南京河西地区软土卸荷状态下的强度特性研究  

Study on shear strength of the soft soil in Nanjing Hexi under unloading state

作　　者：侯晓亮[1,2,3] 赵晓豹[1,2] 李晓昭[1,2] 周建华[1,2] 

机构地区：[1]南京大学-华东有色地勘局地下空间与地质环境研究所 [2]南京大学地球科学与工程学院,南京210093 [3]合肥工业大学资源与环境工程学院,合肥230009

出　　处：《工程勘察》2011年第10期14-18,79,共6页Geotechnical Investigation & Surveying

基　　金：合肥工业大学校基金(2009HGXJ0060)

摘　　要：以大量的室内抗剪强度试验为基础,分析了南京河西地区软土深基坑开挖时,坑底被动区土体在卸荷条件下的抗剪强度变化规律。通过研究分析表明:坑底被动区土体在卸荷状态下的抗剪强度指标和加荷状态下差别明显,有一定的残留强度;土体卸荷时抗剪强度受卸荷比的影响明显;随着卸荷滞留时间的延长,初期土体抗剪强度损失明显,后期逐渐不显著。最后通过基坑算例分析表明,加荷、卸荷条件下得到的土体强度指标的不同,将会对坑底被动土压力计算、基坑抗隆起稳定性和基底隆起量计算等方面产生显著影响,坑底不同深度土体受开挖卸荷影响的程度不同。所得结论对分析南京河西地区基坑工程的稳定性以及坑底被动区土体的加固设计等具有一定的参考价值。Through a lot of direct shearing tests, the strength variation of the soft soils in passive areas under the unloading condition was analyzed when the deep pit in the soft soil was excavated in Nanjing Hexi. The results show that the indices of shear strength have the clear differences under the conditions of unloading or loading and there is some residual strength in soil samples. The shear strength under unloading condition is affected greatly by the unloading ratio. With the increase of the residence time, the shearing strength decreases significantly at the initial siage and then the influence becomes not so obvious. It is indicated that the differences of the soil strength indices obtained under the conditions of loading or unloading would influence the passive earth pressure, the base heave stability and the amount of the heave significantly. The soils under different depth in the excavation are affected differently by unloading. The conclusions obtained are valuable for analyzing the stability of pits and reinforcement design in the passive areas of soft soil.

关 键 词：卸荷 强度残留率 软土 深基坑 抗剪强度 

分 类 号：TU432[建筑科学—岩土工程]