间隔双排桩在贵州某红黏土深基坑及其加固中的应用

Application of Double Row Piles with Rakersas the Deep Excavation Support Structure in Guizhou Red Clay

某基坑位于贵州红黏土地区,支护桩成孔完毕后设计条件变化,基坑深度增加约3m。经论证,维持原间隔双排桩方案,制定斜抛撑应急预案,采用增强冠梁、增加桩配筋、预留桩前岩层等方式,动态设计,有效控制了基坑变形,确保了施工安全及质量。结合现场实测数据,贵州红黏土地区基坑抗剪强度设计参数应结合工程实际情况,不宜简单的依据规范进行折减;建议对支护桩进行施工勘察,双排桩设计时应取剩余下滑力与岩土压力的不利值;针对区域类似项目,挡土构件在坑底处的水平位移建议可取5 mm。总结了间隔双排桩设计注意事项,可供类似工程参考。

A deep excavation site in Guizhou was in the read clay soils.After completion of the drilling of the planned double row supporting piles,the design excavation depth increased by three meters.After further evaluation,it was decided to maintain the original double row pile supporting structure with additional internal support with rakers.Other measures,improved walers,increasing the reinforcement in the cast-in-place concrete piles,preserving the rock layer in front of the soldier pile were also utilized.Furthermore,the construction monitoring results indicated that the strength of red clay is higher than the code suggested reduction values.The paper also recommends that geotechnical investigation during construction should be performed so that the site conditions could be better understood.The recommended horizonal displacement value at the bottom of the excavation should be 5 mm.