Performance Evaluation of Wicking Geotextiles for Improving Drainage and Stiffness of Road Foundation
Contract #: 1036336-WO3
Project End Date: October 1, 2024
Evaluate performance benefits (e.g., maintaining stiffness, improving drainage, and stabilizing moisture profile) of relatively recent developed single-layer wicking geosynthetic. Construction observation, design analysis, field testing and instrumentation are to be planned for reconstruction of selected MnROAD test cells (Cell 4, 15, and others TBD). Additionally, an accelerated laboratory load testing program is planned. Program will simulate trafficking to determine load-deformation response with controlled drainage/wicking. Research studies on this technology are limited and what is available focuses on only the drainage capabilities and short-term performance.
Task 1: Literature Review
A comprehensive literature review will be conducted on the current practices of pavement foundation stabilizations with wicking geotextiles under different climatic conditions including F-T and W-D cycles. PIs have already conducted a preliminary literature review search not only on wicking geotextiles but other geotextiles that are design to help with moisture removal from the pavement systems (e.g., geocomposites, geonets). Preliminary literature review showed that the majority of the conventional geotextiles are effective in draining subsurface moisture through gravity drainage under saturated conditions (Iryo and Rowe 2003, Bouazza et al. 2006) and utilization of a newly available novel wicking geotextile has the potential to improve the serviceability and long-term performance of the subgrades by removing moisture even under unsaturated conditions, unlike the traditional geotextiles (Han and Zhang 2014, Wang et al. 2017). Furthermore, a single layer of wicking geotextile serves multiple functions, including drainage, capillary action, separation, and reinforcement (Han and Zhang 2014). Several researchers (including the research team) in the past have studied the efficacy of using this wicking geotextile over traditional geotextiles. Laboratory studies indicated the potential benefits of using the geotextile in draining soil moisture under different temperature and humidity conditions (Guo et al. 2017, Wang et al. 2017, Lin and Zhang 2020). Field studies in Alaska and Texas (conducted by Co-PI Dr. Puppala) have shown these geotextiles are effective in mitigating the problems associated with ice-lenses in freeze-thaw soil, as well as swell-shrink problems from wetting and drying in expansive soils (Zhang et al. 2014, Biswas et al. 2021, 2022).
While overall conclusions of the preliminary literature search shows that the wicking geotextiles have a major potential to improve both short- and long-term pavement performance, the research team will conduct more in-depth review of related topics with a specific focus on use of wicking geotextiles in pavement foundation systems under this task. Online research databases available at the University and Texas A&M University (TAMU), including extensive databases of technical papers will be explored. The literature review will focus on studies and practices from published research papers and technical reports, agency practices, guidelines and specifications, and industry groups such as geosynthetic manufactures. This task will mainly be conducted by the University’s team while TAMU will review the task report and provide feedback.
- Deliverable: Literature review report and summary presentation to TAP
- Date due: July 31, 2022
Task 2: Development of Experimental Plan for Accelerated Laboratory Testing
Two types of accelerated laboratory testing will be conducted during the proposed project to determine the impact of wicking geotextile on (1) drainage and (2) stiffness/permanent deformation/pore pressure distribution of pavement foundation systems. In addition, standard soil index and engineering tests (including soil-water characteristic curves) will be conducted on base and subgrade soils before and after the accelerated laboratory tests are conducted. Moreover, wicking geotextiles will be subjected to forensic analyses (before and after the tests) to determine their clogging potential and apparent opening size (AOS) via gradient ratio tests and imaging analyses (light microscopy and scanning electron microscopy (SEM)), respectively. Figure 3 shows the schematic diagram of the experimental work plan for Task 2 along with each team`s responsibility.
This task will involve acquiring the geomaterials (e.g., base, subbase, subgrade materials) needed for the large-scale testing, performing laboratory characterization of the geomaterials used for this project (subgrade and base/subbase materials) which is needed for appropriate moisture selection of the subgrade materials, building the test sections, and performing the cyclic load tests. Therefore, it is important collect the subgrade and base/subbase materials that will be the same as the ones that will be used in the field at MnROAD facility under Task 4. The table below summarizes the proposed experimental plan which can be modified after discussion with TAP. The research team proposes to use one selected aggregate base material type (recycled or virgin Class 5) and compacted subgrade (lean clay compacted to a target resilient modulus of 7,000 psi) and plan to test the selected wicking geotextile (in consultation with the NRRA TAP) along with a control section with no geosynthetic under fully saturated conditions.
- Deliverable: Experimental plan report and presentation to TAP
- Date due: October 31, 2022
Task 3: Accelerated Laboratory Testing
After the approval of Task 2, the research team will conduct accelerated drainage and loading tests, separately. As described in the table above, accelerated tests will be conducted on base+subgrade specimens (with and without wicking geotextiles) under fully saturated conditions. More detailed information about each accelerated test along with forensic analyses are summarized in 2 subtasks below.
