Applied Research On High Strain Dynamic Testing Bearing Capacity Of Pile In Weihai Area

Pile foundation,as an important form of deep foundation,is widely applied in modern civil engineering,and single pile bearing capacity test is an important step in the process of pile foundation application with great necessity.For the reason of that the traditional static loading test is both time and energy consuming,besides,the pile bearing capacity is mainly determined by the engineering nature of site foundation soil,and its test accuracy is closely connected with local geological condition,therefore,the research and promotion of the method of high strain dynamic test for single pile bearing capacity test in Weihai is of great theoretical significance and practical application value.Firstly this paper preliminarily calculates and analyzes some cases of high strain dynamic test method for single pile bearing capacity test through collecting a large number of test records of pile static loading test and hammer-into-the-pile type of construction in Weihai district.In order to improve the calculation accuracy of high strain dynamic test method for single pile bearing capacity test,this paper carries out intensive study on soil counter force calculation model on the basis of the test records of pile static loading test in Weihai district,and analyzes the connection between pile loading and settlement,the change rule of pile loading and settlement curve in a meticulous and deepgoing way and establishes the fitting function for pile loading and settlement(Q-S curve).Furthermore it studies the destructive code for piles and puts forward the hyperbola fitting method as well as the extrapolation method for static loading test of which the maximum design loading can be 1.2-1.5 times.Secondly based on the Q-S curve fitting function and the hyperbola fitting method,this paper sets up hyperbola soil counter force calculation model,and further derives dynamic pile driving formula concerning soil counter force nonlinear variation using this model.At last,to check the effect of application the dynamic pile driving formula in the single pile loading,two construction projects-Weihai Gymnasium and Weihai Sports Stadium,are employed,whose foundation pile records are calculated and analyzed by high strain dynamic test calculation method,and also compared with the popular method of Heily dynamic driving formula.The outcome indicates that the calculation method introduced in this paper is more accurate that the Heily formula,and the maximum absolute value of error can be reduced from 46.5% to 31.2% and not exceeding ±30%.This research shows that the nonlinearity soil counter-force calculation model and dynamic pile driving formula is theoretically correct and reasonable and can be applied in construction.