Study On Soil Layers Fuzzy Analysis And Pile Bearing Effect Based On CPTU

With the rapid development of economy,high speed rail,large span bridge,super high rise buildings are constantly emerging,and the scale of engineering construction is gradually expanding.The accuracy of parameters for rock and soils come more important.However,due to the complex and multi distribution of the soils,it's hard to determine the corresponding mechanical parameters of them.The existing methods of investigation include: drilling sampling,laboratory test,in-situ testing technology and so on.The first two methods are always affected by the disturbance of the samples.Thus there may be large gap between the precision of geotechnical parameters and engineering demand.The in-situ testing technology is a method to reflect geotechnical engineering properties by field measurement.It has the advantages of no sampling,low disturbance,economical and convenience,which is an effective way to get geotechnical parameters.As one of the in-situ testing techniques,the Piezocone Penetration Test(CPTU)is a new technique by applying pore water pressure sensor based on the original Cone Penetration Test(CPT),which has the advantages of high precision,multi-parameter,strong anti-interference and good repeatability.However,it brings some confusion at the same time,the accuracy of the analysis need to be improved because of the large number of CPTU data obtained by the test;Especially during the process of soil classification,it takes a lot of manpower and material resources to analyze the CPTU data directly by using the existing soil classification chart.While the main shortcoming of the existing methods based on CPTU test data is strong subjective as the correction coefficients are obtained through a large number of field tests.The settlement associated with the bearing capacity is one of the most important indexes to control the safety of the project.At present,the accepted pile load settlement analyses are still based on the static load test which is time-consuming and uneconomical,and only a few parts of the pile are checked.Influenced by many factors(such as the nature of rock soil,the effect of pile soil and the size of pile),it's difficult to predict the pile settlement accurately by the existing methods(such as empirical method,theoretical calculation method,numerical calculation method etc.)In this paper,based on CPTU's measured data,fuzzy theory is used to compile the corresponding programs through the MATLAB,so as to realize the recognition and classification of the site soil layers.According to the existing static data of loading test,the GM(1,1)model is modified by the enhanced buffer operator,which can be used to predict the settlement of the pile.The main research contents include:(1)Based on fuzzy clustering theory,a fuzzy clustering procedure is written on the MATLAB platform to identify and classify the soil layer adopting the measured data of CPTU.The merits and demerits of the soil classification as well as the identification and division of the mixed layer of the transition layer are discussed.The results of soil classification and identification are verified through the field drilling sampling results,which indicate that it has certain value for the identification and analysis of soil interface,and is a useful supplement to the existing methods.(2)The possibility of interval-2 type fuzzy clustering is analyzed,that is to further fuzzing the membership degree of a fuzzy clustering,so that it can better adapt to the reasonable situation of soil interface deposition.In view of the problem that the number of site clustering is difficult to judge,judging by introducing the effectiveness index is tried in this paper.At the same time,the evaluation of the macroscopic characteristics of the site may reflect the composition of the soil layers and the scale of the specific development clearly,which provides reference for the practical application of the project.(3)Applying obtained value of cluster center interval type-2 fuzzy clustering,a new method to calculate the bearing capacity of the pile and comparing with results of field static load test are proposed,then,the corresponding accuracy of this method is analyzed.Finally,both the existing typical calculation method and new method are evaluated to verify its reasonable accuracy.(4)Based on the GM(1,1)model,the enhanced buffer operator is introduced to modify the initial static data of loading test.In this case,though a small amount of measured static data of loading test are used to predict settlement,it still meet the needs of engineering construction and has the advantage of economical and efficient.