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16 pages, 8003 KiB

Open AccessArticle

Methodology for Identification of the Key Levee Parameters for Limit-State Analyses Based on Sequential Bifurcation

by Nicola Rossi, Mario Bačić, Lovorka Librić and Meho Saša Kovačević

Sustainability 2023, 15(6), 4754; https://doi.org/10.3390/su15064754 - 7 Mar 2023

Viewed by 1385

Levees are linear structures that are continuously reconstructed throughout the years and whose construction and behavior depends on local soil conditions, as well as requirements regarding impermeability and mechanical resistance. This results in various levee cross sections, even within the same levee. In situations of extreme water events, when timely actions are required, this variability poses a problem for decision-making based on observed behavior, which is highly dependent on the specific section parameters. Creating models for each problematic section becomes impractical, and because of that, in this study, 91 different cross sections from 16 levees are considered to identify the key levee parameters with the largest effects on three observed mechanisms: deformations, exit hydraulic gradients, and factors of safety. The implemented factor screening methodology is based on the sequential bifurcation method (SB) and numerical analyses. The SB method successively investigates groups of factors and uses their cumulative effects to identify the important groups and to discard the unimportant based on a previously selected parameter

Δ

, until the groups are reduced to single factors that may be deemed important. It is found that approximately 30% of all the factors used to describe the most complex sections are considered important by at least one of the investigated mechanisms. Full article

(This article belongs to the Special Issue Geotechnical Engineering towards Sustainability)

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21 pages, 6234 KiB

Open AccessArticle

Evaluation of Creep Behavior of Soft Soils by Utilizing Multisensor Data Combined with Machine Learning

by Meho Saša Kovačević, Mario Bačić, Lovorka Librić and Kenneth Gavin

Sensors 2022, 22(8), 2888; https://doi.org/10.3390/s22082888 - 9 Apr 2022

Cited by 7 | Viewed by 3478

Abstract

To identify the unknown values of the parameters of Burger’s constitutive law, commonly used for the evaluation of the creep behavior of the soft soils, this paper demonstrates a procedure relying on the data obtained from multiple sensors, where each sensor is used to its best advantage. The geophysical, geotechnical, and unmanned aerial vehicle data are used for the development of a numerical model whose results feed into the custom-architecture neural network, which then provides information about on the complex relationships between the creep characteristics and soil displacements. By utilizing InSAR and GPS monitoring data, particle swarm algorithm identifies the most probable set of Burger’s creep parameters, eventually providing a reliable estimation of the long-term behavior of soft soils. The validation of methodology is conducted for the Oostmolendijk embankment in the Netherlands, constructed on the soft clay and peat layers. The validation results show that the application of the proposed methodology, which relies on multisensor data, can overcome the high cost and long duration issues of laboratory tests for the determination of the creep parameters and can provide reliable estimates of the long-term behavior of geotechnical structures constructed on soft soils. Full article

(This article belongs to the Special Issue Advanced Sensing Technologies in Geotechnical Engineering)

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22 pages, 7354 KiB

Open AccessArticle

Fragility Curves for Slope Stability of Geogrid Reinforced River Levees

by Nicola Rossi, Mario Bačić, Meho Saša Kovačević and Lovorka Librić

Water 2021, 13(19), 2615; https://doi.org/10.3390/w13192615 - 23 Sep 2021

Cited by 4 | Viewed by 3419

Abstract

When constructing flood protection structures such as river levees, oftentimes due to various factors engineers must design composite structures, i.e., reinforced earthen structures which comply with all the stability criteria. The most common way of reinforcing such structures is the usage of geosynthetics, or mostly geogrids when talking about stability. Since geosynthetics are man-made materials produced in a controlled environment and go through quality control measures, their characteristics contain a negligible amount of uncertainty compared to natural soils. However, geosynthetic handling, their installation in the levee, and their long-term degradation can all have significant effects of variable magnitude on geosynthetic characteristics. These effects and their variability can be considered as random variables, which can then be used in probabilistic analyses together with soil properties. To investigate the effects of the geogrid’s resistance variability on slope stability compared to soil properties variability, probabilistic analyses are conducted on a river levee in northern Croatia. It is found that the geogrid’s variability generally has very little effect on the total uncertainty compared to the friction angle’s variability, but out of the three geogrid layers used the top grid has the most influence. Full article

