REOB (Recycled Engine Oil Bottom) rejuvenated asphalt can solve the problems of environmental pollution and resource waste. In order to improve the performance of REOB rejuvenated asphalt, an SBS modifier was applied. An orthogonal test was carried out to optimize the preparation scheme of SBS/REOB-modified rejuvenated asphalt, and the physical rheological properties and microscopic mechanisms of modified rejuvenated asphalt with different SBS and REOB dosages were studied. The test results show that the optimal mixture of the SBS/REOB-modified and rejuvenated asphalt is 9% REOB + 4.5% SBS, the optimal shear time is 40 min, and the shear rate is 5000 r/min. SBS modification of the REOB rejuvenated asphalt can obtain the same excellent high temperature performance as ordinary SBS-modified asphalt, and the modification process can greatly improve the high-temperature deformation resistance of rejuvenated asphalt. After SBS modification of the REOB rejuvenated asphalt, its S value is significantly lower than the base asphalt and the REOB rejuvenated asphalt, and its m value is also greatly improved compared with the base asphalt and the REOB rejuvenated asphalt, indicating that the low-temperature performance of the modified rejuvenated asphalt is greatly improved compared with the rejuvenated asphalt and is better than the base asphalt. The fluorescence microscopic test revealed that both the modified rejuvenated asphalt and the SBS-modified new asphalt prepared in the laboratory showed a continuous asphalt phase, and the SBS phase of the modified rejuvenated asphalt could basically reach the level of finished modified asphalt.

Accelerated pavement testing (APT) is an effective method to study the long-term performance of pavement. Therefore, the dynamic strain behavior analysis of asphalt pavement has important guiding significance in the study of pavement failure modes. To explore the dynamic response of a high-content plant-mixed hot-reclaimed asphalt mixture under a dynamic load of vehicles, a full-scale test road was paved, and ALT biaxial accelerated loading test equipment was used to simulate the dynamic loads of vehicles. Based on parameters such as axle load, temperature, speed, and loading times, the development law for the bottom strain of the three pavement structures was analyzed. The test results show that the most unfavorable position of the asphalt pavement load is located just below the centerline of the wheel track on one side, and the damage effect of a single double-axle wheel load is far greater than that of two single-axle wheel loads. Then, the longitudinal tensile strain of the pavement bottom always maintains the alternating state of compression-tension and compression. The longitudinal tensile strain of the pavement bottom is larger than the transverse tensile strain, and transverse fatigue cracks appear first. Under normal temperature conditions, the bottom tensile strains of the three composite pavement structures under different axial loads are close, and the pavement performance of the hot-recycled asphalt pavement of structure A and structure B can meet the specification requirements. The relationship between the bottom strain and axle load is nonlinear and is directly related to the tire ground pressure, and the difference in the tensile and compressive strain values of the bottom of the three composite pavement structures is small. Under high temperature conditions, the bottom layer temperature of structure A and structure B is lower than that of structure C, and the thermal heat transfer efficiency of hot-recycled asphalt pavement is lower than that of ordinary asphalt pavement. Additionally, the longitudinal tensile strain is about 1–1.5 times that of the transverse tensile strain. Based on the Boltzmann function, the accumulative tensile strain prediction model was established to reflect the relationship between the cumulative strain at the bottom and the number of loads.

High-speed railways are built in deep soft-soil foundations interlayered with hard materials. However, the hard layers cannot be penetrated by conventional foundation treatment. Moreover, the project cost is sometimes prohibitive, which is an issue for post-construction subsidence control. The bag grouting pile is a special grouting-pile-reinforcement technique for treating soft-soil foundations interlayered with hard materials. This paper conducted tests on the Ningbo-Taizhou-Wenzhou ballast track passenger railway, combining a conventional mixing-pile-foundation (not through hard layer) processing station and the bag-grouting-pile-processing subgrade line. Using field tests combined with numerical calculation, the lateral displacement, settlement and pile–soil stress were tested to obtain the working properties of the grouting-pile-composite foundation. The variation in the law of lateral displacement, settlement, and pile–soil stress of the foundation was studied. The results showed that the post-construction subsidence of bag-grouting-pile- and conventional mixing-pile-foundation control was less than 15 cm and 30 cm, respectively, which met the design requirements. The results also showed that the design scheme was reasonable (load-sharing ratio of bag-pile-foundation pile soil-based test was reasonable). The numerical calculation showed a change in pile diameter. It also showed that pile spacing could not improve subsidence-control properties, bag grouting pile can promote pore-pressure dissipation and accelerate consolidation, and pile spacing can be increased to cut project costs incurred by the pile-bearing capacity.