Effect of the Presence of Soft Clay on the Structural Design of Highway Sections

Abstract

Construction over soft clay soils have always been a great challenge in the field of geotechnical engineering especially when designing infrastructure. Because of the low shear strength and high compressibility of this soil, many engineering problems such as slope instability, bearing capacity failure and excessive settlement could occur either during or after the construction phase. The design of highway pavements on soft clay soil still remains a very challenging issue, it can cause problems such as roadbed instability or excessive total and differential settlements. The main objective of this research is to study the effect of the presence of the soft clay on the structural design of pavement sections. Results of this study show that the investigated soft clay soil has lower CBR value (0.509%) and modulus of compressibility (Es=129.8 kN/m2), therefore it is not suitable for pavement construction. By using cyclic loading model device manufactured for this study, the settlement under pavement achieved 120.05, 120.32 and 12.28mm for natural soft clay, using geotextile and using geotextile with geogrid together respectively.