A continuous reinforced cement concrete pavement lap joint structure

Abstract

The application discloses a continuous reinforced cement concrete pavement lap joint structure, which comprises an existing pavement structure and a newly-built pavement structure and a connecting and force transmission system arranged at a longitudinal lap joint interface between the two. Specifically, a multilayer reinforcing bar structure arranged at different heights in a plate thickness direction is used to connect the new and old concrete plates; a sleeper beam is arranged longitudinally along the lap joint interface at the bottom of the new plate and used as a force transmission component; the upper ends of a plurality of vertical support components are fixed to the sleeper beam, and the lower ends of the vertical support components extend into the underlying soil foundation; and a polyester glass cloth is laid between the surface layer and the concrete plate and used as a crack-resistant material layer. Compared with the prior art, the application can significantly improve the overall rigidity and settlement resistance of the lap joint area, effectively enhance the interface shear resistance and crack resistance, and inhibit reflection cracks, so as to improve the pavement durability and driving safety.

Description

Technical Field

[0001] This invention relates to the field of road pavement structure technology, and in particular to a continuous reinforced cement concrete pavement lap structure. Background Technology

[0002] With the continuous growth of highway traffic volume and the extension of the service life of existing roads, road widening and reconstruction have become the main means to improve traffic capacity. In widening projects, continuously reinforced cement concrete pavement (CRCP) is widely used in the construction of high-grade highways due to its strong integrity, high rigidity, and good durability. However, when the new and old pavements form an overlap zone along the longitudinal direction, due to the short filling time and relatively low compaction degree of the new subgrade, there are significant differences in modulus and settlement between the new and existing subgrades. Under the repeated action of vehicle dynamic loads and temperature stress, the overlap interface is prone to vertical misalignment due to uneven settlement, and stress concentration can lead to crack propagation, seriously affecting driving comfort and safety.

[0003] Currently, existing solutions for the jointing of new and old cement concrete pavements mainly rely on rebar connections and shallow supports to enhance the integrity of the joint. For example, Chinese patent application CN113265919A discloses a combined widening and reconstruction base course and construction method based on an old road surface. This method involves installing rebar along the longitudinal side of the old road, extending laterally into the widened base course, and simultaneously casting concrete sleeper beams beneath the widened base course, extending below the old road pavement structure layer, to improve the connectivity between the widened base course and the old road. This solution uses a single-layer rebar arrangement, achieving connection between the new and old pavements only at a single height, failing to form a three-dimensional steel reinforcement network in stress concentration areas, resulting in limited shear and crack resistance. Furthermore, the sleeper beams only extend below the old road, relying on the stability of the roadbed itself for support. For soft foundations or high embankment sections, this cannot provide sufficient vertical bearing capacity to completely prevent post-construction settlement of the new roadbed.

[0004] Another approach, disclosed in Chinese patent application CN113622255A, is a splicing structure and construction method for new and old concrete pavement suitable for asphalt-and-white road surfaces. This method involves installing a sleeper beam at the bottom of the longitudinal joint between the new and old concrete sub-base layers and a splicing tie rod in the middle of the concrete sub-base layer to protect the pavement during uneven settlement. However, in this approach, the tie rod is located in the middle of the concrete sub-base layer, representing a single-height planar connection, unlike the multi-layer rebar installation that forms a three-dimensional network at different heights along the slab thickness. Furthermore, the sleeper beam and vertical support components do not form a rigidly connected, collaborative load-bearing system. Under load, the sleeper beam cannot effectively transfer the load to the deep foundation, the line load is not converted into a surface load, the overall stiffness improvement is limited, and vertical misalignment is still prone to occur at the joint.

[0005] Furthermore, Chinese patent application CN106480799A discloses a pavement splicing method and structure applicable to the reconstruction and expansion of old cement concrete pavements. It addresses the insufficient durability of old cement concrete pavement reconstruction projects by connecting the old and new cement concrete panels with double-layer steel reinforcement and applying polymer anti-crack tape to the splice joints. However, this solution targets ordinary cement concrete panels and does not address the handling of the existing steel reinforcement in continuously reinforced concrete pavements (CRCP) during the splicing process. The specific height and staggered arrangement of the double-layer steel reinforcement in the slab thickness direction are not clearly defined, making it difficult to ensure the continuity of the steel reinforcement and increase the steel density without damaging the original continuous reinforcement of the old slab. Additionally, this solution relies solely on steel reinforcement connections and does not establish a deep support system formed by sleeper beams and vertical support components, thus failing to fundamentally solve the problem of differential settlement.

[0006] Therefore, a new technical solution is needed that can effectively control differential settlement through deep rigid support, and at the same time, through refined interface reinforcement design, increase the rebar density and ensure the continuity of the rebar while avoiding damage to the original continuous reinforced concrete pavement reinforcement layout. This will combine the old and new concrete slabs into a composite structure that works together to bear the load, thereby fundamentally solving the problems of modulus difference, settlement difference, stress concentration and crack propagation at the longitudinal overlap of the old and new pavements in widening projects of continuously reinforced concrete pavements. Summary of the Invention

[0007] The purpose of this invention is to overcome the defects of the prior art by providing a continuously reinforced cement concrete pavement overlap structure, which solves the problems of longitudinal joint cracking and misalignment caused by differential settlement when the new and old pavements overlap.

