Application Research And Analysis On High Strain Dynamic Testing Methods For Foundation Pile

Pile foundation is one of the most common in engineering construction of our country foundation form.Due to the pile foundation engineering belongs to the height of underground or underwater concealed work,its quality by the engineering geological conditions,construction technology,and many other factors,relatively difficult to control,it is more easy to pose a safety hazard.If pile foundation accidentally appear quality problem,the difficulty of the repair and reinforcement is self-evident,consequence is unimaginable.As a result,the pile testing is an indispensable key in pile foundation engineering.High strain dynamic testing method for vertical bearing capacity of foundation pile is to use a hammer to pile instantaneous applied load stress spread to the lower part of the pile spread filling pile displacement of soil,to excite one kind of soil around the pile and pile end resistance and support force dynamic detection methods.Its not only the base pile structural integrity testing,but also determines the base pile vertical ultimate bearing capacity can be made reasonably comprehensive description of the entire pile project quality.The study of the high strain dynamic test method has been the hot topics in the study of pile foundation inspection,this testing method as an economical,efficient,and relatively reliable pile quality detection technology,although domestic and foreign has been widely recognized and applied,there are many issues to be resolved.Particularly,the most difficult is in the casting pile of excitation standard and dynamic resistance culling.In addition,the effective elimination of the results of the subjective experience of bearing capacity caused by the uncertainty of parameters is a difficult too.Therefore,to carry out further theoretical research and practical analysis has extremely significant value of theoretical and engineering application.Study and solve the problems in the engineering application,further improve the high strain dynamic test technology to improve the level of detection and determination accuracy is urgent.Theoretical basis of the high strain dynamic test method in this paper,model assumption and calculation principle of the analysis of several aspects,such as for wedged point,research the direction of improvement and engineering application problems,the main content can be divided into four parts:Part one: Mainly analyzed the high strain testing method of wave mechanics basis,expounded the derivation process of one dimensional wave equation,the impact of stress wave propagation in the rod member and the resistance of the soil around the pile pile stress wave propagation.Part two: Analyzed deeply the basic assumptions of high strain CASE method,calculation principles and formula for determining the carrying capacity.Meanwhile,pointed out the CASE method defects in the theoretical assumptions method and limitations of engineering application;According to the soil resistance makes stress wave propagating along the pile will occur the exponential decay regularity.Based on ignoring the difference resistance to mode of action between piles side and soil between piles dynamic,considering the impact of pile lateral damping,improving CASE method of bearing capacity formula about,using MATLAB editor bearing capacity improved formula and examples to verify the results show that the effect of amendments to its friction pile bearing capacity CASE method significantly reduces the static and dynamic contrast errors.Part three: Analyzed High-strain curve fitting method,expounded pile-soil system model fitting,the calculation principle,fit calculation process and its lack of theory and applications.Collected hundreds of CASE method and fit method dynamic-static comparative samples,and a statistical comparison with linear regression analysis.Study was to investigate the accuracy of the two methods of problem in engineering practice.The results show that the fit method dynamic-static comparative sample is more convergence,lower degree of dispersion,linear correlation better fit method static load bearing capacity and the ultimate load of the overall goodness of fit is higher.In a word,the fit method is better than CASE method.Part four: Used the method CASE and fit method to analysis a pile engineering case to determine the bearing capacity of foundation piles,and by comparing of static load test.static to analysis the applicability and reliability of two methods in pile engineering,reliability,found that the applicability of fit method is stronger.Additionally,in the lack of regional experience situation,Identified a site CASE damping value ranges by use of fit method to provide a reference for similar projects.Human factors have great impact on selecting the fitting parameters.Study analyzed the impact of the proposed legal pile and soil parameters on curve fitting,discussed the common problems of high strain testing method.