Gas　safety　in　a　utility　tunnel　is　an　important　scientific　problem.　In　this　study,　explosion　model　tests　of　methane-air　mixed　gas　were　conducted　to　evaluate　the　safety　of　the　gas.　Furthermore,　the　influences　of　the　concentration　of　mixed　air,　ignition　mode,　and　opening　area　on　propagation　and　distribution　law　of　the　blast　wave　were　investigated.　The　results　demonstrated　that　a　significant　explosion　phenomenon　existed　if　the　methane　concentration　reached　10.5%,　manifested　by　the　largest　explosion　overpressure　peak　and　the　highest　overpressure　growth　rate.　Flame　propagation　was　accelerated　after　the　explosion　under　chemical　ignition.　The　overpressure　peak　was　an　average　of　approximately　70%　higher　than　that　under　the　electrode　ignition.　The　explosion　overpressure　and　its　impulse　can　be　reduced　effectively　only　for　a　certain　proportion　of　the　tunnel　opening　area.　Therefore,　the　present　study　can　provide　a　comprehensive　understanding　of　the　loading　characteristics　and　the　corresponding　mechanism　for　a　gas　explosion　in　various　practical　tunnels.