| With the intensification of supply and demand of water resources, conservation of water resources were caused great importance by various industries.it has great potential to construction to water (seepage canal lining) for agricultural water users . In the northwest of China, the special conditions of drought, cold, salinity severely restricts the application of ordinary impermeable material in the area. At present, in the region the main material for channel lining is concrete slab. But it has high cost a, poor performance against frost, construction period long, solid waste after the refractory lining failure caused by environmental and other outstanding series of problems. it is an important issue facing the current irrigated area to filtrate new impervious lining materials.The following seepage properties and related mechanism was researched in the paper through the laboratory and field examination to GCL in cold, arid and saline areas: (1)The basic characteristics of GCL, fall together research region's status and GCL'S producing area make sample selected; (2)The properties of bentonite in different electrolyte solution were researched including expansion properties, rheological characteristics, viscosity and filtration; (3)The effect of freezing and thawing cycle and ion double factors coupling on bentonite properties and GCL anti-seepage permeability; (4)Through the experiments of high temperature, low temperature, and high low temperature cycling, UV rays, soaking the cement mortar and construction site aging experiment, analyzed the changes of GCL's mechanical properties;(5) The microstructure of bentonite was analyzed by microscopic methods, and micro-structural parameters (hydraulic radius, shape index, surface fractal dimension, porosity) reflected the structure's changes of bentonite, to explain GCL impervious performance change mechanism .Through the above study, the valuable conclusions and results are as follows:(1) Bentonite hydration process is carried out in stages; the type and concentration of electrolyte solution have significant impaction on the properties of bentonite. Bentonite free expansion volume, post-expansion water content, filtration and the concentration of the ions in hydration fluid were negatively correlated. Filter cake thickness and permeability coefficient were positive correlation; Bentonite suspension body rheological research shows: system thixotropic loop was anti-clockwise and it was negative thixotropy; When hydration solution was Yellow River water, the suspension shear stress increased and thixotropy decreased. Shear stress of bentonite was positively correlated with particle size and dispersion, and it was negatively correlated with the hydration liquid electrolyte concentrations.(2) The freeze-thaw cycles changed the connection ways of bentonite particles, Led to adhesion and filtration decreased, and dispersion enhance, free swelling volume, post-expansion water content, shear stress increased; Filtration and the cake thickness decreases; When hydration solution was distilled water and the Yellow River water, the free expansion volume average respectively increased 17.8%, 32.8% after 31 freeze-thaw cycles. Moisture content increased 9.3%, 16.8%, EC value increased 32.7%, 24.9%, shear stress increased 38.0%, 37.1%; Filtration average had reduced 24.3%, 23.4%; Cake thickness decreased 19.4%, 15.4%. Permeability coefficient increased about 1 order of magnitude, but the permeability coefficient was still little. It was 0.35%~0.72% that before the canal lining of soil penetration. Bentonite particles filtered out in the process of exudation, and the filtrate EC value decreased 55.3%, 48.0%.(3) GCL stress - strain curve was "M" type, and it had two yield points in four phases: The lower stage of nonlinear deformation of elastic polyacrylamide; The lower limit of fracture stage polyacrylamide; upper polyester or polyethylene co-host of nonlinear elastic deformation stage; Polyester or polyethylene film limit fracture stage. High temperature, low temperature, high-low temperature cycling, coupling temperature and humidity, ultraviolet radiation, soaking cement could decrease mechanical properties of GCL, especially the factors of high temperature and ultraviolet radiation. Field experiments showed that the mechanical properties of the first year decreased obviously, and the aging rate decreased with the layer sediment covering.(4) GCL stress - strain relations could be obtained by fitting Gaussian peaks to the constitutive equation. the result had shown a good correlation. The coefficient had shown an exponential and logarithmic relationship with different aging factors. The service life prediction results showed that the value of the residual stress can reach 30% after 30 years.(5) The X fluorescence spectroscopy results showed that the samples had a good crystallinity and layered structure, and the main component of bentonite were SiO2. When hydration solution was the Yellow River water, the metal oxide content slightly increased with freezing and thawing cycles increased after freeze-thaw. Bentonite SEM images showed that the changes of hydration fluid and electrolyte concentration, freeze-thaw cycles had some influence on bentonite pore distribution. The pore surface characteristics and pore size. The microstructure parameters could be described by pore surface dimension, porosity, hydraulic radius and shape of bentonite microstructure. Hydraulic radius of the selected bentonite sample was between 33.18 and 372.11?m. Porosity was between 6.21% and 69.69%. The surface fractal dimension was between 1.18 and 1.22, morphological index was between 0.05 and 0.52, and pore was mainly irregular. Microstructure of bentonite showed that the gap will increase after 2 years'field experiments.(6) Combining with the research results and situation of test area, the measures of GCL engineering application were raised in the similar regions. |
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