Model tests on piled raft subjected to lateral soil movement

Passive loadings due to lateral soil movement-induced activities are highly influencing the serviceability and safety of constructions. This research aims to investigate the influence of axial loads, sand density and the depth of moving soil on the lateral behaviour of piled raft under progressively moving sand. In order to achieve this goal taking into account the complex interaction effects of piles, cap and subsoil, a laboratory apparatus and small scale models have been designed and fabricated carefully to ensure a reasonable simulation of this geotechnical problem. It is found that the above parameters play an important role in the response of piled foundations. The value of soil displacement at which the measured moment reaches its ultimate value decreases as axial loads increase. Peak displacement of the raft has been found to be a function of soil density

Numerical modelling of passively loaded pile groups

Piled foundations could be affected negatively as a result of passive loadings caused by nearby soil movement-induced activities, and failure of piles could happen in some sever cases. This paper deals with the numerical analysis of passively loaded pile groups and piled raft in sand. The complexity involved in such problems due to pile–soil, pile–pile, pile–cap, soil–cap, and moving soil-stable soil interaction needs a powerful tool to make three dimensional analysis possible. In the current study, PLAXIS 3D software was used to back analyse laboratory tests carried out by the authors. “Embedded pile” feature in which the pile is represented by beam elements, while soil-pile interaction along the pile shaft and at the pile tip is described by special interface elements was employed. The Mohr–Coulomb elastic–plastic constitutive model was used to describe the sand behaviour. Although an overestimation of the predicted deflection was obtained, the general trend of bending moment profiles of piles was in a reasonable agreement with those obtained experimentally. A number of limitations were identified as possible reasons behind the overestimation of the predicted deflections. Furthermore, parametric studies are adopted to consider the effects of pile diameter, pile–soil stiffness and pile group configuration on the response of passively loaded pile groups

Effects of axial loads and soil density on pile group subjected to triangular soil movement

Laboratory tests have been carried out to investigate the response of 2x2 pile group subjected to triangular soil movement. The pile group was instrumented with displacement and tilting devices at the pile cap and strain gauges on two piles of the group. In this paper, results from four model tests were presented to study the effects of axial loads and soil density on the lateral behavior of piles. The responses in terms of bending moment, shear force, soil pressure, deflection, and rotation of piles were compared. Test results indicate that increasing the soil strength could increase the measured moment, shear, soil pressure, and pile deformations. Most importantly, adding loads to the pile cap induces additional moment to the head of frontpile row unlike the back-pile row which was influenced insignificantly

Modelling the response of single passive piles subjected to lateral soil movement using PLAXIS

Response of single pile subjected to lateral displacements of soil mass using 3D finite element software (PLAXIS) is studied. Embedded pile feature in which the pile composed of beam elements with special interface elements to represent pile-soil interaction is used. The Mohr–Coulomb elastic–plastic constitutive model was employed for the soil stress-strain behaviour. A good agreement between laboratory and predicted results is observed in the validation analysis. A parametric study was conducted to investigate the influence of soil Young's modulus and soil movement profile on the response of single "passive pile". The software results revealed that the distribution of bending moment along the pile length vary considerably and was in a very good agreement with the real pile behaviour when adopting a variation of soil elastic modulus with depth instead of choosing a constant value

Experimental investigation of batter pile groups behaviour subjected to lateral soil movement in sand

A series of laboratory model tests on batter pile groups embedded in the sand was carried out in a specially designed testing box. The lateral responses were investigated for 1 × 2 capped batter pile groups when subjected to lateral soil movements (passive loading) with different configurations; Vertical-Vertical (VVL), Batter-Vertical (BVL), Vertical-Batter (VBL), and Both- Batter (BBL). The effect of pile group arrangement and batter angle on the bending moment, shear force, soil reaction, pile rotation and deflection behaviour of the passive batter pile groups were studied. It is observed that the behaviour of the individual piles in a group was significantly affected by the batter angle and the pile group arrangement. It is also shown that under passive loading, batter pile groups with (BBL) configuration of (−10°, +10°) offered more resistance to the lateral soil movement compared to other pile group arrangements, while (VVL) configuration offered the least resistance

Effects of GDNF-loaded injectable gelatin-based hydrogels on endogenous neural progenitor cell migration

Brain repair following disease and injury is very limited due to difficulties in recruiting and mobilizing stem cells towards the lesion. More importantly, there is a lack of structural and trophic support to maintain viability of the limited stem/progenitor cells present. This study investigates the effectiveness of an injectable gelatin-based hydrogel in attracting neural progenitor cells (NPCs) from the subventricular zone (SVZ) towards the implant. Glial cell-line-derived neurotrophic factor (GDNF) encapsulated within the hydrogel and porosity within the hydrogel prevents glial scar formation. By directly targeting the hydrogel implant towards the SVZ, neuroblasts can actively migrate towards and along the implant tract. Significantly more doublecortin (DCX)-positive neuroblasts surround implants at 7 d post-implantation (dpi) compared with lesion alone controls, an effect that is enhanced when GDNF is incorporated into the hydrogels. Neuroblasts are not observed at the implant boundary at 21 dpi, indicating that neuroblast migration has halted, and neuroblasts have either matured or have not survived. The development of an injectable gelatin-based hydrogel has significant implications for the treatment of some neurodegenerative diseases and brain injuries. The ability of GDNF and porosity to effectively prevent glial scar formation will allow better integration and interaction between the implant and surrounding neural tissue