<p>Based on thermoelastic wave propagation theory, a dynamic model of P-wave incidence in bedrock-saturated soil-layered unsaturated soil systems was developed. The transfer matrix method was employed in conjunction with rigorous boundary condition enforcement to systematically investigate the controlling factors governing site seismic responses under thermo-hydro-mechanical (THM) multi-field coupling effects. By establishing the wave amplitude vector transfer relationships between medium layers (via the transfer matrix method), the influence patterns of critical parameters including groundwater level, unsaturated soil layer thickness, and thermal conductivity coefficient on seismic ground motion characteristics were quantitatively analyzed. The results demonstrate that soil stratigraphic properties and thermophysical parameters exert significant control on site displacement responses. For the homogeneous soil stratum (Case1), the peak displacement amplification coefficients corresponding to incident angles are distributed across a wider angular domain, whereas those for heterogeneous strata are predominantly concentrated within smaller angular ranges. Among the stratigraphic configurations analyzed, the soft-over-stiff stratum (Case2) exhibited the most pronounced seismic response, with peak horizontal and vertical displacement amplification coefficients reaching 358.97 and 5,586.33, respectively. Beyond the influence of groundwater level, parameters such as unsaturated soil layer thickness and thermal conductivity coefficient demonstrated nonlinear variation patterns in their modulation of displacement amplification coefficients, deviating markedly from monotonic trends observed under single-variable conditions. Under identical loading scenarios, the peak displacement amplification ratio (<InlineEquation ID="IEq1"> <EquationSource Format="TEX">$u_{z} /u_{x}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>u</mi> <mi>z</mi> </msub> <mo stretchy="false">/</mo> <msub> <mi>u</mi> <mi>x</mi> </msub> </mrow> </math></EquationSource> </InlineEquation>) exhibited a fluctuation range of 0.277 to 289.767. These findings underscore the necessity of comprehensively considering the compound effects of soil stratification characteristics and THM coupling mechanisms on site-specific seismic responses, thereby providing theoretical foundations for seismic-resistant design and dynamic response evaluation of stratified geological systems.</p>

Seismic Ground Motion Analysis of Saturated–Layered Unsaturated Soil Sites Under Thermal–Hydro–Mechanical Coupling

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发表日期：

2026年1月6日

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Yongqin Ma,
Qiang Ma,
Shengjun Shao

摘要

Based on thermoelastic wave propagation theory, a dynamic model of P-wave incidence in bedrock-saturated soil-layered unsaturated soil systems was developed. The transfer matrix method was employed in conjunction with rigorous boundary condition enforcement to systematically investigate the controlling factors governing site seismic responses under thermo-hydro-mechanical (THM) multi-field coupling effects. By establishing the wave amplitude vector transfer relationships between medium layers (via the transfer matrix method), the influence patterns of critical parameters including groundwater level, unsaturated soil layer thickness, and thermal conductivity coefficient on seismic ground motion characteristics were quantitatively analyzed. The results demonstrate that soil stratigraphic properties and thermophysical parameters exert significant control on site displacement responses. For the homogeneous soil stratum (Case1), the peak displacement amplification coefficients corresponding to incident angles are distributed across a wider angular domain, whereas those for heterogeneous strata are predominantly concentrated within smaller angular ranges. Among the stratigraphic configurations analyzed, the soft-over-stiff stratum (Case2) exhibited the most pronounced seismic response, with peak horizontal and vertical displacement amplification coefficients reaching 358.97 and 5,586.33, respectively. Beyond the influence of groundwater level, parameters such as unsaturated soil layer thickness and thermal conductivity coefficient demonstrated nonlinear variation patterns in their modulation of displacement amplification coefficients, deviating markedly from monotonic trends observed under single-variable conditions. Under identical loading scenarios, the peak displacement amplification ratio ( $u_{z} /u_{x}$ $u_{z} / u_{x}$ ) exhibited a fluctuation range of 0.277 to 289.767. These findings underscore the necessity of comprehensively considering the compound effects of soil stratification characteristics and THM coupling mechanisms on site-specific seismic responses, thereby providing theoretical foundations for seismic-resistant design and dynamic response evaluation of stratified geological systems.