روشي ساده براي تخمين توامان هدايت هيدروليكي اشباع و تخلخل موثر خاك

A Simple Method for Simultaneous Prediction of Saturated Hydraulic Conductivity and Drainable Porosity

The saturated hydraulic conductivity K, and the effective porosity f are needed for modeling and many applications in drainage. The current design procedure is based upon calculation of the lateral spacing, using some average values of K, and f within the area to be drained. The objective of this study was to take into account the spatial and temporal variability of these parameters and to introduce a new method for simultaneous estimation of and f The proposed method was based upon measuring water table profiles at different times. The an steady model of Glover-Dumm (1954) for predicting water table profiles was used with a nonlinear optimization technique to find the optimum values for K., and J: Different data sets from the conducted experiments and literatures were used for calibration, using nonlinear optimization technique. A physical drainage model of 2.2 m length, 0.3 m width and 0.5 m bight was established in the laboratory and carefully packed with a sandy loam soil. A perforated drainage pipe of 4.5 cm diameter was established at the bottom end of the model. Some 16 piezometers were inserted in the soil for spatial and temporal water table monitoring. The proposed approach was evaluated with both constant and variable f The pridicted values with new coefficiante showed of the new approach showed good agreement with the measured ones. With variable effective porosity the mothed is even much more successful to predict water table profiles.