自落式贯入仪率相关系数标定方法

The calibration method of rate effect on free-falling penetrometer

自落式贯入仪(free-falling penetrometer,FFP)作为一种新型地质勘察技术,可以高效快速地获取海底沉积物的力学性质参数。FFP贯入过程中锥尖阻力受贯入速率影响,数据处理时需借助速率因子将动贯入阻力转化为与静力触探试验(cone penetration test,CPT)等效的准静态贯入阻力,但目前速率因子中的率相关系数尚无明确测试方法。基于牛顿运动定律对率效应进行理论分析,并利用南海北部陆坡淤泥质沉积物开展室内贯入试验;并采用对数函数和幂次函数拟合锥尖阻力与贯入速率关系,提出了自落式贯入仪率相关系数的标定方法。研究结果表明,释放高度和探头质量都会影响最终贯入深度,但贯入过程中的锥尖阻力变化受探头质量影响较小,提出的率相关系数标定方法能够更准确获取FFP贯入的率相关系数。在实际应用中可采用室内试验标定的系数修正原位试验数据,为FFP实际应用提供技术支持。

As a new type of geological investigation technology,free-falling penetrometer(FFP)can obtain the mechanical properties of seabed sediments efficiently and quickly.During the FFP penetration process,the measured cone tip resistance is significantly influenced by the penetration rate.To process the data,it is essential to convert the dynamic penetration resistance into a quasi-static penetration resistance equivalent to the static penetration resistance of the cone penetration test(CPT).A rate factor correction related to the penetration rate is crucial for data analysis.This paper conducts theoretical analysis of rate effect based on Newton's Law of Motion,and examines mucky soil on the northern slope of the South China Sea through laboratory testing.Logarithmic function and power function are employed to fit the relationship between cone tip resistance and penetration rate,a calibration method for the correlation coefficient of free-falling penetration instrument rate is proposed.Findings indicate that both the release height and the probe quality affect the final penetration depth,but the change of cone tip resistance during penetration is less affected by the probe quality.The method proposed in this paper accurately determines the rate correlation coefficient of FFP penetration.The coefficient,calibrated through laboratory tests,can rectify in-situ test data in practical scenarios,offering technical support for FFP applications.