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This paper describes the geotechnical characteristics of index and deformation properties of Stockholm clays. These clays exhibit large variations both geographically and with depth. The clays range from highly organic clays with high plasticity to silty clays with low plasticity. First, the geological conditions of the clays are outlined to qualitatively explain the typical soil stratigraphy encountered in the Stockholm area. Second, two large generic databases are presented, containing 3,500 and 1,600 data points, respectively. The data originates from routine testing and constant rate of strain oedometer tests conducted in commercial projects. The data is analyzed and compared with results from high quality block sampling. It is seen that a common feature of the clays are low undrained shear strengths, and consequently low yield stresses and oedometer moduli. Further, several deformation properties such as preconsolidation pressure and several oedometer moduli is shown to depend on the soils natural water content and its plasticity. Differences in sample quality is shown to highly affect some properties, highlighting the importance of quality sampling and handling of samples. Criteria for sample quality for this type of clay is proposed based on the oedometer moduli before and after the preconsolidation pressure. The paper can hopefully work as a useful reference to engineers working on similar soils worldwide. [ABSTRACT FROM AUTHOR]

Shear strength parameters are essential factors in many geotechnical problems. These parameters can be obtained by laboratory tests such as the direct shear test or triaxial test and can be interpreted from field tests such as the standard penetration test and the cone penetration test. All these approaches can be considered difficult and time-consuming, especially when dealing with soils containing large-sized particles. This study investigates the application of machine learning techniques to predict the peak friction angle of granular soils based on their index properties. For this purpose, a series of medium-scale direct shear tests were conducted for different soil specimens to construct the dataset needed to explore these techniques. Index properties such as soil classification, effective particle sizes, gradation coefficients, and relative density were used as inputs for the models. The techniques were employed are linear regression, M5 tree, random forest, K-nearest neighbors, locally weighted linear regression (LWL), and artificial neural networks (ANN). It is found that the random forest, the ANN, and the LWL models could reliably predict the peak friction angle of granular soils while the other models have achieved poorer results. Also, it is put forward that picking the proper technique and fine-tuning the model hyperparameters are essential aspects to consider when applying these techniques. [ABSTRACT FROM AUTHOR]

Construction of road or building on soft soil, especially on peat soil, is the most challenging condition where there are consequences that engineers may have faced. Peat has excellent water-holding characteristics, highly fibrous due to the presence of a lot of decomposed materials and organic matter, which makes it highly compressible, weak at shear strength, and low in bearing capacity. This characteristic makes it unsuitable for use as foundation or sub-grade since it would have a large impact on deformation and settlement if not treated very well. Due to the excellent effects, soil reinforcement has been seen as a relevant method in various infrastructural projects in recent years since this technique is the most practical application to improve the strength and stiffness of peat soil by using various methods, including bamboo technology. This paper highlights some of the alternative methods in peat soil reinforcement technology. It combines several techniques based on the floating concept bamboo insights that effectively distributed the load on the embankment over the peat soil. In this strategy, it is observable to reduce the impact of deformation and settlement on peat soil. [ABSTRACT FROM AUTHOR]

Organic soils are considered one of the most problematic soils due to their high compressibility and low shear strength at small strains. Characterizing organic soils based on their simple index properties is useful for the preliminary design stages of construction projects. There are three main index properties used for assessing organic soils properties, namely: the water content, the organic content, and the fiber content. Organic soils are distinguished by their relatively high water content. The organic content includes the carbonaceous and combustible components. Whereas the fiber content accounts for the presence of fibers in organic soils based on their botanical composition and the degree of decomposition. The data available in literature regarding organic soils parameters (index, compressibility and shear strength) were collected and analyzed in this study to obtain new correlations between the different organic soil parameters, and the simple index parameters (water content and organic content). The available correlations found in the literature depend on relating a certain parameter with either the organic content or water content. However, the organic content and the water content are related. Hence, the proposed correlations presented in this study aim to connect the particular soil parameter with both the water content and the organic content, using the same equation. Unfortunately, there is not much data in the literature about the soil texture or fiber content, and their relation with other parameters. Hence, all the proposed correlations in this study are not considering the fibre content or the soil fabric. [ABSTRACT FROM AUTHOR]

Critical and residual states are key soil conditions relevant to slope stability. Evaluating the available shear strength in relation to these conditions is crucial for reliable stability analyses. However, limited availability of direct measurements in the usual engineering practice makes such evaluation seldomly straightforward. The issue is sometimes alleviated by utilising empirical correlations with soil index properties, more easily determinable, yet much care is needed in applying generic correlations to specific materials, as the related uncertainties might override their predictive capability. By analysing soil samples from the Dobkovičky landslide in Czech Republic, we discuss the extent to which some established correlations can be misleading, but also that relationships calibrated on site-specific data are not necessarily performing better. We then demonstrate that empirical models may fail to capture correlations if the sample set is rather homogeneous and noise from reasonable experimental uncertainties is introduced. Finally, we provide some guidelines on the use of different soil strength parameters, laboratory tests, and empirical relationships for slope stability analyses in engineering practice. [ABSTRACT FROM AUTHOR]

