Mathematical Modeling of Frozen Rock Massif Formation During the Shaft Deepening

Abstract

ABSTRACT The paper deals with the formation a mathematical modeling of heat transfer at the freezing well effect on the rock massif during the shaft deepening. The dynamics modeling of the temperature field around the shaft was made in the application package «ANSYS». The approximate formation time of the frozen rock massif of desired thickness, which is necessary for sinking the shaft, was determined.The construction of underground facilities, including vertical shafts, is a knowledge and resource-intensive process. It requires tackling many problems related to safety in the construction and subsequent operation of the facilities. The influence of various factors, such as: loss of stability, the impact of heavy water inflows [1], and others -may result in destructing of the excavation walls. It is well known that brittle materials, such as rocks and concrete, contain pre-existing micro-cracks [2], which significantly affect their behaviour. Rock masses are generally discontinuous in nature, and contain fractures (joints) with corresponding spacing and rock bridges, which play an important role in the strength of a rock formation. The propagation and coalescence of cracks initiating from such pre-existing defects, on a variety of scales, are the dominant failure mechanisms controlling the strength and integrity of brittle materials. A rock mass is not necessarily a continuous medium, nor a totally discrete medium but a kind of defect material which contains cracks, joints and faults. The nonlinear deformation behaviour of a rock mass is induced by the propagation and coalescence of cracks and joints under the external loads.The paper deals with the Talitsky area of Verkhnekamsky deposit. This area is characterized by a complex structure and the presence of several aquifers. The freezing method was proposed to ensure safe penetration and protection from blur and soil destruction [3].The preliminary time of the active freezing to form the frozen rock fence of 6.2m thickness (δ) and the shaft diameter 9m had been calculated before the start of shaft excavation. The calculation of the active rock freezing duration, according to the project documentation, is performed by the rate of frozen rock fence increase, which