Slope movements in limestones and shales, north-east Marlborough, New Zealand

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dc.contributor.advisor Sporli, K. B. en
dc.contributor.advisor Brothers, R. N. en Prebble, Warwick Maynard en 2007-09-04T07:31:37Z en 2007-09-04T07:31:37Z en 1987 en
dc.identifier THESIS 87-221 en
dc.identifier.citation Thesis (PhD--Geology)--University of Auckland, 1987 en
dc.identifier.uri en
dc.description Full text is available to authenticated members of The University of Auckland only. en
dc.description.abstract Rock mass bulges, debris flows and earth flows are common and widespread in the Upper Cretaceous and Paleogene limestones, shales and muddy fine sandstones of north-east Marlborough. These slope movements also affect the undermass grey wackes, adjacent to the undermass-cover fault and along the steep, elevated eastern face of the Inland kaikoura Range. Only four rock slides and rock block slides were found and these are confined to dip slopes in the limestones. The most common and extensive type of slope movement is rock mass bulging which takes place by flexural toppling in dip slopes consisting of extremely fractured limestone with crush zones. In each bulge, toppling extends down to several tens of metres depth over an area approximately 1 kilometre square. Toppling is initiated by undercutting part way down the slope. The undercutting is caused by debris flows and earth flows which erode into very wide crush zones in shales, removing toe support of the limestone above. Each bulge consists of extremely dilated and loosened rock which has a mass strength more like that of angular gravel rather than fractured rock. The rock mass bulges supply large volumes of limestone gravel to streams, creating severe and damaging aggradation. High intensity rainstorms, and also strong earthquakes, generate voluminous stony debris flows from the bulges and may cause partial collapse, leading to large rock debris avalanches. The rock slides and rock block slides take place where the dip of the limestone beds and dominant defects is 25° or less and is parallel to the slope. Bedding-parallel clayey crush zones form the basal rupture surface. Where the dip of beds and dominant defects exceeds 25° toppling takes over as the slope failure mode, where the rock is not closely fractured and has no crush zones, slope movement does not occur. Defects directly influence both location and type of rock slope failure. Strength, slaking and porosity of intact rock do not directly influence either the location or type of initial slope failure. They do however affect the way slope debris behaves. Strength and slaking of intact rock are dependent on micro structure, not mineralogy or porosity. Microstructure is related to total clay content primarily and to a lesser extent, clay mineral type. Low strength and slaking index are caused by turbulent and matrix microstructures. Microdefects drastically reduce strength and increase slaking. All slope movements are probably late Holocene (⋜5,000 yrs) and many are active. Rapid tectonic uplift and stream downcutting have probably combined to release high compressive stresses in north-east Marlborough. The resulting dilation and loosening of the extremely fractured and crushed rock has promoted active slope movement. en
dc.language.iso en en
dc.publisher ResearchSpace@Auckland en
dc.relation.ispartof PhD Thesis - University of Auckland en
dc.relation.isreferencedby UoA9910521714002091 en
dc.rights Restricted Item. Available to authenticated members of The University of Auckland. en
dc.rights Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. en
dc.rights.uri en
dc.title Slope movements in limestones and shales, north-east Marlborough, New Zealand en
dc.type Thesis en The University of Auckland en Doctoral en PhD en
dc.rights.holder Copyright: The author en

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