排桩复合土钉支护结构受力变形机理分析

排桩复合土钉支护结构是近年来在基坑工程实践中得到成功应用的一种新型支护形式,为研究其受力变形机理,在工程案例分析基础上,采用有限元软件建立排桩复合土钉支护结构三维数值模型,模拟基坑分步开挖工况,对排桩侧移、坑后地表竖向沉降、坑底土体隆起变形、土钉轴力及桩身弯矩等进行了研究分析。结果表明:排桩复合土钉支护结构中土钉起着“弱锚杆”作用,相对于纯排桩支护结构,改变了排桩的变形和受力性状;相对于纯土钉支护结构,排桩复合土钉支护结构中土钉轴力峰值较小且靠近基坑侧壁,土钉受排桩-面层系统的拉拔作用,钉头处轴力较大。研究成果可为排桩复合土钉支护结构的设计、施工提供理论参考。

Mechanism Analysis on Strength and Deformation of Row Piles and Soil Nail Composite Supporting Structure

Row piles and soil nailing composite supporting structure is a new type of pit supporting form in application in recent years.In order to study the stress and deformation mechanisms of the composite supporting structure,one project case was analyzed.Then,non-linear 3D models were built using finite element analysis software to stimulate the horizontal displacement of the pile,earth surface setting and horizontal displacement behind pit,pit bottom upheaval,pile axial force and pile moment concerning the contact between soil and pile as well as the contact between nail and soil.From the results,soil nails act as the "weak anchors" in the row piles and soil nail composite supporting structure,which has changed the initial mechanics and deformation status of row piles;compared with soil nail supporting structure,the maximum value of soil nail axial force is smaller and its place is near pit lateral wall,soil nail is in tension and nail tip force is very big.Relevant results got from this study can well serve the optical design and field construction of row piles and soil nail composite supporting structure theoretically.