| 引用本文: | 安文举,李王成,赵广兴,等.干湿循环对宁夏压砂砾石劣化的田间试验研究[J].灌溉排水学报,2022,41(6):80-88. |
| AN Wenju,LI Wangcheng,ZHAO Guangxin,et al.干湿循环对宁夏压砂砾石劣化的田间试验研究[J].灌溉排水学报,2022,41(6):80-88. |
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| 摘要: |
| 【目的】探明宁夏中部干旱带压砂田砾石在干湿循环下的劣化情况。【方法】以压砂地常用覆盖砾石—灰绿板岩为研究对象，通过淋水实现干湿循环试验，得到不同劣化程度砾石试样。利用SEM及PCAS计算得到劣化后砾石试样的各种参数并监测各阶段砾石质量损失。【结果】①初始阶段大粒级砾石劣化程度总体高于小粒级，干湿循环下孔隙连通性增强，出现大量碎屑与絮状矿物；②干湿循环后砾石粒级同孔隙数量成正比，同砾石平均孔隙面积成反比，孔隙的均匀系数较初始大幅升高，最大增幅达129.4%。粒级越大吸水率越小，粒级0.5~2 mm压砂砾石在250、125 mL淋水下较初始增幅最高，分别增加75.05%、56.60%；③干湿循环后压砂砾石阶段质量损失率、累积质量损失量与粒级成反比，其中粒级0.5~2 mm压砂砾石在整个循环中受温度影响较敏感，其累积质量损失量在250 mL淋水量下比125 mL提高27.66%。【结论】在施加干湿循环影响下，小粒级压砂砾石劣化速度和程度总体大于大粒级，砾石首先要从大粒级劣化为小粒级，再劣化成壤。 |
| 关键词: 干湿循环；扫描电镜；孔隙；吸水率；质量损失率；PCAS |
| DOI：10.13522/j.cnki.ggps.2021532 |
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| The Effects of Wetting-drying Cycles on Degradation of Sands and Gravels Used for Soil Mulching in Ningxia Province |
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AN Wenju, LI Wangcheng, ZHAO Guangxin,
JIA Zhenjiang, LIU Qiaoling, WANG Jie, MU Min, LI Yangyang
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1. School of Civil and Hydraulic Engineering, Ningxia University, Yinchuan 750021, China; 2. Engineering Research Center of the Ministry of Education for Efficient Utilization of Modern Agricultural Water Resources in Dry Areas, Yinchuan 750021, China;
3.State Key Laboratory of Land Degradation and Ecological Restoration in Northwest China, Yinchuan 750021, China
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| Abstract: |
| 【Objective】Sand and gravel mulching is a technology widely used for crop production in the arid regions in northwestern China. Continuous weathering could result in their degradation; the purpose of this paper is to study the effects of wetting-drying cycles on degradation of gravels and sand used for soil mulching in the arid belt in central Ningxia province. 【Method】We took lime-green slate - a commonly used gravel and sand for soil mulching - as an example, mimicking wetting-drying cycles in laboratory by spraying. Degradation of the gravels were measured and calculated using SEM and PCAS technologies. 【Result】①Large gravels degraded faster than small ones at the early stage, and wetting-drying increased pore connectivity of the gravel mulch. A great number of debris and flocculent minerals were found. ②At the end of wetting-drying cycles, gravel size was proportional to the number of pores and was inversely proportional to the average pore area of the gravels. Wetting-drying increased the uniformity coefficient of the pores by up to 129.4%. The ability of the gravels to adsorb water decreased as the gravel size increased. The crushed sand and gravel in the size range of 0.5~2 mm had the highest water adsorption under water application of 250 and 125 mL, increasing water adsorption by 75.05% and 56.60% respectively, compared to the initial water content. ③At the end of the wetting-drying cycles, the mass loss rate and cumulative mass loss in the sand and gravel were inversely proportional to particle size. Among them, sand and gravel with size in the range of 0.5~2 mm were more sensitive to temperature. Their cumulative mass loss under water application of 250 mL was 27.66% higher than that under water application of 125 mL. 【Conclusion】Wetting-drying cycles affect degradation of small and compacted sand and gravel more than the large ones. Our results have important implications for improving management of soils mulched by sand and gravel in the arid regions in northwestern China. |
| Key words: drying-wetting cycle; SEM; porosity; water absorption; mass loss rate; PCAS |
