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Analysis and prediction of climate-driven geohazards, such as rainfall-induced landslides and slope failures, are becoming more challenging given the changing climate where extreme events are inevitable. Therefore, there is a need to move beyond conventional sources of data and consider multiple types of data for more accurate analysis and prediction of landslides. In recent years, Data Fusion and Machine Learning techniques have played an important role in paving the path towards a better understanding of the problem and finding more accurate models at regional and local levels that incorporate several contributing factors for slope failures. The purpose of the study is thus to evaluate the capacities of machine learning models in landslide susceptibility prediction and analyze their model performance in comparison of a numerical method, Transient Rainfall Infiltration and Grid-Based Regional Slope-Stability Model (TRIGRS). Classic machine learning models, namely Multi-Layer Perceptron Neural Network (MLP), Random Forest (RF), Gradient Boosted Regression Tree (GBRT) and Extreme Gradient Boosting (XGBoost) are selected and developed respectively. The study is carried out based on a preliminary field survey of rainfall-induced landslides near Kvam village, Norway, in June 2011. A methodology workflow of landslide susceptibility modeling is proposed, in which effective data processing approaches including feature selection, data resampling, data splitting, and feature scaling are discussed and summarized. The optimal hyperparameter optimization method is determined by performing a comparative time efficiency analysis of Bayesian and Grid Search methods. It is concluded that GBRT is the optimal method for landslide susceptibility mapping in the study case of Kvam based on seven popular model evaluation metrics. Other tree-based machine learning algorithms (RF and XGBoost) also show an overall outstanding performance and computational efficiency in comparison to MLP and TRIGRS models. The landslide susceptibility maps developed by prediction results from five models are also presented and statistically analyzed. Corresponding model performance ranks are found with results from model evaluation metrics.

The climate-controlled variations of the glacio-lithostatic load in glaciated terrains can potentially affect the tempo of volcanic eruptions, by modifying the pressure conditions acting on the underlying plumbing system. During glacial periods, increasing ice load hinders magma eruption, thus leading to prolonged residence time in the crust. This allows the magma to crystallise, differentiate and accumulate volatiles over a longer time span with respect to non-glacial periods.In Antarctica, volcanism in glaciated regions has been acting since the Miocene. In detail, in northern Victoria Land, volcanoes are located either in attenuated or thick cratonic lithosphere. Among the volcanic edifices built on thick crust, the quaternary Pleiades Volcanic Complex (PVC) is made up of some 20 monogenetic, partly overlapping scoria and spatter cones, that erupted over the last 900 ka. The erupted products range in composition from hawaiite to trachyte, defining a complete mildly Na-alkaline differentiation trend, which is quite unusual among alkaline monogenetic volcanic fields.Six samples from the PVC, representative of the whole differentiation trend, have been investigated by means of electron microscopy, electron microprobe and laser ablation ICP-MS. The parageneses of the rocks includes dominant feldspar and clinopyroxene with minor olivine. The mafic phenocrysts are characterised by significant resorption textures: specifically, the olivine presents deep embayments with absence of compositional zoning, while clinopyroxene frequently shows spongy texture and compositionally zoned mantle and rims, often with patchy and convoluted patterns.Petrography, textures and mineral chemistry suggest that the magma experienced first a rapid decompression, followed by a prolonged residence time, likely supported by increased ice load. During this time interval, resorption of the early formed mineral phases occurred, probably also enhanced by crustal assimilation processes, coupled with re-crystallization under isobaric conditions. Moreover, the prolonged residence time, coupled with the occurrence of (multiple) magma recharge(s) caused the mixing of a basaltic magma with other differentiated magmas stalling in the plumbing system, yielding to the formation of intermediate magma compositions. Finally, magma refilling of the plumbing system during an ice loss period, favoured the eruption. Machine-learning based thermo-barometric estimates consistently indicate crystallization of clinopyroxene at transcrustal pressures, ranging from the crust-mantle interface (early crystallization) to shallow crust (late crystallization in a shallow plumbing system under glacial load).

