Construction and Long-Term Performance of Transportation Infrastructure Constructed Using EPS Geofoam on Soft Soil Sites in Salt Lake Valley ,
The Utah Department of Transportation (UDOT) and the Utah Transit Authority (UTA) have made extensive use of EPS embankment for several major interstate, light rail, and commuter railway embankments in Salt Lake Valley, Utah. Constructed between 1998 and 2001, the Interstate 15 Design Build Reconstruction Project involved the widening of interstate embankments within a 27 km narrow corridor and limited right-of-way. Approximately, 100,000 m of EPS fill was placed at various locations to minimize post-construction settlements of deep, compressible lake deposits. This paper presents results of long-term monitoring of EPS fills and comparison with other geotechnologies. Geofoam embankments had the best overall settlement performance of the technologies monitored. Gap closure and deformation of the geofoam embankment due to placement of the load distribution slab and overlying roadway materials was about 1% of the embankment height. In addition, at 3300 South Street, the foundation soil settled about 15 mm due to placement of the embankment and overlying loads. The face of the embankment settled an additional 25 mm in a 5-year period due to additional pressure of a 1.5m toe berm placed at the base of the tilt-up wall. Total post-construction settlement (foundation settlement and geofoam creep) is expected to be about 50 mm at the wall face for a 10-year postconstruction period. The trend of post-construction settlements suggest that geofoam embankments are performing as designed and will meet the 50-year post-construction deformation limit of 1% creep strain. Overview of the I-15 Reconstruction Project The Utah Department of Transportation (UDOT) togeth er with Wasatch Constructors finished the $1.6 billion reconstruction of Interstate 15 (I -15) that runs through Salt Lake City, Utah in 2001 just prior to the start of the 2002 Winter Oly mpics. The interstate embankment was widened from eight lanes to ten general-purpose lan s, plus two high occupancy vehicle lanes, within an existing north-south alignment that runs through the middle of the densely populated Salt Lake Valley. In this area, parts of the I-15 a lignment are located atop extensive deposits of relatively compressible lake sediments. Collateral consolidation settlement along this widened alignment had to be minimized to prevent differenti al settlement damage and subsequent
GEOFOAM FILL PERFORMANCE MONITORING
The I-15 Reconstruction Project was the first major design-build infrastructure rehabilitation project in the United States. Geofoam offered a novel solution to challenges of settlement and limited time of construction through an urban corridor. The first challenging application that opened the gate of opportunity to install geofoam was the case of the 100 South utility crossing. This report documents the case history of geofoam embankments in terms of this first application. The project background, construction timeline and monitoring results over a period of almost three years are presented. Settlements were observed with magnet extensometers, horizontal inclinometers and level survey. Pressure beneath the geofoam was monitored by total earth pressure cells. The record of monitoring consists of foundation and geofoam fill settlements divided into construction and post construction phases. Most of the geofoam deformation took place during construction. Both during and after construction, settlements of the foundation have been greater than the geofoam deformation. The field results were carefully reviewed to identify temperature and construction related movements. Pressure cell observations indicate the stresses in the foundation beneath the geofoam are of the general order of the working stresses assumed in design.
Meso-Cenozoic tectonothermal evolution of Ordos basin, central China: Insights from newly acquired vitrinite reflectance data and a revision of existing paleothermal indicator data
Abstract Thermal history reconstruction using paleogeothermal indicators, including vitrinite reflectance (Ro) and apatite fission track (AFT) dating in the Ordos basin indicates that the lower subsection, consisting of the Paleozoic to Middle Triassic sediments, reached its maximum paleotemperatures at the end of the Middle Triassic (T 2 ) and experienced a paleogeothermal gradient of 42–63 °C/km with a mean of 49 ± 9 °C/km, while the upper subsection from the Late Triassic to Middle Jurassic, experienced its maximum paleotemperatures at the beginning of Late Jurassic (J 3 ) and a paleogeothermal gradient of 25–39 °C/km with a mean of 31 ± 6 °C/km. Therefore, at least two heating events are recorded in the Ordos basin since the Mesozoic: the first and most intensive in Middle Triassic as recorded by the lower subsection, the other is a moderate Jurassic thermal event as recorded by the upper subsection. These heating events were followed by a Cenozoic rapid cooling starting at about 21 Ma. In the regional geodynamic context, the Triassic thermal event might be ascribed to hydrothermal activity related to the Triassic collision between the North China Block (NCB) and the South China Block (SCB); the Jurassic thermal event to the Pacific subduction and the Cenozoic rapid cooling event to the Indo-Asian collision, respectively.