Discussion of construction specifications concerning the “instructions on the design of ship locks.” II

Abstract

Having examined the calculation of the stability of two structures differing in weight and acted upon by identical shearing forces, Yu. V. Shreder noted that the stabiluty safety factor increases with a decrease of weight of the structure on cohesive soil.Comparing the shear diagrams for cohesive and cohesionless soils, we are convinced that the angle of shear and hence the coefficient of shear increases with a decrease of vertical pressure on cohesive soil. Therefore, Yu. V. S~eder's noted increase of stability of a structure is regular.Asserting that cohesion is absent in the plane of contact between concrete structure and cohesive soil, Yu. V. Shreder poposes a simplified formula for calculating stability by a plane shear scheme, in which the friction coefficient f is determined by the shear of a concrete footing along this soil.Not the friction coefficient but the shear coefficients will be obtained upon shear of footings along the concretesoit plane, since tests are usually carried out under different normal stresses in the contact plane. As investigations on a number of objects have shown, despite the disturbed structure of the soil, cohesion is present in the contact for a bottomed footing. For instance, field investigations of Neocomian clays in the pit of the Saratov hydroelectric plant by the method of shear of bottomed concrete footings showed that the cohesion is equal to 0.45 kg/cm z. Therefore, the specifications require the consideration of cohesion of the supporting soil.