Experimental and Numerical Studies of Controlling Thermal Cracks in Mass Concrete Foundation by Circulating Water

Abstract

This paper summarizes an engineering experience of solving the problem of thermal cracking in mass concrete by using a large project, Zhongguancun No.1 (Beijing, China), as an example. A new method is presented for controlling temperature cracks in the mass concrete of a foundation. The method involves controlled cycles of water circulating between the surface of mass concrete foundation and the atmospheric environment. The temperature gradient between the surface and the core of the mass concrete is controlled at a relatively stable state. Water collected from the well-points used for dewatering and from rainfall is used as the source for circulating water. Mass concrete of a foundation slab is experimentally investigated through field temperature monitoring. Numerical analyses are performed by developing a finite element model of the foundation with and without water circulation. The calculation parameters are proposed based on the experiment, and finite element analysis software MIDAS/CIVIL is used to calculate the 3D temperature field of the mass concrete during the entire process of heat of hydration. The numerical results are in good agreement with the measured results. The proposed method provides an alternative practical basis for preventing thermal cracks in mass concrete.

Construction methods used for controlling temperature in mass concrete structure

“…A finite element analysis of the foundation was conducted with and without the circulating water. The results were verified using actual measures from the site [18].…”

Nghiên cứu phân bố vùng bề mặt có nguy cơ nứt do nhiệt trong bê tông khối lớn bằng mô phỏng số

“…Do đó, việc kiểm chứng mô hình và cách thức nhóm tác giả mô phỏng là rất quan trọng. Thứ nhất, hiện nay rất nhiều các nghiên cứu trên thế giới đã sử dụng công cụ phân tích nhiệt dạng dòng của chương trình Midas Civil để phân tích trường ứng suất -nhiệt độ trong khối bê tông [13,17,[31][32][33][34][35][36][37][38][39][40]. Bên cạnh đó, trong một nghiên cứu vừa công bố [22], nhóm tác giả đã tiến hành thực nghiệm đo nhiệt độ của một khối bê tông với kích thước 2,5 × 2,5 × 2,5 m (Hình 2, Hình 3) và mô phỏng lại khối bê tông đó với các điều kiện thực tế để kiểm chứng và kết luận tính chính xác giữa mô hình và thực tế.…”

Temperature control and crack prevention during construction in steep slope dams and stilling basins in high-altitude areas

“…Engineering experience indicates that the difficulty in avoiding cracks is due to insufficient understanding of the mechanism of crack formation, the randomness of hydrometeorological conditions, and the failure of material parameters in reflecting actual engineering conditions; in addition, crack formation occurs because of the absence of timely and reasonable measures for temperature control that are tailored to the actual conditions of specific projects. [8][9][10][11][12][13] Therefore, in the current condition in which a major breakthrough in the theory of temperature control is difficult to achieve, [14][15][16][17][18][19][20][21][22][23][24] crack prevention should still be focused on the selection of timely and reasonable measures for temperature control.…”