Owing to stratified profile of the sedimentary soils and shallow groundwater table in the city of Rasht, clay and silt soils possess different consistencies in various locations. Excessive consolidation settlement of the clay and silt governs geotechnical design of structures built in the city. This study aimed at characterising geotechnical properties of Rasht clay and silt from the upper 10 m. It comprised of constructing a database by collecting previous subsurface investigations at 21 project sites (including 70 boreholes), boring four test pits along with laboratory experiments and statistical analyses of the data. Properties investigated herein included bulk unit weight, specific gravity, natural water content, clay fraction, Atterberg limits and plasticity parameters, SPT N value, shear strength and stiffness and consolidation properties. Variation of these properties with depth was highlighted. Consistencies of the clay and silt specimens were determined. Laboratory strength and stiffness values were correlated to SPT N values. Rasht clay and silt were compared to other well-documented fine-grained deposits in literature. New relationships were established to estimate compression and recompression indices of the clay and silt from their index properties. [ABSTRACT FROM AUTHOR]

Loess and loess-derived soils cover much of Canterbury, from the foothills of the Southern Alps to the Pacific Coast. These deposits are of variable thickness, from a few metres up to 40 m at the base of slopes on Banks Peninsula. In many areas the primary, air-fall loess has been reworked by slope processes to form a loess colluvium. Although primarily silty, these soils contain up to 45% clay, giving rise to low plasticity clay behaviour. These deposits are relatively dense, with dry densities of 1.6 t/m 3 and 1.8 t/m 3 , hence they do not display collapse behaviour common to other loess deposits around the World. Loess and loess-derived soils across Canterbury have high dry strength but weaken rapidly with small increases in moisture content. In the wetter parts of the region, on Banks Peninsula in particular, periodic wetting leads to a variety of slope failures related to internal erosion (tunnel gullying) and rapid loss of shear strength (debris flows, soil slides and rotational failure). Elsewhere in the drier parts of South Canterbury loess deposits commonly form vertical exposures and evidence of slope instability is comparatively rare. The current understanding of the geotechnical characteristics of these deposits is based on a limited number of studies with restricted geographic extent. Thus a full understanding of regional and stratigraphic variability is yet to be established. Macroscale heterogeneities, including fissuring, development of fragipan cemented horizons and stratification, indicates that, as well as the general behaviour presented in this paper, there may also be significant local variation. In addition, the effects of soil microstructure, including bonding and particle shape and orientation, on overall soil behaviour are recognised, but have yet to be investigated in detail. [ABSTRACT FROM AUTHOR]

This paper develops probabilistic transformation models that predict the probability density function (PDF) of the preconsolidation stress (σ′ p ) of a clay based on its index properties. These probabilistic transformation models are more versatile than traditional transformation models that only provide point estimates, because the PDF can quantify the transformation uncertainty in σ′ p and also can be further used to develop median and confidence interval estimates for σ′ p . The confidence interval is especially useful because the transformation uncertainty in σ′ p is fairly significant. Three probabilistic transformation models are developed: one is a generic model and the other two are models specialized for contractive and dilative clays. The generic model is applicable to both contractive and dilative clays, but its transformation uncertainty is larger. The two specialized models require the prior knowledge about the contractive/dilative behavior for the clay of interest, but their transformation uncertainties are smaller. The performances of the three probabilistic transformation models are verified by statistical cross-validation and independent validation database. The analytical forms for the median and confidence interval estimates are presented in this paper so that engineers do not need to derive the Bayesian equations. [ABSTRACT FROM AUTHOR]

Soil health is one of the prominent features of the Sustainable Development Goals (SDGs). The SDGs seek to achieve the target of 75% healthy soils by 2030. On the contrary, the growing accumulation of microplastic contamination in soil environments is an issue of worldwide concern. The effect of a variety of microplastic accumulation on soil index and engineering properties is still unclear. Clayey soil is very important in geotechnical engineering because of its complex behaviour. This study investigates the effects of a variety of microplastics such as Low-Density Polyethylene (LDPE), Polyvinyl Chloride (PVC), and High-Density Polyethylene (HDPE) in environmental relevant concentrations (2%,4%,6% w/w) on index and engineering properties of clayey soil with respect to a number of observation days. In the present study, the non-contaminated soil treated as a control. The detailed experimentation revealed a significant change in the liquid limit, plastic limit, and shear strength values of clayey soil with an increasing percentage of microplastic contamination, whereas minute changes are recorded with respect to the number of observation days, this may be due to inert nature of microplastic. The shear strength is one of the critical engineering properties of soil that determines the strength and stability of the soil. The shear strength value of 0.94 kg/cm2 for control decreased to 0.76 kg/cm2 and 0.73 kg/cm2 and 0.85 kg/cm2 for the addition of 2%, 4%, and 6% respectively of LDPE microplastic contamination, similarly, for PVC microplastic contamination of 2%, 4% the shear strength decreases to 0.77 kg/cm2, 0.85 kg/cm2 respectively, the HDPE microplastic contamination of 2%, 4%, and 6% results in shear strength decrease to 0.52 kg/cm2, 0.53 kg/cm2 and 0.65 kg/cm2.The altered values of shear strength along with other index and engineering properties of soil due to microplastic contamination may lead to instability in structures or may increase the chances of harmful natural threats such as landslides. The present study provides evidence of significant changes in the index and engineering properties and therefore the stability of the soil which is the major contribution of the study. [ABSTRACT FROM AUTHOR]