T beam integrated slab and the cast-in-place structural column is poured in one go. Curing is strengthened, and the hidden works are inspected and recorded. Step S8: Continue excavation of the lower central island, and pour and cure the foundation concrete. Before continuing the excavation of the lower central island, steel mesh is first tied to the top truss reinforcement of the precast composite double-T beam integrated slab that has been placed in place. The upper road structure concrete layer is then poured using fine aggregate concrete of at least C30 grade, and this upper road structure concrete layer is poured together with the aforementioned cast-in-place joint concrete. After the upper road structure concrete layer and the cast-in-place joints have cured to their design strength, the excavation of the lower central island can continue. Throughout the entire excavation process, monitoring of the overall structure is crucial, with a focus on monitoring the maximum deformation at the top of the jet grouting piles. During the full excavation of the lower central island, the precast shear wall panels and precast composite double T-beam integrated slabs that have been completed must not be impacted. The earthwork near the precast shear wall panels and precast composite double T-beam integrated slabs shall be excavated manually and the structural surfaces shall be cleaned. After the earthwork of the lower central island is excavated to the top surface of the foundation, the remaining earthwork between the two foundation longitudinal beams shall be excavated manually to the bottom of the design elevation of the cushion layer, that is, excavated to the bottom of the cushion layer under the foundation longitudinal beams. Then the remaining cushion layer shall be poured into shape in one go, and the curing shall be strengthened. The process acceptance and record shall be done well. Step S9: Pouring the lower road structure concrete layer and fully paving the asphalt concrete surface layer: After the subbase concrete has cured to 80% of its design strength, the foundation reinforcement cage is hoisted into place on top of the subbase. Then, using a chalk line, the elevation of the top surface of the lower road structure concrete layer is marked on the bottom of the precast shear wall panel that has been placed. A control line is then marked 100mm above the top surface elevation of the lower road structure concrete layer. After all preparations are completed, fine aggregate concrete is used to reinforce the foundation and the lower road structure concrete layer together and is poured into shape. The concrete vibration at the waterstop steel plate is strengthened. A continuous, cross-operation method is organized. After the lower road structure concrete layer has cured to its design strength, the asphalt concrete surface layer is fully paved. Project acceptance and data archiving are then carried out.

[0011] Compared with the prior art, the beneficial effects of this invention are as follows: 1. This invention adopts a dual reinforcement scheme of "cement-soil mixing reinforcement section + interlocking jet grouting piles" to deeply solidify the soft soil layer on both sides of the road. Combined with the synergistic anchoring effect of dense anchor bolt groups, it greatly enhances the integrity and anti-slip ability of high embankment roadbeds and effectively solves the technical problems of easy collapse and difficult support during cross-excavation. 2. The present invention adopts a double-layer bidirectional prefabricated structure, with the upper and lower road structures working together to bear the load. The interior has sufficient reserved space to optimize the layout of various pipelines, which solves the problems of chaotic pipeline layout and low space utilization in traditional roads. Moreover, the overall structural design can effectively distribute the load, enhance the coordination ability against uneven settlement, reduce road cracking, damage and other defects, and extend the service life of the road. 3. The cast-in-place structural columns, foundation longitudinal beams, and precast shear wall panels of this invention form a stable load-bearing system through reliable connection methods such as steel bar anchoring and grouting lap splicing; the combination of precast composite double-T beam integrated slabs and high-strength concrete pouring of cast-in-place nodes ensures the overall coordinated load-bearing performance of the structure. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the prefabricated road structure of the present invention; Figure 2 This is a three-dimensional schematic diagram of the prefabricated composite double-T beam integrated slab of the present invention; Figure 3 This is a flowchart of the construction process of the construction method of the present invention. Detailed Implementation

[0013] This invention discloses a double-layer, two-way prefabricated road structure traversing a high embankment subgrade, mainly composed of a cement-soil mixing and reinforcement section 11, jet grouting piles 12, foundations 21, foundation longitudinal beams 22, cast-in-place structural columns 3, precast shear wall panels 4, a lower road structure concrete layer 6, a precast composite double-T beam integrated slab 7, an upper road structure concrete layer 5, and anchor bolts 13. (See reference...) Figure 1 The specific structure is as follows: The high embankment subgrade soil layers on both sides of the road are equipped with cement-soil mixing reinforcement sections 11 and interlocking jet grouting piles 12. Anchor bolts 13 are driven into the interior of the cement-soil mixing reinforcement sections 11 through the jet grouting piles 12.

[0014] A foundation 21 is provided between two jet grouting piles 12 in the transverse direction of the road. A foundation longitudinal beam 22 is arranged between the foundation 21 and the jet grouting piles 12 along the longitudinal direction of the road. Both the foundation longitudinal beam 22 and the foundation 21 are located above the cushion layer 20, and a water-stop steel plate 23 is connected between the foundation longitudinal beam 22 and the foundation 21. A cast-in-place structural column 3 is provided on the top surface of the foundation 21 near the inner side of the jet grouting piles 12. The cast-in-place structural column 3 is located on the upper side of the foundation longitudinal beam 22. A precast shear wall panel 4 is also provided on the upper side of the foundation longitudinal beam 22.

