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In order to simulate the characteristics of underwater shield tunnels, a new large-scale model test system with high water pressure and high stress loading capacity was developed. The loading control mode of the hydraulic system can perform uniform loading and gradient loading. Moreover, the vertical and horizontal hydraulic loading can reach 0·8 MPa and 1·6 MPa. The water pressure loading system has a maximum capacity of 0·5 MPa. Based on an actual project, a model test of an underwater shield tunnel lining under real soil and water pressure conditions was carried out. New segment joints of the model were developed during the model testing. The lateral pressure coefficient at rest of the model strata was slightly larger than 0·5, and close to that of the field strata. It was also found that the water pressure had a reducing effect on the soil pressure under large buried depth and high water pressure conditions. This system can mostly meet the requirements of underwater or underground engineering model tests.

In order to evaluate the influence of rock asphalt on the self-healing behavior of asphalt mastics, this study carried out the frequency sweep test, fatigue-healing test and complete process monitoring test of self-healing behavior for four different asphalt mastics. In addition, this study examined a proposed mechanism of self-healing from literatures. The results show that the optimum self-healing temperature of control asphalt mastic is identified as its near-Newtonian fluid transition temperature (slightly higher than softening point), while the optimum self-healing temperature of rock asphalt mastic is lower than its near-Newtonian fluid transition temperature and softening point, which indicates that rock asphalt mastic maximizes its self-healing potential before the near-Newtonian fluid state. This study models the self-healing behavior of the asphalt mastic considering the effect of healing temperature and time to verify the applicability of the capillary diffusion theory that explains the self-healing in asphalt mastics. The proposed model determined the rest times for full healing of asphalt mastics, and results indicate that the self-healing rate of asphalt mastic can be significantly increased by rock asphalt. The results of the self-healing behavior monitoring test and the parameters obtained from the proposed model both indicate that rock asphalt has some adverse effects on the self-healing behavior in the initial stage, but will promote the development of self-healing after a period of time. Overall, the addition of rock asphalt can improve the self-healing properties of asphalt mastic. Based on the aforementioned macroscopic results and the capillary diffusion theory, it can be concluded that the addition of rock asphalt negatively affects the wetting mechanism of self-healing, but positively influences the strength and efficiency of diffusive cohesive healing, thus effectively enhancing the self-healing behavior of asphalt mastic.