In this work, sulfur recovery from sulfur-rich wastes deriving from sulfur filtration was investigated through laboratory experiments and full-scale tests in an industrial combustion rotary kiln, where elemental sulfur is converted to SO2 in a sulfuric acid production plant. Phase equilibria experiments carried out in the temperature range 1100–1400 °C and industrial scale tests demonstrated that temperature is the most important operating parameter in determining the recovery efficiency and the plant operability. The full-scale tests performed on the rotary kiln showed that, at operating temperatures around 1200 °C, a continuous sulfur recovery from the filter cakes was obtained with an average efficiency of 87% and a consequent reduction of about 70% of the solid waste material to be disposed as inert in landfills or used in cement/glass industries. The efficiency of sulfur recovery increases with the increasing operating temperature but, above 1300 °C, the melting of the residual Ca-Fe-Al-silicate phase and the eventual recrystallization at the kiln refractory walls occurred, causing a forced plant shutdown. The chemical-physical interaction between the sulfur-rich filter cake and different refractory materials was further investigated in the temperature range 1100–1300 °C. At the recommended operation temperatures of 1100–1200 °C, the interaction between the refractory material and the combustion ashes is negligible for all tested materials. Nonetheless, the use of Fe- and Cr-free refractory materials for the internal lining of the kiln must be preferred to minimize the deposition/adhesion of Ca-Fe-Al-silicates derived from combustion over long-term operation.

Accurate prediction of soil deformations is important in unloading as well as loading. Historically, however, the loading scenario has been the most common and thus the most extensively studied phenomenon, leaving unloading less well described. Overconsolidated high-plasticity clays are particularly challenging in this regard due to their complex deformation behaviour that has previously shown two conceptually different unloading behaviours. Based on a series of incremental loading and constant rate of strain compression and swelling tests on folded Røsnæs Clay, these unloading behaviours are unified in a framework as different swell modes, and an additional swell mode is identified. These different modes represent a variation in swell-inhibiting structure, seemingly unrelated to the structure in compression. The use of constant rate of strain tests greatly enhanced the detailed description of stiffness development in each mode, which may be characterised by up to three swell phases. The parameters governing the occurrence of the swell modes are identified along with the variables that define the transition between the swell phases and their detailed development.

The need for a reliable estimate of the actual failure probability of existing river embankments under changing boundary conditions represents an ever-demanding task for researchers and designers, and those involved in their maintenance and management. Uncertainty and variability of soil suction and water content spatial and temporal distributions, together with the definition of a suitable soil model that accounts for the partially saturated state of embankment materials, are among the most critical aspects to be possibly included in the advanced analysis and design of such linear earthen infrastructures. The use of specialist integrated monitoring can be here functional to enable calibration and to enhance reliability and consistency of predictive analyses. Site measurements of the main variables at relevant depths are typically rarely available, whereas an accurate soil characterization under partially saturated conditions is only performed in research applications, thus producing limited confidence on stability conditions. To provide a useful and innovative tool to evaluate realistic stability conditions of levees under transient flow conditions, a full-scale monitoring system has been implemented on an existing section of the River Secchia (northern Italy) 11-m-high flood defenses. The complementary use of specific laboratory tests, innovative field measurements and numerical analyses presented in the paper aims at providing a suitable methodological approach to the performance assessment of these vital geotechnical systems throughout their entire lifetime and highlighting possible limitations of typically used methods of analysis.

The reversible mechanical behavior of unbound granular layers (UGLs) is commonly characterized by a stress-state dependent resilient modulus. This paper investigated the dependency of in situ resilient modulus upon a change in temperature above freezing conditions, i.e., the thermal sensitivity of UGLs in pavement systems excluding frost action. Such sensitivity is usually ignored in design and analysis because, on a material level, resilient modulus parameters are temperature independent. A model was developed to analyze this dependency by considering the stress-state changes that arise when UGLs are suppressed from thermally expanding or contracting. The formulation was incremental, based on linear thermoelasticity equations, and required as input readily available information; it assumed that changing temperature conditions are exogenous to the model and that no external loads are applied. A transcendental equation was subsequently derived, from which the sought sensitivity of UGLs could be resolved and quantified. Based on a parametric investigation of the model, covering a wide range of representative parameters, it is concluded that UGLs exhibit non-negligible thermal sensitivity. The extent of the calculated sensitivity coincides with field observations based on deflection testing, and also with seasonal factors that are traditionally applied to adjust field-measured moduli. Ultimately, the study shows that resilient modulus of UGLs is governed by an initial stress-state that is associated with a certain reference temperature level, and also by the temperature change compared to the reference.

