Instrumentation 2
Instrumentation 2 : An arrangement of devices installed into or near dams that provide for measurements that can be used to evaluate the structural behavior and performance parameters of the structure. (a) Borehole extensometers: (single-point or multi-point). An instrument designed to measure axial displacement of a fixed point or points along its length. Extensometers can be a rod-type, or a wire-type and are usually grouted into an uncased borehole. They can be installed horizontally, vertically, or at any angle. (b) Crack monitors: (Whittemore gauges, dial gauges, depth micrometers, and Avongard crack monitors): Measure movements transverse and along a joint or crack. (c) Flow measurement devices: (flowmeters, weirs, and calibrated bucket and stopwatch). Instruments that measure leakage quantities. (d) Inclinometer: An instrument, usually consisting of a metal or plastic casing inserted in a drill hole and a sensitive monitor either lowered into the casing or fixed within the casing. This measures at different points the casing's inclination to the vertical. The system may be used to measure settlement. (e) Joint meters (Carlson type and vibrating-wire): An embedded instrument that uses electrical principles to measure movement across a joint or crack. (f) Observation well: A hole used to observe the groundwater surface at atmospheric pressure within soil or rock. (g) Piezometers: An instrument designed to measure water levels or pore water pressures in embankments, foundations, abutments, soil, rock, or concrete. Open system porus-tube, and slotted-pipe piezmoters, or observation wells. Closed,system - Hydraulic twin-tube, pneumatic or vibrating-wire piezometers. (h) Plumblines: Measures the movement of a concrete dam due to applied reservoir water pressures and temperature changes. Installations consist of a formed shaft, suspension assembly, wire, plumb bob, dash pot and reading stations. (i) Pressure cell: (Gloetzl cell. Carlson Load cell, vibrating-wire gauges, flat jacks and total pressure cell): An instrument for measuring pressure within a mass of soil, rock, or concrete or at an interface between one and the other. (j) Pressure relief pipes: Pipes used to relieve uplift or pore water pressure in a dam foundation or in the dam structure. (k) Settlement sensors (pneumatic and vibrating-wire): Monitors the difference in elevation between the sensor unit and its reservoir. (l) Strain meters (Carlson type and vibrating-wire): An instrument that uses electrical principles to measure the strain at the location of the strain meter. (m) Surveys (Triangulation, trilateration, Global Positioning System (GPS), photogrammetric, and collimation): Measure external vertical and horizontal movement on the surface. (n) Thermometers (resistance temperature devices, thermistors, and thermocouples): Measures temperature using electrical principles of changing resistance in a copper wire as temperature changes, a semiconductor material that changes its resistance very markedly with temperature, or when two dissimilar metal wires are joined together, a change in temperature produces a change in voltage. (o) Tiltmeters: An instrument that monitors the horizontal or vertical tilt of structures and rock masses
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