基坑工程内支撑抱箍式活络头试验研究

摘要

In order to study the stiffness and ultimate bearing capacity of the traditional disconnectable coupling and differ-ent interface hoop-disconnectable coupling (no-knurling,straight-knurling and hatching-knurling),laboratory prototype ex-perimental was done to observe the loading process and failure characteristics as well as analyze different design parame-ters’effect on displacements,strain and bearing capacity.The main conclusions are drawn as follows:the hoop-discon-nectable coupling's stiffness is higher than the traditional and under the same load of 1 200 kN,the displacement of the tra-ditional is 1 .5 or 4 times as large as the hoop-disconnectable coupling’s;the specimens can be reused under normal opera-tion;when the ultimate bearing capacity is reached,the tiny brittle failure occurs on the hoop-disconnectable coupling, which can continue carrying after slipping;due to the clamping of the bottom bolt,when the adjustable length is short, namely the contact area becomes larger,the carrying capacity instead decreases;the bolt’s pretension is essentially un-changed under the axial compression.Overall,the hoop-disconnectable coupling has good mechanical properties which can help improve the security and stability of the supporting system in the excavation engineering.%为了研究传统基坑工程钢支撑活络头和不同接触面处理（无滚花、直纹滚花、网纹滚花）的新型抱箍式活络头刚度特性和极限承载力，进行了室内原型试验，观察其受力过程和破坏特征，分析了不同设计参数对位移、应变、承载力的影响。试验研究结果表明：抱箍式活络头整体刚度高于单缸千斤顶支顶活络头，在荷载为2000 kN时，单缸千斤顶支顶活络头位移约是抱箍式活络头的1．5～4倍；在正常使用状态下，试件可重复使用；在达到极限承载力时，抱箍式活络头发生微小脆性滑移破坏，滑移之后可继续承载；由于底部螺栓的夹持作用，抱箍式活络头调节长度短时，即接触面积大时，承载力反而减小；在轴向压力作用下，抱箍式活络头螺栓预拉力基本不变。总体上看，抱箍式活络头具有良好力学特性，有助于提高基坑工程内支撑体系的安全性和稳定性。