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Although non-isothermal tests are important for many applications in geotechnical engineering, there is no standard for conducting such tests and interpreting the resulting data. This paper describes the development of a temperature-controlled triaxial apparatus, focussing on its thermal performance, and discusses relevant protocols to perform and interpret hydraulic conductivity tests on granular materials at different temperatures. With the aid of thermal cameras, hot spots on the surface of the equipment and instruments were identified. Subsequent modifications to minimise and mitigate heat reaching volume gauges and pore water pressure transducers were introduced. After modifications to reduce the system’s intrinsic head losses, the thermal expansion of the system proved to be significant and needed to be accounted for avoiding overestimation of thermally-induced mechanical strains. The addition of a new probe at the centre of the specimen allowed the characterisation of the temperature field within the system and specimen, as well as assisting with the identification of thermal equilibrium. Significant drops in temperature were flagged by this probe, though these proved to be unimportant in terms of hydraulic conductivity. The use of the average temperature for each pressure step is advised when a specimen probe is available. Alternatively, the use of target temperatures can be chosen, leading to minor underestimations of the intrinsic permeability.

In principle, numerical simulations of boundary value problems that involve fluid-soil interaction should account for the evolution of permeability due to soil deformation. For many applications of interest in geotechnical engineering, an accurate assessment of the permeability is key to an accurate prediction of settlements and pore water pressure changes. Finite element models rely on laboratory or field testing to characterise permeability; however, these methods cannot easily evaluate anisotropy or moderate variations of permeability. Current testing tools have a limited accuracy and a rigid experimental set-up, and are usually restricted to consider one flow direction. In this study, the influence of shearing on the intrinsic permeability and the anisotropy of permeability in medium-loose liquefiable sands is investigated. The discrete element method (DEM) was used to simulate monotonic undrained and drained triaxial test simulations on model soils comprising spherical particles. The particle positions were recorded at discrete strain levels and the data were taken as input into finite volume method (FVM) simulations which were used to evaluate intrinsic permeability in selected subsamples. In the FVM simulations, permeability was evaluated in the three orthogonal directions. The results indicate that shear deformation induces an anisotropy in permeability, in both drained and undrained triaxial conditions and this anisotropy increases with axial strain. Specifically, the results show an increase in permeability in the direction of the major principal stress, whereas a reduction permeability is observed in the orthogonal plane. Undrained simulations exhibit a jump in vertical permeability around the liquefaction onset; this can be attributed to the sudden loss of particle contacts.

Geotechnical engineers need to predict the macroscopic behaviour of clays in terms of strength, stiffness, and permeability and the variation in these properties during deformation. Engineers also need to predict the influence of environmental variables (temperature, pressure, pore-fluid chemistry) on these engineering properties. Particle-based methods, which explicitly model individual clay platelets and their interactions, can help identify the fundamental mechanisms that govern the engineering behaviour. Virtual samples can be created, and simulations can consider application of mechanical loading or change in the environmental conditions to generate data on particle kinematics and interparticle interactions. Particlebased models can be used to simulate stress and strain paths that are not easy to reproduce in physical experiments. This approach to simulation also enables parametric studies to understand the sensitivity of the overall behaviour to various particle characteristics and the nature of the particle interactions. This contribution provides a review of the state-of-theart of existing particle-based models for clays, namely Discrete Element Method (DEM), Monte Carlo method (MC), and Molecular Dynamics (MD). The technical challenges, advantages, and disadvantages of each method for the simulation of clays are presented and discussed, together with the technical developments we would like to see over the next decade to realize the full potential of these modelling tools.

Characterisation of the permeability of soils is of practical importance and, for cohesionless or granular soils, it can be predicted from the void ratio and the particle size distribution (PSD). However, the effect of fabric anisotropy on the permeability is rarely discussed. Restricting consideration to granular (cohesionless) soil, this study combines a variety of numerical methods to investigate (1) how the anisotropy of the permeability evolves as the soil fabric anisotropy evolves in triaxial deformation and (2) establish a link between the anisotropy of the permeability and the fabric anisotropy. The Discrete Element Method (DEM) was employed to create linearly graded virtual samples of spheres (Cu of 1 to 2). Initially isotropic sphere packings were subjected to triaxial compression or triaxial extension up to 30% of absolute axial strain to induce an anisotropic fabric. Pore Network Models (PNMs) present a computationally efficient option for simulation of flow through the pore space. A PNM models fluid flow between pores (nodes) connected by pipes (edges) whose geometry is defined by the topology of the connected pores and the mass balance equation is solved at each pore. After demonstrating the accuracy of the PNM framework adopted here, this contribution presents data from PNM simulations that used the positions of individual particles in the sheared spherical packings as input data. The fabric and permeability anisotropies during triaxial shear deformation were compared at axial strain intervals of 1%. Detailed microscale analyses suggest that the anisotropy in the permeability can be attributed to an increase in the local conductance of fluid pipes in the direction of the major principal stress, which is related to the evolution of the pore topologies during the shear deformation.

