암반 손상대 제어를 위한 선행이완발파 시공 적용 사례
Application of Pre-Fracturing Blast for Blast-Induced Damaged Zone Control
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초록
선행이완발파의 일종인 프리프랙쳐링발파는 기계식 굴착에 선행하여 발파로 암반을 취약화하는 공법이 다. 본 연구에서 프리프랙쳐링발파의 BIDZ (Blast-Induced Damaged Zone) 제어 효과를 검증하기 위 해 실증 현장에서 채취한 코어의 암반 물성을 측정하고 물성 변화를 통해 BIDZ를 평가하였다. 발파와 기 계식 굴착을 병행하는 복합 굴착에 의한 EDZ (Excavation Damaged Zone)에서 일반적으로 기계식 굴 착에 의한 영향 보다 발파에 의한 영향이 주요하기 때문에 BIDZ 제어는 곧 EDZ 제어로 이어진다. 포아송 비, 탄성파 속력, 공극률, 밀도, 인장강도, 수리전도도, 열전도도에 대하여 일반 발파 대비 프리프랙쳐링 발파가 BIDZ를 더 작게 발생시켰다. 그러나 영률과 일축압축강도에서는 BIDZ 저감 효과를 확인할 수 없 었다. 발파 인장 균열 범위에 관한 이론식을 적용해 실내시험의 결과와 비교하여 BIDZ가 합리적인 수준 에서 예측되었으나 지반 조건이나 장약량에 대한 가정으로 인해 BIDZ 범위 예측에 한계도 확인했다.
Abstract
Pre-fracturing, a type of pre-conditioning blast, is a method used to weaken rock masses prior to mechanical excavation. In this study, various laboratory tests were conducted on rock core samples obtained from the field to verify the effectiveness of pre-fracturing in controlling the BIDZ (Blast-Induced Damaged Zone) by measuring the physical properties of rock cores obtained from a test site and assessing changes in these properties. In the EDZ (Excavation Damaged Zone) caused by combined excavation using blasting and mechanical excavation, the effect of blasting is generally more significant than that of mechanical excavation, so BIDZ control directly leads to EDZ control. In terms of Poisson’s ratio, elastic wave velocity, porosity, density, thermal conductivity, tensile strength and hydraulic conductivity, the BIDZ size in pre-fracturing was smaller than that of conventional blasting. However, no clear reduction in the BIDZ was observed in the case of Young’s modulus and uniaxial compressive strength. By applying a theoretical formula predicting the range of tensile cracks caused by blasting and comparing it with the laboratory results, the BIDZ was reasonably predicted. Nonetheless, limitations in accurately predicting BIDZ size were identified due to assumptions regarding ground conditions and charge density in the formula.
참고문헌 (11)
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