Research On Electrical Resistivity Characteristics Of Saline Soil

With the accelerated pace of nation-building, continued construction and improvement of road, railway, industrial and agricultural infrastructure and water resources and hydropower engineering, construction issues under complex sites, which includes saline soil, permafrost, collapsible loess, soft soil, and so on, have gradually increased. It is important to study in depth of physical and mechanical properties and engineering properties of this some special soils. Saline soil widely distributed in china. In saline soil area, because of a lot of salt and migration of salt with water, it makes the salt uneven in spatial distribution and changes dynamically over time. The survey of the construction in saline soil area needs to identify the type of saline soil, thickness, characteristic, the distribution of salt, groundwater conditions and so on. The presence of salt make changes in engineering properties of soil, resulting in swelling of salt, collapsibility, frost heave, a significant reduction in strength after immersed in water, easy to produce corrosion of the foundation. For the exploration in saline soil area, electrical prospecting is more applicable except direct exploration methods, and electrical prospecting methods are widely used in engineering as advantages of various kinds, wide application, low cost and high efficiency. In order to make a better interpretation and application for the results of electrical prospecting, further research is needed. Since the complexity of the material itself, the soil composition, structure, particle size distribution and its connection status, the electrical characteristic of the soil is complex. Many scholars have done the research work from aspects of theoretical and experimental to the resistivity characteristics of soil under different circumstances, they also made a number of resistivity models, these works play well role in promoting subsequent research and applications. However, specific research on resistivity characteristics of different soil conditions is also required.For a better understanding of the characteristics of the soil electrical resistivity and let it play a role in theory and engineering applications, the electrical resistivity laboratory tests on saline soil in Guazhou of Gansu province was made. First, affect of particle size composition to the resistivity was studied, then under the same particle size composition, orthogonal test were carried out by controlling the three factors of water content, salinity and dry density, relationships and characteristics among resistivity and water content, salinity, porosity and saturation were studied. Results show that:Resistivity is high when particle size composition including large particle, while resistivity decreased when higher clay content. Saline soil resistivity decreased like power function with the increase of water content. In the case of completely dry, resistivity of soil particles is very high. When water content is very small, the connectivity through the channel of pore water is not good. When the water content reaches a certain value, it makes the pore water well connected, then the resistivity rapidly decreased. Change with salinity related to degree of salt dissolved, it decreased with the increase of salinity when the pore fluid was unsaturated and did not change significantly when the pore fluid was supersaturated. When the water content is the same, resistivity increases with the porosity increases, for the deterioration of pore water connectivity. Saturation reflects the state of pore filling conditions, the resistivity showed a decrease like power function as saturation increases. Particle size composition, water content, salt content, porosity, clay content is all important factors. Resistivity changes with each factor in different levels, various factors affect each other and work together. We have proposed empirical model formula from the data obtained from laboratory test among resistivity and salinity and saturation, we also analyzed variation of resistivity changes with other factors. According to the results of laboratory tests, we analyzed and explained the cross-sectional view from on-site testing of high-density resistivity electricity method and estimate the salinity of the ground soil, it played an important role in engineering practice.