基坑工程内支撑抱箍式活络头试验研究

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2 000 k N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。

Experimental Study of Hoop-disconnectable Coupling in the Internal Support System of Excavation Engineering

In order to study the stiffness and ultimate bearing capacity of the traditional disconnectable coupling and different interface hoop-disconnectable coupling（ no-knurling,straight-knurling and hatching-knurling）,laboratory prototype experimental was done to observe the loading process and failure characteristics as well as analyze different design parameters＇ effect on displacements,strain and bearing capacity. The main conclusions are drawn as follows： the hoop-disconnectable coupling＇s stiffness is higher than the traditional and under the same load of 1 200 k N,the displacement of the traditional is 1. 5 or 4 times as large as the hoop-disconnectable coupling＇s; the specimens can be reused under normal operation; 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 unchanged 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.