Back analysis of a rock landslide to infer rheological parameters

2012 ◽  
Vol 131-132 ◽  
pp. 45-56 ◽  
Author(s):  
F. Bozzano ◽  
S. Martino ◽  
A. Montagna ◽  
A. Prestininzi
Keyword(s):  
Back Analysis ◽  
Rheological Parameters ◽  
Rock Landslide

Back Analysis Methods in Geotechnical Engineering

2014 ◽  
Vol 1020 ◽  
pp. 423-428 ◽  
Author(s):  
Eva Hrubesova ◽  
Marek Mohyla
Keyword(s):  
Rock Mass ◽  
Geotechnical Engineering ◽  
Back Analysis ◽  
Rheological Parameters ◽  
Analysis Method ◽  
Direct Optimization ◽  
Initial Stress State ◽  
Analytical Functions ◽  
Is Evaluation

The paper deals with the back analysis method in geotechnical engineering, that goal is evaluation the more objective and reliable parameters of the rock mass on the basis of in-situ measurements. Stress, deformational, strength and rheological parameters of the rock mass are usually determined by some inaccuracies and errors arising from the complexity and variability of the rock mass. This higher or lower degree of imprecision is reflected in the reliability of the mathematical modelling results. The paper presents the utilization of direct optimization back analysis method, based on the theory of analytical functions of complex variable and Kolosov-Muschelischvili relations, to the evaluation of initial stress state inside the rock massif.

scholarly journals Debris flow run-out simulation and analysis using a dynamic model

2018 ◽  
Vol 18 (2) ◽  
pp. 555-570 ◽  
Author(s):  
Raquel Melo ◽  
Theo van Asch ◽  
José L. Zêzere
Keyword(s):  
Debris Flow ◽  
Dynamic Model ◽  
Debris Flows ◽  
Back Analysis ◽  
Rheological Parameters ◽  
Economic Damage ◽  
Case Scenario ◽  
Worst Case ◽  
Basin Scale ◽  
Central Portugal

Abstract. Only two months after a huge forest fire occurred in the upper part of a valley located in central Portugal, several debris flows were triggered by intense rainfall. The event caused infrastructural and economic damage, although no lives were lost. The present research aims to simulate the run-out of two debris flows that occurred during the event as well as to calculate via back-analysis the rheological parameters and the excess rain involved. Thus, a dynamic model was used, which integrates surface runoff, concentrated erosion along the channels, propagation and deposition of flow material. Afterwards, the model was validated using 32 debris flows triggered during the same event that were not considered for calibration. The rheological and entrainment parameters obtained for the most accurate simulation were then used to perform three scenarios of debris flow run-out on the basin scale. The results were confronted with the existing buildings exposed in the study area and the worst-case scenario showed a potential inundation that may affect 345 buildings. In addition, six streams where debris flow occurred in the past and caused material damage and loss of lives were identified.

scholarly journals On the use of the calibration-based approach for debris-flow forward-analyses

2010 ◽  
Vol 10 (5) ◽  
pp. 1009-1019 ◽  
Author(s):  
M. Pirulli
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Single Phase ◽  
Back Analysis ◽  
Numerical Approach ◽  
Rheological Parameters ◽  
Trial And Error ◽  
Back Calculation ◽  
Selection Of ◽  
Volume Size

Abstract. In the present paper the problem of modeling the propagation of potential debris flows is tackled resorting to a numerical approach. In particular, numerical analyses are carried out with the RASH3D code, based on a single-phase depth-averaged continuum mechanics approach. Since each numerical analysis requires the selection of a rheology and the setting of the rheological input parameters, a calibration-based approach, where the rheological parameters are constrained by systematic adjustment during trial-and-error back-analysis of full-scale events, has been assumed. The back-analysis of a 1000 m3 debris flow, located at Tate's Cairn, Hong Kong, and the forward-analysis of a 10 000 m3 potential debris flow, located in the same basin have been used to investigate the transferability of back-calculated rheological parameters from one case to another. Three different rheologies have been tested: Frictional, Voellmy and Quadratic. From obtained results it emerges that 1) the back-calculation of a past event with different rheologies can help in selecting the rheology that better reproduces the runout of the analysed event and, on the basis of that selection, can give some indication about the dynamics of the investigated flow, 2) the use of back-calculated parameters for forward purposes requires that past and potential events have similar characteristics, some of which are a function of the assumed rheology. Among tested rheologies, it is observed that the Quadratic rheology is more influenced by volume size than Frictional and Voellmy rheologies and consequently its application requires that events are also similar in volume.

