New Formulations for Dynamic Behavior of Sand-Waste Tire Mixtures in a Small Range of Strain Amplitudes

This paper describes the results of a series of cyclic triaxial tests on sand - waste tire mixtures, and applications of genetic programming (GP) and stepwise regression (SR) for the prediction of damping ratio and shear modulus of the mixtures tested. In the tests, shear modulus, and damping ratio of the geomaterials were measured for a strain range of 0.0001% up to 0.04%. The input variables in the developed GP and SR models are the waste tire content (0%, 10%, 20%, and 30%), waste tire type (tire crumbs or tire buffings), strain, and confining pressures (40 kPa, 100 kPa, and 200 kPa), and outputs are shear modulus and damping ratio. Test results show that the shear modulus and the damping ratio of the mixtures are strongly influenced by the waste tire inclusions. The performance of the proposed GP models (R2 = 0.95 for shear modulus, and R2 = 0.94 for damping ratio) are observed to be more accurate than that of the SR models (R2 = 0.87 for shear modulus, and R2 = 0.91 for damping ratio)

The next-generation constitutive correlations for simulation of cyclic stress-strain behaviour of sand

This paper presents an innovate approach to simulate the stress-strain behaviour of sands subjected to large amplitude regular cyclic loading. New prediction correlations were derived for damping ratio (D) and shear modulus (G) of sand utilizing linear genetic programming (LGP) methodology. The correlations were developed using several cyclic torsional simple shear test results. In order to formulate D and G, new equations were developed to simulate hysteresis strain–stress curves and maximum shear stress (τmax) at different loading cycles. A genetic algorithm analysis was per­formed to optimize the parameters of the proposed formulation for stress-strain relationship. A total of 746 records were extracted from the simple shear test results to develop the τmax predictive model. Sensitivity and parametric analyses were conducted to verify the results. To investigate the applicability of the models, they were employed to simulate the stress-strain curves of portions of test results that were not included in the analysis. The LGP method precisely charac­terizes the complex hysteresis behaviour of sandy soils resulting in a very good prediction performance. The proposed design equations may be used by designers as efficient tools to determine D and G, specifically when laboratory testing is not possible

A hybrid computational approach for seismic energy demand prediction

In this paper, a hybrid genetic programming (GP) with multiple genes is implemented for developing prediction models of spectral energy demands. A multi-objective strategy is used for maximizing the accuracy and minimizing the complexity of the models. Both structural properties and earthquake characteristics are considered in prediction models of four demand parameters. Here, the earthquake records are classified based on soil type assuming that different soil classes have linear relationships in terms of GP genes. Therefore, linear regression analysis is used to connect genes for different soil types, which results in a total of sixteen prediction models. The accuracy and effectiveness of these models were assessed using different performance metrics and their performance was compared with several other models. The results indicate that not only the proposed models are simple, but also they outperform other spectral energy demand models proposed in the literature

Deviatoric stress-strain curve construction with strain-softening account via the damage-modified Duncan-Chang, arctangent and informer models: a comparative analysis

Engineering construction in cold regions cannot be separated from permafrost research. This study aimed to determine the mechanical properties and changing laws of artificially frozen clay through triaxial tests. Two models have been established: a physical model based on the tradi-tional phenomenological constitutive theory and a deep learning model based on the data-driven constitutive theory, taking into account the softening phenomenon. The accuracy and applica-bility of the models were verified, followed by a comparative analysis. The results of the analysis are as follows. The Duncan-Chang model can describe the characteristics of the hardening-type deviatoric stress-strain curve, but it cannot describe the characteristics of the softening-type de-viatoric stress-strain curve. The Modified Duncan-Chang (MDC) model fails to accurately de-scribe the characteristics of a smooth deviatoric stress-strain curve. The Strain-Damage Modified Duncan-Chang (SD-MDC) model exhibits a good fit in both the ascending and descending seg-ments of the curve, but it lacks effectiveness in the convergence segment of the S-shaped sof-tening curve. For this reason, this paper has chosen the arctangent function to establish a Strain-Damage Modified arctangent constitutive model (SD-MAM). This model accurately re-flects the stress evolution process of different types of frozen soils. Additionally, the Informer time series prediction algorithm was utilized to develop the Informer permafrost deviatoric stress prediction model which achieved an R2 value above 99%. In comparison to the SD-MAM model, the Informer model demonstrates higher precision, does not rely on assumptions, is cost-effective, and has a wide range of applications. However, it lacks physical meaning, and interpretability, and requires further discussion regarding the reliability of the results. This study offers valuable insights into the development and application of constitutive models for frozen soils

