Tunnel overloading safety can be gained by overloading experiment. In this paper

the overloading stability of forked tunnel is researched using 3-D geomechanical model test. The displacements

stress distribution and failure of surrounding rock are analyzed. And the model test is simulated by 3-D numerical method (FLAC3D) also. Model test result and numerical simulation result analysis shows that the side displacements increase and vault displacement vector changes from downwards to upwards with the side-pressure coefficient K. The stress of key points achieve high-point at K=3.5; the displacement changes suddenly when K≥ 4.0 and the maximum final displacement achieve 100mm. The plastic zone increases suddenly and surrounding rock at vault begin to crack and fall when K≥ 4.0. Test and numerical result shows that vault and side of forked tunnel are easy to fracturing; the overloading safety degree is 3.5.