Method and apparatus for determining stiffness of a roadway

A method of compacting a multi-layer roadway section with a roller having a compaction analyzer operably associated therewith comprising:

• entering initial input parameters of the first layer of the roadway section into the compaction analyzer;
• making a plurality of passes with the roller over the first layer of a portion of the roadway section;
• applying a vibratory energy to the first layer of the portion of the roadway section with the roller as it moves thereover;
• repeatedly gathering responsive vibration signals of the roller as it moves over the first layer portion of the roadway section;
• generating, with the compaction analyzer, estimated dynamic modulus signals representative of estimated moduli based upon the responsive vibration signals of the roller and the initial input parameters entered into the compaction analyzer;
• measuring the dynamic modulus of the first layer of the roadway section at a plurality of locations on the portion of the roadway section;
• comparing the measured modulus with the estimated modulus at the plurality of locations to determine the difference between the measured and the estimated moduli;
• adjusting selected ones of the initial input parameters to the analyzer based on the difference between the determined modulus and the estimated modulus so that an adjusted modulus output signal generated by the compaction analyzer will more closely approximate an actual modulus of the roadway section than does the estimated modulus signal;
• and
• rolling the remainder of the roadway section until the compaction analyzer with the adjusted input parameters generates a desired adjusted output modulus signal.