土木環境工学ジャーナル

A New Criterion on Designing an Effective Cable Bolt Length Subject to Static Loading in Underground Excavations

Abstract

Fhatuwani Sengani

A simple probability analysis failure criterion for cable bolts in underground excavation is described. The criterion was developed using static loading tests of mechanical anchors (38 tons, 18 mm diameter cable, 2 m length and six strands), and Finite Element Method. Three static loading tests were performed, thereafter, an underground excavation was simulated with several wedges wherein the effectiveness of the bolt was tested in varying spacing, while other parameters remaining constant. A simple probability criterion was therefore developed to bridge the gap on identifying effective bolt length and total effective length of the bolts within the excavation in varying strata control (change in angle of the strata and change in thickness of the strata). The criterion is suitable for predicting the effective bolt length, predicting the total effective bolts length within the excavation provided the orientation and thickness of strata in known and also suitable to classify the excavation as over/under supported. Two practical applications and examples of the criterion are described. These are firstly, identifying of and secondly, predicting the effective bolt length and total effective length of the bolts in strata with varying orientation and thickness in both hanging and side walls.