Vibration response of machine foundations protected by use of adjacent multi-layer geocells

The response of soil beds reinforced with multi-layer geocell systems that support machine foundations is investigated by laboratory testing that incorporates vertical machine vibrations of a square concrete foundation (400 x 400 mm) resting on soil that is unreinforced or reinforced with single-, double- or triple geocell layers. The tests are performed under three different vibration moment levels and three static force levels using a mechanical oscillator and concrete blocks, respectively. The vibration responses are studied in terms of resonant amplitude, resonant frequency, shear modules and damping coefficient. The results reveal that the resonant amplitude significantly reduced in the presence of geocell reinforcement whereas the resonant frequency, shear modulus and damping coefficient increased. In the range of applied vibration load and frequency, and hence the induced amplitude, maximum improvement (i.e., the greatest reduction in vibration amplitude) was observed in the presence of the triple-layer geocell reinforcement. Since the rate of improvement decreases steadily with an increase in the number of geocell layers, thus, further geocell layers would deliver little further benefit. The optimum placement depth of the first geocell layer and vertical spacing of the geocell layers were found to be 0.1 and 0.05 of the foundation's width respectively.