Zhe Liu

Double primary support structures could effectively solve the problem of large deformation of surrounding rock for soft rock tunnels. However, the mechanical behavior of this new support structure is still incomplete, and the design method should be revised. Based on the theory of energy conversion, this paper analyzes the support characteristic curve of double primary support and puts forward the dynamic design method of double primary support. Considering that the secondary lining can be set after monitoring the deformation amount and deformation rate of the first primary support, its support parameters can be dynamically adjusted according to the actual situation. By applying the double primary support design method in the Maoxian tunnel of Chenglan Railway, the field monitoring results show that the double primary support has a significant effect on the energy release of surrounding rocks, greatly reducing the load acting on the secondary lining and ensuring the safety and reliability of the tunnel structure.

In the spaceborne/airborne forward-looking bistatic synthetic aperture radar (SA-FBSAR), due to the system platforms' remarkable velocity difference and the forward-looking mode, the range cell migration (RCM) not only depends on the target's two-dimensional location, but also varies with the range location non-linearly. And the nonlinearity is not just the slight deviation from the linear part, but exhibits evident nonlinear departure in the RCM trajectory. If the RCM is not properly corrected, nonlinear image distortions would occur. Based on the RCM model, a modified two-step RCM compensation (RCMC) method for SA-FBSAR is proposed. In this method, firstly the azimuth-dependent RCM is compensated by the scaling Fourier transform and the phase multiplication. And then the range-dependent RCM is removed through interpolation. The effectiveness of the proposed RCMC method is verified by the simulation results of both point scatterers and area targets.