输电线路强风化软岩挖孔基础抗拔试验研究

Field uplift test of excavated foundation to highly weathered soft rock in transmission line

山区风化程度高的岩基塔位采用挖孔基础,包括直柱挖孔桩、坛子型嵌固、扩底掏挖等3种模型。通过在强风化软岩中开展17组不同模型的挖孔基础上拔试验,分析基础承载性能与破坏机理。荷载位移曲线表明:浅埋时基础呈线性状态分布,深埋时呈缓变型分布;地表竖向位移变化规律表明,基础周围出现显著裂缝表征着基础即将整体破坏,破坏状态为基础本体与周围土体被整体拔出,基础发生整体剪切破坏;基础破裂角随埋深迅速降低,但达到一定埋深后破裂角基本不变;强风化软岩的岩石等代极限剪切强度取32kPa;以单位体积混凝土能承担的上拔承载力为准进行经济性分析,扩底掏挖型模型的经济效益显著。

Excavated foundation of transmission line have been used in mountain weathered soft rock,including column excavated pile model,jar shape embedded model and belled shaft digged model.Field prototype tests of 17 group different models have been carried out for highly weathered argillaceous sandstone.The foundation load bearing characteristics and failure pattern are analyzed based on test data.Load displacement curves show that the distributions are linear for shallow foundation,but the distributions are slowly varying for deep foundation.Based on the surface displacement variation rules,the characterization of foundation overall damaging reflect the significant surface fracture,and the foundation and its surrounding soil are pulled out.The foundation rupture angle reduces quickly with the increasing of foundation depth.But the rupture angle remains constant when the foundation reach a certain depth.By calculation of the test data,the rock equivalent ultimate shear strength of weathered soft rock is 32 kPa.According to the ultimate uplift capacity of unit concrete volume,the economical benefit of the belled shaftdigged model foundation is remarkable.