硅酸盐岩斜坡水岩化学作用

The Chemical Water-Rock Interaction in Silicate Rock Slopes

综合采用现场调查、结构体物理-水理参数的高精度测试及室内试验等研究方法,对硅酸盐岩斜坡的水岩化学作用问题进行了探讨。结果表明,新鲜硅酸盐岩结构体结构致密、孔隙度低、孔隙细小,多属不透水介质。硅酸盐岩斜坡区的水岩化学作用主要发生于非饱和带和水位变动带,地下水多年最低水位以下的饱和带所占份额很小。饱和带内的水岩化学作用只能发生于结构体表面,是一种结构面开度逐渐增大、结构体逐渐变小的缓慢溶解过程。非饱和带及水位变动带水岩化学作用初期的溶解液主要是水气转化的凝结水,所形成的腐岩保留原岩结构、构造和体积,是一种等容转换过程。旱季时,气态水分子扩散到硅酸盐岩结构体表面内侧一定宽度范围内的微孔隙系统之中凝结为液态水并溶蚀造岩矿物;雨季时,入渗降水在结构体表面形成的薄膜水流接受结构体粒间溶液中的溶出组分并将其携入饱水带。当上述过程循环到一定程度时,结构体就会转变为腐岩结构体。覆盖有一定厚度的残坡积土层和植被盖层的硅酸盐岩斜坡有利于水岩化学作用的发生。

Combined with the methods of in situ survey , high-precision testing of physical-water parameters of rock blocks and laboratory tests , the CWRI （ chemical water-rock interaction ） in silicate rock slopes was investigated.The results show that fresh silicate rock blocks are generally impervious media because of their compact texture , low porosity and very fine pore throats.The CWRI in silicate rock slopes occurs mainly in unsaturated and water-table fluctuation zones , and the CWRI in the saturated zones below the lowest groundwater level is weak.The CWRI in the saturated zones only takes place in the surface of rock blocks and is a slow dissolution process in which fracture width becomes wider and wider and rock blocks become smaller and smaller.The solvent in preliminary stage of the CWRI in unsaturated and water-table fluctuation zones is mainly condensation water from moistur.The saprolite deriving from the CWRI in unsaturated and water-table fluctuation zones retains the relic texture , structure and volume of the parent roc.In dry season , the gaseous water molecules in unsaturated zone spread into the pore system of silicate rock blocks at some depth and condense into liquid water which can dissolve forming mineral.In rainy season , the thin water films derived from precipitation on the surface of rock blocks in unsaturated zone absorb the dissolution components in the rock block solution and carry them into saturated zone.When the above process circulates to some extent , the silicate rock blocks turn into saprolite.The silicate rock slope covered by residual soil layer and vegetation is propitious to occurrence of CWRI.