Guidelines for monitoring of rock movements using probe inclinometer
1996 Edition

IS 14395: Scope and Core Specifications for Probe Inclinometer Systems

• Objective: To gauge horizontal deflections and movements within boreholes by recording the tilt angle of a probe inside a guiding tube.

Essential Specifications:

Measurement Principle:

• Records tilt angle ( e ) between probe axis and vertical.
• Calculates horizontal displacement ( d ) at depth ( z ) via integration:

[ d = \int_0^z \tan(e) , dz ]

Rounding Instructions:

• Adhere to IS 2:1960 guidelines.
• Preserve significant digits consistent with specified values.

flowchart LR
    A[Probe Inclinometer] --> B[Probe with Tilt Sensor]
    B --> C[Guide Tube with Keyways]
    C --> D[Grouted Borehole]
    B --> E[Electrical Cable to Readout]
    E --> F[Data Acquisition & Analysis]

This setup guarantees accurate tracking of rock and borehole movements following IS 14395 directives.

IS 14395: Components of Monitoring Systems for Rock Movement Using Probe Inclinometers

Main Elements (Clause 2.1)

The monitoring apparatus includes:

• Probe: Detects angular changes caused by rock shifts within boreholes.
• Transmission System: Transfers probe data to surface equipment via:
  • Mechanical rods
  • Electrical cables for electronic sensors
  • Wireless radiotelemetry
• Readout and Recording Devices: Convert transmitted signals into readable data:
  • Dial gauges
  • Digital displays
  • Magnetic tape recorders or data loggers

Important Notes:

• The inclinometer measures relative angular displacement between successive borehole points.
• Data obtained helps determine deformation profiles and movement rates.

Angular Displacement Formula ((\theta)):

[ \theta = \frac{\Delta x}{L} ] Where:

• (\Delta x) = lateral displacement between two points
• (L) = distance separating measurement points

Summary Table of Monitoring Components

flowchart LR
    Probe --> Transmission --> Readout
    subgraph Monitoring System
        Probe
        Transmission
        Readout
    end

These guidelines provide for dependable, ongoing monitoring of rock stability using probe inclinometers.

Operational Fundamentals of Probe Inclinometers as per IS 14395

• Probe Structure: Features a cylindrical housing with spring-loaded guide wheels spaced at 0.5 or 1 meter intervals, containing a gravity-based tilt sensor that measures the angle ( e ) between the probe axis and the vertical.

• Guide Tube: Constructed from plastic or epoxy-coated aluminum with four orthogonal internal keyways; flexible enough to follow borehole curvature without buckling; annulus filled with grout having rigidity similar to the surrounding rock.

• Measurement Procedure:

  • Probe is lowered incrementally inside the guide tube.
  • Tilt angle ( e ) is recorded at each depth.
  • Horizontal displacement between depths calculated by:

  [ \Delta x = L \times \sin e ]

  where ( L ) is the distance between consecutive readings.

• Accuracy and Sensitivity:

  • Reproducibility of ±0.01°
  • Cable graduation accuracy better than 5 mm or 0.05% of depth
  • Probe rotation limited to ≤1° per 3 meters travel

• Calibration: Utilizes an adjustable inclinometer calibrator with an independent angle measurement device accurate to better than ±0.01°.

Key Formula for Calculating Horizontal Displacement

[ \boxed{ \Delta x = L \times \sin e } ]

flowchart LR
    A[Probe with Tilt Sensor] --> B[Lowered within Guide Tube]
    B --> C[Measure Tilt Angle \(e\)]
    C --> D[Compute Horizontal Displacement \(\Delta x = L \sin e\)]
    D --> E[Monitor Movement of Ground]

This technique enables determination of borehole displacement by accumulating horizontal deviations along its depth.

IS 14395 - Installation Guidelines (Clause 4.2):

• Borehole Drilling: Drill boreholes to the required depth; if steel casing is employed, it must be fully removed prior to guide tube installation.

• Geotechnical Logging: Examine core samples and borehole conditions; document detailed logs highlighting zones of movement.

• Guide Tube Placement:

  • Insert guide tube and record the azimuth of keyways within ±3" accuracy.
  • Secure the guide tube and check for spiraling using a spiral probe.

