非饱和固化淤泥的力学及体变特性试验研究

Experimental study on mechanical and volumetric properties of unsaturated solidified silt

由于降雨、水位升降等自然因素,固化淤泥作为填土材料使用时,其饱和度(基质吸力)常处于变动状态,使固化淤泥力学及体变特性发生改变,对土工构筑物的安全带来潜在隐患。鉴于此,本文通过对不同基质吸力、净围压下的三轴固结排水剪切试验,探讨了基质吸力和净围压对非饱和固化淤泥力学及体变特性的影响。结果表明:随着净围压增大,基质吸力的强度贡献减小,100kPa净围压时基质吸力的强度贡献十分显著,300kPa净围压时基质吸力强度贡献则不明显。当基质吸力小于残余值时,固化淤泥试样的抗剪强度、无侧限抗压强度、粘聚力均随基质吸力增大呈线性增长,但当基质吸力大于残余值时强度增幅均下降,说明基质吸力大于残余值时强度贡献减小。剪切过程中试样均表现为体缩且随基质吸力增大体缩变形减小。吸力摩擦角在土-水特征曲线边界效应区和过渡区之间时几乎不变,进入残余区后开始下降。

When the solidified silt is used as filling material, the degree of saturation(matric suction) is usually in a state of change due to the seasonal rainfalls and fluctuations of water level, resulting in variation of mechanical behaviours and volumetric strain characteristics of the solidified silt. The variation of mechanical behaviours and volumetric strain characteristics brings potential hidden dangers to the safety of the geotechnical structures. Given this, several consolidated drained triaxial tests under different matric suctions and net confining pressures were carried out, the influences of matric suction and net confining pressure on the mechanical behaviours and volumetric properties of unsaturated solidified silt are investigated in this paper. The results show that, the strength contribution of matric suction decreases with the increase of net confining pressure. In addition, significant contribution of matric suction can be observed under net confining pressure of 100 k Pa, while the contribution of matric suction decreased under net confining pressure of 300 k Pa. When the matric suction is lower than the residual value, it can be found that the three indexes increase linearly with the matric suction, including the shear strength, unconfined compressive strength and cohesion of the solidified silt. On the contrary, the strength growthing rate decreases when the matric suction exceeds the residual value, indicating that the strength contribution decreases when the matric suction is greater than the residual value. During the shearing process, compressive volume strain is observed for the solidified silt, and the compressive volume strain decreases with the increase of matric suction. Additionally, the suction friction angle maintains constant when the suction locates between the boundary effect zone and the transition zone of the soil-water characteristic curve, while the suction friction angle decrease when the suction locates on the residual zone.