Piled foundations are widely used to limit the movement of foundations in expansive clays. These piles are subjected to large uplift forces as the clay swells (and downdrag forces when it shrinks). The appropriate method to estimate these forces is not well understood, and estimates from various methods presented in literature result in large variations. The uplift force generated in piles by soil heave was derived from strain measurements in full-scale field tests where a pile was installed in a highly expansive soil profile and flooded for several months. The results were compared to available theoretical estimates to comment on the most appropriate procedure to estimate the generated tension in the pile. The results showed that the use of an elastic solution related to the expected soil heave combined with a limiting shaft friction estimated from total stress capacity methods provided the most appropriate match to the measured results both in terms of the magnitude of the developed tension in the pile and shape of the tension profile along the depth of the pile.

The soil-water retention curve (SWRC) describes the relationship between the soil matric suction and the water content of an unsaturated soil. It is an essential tool in geotechnical engineering and agriculture and is, for example, used in the analysis of unsaturated soil conditions such as those found in tailings dams and in analyzing the water retention capacity of agricultural land. Conventional methods used to obtain the SWRC are laborious and often rely on empirically derived equations to describe the curve. These test procedures can take weeks to complete and usually rely on indirect methods of measuring suction. Recent advances in the development of affordable high-capacity tensiometers (HCTs), the only devices capable of producing a direct and continuous measurement of high matric suctions, enable the introduction of the tensiometer method for the rapid determination of continuous SWRCs. The method requires an HCT, a digital laboratory balance, and a means of sample volume measurement if volume changes are relevant. The method involves continuously monitoring the mass and matric suctions generated in a naturally desaturating soil sample. The method has thus far seen limited implementation owing to the need for measuring specimen volume change to describe the hydraulic and volumetric behavior fully. The performance of the tensiometer method was investigated by determining SWRCs of five different soil types and then comparing them to the SWRCs determined from the filter paper method. A novel method, based on photogrammetry, was adopted for volume change measurement to produce SWRCs for soils that undergo shrinkage during drying. Excellent agreement between the methods was found for both the nonplastic soils and plastic soils tested.

• Successful realisation of a low-cost data acquisition system for geotechnical applications. • Negative pore pressure, soil temperature and dielectric permittivity measurements. • Integrated battery power and SigFox communications for remote operation. • High level of customizability for adding additional sensors.

• Successful open source hardware integration in a geotechnical centrifuge. • Lateral loading and block cave mining controller in a geotechnical centrifuge. • Monotonic and cyclic loading controller in a geotechnical centrifuge. • Raspberry Pi integration for civil engineering physical model studies.

The tensile strength of soil is often neglected. Because of the presence of matric suction, unsaturated soils may have substantial tensile strengths with implications for a range of geotechnical problems, such as slope stability, bearing capacity, and the integrity of clay liners. Direct measurement of the tensile strength of soils is complex to carry out, while the simplicity of the Brazilian tensile strength (BTS) test offers an attractive alternative. However, this method was developed to measure the tensile strength of brittle materials. While suction-bound unsaturated soils may behave in a brittle fashion at low moisture contents, such materials become more ductile as the moisture content increases. This study investigated the application of the BTS test to measure the tensile strength of unsaturated soil samples over a range of moisture contents. Because of the low sample strength of these soils, the use of curved loading platens is recommended. The required load angle depends on the ratio between the compressive and tensile strength of the material tested. When brittle behavior is obtained during testing, conventional interpretation may be used, i.e., the maximum mobilized load during load application is used for tensile strength calculation. This is not appropriate when testing ductile materials. During load application on ductile samples, the initial mobilized load-deformation behavior is approximately linear and becomes nonlinear when tensile yielding starts to occur, originating from the sample center where the full tensile strength is first mobilized. It is recommended that, to obtain a conservative estimate of tensile strength, the inflection point where behavior becomes nonlinear should be taken as representative of soil tensile strength.