scholarly journals Hydraulic hysteresis of natural pyroclastic soils in partially saturated conditions: experimental investigation and modelling

2021 ◽  
Author(s):  
Ana Sofia Dias ◽  
Marianna Pirone ◽  
Marco Valerio Nicotera ◽  
Gianfranco Urciuoli
Keyword(s):  
Experimental Investigation ◽  
Test Site ◽  
Model Parameters ◽  
Hysteretic Model ◽  
Campania Region ◽  
Soil Response ◽  
Hydraulic Hysteresis ◽  
Soil Hydraulic ◽  
Constant Head ◽  
Pyroclastic Soil

AbstractIn many geotechnical applications, especially in the study of weather-induced landslides, a reliable soil hydraulic characterization in unsaturated conditions is required. Currently, the experimental techniques that neglect the hydraulic hysteresis represent the greatest limitation to landslide forecasting. In this paper, a procedure to obtain an unsaturated soil hydraulic characterization on natural pyroclastic samples is proposed and verified. The approach enables the evaluation of the soil hydraulic properties along the main drying path and wetting/drying cycles to fully quantify the effects of the hydraulic hysteresis. Pyroclastic soil samples collected at a test site at Mount Faito in the Campania region (southern Italy) were tested. The experimental investigation consisted of a sequence of testing phases: a constant-head hydraulic conductivity test, a forced evaporation test followed by several wetting–drying cycles, and a drying test in a pressure plate apparatus. The hysteretic model proposed by Parker and Lenhard (1987) was adopted to fit the data, while inverse modelling of the forced evaporation tests allowed to derive the model parameters. Therefore, the main drying and wetting branches and the soil response to drying and wetting cycles from any reversal point were reproduced with the model, which suitably described the hysteretic behaviour of the pyroclastic soil under all conditions and along all paths.

scholarly journals 1-g Experimental investigation of bi-layer soil response and kinematic pile bending

2014 ◽  
Vol 67 ◽  
pp. 219-232 ◽  
Author(s):  
Andrea Chidichimo ◽  
Roberto Cairo ◽  
Giovanni Dente ◽  
Colin A Taylor ◽  
George Mylonakis
Keyword(s):  
Experimental Investigation ◽  
Soil Response

scholarly journals Load-Independent Characterization of Plate Foundation Support Using High-Resolution Distributed Fiber-Optic Sensing

Sensors ◽  
2019 ◽  
Vol 19 (16) ◽  
pp. 3518 ◽  
Author(s):  
Asmus Skar ◽  
Assaf Klar ◽  
Eyal Levenberg
Keyword(s):  
High Resolution ◽  
Mechanical Model ◽  
Fiber Optic ◽  
Soil Parameters ◽  
Soil Reaction ◽  
Model Parameters ◽  
Strain Sensing ◽  
Soil Response ◽  
Monitoring Strategies

The evaluation of soil reaction in geotechnical foundation systems such as concrete pavements, mat- and raft foundations is a challenging task, as the process involves both the selection of a representative mechanical model (e.g., Winkler, Continuum, Pasternak, etc.) and identify its prevailing parameters. Moreover, the support characteristics may change with time and environmental situation. This paper presents a new method for the characterization of plate foundation support using high-resolution fiber-optic distributed strain sensing. The approach involves tracking the location of distinct points of zero and maximum strains, and relating the shift in their location to the changes in soil reaction. The approach may allow the determination of the most suited mechanical model of soil representation as well as model parameters. Routine monitoring using this approach may help to asses the degradation of the subsoil with time as part of structural health monitoring strategies. In this paper, fundamental expressions that relate between the location of distinct strain points and the variation of soil parameters were developed based on various analytical foundation support models. Finally, as an initial validation step and to underpin the idea basics, the proposed method was successfully demonstrated on a simple mechanical setup. It is shown that the approach allows for load-independent characterization of the soil response and, in that sense, it is superior to common identification methods.

