Study On High Stress Variable Measurement Method In Determining The Bearing Capacity Of Foundation Pile

The technology of testing the bearing capacity and integrity of pile by high strain dynamic test has been widely used in the world.It is proved by practice that the method of high response variable measurement can not only greatly improve the efficiency of pile detection,reduce the cost,but also better guarantee the quality of pile foundation engineering.As one of the main methods of high strain change measurement,CASE method is based on traveling wave theory and obtains the closed solution of wave equation by some approximate assumptions.Its advantage is that the calculation is simple and fast,the disadvantage is that it is only suitable for non-complex pile and soil conditions,and depends on the experience of the examiner.CASE method has automatic bearing capacity calculation method and RA2 method which do not depend on empirical coefficient,but each has its own defects.Based on the analysis of relevant theories,this paper mainly makes the following research:(1)Through the analysis and calculation of the resistance of the pile side in the uniform foundation and the characteristic line relation of the fluctuation in the pile body,the formula of the velocity change of the pile body mass point in the uniform foundation is obtained.(2)An improvement has been made to the problem that the RAU method does not consider the unloading of pile side soil resistance.The velocity of pile body mass point is calculated by the measured curve of pile top,and the static resistance and dynamic damping coefficient of pile side soil are calculated.By using the static resistance of the pile side to compensate the unloading of the pile side soil at the calculated time selected by the RAU method,an improved automatic calculation method of bearing capacity is obtained.and analyzed its application limitations.A typical engineering example is used to show that this correction algorithm can be applied to practical engineering.(3)Author use SPSS statistics software to determine whether the improved automatic method can be used in engineering practice.Some piles with good piling effect and static load test data are selected to calculate the improved automatic bearing capacity.Taking the results of automatic method as independent variables and the results of static test as dependent variables,the linear regression analysis and quadratic curve regression analysis of the data were carried out.The results of regression analysis show that both linear regression and quadratic regression are valid.The automatic method has high accuracy in medium and small diameter prefabricated piles,which can effectively judge the quality of the collection curve and estimate the bearing capacity.Considering the soil resistance soil resistance,the RAU of automatic bearing capacity calculation method is improved.practice shows that the improved automatic method solves the problem that the RAU method is only suitable for end bearing piles,and can be applied to the quality analysis of high strain curve and the calculation of bearing capacity of prefabricated piles with medium and lower side resistance.