ACOUSTIC/SEISMIC TECHNOLOGY TO CHARACTERIZE SEDIMENT MOVEMENT AND DEPOSITION IN SURFACE WATERS AND EVALUATE DAM STRUCTURAL STABILITY
Location: Watershed Physical Processes Research Unit
Project Number: 6408-13000-022-01
Specific Cooperative Agreement
Start Date: Sep 01, 2007
End Date: Aug 31, 2012
Objectives are directed toward the development and evaluation of innovative acoustic and seismic measurement techniques for monitoring mechanical, hydrological, and structural properties of soils that are significant to erosion and transport of soil in the upland watershed area, sediment transport processes in fluvial environments, sediment accumulation in impoundment reservoirs, and the structural integrity of earthen dams. The proposed research objectives are: (1) development of measurement and monitoring technologies for assessing the temporal evolution and spatial distribution of the mechanical, hydrological, and structural properties of soils that are significant to erosion and transport of soil in the upland watershed area; (2) development of measurement and monitoring technologies for determining the temporal and spatial distribution, variation, and evolution of both suspended and bedload sediments in fluvial environments; (3) initiate field and laboratory studies using acoustic technologies for spatial delineation and characterization of sediments in relatively shallow reservoirs upstream from flood control dams; and (4) develop acoustic and/or seismic methodologies for identifying piping failure or changes in the structural integrity of earthen dams.
(1) Obtain a better understanding of the phenomenology underlying the relationships between acoustic and physical characteristics of soils and develop acoustic techniques for characterizing and mapping specific soil layers. Methods based on the measurement of acoustic phenomena, such as sound speed, impedance, and nonlinear characteristics, will be used to monitor the internal changes in the soil matrix over time due to variations in temperature, water content, and applied stresses and to quantify soil mechanical, hydraulic, and structural properties. Incorporate laser Doppler vibrometry to facilitate non-contact measurements. Exploit surface wave and acoustic backscatter techniques to characterize the sealing and crusting effects. Develop a non-contact acoustic/LDV technique to measure and map the depth to the horizon of high-strength soil layers, such as fragipans and plowpans. (2) Advance the state-of-the-art in the use of multiple acoustic frequencies for extracting detailed concentration and particle-size distribution information using laboratory tests. Deploy low cost acoustic systems in stream cross sections, and investigate the use of passive acoustic techniques to characterize bedload transport through passive measurements of gravel and sand dune migration. (3) Characterize the relationships between acoustic attributes, such as acoustic velocity, absorption, and impedance of sediments, and sediment physical properties, such as bulk density, grain size distribution, and pore fluid concentrations and study the relevant physical properties of the impoundment sediments and their relationship to acoustic attributes based on laboratory experiments. Develop the use of high-resolution acoustic sub-bottom profiling systems for sediment delineation and characterization by developing complementary acoustic field techniques of mapping and characterizing sediment accumulations in small flood-control reservoirs. (4) Study and evaluate the usefulness of seismic and acoustic techniques (e.g. seismic refraction tomography) for delineating the internal structure of earthen dams.