This standard provides guidelines for monitoring the magnitude, rate, and direction of lateral rock movements using a probe inclinometer. It covers the principle of operation, equipment requirements, installation procedures for the inclinometer casing, and methods for data acquisition, processing, and interpretation. The goal is to assess the stability of rock slopes, foundations, and excavations.
Guidelines for monitoring of rock movements using probe inclinometer
Quick Reference Values
Typical casing outside diameter70 mm to 85 mm
Standard probe reading interval (gauge length)0.5 m
Maximum recommended casing deviation from vertical3 degrees (Clause 6.2.1)
Recommended grout mix (cement:bentonite:water)1:0.3:1 by weight (Annex A)
Initial observation frequencyTwice a day for the first two days (Clause 7.2)
Checksum tolerance for A and B readingsShould be constant, variations indicate errors (Clause 8.2)
Key Formulas
Δx = L * sin(θ) — Incremental lateral deviation at a depth
X = Σ(Δx) — Cumulative lateral displacement from the bottom of the casing
Checksum = Reading(A) + Reading(B) — Used to verify reading quality
Practical Notes
Casing installation is the most critical step; poor installation (e.g., improper grouting, spiraling of grooves) will lead to useless data.
A stable reference point at the bottom of the borehole (socketed into stable rock) is essential for accurate cumulative displacement measurement.
Always take two sets of readings (0 and 180 degrees) to perform a checksum and identify instrument drift or reading errors.