Experimental Study on Sandstone Freezing-Thawing Damage Properties under Condition of Water Chemistry

Abstract

For the purpose of researching the freezing-thawing cycle physical mechanics properties of sandstone in various chemical solutions, taking the red sandstones from Shandong as the example, freezing-thawing cycles experiments under the condition of H2SO4solution (pH≈1.5), NaOH solution (pH≈12.5), NaCl solution (pH≈7, mass fraction is 4%) and water were conducted. The nuclear magnetic resonance (NMR) technique was used to test the porosity of rock samples after freezing-thawing cycles. Brazilian splitting test was also conducted to test the samples with different times of freezing-thawing cycles and soaking solutions. Results show that the quality change of samples in various solutions is different. The mass of sample in water increased, however, the mass change of the sample in other three solutions showed a firstly increasing and then decreasing tendency. The porosity distribution in rock changed obviously after different time’s freezing-thawing cycles. After 30 times freezing-thawing cycles, the porosity in H2SO4solution, NaOH solution, NaCl solution and water has increased by 151.1%, 85.443%, 39.388%, and 17.976% respectively. With the increase of freezing-thawing cycle’s times, tensile strength of the rock reduced, but the damage properties were different in various solutions. The research can provide some mechanical parameters basis to physical mechanics properties of sandstones.

Damage Characteristics of Sandstone Subjected to Coupled Effect of Freezing-Thawing Cycles and Acid Environment

“…Facilities employed in this experiment include the TDS-300 concrete freeze-thaw test machine, AniMR-150 NMR imaging system, vacuum saturation machine, PL4002 electronic balance with precision of ±0.01 g, drying box with precision of ±0.1°C, and pHS-3C pH meter with precision of ±0.01 pH. TDS-300 concrete freeze-thaw test machine is manufactured by Donghua Testing Equipment Company, Ltd., Suzhou; it can apply a temperature range of −40°C to +40°C to rock samples, and it is an automated machine [25].…”

“…e vacuum saturation machine and AniMR-150 NMR imaging system are manufactured by Niumag Electric Technology Company, Ltd., Shanghai. e AniMR-150 NMR imaging system contains two main test systems, namely, nuclear magnetic resonance (NMR) and magnetic resonance images (MRI) test systems, and they were often used in other research studies [22,25,28,29]. Its picture is shown in Figure 1.…”

“…en, they were wrapped with preservative films instantly to prevent water evaporation in the process of NMR and MRI tests. After that, rock samples were put into carrying bed of the AniMR-150 NMR imaging system [25,28] to conduct NMR and MRI tests. e NMR and MRI tests were conducted after each 10 F-T cycles.…”

“…Feng et al [24] immersed sandstone samples of triaxial compression into NaCl, CaCl 2 , and NaHCO 3 solutions and the Yellow river water to investigate the mechanisms of damage evolution of sandstone and proposed a damage model based on the chemical corrosive influence and CT values. Deng et al [25] conducted recurrent F-Tcycle experiments under the condition of H 2 SO 4 , NaOH, and NaCl solutions and pure water to investigate the coupled effect of F-T cycles and chemical solution on sandstone, and the result showed that NaOH causes stronger damage to rock samples used in these experiments than other solutions. By subjecting granite, parent rocks for nuclear waste storage, to strong acid solutions and strong alkaline solutions, Han et al [26] explored the deterioration and mechanical properties of granite under various chemistry environments and found that strong acid solutions may aggravate chemical damage deterioration in granite while strong alkaline solutions have braking effect on chemical damage deterioration in granite.…”

Mechanical Properties of the Hard Sandstone Fracture Surface under Hydrochemical Corrosion

“…Aggravation of sandstone shear strength was the most serious in the acid environment, followed by alkaline environment and neutral environment. Hongwei Deng et al [8] conducted a cyclic test of freezing and thawing under H 2 SO 4 , NaOH, NaCl, and water conditions and tested the porosity of sandstone specimens after cycles of freezing and thawing, with the red sandstone in Shandong as an example. After cycles of freezing and thawing at different times, rock porosity distribution underwent evident changes.…”