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crack gauges
For reinforced soil and geogrid work, Kingmach crack gauges include the JMDL-24XXAT Smart Flexible Displacement Meter. This product is built around patented inductive flux frequency modulation technology and is designed for deformation or strain monitoring in geogrid materials used in reinforced soil and pile-net subgrade foundations. The measuring rod extension is flexible, so it can deform with the geogrid while both ends are clamped by mounting brackets for reliable strain transfer. Listed ranges are 30 mm and 50 mm, with 0.01 mm sensitivity and 0.5%FS accuracy. The non-contact measurement layout keeps the measuring rod and internal coil independent, reducing damage risk during installation and service. A 20-point curve fitting process supports nonlinear correction and accurate displacement output. Kingmach lists a designed service life of up to 30 years for this product, which fits long-term railway, roadbed, slope, and foundation monitoring where buried materials cannot be visually inspected after construction. For this model, the installation record should focus on geogrid layer position, bracket clamping force, fill sequence, compaction stage, cable exit route, and the first stable value after backfilling. Those details are different from crack monitoring because the sensor is working with buried reinforcement deformation rather than an exposed joint. During later review, the curve should be checked with settlement, traffic loading, rainfall, and earthwork records so engineers can understand how the reinforced soil body is behaving.
Application of crack gauges
In tunnel engineering, crack gauges help monitor surrounding rock deformation, lining movement, tunnel portal displacement, clearance change, and crack opening after excavation. Tunnel sites often have wet air, dust, restricted access, and changing support stages, so the instrument must hold a stable baseline through construction disturbance. Kingmach JMDL-31XXAT multipoint displacement meters use drilling and grouting with anchor heads at different depths, allowing engineers to compare the movement of separate rock layers. The series lists 50 mm, 100 mm, and 200 mm ranges with 0.01 mm resolution. JMDL-32XXAT single-point bedrock meters can be embedded with a flange, tie rod, anchor head, and PVC pipe assembly. JMLS-22XXADT wire rope sensors can watch longer displacement paths or tunnel wall clearances. These readings help site teams decide whether deformation is responding to excavation sequence, groundwater, lining timing, nearby blasting, or long-term ground pressure. During operation, the monitoring team should keep the baseline, temperature, inspection notes, and nearby sensor behavior in the same review file. This makes it easier to tell whether a movement trend comes from normal service, a repair event, changing load, water influence, or developing structural risk. Clear records also help owners decide when a field inspection is needed instead of waiting for visible damage.
The future of crack gauges
Longer service life will be a major future requirement for crack gauges. Infrastructure owners want monitoring systems that remain useful beyond the construction phase and into operation, inspection, repair, and renewal. Kingmach lists 30-year designed service life on selected products such as the JMDL-24XXAT flexible displacement meter and JMDL-49XXAT formwork displacement meter, while models such as JMCW-21XXADT use non-contact sensing to avoid mechanical wear. Future specifications will likely ask more directly about waterproof rating, connector durability, cable route protection, sensor replacement access, and data continuity after maintenance. For dams, bridges, railways, slopes, and tunnels, a displacement record over several years is often more useful than a short burst of high-frequency data. This long view supports asset management and helps distinguish slow structural change from normal seasonal movement. The next improvement will be planned service records: expected inspection intervals, spare part notes, replacement dates, and clear links between old and new baselines after a sensor is changed.
Care & Maintenance of crack gauges
For crack gauges installed at cracks, joints, and expansion joints, maintenance should focus on bracket stability, rod alignment, cable protection, and baseline traceability. Kingmach JMDL-22XXAT crack gauges may use different measuring rods and universal bases, so the mounting points must remain firm while the structure moves naturally. Avoid placing rods where they can be hit by workers, tools, vehicles, concrete debris, or repair materials. During inspections, check whether the crack edge has spalled, whether the base has loosened, whether water has entered the connector, and whether the displayed movement agrees with nearby observations. Because the product can store up to 600 measurement results, compare field readings with stored records before resetting values. If temperature versions are used, keep temperature data with displacement data so seasonal opening and structural movement are not confused. Keep the installation photo, point number, zero value, and expected movement direction with the commissioning record for later review. If a reading changes after maintenance work, inspect the base, anchor, cable, and cabinet before assuming the structure itself has moved.
Kingmach crack gauges
crack gauges are used when a structure needs movement data that can be reviewed, compared, and acted on before deformation becomes visible. Kingmach covers short range crack movement, expansion joint travel, rock layer displacement, geogrid deformation, draw-wire movement, and long stroke position tracking. The category includes JMDL-21XXAT general-purpose displacement meters, JMDL-22XXAT crack gauges, JMDL-24XXAT flexible meters, JMDL-31XXAT multipoint meters, JMDL-32XXAT bedrock meters, JMDL-49XXAT formwork meters, JMDL-52XXADT differential meters, JMCW-21XXADT magnetostrictive meters, and JMLS-22XXADT wire rope sensors. On site, this means one product group can cover bridge joints, tunnel portals, slope movement, dam deformation, railway subgrade settlement, and industrial linear motion. The value is not only the displayed millimeter reading. It is the ability to connect movement, time, temperature, construction activity, and warning limits into one record. The point should be named on the drawing, linked with its cable route, and checked against the expected movement direction before the first automatic reading is accepted. For daily review, the reading should be compared with nearby points, recent weather, site operations, and any loading event that could explain the movement.
FAQ
Q: Which crack gauges are used for rock layers or bedrock?
A: JMDL-31XXAT multipoint meters are used for different surrounding rock layers, while JMDL-32XXAT single-point bedrock meters are used for tunnel rock mass, dam bedrock, slope, or foundation pit movement.
Q: How many points can the multipoint meter support?
A: The multipoint installation kit supports three to five monitoring points, with anchor heads fixed at different depths by drilling and grouting.
Q: What ranges are listed for these models?
A: Both JMDL-31XXAT and JMDL-32XXAT list 50 mm, 100 mm, and 200 mm models with 0.01 mm resolution.
Q: Why monitor several depths?
A: Different layers may move differently. Separating shallow and deep movement helps engineers judge whether the problem is surface creep, deeper rock slip, or overall mass movement.
Q: What records should be kept?
A: Keep drilling depth, anchor location, grouting date, channel name, zero value, cable route, and first stable reading.
Reviews
James Thompson
The tiltmeters and accelerometers are very sensitive and provide precise data. Perfect for our structural health monitoring system.
Ryan Lewis
Fast delivery and excellent product quality. The accelerometers and tiltmeters are highly reliable. Strongly recommend this company.
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