Current and future role of instrumentation and monitoring in the performance of transport infrastructure slopes

Instrumentation is often used to monitor the performance of engineered infrastructure slopes. This paper looks at the current role of instrumentation and monitoring, including the reasons for monitoring infrastructure slopes, the instrumentation typically installed and parameters measured. The paper then investigates recent developments in technology and considers how these may change the way that monitoring is used in the future, and tries to summarize the barriers and challenges to greater use of instrumentation in slope engineering. The challenges relate to economics of instrumentation within a wider risk management system, a better understanding of the way in which slopes perform and/or lose performance, and the complexities of managing and making decisions from greater quantities of data

Monitoring the performance of unsaturated soil slopes

Field monitoring is necessary for the geotechnical engineer to verify design assumptions. More importantly, the field data may also be assembled into a comprehensive case record that is available for use when checking validity of any analytical and numerical models. The ongoing process of back-analysis in unsaturated soil engineering can help to refine and improve our understanding, providing guidance for future designs, where the effects of soil suction and hydraulic hysteresis are still being explored. A range of recent field studies of the mechanisms of rainfall infiltration into slopes is presented. In addition, some physical simulations of unsaturated soil slopes subjected to rainfall, rising ground water table and changes of moisture in centrifuge model tests are reported. © Springer Science+Business Media B.V. 2008

Monitoring large-scale tests for nuclear waste disposal

Two large-scale "in situ" demonstration experiments and their instrumentation are described. The first test (FEBEX Experiment) involves the hydration of a compacted bentonite barrier under the combined effect of an inner source of heat and an outer water flow from the confining saturated granite rock. In the second case, the progressive de-saturation of Opalinus clay induced by maintained ventilation of an unlined tunnel is analyzed. The paper shows the performance of different sensors (capacitive cells, psychrometers, TDR's) and a comparison of fill behaviour with modelling results. The long term performance of some instruments could also be evaluated specially in the case of FEBEX test. Capacitive sensors provide relative humidity data during long transient periods characterised by very large variations of suction within the bentonite. © Springer Science+Business Media B.V. 2008

Coupled processes during rainfall: an experimental investigation on a silty sand

he factors that contributed to the initiation of a triggering mechanism in a shallow landslides induced by rainfall are investigated in this work at laboratory scale. The aim of the work was to characterise the behaviour of the soil in triaxial tests, in the light of the possible failure mechanisms in a slope subjected to rainfall. The material study is a silty sand from a steep slope in Ruedlingen in the North-East of Switzerland, where a landslide triggering experiment was carried out. Conventional drained and undrained triaxial tests for the water phase were conducted to detect critical state conditions as well as peak shear strength as a function of confining pressure for three different water content related to the in situ one. Soil specimens with three different gravimetric water contents were exposed to stress paths simulating the in situ anisotropic compression followed by a decrease of mean effective stress at constant axial load. Possible unstable response along the stress paths analysed was investigated by means of second order work

An investigation into the vertical bearing capacity of perforated mudmats

The optimal design of a mudmat foundation for a seabed structure maximizes the ratio of vertical compression to pullout capacity, which can be achieved by adding perforations. This paper describes an investigation led by Technip in which solid and perforated mudmats were installed into soft clay. The installation load of the solid mudmats matched the theoretical bearing capacity. Perforations reduced the installation load in proportion to the perforated area. In heterogeneous conditions, a further change in installation load arose due to the shallower failure mechanism. Peak pullout resistance was governed by separation beneath the mudmat, and depended on the width of the grillage elements formed by the perforation.</p