Abstract: To study the explosion effects in partial confined tunnel structure and perfect the calculation method of overpressure, a dimensionless function of air shock wave overpressure inside the tunnel and outside the portal during explosion in partial confined tunnel structure was established based on dimensional analysis method, and the similarity of physical quantities in scaled model tests of partial confined tunnel structure was illustrated. The geometric similarity of key parameters such as shock wave overpressure was verified by comparing the 1∶6 and 1∶4 test data. Based on the 1∶4 model implosion test data and numerical simulation results of multiple charges, basic form of the shock wave propagation function relationship was introduced, the engineering calculation methods for the overpressure distribution inside the logistics channel and outside the portal was established through data curve fitting. It is found that the engineering calculation methods inside the logistics channel and outside the portal are in relatively high agreement with the test data, with maximum relative errors of 9.5% and 10.6%, respectively. Engineering calculation methods can provide technical support for the structural design of partial confined tunnel structure and the calculation of safety distances.