Design practice of local permanent excavation support under complex conditions
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摘要: 工程中较少遇到拟建地下室外墙距离邻近柱基础边极近（约0.66 m）、且局部为永久性支护的基坑工程，如何设计基坑的围护结构和永久性支撑体系是此类基坑工程的难点。根据笔者的设计实践，对围护结构，采用方形支护桩、将锚杆设置在支护桩上以节约避免设置腰梁空间等措施；对永久性支撑体系，设置压力分散型锚杆及锚头部位设置混凝土罩（砼罩内设置箍筋、表面涂水泥基渗透结晶型防水涂料）等措施。第三方监测的基坑水平位移和沉降较小，说明设计合理。Abstract: There are few excavation supporting projects in which the distance between basement exterior wall and column foundation is very close (about 0.66 m) and local permanent excavation support is included. The design difficulty is how to reasonably select the retaining structures and the bracing system. According to the design practice, the measures of square supporting piles and the anchors installed at supporting piles not to be set at middle beam for saving space are adopted for the retaining structures. And the measures of pressure dispersive anchors and anchor heads sealed by concrete cover where stirrup is installed in them and cementations capillary crystalline waterproofing coating materials are coated on their surfaces are adopted for the bracing system. The horizontal displacement and settlement of the excavation provided by the third party are relatively small, and it means that the design for the excavation is reasonable.
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