STUDENT SPOTLIGHT: Each month, or every other month, a student will provide a 1-page illustrated abstract of the research they are currently conducting. This is a wonderful opportunity for the student, for our International Society for Concrete Pavements (ISCP) Members, and for the transferring and sharing technology/research through our concrete paving industry.
The ISCP “STUDENT RESEARCH SPOTLIGHT” for January 2025 is Nischal Pokhrel, a second-year MSE student in Civil and Environmental Engineering at Youngstown State University (Youngstown, USA).
BIO:
Nischal Pokhrel is a second-year MSE student in Civil and Environmental Engineering at Youngstown State University. He completed his bachelor’s degree in civil engineering at the Institute of Engineering, Tribhuvan University in Nepal and has always been passionate about contributing to the field of transportation for sustainable development. His current research (and MS thesis topic), overseen by his advisor and ISCP board member, Dr. John W. DeSantis, focuses on the investigation of predictive models to simulate pumping beneath concrete pavements. This research has allowed the exploration of key challenges in pavement integrity and performance with an aim to develop a model to improve the prediction of pumping beneath concrete pavements. His ultimate goal as a transportation-focused civil engineer is to improve pavement safety, longevity, and overall reliability. Alongside his studies, he currently works as a transportation engineering intern at OHM Advisors, where he has gained practical experience contributing to roadway design projects using various software tools.
TITLE:
Investigation of predictive models to simulate pumping beneath concrete pavements
Concrete pavement pumping refers to the movement and ejection of fine materials, such as the combination of water and soil or base material particles, from beneath a concrete pavement slab due to repeated traffic loads. This phenomenon typically occurs when water accumulates under the pavement, and the dynamic loads from vehicles cause pressure fluctuations that force the water and fine particles to move (Figure 1). Over time, this can lead to voids or loss of support beneath the slab, resulting in pavement damage, such as faulting, cracking, or settlement. Therefore, pumping poses a significant threat to pavement integrity, safety, and longevity. Understanding the underlying causes, mechanisms, and consequences of pumping is, therefore, imperative for devising effective strategies to mitigate and ensure the resilience of road infrastructure.
In the present scenario, there are several published models for the prediction of pumping beneath concrete pavements. Pumping prediction models are important in the design and economic analysis of rigid pavements. Pumping modeling is a very complex problem which involves many factors: concrete material properties, subbase material properties, pavement drainage properties, environmental factors, and traffic. An ideal pumping model for pavements should incorporate all these factors. Therefore, this study aims to investigate the established pumping models and their effectiveness in accurately predicting pumping under various circumstances.
The primary existing pumping prediction models include:
1. Darter and Barenberg (1977): this model considers slab deflections under traffic loads, the presence of water and fine materials, load transfer efficiency at joints, and the erodibility of the subgrade and base layers to predict pumping potential beneath concrete pavements.
2. Crovetti and Darter (1984): this model provides a more refined understanding of how hydraulic pressure gradients and material erodibility influence pumping.
3. Van Wijk and Larralde (1989): this model is the latest in the field and evaluates the accuracy in estimating material movement under varying conditions of load, moisture, and material properties.
An initial evaluation of the more recent model, Van Wijk and Larralde (1989), revealed some discrepancies in pumping prediction under various circumstances that need to be reevaluated and investigated in greater detail moving forward within this research study. An initial attempt was made for simple model reconstruction to be able to utilize the existing framework and enhance the model by incorporating the significant factors that contribute to pumping. However, the published sensitivity analysis could not be replicated with the same given inputs. As a disclosure, these are preliminary results, and further calculations need to be performed to fully validate the discrepancies.
One of these observed discrepancies is presented below. Figure 2 illustrates an undoweled pavement with a negative trend in pumping as traffic accumulates vs. a doweled section. The input parameters used for the presented comparison include no dowels/dowels, 350,000 ESALs in year one with 4% growth, fair drainage, stabilized subbase, wet climate, poor subgrade, plain PCC pavement. This is the opposite of the phenomenon likely to occur. The undoweled section should generate a larger pumping prediction in comparison to the doweled section.
Figure 3 also shows the relationship of volume of pumped materials over time for a stabilized and unstabilized subbase beneath the concrete pavement. The opposite trend of the hypotheses is observed, in which the volume of pumped materials with a stabilized subbase appears to increase at a faster rate than that of an unstabilized subbase. The input parameters used for the presented comparison include 350,000 ESALs in year one with 4% growth, 10 in slab thickness, fair subdrainage, poor subgrade, wet climate and plain PCC pavement.
The initial investigation has revealed:
- Overestimation by Empirical Models: This model tends to overestimate pumping severity under various conditions like soil stabilization and climatic conditions.
