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非饱和土三轴试验是测试土体非饱和力学参数、研究其变形机理和本构模型的重要手段之一。目前,大都以控制基质吸力的方式研究非饱和土,而施加吸力后达到水气平衡状态的过程非常缓慢,特别对于黏性土更为突出。其根本原因是水气平衡过程中试样的排水路径相对比较长。为此,提出了一套新的制样方法,该方法通过在三轴试样的轴心位置钻取一个小孔径的圆孔;然后,在圆孔内部充填标准细砂,把传统的轴向排水改成径向和轴向同时排水。通过物理试验和数值方法,分析了试样钻孔灌砂前后的吸力平衡时间和应力应变的差异性。结果表明,新的制样方法与传统方法相比其吸力平衡时间大约缩短3~4倍;置换砂率小于2%的情况下,轴心钻孔灌砂后对试样的变形基本没有影响。
Unsaturated soil triaxial test is one of the important means to test unsaturated soil mechanics parameters and study its deformation mechanism and constitutive model. At present, most studies on unsaturated soil by means of controlling the suction of the substrate, and the process of applying the suction to achieve the equilibrium state of water vapor is very slow, especially for the cohesive soil. The fundamental reason is that the drainage path of the sample in the process of water vapor balance is relatively long. To this end, a new sample preparation method is proposed by drilling a small hole with a small diameter at the axial center of the triaxial specimen. Then, a standard fine sand is filled inside the circular hole, and the traditional axial direction Drainage into radial and axial drainage at the same time. Through the physical experiment and the numerical method, the differences of the suction equilibrium time and the stress-strain before and after the borehole irrigation are analyzed. The results show that compared with the traditional method, the new sample preparation method can shorten the suction equilibrium time by about 3 ~ 4 times. When the replacement sand rate is less than 2%, the deformation of the sample has no effect after the shaft drilling and sand filling.