Multi-source solid waste wide road pavement structure and design method thereof

Abstract

This invention discloses a multi-source solid waste-modified pavement structure and its design method, relating to the field of road engineering technology. The multi-source solid waste-modified pavement structure includes an old asphalt pavement subgrade, an old asphalt pavement base course, an old asphalt pavement surface course, a newly modified solid waste-reinforced subgrade, a newly modified pavement base course, and a newly modified pavement surface course. Cracks in the old asphalt pavement base course are reinforced using all-solid waste grouting material. The newly modified pavement surface course consists of a lower layer, a middle layer, and an upper layer, arranged sequentially from bottom to top. This invention also provides a design method for the multi-source solid waste-modified pavement structure. By utilizing multi-source solid waste materials to renovate and expand the old asphalt pavement structure, the construction of the multi-source solid waste-modified pavement structure improves the durability and coordination of the old and new asphalt pavement structures, achieving low-carbon renovation and expansion of the old asphalt pavement structure.

Description

Technical Field

[0001] This invention relates to the field of road engineering technology, specifically to a multi-source solid waste widening pavement structure and its design method. Background Technology

[0002] Currently, expressways have formed a wide-ranging and seamless highway transportation network, making a significant contribution to regional economic development, freight transport, and residents' travel.

[0003] With economic development, highway traffic volume has increased rapidly. Some highways built in the early stages have reached or even exceeded their design capacity, leading to increasing road traffic pressure and a year-on-year decline in road service levels. The increasing traffic flow on highways, along with traffic congestion and accidents, has caused great inconvenience to the travel safety of the general public. Upgrading and expanding existing highways is an effective way to solve this problem.

[0004] During highway reconstruction and expansion, many projects simply treat existing roads for defects and then resurface them, often in conjunction with newly widened pavements. However, the durability and coordination between the old and new pavements are often overlooked. This results in many highways where the widened sections function normally after reconstruction, while the resurfaced sections of the old pavement develop serious defects, leading to a sharp decline in driving quality and comfort. Furthermore, highway reconstruction and expansion generate large quantities of old asphalt pavement material. Disposing of this material requires significant land resources for storage, causing environmental pollution.

[0005] Therefore, there is an urgent need to propose a multi-source solid waste pavement structure and its design method, which comprehensively utilizes multi-source solid waste materials for asphalt pavement structure reconstruction and expansion, thus realizing low-carbon construction of asphalt pavement. Summary of the Invention

[0006] This invention aims to solve the above-mentioned problems and proposes a multi-source solid waste pavement structure and its design method. By using multi-source solid waste materials to renovate and expand the old asphalt pavement structure, the durability and coordination of the new and old asphalt pavement structures are improved, the pollution problem of old asphalt pavement materials is effectively solved, and technical support is provided for the low-carbon construction of asphalt pavement structures.

[0007] The present invention adopts the following technical solution: A multi-source solid waste-reinforced pavement structure includes an old asphalt pavement subgrade, an old asphalt pavement base course, an old asphalt pavement surface course, a newly reinforced solid waste subgrade, a newly reinforced pavement base course, and a newly reinforced pavement surface course.

[0008] Preferably, the thickness of the newly widened solid waste reinforced roadbed is set to 40cm~80cm, the thickness of the newly widened road base layer is set to 30cm~70cm, and the thickness of the newly widened road surface layer is set to 15cm~30cm.

[0009] Preferably, the cracks in the old asphalt pavement base course are reinforced by grouting with a solid waste grouting material; the material formula of the solid waste grouting material is steel slag powder, phosphogypsum, slag, coal ash, alkali activator, stabilizer, foaming agent and water; The newly widened solid waste reinforced roadbed uses a compound of steel slag powder, cement, stabilizer and curing agent, with the curing agent dosage set at 3% to 7% of the original dry soil mass. The newly widened road base layer uses iron tailings as filler, and the curing agent dosage is set to 3.5% to 5.3% of the dry iron tailings mass. The newly widened road surface layer consists of a lower layer, a middle layer, and an upper layer, arranged sequentially from bottom to top. The lower layer is paved with high-content recycled asphalt mixture, the middle layer is paved with hot recycled high-modulus asphalt mixture, and the upper layer is paved with steel slag SMA asphalt mixture.

[0010] Preferably, the mass ratio of steel slag powder, phosphogypsum, slag, coal slag, alkali activator, stabilizer, foaming agent and water in the all-solid waste grouting material is set to 3:2:5:1:4:0.5:0.5:84; The mass ratio of steel slag powder, cement, and stabilizer in the curing agent is 67:28:5.

[0011] A design method for multi-source solid waste widened pavement structures, used to design the multi-source solid waste widened pavement structures described above, includes the following steps: Step 1: Based on the surrounding road traffic conditions of the multi-source solid waste widening pavement structure to be designed, predict the traffic volume at the location of the multi-source solid waste widening pavement structure and determine the cumulative equivalent axle loads of the multi-source solid waste widening pavement structure within the design life. Step 2: Conduct multi-point deflection tests on the old asphalt pavement structure, invert the modulus of each old asphalt pavement subgrade, old asphalt pavement base course and old asphalt pavement surface course in the old asphalt pavement structure, and determine the representative values ​​of the modulus of the old asphalt pavement subgrade, old asphalt pavement base course and old asphalt pavement surface course in the old asphalt pavement structure. Step 3: Conduct radar detection on the old asphalt pavement base layer and perform grouting treatment on the cracks in the old asphalt pavement base layer. Step 4: Based on the predicted traffic volume, initially propose the design parameters of the old asphalt pavement overlay structure, and perform pavement structure performance verification on the old asphalt pavement overlay structure to obtain the performance verification parameter threshold of the old asphalt pavement overlay structure. Adjust the design parameters of the old asphalt pavement overlay structure according to the performance verification parameter threshold until the old asphalt pavement overlay structure passes the pavement structure performance verification and obtains the optimal design parameters of the old asphalt pavement overlay structure. Step 5: Propose the new widened pavement structure initially, and perform pavement structure performance verification calculation on the new widened pavement structure to obtain the performance verification parameter threshold of the new widened pavement structure. Adjust the design parameters of the new widened pavement structure according to the performance verification parameter threshold until the new widened pavement structure passes the pavement structure performance verification and obtains the optimal design parameters of the new widened pavement structure. Step 6: Perform durability coordination calculations on the old asphalt pavement structure and the newly widened pavement structure to verify the coordinated durability of the multi-source solid waste widened pavement structure composed of the old asphalt pavement structure and the newly widened pavement structure.

