Description: The desire to monitor a section of coastal bluff for slope movements along the North County Transportation District/Amtrak tracks in Del Mar, San Diego County, California led to the development of a continuous monitoring system along approximately 1000 m of track. Because of the length to be monitored, conventional single-point monitoring systems such as multiple tiltmeters or in-place inclinometers (IPIs) were deemed impracticable. Instead, horizontal time domain reflectometry (TDR) coaxial cable sensors were installed along high-concern segments of the track.
The Del Mar Bluffs TDR monitoring system uses three on-site dataloggers and reflectometers to monitor three different sections of the bluff. Each reflectometer is connected to two sensors of up to 200 m long through a multiplexer. The sensors are pulsed every several minutes to determine if sensor deformation has occurred. In the event of a deformation, a signal is sent to a central monitoring unit where an automated telephone dialer notifies railway personnel of possible bluff movement.
The system, designed by KANE GeoTech Inc. and Applied Geomechanics, Inc. of Santa Cruz, CA, utilizes a Campbell Scientific MD9 multidrop ethernet with 3 monitoring stations using CR10X dataloggers and TDR100 reflectometers. The Central Monitoring Unit includes power supplies, a CR23X datalogger, and an automated telephone dialing system.
Location: San Diego County, California
Client: North County Transportation District , Oceanside, California