复杂条件下某深大基坑支护结构优化设计

Supporting Structures for a Large Deep Excavation in Soft Soils

某大型深基坑位于湖北荆州市中心城区,地处长江I级阶地,距离有地上悬河之称的长江荆江干堤仅700m,基坑开挖深度达8.0m,基坑重要性等级为一级。地层软弱,孔隙潜水和承压水非常丰富,周边环境安全性要求高,对基坑设计提出了很高的要求。通过理论分析和经验判断,针对各段地层和基坑轮廓形状,优化设计了灌注桩和一道钢管内支撑支护、门式刚架支护、圆拱形支护设计等支护结构。工程实践表明,因地制宜的支护结构设计既能最大限度地方便基坑开挖施工,又能很好地控制周边的沉降和差异沉降,为复杂环境地质条件下深基坑工程的设计、施工提供了宝贵的经验。

The normal water table level in the Yangtze River near Jingzhou City is above the ground surface inside the Jingjiang Embankment. A deep excavation site in the center of Jingzhou City is only 700 m from the embankment along the Yangtze Riv- er. Due to its proposed eight meters of excavation depth, this site is classified as Level I on the Importance Class Scale （most important）. This site is characterized by underlying saturated soft soil strata, high artesian water head and adiacent structuresthat are sensitive to construction disturbance. Therefore, stringent requirements are placed on deep excavation design and con- struction. Using theoretical analysis and empirical iudgments, different supporting structures are selected based on the charac teristics of soil strata and the geometry of the excavations at the various locations. Supporting structures include cast-in-place piles, rigid frame piles and arch-supporting piles. These supporting structures are not only for the excavation construction ease-ment but also for minimizing settlement and differential settlement problems surrounding the structures.