Optimization of Analytical Model and Prediction of Soil Compaction Stress Based on Stress Transmission Coefficient

Predicting soil stress with analytical models requires proper selection of the models' concentration factor. The parameter is a coupled result from both loading condition and the soil environment. Stress transmission coefficient (denoted as STC) was suggested in other study to investigate the soil state's effect on the concentration factor. Because the current limited-scale analytical approach of stress transmission coefficient may prevent accurate estimation of soil stress, there was a desperate need to make loading conditions' impact clear on concentration factor. The function of the concentration factor was transformed and a theory to calculate the soil stress transmission coefficient in-situ soil in field, ΠSTC equation, was derived, which complement, associated with the stress transmission coefficient in a limited scale after splitting the soil profile from large. Totally nine loading conditions were tested using in-situ soil by controlling three plate diameters and three soil thicknesses, and a modified oedometer testing setup with a soil stress sensor was used to measure stress transmission coefficient of different soil layers (0~50 mm, 50~100 mm, 100~150 mm and 150~200 mm) in-door. Stress transmission coefficient for the same depths with field experiment was 0.30, 0.17 and 0.07, and then calculated by ΠSTC equation. Correlation analysis were performed to evaluate both measured and calculated STCs on controlled loading conditions (e.g. equivalent radius of the contact area and soil thickness). Then soil stress was predicted following the concentration factor back-calculated from the acquired STCs. The highly linear correlation between soil stress and applied surface stress indicated a stable STC for a particular soil state in field. In general, a thicker soil layer led to a decreased STC, and there was no significant difference in STCs varied with equivalent radius of the contact area, suggesting that the ΠSTC equation could be used as a specific method to quantify soil stress transmission in field. The back-calculation of concentration factor from measured STCs showed the details of how the concentration factor was affected by the changed loading condition with measured result. A good accuracy of the soil stress prediction based analytical model and ΠSTC equation meant a optimized solution was proposed for soil compacting stress prediction. © 2020, Chinese Society of Agricultural Machinery. All right reserved.