[0012] Preferably, the overlay structure of the old asphalt pavement includes a steel slag anti-skid wear layer and a hot recycled high-modulus asphalt mixture layer; The design parameters for the old asphalt pavement overlay structure include the thickness of the steel slag anti-skid wear layer and the hot recycled high-modulus asphalt mixture layer, and the material replacement rate. The performance verification parameters of the old asphalt pavement overlay structure include the rutting depth of the asphalt layer, the cumulative equivalent axle number corresponding to the fatigue cracking of the semi-rigid layer, the low temperature cracking index, the penetration strength of the asphalt layer, and the antifreeze thickness.

[0013] Preferably, when performing pavement structure performance verification based on the performance verification parameters of the old asphalt pavement overlay structure, and considering the threshold values ​​of each performance verification parameter, if the rutting depth of the asphalt layer of the old asphalt pavement overlay structure does not exceed the preset rutting depth threshold, the cumulative equivalent axle number value corresponding to fatigue cracking of the semi-rigid layer is not less than the preset cumulative equivalent axle number threshold for fatigue cracking of the semi-rigid layer, the low-temperature cracking index does not exceed the preset low-temperature cracking index threshold, the penetration strength of the asphalt layer is not less than the preset penetration strength threshold, and the antifreeze thickness is not less than the preset antifreeze thickness threshold, it indicates that the old asphalt pavement overlay structure has passed the pavement structure performance verification. Otherwise, the design parameters of the old asphalt pavement overlay structure are adjusted, and the pavement structure performance verification of the old asphalt pavement overlay structure continues until the old asphalt pavement overlay structure passes the pavement structure performance verification, thus obtaining the optimal design parameters of the old asphalt pavement overlay structure.

[0014] Preferably, the newly widened pavement structure includes a newly widened solid waste reinforced subgrade, a newly widened pavement base course, and a newly widened pavement surface course; The design parameters of the newly widened pavement structure include the thickness and material ratio of the newly widened solid waste reinforced subgrade, the newly widened pavement base course, and the newly widened pavement surface course. The performance verification parameters of the newly widened pavement structure include the rutting depth of the asphalt layer, the cumulative equivalent axle number corresponding to the fatigue cracking of the semi-rigid layer, the low-temperature cracking index, the penetration strength of the asphalt layer, and the antifreeze thickness.

[0015] Preferably, when performing pavement structure performance verification based on the performance verification parameters of the newly widened pavement structure, and considering the threshold values ​​of each performance verification parameter, if the rutting depth of the asphalt layer of the newly widened pavement structure does not exceed the preset rutting depth threshold, the cumulative equivalent axle number value corresponding to fatigue cracking of the semi-rigid layer is not less than the preset cumulative equivalent axle number threshold for fatigue cracking of the semi-rigid layer, the low-temperature cracking index does not exceed the preset low-temperature cracking index threshold, the penetration strength of the asphalt layer is not less than the preset penetration strength threshold, and the antifreeze thickness is not less than the preset antifreeze thickness threshold, it indicates that the newly widened pavement structure has passed the pavement structure performance verification. Otherwise, the design parameters of the newly widened pavement structure are adjusted, and the pavement structure performance verification is continued until the newly widened pavement structure passes the pavement structure performance verification, thus obtaining the optimal design parameters of the newly widened pavement structure.

[0016] Preferably, when performing a durability coordination calculation on the overlaid old asphalt pavement structure and the newly widened pavement structure, if the difference in fatigue life between the overlaid old asphalt pavement structure and the newly widened pavement structure is not greater than 5% and the difference in rut depth is not greater than 3%, then the durability coordination calculation on the old and new pavements is passed; otherwise, the durability coordination calculation on the old and new pavements is not passed.

[0017] The present invention has the following beneficial effects: This invention proposes a multi-source solid waste-based pavement structure and its design method. On the one hand, this invention makes full use of solid waste resources and saves sand and gravel materials, which is in line with the green highway strategy of low carbon throughout the entire life cycle. On the other hand, this invention also fully considers the durability synergy between new and old asphalt pavement structures, extends the life of old asphalt pavement structures, and provides technical support for the durability synergy between new and old asphalt pavements. Attached Figure Description

[0018] Figure 1 This is a flowchart of a method for designing a multi-source solid waste widening road surface according to the present invention.

[0019] Figure 2 This is a schematic diagram of the multi-source solid waste pavement widening structure in Example 3; in the diagram, the red part is the old asphalt pavement structure.

[0020] Figure 3 This is a schematic diagram of the multi-source solid waste pavement structure in Example 4; in the diagram, the red part is the old asphalt pavement structure.

