添加粉煤灰对煤矸石基质有效水和持水性能的影响

Effect of adding fly ash on water availability andholding capacity of coal gangue matrix

【目的】探索添加粉煤灰对煤矸石基质有效水分和持水能力的影响,为推进矿区生态修复和废弃物的资源化利用提供理论依据。【方法】以煤矸石和生土按照1∶1质量比混匀的煤矸石基质为研究对象,分别添加不同质量分数(0%(CK)、10%(F1)、20%(F2)和50%(F5))粉煤灰,经浇水处理后,取一部分煤矸石基质测定其颗粒组成,同时用环刀取不同处理的煤矸石基质测定其水分特征曲线,计算不同处理煤矸石基质的体积含水率(θ)和水吸力(S),用Gandner幂函数经验公式(θ=aS^(-b))对参数a(表征持水能力)和b(表征体积含水率变化的快慢)进行拟合。在此基础上,计算不同处理煤矸石基质的比水容量、大中小孔隙占比、田间持水量、萎蔫系数及速效水、缓效水和有效水含量。【结果】①与CK相比,添加粉煤灰使煤矸石基质的粉粒含量显著增加了3.81~15.62个百分点,砂粒和黏粒含量显著减少了3.87~9.87个百分点和0.10~6.01个百分点。②不同处理煤矸石基质的Gardner幂函数方程拟合系数(R2)在0.9538~0.9947。随着粉煤灰添加量的增加,方程拟合参数a呈增加趋势,b呈减小趋势,煤矸石基质的水分特征曲线也逐渐升高。煤矸石基质的比水容量随水吸力的增大呈现出先增大后减小的趋势。在任一水平的水吸力状态下,添加了粉煤灰的煤矸石基质的比水容量均大于CK,并且随着粉煤灰添加量的增加而增大。添加粉煤灰可以减少煤矸石基质的大孔隙比例,增加中小孔隙比例,其中F1、F2、F5的中、小孔隙比例分别较CK上升1.820,3.223,4.180个百分点和4.256,6.890,12.083个百分点。③随着粉煤灰添加量的增加,煤矸石基质的田间持水量及速效水、缓效水和有效水含量显著增加,但萎蔫系数无显著变化。【结论】添加粉煤灰可以改善煤矸石基质的颗粒组成和孔隙状况,提高其有效水含量和持水能力。

【Objective】This study explored the effects of fly ash addition on available water and water holding capacity of coal gangue matrix to provide basis for promoting ecological restoration and waste resource utilization in mining areas.【Method】The coal gangue matrix mixed with coal gangue and raw soil at a mass ratio of 1∶1 was tested with addition of fly ash at different mass fractions(0%(CK),10%(F1),20%(F2)and 50%(F5)).After watering treatment,partial coal gangue matrix was taken to determine particle composition,volume water content(θ)and water suction(S).The Gandner power function empirical formula(θ=aS^(-b))was used to fit the parameters of a(representing the water holding capacity)and b(representing the changing rate of volumetric water content).Then,the specific water capacity,proportions of large,medium and small pores,field water holding capacity,wilting coefficient,rapid available water,slow available water and available water were calculated.【Result】①Compared with CK,the addition of fly ash significantly increased silt content of coal gangue matrix by 3.81%-15.62%,while reduced sand and clay contents significantly by 3.87%-9.87%and 0.10%-6.01%,respectively.②The fitting coefficients(R 2)of the Gardner power function equation of the coal gangue matrix with different treatments were 0.9538-0.9947.With the increase of fly ash amount,the equation fitting parameter a showed an increasing trend,b showed a decreasing trend,and the water characteristic of the coal gangue matrix gradually increased.The specific water capacity of the coal gangue matrix showed a trend of first increasing and then decreasing with the increase of water suction.At any level of water suction,the specific water capacity of the gangue matrix with fly ash was greater than that of CK,and it increased with the increase of fly ash addition amount.The addition of fly ash reduced the proportion of large pores of coal gangue matrix and increased the proportions of medium and small pores.Compared with CK,the proportions of medium and small pores of F1,F2 and F5 were increased by 1.820%,3.223%,4.180%and 4.256%,6.890%,12.083%,respectively.③With the increase of fly ash addition,the field capacity,available water,rapid available water,slow available water and available water increased significantly,whereas wilting coefficient showed no significant changes.【Conclusion】Adding fly ash can improve the particle composition and porosity characteristics of coal gangue matrix and increase its available water content and water holding capacity.