坑中坑开挖对基坑抗隆起稳定性的影响分析  

Analysis of Influence of Pit-in-pit Excavation on Heave-resistant Stability of Foundation Pit

作　　者：熊中华[1,2] 丰土根[1,2] 钱秋莹 李昂[1,2] 

机构地区：[1]河海大学岩土力学与堤坝工程教育部重点实验室,江苏南京210098 [2]河海大学岩土工程研究所,江苏南京210098

出　　处：《土木工程与管理学报》2013年第4期8-12,16,共6页Journal of Civil Engineering and Management

基　　金：国家自然科学基金(51009054);教育部科学技术研究重点项目(109077);江苏省自然科学基金(BK2010513)

摘　　要：在既有基坑内部进行二次开挖形成坑中坑的过程也是对基坑被动区土体卸载的过程,被动区土体的卸载加大了坑底隆起变形的趋势,对基坑抗隆起稳定性产生较大影响。根据坑中坑与圆弧滑动面的位置关系的不同,对坑中坑类型进行了分类,推导了不同类型坑中坑基坑抗隆起稳定安全系数的计算公式。研究结果表明:坑中坑基坑抗隆起稳定性与坑中坑开挖位置有关,当坑中坑在圆弧滑动面影响区域内开挖时会减小抗滑力矩,降低基坑抗隆起稳定安全系数。外部型坑中坑对基坑抗隆起稳定性无影响。内部型坑中坑基坑抗隆起安全系数随内外坑壁距离、内坑宽度、内坑深度的增大而减小。坑底相交型坑中坑基坑抗隆起安全系数与内坑宽度无关,随内外坑壁距离的增大而先减小后增大,随内坑深度的增大而减小。坑壁相交型坑中坑基坑抗隆起安全系数与内坑宽度、内坑深度无关,随内外坑壁距离的增大而增大。The pit-in-pit excavating process is also the process of unloading in passive zone of foundation pit. However,unloading in passive zone increases the trend of upheaval deformation. The deformation has a great impact on heave-resistant stability of foundation pit. The pit-in-pit is categorized into different types according to positional relationship between the pit-in-pit and the circular sliding surface. Specific formula to calculate the safety coefficient of heave-resistant stability has been proposed for each type. The results show that the heave-resistant stability of pit-in-pit is related to the position of the inner pit. If the pit-in-pit excavation occurs inside the zone influenced by the circular sliding surface,the safety coefficient decreases. But external pit has no influence on heave-resistant stability. The safety coefficient of heave-resistant stability decreases with increasing width,depth of the inner pit and the distance between the outer pit and the inner pit for internal pit-in-pit type. For bottom intersection pit-in-pit type,the safety coefficient is unrelated to the width of the inner pit,it increases with increasing distance between the outer pit and the inner pit first then decreases,but it performs in the opposite way when considering the depth of the inner pit. For wall intersection type, the safety coefficient is unrelated to the width and depth of the inner pit,but it still increases with increasing distance between the outer pit and the inner pit.

关 键 词：基坑 坑中坑 抗隆起稳定性 圆弧滑动面 

分 类 号：TU470[建筑科学—结构工程]