[0008] The objective of this invention can be achieved through the following technical solutions: This invention provides a continuously reinforced cement concrete pavement overlap structure, comprising an existing pavement structure and a newly constructed pavement structure, wherein the existing pavement structure and the newly constructed pavement structure form an overlap interface in the longitudinal direction, and further comprising: A multi-layer rebar structure, wherein each layer of rebar is set at a different height position in the thickness direction of the continuous reinforced concrete slab, and adjacent layers of rebar are arranged in an alternating manner. The multi-layer rebar structure penetrates the lap interface and connects the old continuous reinforced concrete slab of the existing pavement structure with the new continuous reinforced concrete slab of the newly built pavement structure. The force transmission component includes a bolster beam extending longitudinally along the lap interface, the bolster beam being disposed at the lap interface, and the upper surface of the bolster beam abutting against the bottom of the new continuously reinforced concrete slab. Multiple vertical support members, the upper ends of which are fixedly connected to the sleeper beam, and the lower ends of the vertical support members extend to the subgrade below the newly constructed pavement structure; The crack-resistant material layer is a polyester fiberglass cloth disposed between the surface layer and the continuously reinforced concrete slab at the lap interface.

[0009] Furthermore, the newly constructed road structure includes, from top to bottom, a new asphalt mixture surface layer, a new continuously reinforced concrete slab, a new cement-stabilized crushed stone base course, a new low-dose cement-stabilized crushed stone subbase course, and a new roadbed.

[0010] Furthermore, the existing road structure includes, from top to bottom, an old asphalt mixture surface layer, an old continuously reinforced concrete slab, an old cement-stabilized crushed stone base course, an old lime-soil subbase course, and an old roadbed.

[0011] Furthermore, the multi-layer rebar structure is a double-layer rebar structure, wherein the two layers of rebar are located at 1 / 3 of the slab thickness and 2 / 3 of the slab thickness from the top surface of the continuously reinforced concrete slab, respectively. The double-layer rebar structure uses HRB400 steel bars with a diameter of 12-20mm.

[0012] Furthermore, the vertical support member is a steel pipe pile arranged at intervals along the length direction of the sleeper beam; The bolster beam is embedded in the new cement-stabilized crushed stone base layer, with the top surface of the bolster beam flush with the top surface of the new cement-stabilized crushed stone base layer and the bottom surface of the bolster beam abutting against the upper surface of the new low-dose cement-stabilized crushed stone base layer.

[0013] Furthermore, the vertical support member is a steel pipe pile with a diameter of 150-250mm, a wall thickness of 6-10mm, a length of 0.8-1.5m, and a spacing of 1.5-2.5m between the steel pipe piles along the length of the force transmission member.

[0014] Furthermore, one end of the steel pipe pile is fixedly connected to the sleeper beam, and the other end of the steel pipe pile extends downward and is embedded in the new roadbed.

[0015] Furthermore, the sleeper beam is a concrete beam, the concrete strength grade of the concrete beam is not lower than C30, the width of the concrete beam is 40-60cm, and the height is 15-25cm; The polyester fiberglass cloth is laid laterally with a width of 0.8-1.2m along the overlap interface.

[0016] Furthermore, two rows of rebar holes are arranged on the side of the old continuously reinforced concrete slab at 1 / 3 and 2 / 3 of the slab thickness from the top of the slab. The rebar is anchored to the old continuous reinforced concrete slab through the anchoring adhesive injected into the hole. The anchoring adhesive is a modified epoxy resin adhesive with a tensile strength of not less than 30 MPa and a shear strength of not less than 15 MPa.

[0017] Furthermore, the cement dosage of the new low-dose cement-stabilized crushed stone subbase is controlled to be below 3 wt%. The 90-day compressive strength of the new low-dose cement-stabilized crushed stone subbase shall not be less than 95% of its design strength.

[0018] Compared with the prior art, the present invention has the following beneficial effects: (1) Through the fixed connection between the force transmission component and the vertical support component, a collaborative force-bearing system of vertical pile foundation support, horizontal force transmission beam, and interface connection reinforcement is formed. The force transmission component effectively distributes the line load into a surface load and transfers it to the vertical support component, which in turn transfers the load to the deep foundation. This significantly improves the overall stiffness and settlement resistance of the overlapping area, and fundamentally solves the problem of longitudinal joint cracking and misalignment caused by differential settlement between the old and new roadbeds.

