Dynamic Foundation Investigation for MMW Radar Facility, Roi-Namur, Kwajalein Atoll, Marshall Islands

摘要

Surface refraction and vibratory seismic investigations were performed at the proposed location of the MMW radar facility on Roi-Namur Island, Kwajalein Atoll, Marshall Islands, for the purpose of determining Young's moduli, Poisson's ratio, and shear moduli as functions of depth for foundation materials at this site. These elastic properties are necessary for the design of foundations that require a high degree of stability under dynamic loading conditions. Foundation materials encountered at this site consist of loose coral sands and topsoil silts to a depth of 7 ft, which are underlain by medium to dense coral sands that extend to depths of at least 75 ft. Occasional coral heads and cemented lenses were also encountered in this area. Results of the investigations indicated that the shear modulus increased from about 5,000 psi near the surface to 20,000 psi at a depth of 28 ft. Young's modulus was about three times greater than the shear modulus for a given depth. Poisson's ratio averaged 0.34 from a 0- to 4.5-ft depth and 0.49 below 4.5 ft. In addition to the foundation tests, ground motion measurements were made at the MMW site in an attempt to ascertain amplitudes caused by operation of existing radar facilities in proximity to the site. The largest particle velocity measured was 0.003 ips. (Author)