An improved equation for unsaturated shear strength behavior of soils

Abstract

The mechanical behavior of unsaturated soils is one of the challenging topics in the field of geotechnical engineering due to world-wide distributions and construction of most engineered earth structures within these soils. However, the study of unsaturated soil behavior is complex because its pore space is partially filled with water and air. The shear strength of unsaturated soils is defined by using two independent stress state variables i.e. net normal stress (σ-μa) and matric suction (μa-μw). Direct measurements of unsaturated shear strength in laboratory are complicated, expensive, time consuming and required specialized testing equipment. An improved equation for unsaturated shear strength behavior of soils is proposed in this paper. The validity of the proposed improve method is examined for a number of suction strength data of different kind of soils available in the literature. It is found that the suction strength values predicted from the proposed equation are in well agreement with the experimental results. Furthermore, the proposed improve equation is also compared with some previously published suction strength equations using those known experimental data. The results show that most of the previously published equations are suitable for particular types of soil whereas the proposed equation provides well agreement for different types of soils. Therefore, the proposed improve equation is more suitable for the prediction of the suction strength and quite adequate for practical engineering purposes.