ارائه معياري جهت تعيين كمترين فاصله بين تونلهاي موازي (دوقلو)توسط منحني واكنش پايه ( PRC )

A criterion for determination of minimum distance between twin tunnels by pillar reaction curve (PRC

ﯿﯿﻦ ﻓﺎﺻﻠﻪي ﺣﻔﺎري ﺑﻬﯿﻨﻪ ﺑﯿﻦ ﺗﻮﻧﻞﻫﺎي ﻣﻮازي از اﻫﻤﯿﺖ ﻓﺮاواﻧﯽ ﺑﺮﺧﻮردار اﺳﺖ. ﻣﺪلﻫﺎي ﺗﺠﺮﺑﯽ ﻓﺮاواﻧﯽ ﺟﻬﺖ ﺗﺨﻤﯿﻦ ﻋﺮض ﭘﺎﯾﻪ ﺗﻮﻧﻞ وﺟﻮد دارد ﮐﻪ ﻫﺮ ﯾﮏ ﻣﺤﺪودﯾﺖﻫﺎﯾﯽ دارﻧﺪ. در اﯾﻦ ﻣﻘﺎﻟﻪ، ﻣﻌﯿﺎري ﺟﻬﺖ ﻃﺮاﺣﯽ ﻋﺮض ﭘﺎﯾﻪ ﺑﯿﻦ ﺗﻮﻧﻞﻫﺎي ﻣﻮازي )دوﻗﻠﻮ( اراﺋﻪ ﺷﺪه اﺳﺖ. اﯾﻦ ﻣﻌﯿﺎر ﻣﺒﺘﻨﯽ ﺑﺮ ﻣﻨﺤﻨﯽ واﮐﻨﺶ زﻣﯿﻦ و ﺑﺎ اﺳﺘﻔﺎده از ﻣﺪلﺳﺎزي ﻋﺪدي در ﺷﺮاﯾﻂ ﻣﺨﺘﻠﻒ اﺳﺖ. ﻣﻘﺪار ﮐﺮﻧﺶ در ﻟﺤﻈﻪ رﺳﯿﺪن ﻣﯿﺰان ﺗﻨﺶ ﻋﻤﻮدي )1σ( در ﭘﺎﯾﻪ ﺑﻪ ﻣﻘﺪار ﻣﻘﺎوﻣﺖ ﻓﺸﺎري ﺗﻮده ﺳﻨﮓ )σcm( ﻧﺸﺎﻧﮕﺮ ﻧﺴﺒﺖ ﻗﺎﺑﻞ ﻗﺒﻮل ﻋﺮض ﺑﻪ ارﺗﻔﺎع )w/h ﻣﯽﺑﺎﺷﺪ ﮐﻪ ﺑﯿﺎﻧﮕﺮ ﻓﺎﺻﻠﻪ ﺑﻬﯿﻨﻪ ﺑﯿﻦ ﺗﻮﻧﻞﻫﺎي دوﻗﻠﻮ اﺳﺖ. ﺑﺪﯾﻦ ﻣﻨﻈﻮر ﺗﻮﻧﻞ دوﻗﻠﻮي ﭘﻮﻧﻪ ﮐﻪ در آزاد راه اراك- ﺧﺮمآﺑﺎد ﻗﺮار دارد ﺑﻪ ﻋﻨﻮان ﻣﻄﺎﻟﻌﻪ ﻣﻮردي اﻧﺘﺨﺎب ﺷﺪه اﺳﺖ. اﯾﻦ ﺗﻮﻧﻞ از ﻫﺸﺖ زون در ﻻﯾﻪﻫﺎي ﺳﻨﮓ آﻫﮏ ﻣﺎرﻧﯽ و ﯾﮏ زون در ﻧﻬﺸﺘﻪﻫﺎي آﺑﺮﻓﺘﯽ ﻣﯽﮔﺬرد. ﻧﺘﺎﯾﺞ ﺣﺎﮐﯽ از آن اﺳﺖ ﮐﻪ روش ﭘﯿﺸﻨﻬﺎدي ﺗﻄﺎﺑﻖ ﺧﻮﺑﯽ ﺑﯿﻦ اﺑﻌﺎد ﭘﺎﯾﻪ در ﻣﺸﺎﻫﺪات ﺗﻮﻧﻞ ﻣﻮرد ﻣﻄﺎﻟﻌﻪ ﺑﺎ در ﻧﻈﺮ ﮔﺮﻓﺘﻦ اﺑﺰار دﻗﯿﻖ ﻧﺼﺐ ﺷﺪه در ﺗﻮﻧﻞ دارد. درﻧﺘﯿﺠﻪ ﺑﺎ در ﻧﻈﺮ ﮔﺮﻓﺘﻦ اﯾﻦ ﻣﻌﯿﺎر ﻣﯽﺗﻮان ﺑﻬﯿﻨﻪﺗﺮﯾﻦ ﻋﺮض ﭘﺎﯾﻪ را در ﻃﺮاﺣﯽ ﺗﻮﻧﻞﻫﺎي دوﻗﻠﻮ در ﺣﺎﻟﺖ اﺳﺘﺎﺗﯿﮏ ﺑﺎ دﻗﺖ ﻣﻨﺎﺳﺒﯽ در ﺗﻮﻧﻞﻫﺎي اﯾﺮان ﺑﺪﺳﺖ آورد. ﺑﺮاي ﻧﻤﻮﻧﻪ در زون 3 ﻣﻘﺪار ﻣﻘﺎوﻣﺖ ﻓﺸﺎري ﺗﻮده ﺳﻨﮓ 3/23 ﻣﮕﺎﭘﺎﺳﮑﺎل و ﻣﻘﺪار ﮐﺮﻧﺶ در ﻣﺤﺪوده ﭘﺎﯾﻪ 0/053 ﻣﯽ ﺑﺎﺷﺪ. ﺑﺮ اﺳﺎس ﺗﺤﻠﯿﻞﻫﺎدر اﯾﻦ زون ﻣﻘﺪار 1/8=w/h ﺑﻪ دﺳﺖ آﻣﺪه ﮐﻪ ﻋﺮض ﭘﺎﯾﻪ ﭘﺎﯾﺪار ﺣﺪاﻗﻞ 17/1 ﻣﺘﺮ ﻣﯽ ﺑﺎﺷﺪ.

Determination of optimum distance between twin tunnels is very important. There are many empirical models to estimate width of the pillar, all of which have their own limitations. In this study an attempt was made to present a new criterion for design of the pillar between twin (parallel) tunnels. It is based on ground reaction curve and numerical modelling. Strain magnitude observed when normal stress (σ1) in the pillar reaches the value of compressive strength of the rock mass (σcm), denotes the allowable ratio of width to height (w/h) which shows the optimum distance between twin tunnels. Pooneh twin tunnels located in Arak-Khoramabad Expressway, was selected as a case study. This Tunnel is made of eight zones in layers of marly limestone and one zone in alluvial deposits. Results of the suggested method show a good agreement between the pillar dimensions seen in the case study obtained from instrumentation and the method (new criterion). In zone 3, as an example, the amounts of rock mass compressive strength and strain in the pillar are 3.23 MPa and 0.053, respectively. In this zone, 1.8 was obtained for the w/h ratio, according to the analysis the minimum width for the stable pillar must be 17.1 m. Taking all aspects of geomechanical and geometrical characteristics of the tunnels into consideration, this method is capable of determining the optimum width of the pillar when designing the twin tunnels in static conditions with a high level of precision in all Iranian tunnels.