Time-dependent boundary conditions, uncertainties and variability of soil suction and water content of the filling material together with the use of proper retention and strength soil models are crucial aspects to be included for reliable analyses of the actual stability of river embankments. However, due to a typical lack of information in many practical cases, the use of simplistic assumptions on both hydraulic and mechanical response of earth infrastructures to hydrometric water level fluctuation and atmospheric loading is largely diffused, thus providing erroneous conclusions on the effective safety margins towards possible slope instability and collapse. Within this context, site measurements down to relevant depths, combined to an accurate soil characterization under partially saturated conditions, can be extremely useful to evaluate unsaturated variables (i.e. soil water content and suction) under transient flow conditions and hence carry out realistic stability analyses. A comprehensive monitoring system has been therefore designed and installed on a relevant representative section along river Secchia, a right-hand tributary of river Po (Northern Italy). The paper aims at presenting a methodological approach for a sustainable performance assessment of such geotechnical infrastructures, based on the complementary use of laboratory tests, field measurements and numerical analyses.

Scanning Electron Microscopy (SEM) has been widely used to investigate the microstructure of clays, and several studies have examined the influence of the particles orientation on the mechanical behaviour of the soil. However, as the effect of the sample preparation that precedes the imaging on the orientation of the soil particles has not been systematically studied yet, the extent to which the clay microstructure is disrupted is not quantified. This work investigated samples having different mineralogy, stiffness, particles orientation and aggregation, and stress history imaging them at different magnifications in their Freeze, Oven and Air dried state using SEM, and wet state using the Environmental SEM (ESEM) and CryoSEM. The particles orientation imaged in the different micrographs was quantified with MiCA (Microstructural Clay Analyser), a Computer Vision based tool. The results shows the greatest effect for the dispersed soft samples, where the detected order increases with decreasing drying speed, regardless of mineralogy. However, this seems to affect the degree of the particles orientation when the CryoSEM technique is employed. Moreover, soft flocculated samples generated at acidic sedimentation environment overall experience a lower degree of reorientation. Finally, the fabric of stiff undisturbed samples is not significantly influenced by the applied method.

The discovery of metals and how to extract and use them was a turning point in human history, because it changed the economy and socio-cultural structure of ancient civilisations and started to severely affect the impact of human activities on the environment. In fact, a lot of societies developed near extraction sites and founded their economy on the use and trade of metals.In Tuscany (Italy) there has been a long history of mining and metal extraction. From archaeological studies it has been reconstructed that the earliest records of these activities date back to the Etruscan period (VII century B.C.). Exploitation continued intermittently until a few decades ago. This extended period of mining exploitation left a wealth of both iron and copper metallurgical slags that can usually be found as abandoned and unsupervised heaps.These slags, apparently just a waste from the metallurgical process, actually carry information about the evolution of the metallurgical process through which they were generated. Information about the charge, flux and fuel can be inferred from chemical and mineralogical composition of the slags.Slags from three different smelting districts, ranging from ancient Etruscan-Roman period to modern age (1900 A.D.) were studied macroscopically, identifying distinctive features related to the smelting process in different time periods. Then, thin sections obtained from representative samples were examined, using optical microscopy and electron microscopy. Chemical analyses were performed for major and trace elements by X-ray fluorescence spectroscopy and by inductively coupled plasma mass spectrometry, respectively.Leaching experiments on some carefully selected samples were also completed, to investigate the release of potentially toxic elements during the interaction of the slags with the surrounding environment.This kind of investigation allows to reconstruct part of the history of metal utilisation as well as to predict the impact that these remains will have on the environment.

The soil microstructure is recognised to strongly influence the mechanical behaviour of both coarse and fine geomaterials. Proper identification and tracking of the shape and position of the particles has become more and more critical to form a link between the micro and macro behaviour. Scanning Electron Microscopy (SEM) has been widely used in the last decades to study the clay fabric variation with its mechanical behaviour and physical properties. However, the particles orientation has so far been discussed only from a qualitative point of view due to the lack of updated, automatised quantification tools. Consequently, developing constitutive models that correlate the soil micro structure to its mechanical behaviour is not feasible. In order to make a step forward in this direction, an Image Analysis based code called MiCA (microstructural clay analyser) capable of quantifying the particle orientation and the porosity of clay samples through the analysis of SEM micrographs was developed in this study. The code reliability was first validated through the application to geometrical reference patterns, then to textbook micrographs illustrating typical clay fabrics (dispersed, honeycomb, flocculated and aggregated), and finally to high quality images. MiCA showed good accuracy in the results obtained, regardless of the number of lines in the image, the complexity of the geometrical shapes and the pixel size of the analysed graphs. Therefore, MiCA can be considered suitable for quantitative analysis of the particle orientation and/or pores shape in clay materials.

