B in Fig. 9.2). The vehicle then draws the beam assembly forward to the next
measurement position where the cycle is repeated.
The correlation between the results from the two mechanisms is given in Fig.
9.3. The deflectograph and the Benkleman beam give similar but not identical
results, with the deflectograph giving lower readings. The results are reasonably
independent of temperature changes, within a range of 10°C to 30°C. The
relationship illustrated is derived from measurements of pavements with
rolled asphalt, bitumen macadam and tarmacadam surfacings, bitumen-bound,
cement-bound and crushed stone roadbases and subgrades with CBR values
between 2.5 and 15%.
Pavement Maintenance 257Position APosition BFigure 9.2Operation of deflectograph.
Deflectograph deflection
(mm ¥ 10 -2)20016012080400 40 80 120 1600Deflection beam deflection(mm¥^10-2)Figure 9.3
Correlation between
deflectograph and
deflection beam
measurements.
(Crown copyright
1978)