Matric suction effect on distribution of stresses caused by vehicle wheels on a bare silty sand

Juan Alfredo Torrico Bravo,Salvador Miranda,Adam Bezuijen,Juan Carlos Rojas,Wim Cornellis,Gemmina Di Emidio

doi:10.1051/matecconf/202133703004

Juan Alfredo Torrico Bravo, Salvador Miranda + Show 4 more

Open Access

https://doi.org/10.1051/matecconf/202133703004

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Abstract

-Soil compaction in cropping systems, caused by the external pressure of machinery, creates impermeable layers that restrict water and nutrient cycles reducing agricultural production. To evaluate the matric suction effects on distribution with depth of stresses in a soil, caused by the use of agricultural machinery, Jet Fill tensiometers were installed at two different depths (i.e. 0.15 m, 0.30 m) in a soil profile constituted by silty sand with gravel (SM); to register the increments on subsoil vertical stresses, two miniaturized load cells (i.e. 16. 5 mm in diameter) were installed in a horizontal position under the centre line of the vehicle wheels’ path, at approximately 0.15 m and 0.30 m depth. Care was taken to calibrate the load cells in field conditions. A vehicle was made to pass over the soil surface, at a speed less than 5 km/h; the tyre inflation pressure applied on wheel was 380 kPa. Response of load cells to vehicle loading was evaluated at different average matric suction measured on soil profile. Finally, measured stresses have been compared with values obtained by applying well-known elastic theoretical methods used to assess stresses applied by tyres on bare soils. The corresponding results show that the increment of vertical stresses decreases as matric suction increases, and a good correlation between measurements and simulations of the increment on subsoil vertical stress.

Highlights

It takes a second to compact the soil, but it takes a generation to recover it; soil compaction caused by machinery has increasingly recognized as a considerable problem on agricultural soils.The measurement and simulation of stress in soil is a challenging task
Many researchers (Keller 2005 [1]; Arvidsson et al 2007 [2]) have investigated the effect of loading characteristics in order to predict the increment on subsoil vertical stress; they used the equations formulated by Boussinesq (1885) [3] and later modified by Fröhlich (1934) [4] in which the increment of subsoil vertical stress under a point load is calculated; by dividing the contact area into subareas representing point loads, increment on subsoil vertical stresses beneath a tyre can be simulated with Söhne model (1958) [5]
On the field experimentation site, along the two wheeling events and using the tyre data listed in (Table 1), the increase of vertical stress in the soil profile was measured with the compression load cells at two depths specified

Summary

Introduction

The measurement and simulation of stress in soil is a challenging task. Most of the models and papers have neglected an important stress variable for unsaturated soils: That is the matric suction. Matric suction is fundamental when solving engineering problems associated with unsaturated soil mechanics. In agricultural soils, it affects seriously in soil compaction. Tyre inflation pressure ptyre, recommended tyre inflation pressure precommended and wheel load Fwheel of the equipment used in the field experiments

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