Abstract: Taking some mine as the engineering background, the 105 groups of numerical simulation project have been designed according to the possible existence of ground stress type of deep soft rock roadway and to the angle alpha which represents the numerical value between roadway axis and the direction of maximum horizontal principal stress. The law of the stability of surrounding rock of deep soft rock tunnel excavation, changing along the coefficient of axial and radial lateral pressure coefficient (λy， λx) and the angle of the roadway axial (α), has been studied. Besides, both the weight of Nλn that stands for the factor of lateral pressure coefficient and Nα that represents the factor of axial angle in complex stress field have been studied. The results have shown that the suitable axial angle for the layout of roadway is related to the type of stress field, and that not only laying along the maximum horizontal principal stress is the most conducive to the stability of roadway surrounding rock; When the axis of roadway in deep rock does not parallel with the direction of horizontal principal stress, the horizontal principal stress (be it the maximum or the minimum) that is closer to the axis of roadway could be regarded as the axial stress, while the other horizontal principal stress could be taken as the radial stress.

Key words: principal stress, roadway layout, impact factor, deep soft rock roadways, the stability of surrounding rock