Calculation of the foundation with allowance for the shear modulus at small deformations

Abstract

Continuous improvement of mathematical models of soil and software complexes implementing numerical simulation methods allows taking into account the effects characteristic of the ground environment, such as nonlinearity of deformations, creep, hardening and softening. These models require a large number of parameters to be determined during laboratory tests. The methods for determining these parameters are for the most part not represented in modern normative literature. A typical example of such parameters is the shear modulus for small deformations.The study of small deformations is of great importance in the calculation of underground structures. When designing such structures it is necessary to take into account the nonlinearity of unloading of the ground base. The currently widely used model of hardening soil [HS] does not take into account the nonlinearity of the unloading, while the improved model of hardening soil in view of small deformations [HSsmall] allows to take into account the hysteretic behavior of soils.The account of the hysteretic behavior of the soil during the cycles of unloading and repeated loading is carried out under the condition that the shear modulus at unloading is equal to the initial tangent module for the initial loading curve. In this case, the unloading and reloading curve has the same shape as the initial loading curve, but in the doubled size.Since elastoplastic soil models are not able to describe the hysteretic behavior of soils, the solution of the range of problems associated with the accumulation of deformations under vibrational and cyclic influences with the use of these models is impossible. In such cases, the forecasting of the stressed-deformed state of soil bases under the action of dynamic loads of a different nature can be performed only on the basis of the use of an elastoplastic model of a toughening ground with allowance for ultra-small deformations.In the present work, the results of laboratory determination of soil stiffness for small deformations are presented and the use of these data in numerical modelling of the problem of sediments of a foundation of finite width on a base in the PLAXIS software complex.