Research On Expansion Test Of Mudstone Property And Modificaiton Mechanism

In coal measures strata, mudstone is the main composition, account for around50%of all sedimentary rock. Mudstone is composed of many small particles, these tiny particles contain a lot of clay minerals, also include a lot of quartz, feldspar and other minerals, etc. Due to the presence of clay minerals in mudstone, its physical and chemical properties and its own state are susceptible to environmental factors (water, temperature, humidity and pressure), especially, when the outside humidity changed, mudstone could show strong water sensitivity, swell, dehydrate contraction, and prone to softening disintegration. In recent years, with the continuous development of engineering construction in our country, in the field of geotechnical engineering, mine engineering, and many other engineering, structure damage caused by the mudstone increases the unstability of the engineering accident. This brings not only to builders safety hazard, but caused huge economic loss. Therefore, it is very necessary to study the physical and chemical characteristics of mudstone systematically and to understand the mechanism of mudstone break, for providing to engineering theoretical guidance.In view of these, this article based the mudstone rich in clay minerals as object, deeply researched the diagenetic history, material composition, chemical composition and harmfulness of mudstone in coal measures strata, and further tested the shale swelling, shale collapse cycling, compression-shear destructive of mudstone and organosilicone modification. Experimental study of mudstone made the following progress, as follows:1. Through the analysis of the typical soft rock mining area in our country and material and chemical composition in different diagenetic mudstone geological period, that clay minerals in mudstone content was of large span, ranged from5%to74.2%, the content of montmorillonite was also high and low range, the highest was54.2%. For the influence of different diagenetic period, diagenestic sites and diagenetic environment, the main chemical components in coal measures strata shale was SiO2and Al2O3, the content was about75%of the total content; But the SiO2was more of48.08～78.25%; Al2O3was of10.18～29.18%; Some physical and mechanical index of mudstone were large controlled by the composition of the rock, such as grain size, cementation characteristics.2. Study on the distribution of hole crack and water absorption in mudstone, we concluded that the mudstone was of small aperture, low degree of fracture and poor connectivity between fracture, this distribution characteristics of hole crack made it difficult for the liquid to migrating in the pore. So mudstone has strong water insulation capability under natural conditions. But with the artificial disturbance, we broke up the "natural barrier" of mudstone, the macroscopic structure of mudstone was destroyed, combined with weathering process, water absorption, water loss and so on, they further speeded up the structural damage from macroscopic to microcosmic, accelerated the development of crack, and enhanced connectivity between the fissure, conduced to the erosion of water.3. Mudstone swell-shrink experiment was carried out, and we concluded that the layer of bearing influenced swelling of mudstone, with the enlargement of the angle between layer and end face, expansion rate gradually decreased; Different hydrochemical environment (concentration, cationic) made different effects on the shale swelling. With the decreasing concentration of aqueous solution, expansion rate of sample increased in turn and terraced; Defined the absolute expansion rate, relative expansion rate, and the concept of relative reduction, dry-wet cycles and absolute expansion rate were positively correlated, and negatively correlated with relative expansion ratio and relative reduction.4. Mudstone disintegration cycling experiment was carried out, we discussed the inner mechanism of mudstone clay and disintegration, and used nonlinear fractal theory, qualitatively revealed the relationship between fractal dimension value and shale collapse. The mechanism of disintegration was introduced.5. Mudstone compression shear destruction experiment was carried out, and every process of crack in each period of mudstone fractures was analysed, and using the nonlinear fractal theory, the fractal characteristics of broken block were described. It is concluded that the fractal dimension value D could better reflect the compression-shear damage characteristics of rock mass.6. Organic silicon modified experiment was carried out, we comparative studied the physical characteristics of hydrophobic, swell-shrink and pore fissure of mudstone before and after the modification. It is concluded that the modification of organic silicon increased the permeability and hydrophobic of mudstone; Because of the infiltration of modified liquid, number of pores on the surface of mudstone was significantly reduced, and the size of aperture was obviously decreased, but the hardness of mudstone was increased. The expansion rate of modified sample was14.7%of the mudstone before modification, and the compressive strength and tensile strength respectively increased2.83times and1.92times.