上拔式静力触探试验的力学机理研究

The physical mechanical property of marine soil is important to the design and construction in offshore engineering. Generally, it can be obtained by cone penetration test. However, this method is easy to be affected by wave and tide, and hence the reaction force of the equipment is difficult to be applied. Furthermore, it costs a lot of money if the large foreign survey vessel is used. However, the pull-out cone penetration test can avoid the disadvantages mentioned above. It is easy to be used and the soil parameters can be derived from the change of pull-out resistance when pull out the dedicated device from a drilling hole. In this project, the mechanical mechanism of pull-out cone penetration test was investigated using the large model test. The size effect and the effect of pull out rate to the result of pull-out cone penetration test were studied firstly, and then the relationship between uplift resistance and the physical mechanical property of soil were also investigated in depth. Finally, the method to derive the strength and deformation parameters of soil using pull-out resistance was proposed. This study will provide a new way to obtain the physical mechanical property of marine soil.

海洋土的物理力学性质在海洋工程的设计与建设中是非常重要的参数，传统的方法是采用静力触探试验获得，但是存在受波浪、潮汐等因素的影响大，不易提供固定反力的问题，而采用国外大型勘探船的费用又十分昂贵。上拔式静力触探通过在钻孔内放入专用设备，利用海床提供反力向上拉拔，可根据上拔阻力获得相应的土体参数，简单易行，可以很好的避免以上问题。本项目以上拔式静力触探试验的力学机理为研究对象，首先通过大型模型试验技术研究锥头尺寸和上拔速率对上拔式静力触探试验结果的影响，而后探索了上拔阻力与土体物理力学性质的关系，最后提出一套通过上拔式静力触探试验结果获得土体强度与变形参数的方法。研究成果将为获取海洋土物理力学性质提供一个新的手段。

上拔式静力触探测试技术是一种有别于传统静力触探的新型原位测试技术，它通过在钻孔内放入一种专用设备并向上拉拔，而后根据所测得的拉拔阻力获取相应的土体物理力学参数。本项目以上拔式静力触探试验的力学机理为研究对象，通过一系列的室内试验，研究了刃口角度、刃口长度、拉拔速率、压实度和相对密实度等因素对拉拔阻力的影响。结合三轴试验结果，探索了拉拔阻力与土的抗剪强度参数的相关关系。此外，通过现场上拔式静力触探试验、传统静力触探试验和旁压试验结果的对比，验证了上拔式静力触探试验技术的可重复性、准确性以及与传统静力触探结果的一致性。结果表明：（1）拉拔阻力随着刃口角度、刃口长度、拉拔速率的增加而增大；（2）上拔式静力触探拉拔曲线与传统静力触探的贯入曲线具有相似的规律，拉拔阻力与土的相对密实度或压实度之间具有拟合度较高的相关关系；（3）拉拔阻力与土体强度参数之间存在线性关系；（4）上拔式静力触探技术采用拉拔阻力这个测试参数反映土层性质是可行的。研究成果为上拔式静力触探技术的进一步研究和推广应用奠定了基础。