China
Africa
Explore chapters and articles related to this topic
Sills
Published in G.J.C.M. Hoffmans, H.J. Verheij, Scour Manual, 2021
G.J.C.M. Hoffmans, H.J. Verheij
In an estuary or a river, a sill may be the initial foundation or the lower part of a structure that has to be constructed on a bed of alluvial materials. A sill is a horizontal, structural part of a structure near the bed level on a foundation or pilings or lying on the ground in earth-fast construction. Sometimes a sill is used to reduce the mixing of different types of water in an estuary. In an estuary, a sill has to be designed for flow in two directions: flood flow and ebb flow. In rivers, for example, a sill may be used as part of a scheme to maintain a minimum water level. Figure 6.1 shows example sketches with characteristics of sills in a river.
Minerals and rocks
Published in A.C. McLean, C. D. Gribble, Geology for Civil Engineers, 2017
The common hypabyssal intrusions (Fig. 2.25) are sheet-like in form, with widths usually between 1 and 70 m. They are labelled according to whether or not they conform to the structure of the strata in which they are emplaced. A concordant hypabyssal intrusion injected along the layering in the country rocks is called a sill. A discordant hypabyssal intrusion cutting steeply across the layering is called a dyke (Fig. 2.25). Most sills are subhorizontal and most dykes are near-vertical, so the terms are often used loosely with this relative orientation in mind. An intrusion (Fig. 2.25) consisting of several segments, mostly concordant but at different levels in the column of strata and linked by discordant segments, is called a transgressive sill.
Windows
Published in Michael McEvoy, External Components, 2014
The sill must be weathered at a sufficient slope to throw off the water and throated with a groove near the front of its underside so that the water will drip off and not run back to the bed of the sill. In the past, timber sills have been built into the brickwork and pointed in mastic at the vulnerable junction between the end grain of the timber and the brickwork jambs of the opening; only the most durable hardwood will not rot under these circumstances. It is preferable for a metal sill to be used, as is common practice on the continent (see fig 4.5). Alternatively, sub-sills may be made from stone, canted brick or concrete, perhaps incorporating a water bar to locate the timber sill horizontally and act as an additional check against the penetration of moisture (see fig 4.18). A sub-sill will anyway be required if the window is set far back into the opening, resulting in a timber section that would be too large. The sub-sill must be provided with a throating or drip in order to shed water as far away as practicable from the wall face below. Traditionally, in the best work, projecting sills of stone or hardwood had stooled ends to direct water away from the junction with the wall (where staining below the sill is otherwise commonplace); drainage grooves can be cut into sill, just short of the ends, to achieve the same result (see fig. 4.23(b)). Whatever the material used for their construction, sills are very susceptible to defects caused by dampness. Either the weathering is not sufficiently steep to shed the water, or water can get back to the bed joint of the sill because the drip does not function, or because the slope of the concrete, stone or brick subsill allows the water to run back instead of outwards. Paint must not be relied upon to protect timber at this critical point.
Taupōinflate: illustrating detection limits of magmatic inflation below Lake Taupō
Published in New Zealand Journal of Geology and Geophysics, 2022
Susan Ellis, Simon J. Barker, Colin J. N. Wilson, I. Hamling, Sigrun Hreinsdottir, Finnigan Illsley-Kemp, Eleanor R. H. Mestel, James D. Muirhead, Bubs Smith, Graham Leonard, Martha K. Savage, Pilar Villamor, Peter Otway
Our spreadsheet calculator uses existing solutions for inflation of finite-volume spheres, sills, prolate ellipsoids and dikes (McTigue 1987; Yang et al. 1988; Okada 1992; Fialko et al. 2001). The solutions assume inflation of a low-strength magma chamber into an elastic half-space, where surface displacements are computed as a function of the distance from the source (location and depth), change in volume of the magma body (magma overpressure for inflation of a sphere, ellipsoid or sill; or opening of a vertical dike), and elastic parameters of the half-space (shear modulus and Poisson’s ratio). It is important to note the limitations of this simple approach, particularly the neglect of inelastic crustal deformation (e.g. due to thermally activated ductile creep and/or frictional plasticity: Gerbault et al. 2012; Currenti and Williams 2014; Head et al. 2021) and also the simplified behaviour of the inflating magma. We discuss some of these limitations later.
Warrumbungle Volcano: facies architecture and evolution of a complex shield volcano
Published in Australian Journal of Earth Sciences, 2021
K. F. Bull, A. L. Troedson, S. Bodorkos, P. L. Blevin, M. C. Bruce, K. Waltenberg
Coherent facies, those volcanic rocks that crystallised from a magma, include lava flows, subvolcanic sills, dykes, lava domes, and cryptodomes, and make up the most common, well-distributed and voluminous facies of Warrumbungle Volcano. It is commonly difficult to distinguish coherent facies in terms of emplacement mechanism (i.e. lava flow deposit vs subvolcanic sill, or effusive lava dome vs cryptodome) from field relationships or available data, and this map area is no exception. In many cases, we were able to divide coherent facies into one of two emplacement groups labelled ‘intrusions and lava domes’ or ‘lavas’. We define ‘intrusions and lava domes’ as coherent units that have a round morphology (i.e. the length is roughly equal to the width) and commonly exhibit horizontal or radial columnar joints. Intrusions and lava domes on the volcano tend to be tens to hundreds of metres in diameter. In contrast, ‘lavas’ include lava flow deposits and subvolcanic sills, and have a greater length than width, and commonly exhibit vertical columnar joints. Lavas on Warrumbungle Volcano range from metres to tens of metres thick.
The Dunedin Volcanic Group and a revised model for Zealandia's alkaline intraplate volcanism
Published in New Zealand Journal of Geology and Geophysics, 2020
James M. Scott, Alessio Pontesilli, Marco Brenna, James D. L. White, Emanuele Giacalone, J. Michael Palin, Petrus J. le Roux
The Maniototo area in the NW of the province comprises the Haughton Hill, Kokonga, Swinburn and Waipiata basalts, with the publicly accessible results of the 2007 Glass Earth-Dunedin City Council aeromagnetic programme showing several shallow magnetic highs that may represent buried volcanic rocks (Figure 2). Swinburn South (south side of the State Highway 85) comprises a pile of basaltic rocks that overlie scoria-fall deposits, which in turn overlie Eocene-Oligocene marine sediments (Giacalone 2018). It is unclear whether the remarkably coarse doleritic textures of most of the Swinburn South rocks formed in a sill or one or more lava flows (Giacalone 2018). At its southern end, the lavas exceed 100 m thickness and are cut by small diatremes. The basalt in this area contains rare xenoliths of peridotite, schist and now porcellanitised Cenozoic sediment. Swinburn North (mainly north of State Highway 85) comprises thin aphanitic basanitic lavas that overlie Miocene sediments (Youngson et al. 1998; Giacalone 2018). These lavas, which have subsequently been tilted and now mostly dip to the north and northeast, and a thick elongate belt of bedded pyroclastic rocks, are truncated by the Waihemo fault system (Bishop 1974). Basalt at Haughton Hill, which like Swinburn South has portions with doleritic textures, also overlies Miocene sediments. The Waipiata-Kokonga basanitic lava (or lavas?) remain little-studied (Donnelly 1996) despite the Waipiata flow apparently being one of the largest single flows outside of the Dunedin Volcano.