The tunnel drilling operation with the microtunneling method under the seabed, which is a part of the Negin Mokran Petrochemical Water Treatment Project in Chabahar region, is considered as one of the most difficult and challenging mechanized excavation projects in the world, which will be implemented for the first time in Iran by Tunnel Saz Mashin Company.
This project includes the implementation of 2080-meter long pipe-laying operations with the microtunneling method and using the technology of micro TBM machines, that has been designed and built by Tunel Saz Mashin Company. The prepared device has a drilling diameter of 2500 mm and is a slurry type (Slurry TBM) and equipped with an Air Lock system while providing the ability to perform hyperbaric operations under the seabed. For more information about this device, you can refer to the related information page of ASM 2000 machine.
Negin Mokran Petrochemical water intake tunnel project will be carried out with a negative slope of 3% and the use of concrete pipes, which includes a 380-meter tunnel for the implementation of the outfall line and two 850-meter tunnels for the construction of the intake lines with an inner diameter of 2000 mm. All three tunnels are excavated from the shore (land) side towards the sea. Following completion of each tunnel section, the machine is slated to be pulled up from the sea bed with recovery operations and carried out using marine equipment such as barges and ships, and after being transferred to land, it will be ready to dig the next tunnel.
The Geology of zone includes sand, silty and marl layers, coral stones and sandstone, so due to their low resistance (uniaxial compressive strength less than 7 MPa) and the mixed nature of the tunnel work front in sections of the path, the risk of machine deviation as well as the creation of a plastic zone around the cutterhead and the drilling machine is probable.
Considering that the drilling operation will be carried out at a depth of 20 meters from the sea level, a pressure of about 2 bars will be applied to the surroundings of the device and pipelines, which will cause the floating (weightlessness) of the machine and pipes, which is one of the serious challenges considered in the implementation of this project. Besides the mentioned challenges, the problems of advancing long drives with the microtunneling method, as well as the risk of water ingress into the tunnel and the possibility of the device sinking are also other risks of this project.
It is hoped that by the grace of God and relying on the knowledge of native experts, this project will be successfully run and will be introduced as a new method of digging water intake and drainage lines from the sea. A method that will provide entrepreneurship for a wide range of native personnel of the region and will follow the economic prosperity of the southern provinces of our dear country along with minimizing the environmental damage of implementing such projects.