Soil resistance during vibratory driving in sand Available to Purchase

A mechanism to explain pile shaft resistance during vibratory driving is discussed. One hypothesis is that horizontally oscillating stresses temporarily reduce shaft resistance. Vibration measurements were conducted in medium-dense to dense sand during vibratory driving. A large compaction probe was installed by a vibrator with variable frequency. The driving process and ground response were documented in detail. Geophones were installed on and below the ground surface. Horizontal ground vibrations were measured at three levels below the ground surface. The difference in vibration response of the ground during driving at a high frequency (27 Hz) and at the system resonance frequency (15 Hz) showed the effect of the vibrator operating frequency on penetration speed and emitted ground vibrations. Horizontal stress pulses are emitted along the probe shaft, which can temporarily reduce static horizontal stresses acting against it. This phenomenon can explain the temporary reduction of shaft resistance and efficiency of vibratory driving in granular soils. As a result of these pulses, the horizontal stresses are increased permanently. Using a monitoring and process control system, the system resonance frequency can be determined in the field – a critical parameter for vibratory driving resistance, emission of ground vibrations and vibratory compaction of granular soils.