Monitoring seasonal changes
Damages caused by seasonal changes and freeze-thaw process are the most significant factor affecting the road condition of northern cold climate road networks in Europe, Asia and North America. It can be stated that 60-80 % of the distresses appeared during spring when the road is weakest. Since year 2000 Roadscanners has offered Percostation services in Finland, Sweden and Scotland for monitoring seasonal changes, making forecast for spring thaw weakening and providing weekly reports on the current status of road structure and subgrade moisture content and the risk for permanent deformations under heavy axle loading.
Roadscanners has developed, in cooperation with the Estonian Adek Ltd, the Percostation; a system for the monitoring critical bearing capacity. The system consists of sensors installed in a problematic road section, at different depths in the road structure and subgrade soil; a data collecting unit installed roadside; and data transfer and analysing systems, which transfer the measurement results via gsm network or telephone cable to the pc screen of the road authority, for use in load restriction planning.
Technically, the Percostation deviates from the Percometer in so far, as it enables measurements of dielectric value, electrical conductivity, and temperature from eight channels. The measurement interval can be set to a minimum of 60 seconds (four channels). The measurement results are stored in the memory of the data-collection unit, where they can be read through a modem connection. The memory of the collection unit is sufficient enough to store 360 measurements at once. The settings of the data-collection unit can also be modified through the modem connection.
Percostation in use
The Percostation operates on 12 V of electricity. A sufficient energy supply can be provided by a 260 Ah battery, which is recharged by a solar panel. Without recharging, 260 Ah provides sufficient energy to power the Percostation for approximately 1,5 months.
In operation, Percostation software connects to the measurement station(s), reads the last measurements from its memory and transfers them to a mainframe database where they are stored in files for each individual station. Each file also stores information on the structure, materials, and calculated critical tensions, dielectric values, and electrical conductivity values for the road structure being monitored. Based on this information, the Percostation software can warn the operator when conditions in different layers of the road structure and subgrade are approaching a critical state. The operator can use this information when deciding to impose or lift load restrictions, and for determining the maximum allowed axle weights and/or number of axles.