New Analytical Solutions for Cohesive-Frictional Soils above Deep Active Trapdoors

Even though extensive research works have been carried out to understand the trapdoor responses in frictional materials, those in cohesive-frictional materials have not yet been well studied due to the complexities involved. This paper focuses on formulating new analytical solutions for cohesive-frictional soils above deep active trapdoors. Finite-element limit analyses (FELA) were conducted to study the failure mechanisms of a deep active trapdoor considering various cover ratios, soil cohesion, and soil friction angles. Three distinct failure modes could be observed, depending on various combinations of cover ratio and soil strength parameters: internal, vertical, or external collapses. The analytical solutions, allowing the failure mechanisms and load-transfer mechanisms to be taken into account, were further proposed to calculate the modified lateral earth-pressure coefficient and vertical stresses in soils. The results from previous works and FELA solutions were compared with validate the proposed solutions. A parametric study was performed to explore the effects of cover ratios and soil-strength parameters on soil-arching ratio. The proposed solutions provide a theoretical guideline available for the initial design of geo-infrastructures spanning voids.

Automated summary

This paper focuses on the trapdoor responses in cohesive-frictional materials above deep active layers and proposes new analytical solutions. Based on finite-element limit analyses (FELA), the failure mechanisms of a deep active trapdoor are studied. Three distinct failure modes are observed and analytical solutions are proposed to calculate the modified lateral earth-pressure coefficient and vertical stresses in soils. The proposed solutions are validated and their effectiveness is demonstrated through comparison and parametric study.