To limit the probability that dead load due to soil, superimposed earth, plants and trees will not be taken into account in the structural design, with respect to how these loads impact on the total load, which could lead to structural failure, which could lead to harm to persons.
To allow a reduction in the dead load factor for soil, superimposed earth, plants and trees, where the depth of the soil is greater than 1.2 m, on the basis that a slight variation in the depth will not have as big an impact on the total load.