Research On The Theory Of Canal Seepage-proofing By Geomembrane And The Key Technology Of Paving Lining By Machine

China is a relative indigent country about the water resource and is also a bigagricultural country. The use amount of water on the agriculture occupies 73% ofwhole state using water amount each year, but the efficiency is lower. Using rate ofthe irrigation water is only 30%~40%( using rate in the developed countries are70~80%), thereinto, 50% of irrigation water is lost in the course of the transportationfrom water resource to field, that is173 billion m3 .At present, canal is a main transportation water mode in field irrigation in China,but more than 80% of the canals are not dealt with on the seepage-proofing, theamount of losing water reaches 70% in some poor soil canals. Therefore, it isnecessary and impendent to study the theory and search after methods for decreasingcanal seepage. In this paper, author mainly conducts the basic theory ofseepage-proofing with geomembrane and the key technology of machine pavinglining in canal. The study is of practical engineering significance to popularizingseepage-proofing saving water technology in a large area of China. The maincontents and conclusions of the paper are following:1. By theory analysis and experiment, the performance of plastic lining(geomembrane) which is taken as the principal part of canal seepage-proofing areresearched. Analyzes how damages affect the strength of plastic lining, testifies thatthe geommbrane breakage is asymptotic under the undamaged condition, and thebreakage is paroxysmal under the damage condition and its elongation rate is onlyabout 1/10 of the undamaged geomembrane. Analyzes the stress-strain relation of thegeomembrane under the effect of water pressure, gives the mathematics models ofstress-strain relation of the geomembrane under the conditions of special boundaries(rectangle, rotundity, square). On theory analyzes and deduces the expansion strengthand piercing-strength of the geomembranes and establishes the mathematics modelof expansion strength, piercing-strength of the geomembranes. Analyzes the strengthof plastic lining above a cavity and deduces the strength calculation formulas in thecondition of the crack and hole.2. The theory researches and discusses are conducted on the slope stability ofgeomembrane-seepage-proofing canal on which protective layer is soil. Establishesthe mathematics model of the canal slope stability for two bad states (the water levelin canal is abruptly changed, as well as rainfall);analyzes the impact rule of thevarious desige parameters to the stability of canal slope, points out that the safetyfactor of canal slope FS rises with friction angle between canal and geomembraneδ ,inter friction angle of soilΦ and thickness of soil protective layer h rising;descendswith the increase of slope angle β , slope length L and HSR(PSR) rising , gives thebase for the design of the slope stability of geomembrane-seepage-proofing canalon which protective layer is soil.3. The fuzzy optimal mathematics model of multi-objectives is established bygoals of economical efficiency and transportation ability about seepage-proofingsoil protective canal with geomembrane.A design and calculation method for thecanal which takes geomembrane lining as seepage-proofing part and soil asprotective layer under the multi-objective, multi-constraint conditions put forward,and a calculating program is worked out. The fuzzy optimal results of the canaldesign parameters under the different submerging degree condition is presented,and taking HSR= 0.8 as example the affecting rules of design parameters canalslope angle β , width of canal bottom b , height of canal H, thickness of soil layer hto the whole goal level is analyzed. Prove that hydraulic optimal section of canaldoes not equal to engineering optimal section.4. Taking the arc base trapezoid canal which is of generality as an example,the section structure of concrete protective canal which is lined with geomembraneis analyzed and optimized;an optimal mathematics model is established, works outa counting program and with a example proves that the price of complexseepage-proofing structure in which concrete is combined with geomembrane isonly 81.2% of the price of single concrete seepage-proofing structure.5. Puts forward the design theory of mechanically paving lining incanal.Develops the kinematics and dynamics model of the geomembrane rollmoving. Analyze the difference between the ideal angle acceleration of thegeomembrane roll Lθ&& and the angle accelerationJθ&& under the action of practicalfriction force. On theory prove that the problem that geomembrane is drawed in theprocessing of paving can be solved and the quality may be ensured through thereasonable choose of drive ratio, therefore, give a reference for the design ofmachine to pave lining.6. At first, presents the technology that geomembrane roll paves the lining ininitiative and synchronism, ensures the geomembrane being in moderate relaxationstate. At first adopts the technology that the brush follows and contours and unfoldsthe geomembrane, the geomembrane is unfolded on the canal surface andupper-edge (trapezoid U shape and step shape). These technologies have gainednational utility model patent and have declared national invention patent.7. By 3ds Max5 software, the entity model of the machine to pave lining fortrapezia canal and the mechanism of minim adjusting discharging geomembraneamount are established.The computer emulation analysis in the processing ofpaving lining is realized. Analysis results indicate that the system to adjustdischarging geomembrane amount may not only solve the minim fluctuatingamount of 2% that the discharging geomembrane mechanism produces in work, butalso is of the ability to solve larger fluctuating amount.8. Unfolding process of the geomembrane in canal is analyzed and the trackequation of "front edge of genmembrane unfolding" is given. It is of directionsignificance for the design of the discharging-geomembrane system.9. Three kinds of model machines to pave lining in trapezoid, U shape andstep shape canals are developed. Through experiment, verifies the theorymechanically to pave plastic lining in canal. By means of uniform design theoryand software, the main factors to affect the effect of paving lining are analyzed andtested, and following rules are gained: the velocity of machine moving is the mainfactor to affect the effect to pave the lining for three kinds of canal shapes. Theeffect to pave lining gradually becomes bad with the increase of machine velocity.The geomembrane presents the trend to be tensioned when the machine velocityincreases, its causes are because the skid rate increases between the driving wheeland canal, as well as between discharging-rubber-roll and geomembrane roll. Fortrapezoid and U shape canal, the effect to pave lining is better when brushinclination respectively equal to 15°and 12°. if inclination is smaller it is difficultthat the air under the lining is eliminated so that it is possible to separate betweengeomembrane and canal bed, further more, the lining to be pave is not smoothenough, conversely, that inclination is larger will lengthen the longitudinal size ofmachine, which is unfavorable for the brush following and contouring. Theeffect to pave lining becomes better with the increase of geomembrane thickness,but it is not obvious. When height of brush (distance between brush stem and canalbed) is 3～4mm the effect to pave lining is best.10. Presents the evaluation standard and measure method about the effectmechanically to pave lining in canal. Measure the slippage coefficient ofgeomembrane roll and the tensile rate of geomembrane in the process of paving. Inthe range of test, the slippage coefficient the between discharging-geomembranerubber roll and geomembrane roll is about 1%-3%.11. In the process of paving lining for three kinds of canal shape, the testedtensile rate of geomembrane is 3～5/1000,which is much less than about 10% ofpaving geomembrane in field, indicate that the mechanism to pave geomembranehas less impact on the mechanics performance of geomembrane, prove that thetechnique to pave lining in initiative and synchronism fits to paving the lining incanal.