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| [[Category:Movement Surveillance and Monitoring]] | | [[Category:Movement Surveillance and Monitoring]] |
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| | In assessing a concrete gravity or arch dam, it is important to monitor its rotational and sliding [[stability]]. |
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| ==Measurement Devices== | | ==Examples== |
| '''Inclinometer'''
| | {{Website Icon}} [https://damfailures.org/lessons-learned/concrete-gravity-dams-should-be-evaluated-to-accommodate-full-uplift/ Learn more about the need to consider uplift forces in evaluating concrete gravity dams at DamFailures.org] |
| *“The terms ‘inclinometers’ and ‘deflectometers’ are used interchangeably regarding Bureau concrete dams… Inclinometers are used to measure lateral movements in abutments and foundations of concrete dams. Inclinometer installations may consist of the ‘normal’ type, where a casing is installed and a movable inclinometer probe is used to take readings; or a ‘fixed-type’, where the inclinometer is fixed at a certain location in the casing.<ref name="CDIM">[[Concrete Dam Instrumentation Manual | Concrete Dam Instrumentation Manual, USBR, 1987]]</ref>
| | {{Website Icon}} [https://damfailures.org/case-study/austin-bayless-dam-pennsylvania-1911/ Learn more about the potential for sliding instability from the 1911 failure of Bayless Dam at DamFailures.org] |
| #"''Advantages and limitations. –'' Inclinometer installations have proven to give reliable and accurate data over an extended period provided proper installation, maintenance, and monitoring procedures are used. The only major limitation using this type of instrumentation is that a significant degree of specialized training is required for the personnel reading the devices. Such personnel must be trained in the proper care and [[operation]] of the equipment and should possess the ability to recognize erroneous or anomalous field data.<ref name="CDIM" />
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| #"''Description of devices. –'' Inclinometer systems may consist of special casings, casing couplings, inclinometer probe, cable, readout unit, data transmittal system, backfill material and, in some instances, a surface protective pipe with a locking cap.<ref name="CDIM" />
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| #"''Installation procedures. –'' Inclinometer casings must provide reliable orientation for the inclinometer probe; therefore, proper installation procedures must be observed. The locations for the installations are selected because of subsurface conditions, topography, and depth of any anticipated movements…<ref name="CDIM" />
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| #"''Monitoring procedures. –'' The inclinometer installations are monitored at prescribed intervals. Inclinometer devices consist of a probe, cable, and digital readout unit. The prove is designed to fit any of the three standard casing sizes, which are 1-7/8, 2-3/4, and 3-3/8 inches (48, 70, and 86 mm). While setting up this instrument to take a set of readings, the guide wheels should be checked for bearing freeplay and tightened if necessary. A small amount of lubricant should be applied to each wheel bearing assembly. The cable connectors should be protected with caps to prevent damage or contamination to the connector contacts. An O-ring provides a watertight seal between the cable and probe; however, some probes are permanently connected to the cable. For the latter case, especially with lighter cables, the cable should be checked for damage near the connection…<ref name="CDIM" />
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| #"''Maintenance. –'' A regular maintenance program is essential to the proper conduct of inclinometer monitoring. Repair or [[replacement]] of an inclinometer probe or readout unit due to misuse or failure to properly maintain the devices can be expensive and result in loss of data due to downtime”.<ref name="CDIM" />
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| </br>'''Shape Arrays'''
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| | ==Measurement of Rotational or Horizontal Movement== |
| | *[[Inclinometer]] |
| | *[[Shape Array]] |
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