Assessment of the Contact between Piles and Soil via the Dynamic Attributes of Acoustic Signals
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ssment of the Contact between Piles and Soil via the Dynamic Attributes of Acoustic Signals V. V. Kapustina, * and A. A. Churkinb, ** a
Department of Geology, Moscow State University, Moscow, 119991 Russia bLLC AIGEOS, Moscow, 117198 Russia *e-mail: [email protected] **e-mail: [email protected]
Received December 12, 2019; revised January 15, 2020; accepted January 15, 2020
Abstract—The low-strain impact method is one of the most commonly used nondestructive geophysical methods in pile integrity testing. Data analysis of the low-strain method in the frequency domain allows a researcher to obtain additional information about a foundation. The authors of this article propose a methodology for assessing the contact of piles with soils based on an analysis of the dynamic attributes of the frequency response. Conclusions drawn from using the above-described method can be used by engineers to study the quality of piles and to plan direct static load tests to determine the bearing capacity of piles. Keywords: pile testing, defectoscopy, low-strain impact method, transient response method, acoustic emission, acoustic contact, bearing capacity DOI: 10.3103/S0145875220040092
INTRODUCTION The surface seismoacoustic method (low-strain impact method) is one of the most common and recognized methods for monitoring the length and integrity of reinforced concrete piles. The high volume of work, high productivity, and integration into various regulations and normative documents allow large amounts of data to be collected and systematized (Kapustin et al., 2018). The data from the low-strain impact method applied for pile quality control can be subject to both timing and frequency analysis, depending on the pile type and local soil properties. Qualitative assessment of the contact between a pile and the surrounding soil obtained when studying the response of piles to acoustic impact is of great interest. The easiest way to assess contact conditions between a pile and soil is to find the ratio of the input signal to the response, which can be characterized by a set of dynamic attributes. The steady-state frequencyresponse method, which is based on such principles, which is widespread abroad, was developed almost simultaneously with the low-strain impact method, and relied on the acoustic-resonance phenomenon to obtain information about piles (Amir, 2017). Initially, the main problem with this method was the use of a vibrating source to trigger the signal (Davis and Dunn, 1974). The modification of the method, which enabled resonance analysis by simultaneous recording of the parameters of the impact force and the response of the structure under investigation, was called the
transient response method (TRM, Liang and Beim 2008). MATERIALS AND METHODS The Connection between the Contact of a Pile and Soil and the Bearing Capacity of a Pile The bearing capacity of a pile is mainly determined by three parameters: pile strength, the bearing capacity of the underlying soil, and the adhesion of the pile side surface to the surrounding soil (Flemi
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