With the increase of the magnetic field on the cathode surface, wave amplitude and equilibriumradius of the electron beam increase;
随着阴极表面磁场的增大，电子注注腰半径增大，电子注波动增大；
2
The assumed presupposition of limit equilibrium theory is recounted. Based on this, the expressive formula of radius of the non-elastic zone and rock displacement of tunnel outline was given.