高温高含冰量冻结砂土的三轴压缩力学特性

Experimental study on triaxial compression mechanical characteristics of warm and ice-rich frozen sand

摘要:

为深入研究高温高含冰量冻土的力学特性与变形机制,以不同含冰量的冻结砂土为研究对象,通过开展-1.5 ℃下的三轴压缩试验,讨论了围压和含冰量对冻结砂土力学特性的影响,并分析了常规饱和冻土与高含冰量冻土在变形机制上的差异。结果表明:针对砂土提出的“冰砂混合,分层压实,下部补水”的制样方法可制出土颗粒分布均匀的高含冰量饱和冻土试样；高含冰量冻结砂土与饱和冻结砂土的强度和体变差异很大,但不同含冰量的高含冰量冻结砂土的应力应变关系和体变很接近；不同围压下的67%含冰质量分数冻结砂土均为应变软化型,且随着围压的增大,试样应变软化的程度逐渐降低,体变逐渐由体胀向体缩转化；饱和冻结砂土受力时是由土颗粒、冰和未冻水共同承担；而高含冰量冻结砂土主要由冰直接承担外力,冰中夹杂的土颗粒间接地影响了冰的力学性质。

Abstract:

The mechanical characteristics of warm and ice-rich frozen sand are the key and difficult problems in frozen soil engineering. In order to study the frozen sand with different ice contents, triaxial tests at -1.5 ℃ were carried out on conventional saturated frozen sand and ice-rich frozen sand. Based on the experimental results, the effects of confining pressure and ice content on the mechanical characteristics of frozen sand are discussed. And the differences in deformation mechanisms between conventional saturated frozen sand and ice-rich frozen sand are analyzed. The results show that: the proposed method of "mixing ice particles and sand, compacting in layers, and replenishing water from below" can make ice-rich frozen sand with uniform distribution of soil particles. The strength and volumetric strain of ice-rich frozen sand differ greatly from conventional saturated frozen sand, but the stress-strain relationship and volumetric strain of ice-rich frozen sand with different ice contents are very close. The ice-rich frozen sand with 67% ice content under different confining pressure are strain-softening type; and with the increase of confining pressure, the degree of strain-softening gradually decreases, and the volumetric strain gradually transforms from volumetric dilation to volumetric contraction. The external force on conventional saturated frozen sand is shared by soil particles, ice and unfrozen water, while the external force on the ice-rich frozen sand is mainly borne directly by ice, in which the entrained soil particles indirectly affect the mechanical characteristics of ice.