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对于库底采用土工膜水平防渗的围坝型平原水库,由于库水渗漏、地下水位上升等多种原因,使库区非饱和土层中孔隙气体聚集、上升,并在土工膜膜下形成有压气体,使土工膜产生局部隆起的气胀现象。根据土工膜气胀鼓起变形的特点,将土工膜气胀变形近似简化为环向约束球形鼓胀变形。为了解土工膜环向约束条件下球形鼓胀变形的特性,研制了4种不同规格的土工膜气胀变形专用试验设备,分析了试验设备孔径对土工膜胀破压力的影响,选择外径20 cm试验设备作为土工膜气胀变形试验的基本设备。利用选定的土工膜气胀变形基本试验设备,进行了环向约束条件下土工膜气胀变形和气胀破坏试验,总结了土工膜气胀变形和破坏的规律,得出结论:1土工膜气胀应力应变曲线可分为线性变形、强化变形、弱化变形和胀破拉断4个阶段;2气胀变形表现为不均一性,气胀破坏为张拉破坏,破坏形态表现为一条通过球冠顶点的大圆曲线或不通过球冠顶点的小圆曲线;3对于厚度0.35~0.6 mm的土工膜,其气胀胀破压力为0.08~0.12 MPa,胀破冠顶高度为4.6~5.5 cm;4对于厚度0.35~0.6 mm的土工膜,其气胀延伸率为17.6%~18.5%,远小于土工膜单向拉伸延伸率。
For the dam-type plain reservoirs with geomembrane horizontal seepage control at the reservoir bottom, the gas in the unsaturated soil layer accumulates and rises due to various reasons, such as reservoir water leakage and groundwater level rise, The formation of a pressure gas, the geomembrane produced a partial bulge inflation phenomenon. According to the characteristics of geomembrane inflation swelling deformation, the geomembrane inflation deformation is approximately reduced to the annular constraint spherical bulge deformation. In order to understand the characteristics of spherical bulge deformation under the constraint of geomembrane circumfluence, four kinds of special test equipment for geomembrane expansion and deformation were developed. The influence of aperture of test equipment on the rupture pressure of geomembrane was analyzed. Test equipment as geomembrane inflatable deformation test of the basic equipment. With the selected basic geomembrane deformation and rupture test equipment, under cyclic restraint condition, the geomembrane swell deformation and gas expansive failure test were summarized, and the law of geomembrane deformation and failure was summarized. The conclusions are as follows: 1 Geomembrane gas The stress-strain curves can be divided into four stages: linear deformation, strengthening deformation, weakening deformation and rupture. 2 Inflatable deformation is inhomogeneous, inflatable failure is tensile failure, A large circular curve of the apex or a small circular curve that does not pass through the apex of the spherical cap; 3 for the geomembrane with a thickness of 0.35-0.6 mm, the inflation pressure is 0.08-0.12 MPa and the crown height is 4.6-5.5 cm; 4 The geomembrane thickness of 0.35 ~ 0.6 mm, the inflatable elongation of 17.6% ~ 18.5%, far less than uniaxial tensile elongation of geomembrane.