[0015] The precast composite double T-beam integrated slab 7 is supported on the top of the cast-in-place structural column 3 and the precast shear wall slab 4. The top of the precast composite double T-beam integrated slab 7 is provided with an upper road structure concrete layer 5, and the lower road structure concrete layer 6 is provided between the two precast shear wall slabs 4 in the transverse direction of the road and above the foundation 21, thus forming a double-layer bidirectional prefabricated road structure that crosses the high embankment subgrade.

[0016] The double-layer, two-way prefabricated road structure that traverses a high embankment subgrade aims to promote high-quality development of the industry through technological innovation. The overall structure is designed with the following concept: "11 cement-soil mixing and reinforcement section strengthens the soil layers on both sides of the road; 12 jet grouting piles are arranged in an interlocking manner; the central island type earthwork is excavated in layers; 4 precast shear wall panels and 3 cast-in-place structural columns provide vertical support; 22 foundation longitudinal beams are symmetrically arranged; 7 precast composite double T-beam integrated slabs provide dual support and retaining function; and 13 groups of anchor bolts enhance the overall retaining structure's synergistic bearing capacity."

[0017] To ensure the safety of earthwork excavation for roads crossing high embankment subgrades, the earthwork reinforcement and retaining structure adopts a "cement-soil mixing reinforcement section 11 + interlocking jet grouting piles 12" technical solution. Specifically, the high embankment subgrade earthwork within a 5.0m radius on both sides of the road is treated using a cement-soil mixing reinforcement method. The design employs cement-soil mixing reinforcement section 11 to appropriately solidify the loose soil layers such as sand and silt on both sides of the road. The depth of cement-soil mixing reinforcement section 11 is no less than 3.0m below the bottom elevation of foundation 21. Interlocking jet grouting piles 12 are installed between cement-soil mixing reinforcement section 11 and the road structure. Each jet grouting pile 12 has a diameter of no less than 500mm. The piles are installed on the foundation 21 of the cement-soil mixing reinforcement section, perpendicular to the longitudinal direction of the high embankment subgrade. The interlocking jet grouting piles 12 are arranged in a "parabolic" pattern, serving a dual purpose of solidifying the high embankment subgrade soil layers.

[0018] To better stabilize the high-fill subgrade soil layer, dense anchor bolts 13 are driven into the cement-soil reinforcement section on the surface of the jet grouting piles 12 near the excavation side of the high-fill subgrade soil layer. The spacing between adjacent anchor bolts 13 does not exceed 450mm, and the length of each anchor bolt 13 is not less than 3.0m. The top row of anchor bolts 13 at the top of the jet grouting pile 12 is not less than 300mm and not more than 750mm from the pile top. The row of anchor bolts 13 at the bottom of the jet grouting pile 12 is not less than 200mm from the bottom surface of the foundation 21 and is located within the height range of the foundation longitudinal beam 22. The end of each anchor bolt 13 is anchored to the outer surface of the jet grouting pile 12 using an "anchor + steel washer" method. The steel washer is not more than 2.0m long, not less than 250mm wide, and not less than 20mm thick. The design of multiple anchor bolts 13 sharing a single steel washer enhances the collaborative bearing capacity of the anchor bolt group 13.

[0019] The design height of the foundation longitudinal beam 22 shall not be less than the thickness of the foundation 21, the cross-sectional width shall not be less than 1000mm, and the end face near the foundation 21 shall extend beyond the corresponding edge of the precast shear wall panel 4 by not less than 200mm. The foundation longitudinal beam 22 shall be reinforced with not less than 8 threaded steel bars with a diameter of 16mm, and the concrete strength shall not be less than C35. The vertical reinforcing bars of the cast-in-place structural column 3 shall be anchored into the foundation longitudinal beam 22 with an anchorage length of not less than 500mm. At the corresponding position in the foundation longitudinal beam 22 at the bottom of the precast shear wall, there shall be protruding reinforcing bars designed under the same conditions as the vertical distributed reinforcing bars of the precast shear wall. The lower part of the protruding reinforcing bars shall be anchored into the foundation longitudinal beam 22 by not less than 500mm, and the protruding reinforcing bars shall extend beyond the top surface of the foundation longitudinal beam 22 by not less than 300mm. The lower part of the precast shear wall shall be equipped with a grouting corrugated pipe for grouting and anchoring connection. The protruding reinforcing bars on the top surface of the foundation longitudinal beam 22 shall be inserted into the grouting corrugated pipe and fixed by grouting through the grouting and anchoring connection method of the precast shear wall.