River embankments are usually designed as earthen structures to retain hydrometric level fluctuations. Filling materials generally adopted are intermediate soils, consisting of natural silty soils with limited sand and clay content, compacted during construction process for both ensuring their mechanical stability and limiting the water flow through the embankment itself. The evaluation of time-evolving seepage and stability characteristics of riverbanks, which represents a crucial step for their vulnerability assessment, is strongly influenced by the unsaturated soil behaviour. In this framework, a comprehensive experimental study has been performed to explore the mechanical and retention properties of a river embankment silty soil in partially saturated conditions. Oedometric and direct shear tests under suction-controlled conditions have been carried out on soil sampled from an in-situ instrumented riverbank section, where an extensive monitoring system with suction and water content measurements has been recently implemented. The results of laboratory investigations are presented and discussed. Comparisons with monitoring data and similar laboratory tests performed in saturated conditions are also provided, in order to highlight the importance of an accurate characterization of the unsaturated soil behaviour as fundamental step for a realistic estimate of the river embankments slope stability and for reliable safety assessment.

Dispersive soils are a common problematic soil that may pose engineering distress if not adequately taken care of. On the other hand, the stabilization of problematic soils with waste materials has recently gained more interest from an environmental and sustainable point of view. Hence, this study utilized sulfur-free lignin (SFL), which is a bioethanol-based by-product, to improve dispersive silt clay and investigated the stabilization effectiveness considering combine impacts of water and freeze-thaw (F-T). The SFL was added to five sample groups ranging from 3 to 15%. Then, a series of experiments was performed to study the water stability of the SFL stabilized soil from a mechanical, chemical and micro-structural point of view. The results reveal that the dispersive soil moisture resistance can be significantly improved with addition of SFL and low content SFL (3%) is slightly better than high content (15%) under no cyclic F-T. This is attributed to the increased cation exchange capacity (CEC) owing to the exchangeable sodium ions used during the pretreatment process of bioethanol. Nevertheless, the high content SFL stabilized samples exhibit superior water stability characteristics when considering the adverse effects of F-T cycles. According to X-ray fluorescence analysis (XRF), no new elemental composition was found indicating that SFL does not bring chemical contamination risk to the soil. However, the organic matter content increases with SFL content. Scanning electron microscopy (SEM) provided visual evidence that the formation of physical bonds and denser soil structure due to SFL, is responsible for the improvements observed. In addition, cracks in the soil matrix caused by F-T cycles were also observed. Overall, utilization of the studied SFL shows good potential to improve the engineering performance of dispersive soils.

The present paper presents three extensive datasets of laboratory testing on weathered geomaterials, which are emblematic of soil types widely found worldwide. The overall dataset includes soils originating from igneous and metamorphic rocks, either coarse or fine grained and having either felsic or mafic minerals. In particular, the data are interpreted to highlight the effects that weathering has on the physical and mechanical properties of these natural geomaterials comparing them with published data with the aim to provide a general framework of interpretation that takes into account this geological process and links soil mechanics to engineering geology. Generally, weathering induces a reduction in the grain size, both due to physical actions (e.g. opening of grain contacts) and to the chemical decomposition of minerals resulting in the formation of clay minerals. As weathering proceeds and the soil becomes finer, the in situ specific volume and the location of the normal compression and critical state lines move upwards in the volumetric plane. On the other hand, the clay minerals cause its angle of shearing resistance to reduce. When analysing the behaviour of the intact soil, in all cases positive effects of structure, albeit small compared to some sedimentary soils, were observed and these reduced as a consequence of weathering.

