Numerical Modelling of Soft Soil Improvement Using Expanded Polystyrene Geofoam for Road Embankment

Soft soil brings abundant engineering issues due to low bearing capacity and shear strength. A comprehensive study of soft ground needs to be reviewed and identified before construction can start. Various techniques can be used to improve the soil. However, this study focuses on using material, namely expanded polystyrene. The geotextile is embedded with expanded polystyrene to strengthen the soil condition. This study adopted the soil parameters from East Coast Expressway 2. There are two models in this study, which are earth embankment and EPS embankment. The settlement of the earth embankment is compared with the EPS embankment after construction. The Mohr-Coulomb parameters are used to model soft soil and embankments, while the linear elastic parameters were adopted to model the EPS and geotextile. This study produced two embankment models, the conventional embankment models with and without surcharge. The second model is an EPS embankment with various densities (22 kg/m3, 29 kg/m3, and 39 kg/m3). The settlement is recorded for ten years after the embankment construction was completed. The difference settlement value for the conventional model is 28 mm. The settlement value for EPS 22 is 3.18 mm, EPS 29 is 2.06 mm, and EPS 39 is 1.51 mm. For the geotextile embedded with EPS settlement value, EPS 22 is 3.17 mm, EPS 29 is 2.04 mm, and EPS 39 is 1.49 mm. Since EPS uses three different densities, from the prediction of PLAXIS 2D, the higher density gives the lower value of the settlement. However, when the geotextile is embedded with EPS, there is no significant difference when using geotextile. In conclusion, the model with a surcharge gives a lower settlement than the model without a surcharge. But the expanded polystyrene block is the best model to reduce the settlement compared with the conventional model with a surcharge. Different density of EPS gives different settlement value, and EPS 39 gives the lowest settlement value. In terms of the geotextile embedded with EPS, it does not give a significant settlement

A decision support system for ground improvement method selection

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Rapport général du TC202 Géotechnique pour les infrastructures de transport

Today’s needs of urban transportation including roads, railways, airports and harbours demand significant resources for infrastructure development in view of rapid and efficient public and commercial (freight) services. In most cases, authorities have had difficulties in meeting these service demands due to the rapidly growing public, industrial, mining and agricultural sectors in many parts of the world. In order to maximise efficiency and to reduce the costs of maintenance, sound technical knowledge is required. This general report presents major technical advancements around the globe encompassing 33 articles from 19 countries and it is classified into 6 key categories, namely: compaction and subgrade improvement, laboratory testing, theoretical advancements and contributions to design, applications of geosynthetics, numerical modelling and field performance evaluation.De nos jours, les besoins en transports urbains (routes, chemins de fer, aéroports aériens et maritimes) nécessitent d’importantes ressources pour le développement des infrastructures en vue d’assurer des services commerciaux rapides et efficaces. Dans la plupart des cas, en raison de la croissance rapide des secteurs public, industriel, minier et agricole, les autorités se trouvent confrontées à des difficultés pour atteindre les services escomptés. Un savoir technique est alors nécessaire en vue de maximiser l’efficacité et de réduire le coût d’entretien. Le présent rapport général expose les avancées techniques majeures à travers le monde synthétisant 33 articles émanant de 19 pays ; six thèmes clés sont classés : compactage et amélioration des assises, expérimentation en laboratoire, développements théoriques et contributions au dimensionnement, applications des géosynthétiques, modélisations numériques et évaluation des performances sur le terrain.(undefined

Surrogate-assisted uncertainty modeling of embankment settlement

The structural optimization of basal reinforced piled embankments is usually conducted by examining design alternatives while ignoring the inherent variability of soil properties and studying only a limited number of structural variables. As an alternative, this paper proposes a hybrid modeling framework to introduce soil property uncertainty into embankment settlement calculations. This is important because settlement is critical in the serviceability assessments considered during structural optimization. The proposed framework consists of uncertainty modeling, finite element method, surrogate modeling, and probabilistic analysis. More specifically, a neural network with Monte Carlo dropout that accounts for uncertainty is employed to correlate the soil properties which affect the long-term performance of embankments over soft clay. Next, a coupled finite element analysis is performed using two constitutive soil parameters generated by the neural network to predict post-construction settlements. Combining the finite element (input source) with a surrogate model (data-driven approximation) yields substantial settlement outcomes for structure evaluations. A case study is then used to validate the effectiveness and applicability of this framework. Finally, an exhaustive search approach is used to design a cost-effective improved ground within ultimate and serviceability limit state constraints. Pareto front is computed using a logistic function at different settlement reliability levels

General report TC202: transport geotechnics

Today\u27s needs of urban transportation including roads, railways, airports and harbours demand significant resources for infrastructure development in view of rapid and efficient public and commercial (freight) services. In most cases, authorities have had difficulties in meeting these service demands due to the rapidly growing public, industrial, mining and agricultural sectors in many parts of the world. In order to maximise efficiency and to reduce the costs of maintenance, sound technical knowledge is required. This general report presents major technical advancements around hte glob encompassing 33 articles from 19 countries and it is classified into 6 key categories, namely: compaction and subgrade improvement, laboratory testing, theoretical advancements and contributions to design, applications of geoysynthetics, numerical modelling and field performance evaluation