(This article belongs to the Special Issue Dam Safety. Overtopping and Geostructural Risks)

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19 pages, 6860 KiB

Open AccessArticle

Development of Fragility Curves for Piping and Slope Stability of River Levees

by Nicola Rossi, Mario Bačić, Meho Saša Kovačević and Lovorka Librić

Water 2021, 13(5), 738; https://doi.org/10.3390/w13050738 - 9 Mar 2021

Cited by 19 | Viewed by 5007

Abstract

The design code Eurocode 7 relies on semi-probabilistic calculation procedures, through utilization of the soil parameters obtained by in situ and laboratory tests, or by the means of transformation models. To reach a prescribed safety margin, the inherent soil parameter variability is accounted for through the application of partial factors to either soil parameters directly or to the resistance. However, considering several sources of geotechnical uncertainty, including the inherent soil variability, measurement error and transformation uncertainty, full probabilistic analyses should be implemented to directly consider the site-specific variability. This paper presents the procedure of developing fragility curves for levee slope stability and piping as failure mechanisms that lead to larger breaches, where a direct influence of the flood event intensity on the probability of failure is calculated. A range of fragility curve sets is presented, considering the variability of levee material properties and varying durations of the flood event, thus providing crucial insight into the vulnerability of the levee exposed to rising water levels. The procedure is applied to the River Drava levee, a site which has shown a continuous trend of increased water levels in recent years. Full article

(This article belongs to the Special Issue Dam Safety. Overtopping and Geostructural Risks)

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17 pages, 8931 KiB

Open AccessArticle

The Usefulness of Seismic Surveys for Geotechnical Engineering in Karst: Some Practical Examples

by Mario Bačić, Lovorka Librić, Danijela Jurić Kaćunić and Meho Saša Kovačević

Geosciences 2020, 10(10), 406; https://doi.org/10.3390/geosciences10100406 - 11 Oct 2020

Cited by 17 | Viewed by 8503

Abstract

Having in mind uncertainties linked with the nature of rock masses, it is a challenge for geotechnical engineers to characterize them in a credible manner, especially if the rock mass in question is a notoriously complex karst with its distinctive features such as voids and discontinuities. A large range of geophysical methods are useful tools in the characterization efforts and their utilization in karst environments nowadays is a non-negotiable requirement, even though near-surface scattering significantly affects the acquired data. This paper demonstrates the versatile applications of seismic geophysical methods for geotechnical engineering in karst, from mapping of near-surface karstic features to the application of elastic wave velocities in determination of small to large strain stiffness of karst. The highlighted practical examples offer a step forward from the traditional interpretation of seismic surveys, making them a prosperous tool in geotechnical engineering investigation works, design and quality control campaign. Full article

(This article belongs to the Special Issue Modern Surveying and Geophysical Methods for Soil and Rock)

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17 pages, 4270 KiB

Open AccessArticle

Application of Reliability Analysis for Risk Ranking in a Levee Reconstruction Project

by Meho Saša Kovačević, Lovorka Librić, Gordana Ivoš and Anita Cerić

Sustainability 2020, 12(4), 1404; https://doi.org/10.3390/su12041404 - 14 Feb 2020

Cited by 6 | Viewed by 2921

Abstract

Levees are embankments designed for passive flood protection. In order to reduce the potential of climate-induced flooding risks, it is necessary to reconstruct or upgrade the existing levees. Flood risk management aims to reduce the probability of floods and their potential adverse effects on the population, economy, and environment. This paper presents the novel application of reliability analysis for risk ranking in the Otok Virje-Brezje levee reconstruction project in the Republic of Croatia. To identify, verify and analyse key risks, a group of 35 experts, who were directly involved in the levee reconstruction project or have extensive experience in similar projects, was selected. An Analytic network process (ANP) was used for group multi criteria decision-making. Quantitative and qualitative approaches to risk analysis were combined. Different experts from the various organisations may have diverse interests and goals. The geometric mean method was chosen to reach group consensus. The resources that will be allocated to the risk responses are proportional to the risk exposures. To analyse the reliability of the group consensus-reaching method a determination of the risk ranking probability matrix is proposed by using the Monte Carlo simulation method. Different decision-making approaches are proposed for cases in which consensus is not reached with satisfactory reliability. Full article

(This article belongs to the Special Issue Sustainability and Risks in Construction Management)

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