Experimental Study On Spherical Bulging Deformation Of Geotextile

Most plain reservoirs are usually laid with geosynthetics at the bottom of the reservoir basin to prevent seepage.The air expansion of geosynthetics is caused by the rise of groundwater table,the rapid decrease in the reservoir water table,and the uneven settlement of the dam foundation.With the deepening of the research on the mechanical properties of composite geomembrane,it is found that the geotextile in composite geomembrane not only play a protective role,but also have an important contribution to the overall mechanical properties of the composite geomembrane.The current research on the mechanical properties of the geotextile is only through uniaxial tensile test.However,in practical applications,geotextiles are in multi-axial stress state.Therefore,it is of great practical significance to study the mechanical properties of the geotextile spherical bulging deformation for seepage control design and reservoir safe operation.In this paper,the characteristic and influencing factors of the geotextile spherical bulging deformation are analyzed,and the geomembrane air expansion equipment is improved to carry out the study of geotextiles spherical bulging deformation under ring-restrained conditions.The mechanical model of geotextile bulging deformation is simplified and the stress-strain relationship is deduced.The rule of bulging deformation and failure of geotextile are summarized in this paper,and the mechanical properties of geotextiles under different influencing factors are explored.The main research results and conclusions are as shown below.(1)The calculation formula of tensile stress is selected to better describe and analyze the mechanical properties of geotextile bulging deformation by the theoretical analysis of several calculation formulas of stress-strain relationship of geomembrane.(2)The failure form of geotextiles under spherical bulging deformation is tear failure,and the failure appearance is similar as spindle shape.The relation between tensile stress-bending strain can be divided into four stages: linear elastic stage,yield stage,strengthening stage and failure stage.(3)The factors affecting the geotextile spherical bulging deformation of geotextiles are the loading rate,the constraint diameter of equipment,properties of nonwoven geotextiles including fiber type,fiber length,mass per unit area.The effects of different influencing factors on tensile stress-strain curve,burst crown height and burst pressure of geotextile were in-depth analyzed.The loading rate of 140mL/min was selected as the basic loading rate for spherical bulging deformation of geotextiles under the ring-restrained conditions.The constrained diameter of 100 mm was selected as the basic equipment for spherical bulging deformation of geotextiles under the ring-restrained conditions.The burst crown height and burst pressure of PP staple fiber and nonwoven geotextiles are higher that of PET staple fiber and nonwoven geotextiles with the same mass per unit area.The burst crown height and burst pressure of PET filament fiber nonwoven geotextile are higher that of PET staple fiber and nonwoven geotextile with the same mass per unit area.The burst crown height and burst pressure of PET staple fiber and nonwoven geotextiles,PET filament fiber and nonwoven geotextiles,PP staple fiber and nonwoven geotextiles are directly proportional to the mass per unit area.