总氮对土物理力学性能影响的试验研究

通过室内试验，考察了去离子水及不同浓度总氮溶液对土体物理力学性能的影响，并通过土体矿物成分含量及微观形貌分析，对总氮溶液与土体作用机制进行了初步探讨。结果表明，总氮对土体物理力学性能影响明显：（1）土体塑性指数、相对密度和有效黏聚力随总氮溶液浓度增大而减小，有效内摩擦角随溶液浓度的增大而增大；（2）各浸泡条件下，土体应力-应变关系曲线变化规律基本一致，均呈应变硬化现象，土体剪切峰值随总氮溶液浓度的增大先减小后增大；（3）孔隙水压力随轴向应变的增加先增加，然后缓慢降低，最后曲线逐渐趋于水平，表现出较大的剪胀性；（4）总氮溶液与土体间相互作用主要包括离子交换作用、微生物分解作用和溶蚀及胶结作用，这些作用通过改变土体的矿物成分含量，使其微观形貌及孔隙特征发生明显变化，最终导致土体的宏观力学特性改变。

Effect of total nitrogen on physico-mechanical performance of soil

In order to find the effect of total nitrogen on soil physico-mechanical performance, samples have been tested with deionized water and total nitrogen solution with different concentrations in laboratory, and the interaction mechanisms of soil and total nitrogen was revealed by mineral and microscopic analysis. The results show that the total nitrogen has significant influence on soil physico-mechanical performance. Plasticity indices, specific density and effective cohesive strength of samples decrease with increasing of concentration of total nitrogen solution, and the effective friction angle increases; Strain hardening phenomenon appears in the stress-strain relationships, and the variation of stress-strain curves of samples soaked in deionized water and total nitrogen solution are almost the same. The peak shear strength of samples manifests as a trend of decreases at first and then increases with increasing of concentration of total nitrogen solution; with the increase of axial strain, pore water pressure of sample is increased at first and then decreased gradually, and tends to be horizontal direction in the end; while the shear dilatation is evident; mineral composition, microstructure and physico-mechanical performance of soil are affected by the interaction between total nitrogen and soil, including ion exchange, microbial decomposition, dissolution and cementation.