To forecast gas leakage of a planned experiment,harmful gas leaking time from a scaled underground explosion cavity and ratio of leaked harmful gas to entire harmful gas are studied with theoretical analysis and numerical simulation.The leakage mechanisms are:(1) gas leaks through uniform porous media,(2) gas leaks through non-uniform porous media,(3) gas leaks through fractures.It shows that leakage time is proportional to two thirds power of explosive amount in scaled underground explosions.Percentages of leaked gas are approximately same for scaled explosions in same media.Theoretical results about leakage time is basically in line with scaled experimental results.

A mathematical model is built for cavity temperature and pressure in underground detonation after the completion of cavity growth.It incorporates gas permeation in porous media,heat radiation between gas and cavity-wall and heat conduction between gas and ambient media.A corresponding one-dimensional code on the basis of spherical symmetry finite volume method is developed. Catty pressure and temperature of an underground nuclear test in alluvium at Nevada Test Site are computed.Measurment data of cavity pressure are analyzed in detail.