Investigation into the shear behaviour of rammed earth using shear box tests

Scientific investigations into the structural properties of rammed earth (RE) are gaining momentum and a number of parameters (e.g. suction, particle size distribution and water content), influential on material strength and other properties, have been identified and investigated. Cement stabilisation is undergoing continued investigation, while fibrous stabilisation, also known as fibre reinforcement, is beginning to gain attention. Recent experiments have shown that the addition of fibres such as straw or wool to RE or other earthen materials can improve its flexural strength. Less attention, however, has been paid to the fracture behaviour of RE, and to its shearing behaviour. This paper presents a preliminary investigation into the shearing behaviour of stabilised and unstabilised RE reinforced with waste natural fibres. The Direct Shear Test (DST) is used to obtain peak shear stresses and displacements, from which strength parameters (φ’) and cohesion (c’) are obtained. This paper also presents some scanning electron microscope (SEM) images of these materials. The results show that wool fibres decrease the density and peak shear strength of RE. The effect of water, wool and cement content on φ’ and c’ are also discussed