PSI - Issue 32

E.A. Gubanova et al. / Procedia Structural Integrity 32 (2021) 42–48 E.A. Gubanova / StructuralIntegrity Procedia 00 (2021) 000 – 000

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retrospective analysis of the subsidenceprocess of the earth ’s surface, starting from the moment of mining. Also, within these options, a long-term stability prediction of the salt mass was made. The geomechanicalestimation of the state of the undermined mass was carried out in the dynamics of the increase of the subsidence of the earth ’s surface and was based on constructing predictive graphs of this increase according to by Baryakh et al. (2005). The safety of the undermined strata of the rocks in the computations was estimated by the progressin the subsidence of th e earth’s surface and the nature of the formation of the zones of the subvertical technogenic disturbance over the mined-out

space both at the current time and at the time of reaching the final displacements. The estimated subsidence curves of the earth ’s surface are shown in Fig. 2.

Fig. 2. Estimated subsidence curves of the earth’s surface for 2004 -2020 (Curves 1-13), at the present moment (Curve 14), and at the end of the displacement process (Curve 15)

As is seen, on the earth ’s surface, the shear trough by the present time (Fig. 2, Curve 14) has a relatively flat form with two local subsidence maxima separated by an obvious bend of the subsidence curve. Despite the value of the subsidence (about 1.6 and 1.0 m) and rather significant gradients in the bend of the curve, there is no significant discontinuity of the layers of the undermined mass along the estimated profile (Fig. 3, a). The progress of the shear cracks covers mainly the carnallite layers (V, G, D, E, ZH, Z) of the lower and middle parts of the salt strata section only in some areas where the mining parameters are changed. At the same time, in particular due to the loss of the bearing capacity of the interchamber pillars of the carnallite layer V, the destruction of rocks could take place at an earlier stage of the mass deformation. The estimations have shown that in the retrospective analysis of the salt state, the mining conditions of the carnallite layer V predetermine the nature of the subsidence of the earth ’s surface, which is significantly variable within the study area (Fig. 2, Curves 1-13). The shift trough at the initial stage of the formation in its western marginal part of the local subsidence maximum, the subsequent displacement and flattening in time of its northern slope, as well as the formation of a contrast bend in the central partof the trough are caused by a later mining period of the carnallite layer V. Its subsequent flattening indicates a rather intense anthropogenic load at the earlier stages of stoping.