Trapdoor Stability of Drained Cohesive-Frictional Soils Using Terzaghi’s Superposition Method

Jim Shiau1

Rungkhun Banyong2

Suraparb Keawsawasvong2,Email

Viroon Kamchoom3

1School of Engineering, University of Southern Queensland, QLD, Toowoomba, 4350, Australia.

2Department of Civil Engineering, Faculty of Engineering, Thammasat School of Engineering, Thammasat University, Pathumthani 12120, Thailand.

3Excellent Centre for Green and Sustainable Infrastructure, Department of Civil Engineering, School of Engineering, King Mongkut's Institute of Technology Ladkrabang (KMITL), Bangkok, Thailand.
 

Abstract

Most previous trapdoor stability studies were centered on undrained clay in two dimensions in the past few decades. Very few works were reported for cohesive-frictional soils in two- and three-dimensions. This paper sets out to examine the stability of trapdoors in c-Φ soils under both 2D planar and 3D circular (axisymmetric) conditions using a superposition method that is similar to Terzaghi’s bearing capacity coefficients approach. Using lower bound and upper bound limit analysis with finite elements, the proposed three coefficients (Fc, Fs, and Fγ) are determined with respect to a series of parametric changes of depth ratios and soil internal friction angles. Novel design charts and tables are presented, and several examples are provided to show how to use the three coefficients to evaluate soil stability under planar and circular trapdoors. The numerical results presented in the paper should be of interest to the geotechnical engineering community.

Trapdoor Stability of Drained Cohesive-Frictional Soils Using Terzaghi’s Superposition Method