PHASE TRANSITIONS IN THE DEBRIS FLOW GEOSYSTEMS

Abstract

The evolution of a geosystem can be described as a continuous process. Stages of geosystems evolution: the formation of a massif of loose rocks in a site, its transformation to potential massifs due to diagenesis and morphogenesis, the occurrence and movement of a debris flow, unloading of large-block and then – fine-dispersed material and the passage of a debris-flow. Each stage of the geosystem evolution can be described as a transition from one subsystem level to another and the change of states of the system – as phase transitions of first kind. Physical processes occurring within the system cause it. The most important transition is from a solid state (potential debris-flows massif-conditionally homogeneous solid having an internal structure) to a and mudflow (quasi-liquid state). The transition of a potential massif to another phase state is due not only to external factors (the inflow of free water into the site), but also internal: the mineralogical composition of rocks of the potential massif (the content of hydrophilic minerals). The most important parameter that determines both the connectivity of the soils of the potential massif and the conditions of its transition to the liquid phase are the electric forces at the contacts between the elements of the mineral skeleton (soil particles). Electrical forces provide a connection between the ground particles. The liquid component of the mudflow is traditionally described as a debris-flow suspension, but a coherent and mudflow is not a suspension. A suspension is a dispersed system consisting of a solid dispersed phase and a liquid dispersion medium in which the solid is uniformly distributed as minute particles in a liquid substance in suspension. Such a medium is not able to carry over long distances block-boulder material having a higher density than the suspension. Nevertheless, a coherent and mudflow is a conditionally single-phase system in which water is predominantly in a molecular bound state. The physical analogue of a coherent and mudflow is a colloidal system, since in a connected village fine-earth particles are distributed in a continuous dispersion medium and do not precipitate. This circumstance is key in the physical modeling of connected debris-flows and mudflows.