Trends and Prospects in Geotechnics

The Special Issue book presents some works considered innovative in the field of geotechnics and whose practical application may occur in the near future. This collection of twelve papers, in addition to their scientific merit, addresses some of the current and future challenges in geotechnics. The published papers cover a wide range of emerging topics with a specific focus on the research, design, construction, and performance of geotechnical works. These works are expected to inspire the development of geotechnics, contributing to the future construction of more resilient and sustainable geotechnical structures

Comminution in the Minerals Industry

Size reduction processes represent a significant part of the capital as well as the operating cost in ore processing. Advancing the understanding of and improving such processes is worthwhile since any measurable enhancement may lead to benefits, which may materialize as reductions in energy consumption or wear or improved performance in downstream processes. This book contains contributions dealing with various aspects of comminution, including those intended to improve our current level of understanding and quantification of particle breakage and ore characterization techniques that are relevant to size reduction, as well as studies involving modeling and simulation techniques. The affiliations of the authors of the articles published in this book span 14 countries around the globe, which attests to the highly international nature of research in this field. The themes of the manuscripts also vary widely, from several that are more focused on experimental studies to those that deal, in greater detail, with the development and application of modeling and simulation techniques in comminution. Size reduction technologies more directly addressed in the manuscripts include jaw crushing, vertical shaft impact crushing, SAG milling, stirred milling, planetary milling, and vertical roller milling. Ores involved directly in the investigations include those of copper, lead–zinc, gold, and iron as well as coal, talc, and quartz

Mining Safety and Sustainability I

Safety and sustainability are becoming ever bigger challenges for the mining industry with the increasing depth of mining. It is of great significance to reduce the disaster risk of mining accidents, enhance the safety of mining operations, and improve the efficiency and sustainability of development of mineral resource. This book provides a platform to present new research and recent advances in the safety and sustainability of mining. More specifically, Mining Safety and Sustainability presents recent theoretical and experimental studies with a focus on safety mining, green mining, intelligent mining and mines, sustainable development, risk management of mines, ecological restoration of mines, mining methods and technologies, and damage monitoring and prediction. It will be further helpful to provide theoretical support and technical support for guiding the normative, green, safe, and sustainable development of the mining industry

