John Ruck

B.A., Geosciences & Business, Franklin and Marshall College, 2020

Current Projects

  1. Understanding the rheology of ice-debris mixtures. These types of mixtures have previously been thought of as dense suspensions. We use suspension rheology to empirically determine how suspended particles behave in a marginally solid, yield stress, model ice system, particularly as they transition from mobile to jammed regimes. We then address these behaviors in icy systems to investigate the volume fraction dependence on the mechanical strength of permafrost at appropriate temperature and pressure conditions.
  2. Using robotics to measure shear and intrusion forces in granular media. We are using a mechanically sensitive and time efficient method for measuring in situ soil strength in the form of a robotic intruder leg. We use these measurements to address the dominant mechanical strength controls of soil-mantled landscapes, and isolate these controls in laboratory experiments that test the mechanical strength of granular materials under different forcing methods by varying intruder tip geometry, intruding velocity, and material volume fraction.

Certifications and Awards

  • 2021 - Graduate and Professional Student Assembly Student Travel Award, University of Pennsylvania
  • 2020 - Nancy Juerges Geomorphology Award, Franklin & Marshall College
  • 2019 - Pennsylvania Council of Professional Geologists Poster and Research Presentation, Finalist


  • Ruck, J., Jerolmack, D.J., Qian, F., Wilson, C.G., Shipley, T.F., Koditschek, D.E. (2022) Using Legged Robots as Soil Rheometers: Understanding the Mechanical Behaviors of Granular Mixtures Related to Robotic Kinematics, American Geophysical Union Fall Meeting, Poster Session.
  • Ruck, J., Qian, F., Wilson, C.G., Shipley, T.F., Koditschek, D.E., Jerolmack, D. (2021) Understanding Downslope Changes in Soil Strength: In-situ Robotic Measurements Reveal Mechanical Properties Along a Soil Catena, American Geophysical Union Fall Meeting, Poster Session.
  • Ruck, J., Villari, Z., Wachino, I. (2019) Fracture control of long-distance groundwater flow with relevance to the anomalously high discharge from The Bubble, Boiling Springs, PA, Pennsylvania Council of Professional Geologists Poster and Research Presentation. Poster Session.

Contact Information

  • Please contact me by email: 

Research Pictures (Selected)

(a) Fluidized silica sand in our cylindrical fluid chamber. Granular media is fluidized prior to intrusion tests for the purpose of maintaining an initial and reproducible bed condition and volume fraction, (b) Robotic arm intruding into silica sand for strength measurements.

(a) Slopeshade image of the selected hillslope in Wissahickon Valley Park, PA, with transect locations where the robot intruder leg was deployed for soil strength measurements, (b) Mean elevation profile from topography data for the selected hillslope, (c) Normal force vs. depth data from robot intruder tests for selected locations along Transect A, with dotted fit lines for each location referring to the stiffness of the material, which assumes a spring-like behavior.

Cylindrical ice samples with approximately 50% sand by volume, fabricated in the Ice Dynamics Lab at the University of Pennsylvania for experiments exploring the role of solid volume fraction on the strength of icy-debris mixtures.