Rockfall Hazard Analysis at Small Scale: A Numerical Study for the Estimation of Representative Slope Parameters

The identification of rockfall-affected areas depends on a large number of stochastic variables influencing both triggering and propagation phases. Therefore, rockfall hazard assessment presents huge uncertainties linked to the various scales of analysis. At the small scale (e.g. valley scale), a quick evaluation of rockfall hazard zones is generally required in order to highlight the most critical situations where more detailed analyses should be carried out. The Cone Method (Jaboyedoff and Labiouse 2011), recently implemented in the QPROTO plugin for QGIS, allows to reach this goal with simplified geometrical considerations. In a 3D analysis, the energy line angle and the lateral spreading angle α define a cone of propagation whose apex is located in the rockfall source point. The most significant issue in using the plugin is the evaluation of these angles, which must be defined by the users to consider all the rockfall dissipative processes included in the energy line method (Evans and Hungr 1993). In this paper a study concerning the influence of slope properties (forest coverage and slope inclination) and block characteristics (shape and volume) is proposed, in order to provide to the users of the plugin a preliminary dataset of calibrated angles

Recommendations for the quantitative analysis of landslide risk

This paper presents recommended methodologies for the quantitative analysis of landslide hazard, vulnerability and risk at different spatial scales (site-specific, local, regional and national), as well as for the verification and validation of the results. The methodologies described focus on the evaluation of the probabilities of occurrence of different landslide types with certain characteristics. Methods used to determine the spatial distribution of landslide intensity, the characterisation of the elements at risk, the assessment of the potential degree of damage and the quantification of the vulnerability of the elements at risk, and those used to perform the quantitative risk analysis are also described. The paper is intended for use by scientists and practising engineers, geologists and other landslide experts

The Influence of Shape on the Inherent Rolling Potential of Loose Rocks

The likelihood that rolling of a rock will be initiated and/or sustained on a slope depends on many factors related to the characteristics of the block and the slope. However, all other things being equal, some solid shapes have a greater potential to roll on a slope than others. This paper describes the results of a systematic laboratory study to determine how shape affects the ease with which rolling of ball-like blocks can be initiated, and its likelihood of being sustained. A simple scheme is presented to group basic shapes with similar rolling tendencies. Through systematic tests with polyhedral blocks on a frictional ramp with a range of inclinations, different basic ball-shaped forms are compared in terms of the ease with which rolling can be initiated, and the likelihood that it will be sustained. The results show that "ball" shapes (with principal dimensions of roughly similar size) are more prone to rolling but that even between shapes within this group, such as cubes and octahedra, the tendency to roll is strongly influenced by other factors including the number of faces. The importance of the starting position on the initiation of rolling is also demonstrated and quantified

Study on the support–anchor combined technique to control perilous rock at the source of avalanche by fracture mechanics

As a kind of existing and potential geological disaster at source of avalanche on cliffs or steep slopes, perilous rock has developed in the western area of China widely and it poses a serious threat to highways, railways, pipelines, cities, and mining for a long time. More than ten years of engineering experience have shown the necessity and importance to pay our attention to the avalanche sources in active collapse mitigation. The support - anchor combined technique is devoted to the active hazard mitigation measures of perilous rock. This paper introduces fracture mechanics to investigate the design procedure of the support - anchor combined technique. To obtain reasonable design parameters of the technique, both stability assessment criterion and three safety classes of protection engineering for perilous rock is proposed, further, stable analysis methods for various types of perilous rock are established by using fracture mechanics. Abiding by the idea that to improve stability coefficient to a higher level, the support force of structure and the anchorage force of anchorbolt from the support - anchor combined technique are introduced into stability analysis methods established above, which can estimate the section dimension of support subunit and the amount of anchorbolt of the technique. Engineering applications of the technique in thousands of protection engineering have identified the remarkable effectiveness.Більш ніж десять років інженерного досвіду в західній частині Китаю показали необхідність і важливість уваги до джерел лавин з метою активного зменшення катастроф. Для вимірювання активного зменшення ризику від небезпечних грунтів розроблена об‘єднана методика «опора-анкер». У роботі застосована механіка руйнування для дослідження процедури створення розрахункової схеми об‘єднаної методики «опора-анкер». Для отримання коректних параметрів схеми запропоновано критерій оцінки стійкості і три класи безпеки інженерного захисту для небезпечних грунтів. Далі на основі механіки руйнування розвинуті стійкі методи аналізу для різних типів небезпечних грунтів. На основі ідеї про покращення коефіцієнтів стійкості до вищого рівня в методи аналізу стійкості введено силу опори в конструкції та силу анкера для анкерного болта в опорі з об‘єднаної методики «опора-анкер». Це дозволяє оцінити в застосованій методиці розмір секції в опорі і кількість анкерних болтів. Інженерні застосування запропонованої методики показали суттєву ефективність у тисячах випадків інженерного захисту