1,720,983 research outputs found
Pleistocene Geology of the Country around Bromsgrove
No full textThe Pleistocene Deposits of a triangular area in Worcestershire, enclosed by the villages of Romsley, Barnt Green and Upton Warren, are divided into Older and Newer Drifts. The Older Drifts are of higher level and consist of gravels below and a boulder clay above. The Newer Drifts are valley terraces deposited in the valleys, cut below the Older Drift level. Five such terraces are recognised and they are correlated with the terrace stages established by Professor Wills for the Severn Valley. Finally, the nature of the sub-Older Drift surface is described. This shows a deep, buried channel which is interpreted as an ice marginal overflow channel
Model experiments of soil erosion by V.T.O.L. aircraft downwash impingement
No full textAbstractThe paper describes research currently being carried out on the processes involved in the initiation of erosion of soil by the downwash from V.T.O.L. aircraft engines. Apparatus for simulating jet downwash is described together with the results of preliminary tests on erosion behaviour of moist sands. Pore air pressures generated in the sand by the downwash have been measured and shown to be in excess of the surface static pressures beyond a certain radius from the stagnation point.RésuméL'article décrit les recherches effectuées actuellement sur le phénomène de début d'érosion provoqué par les turbulences sous les avions à décollage vertical. L'appareil de simulation est décrit ainsi que le résultat des essais préliminaires sur le processus d'érosion des sables humides. La pression dans les pores du sable provoquée par la turbulence a été mesurée et est apparue supérieure à la pression statique de surface, au-delà d'une certaine distance du point de stationnement.ZusammenfassungDer Aufsatz beschreibt Forschungsarbeiten, die kürzlich über die Vorgänge durchgeführt wurden, welche mit de Einleitung der Erosion von Boden durch Abwärtsstrahl von senkrecht startenden Luftfahrtzeugen mit Strahltriebwerken zusammenhängen. Ein Apparat zur Simulierung des Abtriebsstrahls von Strahltriebwerken wird zusammen mit den Ergebnissen von früheren Versuchen über das Erosionsverhalten von feuchten Sanden beschrieben. Der Druck in den Lurtporen, der im Sand bei dem Abwärtsstrahl erzeugt wird, wurde gemessen und es wurde gezeigt, daßerheblich höher ist, als der statische Druck an der Bodenberfläche außerhalb eines bestimmten Radius von dem mittleren Staupunkt
Seepage characteristics and landsliding of the A3 zone of the Barton Beds
No full textThe most characteristic feature of the Barton Clay cliffs of Christchurch Bay is the presence of a number of preferred bedding plane surfaces of shearing. Most of these are contained within clay horizons and the reason for their preferential use by the coastal landslides is unknown. One surface, however, is at the base of the 2.7 m thick A3 Zone which consists of inter-bedded sand and clays. This surface is well exposed and forms a distinct feature in the cliffs throughout nearly the whole of the 1.5 mile coastal outcrop of the A3 Zone.The paper discusses the reason why a shear surface is preferentially developed at this stratigraphic location. Three possible causes are discussed under the headings of (i) pore pressure fluctuation, (ii) seepage erosion and piping and (iii) equilibration response time. The first two are well established theories but the third is a new hypothesis derived from the original Bishop and Bjerrum theory of delayed equilibration. It is considered that the discussion is useful in the general context of landsliding at sand/clay junctions in overconsolidated soils
Reply to discussion on ‘Reactivation of landsliding following partial cliff stabilization at Barton-on-Sea, Hampshire’ by M. E. Barton & P. Garvey Quarterly Journal of Engineering Geology and Hydrogeology, 44, 233–248
No full textLateral shaking during sedimentation - a new technique for obtaining the minimum porosity of granular soils
No full textThe relative density of geologically aged British Fine and fine-medium sands
No full textValues of relative density (Dr) have been measured on 20 samples of uncemented, virtually matrix-free, fine and fine-medium quartzose sands ranging in age from Recent to Jurassic. For all except Recent and younger Pleistocene sands, which were impregnated in situ, the in situ dry density (ρd) was measured on intact, block samples. A single method was used for ρd min (Kolbuszewski's tilting method) and three methods for ρd max: namely the vibrating hammer procedures of Kolbuszewski, B. S. 1377 Test 14 and slow pouring. A general trend of increasing Dr with geological age was given by all the methods used for determining ρd max. Even with the Kolbuszewski method, values of Dr > 100% were obtained on some of the sands: a maximum of 112 % being recorded on the Grantham Sand of Jurassic age. Values of Dr using the B.S. 1377 procedure ranged between 23 and 57 % for the Recent and Pleistocene sands and between 90 and 122 % for the Tertiary and Mesozoic sands. The ease of the slow pouring method for ρd max recommends it as a potentially useful diagnostic test to determine the degree of locking in geologically aged sands
The Folkestone Bed sands: microfabric and strength.
