An Engineering Geological Analysis of the Tutira Landslide Dam, Hawke’s Bay, New Zealand.

摘要

The Tutira landslide dam is located in northern central Hawke’s Bay, and has resulted in the formation ofrnthree lakes: Tutira; Waikapiro; and Orakai. The landslide occurred approximately 7200 years ago, asrndetermined by carbon dating of lake-core sediments. The slope failure occurred in a Plio-Pleistocenernsedimentary sequence of interbedded limestones, mudstones, and sandstones. Traditional field mappingrn(including the use of the Geological Strength Index) and terrestrial photogrammetry were used torncharacterize the lithology, rock mass conditions and discontinuities present in the headscarp. There wasrngood correlation between the compass and photogrammetric discontinuity measurements, revealing threerndistinct discontinuity sets. The bedding dips at a shallow angle into the slope, and intersects with twornvertical and orthogonal joint sets, forming large sized blocks in the headscarp. Kinematic analysis wasrnundertaken, and showed that the landslide could not have failed by simple sliding, wedge, or topplingrnfailure. The structural and geological data along with lab strength data were used as input for 2D limitrnequilibrium models. These were designed to analyse the triggers and mechanisms of movement of thernTutira landslide. The Hawke’s Bay is a region which experiences both intense precipitation storms, andrnfrequent seismic activity, therefore high pore pressure and seismic loading, as well as fluvial incision arernimportant parameters included in the models. The results of these models and a discussion about themrnare detailed in this paper.