海底沉积物纵波速度与强度参数关系模型研究

Study on the relationship model between P-wave velocity and strength parameters of marine sediments

海底沉积物具有质地松软、强度低的特点,其强度参数与海上平台插桩就位、导管架的安装等工程关系紧密,与海上作业安全息息相关。常规钻孔取芯与静力触探等强度参数获取方法成本较高、取样点少,且对沉积物扰动较大,利用易获取的声学资料预测海底沉积物的强度参数具有重要研究意义。本文基于Wood方程、Biot-Stoll模型、Dvorkin等效介质模型等声波传播理论,计算不同物性参数(密度、孔隙度)梯度下的理论纵波速度,结合室内模拟地层声学实验,对比了模型计算声速与实测声速的变化特征,建立了声速与物性参数关系模型。基于室内模拟地层土力学试验,揭示了沉积物物性与抗剪强度、黏聚力等参数之间的关系,建立了物性与强度参数关系模型。以物性参数为桥梁,建立基于声学特征的海底沉积物强度参数预测模型。此模型既避免了原位取样沉积物失水扰动的问题,又弥补了经验公式局限性的缺点,具有普适性与准确性,有效提高无法取样地区沉积物强度参数的精度,提高了经济效益,对浅层的勘探与开发起到了理论指导的作用。

Marine sediments are characterized by soft texture and low strength,and their strength parameters are closely related to offshore platform pile placement and jacket installation,and are closely related to offshore operation safety.Conventional methods for obtaining strength parameters,such as drilling and cone penetration test,have high cost,few sampling points,and great disturbance to the soil.Therefore,it is of great significance to predict the strength parameters of marine sediments with easily accessible acoustic data.Based on the acoustic propagation theories such as Wood equation,Biot-Stoll model and Dvorkin equivalent medium model,the theoretic-al P-wave velocity under different physical parameter(density,porosity)gradients was calculated.Combined with the indoor simulated stratum acoustic experiment,the variation characteristics of the calculated and measured sound velocity were compared,and the relationship model between sound velocity and physical parameter was es-tablished.The relationship between soil physical parameter and shear strength,cohesive force and other parameters was revealed based on laboratory geotechnical test,and the relationship model between soil physical parameter and strength parameters was established.A prediction model for strength parameters of marine sediments based on acoustic characteristics was established by using physical parameters as bridge.This model not only avoids the problem of water loss disturbance of in-situ sampled soil,but also makes up for the limitation of empirical formula.It has universality and accuracy,and can effectively improve the precision of strength parameters of soil in un-sampled areas,improve economic benefits,and play a theoretical guiding role in shallow exploration and develop-ment.