This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).
Permeable granular piles (i.e., sand compaction piles, stone columns and rammed aggregate piers) are commonly used to support structures and highway facilities constructed on soft or loose soils subjected to static and seismic loading. Although the use of permeable granular piles increases the time rate of consolidation, reduces liquefaction potential, improves bearing capacity and stability, and reduces settlement of poor soils, these piles have a low stiffness and strength that depend on the properties of surrounding soil. Therefore, granular piles have limited use in very soft clays and silts, and in organic and peat soils. This research focuses on developing a new ground improvement alternative using pervious concrete piles to provide high permeability coupled with high stiffness and strength that are independent of surrounding soil properties.
When compared to the properties of granular piles, pervious concrete materials provide comparable permeability, more than ten times the strength, and an increase of two orders of magnitude in modulus. The higher elastic modulus and strength of pervious concrete improves the load transfer and load-carrying capacity of the piles without compromising the benefits of high permeability. Using pervious concrete material will ultimately result in reducing the required area replacement ratio, which will significantly reduce construction time and cost. Pervious concrete piles, which have strength and stiffness properties that do not depend on confinement provided by surrounding soil, will provide an effective ground improvement method for very soft clays and silts, and in organic and peat soils. In addition, pervious concrete piles can be reinforced with longitudinal corrosion-resistant steel rebars to improve their ductility and performance when subjected to seismic loading.
The research objectives focus on developing pervious concrete mixtures for ground improvement applications and on experimentally characterizing the effects of several construction procedures on soil and pile properties and on soil-pile interaction. Small-scale laboratory experiments using instrumentation and advanced sensors are designed to understand the effects of installation procedures on the behavior of single pervious concrete piles and groups of pervious concrete piles subjected to vertical, uplift, lateral, and embankment loading conditions. The analytical work focuses on developing computational models that accurately predict the behavior of pervious concrete pile systems through three stages: pile installation, consolidation, and in-service loading. The analytical models will be calibrated using the results of the laboratory material and pile load tests and both sophisticated analytical methodologies for use by researchers and simplified analytical tools recommended for practicing engineers will be developed. The Soil-Structure Interaction Facility at Lafayette College, which was recently funded by the National Science Foundation?s Major Research Instrumentation Program, will be used to conduct the experimental and analytical studies. The research will benefit significantly from the collaboration of the Geopier Foundation Company in the design and conduction of the experimental program.
The research project team consists of faculty and students from Lafayette College, which is an undergraduate non-Ph.D. granting institution, and engineers from Geopier Foundation Company. Two undergraduate students will be funded by the project each year. Two additional students will be funded through Lafayette College?s EXCEL Scholars Program, which supports collaborative research between high-performing students and faculty. The research team will also collaborate with the Pennsylvania STEM Initiative and an enrichment/gifted support specialist and teacher from the Easton Area School District, PA, in several outreach programs. The partnerships formed through these activities support the Pennsylvania?s STEM Initiative to dramatically increasing the number of P-20 students (especially females, minorities and the underrepresented) in Science, Technology, Engineering and Mathematics careers. The project team, in collaboration with the Northeast Regional Network of PA STEM, will work with students and teachers in several area K-12 schools (total ~4000 students). Specifically, participating in yearly workshops and ?Project Lead the Way? that engage students in high school pre-engineering programs and the YWCA?s ?Tech Gyrl? program that empowers middle school girls by developing computing skills will expose students and their teachers to the challenges associated with designing structures supported on poor soils. Through professional committee work and service, conference presentations, journal papers, and participating in the CMMI annual meeting; the PIs and students will disseminate the data, methods, and tools produced by this research effort nationally and internationally.
