Expansive Subgrade Behavior on a State Highway in North Texas

Expansive soil in pavement subgrade experiences volume change due to the seasonal moisture and temperature. For the clear understanding of the subgrade behaviour, it is necessary to study the pavement behaviour in real time which connects the gap between moisture, temperature and suction variation with induced pressure on the pavement and pavement deformation. The current study presents an extensive instrumentation program on a subgrade soil and performance of an asphalt pavement over expansive clay subjected to seasonal variation of moisture temperature and suction. A section over 2- lane State Highway (SH) 342 in Lancaster, Texas, maintained by Texas Department of Transportation (TxDOT) was instrumented with moisture and temperature sensor, water potential probe, pressure sensor and piezometer to monitor the seasonal variation on continuous basis using automated data collection system. In addition, horizontal inclinometer was installed across the pavement and routine topographic survey was conducted to monitor the pavement deformation. Based on the preliminary monitoring results of almost a year, a 5-7% variation of moisture was observed in the subgrade soil whereas; 2 inch of movement was noticed over the pavement. Additionally, a temperature prediction model was developed based on 15 months monitoring data.