[0019] (2) A multi-layer rebar structure is adopted, with each layer of rebar set at different heights in the thickness direction of the slab and adjacent layers arranged in an alternating manner. A three-dimensional steel reinforcement network is formed in the stress concentration areas at 1 / 3 and 2 / 3 distance from the top of the continuously reinforced concrete slab, avoiding damage to the original steel reinforcement layout of the continuously reinforced concrete slab. While ensuring the continuity of the rebar installation, the steel reinforcement density is increased, enabling effective stress transfer between the old and new concrete slabs under stress, and significantly enhancing the shear resistance and crack resistance of the interface.

[0020] (3) A crack-resistant material layer is installed at the overlap interface. The newly constructed pavement structure adopts a low-dose hydraulic material stabilized subbase, which together with the multi-layer rebar structure and the deep support system of force transmission components-vertical support components constitutes a multi-layer protection system. The crack-resistant material layer effectively inhibits the upward extension of reflective cracks and has good water-proof performance; the low-dose hydraulic material stabilized subbase reduces shrinkage cracks caused by early temperature and humidity; the multi-layer protection system works synergistically to comprehensively improve the long-term durability and driving safety of the overlap structure. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the lap joint structure of continuously reinforced cement concrete pavement.

[0022] The meanings of the markings in the attached diagram are as follows: 1-Old asphalt mixture surface course, 2-Old continuously reinforced concrete slab, 3-Old cement-stabilized crushed stone base course, 4-Old lime-soil subbase course, 5-Old roadbed, 6-New asphalt mixture surface course, 7-New continuously reinforced concrete slab, 8-New cement-stabilized crushed stone base course, 9-New low-dose cement-stabilized crushed stone subbase course, 10-New roadbed, 11-Polyester fiberglass cloth, 12-Double-layer rebar structure, 13-Sleeper beam, 14-Steel pipe pile. Detailed Implementation

[0023] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. Component models, material names, connection structures, circuit structures, and construction methods not explicitly stated in this technical solution are considered common technical features disclosed in the prior art.

[0024] Example 1 like Figure 1 As shown, this embodiment provides a continuously reinforced cement concrete pavement overlap structure, including an existing pavement structure and a newly constructed pavement structure, which form an overlap interface in the longitudinal direction, and a connecting component and a supporting component are provided at the overlap interface.

[0025] The existing road structure consists of, from bottom to top, the old roadbed 5, the old lime-soil subbase 4, the old cement-stabilized crushed stone base 3, the old continuously reinforced concrete slab 2, and the old asphalt mixture surface layer 1. The old roadbed 5 is an existing roadbed soil that has been compacted and settled over a long period of time, and its bearing capacity is stable.

[0026] The old lime-fly ash subbase 4 is formed by mixing lime, fly ash, and soil in the conventional proportions used in existing technology. Its thickness is determined according to the original pavement design, typically 15-20cm. The old cement-stabilized crushed stone base 3 is formed by mixing and compacting cement and crushed stone in the conventional proportions used in existing technology. The cement dosage is typically 4-6%, and the thickness is determined according to the original pavement design, typically 20-30cm, providing the main load-bearing capacity. The old continuously reinforced concrete slab 2 is the existing continuously reinforced cement concrete pavement slab, typically 20-30cm thick. Continuous longitudinal reinforcement is arranged within the slab, with a reinforcement ratio typically 0.6-1.0%. Lateral dowel bars are installed at intervals of 1.0-1.5m, forming a continuously reinforced concrete pavement structure. The old asphalt mixture surface layer 1 is the existing pavement wearing course, typically 4-6cm thick, using existing SBS modified asphalt concrete material, providing a smooth driving surface and anti-skid performance.

[0027] The new road structure includes, from bottom to top, a new roadbed 10, a new low-dose cement-stabilized crushed stone subbase 9, a new cement-stabilized crushed stone base 8, a new continuously reinforced concrete slab 7, and a new asphalt mixture surface layer 6.

[0028] The new roadbed 10 is the newly filled subgrade soil on the widened side, constructed using a layered filling and compaction process, with a compaction degree required to reach over 96% to ensure the stability of the subgrade. The new low-dosage cement-stabilized crushed stone subbase 9 is formed by mixing and compacting cement and crushed stone according to conventional usage ratios in existing technologies. The cement dosage is strictly controlled below 3wt%, preferably 2.5-3.0wt%, with a thickness of 15-20cm. The cement dosage setting for the low-dosage cement-stabilized crushed stone subbase is based on the following: when the cement dosage is below 3wt%, the early strength growth of the material is slower, the heat release of hydration is smaller, and temperature shrinkage and drying shrinkage deformation are significantly reduced, effectively reducing shrinkage cracks caused by early temperature and humidity; at the same time, low-dosage cement-stabilized crushed stone can still provide sufficient long-term strength and stability to meet the load-bearing requirements of the pavement structure. The new cement-stabilized crushed stone base 8 is formed by mixing and compacting cement and crushed stone according to conventional usage ratios in existing technologies, with a cement dosage typically 4-6wt% and a thickness of 20-30cm, providing the main load-bearing capacity. The new continuously reinforced concrete slab 7 is a newly constructed continuously reinforced cement concrete pavement slab. Its thickness is the same as the old continuously reinforced concrete slab 2, typically 20-30 cm. Continuous longitudinal reinforcement is installed within the slab, with the same reinforcement ratio as the old slab. Lateral dowel bars are also installed, forming a continuously reinforced concrete pavement structure that matches the existing pavement. The new asphalt mixture surface layer 6 is the wearing course of the newly constructed pavement. Its thickness and material type are the same as the old asphalt mixture surface layer 1, forming a smooth and continuous driving surface.

