Showing papers by "Jacques Locat published in 2003"
TL;DR: In this paper, a conceptual model of the development of strength over a period of time and the parameters of the material for use in slope stability analysis and risk assessment is presented. But the main objectives are to define the geomechanical behaviour of various formations using different characterisations (grain size distribution, mineralogy, retention capacity, consolidation test, direct shear test and triaxial test) and to demonstrate how such soils can affect the stability of natural slopes.
109 citations
TL;DR: This study demonstrated that each erosional event could be followed by a rapid formation of biogenic structures, allowing the re-oxidation of old deposits and the importance of the production and destruction rates ofBiogenic structures and the sedimentation rate for the preservation of burrows and potentially reactive components.
57 citations
01 Jan 2003
TL;DR: In this article, the rheological response of these remoulded fine-grained flow-like landslide deposits have been investigated using several techniques (parallel-plate rheometry, coaxial rheometric, slump tests and inclined plane tests).
Abstract: Earthflows, debris avalanches and debris flows occurring in black marls in Southeast France present differentiated morphological characteristics and velocities. The rheological response of these remoulded fine-grained flow-like landslide deposits have been investigated using several techniques (parallel-plate rheometry, coaxial rheometry, slump tests and inclined plane tests). This contribution shows that rheological characteristics can be useful in establishing the transformation process of the materials into flow-like phenomena and identifying the natural mixture of basic formations which present the weakest yield stress and viscosity. Results show that the simple shear behaviour of all these natural flows clearly distinguishes the type of movement, in particular for earthflow and debris flow. Furthermore, some proportion mixtures present the highest mobility properties, and thus the highest susceptibility for transformation into high-speed flow-like phenomena. Results may be useful for identifying potential source zones in muddy flow-like landslide prone areas.
48 citations
TL;DR: In this article, the mean pore size distribution (PSD) of naturally deposited clayey soil samples recovered from various parts of the world and at varying depths was measured by Mercury Intrusion Porosimetry (MIP).
41 citations
01 Apr 2003
TL;DR: In this paper, extensive submarine mass movements have been mapped in the upper reaches of the Saguenay Fjord, Quebec, Canada, indicating that they were most likely triggered by the 1663 earthquake which shook a large area in Eastern Canada.
Abstract: Extensive submarine mass movements have been mapped in the upper reaches of the Saguenay Fjord, Quebec, Canada. Our analysis indicates that they were most likely triggered by the 1663 earthquake which shook a large area in Eastern Canada. Signs of instabilities have been observed at various places and although the triggering mechanism is the same, the types of mass movements differ largely including slides, spreads and flow failures in the soft Holocene sediments. Seismic and morphological investigations have revealed the presence of a fault -like deformation possibly linked to terrestrial fractures suggesting that the epicentre of the 1663 earthquake may be located in the area.
28 citations
01 Apr 2003
TL;DR: In this paper, the authors present three case studies of submarine landslide environments off the west coast of the United States, including Alaska, using multibeam technology allowing excellent resolution of the morphology of the seafloor.
Abstract: Submarine landslides are becoming recognized as a potential source of damaging local tsunamis. However, there are presently few documented case studies of landslide events that have caused historic tsunamis or likely caused prehistoric tsunamis. We present three case studies of submarine landslide environments off the west coast of the United States, including Alaska. Each environment has been imaged using multibeam technology allowing excellent resolution of the morphology of the seafloor. Based on this imagery and the historic record, we document the character of these environments and the resulting tsunamis. In the case of one of the failures, we present a model of the motion of the landslide and the size of tsunami that this motion would have produced.
25 citations
TL;DR: In this article, a flash flood resulted in the input of 9 million m3 of sediment toward the Bay of Ha! Ha!, leading to the elimination, partly or totally, of the benthic fauna of the bay.
Abstract: In July 1996, a flash flood resulted in the input of 9 million m3 of sediment toward the Bay of Ha! Ha!, leading to the elimination, partly or totally, of the benthic fauna of the bay. In this stud...
24 citations
01 Apr 2003
TL;DR: In this article, the authors proposed an approach for the assessment of risk associated with submarine mass movements based on geotechnical characterisation, which can be used to assess the risks associated with mass movements.
Abstract: With the growing development of offshore natural resources, use of sea-floor transport and communication routes, considerations for the environment and the effects of global climate changes, and will for protecting populations and their infrastructures, the need for assessing risk associated with submarine mass movements is increasing. The present paper proposes an approach for the assessment of risk associated with submarine mass movements based on geotechnical characterisation.
11 citations
01 Apr 2003
TL;DR: The submarine flow-slide of Pointe-du-Fort is situated on the south shore of the Saguenay Fjord, near the mouth of the Baie des Ha!Ha!, Quebec, Canada as mentioned in this paper.
