On effects of a sudden increase of atmospheric pressure on unsaturated tropical soils

In January 2011, catastrophic landslides occurred in Rio de Janeiro. Still, rainwater infiltration in the unsaturated slopes was not considered the only reason for the deflagration of the slides, and investigations were started to evaluate if further environmental events could help to explain the disaster onset. Knowing that thunderclaps cause an abrupt increase in atmospheric pressure during tropical rainstorms, a research program was set to evaluate if such events could compromise the stability of unsaturated soil slopes. To do so, the results of triaxial experiments conducted on two unsaturated soils from Rio de Janeiro's natural slopes are presented and analyzed. Triaxial tests were run in a double-walled cell with bender elements located at the top and bottom of the specimens, and the total specimen volume change was measured. To simulate an abrupt increase in atmospheric pressure, air pressure peaks were applied at the top of the specimens before shearing under constant moisture content. Shearing was conducted under two net stresses and matric suctions. Comparing the stress–strain–strength and shear-wave velocity data of similar specimens with and without a sudden increase in air pressure, it was found that an increase in air pressure impacted the mechanical behaviour of the unsaturated soils.