大断面深埋黄土隧道锚杆作用效果的试验研究

 黄土隧道系统锚杆的作用效果问题一直是争论的焦点，依托正在修建的郑州—西安铁路客运专线大断面黄土隧道工程，采用现场对比试验方法对深埋黄土隧道系统锚杆的作用效果问题进行研究。为了使试验结果有可比性，选取试验条件基本相同的函谷关隧道洞身段作为试验段，分别设置有系统锚杆段45 m和无系统锚杆段45 m进行对比试验。对比试验的测试项目有：拱顶沉降、拱脚沉降、水平收敛、围岩压力、初支钢架应力及锚杆轴力等。试验结果表明：有系统锚杆段与无系统锚杆段的拱顶沉降和水平收敛基本相等；两者的土压力和钢架应力相差不大；锚杆轴力较小，且拱部锚杆受压，边墙锚杆受拉。综合分析后认为，拱部系统锚杆作用效果不明显，取消拱部系统锚杆可减少施工工序，加快开挖面的封闭和全断面初期支护的及早闭合，从而能更好地控制支护结构变形，并节约工程投资。

EXPERIMENTAL RESEARCH ON BOLT ANCHORAGE EFFECT ON LARGE-SECTION DEEP-BURIED TUNNEL IN LOESS

It has been a focus under debate on how the system bolts operate in the loess tunnel for a long time. Associating with the large-section loess tunnel construction of Zhengzhou—Xi¢an high-speed passenger railway， many in-situ comparative tests on evaluating the effect of systematic bolts are performed. For the good comparability of the testing results，the tunnel that has the similar test condition is considered. In this case，the Hanguguan tunnel with experimental sections of 40 m in length with/without systematic bolts is selected. The main comparisons are covered in the settlement of arch crown and foot of the tunnel，horizontal convergence，surrounding rock pressure，the stress of initial supporting steel framework，axial force of bolt，etc.. The test results indicate that both the two sections have almost the same settlement in the tunnel arch crown；and the section with systematic bolts has a little higher horizontal convergence than the one without systematic bolt system. It also shows there is little difference in the soil pressure and steel framework stress between the two sections；there is lower axial force for the systematic anchorage and the corresponding part of arch crown is in compression state. Through comprehensive analysis，it is found there is little improvement of supporting effect on the arch crown bolt，thus it is suggested the bolt to induce the construction procedure and quicken the enclosed time of the initial supporting section of the tunnel can be ignored. It will be helpful for controlling the supporting settlement and deformation；and it can also reduce the investment and cost.