循环荷载作用下泥炭质土的动变形特性试验研究

Experimental study of dynamic deformation properties of peaty soil under cyclic loading

泥炭质土是一种具有明显区域性的特殊土。通过一系列不同围压、固结比、加载频率等条件下的分级加载动三轴试验,研究了昆明泥炭质土在循环荷载作用下的动变形特性。从动骨干曲线、应力-应变滞回曲线和动弹性模量等方面重点分析了围压、固结比、加载频率对泥炭质土变形特性的影响。试验结果表明:泥炭质土的动应变随动应力幅值非线性增长,且存在某一临界动应力,当动应力幅值达到临界动应力值后,应变急剧增长,土体结构发生破坏;围压对泥炭质土动变形的影响最为显著,固结比次之,加载频率最小;固结比对泥炭质土动变形的影响程度依赖于围压,围压越大,固结比的影响越明显;相同循环振级下,泥炭质土的弹性变形随围压和固结比增大而减小,加载频率愈低,土体的弹性变形愈大;随着循环振次的增加和振级水平的提高,泥炭质土刚度逐渐下降,塑性变形产生并累积增长,围压和固结比越大,加载频率越低,泥炭质土的塑性变形越大。

The peat soil is a special soil which has obvious regional characteristics.A series of staged cyclic loading triaxial tests is performed to investigate the dynamic deformation properties of the peat soil in Kunming under the conditions of different confining pressures,different consolidation ratios,and different loading frequencies.The effects of confining pressure,consolidation ratio,and loading frequency on the deformation properties of the peat soil subjected to cyclic loading are evaluated through analyzing the dynamic backbone curve,stress-strain hysteretic curve and dynamic elastic modulus.Results show that the dynamic strain of peat soil increases nonlinearly with the dynamic stress amplitude,and there exists a critical stress value at the backbone curve.When the dynamic stress amplitude acting on the soil reaches its critical stress value,the strain of peat soils grows rapidly,and then the soil structure is destroyed;the confining pressure has the most significant effect on the dynamic deformation properties of peat soil,followed by the consolidation ratio,loading frequency is the minimum;the effect of consolidation ratio on the dynamic deformation properties of peat soil depends on the value of confining pressure,which is greater under higher confining pressure;the elastic deformation of peat soil decreases as confining pressure and consolidation ratio increase,while increases as loading frequency decrease,at the same loading level;the stiffness of peat soil decays as loading cycles and loading level increase,the plastic deformation appears and cumulatively grows up;the larger plastic deformation is observed in peat soil with increasing confining pressure and consolidation ratio,decreasing loading frequency.