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The laboratory determination of maximum dry density ( ρ dmax ) and optimum moisture content ( w opt ) of soils requires considerable time and energy. Efforts have been made in the past to present models to predict the soil compaction parameters ( ρ dmax and w opt ), but the existing models are either applicable to specific soil types, plasticity range, compaction energy, or they have low prediction accuracy. This study aims to develop novel prediction models of soil compaction parameters using Gaussian Process Regression (GPR) incorporating different soil types, plasticity ranges, and compaction energies. The database used to develop prediction models consists of the index properties and compaction parameters of soils. GPR models were developed based on different kernel functions. To assess the accuracy of the predictive models, various error metrics were used, including coefficient of determination ( R 2 ), mean absolute error, and root mean square error. The validity of the models was verified by conducting laboratory experiments, where satisfactory results were obtained for the prediction of compaction parameters. A comparison of the performance of the proposed models in this study was also made with the existing models in the literature which showed that the models presented in this research performed better than those in the literature both during the model development and also in experimental validation. Finally, a sensitivity analysis was performed which indicates that the prediction models are greatly affected by plastic limit and fine contents.

Wood density is a key property since it affects almost every other property of wood such as its elasto-mechanical, acoustic, thermal, or electrical properties. Hence, it is essential to determine wood density for the interpretation of any other property test. Density measurements are usually carried out gravimetrically by measuring the wood specimens’ dimensions and taking their weight. In order to be independent of moisture, wood density is measured at an absolute dry state. However, depending on which wood properties shall be measured after the oven-dry density is determined, heating the wood up to 103 °C can be problematic because the volatile components of the wood can evaporate. For this reason, the drying conditions (temperature in °C (60, 80, 103 °C)), duration in h (8, 16, 24, 48 h)) required to achieve an absolute dry state inside wood specimens—being obligatory for the analysis of various physical, mechanical, or even biological properties—were examined for different softwood and hardwood species. Basically, oven-dry measurements (i.e., 48 h at 103 °C) themselves contained a significant error, which was considered to be the result of deviations in the handling of the specimens and the scales used. Using temperatures below 103 °C was critical for the determination of absolute dry mass and dimensions. Wood specimens with a high content of volatile ingredients led to an apparently increased residual MC (e.g., shown for Scots pine heartwood), thus volatile ingredients were considered an additional source of error during oven-dry measurements.

Compacted Gaomiaozi bentonite–sand mixtures are regarded as attractive buffer/backfill materials for nuclear waste deep geological disposal. When the mixture blocks are emplaced, the bentonite dry density as well as the salinity of groundwater is of primary importance for their hydro-mechanical behavior. In this study, the influences of bentonite dry density and water salinity on the swelling pressure and saturated hydraulic conductivity of such mixtures are investigated using the constant volume method. Results indicated that for mixtures having a low sand content, the swelling pressure was only associated with the bentonite dry density, while the hydraulic conductivity was influenced by the presence of sand particles. Exponential relationships were noted among the final swelling pressure, the saturated hydraulic conductivity, and bentonite dry density on the case of distilled water and salt solutions infiltrating. As the salt concentration increased, the swelling pressure and hydraulic conductivity decreased and increased, respectively, and the effects became less significant as the bentonite dry density increased. The higher swelling pressure and lower hydraulic conductivity on specimens infiltrated with calcium chloride solutions were a result of cation exchange reactions and a competition between the swelling potential change caused by the calcium ions in the interlayer of smectite and electrolyte solutions. The present work can provide a reference for the design of dry density of bentonite–sand mixtures as buffer/backfill materials for deep geological disposal.

