Document Type : Research Paper
Hydraulic conductivity coefficient of saturated soil as one of its important physical properties indicates water movement in soil. However Guelph permeameter method is very simple, it has a robust theoretical fundamental. The main difficalty of the Guelph method is the double depth experiments which causes negative or irrational results in some of Kfs values because of its heterogeneous equations This difficalty can be resolved by single depth analyses of Guelph equation set. This research is based upon the results of single and multiple depth analysis of Guelph method in comparison to inverted auger hole method at three different depths. Hydraulic conductivity depth variation was assessed by both inverted auger hole and Guelph permeameter methods. The experiments were performed in 30 holes at three different depths of 60, 90 and 120 centimeters and simultaneously the samplings were done at the holes for exploration experiments. The experimental results show that Guelphpermeameter analyses estimates three times at 60 centimeter depth and five times at 90 and 120 centimeters depth less than the results got by inverted auger hole method. Laplace analysis gets higher values and the results made by basic regression analysis of Richards have the least variations and were close to the two depth analysis. The variation of hydraulic conductivity had a decreasing trend with depths This lands. But, this variation was not constant and its gradient decreases through depth.