Abstract
Acidic fluids will cause rock erosion and further endanger the safety of rock engineering. To explore the aging characteristics of the mechanical damage under acid condition, diorite specimens were saturated in neutral water and acid solutions with pH values of 3 and 5 for 49 days. The masses and sizes of the specimens and the pH values of the acidic solution were tracked and measured. Besides, the specimens before and after saturations were observed by an electron microscope scanner. Meanwhile, triaxial compression tests were carried out under neutral water, pH = 5 and pH = 3 hydrochloric acid solutions, respectively. The mass damage features and mechanical properties of diorite specimens saturated in solutions with different pH values were analyzed. The results show: (1) after acidic saturation, the original lamellar structures and crystal forms were spongy or flocculent. The structure loosened and the boundary between layers became fuzzy. Meanwhile, the number of micro-cracks and micro-pores increased, which weakened the macro-mechanical performances of diorite; (2) the acid condition with pH value of 3 could be used to simulate the long-term effect of the weakly acidic environment in nature; (3) internal friction angle of diorite was more sensitive to acidic solutions than its cohesion; (4) at the initial stage of saturation, diorite broke rapidly. With increasing saturation time, the damage rate slowed down and finally stabilized. The established damage strength model considering acidification could properly describe the test results.
Highlights
The mechanical properties of rock masses could be affected by water erosion [1,2,3]
The time scale refers to the ratio of the amount of H+ substances consumed per unit time for two solutions with different initial pH values [52, 54]
Assuming that under a strongly acidic solution, the amount of H+ substances consumed per unit time is Δn1, and that in weak acid is Δn2, the time scale ƞ(t) of two different acidic solutions can be defined as: η(t)
Summary
The mechanical properties of rock masses could be affected by water erosion [1,2,3]. the differences in water fluid chemicals significantly affect their mechanical properties and chemical composition [4,5,6,7]. DJ-2 and DJ-3 were scanned after saturation in acid solutions with pH values of 3 and 5 for the same time, respectively (Figure 1A). After saturation for 49 days in acidic solutions with pH 3 and pH 5, powders were stripped from the surface of the rock samples.
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