A NEW IN-SITU TEST METHOD OF GAS PERMEABILITY AND IT'S UTILITY ON THE FIELD OF SUFFOSION LOESS

The gas permeability values of in-situ and undisturbed Malan loess samples at different areas are measured with improved air permeameter. The reliability of the in-situ gas permeability test is verified by comparing the results of in-suit and indoor gas permeability. The effects of particle size, pore ratio and water content on the gas permeability are compared and analyzed with a method of combining the two kinds of gas permeability. The effects of collapsible cracks(fractures) and suffosion caves on the gas permeability of loess are analyzed with in-situ test. The results show that the indoor and the in-situ gas permeability are basically consistent, the in-situ gas permeability test results are reliable. The in-situ gas permeability test removes the impact of transport disturbances and can be more accurate and reflect the real situation of loess. The indoor gas permeability test is only suitable for the uniform loess sample without obvious cracks. As the coarse particles of the Malan loess increase the gas permeability increases, otherwise the gas permeability decreases. As the loess depth increases, the void ratio decreases, the water content increases, and the gas permeability decreases. As the loess near the collapsible cracks(fractures) and suffosion caves, the gas permeability increases obviously. As the loess far from the collapsible cracks(fractures) and suffusion caves the gas permeability is tend to an average value. The in-situ gas permeability measurement process is fast and convenient. This method has broad application prospects in evaluating the permeability and structural defects in the loess.