| River valley landslides are common in central Alberta, where several large rivers and tributaries cut the Upper Cretaceous bedrocks and overlying glacial deposits post-glacially, forming steep valleys. Failure mechanisms of river valley landslides are complex and there are uncertainties in the use of pore pressures and mobilized shear strength for stability analyses.;To improve long term pore pressure measurements in weak rock, a flushable piezometer was developed and tested the field. The instrument, comprising a flushable adaptor, flushing tubes, a high air entry filter, and a normal vibrating wire piezometer, has ability to remove air bubbles from the piezometer cavity. Unlike a twin-tube hydraulic piezometer, the flushable piezometer installation depth is not limited by the water columns inside the flushing tubes. This ability to flush out air from the piezometer cavity significantly improves long-term pore pressure measurements in weak rock.;A detailed study of three landslides along the North Saskatchewan River Valley in Edmonton, Alberta was conducted. The study revealed that the river valley landslides are caused by a combination of several factors, including toe erosion by the river, residential developments behind the slope crests, the rise of groundwater levels due to urban development, and softening of the bedrock at the valley wall.;Observations of the river valley landslides also revealed that these landslides can be idealized into five kinematic stages. In order to account for the formation of a graben in the stability analysis, a simple two inclined block model is introduced. This model can be used to analyse different landslide stages, starting from a single-block to a two-block movement. The results also revealed that the formation of a counter scarp, separating the active and passive blocks, triggers an acceleration of slope movement.;A series of laboratory and field investigations were conducted to improve the pore pressure measurements in weak rock. The laboratory investigation included a determination of the cement-bentonite grout properties and pore pressure response testing of grout and clay shale samples. Investigation results revealed that the grout mix with a water:cement:bentonite ratio of 2.0:1.0:0.3 could be successfully used for grout-in piezometer installation in weak rock. |
