大断面黄土隧道初期支护与围岩相互作用机理研究

摘要

Based on the large-section (excavation area of 170m2) loess tunnel on the Zhengzhou-Xi'an High Speed Railway,the action mechanisms of different steel frames were studied in order to identify the applicable conditions for the profile steel frame and the lattice girder frame.In addition,site tests were carried out in the shallow old-loess tunnel with the aim of comparing the performances of the profile steel frame and lattice girder frame.The results show that the deformations of the two types of steel frames are equivalent and both their stresses are within the allowable range.However,there is less stress in lattice girder frame.Additionally,the contact pressure distribution between the rock mass and primary support with the lattice girder frame is relative uniform.There are no obvious differences between the two compound supports when it comes to controlling crown subsidence in the large-section loess tunnel,and their horizontal convergences are almost the same.Based on a concrete early strength test,the characteristic curves of the compound support and rock mass were obtained,the interaction mechanism of the rock mass and compound support was studied,and the applicable conditions of the lattice girder frame in the large-section loess tunnel and the design parameters of the primary support under different surrounding rock conditions were determined.%依托已修建并投入运营的郑西高速铁路,针对开挖面积达170m2的大断面黄土隧道,进行了不同钢架形式作用机理的研究,明确了型钢拱架和格栅拱架的适用条件；采用现场对比试验等研究手段,在浅埋老黄土隧道中分别设置了型钢钢架、格栅钢架对比试验段.试验结果表明,两种钢架初期支护变形相当；两种钢架的应力均在允许值范围之内,但格栅钢架应力较小；格栅钢架的围岩-初期支护接触压力分布较均匀；两种钢架组合支护在控制大断面黄土隧道拱顶下沉方面无明显差异,水平收敛基本相等.另外,基于混凝土早期强度试验,采用围岩-结构法,根据组合支护与围岩的特征曲线,研究分析了围岩与组合支护的相互作用机制,最终得出了格栅钢架在大断面黄土隧道中的适用条件,以及在不同围岩条件下初期支护的设计参数.