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GNSS
Kingmach GNSS include the JMDL-31XXAT Smart Multipoint Displacement Meter for tunnels, rock slopes, foundation pits, and surrounding rock layers. The product uses displacement gauges, PVC measuring rod protective tubes, anchor heads, and multipoint installation kits that support three to five monitoring points. Installation is performed by drilling and grouting, with anchor heads fixed at different depths so each layer can be observed separately. Listed models include 50 mm, 100 mm, and 200 mm ranges, all with 0.01 mm resolution. The sensing principle uses an LC oscillation circuit: as the measuring rod moves inside the coil, magnetic reluctance and inductance change, causing the output frequency to change in a linear relationship with displacement. Because the rod and coil work without contact, the structure is less vulnerable to mechanical damage during installation. The built-in memory stores model, serial number, calibration coefficients, and up to 600 measurement records for later traceability. During project setup, the measuring point should be matched with the expected travel direction, available mounting space, cable route, and required acquisition interval. This prevents a short-range joint instrument from being used on a long-travel point, or an exposed sensor from being placed where an embedded anchor is needed. It also helps the monitoring team set a baseline that can be defended during acceptance and later maintenance review.
Application of GNSS
In foundation pit and deep excavation projects, GNSS are used to watch retaining walls, soldier piles, soil nails, nearby pavements, basement walls, and adjacent structures as excavation stages remove support from the ground. The main site concern is not only how far one point moves, but whether movement grows after each excavation layer, support installation, dewatering step, or backfill stage. Kingmach JMDL-32XXAT single-point bedrock meters can measure embedded displacement at a selected reference layer, while JMDL-22XXAT crack gauges follow opening at nearby structures or retaining elements. JMDL-52XXADT differential meters provide high-resolution relative movement at joints or structural interfaces, and JMLS-22XXADT wire rope sensors can cover longer exposed paths where access is available. A useful pit monitoring plan records excavation depth, support timing, groundwater level, construction vibration, and surrounding building observations beside each displacement curve. This helps engineers distinguish bracket disturbance from real ground movement, and it supports faster decisions when a wall, road edge, or adjacent building begins to respond to excavation. During review, the same point should be compared with nearby settlement, tilt, support force, groundwater, and inspection notes so the movement is interpreted as part of the excavation behavior rather than as a single isolated value. during maintenance.
The future of GNSS
Wireless and low-power networks will change how GNSS are deployed on difficult sites. Many displacement points are located on slopes, dam shoulders, tunnel portals, remote rail subgrades, or temporary construction zones where cabling is expensive and easy to damage. Kingmach displacement products already support automatic acquisition in several forms, and future field layouts can combine wired RS485 points, LoRa or 4G gateways, solar power, and compact edge devices. The engineering task will be to preserve reliable baselines while reducing field maintenance. Sensors with built-in memory and stored calibration data help because the point can retain key identity information even when a gateway is replaced. Remote power planning, connector sealing, lightning protection, and clear channel naming will become as important as the sensor range itself. For remote terrain, the biggest gain will be fewer unnecessary site visits: teams can review battery status, data gaps, and movement direction before sending technicians into a hazardous or hard-to-access location.
Care & Maintenance of GNSS
For embedded GNSS such as multipoint and bedrock displacement meters, maintenance depends heavily on installation records because the sensing parts may not be visible after grouting or backfilling. For JMDL-31XXAT multipoint meters, keep drilling depth, anchor head depth, grouting date, point number, cable route, and baseline readings in one record. The system may monitor three to five points, so channel naming must be exact. For JMDL-32XXAT single-point bedrock meters, record flange position, tie rod condition, anchor point, PVC pipe route, and expected movement direction. During service, compare adjacent depths rather than reading each channel alone. A shallow layer moving while deeper layers remain steady has a different meaning from full-depth displacement. Do not pull or shorten cables during cabinet work, and protect exposed sections from water, rodents, sharp edges, and construction traffic. 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 GNSS
GNSS are especially useful when the movement path is known but the rate and timing are uncertain. Kingmach's differential displacement meter uses two coupled inductive coils so equal and opposite magnetic flux changes can reduce environmental interference and thermal drift. The magnetostrictive JMCW-21XXADT provides non-contact absolute displacement measurement over 0 to 1000 mm, with 0.01 mm resolution, plus RS485 communication and IP67 protection. The wire rope JMLS-22XXADT converts cable extension into digital data for long or curved movement paths. These different mechanisms let designers match the sensor to the physical path instead of forcing one format into every project. A short expansion joint, a hydraulic cylinder, a landslide monitoring line, and a tunnel clearance point may all be called displacement, but each one needs its own mounting, range, and data plan. 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 GNSS 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
Daniel Brown
Excellent environmental monitoring sensors. The data is consistent, and the system integrates smoothly with our existing setup.
James Thompson
The tiltmeters and accelerometers are very sensitive and provide precise data. Perfect for our structural health monitoring system.
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