Study On The Influence Factors Of Low Strain Reflection Wave Method To Detect The Rock-Socketed Pile Quality

In the area of shallow buried bedrock, the rock-socketed piles usually is adopted as the foundation for the engineering of high-rise building or Bridge, which rock-socketed effect has attracted a lot of attention recently. In an important project the piles about one hundred percent is usually detected by low strain reflected wave method in combination with a small amount of rock-socketed piles by core drilling method, through which the rock-socketed depth and pile bottom sediment are determined and the project quality overall is controlled strictly. At present problem is that a small amount of rock-socketed piles selected for core drilling is more casual and blind, the influencing factors of the low strain reflected wave method is more, and especially the characteristics of rock-socketed pile increases the detection complexity. Therefore the testing evaluation effect of pile embedded in rock is not the best, and further research to explore the detection mechanism and methods is needed.In this article, with the results of concrete core compression testing for core samples through one project of rock-socketed pile quality inspection activities in Nanchang, there are a lot of pile having the phenomenon that concrete compressive strengthes at different depth pile parts in a pile vary widely. But in the actual concrete Bored pile examination analysis, a much complete pile, are usually considered along the entire pile as a homogeneous material. So the low strain stress reflection method easily produces certain miscalculation during detection message change. Therefore, in order to understand the influence of pile body concrete compressive strength to low strain stress reflection wave, special selection of five piles drilling core, from which the pile body concrete core samples are taked by meter for compressive strength testing. The changes of the concrete compressive strength of 5 piles are compared with detection results of low strain stress reflection wav method. The result shows that with the concrete strength changes of pile body much more drastic, pile bottom reflection signal is Is not obvious, low strain wave reflected signal is much complex.To study the influence of the relevant parameters to the low strain reflected wave curve, pile soil simulated vibration calculation model was established by MIDAS/GTS NX software. The changes of reflection wave time ~ velocity curve For a complete pile are discussed with the exciting force, pulse width, signal receiver position, and pile length; Stress wave time velocity curve change rules are studied with the pile body imperfections such as pile diameter expanding and reducing, defect location factor; the changing rules of the stress wave are analyzed from radius size, pile length, concrete grade, pile bottom sediment thickness. pile side soil elastic modulus, poisson’s ratio, cohesive force and the interior friction Angle. This paper gets Some beneficial conclusions and demonstrates the complex influence of pile body concrete changes to low strain stress wave reflection. It is useful to guidance of pile quality inspection.