It is now viable to use coarse-grained molecular dynamics (CGMD) to model interacting clay particles in simulations of soil mechanics element tests. In CGMD, particle interactions are described by the Gay-Berne (GB) potential, which can approximate the potential energy between clay particles as a function of their separation and relative orientations; however, a previous study identified a significant shortcoming of the GB potential, which is that it lacks a local maximum called the “energy barrier” that the true interaction possesses at very close range. In this study, we propose a modified GB potential which can capture the energy barrier at and we use this new potential function to simulate the clay mineral kaolinite under isotropic compression. Our simulations show that the energy barrier is a crucial ingredient required to reproduce the elastoplastic behaviour observed in laboratory tests upon unloading from an isotropic normally consolidated state. Our data show that the difference in mechanical behaviour between normally consolidated clay and overconsolidated clay can be explained by the fact that, during the initial loading, some pairs of interacting particles surmount the energy barrier so that they then experience a large attractive force. Effectively, these particles become bounded and do not separate when the stress applied to the sample is released. The response of overconsolidated clay to applied stress is stiffer than that of normally consolidated clay because a larger proportion of the clay particle interactions exist in this bonded state.

The Journal of Geotechnical and Geoenvironmental Engineering (JGGE) is a prestigious journal that recently celebrated its 150th volume. Published by ASCE and sponsored by ASCE's Geo-Institute (G-I), it stands out from other journals in the field. The journal has a strong international presence, with contributors and editorial board members from various countries. To mark this milestone, the journal made 10 important papers available for free and organized a special session at a conference. Over the years, the journal's name has changed to reflect the expanding focus on environmental considerations in geotechnical engineering. It has published groundbreaking research in areas such as soil mechanics, geotechnical earthquake engineering, geoenvironmental engineering, and ground engineering. The field of geotechnical engineering is adapting to address global challenges like climate change and the shift to low-carbon energy. The journal maintains its commitment to the peer review process and remains a valuable resource for researchers, practitioners, and students worldwide. [Extracted from the article]

Coarse-grained molecular dynamics (CGMD) simulations can advance the understanding of clay behavior. In CGMD simulations, the interactions between clay platelets are modeled and the data generated can be used to quantitatively link the clay fabric to the overall material behavior and examine its sensitivity to changes in the pore-fluid chemistry. A key element of a CGMD model is the potential function employed for particle interactions. One approach is to use Derjaguin–Landau–Verwey–Overbeek (DLVO) theory to calibrate the contact models; however, DLVO theory does not account for a frictional component in the interaction. This contribution shows that omitting a frictional force results in an unexpected overall system response. The conclusion is developed by considering CGMD data generated during one-dimensional compression tests of assemblies of 10,000 kaolinite particles modelled as flat ellipsoids. When the Gay–Berne potential function, calibrated against DLVO predictions, is used to simulate the interactions and interparticle friction is not explicitly modeled, the resulting coefficient of earth pressure at rest K0=(σh′)/(σv′) is equal to 1. Furthermore, the packing density obtained in the CGMD is lower than that observed experimentally. Additional data generated using DEM simulations on assemblies of spherical particles demonstrate the sensitivity of K0 and packing density to the interparticle friction coefficient. Data presented here clearly support the need to explicitly consider a frictional-type component in particle interactions when simulating systems of clay platelets. [ABSTRACT FROM AUTHOR]

Background and Aims: This study aimed to assess the comparative effectiveness of the etanercept (ETN) originator (Enbrel) and ETN biosimilar SB4 (Brenzys) as first‐line treatment in patients with rheumatoid arthritis (RA), while also exploring the potential cost‐savings associated with this approach in Australia. Methods: Clinical data were obtained from the Optimising Patient outcomes in rheumatoLogy Australian real‐world data set. Adult patients with RA who had initiated treatment with the ETN originator or biosimilar as their first‐recorded biologic or targeted synthetic disease‐modifying antirheumatic drug between 1 April 2017 and 31 December 2020 were included. Treatment persistence was analysed using survival analysis. Cost‐savings were estimated based on data reported by the Australian National Prescribing Service MedicineWise. Results: Propensity score matching followed by inverse probability of treatment weighting selected patients taking originator (n = 209) or biosimilar (n = 141) with similar baseline characteristics and eliminated small differences in baseline disease activity. The median time for 50% of the patients to stop treatment was 19.4 months (95% confidence interval [CI], 14.7–36.4 months) for the originator and 22.4 months (95% CI, 15.0–33.1 months) for the biosimilar (P = 0.95). As a result of pricing policies established by the Australian Government, introduction of the ETN biosimilar would have resulted in a cost‐savings of over AU$9.5 million for 1 year of treatment for the patients reported in this study. Conclusion: Treatment persistence using either ETN originator or biosimilar was similar. The cost of all brands of ETN markedly reduced upon listing of the ETN biosimilar, resulting in significant savings for the Australian Government. [ABSTRACT FROM AUTHOR]