Hydraulic Characterization of a Self-Weight Compacted Coal

AbstractWater infiltration through coal stocks exposed to weather elements represents a key issue for many old mining sites and coal-fired power plants from the environmental point of view, considering the negative impact on human health of the deriving groundwater, soil and air pollution. Within this context, the paper investigates the hydraulic behaviour of a self-weight compacted unsaturated coal mass and its impact on the numerical prediction of infiltration induced by rainfall events. In particular, the work focuses on the experimental investigation carried out at different representative scales, from the grain scale to physical modelling. The material, when starting from uncompacted conditions, seems to be characterized by metastable structure, which tends to collapse under imbibition. In addition, direct numerical predictions of the seepage regime through a partially saturated coal mass have been performed. As the compaction of the coal stock induced by dozers has not been taken into account, the numerical simulations represent a conservative approach for the assessment of chemical pollution hazard associated to water infiltration into a real stockpile under operational conditions

A Geomechanical Approach to Landslide Hazard Assessment: The Multiscalar Method for Landslide Mitigation

AbstractThe landslide hazard assessment, when based on the deterministic diagnosis of the processes, can be pursued only through the interpretation and the geo-hydro-mechanical modelling of the slope equilibrium. In practice, though, landslide hazard assessment is still seldom dealt with slope modelling, in particular when it addresses vast areas, where either heuristic or statistical methods do not entail any geo-hydro-mechanical knowledge of slope features and stability. The Multiscalar Method for Landslide Mitigation (MMLM) is an original methodological approach for intermediate to regional landslide hazard assessment. It is based on the geo-hydro-mechanical knowledge achieved from the application of a stage-wise diagnostic methodology of the landslide mechanism at the slope scale. The paper discusses the main steps of the MMLM aiming at diagnoses of landslide hazard based on hydro-mechanics, for small scale hazard mapping (at the large area)

Two-Scale Investigation of the Retention Behavior of a Well-Graded Mixed Soil

The hydraulic characterization of mixed compacted soils is helpful for the design of earthworks subjected to drying–wetting cycles. When the mixed soil is well-graded and made of both coarse and fine fractions, its matric suction may also be due to the short-range adsorption phenomena, as for the soil investigated in this research work. A silty–clayey sand was created by a mixing procedure and experimentally investigated at two different scales. Physical modeling of an infiltration process was performed, allowing an inverse numerical analysis to infer the water retention and the hydraulic conductivity functions of the soil, whereas element testing on soil specimens allowed direct determination of the same equations. In the article, problems related to the employed suction measurement techniques have been pointed out and discussed. By this two-scale combined strategy, features of the soil hydraulic behavior, such as the wetting collapse, the shrinkage during drying, and the loop of hysteresis, were also determined

Hydraulic Characterization of a Self-Weight Compacted Coal

Water infiltration through coal stocks exposed to weather elements represents a key issue for many old mining sites and coal-fired power plants from the environmental point of view, considering the negative impact on human health of the deriving groundwater, soil and air pollution. Within this context, the paper investigates the hydraulic behaviour of a self-weight compacted unsaturated coal mass and its impact on the numerical prediction of infiltration induced by rainfall events. In particular, the work focuses on the experimental investigation carried out at different representative scales, from the grain scale to physical modelling. The material, when starting from uncompacted conditions, seems to be characterized by metastable structure, which tends to collapse under imbibition. In addition, direct numerical predictions of the seepage regime through a partially saturated coal mass have been performed. As the compaction of the coal stock induced by dozers has not been taken into account, the numerical simulations represent a conservative approach for the assessment of chemical pollution hazard associated to water infiltration into a real stockpile under operational conditions

Hydraulic Characterization of a Self-Weight Compacted Coal

Water infiltration through coal stocks exposed to weather elements represents a key issue for many old mining sites and coal-fired power plants from the environmental point of view, considering the negative impact on human health of the deriving groundwater, soil and air pollution. Within this context, the paper investigates the hydraulic behaviour of a self-weight compacted unsaturated coal mass and its impact on the numerical prediction of infiltration induced by rainfall events. In particular, the work focuses on the experimental investigation carried out at different representative scales, from the grain scale to physical modelling. The material, when starting from uncompacted conditions, seems to be characterized by metastable structure, which tends to collapse under imbibition. In addition, direct numerical predictions of the seepage regime through a partially saturated coal mass have been performed. As the compaction of the coal stock induced by dozers has not been taken into account, the numerical simulations represent a conservative approach for the assessment of chemical pollution hazard associated to water infiltration into a real stockpile under operational conditions

Performance of Lunar Regolith Shield under Meteoroid Impact: Uncertainties of a Numerical Prediction

The protection of the future lunar base from radiation, thermal stresses and impacts of meteoroids can be achieved by several options, generally consisting in a shielding system, made of either regolith or combined materials. In the present paper, the incidence of two sources of uncertainty on the FEM calculation of stress propagation through the covering regolith layer has been assessed. First, the investigation has pointed out, for a given impact and a given constitutive model, the uncertainty in the stress prediction related to the strain interval adopted for the soil stiffness measurement. Thereafter, calculation has been performed, for a given stiffness value, changing the assumed collision duration of one order of magnitude for equal impact momentum, that is, changing the maximum impact force too, correspondingly. The simulation has been performed based on physical and mechanical parameters of DNA-1A lunar simulant. The results provide indication of the relative importance of the calculation assumptions, which could address the design of a regolith shield

An Investigation into the Water Retention Behaviour of an Unsaturated Natural Fissured Clay

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

An Investigation into the Water Retention Behaviour of an Unsaturated Natural Fissured Clay

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