Barton - Bandis Shear Strength Estimation

Barton - Bandis shear strength estimation criterion for rockmass discontinuities (upper and lower bound approach and rock shear test data).

Rock masses contain discontinuities such as bedding planes, joints, shear zones and faults. The shear resistance along discontinuities, which governed the shear resistance of the rock mass, depends on acting normal stresses, interface lentgh, interface roughness etc.  By measuring the shear strength of rock discontinuities of similar length, a significant variation occurs for the τ values, at low confinying stresses. The shear strentg criterion proposed by Barton make use of the following parameters to estimate the shear resistance and the shear strentgh parameters c (cohesion) and φ (angle of internal friction):

·         basic friction angle (Φ_b) determined as the strenth resistance on smooth planar surface

·         joint roughness coefficient (JRC)

·         joint compression strength (JCS)

·         probable filling material and its mechanical properties (such as clay gouge)

It should be also noted that the range of stength variation is reduced as the stresses are increased.