Accuracy of soil stress measurements as affected by transducer dimensions and shape

• Four types of stress transducer calibrated in traffic conditions in the field.
• The four transducer types differed in shape and dimensions.
• Deviation of measured stress range from 18% overestimation to 15% underestimation.
• Measurements were influenced mostly by thickness to width ratio of transducers.
• Measurements were not influenced by changes in physical conditions in the soil.

Accurate measurements of soil stress are needed to evaluate the impact of traffic on soil properties and prevent soil compaction. Four types of transducer commonly used to measure vertical stress were calibrated in realistic traffic conditions in the field. The four transducer types differed in shape and dimensions, which are important factors influencing stress. Deviation of measured stress from true stress ranged from 15% underestimation to 18% overestimation, with transducer thickness to width ratio being the most important shape factor influencing the stress recorded. Changes in physical conditions in the soil above the transducers due to their installation did not influence the accuracy of vertical stress measurements. The results of this calibration are valid for correcting stress measurements in topsoil, but should be used with caution for vertical stress measurements in subsoil. All stress transducers should be calibrated in field conditions before use. More research is needed to characterise the stress distribution in the measuring face of transducers and better predict interactions between transducer and soil during loading.