EFFECTS OF LOW-TO-MEDIUM SLIP, LUG SPACING AND MOISTURE-CONTENT ON LUG FORCES

The effects of low-to-medium slip, lug spacing and moisture content on lug forces in day soil were investigated in a laboratory soil bin wit h the help of two model lugs. Perpendicular and radial soil reactions on the lug were measured and they were converted to lug pull and lift forces. The lug slip was varied from 5 to 10, 15, 20 and 25%. The meas urements were conducted in clay soils with 6.3, 27.4 and 51% soil mois ture contents. The lug spacing was varied from 20 degrees to 30 degree s and 40 degrees. The perpendicular, pull and lift forces increased af ter lug entry into the soil and, after attaining a certain peak value, they decreased and reached a zero value at lug exit. The increase in lug slip from 5 to 25% caused an increase in lug forces on both lugs. The increase in the soil moisture content from 6.3 to 27.6% caused inc rease in lug forces on both lugs, but further increase in moisture con tent to 51% decreased the lug forces. Lug spacing showed a significant effect on lug forces produced by the succeeding lug. The increase in lug slip increased the lug forces at any given lug spacing and moistur e content.