Study On The Characteristics Of Loess Pore Throat And Water Film Flow In Weibei Of Shaanxi Province

The study on the permeable mechanism of deep loess is evaluate collapse depth of loess with great thickness,it also is the basis and the theory source for foundation design and foundation treatment in loess area.When the water content is very small,water in the soil is mainly in a way of membrane water transfer.The permeable mechanism of deep loess is to further study the basis of loess with great thickness collapsibility problems,which can help explain the phenomenon of permeability in the process of loess collapsibility,explore the movement of water molecules in permeability for deep loess,find mechanism of deformation of collapse loess with great thickness,and develop foundation treatment methods.Eventually,it has very important theoretical and practical value to determine the critical phreatic surface of loess seepage.In order to better explain the permeable mechanism of deep loess,we study the characteristics of unsaturated loess pore throat and water film flow,Through water-film theory,Mercury injection,Nitrogen Adsorption Method?NAM?,Nuclear Magnetic Resonance?NMR?and so on.We study the loess in Weibei of shaanxi province,and we have achieved some results:?1?Based on the calculation and analysis of mercury saturation and movable fluid saturation,it is concluded that the lower limit of the pore water flow in the loess is 0.6?m,In other words,pore throat radius is less than 0.6?m,pore water is adsorbed water that can not flow.whereas the pore throat radius is greater than 0.6?m,pore water is free water that can flow;The micropore radius of the loess is less than 0.6?m,so the water in the micropore is adsorbed water and it cannot flow freely.?2?In natural condition,the pore of loess is mainly distributed in the interval of 0.02?m to 10?m;The macropore and mesopore of loess affected its collapsibility,due to the small amount of macropore content in loess,the loess collapse is mainly related to the mesopore content.?3?The pore changes of Q₃ loess in the test site mainly show the changes of macropores,mesopores and small pores.In the range of 3m⁵m,due to the influence of rain water and farmland irrigation,some soluble substances are dissolved,and so on,the macropores content increases,and the content of mesopores and small pores decreases.In the range of 5m¹1m,with the increase of depth,the content of macropores,mesopores decreases,and the content of small pores increases.?4?In the permeable of deep loess,water is mainly permeated with the form of water film,and the water film thickness affects its permeability.The experiment results show that the thickness of water film decreases with soil depth increase.?5?The formation pressure has a very good linear relationship with the water film thickness,According to the statistical relationship between formation pressure and water film thickness,the formation pressure can be predicted,which provides a new method for the calculation of formation pressure.