You can dig the ground without a tent and heater. Also exactly on the site, remove all the snow and dilute a large bonfire on the site of the pit. When the fire burns out, cover the coals with a thick non -combustible material. The heat reflected down will warm the earth faster. After about fifteen minutes — forty the coals and begin to remove the ground with ordinary scrap and a soviet shovel. When you reach the frozen earth, make a bonfire again and wait for the earth to warn, and start digging again. If you have the opportunity to carry out explosive work, drill the pits, and lay out the explosive. After the explosion, you just have to remove the clods of the earth.