HR: 1340h
AN: H23C-1513    [Abstracts]
TI: Conditions of Fissuring in a Pumped-Faulted Aquifer System
AU: * HERNANDEZ-MARIN, M
EM: mhmarin@vt.edu
AF: DEPT. OF GEOLOGICAL SCIENCES VIRGINIA TECH, 4044 DERRING HALL, BLACKSBURG, VA 24061, United States
AU: BURBEY, T J
EM: tjburbey@vt.edu
AF: DEPT. OF GEOLOGICAL SCIENCES VIRGINIA TECH, 4044 DERRING HALL, BLACKSBURG, VA 24061, United States
AB: Earth fissuring associated with subsidence from groundwater pumping is problematic in many arid-zone heavily pumped basins such as Las Vegas Valley. Long-term pumping at rates considerably greater than the natural recharge rate has stressed the heterogeneous aquifer system resulting in a complex stress-strain regime. A rigorous artificial recharge program coupled with increased surface-water importation has allowed water levels to appreciably recover, which has led to surface rebound in some localities. Nonetheless, new fissures continue to appear, particularly near basin-fill faults that behave as barriers to subsidence bowls. The purpose of this research is to develop a series of computational models to better understand the influence that structure (faults), pumping, and hydrostratigraphy has in the generation and propagation of fissures. The hydrostratigraphy of Las Vegas Valley consists of aquifers, aquitards and a relatively dry vadoze zone that may be as thick as 100m in much of the valley. Quaternary faults are typically depicted as scarps resulting from pre- pumping extensional tectonic events and are probably not responsible for the observed strain. The models developed to simulate the stress-strain and deformation processes in a faulted pumped aquifer-aquitard system of Las Vegas use the ABAQUS CAE (Complete ABAQUS Environment) software system. ABAQUS is a sophisticated engineering industry finite-element modeling package capable of simulating the complex fault- fissure system described here. A brittle failure criteria based on the tensile strength of the materials and the acting stresses (from previous models) are being used to understand how and where fissures are likely to form. , Hypothetical simulations include the role that faults and the vadose zone may play in fissure formation
DE: 1822 Geomechanics
DE: 1847 Modeling
SC: Hydrology [H]
MN: 2007 Fall Meeting