INVESTIGATION OF MUD INTRUSION INTO SAND AND ITS EFFECT ON SOIL PROPERTIES
This research explores drilling mud intrusion into sand surrounding a horizontal boring and its effects on the soil properties. At the first stage, small-scale laboratory experiments investigated the effects of bentonite mud on soil gradation of sand in horizontal directional drilling (HDD). Two pressure vessels were used, one as the test chamber and the other one as a mud tank. A hose connected the bottom of the mud tank, pressurized by connecting it to a compressor, to the lid of the test chamber. The pressurized mud was applied on top of the sand. Eight tests were run on dry sand to monitor the effects of mud penetration into sand of four different factors: mud pressure, bentonite concentration, soil density, and test duration. At the end of each test, the % bentonite intruded into sand was determined for every 10 mm soil layers as the difference between the % finer than of the initial sand and the mud-sand mix. The results showed a higher % bentonite intruded into sand for loose sand compared with the dense one at the same pressure and bentonite content of the drilling fluid. Also, a higher % bentonite was obtained in the first 4 layers of the soil for the test with a 5% bentonite drilling fluid compared with 3% and 4% ones on the same loose sand and at the same mud pressure; however, this percentage of bentonite intrusion for the bottom layers of the specimen with a 5% bentonite drilling fluid is less than 3% and 4% ones. As expected, more bentonite penetrates into the sand for a constant mud pressure and the same loose state of the sand when tests have longer duration. In the second stage of the project, triaxial tests were run on remolded sand samples mixed with the measured percentages of bentonite intruded into soil samples seen during the mud intrusion tests. Thus, the soil strength parameters and the undrained shear strength of the sand-mud mixes were obtained at different confining stresses were obtained, considering the effects of mud intrusion on the short-term response of the soil expected during a directional drilling project.
URI for this recordhttp://hdl.handle.net/1974/24966
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