The fractal structure is a common phenomenon of soil. Through analyzing influence domain(Voronoi domain) of the fractal structure connection point

the bearing capacity of particle connection is converted to stress intensity. Some beneficial results are obtained. Values of fractal dimension of particle system structure influence soil strength obviously. The particle of basic unit is more

the ring from the particle is longer

the space for the ring is larger; it is more instable in mechanical property

the strength is lower. The stage number of fractal structure determines the size of the maximum pore. The stage number of fractal structure is more

the size of the maximum pore is larger

the equivalent stress intensity is lower. The couple stress intensity is inversely proportional to the area of basic structure unit (two-dimensional). That is to say

the basic structure unit is larger

the couple stress intensity is lower. Therefore

it can be concluded that the particle is larger

the couple stress intensity is lower when other conditions are same.