自由落体贯入试验获得土体强度的简化分析

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。

Simplified analysis of determining undrained shear strength from FFP tests

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.