| Landfill technology is widely applied in the ultimate disposition of waste, due to its low cost, easy operation, and large disposal capacity. The areas where surrounding the landfill often are polluted to different degrees because of the low landfill technology in our country. It is necessary to design an antiseepage liner to prevent ground water from pollution and separate the waste from environment. Impervious geomembrane is extensively applied in the design of the antiseepage liner because of its low permeability coefficient, low cost, and convenient installation. The antiseepage geomembrane in the landfill is subject to upper pressure of the wastes and the mechanical compaction when cover operation. The avulsion of the antiseepage geomembrane is a common phenomenon. In order to measure the tensile property of the antiseepage geomembrane in model experiment or in the field condition, strain gauge (Actually it is a sensor) is used to detect and evaluate the performance of the antiseepage geomembrane. However, the elastic modulus of the strain gauge is larger than that of common antiseepage geomembrane, so the strain measured value in a spot is smaller than that of other surrounding sites. It makes the strain gauge had some limitations in strain measurement of antiseepage geomembrane in project.The standard sample used in this experiment is a rectangle sample with effective length of 238mm, width of 100mm. The tensile tests with the changing adaptive factors in the engineering measurements are carried out on impermeable synthetic membrane materials PVC, LLDPE, HDPE with low, medium, high elastic modulus respectively. Then the lead length correction and temperature correction are conducted on the data obtained from the strain measurement, and after multiple conversions, the image data is processed by using the binary image analysis software PTV. Two indexes for evaluating adaptability of strain gauge are proposed, they are correction coefficient of spacing and correction coefficient of image analysis. The results indicate that:(1) It is found that Strain gauge has a binding effect on antiseepage geomembrane PVC, LLDPE, HDPE, and the bigger elastic modulus of the material has, the smaller restraint is subjected to. The shorter and thinner the sample is, the longer the interval is, the larger the rate is, the larger correction factor is. The movement of the specimen is not even in the course of stretching, each marked point has its own moving track. (2) HDPE geomembrane has character of anisotropy. Due to the varied directions, the maximum stress which the geomembrane can bear is different, leading to the different correction coefficients.(3) Based on previous theoretical model, a new model to evaluate deformation of impermeable geomembrane in the process of uneven settlement of foundation is raised, the calculative method of the maximum stress and tension of fixed end is also proposed, and the calculation results by this method are consistent with the experimental results.In this study, strain measurement experiments with several kinds of common antiseepage geomembrane are carried out. The adaptability of strain gauge using in strain measurement of antiseepage geomembrane is evaluated, and the accuracy of the measurement is improved by the corresponding correction factor. |
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