There are many types of methods of monitoring the stability of slopes and Norpac crew members have been involved in most of these types of installation in the past. We will give a quick explanation of some of the most common tools used in the field today.
Prisms are often installed on slopes to measure any consistent or catastrophic movement of a slope. The prisms can be fastened to the slope in a variety of ways to help deal with specific site conditions. We have developed adjustable stands that have provide excellent protection from snow build up and rock fall. These stands have been widely used in many environments. A control unit collects data from these prisms and can be setup through GPS to warn people if a failure has occurred or if a slope is failing. These systems are used on many mine sites and on slow moving slopes that threaten the safety of public and work force individuals.
Piezometers also known as vibrating wire instruments are used to measure the pore pressure of zone within the slope. A hole is drilled to an elevation that the engineer requests. The piezometer/s are installed at various locations within the hole. Normally a grout/bentonite mixture is pumped down the hole fully encapsulating the piezometers. Once cured readings from these instruments can be taken and engineering can decipher the pore pressures in each zone. Norpac has installed many Piezometers in all types of conditions.
Extensometers are simple instruments that measure slope movement. A base stand is setup on the top of a slope with a wire feeding system. Wire is run from this stand down to a fixed point on the slope below. As the fixed point moves down the failing slope it pulls out the wire from the base stand. This wire can be monitored regularly and the movement can be recorded. This system can also be setup to trigger a visual or audio alarm that warns bystanders if the slope has moved too much.
Inclinometers are used to measure the deviation of slope’s internal structures. A hole is drilled though the substrate needing monitoring. A specialized PVC is installed in the drilled hole to total depth. One the PVC is installed a special tool can be run down the PVC to measure the inclination of the hole. This hole can be regularly monitored by running the instrument down the hole and collecting new data. This allows engineering staff to see at what elevations the slope is failing, how much it is failing and in what direction.