Conway HowardRelease Date: 01 October 2007
Format: Paperback
Pages: 76
Category:
EngineeringISBN: 9781406784657
ISBN-10: 1406784656
PREFACE. THIS work claims to present a new and systematized method of finding the prismoidal contents of Earthwork by means of Tables accompanied by Eules so plain and simple of application as to fit it for the.common uses of Engineers. When the ratios of the side slopes are constant between end sec- tions of which the transverse surface lines are sensibly similar, all ordinary cases of thorough cut and fill, terminal pyramids, side-hill work, and borrow pits are covered by Formulae 17, 18, and 19, and the prismoidal contents for all side slopes and bases are taken from Tables 4 and 5 by Eules 1, 2, and 3. In the method used, the heights of equivalent level sections are not involved, nor is any calculation needed for 100-feet lengths beyond ascertaining the half-sum and the difference of two quantities. For the most part Tables do the work of the calculator, and any one who can approximate cubic contents by the rough method of Average Areas is competent to obtain the prismoidal contents by the Eules given. The tables of level cuttings are not needed when areas are given, and are included chiefly for use in preliminary estimates when the only data are the centre heights and the angles of the transverse surface slopes. With these, the heights of equivalent level sec- tions are readily found by Mr. Trautwines well-known and very ingenious diagrams, thanwhich for the purpose intended probably no bettermeans canbe devised. When these heights havebeen ascertained, the use of the special Correction Tables in connection with those of level cuttings will reduce to a minimum the labor of computing the prismoidal contents. If further tables of level cuttings are considered necessary, the reader isreferred to Mr. Trautwines Excavation and Embankment, or to the example given at the end of this work, by careful attention to which any required table may be written out with entire accuracy in a few hours. Special corrections for any side slopes may be obtained by Eule 12. Not an inconsiderable advantage of the present method is that, by giving accurate corrections for the familiar approximations in general use, the calculator has the element of error constantly before him, and must speedily learn by practice, if not by theory, the cases in which such corrections become important. But while enough is given, both by rule and example, in Part II. to guide the least theoretical in the use of the tables, in Parti, a strictly mathematical investigation of principles and derivation of formulae is submitted to the careful reader. The article on Correction of Contents for Curvature was sueo gested by that on the same subject in Hencks Field-Book, but, by the formulae and table of factors given, in ordinary cases the corrections are much more readily obtained in practice...
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