![]() ![]() The longitudinal settlement profiles with corresponding waiting period for the East Runway and West Runway are shown in Figures 6.12 and 6.13, respectively. Settlements at runways and taxiways varied from 1000 to 1500 mm. In general, the apron area encountered average settlements of 14 mm under 7.65 and 8.67 t/m 2 loading, respectively. A relatively uniform settlement was observed throughout most of the ground improvement area. ![]() Table 6.4 summarizes the maximum, minimum, and average settlement data and Figures 6.10 and 6.11 present the settlement contours for Ground Improvement (G.I.) Phases I and II projects, respectively. A marked increase in settlements was observed immediately after placing the first and second stage of surcharge fill loading. In general, most of the field surface settlements prior to surcharge removal were less than the design estimate. ![]() Research reported by FHWA (2011) indicates that GRS (GCS) can have up to 5 times greater capacity than traditional MSE walls. While the main thrust of using GRS walls by the FHWA has been for rapid construction of abutments for integrated bridge systems, other contractors have used this technology for stand-alone retaining walls, support of utility pipes, and rehabilitation of unstable slopes. The close spacing of the reinforcement provides a similar type of pullout resistance as provided by traditional MSE walls, but in addition, GRS provides a significant component of confinement resulting in greatly increased capacity and stiffness. These walls employ techniques similar to those for construction of MSE walls, but use much closer vertical spacing (typically 20 cm = 8 in.) lighter-weight reinforcement (typically a woven polypropylene geotextile) well-compacted, select granular fill and smaller facing elements primarily secured to the reinforced soil mass only by friction. The Federal Highway Administration (FHWA) has recently embraced a newer version of the MSE wall referred to as geosynthetic reinforced soil (GRS) (or geosynthetically confined soil, GCS, by others) ( Figure 14.15). ![]()
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