Energy and Carbon Assessment of Ground Improvement Works. II: Working Model and Example

Abstract

A streamlined energy and emissions assessment model (SEEAM) is presented that is based on life cycle analysis (LCA) methods. The SEEAM provides geotechnical engineers with the means to quantify the embodied energy (EE) and carbon dioxide (CO2) emissions associated with ground improvement projects. A companion paper (Shillaber et al. 2015) provides detailed background for sustainable development and environmental impact assessment, which are at the foundation of the SEEAM. This paper presents the boundary conditions and methodology for this model. Construction of levee LPV 111 in New Orleans, LA is used as a case history example to illustrate the use of the model. This project involved supporting an earthen embankment by deep soil mixing (DSM) elements. Results of a SEEAM analysis of the DSM supported embankment indicate that constructing the levee involved 1,174,000 GJ of EE and 147,000 t of CO2 emissions. For comparison, the SEEAM was also used to estimate the EE and CO2 emissions associated with two other LPV 111 design alternatives; one utilizing prefabricated vertical drains (PVDs) to increase the rate of primary consolidation in the foundation soils, and the other a pile-supported reinforced-concrete T-wall. The results show that the PVD design has the lowest EE and CO2 emissions at 809,000 GJ and 64,000 t, respectively. The concrete T-wall has the greatest EE and CO2 emissions, at 2,755,000 GJ and 211,000 t, respectively (for the materials alone). Despite having the lowest EE, CO2 emissions and cost, the PVD design was not a viable solution because it could not meet a 20-month time constraint placed on the construction to achieve the needed flood protection. When performance criteria are met, quantitative information about environmental impacts, such as EE and CO2 emissions, is useful for making geotechnical decisions for sustainable development.