Solve the thermal stress when the dam heightening -

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Solve the thermal stress when the dam heightening new ideas and technologies

Vertical stress, most of the old and new dams are compressive stress, but lower in winter near the surface of the local tensile stress, the maximum was 0.73MPa,[link widoczny dla zalogowanych], the tensile stress range is small. -0-00822 7 Figure 7 Danjiangkou dam section (unit: m) Figure 8 after the completion of the vertical stress due to temperature (unit: Mva) Reservoir surface average temperature is 18.2 ~ C, of amplitude 11. O ~ C, with the water depth increases, the average water temperature and water temperature were gradually decreased in amplitude and delayed compared with the temperature some. 4.1 The new concrete from temperature control measures on 1 October 1 start pouring, increased by 6.0m, temperature control measures are as follows: (1) pouring temperature. When the temperature of +2 ~ C lower than the 12 ~ C when calculated according to +2 ℃; when the temperature +2' E> 12 ~ C when the pre-cooling, (2) Short-term insulating the downstream side (removed after the completion of the following year in May insulation board.) After the completion of short-term thermal stress state of the dam heel is always stress, stress and long-term thermal insulation than the internal stress is similar to the dam, but the stresses near the downstream dam face have some changes. This is the downstream surface air temperature changes caused by the stress of all the gravity of this problem exists, not the problems caused by the dam heightening. We also carried out with a lot of three-dimensional finite element simulation of the whole process, whether long or short-term thermal insulation in the hydroelectric dams are compressive l1 2003 7258 Figure 9 after the completion of comprehensive vertical stress under the load (unit: MPa) force,[link widoczny dla zalogowanych], and the plane finite element results are similar, as shown in Figure 10, l1 shown; but if short-term holding, near the downstream dam face, mainly due to annual temperature changes, stress is more complex. Winter, the dam blocks the lateral (near the transverse plane) tensile stress, have less stress in central; summer, the lateral compressive stress, tensile stress produce a smaller central. This is not a heightened stress caused mainly in the downstream changes in surface temperature caused. : Figure l0 after the completion of the long-term preservation of the dam caused the temperature outside the side (transverse plane) vertical stress (unit: MPa) 8756 n long-term preservation plans after the completion of the dam due to temperature stress in the vertical plane (unit: MPa ) nonlinear results show that the combination of the outside near the dam face block the winter may partly torn off, but the middle will not disengage, with the role of the keyway, dam integrity can be assured that will not affect the operation of dams . If long-term thermal insulation in the downstream side, you can avoid the joint surface of the disengaged. 5 Conclusion (1) The temperature difference is usually calculated based on concrete dam is a concrete starting point for the maximum temperature +, but the starting point of gravity is not a heightening of the temperature calculation of the maximum temperature of +, but increasing the height of the average new concrete upon completion of the initial temperature. (2) heightening of the temperature difference may be gravity △ = a calculation, the conclusion of which is to raise the average temperature of new concrete, the stability of the new dam block temperature, roughly equivalent to the annual average temperature increase solar radiation. (3) ultra-cold water and strong insulation, can be completed when the new concrete dam heightening the average temperature control to equal or even lower, making the temperature difference between gravity heightening △ ≤ 0, and less than the rate for manual control , so that we may be increasing the height of the thermal stress caused by active control of gravity. (4) Dam Heightening the simulation proved that the thermal stress problem solving dam heightening of new ideas and technology is feasible. Heightening the dam,[link widoczny dla zalogowanych], the dam heel is not only harmful to the tensile stress does not appear, but there stress. New concrete tensile stress is not large,[link widoczny dla zalogowanych], not cracks. (5) surface insulation is an important factor,[link widoczny dla zalogowanych], our next step to be further studied to ensure that seams are not torn off the structure and temperature control measures. (6) increasing the height of the proposed settlement when the temperature stress of gravity of the new ideas and new technologies to solve the problem of gravity proposed increasing the height of a brand new and effective method.

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