Abstract: The submarine flow-slide of Pointe-du-Fort is situated on the south shore of the Saguenay Fjord, near the mouth of the Baie des Ha!Ha!, Quebec, Canada. About 1.5 million m3 of material, constituted of clayey silt rhythmites and thin sand layers, were involves in the slide. Surface of rupture would have reach a till contact. Seismic surveys over the displaced mass revealed a multiphase accumulation of the debris. Stratigraphic position of the debris link the event to the 1663 (Ms~7) earthquake. The slide was approximately dated to be over 260 years old (from present day) using sedimentation rates.
9 citations
01 Jan 2003
01 Apr 2003
TL;DR: In this article, the authors performed a detailed slope stability analysis of the Hudson Apron area and found that an excess pore pressure of more than 90% would be required for failure under normal conditions.
Abstract: As part of the STRATAFROM project, the Hudson Apron area was selected for a detailed slope stability analysis. Results indicate that high pore pressure is necessary to trigger a failure. Under normal conditions, an excess pore pressure of more than 90% would be required for failure. On the other end, the actual strength profile would indicate a remaining marginal stability. Aggravating factors were the high sedimentation rate cyclicity and esulting layering inducing high excess pore pressures, and potentially gas pressures and earthquakes.
01 Jan 2003
01 Apr 2003
TL;DR: In this paper, multibeam, seismic and CAT-scan imagery evidences reveal that the Pointe-du-Fort deposits are the result of a multiphase build-up which includes many episodes of erosion and sedimentation by debris flows.
Abstract: The Pointe-du-Fort deposits have been previously interpreted as the result of a single sedimentation event triggered by the 1663 Ms ~7 Charlevoix earthquake. It has been proposed that these deposits represent the spread of a failed mass coming from the south fjord wall. This paper presents multibeam, seismic and CAT-scan imagery evidences revealing that the Pointe-du-Fort deposits are the result of a multiphase build-up which includes many episodes of erosion and sedimentation by debris flows. These processes were induced by bottom slope erosion caused by the passage of a major debris flow coming upstream from the surveyed area, which was previously triggered by the 1663 Ms ~7 earthquake.
01 Jan 2003
TL;DR: In this article, the authors present the results of various rheological tests and numerical modelling for assessing torrential risk scenarios in the Faucon torrential stream where a debris-flow occurred in 1996, after a severe thunderstorm over the catchment basin and the breaking of a natural dam.
Abstract: Debris-flows are able to transport large quantities of sediment downslope, producing complex distributions of deposits and eroded surfaces along their flow path. Incorporation of surficial deposits during a debris-flow may change the mechanical behaviour of the flow. This paper presents the results of various rheological tests and numerical modelling for assessing torrential risk scenarios in the Faucon torrential stream where a debris-flow occurred in 1996, after a severe thunderstorm over the catchment basin and the breaking of a natural dam. Grain-size distribution and petrographic analysis have shown that this debris-flow can be characterized as a granular then a muddy debris-flow. Rheological tests using either a parallel-plate rheometer, a coaxial rheometer, slump tests, or a inclined plane were carried out on several samples. Results have shown that the flow behaviour could be described by a Heschel-Bulkley constitutive equation. Rheological response of several natural suspensions collected from quaternary deposits were also investigated. In order to model the runout of the flow, we used the BING code. Model describes well the influence of each type of sediment on the behaviour (runout distance, deposit thickness) of the flow, neither the velocities were overestimated. Different risk scenarios are tested and discussed.
01 Jan 2003
TL;DR: In this article, the erodability of surficial sediment in Saguenay Fjord, Quebec, was investigated over a three-year period at fourteen sites in Baie des Ha! Ha! and the North Arm using a benthic flume, Miniflume.
Abstract: The erodability of surficial sediment in Saguenay Fjord, Quebec, was investigated over a three-year period at fourteen sites in Baie des Ha! Ha! and the North Arm using a benthic flume, Miniflume. Previous studies showed that Saguenay Fjord sediment characteristics vary greatly on small and large scales. The critical shear stress (τc) reflect this variability, with τc between 0.07 and 0.48 Pa. The measured critical shear stress and erosion rates were consistent with those of other in situ studies in other area. The variability in the results is linked to the great spatial variability of benthic sediments rather than to temporal variability. Some of the results were integrated in the Parchure and Mehta (1985) erosion law since the upper portion of the active sediment layer is typically a stratified bed. The identification of erosion parameters (critical shear stress, erosion rate, parameters α?and Ef in erosion law) and their high variability is the first step in defining the erosion susceptibility hazard in Saguenay Fjord.