冻融作用下木质素纤维改良黄土力学与热学特性试验研究

Experimental study of the mechanical and thermal properties of lignin fiber-stabilized loess under freeze-thaw cycles

冻融循环作用是造成寒区工程病害的主要因素之一。为探究冻融循环对木质素纤维改良黄土力学和热学的影响,通过轻型击实试验、冻融循环试验、不固结不排水三轴剪切试验、热常数分析试验和X射线衍射试验,以木质素纤维掺量、冻融循环次数和围压为变量展开研究。结果表明:随着掺量的增加,改良黄土的最大干密度降低,最优含水率升高;随着冻融循环次数的增加,试样的应力-应变曲线由应变硬化型向应变弱软化型转变;试样的质量损失率、破坏强度、弹性模量、黏聚力、内摩擦角和导热系数均随着冻融循环次数的增加呈下降趋势,在经历第1次冻融循环后衰减率最高,并且总是在掺量为5%时达到最大值;试样的破坏强度和黏聚力在经历6~9次冻融循环后趋于稳定;黄土及掺量为5%的改良黄土在X射线衍射分析中成分相似,未发现新的物质生成,因此,木质素纤维是一种绿色的物理固化材料。该研究成果可为寒区土体加固提供新思路。

Freeze-thaw cycle is one of the main factors cause engineering damage in cold regions. In order to investigate the effect of freeze-thaw cycles on the mechanical and thermal properties of lignin fiber stabilized loess,light compaction test,freeze-thaw cycles test,unconsolidated undrained triaxial shear test,thermal constant analysis test and X-ray diffraction test are used in this study. lignin fiber admixture,number of freeze-thaw cycles and envelope pressure are used as variables for this study. The results showed that the maximum dry density of the lignin fiber stabilized loess tend to decrease and the optimum moisture content tend to increase with increased admixture;As the number of freeze-thaw cycles increase,the stress-strain curve of the specimens change from strain-hardening to strain-weak softening. In addition,the rate of mass loss,break strength,modulus of elasticity,cohesion,angle of internal friction and thermal conductivity of the specimens all tended to decrease with the number of freeze-thaw cycles,with the highest decay rate after the first freeze-thaw cycle and always reach a maximum at a admixture level of 5%;the break strength and cohesion of the specimens stabilize after 6~9 freeze-thaw cycles;the loess and the composition of the lignin fiber-stabilized loess with 5% admixture was similar in the X-ray diffraction analysis and no new material was found to be produced;therefore,the lignin fiber is a green physically cure material. The results of this study can provide new ideas and methods for research related to soil stabilization and consolidation in cold regions.