Application Of Low Elastic Modulus Concrete In Dam Cutoff Wall

In order to improve the defense capabilities of water disasters and give full play to the combined effects of water resources, since the establishment of our country, Zhejiang Province has built more than 4000 different scale reservoirs. However, most of the reservoirs were build according to low construction standards in earlier years, as the running time went, the hidden dangers of dam appeared gradually. In all the dams in Zhejiang Province, rock-earth dam accounted for more than 90%, and the work of anti-seepage and reinforcement is very important and pressing. In recent years, a new type concrete was proposed in Zhejiang Province, which is called low elastic modulus concrete, its elastic modulus is between the proposed normal rigid concrete and plastic concrete, and it was applied to the anti-seepage wall of Qingshan Reservoir in Zhejiang Province, which achieved good results. Thus, in order to know more about application of low elastic modulus concrete in cutoff wall and for better engineering practice, it is necessary to do some analysis and research.In this paper, as an engineering example, the cut-off wall in main dam of Zhejiang Qingshan Reservoir is simulated and analyzed using the finite element software ADINA.First, the numerical model was built using the finite element software ADINA. Based on the model, the properties of stress and deformation of low elastic concrete cutoff wall in dam body was analyzed in two different conditions, which were under normal operation water level and under check flood water level. In the analysis, the low elastic modulus concrete adopted linear elastic model, the dam body and foundation adopted Duncan-Chang E-B nonlinear elastic model. Meanwhile, the calculation results of horizontal displacement were compared with the actual measurement values, and the properties of stress of cutoff wall in actual operation condition were detailed analyzed.Then, based on the simulation model above, the effect of dam constitutive model, elastic modulus of cutoff wall, the height of dam on the stress and deformation of the cut off wall are analyzed systematically. A critical value of cutoff wall's elastic modulus values is proposed, when the elastic modulus overruns the value, the stress of wall increases faster, while almost doesn't change when the elastic modulus is lower than the value. By comparing the sensitivity of cut off wall's stress and deformation to the change of wall's elastic modulus and dam's elastic modulus, the effect of reducing the wall's elastic modulus on the stress and deformation of wall is proved to be better than the way of enhancing the dam's elastic modulus. Meanwhile, by comparing the results between two-dimensional model and three-dimensional model, two-dimensional model is proved to be only suitable for the analysis of middle section of the dam. while three-dimensional model is suitable for the whole section, including the edge part.The Goodman element is widely used to simulate the contact of two different materials, however sometimes it causes large error in stress calculation and element overlapping. In this paper, a further modified contact element is proposed, the better element has its own thickness, furthermore, when composed, the connection in normal direction changes from innumerous springs to innumerous rigid rods while the displacement changes from less than to larger than thickness.