泥岩地基中动力打入桩竖向承载特性现场试验

Field Test of Vertical Bearing Characteristics of PowerDriven Piles in Mudstone Foundation

为深入研究泥岩地基动力打入桩的竖向承载特性,开展了泥岩地基打入桩单桩竖向抗压静载试验,分析了试桩的沉贯与承载特性,探讨了地下水对试桩承载性能的影响,基于静载试验结果,对比分析不同理论预测模型的单桩极限承载力计算值,评估了模型的适用性。结果表明:试桩的极限承载力与打桩能量有关,不同的打桩能量对桩周泥岩造成不同程度的扰动损伤,进而影响试桩的承载性能;对比桩周泥岩遇水与试桩破坏情况,发现桩周泥岩浸水软化与否,与桩的破坏无直接关系;对比不同模型的极限承载力预测结果,认为双曲线模型更适合本试验场地泥岩的性质,预测曲线变化趋势和实测值吻合度较高;指数模型预测值与实测值产生较大差异的原因为试桩在最后一级荷载的非正常破坏,泥岩地基打入桩受超孔隙水压力、软硬互层及打桩过程扰动的影响,单桩承载力在很大程度具有不稳定性。

In order to study the vertical bearing characteristics of dynamically driven piles on mudstone foundation,the vertical compressive static load test of single piles driven on mudstone foundation was carried out to analyze the sink penetration and bearing characteristics of the test piles,and to discuss the influence of groundwater on the bearing performance of the test piles,and to evaluate the applicability of the model by comparing and analyzing the calculated values of the ultimate bearing capacity of single piles from different theoretical prediction models based on the results of the static load test.Research shows that the ultimate bearing capacity of the test pile is related to the piling energy,and different piling energies cause different degrees of disturbance damage to the mudstone around the pile,which in turn affects the bearing performance of the test pile.Comparing the damage of the test pile with the mudstone around the pile in water,it is found that there is no direct relationship between the softening of the mudstone around the pile in water and the damage of the pile.Comparing the predicted ultimate bearing capacity results of different models,it is considered that the hyperbolic model is more suitable for the nature of the mudstone at this test site,and the predicted curve variation trend and the measured value are in good agreement.The reason for the large difference between the predicted value of the exponential model and the measured value is the abnormal damage of the test pile at the last level of loading.The pile driven into the mudstone foundation is affected by the super pore water pressure,soft and hard interlayer and the disturbance of the piling process,and the single pile bearing capacity has instability to a large extent.