[0021] In the diagram, 1 is the roadbed, 2 is the subbase, 3 is the base course, 4 is the lower layer, 5 is the intermediate layer, 6 is the upper layer, 7 is the iron tailings base course, 701 is the first iron tailings base course, 702 is the second iron tailings base course, 8 is the high-performance cold recycled asphalt mixture layer, 9 is the high-content hot recycled asphalt mixture layer, 1001 is the steel slag hot recycled high modulus asphalt mixture layer, 1002 is the oxygen-heat recycled high modulus asphalt mixture layer, and 11 is the steel slag anti-skid wear layer. Detailed Implementation

[0022] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0023] Example 1 This embodiment proposes a multi-source solid waste pavement widening structure, including an old asphalt pavement subgrade, an old asphalt pavement base course, an old asphalt pavement surface course, a newly widened solid waste reinforced subgrade, a newly widened pavement base course, and a newly widened pavement surface course. The thickness of the newly widened solid waste reinforced subgrade is set to 40cm~80cm, the thickness of the newly widened pavement base course is set to 30cm~70cm, and the thickness of the newly widened pavement surface course is set to 15cm~30cm.

[0024] Furthermore, the cracks in the old asphalt pavement base layer are reinforced by grouting with a solid waste grouting material. Specifically, the material formula of the solid waste grouting material is steel slag powder, phosphogypsum, slag, coal ash, alkali activator, stabilizer, foaming agent, and water, wherein the mass ratio of steel slag powder, phosphogypsum, slag, coal ash, alkali activator, stabilizer, foaming agent, and water is set to 3:2:5:1:4:0.5:0.5:84.

[0025] Furthermore, the newly widened solid waste reinforced roadbed uses a compound curing agent made of steel slag powder, cement, and stabilizer. The curing agent dosage is set at 3% to 7% of the original dry soil mass, and the mass ratio of steel slag powder, cement, and stabilizer in the curing agent is 67:28:5. The newly widened road base layer uses iron tailings as filler, and the curing agent dosage is set at 3.5% to 5.3% of the dry iron tailings mass. The newly widened road surface layer consists of a lower layer, a middle layer, and an upper layer, arranged sequentially from bottom to top. The lower layer is paved with high-content recycled asphalt mixture, the middle layer with hot recycled high-modulus asphalt mixture, and the upper layer with steel slag SMA asphalt mixture.

[0026] Example 2 This embodiment proposes a design method for a multi-source solid waste pavement widening structure, used to design the multi-source solid waste widening pavement structure as described in Embodiment 1. Figure 1 As shown, it includes the following steps: Step 1: Based on the surrounding road traffic conditions of the multi-source solid waste widened pavement structure to be designed, predict the traffic volume at the location of the multi-source solid waste widened pavement structure, and determine the cumulative equivalent axle loads of the multi-source solid waste widened pavement structure within the design life according to the "Specification for Design of Highway Asphalt Pavement JTGD50-2017".

[0027] Step 2: Conduct multi-point deflection tests on the old asphalt pavement structure, which includes the old asphalt pavement subgrade, old asphalt pavement base course, and old asphalt pavement surface course. Invert the modulus of the old asphalt pavement subgrade, old asphalt pavement base course, and old asphalt pavement surface course in the old asphalt pavement structure, and determine the representative values ​​of the modulus of the old asphalt pavement subgrade, old asphalt pavement base course, and old asphalt pavement surface course in the old asphalt pavement structure.

[0028] Step 3: Conduct radar detection on the old asphalt pavement base layer and perform grouting treatment on the cracks within the old asphalt pavement base layer.

[0029] Step 4: Based on the predicted traffic volume, initially propose the design parameters of the old asphalt pavement overlay structure, and perform pavement structure performance verification on the old asphalt pavement overlay structure to obtain the performance verification parameter threshold of the old asphalt pavement overlay structure. Adjust the design parameters of the old asphalt pavement overlay structure according to the performance verification parameter threshold until the old asphalt pavement overlay structure passes the pavement structure performance verification and obtains the optimal design parameters of the old asphalt pavement overlay structure.

[0030] Furthermore, the old asphalt pavement overlay structure includes a steel slag anti-skid wear layer and a hot recycled high-modulus asphalt mixture layer. The design parameters of the old asphalt pavement overlay structure include the thickness of the steel slag anti-skid wear layer and the hot recycled high-modulus asphalt mixture layer, and the material replacement rate. The performance verification parameters of the old asphalt pavement overlay structure include the rutting depth of the asphalt layer, the cumulative equivalent axle number corresponding to the fatigue cracking of the semi-rigid layer, the low-temperature cracking index, the penetration strength of the asphalt layer, and the antifreeze thickness.

[0031] When verifying the pavement structure performance based on the performance verification parameters of the old asphalt pavement overlay structure, and considering the threshold values ​​of each performance verification parameter, if the rutting depth of the asphalt layer of the old asphalt pavement overlay structure does not exceed the preset rutting depth threshold, the cumulative equivalent axle number value corresponding to fatigue cracking of the semi-rigid layer is not less than the preset cumulative equivalent axle number threshold for fatigue cracking of the semi-rigid layer, the low temperature cracking index does not exceed the preset low temperature cracking index threshold, the penetration strength of the asphalt layer is not less than the preset penetration strength threshold, and the antifreeze thickness is not less than the preset antifreeze thickness threshold, it indicates that the old asphalt pavement overlay structure has passed the pavement structure performance verification. Otherwise, the design parameters of the old asphalt pavement overlay structure are adjusted, and the pavement structure performance verification continues until the old asphalt pavement overlay structure passes the pavement structure performance verification, thus obtaining the optimal design parameters of the old asphalt pavement overlay structure.