With the rapid process of urbanization, more and more infrastructures are inevitably built on problematic soils, which require improvement and reinforcement. In this study, a novel material Sulfur-Free Lignin (SFL), which is a by-product of bioethanol industry, was used to improve the soil's geotechnical behavior as a sustainable, non-toxic and eco-friendly stabilizer. To systematically investigate the geotechnical properties of SFL-stabilized soil, the natural soil was modified by adding five different contents (3, 7, 10, 12 and 15%) and then a series of geotechnical experiments including Unconfined Compressive Strength (UCS), Atterberg limits tests, electrical resistivity and pH were carried out after 1, 7, 28, 60-days curing. In addition, to investigate the stabilization mechanism, the mineral composition, function group and microstructure characteristic were also studied through X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Mercury Intrusion Porosity (MIP) and Scanning Electron Microscopy (SEM) tests. The test results demonstrate that with increasing SFL content, the electrical resistivity gradually decreases, on the contrary, the Atterberg limits show a slight increase. However, the pH values are unchanged indicating the SFL would not lead to pH contamination risk. The 10% SFL-stabilized soil after 60 days of curing shows the greatest strength, which increases about 600% compared to the natural soil. Furthermore, the relationship between stiffness and UCS is generally proportional. According to the results of MIP and SEM, the strength improvement can be attributed to a smaller total volume of pores, reduction in the mean size of the pores and stronger bonds formed by SFL between isolated grains. The results of XRD and FTIR tests reveal there is no new mineral nor function group generated after adding SFL. Above all, the natural soil stabilized by SFL shows a satisfactory engineering performance and it would be a win-win solution to utilize SFL as a soil stabilizer for soil improvement in civil engineering and for waste elimination in bioethanol industry.

Soil mechanical behaviour is strictly related to its natural water content, which is primarily dependent on hydraulic boundary conditions. When soils are partially saturated, as frequently occur in river embankments, soil suction also turns into a fundamental variable worth of investigation and monitoring, both in laboratory and in the field, for a reliable interpretation of the related soil response to external actions. The case of earthen water retaining structures and their safety condition assessment towards local or global collapse mechanisms requires special attention for soil characterization and site measurement of unsaturated soil states. Moreover, strength and hydraulic models used for relevant stability analyses should be adequate for representing the site-specific behaviour of soil in terms of water content, pore water pressure and suction values, relying on the effective possibility to properly calibrate all required parameters. Nevertheless, these aspects typically receive only limited attention, especially in standard practice, leading to inaccurate estimates of flood hazard and related risk management. In this context, with the aim of comprehensively studying the strength and retention properties of a riverbank silty soil, a series of laboratory investigations – including oedometric and direct shear tests under suction-controlled conditions – have been performed. Laboratory tests are here used as the main direct source of information to model unsaturated soil behaviour, monitoring different state variables under suction-controlled conditions. The results have been then interpreted using both literature and soil-specific mechanical and hydraulic models, to be possibly implemented in integrated methodologies for the stability assessment of river embankments.

The North Sea Basin is characterized by the presence of highly plastic, stiff Paleogene clays sedimented between 65.5 and 43 millions of years ago. During the Quaternary Period, this area underwent a series of cyclic glaciations that overconsolidated the underneath clay deposits and sheared the shallower layers. Different studies focusing on these superficial, folded strata are present in literature. On the other hand, less information are available regarding the mechanical behaviour of the deeper, intact layers. However, a good knowledge of these layers mechanical properties is necessary to guarantee an efficient design of the infrastructures built on these formations. This work focusses on the characterization of the Paleogene Røsnæs Clay Formation present in the Fehmarn Belt area, between southern Denmark and northern Germany, where a submerged tunnel will be constructed. The mechanical properties of the Intact Røsnæs Clay layer were determined and compared with those of the Folded Røsnæs Clay. Incremental Load Oedometer tests were performed by applying different load cycles in order to stress the sample below, in correspondence and above the estimated preconsolidation stress. The results were compared with those obtained from testing reconstituted samples in order to assess the influence of structure. This was done quantitatively by analysing the stiffness, the compressibility, and swelling indices. Environmental Scanning Electron Microscope micrographs were used to detect the presence of micro-folding. The mineralogical consistency among the different Oedometer tests was evaluated by means of X-Ray Diffraction. Despite the homogeneity in the mineralogy, differences in both the microstructure and the 1D behaviour of the Folded and Intact layers were observed. In particular, the Folded layers appear to have greater compressibility and swelling potential. These differences should be taken into consideration when building on partially pre-sheared Paleogene formations.

