分散性土的综合判别准则与针孔试验方法的改进  

Comprehensive criterion of dispersive soil and improvement of pinhole test

作　　者：樊恒辉[1] 赵高文[1] 路立娜[1] 李振[1] 

机构地区：[1]西北农林科技大学水利与建筑工程学院,陕西杨凌712100

出　　处：《水力发电学报》2013年第1期248-253,262,共7页Journal of Hydroelectric Engineering

基　　金：国家自然科学基金(50979094);"十二五"国家科技支撑计划(2011BAD31B05);西北农林科技大学基本科研业务(QN2009089)

摘　　要：采用分散性土修建的土工建筑物,遇水容易发生表面侵蚀或管涌破坏。通常采用双比重计试验、针孔试验、碎块试验、孔隙水可溶性阳离子试验和交换性钠离子百分比试验等5种试验方法判别土的分散性,但不同的试验往往会给出不一致的判别结果,难以对其进行综合判别。以松塔水电站大坝防渗土料的分散性判别试验为例,研究分散性土的综合判别准则,并对针孔试验的方法进行改进。研究表明,赋予双比重计试验、碎块试验、针孔试验、孔隙水可溶性阳离子试验和交换钠离子百分比试验的权重值,其值分别取20%、20%、40%、10%、10%,计算土样的分散性、过渡性、非分散性的权重。①如果分散性的权重大于50%,土样属于分散性土。②分散性的权重等于50%时,如果过渡性的权重大于等于20%,则属于分散性土;反之,则属于过渡性土。③分散性的权重小于50%时,如果"过渡性+分散性"的权重大于等于50%,则为过渡性土,否则属于非分散性土。在针孔试验结束后,非分散性土的针孔不会发生冲蚀;分散性土的针孔孔径扩大,但孔道较为通直整齐。如果针孔呈喇叭口形状,土体有软化现象,则可在针孔周围3～4mm以外涂黏结材料保护临空面,以防止误判。Surface erosion or piping failure often occurs in the earth-work constructions with dispersive soil once subject to water. The dispersivity of soil is usually identified with five methods of double-hydrometer test, pinhole test, crumb test, pore water salts test and exchangeable sodium percent test, but sometimes all these methods produce different results, making the identification practically difficult. This paper studies the dispersivity criterion and the improvement of pinhole test through a case study of the core soil in the Songta hydropower. The results indicate that comprehensive identification criteria can be calculated by assigning a suitable weight to each of the methods. The results indicate that the weight values are given to the double- hydrometer test, pinhole test, crumb test, pore water salts test and exchangeable sodium percent test, which is 20% , 20% , 40% , 10% and 10% respectively, then the total of dispersive, intermediate and non-dispersive values are calculated separately. （1） If the dispersive value exceeds 50% , the soil is dispersive; （2） If the dispersive value is 50% and the intermediate value is no less than 20% , the soil is dispersive. Otherwise, it is intermediate. （ 3 ） If the dispersive value is less than 50% and the dispersive and intermediate values are no less than 50% , the soil is intermediate. Otherwise, it is non-dispersive. This study reveals that after the pinhole test is finished, the pinhole of non-dispersive soil is not changeable, soil becomes larger, but it is almost straight and trim. If the pinhole is trumpet while the pinhole of dispersive -like and became softened, it issuggested that the pinhole wall is coated with adhesive material of 3 ～4mm thick to protect its free surface and prevent wrong identification.

关 键 词：水工材料 判别准则 试验方法 分散性土 针孔试验 

分 类 号：TV443[水利工程—水工结构工程]