大断面黄土隧道中型钢与格栅适应性的对比试验

正在修建的郑州-西安铁路客运专线大断面黄土隧道,开挖面积达160m2,因此,开展型钢拱架与格栅拱架研究,明确型钢拱架和格栅拱架的适用条件对设计和施工都具有重要的指导意义。研究方法采用现场对比试验,为了使试验结果有可比性,选取试验条件基本相同的贺家庄隧道洞身段作为试验段,分别设置型钢拱架段40m和格栅拱架段40m。测试内容有:拱顶下沉、拱脚下沉、水平收敛、围岩压力、初支钢架应力等。试验结果表明:格栅拱架比型钢拱架的沉降略大,水平收敛基本相等;格栅拱架比型钢拱架应力小,且应力分布相对均匀;土压力普遍很小,但格栅拱架土压力更小些;隧道掘进四榀钢架(3.2m)后,钢架沉降达总沉降的26%左右,最大应力达总应力的33%左右。经综合分析认为型钢拱架及格栅拱架均能适用于IV级黏质老黄土隧道,但格栅拱架更具优越性。

Comparative tests on section steel and steel grid for loess tunnels with large section

The excavation area is about 160 m2 in the loess tunnel of Zhengzhou-Xi’an high-speed passenger railload, so it is necessary to study different application effect of the section steel and steel grid. It is of important significance to identify the application situation of the section steel and steel grid for the design and construction. Comparative tests are adopted. For the good comparability of the experimental results, the tunnel which has the similar experimental condition is chosen. The Hejiazhang Tunnel is taken as the experimental section in which the section steel and steel grid of 40 meters in length are set, respectively. The main comparison included the settlement of tunnel crown and arch foot, horizontal convergence, surrounding rock pressure, stress of initial supporting steel framework, etc. It is indicated: the section with the steel grid has more settlement and mostly equal horizontal convergence than the one with the section steel; there are less stresses in the steel grid than in the section steel and the former has relatively uniform distribution of stresses; the value of soil pressure is commonly small; but the soil pressure is much higher in the steel grid. After 4 steel frames (3.2 m) of the tunnel are excavated, the settlement of the steel frame reaches about 26 percent of the total settlement and the maximum stress is about 33 percent of the total stress. It is shown by the analysis that the steel grid and section steel are both applicable to the tunnel in the viscous old accumulation loess of degree IV, but steel grid is more advantageous.