环梁-桁架支撑体系在大型基坑工程中的应用

研究目的：北京西站地下行包库是北京西站改扩建工程中的一个重大项目,对整个工程的进度起着控制作用。通过本研究,拟找到一个施工便捷、结构合理的支护体系。研究方法：根据地质情况、周围环境要求、工程功能、当地的常用施工工艺设备以及经济技术条件综合考虑、因地制宜地选择支护结构的类型。采用理正单元计算、理正整体计算与SAP84计算相校核的计算方法,并对极限平衡法和弹性支点法的计算结果进行对比分析。研究结果：采用人工挖孔桩围护结构＋圆形环梁-桁架支撑的支护体系,其结构受力体系合理,便于施工,经济指标合理。研究结论：圆形环梁-桁架支撑的支护体系结构受力合理,适用于平面尺寸大、长宽尺寸接近、四周地层性质接近、抗力接近的基坑;混凝土圆形环梁结构受压合理,整体稳定性好;桁架体系整体性强,采用钢构件施工速度快;单撑式围护结构可以采用极限平衡法计算。

Application of Rounded Ring and Beam-trussed Bracing System in Excavation of Large Foundation Pit

Research purposes:Construction of the underground luggage warehouse in Beijing Xi Station is an important part of reconstruction of Beijing Xi Station,which has significance to the process of the reconstruction,so it is necessary to seek a bracing system with rational structure for rapid reconstruction through doing researches.Research methods:The rational type of bracing system should be selected according to the geologic conditions,surrounding environmental requirements,project functions and local commonly-used construction technique and facilities as well as technical and economic conditions.The comparison and analysis of the computing results obtained by limiting equilibrium method and elastic fulcrum method are made with logic unit computing,logic united computing and SAP84 computing.Research results:The bracing system of artificial pile exterior-protecting structure-rounded ring-beam-trussed support is adopted with rational bearing system to the structure,easy construction and rationalization in economy.Research conclusions:The bracing system of rounded ring beam and trussed beam has the feature of rational bearing to structure and is suitable for supporting the foundation pit with large plane size,quasi-long and wide sizes,quasi-surrounding-stratum nature and quasi-resisting force.The concrete circular ring structure has the feature of rational bearing with good entire stability and the truss system has the feature of good unity.The construction can be conducted rapidly with steel component and the limiting equilibrium computing can be adopted to single exterior-protection structure.