倾斜沉积砂土空心圆柱试样制备方法研究

Preparation method of hollow cylindrical sample of inclined sedimentary sand

受现有土工试验仪器功能的限制,目前仅能实现绕单一应力主轴旋转的应力路径,对应力绕2个及以上应力主轴旋转的研究仍是土力学的空白。从控制试样沉积面旋转和控制应力加载方向2个角度,系统梳理应力方向依赖性的试验研究方法。设计研发倾斜沉积砂土空心圆柱试样的制样装置,在砂雨法制备空心圆柱试样技术的基础上,通过控制电机转速使成样模具整体定速转动,使得砂土颗粒在重力和离心力的作用下沿径向倾斜沉积,进而制得沉积面与水平面夹角为定值的倾斜沉积砂土空心圆柱试样,实现试样沉积面绕σ_(3)的定向旋转。再借助扭剪仪控制应力绕σ_(2)旋转,即可实现对应力的3个大小量和2个方向量的定量控制。采用生石灰-彩砂试制18个沉积面倾斜的试样,对沉积面倾角进行图像分析和统计学分析,结果表明,所制试样的沉积面倾角与理论计算值较为接近,倾角偏差的分布较符合正态分布,倾斜沉积砂土空心圆柱试样制样装置的制样可靠度较高,为进一步揭示岩土材料特殊的力学性质、丰富和完善土力学理论奠定了技术基础。

Limited by the functions of existing geotechnical test instruments,the stress path can only be controlled to rotate around a single stress axis at present.The research on the rotation of stress around two or three stress axes is still a blank in soil mechanics.In this paper,the experimental research methods of stress directional dependence are systematically combed from two aspects:controlling the rotation of sample deposition surface and controlling the principal stress direction.The sample preparation device of hollow cylindrical sample of inclined sedimentary sand was designed and developed.Based on the technology of sand rain method,the whole mould rotates at a constant speed by the motor of the sample preparation device.So that sand particles are inclined deposited along the radial direction under the action of gravity and centrifugal force.Then,the inclined sedimentary sand hollow cylindrical samples with a fixed angle between the deposition surface and the horizontal plane can be prepared.The directional rotation of the sample deposition surface around σ_(3)is realized.Then,with the help of hollow cylinder apparatus to control the stress rotating angle around σ_(2),controlling of the three magnitudes and two directions of the three principal stresses can be achieved.Eighteen samples with inclined sedimentary surface were produced with the mixture of quicklime and colored sand.Image analysis and statistics analysis on the inclination of sedimentary surface show that inclined angles of deposited surfaces are close to the theoretical value,and the distribution of inclined angle deviation conforms to the normal distribution.It proves that the sample preparation device of hollow cylindrical sample of inclined sedimentary sand is reliable.It lays the foundation for further revealing the special mechanical properties of geotechnical materials and enriching and perfecting the theory of soil mechanics.