International Journal of Engineering and Technical Research (IJETR) ISSN: 2321-0869 (O) 2454-4698 (P), Volume-7, Issue-5, May 2017 178 www.erpublication.org Abstract— It has been observed at several instances that pavement performance is greatly affected by the usage of poor quality of soil subgrade which causes severe damage and distress. With the growing tendency to utilize marginal soils, there arises the need to understand the fundamental behavior of the materials in order to make suitable amendments in design parameters, especially in the subgrade construction of pavements. This paper presents the shear strength behavior of geotextile reinforced marginal soil without and with cement modification and compares its performance with that of conventional soil subgrade (gravel). The cement modified reinforced marginal soil has shown significant improvement in shear strength parameters both under un-drained and drained conditions. Further, the study revealed that the cement modified marginal soil has become non-plastic with its performance close to that of gravel subgrade. The mechanisms of geotextile reinforced soil in mobilizing the shear strength parameters are observed to be relevant even for cement modified marginal soil. Index Terms— Marginal soil; Cement modification; Geotextile reinforcement; Shear strength I. INTRODUCTION In view of the scarcity for suitable backfill soils at several project sites, there is a growing tendency to utilize locally available marginal soils in the pavement construction (Glendinning et al. 2005; Won and Kim, 2007). Some investigators have also studied the shear strength behaviour of reinforced cohesive soils (Swami Saran, 2006), though there exists numerous studies carried out on conventional soils (Haeri et al. 2000; Latha and Murthy, 2006). It is unanimously felt that the cohesive soils and other marginal soils suffer from poor drainage and the consequent low shear strength parameters. Failures of pavement structures made of cohesive backfills were also reported by various investigators (Koerner, 2000; Goel, 2006; Yoo and Jung, 2006). Despite these problems, several investigators favours the use of marginal soils with suitable amendments to the material (Swami Saran, 2006). Even few investigators have attempted to use cement modified backfill soils in the geosynthetic reinforced soil (Watanabe et al. 2002; Aoki et al. 2003; Lawson, 2003) to improve their stability under earthquake loading. Mr. Pandu Kurre, Research Scholar, in Civil Engineering, University College of Engineering, Osmania University, Hyderabad Dr. M. Kumar, Prof. in Civil Engineering, University College of Engineering, Osmania University, Hyderabad Dr. G. V. Praveen, Prof. in Civil Engineering, S. R Engineering College, Warangal Dr. M. Heeralal, Assoc. Prof. in Civil Engineering, National Institute of Technology, Warangal Mechanically stabilized earth (MSE) has gained its wide acceptance for variety of applications such as road and railway embankments, earth dams, hill roads, abutments and retaining walls, spillways, area foundations and land scaping to name a few in civil engineering practice (Koerner, 2000; Wartman et al. 2006). Since its inception in France by Henri Vidal (1969), several investigators have attempted to understand the basic mechanisms of MSE and broadly arrived at a common understanding of shear strength parameters based on rupture and slippage failures through extensive triaxial testing (Swami Saran et al. 1992; Latha and Murthy, 2006). However, there exists still varied opinion among researchers regarding the basic mechanisms, especially with the use of different backfill materials and a wide variety of reinforcing materials (Haeri et al. 2000; Yoo and Jung, 2006; Latha and Murthy, 2006). In the present work, locally available marginal soil was stabilized using cement to overcome the ill-effects of its plasticity and a detailed laboratory testing was carried out on fabric reinforced marginal soil samples without and with cement content to understand the shear strength mechanisms through large triaxial tests. These results were compared with those obtained from reinforced gravel samples. II. MATERIALS AND METHODOLOGY The present investigation is undertaken to understand the shear strength behaviour of reinforced marginal soil without and with cement modification for which the following materials and methodology were adopted. 2.1 Materials Gravel/Murrum: Gravels are coarse grained soils with particle size under 2.36 mm with little or no fines contributing to cohesion of materials. Murrum is the product of decomposition and weathering of the pavement rock. Visually these are similar to gravel except presence of higher content of fines. Marginal soil: Locally available marginal soil was used to simulate the marginal backfill soil. The properties of marginal soil were determined as per Bureau of Indian Standards (SP 36-Part 1): 1987). Gravel (9%); Sand (52%); Silt (24%); Clay (15%); Liquid limit, wl (37%); Plastic limit, wp (20%); Unified soil classification (SC); Optimum moisture content (16%); maximum dry density (1.78); Shear strength parameters: UU conditioncu(53kPa);  u(160); CD condition c' (11 kPa);' (300); Coefficient of permeability, k (7.62 × 10 –5cm/sec). Cement: Ordinary Portland cement of 53 grade is used to modify the marginal soil. Study of Triaxial Behavior of Geotextile Reinforced Marginal Soil Without and with Cement Modification for Subgrade Construction of Pavements Mr. Pandu Kurre, Dr. M. Kumar, Dr. G. V. Praveen, Dr. M. Heeralal