基于主成分分析法的黄土灌溉区水-岩（土）相互作用研究

文章以甘肃省永靖县黑方台地区为对象，该地区是受长期灌溉水下渗导致地下水位抬升，进而诱发了大量黄土滑坡。为了进一步研究黑方台地下水的水-岩（土）相互作用对岩土体的影响，本文借助主成分分析法，对黑方台的地下水化学特征进行分析，并结合滑坡岩土体的易溶盐成分和矿物组成等特征做综合研究。采集滑坡体出水口处的地下水样测试水化学组成，选择前2个变量因子Z1、Z2作为主成分（分别占总方差的68.166%和20.576%），分析地下水的水化学特征，便可反映90%左右的信息。主因子Z1主要反应易溶盐含量和水敏性矿物（长石类、方解石等）的水解作用对地下水化学成分的控制作用，主因子Z2反映微溶盐石膏（硫酸钙）矿物的溶解度随地下水离子浓度增加而增大和CaCO3的溶解、沉淀过程。研究表明，水-岩（土）相互作用会导致岩土体胶结性变差，微结构破坏，进一步累积会使岩土体产生大量裂隙和孔洞，最终将影响岩土体稳定性；另外，黄土中CaCO3的淋溶和迁移证明CaCO3淀积层顶部应为地下水入渗方式转变的分界线。地下水主成分分析的结果能反映出黑方台滑坡地下水与岩土体的相互作用的主要过程。

Study on water-rock/soil interaction in loess irrigation area based on the principal component analysis

The paper takes Heifangtai of Yongjing County in Gansu province area as the object. This area is affected by the long-term irrigation water seepage, which causes the groundwater level rise, so induces a large number of Loess Landslides. In order to further study the Heifangtai''s groundwater water rock (soil) interaction effects on rock and soil, the paper uses principal component analysis method, which analyses the chemical characteristics of the Heifangtai''s groundwater while combines with the characteristics of soluble salt and mineral composition of landslide rock/soil doing a comprehensive research. The collection of the landslide groundwater samples in the water outlet is tested the water chemical composition. Selecting the first 2 variables Z1, Z2 as the principal component (respectively accounted for the total variance of 68.166% and 20.576%), it analyses of Groundwater Hydrochemical Characteristics, can reflect about 90% of the information. Main factors Z1 reacts that soluble salt content and the hydrolysis of water sensitive minerals (feldspar, calcite, etc.) control the groundwater chemical composition; The main factor Z2 reflects the solubility of slightly soluble salt gypsum (calcium sulfate) minerals increases with the increase of water ion concentration and the dissolution and precipitation process of CaCO3. The study shows that the interaction of water rock (soil) will lead to the poor cementation of rock/soil, the destruction of microstructure, and some cracks and holes in rock/soil gradually. In addition, CaCO3 leaching and migration prove that the top of CaCO3 deposition should be the dividing line of groundwater infiltration mode in loess. The results of principal component analysis of groundwater can reflect the interaction between the main Heifangtai landslide groundwater and rock/soil.