Abstract: The composition and mechanical strength of gravel are highly heterogeneous. The gravels would be separated and destroyed when bearing stress. Part of the strength would regain when it was stacked again. It is difficult to describe it's mechanical behavior of gravel by means of continuum mechanical model. The onsite direct shear test result is simulated by means granule numerical simulation software PFC2D on basis of granule mechanics theory. The influence on granule mechanics mode of size effect is cleared up by means of granule parameter conversion test. The typical granule parameters are gained and the subsidence of gravel strata induced by shield tunnelling is discussed. The study show that the tunnel behavior under gravel strata can be effectively simulated by means of granule mechanics numerical simulation technology.

Key words: gravel strata, shield tunneling, settlement curve, granular mechanics, numerical simulation