Successive reintrusions in a granular medium

Area of Science:

• Physics
• Materials Science
• Geophysics

Background:

• Understanding the mechanics of objects interacting with granular media is crucial in various fields.
• The drag force experienced during object penetration is complex and influenced by material properties.

Purpose of the Study:

• To measure and analyze the drag force on a rigid rod during vertical penetration and partial withdrawal into a granular medium.
• To investigate the reduction in drag force during successive reintrusions compared to the initial penetration.
• To develop a theoretical model explaining the observed drag force behavior.

Main Methods:

• Experimental measurement of drag force using a rigid rod penetrating and withdrawing from a granular medium.
• Analysis of force regimes based on reintrusion depth and withdrawal distance (Δ).
• Development and application of a theoretical model for stress field modification in granular materials.

Main Results:

• Drag force significantly decreases during reintrusions compared to the first penetration.
• Two distinct force regimes with different curvature characteristics are observed, separated by an inflection point.
• A theoretical model successfully rationalizes experimental results and introduces a crossover length (λ) dependent on withdrawal distance (Δ).

Conclusions:

• Partial withdrawal of a rod modifies the granular medium's stress field, reducing subsequent drag forces.
• The proposed theoretical framework accurately predicts the observed drag force behavior and inflection points.
• The crossover length (λ) is a key parameter governing stress modification and drag force reduction in granular media.