Development of Nonlinear Coupled Mode Bushing Model Based on the Bouc-Wen Hysteretic Model

2007 ◽  
Author(s):  
Jin-Kyu Ok ◽  
Jeong-Hyun Sohn ◽  
Wan-Suk Yoo
Keyword(s):  
Sensitivity Analyses ◽  
Model Parameters ◽  
Hysteretic Model ◽  
Torsional Mode ◽  
Coupled Mode ◽  
Sensitivity Indices ◽  
Rubber Bushing ◽  
Hysteretic Characteristics ◽  
Vehicle Suspension System ◽  
And Behavior

In this paper, a coupled bushing model for vehicle dynamics analysis based on the Bouc-Wen hysteretic model is proposed. Bushing components of a vehicle suspension system are tested to capture the nonlinear and behavior of the typical rubber bushing elements using MTS machine. Test results are used to define the parameters of the Bouc-Wen bushing model. The Bouc-Wen model is employed to represent the hysteretic characteristics of the bushing. A coupled relation for radial mode and torsional mode are suggested. Model parameters are obtained by using the genetic algorithm, and sensitivity indices of parameters are also extracted from the sensitivity analyses. ADAMS program is used for the identification process and VisualDOC program is employed to find the optimal parameters of the proposed model. A half-car simulation is carried out to validate the proposed bushing model.

Application of Karray-Bouc Hysteretic Model for Cumulative Damage Calculation Using Energy Fatigue Curve

2014 ◽  
Vol 611 ◽  
pp. 32-39 ◽  
Author(s):  
Milan Sága ◽  
Milan Vaško ◽  
Peter Kopas ◽  
Lenka Jakubovičová
Keyword(s):  
Energy Density ◽  
Fatigue Curve ◽  
Cumulative Damage ◽  
Model Parameters ◽  
Hysteretic Model ◽  
Computational Tools ◽  
Hysteretic Energy ◽  
Energy Version

The paper deals with the application of numerical computational tools for the hysteretic curve identification using Karray-Bouc and Ramberg-Osgood models. The Karray-Bouc model parameters will be determined from Ramberg-Osgood model and Manson-Coffin curve parameters. Using special MATLAB’s procedures we can calculate dissipative (hysteretic) energy density per cycle and express Manson-Coffin curve in energy version.

scholarly journals Quantifying soil hydraulic properties and their uncertainties by modified GLUE method

2017 ◽  
Vol 31 (3) ◽  
pp. 433-445
Author(s):  
Yifan Yan ◽  
Jianli Liu ◽  
Jiabao Zhang ◽  
Xiaopeng Li ◽  
Yongchao Zhao
Keyword(s):  
Confidence Interval ◽  
Least Squares ◽  
Water Content ◽  
Soil Water ◽  
Nonlinear Least Squares ◽  
Uncertainty Estimation ◽  
Model Parameters ◽  
Retention Curve ◽  
Least Squares Algorithm ◽  
Soil Hydraulic

AbstractNonlinear least squares algorithm is commonly used to fit the evaporation experiment data and to obtain the ‘optimal’ soil hydraulic model parameters. But the major defects of nonlinear least squares algorithm include non-uniqueness of the solution to inverse problems and its inability to quantify uncertainties associated with the simulation model. In this study, it is clarified by applying retention curve and a modified generalised likelihood uncertainty estimation method to model calibration. Results show that nonlinear least squares gives good fits to soil water retention curve and unsaturated water conductivity based on data observed by Wind method. And meanwhile, the application of generalised likelihood uncertainty estimation clearly demonstrates that a much wider range of parameters can fit the observations well. Using the ‘optimal’ solution to predict soil water content and conductivity is very risky. Whereas, 95% confidence interval generated by generalised likelihood uncertainty estimation quantifies well the uncertainty of the observed data. With a decrease of water content, the maximum of nash and sutcliffe value generated by generalised likelihood uncertainty estimation performs better and better than the counterpart of nonlinear least squares. 95% confidence interval quantifies well the uncertainties and provides preliminary sensitivities of parameters.