[0029] The lap joint assembly includes a wide polyester fiberglass cloth 11 and a double-layer rebar anchoring structure 12. The double-layer rebar anchoring structure 12 is positioned at the lap interface between the old continuous reinforced concrete slab 2 and the new continuous reinforced concrete slab 7. Two rows of rebar anchoring holes are arranged on the side of the old continuous reinforced concrete slab 2 at 1 / 3 and 2 / 3 of the slab thickness from the top. The anchoring positions are determined based on the fact that when the continuous reinforced concrete slab is subjected to bending, the 1 / 3 and 2 / 3 of the slab thickness from the top are stress concentration areas. Anchoring at these two heights creates a three-dimensional steel reinforcement network in the stress concentration areas, effectively bearing the shear stress and bending moment at the interface, significantly enhancing the interface's shear resistance and crack resistance. The rebar anchoring holes are arranged in a staggered, quincunx pattern on the plane, with a longitudinal spacing of 40 cm. The purpose of the quincunx-shaped cross arrangement of rebar holes is twofold: Firstly, the staggered distribution of the rebar holes on the plane effectively avoids the original longitudinal reinforcement positions of the existing continuous reinforced concrete slab, preventing damage to the original reinforcement layout during drilling. Secondly, the staggered arrangement optimizes stress distribution, avoids stress concentration, and ensures the continuity of the rebar installation. The 40cm rebar spacing is determined based on the following: This spacing ensures that the rebar density meets the connection strength requirements. According to the design principles of reinforced concrete structures, a rebar spacing of 25-30 times the rebar diameter fully utilizes the tensile strength of the rebar while also considering construction convenience and economy.

[0030] HRB400 steel bars with a diameter of 16mm are used for rebar installation. The selection of the steel bar diameter is based on the following: a single 16mm diameter steel bar has a tensile bearing capacity of approximately 80kN, which can withstand the shear force and bending moment at the lap joint interface. At the same time, the steel bar diameter should not be too large to avoid excessive disturbance to the existing continuous reinforced concrete slab during drilling. HRB400 steel bars have a yield strength of 400MPa, possessing good tensile properties and ductility, which can meet the strength requirements of the interface connection. During rebar installation, specialized drilling equipment is used to drill holes on both sides of the existing continuous reinforced concrete slab. The hole diameter is typically 1.2-1.5 times the rebar diameter (19-24mm), and the hole depth is 15-20 times the rebar diameter (24-32cm) to ensure the anchorage length of the rebar. After drilling, high-pressure gas or a brush is used to remove dust and debris from the holes to ensure the hole walls are clean. High-strength anchoring adhesive is then injected. This adhesive is a modified epoxy resin-based adhesive with a tensile strength of not less than 30 MPa and a shear strength of not less than 15 MPa, ensuring a reliable bond between the reinforcing steel and the concrete. After the reinforcing steel is inserted, ensure the insertion depth meets design requirements. The exposed ends of the reinforcing steel are treated with rust prevention, and sufficient length is reserved for connection to the reinforcing steel of the new continuously reinforced concrete slab 7. The exposed length is typically 30-40 cm.

[0031] Wide polyester fiberglass cloth 11 is laid between the asphalt mixture surface layer and the continuously reinforced concrete slab at the overlap interface, with a transverse laying width of 1m along the overlap interface. The polyester fiberglass cloth is formed by composite weaving of polyester fiber and glass fiber, with a tensile strength of not less than 50kN / m and an elongation at break of 3-5%, exhibiting high tensile strength and good flexibility. The function of the polyester fiberglass cloth is as follows: At the overlap interface, due to the differential settlement of the old and new pavements and the effect of temperature stress, reflective cracks are prone to form on the top surface of the continuously reinforced concrete slab, extending upwards to the asphalt surface layer. Laying the polyester fiberglass cloth between the asphalt surface layer and the concrete slab, it can absorb and disperse the stress concentration at the crack tip through its high tensile strength, effectively inhibiting the upward extension of reflective cracks. Simultaneously, the polyester fiberglass cloth has good water-proofing properties, preventing rainwater from seeping down through cracks and eroding the base layer. The determination of the 1m laying width of the polyester fiberglass cloth is based on the fact that the stress influence range at the overlap interface is typically 0.5m on each side of the interface; a laying width of 1m can cover this stress influence range, fully utilizing its crack-resistant effect. When installing polyester fiberglass cloth, first apply asphalt tack coat to the top surface of the continuously reinforced concrete slab, using 0.5-0.8 kg / m². 2 Then, lay the polyester fiberglass cloth. The fiberglass cloth should be laid flat and firmly bonded to the base layer. The overlap width should not be less than 20cm to ensure the continuity and integrity of the fiberglass cloth.

