Procedure for stability assessment of underground storage cavities in permafrost rocks

The article analyzes the procedure now in force for the stability assessment of underground storage cavities in permafrost rocks. It is found that the procedure lacks damage evaluation of an underground cavity with time as there is no adequate criterion. Failure prediction of an underground cavity disregards the major appropriateness index of a cavity for storage/disposal of petroleum products—loss of active storage capacity. In this regard, the current procedure offers an incomplete stability prediction of underground storage cavities in permafrost rocks. This study presents a modification of the procedure for the stability assessment of underground storage cavities in permafrost rocks. It is proposed to implement stability prediction in two stages. The first stage is the emergency risk assessment for an underground cavity based on the plastic yield zone size in rocks. The second stage is the estimate of impaired serviceability of an underground cavity for storage/disposal of petroleum products (operational integrity). The impaired serviceability is a result of the cavity wall convergence under the action of frozen rock creep and rock fall from roof and sidewalls when the ultimate strength of frozen rocks is overrun. Considering the above-specified processes, it is found that the impaired serviceability of underground storage cavities can be evaluated using such criteria as the roof displacement and the loss of active storage capacity of an underground cavity with time. Based on the corrected criteria, a stability classification is proposed for underground storage cavities. Methods of further operation are determined for each stability category of underground cavities. A case-study of sequential fill of underground cavities based on the predicted loss in their active storage capacity is discussed.

Mosina A. S., Mirnyy A. Y., Skvortsov A. A., Surin S. D. Procedure for stability assessment of underground storage cavities in permafrost rocks. MIAB. Mining Inf. Anal. Bull. 2021;(3-1):223—237. [In Russ]. DOI: 10.25018/0236_1493_2021_31_0_223.

Mosina A. S.¹, postgraduate student of the Department of Engineering and Ecological Geology, Faculty of Geology;
Mirnyy A. Y.¹, Cand. Sci. (Eng.), senior researcher, Faculty of Geology;
Skvortsov A. A.², Cand. Sci. (Eng.), head of the Department of Geomechanical and Hydrodynamic Modeling;
Surin S. D.², Cand. Sci. (Eng.), leading research worker;
¹ Lomonosov Moscow State University, Moscow, Russia
² Gazprom Geotechnology LLC, Moscow, Russia.

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