模拟酸雨干湿循环条件下红砂岩的崩解特性

Characteristics of red sandstone's disintegration under dry-wet cycle by simulated acid rain

为研究酸雨作用下红砂岩干湿循环崩解特性,在室内配制pH值分别为4.7、5.3、6.0、7.0的溶液以模拟雨水,对恩施红砂岩开展干湿循环条件下的崩解试验,获得了崩解颗粒含量、崩解率与干湿循环次数、溶液pH值关系。结果表明:溶液pH值越低,试样崩解速率越快,完全崩解所需干湿循环次数越少;试样崩解曲线具有明显的阶段性,可分为前期缓慢崩解阶段、中期快速崩解阶段、后期缓慢崩解阶段;对红砂岩进行X射线衍射试验,获得其矿物成分及含量。在此基础上,探讨了酸溶液对红砂岩崩解特性影响机理,主要原因是红砂岩中碳酸钙与盐酸的化学反应导致孔隙、裂隙形成、扩展并贯通;崩解曲线具有阶段性,是由于干湿循环的不同阶段岩块表面积变化所导致。

In order to study the disintegration law of red sandstone induced by the dry-wet cyclic action of acid rain,solutions with pH of 4. 7、5. 3、6. 0、7. 0 were prepared indoors to simulate acid rain,the – wetting-drying test was carried out on red sandstone from Enshi,Hubei Province. Then,relationships between contents of disintegrating particles,disintegration rate,cycle index and solution pH were obtained. The results show that,the pH value of the solution decreases with the increasing of the dissolution rate,and so the cycle indexes required for complete disintegration are less. The disintegration curve is phased,it can be divided into 3 stages,the early-slow disintegration stage, the medium-term rapid disintegration stage and late slow disintegration stage. X-ray diffraction test was also carried out on red sandstone,mineral composition and content of the samples were obtained. and the disintegration mechanism of the red sandstone induced by the acid solution was discussed,the main reason is that the chemical reaction between the calcium carbonate and the hydrochloric acid leads to formation,expansion and penetration of pores and fractures. The disintegration curve is phased due to the variation of surfacial area of the rock samples at different stage in the wetting-drying test.