基于强度折减法的狭长基坑坑底抗隆起稳定研究

Strength Reduction Approach for Analyzing Safety against Basal Heave of Long Narrow and Deep Excavation

以电力电缆隧道基坑为代表的狭窄、长条型基坑,由于开挖宽度小于深度,基坑内外侧土层不符合半无限体的假设,其坑底抗隆起稳定破坏模式就与常规建筑基坑不同,采用国家标准GB 50007和建筑行业标准JGJ 120推荐的算法会产生较大误差。文章以强度折减法为分析工具,研究采用支挡结构围护的狭长基坑坑底稳定破坏模式,分析结果显示狭长基坑不再以圆弧滑动形式破坏,而是形成了以基坑外两侧圆弧主动区、坑内整体被动区的新型破坏模式;同时,针对厦门电力进岛第二通道工程的典型基坑断面,进一步分析基坑抗隆起稳定安全系数与支挡结构插入深度的关系,为工程建设提供依据。

Represented by the HV cable tunnel foundation pit,the width of long and narrow excavation is smaller than the depth,which makes the soil inside the foundation pit do not meet the assumption of semi-infinite body,and the failure mode against basal heave is different from that of the building foundation pits. It would bring error when calculated the safety against basal heave of long narrow and deep excavation with the algorithms recommend by the Chinese standard GB 50007 and the Chinese construction industry standard JGJ 120. This paper analyzes the failure model of the long narrow and deep excavation foundation pit supported by the supporting and retaining structure with strength reduction approach,the analyzed result shows that the kind of foundation pit do not fail as a circle arc slide model,which form a new failure model with active circle arc zoom outside the retaining structure and passive triangle range between retaining structures. This paper uses the simulation method to analyze the represented tunnel foundation pit in Xiamen No. 2 electrical access and further analyzes the relationship between safety factors and the depth of the retaining structures,to provide a basis for the engineering work.