长江口软基围堤施工的加载速率效应

Loading rate effect of soft foundation in causeway construction in the Yangtze River Estuary

针对长江口某围堤施工软土堆载过程中的稳定性问题,进行不同加载模式下的应力路径试验,分析长江口软黏土的应力-应变关系、结构损伤特性、强度及应变率发展模式,为该围堤工程的施工速率选取及施工过程中的稳定性控制提供技术依据。结果表明:在不考虑固结的前提下,土体的不排水抗剪强度几乎不受加载模式影响;最终强度与达到破坏时的应变大小无关,但与分级加载时间和分级静置时间存在相互作用关系;土体失稳时的应变率与加载速率和静置时间均有一定关系,且加载速率的影响更大;当加荷超过不排水抗剪强度的80%时,或分级最大应变率逐渐偏离加载初期的线性变化,土样濒临破坏。

For the stability problem of surcharge loading on soft foundation for the causeway construction in the Yangtze River Estuary,we carry out a series of stress path tests under different loading patterns,and analyze the stress-strain relationship,structural damage characteristics,strength and strain rate development for the soft clay in the Yangtze River Estuary to provide technical references in the construction rate selecting and the stability control in the construction for this project.The results show that the undrained shear strength of the soil,without concerning the influence of consolidation,is almost independent on the loading pattern.The ultimate strength is independent of the strain at failure,and it shows strongly interacted with the loading time and the standing time.In addition,the strain rate at instability of soil is related to the loading rate and the standing time,and the loading rate is more predominant.The soil sample is nearly failure when the maximum stage-strain rate gradually deviates from the linear tendency or the surcharge loading reaches over 80%of the undrained shear strength.