The Law Of Water And Salt Migration And Its Effect On The Deformation Of Foundation Soil In Luozhong District

The k385-390 section of the proposed highway is located in luo zhong district on the northeast edge of Lop Nor lake heart area.The surface of luozhong district has not only the saline soil of strong^ultra chloride,but also the shallow groundwater,and the groundwater type is saturation bittern.The water salt migration of unsaturated soil has resulted in the accumulation of surface salt,and the halite with high salinity and low permeability is formed on the surface.Therefore,the study that the influence of water salt migration on the foundation soil in highway engineering has important guiding significance for the construction design and construction in the later stage.In this paper,the geological environment conditions of luozhong district were determined by field investigation,drilling and sampling.The characteristics of groundwater,the characteristics of soluble salt in saline soil and the physical properties of soil in luo zhong district are studied by laboratory experiments.According to the water content of saline soil and the distribution of CL^-mass concentration,the mathematical model of water salt migration law in luozhe district is studied.Through the mathematical model,the water content distribution and salt accumulation rule of soil under different condition are studied.Through the analysis of the influence of salt migration on the mechanical parameters of foundation soil under different conditions,the effect of water salt migration on soil deformation under different groundwater level and halite thickness is studied.The main conclusions are as follows:?1?The outcrop layer is the fourth series holocene?Q₄?silt and silty clay in luozhong district.The surface covers a thickness of 0.4¹.0m of halite.The soil in the study area is the saline soil of strong^ultra chloride,and the soil surface has obvious salinity accumulation.The groundwater in this area is shallow,and it belongs to the saturated brine.?2?The shear strength of soil in research area increased with the accumulation of salt.The shear strength of soil in a small area decreased with the accumulation of salt.0⁰.5 m soil freezing soil temperature below-20?in luozhong district,won't produce frozen soil.0.5².0 m depth soil freezing temperature between 0.5?to-8?.The salt soil in luozhong district has the characteristics of strong solubility,strong causticity and strong salt expansion.The salt soil in the study area is inhibited by chlorine salt.With the increase of Na₂SO₄ content,the increase of salt expansion is less.?3?The distribution of water salinity and water salinity in luozhong district under different conditions is studied.Draw the following conclusions:?1?When the groundwater level is certain,the distribution law of the volume moisture content in soil is constant,and the change of salt mass concentration is mainly concentrated in the soil area of 0.5¹.0m.With the continuous accumulation of salt,the thickness of halite increases.?2?When the water level drops in the local area,the volume moisture content of the same position is reduced,and the soil salinity accumulation in the buried depth of0.5¹.0m gradually decreases;When the water level reaches 3.1m,the surface of soil does not produce salt accumulation.?3?The groundwater of high salinity is one of the main reasons for the formation of ultra-chlorine saline soil in the surface soil of luoyang district.?4?Because the halite has extremely low moisture content and unsaturated hydraulic conductivity,water salt migration has no effect on the distribution of halite.?4?The influence of water salt migration on soil deformation under the load of embankment is studied by the parameters of soil physical strength under different water salt migration conditions.Draw the following conclusions:?1?For the water and salt migration under natural conditions,the high salinity soil and the thicker rock salt layer in the study area are beneficial to the stability of the foundation soil.?2?The stability of foundation soil increases with the increase of groundwater level.When the groundwater level is certain,the vertical displacement value of the foundation soil decreases with the increase of the thickness of halite.It shows that the increase of the thickness of halite is beneficial to the stability of the foundation soil.?5?The surface halite has lower moisture content and is a natural confining bed.Due to the good mechanical properties of the halite and the extreme arid environment in the study area,it is not necessary to replace the halite in the construction process to remove the salt crust that is strongly raised in the surface.