Unconfined strength of an unsaturated residual soil struck lightning

¹ PUC-Rio, Civil Engineering Department, 22451-900 Rio de Janeiro, Brazil
² UERJ, Physics’ Department, 20550-900 Rio de Janeiro, Brazil
³ CEPEL, LabDig, 21941-911 Rio de Janeiro, Brazil

^a Thiago de S. Carnavale: thicarnavale@gmail.com

Abstract

It is well known that different triggering factors are related to landslides occurrence. However, in many cases, it is not possible to identify main factors that may contribute to start a landslide. Following that, lightning phenomena is herein considered as a possible factor that may promote changes in the structure, and eventually, in the strength of soils. The current study aims to analyse the influence of laboratory simulated lightning in the structure of undisturbed granite-gneiss residual soil samples. The main focus is to compare the peak strength of unsaturated samples that were not struck by replicated lightning with the peak strength of soil samples struck by replicated lightning. The methods used are: Soil sampling and physical characterization; unconfined compression strength tests on unsaturated undisturbed samples; submission of soil samples to replicated lightning; unconfined compression strength tests on samples struck by replicated lightning and micro tomography of samples submitted to lightning. As results, it is seem that lightning may cause a hole with irregular geometry inside the soil. Analysing the tests of the samples struck by laboratory simulated lightning, a peak strength reduction with the charge incidence was observed. Comparing the variation of soil matric suction on the peak strength of the soil that was not struck by replicated lightning with that of the soil struck by the higher charge of the replicated lightning, it is observed that the samples struck by high-voltage presents lower values of peak strength.