This is where I got my numbers on radiation shielding for Mars One

CEO Bas Lansdorp writing for Space.com:

The Mars One habitat will be covered by a necessary layer of soil that provides shielding even against galactic cosmic rays. Sixteen feet (5 meters) of Martian soil provides the same protection as the Earth's atmosphere — equivalent to 1,000 grams per square cm(227.6 ounces per square inch) of shielding. The Mars One habitat can support a soil layer 36 feet (11 m) thick. If the settlers spend, on average, two hours per day outside the habitat, their individual exposure adds up to 22 mSv per year.