- Parameter sensitivity: When attempting to replicate plots of the amount of pumped material over time under two conditions: 1) transverse joints with dowel bars and those without, and 2) stabilized and unstabilized subbase, it was observed that the amount of pumped material generally follows an incorrect trend. This is suggesting a potential error or discrepancy in the empirical equations. As previously mentioned, these are preliminary results, and further calculations need to be performed to fully validate the aforementioned discrepancies.
Building upon these initial investigations, it is conclusive that the existing models lack several considerations such as water velocity, pressure, and other hydrodynamic parameters. It is, therefore, of high significance to include parameters of such to capture the actual dynamic interplay and to enhance existing models by incorporating moisture variations and hydrodynamics.
ISCP would like to feature a “STUDENT RESEARCH SPOTLIGHT” each month, or every other month. If you would like to nominate a student, or if you are a student and would like to nominate yourself or a colleague, please send ISCP an email to: newsletter@concretepavements.org
ALL SPOTLIGHTS:
DECEMBER 2021—Inaugural: Katelyn Kosar, PhD Student-Department of Civil and Environmental Engineering, University of Pittsburgh (Pitt): www.concretepavements.org/2021/12/14/new-at-iscp-student-research-spotlight/
JANUARY 2022: Aniruddha Baral, Ph.D. Candidate-Department of Civil and Environmental Engineering, University of Illinois-Urbana-Champaign: www.concretepavements.org/2022/01/15/student-research-spotlight-jan-2022/
FEBRUARY 2022: Jordan Ouellet, Tech, BEng, MASc, PhD Candidate, Teaching and Research Assistant, University of Illinois at Urbana-Champaign: www.concretepavements.org/2022/02/26/student-research-spotlight-february-2022/
MARCH 2022: Sampath Kumar Pasupunuri, Ph.D. candidate, Pavement Engineering-School of Civil Engineering, University of Nottingham, UK: https://www.concretepavements.org/2022/03/31/student-research-spotlight-march-2022/
APRIL 2022: Anupam B R, Pursuing his doctorate-Indian Institute of Technology Bhubaneswar, India: https://www.concretepavements.org/2022/04/15/student-research-spotlight-april-2022
MAY 2022: Andréia Posser Cargnin, Ph.D. Candidate, Polytechnic School, University of São Paulo (São Paulo, Brazil): https://www.concretepavements.org/2022/05/09/student-research-spotlight-may-2022/
JUNE 2022: Charles Donnelly, Ph.D. Candidate, Department of Civil and Environmental Engineering, University of Pittsburgh (Pittsburgh, USA): https://www.concretepavements.org/2022/06/24/student-research-spotlight-june-2022/
JULY 2022: Amir Malakooti, Ph.D. Candidate, Department of Civil and Environmental Engineering, Iowa State University (Ames, Iowa, USA): https://www.concretepavements.org/2022/07/30/student-research-spotlight-july-2022/
AUGUST 2022: Haoran Li, Ph.D. Candidate, Department of Civil and Environmental Engineering, University of Pittsburgh (Pittsburgh, USA): https://www.concretepavements.org/2022/08/24/student-research-spotlight-august-2022/
SEPTEMBER 2022: Sumit Nandi, Ph.D. Candidate, Department of Civil Engineering, Indian Institute of Technology Roorkee (Roorkee, India): https://www.concretepavements.org/2022/09/18/student-research-spotlight-september-2022/
OCTOBER 2022: Eric Ribeiro da Silva, Ph.D. Candidate, Department of Civil Engineering, Polytechnic School of the University of São Paulo (São Paulo, Brazil): https://www.concretepavements.org/2022/10/20/student-research-spotlight-october-2022/
NOVEMBER 2022: Zachary Brody, Ph.D. Candidate, Department of Civil and Environmental Engineering, University of Pittsburgh (Pittsburgh, USA): https://www.concretepavements.org/2022/11/18/student-research-spotlight-november-2022/
DECEMBER 2022: Jesús Castro Pérez, Ph.D. Candidate, Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign (Urbana, USA): https://www.concretepavements.org/2022/12/17/student-research-spotlight-december-2022/
JANUARY 2023: Dan King, Ph.D. Candidate, Department of Civil and Environmental Engineering, Iowa State University (Ames, USA): https://www.concretepavements.org/2023/01/26/student-research-spotlight-january-2023/
