Three-dimensional slope stability analysis of South Peak, Crowsnest Pass, Alberta, Canada

South Peak is a 7-Mm³ potentially unstable rock mass located adjacent to the 1903 Frank Slide on Turtle Mountain, Alberta. This paper presents three-dimensional numerical rock slope stability models and compares them with a previous conceptual slope instability model based on discontinuity surfaces identified using an airborne LiDAR digital elevation model (DEM). Rock mass conditions at South Peak are described using the Geological Strength Index and point load tests, whilst the mean discontinuity set orientations and characteristics are based on approximately 500 field measurements. A kinematic analysis was first conducted to evaluate probable simple discontinuity-controlled failure modes. The potential for wedge failure was further assessed by considering the orientation of wedge intersections over the airborne LiDAR DEM and through a limit equilibrium combination analysis. Block theory was used to evaluate the finiteness and removability of blocks in the rock mass. Finally, the complex interaction between discontinuity sets and the topography within South Peak was investigated through three-dimensional distinct element models using the code 3DEC. The influence of individual discontinuity sets, scale effects, friction angle and the persistence along the discontinuity surfaces on the slope stability conditions were all investigated using this code.     

Using GRASS GIS to Model Solar Irradiation on North Carolina Aquatic Habitats with Canopy Data

Sunlight can have a significant impact on freshwater aquatic communities. Using 64‐ bit GRASS, a previously generated 18.2 m resolution forest canopy height grid for the State of North Carolina was used as a base elevation layer for calculation of 18.2 m resolution total irradiance (Watt‐hours/square meter/day) grids for 365 days of the year. Daily calculations were aggregated annually and overlaid on rasterized 1:24,000‐scale USGS hydrology with canopy type and seasonal filters to quantify annual solar irradiation input to streams and rivers in North Carolina. Bare earth calculations of solar irradiation for the aquatic habitats were compared to the canopy filtered calculations. There was substantially less solar irradiation in aquatic habitats under the canopy filtered model. Total solar irradiation for subbasins created from point locations of occurrences of Dwarf wedgemussel (Alasmidonta heterodon) were compared with total solar irradiation for watersheds created from locations with no mussels for the full subbasin, 1 km, and 500 m upstream from the sampling point. There was no significant difference in the amount of total solar irradiation modeled for the subbasins with Dwarf wedgemussel and watersheds with no mussels.     

Grain growth by radiation pressure induced coagulation

A theoretical treatment is given of the growth of grains as a consequence of their mutual coagulation brought about by relative motions induced by radiation pressure. Analytical and numerical techniques are employed to tackle the relevant coagulation equation. The results are of particular astrophysical significance in the context of forming very small grains following a nucleation process, in the production of grains large enough to allow condensation of volatiles onto their surface, and in any situation where the supply of volatiles has been exhausted. It was found that in interstellar clouds, grains composed of iron, graphite and glassy carbon, being typical examples of three basic types of material, could grow to a size where condensation of the volatiles was possible. On the other hand, olivine, a typical silicate, could not. If a source of radiation existed at the centre of the cloud, then growth could occur if the cloud was turbulent or if the density was high enough; otherwise the grains were driven out of the regions of interest at high velocity. In the latter case, with a high cloud density, re-radiation has to be taken into account.     

Comparison of transmitting boundaries in dynamic finite element analyses using explicit time integration

Explicit time integration schemes provide an efficient solution to non-linear dynamic finite element analyses of geotechnical problems especially when high frequency response is important. Such explicit time integration schemes require one of two distinct transmitting boundary formulations to overcome the problem of radiation damping. These are the superposition boundary approach, which involves the cancellation of the reflected waves by combining the solutions of two different boundary conditions and the viscous boundary approach, which involves the absorption of incident wave energy by frequency independent viscous dashpots. The theoretical justification of these two approaches and their means of implementation are reviewed. The solutions obtained using the two different boundary approaches to the problem of a rigid massless circular footing vibrating on an elastic half-space are compared with an independent theoretical solution. The performance of the boundaries for problems involving step loading is also examined and the implications for any loading pattern with a non-zero time average are discussed.     

Stall markets in metropolitan Sydney

Stall markets on open air, suburban sites are an important new form of retailing in Sydney. The existing literature on petty commodity forms of production argues that stall markets are conserved in underdeveloped economies for a variety of reasons but the relevance of these ideas to the markets in many cities in advanced economies has not been considered. This paper identifies the basic types of stall markets in Sydney, establishes that these markets are not ephemeral and shows that they have characteristics and parameters which are similar to those of conventional shopping centres. Thus the way is open to compare stall markets with conventional retailing, to assess the role of stall markets in post‐industrial societies and to investigate the reasons for their recent appearance in Sydney.