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Development of Soil Stiffness Measuring Device for Pad Foot Roller Compaction

Project Information

Project ID: 
FHWA-PROJ-07-0025
Project Status: 
Completed
Start Date: 
Thursday, September 27, 2007
End Date: 
Thursday, June 30, 2011
FHWA Program: 
Exploratory Advanced Research
FHWA Subprogram: 
Breakthrough Concepts in Material Science
FHWA Topics: 
Research/Technologies--FHWA Research and Technology
TRT Terms: 
Construction and Maintenance; Materials; Infrastructure; Research; Soils; Wireless Communications Systems; Global Positioning System
FHWA Discipline: 
Geotechnical, Pavement and Materials
TRB Subject Area: 
Geotechnology, Construction, Pavements

Contact Information

First Name: 
Michael
Last Name: 
Adams
Telephone: 
(202) 493-3025
Email Address: 
Team: 
Bridge Engineering Team
Office:
Office of Infrastructure Research and Development
Office Code: 
HRDI-40

Project Details

Project Description: 

This project proposes to develop and test a "smart pad" for pad foot roller compactors, which is very different from vibratory compaction systems. This project will integrate static soil stiffness measurement capabilities with wireless communications and the global positioning system for continuous real-time feedback on soil stiffness for fine-grained and mixed soil types.

Goals

Improve construction practices through new technology.

Project Findings: 

Measurement of soil stiffness during compaction of foundations for highway structures is critical to ensuring that design-life specifications are met. In this study, investigators developed a conceptual framework for determining pad?soil contact force and displacement (and, thus, soil stiffness) from sensors built into the pads and roller, constructed a prototype measurement system, and devised a wireless data acquisition system to enable fieldscale testing. The researchers successfully measured plastic and elastic soil deformation during compaction using laser-based distance sensors and pad-strain?based techniques. Laboratory and field testing confirmed the predicted strain field changes. Some elements of the model need further refinement to ensure repeatable and accurate measurement across various soil conditions.

Deliverables

Deliverable Name: 
Development of a conceptual, implementable design for in situ measurement of pad force and deflection
Deliverable Type: 
Other
Deliverable Description: 
Development of the technology and a measurement system to monitor soil stiffness during the static compaction of fine-grain soils.
Deliverable Name: 
Implementation of a contact force, contact stress, and deflection measurement system
Deliverable Type: 
Other
Deliverable Description: 
Development of a working method to measure contact pad force via a load cell.
Deliverable Name: 
Performance of field testing.
Deliverable Type: 
Research report or guidelines
Deliverable Description: 
Installation of a contact stress sensor on a pad foot roller for field evaluations.
Deliverable Name: 
Analysis of field data
Deliverable Type: 
Research report or guidelines
Deliverable Description: 
Analysis of field data from several different rollers to characterize force contact stress and pad deflection during the rolling process.
Deliverable Name: 
Prototype system
Deliverable Type: 
Hardware
Deliverable Description: 
Development of an implementable device to monitor soil stiffness, complete with integrated sensor power, signal processing, and wireless communication.