# Experimental Study on Shear Creep and Long-Term Strength of Clay-Type Muddy Interlayer
[29], based on the shear creep mechanics test of the interlayer dislocation zone of a high abutment slope rock mass, studied the interlayer dislocation zone shear creep mechanical properties and proposed a creep constitutive equation considering the accelerated creep process. In the construction of underground structures such as tunnel excavation, it is often necessary to consider the interaction between the tunnel lining structure and the surrounding soil [30; 31]. [PERSON] et al. [32] investigated the load-bearing behavior of tunnel-type anchor rods in underlying soft interlayered soft rocks through on-site model testing and numerical simulation. [PERSON] et al. [33] took the soft interlayer of a potential landslide zone in an open-pit limestone mine in Sichuan Province as the research object, and conducted ring shear test analysis in the various strength and deformation properties of weak interlayers under different water contents and normal stresses. Scholars have conducted extensive experimental research on muddy interlayers; however, there is a lack of research on \"lower-quality\" classifications within muddy interlayers, such as clay-type muddy interlayers. A clay-type muddy interlayer is defined as having a clay content greater than 20%, a gravel content less than 10%, and the sum of gravel and sandy particles greater than fine particles [1]. Clay-type muddy interlayers further develop from the formation of muddy interlayers and can gradually evolve into multiple layers. Its degree of clay mineralization is high, making creep more likely to occur. As a unique type of muddy interlayer, they possess representativeness and research value. [PERSON] et al. [3] reported that muddy interlayers are widely distributed in the red bed regions of Southwest China. They are the poorest engineering features in rock masses on slopes and are critical factors in controlling geological hazards in the red bed regions of Southwest China. Muddy interlayers often lead to various engineering geological problems and, therefore, studying them is of significant engineering importance. In the long-term creep process of clay-type muddy interlayers within slopes containing multiple layers of muddy interlayers, the presence of multiple layers of clay-type muddy interlayers sandwiched between relatively hard rock masses can pose significant risks, similar to a \"sandwich\" structure. We discovered that the sampling site had poor engineering conditions, with 13 layers of muddy interlayers superimposed. Other scholars' sampling sites also had unfavorable engineering conditions, but the occurrence of 13 layers of muddy interlayers superimposed has not been previously reported. Due to certain limitations, researchers have not conducted further experimental studies on clay-type muddy interlayers. These interlayers are located within unstable slopes, have thin thickness and on-site strength testing primarily relies on large-scale in situ tests, which are costly. Obtaining undisturbed samples is also challenging, and conducting a limited number of on-site tests often fails to yield convincing results. In addition, through indoor direct shear-creep tests, it is more convenient to observe how its deformation changes over time under the influence of normal stress, which is the creep behavior. To sum up, a great deal of research has been carried out on the creep characteristics of weak interlayer and muddy interlayer, which has always been a research hotspot. Because of the difficulty of sampling in the field, the field test is expensive, a small number of experiments are difficult to obtain convincing results and the indoor creep experiment takes a long time, and the creep experimental study of clay interlayer has not been reported. The study of its creep characteristics and long-term strength can fill the gap in the study of muddy interlayer and provide a powerful reference for its research.