Behavior of soil under a brief dynamic load

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1. The damping coefficients both of cohesive and noncohesive soils practically do not depend on the state of the soils relative to the limit state almost up to loss of strength by the soil specimen. An increase of the initial lateral pressure and dry density of the noncohesive soil as well as a decrease of the moisture content of cohesive soil noticeably reduce the value of the damping coefficients (from 0.6 to 0.05 for noncohesive and from 0.3 to 0.15 for cohesive). The interval of variations of the damping coefficients obtained under conditions of small values of the initial lateral pressure (within 0.1 MPa) and combined stress state leads to the need for an experimental determination of the damping coefficients, at least for similar conditions. 2. The shear moduli for small values of the initial lateral pressure and under conditions of a combined stress state for cohesive soil depend on the level of the initial lateral pressure and for the noncohesive on the change in the moisture content. In the interval of stresses created in the specimen, when the initial lateral pressure does not exceed 0.098 MPa and the average static stress does not exceed 0.3 MPa, the shear moduli are practically proportional to the average stress. 3. Both volumetric strains and distortional strains under a brief dynamic shear load and under conditions of a combined stress state are far less than the strains from an equal static load. In this case, whereas the volumetric strains in shear for noncohesive soil have the character of compacting, for cohesive soils they are always loosening. 4. The description of the process of soil deformation as a result of a brief dynamic load obtained shows the possibility of determining the nonlinear reaction of soil to this load by means of the linear acceleration method, if the system under consideration can be represented as a system with one degree of freedom.