毛细导水布料排水性能及孔隙结构试验研究

EXPERIMENTAL STUDY ON THE DRAINAGE PERFORMANCE AND PORE STRUCTURE OF THE CAPILLARY WATER-CONDUCTING MATERIALS

本文选取了5种具有毛细导水特性的布料进行了水中的排水试验、土中的排水试验、毛细上升试验以及核磁共振试验,对其排水性能和孔隙结构进行系统研究。旨在揭示其毛细吸水排水性能的机制,为寻找或生产出能够应用到我国一些含水率较高的非饱和土地区的土工材料做参考。结果表明,毛细导水材料在非饱和土中具有良好的排水效果,能够一定程度上提高非饱和土的排水速率。毛细导水材料在水中的排水试验表明,各材料的排水效果受毛细上升距离和空气相对湿度的影响。此外,通过对比不同种类的毛细导水材料在土中和水中排水性能的强弱,发现试验布料的排水性能大致可以分为两类:COOLPASS、COOLMAX和普通网布的排水性能最好,而SHCOOL和COOLPLUS的性能稍弱。通过核磁共振试验测得COOLPASS、COOLMAX和普通网布的孔隙大小约为53.4μm,SHCOOL和COOLPLUS的孔隙大小约为37.8μm。布料吸排水的强弱与其孔径大小及孔隙分布特征有关,综合考虑毛细导水材料毛细吸水和蒸发排水的两个过程,发现孔径较大且孔隙分布特征表现为稀疏的普通网布材料在非饱和土中的排水效果最佳,相同条件下比未设置毛细导水布料的土样含水率多降低了2.19%。在毛细上升高度试验中,COOLMAX的毛细上升高度最大,表明毛细导水材料的吸水能力与其孔隙分布特征有关,孔隙分布越密集,其吸水能力越强。

In this study,5 different types of capillary water-conducting materials(i.e.,COOLPASS,COOLPLUS,COOLMAX,SHCOOL,and Ordinary Mesh Fabrics)are selected for water absorption and drainage test,NMR test,and capillary rising test to investigate their drainage performance and pore structures.The purpose is to reveal the mechanism of capillary water absorption and drainage performance,and as a reference for finding or producing a geotextile that can be applied to some unsaturated soil with high moisture content in the country.Results show that these capillary water-conducting materials have good water absorption and drainage effect in both soil and water.Through the drainage test of capillary water-conducting materials in water,it is found that capillary rising distance and air relative humidity affect the water removal effect.Generally,we divide these five kinds of fabrics into two levels by their performance:the COOLPASS,COOLMAX and Ordinary Mesh Fabrics have the best drainage performance,while the performance of SHCOOL and COOLPLUS are slightly weaker.The pore sizes of COOLPASS,COOLMAX and Ordinary Mesh Fabric are about 53.4μm and the pore size of SHCOOL and COOLPLUS are 37.8μm through the NMR test.According to the NMR test of these materials,it is found that the ability of drainage is related to their pore diameters and distribution characteristics.Considering the two processes of capillary absorption and evaporation drainage of the water-conducting capillary materials,the drainage effect of the material with a large pore diameter and sparse distribution is better in unsaturated soil,the moisture content of the soil sample decreases by 2.19%more than the soil sample without capillary drainage material under the same condition.In the capillary rising test,the capillary rise height of COOLMAX is the highest.Therefore,the water absorption capacity of capillary water-conducting material is related to its pore distribution characteristics,the denser the pore distribution is,the stronger the water absorption capacity is.