Study on Thermal Stress Field and Cracking Control of Cast-in-situ Mass Concrete in a Box Tunnel
(1 Chongqing Jiaotong University, Chongqing 400074; 2 Key Municipal Laboratory of Chongqing Colleges for Geological Disaster Reduction in Highway and Water Transportation in Mountainous Areas, Chongqing 400074)
Abstract：
Cracking in mass concrete has always been an urgent research topic in the engineering field. So, in this paper, taking the cast-in-situ mass concrete of a multi-span multi-arch box tunnel in the Mountain Restoration Project in Xuzhou City, Jiangsu Province as the research background, temperature monitoring points are installed and the temperature at each monitoring point is measured during the pouring process of mass concrete, and then the secondary development function of ABAQUS finite element software is adopted to establish a finite element model of the single span tunnel, so as to simulate the thermal stress field of the mass concrete. Meanwhile, taking into consideration of the variations of concrete molding temperature, curing temperature, formwork removal time, pouring layer and so on, it analyzes the peak temperature at the center point, the maximum temperature difference between the core and surface as well as the surface tensile stress of the mass concrete in the tunnel. Finally, the variation law is concluded for thermal stress field of cast-in-situ mass concrete in the tunnel. The results show that: the variation law of the simulated temperature is basically consistent with the one measured on the site; when the concrete molding temperature and curing temperature increase by 20 ℃ , the peak temperature at the central point increases by 8.47 ℃ and 10.48 ℃, respectively, the maximum temperature difference between the core and surface increases by 6.35 ℃ or decreases by 6.79 ℃, respectively, and the tensile stress on the surface increases by 0.61 MPa or decreases by 0.52 MPa, respectively; Formwork removal and curing should be carried out about 3 days after pouring (when the concrete began to cool down) to minimize the peak temperature at the central point, the maximum temperature difference on inner surface and the tensile stress on the surface; the appropriate number of pouring layers is also conducive to the cracking control of the mass concrete. The on-site cracking control measures formulated according to the simulation results could effectively control the cracks of concrete structure and achieve good practical results.
FU Yifan1,
2 WANG Linfeng1,
2 CHENG Ping1 etc
.Study on Thermal Stress Field and Cracking Control of Cast-in-situ Mass Concrete in a Box Tunnel[J] MODERN TUNNELLING TECHNOLOGY, 2021,V58(6): 173-181
2021, Vol. 58 