Showing papers by "Jacques Locat published in 2002"
TL;DR: In this paper, it is known that organic matter may affect the cementing process in soils, but what happens when cement is added to an organic soil? Both the organic matter content and the nature of this orga...
Abstract: It is well known that organic matter may affect the cementing process in soils, but what happens when cement is added to an organic soil? Both the organic matter content and the nature of this orga...
259 citations
TL;DR: A reassessment of these features strongly suggests that numerous turbidity currents, separated by intervals of ambient hemipelagic sedimentation, deposited the wave fields over thousands of years as discussed by the authors.
209 citations
TL;DR: In this article, the authors examined how geotechnical characteristics of soils can be influenced by the presence of diatom microfossils, using an artificially prepared mixture of soil and diatomite.
102 citations
TL;DR: The Outardes Bay delta has been investigated over the past 20 years with a Raytheon model RTT1000 boomer (3.5 kHz, 400 J) and most recently with a Simrad model EM 1000 multibeam sonar (95 kHz) on the slope to provide high-resolution seismic and bathymetric data as mentioned in this paper.
Abstract: The Outardes Bay delta constitutes one of the best sites to study the formation of failure deposits in a modern lowstand environment. These deposits are located in a pseudo-shelf-edge position along the northern part of the Laurentian Channel in the St. Lawrence Estuary. The site has been investigated over the past 20 years with a Raytheon model RTT1000 boomer (3.5 kHz, 400 J) on the shelf, and most recently with a Simrad model EM 1000 multibeam sonar (95 kHz) on the slope to provide high-resolution seismic and bathymetric data. The seismic data show wavy, chaotic and contorted reflectors which are typical in marine environments characterised by instability features. The multibeam sonar data have revealed many slope instability features such as creep folds, channel incisions, debris flows, and rotational slide scars. Thus, these interpreted features are in direct relationship with the seismic interpretation of the data collected upslope. These geomorphological and geophysical signatures express both past and present sedimentological processes. Some of the mass movement signatures observed in the surveyed area are believed to be related with the great MS~7 Charlevoix earthquake in 1663.
20 citations
01 Jan 2002
TL;DR: In this article, des analyses rheologiques ont ete menees sur les depots de divers mouvements de terrain declenches dans les marnes noires du bassin de Barcelonnette (glissements evoluant en coulees, coulees de debris, laves torrentielles) a l'aide d'un rheometre plan-plan and of un rheometric coaxial.
Abstract: Des analyses rheologiques ont ete menees sur les depots de divers mouvements de terrain declenches dans les marnes noires du bassin de Barcelonnette (glissements evoluant en coulees, coulees de debris, laves torrentielles) a l'aide d'un rheometre plan-plan et d'un rheometre coaxial. Les resultats indiquent un comportement, en cisaillement simple, de type Herschel-Bulkley. Les parametres rheologiques influent clairement sur le type d'ecoulement, en particulier pour les glissements-coulees et les laves torrentielles. Enfin, l'influence de la concentration solide peut etre presentee en definissant un rheogramme sous forme adimensionnelle pour chacun des materiaux.
16 citations
TL;DR: In this article, a series of cores were obtained from the Eel River Margin area of Eureka, California and geotechnical analysis of intact specimens and of reconstituted samples provided some insight on the development of shear strength with burial.
Abstract: As part of the STRATAFORM project, a series of cores were obtained from the Eel River Margin area of Eureka, California. The geotechnical analysis of intact specimens and of reconstituted samples provides some insight on the development of shear strength with burial. The results show the effect of bioturbation in the early part of the lifetime of a sediment. SEDCON tests were used to proposed various relationships which help predict the changes in density, liquidity index, and strength as a function of depth. These relationships are found useful from near the water sediment-interface down to a depth of at least 400 m in the sediment column.
14 citations
01 Jan 2002
TL;DR: In this article, an approach combining geomorphology, geotechnics and rheology is adopted to model the debris-flow runout (post-failure stage) and results show a very good agreement between the yield stress values measured by laboratory tests, these estimated in the field according to the morphology of the levees, and these back-analysed using the debrisflow modelling code Bing.
Abstract: Clayey flow-like landslides are characterized by their capability to suddenly change behaviour. Under specific hydrogeological conditions, these complex earthflows can transform into induced debris-flows. Due to their sediment volume, and their high mobility, debris-flow induced by flow-like landslides are far much dangerous than these resulting from continuous erosive processes and associate potential high hazard magnitude on the alluvial fans. In this paper a case of transformation from earthflow to debris-flow is presented. An approach combining geomorphology, geotechnics and rheology is adopted to model the debris-flow runout (post-failure stage). Results show a very good agreement between the yield stress values measured by laboratory tests, these estimated in the field according to the morphology of the levees, and these back-analysed using the debris-flow modelling code Bing. The runout distances and the deposit thickness in the depositional area are also well reproduced. This allows to propose debris-flow risk scenarios. Results show that clayey earthflow can transform under 5-years return period rainfall conditions into 1 km runout debrisflow of volumes ranging between 2,000 to 5,000 m. The release of a volume of debris ranging between 30,000 to 50,000 m is necessary to reach the alluvial fan. Position of the debris-flow front can easily be mapped to delineate potential risk zones.
4 citations