Soil-tine interactions in loam soil | |
| Author | Makanga, Jacob Tsuma |
| Call Number | AIT Diss. no.AE-97-01 |
| Subject(s) | Soil mechanics Tillage |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Engineering, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. AE-97-01 |
| Abstract | One of the methods of reducing costs in tillage is through efficient design of tillage tools. These tools have for a long time been designed on a trial and error basis as the soil- tool interactions involved have not been well defined and quantified. Classical soil mechanics theories have extensively been used in various attempts to study soil-tool interactions and predict tool forces. Previous soil-tine interaction studies left quite a number of gaps. The results from these studies therefore do not give an insight of the soil-tine interactions along the whole spectrum of soil types. The main objective of this study was to investigate soil-tine interactions in loam soil as affected by changes in rake angle, tine aspect ratio, in this case tine width / tine depth (by varying both width and depth) and moisture content under quasi-static conditions. The studies were conducted in a laboratory glass sided soil bin. Soil deformation patterns were analyzed for failure angle, soil wedges and forward rupture and surcharge profiles. The deformation patterns were observed for determination of failure angles, noting soil wedges and correlation of the soil deformation patterns with the corresponding soil reactions. Forward rupture profiles were determined by using two parallel scales and a measuring scale while soil surcharge profiles were determined with the use of a three-way coordinate measuring system. Soil reactions (horizontal and vertical) from two identical tines (glass side and central) were measured by L—shaped force transducers while a ten-turn potentiometer recorded the forward Speed. The data was amplified, logged and transferred to a computer for saving and further processing. Observed cyclic variations in the force-time curves of the soil reactions were analyzed in terms of wave length, peak to trough ratio and amplitude. The observations from this study indicated that soil deformation patterns are affected by variations in tine design parameters and moisture content. Progressive shear failure was observed in dry soil (5.2% me) in all the three angles studied with variations in each angle. Soil deformation patterns by 50° rake angle tines consisted of inclined shear lines starting from the tine tip and gradually moving Upwards towards the horizontal soil surface intersecting it at an average failure angle of 32". In the case of a 90° rake angle. the inclined shear line was at a distance from the tine tip and the average failure angle was 31°. Formation of prismatic shaped soil wedges, which remained stationary throughout the tine travel, was observed with while using a backward raked 130° rake angle tines. The soil deformation patterns in all the three cases were periodic and correlated quite well with the corresponding soil reactions. Investigation on individual effect of width and depth revealed that the apparent effect of aspect ratio on soil deformation patterns, their corresponding soil reactions, forward rupture and surcharge profiles is in fact mainly due to variations in width and depth. Soil deformation patterns for 21% moisture content were basically the same as those for 5.2% moisture content except for a rise in their corresponding soil reactions. Plastic type of failure was observed in 33.5% moisture content with very high corresponding soil reactions whose periodicity was dying off. Rises in soil reactions with increase in moisture -iv-content was found to be a result of increase in soil cohesion and adhesion. The soil reactions (horizontal and vertical) were cyclic in nature and in phase as observed from the force-time curves. They matched quite well with the soil deformation patterns and again. variations in their wave length, peak to trough ratio and amplitude was mainly due to changes in width and depth and not just the tine aspect ratio. Correlation of these observations with previous research indicated that, soil deformation patterns and their corresponding reactions are mainly affected by moisture content, tool rake angle and tool width and depth Other parameters include soil specific weight and speed. This information is expected to be useful for the tillage machinery design. |
| Year | 1997 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. AE-97-01 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Agricultural and Food Engineering (AE) |
| Chairperson(s) | Salokhe, V.M.;Gee-Clough, D.; |
| Examination Committee(s) | Balasubramaniam, A.S.,; |
| Scholarship Donor(s) | Japan International Cooperatin Agency (JICA),; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 1997 |