四、 Soil swell-shrink The function of various cations to soil swell-shrink Nat. K+> Ca2+ Mg2+>H+ soils with more than 30% clay have a high Swell Shrink >clay more ss Potential (if clay is 2: 1) to avoid this problem soil must be compacted and water must be kept out Without the above Swell/shrink will crack foundations and pavements or move telephone poles Poles leaning due to shrink-swell of the soil四、Soil swell-shrink • soils with more than 30% clay have a high Swell Shrink > clay more S.S. Potential (if clay is 2:1) • to avoid this problem soil must be compacted and water must be kept out. • Without the above - Swell/shrink will crack foundations and pavements or move telephone poles. The function of various cations to soil swell-shrink: Na+ , K+ > Ca2+, Mg2+ > H+