Influence Of Gas In Soil On Seepage Characteristics Of Unsaturated Loess

At present,a large number of unsaturated soils are encountered in people,s frequent project construction activities.unsaturated soil has become the most important research object in the field of geotechnical engineering,and the study of seepage in unsaturated soil is one of the important issues.Due to the presence of gas in unsaturated soils,the unsaturated seepage process becomes extremely complicated.And the gas in the soil has a great influence on the permeability and infiltration mechanism of unsaturated soil.Therefore,it is of great significance to study the effect of gas in soil on the seepage characteristics of unsaturated soils.particularly,the impact of rainfall infiltration on soil slopes in irrigation,environmental issues and geotechnical engineering.This paper mainly studies the seepage of unsaturated loess.The seepage test was conducted through a self-made simple seepage device to study the effects of different dry density,moisture content,and surface water depth on the pressure and moisture peaks of unsaturated soils in a closed environment.As well as compared to closed environments,The effect of gas pressure in soil on seepage of unsaturated loess was studied in an open environment.And using the SEEP/W module in Geo-studio software and the AIR/W board,the seepage model under consideration of air pressure was calculated.The following conclusions have been obtained:(1)In the same conditions,the greater the dry density,the slower the infiltration rate,the smaller the final cumulative infiltration volume,the greater the maximum peak value and the final stable pressure value.The cumulative infiltration volume in the test group at a dry density of 1.43 g/cm3 was 1.5 times and 1.9 times the cumulative infiltration volume in the test group at a dry density of 1.60 g/cm3 and 1.72 g/cm3,respectively.Under the same conditions,the greater the moisture content,the faster the infiltration rate of water,and the greater the cumulative infiltration,the greater the corresponding maximum peak air pressure and the final stable pressure value.The final infiltration depth of the moisture content of 14% in the test group was 1.26 and 1.06 times the moisture content in the 6% and 10% test groups,respectively;The deeper the accumulated water,the greater the final infiltration depth and the faster the infiltration rate,the higher the corresponding peak air pressure and the final stable pressure value.The final infiltration depth of the experimental group with a depth of 15 cm depth was 1.46 and 1.2 times the final infiltration depth of the 5 cm and 10 cm depth of the test group,respectively.(2)The final infiltration depth in the open environment is 1.6 times the depth of the final infiltration in a closed environment.It shows that under the same conditions,the infiltration pressure in unsaturated soil is about 62.5%.(3)When the dry density is small,the gas in the soil layer close to the soil surface can easily escape.In deeper soil layers,the peak pressure achieved is also greater;At the same initial moisture content,the variation of air pressure at different depths is similar,and the peak air pressure shows a slight increase with depth.At the same water depth,the deeper the soil,the greater the maximum peak value.(4)With the infiltration of water,at the same depth,pore water pressure and volumetric water content gradually increase in soil.Along the depth direction,pore water pressure and volumetric water content in the soil gradually decrease.When considering the air pressure in the soil,the pore water pressure and volumetric water content in the soil are small at the same infiltration time and the same depth.In addition,the air flow rate in the soil is elliptical,the middle velocity is large,and the air flow velocity is gradually reduced as it extends around.With the progress of infiltration,the maximum air velocity moves down in the depth direction.Under the same conditions,with the increase of infiltration volume,the pore water pressure and volumetric water content in the soil are also greater,and the change of air velocity in the soil is small.The greater the air pressure,the less impact on the pore water pressure in the soil,the smaller the volumetric moisture content,and the larger air flow rate.