自由落体贯入试验获得土体强度的简化分析

Simplified analysis of determining undrained shear strength from FFP tests

自由落体贯入仪(FFP)用于量测黏性土的不排水抗剪强度,具有操作快捷、经济性好等优点,在海洋原位勘察中有相当大的应用潜力。但FFP在土中的动力贯入机制复杂,其试验数据解释还存在较大的不确定性。进行FFP的室内缩比尺模型试验,同时改进现有的简化分析模型,比较预测与试验结果,验证了借助简化分析模型推算不排水强度的合理性。进而提出FFP"质量初始贯入速度"图,根据场地土强度的大致范围和贯入深度要求,能够快速设计现场试验需要的FFP质量与初始贯入速度。

Free-fall penetrometers(FFPs)are used to measure undrained shear strength of cohesive soils.FFPs are featured with quick operation and good economical efficiency,with significant potential in offshore in-situ investigations.However,the data interpretation of FFP tests is impaired by uncertainty in the dynamic penetration mechanism of FFPs.Reduced-scale model tests were conducted in kaolin clay with different strength profiles,whilst a simplified analytical model was modified to predict the undrained strength through the penetration velocity profile.The analytical model was validated by comparison with the testing data.Based on parametric study,the'FFP mass-impact velocity'contours are proposed for quick design of the in-situ tests given the rough range of undrained strength from local experiences.