River embankments stability is a key aspect in geohazard assessment and underestimating its failure risk may result in unexpected and severe damages. Changes in hydraulic and climatic boundary conditions are responsible for transient water flow within the embankments, consequently the related soil water content and pore-water pressure distributions vary with time. Therefore, it is crucial to investigate their hydraulic and retention behaviour in order to assess in a reliable way the safety margins towards instability mechanisms. To obtain a realistic estimate of key variables in time and space, as a function of external conditions, a combination of field measurements, laboratory testing and suitably calibrated numerical analyses should be used. To achieve this purpose, a full-scale monitoring system was implemented on a cross section of an embankment along the river Secchia (Modena, Italy), mainly measuring the pore-water pressure (including suction) and the water content at different depths. A relatively large variety of different sensors have been installed, to compare their performance in terms of robustness and reliability, and collected data have been interpreted with the help of laboratory and field geotechnical characterisation. The article describes such system and the sensors used, their capabilities and the installation techniques, resulting in quite innovative solutions for the specific application. The spatial variability of the monitored variables is also finally presented and discussed. The proposed integrated monitoring system, which aims at making use of affordable and commercially available sensors that can be therefore installed along extensive river stretches, appears a fundamental starting point to assess potential risks of such geotechnical infrastructures in real-time and to devise well-balanced related mitigation measures.

High plasticity clay of Paleogene origin in Denmark, possess unique deformational behaviour with significant stress dependent stiffness in oedometric loading/unloading. This is challenging settlement/heave predictions. The behaviour has been so far associated with high smectite content and complex geological loading history. Burial followed by erosion and then glaciotectonic activity, has resulted in fissures and slickensides, along with a high level of overconsolidation. Several currently planned and existing Danish construction projects encounter problems with such clays. Specifically, the immersed tunnel project connecting Denmark and Germany: “Fehmarn Fixed Link”, for which an extensive laboratory campaign of IL and CRS oedometer tests, has been carried out. These tests have been re-analysed, to obtain a better description of the swelling behaviour of Paleogene clays, due to the net unloading state expected for this immersed tunnel. The development of the swelling index during unloading, although non-linear, tends to reach a constant value at sufficient stress reduction. This constant value as well as the average swelling index increases with the stress at which unloading starts and increased smectite content. These trends are confirmed by an additional CRS test.

This study investigates using Sulfur-Free Lignin (SFL) as a stabilizer to reinforce soil for civil engineering construction. To comprehensively evaluate the engineering performance of SFL stabilized soil, 3, 7, 10, 12 and 15% mixtures were tested and the influence of climate factors (assessed subjecting the soil to different freeze-thaw cycles) was also considered. The experimental program investigated mechanical strength (unconfined compressive strength) and physicochemical properties, which included grain size distribution, Atterberg limits, variation of elemental and mineral composition, pH, cation exchange capacity, X-ray diffraction/fluorescence and thermal conductivity. In addition, micro-characterization through SEM and pore size distribution was also performed. A considerable improvement of the mechanical properties was observed, which increases with SFL content up to 12%. This was based on changes in the physical and not chemical properties, hinting that the stabilization mechanism consists in physical binding unlike for traditional soil stabilizers. Moreover, it was found that SFL addition improved frost resistance. Based on these results, utilizing SFL as a soil stabilizer for application in earthworks shows great potential and would promote the bio-ethanol industry and engineering construction to be more sustainable and greener, particularly because it does not risk inducing soil pH contamination unlike traditional chemical agents.

Soils originating from weathering processes present considerable heterogeneity in their composition, which can make it difficult to analyse their behaviour in a systematic way. For the granitic saprolites discussed in this paper, based on a trend between soil density and weathering degree, there appears to be two different domains of behaviour, a granular domain and a clay matrix one, according to the degree of weathering reached. Recognition of these domains can reduce the apparent scatter of data for the engineering behaviour of weathered soils. A number of one-dimensional compression tests are presented for saprolitic soils from Hong Kong having different weathering degrees. In addition, isotropic and one-dimensional compression tests from the literature on other saprolites from Hong Kong and around the world were reanalysed and used to identify possible trends in the mechanisms of compression for these two domains. From practical considerations, the trends considered were between compressibility and common engineering grading descriptors. An attempt was also made to provide the physical explanations behind the behaviour observed, and the particle breakage was investigated in detail, both from a quantitative and qualitative point of view. It was found that the values of relative breakage (Hardin in ASCE J Geotech Geoenviron Eng 111(10):1177–1192, 1985), for a same stress level, might be very similar for soils having different compressibility values and different initial gradings. When studying particle breakage in further detail, it can be observed that it is linked to the amount of large particles and their characteristics. The maximum particle size, rather than the amount of fines in a mixture, may be a better predictor for differences in compressibility and breakage.

