Study On Engineering Application Of Soil Classification And Pile Bearing Characteristics Based On CPTu

With the emergence and rise of large civil engineering,such as high-rise building,high speed railway and long span bridge,the accuracy of the test parameters of geotechnical engineering was demanded more and more precise.At present,In suit testing was one of the most widely used methods in geotechnical engineering with the advantages of no sampling,no disturbance,convenient test and so on.The technology of static penetration test(CPTu)has increased the number of functional components and the testing accuracy has been greatly improved based on static cone penetration test(CPT).However,due to the huge amount of data in CPTu test,it is necessary to require a lot of manpower,material resources and time which used the traditional chart method to classify and recognize the soil layer.The bearing capacity of the pile changes with the time,and the ultimate bearing capacity of the pile will eventually converge when estimating the bearing capacity of jacked pile.However,the existing estimation methods are not reflected,and just only empirical correction factor are given generally.In the case of single pile load settlement prediction,the traditional static load test is the most common method,which is a high reliability method.However,the time and cost of the static load test are higher,and the evaluation of the whole site depends on the number of static load test piles.Under the above background,the measured data and engineering data of the engineering site are obtained by using the multifunctional CPTu test system of geotechnical Engineering Institute of Southeast University.This paper makes a systematic study on soil classification,estimation method of bearing capacity of jacked pile and the settlement prediction of the single pile based on CPTu by using the methods of MATLAB program simulation analysis,field test and finite element simulation.The main work in this paper including:(1)Study on the corresponding soil interface identification program by using the CPTu data has been written with MATLAB platform based on Superiority of probabilistic neural network in classification and pattern recognition,which applied and analyzed in the practical engineering.Then,we discussed the applicability and effectiveness of the classification of soil layers in different geological sites and the recognition of thin inter-beds using the CPTu data based on probabilistic neural network.Finally,the map of the regional soil layer has been tried to draw based on the continuous CPTu data is analyzed and the results are reasonably merged.(2)Firstly,the influence area of the pile end resistance is determined by the method of logarithm spiral curve correction,and the influence area of the pile end resistance of the pile end soil is analyzed.There is a new method for estimating the bearing capacity of jacked piles based on CPTu has been presented considering the effect of lateral resistance degradation in the process of pile sinking and the conversion relation between final pressure and bearing capacity of jacked pile based on the field measured CPTu data and pile data in Zhenjiang area.The validity of the method for estimating the bearing capacity of static pressure pile has verified by comparing with the similar engineering examples in the literature.Finally,the reliability of the pile bearing capacity is estimated by means of the first order two moment method based on based on a large number of measured data from statistics.(3)Study on the prediction model of single pile load settlement has been established by the initial shear modulus and elastic modulus of soil were estimated through measured soil shear wave velocity and the hyperbola method of soil elastic modulus with axial load.The single pile settlement prediction model is used to predict the load settlement of single pile in an engineering example,which contrast with the results of single load test and finite element simulation of ABAQUS.