• Grouting:

  • Completely fill the annular space between borehole and guide tube with grout.
  • Utilize tremie pipe techniques especially in water-filled or deep boreholes to prevent grout contamination.
  • Flush and clean the interior of the guide tube after grouting.

• Protection:

  • Fit a lockable protective cap at the guide tube opening to prevent debris ingress and vandalism.
  • Record collar position and elevation with ±5 mm accuracy for reference.

• Initial Measurement:

  • Take multiple readings after grout has set; average these for baseline establishment.

• Measurement Methodology:

  • Lower the probe with wheels engaging the keyways; take readings at intervals equal to or twice the wheel spacing.
  • Conduct two traverses per keyway, rotating the probe 180° to detect face errors.
  • Optionally repeat for the second pair of keyways.

• Data Treatment:

  • Average readings from opposite faces to correct face error.
  • Calculate incremental angle and displacement changes:

  [ \Delta d = L \sin \Delta \theta ]

  where

  • (L) = distance between readings (mm),

  • (\Delta \theta) = incremental angle in radians (approximately 80° between readings).

  • Sum incremental displacements from the bottom upward to plot total displacement versus depth.

Installation Checklist Summary

flowchart TD
    A[Borehole Drilling] --> B[Core Inspection & Logging]
    B --> C[Guide Tube Installation]
    C --> D[Azimuth Recording]
    D --> E[Clamp & Spiral Check]
    E --> F[Grouting with Tremie Pipe]
    F --> G[Tube Flushing & Cleaning]
    G --> H[Protective Cap Installation]
    H --> I[Initial Measurement Readings]

This process ensures accurate inclinometer function in line with IS 14395.

IS 14395 – Key Points on Data Processing

• Rounding Off: Final measurement results should be rounded in accordance with IS 2:1960, maintaining the significant digits of the specified values.

• Data Validation: Field measurements must be reviewed for obvious anomalies; any corrections should be clearly documented.

• Face Error Adjustment: Average readings from opposite probe faces to mitigate face error.

• Incremental Calculations:

  • Determine incremental changes by subtracting baseline readings from subsequent measurements at the same guide tube location.

  • Convert incremental angular changes ((\theta) in degrees) to incremental displacement ((\Delta) in mm) using:

    [ \Delta = L \times \sin \theta ]

    where L is the spacing between successive readings in mm, and (\theta) is the incremental angle in degrees.

• Summation and Graphing: Add incremental displacements from bottom to top to construct a total displacement profile against depth, facilitating identification of movement zones.

Data Processing Summary Table

flowchart TD
    A[Initial Reading] --> B[Face Error Correction]
    B --> C[Calculate Incremental Change]
    C --> D[Convert Angle to Displacement]
    D --> E[Sum Displacements]
    E --> F[Plot Displacement vs Depth]

This approach ensures accurate tracking of ground movement using inclinometer data consistent with IS 14395.

IS 14395 - Committee Membership and Installation/Data Processing Specifications

Committee Members (Annex A)

The Rock Mechanics Sectional Committee (CED 48) comprises:

(Complete list available in Annex A of IS 14395)

Installation and Data Processing Highlights (Clauses 4.2 & 5)

• Drill boreholes to full depth; withdraw any casing before guide tube placement.

• Achieve ±3" accuracy in guide tube azimuth recording; grout annulus fully using tremie pipe in water-filled holes.

• Protect guide tube ends with lockable caps against debris and vandalism.

• Take readings at intervals matching probe wheel spacing; perform two opposite-face traverses for error verification.

• Correct face errors by averaging opposite faces.

• Calculate incremental displacement (\delta) from angle (\theta) using:

  [ \delta = L \sin \theta ]

  where

  • (L) = spacing between readings in mm,
  • (\theta) = incremental angle in radians (typically 80° per IS 14395).

• Plot cumulative displacement against depth to identify zones of movement.

flowchart TD
    A[Borehole Drilling] --> B[Guide Tube Installation]
    B --> C[Grouting and Protection]
    C --> D[Measurement and Data Recording]
    D --> E[Data Processing and Analysis]