Improved Method For Nonlinear Settlement Calculation Of Strip Foundation

The subsoil settlement is one of the main research subjects in soil mechanics. From the existing methods of settlement calculation, layerwise summation method is still the mainstream of engineering designs currently because of simplicity and practicability. However, such method adopts calculation indexes generally measured by confined compression test, which can not be better to reflect the effect of stress condition on deformation parameters. The soil has strong porosity and voluminal compressibility, resulting in deformation mechanic parameters changing obviously under different conditions of stress level and stress history, especially the deformation modulus or compression modulus. Therefore, foundation settlement or deformation present highly nonlinear variation. Upon that, how to think about the impacts of soil parameters change is the key to establish nonlinear calculation methods of foundation settlement. In view of this, the nonlinear settlement calculation method of strip foundation was studied and improved in this paper, in which the traditional layerwise summation method and an idea for step loading were incorporated. Main results and conclusions are as follows:Firstly, according to the variation characteristics of deformation mechanical parameters caused by the interstitial compressibility of foundation soils, this paper further studied the mechanical mechanism about the effect of additional stress and stress history to foundation soil modulus, and the analysis models that reflect the deformation mechanical parameters of foundation soils which changing with additional stress and stress history were established respectively. A new nonlinear elastic computational method for settlement of strip foundation was put forward based on the Hooke's law. This method not only reflects the characteristics that deformation mechanical parameters of foundation soils change with additional loads, but also the effect of different soil modulus induced by different initial stress level or different stress history on foundation settlement computation. Moreover, the using of the compression test curves in foundation settlement calculation is avoided efficiently.Next, combining the improved nonlinear elastic model established in this text with the Mohr-Coulomb plastic model to form a new inelasto-plastic constitutive model, so as to replace the latter on the assumption that elastic zone was linear elasticity. The new model was applied to the calculation of foundation settlement, and then proposed the method of settlement calculation based on elastoplastic theory. The theory has the advantage of layerwise summation method, it can consider the character of elastic nonlinearity and plastic deformation of soil, what is more, the effect of 3-D stress on deformation can be taken into account also.Finally, by comparing the computation and analysis of two engineering examples with actually measured and calculated settlement results by other methods, it shows that the proposed methods in this text are reasonable and feasible.