Rock slide in spillway cut projecto trasvase olmos

The Olmos Diversion Project, Peru currently under construction, includes a dam across the Huancabamba River and a tunnel conveying the water across the continental divide from east to west where it will be used for irrigation in the Lambayeque district.
The more that 100 m deep cut is being constructed in the left abutment for a combined dam spillway and bottom outlet structure. On 16 March 2007 a large slide took place as the cut was excavated close to its final depth. The slide measured 90 m in height, 100 m in width and having a volume of more that 100 000 m3.
The presentation will focus on back analysis of the slide to estimate the rock mass properties and how that was used for design of reinforcement of the rock mass behind the slide area. The issues to be covered are: lithology (Andesite, Dacite, Granodirite), structures (joints, dikes, faults, weathering), design of reinforcement (prestressed anchors, concrete ribs, shotcrete cover, rock bolts) and instrumentation (inclinometers, survey markers, load cells, ground water wells).
The case demonstrates how the observational method may be used in design of rock mass reinforcement.