Comprehensive system of construction quality control of monolithic reinforced concrete structures at sites in the permafrost zone, taking into account the thermally stressed state of the base

Abstract

The article is devoted to the development of a comprehensive system for construction quality control of monolithic reinforced concrete structures erected in permafrost areas, taking into account the actual thermo-stressed state of the foundation and associated structures. The aim of the study is to shift from fragmentary fixation of strength and geometric indicators to predictive management of the «foundation – substructure – superstructure» system based on continuous monitoring of thermal and deformation processes. The methodology relies on a systematic analysis of construction control data from 14 industrial and civil facilities, including more than 3500 concrete test series, results of temperature monitoring using 1240 sensors in the body of the structures and soil, geodetic observations of settlements, as well as numerical modeling of the thermomechanical behavior of elements using the finite element method with subsequent verification by in-situ measurements. It is shown that the actual curing temperature regimes differ significantly from the design ones, leading to an excess of design temperature gradients by 25-30%, acceleration of the exothermic peak, and an increase in the depth of foundation soil thawing. A statistically significant stochastic relationship is established between early temperature gradients, the kinetics of strength and elastic modulus development of concrete, as well as defect parameters: specific crack length, crack width, and ultrasonic integrity index; the influence of the gradient on crack formation probability is described by a logistic curve with a critical range of 28-32 °C. The novelty of the approach lies in the introduction of the thermo-stressed state criterion and the «thermal crack resistance» parameter, calculated in real time based on monitoring data and allowing differentiation of permissible temperature gradients by massiveness and concrete class. It is shown that the use of predictive monitoring and adaptive control of thermal protection and heating regimes allows for more than a threefold reduction in the share of blocks with unacceptable defects compared with traditional discrete control. The system’s testing at facilities in the Far North demonstrated more than a threefold reduction in the frequency of critical defects and an economic effect due to the reduction of reinforcement and repair works. A concept of a digital integrated system is proposed, integrating sensors, computational models, and machine learning algorithms into a unified quality management loop, ensuring increased reliability and durability of structures in the permafrost zone while simultaneously reducing costs for repair and restoration work.