## 1 Introduction  
Green highways are a current trend in the construction of sustainable development projects [1]. The construction of a new road disturbs the lives of people and animals along the route of the road [2]. Historical data indicate that each additional mile of interstate highway reduces agricultural land [3]. However, the growth of highway transportation is necessary for the economic and social development of a country [4]. Therefore, the rehabilitation, widening, and addition of new carriageways in old roads are important to maintain the level of service (LOS). In road widening projects, most deformations in the embankments develop due to differential settlement between the old and widened portions [5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22]. The impact of traffic load on the widened portion of the road is more dominant than the volume [23, 24]. In road widening, the subgrade of the new road is more affected by the dynamic load than the old road subgrade [9]. Differential settlement ultimately develops due to expansion of the road [25], which increases and decreases later [26]. The differential settlement increases with increasing groundwater level and subgrade height [27]. The differential settlement creates a soil archive effect in the embankments [28], which is higher at the edge of the slope than at the centerline [29]. Aiming at the above-mentioned issue, this research is based on the road widening project of National Highway-120 (N-120), Sindh, Pakistan. In particular, the study is focused on the weak sections of N-120, where differential settlement developed and caused pavement failures. The characteristics and progression of settlement because of road widening construction activities have been examined through small- and large-scale model tests [9, 30],centrifuge tests [11; 31], numerical modeling [12; 14; 17; 27; 32; 33; 34; 35; 36; 37], and field tests [20]. As differential settlement develops in the middle of the embankment, transverse cracks simultaneously appear at the surface [38]. The self-weight of the widened embankment and pavement creates uneven settlement above weak road foundations, which consequently causes cracks in the pavement structure [21]. Failures appear in the pavement layers in the form of spalling, loose binders, changes in the horizontal slope of the road, and longitudinal cracks at the junction of the old and widened portions of the road constructed on weak soils [39]. Vehicle speed, traffic load area, and temperature contribute to the load rate on the asphalt layers [40]. It is pertinent to mention that the mid-pavement-layer strains are more significant than in the top layers [21]. Shear and transverse tensile strains are more sensitive to fluctuations in contact pressure than longitudinal tensile strains at the bottom of asphalt concrete [41]. For the maintenance and construction of weak sections in road widening projects, the study of the mechanism of differential settlement is necessary because the joint between the old and widened portions of the road needs to be strengthened by necessary remedial measures. Several techniques are applied to enhance subgrade performance when it is necessary to construct over weak soils [9]. The research outcomes show that reinforcement is crucial at the junction of old and widened portions of roads for compaction and reduction of differential settlement [7; 9; 15; 30; 38]. Pile-supported embankments are now widely used in foundation treatments because of their cost, safety, and simple construction [42]. Several research projects have aimed to produce new sustainable construction materials, especially lightweight concrete, to move toward sustainable construction [43]. The effective use of geosynthetic products as soil reinforcement was identified in the 1970s [44]. Considering the features of the project, three reinforcement techniques are selected for analysis in this study. First, geogrid reinforcement is widely used, which increases the resilience modulus of the subgrade and reduces inhomogeneous deformation.