Effects of Acid Sulfate and Chloride Ion on the Pore Structure and Mechanical Properties of Sandstone Under Dynamic Loading

Autor: Zhentang Liu, Junjun Feng, Xiaojun Feng, Xiaoliang Li, Huajie Zhang
Rok vydání: 2021
Předmět:
Zdroj: Rock Mechanics and Rock Engineering. 54:6105-6121
ISSN: 1434-453X
0723-2632
Popis: Underground rock is often subjected to the coupled action of acid sulfate, chloride ion corrosion, and external dynamic disturbance: the degree of corrosion and dynamic load can significantly affect the pore structure and mechanical behavior of rock. To quantify the microscopic pore structure changes and macro-dynamic behavior characteristics of acidified corroded sandstone, first, a mixed acidic solution of NaHSO4 and HCl with different pH values was used for immersion corrosion of sandstone; second, the pore structure of sandstone before and after corrosion was quantitatively evaluated by nuclear magnetic resonance (NMR), dynamic loading tests of corroded sandstone were conducted on an SHPB experimental system and scanning electron microscopy (SEM) was used to observe the morphology of corroded sandstone section; and finally, the mechanism of water–rock interaction and damage and fracture of acid-corroded sandstone were analyzed. The results show that, after acidizing corrosion of sandstone, the macropores increase significantly in number and volume, the boundary of the pore structure tends to be fuzzy; the effective porosity, the number of effective pores, and the total porosity increase significantly; the residual porosity, the number of residual pores, and T2 cut-off value decrease. The proportion accounted for by the elastic stage in stress–strain curves of corroded sandstone is lowered; the proportion accounted for by the plastic yield stage is increased; and post-peak rebound is diminished. With the decrease of pH value, the peak stress on acid-corroded sandstone decreases and the peak strain increases. The peak stress on corroded sandstone is negatively correlated with effective porosity and the number of effective pores, but positively correlated with residual porosity, the number of residual pores, and the T2 cut-off value. The reaction of acidic solution with sandstone minerals causes the free fluid space to increase, the bound fluid space decreases, and the number of pores increases, resulting in a decrease in the dynamic strength of acidified sandstone. The fracture of original sandstone after impact failure has no obvious directionality, and the failure mode of grain is the coexistence of intergranular fracture and trans-granular fracture. The fracture of sandstone after acidizing corrosion is obviously directional after impact damage, and the fracture form is single, which is intergranular fracture. The research results can provide a certain reference for the protection of rock engineering under acidic water chemical environment.
Databáze: OpenAIRE
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