In situ effect of combined utilization of fly ash and polyacrylamide on sand stabilization in North China

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A field experiment was conducted to investigate the resistance to wind erosion of consolidated soil layer (CSL) on the edge of Ulan Buh Desert in Inner Mongolia, China under natural conditions during Aug. 2015–Apr. 2016. The CSLs consisted of sandy soil, fly ash (FA) (5%, 10% and 15% (w/w) soil) and polyacrylamide (PAM) (0.05% and 0.1% (w/w) soil). The experimental site was divided equally into Regions A and B where dry FA and PAM powder were applied in two ways in mid-Jul. 2015. In Region A, FA and PAM were mixed homogeneously with the 0–0.3 m depth topsoil. In Region B, FA alone was mixed homogeneously with the 0–0.3 m depth topsoil. PAM was then scattered uniformly on top of the surface layer. Finally, CSLs were formed by spraying an appropriate amount of water onto the surface to dissolve PAM fully and being equilibrated for one week to achieve a moisture content close to the initial soil moisture content (0.6%). It was found that during 2–26 Aug. 2015, the wind erosion rate (WER) was reduced most significantly by 77% in CSL (10%FA + 0.05%PAM) in Region A and by 58% in CSL (10%FA + 0.1%PAM) in Region B compared with control (CK) (WER = 10.2 kg/m2). However, during 3–27 Sep. 2015, there was no significant difference in WER between treatments in Regions A and B compared with CK (WER = 1.4 kg/m2). Whereas, during the following longer period of wind erosion (viz. 27 Sep. 2015–21 Apr. 2016), the WER was reduced most significantly by 69% in CSL (5%FA + 0.1%PAM) in Region A and by 32% in CSL (5%FA + 0.05%PAM) in Region B compared with CK (WER = 80.7 kg/m2). The resistance to wind erosion of CSL in Region A was much stronger than in Region B. The WER of CSL was influenced by wind conditions including wind speed and direction. Precipitation also had an impact on the WER of CSL as the cohesive effect of PAM can be influenced by precipitation. The CSL as a mixture of sandy soil, FA and PAM is recommended for wind erosion control.