Theoretical Analysis Based On The Variational Method Of Composite Foundation Settlement And Calculation In Homogeneous Soil

With the development of foundation treatment technology and the theory of composite foundation, composite foundation technology in recent years has been widely used in our country.Is particularly important to reasonable control the settlement of composite foundation, composite foundation settlement calculation theory is not mature enough, however, are under development.In this paper, according to the principle of the xiao yu can, using the variational method to establish the theory of a new kind of composite foundation settlement. This paper, using the single pile load transfer method and on the basis of the three line load transfer model of the establishment of a single pile load-settlement analytical solution.By introducing displacement hypothesis, the interaction between two piles of analytical solutions, on the basis of the analysis of pile group interaction of "the barrier effect" and "reinforcement effect", and reveals the mechanism of the two.Based on the load transfer method and the single pile displacement field of composite foundation in the assumption of homogeneous soil, the pile foundation were first established the isometric directly over the total expression, only use directly on the basis of the analysis methods included in the role of soil between piles can get more than the total of composite foundation, the ritz variational method is used to direct the load-settlement relationship length of pile composite foundation is established.For the length of pile composite foundation quoting the concept of "virtual" soil pile, the calculation and analysis into the category of isometric pile in the load-settlement relationship length pile composite foundation.By studying some can get the following main conclusions:1. The analysis of the single pile with double broken line model is simpler, but is not consistent with actual situation, and calculation precision is poor;The three broken line model could be a good simulation of soil nonlinear effect.2. Reinforcement-curtain effect is objective existence.Through the analysis of interaction between two piles, which is caused by additional shear force acting on the pile, and is inversely proportional to the pile spacing, is proportional to the diameter than the size of the pile is proportional.3.In this paper, the variational method is used by the length of pile composite foundation model for calculating the pile settlement when its length is longer than the calculation result is smaller.On the contrary, the pile length is small the calculation settlement settlement;Using the variational method is studied with calculating the length of pile composite foundation model under the same load, with the increase of pile number of final settlement calculate the has no obvious change;Using the variational method is studied with calculating the length of pile composite foundation model under the same load, with the increase of cushion layer thickness calculation the final settlement is increased.4. Measured by means of model test of various models of the experimental results and calculation results in this paper, the variational method of theory is analyzed and compared.Found that the error between the two decreases with the increase of the load;Linear analysis and calculation results in the linear elastic stage of the load displacement error is small.While the results of nonlinear analysis and calculation in the whole phase error is small.The theoretical calculation method of this paper is verified, determine the rationality of the method and the feasibility of engineering practice.5. Presently, it can’t calculate the settlement of the pile group theory of large-scale pile integrity analysis.In order to analysis of a large group of piles, the interaction coefficient of the traditional method of analysis, but its not good to consider reinforcement-curtain effect, and therefore easy to overestimate the pile group under the condition of the interaction between piles, the calculation result is too large.Variational method can be used for large-scale pile group overall analysis which can be a very good considering reinforcement-curtain effect and is convenient to calculate, small amount of calculation.