Synopsis An investigation has been made into some factors not closely specified for laboratory compaction tests. In particular, work has been directed towards determining to what extent the results of the British Standard Compaction Test for Soils are affected by the sub-base on which the mould is placed. Optimum dry densities were found to be ½–1½ 1b per cubic foot lower when the test was performed on a stout wooden table instead of a concrete floor. The difference in optimum moisture content was O-l per cent for the seven soils tested. These differences were shown to depend on the effective mass of the mould, base-plate, and sub-base, rather than on the spring constant of the sub-base. This conclusion is confirmed by a theoretical treatment. It is recommended that specifications for the compaction test should include a minimum requirement for the effective mass of the sub-base on which the test is performed. The tests also demonstrate the effect of an uneven floor or of a warped base-plate to the compaction mould, either of which allows the mould to rock. Further tests show the errors which may arise if the water is inadequately mixed with the soil; errors which, for the soils tested, were of the order of 1–½ 1b per cubic foot in optimum dry density and ½–1½ per cent in optimum moisture content. It is demonstrated that, for soils with a plasticity index greater than about 20 per cent, it is necessary to allow a maturing period before performing the test. Des recherches ont été effectuées en ce qui concerne certains des facteurs qui ne sont pas strictement spécifiés pour les essais de compactage en laboratoire. En particulier, les travaux ont eu pour but de determiner jusqu'à quel point les résultats de l'Essai de Compactage Standard Britannique des Sols subissent l'influence et dependent du soubassement sur lequel est placé le moule. On a constatć que les densitiés sèches optima étaient de 0·008 à 0·024 grammes/centimetre cube plus faibles lorsque l'essai avait lieu sur une table robuste de bois plutôt que sur un plancher en beton. La différence dans la teneur en eau optimum était de 0 à 1 pour cent pour les sept sols essayés. Ces différences, a-t-i1 été vérifie, dépendaient de la masse effective du moule. du socle et du soubassement plutôt que de la conante d'élasticité du soubassement. Cette conclusion est contirmée par un traitement théorique. Il est recommandé que les spécifications pour les essais de compactage comprennent une exigence minima concernant la masse effective du soubassement sur lequel les essais doivent être faits. Ces essais ont également montre l'effet d'un plancher inégal ou d'un socle gauchi sur le moule de compactage, en ce que l'un ou l'autre permet une oscillation du moule. D'autres essais font ressortir les erreurs que peut provoquer un mauvais mélange d'eau et de terre, erreurs qui, pour les sols essayés, étaient de l'ordre de 0·008 à 0·024 grammes/centimetre cube en ce qui conceme la densité sèche optimum à set et de 1 à 1#x00BD; pour cent en ce qui concerne la teneur optima en eau. I1 a été démontré que, pour des sols dont l'indice de plasticité est supérieur à 20 pour cent, il est nécessaire de permettre une période de maturation avant d'effectuer les essais.
From humble cottages to super tall structures, human beings have progressively developed the living and working space with time. This paper describes the origin and growth of modern skyscrapers, the subsequent challenges faced, and the way it was outdone. Research papers and case studies have been thoroughly studied and important excerpts from them have been explained to show how the modern structures have been evolved. The sources and causes of evolution is debatable among researchers, this paper has taken into account 7 most vital milestones in the growth of current generation skyscrapers and their contribution to the construction industry and concludes with the ideas and scopes where growth is still possible and challenges need to be solved.
Stress controlled cyclic triaxial tests have been done on coastal sand of Digha, West Bengal, India, at different frequencies, confining pressures, and relative densities and cyclic stress ratios. Number of cycles for initial liquefaction (N L ) has been determined for that number of cycle when excess pore pressure ratio has become equal to 1. Significant influences of density of sand, confining pressure and number of cycles for initial liquefaction on coastal Digha sand have been found. The test results have shown that increasing density of sand increases liquefaction potential, whereas cyclic strength of sand decreases with increase of confining pressure. An empirical correlation has been developed on cyclic strength of sand based on these parameters and this correlation fits quite well with the observed experimental results. Bender Element tests have been performed to determine maximum shear modulus (G max ) of Digha sand at different densities and confining pressures. A high correlation coefficient between cyclic strength and G max of Digha sand at any N L has been found. A new pore water pressure generation model has been introduced for this sand along with upper bound and lower bound curves to predict excess pore water pressure build up due to seismic loads.
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