[0032] The supporting components include longitudinally arranged sleeper beams 13 and steel pipe piles 14. Sleeper beams 13 are located at the bottom of the new continuously reinforced concrete slab 7, extending longitudinally along the lap joint interface. During sleeper beam construction, a rectangular trench is excavated longitudinally along the splicing position in the new cement-stabilized crushed stone base course 8. The height of the rectangular trench is consistent with the new cement-stabilized crushed stone base course 8, typically 20-30cm, and the width is 50cm. The 50cm width of the rectangular trench is determined because a 50cm width provides sufficient load-bearing area to effectively distribute the concentrated load at the lap joint into a surface load transferred to the steel pipe piles. Simultaneously, the width should not be too large to avoid excessive disturbance to the base course and affecting its integrity. After the rectangular trench excavation is completed, steel pipe piles 14 are installed at 2m intervals at the bottom of the trench.

[0033] Steel pipe pile 14 uses Q235φ219×8 seamless steel pipe, with an outer diameter of 219mm, a wall thickness of 8mm, and a length of 1m. The selection of steel pipe pile materials and dimensions is based on the following: Q235 steel has a yield strength of 235MPa, possessing good strength and toughness, capable of bearing vertical loads and resisting bending moments; with an outer diameter of 219mm and a wall thickness of 8mm, the bending stiffness and compressive bearing capacity of the steel pipe can meet the requirements of deep support. According to the calculation of the bearing capacity of steel pipe piles, the vertical bearing capacity of a single steel pipe pile is approximately 150-200kN, which can effectively control differential settlement at the joints; the determination of the steel pipe length of 1m is based on the following: the steel pipe pile penetrates the new cement-stabilized crushed stone base course 8 and the new low-dose cement-stabilized crushed stone subbase course 9, extending approximately 30-40cm into the new roadbed 10. In soft foundations or high embankment sections, the steel pipe piles extending into the roadbed can transfer the load to deeper stable soil layers, providing reliable deep support and fundamentally controlling post-construction settlement of the new roadbed. The spacing of the steel pipe piles along the length of the sleeper beam 13 is 2m. The basis for determining the spacing is that when the spacing of the steel pipe piles 14 is 2m, the support density can meet the requirements for anti-settlement. According to the foundation bearing capacity calculation, when the spacing of the steel pipe piles is 9-10 times the pile diameter, the stress influence range between each pile does not overlap, which can give full play to the bearing capacity of each pile, while also taking into account economy.

[0034] After the steel pipe piles 14 are installed, C30 concrete is poured into the rectangular groove to form the sleeper beam 13. The sleeper beam and the steel pipe piles are rigidly connected by cast-in-place concrete. The C30 concrete strength grade of the sleeper beam is selected based on the following: C30 concrete has a compressive strength of 30MPa and a flexural strength of approximately 3.0MPa, which can withstand the concentrated load and bending moment at the joint. Simultaneously, the elastic modulus of C30 concrete is approximately 30GPa, which matches the elastic modulus of continuously reinforced concrete slabs, resulting in good force transmission. The sleeper beam is 50cm wide and 20cm high. The width and height are determined based on the fact that when the sleeper beam is 50cm wide and 20cm high, the flexural modulus of the sleeper beam section is approximately 0.0033m. 3The bolster beam can withstand the bending moment at the lap joint. According to the beam's bending resistance calculation, the bolster beam can withstand a bending moment of approximately 100 kN·m, meeting the force transmission requirements. Simultaneously, the bolster beam's height of 20 cm matches the thickness of the new cement-stabilized crushed stone base layer 8, and the top surface of the bolster beam is flush with the top surface of the base layer, ensuring the smooth laying of the upper new continuously reinforced concrete slab 7. During bolster beam pouring, the concrete should be vibrated to ensure a reliable rigid connection between the bolster beam and the steel pipe piles. The connection between the bolster beam and the steel pipe piles serves two purposes: the bolster beam, as a horizontal force transmission member, distributes the line load at the bottom of the continuously reinforced concrete slab at the lap joint into a surface load, which is then transferred to multiple steel pipe piles. The steel pipe piles, as vertical support members, transfer the load to the deep foundation. The two, through rigid connection, form a collaborative force-bearing system of vertical pile foundation support, horizontal force transmission beam, and interface connecting reinforcement.

[0035] During the construction of the new continuously reinforced concrete slab 7, the transverse reinforcing bars are first positioned by passing them through the anchor holes of the double-layer rebar structure 12. The diameter of the transverse reinforcing bars is typically 16-20mm, with a spacing of 20-30cm. Then, the longitudinal reinforcing bars are arranged. The longitudinal reinforcing bars are continuously reinforced, with a diameter typically 16-20mm and a spacing of 10-15cm, resulting in a reinforcement ratio of 0.6-1.0%. The thickness of the protective layer is strictly controlled during rebar tying: 5-8cm for the bottom layer, 5-8cm for the top layer, and 5cm for the sides, to ensure the durability of the reinforcing bars. After the rebar tying is completed, concrete is poured. The concrete strength grade is C30-C40, and the slump is controlled at 3-5cm to ensure the workability and density of the concrete. Concrete pouring should be continuous to avoid cold joints. The concrete should be vibrated to ensure compaction, the surface smoothed, and cured promptly for at least 14 days to ensure full strength development.

