[S-CG48] Petrology, Mineralogy & Resource Geology

[SCG48-P12] Cross-scale comparison of water loss-expansion characteristics of mudstone and argillaceous siltstone under temperature effect

*ZhuoWu XIE¹, Guodong Zhang¹, SiXiang Ling¹, XiYong Wu¹, Qian Duan² (1.Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, 2.School of Mathematics, Southwest Jiaotong University)

Keywords:mudstone & argillaceous siltstone; , heat treatment temperature, microstructure, expansion characteristics

Moisture is the key factor determining the expansion performance of muddy soft rock, which seriously affects the safety of high-speed railway embankment. The red bed of the Shaximiao Formation in central Sichuan (commonly mudstone-argillaceous siltstone interbed) was tested for the whole process of weight loss and expansion at different drying temperatures, and the two rocks were analyzed by field emission electron microscopy and N₂ adsorption porosity measurement. The microstructural differences and microscopic pore characteristics of sample heat treatment were studied. The results show that: (1) During the high-temperature drying process, the weight loss curve of mudstone is "convex", and the weight loss curve of argillaceous siltstone is "concave", and this difference weakens with the decrease of drying temperature; The two samples in the sample are both "convex"; (2) The heat treatment process will significantly increase the total amount of pores in the mudstone and change the distribution of pore throats, and the distribution of mudstone mesopores has changed from "single peak" to "double peak"; The mesopores of argillaceous siltstone show a negative correlation with temperature. (3) The cementation degree of argillaceous siltstone is much greater than that of mudstone, and a large amount of chlorite is filled in the cracks between the aggregate structures. Compared with the block cluster structure in argillaceous siltstone, the "face-to-face" and interlayer opening structure in mudstone is more conducive to the release of expansibility.(4) The expansion laws of the two rock samples with similar sedimentary conditions and similar mineral composition are constrained by the differences in their microstructures, and the difference in drying temperature has less effect on argillaceous siltstone than mudstone. The research results reveal the microstructure characteristics of mudstone and argillaceous siltstone under different heat treatment temperatures, and prove the influence of drying temperature and the structural properties of specific samples on the expansion law.