In order to study the influence of the intermediate principal stress coefficient and confining pressure on the strength and deformation of frozen sand, a true triaxial instrument was used to conduct equal-proportion increment loading tests under three-dimensional (3D) stress. Test results indicate that, under a 3D equal-proportion incremental loading stress path, the stress–strain curves of artificial frozen sand exhibit a trend of strain hardening, showing a strength increase upon increasing the intermediate principal stress coefficient and confining pressure. As the intermediate principal stress coefficient increases from 0 to 1, the intermediate principal stress direction changes from expansion to compression, while expansions occur in all minor principal strain directions, and the expansion continuously increases. When the intermediate principal stress coefficient is 0.25, the samples are in a plane strain state. As the intermediate principal stress coefficient increases, the cohesion of artificial frozen sand first decreases and then increases, while the internal friction angle continues to increase, and the failure stress ratio gradually decreases. The failure line of artificial frozen sand increases linearly under symmetrical stress with a low confining pressure. Multiple strength criteria for geotechnical materials are compared in the π-plane, and a shape function for artificial frozen sand is proposed. In combination with the yield functions for the meridian plane and the π-plane, a 3D strength criterion for artificial frozen sand under low confining pressure is proposed, and the shapes in the principal stress space and π-plane are obtained.

为研究中间主应力系数和围压对冻砂强度和变形的影响，采用真三轴仪进行三维（3D）应力下等比例增量加载试验。试验结果表明，在三维等比增量加载应力路径下，人工冻砂的应力-应变曲线呈现应变硬化趋势，随着中间主应力系数和围压的增加，强度增加。随着中间主应力系数从0增加到1，中间主应力方向由膨胀变为压缩，同时在所有次主应变方向都发生膨胀，并且膨胀不断增大。当中间主应力系数为 0.25 时，试样处于平面应变状态。随着中间主应力系数的增大，人工冻砂的内聚力先减小后增大，而内摩擦角继续增大，破坏应力比逐渐减小。人工冻砂破坏线在低围压对称应力作用下呈线性增加。土工材料的多个强度标准在 人工冻砂破坏线在低围压对称应力作用下呈线性增加。土工材料的多个强度标准在 人工冻砂破坏线在低围压对称应力作用下呈线性增加。土工材料的多个强度标准在π平面，并提出了人工冻砂的形状函数。结合子午面和π平面的屈服函数，提出了人工冻砂低围压三维强度准则，得到了主应力空间和π平面的形状。