Initial shock pressure analysis for hole wall with air-decked charge

In order to analyze the initial shock pressure of hole wall with air-decked charge, the column charge is equivalent to a certain number of the spherical charges with Starfield method. Considering the attenuation and super- position of the pressure in the axial direction,the theoretical solution of the initial pressure acting on the hole-wall can be obtained for the charge conditions of up-air-deck and middle-air-deck,respectively. The stress monitoring is carried out with the numerical modeling by the software of ANSYS / LS-DYNA. Meanwhile,the stress field of explosion around the blast hole is also measured for the concrete model via the high-speed dynamic stress testing system. The comparison is conducted between the results obtained from the numerical measurements and theoretical solutions. Results show that the maximum stress occurs in the charging section for the up-air-deck charge condition. With the increase of the distance away from the charging section,the stress presents a sharp decrease first and maintains a relatively constant value. For the middle-air-deck condition,the minimum stress occurs at the middle of the air column and the maximum stresses occurs at the both end of borehole. The relative errors between the initial impact pressures obtained from the theoretical solution and numerical model are relatively small for both the two charging structures. The above mentioned results indicate that the pressure distribution is nonuniform along the axial direction of the borehole. Meanwhile,the stress distribution characteristics for the two charge structures agree well with the theoretical results,which verifies the rationality of the theoretical solutions.