A new inclinable shear apparatus for large sample testing: design and perspectives

The apparatus allows investigations on soil block samples with roots of different plant species commonly used for remediation and habitat restoration purposes under almost natural conditions. Shear stress results of rooted soils can be compared to those of un-vegetated soils with similar soil types. New and different to conventionally applied concepts, shear tests can be performed at variable inclinations up to 45˚, considering plant growth at the corresponding angle of slope. Furthermore, experiments can be conducted at variable depth of the shearing zone, with low normal stresses and low shearing rates of 0.01 mm/min. The measurements involve shearing force, shearing displacement (up to 200 mm), normal stress, normal displacement (dilatancy/consolidation) all recorded with high accuracy. Saturated and partially saturated soil samples containing roots can be tested with the soil humidity measured near the shearing zone. An automatic data logging system was designed for real-time visualisation of the different parameters and recording all required data in conjunction with the described direct shear apparatus.