纤维和纳米材料改良花岗岩残积土的力学试验及机理研究

Mechanical test and mechanism study of granite residual soil modified by fiber and nanomaterials

在处理特殊土时,采用性能好、环保和成本低的材料加固土体有着非常重要的意义。为了研究玄武岩纤维和纳米氧化铁对花岗岩残积土力学性能的影响,采用单掺和复掺的方式,制备不同掺量的试样进行固结不排水三轴剪切试验,并取剪切后的土样进行扫描电镜试验分析其微观机理。试验结果表明:土样抗剪强度随玄武岩纤维掺量的增加呈先增大后减小的变化规律,在掺量为1%时出现峰值,土样抗剪强度随纳米氧化铁掺量的增加而呈单调增加的变化规律;两种改良方法均能较大幅度提升土体的黏聚力,对内摩擦角的提升效果不明显,此外,复合改良土样提升土体抗剪强度的效果比单掺改良土样更加明显;土体抗剪强度的提高是由玄武岩纤维与土体之间产生互锁网、纳米氧化铁填充土颗粒之间的空隙所致,采用复合改良土样的方式能有效改善花岗岩残积土的剪切强度特性。

When dealing with special soil,it is very important to choose environment-friendly and low cost materials with good properties for the strengthening.In order to study the effect of basalt fiber and nano-iron oxide on the mechanical properties of granite residual soil,samples with different dosages and mixing methods were prepared for the consolidation and undrained triaxial shear test,and the micro-mechanism of the processed samples was analyzed by scanning electron microscope(SEM).The experimental results show that the shear strength of soil samples first increases then decreases with the increase of the dosage of basalt fiber,and peaks when the dosage reaches 1%;whereas the shear strength of soil samples increases monotonously with the increase of nano-iron oxide content.Both the single agent and composite agents methods can improve the cohesion of the soil,but not the internal friction angle.In addition,the effect of composite modified soil sample on soil shear strength is more obvious than that of single modified soil sample.The improvement of soil shear strength is contributed by the interlocking mesh between the basalt fiber and soil,and the filling of the gaps between soil particles by nano-iron oxide.The method of composite soil sample modification can effectively improve the shear strength characteristics of granite residual soil.