[0020] The reinforcing bars inside the cast-in-place structural column 3 are led out from the foundation longitudinal beam 22, with a cross-sectional dimension of not less than 400mm×400mm. There are not less than 12 reinforcing bars with a diameter of 22mm inside, and closed stirrups of not less than Φ10@150mm are used. The stirrups are densified within 1000mm of the bottom and top of the precast column. The spacing of the stirrups in the densified area does not exceed 100mm. 100% of the longitudinal reinforcing bars of the cast-in-place structural column 3 are provided with anchor plates at the top.

[0021] Figure 2 The diagram shows a structural schematic of the precast composite double-T beam integrated slab 7. The precast composite double-T beam integrated slab 7 includes a composite slab 71, composite beams 72 and truss reinforcement 73. Two parallel composite beams 72 are integrally formed on the lower side of the composite slab 71, and each composite beam 72 shares a steel cage with the composite slab 71. Multiple truss reinforcements 73 are provided on the upper side of the composite slab 71 to form a double-T beam structure. The precast composite double-T beam integrated slab 7 is hoisted onto the top of the cast-in-place structural column 3 and the precast shear wall panel 4. The ends of the precast portion of the precast composite double-T beam integrated slab 7 rest on the precast shear wall panel 4 for at least 10mm, and its two ends form cast-in-place nodes 8 with the cast-in-place structural column 3 and the precast shear wall panel 4. The longitudinal reinforcing bars at both ends of the precast composite double-T beam integrated slab 7 at the cast-in-place node 8 are anchored into the interior of the cast-in-place structural column 3, and all the vertical reinforcing bars of the precast shear wall panel 4 are anchored into the interior of the cast-in-place node 8. The concrete strength of the cast-in-place node 8 is at least one grade higher than the designed strength of the cast-in-place structural column 3 and the precast shear wall panel 4. The thickness of the precast composite floor slab in the precast composite double-T beam integrated slab 7 structure is not less than 120mm, and the dimensions and reinforcement of its precast double-T beams are determined according to the specific engineering design.

[0022] Based on the aforementioned double-layer, two-way prefabricated road structure that traverses a high embankment subgrade, the following construction methods are provided for reference. Figure 3 The overall construction process is as follows: Step S1: Measure and set out the road location, and construct the cement-soil mixing and reinforcement section; Step S2: Verify and determine the pile position, and construct the double-interlocking jet grouting piles; Step S3: Excavation of the first layer of earthwork and surface treatment of jet grouting piles; Step S4: Install the first layer of anchor bolts and excavate the lower layer of earthwork in a central island style. Step S5: Install lower-level anchor bolts and construct foundation longitudinal beams; Step S6: Construction of cast-in-place structural columns, hoisting and temporary support of precast shear wall panels; Step S7: Hoisting of precast composite double T-beam integrated slabs and post-casting of joints; Step S8: Continue excavation of the lower central island, pour and cure the foundation concrete; Step S9: Pour the lower road structure concrete layer and fully pave the asphalt concrete surface layer.

[0023] The specific details and core technical solutions of the above construction method are as follows: Step S1: Survey and set out the road location, and construct the cement-soil mixing and reinforcement section. First, excavation is carried out on the top of the high embankment subgrade, within the designed road area and at least 15m to the left and right. The excavated soil is then compacted to provide sufficient working face for subsequent processes. A total station is used to determine the specific locations of the excavation area, jet grouting piles, and cement-soil mixing reinforcement section. The boundaries of each area are clearly marked using lime powder. Then, starting from the designed road edge and working outwards, deep mixing machinery is used to forcibly mix cement (the main curing agent) with the high embankment subgrade soil in situ, with a cement content of at least 15%, thereby reinforcing the high embankment subgrade soil layer. After the cement-soil reinforcement section is completed, the top and slope of the high embankment within the cement-soil reinforcement section will be reinforced by hanging wire mesh and high-pressure shotcreting. If the conditions are complex, such as sandy soil, silty soil, rainy season, or long-term vibration, the top and slope of the high embankment within the cement-soil reinforcement section will be reinforced by hanging wire mesh, high-pressure shotcreting, and anchor bolt installation. Process acceptance and recording should be carried out.

[0024] Step S2: Verify and determine pile positions, and construct double-interlocking jet grouting piles. After the cement-soil mixing and reinforcement section is completed, high-pressure equipment is used to continuously construct jet grouting piles at the high embankment subgrade. The jet grouting pile construction adopts the technical scheme of "double-interlocking arrangement of jet grouting piles with H-shaped steel piles inserted inside". The bottom of the jet grouting piles is at least 2000mm below the bottom elevation of the subgrade. The total width of the double-row jet grouting piles is not less than 1200mm. After all the jet grouting piles are constructed, before the cement grout sets, H-shaped steel piles of the same length as the jet grouting piles are statically driven one by one. The cross-sectional dimensions of the H-shaped steel piles inserted inside the jet grouting piles are not less than 600mm×800mm×30mm. The spacing between the H-shaped steel piles does not exceed 900mm. Static curing is carried out for at least 2 days to avoid large vibrations or large machinery operations on the top of the high embankment subgrade during the curing period. Process acceptance and recording are carried out.

