Experimental Study On Infiltration And Static Characteristics Of Dam Materials In Silt Dams In Northern Shaanxi

Loess and loess-like soils in China cover a vast area of 640,000 Km~2,accounting for 6.3%of the total land area.In the northwest region,for example,the soil is weak in erosion resistance and prone to soil erosion when encountering heavy rainfall,leading to an increasingly poor ecological environment and restricting sustainable socio-economic development.People have found that damming and siltation is an effective means to control soil erosion after a long-term management process.Silt dam as the highlight project of loess plateau area,plays a vital role in managing soil erosion,silting dam not only can manage soil erosion,silting land can be planted crops,silting dam has obvious ecological benefits and socio-economic benefits.Silt dam is poor impermeability,it can be used as a small reservoir for ordinary agricultural and animal husbandry water after the transformation of water storage.As the country further promotes the western development and"one belt and one road"development strategy,the northern Shaanxi region ushered in a high-speed development stage,and extreme weather occurred frequently in recent years,based on the study of the safety of the silt dam as a livelihood project,this paper mainly focuses on the northern Shaanxi silt dam material as the research object to conduct a series of indoor experimental research,the main work and The main work and research results are described below.(1)The basic physical parameters of the dam material were determined by indoor basic physical experiments;the wetting and disintegration of the soil material was studied by disintegration tests on the in-situ soil samples of the dam material through disintegration apparatus;variable head permeability experiments were conducted for different dry densities and different soil-water ratios of the dam material to obtain the permeability coefficients of the dam material under different conditions and to analyze the influence of dry density and soil-water ratio on the permeability coefficients of the dam material;the compression tests were conducted to The variation law of compression coefficient and compression modulus of dam materials at different dry densities was studied by compression test;the variation law of shear strength of dam materials at different dry densities was analyzed by direct shear test,and the values of shear strength parameters c andφwere obtained by linear fitting curve;(2)Based on the conventional triaxial shear test,consolidation undrained shear tests were conducted on dam materials with different dry densities,surrounding pressures and shear rates,and the effects of dry density,surrounding pressure and shear rate on the stress-strain curve,pore water pressure and shear strength parameters of the dam materials were analyzed.During the analysis,it was found that:the increase of dry density,surrounding pressure and shear rate could increase the peak strength of the specimen,the surrounding pressure and shear rate could promote the generation of pore water pressure,and the dry density had an inhibitory effect on the generation of pore water pressure;the cohesion c also increased gradually with the increase of shear rate,and the internal friction angleφhad a small increase.(3)Infiltration and consolidation without drainage shear tests were conducted for dam materials with different powder/clay particle contents.It was found that the permeability coefficient of the specimens gradually decreased as the powder/clay content increased,indicating a gradual decrease in the permeability of the specimens and an increase in the impermeability of the silty dams with the powder/clay content.The solidification undrained shear test was conducted on specimens with 10%,20%,and 35%of the content,and it was found that liquefaction occurred at the lower content,and the liquefaction disappeared gradually with the increase of the powder/clay content,which proved the existence of a limit value of liquefaction and non-liquefaction.(4)Ring shear experiments were conducted on the dam material based on the ring shear instrument.The peak strength and residual strength of the dam material showed an increasing trend as the dry density,vertical stress and shear rate increased,with the dry density and vertical stress having a greater effect on the residual strength of the dam material and the shear rate having a smaller effect on the residual strength.