The growth and melting of internal ice crystals reorganizing the pore structure and internal skeleton of soil-rock mixture (S-RM), which leads to the deterioration of the S-RM shear strength after freeze–thaw cycles and its strength characteristics after the cycles are different from the normal temperature one. Due to unclear S-RM strength deterioration mechanism after freeze–thaw cycles, stability of S-RM cutting slopes in cold regions cannot be effectively evaluated. In this paper, particle flow code (PFC) simulation as well as direct shear and nuclear magnetic resonance (NMR) tests were carried to study strength degradation behaviors and pore structure changes of S-RMs containing various amounts of rock after freeze–thaw cycles. The results show that the shear strength and internal friction angle of S-RM are no longer positively correlated with the rock content after the cycles, and the strength parameters will decrease at rock contents of above 45%. Based on the simulation test, shear band thickness variation after the cycles was quantitatively evaluated, and an innovative method to obtain the fluctuation value of shear failure surface was proposed. It is found that the change laws of shear band thickness and failure surface fluctuation value with rock content after the cycles are consistent with that of shear strength, and they all reach the maximum value when the rock content is 45%. Fractal theory was introduced for quantitative evaluation of changes in S-RM pore structure after the cycles, and combined with the strength parameter attenuation, the strength deterioration mechanism of S-RM was revealed: The deterioration of shear strength in samples containing low rock content is mainly due to changes in the contact form between particles caused by internal inclusion structure formation after the cycles. The deterioration of S-RM with rock content of 55% and 65% is mainly due to attenuation of the internal skeleton effect caused by the appearance of overhead structures. The internal pores and skeleton structure of the sample with 45% rock content have little change, so the attenuation changes of the strength parameters and the undulation value of the failure surface are minimal.

内部冰晶的生长和融化重组了土壤-岩石混合物（S-RM）的孔隙结构和内部骨架，导致冻融循环后的S-RM剪切强度及其在循环后的强度特性下降与常温不同。由于冻融循环后 S-RM 强度退化机制尚不明确，无法有效评价寒区 S-RM 边坡的稳定性。在本文中，通过粒子流代码（PFC）模拟以及直接剪切和核磁共振（NMR）测试，研究了含有不同数量岩石的S-RMs在冻融循环后的强度退化行为和孔隙结构变化。结果表明，循环后S-RM的抗剪强度和内摩擦角与含岩量不再呈正相关，在含岩量45%以上时强度参数会下降。在模拟试验的基础上，定量评价循环后剪切带厚度的变化，提出一种创新的获得剪切破坏面波动值的方法。研究发现，循环后剪切带厚度和破坏面波动值随含岩量的变化规律与抗剪强度的变化规律是一致的，均在含岩量为45%时达到最大值。引入分形理论定量评价循环后S-RM孔隙结构的变化，并结合强度参数衰减，揭示了S-RM的强度劣化机制：低含岩量样品的抗剪强度劣化主要是由于循环后内部包裹体结构形成导致颗粒之间的接触形式发生变化。岩石含量为55%和65%的S-RM的劣化主要是由于架空结构的出现导致内部骨架效应衰减。含岩量为45%的试样内部孔隙和骨架结构变化不大，因此强度参数的衰减变化和破坏面的起伏值最小。低岩石含量样品的抗剪强度劣化主要是由于循环后内部包裹体结构形成导致颗粒之间的接触形式发生变化。岩石含量为55%和65%的S-RM的劣化主要是由于架空结构的出现导致内部骨架效应衰减。含岩量为45%的试样内部孔隙和骨架结构变化不大，因此强度参数的衰减变化和破坏面的起伏值最小。低岩石含量样品的抗剪强度劣化主要是由于循环后内部包裹体结构形成导致颗粒之间的接触形式发生变化。岩石含量为55%和65%的S-RM的劣化主要是由于架空结构的出现导致内部骨架效应衰减。含岩量为45%的试样内部孔隙和骨架结构变化不大，因此强度参数的衰减变化和破坏面的起伏值最小。