This paper presents a rigorous, semi-analytical solution for the drained cylindrical cavity expansion in transversely isotropic sand. The constitutive model used for the sand is the SANISAND-F model, which is developed within the anisotropic critical state theory framework that can account for the essential fabric anisotropy of soils. By introducing an auxiliary variable, the governing equations of the cylindrical expansion problem are transformed into a system of ten first-order ordinary differential equations. Three of these correspond to the stress components, three are associated with the kinematic hardening tensor, three describe the fabric tensor, and the last one represents the specific volume. The solution is validated through comparison with finite element analysis, using Toyoura sand as the reference material. Parametric analyses and discussion on the impact of initial void ratio, initial mean stress level, at-rest earth pressure coefficient and initial fabric anisotropy intensity are presented. The results demonstrate that the fabric anisotropy of sand significantly influences the distribution of stress components and void ratio around the cavity. When fabric anisotropy is considered, the solution predicts lower values of radial, circumferential and vertical stresses near the cavity wall compared to those obtained without considering fabric anisotropy. The proposed solution is expected to enhance the accuracy of cavity expansion predictions in sand, which will have significant practical applications, including interpreting pressuremeter tests, predicting effects of driven pile installation, and improving the understanding of sand mechanics under complex loading scenarios.

In recent years, there has been an increased focus on the research of earthen construction, driven by the rising demand for low-cost and sustainable building materials. Numerous studies have investigated the properties of compressed earth blocks (CEBs), however, very few have examined the properties of earth-based mortar. Mortar is an essential component and further investigation is required to enhance the mechanical performance of CEB structures. The study focuses on raw earth mortar (REM), which is a rudimentary mix of water with natural earth consisting of sand, silt and clay. Through experimental investigation, the fresh and hardened properties of three REM mixes were examined to determine the influence of cement stabilisation and jute fibre reinforcement. Shear triplet CEB assemblages were manufactured and tested to determine the initial shear strength of each mortar mix. The addition of 20 mm jute fibre at 0.25 % by weight increased the compressive and flexural strength of cement-stabilised raw earth mortar by 12 % and 20 % respectively. The addition of jute fibre also enhanced the initial shear strength, angle of internal friction and coefficient of friction during shear triplet testing. Finite element analysis (FEA) was undertaken to model the failure mechanism of the CEB assemblages, employing the use of cohesive zone modelling. The results of the FEA provided a satisfactory correspondence to the behaviour observed during experimental analysis and were within +/- 5.0 % of the expected values. The outcome of this investigation demonstrates the potential of REM and contributes to the development of low-cost and sustainable earth construction.

Precise calibration of constitutive models for cyclic liquefaction is essential but often time-consuming and requires significant expertise, limiting broader application in geotechnical practice. This paper introduces an automatic calibration tool designed to streamline the process for advanced constitutive models under both monotonic and cyclic loading. The tool supports various types of monotonic and cyclic laboratory test data, offers multiple choices of suitable comparison planes for error calculation, with a focus to also suit cyclic liquefaction problems, and employs advanced optimization techniques. The calibration follows a two-stage approach: first, optimizing parameters governing monotonic response using monotonic test data; second, refining these and additional parameters with both monotonic and cyclic data. The critical state parameters are fixed throughout, while the elasticity parameters are fixed in the second stage, all within defined bounds. Using this automatic calibration tool and the adapted calibration strategy, extensive element-level test data was used to determine the parameters of the SANISAND-MSf model for a given sand. These calibrated parameters were then used to simulate boundary value problems, including centrifuge tests of liquefiable sand slopes and sheet-pile-supported liquefiable sand deposits, all subjected to base excitations, demonstrating excellent alignment with experimental results. This validation highlights the robustness, reproducibility, and accuracy of the tool to model cyclic liquefaction while significantly reducing the expertise and time required for calibration. This represents a significant advancement toward the broader adoption of advanced constitutive soil models in geotechnical engineering practice.