In the current work, a systematic approach is exercised to monitor amended soil reliability for a housing development program to holistically understand the targeted material mixture and the building input derived, focusing on the three governing parameters: (i) optimum moisture content (OMC), (ii) maximum dry density (MDD), and (iii) unconfined compressive strength (UCS). It is in essence the selection of machine learning algorithms that could optimally show the true relation of these factors in the best possible way. Thus, among the machine learning approaches, the optimizable ensemble and artificial neural networks were focused on. The data sources were those compiled from wide-ranging literature sources distributed over the five continents and twelve countries of origin. After a rigorous manipulation, synthesis, and results analyses, it was found that the selected algorithms performed well to better approximate OMC and UCS, whereas that of the MDD result falls short of the established threshold of the set limits referring to the MSE statistical performance evaluation metrics.

The present study investigated the effect of recycled polyester fiber in combination with nano-SiO 2 as a new stabilizer for improving the geotechnical properties of the loess soil. In addition, it intended to evaluate the effect of adding recycled polyester fiber and nano-SiO 2 on engineering properties of the soil, especially the maximum dry density and shear strength using silty loess with low liquid limit. To this end, three different combinations of fiber and nano-SiO 2 ratios were used ranging between 2 and 6% in proportions of 33% and 50% for the total dry weight of the soil. Furthermore, three different combinations of fiber-soil ratios were employed which ranged between 0.5 and 1.5% for the total dry weight of the soil, as well as three different combinations of nano-SiO 2 ratios ranging between 2 and 6% for the total dry weight of the soil. The results from the compaction test indicated that the maximum dry density of the stabilized loess decreased while the optimum water content increased by adding recycled polyester and nano-SiO 2 . Based on the results of the direct shear test, the shear strength improved by increasing the contents of the recycled polyester fiber and nano-SiO 2 in the soil mixture. Thus, the addition of recycled polyester and nano-SiO 2 improved the strength properties of the loess soil. In order to obtain the maximum increase in shear strength, the optimum content of the recycled polyester fiber and nano-SiO 2 was 4% of loess soil dry weight in proportions of 33% and 50% in the mixture.

Large quantities of steel slag are generated annually throughout the world. Some slag from steel manufacturing is reused in the generation of other materials, such as hot mix asphalt aggregate, pipe filling, concrete, among others. The research aims to enrich the mechanical characteristics of soils and minimize road construction costs. The objective of this research is to find a material that increases the mechanical properties of the subgrade in clay soils with different plasticity indices using Electric Arc Furnace Slag (EAF) in percentages: 5%, 15% and 25% of the weight of the soil. From the tests carried out on the soil samples using parameters, it was possible to classify them by the Unified Soil Classification System (USCS) and also by the American Association of Highway Transportation (AASHTO) as low and high clays. plasticity. When testing the samples in their natural state and the samples with EAF, results were obtained that showed an improvement in the physical and mechanical properties of the clay soils with the addition of EAF, increasing the values of the Bearing Capacity Ratio (CBR) and the maximum dry density. of the clay soil as the percentage of HAE in the mixture increased. The optimal HAE addition content corresponds to 25% of the weight of the soil.

Using traditional materials to improve the permeability of silty soils can cause irreversible damage to the environment. Therefore, it is necessary to develop environmentally friendly biopolymers, such as xanthan gum (XG), to replace traditional materials to improve resistance to water erosion by reducing the permeability coefficient. In this study, a series of permeability tests and scanning electron microscope (SEM) tests were conducted on xanthan gum-improved silty soil (XGS). The variations in the permeability coefficient of XG-improved silty soil and the effects of initial dry density, XG-soil ratio, and curing age on the permeability were investigated. Test results show that the permeability coefficient of XGS decreased with the increase of initial dry density, XG-soil ratio, and curing age. With increasing the initial dry density, soil particles compressed against each other, decreasing the actual water flow crossing area, which leads to a decrease in the permeability coefficient. With the increase of the XG-soil ratio, the fill-blocking effect of xanthan gum with hydrogel connections becomes more and more obvious, which leads to a reduction in the permeability coefficient. Xanthan gum hydration takes time, and a lot of crystals are produced in XGS as the curing age increases; these crystals fill larger pores, resulting in the permeability coefficient decrease. At last, a model was developed to predict the permeability coefficient of XG-improved silty soil by using the initial dry density, XG-soil ratio, and curing age. The model can be used to rapidly predict the permeability coefficient of the improved silty soil under different conditions. This research can provide a scientific basis for the safe and scientific application of xanthan gum in seepage damage control and prevention projects.

