南京盾构渣土工程特性及其微观结构

城市地铁建设将产生大量的盾构渣土,为探讨泥态废弃物的充分处理和资源化利用,本文以南京地铁盾构渣土为研究对象,进行无侧限抗压强度,侧限压缩和抗剪强度等室内试验得到其基本物理力学特性,分析其力学性质随风干天数增加的变化规律,并观测风干至恒重试样的微观结构形貌特点。结果表明：该区域盾构渣土成分主要以石英、方解石等为主,具有流塑性、天然含水率高和级配良好等基本物性特征,随着风干天数的增加,无侧限抗压强度不断增大,强度增量系数降低,压缩曲线的整体斜率增大,极限压应变前的压密阶段和屈服阶段的范围减小；压缩曲线在低压阶段能产生较大的压缩变形而高压阶段压缩变形有限,压缩性类别由高压缩性向中等压缩性转变；抗剪强度持续增大,内摩擦角增长幅度缓慢,而粘聚力增长幅度较急剧。微观结构表明试样具有大量的团聚体主要以边-面、面-面的形式接触,接触较为松散,外包颗粒,结构易发生错位移动,符合本文所测中高压缩性和低剪切强度特征。此研究成果能够为我国盾构渣土的再利用提供可靠的基础研究。

Engineering Properties and Microstructure of Shield Muck in Nanjing

The construction of urban metro could produce a large amount of shield slag. In order to explore the adequate treatment and resource utilization of mud waste, this paper took Nanjing subway shield slag as the research object and conducted indoor tests of unconfined compressive strength, confined compression and shear strength to obtain its basic physical-mechanical properties. The changes of mechanical properties with the increase of air-drying days were analyzed, and the microstructural morphological characteristics of air-drying to constant weight specimens were observed. The results presented that the shield residue was mainly composed of quartz and calcite, and possessed basic physical characteristics including flow plasticity, high natural water content and ideal gradation. With the increase of air-drying days, the unconfined compressive strength increased continuously, the strength increment coefficient decreased, the overall slope of the compression curve increased, and the range of the compression-density stage and yielding stage before the ultimate compressive strain decreased. The compression curve could generate large compressive deformation in the low-pressure stage and limited deformation in the high-pressure stage. The compressibility category changed from high to medium level. The shear strength continued to increase, the internal friction angle increased slowly, while the cohesion increased significantly. The microstructure showed that the specimen possessed multiple agglomerates mainly in the form of edge-face and face-face contacts. The contact was looser, outer wrapped particles, and the structure was prone to dislocation movement, in line with the high compressibility and low shear strength characteristics measured in this paper. This research result could provide basic research for the domestic reuse of shield slag.