Research On Slope Soil Improvement And Frost Resistance Of Plain Reservoir

Plain reservoirs are mostly built in the middle and lower reaches of the rivers and in the coastal areas.They have poor geological conditions.Most of the soil is silt,silty soil,soft clay and other soft soils.In the case of the built-up plain reservoir on the east line of the South-to-North Water Transfer Project,the dam formation is mostly a Quaternary newly flushed alluvium.The main lithology is sandy loam,fissured clay and silty sand,with loose structure,low strength,and high water permeability..Due to the characteristics of the plain reservoir,the slope protection is prone to infiltration damage,frost heaving,freeze-thaw damage,and other accidents,endangering the dam safety of the reservoir,and even forcing the abandoned reservoirs to resume cultivation.The improvement of reservoir slope protection soil to ensure the long-term safe operation of the plain reservoir is the fundamental guarantee for the benefit of the plain reservoir.Therefore,it is of great significance to study the soil improvement of plain reservoirs.In order to investigate the influence of cement and a curing agent in China on the soil and soil mechanical properties of plain slope protection,the slope protection soil of Datun Reservoir in Dezhou,Shandong Province was studied.After the cement was incorporated into the slope protection soil,an improved test was performed and the mechanical properties such as compressive strength and shear resistance were tested.At the same time,an orthogonal test was conducted on the composite materials of cement and a curing agent in China to find the main factors affecting the combination ratio strength and the optimal ratio,and the freeze-thaw test was conducted on the optimal ratio group.Provides beneficial experimental basis and theoretical reference for plain reservoir slope protection soil treatment measures.The results showed that:(1)The unconfined compressive strength of the improved soil sample is 6-10 times higher than that of the improved soil sample;the internal friction angle of the improved soil sample is higher than that of the modified soil sample of 10.34°.-4 times;the improved cohesion of the soil sample was 1-3 times higher than that of the 100.28 kPa soil sample.Mechanical properties have been significantly improved.The freezing temperature of the improved soil is reduced by 2 to 5 times than the freezing temperature of the improved soil of-0.68°C.The frost heave of the improved soil is reduced by 5 to 6 times than that of the improved soil,and the frost resistance of the improved soil is improved.Significantly improved performance.(2)The primary and secondary factors affecting the internal friction angle are cement dosage,age,curing agent content and dry density.The optimal ratio of internal friction angle to the index is A4B2C4D4;the primary and secondary factors affecting the cohesion are cement dosage,age,curing agent content and dry density.The optimal ratio of the cohesion force to determine the index is A4B3C3D4;the primary and secondary factors affecting the unconfined compressive strength are age,cement content,dry density,and curing agent content.The optimal ratio of the unconfined compressive strength is A4B3C3D4.The primary and secondary factors affecting the freezing temperature are cement dosage,age,dry density,and curing agent content.The optimal ratio of the freezing temperature as the judgement index is A4B4C3D4,and the combination of the above-mentioned index’s range-to-valley analysis makes the mechanical property and frost resistance performance the optimal ratio for 15 groups of A4B3C2D4.(3)The unconfined compressive strength of the improved soil decreased gradually after 1,3,and 5 cycles of freeze-thaw cycles,and the largest reduction occurred after the first freeze-thaw cycle,indicating that the first cycle had no effect on the soil.The impact of the lateral compressive strength was the greatest;the decreasing amplitudes decreased sequentially after 3 and 5 times.After 7 cycles,the unconfined compressive strength increased,but it was still smaller than the value without the freeze-thaw cycle,9 cycles.Afterwards,the unconfined compressive strength decreased significantly,well below the value before the increase(ie after the 5th cycle).(4)When the number of freeze-thaw cycles does not exceed 10 times,the content of particles in the soil of <0.005 mm gradually increases,which is the reason that the unconfined compressive strength of the soil increases with the number of freeze-thaw cycles.The void content with an equivalent diameter of more than 10 μm increases with the increase in the number of freeze-thaw cycles.The pores with an equivalent diameter of 1 1010 μm also tendto increase,while the pores with a pore size of 0.1 μm to 1 μm tend to decrease.The pore content of um remains essentially unchanged.In other words,the overall content of macropores increases,the content of medium and small pores decreases,and the content of micropores remains basically unchanged.(5)The effect of curing agent was not significant within 4 h,but its effect was prominent after 8 h.This greatly accelerates the cement’s coagulation speed,so that its unconfined compressive strength reaches 0.8 MPa at 8 hours.The single-doped 9% cement requires 3days of age,and its unconfined compressive strength can reach 0.8MPa.The curing time of the cement is greatly shortened,the mechanical properties of the soil can be improved in a short time,and the compressive strength of the improved soil is significantly improved.It is of great significance in emergency rescue projects.