Abstract
Pipe cooling systems are among the potentially effective measures to control the temperature of mass concrete. However, if not properly controlled, thermal cracking in concrete, especially near water pipes, might occur, as experienced in many mass concrete structures. In this paper, a new numerical approach to simulate thermal cracking based on particle flow code is used to shed more light onto the process of thermal crack propagation and the effect of thermal cracks on thermal fields. Key details of the simulation, including the procedure of obtaining thermal and mechanical properties of particles, are presented. Importantly, a heat flow boundary based on an analytical solution is proposed and used in particle flow code in two dimensions to simulate the effect of pipe cooling. The simulation results are in good agreement with the monitored temperature data and observations on cored specimens from a real concrete gravity dam, giving confidence to the appropriateness of the adopted simulation. The simulated results also clearly demonstrate why thermal cracks occur and how they propagate, as well as the influence of such cracks on thermal fields.
Highlights
Mass concrete plays an important role in modern civil and hydropower engineering
In an effort to address the above knowledge gaps, this paper reports outcomes of an ongoing research into thermalinduced cracking near water pipes and the influence of thermal cracks on thermal fields
T (y, 0) = Tc (τ = 0, 0 < y ≤ rc), where τ is the age of concrete; a is the thermal diffusivity of concrete; Tc is the initial temperature of the concrete slab; Tw is the temperature of cooling water; λc and λ are the coefficients of thermal conductivity of concrete and water pipes; r1 and r0 are the outer and inner radius of water pipe; and rc is the width of the concrete slab in y-direction
Summary
Mass concrete plays an important role in modern civil and hydropower engineering. The American Concrete Institute (ACI) [1] stipulates that artificial measures must be taken to solve the problems caused by volumetric deformation and hydration heat during mass concrete construction. If the pipe cooling system is not controlled properly, serious problems can occur, including concrete cracking. The heat-fluid pipe element method has been created as a better simulation method [8] This method can reflect the effect of water flow and water temperature on thermal fields, so the distribution near water pipes can be precisely simulated. Particle flow code (PFC) has been widely used to simulate mechanical behavior of rock and concrete [13,14,15], there are still few samples using it to solve thermal problems of concrete. Thermal cracking induced by pipe cooling: (i) confirmation of the microparameters of concrete, including thermal and mechanical parameters, and (ii) simulation of the temperature history of pipe cooled concrete. The final simulation results demonstrated that the obtained heat flow boundary was available
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