A Case Study of Thaumasite Sulfate Attack in Tunnel Engineering
Table 2
Identification results of surrounding rock samples in section YK34 + 500.
No.
Test items
Test results/descriptions
1
Name of rock sample
Gypsum rock
2
Naked-eye observation on color
Grey-white
3
Sample preparation
Thin slice
4
Structure
Granular structure
5
Tectonics
Lump
6
Identification basis
GB/T17412.1
7
Essential mineral
97%-98% gypsum
8
Secondary minerals
2-3% dolomite
9
Accessory mineral
Apatite
10
Microscopic observation
The rock has lump tectonics and a granular structure. Gypsum is tabular and colorless with a particle size distribution of 0.01–2.0 mm and has a negative protrusion. The highest interference color is first-order yellow and white, and cleavage in one direction is observed. Dolomite has a semi-automorphic rhombohedral shape with a particle size distribution of 0.01–0.03 mm and is unevenly distributed. It has a prominent flash protrusion and high-order white interference color.
