Research Needs: The Academic Perspective International Workshop on Micropiles 2003 Research Needs: The Academic Perspective by Adrian Rodriguez-Marek Washington State University Seattle, September 2003 Say: My objective is to paint a picture of where we have the greatest need for research. This is not a lecture on the state of the art of research, but rather the creation of a “laundry-list” of items where research within the academic community can result in an improvement in practice. I will make mention to where research has been done, but by no means I will paint a comprehensive picture of the state of the art in research.

Outline User driven research needs Tools for performance prediction Design methodology “Academic” driven research Advancement of the State of the Art of methods for performance prediction

Design Specifications Practical design tools Capacity Displacement Design Specifications State of the Art Methods Behavior Prediction Soil-Micropile- Structure Interaction

User-Driven research needs p-y curves “Shadow effect”: Currently: use factors from drilled shafts or pile groups Does s/d extrapolate to small diameter micropiles? Scale effects Scale effects: in dense sands, research for large diameters CIDH piles showed insensitivity of p-y curve stiffness to diameters. Not so in loose sand.

User-Driven research needs Simplified design methods: group efficiency factors No database of field tests to correlate factors with performance

User-Driven research needs Guidelines for structural design What is the fixity condition? Connection detailing Full Scale Field tests are needed

FIELD AND MODEL TESTING Practical design tools Capacity Displacement Design Specifications State of the Art Methods Behavior Predicition Soil-Micropile-Structure Interaction

Role of Academia Partnership with industry to perform field tests Dissemination Peer-review Quality control Push for testing in projects involving Micropiles Innovation in testing methodologies Is the Micropile-soil mass behaving as a unit?

Advancement of the State of the Art State of the art tools for performance assessment Numerical Tools: FE, FD 3-D, Dynamic Adequate modeling of Boundary Conditions Constitutive models of soil behavior Evaluation of “as-built” Micropiles Non-destructive evaluation methods Effects of construction methodology on soil properties

Advancement of the State of the Art Constitutive Models for Dynamic Soil Behavior Must be able to describe change of stiffness and damping with strain Must be able to adequately describe small strain non-linearity Must adequately model effect of confining pressure on stiffness Essential for Networks

Advancement of the State of the Art Effects of construction method Soil model must be sensitive to the effect of increased confining stress due to network effects How do soil properties change with Micropile construction? Cavity expansion modeling

Non-destructive Testing Three problems with NDE techniques High length-diameter ratios Non-uniform diameters Small diameter heads

Role of Academia Technology “transfer” Model Development Models that at the same time have confining-stress dependent stiffness, small strain nonlinearity, adequate large strain non-linearity Models that incorporate elemental soil behavior (e.g. state-parameter based models)

Role of Academia Analysis of full soil-pile-structure interaction problems Structural detailing: model and full scale tests