胶结土中的超长钢管桩高应变试桩分析模型

With the progress of the “Maritime Silk Road” construction, many overseas port engineering projects are contracted. Due to different sedimentary environment, soils with varying amounts of cementation are frequently encountered along the “Maritime Silk Road”, eg., diatomaceous clays, coral sand, cemented sand. The engineering properties of these materials are quite different to those of silica sands and clays, and need further study. The strength and stiffness are reduced significantly if the cementation is disturbed. The present models of high strain dynamic testing are not well applicable to the piles installed in these soils. To solve this newly emerged urgent problem, the proposed research focuses on the models of high strain dynamic testing of super-long steel pipe piles in typical soils in the Mediterranean Sea area. The stresses in the piles are measured by using distributed fiber Bragg gratting and dynamic strain sensors under impact and working conditions. The static resistance of soil to pile is determined based on the measured stress at working load condition and at zero particle velocity after impact. The dynamic resistance of soil to pile is established based on measured and calculated stress during impact by adjusting and optimizing the soil dynamic terms to obtain a new model for high strain dynamic testing of steel pipe piles. The bearing capacity of other piles in the area are predicted and analyzed using the new model. The results of the proposed research will support the design, construction and quality control for super-long steel pipe piles in the port engineering projects in the Mediterranean Sea area.

随着“海上丝绸之路”建设的推进，码头施工逐步走向海外。因特定的沉积环境，丝绸之路沿线常遇到有较大结构强度的土层，如硅藻土、珊瑚砂、胶结砂层等。这些土的胶结状态在施工中会受到改变，桩基的承载力常减少很多。对这些土中的打入桩研究还不深入，目前的动测法不能较好地适应这种土层情况。针对海上丝绸之路建设中迫切需要解决的新课题，本项目围绕地中海近海区典型土中超长钢管桩的检测理论进行研究。设计测量方案，用布拉格光纤光栅和动态应变计研究打桩时桩身的动应力和工作状态时的桩身应力，建立土的静阻力模型，根据测量的桩身动应力和计算的桩身动应力的差别，调整优化土阻力模型的动力项，建立适合胶结土中的钢管桩高应变试桩分析模型，给出适合地中海地区的高应变分析模型参数，对场地其它桩的承载力进行分析预测。通过本研究，为我国码头施工技术走向海外，特别是地中海近海区桩基础的设计、施工与质量控制提供相应的理论依据和技术支持。

随着“海上丝绸之路”建设的推进，码头施工逐步走向海外。因特定的沉积环境，丝绸之路沿线常遇到有较大结构强度的土层，如硅藻土、珊瑚砂、胶结砂层等。这些土的胶结状态在施工中会受到改变，桩基的承载力常减少很多。对这些土中的打入桩研究还不深入，目前的动测法难以适应这种土层情况。针对海上丝绸之路建设中迫切需要解决的新课题，本项目围绕地中海近海区典型土中超长钢管桩的检测理论进行研究。通过本研究，提出了一种新的基桩承载力动测方法  直接动测法，并获得发明专利；以地中海沿岸一灌注桩的现场静载试验为对象，建立了详细的基桩有限元静力、动力分析模型。根据有限元分析计算结果，证明了新的直接动测法确定的承载力和静载法一致，该直接动测法消除了现有高应变法存在的多解性问题，避免了现场检测的主观因素; 用有限元法首次模拟了将桩锤击打入饱和黏土地基的全过程，得到了地基在打桩过程中的反应规律，确定了打桩对地基的影响范围；得到了地基中一点的超孔隙水压力随打桩过程的变化特性，阐明了圆柱孔扩张理论得出的超孔隙水压力分布与实际测量结果有较大差别的原因是圆柱孔扩张理论忽略了打桩过程中桩周土所受的较大竖向剪力。