Study On Optimizing Of Calculation Method Of Settlement Of Paleo-clay Foundation

Calculation of foundation settlement has always been a basic problem which has not been solved well in soil mechanics.At present,the unidirectional layered summation method and the stress area method(recommended by specification)that are both based on the theory of layered summation have be widely used in engineering field.Although the two methods aboved have the advantages as follows:simple constitutive model,clear theory,easy calculation and strong practicability in engineering,but their calculated values are always different from observation data of filed.In order to find out the suitable method of settlement calculation for the paleo-clay foundation in Hefei,by comparing and analyzing advantages and disadvantages of the existing methods of settlement calculation,studying properties of physical and mechanical and engineering of paleo-clay in Hefei and considering practicability of engineering and easy calculation,the paper bases on the idea of layered summation,focus on studying the three aspects including normalization processing of stress-strain curve of paleo-clay,majorization of calculated depth of compression layer and experienced modified coefficients of settlement to explore the method of settlement calculation with high precision.The main contents include as follows:(1)Paleo-clay’s properties of physical and mechanical and engineering have been studied,especially statistical analysis of the index relating to deformation characteristics has been done,and the results show that paleo-clay of Hefei belongs to the medium&low compressible soil and its compression modulus is increasing with depth,the shallow soil displays weak expansive potential and the effects of the expansion to calculation of settlement can be ignored.(2)Stress-strain curves measured by confined compression test of paleo-clay have been analyzed,and fitting the stress-strain curves with hyperbola model provided by Kondner,the fitted effect performs well.(3)Combined with practical engineering,stress-strain curves of paleo-clay can be normalized well by utilizing preconsolidation pressure as normalized factor,method of settlement calculation after normalizing has been put forward.(4)Combined with practical engineering,the depth of compression layer has be calculated with several different methods,comparing and analyzing the calculated values,the result shows that method for calculating depth of compression layerdetermined by control stress is appropriate for paleo-clay foundation in Hefei.The stress ratio ranged from 0.2 to 0.3 has been recommended for paleo-clay foundation.(5)Comparing the improved calculation method of settlement with he unidirectional layered summation method and the stress area method(recommended by specification)by combining with practical engineering,the result shows that computational accuracy of improved calculation method is higher than others.And linear regression equation of experienced modified coefficients which applied to Hefei’s paleo-clay foundation has been put forward and providing a certain reference for designers when choosing the value ofs?.