Upon realizing he was trapped, Yan Fei didn't hesitate to detonate a hugely powerful bomb to halt Tripiṭaka's pursuit. However, Yan Fei didn't resort to a mutual destruction tactic as Tripiṭaka might have assumed; he did it with absolute certainty of his own survival.
As the bomb exploded, Yan Fei quickly pulled out a sturdy steel bucket from the Universal Space and covered himself with it as protection. Then, the massive explosion occurred, collapsing all of the nearby tunnels.
Because of the protection from the steel bucket, Yan Fei inside didn't suffer any direct harm from the collapse. The steel bucket was specifically prepared by Yan Fei for emergencies, mainly for fire and explosion protection, and now it finally served its purpose by offering him unique protection. Although the force of the collapsing tunnels didn't directly impact Yan Fei, it was transmitted through the steel bucket, causing him some injury.