Geology topics

Chyan-Deng Jan

Publications and source records attributed to Chyan-Deng Jan.

3 recordsLinked to original sources

USGS1992

Computer simulation of dry layered granular flow down an incline composed of grains

Experiments show that gravity-driven dry granular flows are essentially layered for smooth spheres. This paper describes layer-to-layer interaction in the flow. Assuming two-dimensional flow and neglecting the interaction of grains within the same layer, one may idealize the problem as an elastic sphere under external forces moving down an incline within a layer of identical spheres placed equally apart. The moving sphere is thus subjected to the total gravitational force which includes the weight of a specified number of layers of spheres above it and its own weight. With such a mechanical approach, estimates can be made for the magnitudes of collisional and non-collisional stresses.

Conference Paper↗

USGS1992

Numerical simulation of a sphere moving down an incline with identical spheres placed equally apart

This paper describes a numerical study of an elastic sphere moving down an incline with a string of identical spheres placed equally apart. Two momentum equations and a moment equation formulated for the moving sphere are solved numerically for the instantaneous velocity of the moving sphere on an incline with different angles of inclination. Input parameters for numerical simulation include the properties of the sphere (the radius, density, Poison's ratio, and Young's Modulus of elasticity), the coefficient of friction between the spheres, and a damping coefficient of the spheres during collision.

Conference Paper↗

USGS1990

Rheological properties of simulated debris flows in the laboratory environment

Steady debris flows with or without a snout are simulated in a 'conveyor-belt' flume using dry glass spheres of a uniform size, 5 or 14 mm in diameter, and their rheological properties described quantitatively in constants in a generalized viscoplastic fluid (GVF) model. Close agreement of the measured velocity profiles with the theoretical ones obtained from the GVF model strongly supports the validity of a GVF model based on the continuum-mechanics approach. Further comparisons of the measured and theoretical velocity profiles along with empirical relations among the shear stress, the normal stress, and the shear rate developed from the 'ring-shear' apparatus determine the values of the rheological parameters in the GVF model, namely the flow-behavior index, the consistency index, and the cross-consistency index. Critical issues in the evaluation of such rheological parameters using the conveyor-belt flume and the ring-shear apparatus are thus addressed in this study.

Conference Paper↗