Dangerous Radiation on Mars

Mars's surface receives more radiation than the Earth's but still blocks a considerable amount. Radiation exposure on the surface is 30 µSv per hour during solar minimum; during solar maximum, dosage equivalent of this exposure is reduced by the factor two.

If the settlers spend on average three hours every three days outside the habitat, their individual exposure adds up to 11 mSv per year.
The Mars One habitat will be covered by several meters of soil, which provides reliable shielding even against galactic cosmic rays. Five meters of soil provides the same protection as the Earth's atmosphere-- equivalent to 1,000 g/cm2 of shielding. With the help of a forecasting system taking shelter in the habitat can prevent radiation exposure from SPEs.

There is a studying on tungsten alloy material for radiation protection, radiation ability could be calculated basing on the following formula:

Formula: K = e0.693 d / △1/2
K: Shield weakened multiple
△ 1/2: The shielding material of the half-value layer values
d: Shielding thickness, with the half-value layer thickness of their units, people need to half-value layer thickness of the quality of translation into the thickness of the material, divided by the density of the material can be obtained.

As there is a high density for tungsten heavy alloy material, then thickness could be reduced if there is a need of the same radiation protection ability.

For more information, you could click tungsten alloy radiation protection.