Yes, ground regolith and other local minerals might be available to mine - grind to powder, press into a shape(s) that can be Lego'd into the tunnel you want. S

Yes, ground regolith and other local minerals might be available to mine - grind to powder, press into a shape(s) that can be Lego'd into the tunnel you want. Sintered blocks are very strong in compression and 1-2 layers will allow long buildings to be made in the lava tubes or on the surface. crushed regolith will serve as insulating berms that embed structures.