#### Comparative performance of some constitutive models in stress rotation

The dilatancy/contractancy of soil is of particular importance for compaction, consolidation, liquefaction, etc. Interestingly, constitutive relations are often unsatisfactory in modelling volume changes in the sense that their predictions deviate considerably from each other. This scatter is pronounced in problems with stress rotation. Therefore, in this paper some selected constitutive relations are investigated with respect to their performance at stress rotation. The obtained numerical simulations are compared with each other and also with experimental results from the $1\gamma 2\epsilon$ and the hollow cylinder apparatuses.

Published: 2019-11-25

#### Frictional Plasticity in a Convex Analytical Setting

A very simple frictional plasticity model for a granular material is presented, including the effects of dilation. The novelty lies in the fact that this is described within the hyperplasticity framework, expressed using the terminology of convex analysis. This allows a consistent mathematical treatment of the dilation constraint. The Fenchel Dual is used to link the force and flow potentials. The resulting model accommodates non-associated flow within a rigorous mathematical framework that ensures compliance with the Laws of Thermodynamics.

Published: 2019-09-12

#### Proppant-Induced Opening of Hydraulically Created Fractures

The paper examines the problem of the open configuration created when a hydraulic fracture fluid containing a granular proppant is introduced into the fracture. The mathematical modelling examines the problem of an extended cracked region that is wedged open by a granular material present over a finite region of the crack. The combination of the geostatic stress state and the contact stress created between the granular proppant and the elastic rock mass is used to develop a consistency relationship for estimating the dimension of the region of the fracture that will remain open when the pressures applied to create the fracture are released. The interactive mechanics of the fracture and the proppant has an influence on the geometry of the open region that provides the pathway for extraction of the resource.

Published: 2019-07-22

#### Editorial

This Editorial is the first publication from the journal Open Geomechanics, a radically open-access scientific journal for Geomechanics Research, edited by Geomechanics researchers for Geomechanics researchers. We believe that the results of scientific research should be available to all. For this reason, this journal is committed to publishing high quality work within the remit of diamond open access — free to publish and read. Our aim is to become a recognised journal in the field of geomechanics, and a launchpad for new ideas for the dissemination of research in this field. Research manuscripts (in any geomechanics related topics such as analytical, numerical or experimental studies) or case studies, negative results, as well as replicability or reproducibility studies are welcome.

Published: 2019-01-28