Cut Slope Failure of Mudstone Formations in Southern Taiwan

摘要

Several small scale surface slips were reported on cut slopes when a new trans-island highway was constructed through the mudstone area in southern Taiwan. Ironically, tied-back slopes with ground anchors were extensively used in some of those slopes experiencing slip failure. Certain factors of mudstone formations seem to have been overlooked by the designers. To identify the problems, the influence of rock strength reduction with time and the variation of groundwater level on the stability of a cut slope were evaluated numerically. It has been found that the slope failure mechanism of the weak rock is similar to that of the soil rather than the plane failure mechanism of the hard rock. To provide good slope surface reinforcement and reduce the number of tension cracks; rock bolts and grillage structures have proven their ability to prevent surface slip failure in cut slopes of the mudstone formations.