Response characteristics of sound fields of stratum frozen wall of water-rich sand during developing process

The ultrasonic tests on artificial frozen wall of water-rich sand stratum at depth of 16 m in Guangzhou Metro Line 3 are conducted by using NM-4A nonmetal ultrasonic test meter to study the response characteristics of sound fields during developing process of frozen wall. A thermoacoustic coupling numerical simulation method is proposed based on the heat conduction and pressure acoustic theory. The variation rule of temperature-sound field and acoustic characteristic value are obtained. The relationship among freezing front, unclosed distance and wave velocity is grasped. The application process of the thermoacoustic coupling model is summarized. The results are as follows: (1) The accuracy range of wave velocity is 89.7% to 96.97% betweenJ₁and J₂ holes by the numerical model. (2) The reflection and refraction are obvious when ultrasonic waves transmit from unfrozen soil to frozen soil. The average reflection and refraction coefficients are 0.278 and 1.278 betweenJ₁ and J₂holes. (3) The concentration area of acoustic pressure appears near the interface between unfrozen and frozen soils, and the sound field is inhomogeneous during early freezing period. Conversely, the sound field is homogeneous, and there is no pressure concentration area. (4) The wave velocity increases with the increasing freezing time, while both the acoustic pressure and the sound intensity increase first, then decrease as the freezing time increases. (5) Both the freezing front and the unclosed distance increase with the increasing wave velocity, and they meet quadratic function relations, indicating that the correlation is very good. (6) The application process of the thermoacoustic coupling model is summarized, which can achieve good effect on developing evaluation of frozen wall.