Cross-section of Chicago soil layers with data visualizations during sheetpile excavation.

Deep Dive: How Chicago's Clay Secrets are Revolutionizing Construction

Lena Voss in Tech & Innovation September 2025 • 4 min read.

"Unearthing Hidden Patterns in Sheetpile Excavations to Build Safer, Smarter Cities"

Building in bustling cities is a tough puzzle. Ground movements during construction can hurt nearby buildings and essential utilities. Engineers often depend on sturdy support systems to keep things stable, but understanding how the earth shifts is crucial. Accurate monitoring and smart design are key to preventing damage and ensuring safety.

Enter the Louis A. Simpson and Kimberly K. Querry Biomedical Research Center (SQBRC) project in Chicago. This ambitious build required digging deep—13.1 to 18.0 meters—for its foundation. The team used sheetpile walls, braced with tiebacks and internal supports, to hold back the earth. Careful measurements were taken throughout the project to track ground and wall movements.

This article delves into the data collected during the SQBRC excavation. We'll explore how the ground and walls behaved, what factors influenced these movements, and how these observations stack up against predicted models. By examining this case study, we can gain valuable insights into excavation practices in urban environments.

Chicago's Clay: What Makes It So Unique?

Cross-section of Chicago soil layers with data visualizations during sheetpile excavation.

The SQBRC site, located on Northwestern University's Chicago campus, shares similar ground conditions with the nearby Lurie Center. The soil profile begins with a layer of urban fill and beach sand, followed by progressively stiffer layers of ice-margin clays. A significant stratum of medium stiff clays, known as Blodgett/Deerfield, lies beneath the sand. Both the SQBRC and Lurie Center excavations bottomed out within this layer.

Understanding the properties of Chicago's clay is crucial for predicting how it will behave during construction. Factors such as water content, undrained shear strength, and stress-strain characteristics all play a role. These properties were carefully assessed through field vane tests and laboratory analyses to inform the design of the excavation support system.

Here are some key factors of Chicago's clay that are valuable to note:

Water Content: The amount of water in the soil influences its strength and compressibility.
Undrained Shear Strength: This measures the soil's resistance to deformation under rapid loading conditions.
Stress-Strain Behavior: Understanding how the soil deforms under different stress levels is essential for predicting ground movements.

For the SQBRC project, hot-rolled H3707 sheetpiles were used to construct the support walls. These walls were braced with multiple levels of tieback anchors and internal diagonal supports. The design accounted for factors such as active Rankine pressures, surcharge loads, and the presence of granular soils at the surface.

Key Takeaways for Smarter, Safer Excavations

The SQBRC project provides valuable lessons for urban construction. By carefully monitoring ground movements, understanding soil properties, and adapting designs to real-time data, engineers can minimize risks and ensure the stability of excavations. The insights gained from this case study contribute to safer and more sustainable urban development practices.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1061/(asce)gt.1943-5606.0002010, Alternate LINK

Title: Observed Performance Of A Sheetpile-Supported Excavation In Chicago Clays

Subject: Geotechnical Engineering and Engineering Geology

Journal: Journal of Geotechnical and Geoenvironmental Engineering

Publisher: American Society of Civil Engineers (ASCE)

Authors: Richard J. Finno, Sangrae Kim, Justin Lewis, Nathan Van Winkle

Published: 2019-02-01

Everything You Need To Know

What kind of support system was implemented in the SQBRC project, and what design factors were taken into account?

In the SQBRC project, sheetpile walls were used, braced with tieback anchors and internal diagonal supports. The design considered factors like active Rankine pressures, surcharge loads, and the presence of granular soils at the surface. These H3707 sheetpiles helped to stabilize the deep excavation, but the effectiveness of such systems depends heavily on accurate soil data and real-time monitoring to adapt to actual ground behavior.

How do the unique properties of Chicago's clay affect ground stability during construction, and why is it essential to understand them?

The unique properties of Chicago's clay, like water content, undrained shear strength, and stress-strain behavior, significantly influence how the ground shifts during construction. High water content can reduce soil strength, while undrained shear strength indicates its resistance to deformation. Understanding the stress-strain behavior helps predict ground movements, making these factors critical for designing stable excavation support systems. Ignoring these could lead to inaccurate predictions and potential instability.

What is the Blodgett/Deerfield layer, and why is its understanding important in the context of Chicago excavations such as the SQBRC project?

The Blodgett/Deerfield layer is a significant stratum of medium stiff clays beneath the sand and urban fill at the SQBRC site. Both the SQBRC and Lurie Center excavations reached into this layer. Its properties are crucial for understanding ground behavior during excavation, and careful assessment through field tests and lab analyses are essential to inform the design and prevent ground movement. Its composition dictates the stability and deformation characteristics during deep excavation.

What are the potential consequences of ground movements during urban construction, and how can these risks be minimized based on the learnings from the SQBRC project?

Ground movements during construction can adversely affect nearby buildings and utilities. Accurate monitoring and smart design, informed by real-time data and a deep understanding of soil properties such as Chicago's clay characteristics, are essential for preventing damage. The SQBRC project highlights the importance of continuous monitoring and adaptive strategies to minimize risks associated with urban excavation projects. Without careful monitoring and adaptation, unforeseen ground movements could compromise the stability of adjacent structures.

What specific soil properties were monitored during the SQBRC project, and how did this monitoring influence the design and execution of the excavation?

The SQBRC project monitored factors such as water content, undrained shear strength, and stress-strain behavior to inform decisions about the excavation support system. By carefully tracking ground movements and comparing them against predicted models, engineers could adapt their designs to ensure the stability of the excavation. This adaptive approach, grounded in real-time data, is crucial for minimizing risks and ensuring the safety and sustainability of urban construction projects. Integrating these observations with design models allows for more precise adjustments and safer outcomes.