Study on Evolution of the Thermophysical and Mechanical Properties of Inner Shaft Lining Concrete during Construction Period

Abstract

The asymmetric temperature field is one of the main factors inducing the cracking of the inner shaft lining during freezing-shaft sinking. The evolution equation for the thermophysical and mechanical properties of shaft lining concrete during construction period is the basis for revealing the cracking mechanism. In this study, several experiments were conducted to reveal the evolution of the temperature field, thermal conductivity, specific heat capacity, compressive strength, tensile strength, and elastic modulus of shaft lining concrete with age and lining thickness within the first 7 d after pouring. Results show that the shaft lining concrete temperature curve after pouring can be divided into five stages: induction, slow heating, rapid heating, rapid cooling, and slow cooling. Thermal conductivity and specific heat capacity reached the maximum on Day 1 and gradually decreased with an increase in age. The compressive strength, tensile strength and elastic modulus significantly increased with age. With an increase in thickness, the shaft lining concrete at the same age improved its three mechanical parameters. Finally, the evolution equation for these thermophysical and mechanical parameters with age within the first 7 d after pouring was fitted based on experimental data. This study is expected to provide a thermophysical and mechanical basis for studying the cracking mechanism of the inner shaft lining.