大石峡水电站筑坝土料分散性综合判定及改性研究

Study on Dispersivity Identification and Modification of Dam Soil in Dashixia Hydropower Station

分散性土的抗冲蚀能力很低,对许多工程的安全性造成严重威胁。在分析土样物理化学性质和矿物学性质的基础上,采用双比重计、碎块、针孔、孔隙水阳离子和交换性钠百分比等试验方法,对大石峡水电站大坝防渗土料的分散性及其改性措施进行了研究。研究结果表明,土样1号和4号属于分散性土,2号、3号、5号属于过渡性土。土样产生分散的主要原因:一是土样中含有数量较多的钠离子,使得伊利土也像那钠基蒙脱土一样具有较强的分散性;二是酸碱度较高,使得土颗粒之间的斥力能大于引力能,促使土样分散;掺入质量分数0.26%的AlCl_3·6H_2O或质量分数0.35%的CaCl_2都会对分散性土样产生显著的改性作用。结果表明:土样产生分散的条件是土样中含有大量的钠离子和较高的p H值;AlCl_3·6H_2O的改性效果明显优于CaCl_2,是一种有效的分散性土改性剂。

Dispersive soil has very low erosion resistance capacity, so it seriously threatens engineering safety. Based on the analysis of physical and chemical properties, the dispersivity and modification of dam soil in Dashixia Hydropower Station are studied by using double-hydrometer test, crumb test, pinhole test, pore water salt test and exchangeable sodium percent test. The results show that the No. 1 and 4 soil samples are dispersive, and No. 2, 3 and 5 soil samples are transitional soil. A great quantity of sodium-ions in gerundive soil and higher alkalescence make the soil as well as montmorillonoid which is intense dispensability. When 0. 26% of AlCl3. 6H2O or 0. 35% of CaCl2 is added,：the dispersion of soil can be restrained effectively. It is shown that the soil becomes dispersive clay only under the conditions of more sodium-ions and the higher pH, and compared with CaCl2, AlCl3. 6H2O is an affective modifier of dispersive soil.