基于突变理论的第三系弱胶结砾岩掌子面稳定性

Tunnel face stability of tertiary weakly cemented conglomerate based on catastrophe theory

为了评价第三系弱胶结砾岩掌子面稳定性,基于突变理论对强度折减法进行改进,提出了适合砾岩掌子面稳定性评价的失稳判据,结合室内试验,采用数值方法研究了颗粒级配和胶结程度对掌子面稳定性的影响.结果表明,位移判据最适用于掌子面稳定性分析,通过分析掌子面不同特征点的安全系数可以判断掌子面破坏形式,选择最易失稳点得到掌子面的安全系数.弱胶结砾岩掌子面安全系数为3.79,极弱胶结砾岩掌子面安全系数均小于1,掌子面开挖前必须进行超前支护.胶结程度是影响弱胶结砾岩掌子面稳定性的决定性因素,胶结程度一致时,增加砾岩中砾石含量能显著提高掌子面自稳能力.第三系弱胶结砾岩掌子面拱底处为最不稳定点,掌子面失稳破坏时首先表现为拱底隆起.

To evaluate the tunnel face stability of tertiary weakly cemented conglomerate, a strength reduction method was improved based on the catastrophe theory. A criterion of instability was proposed for evaluating the tunnel face stability of weakly cemented conglomerate. Combining with the results of the laboratory tests, the influence of the particle gradation and the cementing degree on the stability of the tunnel surface was studied by the numerical method. The research results show that the displacement criterion is most suitable for the stability analysis of the tunnel face. By analyzing the safety factors at different feature points of the tunnel face, the damage forms of the tunnel face can be judged, and the most unstable point is chosen to obtain the safety factor of the tunnel face. The safety factor of the tunnel face of weakly cemented conglomerate is 3.79, and the safety factors of the tunnel face of extremely weakly cemented conglomerate face are less than 1, which means advance support must be carried out before the excavation of the tunnel face. The cementation degree is the decisive factor affecting the stability of the tunnel face of weakly cemented conglomerate. The increase of the gravel content in conglomerate can significantly improve the self-stabilizing ability of the tunnel face when the cementation degree is consistent. The inverted arch of the tunnel face is the most unstable point, and inverted arch extrusion is the first sign of the instability failure of the tunnel face of weakly cemented conglomerate.