The Soil Compaction Detection Model Based On Ground Penetrating Radar In Reclamation Area

Human-land conflict is quite prominent in China.Mining caused environmental degradation and large number of land destruction.The task of land reclamation is urgent and arduous.To achieve balance of cultivated land coupensation, land development, land reclamation and land consolidation are implemented.Land reclamation project require large amounts of machinery and equipment.Mechanical operation results in soil compaction,supply reduction of water and nutrients, increased soil hardness, reduced soil fertility and nutrient cycling, decreased soil microbial activity, hindered the growth of crop roots and even degradation of soil structure.Traditional methods of soil compaction detection are usually time-consuming and cause serious land damage, and require skilled labor.Ground-penetrating radar (GPR) is one of the non-destructive detection method,developing rapidly. It has been effectively applied in dynamic monitoring in soil erosion and soil moisture monitoring.This paper aims to study the application and effectiveness in soil compaction monitoring used GPR.Under unsaturated water conditions, the research of soil compaction was executed with GPR of250MHz frequency. To analyze the characteristics on compacted soil.Soil bulk density and soil penetration resistance are selected to reflect soil compaction.Volumetric water content, organic matter content, soluble salt content are selected as the related factors to the electromagnetic wave velocity propagation speed and the amplitude.Analyzing the soil compaction characteristics and regulation evolution in different reclamation area and soil types.The main conclusions are:(1) To test bulk density with GPR signal changes,radar wave velocity and amplitude attenuation,three relevant factors were chosen:volumetric water content, organic matter content, soluble salt content.Establish the regression equations of electromagnetic wave velocity propagation speed. When we used the substitute mathematical equations into the field tests,soil bulk density value was inverted;and by contrast with traditional measurement results,we acquired the accuracy more than70%.Under unsarurated soil moisture case, soil bulk density significantly positively related with GPR wave velocity,with partial correlation coefficient of0.933;negatively related with volumetric water content.Every plots in the test model designed same water content value and exclude moisture interference on electromagnetic.(2)Through the analysis of the relationship negatively correlation were found between soil penetration resistance and electromagnetic wave amplitude, with partial correlation coefficient of-0.719.Three factors of soil volumetric water content, organic matter content, soluble salt content and soil penetration resistance were selected to analyze their influences on electromagnetic wave amplitude.The results show that the electromagnetic wave amplitude was negatively related to the soil penetration resistance, with partial correlation coefficient of-0.818.(3) The mechanical compaction in reclamation process mainly affected the new soil layer after the reclamation. The principal effects appeared in surface soil lwyers(20cm),and there are little effects on basement soil.Using GPR electromagnetic wave velocity invert soil bulk density, and by the changes in the electromagnetic wave amplitude to invert soil penetration resistance, we found that applying GPR in soil compaction detection at large-scale reclamation project is convenient and effective.(4)According to the typical regional soil compaction in different reclamation period,the highest soil compaction was appeared in the first year after reclamation and was impossible to cultivate.The compaction variation between ten years after reclamation with undisturbed soil is not obvious, indicating that field farming can alleviate and improve soil compaction, but the process is slow.