Introduction: A reasonable advanced support system is crucial for ensuring stable excavation in tunnels with weak surrounding rock. This study aims to address the problems of instability, large deformation, and prolonged construction period in the sidewalls of tunnel faces in plateau high-geostress carbonaceous slate tunnels in western mountainous areas. Methods: Based on lithology analysis and creep tests, we propose enhanced over-head pre-support, rapid initial support closure, and increased steel arch stiffness. The proposed approach was validated via numerical modeling and field tests. Results: Results show that compared to no forepoling (Case I), Cases II–V reduced deformation by 17%, 21%, 44%, and 46%, respectively. The additional arch over-support improves stability and reduces sidewall deformation. The combined "arch-wall over-support + HW175 steel arch + 6m anchors" system shortened initial support formation from 20 to 12 days. Discussion: These findings support the design of active-passive support systems for high-stress weak rock tunnels and offer insights for similar projects.

A fire can pose a significant threat to a building’s occupants and leads to property damage. The burning characteristics usually determine the severity of the accident. Environments in high-altitude areas feature low oxygen content and ambient pressure, which can influence the burning characteristics of combustibles. In this paper, a series of field experiments were conducted to investigate the burning characteristics of gasoline at different altitudes considering heat release rate (HRR), flame height, and smoke release rate. Results show that the combustion process can be divided into three stages: initial stage, stable stage, and attenuation stage. Lower oxygen content and ambient pressure reduce the HRR; for example, the HRR at an altitude of 4150 m is nearly half at an altitude of 500 m, contributing to a lower smoke release rate. The HRR is proportional to 1.3 power of atmospheric pressure, and a fitting equation was brought out in this paper. Flame height increases with the increase in altitude due to the demand for more oxygen during the combustion process since the oxygen content is low in high-altitude areas.