In the upper soft and lower hard composite strata, it is very difficult to sample the rock and test the mechanical properties of the samples. The study of the mechanical properties of similar material samples by artificial manufacture may enable an alternative method to solve this problem. Therefore, the feasibility of artificial sample preparation and the test of mechanical properties of rock samples in the composite strata become the key to solve the study of mechanical properties of the upper soft strata and the lower hard composite strata. For this purpose, the artificial composite samples composed of two kinds of materials with different strengths were prepared by using cement and kaolin as similar materials. Through the uniaxial compression test of artificial composite rock samples, the effects of the strength ratio of similar materials and the thickness ratio of higher strength materials on the mechanical properties of composite specimens were analyzed. The results of uniaxial compression test show that artificial similar materials could be used to simulate the composite rock samples which are difficult to sample. Without considering the structural interface effect, the greater the strength ratio of similar materials, the greater the impact on the overall strength of composite specimens. The change of volume proportion of high-strength materials has a significant impact on the overall strength of composite specimens. Moreover, the numerical simulation and the experimental stress-strain curves both show a similar trend, indicating that the deformation of the composite strata mainly occurs in the soft part. The research results can provide reference for the test and analysis of mechanical properties in similar complex strata with difficult sampling.

中文翻译：

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软硬复合地层岩样的单轴压缩力学特性

在上软复合层和下硬复合层中，很难对岩石取样并测试样品的力学性能。通过人工制造对相似材料样品的机械性能进行研究可能会为解决该问题提供一种替代方法。因此，在复合地层中进行人工样品制备和岩石样品力学性能测试的可行性，成为解决研究上部软地层和下部硬质复合地层力学性能的关键。为此，以水泥和高岭土为相似材料，制备了两种强度不同的人造复合材料样品。通过人造复合岩石样品的单轴压缩试验，分析了相似材料的强度比和高强度材料的厚度比对复合材料试样力学性能的影响。单轴压缩试验结果表明，人工相似材料可用于模拟难以采样的复合岩石样品。如果不考虑结构界面效应，相似材料的强度比越大，对复合材料试样整体强度的影响越大。高强度材料的体积比例的变化对复合材料试样的整体强度有重大影响。而且，数值模拟和实验应力-应变曲线都显示出相似的趋势，表明复合地层的变形主要发生在软部分。