Abstract: This paper presents a case history of construction of the segment between Huanghe Road Station and Huaihe West Station of Qingdao Metro No. 6 Line. A finite element analysis model of the cutting blade in the upper soft and lower hard strata is established by using the three-dimensional dynamic numerical model. The relationships among the load on the cutting blade at the soil-rock interface, the penetration depth and the speed of the cutting head are analyzed. The possible reasons for the slow tunneling rate of the shield in hard-soft heterogeneous ground are explained. The results show that: (1) the greater the penetration depth, the greater the steep load increase at the soil-rock interface; (2) the faster the cutting head rotates, the load increase at the soil-rock interface remains essentially unchanged, but the load growth rate increases (3) In order to reduce the adverse effect of the mutation load at the soil-rock interface on the stability of the blade ring, it is necessary to reduce the penetration depth and the rotating speed of the cutting head, so the tunneling speed of the shield in hard-soft heterogeneous ground is much slower than that of the single formation.

Key words: Hard-Soft Heterogeneous Ground, Shield Cutting Blade, Driving Speed, ABAQUS Simulation