木质素改良红黏土的抗剪能力及动剪切特性研究

Study on shear resistance and dynamic shear properties of lignin modified red clay

针对红黏土具有高含水率、高塑性、高孔隙比等不良工程性质,不宜直接作为路基填料这一现象,采用静三轴、动三轴试验方法研究了干湿循环下木质素改良红黏土抗剪强度指标(黏聚力和内摩擦角)及动剪切模量变化规律。结果表明,木质素可以显著提高红黏土的抗剪强度指标和动剪切模量,抗剪强度指标及动剪切模量随木质素掺量的增加先增加后减小,最佳掺量在9%~12%。木质素改良红黏土动剪模量与动应变关系可用H-D模型表示。改良土与素土最大动剪切模量与木质素掺量关系可以用三次函数表示。素土与改良土最大动剪切模量与围压关系可以用过原点的线性函数表示。经历相同次数的干湿循环,改良土抗剪强度指标及动剪切模量均较素土有明显提高,抗剪强度指标与干湿循环次数关系可以用倒数函数表示。建议在实际工程中木质素掺量为9%,养护时间为1 d。

Aiming at the problem that red clay has poor engineering properties such as high moisture content,high plasticity and high void ratio,so it is not suitable to be directly used as subgrade filler,static triaxial and dynamic triaxial tests were used to study the shear strength indexes(cohesion and internal friction angle)and dynamic shear modulus of lignin modified red clay under dry wet cycles.The results show that lignin can significantly improve the shear strength index and dynamic shear modulus of red clay.With the increase of lignin content,the shear strength index and dynamic shear modulus first increase and then decrease,and the optimal content is between 9%and 12%.The relationship between dynamic shear modulus and dynamic strain of lignin modified red clay can be expressed by H-D model.The relationship between the maximum dynamic shear modulus and lignin content of improved soil and plain soil can be expressed by cubic function.The relationship between the maximum dynamic shear modulus and confining pressure of plain soil and improved soil can be expressed by a linear function passing through the origin.After the same number of dry wet cycles,the shear strength index and dynamic shear modulus of the improved soil are significantly higher than those of the plain soil.The relationship between the shear strength index and the number of dry wet cycles can be expressed by the reciprocal function.It is suggested that the lignin content should be 9%and the curing time should be 1 day in the actual project.