Use of chalk as material for hydraulic earth structures

Conclusions

• 1. Chalks or rocks similar to them in lithology can be used as natural construction materials for constructing directly placed fill and hydraulic-fill structures. The characteristics of the lithologic composition of chalks and the technical requirements imposed on elements of the structures can affect the technology of placing or hydraulic filling of the rocks, but they should be examined in each case with respect to the specific conditions.

• 2. Depending on the requirements imposed on the element of the structure and technology of placing the rock used, the created fill can have a different density (strength) and permeability. It is possible to obtain fills with a density to 1.60 g/cm³ with shear strength tan ϕ=0.30 at C=0 or C=0.10·10⁵ Pa and K_p equal to hundredths or thousandths m/day.

• 3. In the case of rolled fills it is exceptionally important to regulate the water content of the fill correctly with bringing of the degree of saturation to 0.9. Another important factor is the preliminary (before rolling) destruction of the structure of chalk, which is best achieved by wetting the fill, also to the indicated limits. The optimal height of the fill layer is apparently 30 cm, but depending on the specific conditions and requirements imposed on the structure it can be increased to 40–50 cm.

• 4. Placement of chalk in water complicates subsequent compaction and leads to the formation of fills with a low density and high permeability. Hydraulic filling of a chalk — water mixture is possible, but the conditions of using this method require additional study.

• 5. Various vehicles can be used as compacting mechanisms; the specific choice of machines should be made in relation to the technical requirements imposed on the finished fill.