Investigation On Crack Prevention For Concrete Gravity Dams In High Altitude Region Under Cold Wave

During the construction and operation period, the concrete dam will inevitably encounter change of temperature because of its large volume and long duration. In the western region of our country, the high altitude, temperature difference between day and night, the low average temperature of the year, the cold wave attacks frequently in winter. The large tensile stress appears in the dam because of the drastic changes in temperature. When the tensile stress exceeds the ultimate tensile strength of the concrete, the dam often cracks even worse.In this paper, according to the finite element computational theory of the concrete temperature field and thermal stress filed, based on ANSYS, using APDL language to design the simulation calculation program of the concrete gravity dam about the temperature field and thermal stress filed in pouring stage. During the programming, the changes of modulus of elasticity, the change of temperature, concrete creep, the adiabatic rise of temperature were considered and so on. The temperature field and thermal stress of the concrete dam were analyzed under the cold wave. When using different insulation materials, Temperature field and thermal stress field of the dam were comparatively analyzed.The results showed that bare concrete surface could easily produce tensile stress under the cold wave which led to surface cracks. The dam pouring on the bedrock constrained by the strong binding effect of the bedrock, would produce a large temperature stress. After the surface of the dam was insulated, the heat transmission was weakened between the external environment and concrete. Surface temperature increased, the temperature between inside and outside and temperature gradients of its surface were reduced, thereby effectively reducing the surface temperature during cold wave. Insulation effects were closely related to the changes of the external environment, the type and thickness of the heated board, selection of suitable heated board is significant in reducing the cracks.