On the mechanical vibrator-earth contact geometry and its dynamics

Abstract

The geometry of the contact between a vibrator and the earth underneath influences the dynamics of the vibrator. Although a vibrator might appear to be well-coupled with the earth on a macroscale, perfect coupling certainly does not occur on the microscale. With the aid of contact mechanical modeling and concepts, it can be shown that this lack of contact at the microscale, or rather the change thereof during a sweep, can have a significant effect on the dynamics of the vibrator-earth system. Modeling of such changing contact predicts that the dynamic behavior varies considerably with the vibrator drive level. The most significant effect predicted by the model is a decrease in the base-plate resonance frequency with an increasing drive level. Extensive drive-level tests carried out in a field experiment confirm this change of resonance behavior with drive level.

Response of a Two‐Degree‐of‐Freedom Vibration System with Rough Contact Interfaces

“…According to the numerical results, it is inferred that the natural frequency of the baseplate decreases with the increase of the excitation force when the vibrator is in contact with rough ground surfaces. e result is similar to the research of Rik and Guy [34]. Meanwhile, the decrease rate of natural frequency for rougher ground surface is larger.…”

Ground force analysis of a portable electromagnetic seismic vibrator for different surface environments and driving voltages

“…For example, Wei and Phillips (2010) studied the non‐linearity of the hydraulic system and baseplate in a hydraulic vibrator. To study the nonlinear mechanism and obtain the AGF, much research effort has been focused on the baseplate‐ground coupling system, and some baseplate‐ground coupling models have been established (Lebedev & Beresnev, 2004; Noorlandt & Drijkoningen, 2016; Wei, 2017).…”

Nonlinear 3D finite element analysis of a shear-wave vibrator-ground interaction system

“…In order to study the influence of the nonlinear contacts on the performance of the system, Lebedev [15] and Beresnev and Lebedev et al [16] propose a model with nonlinear contact springs. Noorlandt and Drijkoningen [17] and Huang et al [18] established nonlinear theoretical models that consider the effects of the surface topography at the interfaces between the vibrator and ground. In addition, to account for the dynamics of the coupling ground, some researchers introduced dynamic stiffness and dynamic damping into the theoretical model to simulate the performance of the vibrator at the elastic half-space surface [19].…”