Highway Tunnel Ahead Geological Study Of Advanced Drilling Geological Prediction In Mountain Tunnel On The Shitian Highway In Gansu Province

In the few years, tunnel construction in China are mainly in the northwest, southwest andother complex geological region, and gradually develops in the deeper buried andlonger-range direction. So, in the tunnel construction, we often can’t avoid encountering suchbad geological bodies，like karst cave、the weak rock、the rich water and gas formation, if thecorresponding construction measures are not on time or improper, which will impact theconstruction progress and increase the construction investment, moreover,will threaten the lifesafety of construction personnel. However, at present, we mainly adopt geophysicalprospecting forecast in tunnel construction, due to many factors, which often fail to reach aquite accurate prediction effect. In contrast, the advanced geological drilling forecast has lessinterference factors, whose drilling data results are more clear and whose interpretation aremore accurate, so it should be paid more attention.Xiaochuan and Chengzhou tunnel are as the engineering support in the paper, which arethe part of the Shitian Highway in Gansu province. We made percussive drilling and coredrilling respectively in the two tunnel, and made geological interpretation of their results.Then, we can make a comparison with the practical geological conditions of thecorresponding tunnel face, in order to get the correlation of the drilling parameters ofpercussive drilling with the actual geological conditions of rock mass, and get the degree inwhich the drilling core samples can reflect the actual rock mass condition, so as to improvethe accuracy of advanced drilling geological prediction. The main results are as follows:1.There are some relevant contacts in the geological characteristics of rock with the fourdrilling parameters, torque、boost pressure、drilling speed and rotational speed, such asmudstone interbedded with breccia, basal conglomerate, conglomerate with water,conglomerate bedding development, fractured joints etc. Meanwhile, limestone, conglomerate,and mudstone, due to the different geological composition and structure, form a differentvariation of the parameters in the whole.2.Core drilling prediction is intuitive and accurate, but there is deviation in thepredication of the specific location of rock, especially in the complex geological area wheregetting the core is very difficult. And as the percussive drilling prediction, core drillingprediction also has the fault with the quite a little predication section. So after the completionof the drilling, we still need to continue the description of the working face geologicalcondition, as a supplement and perfect to forecast results.