分离式复合土工膜鼓胀变形的膜布复合规律

Geomembrane-Geotextile Composite Rules for Bulging Deformation of Separated Composite Geomembrane

分离式复合土工膜广泛应用于平原水库全库盘水平防渗工程中。为研究鼓胀变形及破坏时其中土工膜和土工布的作用规律,基于环向约束球形鼓胀变形模型,利用室内鼓胀变形试验和层状复合材料理论方法,分析了分离式复合土工膜(两布一膜250 g·m^(–2)/HDPE(高密度聚乙烯土工膜)0.4 mm/250 g·m^(-2))的鼓胀变形及破坏特征、鼓胀压力和应力的膜布复合规律,并探讨了该规律的初步应用。结果表明:由于土工布的透水透气性,分离式复合土工膜发生鼓胀变形时,与压力介质接触的最下层土工布为鼓胀变形无效层,其上方的土工膜和土工布为鼓胀变形有效层;有效层中最上层土工布首先发生裂口型破坏,土工布破坏后土工膜也会瞬间破坏;分离式复合土工膜的鼓胀压力(含胀破压力)等于有效层土工膜和土工布的鼓胀压力之和,应力(含胀破应力)等于有效层土工膜和土工布的应力与其相应厚度百分比的乘积之和,胀破高度和胀破应变与单层土工布的近似相等;有效层土工膜/布材料本身的应力越大,所组成的复合材料应力也越大;有效层中某一材料厚度百分比越大,复合材料应力越接近该材料的应力值,且接近的快慢程度与有效层材料之间的应力差值大小成正比。对于不同规格、类型基础材料组合成的不同种分离式复合土工膜,研究结果有助于确定其鼓胀变形力学特性,并能为实际应用中的材料选型提供参考。

The separated composite geomembranes are widely used in the horizontal anti-seepage engineering of plain reservoir bases.To study the action principles of geomembrane and geotextile in bulging deformation and failure,based on the ring-constrained spherical bulging deformation model,laboratory bulging deformation test and theoretical analysis method of layered composite materials were adopted to analyze the bulging deformation and failure characteristics of the separated composite geomembrane(two geotextiles and one geomembrane 250 g·m^(–2)/HDPE0.4 mm/250 g·m^(–2))and geomembrane-geotextile composite rules of bulging pressure and stress.The preliminary application of the rules was also discussed.The results showed that:When the separated composite geomembrane bulges,due to water/air permeability,the lowest geotextile in contact with the pressure medium was defined as ineffective bulging layers,while the upper geomembrane and geotextile layers were considered as effective bulging layers.The uppermost geotextile in the effective layer was the first to undergo fissure-type damage,and the geomembrane also failed instantly after the geotextile broke.The bulging pressure(including bursting pressure)was the total pressure of each effective layer,while the bulging stress(including bursting stress)was the sum of the product of each effective layer’s thickness percentage and stress.The bursting height and bursting strain of the separated composite geomembrane were approximately equal to that of the geotextile.The higher the stress in the effective layer of geomembrane/geotextile material itself,the higher the stress in the resulting composite materials.The greater the percentage of thickness of a material,the closer the stress of the composite materials was to the stress value of that material,and the degree of rapidity of approach was proportional to the magnitude of the stress difference between the effective layers.For different kinds of separated composite geomembranes combined with different sizes and types of base materials,the research results are helpful for determining the mechanical properties of bulge deformation and can provide a reference for material selections in practical applications.