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Saturated permeability properties and mechanism of remolded loess in osmotic solutions with different pH: A case study from the Loess Plateau of China
Engineering Geology ( IF 7.4 ) Pub Date : 2020-12-01 , DOI: 10.1016/j.enggeo.2020.105978
Panpan Xu , Qiying Zhang , Hui Qian , Faxuan Yang , Le Zheng

Abstract The service life of loess buildings or structures is threatened because they are exposed to acid rain, industrial wastewater leakage, or other chemical environments contaminated with acids and bases. This paper attempts to explore the effects of acidic and alkaline waters on the saturated permeability of remolded loess, a series of the saturated permeability tests was designed. In order to produce the underlying mechanism of soil-water chemical interaction, the chemical components in leachates were tested, and the zeta potentials in different soil and water systems were measured. The results demonstrated when acid entered the soil, massive amounts of carbonate minerals (mainly calcite and dolomite) and chemical cements (Al2O3 and Fe2O3) were leached, which destroyed the skeleton structure of the soil. In addition, ion exchange adsorption reduced the thickness of the diffuse double layer and promoted pore space development. Hence, the Ksat significantly increased over time in the acidic solution. In deionized water, Ksat showed similar behavior to the acidic condition, but calcite and dolomite leaching was the dominant factor that increased the permeability. In the case of alkali intrusion into the soil, the effect of geochemical processes was weakened, especially the dissolution of carbonate minerals. Al(OH)3, Fe(OH)3, and H2SiO3 colloids were formed in the pore water, which all plugged the pores. Moreover, the development of a diffuse double layer provided space for gravity water to pass through the smaller pores, causing Ksat to decrease over time. These findings will provide a basis for geological environmental engineering in the Loess Plateau.
更新日期:2020-12-01
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