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本项目为北京市二环内中心城区单体最大的基坑之一,基坑深度15 m,占地面积33000 m2。基坑地下管道和洞穴密布,西侧紧邻主干道、管线复杂并有管道埋深达9 m,基坑边沿存在3棵国家一级名贵古树。对于古树保护,设计考虑了风荷载的不利影响,提出了近似计算模型,采用了2道预应力锚杆的桩锚支护体系,并结合古树的生长特性进行适度浇水,保障了百年名贵古树的安全;西侧支护体系为上部7 m土钉墙、下部护坡桩,在联梁位置设1排锚杆,锚杆调整角度避开管道;其它区域针对大量不明地下通道和洞穴管线,调查处理了周边所有上游入口,防止雨水冲刷,成功地采用了复合土钉墙支护体系。以上处理方案对于涉及古树保护和地下管线复杂的基坑工程具有一定的借鉴意义。
The project is one of the largest single foundation pits in the downtown area of Beijing’s Second Ring Road, with a foundation pit depth of 15 m and a land area of 33000 m2. The underground pipes and caves of the foundation pit are densely covered, and the west is close to the main road. The pipeline is complex with a buried depth of 9 m. There are 3 valuable ancient trees at the edge of the foundation pit. For the protection of ancient trees, the design considered the adverse effects of wind load, put forward an approximate calculation model, using two prestressed anchor pile and anchor support system, combined with the growth characteristics of ancient trees to moderate water, guaranteed a hundred years Valuable ancient tree security; west of the support system for the upper 7 m soil nailing wall, the lower slope protection pile, the bolt position in the row of bolt 1, anchor to adjust the angle to avoid the pipe; other areas for a large number of unknown underground passage and cave Pipeline, the investigation and treatment of all upstream upstream entrance to prevent rain erosion, the successful use of composite soil nailing wall support system. The above treatment scheme is of some reference to the excavation engineering involving the protection of old trees and complex underground pipelines.