Effect of gravitational force on the nature of breakdown of the upper layer of a two-layer model

Under existing conditions at depths on the order of hundreds of meters, gravitational force is comparable with the strength of rocks, and with an increase in depth it becomes controlling. In this paper, a two-layer model is considered in which the upper layer is almost dry sand, a material where gravitational force is controlling. A study is done of mechanisms for deformation and breakdown of the upper layer of a two-layer model in which gravitational force is controlling with uniform tension or compression for the lower layer. A diagram of the experimental device is shown. Both uniaxial and biaxial deformation were studied. Diagrams show the formation of different fissure families, and the dependence of average distance between neighboring fault planes on sand layer thickness is presented.