[0036] After the new continuously reinforced concrete slab 7 is poured and cured to its design strength, the asphalt surface layer will be applied. Before construction, an asphalt tack coat will be applied to the top surface of the new continuously reinforced concrete slab 7 at the overlap interface, at a rate of 0.5-0.8 kg / m². 2 Then, lay a 1m wide strip of polyester fiberglass cloth (11). The fiberglass cloth should be laid flat and firmly bonded to the base layer, with an overlap width of not less than 20cm. After the fiberglass cloth is laid, the asphalt mixture surface layer is spread and compacted. The thickness of the asphalt mixture surface layer is 4-6cm, using modified asphalt concrete material. The spreading temperature is controlled at 140-160℃, the compaction temperature is controlled at 120-140℃, and the compaction degree reaches more than 96%, forming a smooth and continuous driving surface.

[0037] The working principle of the continuously reinforced cement concrete pavement lap joint structure provided in this embodiment is as follows: When vehicle loads are applied to the overlap interface, the load is first transferred through the new asphalt mixture surface layer 6 and the old asphalt mixture surface layer 1 to the new continuous reinforced concrete slab 7 and the old continuous reinforced concrete slab 2. Due to the differences in materials, structure, and construction time between the new and old pavements, there are significant differences in modulus and settlement at the overlap interface. Under the repeated action of vehicle dynamic loads and temperature stress, the overlap interface is prone to vertical misalignment due to uneven settlement, and stress concentration can lead to crack propagation.

[0038] This embodiment employs a double-layer rebar structure 12 at the lap joint interface. The two layers of rebar are located at 1 / 3 and 2 / 3 of the slab thickness from the top surface of the continuously reinforced concrete slab, respectively, forming a three-dimensional steel reinforcement network in the stress concentration area. When a load is applied to the lap joint interface, the relative displacement and stress between the old and new continuously reinforced concrete slabs are transferred through the double-layer rebar structure. The double-layer rebar, positioned at different heights along the slab thickness, effectively bears the shear stress and bending moment at the interface. According to the theory of reinforced concrete composite structures, the three-dimensional steel reinforcement network formed by the double-layer rebar in the stress concentration area can evenly distribute the stress at the interface to the surrounding concrete, preventing crack initiation and propagation caused by stress concentration, and significantly enhancing the shear resistance and crack resistance of the interface. Simultaneously, the double-layer rebar is arranged in a staggered, quincunx pattern, avoiding damage to the original reinforcement layout of the old continuously reinforced concrete slab 2, ensuring the continuity of the rebar, increasing the reinforcement density, and enabling effective stress transfer between the old and new concrete slabs under load, forming a composite structure with overall synergistic stress distribution.

[0039] When the load is transferred to the bottom of the new continuously reinforced concrete slab 7, the sleeper beam 13 distributes the line load at the bottom of the continuously reinforced concrete slab into a surface load, which is then transferred to multiple steel pipe piles 14. As a horizontal force-transferring member, the sleeper beam's mechanism is as follows: the load at the lap joint is concentrated on the sleeper beam, and the sleeper beam, through its own rigidity, converts the line load into a wider surface load. According to the theory of elasticity, the stress concentration factor is high during the transfer of a line load, which easily leads to local failure, while the stress distribution of a surface load is more uniform, and the stress concentration factor is significantly reduced. The sleeper beam is 50cm wide and 20cm high, with a section bending modulus of approximately 0.0033m. 3 It can withstand the bending moment at the joint and effectively transfer the load to multiple steel pipe piles arranged at 2m intervals along the length of the sleeper beam.

[0040] The steel pipe pile 14 serves as a vertical support member, forming a rigid connection with the sleeper beam through cast-in-place concrete, thus creating a collaborative load-bearing system. When the sleeper beam is subjected to load, the load is transferred to the steel pipe pile through the rigid connection, and the steel pipe pile then transfers the load downward to the deep foundation. The steel pipe piles are 1m long and penetrate the new cement-stabilized crushed stone base course 8 and the new low-dose cement-stabilized crushed stone subbase course 9, extending approximately 30-40cm into the new roadbed 10. In soft foundations or high embankment sections, the steel pipe piles can transfer the load to deeper stable soil layers. According to the pile foundation bearing capacity theory, the pile end resistance and pile side friction jointly bear the vertical load. The steel pipe piles have an outer diameter of 219mm and a wall thickness of 8mm. The vertical bearing capacity of a single steel pipe pile is approximately 150-200kN. Multiple steel pipe piles are arranged at 2m intervals along the length of the sleeper beam to form a deep support system, significantly improving the overall stiffness and settlement resistance of the overlapping area, and fundamentally solving the problem of longitudinal joint cracking and misalignment caused by differential settlement between the old and new roadbeds.