[0025] Step S3: First layer excavation, surface treatment of jet grouting piles After the double-interlocking jet grouting piles are completed, the high embankment subgrade outside the planned road area will be hardened. The first layer of soil will be excavated in layers to 200mm-300mm below the bottom elevation of the upper road structure concrete layer. Then, the surface of the first layer of double-interlocking jet grouting piles will be cleaned, and loose soil will be removed. A total station will be used to verify the positional relationship of the first layer of double-interlocking jet grouting piles after their formation, and the error will be calibrated. The error handling plan for the first layer of double-interlocking jet grouting piles will be revised to ensure that the positional relationship of the first layer of road retaining structure after construction meets the design requirements. To meet the technical requirements for full-process construction monitoring, Beidou / GNSS foundation pit monitoring technology will be used to dynamically monitor and warn of indicators throughout the entire process of high embankment subgrade excavation, retaining, and construction, and process acceptance and monitoring data collection will be carried out.

[0026] Step S4: Install the first layer of anchor bolts, and excavate the lower layer of earthwork in a central island style. After the first layer of earthwork is excavated to the design elevation and the surface of the first layer of double-interlocking jet grouting piles is cleaned, a distribution diagram of the anchor group of the first layer retaining structure is first drawn. According to the distribution diagram of the anchor group of the first layer retaining structure, the specific position of each anchor is marked on the surface of the jet grouting piles. Then, the anchor positions are drilled one by one using equipment to install the anchor group of the first layer. Finally, a steel mesh is hung on the surface of the first layer of double-interlocking jet grouting piles with the anchor group installed. A two-way steel mesh with a diameter of not less than 6mm and a spacing of not more than 150mm is used. Taking into account the error of the retaining structure in the above process, a high-pressure spray gun is used to spray high-strength mortar on the surface of the first layer of double-interlocking jet grouting piles. After spraying, the surface is smoothed and polished. Once the first-layer anchor bolt group is installed and the high-pressure shotcrete is completed, the excavation of the lower-layer soil can begin. The lower-layer soil excavation adopts the central island excavation method. The top of the central island retains the original elevation, and its bottom is retained to 300mm~500mm inside the foundation longitudinal beam. That is, all the soil above the foundation longitudinal beam is excavated first, and the soil in the central island is temporarily retained, so as to provide a favorable working surface and support conditions for the subsequent hoisting of the foundation longitudinal beam, precast shear wall panel and precast composite double T beam integrated slab.

[0027] Step S5: Install lower-level anchor bolts and construct foundation longitudinal beams. After the lower layer of soil is excavated using a central island method, the surface of the lower layer double-interlocking jet grouting piles is cleaned, and the lower layer anchor group is comprehensively constructed and treated using the same technical methods as in step S3 above. For the construction of the foundation longitudinal beam under the jet grouting piles, the soil at the foundation longitudinal beam is first excavated manually to the design bottom elevation of the cushion layer. The cushion layer on both sides of the central island soil layer is poured in one go using fine aggregate concrete of not less than C25, and then cured. Then, the foundation longitudinal beam reinforcement cage is hoisted on the top surface of the poured cushion layer, and the water-stop steel plate, the longitudinal reinforcement of the cast-in-place structural column, and the vertical reinforcement at the position of the precast shear wall panel are pre-embedded. After the formwork is erected, the foundation longitudinal beam concrete is poured. It should be noted that the foundation longitudinal beam formwork only needs to be erected on the side formwork near the inside of the foundation pit. The concrete strength of the foundation longitudinal beam is not less than C35. The concealed works acceptance and recording should be done well.

[0028] Step S6: Construction of cast-in-place structural columns, hoisting and temporary support of precast shear wall panels. After the foundation longitudinal beam concrete has cured to 75% of its design strength, the longitudinal reinforcement of the cast-in-place structural column is connected and traced from the top of the foundation longitudinal beam. All the reinforcement of the cast-in-place structural column is then tied. The formwork support system for the cast-in-place structural column is quickly assembled using aluminum formwork. Fine aggregate concrete is poured from the top of the cast-in-place structural column in one go, leaving no construction joints, and vibration and curing are strengthened. After the cast-in-place structural column concrete has cured to its design strength, the precast shear wall panels are constructed using hoisting machinery. The vertical reinforcement bars pre-reserved on the top surface of the foundation longitudinal beam are inserted one by one into the grouting sleeves at the bottom of the precast shear wall panels. Micro-expansion high-strength low-shrinkage grouting material is used to grout each of the precast shear wall panels in place. Multiple horizontally adjustable steel supports are used for temporary support between the cast-in-place structural column and the fixed precast shear wall panels. The positional relationship and verticality of the precast shear wall panels after placement are checked, and the concealed works are inspected and recorded.

