The study on the mechanism of imbricate fan using numerical methods

Taiwan is an active orogenic belt formed by oblique convergent between the Philippine Sea Plate and the Eurasian Plate. This active orogeny consists of serials of folds and faults of typical accretionary wedge. Because of high activity, the Island has abundant geological structures. Serials of overlapped fold and fault structures in the foreland regime have been recognized as an imbricated fold-and-thrust belt. Despite of numerous regular distributed imbricate structure has been identified, the conditions and the mechanics still not been fully resolved. By the way, the mechanism of imbricate structure is also a key to discover the orogenic processes. his research uses distinct element method, PFC2D, as well as the finite element method, ABAQUS, to simulate the formation of imbricated thrust system. By means of numerical simulation, we would be able to understand the mechanism of imbricate fan, the change of principal stress direction, the stress field and stress state, as well as the material proprieties etc. that might affecting the structure evolution. he primary result demonstrates that the so-called “imbricate fault system” could be achieved under certain conditions, including sufficient overburden and the moment transmission between particles.imulating the imbricate trust system, the deformation of competent layer may be divided into three parts: the constant speed domain, the faulted domain, and the speed drop domain. These regions of velocity discontinuity illustrate the phenomena of strain or energy accumulation during the squeezing experiments. Since the threshold has been achieved, the faulting process may occur in order to reduce the strain energy. As a single fault has been developed and confined by the confining pressure, the fault system could not prorogate infinitely. However, a series of thrust system will be formed, and the stick-slip phenomena could be identified in a single fault plane. A serial of faults finally linked together in order to accommodate the total deformation. In this case the decollements have been generated between the interface of competent layer and the matrix.his research demonstrate the influence of confining pressure, the friction coefficient, the bonding types and strengths, as well as ratio of stiffness of rock materials that strongly affect the development of imbricate thrust system.