ارزيابي پارامترهاي هندسي موثر بر طراحي شيب بهينه ديواره نهايي معدن طلا-مس شادان

Evaluation of geometrical parameters affecting on the optimal slope design of Shadan Gold-Copper Open Pit Mine

اﻧﺘﺨﺎب ﺷﯿﺐ ﺑﻬﯿﻨﻪ و ﭘﺎﯾﺪار ﺑﺮاي ﺟﻠﻮﮔﯿﺮي از اﺿﺎﻓﻪ ﺑﺎﻃﻠﻪﺑﺮداري و ﮐﺎﻫﺶ رﯾﺴﮏ رﯾﺰش دﯾﻮاره ﻣﻌﺎدن روﺑﺎز ﯾﮏ اﻣﺮي ﺿﺮوري اﺳﺖ. ﻫﺪف اﺻﻠﯽ اﯾﻦ ﺗﺤﻘﯿﻖ، اراﺋﻪ ﯾﮏ ﻃﺮاﺣﯽ ﭘﺎﯾﺪار و ﺑﻬﯿﻨﻪ از ﺷﯿﺐ ﻧﻬﺎﯾﯽ دﯾﻮاره ﺷﺮﻗﯽ ﻣﻌﺪن ﻃﻼ-ﻣﺲ ﺷﺎدان ﺑﺮ ﻣﺒﻨﺎي ﻣﺤﺎﺳﺒﻪ ﺣﺪاﻗﻞ ﻓﺎﮐﺘﻮر اﯾﻤﻨﯽ )1/20( ﺑﻪ روش ﻣﺪلﺳﺎزي ﻋﺪدي و ﺗﺤﺖ ﺷﺮاﯾﻂ ﻣﺨﺘﻠﻒ ﻣﺸﺨﺼﺎت ﻫﻨﺪﺳﯽ ﺷﯿﺐ اﺳﺖ. ﻣﺪلﺳﺎزي ﻋﺪدي ﺑﻪ روش ﺗﻔﺎﺿﻞ ﻣﺤﺪود )FDM( و ﺑﺎ اﺳﺘﻔﺎده از ﻧﺮماﻓﺰار FLAC3D ﮐﻪ ﻗﺎﺑﻠﯿﺖ ﻣﺤﺎﺳﺒﻪ ﻓﺎﮐﺘﻮر اﯾﻤﻨﯽ )FS( ﺑﻪ روش ﮐﺎﻫﺶ ﻣﻘﺎوﻣﺖ ﺑﺮﺷﯽ را دارد، اﻧﺠﺎم ﮔﺮﻓﺖ. ﺑﻨﺎﺑﺮاﯾﻦ، ﻣﺠﻤﻮﻋﻪاي از ﻣﺪلﻫﺎي ﻋﺪدي ﺳﻪ ﺑﻌﺪي )3D( در ﻗﺎﻟﺐ ﺳﻨﺎرﯾﻮﻫﺎي ﻣﺨﺘﻠﻒ ﺑﺎ ﺗﻐﯿﯿﺮ در ﻣﺸﺨﺼﺎت ﻫﻨﺪﺳﯽ ﺷﯿﺐ دﯾﻮاره ﻧﻬﺎﯾﯽ ﮐﺎواك ﻣﻌﺪن )ﻋﺮض، ارﺗﻔﺎع و ﺷﯿﺐ ﭘﻠﻪ، ارﺗﻔﺎع ﭘﯿﺖ و زاوﯾﻪ ﮐﻠﯽ ﺷﯿﺐ(، ﺑﺮرﺳﯽ و ارزﯾﺎﺑﯽ ﺷﺪﻧﺪ. ﺑﺮ اﺳﺎس ﺗﺤﻠﯿﻞﻫﺎي اﻧﺠﺎم ﺷﺪه در ﻃﻮل ﺳﻨﺎرﯾﻮﻫﺎي ﻣﺨﺘﻠﻒ، ﻧﻬﺎﯾﺘﺎ ً ﺳﻨﺎرﯾﻮي ﭘﻨﺠﻢ ﺑﺎ ﺣﺪاﻗﻞ ﻓﺎﮐﺘﻮر اﯾﻤﻨﯽِ 1/20 ﺑﻪﻋﻨﻮان ﻃﺮح ﭘﯿﺸﻨﻬﺎدي ﻣﻌﺮﻓﯽ ﺷﺪ. ﺑﺮ اﺳﺎس ﻃﺮح اوﻟﯿﻪ ﻣﻌﺪن )ﺳﻨﺎرﯾﻮي اول( ﺑﺎ ﻓﺎﮐﺘﻮر اﯾﻤﻨﯽ 1/39، در ﺳﻨﺎرﯾﻮي ﭘﻨﺠﻢ ﺑﺎ ﮐﺎﻫﺶ ﻋﺮض ﭘﻠﻪﻫﺎ از 6/8 ﻣﺘﺮ ﺑﻪ 5 ﻣﺘﺮ و ﻧﯿﺰ اﻓﺰاﯾﺶ ارﺗﻔﺎع آنﻫﺎ از 10 ﻣﺘﺮ ﺑﻪ 12 ﻣﺘﺮ ﮐﻪ ﻣﻨﺠﺮ ﺑﻪ اﻓﺰاﯾﺶ زاوﯾﻪ ﺷﯿﺐ ﺳﻄﺢ ﭘﻠﻪ-ﻫﺎ )از 70 درﺟﻪ ﺑﻪ 73 درﺟﻪ( و ﻣﺘﻌﺎﻗﺒﺎً اﻓﺰاﯾﺶ زاوﯾﻪ ﮐﻠﯽ ﺷﯿﺐ )از 43 درﺟﻪ ﺑﻪ 52 درﺟﻪ( ﻣﯽﺷﻮد، ﻓﺎﮐﺘﻮر اﯾﻤﻨﯽ ﺷﯿﺐ ﻧﻬﺎﯾﯽ دﯾﻮاره ﮐﺎواك ﻣﻌﺪن ﺑﻪ ﻣﻘﺪار ﺣﺪاﻗﻞ 1/20 ﮐﺎﻫﺶ ﯾﺎﻓﺘﻪ اﺳﺖ. ﺑﯿﺸﺘﺮﯾﻦ ﺗﺄﺛﯿﺮ ﻧﺎﺷﯽ از ﺗﻐﯿﯿﺮ ﻓﺎﮐﺘﻮر اﯾﻤﻨﯽ ﻣﺮﺑﻮط ﺑﻪ ﮐﺮﻧﺶ ﺑﺮﺷﯽ و ﺟﺎﺑﺠﺎﯾﯽ اﻓﻘﯽ در ﻣﺪل اﺳﺖ ﺑﻪ-ﻃﻮريﮐﻪ ﺣﺪاﮐﺜﺮ ﮐﺮﻧﺶ ﺑﺮﺷﯽ )2-1/12e( و ﺣﺪاﮐﺜﺮ ﺟﺎﺑﺠﺎﯾﯽ اﻓﻘﯽ )25/75- ﺳﺎﻧﺘﯽﻣﺘﺮ( ﻣﺮﺑﻮط ﺑﻪ ﺳﻨﺎرﯾﻮي ﭘﻨﺠﻢ ﺑﺎ ﺣﺪاﻗﻞ ﻓﺎﮐﺘﻮر اﯾﻤﻨﯽ )1/20( اﺳﺖ. در ﺣﺎﻟﯽﮐﻪ ﺑﯿﺸﺘﺮﯾﻦ ﻣﻘﺪار ﺟﺎﺑﺠﺎﯾﯽ ﻗﺎﺋﻢ )29/63 ﺳﺎﻧﺘﯽﻣﺘﺮ( ﻣﺮﺑﻮط ﺑﻪ ﻣﺪل ﺳﻨﺎرﯾﻮي اول )1/39=FS( ﺑﺎ ﺑﯿﺸﺘﺮﯾﻦ ارﺗﻔﺎع دﯾﻮاره در ﺣﺪود 219 ﻣﺘﺮ ﻣﯽﺑﺎﺷﺪ ﮐﻪ ﮐﻤﺘﺮﯾﻦ ﺗﺄﺛﯿﺮﮔﺬاري از ﻣﻘﺪار ﻓﺎﮐﺘﻮر اﯾﻤﻨﯽ را ﻧﺸﺎن ﻣﯽدﻫﺪ