[0041] The synergistic force-bearing system formed by the rigid connection of the sleeper beam and the steel pipe pile has the following technical advantages: Traditional support structures mostly rely on the stability of the roadbed itself. For soft foundations or high embankment sections, they cannot provide sufficient vertical bearing capacity to completely curb the post-construction settlement of the new roadbed. However, the synergistic force-bearing system of the sleeper beam and the steel pipe pile in this embodiment effectively disperses the line load into a surface load through the sleeper beam and transfers the load to the deep foundation through the steel pipe pile, forming a multi-level force transmission path of "vertical pile foundation support - horizontal force transmission beam - interface connection reinforcement". According to structural mechanics theory, the multi-level force transmission path can effectively disperse stress, reduce stress peak, improve the overall stiffness and deformation resistance of the structure, fundamentally control differential settlement, and prevent vertical misalignment and longitudinal cracking at the overlap interface.

[0042] At the overlap interface, polyester fiberglass cloth 11 is laid between the asphalt mixture surface layer and the continuously reinforced concrete slab. Its function is as follows: Due to the differential settlement and temperature stress of the old and new pavements, reflective cracks are prone to form on the top surface of the continuously reinforced concrete slab. These cracks extend upwards along the thickness of the slab to the asphalt surface layer, causing cracking of the asphalt surface layer. Rainwater seeps down through the cracks and erodes the base layer, accelerating structural damage. The polyester fiberglass cloth is formed by composite weaving of polyester fiber and glass fiber, with a tensile strength of not less than 50 kN / m and an elongation at break of 3-5%. When reflective cracks extend upwards to the polyester fiberglass cloth, the polyester fiberglass cloth absorbs and disperses the stress concentration at the crack tip through its high tensile strength. According to fracture mechanics theory, the stress concentration factor at the crack tip is related to the tensile strength and fracture toughness of the material. The high tensile strength of the polyester fiberglass cloth can significantly reduce the stress concentration factor at the crack tip, effectively inhibiting the upward extension of reflective cracks. At the same time, the polyester fiberglass cloth has good water-proof performance, which can prevent rainwater from seeping down through the cracks and eroding the base layer, improving the long-term durability of the overlap structure.

[0043] The function of the new low-dosage cement-stabilized crushed stone subbase 9 is as follows: Traditional cement-stabilized crushed stone base layers typically have a cement dosage of 4-6%. During cement hydration, a large amount of heat of hydration is released, leading to an increase in material temperature. Temperature shrinkage occurs during cooling, and the material undergoes significant drying shrinkage deformation after cement hydration. Under the combined effect of temperature shrinkage and drying shrinkage deformation, the base layer is prone to shrinkage cracks, which reflect upwards to the surface layer, accelerating structural damage. This embodiment uses a low-dosage cement-stabilized crushed stone subbase layer, with the cement dosage strictly controlled below 3%, preferably 2.5-3.0%. According to research on the performance of cement-stabilized materials, when the cement dosage is below 3%, the early strength growth of the material is slower; the 7-day strength is approximately 50-60% of the final strength, and the 28-day strength is approximately 80-90% of the final strength. The heat of hydration release is smaller, the peak temperature is reduced by about 10-15℃, and the temperature shrinkage deformation is reduced by about 30-40%. Simultaneously, the drying shrinkage coefficient of low-dosage cement-stabilized crushed stone is approximately 60-70% of that of high-dosage cement-stabilized crushed stone, significantly reducing drying shrinkage deformation and effectively reducing early-stage shrinkage cracks caused by temperature and humidity. Although the low-dose cement-stabilized crushed stone subbase has low early strength, its long-term strength can still meet the load-bearing requirements of the pavement structure. Its 90-day strength can reach more than 95% of the design strength. At the same time, the low-dose cement-stabilized crushed stone has good erosion resistance and frost resistance, which can meet the usage requirements of the subbase.

[0044] Polyester fiberglass cloth 11, together with the new low-dose cement-stabilized crushed stone subbase 9, a double-layer rebar structure 12, and a sleeper-beam-steel pipe pile support system, constitute a multi-layer protection system. The synergistic effect of this multi-layer protection system is as follows: the double-layer rebar structure forms a three-dimensional steel reinforcement network in stress concentration areas, enhancing the shear resistance and crack resistance of the interface and preventing the initiation and propagation of cracks at the interface; the sleeper-beam-steel pipe pile support system provides deep vertical bearing capacity, controls differential settlement, and prevents vertical misalignment at the overlap interface; the polyester fiberglass cloth inhibits reflective cracks from extending upwards to the asphalt surface layer, preventing rainwater infiltration; and the low-dose cement-stabilized crushed stone subbase reduces shrinkage cracks caused by early temperature and humidity, controlling crack formation at its source. This multi-layer protection system works synergistically from multiple levels, including interface connection, deep support, crack suppression, and shrinkage control, comprehensively improving the settlement resistance, crack resistance, and long-term durability of the overlap structure, ensuring the structural safety and traffic safety of the longitudinal overlap between the old and new pavements in widening projects for continuously reinforced cement concrete pavements.

