2

Long
Term Pavement Analysis (LTPP) was used 
to extract the data required for this report. LTPP is an important
source to obtain the information required for the study of the pavement
structures. It was introduced in 1987 as a Strategic Highway Research
Program(SHRP).

The
database of LTPP undergoes extensive quality control checks meaning data
extracted from LTPP is authentic . LTPP consist data in various categories Resistivity
parameters ( resistance and voltage) and Resistance, Voltage, Interpreted soil
temperature were used as input data to obtained the output frost penetration
depth.Data were recorded for  13 states
of USA and 3 states of Canada. During the data extraction a  section was chosen for a particular  state, for 
the same day corresponding resistance, voltage and temperature data was
recorded. Recorded electrical resistivity data was normalized between 0 to1
using simple normalization equation given below. Normalization was done in
order to reduce the noise due to material variability.   

RN,i
 =   ( Ri – Rmin, i ) /( Rmax,i – Rmin,i)

RN,i  = normalized resistance at
measured depth i

Ri = actual
resistance at  measured depth i

Rmax,i  = maximum
resistance value measured at  

measured
depth i

 Rmin,i  =
minimum
resistance value measured at measured depth 
. Similarly  voltage was
calculated using same equation.

For different years. LTPP
is easy to use so one of the most popular source for pavement engineers. Data
for various          years could be
extracted along with section information where study was conducted. Data  in LTPP are stored in excel sheet format which
can be directly downloaded by the user.

 

 

 

               

                                 

       Fig   
Scatter Plot for Frost depth Vs Voltage

 

 

 

 

 

 

 

 

 

Individual
regression analysis was performed to check the interrelationship between the 3
variables and  frost depth.. Scatter plot
result showed did not display a  good
relationship that exist between  resistance,
voltage vs frost depth. The result of scatter plot  is showed in Fig 1 and Fig 2 for voltage and
resistance. The accuracy of the resistance and voltage data also depends upon
the electrical resistivity. For the required section LTPP database lacked
resistivity data points. However the correlation for temperature vs frost depth
was good. The scatter plot result showed the r^2 value of 0.74 for the plot. As
only temperature was the parameter which affected the frost depth, prediction
model was based  on temperature.