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Blasting in tunnel is still the major excavation method due to the complexity of Taiwan’s geology. To control the overbreak of blasting is the major task to insure the quality in a tunnel excavation. It also increases the operation safety and reduces the excavation cost. However, blasting control has not been focused in the past, and the blasting overbreak has caused probloms such as insufficient tunnel lining and ctc. To insure the construction quality of tunnel, this study is to find a new method of changing the content of a tunnel contract by adding a blasting control and monitoring items. Use the reasonable execavation quantity to pay contractors, and changc the tunnel lining method in the specification to control blasting overbreak. The results are listed in this study. After comparison with the past tunnel blasting, it shows the following improvents:(1)reducing overbreak, the average overbreak is controlled within 10-20㎝ which is largely reduccd from the past, (2)reducing the consumption of explosives. The powder factor is reduced from the previous 1.12∼1.78㎏/m3 to 0.85∼1.12㎏/m3, a 25%∼38% explosive amount reduced,(3)changing the blasting pattern and obtain the better fragmentation, (4)the secondary lining thickness is sufficient, (5)increasing the operation safety and reducing the accident.The study shows by adding the blasting monitoring and controlling items in the tunnel construction contract,it can reduce the blasting overbreak, reduce explosive amounts, reduce secondary lining amount, increase fragmentation, and increase construction quality and operation safety.
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