基坑钢支撑伺服系统应用技术研究

为提高钢支撑轴力伺服系统的应用水平,充分发挥其变形控制能力,以深圳城市轨道交通12号线的下穿城际铁路高架结构车站基坑—和平站基坑为依托,采用数值模拟和理论分析等方法,对伺服系统应用下的轴力设定值确定方法、伺服系统布置方式、伺服支撑体系节点计算3个方面展开系统研究,并形成一套完整的伺服系统应用方法。结果表明： 1）通过双控法指导数值模拟计算,可以确定各道钢支撑较为合理的轴力设定值。2）伺服系统作用效果与其数量及布置位置有关。在数量一定的情况下,伺服系统的平均标高越低,变形控制效果越好,但浅层伺服系统的控制效能欠佳。3）对于直径800 mm、壁厚20 mm的伺服支撑,采用4.6级或4.8级的普通螺栓即可满足受力要求; 对于两端的钢围檩,建议在其与支撑管节接触范围背后添加2道加劲肋以改善变形及受力状态; 设置抱箍结构可有效抑制管节体系的空间侧向屈曲变形,且设置在二分点处可最大程度发挥变形控制能力。

Research on Application Technology of Steel SupportServoSystemfor Foundation Pit

The application level of steel support axial forceservo system are needed to improve andtheir ability to control deformation should be given full play. The elevatedstructure Heping Station foundation pit of Shenzhen Urban Rail Transit Line 12undergoes the inter city railway. Based on this projectand with the method of numerical simulation and theoretical analysis, the paperconducts a systematic study on three aspects of servo system, namely, thedetermination method of the axial force setting value, arrangement and nodecalculation. Thus a complete set of servo system application method is formed.The results show that: (1)The reasonable axial force setting value of eachsteel support can be determined by using the double controlmethod to guide numerical simulation calculation. (2)The effect of servo systemdepends on its quantity and position. Under a certain number of conditions, thelower the average elevation of the servo system is, the better the deformationcontrol effect is, while the control efficiency of the shallow servo system ispoor. (3)For servo straighteners with diameter of 800 mm and wall thickness of20 mm, ordinary bolts of level 4.6 or level 4.8 can meet the stressrequirements. For steel enclosing purlin at both ends, it is suggested to addtwo stiffeners behind the contact range between steel and support pipe joint toimprove deformation and stress state. The hoop structure can effectivelyrestrain the lateral buckling deformation of the pipe joint system, and it cangive full play to its deformation control ability at the equinox.