Pierre3D: a 3D stochastic rockfall simulator based on random ground roughness and hyperbolic restitution factors

2015 ◽  
Vol 52 (9) ◽  
pp. 1360-1373 ◽  
Author(s):  
Valentin S. Gischig ◽  
Oldrich Hungr ◽  
Andrew Mitchell ◽  
Franck Bourrier
Keyword(s):  
Stochastic Process ◽  
Slope Angle ◽  
Test Site ◽  
Fine Tuning ◽  
Model Parameters ◽  
Observation Data ◽  
Lumped Mass ◽  
Forest Road ◽  
Rockfall Hazard ◽  
The Impact

The use of dynamic computational methods has become indispensable for addressing problems related to rockfall hazard. Although a number of models with various degrees of complexity are available, model parameters are rarely calibrated against observations from rockfall experiments. A major difficulty lies in reproducing the apparent randomness of the impact process related to both ground and block irregularities. Calibration of rigorous methods capable of explicitly modeling trajectories and impact physics of irregular blocks is difficult, as parameter spaces become too vast and the quality of model input and observation data are insufficient. The model presented here returns to the simple “lumped-mass” approach and simulates the characteristic randomness of rockfall impact as a stochastic process. Despite similarities to existing approaches, the model presented here incorporates several novel concepts: (i) ground roughness and particle roughness are represented as a random change of slope angle at impact; (ii) lateral deviations of rebound direction from the trajectory plane at impact are similarly accounted for by perturbing the ground orientation laterally, thus inducing scatter of run-out directions; and (iii) a hyperbolic relationship connects restitution factors to impact deformation energy. With these features, the model is capable of realistically accounting for the influence of particle mass on dynamic behaviour. The model only requires four input parameters, rendering it flexible for calibration against observed datasets. In this study, we calibrate the model against observations from the rockfall test site at Vaujany in France. The model is able to reproduce observed distributions of velocity, jump heights, and runout at observation points. In addition, the spatial distribution of the trajectories and landing points has been successfully simulated. Different parameter sets have been used for different ground materials such as an avalanche channel, a forest road, and a talus cone. Further calibration of the new model against a range of field datasets is essential. This study is part of an extensive calibration program that is still in progress at this first presentation of the method, and focuses on fine-tuning the details of the stochastic process implemented both in two-dimensional (2D) and three-dimensional (3D) versions of the model.

scholarly journals The Influence of Seabed Response on Fatigue Performance of Steel Catenary Risers in Touchdown Zone

2010 ◽  
Author(s):  
Hodjat Shiri ◽  
Mark Randolph
Keyword(s):  
Fatigue Performance ◽  
Model Parameters ◽  
Hysteretic Model ◽  
Normal Range ◽  
Critical Question ◽  
Moderate Number ◽  
Steel Catenary Risers ◽  
Different Depths ◽  
Seabed Interaction ◽  
The Impact

The significant influence of the riser-seabed interaction on the fatigue performance of steel catenary risers is now widely accepted. Most design, however, is still carried out using linear seabed springs, and assuming a flat seabed. Improved nonlinear hysteretic seabed models have recently been proposed, which automatically simulate the different stiffness in the seabed response through the touchdown zone. A further consideration, however, is the influence of the trench that forms at the seabed. ROV surveys have shown that trenches several diameters deep can develop beneath the riser in the early stages of the SCR life, and a critical question is how this affects the fatigue life. A non-linear soil hysteretic model has been used to model gradual trench development in the touchdown zone. Initially, the seabed model parameters are adjusted to allow trenches of varying depth to be developed over a moderate number of displacement cycles of the SCR. Design wave spectra are then applied, simulating a generic Spar system, after correcting the model parameters to more typical values normal range. The paper presents results that show the impact of trenches of different depths on the fatigue performance of SCRs in the touchdown zone.

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