scholarly journals Assessing potential debris flow runout: a comparison of two simulation models

2008 ◽  
Vol 8 (4) ◽  
pp. 961-971 ◽  
Author(s):  
M. Pirulli ◽  
G. Sorbino
Keyword(s):  
Debris Flow ◽  
Back Analysis ◽  
Simulation Models ◽  
Numerical Code ◽  
Rheological Parameters ◽  
Rheological Parameter ◽  
Safe Side ◽  
Study Sites ◽  
Comparison Of The Results ◽  
Parameter Values

Abstract. In the present paper some of the problems related to the application of the continuum mechanics modelling to debris flow runout simulation are discussed. Particularly, a procedure is proposed to face the uncertainties in the choice of a numerical code and in the setting of rheological parameter values that arise when the prediction of a debris flow propagation is required. In this frame, the two codes RASH3D and FLO2D are used to numerically analyse the propagation of potential debris flows affecting two study sites in Southern Italy. For these two study sites, a lack in information prevents that the rheological parameters can be obtained from the back analysis of similar well documented debris flow events in the area. As a prediction of the possible runout area is however required by decision makers, an alternative approach based on the analysis of the alluvial fans existing at the toe of the two studied basins is proposed to calibrate rheological parameters on the safe side. From the comparison of the results obtained with RASH3D (where a Voellmy and a Quadratic rheologies are implemented) and FLO2D (where a Quadratic rheology is implemented) it emerges that, for the two examined cases, numerical analyses carried out with RASH3D assuming a Voellmy rheology can be considered on the safe side respect to those carried out with a Quadratic rheology.

scholarly journals Debris flow run-out simulation and analysis using a dynamic model

2017 ◽  
Author(s):  
Raquel Melo ◽  
Theo van Asch ◽  
José L. Zêzere
Keyword(s):  
Debris Flow ◽  
Dynamic Model ◽  
Debris Flows ◽  
Back Analysis ◽  
Quantitative Information ◽  
Rheological Parameters ◽  
Case Scenario ◽  
Worst Case ◽  
Basin Scale ◽  
Central Portugal

Abstract. Only two months after a huge wildfire occurred in the upper part of a valley located in Central Portugal, several debris flows were triggered by intense rainfall. The event caused infrastructural and economical damage, although no life was lost. The present research aims to simulate the run-out of two debris flows occurred during the event as well as to calculate by back-analysis the rheological parameters and the excess rain involved. Thus, a dynamic model was used, which integrates surface runoff, concentrated erosion along the channels, propagation and deposition of flow material. The rheological and entrainment parameters obtained for the most accurate simulation were then used to perform three scenarios of debris flows run-out at the basin scale. Due to the lack of quantitative information to validate these models, the results were compared with historical references of debris flow events in the study area. Six streams were identified, where debris flows occurred in the past and caused material damage and loss of lives. The worst-case scenario carried out at the basin scale shows a potential inundation that may affect 345 buildings at the present day.

scholarly journals Operational Estimation of Landslide Runout: Comparison of Empirical and Numerical Methods

Geosciences ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 424 ◽  
Author(s):  
Marc Peruzzetto ◽  
Anne Mangeney ◽  
Gilles Grandjean ◽  
Clara Levy ◽  
Yannick Thiery ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Back Analysis ◽  
Rock Avalanche ◽  
Power Laws ◽  
Travel Distance ◽  
Lesser Antilles ◽  
Rheological Parameters ◽  
Debris Slide ◽  
Empirical Relations ◽  
Empirical Approaches

A key point of landslide hazard assessment is the estimation of their runout. Empirical relations linking angle of reach to volume can be used relatively easily, but they are generally associated with large uncertainties as they do not consider the topographic specificity of a given study site. On the contrary, numerical simulations provide more detailed results on the deposits morphology, but their rheological parameters can be difficult to constrain. Simulating all possible values can be time consuming and incompatible with operational requirements of rapid estimations. We propose and compare three operational methods to derive scaling power laws relating the landslide travel distance to the destabilized volume. The first one relies only on empirical relations, the second one on numerical simulations with back-analysis, and the third one combines both approaches. Their efficiency is tested on three case studies: the Samperre cliff collapses in Martinique, Lesser Antilles (0.5 to 4×106 m3), the Frank Slide rock avalanche (36×106 m3) and the Samperre cliff collapses in Martinique, Lesser Antilles (0.5 to 4×106 m3) the Fei Tsui debris slide in Hong Kong (0.014×106 m3). Purely numerical estimations yield the smallest uncertainty, but the uncertainty on rheological parameters is difficult to quantify. Combining numerical and empirical approaches allows to reduce the uncertainty of estimation by up to 50%, in comparison to purely empirical estimations. However, it may also induces a bias in the estimation, though observations always lie in the 95% prediction intervals. We also show that empirical estimations fail to model properly the dependence between volume and travel distance, particularly for small landslides (<20,000 <0.02×106 m3).

