How does inclinometer casing behave in soft soil? Does it deform sufficiently to detect the shear zone or does its stiffness simply distribute the movement?
Erik Mikkelsen says: I have heard this concern voiced from time to time, but the evidence from measurements in slopes and landslides suggest that it should not be a big concern, particularly in soft (loose) soil. In soft soils, shear displacements are more distributed than in harder soils. For example, the shear zone in a basalt landslide complex was measured to be 15 inches thick using special inclinometer procedures. On the south Oregon coast (Arizona Inn landslide) in mélange, the shear zone is on the order of 2 to 3 feet thick after a major rupture and repair work. Measurements at the toe of an embankment in soft silts and clays next to the Puyallup River in Tacoma indicated a shear zone of 4 to 6 feet. Based on the experience above, I think that within the measurable range of the inclinometer system, the stiffness of the inclinometer casing will not appreciably redistribute displacements. A significant rupture occurs most likely on a plane or a thinner zone, but that is the beyond
