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在黄土高原地区,由于沟壑众多,在隧道选线过程中出现了一种最不利的地形条件,即隧道需穿越超浅埋大偏压地段。为了研究其经济、安全、可靠的穿越方案,提出经济安全系数比的概念及计算原理。对隧道穿越超浅埋大偏压段的方案先进行设计,然后采用有限元强度折减法和相关定额计算出各方案的经济安全系数比,并结合数值模拟方法对3种典型穿越方案下的隧道围岩应力、洞室变形和初期支护应力等进行计算分析。经过综合对比,得出按反压法设计的穿越方案最优。该方案既有利于超浅埋大偏压隧道的整体稳定,又有利于减少工程造价。
In the Loess Plateau, due to numerous ravines, one of the most unfavorable topographical conditions occurred in the process of tunneling, that is, the tunnel needs to cross an ultra-shallow buried and heavily biased section. In order to study its economical, safe and reliable cross-over plan, the concept and calculation principle of economic safety factor ratio are proposed. The scheme of tunnel crossing ultra-shallow buried and large biasing section is designed first, and then the economic safety factor ratio of each scheme is calculated by the finite element strength reduction method and the related quotas. Combined with the numerical simulation method, the tunnels under three typical crossing schemes Rock stress, cavern deformation and initial support stress are calculated and analyzed. After a comprehensive comparison, it is concluded that the cross-over design scheme based on backpressure method is optimal. The scheme not only benefits the overall stability of ultra-shallow buried large biased tunnels but also helps to reduce the construction cost.