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The development of progressive failure in slopes is a poorly understood process, and relatively few advances in terms of the mechanics of the development of failure have been made since 1967. However, advances in the understanding of the development of fractures in brittle materials provide new insights into landslide mechanics. In addition, the link between the deformation mechanism and movement type allows interpretation of displacement records to determine the mechanisms acting within a slope. This paper utilizes these insights into deformation processes, combined with 'reinflation' stress-path triaxial experiments, to propose a new model for the development of a progressive, first-time failure within a slope. This model is able to explain the development of failure when the factor of safety is greater than unity, the existence of 'Saito' linearity (a linear trend when the reciprocal of velocity prior to failure is plotted against time) during tertiary creep, and the development of failures during periods of apparently increasing normal effective stress. Keywords: landslides, deformation, microcracks, failure, strain.

The movement of rotational and translational landslides occurs as a result of either sliding on discrete shear surfaces or ductile deformation within a shear zone. In this paper we examine the movement histories of a number of landslides that occurred in a variety of materials in a range of settings, and demonstrate that one of two movement styles is evident during accelerating phases for all landslides observed. The first style, which has previously been noted, has a linear form in a plot of 1/v against time (v is velocity). The second style has an asymptotic form in the same plot, trending toward steady-state movement rates. We propose that the linear form occurs in landslides in which crack propagation (i.e., shear surface generation) is the dominant process, whereas the second style occurs where movement is taking place across existing planes of weakness or as a result of ductile deformation processes. This study demonstrates that the evaluation of plots of 1/v against time for landslides is a useful technique for forecasting movement styles and rates, and for interpreting ongoing deformation processes in real time. Keywords: landslides, acceleration, brittle deformation, ductile deformation displacements.

Landslides represent the most frequent geological hazard in mountainous environments. Most notably, landslides are a major source of fatalities and damage related to strong earthquakes. The main aim of this research is to show through three-dimensional engineer-friendly computer drawings, different mountain environments where coseismic landslides could be generated during shallow crustal and megathrust earthquakes in the Andes of central Chile. We have determined topographic, geomorphological, geological and seismic controlling factors in the occurrence of earthquake-triggered landslides from: (1) a comparison of local earthquake-induced landslide inventories in Chile (the Mw 6.2, shallow crustal Aysén earthquake in 2007 (45.3° S) and the Mw 8.8, megathrust Maule earthquake in 2010 (32.5°S–38.5°S)) with others from abroad; and (2) analysis of large, prehistoric landslide inventories proposed as likely induced by seismic activity. With these results, we have built four representative geomodels of coseismic landslide geomorphological environments in the Andes of central Chile. Each one represents the possible landslide types that could be generated by a shallow crustal earthquake v. those likely to be generated by a megathrust earthquake. Additionally, the associated hazards and suggested mitigation measures are expressed in each scenario. These geomodels are a powerful tool for earthquake-induced landslide hazard assessment. Thematic collection: This article is part of the Ground models in engineering geology and hydrogeology collection available at: https://www.lyellcollection.org/cc/Ground-models-in-engineering-geology-and-hydrogeology [ABSTRACT FROM AUTHOR]

Landslides are a ubiquitous hazard in terrestrial environments with slopes, incurring human fatalities in urban settlements, along transport corridors, or at sites of rural industry. Assessment of landslide risk requires high quality landslide databases. Recently, global landslide databases have shown the extent to which landslides impact on society and identified areas most at risk. Previous global analysis has focused on rainfall-triggered landslides over short ~ 5 year observation periods. This paper presents spatio-temporal analysis of a global dataset of fatal non-seismic landslides, covering the period from January 2004 to December 2016. The data show that in total ~ 56 000 people were killed in 4862 distinct landslide events. The spatial distribution of landslides is heterogeneous, with Asia representing the dominant geographical area. There are high levels of inter-annual variation in the occurrence of landslides. Although more active years coincide with recognised patterns of regional rainfall driven by climate anomalies, climate modes (such as ENSO) cannot yet be related to landsliding, requiring a 30+ year landslide dataset. Our analysis demonstrates landslide occurrence triggered by human activity is increasing, in particular in relation to construction, illegal mining and hill-cutting. This supports notions that human disturbance may be more detrimental to future landslide incidence than climate. [ABSTRACT FROM AUTHOR]

Results are presented of a sequence of laboratory tests undertaken to elucidate the behaviour of deep-seated landslides. In deep-seated failures deformation has been reported at depths of up to 250 m. In the movement zone, owing to the weight of the overburden and the surrounding stress environment, conventional soil mechanics cannot be used to explain effectively associations between the landslip activity andthe deformation mechanisms operating within the moving mass. A series of experiments has been undertaken on London Clay using a high pressure, servohydraulically controlled triaxial deformation system, to replicate the stresses acting at the base of a large, deep-seated landslide. A number of tests were undertaken, the most significant focusing on the transition between ductile and brittle behaviour. Although sediments usually behave in a brittle manner at low effective stresses (common to many geomorphological studies) and in a ductile manner at high effective stresses, the results presented here identify for the first time in mudrocks a transitional phase of behaviour in which creep-like movement will manifest itself at the base of a deep-seated landslide as the growth of microcracks. The microcracks may eventually coalesce to form a shear surface, a consequence of which is likely to be sudden failure. The results thus have important implications inthe understanding of movement mechanisms in large, deep-seated failures, rates of displacement and how they may change through time. [ABSTRACT FROM AUTHOR]