基于开挖面实际破坏模式的盾构隧道稳定性分析模型

基于开挖面实际破坏模式，考虑分层土体的差异性和土体拱效应，对太沙基松动土压力计算公式进行修正，提出了一种新型楔形体计算模型，并由此算出开挖面的临界支护压力.结果表明：上覆土压力影响临界支护压力的取值，且随着隧道埋深的增加，其影响程度急剧增大；所得开挖面的临界支护压力的大小与楔形体张开角α及其倾角θ密切相关，当α=90°－θ时，可以确定所对应的临界支护压力值.同时，通过工程实例，验证了所提出的新型楔形体计算模型及临界支护压力确定方法的可靠性.

Calculation Model of Shield Tunneling Stability Based on Real Face Failure Modes

The assumption of excavation failure mode is based on the traditional wedge model which is not suited to usual clay soil and sandy clay layered soil. This paper presents a novel wedge model for the analysis of face stability, taking into consideration the real failure modes, the character difference of layered soil and the arching effect of soils. This model is an extension of the widely-used Terzaghi’s pressure equation. The results show that the critical supporting pressure, greatly affected by the overburden soil pressure, increases sharply with the increase of embded tunnel depth. The critical supporting pressure could be determined accurately by the suggested novel wedge model. The value of supporting pressure is closely related to the open angle α and dip angleθ of the wedge itself and is unique when α=90°－θ. The rationality and feasibility of the novel wedge model and the determining method for critical supporting pressure were verified by a field case and the results could provide a reasonable reference for similar engineering conditions.