Energy Propagation and Coupling Studies for Line Transducers.
Final technical rept. 6 May 75-5 May 76,
HONEYWELL INC HOPKINS MINN GOVERNMENT AND AERONAUTICAL PRODUCTS DIV
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This program is an investigation of the effect of various soil compositions and frost conditions on performance of buried line transducers. The program encompasses theoretical modeling of transfer function of a MILES-type line transducer, controlled experiments in loam, clay and sand soils for various frost conditions, and correlations between theory and experiment. Experiments were conducted in an indoor test facility where frost conditions could be produced. Response of transducers was measured with vertical cyclic and impulse loads of defined magnitude applied at the soil surface. Experimental data indicates that as long as frost does not penetrate below the burial depth of the transducer, often there is no significant attenuation of line sensitivity such cases occur when the frozen layer above the transducer does not form a continuous shelf of frozen ground. When a continuous shelf forms, or when frost penetrates below the transducer burial depth, some upward gain adjustment is necessary for satisfactory performance. Several approaches to minimizing performance problems in frozen ground are identified. Lines may be buried as significantly greater depths. Frost penetration may be artificially limited by insulating materials. Adaptive gain control may be introduced based on either frequency domain information or soil temperature measurements. Author
- Soil Mechanics
- Snow, Ice and Permafrost
- Seismic Detection and Detectors