地应力对碳酸盐岩溶解和岩溶发育的影响

Effects of Geo-stress on Carbonate Dissolution and Karst Evolution

地应力对碳酸盐岩溶解和岩溶发育的影响研究是一个值得注意但又长期被忽视的问题,结合地球化学、地质热力学、矿物岩石学、岩石弹塑性力学方面的知识,在理论上全面地分析地应力的影响.研究表明,在应力作用下,碳酸盐岩岩体内应变能提高、溶解反应自由能增加、裂隙发育特征与水流运动条件发生变化,使得碳酸盐岩固体表面处溶解物饱和浓度增大,改变了岩体内水流的厚度、水流流态以及水中碳酸盐岩溶解物浓度,从而影响了碳酸盐岩的溶解速率;且应力的存在改变了有效的水岩相互作用面积;应力作用下碳酸盐岩溶解存在的"应力-溶解"耦合竞争循环机制使得岩溶发育出现混沌现象和自组织行为,初始应力介入所导致的一个很微小的影响因可被迅速放大至成百上千倍而不可忽略,自然界中碳酸盐岩岩体内溶解和结晶并存、串珠状溶洞以及孤立溶洞的形成发育机制一定程度上可归结为应力溶解自组织行为的结果.

It is worthy of attention yet has been neglected for long time to explore effects of geo-stress on carbonate dissolution and karst evolution.A comprehensive analysis about the effects of geo-stress is carried out based on theories of geochemistry, mineralogy,petrology,geo-thermodynamics,and plastoelasticity in this study.The results reveal that the involvement of stress can change the dissolution rate of carbonate rocks by raising the strain energy and free energy of dissolution and changing the fracture characteristics and groundwater movement in carbonate rock,which leads to an increase of saturated concentration dissolved carbonate matters on the water-rock interface and changes of the depth and flow pattern of water and concentration of dissolved carbonate matters in water in carbonate rock fractures,and which can change the active area of interaction between carbonate rock and water in turn.Moreover,there exists a coupling and competitive mechanism because of stress-dissolution in carbonic rocks,which leads to behaviors of chaos and self-organization in the karst evolution.And so the effect of stress should not be ignored due to the fact that a minor change in the beginning aroused by stress can lead to great change in the evolution progress of karst,and the natural phenomenon of coexistence between dissolution and precipitation,moniliform distributed karst caves and isolated karst caves may be the results of the self-organization because of coupling and competitive behaviors aroused by stress-dissolution.