Analysis and comparison of displacement granular pile anchors

Granular piles can resist only compressive and shear loads owing to their inherent nature. By a simple modification of providing a pedestal/geogrid at the bottom and attaching a cable to the same, they are made to resist pullout/uplift forces. This paper presents an analysis of granular pile anchor (GPA), considering it and the in situ soil to behave linearly and the in situ ground to be semi-infinite. A parametric study presents results in the form of variations of normalised shear stress, displacement influence coefficient and axial uplift force with depth with relative stiffness factor. Two methods for the estimation of deformation moduli of the GPA and the in situ soil are proposed. Based on the estimated values of the moduli, the displacements of GPA were estimated and the results compared with test results of Kumar (2002). The predicted displacements compare well with the measured ones.

The settlement performance of stone column foundations

Vibrated stone columns are frequently used as a method of reinforcing soft ground as they provide increased bearing capacity and reduce foundation settlements. Their performance in relation to bearing capacity is well documented, but there is also a need for enhanced understanding of their settlement characteristics, particularly in relation to small-group configurations. This paper presents results obtained from physical model tests on triaxial specimens 300 mm in diameter and 400 mm high. Parameters investigated include column length to diameter ratio, area replacement ratio and single/group configuration. The findings of the work are as follows. The design is flexible: settlement can equally be controlled using short columns at relatively high area replacement ratios, or longer columns at smaller area replacement ratios. An optimum area replacement ratio of 30-40% exists for the control of settlement. The settlement performance of a small column group is highly influenced by inter-column and footing interaction effects.

The pressure distribution along stone columns in soft clay under consolidation and foundation loading

The mechanism whereby foundation loading is transmitted through the column has received little attention from researchers. This paper reports on some interesting findings obtained from a laboratory-based model study in respect of this issue. The model tests were carried out on samples of soft clay, 300 mm in diameter and 400 mm high. The samples were reinforced with fully penetrating stone columns, of three different diameters, made of crushed basalt. Four pressure cells were located along each stone column. The 60 mm diameter footing used in the model was supported on a clay bed reinforced with a stone column and subjected to foundation loading under drained conditions. The results show that the dissipation of excess pore water pressure developed during the initial application of total stresses, when the foundation was subjected to no loading, generated considerable stresses within the column, and that this was directly attributable to the development of negative skin friction. The pressure distributions in the column during foundation loading showed some complex behaviour.

Granular anchors under vertical loading - axial pull

Granular anchors are a relatively new concept in ground engineering with relatively little known regarding their load–displacement behaviour, failure modes, ultimate pullout capacity and also potential applications. A granular anchor consists of three main components: a base plate; tendon and compacted granular backfill. The tendon is used to transmit the applied load to the base plate which compresses the granular material to form the anchor. A study of the load–displacement response and ultimate pullout capacity of granular anchors constructed in intact lodgement till and made ground deposits is reported in this paper. Parallel tests were also performed on cast insitu concrete anchors which are traditionally used for anchoring purposes. A new method of analysis for the determination of the ultimate pullout capacity of granular anchors is presented and verified experimentally, with the dominant mode of failure controlled by the column length to diameter ratio. Granular anchors with L/D > 7 principally failed on bulging whereas short granular anchors failed on shaft resistance, with the latter mobilising similar pullout capacities as conventional concrete anchors.

Under-water scene investigation using ground penetrating radar (GPR) in the search for a sunken jet ski, Northern Ireland

A search for a submerged jet ski and the lost limb of its driver involved in a collision with a speedboat was made in a shallow lake in Northern Ireland. The location of both was crucial to establishing events at the time of the accident. Local intelligence suggested both objects were likely to be partially-buried by lacustrine silt. To avoid sediment churning, this required non-invasive, completely non-destructive assessment and mapping of the scene. A MALA RAMAC ground-penetrating radar system (GPR) mounted on floats for surveying from walkways and jetties or placed in a small rubber dinghy for offshore profiling was used. A grid was established and each line surveyed with 100, 200 and 400MHz antennae. In waters over 6m deep GPR data showed the form of the lake floor but excessive ringing occurred in the data. In waters less than 6m deep ringing diminished on both 100 and 200MHz data, the latter displaying the best trade-off between depth penetration and horizontal object resolution. 400MHz data failed to be of use in waters over 2m deep and at these depths showed only limited improvement of image quality compared to 200MHz data. Surface objects such as a wooden walkway caused interference on 200 and 400MHz data when antennae were oriented both normal and parallel to survey direction; this may be a function of the low attenuation of radar waves in freshwater, allowing excellent lateral and vertical radar wave penetration. On 200MHz data the damaged jet-ski was clearly imaged in a location that contradicted the speedboat driver's account of the accident.

Reaching common ground:A patient-family-based conceptual framework of quality EOL care

Improvement in the quality of end-of-life (EOL) care is a priority health care issue since serious deficiencies in quality of care have been reported across care settings. Increasing pressure is now focused on Canadian health care organizations to be accountable for the quality of palliative and EOL care delivered. Numerous domains of quality EOL care upon which to create accountability frameworks are now published, with some derived from the patient/family perspective. There is a need to reach common ground on the domains of quality EOL care valued by patients and families in order to develop consistent performance measures and set priorities for health care improvement. This paper describes a meta-synthesis study to develop a common conceptual framework of quality EOL care integrating attributes of quality valued by patients and their families. © 2005 Centre for Bioethics, IRCM.