[0029] Step S7: Hoisting of precast composite double T-beam integrated slabs and post-casting of joints. Because the excavation of the lower-level high-fill roadbed adopts the central island excavation method, before hoisting the precast composite double-T beam integrated slab, the top of the central island soil is first manually trimmed to the bottom elevation of the precast composite double-T beam integrated slab. The central island soil is fully utilized to assist in the hoisting and positioning of the precast composite double-T beam integrated slab. Then, hoisting machinery is used to hoist the precast composite double-T beam integrated slab to the top of the central island soil. All the reinforcing bars at the ends of the precast composite double-T beam integrated slab are anchored into the cast-in-place joint at the top of the cast-in-place structural column. At the same time, the reinforcing bars at the top of the precast shear wall slab that has been hoisted into place are also anchored into the cast-in-place joint. Finally, the formwork at the cast-in-place joint is erected, and fine stone concrete of a grade one higher than that of the precast composite double-T beam integrated slab and the cast-in-place structural column is poured in one go. Curing is strengthened, and the hidden works are inspected and recorded.

[0030] Step S8: Continue excavation of the lower central island, and pour and cure the foundation concrete. Before continuing the excavation of the lower central island, steel mesh is first tied to the top truss reinforcement of the precast composite double-T beam integrated slab that has been placed in place. The upper road structure concrete layer is then poured using fine aggregate concrete of grade no lower than C30, and is cast together with the aforementioned cast-in-place joint concrete. After the upper road structure concrete layer and cast-in-place joints have cured to their design strength, the excavation of the lower central island can continue. Throughout the entire excavation process, the overall structure is monitored, with a focus on monitoring the maximum deformation at the top of the jet grouting piles. During the full excavation of the lower central island, the precast shear wall panels and precast composite double-T beam integrated slabs must not be impacted. Excavation near the precast shear wall panels and precast composite double-T beam integrated slabs is carried out using manual assisted excavation and structural surface cleaning. After the earthwork of the lower central island is excavated to the top surface of the foundation, the remaining earthwork between the two foundation longitudinal beams is excavated manually to the bottom of the design elevation of the cushion layer, that is, to the bottom of the cushion layer under the foundation longitudinal beams. Then the remaining cushion layer is poured into shape in one go, and the curing is strengthened. The process acceptance and record are done well.

[0031] Step S9: Pour the lower road structure concrete layer and fully pave the asphalt concrete surface layer. After the subbase concrete has cured to 80% of its design strength, the foundation reinforcement cage is hoisted into place on top of the subbase. Then, using a chalk line, the elevation of the top surface of the lower road structure concrete layer is marked below the precast shear wall panels. A control line is then marked 100mm above the top surface of the lower road structure concrete layer. Once all preparations are complete, fine aggregate concrete is used to reinforce the foundation, and the lower road structure concrete layer is poured together. The concrete at the waterstop steel plate is vibrated to enhance compaction. A continuous, overlapping work process is implemented. After the lower road structure concrete layer has cured to its design strength, the asphalt concrete surface layer is fully paved. Project acceptance and documentation are then completed.

[0032] In summary, this invention, through its prefabricated and assembled double-layer bidirectional structural design, enables rapid assembly and construction, significantly shortens the construction period and reduces environmental impact. Its internal space allows for optimized pipeline layout, enhancing the comprehensive function of the roadbed. The unique integral structure effectively disperses loads and significantly enhances the roadbed's ability to coordinate with uneven settlement, thereby improving the safety and durability of the road during its service life.

[0033] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A double-layer, two-way prefabricated road structure traversing a high embankment subgrade, characterized in that: The road structure includes a cement-soil mixing reinforcement section, jet grouting piles, anchor bolts, foundations, foundation longitudinal beams, cast-in-place structural columns, a lower road structure concrete layer, precast shear wall panels, a precast composite double-T beam integrated slab, and an upper road structure concrete layer. The high embankment subgrade on both sides of the road is reinforced with cement-soil mixing and interlocking jet grouting piles. Anchor bolts are driven into the cement-soil mixing reinforcement section through the jet grouting piles. A foundation is located between two jet grouting piles in the transverse direction of the road. Foundation longitudinal beams are arranged longitudinally along the road between the foundation and the jet grouting piles. A cast-in-place structural column is located on the top surface of the foundation near the inner side of the jet grouting pile, above the foundation longitudinal beams. A precast shear wall panel is also located above the foundation longitudinal beams. The precast composite double-T beam integrated slab is supported on top of the cast-in-place structural columns and the precast shear wall panels. The upper road structure concrete layer is located on top of the precast composite double-T beam integrated slab. A lower road structure concrete layer is located between two precast shear wall panels in the transverse direction of the road and above the foundation.

2. The road structure according to claim 1, characterized in that: The depth of the cement-soil mixing reinforcement section is not less than 3.0m below the bottom elevation of the foundation; the jet grouting piles are installed on the basis of the cement-soil reinforcement section, perpendicular to the longitudinal direction of the high embankment subgrade, and the diameter of each jet grouting pile is not less than 500mm. The interlocking jet grouting piles are arranged in a "parabolic" shape to play a role in double solidification of the high embankment subgrade soil layer.