The evaluation of riverbank stability is a fundamental problem in flood risk management, representing a critical task for engineering practice. Soil heterogeneity together with initial and boundary conditions are among the crucial issues that should be considered to obtain an accurate solution of the problem. Generally, attention and efforts are mostly devoted to the soil characterization, the hydrometric level forecasts and the estimation of the rainfall intensity, while in situ measurements usually receive less attention. Nevertheless, suction and soil water content have a strong influence on the reliability of seepage and stability analyses. A preliminary study aiming at the design of a monitoring system for the measurement of soil moisture and suction in the unsaturated silty soils of a river embankment has been carried out, with the purpose of linking the collected data to the boundary conditions and hence obtaining a more accurate estimate of the riverbank probability of failure. Furthermore, a general outline of the research project, its methodology and application are presented in the paper.

Less research has been carried out on the changes induced by weathering to the mechanical properties of reconstituted and intact soils that originate from chemical decomposition of rocks (saprolites) than has been done for sedimentary soils. One-dimensional compression and triaxial tests were performed on reconstituted and intact specimens along a weathered profile to investigate the changes in their physical and mechanical properties. Some heterogeneity in the weathering tends to cloud the trends observed, but it was still clear that the grading varies the most, while the mineralogy changes less and the particle morphology is nearly unchanged. The gradient of the normal compression line is fairly constant with weathering, but reduces significantly at shallower depths. The gradient of the critical state line in the stress plane reduces with weathering, while its intercept in the volumetric plane has a more complex trend, but generally also reduces with decreasing depth. The value of the specific volume in situ increases with weathering and so the in situ state becomes closer to the critical state line. The effects of structure were quantified using a pseudo strength sensitivity defined by the location of the intact state boundary surface at the critical state. This parameter generally reduces with weathering and increases with depth.

In situ measurements of soil suction and water content in deep soil layers still represent an experimental challenge. Mostly developed within agriculture-related disciplines, field techniques for the identification of soil retention behaviour have been so far employed in the geotechnical context to monitor shallow landslides and seasonal volume changes beneath shallow foundations, within the most superficial ground strata. In this paper, a novel installation technique is presented, discussed and assessed, which allows extension of the use of commercially available low-cost and low-maintenance instruments to characterise deep soil layers. Multi-depth installations have been successfully carried out using two different sensor types to measure the soil suction and water content up to 7 m from the soil surface. Preliminary laboratory investigations were also shown to provide a reasonable benchmark to the field data. The results of this study offer a convenient starting point to accommodate important geotechnical works such as river and road embankments in the traditional monitoring of unsaturated soil variables.

The paper describes part of a study carried out to develop the geotechnical model of a coastal area on the Adriatic Sea, between the municipalities of Cesenatico and Bellaria-Igea Marina in the Emilia-Romagna region (Italy). A large experimental database, provided by the Geological, Seismic and Soil Survey of the Emilia-Romagna Authority, was used to develop a stratigraphic model of the upper 30 m subsoil of this coastal area, together with estimates of the mechanical parameters of the different soil units. A Bayesian approach was used to identify the most probable number of soil layers and their thicknesses, based on the Soil Behaviour Type Index obtained from CPTU results. This tool has already been used for small scale areas and its implementation in large datasets could eventually provide a preliminary estimate of the expected soil conditions at a site, taking into account statistically the inherent spatial variability in a rational and transparent way.

Paleogene clays are highly plastic, stiff clays deposited between 65.5 and 43 millions of years ago, frequently met in northern Europe. As they were deposited before the Quaternary, they experienced the glacial cycles that occurred in that period. The evolution and movement of the ice masses above the Paleogene clays highly influenced their stress history. During the interglacial periods the glaciers melted, unloading the underlying formations while during the glacial periods the glaciers mass loaded the Paleogene clays and sheared their shallower layers. Previous studies examined the compressibility and swelling of Danish Paleogene clays, and showed an early preconsolidation stresses, lower than that associated with the overburden pressure. This phenomenon was attributed to the effects of the glaciers movements. Other factors that have not been investigated yet and influence the deformation behaviour, can be associated with the micro and nano structure, meaning the particle orientation, and the mineralogical composition of the clays. This study focuses on a Danish Paleogene Formation called Røsnæs clay and the aim is to investigate the macromechanical swelling behaviour and its relation with particle rearrangement. A combination of 1D compression tests, microscopy imaging, mercury intrusion porosimetry and X-ray diffraction tests were performed on reconstituted and undisturbed samples in order to investigate the fabric, the pore structure and the mineralogy of the soil. A synthetic saline solution reproducing the in situ water was used to prepare the reconstituted samples and for the water bath. Variations with the swelling index were correlated with the clay particles rearrangement taking in to account the mineralogical composition. The compression curves and the scanning electron microscope micrographs were correlated with the mercury intrusion porosimeter results.

