Table 2. Comparison of swelling pressures in 1997 and 1998 R.D. Swelling Pressure in kg per cm2 in the year 1997 1998 39.5 10.45 0.56 40 11.52 0.78 42.5 10.8 1.58 45 10.15 2.60 47.5 14.81 0.68 50 6.97 0.20 52.5 4.57 0.16 55 3.93 0.16 57.5 2.30 0.22 60 2.50 0.10