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Study On The Law Of Dielectric Constants And Water And Salt Transport In Unsaturated Soils Under Freezing And Thawing

Posted on:2019-06-14Degree:MasterType:Thesis
Country:ChinaCandidate:S XuFull Text:PDF
GTID:2370330548474814Subject:Geotechnical engineering
Abstract/Summary:PDF Full Text Request
The hazard of frost heaving and volume sinking of foundation soil has become a major obstacle to the construction and operation of various types of projects in cold regions.One of the main reasons for the formation of this disease is the migration of soil water and salt caused by seasonal climate change,especially in saline soil areas.As the soil contains a large number of soluble salts,in addition to frost heaving thawing,it will be accompanied by a variety of saline soil diseases.Therefore,the study of water and salt migration in saline soil has important practical significance for the prevention and treatment of diseases.At the same time,sensors based on the empirical formula of dielectric constant are often used in the methods of determining soil moisture migration.However,such empirical formulas only consider the single relationship between the dielectric constant and volumetric water content at the positive temperature.Neglecting the effect of salt content,temperature,bulk density,and other factors on the dielectric constant,resulting in lack of universal measurement results,often can not reflect better accuracy,so the study of the factors affecting the soil dielectric constant,the establishment of various factors and The relationship between the dielectric constants is very important to improve the accuracy of the measurement.In addition,in the construction of cold regions,accurate and rapid determination of permafrost in foundations is of great significance for prevention and control of various types of infrastructure facilities.If the permittivity and other parameters can be used to determine the location of permafrost,it will be able to The engineering geological survey work brings a good supplement effect.In view of this,this paper starts from the following aspects and studies relevant contents.Firstly,according to the commonly used measurement method of soil dielectric constant,this paper determined the measuring equipment of soil dielectric constant,and took the low liquid limit yellow clay in the suburb of Harbin as the research object,and added different levels of NaCl to simulate the salting on the basis of plain soil.Soil,through the dielectric constant test of indoor remodeling soil,studied the influence of different temperature,initial moisture content,dry density and salt content on the dielectric constant of yellow clay,the results show that all factors will bring about the dielectric constant.Certainly affected.Secondly,on the basis of the dielectric constant model of unsaturated soil mixed media established by previous researchers,a theoretical model for the dielectric constant of unsaturated frozen soil mixed media was deduced and established,and verified by the experimental data of dielectric constant of indoor remodeled yellow clay.The practicability of the model shows that the measured value of the soil and the calculated value of the model are very close,and the measured value of the salt-containing yellow clay is somewhat different from the calculated value of the model.Finally,according to the commonly used detection methods for soil moisture content and electrical conductivity,the soil water and salt monitoring equipment was determined,and the research was conducted on the typical low-lying saline soils of Heyu yellow clay along the Mana-Al highway.The water remobilization test of indoor remodeling soil under unidirectional freezing and two-way melting environment was carried out.Based on the analysis of the dielectric constant test results of yellow clay,the dielectric constant of saline soil under positive temperature was fitted with multi-factors.The formula is used to calculate the moisture change during the experiment and analyzes the salt and water migration characteristics of saline soil under different initial moisture content,dry density,cold junction temperature and salt content.
Keywords/Search Tags:saline soil, dielectric constant, dielectric model, water and salt migration
PDF Full Text Request
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