Cause analysis and treatment measures to the abnormal subsidence of Gantangjiang bridge No.19&20 piers of Guiyang-Guangzhou railway
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摘要: 2014年5月15日~9月1日期间,已建成的贵广铁路甘棠江特大桥19号墩基础产生了50.6~52.2mm的异常下沉,20号墩基础产生了12.4~16.3 mm的异常下沉.现场补充完成了机动钻探、原位测试及室内试验工作.分析认为在多年强降雨条件下,深覆盖型岩溶强烈发育区的岩溶水水位波动产生潜蚀引起的岩溶塌陷,是导致该桥19、20号墩(采用摩擦桩基础,桩长约20 m)产生异常沉降的主要原因.对19、20号桥墩基底采取端承桩基础补强后,经过近2年的沉降观测,没有再发生异常沉降.文章认为在类似深覆盖型岩溶强烈发育区实施桥梁工程时,原则上应采用置于完整基岩内的端承桩基础.Abstract: From May 15,2014 to September 1,the No.19 and No.20 piers of Gantangjiang super major bridge at Guiyang-Guangzhou railway had experienced abnormal subsidence with the downward displacement of 50.6-52.2 mm and 12.4-16.3 mm,respectively.In order to understand the reason of the subsidence and to propose appropriate measures to the problem of bridge pier displacement,mobile drilling,in situ and laboratory geotechnical tests were completed.Field observation and testing data jointly shew that the agelong heavy rainfall condition and subsequent underground karst water fluctuation caused karst collapse occurred at the underlying strongly karstified limestone.This was the main reason of geological impact on the subsidence of No.19 and No.20 piers with friction pile foundation and the pile length of about 20 m.For engineering remediation,end bearing pile foundations were respectively added in the both bridge piers.After about 1 year's displacement monitoring,the subsidence of the piers has been properly controlled,which suggest that the reinforced measurement is safe and reliable;and the end bearing pile foundation is generally suitable when other railway bridges are carried out in the similar case of deep covered strong karst limestone area.
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