PSI - Issue 32

N.A. Samodelkina et al. / Procedia Structural Integrity 32 (2021) 173–179 N.A. Samodelkina / Structural Integrity Procedia 00 (2019) 000 – 000

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such problems. This paper shows that, subject to certain conditions, it is still possible to perform safe stoping operations in an anomaly zone. 2. Problem Setting and Numerical Implementation According to the structure and composition of rocks in the WS, three parts can be distinguished: the lower one, the carnallite-sylvinite zone (CSZ), consists of alternating potassium-magnesium salts and rock salt; the middle one is composed of the overlying salt rock (OSR), and the upper one is a transitional formation member (TFM), which is represented by alternating layers of marls and rock (Fig. 1).

Fig.1. Design scheme

An anomaly in the structure of the WS is considered to be in the form of a wedge-shaped zone in the TFM and OSR. During mining operations in the wedge-out areas, a possible contact opening formsbetween the CSZ and the OSR. In this case, a hydraulic connection of the overlying waterbearing horizons with the roof of the CSZ is formed. The implementation of such a scenario entails a decrease in the total capacity of the WS by the value of the integrated capacity of the TFM and OSR. A laminated rock mass is considered, which has been undermined by the pillar mining system in the wedge-out area of the TFM and OSR. It is assumed that the mass is under the plain strain state and under the mass forces of  intensity (  is the specific weight of the rocks). The boundary conditions are standard (i.e. at the vertical boundaries, the horizontal displacements are equal to zero), the upper boundary (the earth surface) is free and, at the bottom boundary, zero vertical displacements are set (Fig. 1). The selected dimensions of the computational domain made it possible to exclude the influence of the boundary effects. The following problem was set to determine the mining conditions which make it is possible to open the contact between the CSZ and the OSR, as well as the main parameters characterising the human-induced impact of the stoping on the anomaly. The following weretaken: the maximum subsidence of the earth surface ( )  and the distance ( t ) from the goaf boundary to the wedging-out zone of the OSR. The problem was solved in the elastoplastic formulation using the Mohr-Coulomb plasticity condition

C tg n

  ,

(1)

 p    max 