Failure in the Tension Zone around a Circular Tunnel Excavated in Saturated Porous Rock

Rock failure during tunnel excavation is still a matter of concern. The influence groundwater generally taken into account along discontinuities or in “soil-like” formations. However, brittle saturated porous rocks can be subject to undrained conditions excavation. Negative effective stresses develop close the boundary. This study aims at identifying limit pore pressure rock around tunnel, which induces tension zone. A discussion related strength parameters zone, with Hoek and Brown criterion, presented. comparative analysis different far-field properties indicates that decreases depth tunnel. directly proportional uniaxial compressive inversely constant m. When state stress role m reduces. Numerical models set up FLAC indicate zone has thickness about 1 Due uncertainties stresses, hydro-mechanical behavior, rock, requires careful investigation, order avoid stability problems.