Feature Photo: Optimizing soil improvement for embankments and retaining walls is key for efficient construction. Image: Facebook.
Posted: 4-4-2025
Houston (Harris County) — Roads and highways are a country’s lifeline. The United States has over 4 million miles of public roads, including the Interstate Highway System. Preventing damage and maintaining roads and highways is critical to supporting the longevity of the sprawling transportation infrastructure within the United States.
Toward that effort, Texas A&M researchers recently published a report in the journal Transportation Geotechnics on a forensic investigation of a collapsed slope of a Texas highway embankment using a variety of methods, including numeric modeling and laboratory tests.
“Failures of embankment slopes are quite common every year,” said Dr. Anand Puppala, Zachry Department of Civil and Environmental Engineering professor. “Repairing these failures involves a tremendous amount of work, especially if the highways are in the middle of a city, for example. In our study, we investigated the reasons for failure of embankment slopes and the best way to repair such damages.”
According to the Federal Highway Administration, embankments are structures made of compacted earthen materials, such as soil, rock, or aggregate. They raise roadways above the level of the existing surrounding ground surface to provide structural support, prevent flooding, and improve drainage from roads by directing water through defined paths.
But even embankments can fail over time due to heavy rainfall, snowmelt, seismic activity, and construction defects. These failures can lead to loss of life and property damage. Highway embankments made of heavy materials are often built over soft ground, which can sometimes lead to settlement and instability.
“Most of the embankments in Texas, for example, are built with the local clayey soils,” added Puppala. “Embankment slopes made with compacted clayey soils are highly problematic. After 10 to 15 years of continuous use along with the natural impact of weather, embankments tend to fail.”
The researchers selected a collapsed highway embankment slope in Houston for their study. They performed an in-situ site investigation, collected soil specimens using a coring barrel, and transported the specimens to the laboratory for testing and analysis. Here, the team performed a variety of tests, including basic soil characterization and laboratory experiments, to determine the soil’s shear strength.
Next, they used the results from these tests, such as the soil strength, as parameters for a numerical model that could analyze the stability of the embankment slope. They also used the model to explore scenarios of extreme rainfall on the embankment slope.
“The model was telling us that a 24-hour rainfall or an extreme flooding event, for example, can lead to the development of a water table on the top surface, which generally results in the failure of the slope,” said Ayush Kumar, a graduate student in Puppala’s laboratory and lead author on the study. “Texas soils tend to be quite plastic that increase and decrease in volume based on wetting and drying cycles, making them more susceptible to moisture change.”
Based on their findings, the researchers noted practical solutions that could have prevented the collapse of the embankment slope investigated in this study. Their recommendations include using stabilizing agents, like cement, to reduce the impact of moisture and placing perforated pipes to drain the water quickly.
Although the study is a forensic analysis on the reasons underlying the failure of a specific embankment slope, the researchers noted that a similar comprehensive analysis can be carried out for different slopes and weather scenarios.
Thus, this research has the potential to be useful for transportation workers who maintain roads and highways across the country.
“This study is a result of good teamwork,” said Puppala. “We’ve been fortunate to get a lot of help from TxDOT Houston district personnel to get the right samples and then point us to places where the embankment failures have happened. We hope that our study in turn provides a rehabilitation strategy that can be used by different transportation agencies to prevent failure in the future.”
Edited from news release.
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