Analysis Of The Electrical Resistivity Characteristics Of Sodium Salt Saline Soil

Saline soil is one of the special soils studied in the geotechnical engineering community.It has the characteristics of collapsibility,salt expansion and corrosion.The foundations and pavements in the saline soil area will suffer from various damages such as collapsibility,mud,corrosion,salt expansion,subgrade mudding and frost heaving.Therefore,it is necessary to survey the saline soil site before the construction of the saline soil area.The exploration methods include direct prospecting and electrical prospecting.The electrical resistivity method is a convenient and simple method of electric prospecting.At present,the indoor experimental research on the characteristics of soil resistivity has involved sand,sandstone,clay,loess,dispersive soil,expansive soil,cement soil,etc.,and the electrical resistivity method is widely used in engineering,but the research on the engineering properties of saline soil by the electrical resistivity method is relatively insufficient,especially the variation of engineering characteristics of sodium salt saline soil in the process of sodium salt accumulation needs further study.To understand the electrical resistivity characteristics of sodium salt saline soil in depth,the preparation of sodium salt saline soil with different types and contents is prepared indoors.The electrical resistivity and unconfined compressive strength of sodium salt saline soil were tested by TH2827C digital AC bridge and YSH-2 unconfined pressure gauge.The failure process of sodium salt saline soil samples was recorded,and the effects of sodium salt type,sodium salt content and water content on the electrical resistivity and unconfined compressive strength of sodium salt saline soil were analyzed,and then the relationship between the electrical resistivity and the unconfined compressive strength were analyzed.The main findings are as follows:?1?With the increase of monosodium salt content,the electrical resistivity of sodium salt saline soil first decreases and then stabilizes,which is in accordance with the exponential function and has a high degree of fit.For mixed sodium salt saline soil,The electrical resistivity also decreases first with the increase of the mixed sodium salt content and then tends to be stable,and the fitting degree is good;Whether it is single sodium salt or mixed sodium salt saline soil,when the salt content increases to a certain value,The change in water content has a smaller effect on its electrical resistivity.Combined with the Archie electrical resistivity model and experimental data,the electrical resistivity formula of sodium salt saline soil was established.?2?The electrical resistivity of sodium salt saline soil is affected by different types of sodium salt.Under the same salt content,the electrical resistivity of single sodium salt saline soil shows a trend of Na₂SO₄>NaCl>Na₂CO₃.When the mixed salt content is the same,the mixed sodium salt saline soil shows a tendency of?NaCl and Na₂SO₄?>?Na₂CO₃and Na₂SO₄?>?NaCl and Na₂CO₃?.?3?The stress-strain curves of single-sodium salt?NaCl,Na₂CO₃,Na₂SO₄?saline soil and mixed sodium salt?NaCl and Na₂CO₃,NaCl and Na₂SO₄,Na₂CO₃ and Na₂SO₄?have similar changes and will undergo three different stages of change.However,the magnitude of the change and the peak value of the stress at each stage will be different.?4?No matter the single sodium salt saline soil and the mixed sodium salt saline soil,the unconfined compressive strength showed a slow downward trend with the increase of salt content under the same water content.For the sodium salt saline soil with the same salt content,the unconfined compressive strength will decrease with the increase of water content.The effects of water content and salt content on unconfined compressive strength were compared.It can be seen that the effect of water content on strength is greater than the effect of salt content on strength.?5?At the same water content,the compressive strength of the single-sodium salt?NaCl,Na₂CO₃,Na₂SO₄?and mixed sodium salts?NaCl and Na₂CO₃,NaCl and Na₂SO₄,Na₂CO₃ and Na₂SO₄?are nonlinearly increasing with the increase of resistivity,and the logarithmic curve fitting correlation coefficient was higher.Under the same water content condition,the change rule of soil electrical resistivity is more obvious in the process of accumulating the sodium salt content from 0 to 0.3%;In the process of accumulating the sodium salt content from 0.3%to 0.5%,The change rule of unconfined compressive strength of sodium salt saline soil is obvious.