Mechanism Of Rock Structure Weathering Front Expanding And Mechanics Effect In Slope Damp Vadose Zones

Low permeability rock has the characteristics of narrow pore, bad connectivity, big flow resistance, in which low seepage velocity result. Analysis upon monzonite and basalt weathering process demonstrate that low permeability rock weathering front is promoted by moisture diffusion of which mode is composite between Fick and Knudsen diffusion. Some minerals in fresh rock are preferential weathered because of moisture diffusion. Hence, initial compact structure is destroyed. Microfracture developed with the outward transferring of weathering production. On the one hand carbonic results acid from which moisture combined with CO₂ can accelerates mineral weathering. On the other hand water and other acid medium can enter into rock more effectively and increase weathering speed. Order for sensitive to weathering is: changes of Fe²⁺and Fe³⁺, changes of LOI and transfer of alkaline metal elements. Rocks are weathered more easily in damp vadose zones in which exists gaseous water.Observations of ground water dynamic changes found that slope ground water commonly originate from atmospheric rain. Corrupt ability of ground water enhanced when it dissolved humic acid and other acid matters. Congruent dissolution of salt, redox and incongruent dissolution of mineral happed during the process that rain flow through slope. Fountain composition and pH value mainly influenced by incongruent dissolution of mineral. The time of water soil interaction is direct ration with composite concentration, although the process is slow. The scale of water rock interaction is inverse ration with rock diameter, while the regulation is not always restrictly obeyed. Ground water fluctuant level is the slope weathering front.Researches into Touzhai slide indicate that: the impact of mechanics effect to rock induced by weathering can not be ignored. Weathering degree of that slide rock is not high, most corestones are still fresh. The key for that slightly-moderately weathering degree can evidently speed slope failure is that the character of chemical weathering is discrete and weathering product is special. Because of structure plane's weathering in deep slope, stress concentration or stress resistance are induced, then it become the weakest tache, and result in slide.