Influence of lubricant fluids on swelling behaviour of Queenston shale in southern Ontario

The feasibility of using the microtunnelling technique to install pipelines through Queenston shale of southern Ontario is being investigated. In the microtunnelling technique, lubricant fluids - such as bentonite slurry and polymer solution - are used to facilitate excavation during installation of the pipeline sections. In this regard, a comprehensive testing program was performed to investigate the time-dependent deformation behaviour of Queenston shale considering lubricant fluids used in construction. The free swell test, semi-confined swell test, and the null swell test were utilized to perform this study. Results of 144 tests are presented and the variation of swelling characteristics of Queenston shale in lubricant fluids and in water is discussed briefly. The swelling model suggested by Lo and Hefny in 1996 was adopted to develop the swelling envelopes of Queenston shale in lubricant fluids and water in both horizontal and vertical directions with respect to the rock bedding. In comparison to swelling in fresh water, the study revealed that the polymer solution has substantially reduced the swelling of Queenston shale in all directions, while the bentonite solution was less efficient in reducing the swelling of Niagara Queenston shale, and has a slight negative influence on the swelling (i.e., increased swelling) of Milton Queenston shale.