Experimental Research On The Disintegration Characteristics Of Expandable Tuff

The tuff is a very special expansive soft rock. It can be easily disintegratedowing to its complex composition and specific structure. Because of its disintegration,it’s apt to deformation and failure in the underground mine excavation which affectsthe normal construction. Considering the insufficient domestic study of the soft tuffdisintegration, this article based on the lead and zinc tuff in Lancang Yunnan throughthe laboratory experiments and microscopic measurements to analyze thedisintegration mechanism before and after the disintegration. The results in this papermay be a reference for practical engineering.First,select the representative pure tuff rocks from the sample rocks. Do somephysical and mechanical researches, including its moisture content, density, porosity,water absorbability, free expansion, point load, so as to get a conclusion that tuff rockscontains a lot of clay minerals such as montmorillonite. it is hydrophilic and its freeexpansion are different under different moisture conditions. This kind of rock has lowintensity being called the very soft rock.Second, do a series of disintegration experiments, including the crumbling, dryand wet moist circulation experiment, disintegrative resistance index. The results ofthese experiments shows that the tuff in water is extremely easy to disintegrate, andits disintegrative speed is direct related to the content of hydrophilic clay mineral initself. That is to say, the more the hydrophilic clay mineral, the faster it apart. In thedry-wet circulation conditions, tuff disintegrates more quickly. It can absolutelycollapse only in two circles. Experiments determination show that the disintegrativeresistance index is relatively low, its water stability and durability are very low, andthe degree of cementation between particles is weak.Finally, combining with series of disintegrative experiments, detecting themineral and chemical composition of the tuff before and after the disintegration withthe help of XRD and spectral analysis, observing its microscopic structure with theuse of polarized microscopic technology, through the water expansion mechanism of the contenting mineral clay, the wedge crack pressure principle of micro-cracks andmicro-pore adsorption, and weakening mechanism of the cementation betweenparticles, all the steps above reveals the disintegration mechanism. After detailedanalysis a consequence comes out, that is the performance of tuff disintegration isaffected by the mineral clay content, types and the degree of consolidation betweenthe particles.