| dc.description.abstract | This research using MX-80 bentonite as buffer to conduct a series of related researches on simulating groundwater flowing through the fracture aperture. Through the erosion test device completed by the team in the past, two transparent acrylic plates were used erosion and sedimentation test in fracture aperture. The environmental factors studied include mass loss comparisons with different flow rates, fracture aperture, crack inclination angles and water chemistry. In the erosion test, the water solution was pumped by the pump to make it contact with the suspension of bentonite, and then the turbidimeter and camera were used to measure the daily erode mass loss and record the expansion process. The sedimentation test is made of steel to design a platform with a controllable inclination angle. The acrylic plate to simulate the fracture aperture is placed on the platform, and the daily sedimentation of bentonite in the crack with different water chemical solutions and different fracture aperture angles is recorded by camera photography.
The results of the test show that the mass loss of the erosion test in the low flow rate is still affected by the water chemistry. In an alkaline hydrochemical environment, bentonite is affected by the strength of cations to develop the diffuse double layer, and the resulting flocculated or dispersed structure will affect the mass loss caused by erosion. In the sedimentation test comparing different inclination angles and different water chemistries, under the environment of cation strength of 4 mM and 8 mM, because the bentonite sample just came into contact with water in the first 5 days of the test, it was in the stage of unsaturated to saturation, and the outside of the sample was easier to deposition behavior occurs due to exfoliation. When the cation strength develops into a flocculation structure (about the 6th day), there is no obvious deposition behavior.The deionized water environment is easily affected by gravity, and sedimentation still occurs in the environment with an inclination angle of 30 degrees. In the erosion test with angle of 60 degrees, the interaction of gravity and water flow shear stress has an effect on the mass loss of bentonite. In the deionized water environment, its mass loss has reached 69% of the total sample mass in 30 days, which is the most serious mass loss environment in the test.
Therefore, it can be judged that among the factors affecting the quality loss of bentonite, the influence of water chemistry is the most significant. Therefore, it can be judged that among the factors affecting the mass loss of bentonite, the influence of water chemistry is the most significant. The structure of flocculated or dispersed will affect whether the bentonite is easily taken away from the original sample. The shear stress and gravity by the flow rate and the inclination angle will cause the movement of the bentonite particles to cause the mass loss of the sample. | en_US |