FEBRUARY 2023: Kathryn Kennebeck, Ph.D. Candidate, Department of Civil and Environmental Engineering, University of Pittsburgh (Pittsburgh, USA): https://www.concretepavements.org/2023/02/28/student-research-spotlight-february-2023/
MARCH 2023: Sinan Kefeli, Ph.D. Candidate, Department of Civil and Environmental Engineering, Iowa State University (Ames, USA): https://www.concretepavements.org/2023/03/13/student-research-spotlight-march-2023/
APRIL 2023: Niwesh Koirala, Ph.D. Candidate, Department of Civil and Environmental Engineering, Texas Tech University (Lubbock, USA): https://www.concretepavements.org/2023/04/07/student-research-spotlight-april-2023/
MAY 2023: Christian A. Sabillon, Ph.D. Candidate, The University of Texas at Austin (Austin, Texas, USA): https://www.concretepavements.org/2023/05/05/student-research-spotlight-may-2023/
JUNE 2023: Saima Yaqoob, Ph.D. Candidate, KTH (the Royal Institutes of Technology) (Stockholm, Sweden): https://www.concretepavements.org/2023/06/15/student-research-spotlight-june-2023/
JULY 2023: Ricardo Hungria, Ph.D. Candidate, Louisiana State University (Baton Rouge, USA): https://www.concretepavements.org/2023/07/11/student-research-spotlight-july-2023/
AUGUST 2023: Megan Darnell, Ph.D. Candidate, University of Pittsburgh (Pittsburgh, USA): https://www.concretepavements.org/2023/08/07/student-research-spotlight-august-2023/
SEPTEMBER 2023: Jitendra Patel, Ph.D. Candidate, Alma Mater Studiorum – Università di Bologna (Italy): https://www.concretepavements.org/2023/09/05/student-research-spotlight-september-2023/
OCTOBER 2023: Omar K. Omar, Ph.D. Candidate, Louisiana State University (Baton Rouge, USA): https://www.concretepavements.org/2023/10/05/student-research-spotlight-october-2023/
NOVEMBER 2023: Mason Smetana, Ph.D. Candidate, University of Pittsburgh (Pittsburgh, USA): https://www.concretepavements.org/2023/11/07/student-research-spotlight-november-2023/
DECEMBER 2023: Avinash Jha, M.Tech Student, Indian Institute of Technology Gandhinagar (India): https://www.concretepavements.org/2023/12/10/student-research-spotlight-december-2023/
JANUARY 2024: Matthew Sheffield, Ph.D candidate, University of North Carolina at Charlotte (Charlotte, USA): https://www.concretepavements.org/2024/01/13/student-research-spotlight-january-2024/
FEBRUARY 2024: Chintada Chandrasekhar, Ph.D candidate, Indian Institute of Technology Roorkee (Roorkee, India): https://www.concretepavements.org/2024/02/08/student-research-spotlight-february-2024/
MARCH 2024: Subham Jain, Ph.D candidate, Indian Institute of Technology Kanpur (Kanpur, India): https://www.concretepavements.org/2024/03/08/student-research-spotlight-march-2024/
APRIL 2024: Etienne Beya Nkongolo, Ph.D candidate, University of Missouri Kansas-City (Kansas City, USA): https://www.concretepavements.org/2024/04/11/student-research-spotlight-april-2024/
MAY 2024: Shivani Sharma, Ph.D candidate, Indian Institute of Technology Gandhinagar (Gandhinagar, India): https://www.concretepavements.org/2024/05/14/student-research-spotlight-may-2024/
JUNE 2024: Isaac Oyawoye, Ph.D candidate, University of North Carolina at Charlotte (Charlotte, USA): https://www.concretepavements.org/2024/06/16/student-research-spotlight-june-2024/
JULY 2024: Tianzhen Li, Ph.D candidate, Xi’an Jiaotong-Liverpool University and the University of Liverpool (Suzhou, China): https://www.concretepavements.org/2024/07/04/student-research-spotlight-july-2024/
AUGUST 2024: Andrés Gabriel César Torres, Ph.D candidate, Polytechnic School of the University of São Paulo (São Paulo, Brazil): https://www.concretepavements.org/2024/08/06/student-research-spotlight-august-2024/
SEPTEMBER 2024: Bhabya Thakur, Masters student, Indian Institute of Technology Gandhinagar (Gandhinagar, India): https://www.concretepavements.org/2024/09/21/student-research-spotlight-september-2024/
OCTOBER 2024: Alberto Castillo, PhD student, Purdue University (West Lafayette, USA): https://www.concretepavements.org/2024/10/22/student-research-spotlight-october-2024/
NOVEMBER 2024: Salman Amin, MSE student, Youngstown State University (Youngstown, USA): https://www.concretepavements.org/2024/11/07/student-research-spotlight-november-2024/
DECEMBER 2024: Lara Guizi Anoni, PhD student, University of São Paulo (São Paulo, Brazil): https://www.concretepavements.org/2024/12/05/student-research-spotlight-december-2024/