Tanya Niyamapa

Force and pressure distribution under vibratory tillage tool

Abstract Experiments were conducted to study the force requirement and pressure distribution under vibratory tillage tools in a soil bin with a sandy loam soil. The tool was oscillated sinusoidally in the direction of soil bin travel. An octagonal ring transducer and pressure sensors were used to measure the forces and soil pressure on the blade. The tool was operated at oscillating frequency of 4.5–15.6 Hz and amplitude of 11–26 mm. The soil bin travel speed was varied from 0.05 to 0.224 m/s. The test results obtained showed both the horizontal force and the vertical force decreased with increase in oscillating frequency. The normal pressure on the blade surface varied considerably. The peak normal pressure was found to increase with increase in oscillating frequency, oscillating amplitude and soil bin travel speed. The change in average normal pressure with change in oscillating frequency and amplitude was also investigated.

Soil disturbance and force mechanics of vibrating tillage tool

Abstract Experiments were conducted with vibrating tillage tools in a sandy loam soil. It was observed that during oscillating operation, initially draft increased slightly with an increase in forward speed but later it decreased. For the non-oscillating operation, draft increased continuously with increase in forward speed. The ratio of draft from oscillating to non-oscillating mode varied from 0.63 to 0.93. The total power required for oscillating operation was 41–45% more than the power required for non-oscillating operation. The soil surface was cracked due to tool motion showing the characteristics of lifting up of soil clods during the oscillating operation, whereas it showed the characteristics of soil flow during non-oscillating operation. The soil was pulverized more due to oscillating than non-oscillating operation. The reduction in dry bulk density of soil mass in the oscillating operation was about 70–270% more than that during the non-oscillating mode.

Soil failure under undrained quasi-static and high speed triaxial compression test

Abstract Experiments were conducted in unsaturated silty loam and sandy loam soils under undrained conditions. Soil failure under quasi-static and high speed triaxial compression were studied. The amount of energy used in breaking soil specimens was found to be a function of soil moisture content. During undrained quasi-static triaxial compression tests, two cases of brittle failure, a general shear failure and a fragmentation were observed. The test soil specimen broke more by fragmentation than by general shear failure. During undrained high speed triaxial compression tests, the energy use for breaking the soil specimen increased with increase in loading speed up to a certain critical speed range of 4.5–5 m/s, and then it decreased. Two types of soil failure, brittle failure and plastic flow, which were a function of the loading speed, were noticed. At lower speed, dilation of shearing along a slip plane was observed. However, at higher speed, barreling of the cylindrical specimen with top and bottom conical shaped wedges, or only a single wedge with a small crack or fluidization, was observed.

Cyclic torsional shear loading test for an unsaturated, hollowed specimen using Bangkok clayey soil

Cyclic torsional shear loading was applied to simulate the loading characteristics which take place particularly during quick turning operations of a tractor in the field. Indoor experimental tests using a cyclic torsional shear loading method were conducted to clarify the dynamic behavior of Bangkok clayey soil. Since most agricultural soils in the field are normally unsaturated, this test method was used to better match field conditions. The dynamic behavior of our test soil was observed in conjunction with various factors including stress, strain, loading frequency, bulk density, moisture content, and number of loading cycles. Some related results were also obtained under static loading using a triaxial test method.

Laboratory investigations into soil failure under vibratory tillage tools

Abstract Experiments were conducted to study the soil failure and soil disturbance of sandy loam soil under vibratory tillage tools in a soil bin. The experimental results showed a brittle failure characteristic with a crescent shaped soil failure area. There were cracks in radial and transverse directions in the crescent shaped failure area. Two main zones (deep layer and near surface) of soil disturbance were observed due to the action of the vibratory tool. It was observed that the size of soil fragment decreased with increase in velocity ratio.