Soil behavior and excavation instrumentation layout

During the construction of urban excavations, instruments are installed to monitor ground response to various construction activities, to verify design assumptions and to effectively apply the observational approach. Data collected from these instruments are also used in inverse analyses to develop improved soil models suitable for representing soil response during excavation. This study examines the relationship between various instruments typically used on an excavation project and the quality of information that can be extracted for excavation modeling. A synthetically generated set of instrument measurements using an idealized soil profile are used. Instrument readings considered include inclinometers placed in the support wall and in the retained soil, surface settlement points, extensometers, heave gages, piezometers and strain gauges in the bracing system. Various combinations of measurements are used in a novel inverse analysis approach, SelfSim, to extract the soil behavior. The study shows that in addition to the measurements of lateral wall deflections and surface settlement, measured forces in the struts significantly improve the quality of the extracted soil behavior and the overall predictive capability of the model. Inclinometers placed some distance behind the wall also improve the predictive quality of the model especially small strain soil non-linearity and provide some redundancy to measured settlements.