Abstract: The cracking of stiffness and strength, due to existing and development of micro cracks in elastic region, causes the loosening scope of roadway surrounding rock expanded. By defining stiffness cracking coefficient and strength cracking factor, considering characteristics of strain softening and plastic dilatancy after post-peak, the article established an elastic-plastic flow damage model for weakly consolidated soft rock under non-uniform initial stress field on the basis of damage theory and strain softening model with three linear steps; inferred analytical solutions of stresses, displacements when surrounding rock generate three different failure areas: elastic zone, elastic and plastic softening zone, and plastic flow zone; and discussed the rule on the influence of original rock stress, strength cracking, dilatancy gradient of soft surrounding rock in Luxin coal mine on damage evolution, displacement and plastic circle of surrounding rock. Results show that dilatancy gradient has great effect on damage speed and displacements in plastic zone while it has little effect on the size of plastic circle and stress responses; that original rock stress level has remarkable influence on the distribution of plastic circle of the roadway; and that the rising of stiffness and strengthen cracking coefficient will accelerate the cracking speed of surrounding rock, which should be paid enough attention in analyzing the stability of the surrounding rock and designing weakly consolidated soft rock tunnel.

Key words: weakly consolidated soft rock, tunnel surrounding rock, stiffness cracking, strength cracking, non-uniform stress field, damage evolution