To study the combined effects of freeze–thaw cycles and chemical corrosion on deterioration mechanism of triaxial mechanical properties of sandstone in cold regions, triaxial compression tests were carried out on homologous sandstone specimens after corrosion action of acidic, alkaline or neutral solution and cyclic freeze–thaw action, by taking the pH value of the hydrochemical solution and the number of freeze–thaw cycles as control parameters. The failure mode of triaxial compression is shear-slip failure, and the deviatoric stress–strain curves can be divided into four stages of compaction, linear elastic, yield, and failure. The stress–strain curves and deterioration law of triaxial mechanical properties were analyzed. With the increase of freeze–thaw cycles, the peak stress, peak strain and modulus all decrease, the deterioration degree of the rock specimens increases, and the yield plateau and plastic characteristics in the yield stage become weaker. The strong acid solution shows the largest degree of damage, and the peak stress, peak strain and modulus decreased significantly. The precipitates produced by the reaction between the strong alkaline solution and the specimens adhere to the specimen surface, pores, and fissures, thereby inhibiting further damage and deterioration. Confining pressure is an essential factor affecting the rock mechanical properties. As confining pressure increases, the strength and deformation-resistant ability of specimens increase, and the yield stage on the stress–strain curve is more obvious. The sensitivity of acidic solution to the deterioration of mechanical properties of sandstone is obviously greater than that of alkaline solution. These results provide a theoretical basis for the construction of geotechnical engineering structures in cold regions.

The intrinsic endpoint effect of empirical mode decomposition (EMD) will lead to serious divergence of the intrinsic mode function (IMF) at the endpoint, which will lead to the distortion of IMF and affect the decomposition accuracy of EMD. In view of this phenomenon, an EMD endpoint effect suppression method based on boundary local feature scale adaptive matching extension was proposed. This method can consider both the change trend of the signal at the endpoint and the change rule of the signal inside. The simulation results showed that the proposed method had better suppression effect on the intrinsic endpoint effect of EMD than the traditional EMD endpoint effect suppression method and achieved high‐precision IMF. The endpoint effect suppression method of EMD based on boundary local feature scale adaptive matching extension was used to process the actual blasting seismic signal. The decomposition results showed that the method can effectively suppress the endpoint effect of EMD of blasting seismic signal and are helpful to extract the detailed characteristic parameters of blasting seismic signal.

Because fault core zones and damage zones overlap, when a tunnel crosses the intersecting faults the groundwater flow characteristics of the tunnel-surrounding rock will be different compared to that from a single fault. By using the theory of “Three-district zoning of faults”, an improved Darcy–Brinkman numerical model for a tunnel crossing the intersecting faults was established in this work. Based on the relative vertical positions between the tunnel axis and the intersection center of faults, the underground water seepage field was analyzed at steady-state by solving the improved Darcy–Brinkman equation for the host rock zone and the fault zone. The simulation results show that the flow field around the tunnel is almost unaffected by the relative positions but is mainly dependent on the relative heights. Specifically, the relative position variation of the fault intersection to the tunnel axis has little effect on the pore pressure. In terms of flow velocity, regardless of the relative positions of the fault intersection and the tunnel, the maximum value of flow velocity almost occurs near the bottom of the tunnel excavation face and consistently displays high values within a small distance ahead of the excavation face, and then decreases quickly as the distance increases. Furthermore, the flow velocity changes minimally in the host rock. It will likely encounter the maximum water inflow rate when the tunnel excavation face passes through the intersection. The numerical simulation results can provide a practical reference for predicting water inflow into deep-buried tunnels passing through overlapped intersecting faults.