The disintegration of expansive stiff clay will cause irreversible damage and deterioration of mechanical properties of the soil. The latest studies show that the disintegration is related to the swelling capacity of soil. In this study, a series of hydration disintegration tests and swelling pressure tests were performed on compacted Nanning expansive stiff clay samples with different initial water contents and dry densities. The observed disintegration process of all samples could be divided into initial, rapid and residual disintegration stages, among which the rapid stage dominated the whole process. By introducing relevant indicators to quantify the disintegration process, it was found that at a given dry density, the average disintegration rate of the sample decreased with increasing initial water content; while at a given water content, it decreased with increasing initial dry density. Such phenomena coincided well with the obtained evolution of swelling pressure at different initial water contents and dry densities. Based on these findings, the expansion-disintegration interaction mechanism of expansive stiff clay was finally analyzed from the perspectives of microstructure and hydration cracking. The initial conditions of the compacted samples determine the volume of inter-aggregates pores and thus the water transfer rate in soils, which affects the formation of hydration cracks. The cracking is induced by tension failure due to the expansion gradient formed during the hydration of sample, destructing the soil integrity to facilitate the disintegration. The disintegration, in turn provides preferential water infiltration channels to accelerate further soil expansion and hydration cracking. Such interactions proceeded until the completion of sample disintegration.

Compacted bentonite/sand mixtures are often considered as sealing/backfilling materials in deep geological disposal for radioactive waste. This study investigates the swelling pressure of compacted bentonite/sand mixtures with different bentonite fractions and dry densities upon hydration under constant-volume conditions. It was found that the swelling pressure of bentonite/sand mixtures is strongly dependent on their bentonite fraction and final montmorillonite dry density. For the samples with a bentonite fraction larger than a critical value, there is a linear relationship between the swelling pressure and final montmorillonite dry density. By contrast, for the samples with a bentonite fraction lower than the critical value, the sand particles will be skeletonized after strong compaction and lead to a heterogeneous distribution of montmorillonite, resulting in a larger swelling pressure compared to the samples with higher bentonite fractions. The maximum sand skeleton void ratio, corresponding to that at which the sand skeleton is just formed, is used to estimate the critical montmorillonite dry density and the critical bentonite fraction. Comparison between the test data and the estimated results shows good agreement, indicating the relevance of the identified swelling mechanism for compacted bentonite/sand mixtures.

Lateritic soil, a prevalent geological material in tropical regions, often exhibits poor engineering properties, leading to road pavement failures. Meanwhile, the alarming rise in plastic waste poses environmental concerns. This innovative study explores the potential of utilizing waste plastics as a lateritic soil addictive for sustainable road construction. Varying percentages by weight of shredded waste plastic (2%, 4%, 6%, 8%, and 10%) were incorporated into lateritic soil samples, evaluating its effects on soil geotechnical properties. The results revealed that lateritized plastic (shredded plastic waste and lateritic soil) containing 2% shredded plastic waste gave the optimum maximum dry density of 1.985 g/cm3, and the lateritized plastic containing 10% shredded plastic waste gave the highest optimum moisture content of 18%. However, the lower California bearing ratio obtained on the addition of plastic waste showed that the lateritized plastic is relatively weak and can only be used for roads with low traffic. The incorporation of shredded plastic waste into lateritic soil for stabilization is a promising polymer science-based method. By reducing the need for conventional materials and diverting plastic waste from landfills, this approach contributes to a more environmentally friendly infrastructure supporting the achievement of United Nation Sustainable Development Goals.