L’invenzione ha ad oggetto uno strumento di verifica del grado di saturazione di un gruppo sensore di pressione di un piezocono, e un metodo per effettuare tale verifica. Il metodo e l'apparecchiatura stabiliscono un criterio quantitativo per definire il grado di saturazione della punta di un piezocono, e conseguentemente l’affidabilità delle misure ottenute. La procedura, da realizzarsi prima della prova, può efficacemente essere utilizzata anche al termine di questa, al fine di verificare l’insorgere di eventuali fenomeni di desaturazione nel corso della prova, dovuti all’attraversamento di strati di terreno non saturi o per venute di gas.

Drainage behaviour of intermediate soils (e.g. silts, sandy silts, clayey silts) during standard cone penetration rate (20 mm/s) typically falls between that of sand and clay, for which fully drained and fully undrained conditions are expected to apply, respectively. Partial drainage phenomena may be evaluated by varying the penetration rate within a range which depends on the consolidation characteristics of the soil to be tested. This paper presents the results of a variable rate piezocone test (CPTU) campaign carried out in a clayey silt deposit of the southern margin of the Po river valley (Forlì, Italy). In order to assess the in situ drainage conditions, normalized piezocone measurements have been interpreted in terms of a nondimensional penetration rate. In this way, it is potentially possible to detect the transition point from undrained to partially drained and drained responses. Results have been compared to previously reported data on both natural deposits and laboratory reconstituted soils.

Soils originating from chemical decomposition do not undergo any sorting in their grading resulting in a well-graded material. Their composition may be influenced by weathering in one or more aspects, e.g. particle size, particle size distribution, mineralogy or particle morphology. Each of these aspects and their effects on the mechanical behaviour have been studied separately in the past. To identify the dominant parameters a series of standard oedometer tests was carried out to investigate the influences of the grading and mineralogy on the Normal Compression Line (NCL) separately. This was achieved taking the most and least decomposed granite sampled at a same location and reconstituting them to the same grading to study the influence of mineralogy or reconstituting one of them to both the gradings to study that of grading. In the first case, the NCLs were practically coincident, while in the second they were further apart, showing that the grading has greater importance in determining the mechanical behaviour in compression.

Many advanced soil models rely on the current state relative to normal and critical state lines to describe soil behavior. The position of these lines, therefore, requires an accurate estimation of the specific volume or void ratio. A series of one-dimensional compression tests was performed both on a coarse and a fine grained soil to investigate the experimental accuracy of the initial specific volume. This was obtained comparing independent calculations of the initial specific volume that were based on redundant measurements of height and weight of the specimen, both at the beginning and at the end of the test. The redundancy in the measurements was a key factor to obtain independent calculations. It was found that the excess water, such as may be stored in the filter papers, was the main cause of inaccuracy, when gross errors did not occur. Two novel confining rings having a closed-base were designed to reduce this effect. Although this was possible for the coarse grained soils tested, the fine grained soils retained more water due to the higher suction at the end of the test and water adsorption could not be avoided. The assumption of saturation is shown to be far from accurate, meaning that both the bulk unit weight and the water content should be measured independently to obtain a reliable measurement of the specific volume. The specific volume of the intact soil was found to be less accurate than when reconstituted. The experimental scatter was compared with the theoretical accuracy obtained from the error propagation theory. Good agreement was found between the theoretical and experimental accuracy. © ASTM Int'l.

High plasticity clays of Paleogene origin are frequently met in northern Europe, typically overconsolidated as a result of overburden pressure during the ice age. Moreover, the advancing and melting of the glaciers has affected their macro-structure, and clays are found pre sheared in some zones, while deeper layers are intact. Compressibility and swelling dominate the mechanical behavior, with con-siderable impacts in the design of modern infrastructure. This study focuses on the Paleogene Røsnæs Clay found between southern Denmark and northern Germany, which is characterized by high plasticity attributed to the smectite mineral content (20 – 50 %). Incremental loading one-dimensional compression tests were carried out on undisturbed Folded and Intact Røsnæs Clay using different salinity levels of the water in the oedometric cell and comparing the behavior with that of reconstituted samples having similar mineralogical composition to assess the influence of structure. Furthermore, the stress dependency of stiffness and creep rate was analyzed during unloading-reloading cycles achieving progressively higher stress levels.