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The characteristics of expansive soil, including over consolidation, swelling-shrinkage, fissures, and strength attenuation, can cause potential hazards in road construction, which are mainly manifested as subgrade swelling-shrinkage deformation and slope collapse. Effective treatment can not only ensure long-term subgrade stability but also reduce investment costs and environmental impact. In this review, the current development status of embankment filling and cutting slope treatment technology in expansive soil areas were summarized, and the classification standards of expansive soil filler, moisture retention, and antiseepage technology were described. Then, the utility of chemical, physical, biological, and solid waste modification materials in improving the engineering characteristics of core-filled expansive soil was discussed, and the cost and technical characteristics of these modification technologies were compared and analysed. Next, the application of rigid and flexible support technology in the treatment of cutting slope collapse was analysed, and the advantages and disadvantages of rigid and flexible supports were summarized. Finally, the development direction of expansive soil subgrade treatment technology was discussed. This review includes a summary of the treatment methods of highway subgrade in expansive soil areas and can provide a technical reference for treatment methods of expansive soil subgrade.

Considering the effects of time-varying meshing stiffness, time-varying support stiffness, transmission errors, tooth side clearance and bearing clearance, a nonlinear dynamics model of the coupled gear-rotor-bearing transmission system of a new energy vehicle is constructed. Firstly, the fourth-order Runge–Kutta integral method is used to solve the differential equations of the system dynamics, and the time-varying meshing force diagram, time history diagram, phase diagram, FFT spectrum diagram, Poincaré map and bifurcation diagram of the system are obtained to study the influence of the external load excitation frequency on the dynamics characteristics of the system. In addition, the multiscale method is used to analyze the main resonance characteristics of the system and to determine the main resonance stability conditions of the system. The effect of time lag control parameters and external load excitation frequency on the main resonance of the system is analyzed by numerical methods. The results show that the gear-rotor-bearing coupled transmission system of the new energy vehicle has obviously nonlinear characteristics, avoiding the system instability interval reasonable selection of external load excitation frequency, meshing damping, time lag parameters and load fluctuations, which can be used to improve the stability of the transmission system of the new energy vehicle.