Analysis Of Propagation Characteristics Of Thermoelastic Waves In Unsaturated Soil

Geotechnical materials are widely existed porous media in nature,and the propagation phenomenon of elastic waves in geotechnical materials has always been one of the research hotspots in many subjects,such as mathematical physics,geotechnical engineering and seismic engineering.With the rapid development of petrochemical engineering,geotechnical and earthquake engineering,construction of landfills,nuclear waste management and other fields,the influence of thermal effects such as temperature change and thermal diffusion on the propagation characteristics of elastic waves in soil is becoming more and more obvious.So many researchers have begun to work on the propagation of thermoelastic waves in single-phase solid media and two-phase saturated porous media.However,unsaturated materials such as solid-liquid-gas three-phase unsaturated porous elastic media exist in nature and engineering in large quantity.Therefore,it will be of more practical value and significance to study the propagation characteristics of thermoelastic waves in unsaturated porous media considering the influence of the thermal effect.Firstly,based on the theory of porous media and the generalized thermoelastic model,the wave equations of unsaturated porothermoelastic media are established through theoretical derivation by using the mass balance equation,the seepage continuity equation,the momentum balance equation and the generalized non-Fourier heat conduction law.Using Helmholtz potential function decomposition theorem to solve the wave equations,the dispersion equation of thermoelastic body waves in unsaturated porothermoelastic medium is obtained.Numerical calculations and parameter analysis are used to discuss the variation of the wave velocity of various types of thermoelastic body waves with thermophysical parameters such as the thermal expansion coefficient,thermal conductivity,and medium temperature.At the same time,the dispersion equation of thermoelastic body waves in saturated porothermoelastic medium is derived through the theoretical degradation of unsaturated porothermoelastic medium,and correlative calculations and parameter analysis of propagation characteristics of the thermoelastic body waves are also performed.The results show that there are not only three compression waves?P₁ wave,P₂ wave and P₃ wave?and a shear wave?S wave?,but also a thermal wave?T wave?in the unsaturated porothermoelastic medium compared with the previous research results under isothermal conditions.The thermal expansion coefficient only has a considerable effect on the wave velocity of P₁ wave and T wave.The thermal conductivity only affects the wave velocity of the T wave.The increase of the wave velocity of various types of thermoelastic body waves will accompany the enlargement of medium temperature.The propagation characteristic of thermoelastic body waves in saturated porothermoelastic medium is similar to that in unsaturated porothermoelastic medium.Secondly,based on the propagation characteristics of thermoelastic wave s in unsaturated porothermoelastic medium,the propagation phenomenon of thermoelastic Rayleigh waves at the boundary of the unsaturated porothermoelastic medium is studied.The dispersion equation of thermoelastic Rayleigh waves in unsaturated porothermoelastic medium is derived theoretically by introducing the potential function and combining the boundary conditions of free,water-permeable,gas-permeable and adiabatic.Using numerical examples,the variation of the wave velocity of thermoelastic Rayleigh waves with thermophysical parameters such as the thermal expansion coefficient,thermal conductivity and medium temperature is discussed through parameter analysis.The results show that the increase of the wave velocity of Rayleigh waves will accompany the enlargement of the thermal expansion coefficient and medium temperature,and the thermal conductivity will have negligible effect on the wave velocity of Rayleigh waves.Finally,based on the research results of the propagation characteristics of thermoelastic body waves and Rayleigh waves in unsaturated porothermoelastic medium,the reflection characteristics of plane-S-wave and plane-P₁-wave at the boundary of the unsaturated porothermoelastic medium and the reflection-refraction of plane-P₁-wave at the interface between a thermoelastic solid medium and an unsaturated porothermoelastic medium are discussed.Theoretical expressions of amplitude reflectivity/refractivity for all kinds of reflected/refracted waves generated by the incident wave are derived by taking into consideration the boundary conditions.The effects of different thermophysical parameters on the amplitude reflectivity/refractivity for each reflected/refracted wave are discussed using numerical calculations.The results show that the amplitude reflectivity/refractivity for each reflected/refracted wave is affected by not only the incident angle but also the thermal expansion coefficient,thermal conductivity and medium temperature.The article obtained the propagation characteristics of thermoelastic body waves and Rayleigh waves in unsaturated porothermoelastic media under the influence of thermal effects through parameter analysis.The conclusions indicate that the influence of thermal physical parameters such as the thermal expansion coefficient,thermal conductivity and medium temperature on the propagation characteristics of elastic waves should be emphasized in the study of soil dynamics,which has important practical engineering significance for practical activities such as engineering seismic survey.