This study investigated seasonal changes in litter and soil organic carbon contents of deciduous and coniferous forests at two altitudes (500 and 1000 m a.s.l.), which were used as proxies for temperature changes. To this aim, adjacent pine (P500 and P1000) and deciduous forests (downy oak forest at 500 m a.s.l. and beech forest at 1000 m a.s.l., D500 and D1000, respectively) were selected within two areas along the western slope of a calcareous massif of the Apennine chain (central Italy). Periodic sampling was carried out within each site (a total of 19 sampling dates: 6 in autumn, 4 in winter and spring, and 5 in summer), taking each time an aliquot of the upper mineral soil horizon and measuring litter thickness and CO2 emission from the soil. The samples were then analyzed for their content of organic C, total N, water-soluble organic C and N (WEOC and WEN, respectively), and the natural abundance of 13C and 15N. Soil and litter C and N stocks were calculated. The chemical and isotopic data suggested that organic C and N transformations from litter to the upper mineral soil horizon were controlled not only by temperature but also by the quality (i.e. C:N ratio) of the plant material. In particular, the more the temperature decreased, the more the quality of the organic matter would influence the process. This was clearly showed by the greater 13C fractionation from litter to soil organic matter (SOM) in D1000 than in P1000, which would indicate a higher degree of transformation under the same thermal condition of the plant residues from the deciduous forest, which were characterized by a more balanced C:N ratio than the pine litter. However, while at 500 m altitude a significant SOM 13C fractionation and a parallel increase in soil CO2 emissions occurred in the warmer seasons, no seasonal delta 13C variation was observed at 1000 m for both forests, despite the different quality of SOM derived from deciduous and coniferous forests. Our findings suggested that organic C and N transformations from litter to the upper soil mineral horizon were greatly controlled by the quality of the plant residues, whereas soil temperature would seem to be the major driver for the seasonal evolution of SOM. This study, by considering two different vegetation types (deciduous and coniferous), allowed to evaluate the combined interactions between the plant residue quality and temperature in controlling litter and SOM mineralisation/accumulation processes.

Expansive clay soil is known to cause damage to pavements due to its volume fluctuations with changes in moisture content, a phenomenon observed globally in many countries. Implementing suitable stabilisation treatments is crucial for improving the mechanical and hydraulic properties of the expansive clay subgrade. While cement and lime have traditionally been widely used as soil stabilisers, there is a growing emphasis on sustainable engineering due to increased awareness of global warming. Seeking alternative green and sustainable materials for soil stabilisation is demanded now, and one such alternative is using ethylene-vinyl acetate (EVA) copolymer emulsion. However, the use of EVA copolymer emulsion for stabilising expansive clay has been relatively underexplored in existing studies. This study evaluates the feasibility of utilising EVA copolymer emulsion for stabilising expansive clay subgrade through comprehensive laboratory tests to assess the mechanical (compaction, unconfined compressive strength, California bearing ratio, resilient modulus, and direct shear), hydraulic (soil-water retention curve and swellshrinkage), and micro-chemical (thermogravimetric analyses and scanning electron microscopic) performance of the soil. The experimental results indicate that the inclusion of 1 % EVA copolymer emulsion into the expansive clay provided the highest mechanical properties, resulting in an increase in the unconfined compressive strength, soaked California bearing ratio, resilient modulus, and cohesion by 8.8 %, 177.8 %, 35.8 % and 19.4 %, respectively. Swell-shrinkage behaviour was also improved with the addition of EVA copolymer, with 1 % EVA copolymer presenting the lowest swell-shrinkage index of 3.19 %/pF (14 % decrease in shrink-swell potential compared to the untreated clay).

Stinging nettle (Urtica dioica L.) has been observed to grow spontaneously on metal-contaminated soils marginalised by heavy industrial use, thereby presenting an opportunity for the economic utilisation of such lands. This study explores the potential of nettle as a fibre crop by producing short fibre-reinforced polylactic acid (PLA) composites through compounding and injection moulding. Whole stem segments from three nettle clones (B13, L18, and Roville), along with separated fibre bundles from the L18 clone, were processed. The fibre bundles were separated using a roller breaker unit and a hammer mill. From separation with the hammer mill, not only cleaned fibre bundles but also the uncleaned fibre-shive mixture and the undersieve fraction were processed. The Young's modulus of all composites exceeded that of unreinforced PLA, with mean values ranging from 5.7 to 8.1 GPa. However, the tensile strength of most composites was lower than that of pure PLA, except for the two composites reinforced with cleaned fibre bundles. Of these two, the reinforcement with fibre bundles from separation with the hammer mill led to superior mechanical properties, with a higher Young's modulus (8.1 GPa) and tensile strength (61.8 MPa) compared to those separated using the breaking unit (7.2 GPa and 55.9 MPa). This enhancement is hypothesised to result from reduced fibre damage and lower fibre bundle thickness. The findings suggest that nettle cultivation on marginal lands could be a viable option for producing short-fibre composites, thereby offering a sustainable use of these otherwise underutilised areas.

