Geotechnique Letters 

About: Geotechnique Letters is an academic journal published by ICE Publishing. The journal publishes majorly in the area(s): Pile & Geotechnical engineering. It has an ISSN identifier of 2045-2543. Over the lifetime, 571 publications have been published receiving 8611 citations.

Experimental micro-mechanics of granular media studied by x-ray tomography: Recent results and challenges

Abstract: Combining x-ray tomography and three-dimensional (3D) image analysis has finally opened the way for experimental micro-(geo)mechanics, allowing access to different scales of interest. When these correspond to a scale that has been imaged at high spatial resolution, high-quality measurements can be obtained (e.g. 3D displacements and rotations of individual grains of sand sample under load). However, there are issues when the scale of interest is smaller, for example the characterisation of grain-to-grain contacts (their orientations and evolution) or production of fines by grain breakage. This paper presents a short selection of new grain-scale measurements obtained using existing techniques. The challenges associated with smaller scale measurements on the same images are also discussed through a few examples from ongoing work.

3D assessment of fracture of sand particles using discrete element method

Abstract: Shearing or compression of granular materials causes particles to translate and rotate relative to each other, interlock or fracture depending on their mineralogy, morphology, porosity, applied stresses and boundary conditions. Conventional soil plasticity theories consider mainly the stress level and density to predict soil failure and ignore the influence of particle fracture. However, recent research has shown that there is a strong relationship between granular particle fracture and plastic yielding and hardening. In this study, the fracture of individual silica sand particles was modelled by adopting the bonded particle model concept within the framework of the discrete element method (DEM). Individual three-dimensional (3D) particles were generated as an agglomerate of a large number of small spherical sub-particles that were connected by parallel bonds that resist moment and tension at contact points. The tensile strength variation observed when testing natural silica sand was achieved by changing ...

Flume investigation of landslide granular debris and water runup mechanisms

Abstract: The heights of rigid debris flow barriers are designed to provide adequate retention and prevent debris from over-spilling. Designers need to predict potential runup height against a vertical wall to account for potential over-spilling. Experimental investigations of debris flow runup have previously been conducted using dry sand. A 5 m long rectangular flume was used to conduct runup experiments using both dry sand and water, separately. A combination of high-speed imagery, photoconductive sensors and laser sensors was used to study runup along the vertical face of a rigid barrier. The effect of Froude number (Fr) on runup was examined by varying the channel inclination. Commonly adopted energy and momentum approaches for predicting runup were compared with experimental results. The results reveal that runup mechanisms are dependent on approach Fr conditions and whether the flow medium is frictional in nature. For water, subcritical flows did not exhibit significant runup (reflective wave mechanism), whe...

Thermo-mechanical radial expansion of heat exchanger piles and possible effects on contact pressures at pile–soil interface

Abstract: This letter shows that the increase of heat exchanger pile capacity in response to heating, observed in several small-scale laboratory studies, cannot be directly attributed to the increase of contact pressure at the soil–pile interface. The main thermo-hydro-mechanical processes that influence the capacity and behaviour of heat exchanger piles include thermal hardening of the soil, thermally induced water flow, excess pore pressure development and volume changes upon thermal consolidation. Due to the lack of understanding of the behaviour around the soil–pile interface, thermo-mechanical interactions between the heat exchanger pile and the ground are not taken into account appropriately in energy foundation design. However, in situ and reduced-scale experiments provide evidence about temperature-induced changes in pile capacity, presumably as a result of the altered stress state around the test pile. A finite-element analysis was conducted to quantitatively assess the radial stresses and strains undergon...

The influence of surface roughness form on the strength of sand–structure interfaces

Abstract: Laboratory experiments performed on friction sleeves sheared against sands of varying particle angularity and size have shown the important role of surface texture on the strength of sand–material interfaces. This paper presents the first study that characterises the influence of surface roughness form on the shear response of sand–material interfaces. The results presented show that artefacts with periodic non-clogging surfaces (i.e. of structured roughness form) mobilise interface friction angles that readily reflect ‘δ > ϕ conditions’. On the other hand, artefacts with clogging-prone surfaces (i.e. of random or ribbed roughness form) mobilise interface friction angles that are restricted to ‘δ = ϕ conditions’. This difference is dictated by interface clogging. The surfaces of structured form avoid clogging and mobilise additional passive resistances during shear, as opposed to surfaces of random and ribbed form which clog and only mobilise sand–material or sand–sand friction. This observation is valida...