Study On The Long-term Resistance Reduction Of Super Absorbent Polymer Modified Soil Near Grounding Electrode

Studies have shown that the super absorbent polymer(SAP),as a new type of soil resistance-reducing material,can reduce the soil resistivity effectively and improve the impulse dispersion performance of soil.The material can meet the requirements that reduce the grounding resistance of grounding devices in high soil-resistivity areas.However,when the super absorbent polymer is used as a soil modification material,it will be exposed to the natural environment for a long time.Under the influence of factors such as temperature,impulse current and ultraviolet ray,it is an urgent problem to evaluate the long-term performance of the material.Therefore,in this paper,these questions were studied,which are the thermal aging characteristics of the material,the resistance stability under the action of impulse current and the corrosivity of modified soil to the grounding conductor.The specific research work includes:(1)In this paper,in the process of useing the soil modification materials,the main environmental factors are considered,such as temperature and impulse current.And the thermal oxygen aging law and the impulse currents degradation law of SAP caused are studied.We can get that aging time of SAP is 8.2 years under the room temperature.Besides,the reduction of SAP’s saturation water absorption is much less than 20%after impulse current endurance tests,which meets the requirements impulse current tolerance in the regulations.(2)In this paper,the corrosion rate of the grounding conductor in the modified soil with different contents was studied by electrochemical test and field test of buried samples in the soil.We can get when the SAP content is greater than 0.5%,the corrosion resistance is better than that in the unmodified soil.Therefore,in actual project,the SAP content in the modified soil should be greater than 0.5%.(3)This paper proposes a method to evaluate the soil impulse current divergence performance and the evaluation index of this method is the volume of soil in which partial discharge occurs per unit impulse current.Using this method,the V_I of the modified soil can be measured regularly,so the long-term effectiveness of the modified soil’s resistivity reduces efficiency can be monitored.At the same time,the evaluation test of the impulse current divergence performance of the modified soil shows that,when the SAP content is 0.5%,the V_I of the modified soil is 24.59cm~3/k A.Compared with the unmodified soil,the impulse ground resistance value of the modified soil is reduced by 10.26%,and the V_I value is increased by 3.54 times,indicating that the modified soil has a better impulse current divergence performance.