Andreas Giannakogiorgos: Οκτωβρίου 2011

25.10.11

Wellpoint dewatering design layout

23.10.11

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.

Hoek - Brown Failure Criterion

The criterion starts from the properties of intact rock and then introduced factors to reduce these properties on the basis of the characteristics of joints in a rock mass. The rock mass shear strength is estimated using the Hoek and Brown failure criterion (edition 2002), where rock mass is considered as homogeneous material and an average value is determind by fitting a linear Mohr - Coulomb relationship by least squares method.

In the above example a rockmass of conglomerate is considered, and taken into account the variation of data and parameters (upper and lower bound).

13.10.11

Reverse fault

12.10.11

Massive rock slope failure (Cornwall cliff collapse)

http://www.bbc.co.uk/news/uk-15251292

Geologist Richard Hocking. who filmed a massive cliff fall in Cornwall, says it was the most exciting thing that he has ever seen.

Thousands of tonnes of rock fell into the sea at North Cliffs near Hayle two weeks ago - just days after part of the coastal footpath was diverted.

Mr Hocking, who is a soils and materials engineer for Cornwall Council, was there to assess the situation when the collapse happened. He had his camera with him and managed to capture the event on it.

7th class slope failure (after Cruden & Varnes '96)