Failure Mechanisms and Strength of Non-Persistent Rock Joints

Jennings method which assumes full shear strength along joint and rock bridge is a useful reference condition. The Bridge Mobilized Strength Ratio, BMSR, provides a means of assessing how much of the reference strength along the bridge is mobilized. The MBSR is the ratio of (mobilized shear strength minus shear strength of joint) to (Jennings shear strength minus shear strength of joint), for the average normalized stress at failure. Conditions causing BMSR to be different from the reference value include: (a) for mode 1, shear failure in the plane of the joints through bridge and non-persistent joints, BMSR decreases, as the ratio of normal stress, σ\sb{\rm n}, to compressive strength, σ\sb{\rm n}/σ\sb{\rm c}, decreases below 0.2. (b) for mass stiffness $<$ bridge stiffness, and as number of bridges increases, progressive failure can develop reducing BMSR. (c) for the case of $\phi\sb{\rm j} \ll \phi\sb{\rm i}$, it was observed for single joints that the BMSR was above one. It is concluded that the higher value was due to concentration of the normal stress on the stiffer bridge, thus giving a higher shear strength than computed by Jennings method, which assumes a uniform normal stress distribution. (d) offset of joints reduces confinement and increases tensile stress conditions between joint segments causing a reduction of strength.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Civil Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Mughieda, Omer Sulieman

Contributors dc:contributor

• E. Cording

• Engineering, Civil

Language dc:language

eng

Identifier

(MiAaPQ)AAI9812716

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/83445