HDPE膜的力学特性受损伤影响初步研究

Effect of damage on mechanical behavior of HDPE geomembrane

为分析某一现代卫生填埋场边坡上铺设的高密度聚乙烯膜(HDPE膜)因施工损伤而引发的断裂机制,开展了条带拉伸试验和土工离心模型试验.拉伸试验测试了无损膜和4种情形损伤膜试样,发现损伤HDPE膜受力达到峰值强度并被拉长至一定程度后,其拉伸变形不再在整个试样长度范围内均匀发生,而主要集中在受损部位发生,故实测到的损伤膜极限伸长率仅为无损情形时的1/10左右.这一影响实际上改变了HDPE膜的破坏机制,使其由原先的渐进性破坏变成受损后的突发性破坏.两组初步离心模型试验结果发现,在轻质高压缩性的模型MSW作用下,模型膜上的损伤明显扩大,受损部位的拉伸变形十分明显并接近断裂,表明损伤对膜的实际工作性状有很大影响.

For investigation of the failure mechanism of the HDPE geomembrane on the slope of a newly constructed landfill, which is related to a series of small boreholes during the construction, tensile tests and geotechnical centrifuge model tests are carried out on the intact and damaged HDPE geomembranes as well as their simulants. Four kinds of damages to the HDPE geomembrane are simulated by folding of the membranes, drilling of holes through the membranes, and combination of boreholes and defects remaining on the edge of the samples. It is found from the tensile tests that, when the tension load of the damaged geomembrane reaches its ultimate value, the load drops abruptly, and that the development of the tension strain concentrates in damaged parts. As a result, the ultimate ratio of elongation of the damaged HDPE geomembrane is much less than that of the intact HDPE geomembrane, only about one-tenth. Two preliminary centrifuge tests show that, under the large MSW settlement condition, holes on the simulant geomembrane at the top of the slope move a certain distance from their original positions downward the lined slope, their diameters enlarge twice, and silicone glue begins to be detached from the geomembrane, registering an impending rupture of the damaged geomembrane.