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III) Clay Content and CEC Cation exchange capacity can be explained simply as the amount of exchangeable cations attracted by the clay surface. It is known that the type of clay mineral plays a major role in determining this capacity. But it may also be reasonable to expect some relation with CEC and available amount of clay in a soil since it may not be practical at all to talk about CEC without the availability of clay. Thus a graph of clay fraction against CEC is drawn and it is seen that the CEC of the study area increases as the percentage of clay fraction in the sample increases.( Fig. 8) 80 CEC (Meq/100gm) 60 40 20 60 70 80 90 100 Clay Content (%) Fig. 8 CEC and Clay content Relationship of the study area. This could be attributed to the amount of exchangeable cations required to saturate the charge deficiency on the clay surface increases as the clay content increases. 36
5 Determination of Swelling Pressure Swelling Pressure is the amount of pressure a soil exerts upon swelling. The most reliable means of measuring swelling pressure is laboratory determination using one-dimensional consolidometer. This method is called direct measurement and the test is conducted on the soil of the study area. The results of the test are given in tabular form below ( Table 12). Various types of graphs are then drawn to study the relationship between the swelling pressure and different index property values. A multiple regression analysis, finally, is performed to correlate the swelling pressure with these different index properties. 37
Page 1 and 2: ADDIS ABABA UNIVERSITY SCHOOL OF GR
Page 3 and 4: DECLARATION I, the undersigned, dec
Page 5 and 6: List of Tables Page Table 1: Mean M
Page 7 and 8: List of Symbols A c = Activity ω l
Page 9 and 10: 1. Introduction 1.1 General Bahir D
Page 11 and 12: Recent Map of Bahir Dar Area Accord
Page 13 and 14: 1.4 Lithologic Units and Soils Resi
Page 15 and 16: 2. Literature Review 2.1 General Pl
Page 17 and 18: Soil water chemistry Soil water has
Page 19 and 20: 2.3.2 Direct Measurement This type
Page 21 and 22: 3. Identification of Soil in the St
Page 23 and 24: Location Color Depth Northing Easti
Page 25 and 26: Table 4. Atterberg and Shrinkage Li
Page 27 and 28: Swell Potential Plasticity Index Lo
Page 29 and 30: Location Depth Gs Tp4-1 1.5 2.78 Tp
Page 31 and 32: Location Depth Sand (%) Silt(%) Cla
Page 33 and 34: Location Depth ω 24 (%) Kebele 9 2
Page 35 and 36: Table 9 : Free Swell Test Results o
Page 37 and 38: For the study area the CEC is deter
Page 39 and 40: 4. Soil Classification Soil classif
Page 41 and 42: 100 Plastic Index (%) 80 60 40 20 0
Page 43: I ) Clay Content and Plasticity Ind
Page 47 and 48: 5.1 Swelling Pressure and Index Pro
Page 49 and 50: 3 Log Sp (Kpa) 2 1 1 1.2 1.4 1.6 Dr
Page 51 and 52: 600.00 Swelling pressure (Kpa) 500.
Page 53 and 54: 6.1 Models Developed by Various Res
Page 55 and 56: Table 13. Comparison of Previously
Page 57 and 58: Using the above new equations the s
Page 59 and 60: Equation 2 800 Calculated Value (Kp
Page 61 and 62: Equation 6 Calculated Value (Kpa) 9
Page 63 and 64: Conclusion and Recommendation 1. Th

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