An analysis of stress-strain behaviour and wetting effects on quarried rock shells
The analysis of stressstrain behaviour and the effects of submergence on quarried rock shells, used mainly in dams but also in road construction, is of major importance from both economic and safe...
Simulation of collapse settlement in rockfill material due to saturation
In the first impounding of rockfill dams, additional settlements occur in upstream side in saturated rockfills due to collapse phenomenon; even high rainy seasons can cause additional deformation in the dumped rockfills. Unfortunately these displacements are not taken into account in the conventional numerical models which are currently used to predict embankment dam behavior during impounding. In this paper to estimate these displacements, strain hardening-strain softening model in Flac is modified based on the laboratory tests, in which same impounding process in such dams is considered. Main feature of the model is reproduction of nonlinear behavior of rockfill material via mobilized shear strength parameters and using collapse coefficient to display induced settlement due to inundation. This mobilization of shear strength parameters associated with some functions for dilatancy behavior of rockfill are used in a finite difference code for both dry and wet condition of material. Collapse coefficient is defined as a stress dependent function to show stress release in the material owing to saturation. To demonstrate how the model works, simulation of some large scale triaxial tests of rockfill material in Gotvand embankment dam is presented and results are compared with those from laboratory tests, which are in good agreement. The technique could be used with any suitable constitutive law in other coarse-grained material to identify collapse settlements due to saturation.
Community refinement of glaucoma referrals
AbstractAim To describe a Manchester-based glaucoma referral refinement scheme designed to reduce the number of false-positive referrals to the hospital eye service. To report on the first years results of this scheme and its financial costs to the NHS.Methods Patients with suspected glaucoma, instead of being referred to their GP and then on to the hospital eye service, were referred to a group of specially trained community optometrists working to an agreed set of referral criteria. Those patients who did not meet the referral criteria were returned to the referring optometrist, while those who met the referral criteria were referred directly to Manchester Royal Eye Hospital. The patient's GP was informed in all cases.Results The number of suspect glaucoma cases referred to the Manchester Royal Eye Hospital was reduced by 40%. This figure is close to the percentage of false-positive referrals measured at Manchester Royal Eye Hospital prior to the onset of this study. The information accompanying referral has been improved and the scheme produces a small financial cost saving to the NHS of approximately £17 per patient.Conclusion Community refinement of suspect glaucoma offers some important benefits over the current referral pathway.