Research And Application Of Determining The Foundation Bearing Capacity And PHC Pile Ultimate Bearing Capacity Based On CPT

Cone penetration test(CPT)has been widely used in geotechnical engineering investigation because of its advantages of economy,fast speed,continuous testing and dual functions of exploration and testing.However,the penetration mechanism is not clear,and the material composition,structure and engineering properties of soil layers in different regions are different.The engineering application of CPT is mainly to establish the relevant empirical formula of soil layers in specific regions.CPT is widely used in plain areas such as the Undulational Plain between the Yangtze River and Huaihe River,hilly plain along the Yangtze River and Huaibei plain in Anhui Province,and accumulated rich data and application experience for many years,but it has not been able to get systematic and effective analysis and research.In view of this,the paper according to the different geological and stratigraphic conditions of each plain area,this paper based on CPT adopts different methods establishing the empirical formula and neural network prediction model so that the bearing capacity of main soil layers and the ultimate bearing capacity of single pile of PHC Pile are determined in Anhui Province Type.The research work is as follows:(1)In this paper,a large number of engineering geological survey data and natural foundation load test data in the three great plains of Anhui Province are widely collected.The geological and stratigraphic conditions of the three great plains are analyzed,and the CPT data that main soil layers in each plain area,indoor geotechnical test results data,as well as the application standard table method,local experience method and load test method are determined Based on the analysis of the correlation between the CPT test data and the foundation bearing capacity determined with different methods.The corresponding statistical regression equation is established step by step with comprehensive comparative analysis,combined with the regional experience.The method of determining the foundation bearing capacity based on the CPT of the main soil layers in the three plains of Anhui Province is finally established Empirical formula.(2)The paper also collects the load test data of single pile ultimate bearing capacity of PHC Pile in three plain areas,analyzes and calculates the data of CPT and the ultimate bearing capacity of single pile,and modifies the formula of determining single pile ultimate bearing capacity of precast concrete pile by CPT in the "Technical Code for Building Pile Foundations"(JGJ 94-2008)(hereinafter referred to as "pile foundation code")by using multiple linear regression analysis method,so as to make it more suitable for the safety According to the stratum conditions of Anhui Province,the verification results show that the formula established in this paper is obviously better than the formula of "pile foundation code".(3)Artificial neural network has the characteristics of self-learning,self-organization and self-adaptive,which can be used to deal with complex nonlinear and uncertain problems.In this paper,five BP neural network prediction models of PHC pile ultimate bearing capacity based on CPT are established considering various factors such as stratum conditions,pile size and input layer information processing methods.Through verification and comparison,the prediction results of the five models are obviously better than the empirical formula established by multiple linear regression method.Among them,the model 3 which clearly divides the soil layer at pile side and sets the maximum limit value of soil layer ultimate lateral resistance has the best effect,and can be applied to engineering practice.The prove of research results is safe,reliable and easy to be applied,which effectively improve the efficiency and quality of investigation and promote the further normative application of CPT in Anhui Province.