STABILITY OF TRAPDOORS IN COHESIVE SOILS AND IN SANDS
The trapdoor problem is of practical interest, particularly for assessing the stability of abandoned mine workings, anchor plates and the construction of temporary tunnel roofs. Although, this problem is being studied since the times of Terzaghi, for pure sands, for general soils no attention has been given till date.
The present study deals with the construction of lower bound mechanisms to study the stability of trapdoors embedded in pure homogeneous cohesive soils and in sands. Lysmer-Basudhar approach using discrete elements in conjunction with non linear programming has been used. It has been demonstrated that in general, the trapdoors embedded in cohesive soils may be classified in three categories viz., shallow, intermediate and deep. Whereas, trapdoors embedded in sands may be classified in two categories viz., shallow and deep. A detailed analysis and the methodology for such a classification is also presented. Different properties of the soil and the trapdoor have been considered in the analysis.
For sands, the obtained results have been presented in the form of expressions. The study reveals that the stability number has little dependence on the nature of the trapdoor. However, self weight of the soil exhibits a strong influence on the stability number. The obtained results show a close agreement with those available in the literature.
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