Crosshole Sonic Logging Of Casting In-situ Pile

Pile foundation plays an important role in the domain of building, industry,civicism,traffic and electricity etc.Based on the advantages of little noise,lesser steel consumpstion and convenience, casting in-situ pile is popularly applied, especially to high bearing capacity pile and super big diameter pile or to piles formed under complex geological condition or bad condition, and it won't be replaced by other kind piles. But quality of casting in-situ pile depends on construction methods and technical measures,so it is difficult to easure quality compared to precast pile.Casting in-situ pile is poured in place after bore-forming process, so that defects and quality questions such as mud cake around pile,broken pile,shrinking diameter, remained mud, and segregatin etc are easily to form.So how to test quality of pile concrete by convenient way is important to ensure engineering quatity.Fujian Province is a much developed seaside area with more buildings constructed,where casting in-situ pile is widely used.As a popular test method ,crosshole sonic logging needs to be researched and improved to adapt to Fujian Province.Briefly, this paper would mainly talk about the problem as below:①Validation of the equipment, acoustic pipe and the way of installing acoustic pipe;②The influence of in-parallelling of the acoustic pipe to pile test;③Concrete strength measurement by acoustic velocity of pile through measinring the wave speed of mass cube trial;④The influence of defects in Casting in-situ pile to the test of crosshole sonic logging;⑤Programme analytic software for testing casting in-situ pile by crosshole sonic logging.From the research above, such achievements are obtained:①T esting equipment has been validated and the scheme of the material and setting of acoustic pipe according to the condition of constraction was optimized.②T he model of change of acoustic pipe-distance was set up to get real distance by multiple-approaeh fitting according to in-parallelling of the acoustic pipe embedded during constraction.This method can minimize the influence of in- inparallelling of the acoustic pipe embedded in pile.③The conversion curve for calculating concrete strength by ultrasonic inspection was established;④By investigation of model piles indoor,through anylsis of the influence of defects in casting in-situ pile to the test of crosshole sonic logging, the estimate rule was established,and the VC defect–criterion based on acoustic velocity was put forword.So we can estimate the pile quality by integrated estimate method.⑤A nalytic sofeware for testing of casting in-situ pile by crosshole sonic logging was programmed,which can calculate the real distance ,so we can obtain acoustic velocity, calculate the VC defect-criterion,draw curve of ultrasonic time-depth and VC defect-criterion depth etc.