Assessment and stabilization of micaceous soils

Mica is a mineral widely distributed around the world. This mineral generally occurs in igneous, sedimentary and certain metamorphic rocks and, if breaks down from the parent rocks, shows a unique platy structure and high elasticity. These features may affect performance of soils adversely which mica lies in, causing instability concerns to construction work or infrastructure systems involving the micaceous soils. One of the solutions is to assess the adversities arising from occurrence of mica and, using chemical and mechanical techniques, to stabilize the micaceous soils. The research presented in this thesis was conducted to develop the solution and to provide suitable guidance to implement it. The research was divided into three important aspects: i) assessing the effect of mica content on the mechanical properties of clays, ii) stabilizing the micaceous soils mechanically or chemically with jute fiber, lime, granulated blast furnace slag (GBFS), and slag-lime, and iii) formulating the stabilization outcomes using the surface response methodology and optimizing the stabilization. Different contents of mica were added to the soils to form the micaceous soils for testing. The experimental program consisted of consistency limits, standard Proctor compaction, unconfined compression (UC), direct shear and scanning electron microscopy tests. The test results suggested that the liquid and plastic limits exhibited a linearly increasing trend with an increase in the mica content. The rate of increase in the plastic limit, however, was observed to be greater than that of the liquid limit, thereby leading to a gradual transition towards a non-plastic behavior. The spongy nature and high-water demand of the mica minerals led to higher optimum water contents and lower maximum dry unit weights with an increase in the mica content. Under low confinement conditions, the strength properties were adversely affected by mica. However, the closer packing of the clay and mica components in the matrix under high confinement conditions offsets the adverse effects of mica by inducing the frictional resistance at the shearing interface. A series of soil stabilization attempts were made to reinforce the micaceous soils. The combined capacity of mechanical stabilizer, jute fiber and different cementitious binders such as lime, GBFS and slag-lime, were examined towards ameliorating the inferior properties of micaceous clays. The test results indicated that the inclusion of fiber consistently improved the ductility and toughness of the composite, and the addition of cementitious binders into soil-fiber composite further improved the connection interface, and thus led to the improvements in the composites’ strength, stiffness and toughness. Moreover, a non-linear, multivariable regression model was developed to quantify the peak UC strength as a function of the fiber content, slag content and the curing time, and the predictive capacity of the proposed models was examined and further validated by statistical techniques. A sensitivity analysis was also carried out to assess the relative impacts of the independent regression variables on the UC strength. The proposed regression model contained a limited number of fitting parameters, all of which can be calibrated by a standard experimental effort, as well as simple explicit calculations, and hence implemented for preliminary design assessments and predictive purposes. Response surface methodology (RSM) was employed to design the experiments, to evaluate the results and finally to optimize the binders’ content. The results showed that slag exhibited a noticeable synergistic effect and greatly contributed to the stabilization of micaceous soils with the presence of fiber or polyacrylamide. The RSM-based optimization was able to determine the additives dosage in terms of targeted UC strength values, and based on the developed models, to identify the most efficient dosage of improving micaceous soils for backfilling or other construction works. This research has delivered important outcomes for publications. The publications are listed below: J-H Zhang, A Soltani, A Deng and M Jaksa, 2019. Mechanical performance of jute fiber-reinforced micaceous clay composites treated with ground-granulated blast-furnace slag. Materials. DOI: 10.3390/ma12040576 J-H Zhang, A Soltani, A Deng and M Jaksa, 2019. Mechanical behavior of micaceous clays. J Rock Mech Geotech Eng. DOI: 10.1016/j.jrmge.2019.04.001 J-H Zhang, A Deng and M Jaksa, 2019. Mechanical behaviour of micaceous soils stabilized by lime, slag-lime with fibers. Written in manuscript style for submission in one month J-H Zhang, A Deng and M Jaksa, 2019. Optimization of slag and fiber/polymeric agent to reinforce micaceous soils using response surface methodology. Written in manuscript style for submission in one monthThesis (Ph.D.) -- University of Adelaide, School of Civil, Environmental and Mining Engineering, 201

Mathematical Problems in Rock Mechanics and Rock Engineering

With increasing requirements for energy, resources and space, rock engineering projects are being constructed more often and are operated in large-scale environments with complex geology. Meanwhile, rock failures and rock instabilities occur more frequently, and severely threaten the safety and stability of rock engineering projects. It is well-recognized that rock has multi-scale structures and involves multi-scale fracture processes. Meanwhile, rocks are commonly subjected simultaneously to complex static stress and strong dynamic disturbance, providing a hotbed for the occurrence of rock failures. In addition, there are many multi-physics coupling processes in a rock mass. It is still difficult to understand these rock mechanics and characterize rock behavior during complex stress conditions, multi-physics processes, and multi-scale changes. Therefore, our understanding of rock mechanics and the prevention and control of failure and instability in rock engineering needs to be furthered. The primary aim of this Special Issue “Mathematical Problems in Rock Mechanics and Rock Engineering” is to bring together original research discussing innovative efforts regarding in situ observations, laboratory experiments and theoretical, numerical, and big-data-based methods to overcome the mathematical problems related to rock mechanics and rock engineering. It includes 12 manuscripts that illustrate the valuable efforts for addressing mathematical problems in rock mechanics and rock engineering