[0032] Step 5: Propose the initial structure of the newly widened pavement and perform pavement structure performance verification calculations to obtain the performance verification parameter values ​​of the newly widened pavement structure. Adjust the design parameters of the newly widened pavement structure according to the performance verification parameter thresholds until the newly widened pavement structure passes the pavement structure performance verification and obtains the optimal design parameters of the newly widened pavement structure.

[0033] Furthermore, the newly widened pavement structure includes a newly widened solid waste reinforced subgrade, a newly widened pavement base course, and a newly widened pavement surface course. The design parameters of the newly widened pavement structure include the thickness and material ratio of the newly widened solid waste reinforced subgrade, the newly widened pavement base course, and the newly widened pavement surface course. The performance verification parameters of the newly widened pavement structure include the rutting depth of the asphalt layer, the cumulative equivalent axle number corresponding to the fatigue cracking of the semi-rigid layer, the low-temperature cracking index, the penetration strength of the asphalt layer, and the antifreeze thickness.

[0034] When the pavement structure performance is verified based on the performance verification parameters of the newly widened pavement structure, and considering the threshold values ​​of each performance verification parameter, if the rutting depth of the asphalt layer does not exceed the preset asphalt layer rutting depth threshold, the cumulative equivalent axle number value corresponding to fatigue cracking of the semi-rigid layer is not less than the preset cumulative equivalent axle number threshold for fatigue cracking of the semi-rigid layer, the low-temperature cracking index does not exceed the preset low-temperature cracking index threshold, the asphalt layer penetration strength is not less than the preset asphalt layer penetration strength threshold, and the antifreeze thickness is not less than the preset antifreeze thickness threshold, then the newly widened pavement structure has passed the pavement structure performance verification. Otherwise, the design parameters of the newly widened pavement structure are adjusted, and the pavement structure performance verification is continued until the newly widened pavement structure passes the pavement structure performance verification, thus obtaining the optimal design parameters of the newly widened pavement structure.

[0035] Step 6: Perform durability coordination calculations on the old asphalt pavement structure and the newly widened pavement structure to verify the coordinated durability of the multi-source solid waste widened pavement structure composed of the old asphalt pavement structure and the newly widened pavement structure.

[0036] Specifically, a durability coordination calculation is performed on the old asphalt pavement structure and the newly widened pavement structure after overlay. If the difference in fatigue life between the old asphalt pavement structure and the newly widened pavement structure is no greater than 5% and the difference in rut depth is no greater than 3%, then the requirements of the "Specifications for Design of Highway Asphalt Pavement JTGD50-2017" are met, and the durability coordination calculation of the old and new pavements is passed. Otherwise, the durability coordination calculation of the old and new pavements is not passed.

[0037] Example 3 Example 2 was applied to a highway reconstruction and expansion project. The highway to be designed is 137.3 kilometers long, with a design speed of 120 kilometers per hour, and adopts a two-way four-lane design. The total thickness of the old asphalt pavement structure is 67 cm, and it is arranged from bottom to top as follows: subgrade 1, subbase 2, base course 3, lower layer 4, intermediate layer 5, and upper layer 6. The thickness of the subbase is set to 26 cm, the base course to 24 cm, the lower layer to 7 cm, the intermediate layer to 6 cm, and the upper layer to 4 cm. The subbase is paved with lime-soil, the base course is paved with cement-stabilized crushed stone, the lower layer is paved with coarse-grained asphalt concrete (AC-251), the intermediate layer is paved with medium-grained asphalt concrete (AC-201), and the upper layer is paved with fine-grained modified asphalt concrete (AC-13). With the increase in traffic volume, the expressway can no longer meet the traffic requirements, and it is planned to expand it from four lanes to eight lanes. Due to the scarcity of high-quality materials along the expressway, the project investor has confirmed that a multi-source solid waste pavement structure will be constructed to widen the road. Therefore, the multi-source solid waste pavement structure design method described in Example 2 will be adopted for the design of the multi-source solid waste pavement structure. The specific steps are as follows: Step 1: Based on the surrounding road traffic conditions of the multi-source solid waste widening pavement structure to be designed, predict the traffic volume at the location of the multi-source solid waste widening pavement structure, as shown in Table 1.

[0038] Table 1. Traffic volume prediction results for the location of the multi-source solid waste widened road structure. According to the "Specification for Design of Highway Asphalt Pavement JTGD50-2017", the design life of the multi-source solid waste widened pavement structure was determined, and the cumulative equivalent axle loads of the multi-source solid waste widened pavement structure within the design life were determined. Among them, the cumulative number of equivalent axle loads for fatigue cracking of inorganic binder layer was 1,167,352,1943, and the cumulative number of equivalent axle loads for fatigue cracking of asphalt mixture layer was 146,432,830. The cumulative traffic volume of large passenger vehicles and freight vehicles in the design lane within the design life was 62,532,822, and the traffic level was classified as extremely heavy traffic.

[0039] Step 2: Conduct multi-point deflection tests on the old asphalt pavement structure to determine the representative modulus value of the old asphalt pavement subgrade as 8600 MPa, the representative modulus value of the old asphalt pavement base course as 12400 MPa, and the representative modulus value of the old asphalt pavement surface course as 95 MPa.

[0040] Step 3: Conduct radar detection on the old asphalt pavement base layer, and perform grouting treatment at the cracks in the old asphalt pavement base layer. The grouting material formula used in the grouting treatment includes steel slag powder, phosphogypsum, slag, coal ash, alkali activator, stabilizer, foaming agent and water. The mass ratio between steel slag powder, phosphogypsum, slag, coal ash, alkali activator, stabilizer and foaming agent and water is set to 3:2:5:1:4:0.5:0.5:84.