No full textThe Folkestone Beds formation is a marine shallow-water deposit of Cretaceous age. It consists mostly of poorly lithified sands which classify onto the sand/sandstone borderline, having properties neither akin to the classical concept of an engineering soil nor being strong enough to be labelled a rock. Intact samples were obtained by block sampling at 17 locations. Studies of the microfabric were made from thin sections prepared after epoxy resin impregnation. Although predominantly quartzose, the samples have a very wide range of grain sizes, size distributions, porosity and grain contact relations. The random inter-relationships amongst the microfabric parameters suggest that shelf sands, such as this formation, do not fit the patterns reported for deeply buried, and hence more diagenetically altered, sandstones. The majority are weakly cemented but samples from two locations possess negligible binding cement and are classed as locked sands. Measurements of the peak shear strength were carried out on air-dry samples of the intact sand using a 60 mm square, direct shear box. The peak shear strengths were strongly influenced by the intensity of interlocking: this factor being more significant than either porosity or total cement content. The samples possess a tensile strength, uniaxial compressive strengths up to 725 kPa and a cohesion intercept at zero normal stress in the shear box. The fabric cohesion reduces with increasing content of coarse sand and is very poorly developed in coarse sands. <br/
Porosity reduction, microfabric and resultant lithification in UK uncemented sands
No full textStudies of the extent of diagenetic change in matrix-free, uncemented, quartzose sands ranging in age from the Jurassic to the Recent in the UK have been carried out as part of a geotechnical research programme. All the sands studied are thought to have experienced only a relatively small depth of burial and the extent of diagenetic change is consequently small. Previous studies of the in situ fabric of sands in this category have been limited owing to the sampling difficulties created by their very friable nature. Careful sampling, however, has succeeded in obtaining undisturbed material and has facilitated studies of the porosity, microfabric and degree of lithification. Distinctive changes, progressive with age, include reduction of porosity, an increase in the numbers and complexity of grain contacts and an increasing degree of lithification. The cause of these diagenetic changes are discussed and it is concluded that the evidence strongly favours pressure solution of the detrital quartz grains as the dominant process
A geological appraisal of the site of the foundation failure of the giant oil tanks at Fawley, Hampshire
No full textTwo giant oil tanks (79.3 m diameter by 19.5 m high) were constructed at Fawley in 1967-68. The tanks were founded on a reinforced concrete slab supported by piles of varying lengths taken through alluvium and end-bearing in Valley Gravel which overlies Barton Clay (Eocene). Totals of 1580 and 1652 piles, respectively, were used for each tank. The foundations failed during water-loading tests with a maximum depression of 0.425 m in one of the reinforced concrete slabs. Post-mortem examination of the foundations revealed defects in a number of piles, and after further tests and investigations, Professor G. A. Leonards concluded that the failure was due to defective piles.The success of the original design was critically dependent on the geology. Particular problems on which attention was focussed included the continuity and thickness of the gravels, their variation in density, the character of the interface between Valley Gravel and Barton Clay and the lithological variations within the alluvium. These problems are examined here in relation to the existing geological knowledge of the region. Of particular significance is the conclusion that, in part, the variation in density within the gravels is due to the existence of Flandrian gravel overlying Pleistocene terrace gravel. Isopachytes of the gravels have been drawn along with contours on the upper and lower surfaces. These are compared with the settlement contours of the failed foundation slab and it is concluded that there is no correlation between them
- …
