Application of fuzzy Delphi AHP method for the estimation and classification of Ghomrud tunnel from groundwater flow hazard

Water inflow and water pressure controls are needed in the design, construction, and exploitation of tunnels. The objective of this paper is to present a new system which can be appropriate for rating tunnel sites to evaluate the potential of groundwater inflow according to the preliminary site investigation data. In this paper, an evaluation model based on combining the analytic hierarchy process and the fuzzy Delphi method has been presented for assessing tunnel site rating from the groundwater hazard point of view. This research treats the tunnel site classification as a group decision problem and applies the fuzzy logic theory as the criterion to calculate the weighting factors. Afterward, the proposed method was successfully applied to determine the amount of groundwater inflow into tunnels. Results of several case studies in various geological conditions roughly show that it can be used to determine the groundwater inflow into tunnels. The introduced method has been examined successfully in Ghomroud tunnel. Results from the proposed method, analytical equations, and observed groundwater inflow into Ghomrud tunnel have been compared. Results show that, because most of parameters regulating groundwater inflow into tunnels have been considered in the method, results from the method are very close to the observed groundwater inflow. Applying this method, according to preliminary investigations conducted by the designers, provides a more suitable design of the drainage system, drilling method, and tunnel support.     

Optimization of analytical equations of groundwater seepage into tunnels: A case study of Amirkabir tunnel

In this study, with investigation of validity limits of analytical equations in computing groundwater seepage discharge into tunnels in different values of r/h (tunnel radius/water table height above tunnel), using optimization by regression analysis, we have tried to converge the results of analytical equations for any value of r/h. There are various experimental, analytical and numerical methods by which it is possible to calculate the amount of groundwater seepage into tunnels. Due to their simplicity and practical base theory, analytical methods have been applied more frequently. Studies imply that amount of real seepage into tunnel is significantly less than what is anticipated from analytical equations; on the other hand, the results of seepage calculations using these equations are depended on tunnel geometry and medium conditions. Previous investigations confirmed that in a tunnel for which, r/h is more than 0.4; these results are highly different both from one another and from the real seepage inflow. In this paper, optimization has been successfully performed on analytical equations so that the results of these methods are converged to each other for any value of r/h.     

Large-scale replenishment of groundwater depletion by long-lived extreme rainstorms in arid regions: case study of the 2019 floods in Iran

The Dena rainstorm in Iran in March and April 2019 caused about US$ 8.3?×?10⁹ damage in the country; however, it resulted in the replenishment of half of the dam reservoirs and 35% of ponds and lakes. Also, it increased the volume of groundwater stored in aquifers by 3.6?×?10⁹ m³. In arid and semiarid regions such as most parts of Iran, which usually face water scarcity, getting water from rainstorms is essential for replenishing water resources. This research aims to quantify the direct and indirect effects of the Dena rainstorm on the replenishment of Iran’s groundwater storage using the groundwater balance method and water-table fluctuation method. Studies showed that the main mechanisms for replenishment of groundwater storage due to the rainstorm included increases in precipitation recharge, surface runoff recharge, and artificial recharge, and reductions in irrigation withdrawal and evapotranspiration, while the contribution of each factor is estimated to be about 23, 28, 2, 15, and 32%, respectively.