Stratigraphic Classification Based on the Evaluated Difficulty of the Construction by Using Shield Tunneling Machine

There are diverse stratigraphic classifications in tunneling, which played a vital role in engineering practice. Current rock classifications were basically developed for mining method tunnel where the ground stability was the main evaluation index. However, in shield tunneling, we paid more attention to the boreability of strata, the wear of cutters, the stability of heading face, as well as the ground movement. What's more, the current classifications failed to take the complex strata into account, but this factor might have the major impact on shield tunneling, and sometimes even played the decisive role. So the ordinary classifications had certain limitations when were applied in shield tunneling. In order to classify the strata based on the difficulty of shield tunneling, four evaluation factors were selected, including drivage efficiency, cutter wear, heading face stability, as well as ground loss and displacement. According to the difficulty of cutting and deformation control, the ground was divided into four categories, including easy to cut and easy to control, easy to cut and hard to control, hard to cut and easy to control, hard to cut and hard to control as well, and corresponding suggestions for each category were put forward in the end. This stratigraphic classification can make up for the limitations of the current classification and provide practical references for control measures in shield tunneling.