[0041] Step 4: Based on the predicted traffic volume, the design parameters of the old asphalt pavement overlay structure are initially proposed. Specifically, the old asphalt pavement overlay structure includes a 4cm thick steel slag anti-skid wear layer 11 and a 6cm thick steel slag hot recycled high modulus asphalt mixture layer 1001. The steel slag coarse aggregate replacement rate in the steel slag anti-skid wear layer is 75%, and the steel slag coarse aggregate replacement rate in the steel slag hot recycled high modulus asphalt mixture is 45%. All steel slag coarse aggregate replacement rate ratios are mass ratios.

[0042] According to the "Specification for Design of Highway Asphalt Pavement JTGD50-2017", the pavement structure of the overlay structure of the old asphalt pavement was verified, and the verification results are shown in Table 2.

[0043] Table 2. Pavement structure verification results for overlay structures on existing asphalt pavements When verifying the pavement structure performance based on the performance verification parameters of the old asphalt pavement overlay structure, and considering the threshold values ​​of each performance verification parameter, if the rutting depth of the asphalt layer of the old asphalt pavement overlay structure does not exceed the preset rutting depth threshold, the cumulative equivalent axle number value corresponding to fatigue cracking of the semi-rigid layer is not less than the preset cumulative equivalent axle number threshold for fatigue cracking of the semi-rigid layer, the low temperature cracking index does not exceed the preset low temperature cracking index threshold, the penetration strength of the asphalt layer is not less than the preset penetration strength threshold, and the antifreeze thickness is not less than the preset antifreeze thickness threshold, it indicates that the old asphalt pavement overlay structure has passed the pavement structure performance verification. Otherwise, the design parameters of the old asphalt pavement overlay structure are adjusted, and the pavement structure performance verification continues until the old asphalt pavement overlay structure passes the pavement structure performance verification, thus obtaining the optimal design parameters of the old asphalt pavement overlay structure.

[0044] Step 5: Initially design the new widened pavement structure. In this embodiment, the new widened pavement structure, from bottom to top, includes a roadbed 1, an iron tailings base course 7, a high-performance cold recycled asphalt mixture layer 8, a high-dosage hot recycled asphalt mixture layer 9, and an overlay structure for the old asphalt pavement. The old asphalt pavement overlay structure includes a 4cm thick steel slag hot recycled high-modulus asphalt mixture layer 1001 and a 6cm thick steel slag anti-skid wear layer 11. The high-dosage hot recycled asphalt mixture layer is 8cm thick. The high-performance cold recycled asphalt mixture layer... The thickness of the base course is 9cm, and the thickness of the iron tailings base course 7 is 50cm. It includes an iron tailings base course 702 with a cement content of 4.2% and an iron tailings base course 701 with a cement content of 3.7%. The thickness of the iron tailings base course 702 with a cement content of 4.2% and the iron tailings base course 701 with a cement content of 3.7% are both 25cm. The RAP content in the high-content hot recycled asphalt mixture layer is 60%, and the RAP content in the high-performance cold recycled asphalt mixture layer is 40%. The RAP content of each component is a mass ratio.

[0045] The pavement structure of the newly widened pavement was verified according to the "Specification for Highway Asphalt Pavement Design JTGD50-2017". The verification results are shown in Table 3.

[0046] Table 3. Pavement structure verification results of the newly widened pavement. When the pavement structure performance is verified based on the performance verification parameters of the newly widened pavement structure, and considering the threshold values ​​of each performance verification parameter, if the rutting depth of the asphalt layer does not exceed the preset asphalt layer rutting depth threshold, the cumulative equivalent axle number value corresponding to fatigue cracking of the semi-rigid layer is not less than the preset cumulative equivalent axle number threshold for fatigue cracking of the semi-rigid layer, the low-temperature cracking index does not exceed the preset low-temperature cracking index threshold, the asphalt layer penetration strength is not less than the preset asphalt layer penetration strength threshold, and the antifreeze thickness is not less than the preset antifreeze thickness threshold, then the newly widened pavement structure has passed the pavement structure performance verification. Otherwise, the design parameters of the newly widened pavement structure are adjusted, and the pavement structure performance verification is continued until the newly widened pavement structure passes the pavement structure performance verification, thus obtaining the optimal design parameters of the newly widened pavement structure.

[0047] Step 6: Perform durability coordination calculations on the old asphalt pavement structure and the newly widened pavement structure to verify the coordinated durability of the multi-source solid waste widened pavement structure composed of the old asphalt pavement structure and the newly widened pavement structure. In this embodiment, the fatigue life difference between the overlay old asphalt pavement structure and the newly widened pavement structure is 0.096%, and the rutting depth difference between the overlay old asphalt pavement structure and the newly widened pavement structure is 1.05%, meaning that the multi-source solid waste widened pavement structure meets the coordinated durability requirements.

[0048] Ultimately, the multi-source solid waste widening road structure in this embodiment was determined as follows: Figure 2 As shown, the old asphalt pavement structure consists of, from bottom to top, a roadbed 1, a subbase 2, a base 3, a lower layer 4, an intermediate layer 5, and an upper layer 6. The newly widened pavement structure consists of, from bottom to top, a roadbed 1, an iron tailings base course 7, a high-performance cold recycled asphalt mixture layer 8, a high-content hot recycled asphalt mixture layer 9, and an old asphalt pavement overlay structure. The iron tailings base course 7 contains a first iron tailings base course 701 and a second iron tailings base course 702. Specifically, the first iron tailings base course 701 has a cement content of 3.7%, and the second iron tailings base course 702 has a cement content of 4.2%. The old asphalt pavement overlay structure includes a steel slag hot recycled high-modulus asphalt mixture layer 1001 and a steel slag anti-skid wear layer 11.

