J. Cent. South Univ. Technol. (2011) 18: 1304−1310 DOI: 10.1007/s11771−011−0837−9 Stress and deformation due to embankment widening with different treatment techniques WANG Hao(汪浩) 1 , HUANG Xiao-ming(黄晓明) 2 1. Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, IL 61866, USA; 2. School of Transportation, Southeast University, Nanjing 210096, China © Central South University Press and Springer-Verlag Berlin Heidelberg 2011 Abstract: A two-dimensional (2-D) finite element (FE) model was developed to analyze the deformation and stress of embankment on soft ground due to widening with different treatment techniques. It is found that the embankment widening induces transverse gradient change due to differential settlements and horizontal outward movements at the shoulder of the existing embankment. Embankment widening also increases the shear stress along the slope of the existing embankment, especially at the foot of slope. The failure potential due to embankment widening may increase with the increase of widening width when the widening width is smaller than 8.5 m, but may decrease with the increase of widening width as the widening width is greater than 8.5 m. The effectiveness of four ground and embankment treatment techniques, including geosynthetic reinforcement, light-weight embankment, deep mixed columns, and separating wall were compared. The results indicate that these treatments reduce the differential settlements and improve the stability. The light-weight embankment has the most effectiveness among four treatments. By using the fly-ash backfill material in widening, the transverse gradient change decreases from 0.5%−1.3% to 0.26%−0.8% and the maximum horizontal displacement decreases from 2.76 cm to 1.44 cm. Key words: finite element model; ground treatment; road widening; geosynthetic reinforcement; light-weight embankment; deep mixed columns; separating wall 1 Introduction Now, many highways are confronted with embankment and pavement widening for the purpose of increasing traffic capacity. Differential settlements may develop between and within the new and existing embankments due to widening, especially on soft soils. This could cause transverse gradient change at the pavement surface and longitudinal pavement cracking at the vicinity of the joint between the existing and new pavements [1−5]. Various treatment techniques have been reported in the literature to reduce the differential settlements due to widening, such as excavated terrace on the existing slope, staged (gapped) construction, geosynthetic reinforcement, preloading with surcharge, foundation improvement, and a combination of the above alternatives. DESCHAMPS et al [6] emphasized the importance of adequate compaction and consistent permeability of the existing and new embankment material. HAN and AKINS [7] reported using vibro-concrete columns in conjunction with geogrid layers above to support widened embankments. ALLERSMA et al [8] and MEURS et al [9] investigated the effectiveness of the gapped construction method for embankment widening using field study and centrifuge experiment. FORSMAN and UOTINEN [10] and HUANG and WANG [11] studied the effect of geosynthetic reinforcement on the differential settlements and horizontal displacements of embankments after widening. HAN et al [12] concluded that the installing columns under the widened portion and/or the connecting side slope of the existing embankment could reduce the maximum settlement, transverse gradient change, and the shear stress induced by widening of the embankments. Although various treatment techniques have been commonly adopted in practice for widening of embankments, limited researches were conducted to compare the effectiveness of different treatments and the design guideline is still not available for widening projects. In addition, it is important to select the appropriate ground treatment technique based on the geotechnical investigation of the widening site. In this work, a numerical model is developed to analyze the responses of embankment and foundation caused by widening, including the differential settlements, horizontal displacements, and stress distributions. Four Received date: 2010−03−05; Accepted date: 2011−01−10 Corresponding author: HUANG Xiao-ming, Professor, PhD; Tel: +86−25−83795184; E-mail: huangxm@seu.edu.cn