The majority of the Australian road network consists of unbound granular pavements with a thin bituminous surfacing. In Queensland, regional and remote areas, economic and environmental considerations encourage the use of locally available materials for the provision of granular pavements resulting in lower use of finite resources and a reduction in material transportation costs and associated emissions. These materials, known as non-standard or marginal materials, typically do not meet all the Queensland standard specification requirements but provide satisfactory performance when properly managed. At present, a universally accepted testing procedure for assessing the performance of non-standard materials is lacking. This paper reports on the first completed stages of a study aiming to investigate the physical and mechanical properties of non-standard materials using a range of laboratory testing: wheel tracking, modified Texas triaxial, California bearing ratio tests, and physical characterisation testing such as particle size distribution, Atterberg limits, compaction test, and apparent particle density measurement. This paper assessed 10 different non-standard materials together with one standard material using the selected laboratory tests. Later stages of the ongoing project, conducted for the National Asset Centre of Excellence (NACoE), will expand this testing and aims to develop a performance-based non-standard material screening tool to assist in material selection and assessments for road pavement construction and maintenance in low-traffic and low rainfall areas.

Important unsaturated soil mechanics topics for all geotechnical engineers and geotechnical engineering students are reviewed. These key topics include: (1) Soil is an elastoplastic material for which the macro-level response, in general, is controlled by two separate stress variables: total stress (net stress) and negative pore water pressure (suction). (2) Pore water pressures are always negative above the groundwater table-and should not be conservatively assumed zero; (3) shear strength and volume change of unsaturated soils are dependent on soil suction, as well as confining stress, and therefore geotechnical site investigations and testing must account for both stress variables; (4) water flow follows Darcy's law, but hydraulic conductivity is a strong function of water content such that fine-grained soil can have a higher conductivity than course-grained soil, leading to unexpected results when using saturated flow thinking processes; (5) unsaturated soil response is complex and difficult to intuit in the absence of laboratory testing and simulation. Features of unsaturated soil behavior most frequently encountered in geotechnical practice are highlighted, with discussion and demonstration from existing literature. Suggestions are given for relatively simple approaches for first steps in taking unsaturated soil mechanics principles into consideration in site investigation, laboratory testing, and design-related decisions.

Triaxial tests has been routinely used to measure the stress-strain relationship for geomaterials. During triaxial testing, many sources of errors that cannot be completely avoided but are often ignored or approximated using empirical equations. This paper presents a systematic investigation of soil volume change, volume strain nonuniformity, and cross-sectional calculation along the specimen during triaxial testing using a photogrammetry-based method. Consolidated drained triaxial tests were performed in which two parallel measurements were taken: (1) relative volume using the conventional triaxial testing and (2) absolute volume using the photogrammetry-based method. The difference in the observed volume and void ratio measurements between the two methods highlighted the importance of absolute soil volume over the relative volume method. The results revealed the effect of soil volume change in the interpretation of triaxial testing findings. Various preparation steps and procedures during triaxial testing have influenced the initial measured volume and thus caused deviation of the subsequent associated measurements. This method would present a quality control approach for different aspects of triaxial testing to improve the test simulations to accurately measure the soil behavior. The proposed method is important for more refined simulations and identification of setup-induced errors. Additional applications of the current research would allow correct determination of the stress path followed during triaxial testing, the critical-state soil mechanics parameters, and the stress-strain relationship, including deformation and strength parameters.

Integrated field and laboratory characterisation of geomaterial behaviour is critical to foundation analysis and design for a wide range of offshore and onshore infrastructure. Challenges include the need for high -quality sampling, addressing natural and induced micro -to -macro structures, and applying soil and stress states that represent both in -situ and in-service conditions. This paper draws on the Authors' recent research with stiff glacial till, dense marine sand and low -to -medium density chalk, and focuses particularly on these geomaterials' mechanical behaviour, from small strains to failure, their anisotropy and response to cyclic loading. It considers a range of in -situ techniques as well as highly instrumented monotonic and cyclic stress -path triaxial experiments and hollow cylinder apparatus tests. The outcomes are shown to have important implications for the analysis of large driven piles under monotonic -and -cyclic, axial -and -lateral loading, and the development of practical design methods. Also highlighted are the needs for approaches that integrate field observations, advanced sampling and laboratory testing, numerical and theoretical modelling.

The increasing use of finite element analysis in modern infrastructure design emphasizes the importance of determining soil stiffness at small strains. This is usually represented by the normalized shear modulus degradation curve, which is crucial for accurate design. In the absence of specific measurements on the local soil, engineers often rely on empirical correlations and assume comparable behavior of soils with similar intrinsic properties. However, the application of this approach leads to uncertainties, especially for unique geological formations such as the soft cohesive soils of the Ljubljana Marsh. The main objective of this study was to determine the small strain shear modulus of Ljubljana Marsh soil with a plasticity index between 11 and 35%. Isotropic and anisotropic stress conditions were investigated as part of an extensive laboratory test program that included 45 bender element and 89 resonant column tests on 20 soil samples. By emphasizing the importance of measuring soil stiffness at small strains, this study not only provides reliable data for the development of the built environment in the Ljubljana Marsh and similar areas, but also underlines its necessity.

The accumulation of waste tires is a global problem related to natural resources and the environment. The storage or burning of tires causes toxic chemicals to seep into the surrounding environment, which poses a serious ecological threat. Many previous studies have shown that waste tires can be used in geotechnical engineering. It was found that rubber reinforcement can increase the plasticity of sandy soil and improve its shear strength. It can control pore water pressure accumulation and improve dynamic properties. For cohesive soils, rubber additives can reduce dry density and improve compressive strength and soil stability. When mixed with soil with optimum content, waste tires can reduce various adverse effects of waste tire accumulation on the environment. The application of rubber has also a good impact on environmental protection and the promotion of green design. This paper presents the dynamic properties (shear modulus and damping ratio) of the RCA-RTW mixture for small, medium, and large ranges of shear strain levels (from about 1.5 center dot 10(-4)% to 1.3 center dot 10(-2)%). All specimens are constructed using different percentages of granulated tire rubber and concrete aggregate from curb crushing. A series of laboratory tests, resonant, and damping, are performed in the resonant column apparatus. The maximum shear modulus and minimum damping ratio are presented with the percentage of granulated rubber. The normalization is also applied to the G-modulus and D-ratio data set. Furthermore, a comparison is made between the results obtained for the tested geocomposites and a mixture of pure RCA.

The measurement of small strain stiffness of soils is affected by the techniques and procedures used in advanced triaxial tests, including the connection between the internal load cell and the sample top platen, the resolution of the instrumentation, the ratio of shearing axial strain rate to preceding creep strain rate. The interpretation of the measured data needs to consider how these factors have affected the measured stress-strain response of a sample. This paper reviews the current practice for performing advanced triaxial tests and discusses the interpretation of data resulting from advanced triaxial tests aimed at measuring the true stiffness of soils. It is concluded that the interpretation of the small strain stiffness of stiff clays affects the shape of the stiffness curve at medium to large strain levels and it is therefore relevant for engineering problems. Suitable specifications as well as a detailed review of the results of the tests are required to ascertain the reliability of the measured stiffness.