Fracturing behaviors of soil subjected to monotonic and fatigue pneumatic loading

The mechanical behaviors of soil exposed to monotonic and cyclic pneumatic loading are investigated through laboratory testing. The fracture morphology, air pressure, and earth pressure (EP) were monitored and analyzed. In monotonic pneumatic fracturing, pressure of air is the crucial factor that determines the length and number of fractures. In cyclic pneumatic fracturing, the number and propagation of fractures is greater than that under the monotonic loading, as well as the disturbance zone of the pressurized air to the soil. It is found that high-frequency injection maintains higher air pressure inside the soil, coupled with the cyclic loading, the fatigue fracturing effect is much better than that under monotonic loading. The patterns of fractures subjected to monotonic and cyclic loading are presented. It is concluded that the higher the injection frequency and air pressure, the larger the number and propagation range of fractures.