Unconfined strength of an unsaturated residual soil struck lightning Thiago de S. Carnavale, Mariana F.B. Motta, Tácio. M.P. de Campos, Haimon D.L. Alves, Antônio R.M.B. de Oliveira and Hélvio J.A. Martins E3S Web Conf., 9 (2016) 14006 Published online: 12 September 2016 DOI: 10.1051/e3sconf/20160914006