高饱和度含气砂力学特性试验及状态相关本构模拟 English Version
Experimental study of mechanical properties of gassy sand and state-dependent constitutive modeling
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摘要: 高饱和度含气砂（简称含气砂）中的气体以游离气泡的形式存在于土骨架之间，气相的特殊存在形式，使其基本性质不同于一般的非饱和土。目前，含气砂不排水应力-应变响应的试验研究还不充分，临界状态特征也还未清晰。为此，本文对配备双压力室体变量测的三轴试验系统进行改造，实现高饱和度含气砂的制备和三轴试验。基于改造后的含气土三轴试验系统，开展饱和砂排水三轴试验、饱和砂不排水三轴试验和含气砂不排水三轴试验，指出游离气体、初始孔隙比和初始平均有效应力对含气砂不排水应力-应变响应的影响、发现游离气体可以显著提高触发静态液化时的土体抗剪强度，增加触发静态液化所需要的轴向变形，从而提升其抵抗静态液化的能力，并证明含气砂和饱和砂临界状态特征的一致性。此外，本文给出了含气砂状态相关弹塑性本构模型，并证明了其描述含气砂物理力学响应的能力。Abstract: Gas trapped between the soil skeleton in quasi-saturated sand (gassy sand) takes on a special form, which gives it unique basic properties that differ from those of unsaturated soil. Currently, the undrained stress-strain response of gassy sand is insufficient and the critical state of gassy sand is not well-defined. For this purpose, the work modified a double walled triaxial testing system to achieve the preparation and test of gassy sand. Drained and undrained triaxial tests on saturated sand, as well as undrained triaxial tests on gassy sand, are conducted to analyze how entrapped gas affects the stress-strain response of gassy sand under undrained conditions. It was observed that the entrapped gas significantly increased the shear strength at the triggering of static liquefaction of gassy sand, augmented the axial strain required for initiating static liquefaction, and enhanced the ability of loose sand to resist static liquefaction. Besides, experimental evidence is provided to prove the consistency between the critical state characteristics of gassy sand and saturated sand. Moreover, this study provides a state-dependent model of gassy sand and demonstrates its effectiveness in capturing the mechanical behavior of gassy sand.
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