[0049] Example 4 Example 2 was applied to a highway reconstruction and expansion project. The total length of the highway to be designed is 131.45 kilometers, with a design speed of 120 kilometers per hour. The design adopts a method of widening on both sides as the main approach and widening on separate sides as a secondary approach. The total thickness of the old asphalt pavement structure is 69 cm. From bottom to top, it consists of roadbed 1, subbase 2, base course 3, lower layer 4, intermediate layer 5, and upper layer 6. The thickness of the subbase is set to 18 cm, the base course to 34 cm, the lower layer to 7 cm, the intermediate layer to 6 cm, and the upper layer to 4 cm. The subbase is paved with water-stabilized weathered sand, the base course is paved with cement-stabilized crushed stone, the lower layer is paved with coarse-grained asphalt concrete (AC-25), the intermediate layer is paved with medium-grained asphalt concrete (AC-20), and the upper layer is paved with fine-grained modified asphalt concrete (AC-16). With the increase in traffic volume, the expressway can no longer meet the traffic requirements, and it is planned to expand it from four lanes to eight lanes. Due to the scarcity of high-quality materials along the expressway, the project investor has confirmed that a multi-source solid waste pavement structure will be constructed to widen the road. Therefore, the multi-source solid waste pavement structure design method described in Example 2 will be adopted for the design of the multi-source solid waste pavement structure. The specific steps are as follows: Step 1: Based on the surrounding road traffic conditions of the multi-source solid waste widening pavement structure to be designed, predict the traffic volume at the location of the multi-source solid waste widening pavement structure, as shown in Table 4.

[0050] Table 4. Traffic volume prediction results for the location of the multi-source solid waste widened road structure. According to the "Specification for Design of Highway Asphalt Pavement JTGD50-2017", the design life of the multi-source solid waste widened pavement structure is determined, and the cumulative equivalent axle loads of the multi-source solid waste widened pavement structure within the design life are determined. Among them, the cumulative number of equivalent axle loads for fatigue cracking of inorganic binder layer is 1,267,425,2786, and the cumulative number of equivalent axle loads for fatigue cracking of asphalt mixture layer is 115,813,260. The cumulative traffic volume of large passenger vehicles and freight vehicles in the design lane within the design life is 51,238,004, and the traffic level is classified as extremely heavy traffic.

[0051] Step 2: Conduct multi-point deflection tests on the old asphalt pavement structure to determine the representative modulus value of the old asphalt pavement subgrade as 9200 MPa, the representative modulus value of the old asphalt pavement base course as 12800 MPa, and the representative modulus value of the old asphalt pavement surface course as 86 MPa.

[0052] Step 3: Conduct radar detection on the old asphalt pavement base layer, and perform grouting treatment at the cracks in the old asphalt pavement base layer. The grouting material formula used in the grouting treatment includes steel slag powder, phosphogypsum, slag, coal ash, alkali activator, stabilizer, foaming agent and water. The mass ratio between steel slag powder, phosphogypsum, slag, coal ash, alkali activator, stabilizer and foaming agent and water is set to 3:2:5:1:4:0.5:0.5:84.

[0053] Step 4: Based on the predicted traffic volume, the design parameters of the old asphalt pavement overlay structure are initially proposed. Specifically, the old asphalt pavement overlay structure includes a 4cm thick steel slag anti-skid wear layer 11 and a 6cm thick epoxy hot recycled high modulus asphalt mixture layer 1002. The steel slag coarse aggregate replacement rate of the steel slag anti-skid wear layer is 55%, and the steel slag coarse aggregate replacement rate ratio is a mass ratio.

[0054] According to the "Specification for Design of Highway Asphalt Pavement JTGD50-2017", the pavement structure of the overlay structure of the old asphalt pavement was verified, and the verification results are shown in Table 5.

[0055] Table 5. Calculation Results of Pavement Structure for Overlay Structures on Existing Asphalt Pavements When verifying the pavement structure performance based on the performance verification parameters of the old asphalt pavement overlay structure, and considering the threshold values ​​of each performance verification parameter, if the rutting depth of the asphalt layer of the old asphalt pavement overlay structure does not exceed the preset rutting depth threshold, the cumulative equivalent axle number value corresponding to fatigue cracking of the semi-rigid layer is not less than the preset cumulative equivalent axle number threshold for fatigue cracking of the semi-rigid layer, the low temperature cracking index does not exceed the preset low temperature cracking index threshold, the penetration strength of the asphalt layer is not less than the preset penetration strength threshold, and the antifreeze thickness is not less than the preset antifreeze thickness threshold, it indicates that the old asphalt pavement overlay structure has passed the pavement structure performance verification. Otherwise, the design parameters of the old asphalt pavement overlay structure are adjusted, and the pavement structure performance verification continues until the old asphalt pavement overlay structure passes the pavement structure performance verification, thus obtaining the optimal design parameters of the old asphalt pavement overlay structure.

[0056] Step 5: Initially design the new widened pavement structure. In this embodiment, the new widened pavement structure, from bottom to top, includes a roadbed 1, an iron tailings base course 7, a high-performance cold recycled asphalt mixture layer 8, a high-dosage hot recycled asphalt mixture layer 9, and an overlay structure for the old asphalt pavement. The old asphalt pavement overlay structure includes a 4cm thick steel slag hot recycled high-modulus asphalt mixture layer and a 6cm thick steel slag anti-skid wear layer. The high-dosage hot recycled asphalt mixture layer is 8cm thick, the high-performance cold recycled asphalt mixture layer is 9cm thick, and the iron tailings base course 7 is 50cm thick. m, the iron tailings base course 7 is provided with a first iron tailings base course 701 and a second iron tailings base course 702. Specifically, the cement content of the first iron tailings base course 701 is 3.6%, and the cement content of the second iron tailings base course 702 is 4.3%. The thickness of the iron tailings base course with a cement content of 4.3% is 25cm, and the thickness of the iron tailings base course with a cement content of 3.6% is 25cm. The RAP content in the high-content hot recycled asphalt mixture layer is 70%, and the RAP content in the high-performance cold recycled asphalt mixture layer is 30%. The RAP content of each is a mass ratio.

