In-situ Experimental Study on Squeezed Branch Pile Outer Profile Cross-hole Ultrasonic Detection
The quantitative detection methods for squeezed branch pile (SBP) profile are limited to feasibility study by using model tests.There is a lack of systematic in-situ experimental study considering real working conditions for establishing standardized ultrasonic method.The in-situ tests and theoretical studies on SBP were conducted.The technical process for crossing-hole ultrasonic detection was established.Firstly,the detection channels were set up by reusing pile core boreholes and 3 inclinometers at periphery.The Cartesian coordinate system was established through surface openings,and the inclinometer data were used for tube positioning to eliminate tube errors.Subsequently,the crossing-hole ultrasonic tests were conducted within the concrete and surrounding soil to measure the propagation velocity of ultrasonic waves.The ultrasonic first wave diagram of pile body was obtained by using cross-hole ultrasonic method.The relation between first wave arrival time and pile body profile size was established.The linear propagation path was assumed to derive pile profiles.Finally,considering refraction phenomena in different media and Snell's Law,the data correction method was established.The actual contour dimensions were calculated by using SBP geometric relation.The cross-hole ultrasonic detection technique for SBP profile was formed.The result indicates that the ultrasonic velocity in pile body is 4.24-4.36 km/s,which is consistent with 4.27 km/s from in-situ pile core sample.The ultrasonic velocity in surrounding soil of ranges between 1.65 km/s and 1.8 km/s,which is consistent with the tested values.The position and general outline of braches calculated according to the wave diagram are in agreement with the design.The profile diagram reveals pile deformation.The correction algorithm based on Snell's Law enables the more accurate calculation on actual profile.
road engineeringultrasonic transmissionsqueezed branch pile test methodsqueezed branch pilein-situ test
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