Experimental Study On Geosynthetic Clay Liner's Applicability In North And Saline Regions Of China

Water resources limit becomes main factor which constrains agricultural sustainabledevelopment in Hetao areas Inner Mongolia. On the one hand, agricultural irrigation wateris shortage, and on the other hand, water wasting exists universally. Channel systemefficiency is only 0.5 and nearly half of the Yellow River water for irrigation is lost due toleakage during water conveyance process. Although part of leakage supplies togroundwater, the overall water efficiency is low. Many measures have been taken to reducecanal seepage in Hetao areas, but results obtained are not satisfied. In the paper three GCLs(Korea 1#, 2# and 3#) were used to do both lab and field experiment. The results arediscussed and the mechanisms are explained. The paper mainly discussed the different ion,density, freezing and thawing cycle to the seepage coefficient and free expandingvolume's influence of bentonite, and established free volume expanding volumecomputational model of bentonite. This research provided the rationale for promotion andapplication of GCL for anti-seepage in draught cold saline areas. And research obtainsmain conclusions as follows:(1)Analyzed of the essential components, structural characteristic and anti-seepagemechanism of bentonite, obtained conclusion which 3# bentonite free expandingcoefficient is largest, the rate of sedimentation is 1# 15times, but it is not in conformationwith clay's subsidence characteristic in water. Due to adding adhesives during productionprocess, this doesn't affect expansibility of bentonite in short period. The bentonite'swater-content efficiency of 1#, 2# and 3# are respectively 7.84%, 9.32%, 9.14%. Freemoisture mainly occurs in 100 hours ago, water-content efficiency will tend to stable after300h.(2)GCL has strong self-recovery ability, 1# produce's healing is slowest, 3# is quickestafter pierced. And diameter of perforation's influence is remarkable to seepage coefficientof GCL. When aperture is less than 10mm, it can heal entirety in 100h, and seepage reachstabilization. Suggest doing processing of mend when aperture is bigger than 10mm.(3)In Solution, concentration and valence of cation has remarkable influence to seepagecoefficient of GCL, the higher concentration of cationic, the greater seepage coefficient; thehigher valence of cationic, the greater seepage coefficient; when the concentration ofsolution was low (less than 3.0g/L),the experimental time's long or short had a tremendous effect on the result of experiment. In Solution, cation and concentration had obviousinfluence to free expanding volume of bentonite. The free expanding volume of bentonitereduced to stable with the concentration of cationic increasing. Ca²⁺ has obvious influenceto the free expanding volume of bentonite. But K⁺ and Na⁺ has a relatively minor influence.(4) The 40 times of freezing and thawing cycle has a little impact on free expandingvolume of bentonite in -40℃, the times of freezing and thawing cycle has a little impact onfree expanding performance of bentonite. After the low-salinity solution to pre-hydrationthe seepage coefficient of GCL reduce two orders. Using low-salinity (＜0.5 g/L) solutionto pre-hydration is proposed in the project application it can significantly improve seepageresults. Meanwhile, I established free expanding volume of bentonite and seepagecoefficient computational model, which based on Stern-Gouy model. It provided basis tostudy performance of bentonite.(5) 2# and 3# GCL aren't adapted to saline areas' anti-seepage. After using 3 years, the Na⁺were substituted by the Ca²⁺, Mg²⁺from the bentonite, the volume of Ca²⁺, Mg²⁺ inbentonite increased, the effect of leakage prevention reduced obviously; the 1# GCL suit toanti-seepage in saline ares. This product's structure and component is special, it has twopolyethylene protective films which prevented the full contiguity of bentonite and solution,and when the mineralization is smaller than 1.0 g/L, the 1# bentonite's free expandingvolume has the tendency of increment with the concentration of ion increasing; it ispropitious to improve effect of seepage.