岩溶地区既有桩基础病害加固设计及数值分析

某既有线桥梁在上部荷载长期作用下,桥墩产生沉降和倾斜,危及行车安全。勘察表明,该桥墩基础下分布有溶洞。基于突变理论,根据岩溶区桩下卧溶洞顶板失稳破坏条件,确定了位于溶洞顶部原桩的承载力;在此基础上,针对岩溶分布特征和地基承载特性,采用增补桩基-扩大承台主动加固法对其进行加固,通过理论计算确定合理桩长;同时,采用数值模拟软件,分析了桥墩基础加固前后的稳定性,以及增补桩基桩长与桥墩基础沉降和倾斜的关系。结果表明：数值计算结果与理论计算结果吻合,原桥墩基础承载力不满足设计要求,增补桩的合理长度为14.5 m,已穿透溶洞,此时承台中心沉降为6.9 mm,纵桥向承台最大沉降差为0.89 mm。

REINFORCEMENT DESIGN OF THE DISEASE PILE FOUNDATION OF EXISTING BRIDGE IN KARST AREA AND NUMERICAL ANALYSIS

The settlement and inclination of the pier of existing railway bridge is caused by the upper long-term load,which has been affected the running safety.Geological exploration found that a large karst cave is located under the bridge pier foundation.Based on the catastrophe theory,according to the instability conditions of cave roofs the bearing capacity of the original piles was calculated.On this basis,consolidation strengthening was required for the foundation by using the method of adding piles and enlarging bearing platform,according to the distribution of karst cave and the geological characteristics.And the proper length of adding piles was provided by theoretical calculation.What is more,the relationship between the length of adding piles and the settlement and inclination of the pier was analyzed,based on the numerical simulation software.The results showed that the numerical calculation results agreed with those of theoretical calculation.The bearing capacity of the original bridge pier foundation could not meet the design requirements.The proper length of adding piles was 14.5 m.The settlement and the maximum settlement difference in lognitudinal direction of the bearing platform with the proper length of adding piles was 6.9 mm and 0.89 mm respectively under the upper loads.