# Study on Failure Mechanism of Mudstone Based on Digital Core and Digital Volume Correlation Method
## 6 Conclusions  
In this paper, mudstone was taken as the research object, and the failure mechanism of mudstone was studied according to rock microscopic physical property analysis, uniaxial in situ CT scanning, digital core reconstruction, pore network extraction, mineral composition, and pore structure. The following conclusions were drawn:  
1. The diagenetic mineral composition of mudstone was relatively simple, being mainly composed of brittle materials such as quartz and clay minerals, and the proportion of brittle minerals was relatively high, which was the main reason for the high strength of mudstone. Moreover, through the scanning electron microscope, it was found that the brittle mineral quartz and so on often exist in the form of agglomerated strips in the mudstone, resulting in the formation of structural weak surfaces on different mineral interfaces. These results are similar to those reported by [PERSON] et al. (2013).
2. The digital core models of mudstone at different loading stages were established by using a uniaxial loading in situ CT scanning test system. There were a large number of primary intergranular pores near the mineral accumulation zone, and the connectivity of pores will gradually increase with the increase in axial load. Macroscopically, the porosity of the rock increased, and cracks gradually appeared, with the internal pores being abnormally developed. When the rock reached the critical state of failure, the throat number and coordination number of pores clearly increased.
3. There was no obvious difference in the distribution of mineral particles of different sizes, and the interior of mudstone was mainly affected by a large number of small size mineral particles, indicating that the slip between mineral zones was mainly dominated by small-size minerals.  
Figure 18: Variation graph of volume strain mean and equivalent strain mean. (**a**) 0 MPa. (**b**) 18.5 MPa. (c) 48.5 MPa. (**d**) 67.5 MPa.  
* The final propagation shape of the crack was very consistent with that of the mineral zone, indicating that it was easy to form a weak surface in the aggregated mineral zone, and the aggregated mineral zone under loading could easily produce local deformation, which is related to the mechanical properties of the mineral zone and its surrounding rock matrix. When rock breaks, it is easy to produce along the junction of the two kinds of minerals. The results are in good agreement with similar study by [PERSON] et al. (2019).
* The displacement in the polymeric mineral zone was small, the deformation displacement of the rock skeleton dominated by clay minerals near the quartz mineral zone was larger, and the stronger quartz minerals restrained the rock skeleton deformation in the region.  
Methodology, D.D.; validation, D.D., X.C. and X.W.; formal analysis, X.W.; investigation, X.C.; resources, J.S.; data curation, D.D.; writing--original draft preparation, D.D. and X.C.; writing--review and editing, X.F.; visualization, X.C.; supervision, X.F.; project administration, D.D.; funding acquisition, D.D. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Chinese National Natural Science Foundation (no. 51304143) and the Chinese National Natural Science Foundation (no. 51604184).  
Informed Consent Statement: Informed consent was obtained from all subjects involved in the study.  
The authors declare no conflict of interest.