Study On The Influence Of Temperature On The Permeability Of Remolded Malan Loess

As a widely distributed engineering "special soil",loess is often used as an engineering material in various engineering projects.As the main engineering property index,its permeability as an important engineering property index controls the movement of water in the soil,which greatly affects the various engineering properties of the loess.Due to the seasonal changesand day and night changes in temperature,the permeability of loess will change in different seasons and at different times.However,there is still a lack of systematic research on the changes of the permeability of remolded loess with temperature and the correction method of loess permeability coefficient at different temperatures.This paper takes the Malan loess in Gaozhuang Town of Jingyang as the experimental research object.Through the indoor constant head saturated penetration test,the influence of temperature on the permeability of Malan remolded loess is explored.The application range of temperature correction coefficient in Malan loess is discussed,the microstructural changes of the soil during the infiltration process and the bound water conditions are revealed by ESEM and volumetric flask methods,respectively.And the main results obtained are as follows:?1?When the temperature changes,the saturated hydraulic conductivity increases with the increase of temperature.At 4?,the saturated hydraulic conductivity has a significant inflection point,that is,the growth rate of saturated hydraulic conductivity after 4? is faster than 0-4?.And at 25??C,the temperature has the greatest influence on the saturated hydraulic conductivity,that is,the growth rate of the saturated hydraulic conductivity reachs the highest at this temperature.?2?High temperature will enhance the influence of soil density on permeability.High density will weaken the temperature effect of soil permeability,and the stability of soil will increase with the decrease of temperature.?3?The relationship between saturation hydraulic conductivity,temperature and dry density is:LnK=-?T^B+C₂??+C₁?4?Malan loess has deterioration during saturation infiltration.And this phenomenon is affected by both physical and chemical effects.That is,when the soil density is poor,the upward movement of the small particles in the water flow cause the saturated hydraulic conductivity to decrease with the increase of the penetration time,and then tends to be stable.When the density of the soil sample is good,the chemical dissolution of the water flow dominates,so that the saturated hydraulic conductivity tends to be stable after a short-term increase.?5?Although permeability?A:?is an inherent property,its value is not fixed during the infiltration process.Experiments show that there is a linear relationship between the logarithm of temperature and permeability,and the relationship between permeability and time will change from exponential to power function as soil compactness increases.?6?The saturated hydraulic conductivity is affected by the degradation,and the measured value is deviated from the calculated value.The applicable range of the temperature correction coefficientremains to be discussed:When the temperature is 0-4 0C.K_?T??K₀?Except near freezing point?When the temperature is 4-?????When the temperature is 10-25?,the density is poor,and the soil degradation dominates???When the temperature is 10-25?,the density is good,and the dissolution dominates???When the temperature is higher than 25 ?:the effect of temperature on permeability needs to be considered.?7?It can be seen from the microstructure observation that the change of the permeability is due to the pore change during the infiltration process.The action of water flow causes the large-middle pores of soil to change into multi-directional small micro-pores,and the smaller the dry density is,the more significant the phenomenon is.?8?By bound water analysis,it is known that the change in the saturated hydraulic conductivity in the 0-4? stage is mainly due to the change of the bound water.At this stage,the temperature rises and the free water near the particles changes to the weakly bound water,resulting in the amount of seepage water being less than the calculated value.