Characterizing the shear parameters of rammed earth material by using a full-scale direct shear box

Rammed earth (RE) is one of the different techniques of earth constructions. The RE wall is built by compacting the soil in a formwork, layer after layer (about 10-15 cm thick for each layer). RE buildings are recognized for their very low embodied energy and their positive hygrothermal behaviour. Several recent studies have investigated RE material and among different aspects, the seismic performance remains an interesting topic that needs to be explored. In order to propose a robust model for seismic investigation, the shear characteristics of RE material should be appropriately determined. These shear characteristics include the cohesion, the friction angle of the intralayers and also the cohesion, the friction angle of the interlayers (between the layers) as a RE wall contains multilayers. However, few studies have directly identified these parameters by experiments. This is the first time, to our knowledge, that a full-scale shear box (0.5 m width × 0.5 m length × 0.45 m height) was specifically developed to study the shear parameters of the rammed earth. This full-scale shear box was designed to reproduce the manufacturing conditions of a current rammed earth wall in Europe (50-cm-thickness). Direct shear tests were performed both for intralayers and interlayers. The results showed that the shear strength obtained at the interlayers were about 80-90% of the corresponding values obtained at the intralayers. Finally, the influences of the moisture content and the size effect on the obtained results were also discussed.