The main objective of this research is to present a stable and optimal design of the ultimate slope of the eastern wall of Shadan Gold-Copper open pit mine based on the calculation of minimum factor of safety (1.20) by numerical modeling method under different conditions of slope geometry. Numerical modeling was performed using finite difference method (FDM) and FLAC3D software which is capable of calculating the factor of safety (FOS) by shear strength reduction method. Therefore, a set of 3D numerical models in different scenarios were investigated by varying the geometrical properties of the pit slope (width, height and face angle of bench, pit depth and overall slope angle). Based on the analysis carried out during the different scenarios, finally the fifth scenario with minimum safety factor of 1.20 was introduced as the proposed pattern. According to the initial design (first scenario) with a safety factor of 1.39, in the fifth scenario by decreasing the benches width from 6.8 m to 5 m and increasing their height from 10 m to 12 m which increases the slope angle of the bench face (from 70 degrees to 73 degrees) and overall slope angle (from 43 degrees to 52 degrees), safety factor of the ultimate slope was reduced to a minimum of 1.20. The maximum impact of the change in the safety factor is related to shear strain and horizontal displacement in the model such that the maximum shear strain (1.12 e-2 m) and the maximum horizontal displacement (-25.75 cm) are related to the fifth scenario with minimum safety factor (1.20). Whereas, the maximum vertical displacement (29.63 cm) is related to the first scenario model (FOS = 1.39) with the maximum slope height (pit height) of about 219 m, which shows the least influence on the value of the safety factor.