dExto
1 to 6-Point Multi-Point Borehole Extensometer combines a traditional multi-rod design and digital signal processing to result in dramatically improved accuracy.
1 to 6-Point Multi-Point Borehole Extensometer combines a traditional multi-rod design and digital signal processing to result in dramatically improved accuracy.
The dExto is a unique , fully integrated, and miniaturized 1 to 6-point multiple rod Extensometer, which combines internal multi-rod design and digital signal processing, in order to dramatically improve accuracy.
This extremely accurate instrument has six Linear Variable Induction Transducers (LVIT's) and an on-board digital temperature sensor. The digital signals eliminate the necessity for analog-to-digital conversion, resulting in a unit that outputs data in mm and results in a readout unit that reads data in mm and °C.
Data from the dExto can be collected using BluLink, BluLogger and BluGateway dataloggers . These loggers require minimal configuration and are fully interchangeable with any other type of YieldPoint instrument.
| Specifications | |
|---|---|
| Dimensions | 25mm diameter can be placed in 50mm hole. |
| Features | Up to 6 Anchor points over lengths up to 60m |
| Disp. Range (F.S) | 125, 150 (standard), 200 and 250mm. |
| Disp. Resolution: | 0.01mm |
| Disp. Accuracy | 0.5% F.S(<10m) and 0.25% linearity (>10m). Depending on distance between anchor point and head |
| Operational Temp. Range | -40 to 125°C |
| Temp. Resolution | 0.1°C |
| Temp Accuracy | +/-1°C (inside electronics head) |
| Output Signal | RS485 with transmission up to 500m over 2 x tp. |
| Connectivity |
Ethernet, WiFi networks, LTE networks, Loadsensing, Ackcio, Wisen, Senceive, and CSI. |
As part of CEMI’s UDMN project YieldPoint has been working with Vale Canada’s to monitor a pillar in a hard-rock nickel mine located 8000ft underground in Sudbury, Ontario. A dense deployment of instruments was installed, including Borehole Pressure Cells and optical extensometers in addition to d-EXTO’s. By installing a dense deployment of borehole extensometers the deformation pattern in the pillar could be determined in considerable detail. By interpolating and contouring between instruments, Brad Forbes was able to provide the mine with a frame-by-frame playback of progressive deformation as the mining sequence evolved. A shear zone transecting the instrument array had a dramatic effect of the spatial distribution of deformation. The project team has recently submitted an abstract to the upcoming First International Conference on Underground Mining Technology to be held in Sudbury (Punkkinen et al, 2017).
One conclusion is:
“Contouring between adjacent multi-point borehole extensometer measurements has provided an excellent depiction of the pillar behavior as development, using the current face destress procedure, approached a known shear zone.”