Task 3.1: Accelerated Laboratory Drainage Test
A large cubic (3×3×3 ft) test box (made of polycarbonate sheets) will be built to determine the efficacy of the wicking geotextile under a controlled environment considering rapid drainage effects from wicking geotextile. The transparent polycarbonate sheet will help us to visually identify the moisture migrations across the volume of the box. The box will be equipped with a water distribution source which will help to uniformly distribute the water in the soil layers. Moisture and temperature sensors will be installed in the test box to determine the moisture and temperature contours during the tests. Additionally, a deformation sensor (Shape Array Accelerometers (SAA)) will help to detect the vertical strains in the soil matrix from cyclic moisture conditioning.
The moisture box will be used to test the compacted soils, with and without wicking geotextile under fully saturated conditions as mentioned in the table above. The geomaterials (base +subgrade) will be compacted in layers such that it reaches the target density and moisture content that are expected to be achieved in the field. The compaction density will be monitored using a DCP and LWD. The compaction moisture will be monitored continuously during the compaction of each layer. After compacting the soil, different sensors will be installed in the box and subsequently will be tested under controlled environmental conditions that simulates the summer season in Minnesota (MN). In addition, the specimen will be subjected to 2 and 4 freeze-thaw cycles to evaluate the long-term drainage capacity and stiffness (via LWD) of soils with wicking geotextile. Results from these tests will be used to develop moisture contours and the moisture migration patterns with (including the ones from freeze-thaw tests) and without wicking geotextiles and help us to develop a comprehensive design guideline for field applications.
Task 3.2: Accelerated Laboratory Loading Test
The testing will involve using the Ingios Integrated Mobile Accelerated Test System (IMAS) to perform the required testing at Ingios laboratory at Northfield, MN. As a brief background, IMAS offers a relatively large-scale test chamber in a controlled laboratory setting. IMAS is approximately 8 ft long by 6 ft wide by 4 ft tall as configured with the tilt table test box (up to 45-degree tilt angle) with a test ring setup inside with 5 ft diameter by 3 ft high. Materials (base and subgrade) will be placed and compacted within the test ring in accordance with a specific research plan that is approved in Task 2. Following placement, IMAS will be used in concert with an automated feedback control system to perform cyclic testing to achieve the same types of loading conditions as in field. The box is sufficiently large to minimize boundary effects in all directions. This testing provides substantial amounts of performance data over many different conditions in an accelerated fashion without performing costly and lengthy testing or searching for appropriate sites for field testing which is subject to uncontrolled field variability.
The cross-section will include a compacted 6 in. MnDOT Class 5 aggregate base layer (either recycled or virgin crushed limestone) 2.5 ft thick over compacted stiff subgrade. The moisture content of the material will be carefully selected based on laboratory characterization of the subgrade materials. Subgrade materials will be the same as the ones that will be used in the field at the MnROAD test site.
A pipe to introduce water to enter near the center of the loading plate in the top 6 inches of the subgrade will be built into the subgrade. The top 6 inches of the outlet will include a perforated pipe with a filter fabric. Pore pressure sensors will be installed in the subgrade to measure pore pressures near the middle and edge of the plate, and near the edge of the test ring. Testing will involve constructing the cross-sections using controlled compaction and moisture contents, and then applying cyclic loading with a 12-inch diameter loading plate for 250,000 loading cycles at then stress levels (2.5 psi to 43.5 psi) (with 0.15 sec load pulse + 0.45 sec. dwell period). A layered analysis sensor kit will be used to measure plate deformations as well as the deflection at the subgrade layer to determine composite Mr and layered Mr values (individually for base and subgrade layers). Based on the feedback received from the TAP, the University will apply the loading cycles in increments of 50,000 loading cycles to allow time for wicking to occur. Five sets of 50,000 loading cycles will be applied, totaling 250,000 loading cycles. The pressure head should result in a localized wet zone in the subgrade layer beneath the loading plate where the water will migrate out radially. The loading tests will be conducted on control (no geotextile), non-wicking geotextile embedded soil system, and wicking geotextile embedded soil system to determine how much stiffness gain results from the wicking properties of the geotextile. The properties of the non-wicking geotextile (e.g., tensile strength, AOS, surface texture, woven type) will be identical to those of wicking geotextile.
The pore pressure measurements, dp, and Mr values recorded continuously during each loading cycle will be used to directly assess the influence of the localized wet zone and the differences in the behavior between the three test conditions comparing geosynthetic products and the control section. The geosynthetic products will be removed after testing and the samples will be analyzed under light microscopy and scanning electronic microscopy (SEM) to assess damage and clogging. In addition, gradient ratio tests will be conducted on the geotextiles before and after the tests.
