TY - RPRT
T1 - Data Analysis Report
T2 - Preliminary Test Pavement Danish Road Testing Machine
AU - Ullidtz, Per
AU - Zhang, Wei
AU - Baltzer, Susanne
PY - 1997
Y1 - 1997
N2 - Main conclusions: 1) The Asphalt Strain Gauges (ASG), the Soil
Deformation Transducers (SDT) and the Soil Pressure Cells (SPC)
performed well during the experiment, but the SPCs need frequent
in situ calibration. A different installation procedure for the
SPCs should be considered. Due to the variability of the soil more
instruments (than two) are needed for each response value to be
determined. 2) Strains measured using the emu coils did not have a
satisfactory degree of accuracy. Laboratory tests showed the
Kulite pressure cells to be dependent upon loading history and
soil stiffness. For this reason the cells were not used in the RTM
experiment. The volumetric moisture content recorded by the VITEL
moisture probes did not appear to be reliable. 3) Linear elastic
theory did not give a satisfactory agreement with measured
stresses and strains. The measured vertical strains could be
several times larger than the theoretical values. Elsym5 seems to
produce incorrect deflections in some cases. 4) Satisfactory
agreement between measured and theoretical stresses and strains
could be obtained using the Finite Element Method and appropriate
non-linear relationships for the moduli of the unbound materials.
5) The variation of stresses and strains with distance from the
load was found to be in very good agreement with Boussinesgs
equations, with the exception of the horizontal stress. The
relationship between the depth used with Boussinesq's equations
the the actual depth needs further study. 6) The subgrade showed
thixotropyc behavior with strains increasing with the number of
load repetitions and decreasing after a rest period. This behavior
was only observed under the wheel load, not under the FWD. 7)
Existing design criteria for subgrades appear to be reasonable
when used with strains calculated using linear elastic theory and
moduli determined from FWD tests, but ar much too conservative if
used with measured strains. 8) Plastic strain in the subgrade,
surface rutting and roughness could all be related to the measured
resilient strain at the top of the subgrade, with damage being
proportional to the load raised to a power between 6.23 and 6.67.
These relationships can be used to calculate the pavement
condition after a given number of loads or to determine the
permissible number of loads for a given terminal condition of the
pavement. For surface rutting and roughness the contribution from
the individual layers could not be established.
AB - Main conclusions: 1) The Asphalt Strain Gauges (ASG), the Soil
Deformation Transducers (SDT) and the Soil Pressure Cells (SPC)
performed well during the experiment, but the SPCs need frequent
in situ calibration. A different installation procedure for the
SPCs should be considered. Due to the variability of the soil more
instruments (than two) are needed for each response value to be
determined. 2) Strains measured using the emu coils did not have a
satisfactory degree of accuracy. Laboratory tests showed the
Kulite pressure cells to be dependent upon loading history and
soil stiffness. For this reason the cells were not used in the RTM
experiment. The volumetric moisture content recorded by the VITEL
moisture probes did not appear to be reliable. 3) Linear elastic
theory did not give a satisfactory agreement with measured
stresses and strains. The measured vertical strains could be
several times larger than the theoretical values. Elsym5 seems to
produce incorrect deflections in some cases. 4) Satisfactory
agreement between measured and theoretical stresses and strains
could be obtained using the Finite Element Method and appropriate
non-linear relationships for the moduli of the unbound materials.
5) The variation of stresses and strains with distance from the
load was found to be in very good agreement with Boussinesgs
equations, with the exception of the horizontal stress. The
relationship between the depth used with Boussinesq's equations
the the actual depth needs further study. 6) The subgrade showed
thixotropyc behavior with strains increasing with the number of
load repetitions and decreasing after a rest period. This behavior
was only observed under the wheel load, not under the FWD. 7)
Existing design criteria for subgrades appear to be reasonable
when used with strains calculated using linear elastic theory and
moduli determined from FWD tests, but ar much too conservative if
used with measured strains. 8) Plastic strain in the subgrade,
surface rutting and roughness could all be related to the measured
resilient strain at the top of the subgrade, with damage being
proportional to the load raised to a power between 6.23 and 6.67.
These relationships can be used to calculate the pavement
condition after a given number of loads or to determine the
permissible number of loads for a given terminal condition of the
pavement. For surface rutting and roughness the contribution from
the individual layers could not be established.
M3 - Report
BT - Data Analysis Report
ER -