Although electrokinetic treatments for soil remediation and ground improvement have gradually undergone significant experimental development, one of the most important physical phenomena has received very little attention in recent years. Electroosmotic flow, especially in unsaturated conditions, has not been simulated in domains of more than one dimension. In the present work, a modification of the M4EKR code was used to study water movement in partially saturated soils under electrokinetic treatments. Two different configurations were studied: electrodes placed in electrolyte wells and electrodes directly inserted into the soil, and the treatment was started under unsaturated conditions for both. Due to the unrestricted availability of fluid in the first case, soil saturation is inevitable, but in the second case, only a spatial redistribution of water content can be observed. A detailed analysis of a variety of configurations involving several electrolyte wells showed that the number of electrodes, the distance between them and, above all, the ratio between the two magnitudes determines the efficiency of soil saturation and the energy consumed in the process. Full article

Biocementation is a soil treatment technique wherein bacteria living in soil pores promote the precipitation of calcium carbonate. One of the most recent applications of this treatment is to provide resistance against the erosion of slopes by creating a resistant cover but still allowing infiltration to avoid water runoff. For modeling infiltration, it is fundamental to know the water retention curve of the treated material. This may not be an easy task because the soils most suitable for biocementation treatment are sands, due to their large pore sizes and consequent high permeability. The water retention curves (WRCs) of such types of soil are characterized for having a very small air entry value, followed by an almost-horizontal zone, which cannot be measured by using the vapor equilibrium, most of the existing sensors, or a water dewpoint potentiometer. Data from mercury intrusion porosimetry (MIP) tests can be used as an alternative to find the WRC, and this is explored in this paper. The model for the water retention curve presented considers the deformability of the soil during the MIP test, assuming an isotropic elastic behavior. The WRC derived from the MIP tests is well-fitted to the points measured by using a water dewpoint psychrometer (only for suctions above 1 MPa) and vapor equilibrium. Full article

The presence of intensely fissured soils is often found to relate to high geotechnical risks, such as landslide risk. This is especially the case of the Southern Apennines, Italy, where slopes formed of intensely fissured clays are frequently affected by landslides. The latter are generally triggered by rainfall infiltration, which takes place through the outcropping, unsaturated clayey soil cover. With the final aim of reducing landslide risk in areas covered by fissured clays, a detailed hydro-mechanical characterisation of these materials is required. While the behaviour of fully saturated fissured clays has been investigated in the last decade, only a few studies dealing with unsaturated, natural fissured clays are reported in the literature. The present paper aims to give a contribution toward filling this gap by extending an investigation campaign started a few years ago on the Paola Doce fissured clay outcropping on the Pisciolo slope (Southern Apennines, Italy). The physical properties of the material and some of its key micro- to meso-structural features are first analysed, the latter also based on Scanning Electron Microscope (SEM) micrographs of an undisturbed sample taken at 1.4 m depth on the Pisciolo slope, which is mainly formed of Paola Doce clay. Subsequently, water retention data of the soil are presented, which were obtained using both high-capacity tensiometers and the filter paper technique. These data were collected not only on undisturbed samples but also while subjecting the same material to drying paths. The results herein reported aim to make a link between the water retention behaviour of the Paola Doce clay sampled at Pisciolo and its fissured structure. Full article

Compacted clay covers have been the most commonly used materials for hydraulic barrier layers. During their construction, the control of some parameters such as compactive effort and molding water content is required. These last parameters affect the hydraulic conductivity, which is considered as one of the important key parameters for cover design. To reach the target in terms of hydraulic conductivity, the cover must be compacted to a pre-determined dry unit weight that usually corresponds to a certain percentage of the maximum dry unit weight (γ_dmax). During the prefeasibility stage of a project (before conducting the required tests), γ_dmax and the optimum water content (w_Opt) can be estimated to obtain an early overview of the conditions that can be anticipated. In this regard, a new approach was proposed to estimate these parameters using the liquid limit (w_L) and the plastic limit (w_P). The proposed equations were developed using data from 56 compacted clay liners and validated using 44 others taken from published data. Results presented in this paper indicate how the proposed equations can successfully estimate parameters of the optimum compacted point. Full article

