Stress arching effect during the excavation of broken surrounding rock in underground engineering has an important influence on the stability of surrounding rock after underground excavation. To determine the stress arching effect in horizontally layered jointed rock mass, the stress arching characteristics of surrounding rock mass after excavation is analyzed in this study by using a series of numerical tests. The formation mechanism of stress arch is revealed through a comparison of the stress characteristics of a voussoir beam structure and theoretical analysis of multi-block mechanical relationship of jointed rock mass. The method for determining the boundaries of a stress arching zone is proposed, and the influence of various factors on a stress arch is further discussed. Results show that after the excavation of horizontally layered jointed rock mass, the stress arch bunch (SAB) is formed in the lower strata above the cavern, and the global stress arch (GSA) is formed in the higher strata, both of which are symmetrical arch stress patterns. The SAB is the mechanical manifestation of the voussoir beam structure formed by several low-level sandstone layers, and the GSA is caused by the uneven displacement between blocks. Compared with the GSA, the SAB is more sensitive to various influencing factors. The extent of stress arching zone decreases with the increase of an internal friction angle of the joint, lateral pressure coefficient, and overburden depth. In addition, the joint spacing of rock strata is conducive to the development of a stress arch. Results can provide technical support for deformation control and the stability analysis of broken surrounding rock in underground engineering.

SRM (strength reduction method) is a kind of numerical limit method widely used in stability analysis of geotechnical engineering. This paper introduced the origin, basic principles, and operation process of SRM firstly, then introduced a new type of SRM considering the "strength reduction shortest path". Moreover, both two methods were applied to solve the safety factor of an identical simulation model. In addition, sliding-t test was engaged to determine the accurate abrupt change position of the feature point's displacement, which presented considerable operability and accuracy. Finally, it was concluded that this new type SRM is more conservative than the traditional SRM, and the calculated safety factor of the same simulation model is about 25% lower.

Distributed fiber optic sensing technologies have been widely used in leakage monitoring of channels, but most of them are based on the temperature gradient difference, and have not yet formed a unified judgment standard. The relationship between temperature rise ΔT and heating time t is derived from the heat conduction theory, and the critical eigenvalue f is defined to reflect temperature change of heated fiber optical cable. Indoor test under different simulated environments yields that temperatures of the fiber optic cable rise rapidly at first and then rise slowly with the heating time. The critical eigenvalue f decreases with the increase of moisture contents of simulated environments according to the fitting equation of indoor results. In the prototype test, critical judgment conditions are given by analyzing the relationship of ΔT and f, and the error is within 0.5m when compared with the monitoring data of pore water pressure gauges, which is verified the feasibility and accuracy of the active heated fiber optical technique to monitor the leakage of channels.