Comparative Experimental Study On Seepage Failure Mechanism Of Two Kinds Of Dam Soil In Northern Shaanxi

In order to solve the problem of seepage failure of dam in Northern Shaanxi,this test in Northern Shaanxi dam silt silty loam and sandy soil of two kinds of dam soil as the research object of study,The development process of seepage failure was simulated by self-made seepage deformation instrument,calculation of critical hydraulic gradient,using laser particle size analyzer and electron microscopy study of seepage failure of the micro development process,to provide theoretical support and basis for the repair and damage of dam dam site.The main conclusions of this paper:(1)The critical hydraulic gradient and the failure mechanism of the dam soil samples results of seepage failure1)According to the indoor seepage deformation test,the critical hydraulic gradient in the silty loam in the compaction degree of 1.50g/cm3,1.55g/cm3 and 1.60g/cm3 were 3.28,4.68 and 6.78;The critical hydraulic gradient of 1.50g/cm3,1.55g/cm3 and 1.60g/cm3 in the sand soil compaction were 2.28,3.38 and 4.18;2)In the same degree of compaction,the critical hydraulic gradient in silty loam than the sand soil,but the seepage drainage effect is far worse than the sand soil gradation continuity in silty loam in the sand soil,seepage time on sandy soil than in the silty loam;3)For the same kind of dam soil,the critical hydraulic gradient and the seepage velocity and degree of compaction are linear correlation,the greater the degree of compaction,the critical hydraulic gradient is bigger,the better anti permeability performance.(2)The experimental soil samples are stratified to explore the development rule of seepage failureIn the test soil samples of silty loam soil,the third layers of soil samples,namely,the middle and lower reaches of the whole soil sample and the downstream position of the four layer soil sample,which are the most likely to occur.For the sand soil,fourth layers of soil samples are prone to occur in the lower reaches of the river.(3)Microscopic study conclusions of seepage failure specimens1)In the same degree of compaction,the particles in the silty loam the average diameter and porosity were significantly less than the sand soil;average pore diameter is slightly less than the same degree of compaction of the sand soil;particle size and roundness of the sand soil with little difference;2)In the test of the same kind of soil,the porosity and average pore diameter of the sample under the compaction degree of 1.60g/cm3 were less than that of the compacted 1.50g/cm3,but there was no difference between the average particle diameter and the particle roundness;3)In the same situation with the dam soil compaction,in the silt y loam soil column from the bottom to the top soil particle average diameter and porosity showed a decreasing trend,but the 10-15 cm layer is larger than the 15-20 cm layer;pore average diameter were increased.The average particle diameter and porosity of the soil column from the bottom to the top of the sand soil showed a decreasing trend,and the average pore diameter increased.The trend of the roundness of the two kinds of soil particles was not obvious.(4)Analysis of the composition and structure of sediment particles produced by seepage failure1)For the same kind of dam soil,the particle size distribution of seepage and sediment produced by seepage failure is not changed under different compaction degree;2)For the comparison of the seepage and sediment of two kinds of soil materials under the same compaction degree,the proportion of the medium and small particles in the silt sediment in the silty loam soil sample is larger than that of the aeolian sand soil;3)The contrast of the middle and late stage of the seepage sediment in the process of seepage failure of the same soil,with the development of seepage failure in the silty loam,the particle size composition of the sediment is changed from small to large.In the process of infiltration and destruction,the sand soil is dominated by small particles,there is little difference between grain size and grain size in the middle and later stages...