Mechanical strength characterization and seismic performance of rammed earthen walls built on eco-friendly lateritic soil and sustainable stabilizing materials

Underprivileged people in many parts of Asia, Africa, Europe, and Latin America use earthen dwellings because of environmental and economic advantages. However, such non-engineered structures often encounter unacceptable risks from various natural calamities such as earthquakes, floods, etc. The 3rd January 2017 moderate earthquake in Tripura (NE India) is prime evidence of severe damage to earthen houses in rural Tripura. The present research focuses on enhancing the seismic strength of traditional earthen houses through mechanical stabilization with locally available low-cost sustainable natural fibers (i.e., jute and straw) and stabilizing materials (i.e., clay and lime), respectively. Primarily, the shear and flexural strength of both stabilized and unstabilized model rammed earthen wallettes are investigated experimentally. Thereafter, a 3D finite element (FE) numerical model is developed to verify the sanctity of the experimental findings. The study reveals that fiber-reinforced earthen wallettes, especially jute fiber-reinforced wallettes, exhibited significant improvement in shear and flexural strength including ductility behaviour whereas, clay and lime-stabilized wallettes offered improvement in strength exhibiting brittle failure. Finally, the seismic response of a prototype fiber-reinforced rammed earth wall is evaluated through 3D FE-based numerical modelling considering the input motion of the 2017 Tripura earthquake which also indicated significant improvement compared to the unimproved one. However, from the viewpoint of sustainability, it is concluded that carbon emissions of approx. 38% may be reduced in the case of natural fibers such as jute and straw compared to synthetic stabilizing agents (i.e., lime). Hence, the study promotes the use of low-cost sustainable fibers with a lower carbon footprint and minimum energy consumption in earthen houses.