砂质沉积物强度动力贯入室内试验研究

In-Lab Experimental Research on Strength of Sandy Sediments Determined with Free-Fall CPT

自由下落式CPT测试技术(FF-CPT)是新兴的海上沉积物强度测试方法。本文构建了海上FF-CPT原型样机,并以海洋干砂质沉积物为研究对象,分析了FF-CPT的贯入特征、速度相关性及其影响因素。结果表明,装置触底速度与最终贯入沉积物的深度受装置释放高度影响,释放高度越大,则触底速度与贯入沉积物深度越大。贯入过程的阻力分布规律是影响速度变化的主要因素。FF-CPT初始贯入阶段,沉积物贯入阻力随深度线性增加,但增幅不明显,这导致贯入速度变化不大,几乎可视作匀速,该段行程超过总贯入深度的2/3。后段行程贯入阻力骤增,导致贯入速度迅速降低至0。对于干砂质沉积物,FF-CPT贯入阻力与贯入速度不存在正相关关系。FF-CPT贯入阻力的速度相关性与装置质量、沉积物密实度关系不大。

Free-fallCPT testing technology(FF-CPT)is an emerging method of testingstrength of marine sediments.In this paper,on the basis of theoretical analyses and in-lab experiments,an FF-CPTprototype equipment was devised and put to the study of dry marine sandy sediments.The FF-CPT penetration characteristics,correlation between strength of sediments and penetration velocity as well as their influencing factors were analyzed.Results showed that the grounding velocity and final penetration depth of the equipment were influenced by its releasing height.The higher the releasing height was,the larger the grounding velocity and final penetration depth were.Resistance distribution during the penetration course was the main factor that influenced the variation of penetration velocity.During the initial penetration stage,the resistance increased linearly with the increasing of depth with insignificant amplitude,which led to a constant velocity.This stage accounted for two thirds of the total penetration depth.Subsequently,the resistance increased suddenly,and the velocity was reduced to zero rapidly.For dry sandy sediments,there was no positive correlation between the penetration resistance and penetration velocity.The velocity correlation was possibly related to the type,water content,drainage condition and structure of sediments rather than their density or mass of the equipment.