Interaction between Adjacent Soil-Arching Effect in Homogeneous Clay and the Corresponding Stability Analysis of Underground Voids: Insights from Trapdoor Modeling

Nature- and human-induced underground voids appear frequently, posing threats to the performance and stability of infrastructures. The interaction between underground voids in clay lacks attention. This study employed the finite-element limit analysis to conduct a series of two-dimensional twin-trapdoor tests in homogeneous clay. Using twin-trapdoor modeling as an alternative approach to explicit modeling, the interaction of adjacent soil arching effect in the case of dual underground voids was identified by analyzing the soil arching ratio, stress redistribution, and shear bands. Furthermore, the interaction of adjacent soil arching effect is considered to influence the stability of the twin trapdoor, which is quantified by the dimensionless stability factor of the twin trapdoor. The interaction between twin trapdoors vanished with the increase of spacing between trapdoors. A twin trapdoor with a longer normalized fill height requires larger normalized spacing between trapdoors to eliminate the interaction. A prediction expression for the stability factor of the twin trapdoor in homogeneous clays considering the interaction between the twin trapdoors is proposed to define the stability envelope. From that, simple equations for calculating the collapse surcharge, the required supporting pressure, and the factor of safety of twin-trapdoor problems are also presented. The proposed equations provide guidelines for the stability evaluation and initial design of relevant infrastructures considering the interaction of adjacent underground voids.