西北黄土灌溉地区土壤经历了干湿循环作用和盐污染双重作用的影响,导致该地区黄土特性产生明显的劣化。以Na2SO4污染Q3黄土为研究对象,采用直剪试验、电子显微镜扫描试验(SEM),分析其经过次数不同干湿循环作用后的力学性质和微观结构特征变化。结果表明:干湿循环和盐污染双重作用下,黄土强度劣化程度增大,微观结构变化显著;期中,黏聚力产生明显劣化,下降率可达38.24%~ 51.4%;随盐污染和干湿循环次数的增加,黄土体的单体颗粒比例显著增加,团聚体开始解体;Na2SO4随着干湿循环反复结晶和溶解,从而对土体产生了盐胀与盐蚀共同作用;二者作用中,干湿循环对土体结构的破坏作用大于盐污染作用。研究结果可为黄土地区的工程活动和防污治理提供有效参考。
The soil in the northwest loess irrigation area has been affected by the dual effects of dry-wet cycling and salt pollution, leading to significant deterioration of the loess properties in this region. Taking Q3 loess contaminated by Na2SO4 as the research object, direct shear tests and scanning electron microscopy (SEM) are used to analyse the changes in mechanical properties and microstructure characteristics after different numbers of dry-wet cycles. The results show that: Under the dual effects of dry-wet cycling and salt pollution, the strength of the loess deteriorates significantly, and the microstructure changes significantly. Among them, the cohesion shows obvious deterioration, with a decline rate of up to 38.24% to 51.4%. With the increase of salt pollution and dry-wet cycling times, the proportion of individual particles in the loess body increases significantly, and the aggregates begin to disintegrate; Na2SO4 repeatedly crystallizes and dissolves during dry-wet cycling, thereby exerting a combined effect of salt swelling and salt erosion on the soil; among the two effects, the destructive effect of dry-wet cycling on the soil structure is greater than that of salt pollution. The research results provide an effective reference for engineering activities and pollution control in loess areas.
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