基于蠕变试验的冻结红砂岩长期强度

人工冻结法以其独特的优势广泛应用于西部建井工程，因此研究岩石在冻结状态下强度特性尤其重要，基于冻结红砂岩蠕变试验，分别通过过渡蠕变法、等时应力-应变法、裂纹损伤应力法、稳态蠕变速率交点法得到冻结砂岩长期强度。结果表明：（1）通过过渡蠕变法可以得到冻结砂岩长期强度的取值范围，约为三轴压缩强度的45~65%左右；（2）体积应变等时曲线簇更加能够体现时间对岩石变形的关系，长期强度约为三轴压缩强度的48%左右；（3）稳态蠕变速率法能够较为简单的确定岩石长期强度，但因其方法本身具有一定的局限性，综合考虑三向蠕变速率，对其改进得到稳态蠕变速率交点法，可以更加精确反映砂岩强度，长期强度约为三轴压缩强度的49%左右；（4）引入裂纹体积应变计算方法，根据其与时间的关系得到裂纹体积应变等时曲线簇，得到的强度值与等时曲线法及其相近，因此裂纹损伤应力法也可作为确定岩石长期强度依据。将冻结红砂岩的长期强度作为监测冻结壁变形的标准，可为评价冻结壁蠕变诱发失稳破坏提供理论支撑和试验依据。

Long-term strength study of frozen red sandstone based on creep test

The artificial freezing method is widely used in western well construction projects due to its unique advantages. Therefore, it is particularly important to study the strength characteristics of the rock in the frozen state. Based on the creep test of frozen red sandstone, the long-term strength of the rock was obtained by the transitional creep method, isochronous stress-strain method, crack damage stress method, steady-state creep rate intersection method. The results show that: (1) The long-term strength of frozen sandstone can be obtained by the transition creep method, which is about 45-65% of the triaxial compressive strength. (2) The volumetric strain isochronous curve cluster can better reflect the relationship between time and rock deformation, and the long-term strength is about 48% of the triaxial compressive strength. (3) The steady-state creep rate method can easily determine the long-term strength of the rock. However, due to its own limitations, considering the three-dimensional creep rate comprehensively, the steady-state creep rate method is improved to obtain the steady-state creep rate intersection method, which can reflect the strength of sandstone more accurately. The long-term strength is about 49% of the triaxial compression strength. (4) The calculation method of crack volume strain is introduced, and the isochronous curve clusters of crack volume strain are obtained according to its relationship with time. It is found that the long-term intensity value is very similar to the isochronous curve method. Therefore, the crack damage stress method can also be used as a basis for determining the long-term strength of rocks. The long-term strength of frozen red sandstone is used as the standard for monitoring the deformation of the frozen wall, which provides theoretical support and experimental basis for evaluating the instability and failure induced by the creep of the frozen wall.