| The area of Pisha sandstone is the most soil and water loss area in China.Its lithology is fragile,which seriously affects the stability of the slope int his area.At the same time,the climate conditions in this area are bad.In winter,the temperature difference between day and night is large and the ice and snow cover in winter.It belongs to the seasonal frozen soil area.Stabilization of the loose and fragile Pisha with the hydrophilic polyurethane material has been proved to be a time and cost-efficient protocol for the conservation of soil and water.However,the undesirable durability performance of the original W-OH binder material deteriorate its Freeze thaw cycle ability,especially under the freeze-thaw cycles.At first,based on the temperature characteristics of Pisha sandstone area,the W-OH/Pisha sandstone consolidated body made of different concentrations of W-OH and Pisha sandstone is subjected to different freeze-thaw cycles,and its unconfined compressive strength and elastic modulus are measured,and the failure mechanism of freeze-thaw cycles is explored based on the in-situ observation of over depth microscope.The results show that the compressive strength and elastic modulus of W-OH / arsenic sandstone consolidated body decrease with the increase of freeze-thaw cycles,the strength of low concentration W-OH/Pisha sandstone consolidated body decreases rapidly,the higher the W-OH concentration is,the slower the strength decreases,so the high concentration W-OH/Pisha sandstone consolidated body has better freeze-thaw cycle resistance;based on the self built superfield microscope experimental platform,in-situ observation results As a result,the debonding and fracture of W-OH cementation bonded to Pisha sandstone particles are caused by freeze-thaw failure and water erosion,which eventually leads to the frost heaving failure of W-OH/Pisha sand stone cementation body,and the change law of its pores also verifies its freeze-thaw failure mechanism.Based on these mechanism analyses,the modification of the W-OH material was further conducted with the Ethylene-vinyl acetate(EVA)and air entrainer.The compressive strength test results indicate both the added EVA can enhance the freeze-thaw durability of the W-OH composites,which can be caused by the improved cohesion strength of the W-OH binder due to enhanced density.Similarly,the freeze-thaw durability of the W-OH composites was also enhanced with added air entrainer,which provided extra space for the freezing expansion.Finally,EVA particles embedded in w-oh and bubbles mixed with air entraining agent can be observed in the modified w-oh cement by SEM.Based on the theory of statistical strength and damage mechanics,the damage evolution equation of W-OH/Pisha sandstone under load after freeze-thaw is established,and the correction coefficient is introduced to correct the total damage of w-oh soft rock consolidated body under freeze-thaw cycle.Finally,Finally,the constitutive equation is basically consistent with the experimental results,which provides the basis for the general change of stress-strain curve of w-oh / arsenic sandstone consolidated body under the load after freeze-thaw cycle. |
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