Understanding the Mechanics of Intrusion in Soils to Estimate Installation Forces for Buried Cables and Pipelines

This award supports research to improve how buried cables and pipelines are installed, advancing fundamental understanding of the forces exerted on objects driven horizontally through soil. The underground cable and pipeline networks carry the nation’s water, energy, and communications, and require expansion and replacement at unprecedented scale, particularly in dense urban areas where existing utilities are aging and demand continues to grow. These utilities are installed either by open-cut excavation, which requires digging a continuous trench and disrupts traffic, businesses, and other utilities, or by trenchless methods, in which drilling and tunneling equipment advances along the intended path, confining disruption to compact entry and exit points. Trenchless construction has become the preferred approach in urban areas, yet these projects frequently incur cost overruns and schedule delays. A leading cause is that the force required to advance equipment through the ground cannot be predicted reliably. Overestimating that force increases equipment and construction costs, while underestimating it results in costly mid-project equipment changes, delays, and in some cases project abandonment. This research develops a method to estimate these forces, reducing the risk and cost of trenchless installations, and supporting the expansion and resilience of the nation’s underground infrastructure. The work combines physics, geotechnical engineering, and computational mechanics, and supports the training of graduate and undergraduate students. Two engineering firms participate in the validation of the model, and a short course delivered through national industry associations extends the results to the practicing workforce. The goal of this project is to advance the mechanics of horizontal intrusion in granular soils and to develop a reduced-order, mechanistic model for estimating intrusion forces. Existing models are largely empirical and lack generality across the range of soil and depth conditions encountered in practice, while the computational cost of high-fidelity numerical models makes them impractical for design. Three tasks address these limitations. The first characterizes how the failure mechanism around the intruder changes with depth, soil state, and stress, using discrete element simulations together with half-model laboratory experiments imaged by particle image velocimetry. The second develops a computationally tractable force model based on resistive force theory, linking the local force coefficients to stress-dilatancy behavior, and capturing the transition in failure mechanisms with depth. The third validates the model against instrumented large-scale chamber tests and against blind predictions of intrusion forces from completed field drives supplied by two industry collaborators. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.