Determining Weight of Stockpiled Ore Using Microgravity Measurements

摘要

The Defense National Stockpile Center (DNSC) maintains stockpiles of high-gradeores at various locations throughout the country and has a requirement to produce current weight estimates for selected piles as part of a national audit. The ore piles for this study are located at the Seneca Army Depot, NY; Stockton Depot, CA; Somerville and Belle Mead Depots, NJ; and Large, PA. Microgravity measurements were performed over selected ore piles to provide high-resolution surveys of the gravitational field with which to determine the average bulk density of the ore material. Parasnis' method was used to analyze the gravity anomaly data. Ore pile volumes were determined using standard land surveying methods. The computed weights for each ore stockpile are compared to the DNSC reported weights and the differences should be within 10 and 15 percent. Results of this investigation indicated that the computed weights of 24 of the 45 piles surveyed are below or within the expected percent difference error range. Seventeen ore piles have differences ranging from 15 to 25 percent and four stockpiles had differences greater than 25 percent of the reported values. The greatest differences were computed over piles in which settlement of the ore material below the ground surface had taken place or site conditions were such that definition of the true pile base was poor.