Due to the distinctive formation mechanism of columnar joints

columnar jointed basalt exhibits strong discontinuity and anisotropy. The columnar jointed basalt rock mass in Baihetan project is selected as a case study. The structural control effect on the equivalent modulus of deformation is discussed by using jointed finite element method (JFEM). The results show that

on the transverse plane

the equivalent modulus of deformation increases with the column irregularity

which increases about 10% from completely irregularity to completely regularity. This trend also agrees with the increase of the column size. The equivalent modulus of deformation corresponding to a side length of 0.1 m is 5.36 GPa

and this value increases up to 23.4 GPa for a side length of 0.5 m. Columnar joints rock mass may be considered as isotropic on the transverse plane

and basically

the equivalent modulus of deformation varies correspondingly with joint stiffness. But when it comes to the longitudinal plane

the wider joint spacing of the joint set 2 is

the higher equivalent modulus of deformation is. The equivalent modulus of deformation increases firstly then decreases

and reaches its maximum value when the cross-bedding ratio is 50%. The equivalent modulus of deformation on the longitudinal plane shows a similar correspondence relationship with the joint stiffness on the transverse plane. The simulation results obtained by JFEM agree well with the existing field observations and 3D numerical studies.