砂卵石层串珠状溶洞地质条件下大直径单桩水平静载试验及数值仿真分析

Horizontal Static Load Test and Numerical Simulation Analysis of Large-diameter Single Pile under Geological Conditions of Beaded Karst Cave in Sandy Gravel Strata

砂卵石和串珠溶洞地质条件下的桥梁桩基水平承载力和变形机理研究目前并不充分。为合理确定该地质条件下无铰拱桥桩基水平承载力,开展了现场水平静载试验,分析了该类地质条件下桩基水平承载力的合理值,为类似工程提供参考。并运用GTS有限元软件开展了数值模拟,建模以修正摩尔库伦模型模拟砂卵石层,并在桩土之间设置Goodman接触单元,在桩端设置桩端单元。同时假定串珠状溶洞为椭球状分布,为防止计算出现不收敛的情况,对空腔内部进行特殊处理,采用统一理论模拟钢护筒和筒内混凝土。在此基础上,分析了桩顶受荷时H-Y曲线和H-ΔY0/ΔH曲线,并将数值结果与实测结果进行了对比。结果表明,在合理运用本构模型和土工参数情况下,有限元数值仿真结果与现场试验结果吻合度较高,有限元软件可以作为确定这种特殊地质条件下桩基水平承载力的有力技术手段,为确定单桩水平承载力提供新思路。

At present,the research on the horizontal bearing capacity and deformation mechanism of bridge pile foundation under the geological conditions of sandy gravel and beaded karst cave is not sufficient.In order to reasonably determine the horizontal bearing capacity of pile foundation of unhinged arch bridge under this geological condition,the on-site horizontal static load test is carried out,and the reasonable value of horizontal bearing capacity of pile foundation under this kind of geological condition is analyzed in order to provide the reference for similar projects.And the GTS finite element software is used to carry out the numerical simulation.The Mohr Coulomb model is modified through the modeling to simulate the sandy gravel strata.The Goodman contact element is set up between the pile and the soil,and the pile tip element is set up at the pile tip.At the same time,it is assumed that the beaded karst cave is distributed in ellipsoidal state.In order to prevent the calculation from the non-convergent situation,the interior of the cavity is specially treated.The unified theory is used to simulate the steel casing and the concrete in it.On this basis,the H-Y curve and H-ΔY0/ΔH curve of the pile top under loading are analyzed,and the numerical results are compared with the measured results.The results show that the results of finite element numerical simulation are in good agreement with the field test results under the rational use of constitutive model and geotechnical parameters.The finite element software can be used as a powerful technical means to determine the horizontal bearing capacity of pile foundation under this special geological condition,which provides a new idea for determining the horizontal bearing capacity of a single pile.