Experimental Study On Seepage Failure And Long-term Seepage Degradation Of Clay

With the development of urbanization,high-rise buildings across the country have been erected,urban rail transit construction also ushered in the progress of the peak,and water conservancy embankment projects have also been completed.These projects are mostly related to the complex and changeable clay layer.Due to the long-term osmotic effect of the cohesive soil,the physical and mechanical properties and structure of the cohesive soil are degraded slowly.A large number of geotechnical accidents have also proved that the damage caused by the osmotic damage is huge.Therefore,it is very important to explore the damage of cohesive soil under long-term infiltration and destruction.This paper mainly focused on the following aspects:(1)A series of basic physical and mechanical properties tests were carried out for the cohesive soil,and the compressive properties and shear strength of the cohesive soil were described in detail,including the water content,the specific gravity,the specific gravity,the particle analysis,the consolidation and the straight shear.The cohesion increases with the increase of the dry density,and decreases with the increase of the average particle size.The internal friction angle decreases with the increase of the dry density,and increases with the increase of the mean particle size,but the correlation and magnitude are smaller.The cohesion decreases with the increase of the nonuniformity coefficient,and the internal friction angle increases with the increase of the nonuniformity coefficient.The cohesion decreases with the increase of the curvature coefficient,but the correlation and amplitude are small,and the internal friction angle increases basically with the increase of the curvature coefficient.(2)The seepage failure's critical hydraulic gradient of each soil with different particle size and mixed particle size at each dry density was studied by self-made osmotic failure instrument.For the single particle sized clay,the effect of dry density on clay critical hydraulic gradient is the most significant,the average particle size is the second,the critical hydraulic gradient increased with the three cubed dry density's enhancement and decreased with the average particle size's enhancement.For the multi-sized grain clay,the effect of uniformity coefficient on clay critical hydraulic gradient is the most significant,the curvature coefficient is the second,the critical hydraulic gradient decreased with the enhancement of uniformity coefficient and curvature coefficient.(3)The long-term permeation test was carried out on different dry-density soil samples under different PH permeate.The seepage coefficient of each dry soil with long-term osmotic pressure at each PH value decreases with the increase of the permeation time.The initial seepage coefficient of soil samples with distilled water of pH =7 is always larger than that of hydrochloric acid with PH = 3 as the initial seepage coefficient.After long-term infiltration,the seepage coefficient of the smaller dry-density soil samples after the permeation of the acidic permeate is larger than that of the soil samples with distilled water as the permeate,and the larger dry density soil samples are opposite.The concentration of sodium,potassium,calcium and magnesium in the soil leaching solution was lower than that in the high-pressure soil after the infiltration of the PH.And the content of calcium ions in the leaching solution was the highest,and the concentration of sodium and magnesium was the second,and the concentration of potassium was the lowest.