<p>This study investigates the mechanisms of landslides in gentle stable soil slopes triggered by injection of either water or hydrogen peroxide (H₂O₂) solution through flume tests. A cement powder core at the sliding base is used to catalyze the decomposition of a small volume of H₂O₂ into minimal amounts of water and pressurized oxygen gas mass. Both water and H₂O₂ solution can trigger the deep-seated landslide in gentle slopes. The water-triggered landslides require the injection of substantial water of 82.9% sliding soil mass with high injection rates. But the H₂O₂-triggered landslides require only a small amount of solution of 0.63% to 12.05% of sliding soil mass. The failure modes of the landslides triggered by water or H₂O₂ solution are different. The water-triggered landslides exhibit ruptures and deep-seated slides. However, the H₂O₂-triggered landslides display soil upheaval and penetration. And the controlling factors are systematically analyzed with injection mass and rates, gas accumulation zone, and topographic factors. The results shows that the sliding displacement increases with the increasing of the injected H₂O₂ solution. Single-event injections cause more sliding displacements than fractional injections. The soil upheaval is positively correlated with the length of gas accumulation zone and inversely correlated with the sliding base angle. The above findings further confirm that the water triggered landslides can be recognized with a large amount of free water or liquified soil associated with the landslide debris while the gas triggered landslides can only have a small amount of free water or liquified soil in the landslide debris.</p>