By Evangelia Ieronymaki, Ph.D., P.E., Associate Director and Senior Lecturer in the M.S. in Construction Administration, School of Professional Studies
This year, my colleague at MIT, a former student of mine, and I published a paper in the International Journal of Geotechnical Engineering about our research on building response to mechanized tunneling in stiff clay. By applying a simplified structural model, we developed a more practical and effective way for engineers to predict building displacements, particularly in urban environments where tunneling interacts with existing infrastructure.
As underground construction expands in dense cities, understanding soil-structure interactions is more critical than ever. Traditional assessment methods often overestimate structural risks, assuming buildings behave as rigid bodies when, in reality, their stiffness and weight influence settlement patterns. Our research introduces a Shear Slabs Portal Frame (SSPF) model, which provides a simplified yet more accurate approach to predicting building deformations caused by tunneling.
Our key research question was: Can we develop a structural model that better represents real-world building behavior without the complexity of full 3D numerical simulations?
Existing methods typically fall into two categories: (a) empirical approaches that estimate greenfield ground movements and apply them to structures and (b) full finite element (FE) models that incorporate soil-structure interaction but require detailed input parameters and extensive computational resources.
We sought a solution that would capture key structural characteristics while remaining computationally efficient. To test our model, we examined two well-documented case studies of tunneling in London’s stiff clay: (a) Crossrail twin tunnels beneath Avenfield House (a nine-story framed building in London); (b) the Jubilee Line Extension (JLE) tunnel near the Treasury and Institute of Civil Engineers (ICE) buildings, where oblique tunnel angles and structural variations introduced additional complexities.
The SSPF Model: A More Accurate Alternative
Our SSPF model represents buildings as shear slabs with portal frame behavior, allowing for a more realistic estimation of bending and axial stiffness. Unlike conventional elastic beam models, SSPF considers how structural elements distribute loads during tunneling, leading to more accurate displacement predictions.
To validate our approach, we compared SSPF predictions with measured building movements of the Avenfield House, the Treasury, and the ICE. We used finite element analyses with soil properties based on the sophisticated MIT-S1 soil model, calibrated against field data. The results showed that SSPF outperformed traditional methods, particularly for buildings with shallow foundations in stiff London Clay.
Our study analyzed real-world data from the two aforementioned major tunneling projects (Crossrail and JLE tunnels). For the Avenfield House, affected by the Crossrail C300 twin tunnels, the SSPF provided better agreement with measured settlements than traditional elastic beam models, while it successfully captured differential movements and structural tilt, improving displacement accuracy. For the Treasury and ICE buildings, affected by the JLE WB tunnel, the model accounted for complex foundation configurations and skewed tunnel alignments and produced reasonable settlement estimates compared with monitoring data.
Why This Matters
Our findings have practical implications for tunneling engineers and city planners:
- More accurate risk assessments: SSPF provides a better approximation of how buildings react to tunneling, reducing overconservative estimates.
- Efficient decision-making: The model allows engineers to quickly evaluate potential structural impacts without requiring complex 3D simulations.
- Improved urban infrastructure planning: Cities expanding underground can use more reliable predictions to guide construction strategies and protect buildings.
While SSPF offers a strong alternative to existing models, further research is needed to refine 3D effects, foundation interactions, and groundwater influences. However, our study demonstrates that simplified methods can still provide robust predictions, making tunneling projects safer and more efficient in real-world applications.
For me, this research was particularly rewarding, not just because of its engineering significance, but also because it was a collaboration with a student who worked alongside me during their studies and has since continued their career at McLaren Engineering. Seeing their contributions to advancing tunneling analysis highlights the lasting impact of mentorship and the value of academic collaboration.
Views and opinions expressed here are those of the authors and do not necessarily reflect the official position of Columbia School of Professional Studies or Columbia University.
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