[0045] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A continuously reinforced cement concrete pavement overlap structure, comprising an existing pavement structure and a newly constructed pavement structure, wherein the existing pavement structure and the newly constructed pavement structure form an overlap interface in the longitudinal direction, characterized in that, Also includes: A multi-layer rebar structure, wherein each layer of rebar is set at different heights in the thickness direction of the continuous reinforced concrete slab, and adjacent layers of rebar are staggered. The multi-layer rebar structure penetrates the lap interface and connects the old continuous reinforced concrete slab (2) of the existing pavement structure with the new continuous reinforced concrete slab (7) of the newly built pavement structure. The force transmission component includes a bolster beam (13) extending longitudinally along the lap interface, the bolster beam (13) being disposed at the lap interface, and the upper surface of the bolster beam (13) abutting against the bottom of the new continuously reinforced concrete slab (7). Multiple vertical support members, the upper ends of which are fixedly connected to the sleeper beam (13), and the lower ends of the vertical support members extend to the subgrade below the newly built pavement structure; The crack-resistant material layer is a polyester fiberglass cloth (11) disposed between the surface layer and the continuously reinforced concrete slab at the lap interface.

2. The continuously reinforced cement concrete pavement lap joint structure according to claim 1, characterized in that, The newly constructed road structure includes, from top to bottom, a new asphalt mixture surface layer (6), a new continuously reinforced concrete slab (7), a new cement-stabilized crushed stone base course (8), a new low-dose cement-stabilized crushed stone subbase course (9), and a new roadbed (10).

3. The continuously reinforced cement concrete pavement lap joint structure according to claim 1, characterized in that, The existing road structure includes, from top to bottom, an old asphalt mixture surface layer (1), an old continuously reinforced concrete slab (2), an old cement-stabilized crushed stone base course (3), an old lime-soil subbase course (4), and an old roadbed (5).

4. The continuously reinforced cement concrete pavement lap joint structure according to claim 1, characterized in that, The multi-layer rebar structure is a double-layer rebar structure (12), wherein the two layers of rebar are located at 1 / 3 slab thickness and 2 / 3 slab thickness from the top surface of the continuously reinforced concrete slab, respectively. The double-layer rebar structure (12) uses HRB400 steel bars with a diameter of 12-20mm.

5. The continuously reinforced cement concrete pavement lap joint structure according to claim 2, characterized in that, The vertical support members are steel pipe piles (14) arranged at intervals along the length of the sleeper beam (13). The pillow beam (13) is embedded in the new cement-stabilized crushed stone base layer (8), the top surface of the pillow beam (13) is flush with the top surface of the new cement-stabilized crushed stone base layer (8), and the bottom surface of the pillow beam (13) abuts against the upper surface of the new low-dose cement-stabilized crushed stone base layer (9).

6. The lap joint structure of continuously reinforced cement concrete pavement according to claim 2, characterized in that, The vertical support component is a steel pipe pile (14), the diameter of the steel pipe pile (14) is 150-250mm, the wall thickness is 6-10mm, the length of the steel pipe pile (14) is 0.8-1.5m, and the spacing of the steel pipe piles (14) along the length direction of the force transmission component is 1.5-2.5m.

7. The continuously reinforced cement concrete pavement lap joint structure according to claim 6, characterized in that, One end of the steel pipe pile (14) is fixedly connected to the sleeper beam (13), and the other end of the steel pipe pile (14) extends downward and is embedded in the new roadbed (10).

8. The lap joint structure of continuously reinforced cement concrete pavement according to claim 1, characterized in that, The pillow beam (13) is a concrete beam with a concrete strength grade of not less than C30, a width of 40-60cm and a height of 15-25cm. The polyester fiberglass cloth (11) is laid horizontally with a width of 0.8-1.2m along the overlapping interface.

9. The lap joint structure of continuously reinforced cement concrete pavement according to claim 1, characterized in that, The old continuously reinforced concrete slab (2) has two rows of rebar holes arranged on its side at 1 / 3 and 2 / 3 of the slab thickness from the top of the slab. The rebar is anchored to the old continuous reinforced concrete slab (2) by injecting the anchoring adhesive into the injection hole. The anchoring adhesive is a modified epoxy resin adhesive with a tensile strength of not less than 30 MPa and a shear strength of not less than 15 MPa.

10. The lap joint structure of continuously reinforced cement concrete pavement according to claim 2, characterized in that, The cement dosage of the new low-dose cement-stabilized crushed stone base course (9) is controlled below 3wt%; The 90-day compressive strength of the new low-dose cement-stabilized crushed stone base course (9) shall not be less than 95% of its design strength.

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