Centrifugal modelling of the landslides triggering mechanism in layered fill slopes

Concerns over loosely compacted fill slopes stability in Hong Kong arouse in the past few decades, since the Sau Mau Ping disasters in 1972 and 1976. Research conducted on loose fill slopes in the past few years aimed to understand the failure mechanisms of a loosely compacted fill slope. Recently, layering effect has been hypothesised to be a possible condition in the fill slopes leading to a fast flowslide triggered by a rise of water table. Centrifuge experiments were conducted to investigate the layering effect on a model granular slope and hence to determine the triggering mechanisms of seepage induced slope failure. Test results showed that slope failure can be easily triggered in layered fill model slopes when seepage is restricted and localised pore water pressure is allowed to build up within the slope. © 2006 Taylor & Francis Group, London.

Semi-analytic slope delay model for CMOS switch-level timing verification

A novel slope delay model for CMOS switch-level timing verification is presented. It differs from conventional methods in being semianalytic in character. The model assumes that all input waveforms are trapezoidal in overall shape, but that they vary in their slope. This simplification is quite reasonable and does not seriously affect precision, but it facilitates rapid solution. The model divides the stages in a switch-level circuit into two types. One corresponds to the logic gates, and the other corresponds to logic gates with pass transistors connected to their outputs. Semianalytic modeling for both cases is discussed.

Seismic performance of geomembrane placed on a slope in a MSW landfill cell -A centrifuge study

Geomembranes are one of the most commonly used geosynthetics in landfill liner systems. They retain the leachate produced by the waste and prevent leakage. Geomembranes may experience harsh environmental conditions such as extreme temperatures or earthquake loading. Earthquake loading can be an extreme loading case for landfills located in seismic regions. This study, based on dynamic centrifuge testing, investigates the effects of simulated earthquake loading on the tension experienced bythe geomembrane on a landfill slope. The landfill modeled in the dynamic centrifuge test was a municipal solid waste (MSW) landfill cell with a single geomembrane-clay liner system (45° side slope and 10 m slope length). The paper shows that moderate earthquake loading (base acceleration between 0.1g to 0.2g) can result in transient increases of around 20% in geomembrane tension, with permanent tension increases of around 5%.

Centrifuge modelling of submarine landslide flows

Landslides occur both onshore and offshore, however little attention has been given to offshore landslides (submarine landslides). The unique characteristics of submarine landslides include large mass movements and long travel distances at very gentle slopes. Submarine landslides have significant impacts and consequences on offshore and coastal facilities. This paper presents data from a series of centrifuge tests simulating submarine landslide flows on a very gentle slope. Experiments were conducted at different gravity levels to understand the scaling laws involved in simulating submarine landslide flows through centrifuge modelling. The slope was instrumented with miniature sensors for measurements of pore pressure beneath the flow. A series of digital cameras were used to capture the flow in flight. The results provide a better understanding of the scaling laws that needs to be adopted for centrifuge experiments involving submarine landslide flows and gives an insight into the flow mechanisms. © 2010 Taylor & Francis Group, London.

Influence of ground anchors on topographic amplification at slope crests

One feature of earthquake loading in regions containing sloping ground is a marked increase in accelerations at the crests of slopes. Many field cases exist where such increased accelerations were measured. The observed increase in the amount and severity of observed building damage near the edge of cliff-type topographies has been attributed to the topographic amplification. To counter this, it has been shown that anchoring the soil mass responsible for this to the rest of the stable soil mass can reduce the amount of topographic amplification. In this study, dynamic centrifuge modelling will be used to identify the region affected by topographic amplification in a model slope. The soil accelerations recorded will be compared to those measured in a comparable model treated by anchors. In addition, the tension measured in the anchors will be examined in order to better understand how the anchors are transferring the loads and mitigating these amplifications. © 2010 Taylor & Francis Group, London.

Effects of shear band propagation on submarine landslide

Interbedded layers of glacial deposits and marine or glacimarine clay layers are a common feature of offshore sediment. Typically, offshore marine clays are lightly overconsolidated sensitive clay. Some case histories on submarine landslides show that the slip surface passes through these marine clay layers. In this paper a model is proposed for post-peak strain softening behavior of marine sensitive clay. The slope failure mechanism is examined using the concept of shear band propagation. It is shown that shear band propagation and post-peak stress-strain behavior of clay layers are two major factors in submarine slope stability analysis. Copyright © 2012 by the International Society of Offshore and Polar Engineers (ISOPE).