3. The road structure according to claim 2, characterized in that: On the side of the jet grouting pile near the excavation of the high embankment subgrade, dense anchor bolts are driven into the cement-soil reinforcement section. The spacing between adjacent anchor bolts shall not exceed 450mm, and the length of each anchor bolt shall not be less than 3.0m. The top row of anchor bolts at the top of the jet grouting pile shall be no less than 300mm and no more than 750mm from the top of the pile. The bottom row of anchor bolts at the bottom of the jet grouting pile shall be no less than 200mm from the bottom of the foundation and shall be located within the height range of the longitudinal beam of the foundation. The end of each anchor bolt shall be anchored to the outer surface of the jet grouting pile using an "anchor + steel washer" method. The steel washer shall not exceed 2.0m in length, be no less than 250mm in width, and be no less than 20mm in thickness.

4. The road structure according to claim 1, characterized in that: The design height of the foundation longitudinal beam shall not be less than the thickness of the foundation, the cross-sectional width shall not be less than 1000mm, and the end face near the foundation shall extend beyond the corresponding edge of the precast shear wall panel by not less than 200mm. The foundation longitudinal beam shall be reinforced with not less than 8 threaded steel bars with a diameter of 16mm, and the concrete strength shall not be less than C35. The vertical reinforcing bars of the cast-in-place structural columns are anchored into the foundation longitudinal beams with an anchorage length of not less than 500mm. At the corresponding position in the foundation longitudinal beams at the bottom of the precast shear wall, there are extended reinforcing bars designed under the same conditions as the vertical distributed reinforcing bars of the precast shear wall. The lower part of the extended reinforcing bars is anchored into the foundation longitudinal beams for not less than 500mm, and the extended reinforcing bars extend out of the top surface of the foundation longitudinal beams for not less than 300mm. The lower part of the precast shear wall is equipped with a grouting corrugated pipe for grouting anchor lap connection. The outward reinforcing bars on the top surface of the foundation longitudinal beam are inserted into the grouting corrugated pipe and fixed by grouting through the grouting anchor lap connection of the precast shear wall. The reinforcing bars inside the cast-in-place structural column are led out from the foundation longitudinal beam, with a cross-sectional dimension of not less than 400mm×400mm. There are not less than 12 reinforcing bars with a diameter of 22mm inside, and closed stirrups of not less than Φ10@150mm are used. The stirrups are densified within a range of 1000mm at the bottom and top of the precast column. The spacing of the stirrups in the densified area does not exceed 100mm. 100% of the longitudinal reinforcing bars of the cast-in-place structural column are provided with anchor plates at the top.

5. The road structure according to claim 1, characterized in that: The precast composite double-T beam integrated slab is hoisted onto the top of the cast-in-place structural columns and precast shear wall panels. The ends of the precast portions of the precast composite double-T beam integrated slab rest on the precast shear wall panels for at least 10mm, and its two ends form cast-in-place nodes with the cast-in-place structural columns and precast shear wall panels. The longitudinal reinforcing bars at both ends of the precast composite double-T beam integrated slab at the cast-in-place nodes are anchored into the interior of the cast-in-place structural columns, and all the vertical reinforcing bars of the precast shear wall panels are anchored into the interior of the cast-in-place nodes. The concrete strength of the cast-in-place nodes is at least one grade higher than the designed strength of the cast-in-place structural columns and precast shear wall panels. The thickness of the precast composite floor slab in the precast composite double-T beam integrated slab structure is not less than 120mm, and the dimensions and reinforcement of its precast double-T beams are determined according to the specific engineering design.

6. A construction method for a double-layer, two-way prefabricated road structure traversing a high embankment subgrade, characterized in that, Includes the following steps: Step S1: Measure and set out the road location, and construct the cement-soil mixing and reinforcement section; Step S2: Verify and determine the pile position, and construct the double-interlocking jet grouting piles; Step S3: Excavation of the first layer of earthwork and surface treatment of jet grouting piles; Step S4: Install the first layer of anchor bolts and excavate the lower layer of earthwork in a central island style. Step S5: Install lower-level anchor bolts and construct foundation longitudinal beams; Step S6: Construction of cast-in-place structural columns, hoisting and temporary support of precast shear wall panels; Step S7: Hoisting of precast composite double T-beam integrated slabs and post-casting of joints; Step S8: Continue excavation of the lower central island, pour and cure the foundation concrete; Step S9: Pour the lower road structure concrete layer and fully pave the asphalt concrete surface layer.

