Abstract: The cement mortar model tests on the directional pressure relief blasting were carried out to make ultra dynamic strain tests from three directions of protecting borehole wall，free-face wall and bottom wall.Three-dimensional numerical simulation and numerical calculation of tests were made by using ANSYS/LS-DYNA software.The pressure value and the tests results with the same distance from explosives to borehole wall，free-face wall and underside wall were compared，the distribution of pressure was analyzed and the blast hole pressure relief effect by protecting borehole wall materials and bottom interval air column is explicated.The present results indicate that there is an obvious stress concentration phenomenon at one side of the free-face wall，is the same distance apart from the explosive center.The pressure at protecting borehole wall is lowered by the average 26% than that of the free-face wall，where the vibration isolation material，PVCU，plays a good directional protection.Air column at blast-hole greatly affects the pressure，and has a strong pressure relief function.The simulation results were in good agreement with the experimental date.

Key words: Dynamic strain test, Directional pressure relief blasting, Numerical simulation