The escalating environmental challenges posed by waste rubber tyres (WRTs) necessitate innovative solutions to address their detrimental effects on the geoenvironment. Thus, the knowledge about the recent advancements in material recovery from WRTs, emphasising their utilisation within the framework of the United Nations Sustainable Development Goals (SDGs) and the circular economy principles, is the need of the hour. Keeping this in mind, various techniques generally used for material recovery, viz., ambient, cryogenic, waterjet, and so on, which unveil innovative approaches to reclaiming valuable resources (viz., recycled rubber, textiles, steel wires, etc.) from WRTs and various devulcanisation techniques (viz., physical, chemical, and microbial) are elaborated in this paper. In parallel, the paper explores the utilisation of the WRTs and recovered materials, highlighting their application in geotechnical and geoenvironmental engineering development projects while addressing the necessary environmental precautions and associated environmental risks/concerns. This paper incorporates circular economy principles into WRTs utilisation and focuses on achieving SDGs by promoting resource efficiency and minimising their environmental impact.

Collapse pits are highly susceptible to secondary hazards such as underground debris flows and slope instability under mining disturbances. These hazards significantly damage the ecological environment of the mining area. To reduce the geological hazards of collapse pits, grouting is used for management. The diffusion pattern and curing mode of slurry under different grouting pressures were investigated through indoor grouting simulation tests, and industrial tests were carried out to assess grouting effects. The results indicate that the slurry is dominated by penetration diffusion and supplemented by splitting diffusion in the moraine. The penetration distance and diffusion radius of the slurry increase linearly with grouting pressure, while the splitting uplift distance and cured volume increase exponentially with grouting pressure. Splitting diffusion consists of three stages: bulging compaction, splitting flow, and passive uplift. Horizontal splitting has a vertical uplift effect on the formation. The slurry primarily consolidates individual moraine particles into a cohesive mass by filling fractures, binding soil particles, and reinforcing interfaces with the rock mass. For different moraine layer structures, full-hole, segmented, and point-based grouting methods were applied. A composite grouting technique, layered grouting with ring solidification, was also introduced, achieving excellent grouting results. This study provides technical support for managing geological hazards in collapse pits caused by block caving mining disturbances and for green mining practices.

In cold regions, and considering the increasing concerns regarding climate change, it is crucial to assess soil stabilisation techniques under adverse environmental conditions. The study addresses the challenge of forecasting geotechnical properties of lime-stabilised clayey soils subjected to freeze-thaw conditions. A model is proposed to accurately predict the unconfined compressive strength (UCS) of lime-stabilised clayey soils exposed to freeze-thaw cycles. As the prediction of UCS is essential in construction engineering, the use of the model is a viable early-phase alternative to time-consuming laboratory testing procedures. This research aims to propose a robust predictive model using readily accessible soil parameters. A comprehensive statistical model for predicting UCS was developed and validated using data sourced from the scientific literature. An extensive parametric analysis was conducted to assess the predictive performance of the developed model. The findings underscore the capability of statistical models to predict UCS of stabilised soils demonstrating their valuable contribution to this area of study.

A common physical technique assessed for improving expansive clays is by the addition of natural fibres to the soil. A good understanding of the impact of stabilisation using fibres on the clay soil's constituents, microfabric, and pore structure is, however, required. Mixtures of clay and fibre, regardless of type or extent, can never change the natural composition of the clay. Even the smallest part must still consist of spaces with clay with the original physical properties and mineralogy. This suggests that, although the mixture may show beneficial physical changes over the initial clay soil, its spatial attributes in terms of mineralogical characteristics, remain unchanged. This paper discusses some of the fundamentals that are not always adequately considered or addressed in expansive clay research, aiming to improve the focus of current and future research investigations. These include the process, mechanics, and implications of chemical and physical soil treatment as well as the concept of moisture equilibration.