Research On The Effect Of Stress Dispersion In Compound Two-Layer Foundation

At present, the settlement of soft clay ground reinforced by semi-rigid piles or flexible piles is always much bigger than measured in-situ if it's calculated by traditional composite foundation theory. The result calculated by applying two-layer ground theory mechanically sometimes is good enough for us to accept, but actually it's wrong obviously for conception. In view of the existing situation, the author has made efforts and drawn several conclusions in this paper:(1) The conception of "compound two-layer foundation" has been put forward and it also been verified to be reasonable and necessary at the same time;(2) The effect of stress dispersion in compound two-layer foundation was affirmed by the theory of elastic foundation beam. Through the analysis we found that the effect will become more obviously with the increase of thickness or width of superstratum and the decrease of the coefficient of foundation bed;(3) Anisotropy and nonlinear elastic F.E.M. model has been established and the effect of stress dispersion in compound two-layer foundation was analyzed on the base of the model. From the analysis we can conclude that the coefficient of subsidiary stress dispersion will amplify with the increase of thickness or width or stiffness of back-up coat;(4) The formula which can be used in conventional calculation has been deduced for calculating the coefficient of subsidiary stress dispersion and it also has been affirmed to be reasonable through the checking calculation;The whole theory of compound two-layer foundation has been brought forward in this paper and it'll enrich the theory of composite foundation. Profitable searching for the further development of composite foundation theory has been done.