考虑预载固结效应的海底浅基础承载力包络面演化规律研究

Evolution for failure envelope of shallow foundation considering preloading effect

由于预载下土体固结,海底浅基础的承载力会随作业时间的增加而改变,其时变效应评估困难。基于修正剑桥模型,采用水土耦合有限元方法研究了预载作用下浅基础在正常固结黏土海床中承载力破坏包络面的时变规律。在验证数值模型准确性后,通过位移探针测试获取复合加载模式下浅基础的破坏包络面,揭示了预载和固结程度对基础承载力和破坏包络面的影响,给出了预载作用下浅基础承载力包络面计算方法。结果表明:随着预载比增加,固结单轴承载力呈现线性增长,固结承载力增幅在水平向最大;部分固结承载力相对增幅与预载比无关,而随固结度变化;破坏包络面形状由预载比控制,而包络面大小由预载比和固结度共同控制。研究结果可为海洋浅基础的时变承载力评估提供参考依据。

Due to consolidation under preloading,the bearing capacity of the shallow foundation will change with the increase of the insitu time,and it is difficult to evaluate the time-varying effect.Based on the modified Cam-clay model,the water-soil coupled finite element method was used to study the time-varying law of the failure envelope of shallow foundation on normally consolidated clay seabed under preloading.After verification of the proposed finite element model,the failure envelopes of the shallow foundation on the soft clay seabed under composite loading mode were obtained through displacement-controlled probe tests.And then the influences of preloading and the degree of consolidation on bearing capacities and failure envelopes of shallow foundation were discussed.Moreover,the methodology for calculating the failure envelopes of shallow foundation considering preloading was summarized.The results show that:the consolidated uniaxial bearing capacity increases linearly with the preloading ratio,which reaches the maximum in horizontal loading;the proportion of gain in partially consolidated bearing capacity is independent with the preloading ratio,but it changes with the degree of consolidation;the shape of failure envelopes is controlled by the preloading ratio,while the size is controlled by both the preloading ratio and the degree of consolidation.The research provides a reference for time-varying bearing capacities assessment of offshore shallow foundations.