scholarly journals Back analysis numerical modelling of the 19/06/1996 Cardoso (Stazzema, LU - Italy) flood: from gravitational movements to their evolution in rapid flows

2020 ◽  
Author(s):  
Michele Amaddii ◽  
Vincenzo D'Agostino ◽  
Leonardo Disperati ◽  
Pier Lorenzo Fantozzi
Keyword(s):  
Numerical Modelling ◽  
Back Analysis ◽  
Curve Number ◽  
Rheological Parameters ◽  
Drainage Network ◽  
Visual Interpretation ◽  
Discharge Data ◽  
Peak Intensity ◽  
Liquid Discharge ◽  
Flooded Area

&lt;p&gt;During the June 19th of 1996 a storm involved the Tyrrhenian sector of northern Tuscany (Italy), especially hitting the Versilia and Garfagnana areas. Major consequences and damages, due to the extremely intense precipitation (about 500 mm/13 h and 158 mm/h peak intensity), occurred in the surrounding of the Cardoso village (Versilia river basin, Stazzema, LU), with 14 casualties. At 1.20 p.m., the rainfall peak intensity coupled with the development of a large number of shallow landslides, triggered rapid flows and caused severe flooding in the Cardoso area, which was covered by hundred thousand of cubic meters of deposits.&lt;br&gt;The aim of this study was the characterization of the rapid flows occurred during the event and their back analysis numerical modelling by using a hydrological-hydraulic software. First of all, the amount of mobilized solid volume was assessed, differentiating between materials collapsed from the slopes and those eroded from the low-order drainage network. This goal was obtained by visual interpretation of post-event orthophotos and by morphometric analysis. Subsequently, starting from the rainfall data of the event, the hydrological modelling was performed by the Curve Number method, in order to define flood hydrographs along the drainage network of the Cardoso sub-basins. For the hydraulic modelling, the liquid discharge data were used to calculate debris-graphs of rapid flows, by implementing empirical correlations based on peak discharge, debris volume and channel slope. Different rheological parameters were tested to perform numerical modelling.&lt;br&gt;Back analysis results allow to infer that the mass movements initially started as hyperconcentrated flows in the upper parts of the sub-basins and after evolved into muddy debris flows, which caused flooding of the Cardoso valley. The results are in good agreement with the flooded area extent, as estimated by visual interpretation of both archive photos and aerial orthophotos acquired immediately after the event.&lt;/p&gt;

scholarly journals Rheological investigation and simulation of a debris-flow event in the Fella watershed

2010 ◽  
Vol 10 (5) ◽  
pp. 989-997 ◽  
Author(s):  
M. A. Boniello ◽  
C. Calligaris ◽  
R. Lapasin ◽  
L. Zini
Keyword(s):  
Debris Flow ◽  
Back Analysis ◽  
Rheological Parameters ◽  
Viscosity Data ◽  
The Best Approximation ◽  
Territorial Planning ◽  
Future Events ◽  
Sieve Analyses ◽  
Rain Fall

Abstract. To set an approach for the future territorial planning, the Geological Survey of Friuli Venezia Giulia Region, through the researchers of Trieste University, started a program of debris-flow risk analysis using Flo-2D software as tool to delimit the hazardous areas. In the present paper, as a case study, a debris flow, called Fella sx, occurring in a torrent catchment was analyzed. The choice was due to the abundance of information about past events, inundated areas, rain fall, geology and to its representativeness. An initial back-analysis investigation identified a couple of representative rheological parameters. Riverbed samples were collected, sieve analyses were performed and rheological tests were carried out on the fraction finer than 0.063 mm using a rotationally controlled stress rehometer equipped with the serrated parallel plate geometry. The shear dependent behaviour was examined at different concentrations ranging from 33 to 48%, by weight. Viscosity data treatment was performed to determine the most suitable rheological model to provide the best approximation of the debris-flow behaviour. The rheological parameters, derived from experimental data, were used and compared with those obtained through the back-analysis and with the real inundated area. Data obtained through rheological analysis are useful in constructing scenarios of future events where no data for back-analysis are available.

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