Question

0 12 1) A large roadcut with near-vertical walls is planned for through a ridge. Preliminary geologic investigations and map of the location is shown on the attached page, at the sea shown as the dark heavy line, and the sides o original orientation for the roadcut was by the team and are charged with identifying potentia could be a problem for slope stability if, after ex the cut that sits on the fault surface where the fault dip (true or app greater than 20° The general location of the roadcut cannot be the cut can be changed so that the parent din could be reduced to rotation of the roadcut would involve excavation of additional maten cost), the project manager will only allow changing oject manager will only allow changing the orientation the minimal amount necessary to accomplish the goal of safety. planned for a new interstate highway cutting vestigations indicate there is a fault in this area. A ed page, at the scale of 1:12,000. The fault is c, and the sides of the proposed roadcutare dotted lines. The ucut was by the civil engineers you are now part of this de dentifying potential geologic slope stability problems. This fault Stability if, after excavation, there is a rock mass on one side te the fault dip(true or apparent) into the roadcut is the roadcut cannot be moved, but the orientation of apparent dip could be reduced to 20° or less. Since any Ive excavation of additional material (and hence additional Answer the following questions: a) What is the true strike and dip of the fault? b) What is the apparent dip of the fault surface dipping directly (perpendicular) into the roadcut, as the cut is currently oriented? c) What should be the orientation of the cut in order for the apparent dip of the fault surface (dipping directly (perpendicular) into the roadcut) to be at 20° or less? d) What is the apparent dip of the fault along the surface of the cut that faces the road (in other words, what motorists would see inside the cut) after the re-orientation you propose?

Answer 1

aj strike - 106" Con to roadcut) dip = les than 20%. i) Appearant clip tan & = tane x cosp. Here o = 20 and B=-74 tau x = tan 26 x Cos 74° x = 4.12 , c) Orientation must be for the apparent dip be at (2004 20" perpendicular in order of fault surface to 1. 1.d). The road is levelled as much as possible by the application of materice on the side required