穿越充填溶洞时单桩沉降计算方法研究

Study on calculation method for settlement of a single pile crossing filled karst cave

采用圆孔扩张理论提出竖向受荷桩周地层对充填溶洞的水平和竖向作用力计算方法,采用Mindlin解建立溶洞段应力增量计算方法,基于桩-土(岩)界面、桩-溶洞界面的Boxlucas1荷载传递模型提出考虑地层-溶洞-桩共同作用的穿越充填溶洞型单桩沉降迭代计算方法。通过案例分析验证本文计算方法的合理性。根据参数分析结果,研究溶洞与桩顶的距离、溶洞半径、溶洞充填物剪切强度、桩径、桩长等对单桩承载特性的影响规律。研究结果表明:本文建立的计算方法可用于分析单桩穿越单个或多个充填溶洞时的承载特性;充填溶洞距离桩端越远、半径越小、充填物剪切强度越强,单桩承载力越大。

Based on the theory of round hole expansion,the calculation method of horizontal and vertical force of stratum on filling karst cave caused by the vertically loaded single pile was proposed.The calculation method was established to predict the stress increment in karst cave section by using the Mindlin's solution.Based on Boxlucas1 load transfer models of pile-soil or rock interface and pile-karst cave interface,an iterative calculation method was proposed to predict the settlement of single pile crossing filled karst cave considering the interaction of stratum,karst cave and pile.The rationality of the present calculation method was verified by using the case analysis.Furthermore,the influence of the distance between karst cave and pile top,karst cave radius,karst cave filling,pile diameter and pile length on the bearing characteristics of single pile was studied.The results show that the present method is suitable for the analysis on the settlement of a single pile crossing a single or multiple filled caves.The further the filled cavity is from the pile tip,the smaller its radius,and the greater the shear strength of the filling material,the higher the bearing capacity of the single pile.