Abstract
The creep characteristics of rocks are very important for assessing the long-term stability of rock engineering structures. Two loading methods are commonly used in creep tests: single-step loading and multi-step loading. The multi-step loading method avoids the discrete influence of rock specimens on creep deformation and is relatively time-efficient. It has been widely accepted by researchers in the area of creep testing. However, in the process of multi-step loading, later deformation is affected by earlier loading. This is a key problem in considering the effects of loading history. Therefore, we intend to analyze the deformation laws of rock under multi-step loading and propose a method to correct the disturbance of the preceding load. Based on multi-step loading creep tests, the memory effect of creep deformation caused by loading history is discussed in this paper. A time-affected correction method for the creep strains under multi-step loading is proposed. From this correction method, the creep deformation under single-step loading can be estimated by the super-position of creeps obtained by the dissolution of a multistep creep. We compare the time-affected correction method to the coordinate translation method without considering loading history. The results show that the former results are more consistent with the experimental results. The coordinate translation method produces a large error which should be avoided.
Highlights
Time-dependent behavior is one of the most important properties of geomaterials, such as rock and soil
To validate the time-affected correction method proposed in this paper, we calibrated the creep parameters based on the experimental curves under single-step loading, and we used the same creep parameters to estimate the creep curves under multi-step loading
The memory effect of creep deformation caused by loading history is discussed
Summary
Time-dependent behavior is one of the most important properties of geomaterials, such as rock and soil. It is worth noting that it is very difficult to avoid the impact of the heterogeneity of the material on creep test results (Yu et al [37]) Another widely used method is the multi-step loading method. It is possible to estimate the creep curves of several specimens under different single-step loading by one multi-step creep test under several loading steps This method, using specific experimental procedures and a graph method, established the creep deformation super-position law, which is effective regardless of whether the time-effect is linear or non-linear. Many geotechnical materials have significant rheological and memory-effect properties, and for multi-step loading creep testing, the loading history needs to be considered in order to better understand the creep results. We propose an estimation history effect in multi-step loading creep tests
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