A case study on variation of the coefficients K and n with proceeding of blasting works at the felsite zone

규장암지역에서 발파공사중 K 및 n의 변화에 대한 연구

  • 안명석 (기술사 사무소 G&B) ;
  • 박종남 (동아대학교 공과대학 자원공학과)
  • Published : 1998.12.01

Abstract

A case study was made on in site vibration velocity data collected for two months in the construction area of the Daeduck cultural City Hall. Taegu The geology over the area shows distributions of weathered and some crack developed hornfels of mud-shale in the upper part, underlain by less weathered and hard compact quartzite. For the period of 2 months of blasting event, the vibration velocities were measured and these data were analysed for K and n for three different period the test period, first month and second month. The data for the test period show that K and n are 2464 and 1.621 with the cube root method, and 7154 and 1.791 with the sqare root one, respectively. The data for the first month collected mostly from blasting in the upper hornfels show that K and n are 1668 and 1,492 for the cube root and 1219 and 1,366 for the square root, respectively. Such a significant decrease in the K and n values from the test period through the first month for the weathered and comparatively well crack developed rocks hard and compact lower quartzite, may be due to difference in attenuation of waves propagating through physically different media. Therefore, for more effective safety design and blasting, it seems that it may be n to adopt appropriate K and n values, with getting lower step by step while proceeding the operation. In the meantime, the attenuation rate of K and n together with SD cross point for the cube and square root methods indicates that the cube root one appears to be more applicable than the square root for this area with limited distance(The maximum is 100m).

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