Ground Vibration Prediction and Assessment

1
Ground Vibration Prediction and Assessment

• R.M. Thornely-Taylor
• Rupert Taylor Ltd

2
Noise SOURCE ? PATH ? RECEIVER Vibration
SOURCE ? PATH ? RECEIVER
3

• Source term - dependent on excitation, source
  impedance, mounting impedance, foundation
  impedance and surrounding lithology
• Transmission characteristics - dependent on
  geometry of source, geological characteristics
  (Lamé constants, loss factor, layering, water
  tables)
• Building response - consisting of coupling
  between foundations and the ground and the
  dynamic response of the building, and, in the
  case of re-radiated groundborne noise, the
  receiving room characteristics
• Receiver and support impedance. Receiver attitude.

4
(No Transcript)
5
Driving-point impedance (z-axis) of seated human
body
6
Receiver Issues

• Foundation coupling
• transfer functions
• piled foundations
• Structure response
• Power transmission through/up building
• transmission line
• floor impedances
• vary with location
• Receiver impedance
• axes
• support
• standing
• chair
• bed

7
Propagation Issues

• Soil parameters
• on-site measurement
• bore-hole tests
• impedance of spherical source in an elastic
  medium
• departs from inverse-square law for velocity
• pressure and strain dependence of dynamic moduli
• Uncertainties
• unknown features in lithology
• perched water tables
• boulders/limestone layers

8
(No Transcript)
9
Seismic measurement of P-wave and S-wave
velocities
10
Propagation Issues

• Many wave types
• body waves (dilatational)
• shear waves
• Rayleigh waves
• Stoneley waves
• Lamb waves
• two-phase propagation
• liquid in a porous medium
• Wave conversion at interfaces
• SV ? P
• one layer may attenuate
• several layers may increase propagation at
  eigenfrequencies
• progressive change in soil may bend propagation
  path

11
Correct Source Data

• Source power
• dependent on
• source impedance
• source mounting/support
• resilient elements
• dynamic stiffness - frequency dependence
• loss factor - frequency dependence
• Source signal

12
Modelling

• Empirical
• Extrapolating measurements from similar case
• Statistical treatment of large numbers of
  measurements from many cases
• empirical methods of correcting for changes in
  parameters
• Algebraic
• Isolator transmissibility
• Simple distance function
• Numerical
• Finite element (FEM)
• Finite difference (FDM)
• Boundary Element (BEM)
• Hybrid (FEM/BEM)