Resistivity Probe - RP
A "RP" sensor measures the depths of freezing and thawing fronts in the granular base and subgrade. Data for the original installations was collected manually at various times. Some installations became automated. The Resistivity Probe (RP) sensor is a vertical series of electrical resistivity gauges used to indicate when a substantial portion of the pore water in a soil has frozen.
RP sensors were designed by MnROAD staff and fabricated by Shannon and Wilson, the instrumentation consultant involved with the original construction of MnROAD.
Location and Quantity
RP sensors were originally placed in several locations within a test cell to characterize frost profiles. ii. There was originally at least one RP sensor installed in each of the 40 MnROAD test cells. Each probe had 41 sensors, giving a total of 4223 measurement points.
The use of RP sensors was discontinued in spring 1999. Data collection and processing was found to be very labor intensive.
MnROAD Database Table
Data from original RP sensors can be found in the MnROAD database table: MNR.RP_VALUES.