Soil-specific heat capacity (c_p) and volumetric heat capacity (C_v) are recognized as a fundamental soil property essential for the accurate prediction of soil temperature and heat flow. This study presents the analysis of these thermal properties for drained peat soils in Poland. The objectives of this study were to (i) measure and develop a method for determining c_p, (ii) analyze the (C_v) data for undisturbed soil samples from surface layers, and (iii) test the applicability of the c_p value for calculating C_v of drained peat soils using the mixing model concept. The c_p value was measured under laboratory conditions using a modulated differential scanning calorimetry (MDSC) for 18 soil layers sampled in six degraded peat soil profiles. The C_v was estimated for undisturbed triplicate soil samples from the 22 depths (66 samples) by using a dual-needle probe. The c_p data for the organic soils were linearly temperature-dependent (MDSC) for the temperature range considered (−20–30 °C). The overall average c_p value was equal to 1.202 J g⁻¹ K⁻¹ at a temperature of 0 °C. An increment in temperature of 1 °C corresponded to an increase in c_p of 0.0043 J g⁻¹ K⁻¹ on average. Nevertheless, the lowest c_p value was obtained for moss samples whereas the highest value represents alder peats. The C_v data measured using the heat thermal probe (HTP) method changed linearly with changes in the soil moisture content (θ_v) of the moorsh soils. The volumetric heat capacity calculated using the mixing model was comparable to the mean of measured values obtained on the triplicate samples. Full article

The Hunter valley region in NSW Australia is an area with a heavy coal mining presence. As some mines come to their end of life, options are being investigated to improve the topsoil on post mining land for greater plant growth, which may allow economically beneficial farmland to be created. This research is part of an investigation into mixing a mine waste material, coal tailings, with topsoil in order to produce an improved soil for plant growth. Implementing such a solution requires estimation of the drying path of the water retention curves for the tailings and topsoil used. Instead of a lengthy laboratory measurement, a prediction of the drying curve is convenient in this context. No existing prediction models were found that were suitable for these mine materials, hence this paper proposes a simple and efficient model that can more accurately predict drying curves for these mine materials. The drying curves of two topsoils and two tailings from Australian coal mines were measured and compared with predictions using the proposed model, which performs favorably compared to several existing models in the literature. Additionally, the proposed model is assessed using data from a variety of fine- and coarse-grained materials in the literature. It is shown that the proposed model is overall more accurate than every other model assessed, indicating the model may be useful for various materials other than those considered in this study. Full article

For mine wastes such as coal tailings, management of these materials requires complex geotechnical engineering that uses many soil properties, such as water retention. However, coal itself is chemically heterogeneous and often appears to be partially hydrophobic, which affects its water retention properties. This study aims to outline how hydrophobic soil particles and coal alter water retention curves compared to hydrophilic materials. The study involves four materials: sand, hydrophobized sand, crushed rock and crushed coal. Mixtures of sand with different proportions of hydrophobic particles had their water retention curves measured and compared, with the only variable being the particle surface characteristics. The rock and coal were separated into different particle size fractions and had their water retention curves measured and compared, with the only variable being particle hydrophobicity. A clear trend was observed for the sand mixtures: the degree of saturation at any suction was reduced when increasing the hydrophobicity of the material. This trend indicates the fundamental water retention behavior expected for soils more hydrophobic than is typical, which was not clearly demonstrated in previous studies. However, a similar trend was not seen when comparing the rock and otherwise identical hydrophobic coal samples, which actually appeared hydrophilic in terms of water retention. ESEM imaging shows a dual hydrophilic and hydrophobic behavior for coal which may explain the result. However, further research is required to understand the discrepancy, which appears to be caused by an unknown coal–water phenomena. Full article

Several factors control the vulnerability of historic geostructures to climate change. These factors are both temporally and spatially variable depending on construction techniques and climatic conditions. This paper provides a review of both the historical construction practices on the UK transport network and recent developments in the understanding of climate change effects, allowing for an assessment of the impact of climate change on existing geostructures. Geostructures in the UK can be split between pre-regulation and post-regulation construction techniques. In general, highways were constructed after the implementation of modern regulations and are therefore less vulnerable to climate change due to formalisation of construction methods. In comparison, the performance of the railway network has shown to be inferior due to historic construction practices including poor or absent compaction, lack of consideration for foundations, or selection of fill materials. Recent findings have shown that the impacts of climate change are also a multiscale problem, influenced not only by regional geology but also the pore structure of soils and its evolution. While the research into these impacts is critical, the limitations of common methods employed to survey these structures and study the behaviour of their constituent materials requires consideration. In this paper, these aspects are examined in detail in a bid to integrate holistically the complexity of the systems involved. Full article