砂卵石地层通常比较松散、黏聚力低且富含地下水,盾构施工经常导致开挖面失稳而诱发地面塌陷,因此保证开挖面稳定性是盾构在该地层中施工控制的关键内容.本文以成都地铁1、2号线砂卵石地层盾构施工为背景,总结影响盾构开挖面稳定性的主要因素；建立数值计算模型,分析内摩擦角、侧压力系数、盾构直径、盾构埋深和地下水位对开挖面稳定性的影响.研究结果表明:内摩擦角和地下水位是影响开挖面稳定性的主要因素；结合成都地铁2号线砂卵石地层盾构开挖面失稳实例,分析开挖面失稳的主要原因,并提出避免砂卵石地层开挖面失稳具体措施.%Sandy cobble strata are generally characterized by heavily discreetness, low cohesion and rich underground water. Shield excavation constantly causes excavating faces to lose stability and induce ground subsidence accidents. So face stability control is the key of shield excavation in sandy cobble strata. In this paper shield excavation crossing the sandy cobble stratum of the Chengdu Metro Line 1 and Line 2 was taken as the background for case study. The major factors influencing stability of faces excavated in sandy pebble strata were summarized. The numerical calculation model was established. The influence of the factors such as the internal friction angle, lateral pressure coefficient, shield diameters, buried depth and groundwater level on face stability was analyzed. The research results show as follows: The internal friction angle and groundwater level are the main influencing factors of face stability; combining with case study of the Chengdu Metro Line 2, the major reason of face losing stability is defined; measures to avoid face losing stability in sandy cobble strata are specified.
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