A Research On The Technological Method Of Rapidly Sailing To Etect Seabed Soil Resistivity

Soil resistivity contains rich informations of the soil quality and physicalproperties, has a broad application prospects in the study of the seabed soil. In recentdecades, the resistivity of the seabed soil has been gradually applied to the evaluationof offshore engineering geological environment and the stability of foundation soil;various types of marine mineral resources exploration; sediments consolidationsettlement; contaminant migration; corrosion features of seabed pipeline and theerosion monitoring of seabed; and it also has important practical significance indisaster prevention and mitigation.Compared to the widely used in onshore shallow soil testing, few scholarsdirectly used multi-electrode DC resistivity method in the investigation of the seabedsoil. There are three main reasons:(1) The seawater will divert the vast majority ofelectricity, only a small amount of electricity will be supplied into the seabed soil,when the power supplied underwater.(2) The sailing measurement method needs dataacquisition with high speed, general resistivity equipment is hard to achieve;(3) It isdifficult to achieve instantaneous resistivity data collection at different depths. Basedon the present research situation and electrostatic field theory, the paper will calculateelectric-field distribution in seawater and seabed soil at different power supply, todiscuss the best pattern of power supply and measurement. According to the results oftheoretical calculation and the simulation test and in situ test designing a measurementsystem of rapidly sailing to detect seabed soil resistivity. Finally through a practicalexample to evaluate the effectiveness of the system, and put forward proposals toimprove the device.The paper is divided into seven chapters. The first chapter mainly expoundsresearch actuality, the main research contents, research methods and researchachievement. The second chapter introduces the basic theory of the resistivity; thebasic principles of electrical prospecting, some commonly used methods and device; resistivity survey instrument development status at home and abroad. Chapter III setsup the geoelectric model to detect seabed resistivity, solving the potential equation ofthe undersea electric field by the image method, obtaining the distributioncharacteristics of undersea direct current electric field. And it also analyzed theimpact of the location of supply point and measuring point, the changes of sea andseabed soil resistivity for the apparent resistivity changes and discussed the currentshunt in the sea and seabed soil. Research found that supply point and measuringpoint located in the sea water or in the seabed soil, pole-pole and pole-dipole device,all have their own advantages and disadvantages. When detection, it should accord tothe site conditions and the requirements of detection goal body to select the locationof supply point and measuring points and the detection devices. The fourth chapterprovides a preliminary design of sailing multi-electrode DC resistivity testingequipment. ChapterⅤ researches the ability of the multi-electrode DC resistivitymethod to detect the sand layer and target body in seabed soil through the indoorsimulation test and in situ test. Research shows that, the multi-electrode DC resistivitymethod has good detection ability for sandy soil resistivity change in the sea, butrelative to the land environment it needs high precision detection equipment. Whenlaying the electrode underwater, the multi-electrode DC resistivity method also hasgood detection ability for underwater target body especially high resistance body. Thesixth chapter gives an engineering example of the field work of underwatermulti-electrode DC resistivity method. Through the analysis of engineering example,some issues are get which should be paid attention to in engineering application.Chapter VII gives the overall conclusions of the paper and the next steprecommendations.Based on the different DC power supply conditions, analyzing the electrostaticfield characteristics in the seabed soil, we designed sailing multi-electrode resistivitytesting equipment. The test results showed that the system can effectively measure themainland layer resistivity distribution in underwater certain depth and resistivityanomaly body. Through the application of engineering practice, summarized and analyzed some problems in practical application and it will have some guidance forfuture similar projects.