VERTICAL AND ROCKING VIBRATIONS OF MACHINE FOUNDATIONS EMBEDDED IN GRS SAND

Abstract

Machine foundations and neighboring structures can be adversely affected by excessive machine vibration. To minimize vibration amplitude and to meet Richart's Chart (1965) performance requirements, the machine operating frequency must differ sufficiently from the system’s natural frequency. This dissertation studies the influence of different spacing of woven geotextile (Amoco 4800) and foundation-embedded depth on machine foundation behavior under vertical and rocking vibrations, respectively. Large-scale experiments are conducted to simulate machine foundation behavior using a rigid steel soil container (RSSC) measuring 48 inches long by 48 inches wide and 48 inches high. A 12-inch circular steel model foundation of 3 inches thick is used in this study. The foundation is placed at 12, 6, and 0 inches from the top of the first woven geotextile layer. This is done in Ottawa sand prepared to a relative density of 70 percent. Several reinforcing patterns were used to investigate how the reinforcing effect changes with increasing reinforcing layers. The reinforcing spacings are 12, 8, and 4 inches. Material testing system (MTS machine) provides harmonic loads for vertical and rocking vibrations. After the finite element analysis was verified to be effective, parametric studies of the machine foundations were performed. Then, multivariate regression analyses were conducted. These findings reveal that reducing the spacing of woven geotextile layers while increasing embedment depths results in decreased displacement amplitude and increased natural frequencies. Such adjustments enhance the foundation's capacity to withstand dynamic loads.