Study On The Anti-slip And Anti-Frost Heaving Performance Of Composite Canals Lined With Double-layer Geomembranes And Anti-Slip Material In Seasonally Frozen Ground

Seasonal frozen ground is widespread in the country,covering about 53% of the total area.The climate of the seasonally frozen ground is complex and its environment is changeable.As a result,during the freezethaw cycles,the canals in the seasonally frozen ground frequently damage.Damage to canals is caused by a complex problem.Also,after a long period of use,the canals are susceptible to different degrees of damage,which has a significant impact on their ability to function normally.Therefore,research on control measures for canal damage is necessary,moreover,it is the key to solving canal damage in seasonally frozen ground.In this study,a new structure of channel-trapezoidal canals lined with geomembranes and anti-slip material(named as composite canals)-was proposed by using a literature review,laboratory experiments,theoretical analysis,and numerical simulation.The material properties and durability of the composite canals were also investigated,and the results of the study provided parameters for the mechanical model and numerical simulation of the canals.Also,the anti-slip and anti-frost heave properties of the composite canals were investigated through laboratory experiments.Finally,the mechanical model and the numerical model of the composite canals were established and validated.The main conclusions obtained were as follows.(1)In composite cushions,an increase in the width ratio of the anti-slip material caused an increase in the friction coefficient and a decrease in the thermal conductivity.Thus,the anti-slip material in the composite cushions increased the friction coefficient between the two layers of geomembranes,as well as increased the insulation of the composite cushions.The gravel layer was effective in reducing the frost depth of the subsoil and the relationship between the thickness of the gravel layer and the frost depth of the subsoil was negatively correlated.After 160 times of dry-wet and freeze-thaw experiments,the strength of the bonding surface between the composite geomembrane and anti-slip material decreased by 7.8 %.The mass loss rate of concrete with geomembranes was 1.22 %,and the compressive strength decreased by 15.11 %.(2)The maximum frost depth and development rate of frost depth in the slope section and bottom section of composite canals(double-layer geomembranes canals and an anti-slip canal)compared to the traditional concrete canal were less.Composite canals and the traditional concrete canal had almost no migration of gravitational water in the subsoil,almost in situ water is frozen,during the freeze-thaw cycle.The maximum normal displacement and the residual value of the normal displacement were the largest for the traditional concrete canal,the second largest for the double-layer geomembranes canal,and the smallest for the residual value of the normal displacement.However,the maximum normal displacement of the anti-slip canal was minimal,but the residual of the normal displacement was only larger than that of the double-layer geomembranes canal but less than that of the traditional concrete canal.The maximum tangential displacement of the double-layer geomembranes canal was the largest,the maximum tangential displacement of the traditional concrete canal was the smallest,the maximum tangential displacement of the anti-slip canal was less than the tangential displacement of the double-layer geomembranes canal but larger than the tangential displacement of the traditional concrete canal.The initial total contact stress of the doublegeomembranes canal was the highest,followed by the traditional concrete canal,while the initial total contact stress of the anti-slip canal was the smallest,close to zero.In terms of the comparison of the contact stress between the slope slab and the bottom slab,the maximum variation of contact stress of the traditional concrete canal,the double-geomembranes canal,and the anti-slip canal decreased in turn.(3)Mechanics models about frost heave were developed for a traditional concrete canal,a double-layer geomembranes canal,and an anti-slip canal before and after a fracture.The sliding of slope slabs during the thawed period was considered as well,and conditions for the design of slope slabs to be anti-slip were proposed.The canal models of the laboratory experiments were calculated using the mechanical model,and the results of the mechanical model were compared with the experimental results.The maximum values of the mechanical model and the experimental results were the same in magnitude,and the error was within10%.Finally,the reasonableness and accuracy of the mechanical model were verified.(4)The temperature,moisture,and mechanical of the canal models were calculated by numerical simulation.The results of the numerical simulations were compared and analyzed with the results of the laboratory experiment,and it was shown that the results of the numerical simulations were in same as the experimental results.During the freezing process of the subsoil,the double-layer geomembranes canal and an anti-slip canal could reduce the normal frost displacement of the canal slabs.During the thawing process of the subsoil,the slope slabs of the anti-slip canal basically returned to their original position,while slope slabs of the traditional concrete canal had a residual value in tangential displacement and the slope slabs of the double-layer geomembranes canal had to slide possibly.