ﻣﺪل ﺳﺎزي ﻓﯿﺰﯾﮑﯽ ﺑﻪ ﻣﻨﻈﻮر ﺑﺮرﺳﯽ اﺛﺮ زﻣﺎن ﺗﺄﺧﯿﺮ ﺑﺮ روي ﺳﺴﺖﺷﺪﮔﯽ ﻧﺎﺷﯽ از اﻧﻔﺠﺎر

Experimental study of the effect of time delay on blasting weakness

در اﯾﻦ ﻣﻘﺎﻟﻪ ﺗﺄﺛﯿﺮ ﻓﺎﺻﻠﻪ زﻣﺎﻧﯽ ﺗﺄﺧﯿﺮ ﺑﺮ روي ﺳﺴﺖ ﺷﺪﮔﯽ ﻧﺎﺷﯽ از اﻧﻔﺠﺎر ﻣﻮرد ﻣﻄﺎﻟﻌﻪ ﻗﺮار ﮔﺮﻓﺘﻪ اﺳﺖ. ﺑﺮاي اﯾﻦ ﻣﻨﻈﻮر ﺳﻪ ﺑﻠﻮك ﺑﺘﻨﯽ ﻣﺸﺎﺑﻪ ﺑﺎ اﺑﻌﺎد 50*30*14 ﺳﺎﻧﺘﯽ ﻣﺘﺮ ﺳﺎﺧﺘﻪ ﺷﺪه اﺳﺖ و ﺗﻌﺪادي آزﻣﺎﯾﺶ ﺑﺮ روي اﯾﻦ ﺑﻠﻮك ﻫﺎ ﻃﺮاﺣﯽ و اﻧﺠﺎم ﺷﺪه اﺳﺖ. در ﻫﺮ ﺑﻠﻮك 3 ردﯾﻒ ﭼﺎل و در ﺮ ردﯾﻒ 3 ﭼﺎل ﺣﻔﺮ ﺷﺪه اﺳﺖ. ﻗﻄﺮ ﭼﺎل ﻫﺎ 6 ﻣﯿﻠﯽ ﻣﺘﺮ و ﺑﺎرﺳﻨﮓ و ﻓﺎﺻﻠﻪ ردﯾﻔﯽ اﻟﮕﻮي اﻧﻔﺠﺎر ﺑﻪ ﺗﺮﺗﯿﺐ 50 و 75 ﻣﯿﻠﯽ ﻣﺘﺮ ﺑﺎ ﻧﺴﺒﺖ S/B ﺑﺮاﺑﺮ ﺑﺎ 1/5 در ﻧﻈﺮ ﮔﺮﻓﺘﻪ ﺷﺪه اﺳﺖ. ﺑﺮاي اﻧﺪازه ﮔﯿﺮي ﺳﺮﻋﺖ ﻣﻮج ﻓﺮاﺻﻮت ﭘﯿﺶ و ﭘﺲ از اﻧﻔﺠﺎر، دوازده ﻧﻘﻄﻪ ﺑﺮ روي ﺑﻠﻮك ﻫﺎ در ﭼﻬﺎر ﺧﻂ و ﺳ ردﯾﻒ ﭘﯿﺎده ﺷﺪه اﺳﺖ. ﺑﻠﻮك ﻫﺎ ﺑﺎ اﺳﺘﻔﺎده از ﻓﺘﯿﻠﻪ اﻧﻔﺠﺎري 12 ﻣﯿﻠﯽ ﮔﺮم ﺑﺮ ﻣﺘﺮ در ﺳﻪ ﻓﺎﺻﻠﻪ زﻣﺎﻧﯽ ﺗﺄﺧﯿﺮ ﺑﯿﻦ ردﯾﻔﯽ ﻣﺘﻔﺎوت ) 50 ،25 و 75 ﻣﯿﻠﯽﺛﺎﻧﯿﻪ( آﺗﺸﮑﺎري ﺷﺪ. ﺷﺎﺧﺺ ﺳﺴﺖﺷﺪﮔﯽ ﺑﺎ ﺗﺮﮐﯿﺐ ﺗﻔﺎوت ﻣﻘﺪار ﺳﺮﻋﺖ ﻣﻮج ﻓﺮاﺻﻮﺗﯽ در ﺑﻠﻮك¬ﻫﺎي ﺳﺎﻟﻢ و آﺗﺸﮑﺎري ﺷﺪه ﺗﻌﺮﯾﻒ ﺷﺪ. ﻧﺘﺎﯾﺞ ﺑﺮاي ﺟﻬﺖﻫﺎي ﻣﺨﺘﻠﻒ اﻧﺪازهﮔﯿﺮي ﻣﻮرد ﺗﺠﺰﯾﻪ و ﺗﺤﻠﯿﻞ و ﺑﺤﺚ ﻗﺮار ﮔﺮﻓﺖ و ﻧﻘﺸﻪ ﺧﻄﻮط ﻫﻢﺗﺮاز ﺳﺴﺖﺷﺪﮔﯽ ﺑﻠﻮك ﻫﺎ ﻧﯿﺰ ﺗﺮﺳﯿﻢ ﺷﺪ. ﻧﺘﯿﺠﻪ ﺣﺎﺻﻞ از اﯾﻦ ﻣﻄﺎﻟﻌﻪ ﻧﺸﺎن داد ﮐﻪ اﻓﺰاﯾﺶ ﻓﺎﺻﻠﻪ ﺗﺄﺧﯿﺮ زﻣﺎﻧﯽ ﺗﺄﺛﯿﺮ ﻣﺘﻔﺎوﺗﯽ ﺑﺮ روي ﻣﻘﺪار و ﺗﻮزﯾﻊ ﺳﺴﺖ ﺷﺪﮔﯽ دارد.

In this paper, the effect of time delay interval on blast-induced weakness has been studied. For this purpose, three similar concrete blocks with dimensions of 50 ×30×14 cm have been constructed and a number of experiments have been designed and performed on these blocks. In each block, three rows with three blastholes in each row have been drilled. The diameter of the blastholes is 6 mm and pacing and burden were designed 75 and 50 mm, respectively, giving an S/B ratio of 1.5. Twelve points were arranged on the blocks in four lines and three rows to measure ultrasonic wave velocity before and after delay blasting. Blocks were blasted by detonating cord of 12 g/m in three different delay time intervals between rows including 25, 50, and 75 millisecond. Weakness index was defined by incorporating difference of ultrasonic wave velocity in intact and blasted blocks. The results were analysed and discussed for different measuring directions and contour plot of weakness in blocks was plotted. This study concludes that increasing of time delay interval has different effect on the magnitude and distribution of weakness.