Abstract: A substantial amount of research work and superlong and deepburied horizontal drilling tests have been conducted on the survey and design of the SichuanTibet railway to study the feasibility of implementing superlong horizontal drilling in the deepburied tunnel of the SichuanTibet railway and the influence of horizontal drilling on tunnel construction under complex geological conditions. According to the tunneling index and drilling speed, the influence of superlong advance horizontal drilling on the construction period by drilling and blasting and tunnel boring machine (TBM) methods is studied. The results reveal the following: (1) In unit length, the better the geological conditions of surrounding rock, the deeper the drilling depth and the faster the tunneling speed, and the greater the influence of advance horizontal drilling on the construction. (2) When advance horizontal drilling is carried out 180 m behind TBM equipment in the surrounding rock of grades Ⅱ and Ⅲ, horizontal drilling progress is difficult to keep up with the TBM′s construction speed, and the significance of drilling for construction guidance is relatively small. Whereas in the surrounding rock of grades Ⅳ and Ⅴ, it can catch up with the TBM construction tunnel face by a certain distance, making it crucial to guide the tunnel construction in complicated geological conditions such as when TBM construction is interrupted. (3) Longdistance continuous horizontal drilling at the shield has the greatest impact on the tunnel construction, accounting for up to 85.11% of the total. Comprehensive analysis shows that advance horizontal drilling is better suited in the fault fracture zone, strong and highpressure waterrich, karst, and other unfavorable geological sections.

Key words: SichuanTibet railway tunnel, drilling and blasting method, tunnel boring machine (TBM), advance horizontal drilling; construction efficiency analysis