Study On Streaming Potential Effect Of Soil-rock Mixture And Self-electric Field Diagnosis Method Of Embankment Dam And Dike

The streaming potential generated by water flow in the porous medium forms a selfelectric field,which can identify the seepage state by capturing the signal of self-potential,so as to a self-potential detection method(self-potential method)could be developed by measuring the streaming potential as the natural field source.By the way,because of the close relationship between the generation of streaming potential and the seepage process in the porous medium,the self-potential can be used for monitoring and diagnosing the leakage of the embankment dam and dike.However,the current model of the streaming potential effect of rock-soil can hardly reflect the structural characteristics of the soil-rock mixture(SRM),because of the complexity of the SRM’s internal structure and the difference between the streaming potential effect and pure rock-soil.Furthermore,no method can be used to diagnose the self-potential of leakage of embankment dam and dike currently,on account of the poorly researched identification and detection method for it.This limits the thriving future use of self-potential.This thesis is focused on the research on the SRM’s streaming potential effect and the diagnostic methodology for selfelectric of the embankment dam and dike,relying on laboratory experiments,theoretical analysis,numerical simulation,and physical models.All of this research supports by the NSF(51879017).The main research contents and results are as follows:(1)Design,construction,and testing of the apparatus for measuring SRM’s streaming potential: one set of equipment has been designed and manufactured based on the generation principle of streaming potential.This design of the equipment combined with SRM’s structural and construction characteristics of embankment dams in addition to the occurrence environment of SRM.Firstly,the reliability of the apparatus was validated by measuring the stability,response speed,and sensitivity of the apparatus.Secondly,the relationship of streaming potential to salt concentration and temperature of SRM was investigated based on this apparatus.Furthermore,the author proposed the method for measuring the streaming potential of SRM.Finally,streaming potential signals can be detected with high sensitivity and low interference,and might will be solving technical problems effectively in the future.(2)The influence of compaction degree,rock content,and solution concentration on the streaming potential effect of SRM were studied by using the above-mentioned SRM streaming potential apparatus and method.The result of the negative correlation between the streaming potential coupling coefficient and the permeability coefficient was obtained when the compaction degree and rock content changed,meanwhile,the variation of the streaming potential coupling coefficient and the solution concentration was revealed.Then,the empirical relationships between effective excess charge density and compaction,rock content,and solution concentration were obtained.Further investigation revealed the change in the flow regime related to the negative correlation between the streaming potential coupling coefficient and the permeability coefficient.Finally,the author confirmed the reliability of the experimental results and the apparatus by comparing the effective excess charge density from the analytical solution and experimental results.(3)The thin electric double layer capillary model,momentum conservation and Nernst–Planck equation were used to build the coupling equation related to the electric field,seepage and concentration field.Then,the governing equation describing the distribution of the self-electric field and the calculation model of the coupling coefficient of the streaming potential were obtained successfully.In order to forecast the streaming potential coupling coefficient more precisely,the KC equation calibrated by compaction degree and rock content was introduced in the aforesaid equation,resulting in a modified model for describing the streaming potential coupling coefficient related to the compaction degree,rock content,particle shape and particle gradation.The comparison between the experimental results and the calculation results of the modified model shows that the modified model has a good prediction effect under different compaction and rock content conditions.(4)According to the governing equation of the self-electric field distribution,a selfelectric field forecast model with the streaming potential as the power source was established based on the numerical simulation model,and the response characteristics of the self-electric field of the embankment dam and dike with different leakage paths,dam materials and solution concentrations were studied under the condition of changing water level.It was obtained that the inlet and outlet of the leakage path are the negative and positive self-potential anomaly centers,respectively.As the water level rises and falls,the self-potential of the dam body first decreases and then increases.This reveals the variation of self-potential at leakage path with the permeability of leakage path,the conductivity of dam body and solution solubility.By the way,the distribution characteristic of the selfpotential of the dam surface survey line was analyzed.The results show that the up/downstream slope survey lines’ self-potential are concave and convex respectively,and the self-potential value is the largest at the inlet and outlet of the leakage path.On this basis,a self-electric field identification method for leakage of embankment dam and dike was proposed.Following,a method for evaluating leakage strength was established by defining the leakage strength index.(5)A self-electric field detection system for monitoring the leakage of embankment dam and dike was developed from four aspects: measuring instruments,line layout,test methods and data processing.On this basis,combined with the self-electric field identification method for leakage of embankment dam and dike,a self-electric field diagnosis method was constructed.Then,the author built a physical model of the leakage embankment dam,and the performance of the observation system was proved to success by testing the self-electric field observation system from the model.Finally,the selfelectric field identification method for leakage of embankment dam and dike was validated by comparing the results from the numerical simulation and physical model,and the diagnosis method’s reliability was verified further.