Abstract: The research results of engineering mechanical properties on closely jointed basaltic mass were only reported in the open literature from the Basalt Waste Isolation Project in Handford,USA and the Baihetan hydropower project in China. The insitu tests of the closely jointed basaltic mass were summarized from similar projects at home and abroad. The developed plunging colonnade and multilevel structural planes of closely jointed basaltic mass in China were discussed. The deformable discrete element method was applied to the modeling of its 3 dimensional numerical model. Then the scale effect and anisotropy of the insitu tests were studied by numerical bearing plate test with different plate diameters. The results show that the cause is mainly due to scale effect of bearing plate tests. The anisotropy of insitu tests decreases as the diameter of bearing plate increases. The closely jointed basaltic mass can be regarded as an isotropic rock mass when the diameter of bearing plate is over 6 m. The results have some practical value in engineering on utilization and reconstruction of jointed basaltic mass．