Rock Mechanics

Dr. D. V. Sarwade, Scientist ‘E’

The Rock Mechanics (Field) Group comprises of Rock Mechanics (Field) and the Engineering Geophysics divisions. Rock Mechanics Field Investigations involves in-situ rock mass characterisation. The main activities are:

Rock Mechanics Field Division carries out the following tests:

• Shear Strength Properties of Discontinuous Rock Mass by Direct Shear Test on Rock-Rock and Concrete-Rock Interfaces.
• Deformability Characteristics of Rock Mass by:
  • Uniaxial Jacking tests in Drift, Trench or in open.
  • Goodman Jack Tests inside drill holes.
  • Flat Jack Tests.
• In-situ Stress Measurements using Hydraulic Fracturing Technique for:
  • Design and layout of underground structures like tunnels and caverns.
  • Limiting the pressure for consolidation/curtain grouting in dam foundations.
  • Design of support system and permanent lining in pressure tunnels.
• Groutability Test in Rock.
• Pull Out Strength Test on Rock Bolts and Anchor Bars.
• Numerical analysis.

Engineering Geophysics Division involves use of Geophysical Methods for deciphering the sub-surface ground conditions, delineation of bed rock, thickness of overburden, rippability, continuity of rock between drill holes, diagnostic health investigations, effect of vibrations on engineering structures. The broad activities of Engineering Geophysics are:

• Seismic Refraction Survey using Geophones and Hydrophones.
• Electrical Resistivity Surveys.
• Cross Hole Tomography.
• Vibration Monitoring to assess the impact of blast on adjoining ground and other structures and to assist in design and optimisation of blasting operations.
• Underwater Scanning of Submerged Structures using Remote operated Underwater Vehicle (ROV).
• Impart training to engineers from within the country and from overseas for investigation and testing in the fields of Rock Engineering.

Rock Mechanics Field Investigations

Uniaxial Jacking Test in Drift

Uniaxial Jacking Test in Trench

Direct Shear Test in Drift

Direct Shear Test in Open

Goodman Jack Tests in Drillholes

Groutability Test

Hydraulic Fracturing Test

Anchor Bar Pull out Test

Seismic Refraction Survey

Electrical Resistivity Survey

Blast Vibration Studies

Underwater Scanning using ROV

Rock Mechanics - Lab group comprises of Rock Mechanics Laboratory division and Workshop and Instrumentation division. The main activities are:

For detailed and controlled testing of responses of rock under different loading conditions, the Rock Engineering Laboratory is well-equipped to undertake the holistic assessment of the detached rock. The properties determined are:

• Physical Properties (Dry, saturated and grain densities; apparent Porosity and water content at saturation)
• Slake Durability Index
• Strength and Deformability Characteristics of Intact Rock in Uniaxial Compression (UCS, Tangent Modulus and Poisson Ratio)
• Assessment of shear strength properties through triaxial compression (Apparent Cohesion and Angle of Internal Friction)
• Direct shear test on rock discontinuities
• Assessment of Hoek and Brown parameters of intact rock (m and s parameters)
• Indirect Tensile Strengths of Rock
• Compressive and Shear Wave velocities in rock
• Point Load Strength Index
• Schmidt Hammer Rebound Number
• Dorry Abrasion Value

Instrumentation Division

• Instrumentation division is involved in the Hydro-electric Projects at the pre-construction stage, construction stage, and remains active even during the post-commissioning stage. To gain confidence in the functioning/safety of the structures involved, and to check the assumptions involved in the design of the structures, crucial importance of instrumentation cannot be over-emphasised.
• Monitoring the health of the existing structures.
• Dissemination of expertise to in-service engineers of various State Government Departments by establishing regional testing laboratories and impart training in laboratory testing on rock.
• Impart training to engineers from within the country and from overseas for investigation and testing in the fields of Geotechnical Engineering.

Rock Mechanics Laboratory

Testing for UCS and deformation characteristics

Slake Durability Test

Point Load Test

Non Destructive Testing