Performance of soft ground improved by floating bottom ash columns

The stone column approach has been utilized over the past 60 years to stabilise the soft ground by partially replacing the compressible soil with more stable materials such as aggregate and sand. In practice, the granular material with a diameter of 20 mm to 75 mm is used as column filler material. In this research, the bottom ash material was used as a substitute material in the granular columns instead of the natural aggregate. A series of small-scale 1g physical modelling tests were carried out to investigate the behaviour of soft clay after being treated with a group of bottom ash columns beneath a rigid footing. A parametric study was performed to examine the effect of key design parameters such as; area replacement ratio and height penetration ratio on the bearing capacity and settlement characteristics. Whereas, a total of 19 physical model tests were conducted. A set of strain-controlled loading tests were performed to determine the ultimate bearing capacity, while a dead load method was adopted to examine the settlement characteristics. The physical modelling tests were carried out on the untreated and treated ground with bottom ash columns. Three area replacement ratios of 13 %, 20 %, and 26 % and three-column height of 50 mm, 100 mm, and 150 mm were adopted. The deformation and failure mechanism of the ground model was observed through capturing images during the loading test. Then, the Particle Image Velocimetry technique (PIV), GeoPIV: MATLAB software was used to analyse the collected images. The results clearly proved that the bearing capacity of the soft ground improves significantly with the incorporating of the bottom ash columns. Moreover, a higher area replacement ratio with longer columns demonstrated better load capacity enhancement. Also, it was found that the magnitude of total settlement reduced as the area replacement ratio increased. In addition, the total settlement of the reinforced ground showed a decreasing trend with the increase of the column height. In parallel to the physical modelling tests, three-dimensional numerical analysis was conducted via Plaxis 3D foundation software. This method was adopted to validate the experimental outcomes, since it is more economical and takes less time to complete in comparison to the full-scale model. Two different types of constitutive models were used to simulate the soft ground and bottom ash columns namely; the Soft Soil model and Mohr-Coulomb model. Comparisons between the results obtained from the physical model test and numerical simulation were made considering the different area replacement ratios and column height penetration ratios. The finite element analysis results were used to verify the experimental findings and a good agreement was found between the two methods since the difference is less than 20 % and is considered acceptable. The results revealed that the area replacement ratio and column height penetration ratio significantly influenced the overall performance of the treated ground. Whereas, the stiffness, load-bearing capacity, and settlement characteristics of the reinforced ground improved by increasing the area replacement ratio and column height penetration ratio; a 172 % enhancement in bearing capacity was attained with 26 % area replacement ratio and 0.75 column penetration ratio. A similar observation was obtained for LECA- treated ground under a constant rate of loading. The relationships between ultimate bearing capacity and area replacement ratio or column height to diameter ratio were plotted. From the relationships, six proposed design equations were developed for practical use to estimate the ultimate bearing capacity of the reinforced ground under a rigid footing. Another six design equations were also established to predict the normalised bearing capacity factor using the same parameters (area replacement ratio or column height to diameter ratio). Furthermore, the rationality of the proposed design equations was successfully verified using the finite element results

Settlement Analysis of Reinforced Granular Beds near Bridge Abutments

An approach slab is constructed to provide a smooth transition between the bridge deck and the existing roadway pavement. The differential settlement between the bridge deck and the approach slab leads to the formation of a "Bump" at the bridge. This is mainly due to difference support systems for the bridge deck and the slab. A detailed literature review had been done on the causes and the mitigation techniques available

Validity of sand dunes sediments as a fine aggregates for roads works: a case study on sand dunes sediments, Al-Nasiriya city, southern Iraq

In light of the development and urban growth of the city of Al-Nasiriya, the road construction sector consumes the largest amount of aggregates. The research aims to study suitability of the sediments of the sand dunes extending on one side of the international road between Nasiriya – Baghdad near the check point of Fadak as fine aggregate used for the purposes of roads construction. The results of the geotechnical evaluation of physical properties showed that the grain size analysis of the fine aggregate did not meet the requirements of the Iraqi specification and according to these results, the aggregate needs to modify. Based on liquid limits and plasticity indices and according to Iraqi specification the deposits are suitable for using as sub-grade course materials and to construct the shoulders of the road but not suitable for using as sub-base course materials. While the results of chemical tests indicate that incompatibility of the rates of organic matters and calcium carbonates with Iraqi specification. On the other hand, the chemical analysis of the sediments showed that the rates of the chlorides, sulfates, gypsum, total soluble salts and pH they were within acceptable limits of standard specifications. The mineral components of the soils were characterized by clay minerals (kaolinite and montmorillonite) and non-clay minerals (quartz, feldspar, and calcite)