Patent ID: 7500806

Claim:
A method for constructing a filter zone of an earthfill dam, said method comprising the steps of: placing a first particulate material composed primarily of relatively coarser particles and a second particulate material composed primarily of relatively finer particles in a vehicle so that said first and second particulate materials remain segregated therein; advancing said vehicle along a predetermined path that corresponds to horizontal cross-section of said filter zone while discharging said first and second particulate materials simultaneously from said vehicle in uncompacted flows that are convergent towards said path, so that in a single pass said first particulate material composed of relatively coarser particles and said second particulate material composed of relatively finer particles are deposited simultaneously in adjoining relationship generally on first and second sides of said path so as to form a stratum of said filter zone; and repeating the steps of advancing said vehicle along said predetermined path while discharging said particulate materials, so as to form a plurality of said strata in built-up, overlying relationship such that said first particulate material forms a coarse filter portion of said filter zone and said second particulate material forms a fine filter portion of said filter zone.