The basis of the budgetary allowances for the hydraulic method of excavating soils is their classification according to the difficulty of excavation by dredges. This classification, of course, should be determined by the physical and mechanical properties of the soils and the technical and operating characteristics of the equipment used. The presently existing classiRoation of soils according to difficulty of excavation by floating dredges (SNIP, Part i, Volume 2, Issue I, Chapter I0, Table 10-7), introduced in 1954, does not meet these requirements. It is imperfect and represents only the "first tentative outlines" of that time when hydraulicking was in the stage of development as a branch of construction work and still did not provide sufficient scientific, technical, and industrial experience. The standards compiled on the basis of this classification (Table I) long ago ceased to reflect the present-day level of development of hydraulioking in the country. In particular, with respect to the output of the equipment (floating dredges) these standards for more than 20 years, according to the report data, have been easily overfulfilled by a minimum of 30-50~o and often by twofold and more on sandy soils. Average data on the actual output of dredges at a number of construction projects with excavation of different soil types and the amounts of their excess over the standard output are given in Table 2.This excess over the standard output was attained at quite low use factors of the dredges with respect to time, equal to 0.45-0.50. Such high outputs are attained mainly due to the considerably smaller use of water for excavating and transporting the soil than stipulated by the existing soil classification. The imperfection of this soil classification consists first of all in that it is founded practically on one characteristic -the granulometric composition (grain-size distribution). It did not adequately reflect the effect of the output of the dredges (with respect to the soil-water mixture) depending on the content of the gravel-pebble fraction in the soil. Such characteristic physical and mechanical indices of soils as density, consistency, degree of cementation, etc.. are completely omitted in the classification. But what really matters is that the implements of the dredges which differ in power and principle of action (cutter, rotary, multibucket, and other soil-intake devices), which predetermined the rate of soil intake, are not taken into consideration. At the same time, the effect of the content of the gravel-pebble fractions in determining the standard consumption of water for excavating and transporting I m 3 of soil is extremely overstated in the classification. For example, for the first, second, and third soil groups with a dredge output with respect to the soil-water mixture (slurry) of more than 2000 m3/h the respective regulated content of fractions 2-120 mm is from I and 5 to 10%, and its standardized water consumptions per I m 3 of soil in these cases are 7, 9, and II m 3. It is obvious that with r...
