头寨滑坡地下水化学特征及其反映的水-岩(土)相互作用

Hydrochemical characteristics and their implication for the water-rock / soil interaction in the Touzhai landslide

文章以头寨滑坡为对象,分析滑坡岩土体的矿物组成和组构等特征,研究表明造成滑体玄武岩岩体性质劣化的风化过程是一种物理-化学耦合的水-岩(土)相互作用过程,在多尺度(微观、细观、宏观)岩(土)体的"石夹土"结构中得到体现,水岩作用产物主要有绿泥石、伊利石和蒙脱石等黏土矿物。采集滑坡体剪出口处的地下水样测试水化学组成,选取前四个主因子P_1、P_2、P_3和P_4(分别占总方差的39.9%,21.9%,16.7%和13.5%)分析地下水的水化学特征。主因子P_1主要反映玄武岩原生矿物的溶蚀作用对地下水化学成分的控制作用,主因子P_2反映岩(土)体孔隙中有柱状硫酸钙矿物的结晶析出,主因子P_3反映岩(土)体同地下水之间存在阳离子交换,主因子P_4反映岩(土)体水岩作用产物——Si O2矿物在地下水中溶解性与水溶液中CO_2含量的关系。地下水主成分分析的结果能反映出滑坡地下水与岩土体的相互作用的主要过程。

The mineral compositions and fabric characteristics of the basalt rock mass of the Touzhai landslide were firstly analyzed through field analysis,diffraction,etc. The weathering process of the basalt rock mass is the coupling chemical and physical interaction of water-rock / soil from on macro-scale,to on meso-scale,and to on micro-scale,which means that the interface area of the water-rock / soil interaction is high. The main secondary minerals are chlorite,illite,and smectite. Hydrochemical characteristics in the landslide are analyzed by the principal component analysis（ PCA） of 14 consecutive months data derived from a groundwater spring near the shear opening of the landslide. The PCA analysis yields four principal components（ P1,P2,P3 and P4）,which capture 39. 9%,21. 9%,16. 7% and 13. 5% of total variability,respectively.P1 reflects the relation between the dissolution of the primary mineral of basalt and he chemical compositions of groundwater,and P2 shows that the pillars of calcium sulfate crystals crystallizes out in soil pores,P3 indicates that there is cation exchange between groundwater and basalt rock mass,P4 indicates the dissolubility of amorphous SiO2 which is the product of weathering of basalt in water affected by the amount of CO2 in the groundwater. The result of PCA shows the good relation between hydrochemical characteristics and the water-rock / soil interaction in the Touzhai landslide.