Boletín de la Sociedad Geológica Mexicana Volumen 70, núm. 3, 2018, p. 731- 760 http://dx.doi.org/10.18268/BSGM2018v70n3a8

Titan2F code for lahar hazard assessment: derivation, validation and verification

Gustavo A. Córdoba^1*, Michael F. Sheridan², Bruce Pitman³

¹Department of Civil Engineering, University of Nariño, Pasto, 52001, Colombia.
²Center for Geohazards Studies and Department. of Geology, University of Buffalo, Buffalo, NY 14260, USA.
³Center for Geohazards Studies and Department of Mathematics, University of Buffalo, Buffalo, NY 14260, USA

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Abstract

Debris flows, lahars, avalanches, landslides, and other geophysical mass flows can contain material in the order of O(10⁶–10¹⁰) m³ or more. These flows commonly consist of a mixture of soil and rocks with a significant quantity of interstitial fluid. They can be tens of meters deep, and their runouts can extend many kilometers. The complicated rheology of such a mixture challenges every constitutive model that can reasonably be applied: The range of length and timescales involved in such mass flows challenge the computational capabilities of existing models. This paper extends recent efforts to develop a depth averaged “thin layer” model for geophysical mass flows that contain a mixture of solid material and fluid. Concepts from the engineering community are integrated with phenomenological findings in geoscience, resulting in a theory that accounts for the principal solid and fluid forces as well as interactions between the phases, across a wide range of solid volume fractions. A principal contribution here is to present drag and phase interaction terms that conform with the literature in geosciences. The Titan2F program predicts the evolution of the volumetric concentration of solids and dynamic pressure. The theory is validated with data from one-dimensional dam break solutions and with data from artificial channel experiments.

Keywords: Lahar, modeling, depth averaging, two phase flow, debris flow, dynamic pressure.