Page 156 - Numerical Analysis and Modelling in Geomechanics

MODELLING OF GROUND WAVES 137

Table 5.1 Human tolerance of vibration, in mm/s.

Notes
1. Level I Under this level the vibration should be accepted
Level II Acceptable with advanced warning. Complaints possible
Level III Above these values—unacceptable.
2. The above values relate to 4 hrs of vibrations in the working day. For different
durations of vibrations,

where v tc =transverse wave transmission velocity, V 4 =4 hours of vibrations, T 1 =16 hours
and T c is the exposure time in hours per day.
3. The limiting values apply for all environments other than hospitals, precision
laboratories and libraries, in which vibrations of up to 0.15 mm/s should be acceptable.

There is little evidence to suggest that vibrations from piling alone cause even
minor cracking damage to buildings in good repair, BRE Digest 353 (1990).
BS5228 part 4 (1992) and BS7385 part 2 (1993) give recommendations for
limits of transient vibrations. However, their threshold values are significantly
different, with the values from BS5228 being lower in most conditions. Values
for continuous vibrations are taken at 50% of transient values. Values for
domestic and industrial buildings are plotted in Figure 5.4.
Further guidance for old buildings, buried services and retaining walls is
available,

Objectives of the current study
The study takes place against a background of conflicting opinions on vibrations
caused by impact and vibratory pile driving, and their consequences upon
buildings and occupants. The overall objective has been to develop
computational models to estimate outgoing ground vibrations, and to calibrate
and refine the models by reference to a number of high quality site measurement
data sets.
At a more detailed level, the following should be studied:

• Patterns of surface and below-surface ground waves.
• The non-uniform attenuation of transient vibrations from impact driving, and
in particular the ‘quiescent zone’ identified by Hiller (2000).
• Proportionality of vertical and horizontal components of vibration.