Our Research

2019 University of Kansas Transportation Projects

Internal Reinforcement of Backfill behind Bridge Abutments to Mitigate Approach Slab Distresses

Principal Investigator: Jie Han

Co-Principal Investigator: Robert L. Parsons

When embankments are constructed to approach bridge abutments, an uneven approach slab condition often occurs. This uneven approach slab condition is caused by the differential settlement between the embankment soil and the abutment, and the resulting deformation or fracture of the bridge approach slab. Embankment soil settlement is often induced by thermal expansion/shrinkage of the bridge deck, resulting in the movement of the abutment and the embankment soil. Traffic loading on the approach slab also induces settlement of embankment soil. Embankment soil settlement causes the approach slab of the bridge to lose its support from the soil. When the soil support is lost, the slab will bend and even break under the worst case. The loads on the deformed slab will redistribute to its ends, which may result in faulting and bump formation across the roadway at the ends of the approach slab. Such problems have repeatedly occurred in KDOT projects, posed risks to the safety of vehicles and drivers, and required repeated maintenance, repair, and even re-construction. To mitigate the above problems, internal reinforcement is proposed in this research to minimize embankment soil movement behind abutments and under approach slabs. The geosynthetic reinforcement is expected to minimize embankment soil settlement behind the abutment and under the approach slab. The objective of this research is to evaluate the performance of internal reinforcement to mitigate approach slab distresses using large scale model testing in the laboratory. It is expected that KDOT bridge and geotechnical engineers will implement the findings and recommendations from this research into the design of bridge abutments and approach slabs.

Field Monitoring of Wicking Geotextile for Moisture Reduction in Pavements

Principal Investigator: Jie Han

Co-Principal Investigator: Robert L. Parsons

Water is often detrimental to the performance of pavements since it reduces soil strength and modulus and provides sources for erosion and freeze-thaw of base courses and subgrade. Removal of water from pavements can improve the performance of pavements and make them last longer. A common approach to remove water within pavements is to provide a drainage system, which is effective only when the soil beneath the pavement is saturated and water drains out under a hydraulic gradient. However, a majority of pavement soils and aggregate base beneath pavements are mostly unsaturated during their service life. Therefore, the conventional drainage method is not effective in removing moisture in pavements. A newly developed geosynthetic product (also called a wicking geotextile) has been recently introduced into practice. It has been used in Alaska, Wisconsin, and Missouri to effectively solve freeze-thaw problems in subgrade soils and aggregate bases beneath the pavement structure. The research team at the University of Kansas has conducted a series of laboratory tests to evaluate the effectiveness of the wicking geotextile fabric to reduce moisture in Kansas aggregate bases (Guo et al., 2017; Wang et al., 2017). The test results verified the effectiveness of wicking geotextile in reducing moisture in aggregate bases. The aggregate bases with moisture reduction performed much better than those without moisture reduction in terms of base course deformation under cyclic plate loading. Before this product can be widely used in actual subgrade soil and aggregate base moisture reduction applications, a field trial with test sections is necessary to verify its field performance. KDOT has a plan to use this wicking geotextile in a project on US-169 in Allen County as a field trial, which includes two 1000-foot long test sections with a wicking geotextile with each section having different aggregate base type materials. There is a need for field monitoring of the wicking geotextile for moisture reduction in pavements. The purpose of this preproposal is to address this need. The field monitoring includes the installation and measurement of moisture and temperature sensors, sampling and dynamic cone penetration testing, and visual observation of pavement distresses for these two test sections during pavement service. The data collected will be used to evaluate the performance of wicking geotextile in moisture reduction in pavements.

Development of Risk-Based Protocol for KDOT Construction Inspection

Principal Investigator: Daniel Tran

Material quality assurance (QA) for highway construction has been fundamental to meeting the missions of State Departments of Transportation (DOT) and the Federal Highway Administration (FHWA). Traditionally, DOTs specified materials quality standards based on detailed instructions describing the required materials and construction methods. Acceptance was determined based on pass/fail standards or engineering experience and judgment. Although these standards appeared to work well, a grand challenge that DOTs are facing is the ever-growing gap between the demand for inspection and available resources. Many state DOTs including KDOT have lost experienced construction inspection staff while the number of projects are increased with a high level of inspection required. To address this issue, DOTs often rely on a contractor’s quality control (QC) and outsource to the third party for testing and inspection. This strategy, however, is not always a cost-effective approach.

This study will develop a risk-based protocol for KDOT to optimize the allocation of available resources to critical inspection items. The proposed protocol will be developed based on the probability (likelihood) and consequence (severity) of a failure of material testing or construction activities associated with a core list of inspection items. The risk-based protocol will focus on interpreting the risks in a comprehensive but practical manner.

Effectiveness of Entertaining Non-Traffic Related Messages on Dynamic Message Signs

Principal Investigator: Alexandra Kondyli

Co-Principal Investigator: Steven D. Schrock

A large number of transportation agencies across the US use Dynamic Message Signs (DMS) to display traffic-related information to motorists, such as travel times, lane closures, incidents, inclement weather, etc. Recently, several agencies have gone even further and started using entertaining messages in an effort to grab motorists’ attention and change their behavior. These messages focus on seat belt use, distracted driving, aggressiveness, or reinforcing driving rules. There are several examples that have been used by state departments of transportation (DOTs). For example, Massachusetts exploited the regional dialect to display “Use yah blinkah” and “Make yah ma proud, wear yah seatbelt.” Utah displayed “That seat belt looks good on you” and one of Tennessee’s popular messages is “Texting and driving, oh cell no.” The Iowa and Missouri DOTs are also displaying messages such as “Exit to text it”, or “Get your head out of your apps.” In an effort to raise awareness, some DOTs have contests and ask the public to contribute to the pool of entertaining messages. Following the steps of these DOTs, the Kansas DOT (KDOT) is considering displaying these messages along major freeways in the state. Although these messages seem to gain approval from the public, no study has been done to evaluate how effective these are in actually changing behavior and promoting safety. As such, the goal of this project is to investigate how entertaining non-traffic related messages influence driver behavior.

Synthesis of Value Engineering (VE) Study on Mechanically Stabilized Earth (MSE) Walls for KDOT (Phase I)

Principal Investigator: Daniel Tran

State departments of transportation (DOTs) across the nation are continually facing technical complexities, regulatory restrictions, and pressures to deliver quality projects on time and within budget. To successfully deliver transportation projects, DOTs often apply Value Engineering (VE) to balance project needs (safety, quality, and operations) and resources (cost, schedule, and materials). VE has been used to improve transportation projects for more than two decades and is required for federal-aid projects. Currently, the Federal Highway Administration (FHWA) requires that state DOTs perform VE studies for all applicable federal-aid highway projects with an estimated total cost of $50 million or more and $40 million or more for bridge projects.

VE is often applied to a wide range of project elements and activities to provide recommendations for improving project functionality, shortening project schedule, and lowering overall project cost. One of the most common VE recommendations is related to the use of Mechanically Stabilized Earth (MSE) walls. While MSE walls offer a number of advantages over conventional cast-in-place retaining structures, several issues surrounding the use of MSE walls in Kansas remain unclear. These issues include cost-effectiveness, cost savings, the overall stability with long-term performance, the site condition where MSE walls should or should not be used, or materials and construction methods to construct the walls. There is a need for investigating and analyzing the use of MSE walls in Kansas to provide valuable information for decision making within KDOT when reviewing and approving VE recommendations.