Experimental Study On Spherical Bulging Deformation Of Geomenbrane With Coverings In Ring-restrained Conditions

At present, building surrounding-dam plain reservoir is an important way to solve the problem of water shortage in the northern region of China. In the construction of the dam type plain reservoir, due to the existence of leakage and other reasons, it has already started to use the horizontal seepage control scheme of paving geomembranes in whole reservoir bottom, which is the anti-seepage of reservoir basin scheme. For the surrounding dam plain reservoirs that use anti-seepage of reservoir basin, the leakage of reservoirs water, the rise in groundwater table and other reasons lead to the pore gas in unsaturated soil under the geomembrane gather, rise and change into pressure, which can cause geomembrane bulging deformation, even the bulging damage. Geomembrane bulging deformation will further exacerbate water leakage, and the influence of the reservoir seepage safety. Study on mechanical characteristics of geomembrane bulging deformation, to ensure the safety and reliability of the plain reservoir which use geomembrane anti-seepage of reservoir basin has important practical significance.This paper summarizes the characteristics of geomembrane bulging deformation, a set of test equipment for studying on geomembrane bulging deformation under the condition of overlying water pressure was developed independently, the experimental study on influence factors of geomembrane bulging deformation under the covering condition was carried out, and the influence factors, bulging deformation and burst pressure of geomembrane bulging deformation under the condition of overlying water pressure were summed up. The main research contents and results are as follows:(1) The main influencing factors of geomembrane bulging deformation under the condition of overlying water pressure were the diameter of apparatus, loading rate and depth of overlying water.(2) Under the condition of overlying water pressure, geomembrane swelling area is smaller, the rate of the faster, the bursting pressure is greater; on the other hand, the smaller the bursting strength. Under the condition of overlying water pressure, the bigger the area of geomembrane bulging swelling, the greater the bursting strength; the faster the rate of geomembrane bulging, the greater the bursting strength and the larger the burst crown height. on the contrary, the crown height is smaller, the limit value of geomembrane crown height was related to the ultimate elongation of geomembrane, but But the influence on change of crown height is very small.(3) The morphological characteristics of the geomembrane bulging deformation and damage were studied, the characteristics of geomembrane air expansion deformation in ring-restrained conditions under the condition of overlying water pressure were analysed, the corresponding formulas of stress and strain are derived. The stress strain curve of geomembrane air expansion deformation could be divided into four stages: linear elastic stage, strengthen stage, weakening stage and bursting break stage.