Thesis (M.Eng.) - Asian Institute of Technology, 1993

A thesis submitted in partial fulfilment of the requirements for the degree of Master of Engineering.

This st u dy was conducted to inv es ti gate the effect of low slip, lu g spacing a nd moisture co ntent on forces producted by cage wheel lugs. Experime nt s were conducted in a l aboratory soi l bin having Bangkok clay soil to measure the forces under model cage wheel lu gs. A specia l transducers were fabricated to meas ur e the so il perpendicular and radial reactions on the lugs. The s lip s were varied from 53, 103, 153, 203 to 253.T he force measurements on both lu gs were done at 6.33, 27.43 and 50.93 soil moi sture content. The lu g spaci n gs were varied to 20 a n d 30 a nd 40 deg. The meas ur ed perpendicular and radial forces were conver ted to lu g pull a nd lift forces. It was observed that the perpendicular and radial as well as pull a nd lift forces acti n g on the first lug were higher than the forces on the second lug. The perpendicular, pull and lift forces increased after lu g entry into the soil and after attaining a certain peak value they decreased and obtained a zero value at lu g exit. The radial force increased initially as lu g enter the soil and after attaining a positiv e peak value it decreased continuously attaining a negative peak a nd then become zero at lug exit. The radial force was mu ch smaller than the perpendicular but calcu l ated lift force was hi g h er than pull force . The increase of the slip up to 25% caused increase in lu g force s on bot h lu gs . The increase in the soi l moisture conte nt from 6. 3% to 27.43 caused increase in lu g forces on both lu gs but furth er incre ase in mois ture content to 50.9% decreased the lug forces. The lug spacing did not s how any effect on the first lu g forces, but it s how ed s ignifi ca nt effect on the second lu g forces. The increase in lug s pacing increased lug forces at all slips and moi sture contents . The ratio of forces produced under the second lu g to the force s under the fir s t lu g d ecrease d as the lu g s lip increased. I nc rease in lug slip al so increased the lug forces at a n y given spaci n g and moisture content. The pull and lift forces und er multiple lu gs were predicted and it was found that these force s vary in cyc li c nature. It was found that the variation of the output forces can be reduced significant ly by using inclined lugs. At the sa me lug spacin g , s lip and soil moi sture co nt e nt s, the variation of lift can be red u ced by 403, t h e var i ation of pull can be reduced by 2403.