Research

A device for charging concrete in tremie pipe Bored piles and diaphragm walls are important foundation elements with very wide applications. Bleeding in fresh concrete leaves channels in the concrete and leads to loss of quality. The cause lies in the contractor process with contractor pipe. We will carry out modelling tests to better understand the mechanisms. We will also make an umbrella-like device and test it in a plexiglass tube. The experiments will be carried out on small and large scales. The falling speed of the concrete in the contractor tube is to be measured. The segregation of the concrete should be observed.

Wider research context/theoretical framework: Bedding landslides are widely distributed in sediments with inclined structures. They may undergo catastrophic failure, posing considerable threats to society. The localized deformation at the interface between the sliding mass and the bedrock of bedding landslides normally accounted for the majority of sliding movement. Thus, the mobilization of such slides is intimately related to the mechanical behaviour of the interface at the basal shear zone. As a result, a comprehensive investigation on soil-rock interface in bedding landslides are necessary to improve our understanding of the origin of catastrophic failure and to help develop robust numerical models for predicting bedding landslides and similar geohazards. Hypotheses/research questions/objectives: In this project, we will explore the mechanical behaviour of soil-rock interface by employing laboratory experiments and advancing a numerical model to simulate the failure process of bedding landslides along soil-rock interfaces. Approach/methods: This proposal combines innovative experiments and numerical simulations. A well-document bedding landslide occurred in the Three Gorges Reservoir area in China will be chosen to study the mechanical behaviour of soil-rock interfaces. Laboratory tests will be conducted for studying the shearing behaviour of shear-zone soil and soil-rock interface from elementary to model scale; An advanced hypoplastic model will be proposed considering the stress history of soil and the surface properties of the interface; A numerical model with the advanced constitutive model will be developed to mimic the post-failure process of the bedding landslide. Level of originality/innovation: A comprehensive experimental investigation on the shearing behaviour of soil-rock interfaces for bedding landslides is the first time in the discipline of engineering geology; The proposed interface hypoplastic model is for the first time considering the surface properties. The SPFEM simulation with hypoplastic framework is novel for mimicking the post- failure of bedding landslides with soil-rock interfaces. Primary researchers involved: Xuan Kang, as a Ph.D. student at the China University of Geoscience Wuhan, is the PI for this project. Her research focused on landslide stability, in-situ and laboratory tests on landslide materials. During her Ph.D., she has published 4 peer-reviewed papers in high impact journals. Prof. Wei Wu, as the director of the Institute of Geological Engineering, is the mentor for this project. He has made pioneering contributions in the field of constitutive modelling and numerical simulation.

In this research project, a 3D grain-scale continuum-discontinuum hierarchical multiscale computational framework is proposed to improve the deep understanding of compaction banding formations in the sedimentary porous rocks that are of strong interest and of major challenge in the modern geomechanics. The proposed grain-scale continuum-discontinuum multiscale numerical framework for porous geological media consists of three levels including FEM meshes at macro-scale, DEM grains at meso-scale and hypoplastic peridynamic points at micro-scale. Furthermore, the region partitioning search algorithm and CPU-GPU heterogeneous computing architecture both contribute to improvement of computational efficiency to construct an open-source 3D computational platform that is suitable to simulate large-scale geological and geotechnical problems. To systematically investigate the localized failure mechanism of compaction bands in porous geological media at laboratory and field scales, one laboratory-scale and one field-scale numerical models are simulated by 3D computational platform. The influencing factors of boundary conditions, stress fields, geomaterials heterogeneity, nonlocal characteristic length, granular shapes, etc. on the localization failure processes of compaction bands will be summarized and analyzed. Sequentially, effects of microstructural mechanism including pore collapse, grain debonding, intra-granular damage and grain crushing on the nucleation and propagation of compaction bands during the localized failure processes. Furthermore, localized failure mechanism of the geological tectonic phenomena, i.e., coexistence of pure compaction bands and shear enhanced bands, will be numerical explored .