[0057] The pavement structure of the newly widened pavement was verified according to the "Specification for Design of Highway Asphalt Pavement JTGD50-2017". The verification results are shown in Table 6.

[0058] Table 6. Calculation Results of Pavement Structure for Newly Widened Pavement When the pavement structure performance is verified based on the performance verification parameters of the newly widened pavement structure, and considering the threshold values ​​of each performance verification parameter, if the rutting depth of the asphalt layer does not exceed the preset asphalt layer rutting depth threshold, the cumulative equivalent axle number value corresponding to fatigue cracking of the semi-rigid layer is not less than the preset cumulative equivalent axle number threshold for fatigue cracking of the semi-rigid layer, the low-temperature cracking index does not exceed the preset low-temperature cracking index threshold, the asphalt layer penetration strength is not less than the preset asphalt layer penetration strength threshold, and the antifreeze thickness is not less than the preset antifreeze thickness threshold, then the newly widened pavement structure has passed the pavement structure performance verification. Otherwise, the design parameters of the newly widened pavement structure are adjusted, and the pavement structure performance verification is continued until the newly widened pavement structure passes the pavement structure performance verification, thus obtaining the optimal design parameters of the newly widened pavement structure.

[0059] Step 6: Perform durability coordination calculations on the old asphalt pavement structure and the newly widened pavement structure to verify the coordinated durability of the multi-source solid waste widened pavement structure composed of the old asphalt pavement structure and the newly widened pavement structure. In this embodiment, the fatigue life difference between the overlay old asphalt pavement structure and the newly widened pavement structure is 1.64%, and the rutting depth difference between the overlay old asphalt pavement structure and the newly widened pavement structure is 1.29%, meaning that the multi-source solid waste widened pavement structure meets the coordinated durability requirements.

[0060] Ultimately, the multi-source solid waste widening road structure in this embodiment was determined as follows: Figure 3 As shown, the old asphalt pavement structure consists of, from bottom to top, a roadbed 1, a subbase 2, a base 3, a lower layer 4, an intermediate layer 5, and a top layer 6. The newly widened pavement structure consists of, from bottom to top, a roadbed 1, an iron tailings base course 7, a high-performance cold recycled asphalt mixture layer 8, a high-content hot recycled asphalt mixture layer 9, and an old asphalt pavement overlay structure. The iron tailings base course 7 contains an iron tailings base course 702 with a cement content of 4.2% and an iron tailings base course 701 with a cement content of 3.7%. The old asphalt pavement overlay structure includes an epoxy hot recycled high-modulus asphalt mixture layer 1002 and a steel slag anti-skid wear layer 11.

[0061] In summary, the method of this invention utilizes solid waste resources to save sand and gravel materials, fully considers the synergistic durability of new and old asphalt pavements, realizes the scientific design of pavement structures widened by multi-source solid waste, and provides technical support for the synergistic durability of new and old asphalt pavements in pavement structures widened by multi-source solid waste.

[0062] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A multi-source solid waste widening road structure, characterized in that, This includes the old asphalt pavement subgrade, old asphalt pavement base course, old asphalt pavement surface course, newly widened solid waste reinforced subgrade, newly widened pavement base course, and newly widened pavement surface course.

2. The multi-source solid waste widening road structure according to claim 1, characterized in that, The thickness of the newly widened solid waste reinforced roadbed is set to 40cm~80cm, the thickness of the newly widened road base layer is set to 30cm~70cm, and the thickness of the newly widened road surface layer is set to 15cm~30cm.

3. The multi-source solid waste widening road structure according to claim 1, characterized in that, The cracks in the old asphalt pavement base course are reinforced by grouting with all-solid-waste grouting material; the material formula of the all-solid-waste grouting material is steel slag powder, phosphogypsum, slag, coal ash, alkali activator, stabilizer, foaming agent and water. The newly widened solid waste reinforced roadbed uses a compound of steel slag powder, cement, stabilizer and curing agent, with the curing agent dosage set at 3% to 7% of the original dry soil mass. The newly widened road base layer uses iron tailings as filler, and the curing agent dosage is set to 3.5% to 5.3% of the dry iron tailings mass. The newly widened road surface layer consists of a lower layer, a middle layer, and an upper layer, arranged sequentially from bottom to top. The lower layer is paved with high-content recycled asphalt mixture, the middle layer is paved with hot recycled high-modulus asphalt mixture, and the upper layer is paved with steel slag SMA asphalt mixture.

4. The multi-source solid waste widening road structure according to claim 3, characterized in that, The mass ratio of steel slag powder, phosphogypsum, slag, coal slag, alkali activator, stabilizer, foaming agent and water in the solid waste grouting material is set to 3:2:5:1:4:0.5:0.5:

84. The mass ratio of steel slag powder, cement, and stabilizer in the curing agent is 67:28:

5.

