The use of tunnelling parameters and spoil characteristics to assess soil types: a case study from alluvial deposits at a pipejacking project site

Generally, when there are only a few boreholes present along a tunnel design alignment, geological understanding of the worksite may not be adequate and the ability to optimise the tunnelling parameters is limited. This lack of boreholes will cause an increased potential of geo-hazards during tunnelling works. This study proposes an alternative method to determine the major and other components of ground under such circumstances. Five factors, cutter wheel torque, sieve residue, flow rate of feedline, pressure in the feed and discharge lines and density of bentonite slurry, are adopted for determining the major and other ground components. Comparisons of the soil types based upon the results of grading and Atterberg limits tests on the spoil and soil samples, respectively, and those resulting from the proposed method indicate good consistency. The proposed method provides an opportunity for establishing a more comprehensive geological structure for refining the tunnelling parameters, reducing the potential of geo-hazards associated with the inappropriate tunnelling parameters.