The compression moduli of clayey soils are usually assigned with very high correction factors. It is demonstrated that the basic reason for the need to correct these moduli is the requirement to account for the effect exerted by so-called leakage pressures on the skeleton of the soil specimens being tested These leakage pressures develop due to the fact that consolidation filtration in soils is possible only when certain initial pressure gradients are attainedIn calculating the settlements of pile foundations, it is necessary to know the compression moduli of the soils lying at great depth, the determination of which is difficult from results of plate tests of the soils. They are usually estimated, therefore, from data of compression tests of soil specimens extracted from holes.It is normally recommended to assign the dependence between the overall compression modulus E of the soil and its relative compressibility factor my [1] from the well-known equationswhere m is a correction factor, m v is the relative compressibility factor, m o is the compressibility factor, e' is the initial void ratio in the assigned load range, and v is Poisson's ratio.The compression tests indicate that if we set m = 1, as is called for in GOST 12248-96 [2], the E values for clayey soils are several times (by a factor of 2-6) lower when equation (1) is used than the E values obtained from plate tests of the soils and by their determination from the tables in Construction Rule and Regulation 2.02.01-83.To illustrate this position, let us examine, for example, data derived from compression tests of morainic sandy loams and clayey loams of Dneprovsk glaciation and alluvial clayey loams. Plots of the test results for these soils are presented in Fig. 1, and their physicomechanical characteristics obtained from laboratory investigations in Table 1. Table 1 presents test results for saturated clayey soils over a rather broad range of variation in their void ratio (e = 0.35-0.60) and flow index (JL = 0.12-0.70). It is apparent from the table that the overall compression moduli Eo, which are comparable to data presented in Construction Rule and Regulation 2.02.01-83, differ by a factor of 2.5-6 from the compression moduli E determined from equation (1) for m = 1.

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624.154.5:624.159.4 The first developed and scientifically substantiated geotechnical electric-discharge technology is proposed for pile installation. This technology makes is possible to obtain structures with high service properties for extremely low specific outlays.Electric-discharge (ED) geotechnical technologies, which are also known as pulse-discharge (PDT) and electric-spark technologies, are of major interest for pile-foundation engineering.Professor Lomize [1] was the first to use the electric-discharge technology in geotechnics to compact saturated sands, and then sandy loams and loess-like clayey loams. The method was based on the electrohydrodynamic effect [2], which has been in widespread use since the 1950s in machine building and mining.A high voltage discharge in a liquid is accompanied by the formation of zones with a pressure to several tens of thousands of atmospheres in the surrounding soil [1, 2]. These discharges, which can be produced at an interval of several seconds, assume the character of microblast effects. In that case, a shock wave fails the structure of granular sands and results in their diluted state. The soil is then compacted under its own weight, acquiring a denser structure. High-voltage discharges have been generated in a saturated soil by a pulse generator that made it possible to obtain a metered amount of electric energy in the form of a short-lived current pulse.A mobile complex on trailers has been used to compact alluvial sandy dikes. The effect of various components of the production process (voltage, interval between pulses, number of discharges, energy liberated, etc.), as well as the effect of certain soil properties on the quality of the compaction has been investigated in detail on a laboratory device that makes it possible to model various regimes of the dynamic effect, vary the static tension of the soil due to its own weight and a surcharge, etc.In 1978-1981, Ulitskii, Yassievich and others developed the basis of the technology for the fabrication of cast-inplace piles using the electrohydraulic effect in Leningrad. Production equipment was built (authors G. N. Gavrilov and V. A. Polova) for pile installation (discharge station, energy emitters, etc.), which is distinguished from previous equipment by its mobility, small clearance dimensions, and safety, as well as electric parameters. More than 20 projects in Leningrad (Saint Petersburg) and the Oblast have been built around piles fabricated on the basis of the "PDT" [3]. Unfortunately, there is also negative experience with the use of PDT piles [3]; this has virtually closed the road to use of this technology.In 1994, the Scientific-Research Institute of Foundations and Underground Structures (SRIFUS) and the Moscow firm ZAO RtTA began a joint venture on use of ED technology in geotechnical construction.A basic feature of the geotechnology that we proposed is the realization of high-voltage discharges in holes filled with a special grout for the compaction of soil into their walls and face, and also the ...