Use of clay soils in the construction of cutoff curtains

Abstract

1. In the northwestern region of the country there are numerous clay deposits (more than 150) which belong with respect to chemical composition to hydromica-kaolinite and kaolinite having a low ion-exchange complex and, as a consequence, in a pure form are unsuitable for preparing clay slurries. 2. An improvement of the technological properties of clay slurries from hydromica-kaolinite and kaolinite clays is possible in two main directions: replacement of a certain part of the kaolinite clays (10–20%) by high-grade bentonite clays; increase of the activity of the ion-exchange complex of clays by adding chemical reagents of the group of protective colloids — CMC, TSP, and others. 3. Clay slurries obtained from the low-grade clays of northwestern region have normal technological properties with density ρ=1.15−1.25 g/cm3. At smaller values for density all slurries are characterized by considerable segregation. 4. In all cases when solving the problem of using local clays for preparing thixotropic slurries it is necessary to substantiate the possibility of their use not only on the basis of technical and economic indices but also to take into account the hydrogeological conditions of the objects and technological characteristics of creating a curtain and its design. 5. The use of local clays can considerably broaden the area of use of the slurry trench method for constructing cutoff curtains in the northern and northwestern regions of the country. 6. Experience shows that the maximum use of local materials in hydrotechnical construction of cutoff curtains by the slurry trench method practically always produces a positive effect (1.3–3 rubles/m2).