Deep foundation pit supporting system often causes the underground environment pollution,some hidden dangers are buried for the later development of underground space.This problem can be solved well by the recycling technology of supporting system.Taking an existing foundation pit as the engineering background,the safety of existing foundation pit can be ensured by use of the new technology,such as recycled steel piles 、cable,and so on.In order to take advantage of the existing supporting structures,there are two kinds of reinforcement scheme selected,one is recycling anchors + middle beams,it is be applied to the east side and north side of the foundation pit to enforce the original stone masonry retaining wall;to remove the original wall of the south side and west side,vertical excavation,the other scheme is recycling steel pipe pile + recycling anchor + recycling steel top beam.According to the foundation construction schedule,the anchor cables、top beam and steel pipe pile are recovered layer by layer,the construction of recovery is simple and easy,the recovery rate is about 97％ ～ 100％.By monitoring the steel pipe pile displacement、the internal force of anchor rope and the deformation at the top of foundation pit,the support scheme is safe、reasonable,the cost is reduced about 20％ ～30％,meanwhile saving resources,it is a good solution to the supporting structure of the underground pollution problems.This project is a beneficial attempt for the recyclable technology in the reinforcement of existing foundation pit,it provides a reference for the popularization and application of the recycling technology of foundation pit supporting.%深基坑支护往往造成地下环境污染,为后期地下空间开发埋下隐患.支护结构的可回收技术可以较好的解决这一难题.依托某既有基坑工程的改建加固,采用可回收钢管桩、可回收锚索和冠梁等可回收技术将新老支护体系有机融合.充分利用现有支护结构,基坑东侧、北侧对原有砌石挡墙采用四道腰梁+可回收锚索的支护方法;南侧和西侧拆除原有挡墙,垂直开挖,采用可回收钢管桩+可回收锚索+可回收钢冠梁的支护方案.根据基础施工进度,逐层回收锚索、冠梁和钢管桩,回收施工简单易行,回收率为97％～100％.通过对钢管桩深部位移、锚索内力和基坑的变形监测,结果表明支护方案是安全、合理的,而且成本降低20％～30％,节省了资源,很好的解决了支护结构对地下的污染问题.这一工程是可回收技术在既有基坑改造中的有益尝试,为基坑支护可回收技术的推广应用提供了借鉴.
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