ABSTRACT
Wanjiazhai Yellow River Diversion Project is located at Shanxi Province in north part of China. Along the alignment of the diversion tunnel the strata are the loesses of Mid-Pleistocene (Q2) and Upper Pleistocene Series (Q3), red clay (N2) of Pliocene Series and swelling rock of Permian and Triassic Systems. The physical and mechanical properties of them as well as the design and construction counter-measures for tunnelling during the implementation of tunnelling work in these strata are experienced and studied. Furthermore, the main concerns of the methodologies in tunnelling by drill-blasting and TBM excavating are probed too. It is noted that special anti-seepage measures should be taken to the potentially collapsible loesses which will greatly affect the stability of the tunnel. The engineering properties of N2 red clay changes tremendously as the geological condition differs. At the same time, the swelling rock is also introduced in the aspects of methodologies in geological investigation and characteristics of its distribution. It is highlighted from the above that these soils and rocks are characterised by low strength, obviously theological property, and complicated properties upon the influence of water, which will control the self-stablising time and mechanism of failure of the tunnel, therefore, will affect the formulation of methods or plans for excavation and supporting.
