Experimental Study On Mechanical Properties Of Constrained Argillaceous Dolomite With Freezing-thawing Cycles

Guizhou is a mountainous province. More and more western infrastructure construction, a variety of slope engineering, foundation pit, tunnel engineering make the rocks exposed. More and more poor rock entered people’s field of vision. With rock engineering in cold and freezing-thawing conditions, effects of temperature changes on the stability of rock is an important factor that cannot be ignored. This paper focused on the dolomite in Guizhou Province. Researching on constrained argillaceous dolomite mechanics characteristics in freezing-thawing cycles, and providing a theoretical basis for the design, construction and safety operation and maintenance of rock engineering in cold region, is of great practical significance and theoretical significance.This paper is based on 2 main experiments. One is the traditional freezing-thawing cycle test and the other is the test of observing stress loss. The freezing-thawing cycle test, which is indoor fast freezing-thawing test in water saturated state, includes 7 groups of samples. Freezing and thawing every 12 hours is the one period, total 30 cycles. In the circulation process, the author observed and recorded the appearance change of rock, and tracked the physical parameters, for example, quality and P-wave velocity. In addition, a group of rocks were taken for uniaxial compression test in each 5 cycle to obtain the uniaxial compressive strength of rock specimen, elastic modulus and other mechanical parameters in uniaxial compression. Finally, the variation laws of the physical parameters and mechanical parameters were found.The test of observing stress loss is a major innovation point of this paper and applies a method of constraining on the rock. Placing two 10 mm thick square steel plate that connected by four high strength screw in two ends of the sample and adjusting the tightness of the bolts to change stress magnitude. We take the constrained rock for freezing-thawing cycle test. In order to get the attenuation law of strain which react the changing rules of stress, strain gauge was pasted in the screw and the strain of screw was acquired through DH3816 N static strain testing system which is produced by Jiangsu Donghua Limited by Share Ltd test technology.The test results show that the damage and deterioration phenomena of argillaceous dolomite that the longitudinal wave velocity of rock specimen, uniaxial compressive strength, elastic modulus and other parameters decreased are obvious in freezing-thawing cycle. The stress loss of constrained rock presents obvious regularity that loss is more obvious in the cycle of initial section and end section, the middle section is small. Preliminary analyses of the rules show that inherent stress will be affected by the nature of rock itself and external environment of the dual factors.