5. A design method for a multi-source solid waste widening road structure, characterized in that, The method for designing a multi-source solid waste widening pavement structure as described in any one of claims 1 to 4 includes the following steps: Step 1: Based on the surrounding road traffic conditions of the multi-source solid waste widening pavement structure to be designed, predict the traffic volume at the location of the multi-source solid waste widening pavement structure and determine the cumulative equivalent axle loads of the multi-source solid waste widening pavement structure within the design life. Step 2: Conduct multi-point deflection tests on the old asphalt pavement structure, invert the modulus of each old asphalt pavement subgrade, old asphalt pavement base course and old asphalt pavement surface course in the old asphalt pavement structure, and determine the representative values ​​of the modulus of the old asphalt pavement subgrade, old asphalt pavement base course and old asphalt pavement surface course in the old asphalt pavement structure. Step 3: Conduct radar detection on the old asphalt pavement base layer and perform grouting treatment on the cracks in the old asphalt pavement base layer. Step 4: Based on the predicted traffic volume, initially propose the design parameters of the old asphalt pavement overlay structure, and perform pavement structure performance verification on the old asphalt pavement overlay structure to obtain the performance verification parameter threshold of the old asphalt pavement overlay structure. Adjust the design parameters of the old asphalt pavement overlay structure according to the performance verification parameter threshold until the old asphalt pavement overlay structure passes the pavement structure performance verification and obtains the optimal design parameters of the old asphalt pavement overlay structure. Step 5: Propose the new widened pavement structure initially, and perform pavement structure performance verification calculation on the new widened pavement structure to obtain the performance verification parameter threshold of the new widened pavement structure. Adjust the design parameters of the new widened pavement structure according to the performance verification parameter threshold until the new widened pavement structure passes the pavement structure performance verification and obtains the optimal design parameters of the new widened pavement structure. Step 6: Perform durability coordination calculations on the old asphalt pavement structure and the newly widened pavement structure to verify the coordinated durability of the multi-source solid waste widened pavement structure composed of the old asphalt pavement structure and the newly widened pavement structure.

6. The design method for multi-source solid waste widening road surface structure according to claim 5, characterized in that, The overlay structure of the old asphalt pavement includes a steel slag anti-skid wear layer and a hot recycled high-modulus asphalt mixture layer; The design parameters for the old asphalt pavement overlay structure include the thickness of the steel slag anti-skid wear layer and the hot recycled high-modulus asphalt mixture layer, and the material replacement rate. The performance verification parameters of the old asphalt pavement overlay structure include the rutting depth of the asphalt layer, the cumulative equivalent axle number corresponding to the fatigue cracking of the semi-rigid layer, the low temperature cracking index, the penetration strength of the asphalt layer, and the antifreeze thickness.

7. The design method for multi-source solid waste widening road surface structure according to claim 6, characterized in that, When verifying the pavement structure performance based on the performance verification parameters of the old asphalt pavement overlay structure, and considering the threshold values ​​of each performance verification parameter, if the rutting depth of the asphalt layer of the old asphalt pavement overlay structure does not exceed the preset rutting depth threshold, the cumulative equivalent axle number value corresponding to fatigue cracking of the semi-rigid layer is not less than the preset cumulative equivalent axle number threshold for fatigue cracking of the semi-rigid layer, the low temperature cracking index does not exceed the preset low temperature cracking index threshold, the penetration strength of the asphalt layer is not less than the preset penetration strength threshold, and the antifreeze thickness is not less than the preset antifreeze thickness threshold, then the old asphalt pavement overlay structure has passed the pavement structure performance verification. Otherwise, the design parameters of the old asphalt pavement overlay structure are adjusted, and the pavement structure performance verification continues until the old asphalt pavement overlay structure passes the pavement structure performance verification, thus obtaining the optimal design parameters of the old asphalt pavement overlay structure.

8. The design method for multi-source solid waste widening road surface structure according to claim 5, characterized in that, The newly widened pavement structure includes a newly widened solid waste reinforced subgrade, a newly widened pavement base course, and a newly widened pavement surface course. The design parameters of the newly widened pavement structure include the thickness and material ratio of the newly widened solid waste reinforced subgrade, the newly widened pavement base course, and the newly widened pavement surface course. The performance verification parameters of the newly widened pavement structure include the rutting depth of the asphalt layer, the cumulative equivalent axle number corresponding to the fatigue cracking of the semi-rigid layer, the low-temperature cracking index, the penetration strength of the asphalt layer, and the antifreeze thickness.

9. The design method for multi-source solid waste widened road surface structure according to claim 8, characterized in that, When verifying the pavement structure performance based on the performance verification parameters of the newly widened pavement structure, and considering the threshold values ​​of each performance verification parameter, if the rutting depth of the asphalt layer does not exceed the preset rutting depth threshold, the cumulative equivalent axle number value corresponding to fatigue cracking of the semi-rigid layer is not less than the preset cumulative equivalent axle number threshold for fatigue cracking of the semi-rigid layer, the low-temperature cracking index does not exceed the preset low-temperature cracking index threshold, the penetration strength of the asphalt layer is not less than the preset penetration strength threshold, and the antifreeze thickness is not less than the preset antifreeze thickness threshold, then the newly widened pavement structure has passed the pavement structure performance verification. Otherwise, the design parameters of the newly widened pavement structure are adjusted, and the pavement structure performance verification is continued until the newly widened pavement structure passes the pavement structure performance verification, thus obtaining the optimal design parameters for the newly widened pavement structure.

10. The design method for a multi-source solid waste widened road surface structure according to claim 5, characterized in that, When performing durability coordination calculations on the overlaid old asphalt pavement structure and the newly widened pavement structure, if the difference in fatigue life between the overlaid old asphalt pavement structure and the newly widened pavement structure is no greater than 5% and the difference in rutting depth is no greater than 3%, then the durability coordination calculation of the old and new pavements is passed; otherwise, it is considered a failure.

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