7. A construction method for a double-layer, two-way prefabricated road structure traversing a high embankment subgrade, characterized in that, Includes the following steps: Step S1: Surveying and setting out the road location, construction of the cement-soil mixing and reinforcement section: First, excavate the earthwork within the designed road area on the top of the high embankment and within a range of no less than 15m on both sides, and compact the earthwork within the excavation area to provide sufficient working face for subsequent processes. Use a total station to determine the specific locations of the earthwork excavation area, jet grouting piles, and cement-soil mixing reinforcement section, and use lime powder to clearly mark the boundaries of each area. Then, starting from the design road edge line and moving outwards, use deep mixing machinery to forcibly mix cement and high embankment soil in situ, with a cement content of no less than 15%, to achieve the purpose of reinforcing the high embankment soil layer. After the cement-soil reinforcement section is completed, use a combination of wire mesh and high-pressure shotcrete to reinforce the surface of the high embankment top and slope within the cement-soil reinforcement section. If encountering complex working conditions such as sandy soil, silty soil, rainy season, or long-term vibration, use a combination of wire mesh, high-pressure shotcrete, and anchor bolts to reinforce the surface of the high embankment top and slope within the cement-soil reinforcement section. Ensure proper process acceptance and record-keeping. Step S2: Verify and determine pile positions, and construct double-interlocking jet grouting piles: After the cement-soil mixing and reinforcement section is completed, high-pressure equipment is used to continuously construct jet grouting piles at the high embankment subgrade. The jet grouting pile construction adopts the scheme of "double-interlocking arrangement of jet grouting piles with H-shaped steel piles inserted inside". The bottom of the jet grouting piles is at least 2000mm below the bottom elevation of the cushion layer. The total width of the double-row jet grouting piles is not less than 1200mm. After all the jet grouting piles are constructed, before the cement slurry finally sets, H-shaped steel piles of the same length as the jet grouting piles are statically driven one by one. The cross-sectional dimensions of the H-shaped steel piles inserted inside the jet grouting piles are not less than 600mm×800mm×30mm. The spacing between the H-shaped steel piles does not exceed 900mm. Static curing is carried out for at least 2 days to avoid large vibrations or large machinery operations on the top of the high embankment subgrade during the curing period. Process acceptance and recording are carried out. Step S3: First layer excavation, jet grouting pile surface treatment: After the double-interlocking jet grouting piles are completed, the high embankment subgrade outside the planned road area will be hardened. The first layer of soil will be excavated in layers to 200mm-300mm below the bottom elevation of the upper road structure concrete layer. Then, the surface of the first layer of double-interlocking jet grouting piles will be cleaned, and loose soil will be removed. A total station will be used to check the positional relationship of the first layer of double-interlocking jet grouting piles after their formation, and the error will be calibrated. The error handling plan for the first layer of double-interlocking jet grouting piles will be revised to ensure that the positional relationship of the first layer of road retaining structure after construction meets the design requirements. In order to meet the technical requirements of full-process construction monitoring, Beidou / GNSS foundation pit monitoring technology will be used to dynamically monitor and warn of indicators throughout the entire process of high embankment subgrade excavation, retaining, and construction, and process acceptance and monitoring data collection will be carried out. Step S4: Install the first layer of anchor bolts, and excavate the lower layer of earthwork in a central island style: After the first layer of earthwork is excavated to the design elevation and the surface of the first layer of double-interlocking jet grouting piles is cleaned, a distribution diagram of the anchor bolt group for the first layer retaining structure is first drawn. The specific location of each anchor bolt is then marked on the surface of the jet grouting piles according to this diagram. Next, drilling is performed on each anchor bolt location using appropriate equipment to install the first layer of anchor bolts. Finally, a steel mesh is installed on the surface of the first layer of double-interlocking jet grouting piles with the installed anchor bolts. A bidirectional steel mesh with a diameter of not less than 6mm and a spacing of not more than 150mm is used. Taking into account the errors in the retaining structure described above, a high-pressure... High-strength mortar is sprayed onto the surface of the first-layer double-interlocking jet grouting piles using a spray gun. After spraying, the surface is smoothed and polished. Once the first-layer anchor group is installed and the high-pressure spraying is completed, the excavation of the lower-layer soil can begin. The lower-layer soil excavation adopts the central island excavation method. The top of the central island retains its original elevation, and its bottom is retained to 300mm~500mm inside the foundation longitudinal beam. This means that all the soil above the foundation longitudinal beam area is excavated first, and the soil in the central island area is temporarily retained to provide a favorable working surface and support conditions for the subsequent hoisting of the foundation longitudinal beam, precast shear wall panel, and precast composite double T-beam integrated slab. Step S5: Install lower-level anchor bolts and construct foundation longitudinal beams: After the lower layer of soil is excavated using the central island method, the surface of the lower layer double-interlocking jet grouting piles is cleaned. The lower layer anchor group is then fully constructed and treated using the same technical means as in step S3 above. For the construction of the foundation longitudinal beam under the jet grouting piles, the soil at the foundation longitudinal beam is first excavated manually to the design bottom elevation of the