Effect of Different Shape Factor Calculation Methods on Guelph Permeameter's Two head Analysis Results

Saturated hydraulic conductivity () is one of the important physical features of soil that have wide usage in soil and water science. It is one of the important parameter in the irrigation and drainage، ground water flow، some of the road and structure project، river engineering etc. is the important parameter on cost of the projects so it is very important to achieve with most accuracy. The determination of has divided in two ways: laboratory and outdoor way. Outdoor way done in above or under the ground water، depend on the ground water depth. Guelph permeameter (GP) method has done on above the ground water. The GP method has a good accuracy in determination of. However، C is an important parameter in the two head GP. C is calculated with five methods (Pourshe، Pressure، Glour، Half-source and Numerical). Only problem of GP are the negative results that may have seen in some results. In this research the GP experiments were down with different ratio of in 18 holes (Max and Min H are 5 and 20 cm، respectively). Then and (matric flux potential) are determined by two head analysis of GP with different solution methods for well shape factor (C). Result showed if the Pourshe method was used for C factor calculation، negative results have been minimized and other methods for the C calculation (Pressure، Glover، Numerical and Half-source) have been produced low to high negative result of respectively. Pourshe and Pressure methods for C calculation cause the maximum negative result of respectively. So، three other methods of C calculation are suitable for determination of the. However، number of negative result for and are decreased when the increase.