Abstract: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.