cushion layer. The cushion layer on both sides of the central island soil layer is poured in one go using fine stone concrete of not less than C25, and then cured. The foundation longitudinal beam reinforcement cage is then hoisted on the top surface of the poured cushion layer. Water-stop steel plates, longitudinal reinforcement of cast-in-place structural columns, and vertical reinforcement at the positions of precast shear wall panels are pre-embedded. After the formwork is erected, the foundation longitudinal beam concrete is poured. It should be noted that the foundation longitudinal beam formwork only needs to be erected on the side formwork near the inside of the foundation pit. The concrete strength of the foundation longitudinal beam should not be less than C35. The concealed works acceptance and record should be done well. Step S6: Construction of cast-in-place structural columns, hoisting and temporary support of precast shear wall panels: After the concrete of the foundation longitudinal beam has cured to 75% of its design strength, the longitudinal reinforcement of the cast-in-place structural column is connected at the top of the foundation longitudinal beam. All the reinforcement of the cast-in-place structural column is tied. The formwork support system of the cast-in-place structural column is quickly assembled using aluminum formwork. Fine aggregate concrete is poured from the top of the cast-in-place structural column in one go without leaving construction joints. Vibration and curing are strengthened. After the concrete of the cast-in-place structural column has cured to its design strength, the precast shear wall panels are constructed using hoisting machinery. The vertical reinforcement reserved on the top surface of the foundation longitudinal beam is inserted one by one into the grouting sleeve of the reinforcement at the bottom of the precast shear wall panel. Micro-expansion high-strength low-shrinkage grouting material is used to grout each of the precast shear walls that have been placed. Multiple horizontal adjustable steel supports are used for temporary support between the cast-in-place structural column and the fixed precast shear wall panels. The positional relationship and verticality of the precast shear wall panels after placement are checked, and the concealed works are inspected and recorded. Step S7: Hoisting of precast composite double-T beam integrated slab, post-casting treatment of joints: Since the excavation of the lower high embankment subgrade adopts the central island excavation method, before the hoisting of the precast composite double T beam integrated slab, the top of the central island soil is first manually trimmed to the bottom elevation of the precast composite double T beam integrated slab. The central island soil is fully utilized to assist in the hoisting and positioning of the precast composite double T beam integrated slab. Then, hoisting machinery is used to hoist the precast composite double T beam integrated slab to the top of the central island soil. All the reinforcing bars at the ends of the precast composite double T beam integrated slab are anchored into the cast-in-place joint at the top of the cast-in-place structural column. At the same time, the reinforcing bars at the top of the precast shear wall slab that has been hoisted into place are also anchored into the cast-in-place joint. Finally, the formwork at the cast-in-place joint is erected, and fine stone concrete of a grade one higher than that of the precast composite double T beam integrated slab and the cast-in-place structural column is poured in one go. Curing is strengthened, and the hidden works are inspected and recorded. Step S8: Continue excavation of the lower central island, and pour and cure the foundation concrete. Before continuing the excavation of the lower central island, steel mesh is first tied to the top truss reinforcement of the precast composite double-T beam integrated slab that has been placed in place. The upper road structure concrete layer is then poured using fine aggregate concrete of at least C30 grade, and this upper road structure concrete layer is poured together with the aforementioned cast-in-place joint concrete. After the upper road structure concrete layer and the cast-in-place joints have cured to their design strength, the excavation of the lower central island can continue. Throughout the entire excavation process, monitoring of the overall structure is crucial, with a focus on monitoring the maximum deformation at the top of the jet grouting piles. During the full excavation of the lower central island, the precast shear wall panels and precast composite double T-beam integrated slabs that have been completed must not be impacted. The earthwork near the precast shear wall panels and precast composite double T-beam integrated slabs shall be excavated manually and the structural surfaces shall be cleaned. After the earthwork of the lower central island is excavated to the top surface of the foundation, the remaining earthwork between the two foundation longitudinal beams shall be excavated manually to the bottom of the design elevation of the cushion layer, that is, excavated to the bottom of the cushion layer under the foundation longitudinal beams. Then the remaining cushion layer shall be poured into shape in one go, and the curing shall be strengthened. The process acceptance and record shall be done well. Step S9: Pouring the lower road structure concrete layer and fully paving the asphalt concrete surface layer: After the subbase concrete has cured to 80% of its design strength, the foundation reinforcement cage is hoisted into place on top of the subbase. Then, using a chalk line, the elevation of the top surface of the lower road structure concrete layer is marked on the bottom of the precast shear wall panel that has been placed. A control line is then marked 100mm above the top surface elevation of the lower road structure concrete layer. After all preparations are completed, fine aggregate concrete is used to reinforce the foundation and the lower road structure concrete layer together and is poured into shape. The concrete vibration at the waterstop steel plate is strengthened. A continuous, cross-operation method is organized. After the lower road structure concrete layer has cured to its design strength, the asphalt concrete surface layer is fully paved. Project acceptance and data archiving are then carried out.

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