At present earth dams are, on an ever increasing scale, built of weak and weathered rock. Its utilization as a rule gives a big economic effect. When excavating and compacting such a rock, inequagranular material is formed which, depending on its grain size distribution, can be placed in impervious dam elements or dam shells.

A complex of field and laboratory studies made of leached dolomite is one of examples of investigation of such a rock.

Trial excavation and filling of the leached dolomite with thorough study of physical and mechanical and seepage-piping properties of compacted material were conducted to evaluate the possibility of using the leached dolomite in dam embankments.

In the undisturbed conditions, the dolomite is predominantly a weak leached semi-rock characterized by the dry bulk density of 1600+2000kg/m3 and moisture content of 0.01+0.09 at the unit mass of 2850kg/m3

Loosening by the tractor-mounted ripper with simultaneous moistening turns the rock into a material consisting of uniformly distributed Particles 1+60mm in size and dolomitic meal. The content of soluble salts and gypsum in the material does not exceed 2%, that of calcite does not exceed 3%.

The grain size distribution of he dolomite material determined t by washing at the sieves with mesh size 80+0.1mm and by the acrometric analysis of the particles less than 0.1mm in dia is given in Fig. 1. All varieties of material sampled from four most different sites of the dolomite borrow area are characterized by a high content of dolomitic meal represented by the sizes less than 2mm in dia. Larger parti-. Iles are separated by the dolomitic meal.

(Figure in full paper)

The dolomitic meal which is the final product of rock disintegration has a very low plasticity (plasticity index 0+0.04). It does not practically swell and does not shrink.

Therefore should the compactedness be inadequate (dry bulk density 8sm< 1700kg/m3) in the course of saturation, the material tends to acquire the liquid consistency stepwise, like the sandy loam. In such a state, the meal acts as a lubricant between the intact larger sizeparticles. Under unfavourable consolidation conditions it can cause the saturated material to pass into a state of quick ground.

At the hard consistency and Vie dry bulk density over 1700kg/m3, the water saturated dolomitic meal has better mechanical properties. Therefore, it was decided to place the dolomite material into the embankment at the moisture content W = 0.15+0.18 corresponding to the hard consistency of meal and get it compacted until the dry bulk density 8sm71700kg/m3 is obtained. The density of dolomite material placement ensuring these phase characteristics of meal for the real grain size distribution and dry bulk density of rock fragments 1800+2000kg/cm2 amounted to 8s= 1750+1850kg/m3 with the average value being 1800kg/m3.

Laboratory compaction tests of the soil at various moisture contents made under the procedure applied to the cohesive soils (the Proctor method) and under the procedure for the cohesionless soil (relative density test) yielded practically the same results.

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