Crusting and Swelling Effects on Water Infiltration into Soil.

摘要

One-dimensional,horizontal soil-water absorption through a thin but resistive inlet zone of soil was studied theoretically and experimentally. An exact numerical solution was obtained,and also an approximate solution based on similarity reduction that held with good accuracy for early to intermediate times of flow,for both the numerical-analysis data for Yolo soil and the experimental measurements performed on Salkum silty clay loam. Also,the principle of dual-energy gamma-ray attenuation was successfully developed for measuring both water and soil content in swelling soils. The dual-energy gamma-ray beam was produced by a 280-mc source of 137Cs placed behind a 389-mc source of 241Am,all in lead shields and collimators. Single-detector separation of the count intensities from 137Cs and 241Am was achieved by a straightforward calibration. Measurements were nondestructive,and relatively precise and rapid. (Author)