温度效应下考虑非达西渗流的大应变软土地基非线性固结分析

    Nonlinear Consolidation Analysis of Soft Soil Foundations Considering Large Strain and Non-Darcian Flow under Temperature Effects

    • 摘要: 热固结理论在地源热泵、能量桩、及供热管道等工程中得到广泛应用,这些工程涉及岩土体中热-水-力的耦合作用,而温度变化对土体的物理力学性质具有显著影响。研究表明,温度升高会导致土体沉降量增加,此时继续沿用传统的小变形理论进行固结计算将产生较大的误差。此外,温度改变会影响土体的渗透性,但现有分析多基于达西定律,忽略了非达西流效应对热固结过程的影响。本文基于Hansbo渗流模型,综合考虑升温对大应变饱和土体物理力学性质的影响,推导了非线性固结与热传导的控制方程,并给出了孔压和固结度的数值解答。通过特定工况下的对比验证了理论的有效性与适用性,重点研究了大应变与非达西渗流在热固结中的影响,结果表明:温度荷载和非达西渗流的作用均能弱化大、小应变模型间固结度的差异。土体在升温条件下可有效缓解非达西效应明显导致孔压累积的问题。在不同的先期固结压力下,温度对沉降的促进作用几乎相同。多级加载时土层上部的孔压峰值始终维持低水平,且升温作用会使其进一步降低。

       

      Abstract: The theory of thermal consolidation is widely applied in engineering projects such as ground source heat pumps, energy piles, and heating pipelines, which involve thermo-hydro-mechanical coupling in geomaterials. The physical and mechanical properties of soils are significantly affected by temperature changes. It has been shown that elevated temperatures result in increased soil settlement, and the continued use of traditional small-strain consolidation theories can lead to substantial errors in calculations. Moreover, soil permeability is altered by temperature variations, but most existing analyses are based on Darcy flow law, with the impact of non-Darcian flow on the thermal consolidation process often being neglected. In this study, the Hansbo’s flow model is utilized to account for the effects of temperature rise on the physical and mechanical properties of large-strain saturated soils. Governing equations for nonlinear consolidation and heat conduction are derived, and numerical solutions for excess pore water pressure and consolidation degree are presented. The validity and applicability of the theoretical model are verified under specific conditions. The impacts of large strain and non-Darcian flow on thermal consolidation are thoroughly investigated. It is demonstrated that temperature loading and non-Darcian flow both reduce the discrepancies in consolidation degrees between large- and small-strain models. The significant excess pore water pressure accumulation caused by non-Darcian effects is shown to be effectively mitigated under heating conditions. Additionally, the effect of temperature on promoting settlement is found to remain nearly constant under varying preconsolidation pressures. During multi-stage loading, the peak excess pore water pressure in the upper soil layer is consistently maintained at a low level, with heating further reducing it.

       

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