- 3.1. Accelerated tests for drainage report & presentation
- 3.2 Accelerated tests for loading report & presentation
- Date due: April 30, 2023
Task 4: Selected MnROAD Test Section(s) Construction Observation, Field Testing, and Instrumentation
Two identical roadway sections will be built (one with wicking geotextile and one without wicking geotextile) at MnROAD facility in summer 2022. The research team will summarize as built details of both sections (e.g., thickness of each pavement layer, width, material types used along with the locations of temperature, moisture, and matric suction sensors). The research team will also collect the data for construction cost which will include material, transportation, water, and labor costs. It is the research team`s understanding that sensors will be provided by MnROAD, and they will be installed via collaboration with the research team members. Wicking geotextile will be placed between subgrade and base layer. It is important to install the sensors mentioned above at least every 6 inches in depth from top of base layer to 8 ft depth into subgrade to observe the full temperature and moisture profile during monitoring. It is also recommended to place these sensors at the center and edge of the pavements. During construction stage, the research team will conduct the following tests on each test section DCP, LWD, and FWD results. FWD tests will be conducted before and after the surface layer (either rigid or asphalt) is built. Field tests proposed to be collected every 50 ft in all test cells. In addition, both base and subgrade samples will be collected to determine index properties of the materials.
- Deliverable: Construction monitoring and testing report & presentation
- Date due: October 31, 2023
Task 5: Performance Monitoring of MnROAD Wicking Geotextile Cells and Recommendations
Under this task, the research team will analyze the FWD, pavement surface conditions and frost heave-thaw settlement measurements. Dr. Cetin has worked on the analyses of similar data from the recently completed project sites at MnROAD (Cetin et al. 2021). MnDOT will conduct these tests in much the same way as for the Cetin et al. (2021) study so the test methodologies are consistent, and the new data can be compared from all aspects. Each data point reflects the average of EFWD calculated along each of the measurement alignments. It is recommended to run the FWD tests on each cell on both outside lane and inside lane and on outer wheel path (OWP), inner wheel path (IWP), and the middle line of at every 50 ft (it is expected that each cell is 250 ft long as typical MnROAD test cell). Similar analyses and plots will be done for other distress as well including, IRI, rutting, and frost heave-thaw settlement. In addition, using the field-collected temperature and moisture data, the number of freeze–thaw (F-T) cycles and the frost depth of each test section with depth will be determined. Dr. Cetin has completed another NRRA project “Environmental Impacts on Pavement Foundation Layers” (Cetin et al. 2021) which developed a tool to extract data from MnDOT sensors and processed them to be used in predicting frost depth and number of freeze-thaw cycles. From the analyses of this data, the research team will determine the number of F-T cycles of base and subgrade layer for each year as well as in total. Such data will be used to evaluate the impact of the utilization of wicking geotextile on the following parameters: (1) F-T cycles and frost depth; (2) moisture variation; and (3) variation of elastic modulus with the F-T cycles. After all completion of previous tasks, the research team will summarize the findings from the field and laboratory data and conduct analyses on the results. Based on the data analyses, a detailed review will be done on pavement performance data and recommendations on best construction practices will be provided. A guideline about to use of wicking geotextile in pavement foundation systems is also going to be developed.
- Deliverable: Long -term field test results report & presentation
- Date due: April 30, 2024
Task 6: Annual Interim Update 1st year
The research team will provide TAP and NRRA update on the literature review summary, 1st year laboratory and field test results.
- Deliverable: Annual interim summary reports & presentation
- Date due: January 31, 2023
Task 7: Annual Interim Update 2nd year
The research team will provide TAP and NRRA update on the 2nd year laboratory and field test results.
- Deliverable: Annual interim summary reports & presentation
- Date due: January 31, 2024
Task 8: Draft Final Report
The PI will prepare a draft final report to document project activities, findings, and recommendations. This report will be reviewed by the TAP, updated by the PI to incorporate technical comments, and then approved by the Technical Liaison before this task is considered complete.
- Deliverable: Written report & presentation
- Date due: July 31, 2024
Task 9: Final Report
During this task, the PI will work directly with MnDOT’s contract editors to address editorial comments and finalize the document in a timely manner. The contract editors will publish the report and ensure it meets publication standards.
- Deliverable: Written report
- Date due: October 1, 2024
Principal Investigator: Bora Cetin, Michigan State University, email@example.com
Co-Principal Investigators: Anand J. Puppala, Texas A&M University,firstname.lastname@example.org; David White, Ingios Geotechnics, Inc.,email@example.com
Technical Liaison: Raul Velasquez, MnDOT firstname.lastname@example.org
Technical Advisory Panel (TAP) - email the TAP
Contact us to join this TAP
- Robert Arndorfer, WisDOT
- Emil Bautista, MnDOT
- Terry Beaudry, MnDOT
- Deepak Maskey, Caltrans
- Eric Olson, TenCate Geosynthetics
- Joseph Podolsky, MnDOT
- Supraja Reddy, Illinois Tollway
- Heather Shoup, Illinois DOT
- Raul Velasquez, MnDOT (TL)