# Compressive Behavior of Oil Shale with Calcareous Concretion: Parametric Study
###### Abstract  
The non-uniformly distributed calcareous concretion among the oil shale in the Junggar basin of China has led to the difficulty in achieving the slope stability. This paper presents the numerical simulation of the behavior of oil shale with calcareous concretion via the Particle Flow Code (PFC2D) program based on the trial experimental test results. The critical parameters investigated in this research covered the size, distribution, strength, and number of the calcareous concretion. The following conclusions can be drawn based on the discussions and analysis: (1) the hard concretion always results in the high compressive strength of the specimen compared with that without correction; (2) when the radius of the concretion size raised from 2.5 mm to 20 mm, the peak strength of tested specimens is approximately 50 MPa, whereas, the specimen with large concretion is much more ductile under compression; (3) the compressive behavior of tested specimens is similar even when the position of the concretion is variable; and (4) different from the specimens with only one concretion, these specimens contained two concretions featured with the double \"X\" failure mode. Meanwhile, the peak strength of the specimens with two hard concretions is about 2.5 times that of its counterparts with two soft concretions. The numerical simulation results are meaningful in guiding the design and analysis of the oil shale slope with the concretion. oil shale; calcareous concretion; compressive behavior; PFC2D; numerical simulation 2020 2020 23 November 2 shale rock, will generally results in the unique mechanical behavior [15; 16]. As a typical sedimentary shale rock, there are also many concretions observed in the Junggar Basin. These randomly distributed concretions (see Figure 1) will lead to the side effect on the stability of slope, when the rock mass is extracted via open-pit mining. In order to investigate the behavior of rock mass containing the concretions, much experimental and theoretical research was previously conducted. As documented in several literature reviews [18; 19; 20], it is not easy to obtain the natural rock samples containing the same concretion from the laboratory, and thus the result of which is not always reasonable. To fill the research gap and make sure the experimental tests are repeatable, the rock-like material was developed to get the identical specimens containing concretions as designed [9]. Even though the use of rock-like material provided the effective method to obtain the homogeneity specimens, the minor cracks or fractures initially distributed in the rock mass are usually neglected. To change the current situation with the use of rock-like material in the reproduction of the rock mass with concretions further, [PERSON], [PERSON] et al. proposed the new experimental design program [20]. In their research, the specimens were drilled from the single rock mass firstly, and then the holes were cut from the prepared rock sample. After that, the fresh mixture was grouted into these holes to fabricate the rock specimen with concretions. With the wide use of the large storage computing machine, the numerical simulation is accepted by more and more researchers, Numerical modelling is regarded as the other alternative option to understand the behavior of the rock mass with concretion better [21]. Among them, the particle flow code (PFC) program is believed to be one of the most powerful programs for mining engineering, in which the research objective is made of grain particles and is naturally heterogeneous [22; 23]. It was well used in simulating the specimens made of different materials, such as the mixture of soil and rock [24] and the representative rock samples with the single crack [25].