METHOD OF CALCULATING THE MAIN PARAMETERS OF THE THERMAL INTERACTION OF ENGINEERING STRUCTURES WITH FROZEN ROCKS IN PERMAFROST ZONES OIL AND GAS EQUIPMENT

By the fifth or sixth year of operation of almost all of the gas-fields in Medvezh'e, the foundations of a number of the physical structures had unde~one substantial deformation. This in turn has led to distortion of the frames of buildings and equipment, bending of pipelines, and vibration of components of the turbines at the final compressor stations (FCSs). The turbine vibrations have resulted in premature wear of the components, pipeline failures, and other problems. Over time, there has been an increase both in the amplitude of the deformations and the number of sites where they originate [1, 2]. An analysis performed by the ranking method to determine the reasons for the equipment failures and production losses shows that the failures due to the development of unfavorable geological-frost conditions are comparable to the failures that occur due to technological factors and errors in construction [3]. The limited amount of capital that companies have to spend on ensuring the operational reliability of the gas-producing equipment makes it imperative that those resources be used more efficiently. More than twenty years of experience in the operation of the facilities in Medvezh'e shows that in order to determine the steps which must be taken in the short term to keep the stresses from reaching unacceptable levels and eliminate the deformation, develop long-range plans to rebuild and modernize the equipment, and thus make more efficient use of the available funds, it will be necessary to conduct a comprehensive diagnostic evaluation of the objects as integrated geotechnical systems including the soils of the foundations, the foundations themselves, and the superstructures [3-5]. Studies have shown that in most cases the deformations are caused by changes that occurred in the geological-frost conditions in the soils of the foundations of structures and that were not foreseen in the building plans [6, 7]. It was established that the decisive factor determining the load-carrying capacity of a pile foundation of a structure built on frozen ground is the dynamics of the temperature field in the soil surrounding the foundation. A deviation of the actual temperature regime of the soil part of the foundation from the design regime will lead to loss of the load-carrying capacity of the foundation and, thus, to sudden failures requiring reconstruction of the building [8]. The method traditionally used to determine the thermal regime of the soils of foundations at the design stage is calculation of the average annual temperature and the depth of the seasonal thawing and freezing [9]. The method is based on the solution of a homogeneous unidimensional heat-conduction equation in a quasi-steady approximation, which makes it possible to obtain estimates of the required quantities that are close to the steady-state values. The main shortcoming of this method is that it does not allow determination of the actual temperature field under a structure of finite geometric dimensions, since the calculation is based on the solution of a unidimensional problem. The