广东岩溶区某输电塔桩基稳定性数值模拟分析

Numerical simulation research on the stability of transmission tower pile foundations in a karst area of Guangdong Province

采用数值模拟手段研究了广东某岩溶区输电塔桩基与下伏溶洞协同变形的规律。通过不同位置应力、位移、塑性区变化监测,发现覆盖层部分应力分布较均匀,受溶洞影响较小,但溶洞围岩应力变化较大,溶洞顶板出现较大的向下弯曲变形,桩底下移明显,特别是当桩基荷载较大且下伏覆溶洞埋深较浅时,溶洞顶板将可能失稳,进而引起桩基破坏。不同嵌岩深度桩基变形特征表明,桩基嵌岩深度与溶洞变形具有正相关关系。

The research on collaborative deformation of buried caves between transmission tower pile founda-tion in karst area occurred in Ruyuan county,Guangdong Province,China.The geological survey and drill-ing indicated that soils near the transmission tower are mainly alluvial silty clay,alluvial gravel,and residual silty clay.The bedrocks is predominately strongly weathered sandstone,moderately weathered quartz sand-stone,limestone and carbonaceous limestone,which are generally greater than 30m in total thickness. Through drilling,nearly 10 different sizes of caves have been discovered in proximity to the tower.They are beaded or multi-layered in formation,and most are unfilled or half filled,where the overburden is normally 10-30 m,and a minimum of 1-4 m thick.The underlying caves have a large impact on the design,con-struction and operation of the transmission tower foundation.In order to study the stability and deformation of transmission tower foundations in this area,FLAC3D software was used for modele and calculations.By monitoring the stress,displacement and changes in the plastic zone at different positions,it showed that the stress distribution of the overlay is uniform and is minimally impacted by caves.However,the cave rock stress changes greatly.There is large bending down deformation in the roof of caves.Additionally,the bot-tom of the tower foundation moves down significantly,especially when a large stress loads are applied to the foundation and the cave roof,the cave roof would be unstable,leading to structural destruction of the pile foundation.The deformation characteristics of pile foundations with different rock-socketed depth indicate a positive correlation between rock-socketed depth and cave deformation.