Embankments serve as a critical part of virtually all highway infrastructure, enabling design elevation and grades to be met on sections of fill, approach slabs to bridge abutments and across culverts and utilities. Premature cracking, which appears within months after construction has been documented on embankments such as the Monroe Bypass, U.S. 601 and elsewhere in the Piedmont. With cracks emanating from deep within the section, cracks continually propagate and rupture the pavement surface.
This has translated into unexpected maintenance and repair work that has resulted in additional months/years of construction time and tens of millions of dollars of added expense. Without an operational understanding of crack nucleation and propagation as a function of prevailing soils, structural elements, weather and construction, such premature and unexpected failures will remain more likely.
While the typical causes associated with cracking on highway embankments are linked to clays with high plasticity index, the underlying zone beneath several of the above-mentioned embankments have low plasticity silts as fill material. Furthermore, the influence of subsurface
structures (e.g., culverts) and approaching surface structures (e.g., bridge abutments) as well as their geometric characteristics add to the complexity of mitigating crack occurrence on such embankments.
Therefore, to build on and enhance existing criteria used to address longitudinal cracks on flexible pavements, it is necessary to understand the mechanisms of crack nucleation and propagation. These processes are inherently large in scale, multifaceted and complex. As such, we will use advanced three-dimensional technologies to perform long-term monitoring;
integrated with iterative physics and data-driven modeling.
Conceptual process for integrating field data (e.g., GPR, LiDAR) into the modeling environment (e.g., ABAQUS, possibly Plaxis).
The approach will involve identifying the following generalized scenarios
(1) general embankments on fill sections, (2) embankments with subsurface structures and utilities (e.g., culverts), (3) embankments as part of the approach to bridge abutments.
The research objectives of this project are to obtain (1) a representative set of three-dimensional and subsurface imagery of critical embankments in each of the use scenarios, (2) create computer-based embankment
models which can be used to iteratively identify and test contributing factors, (3) create a visualization tool that integrates field and computer-based data to aid in decision making, (4) perform a sensitivity analysis to understand critical physical parameters which could improve the model and design guidelines, (5) identify how critical parameters could beexperimentally measured (i.e., with laboratory-scale, meso-scale (e.g., large geotechnical pits) and field-scale testing) (6) develop a preliminary list of mitigation approaches, including the currently used Type 5 geotextile that could be evaluated experimentally and (7) propose a preliminary set of
recommendations and design guidelines.
Objectives 1-4 address the primary goal of understanding crack formation and propagation with existing data and non-destructive monitoring
(e.g., remote sensing and geophysical techniques). Objectives 5-7 use the acquired knowledge to inform draft guidance as well as possible/future proposed physical experimentation for calibration, validation, and evaluation of mitigation measures. Integrating field data into the
modeling environment is central to this project.