Abstract:In order to further study the effect of group nailing effect on the shear properties of large diameter bolts, finite element analysis was carried out based on previous tests, and the phenomenon of the reduction of shear strength and shear stiffness of large diameter bolts under the influence of group nailing effect was further discussed. Based on the calculation results, the fitting formula of ultimate shear strength and shear stiffness of large diameter bolts was proposed. The results show that the smaller the distance between large diameter bolts is, the more obvious the effect of group nails is. The shear strength and shear stiffness of large diameter bolts both decrease significantly compared with that of single bolts. Under the influence of the group stud effect, the non-uniformity coefficient distribution of shear in the elastic stage is horseshoe shape, and that in the plastic stage is diagonal, but it is crescent shape when the distance between studs is too small. When the studs are in the elastic stage, the shear force of the inner stud is smaller than that of the single stud, and in general the shear force of the outer stud is smaller than that of the single stud,but when the distance between studs is too large the shear force of the outer stud is larger than that of the single stud. When the studs are in the plastic stage, the effective shear section height of the inner stud is higher than that of the single stud, and the effective shear section height of the outer stud is lower than that of the single stud. When the spacing to diameter ratio of large diameter studs is less than 3.33, the group effect is obvious, and when the ratio is higher than 8.33, the group effect has little effect.