| The abundant theoretical and engineering practice has proved that electro-osmosis has unique advantages in treatment of low hydraulic permeability coefficient of deep soft clay foundation,dirt and silt and other geotechnical materials.However,there are negligible anode corrosion,high energy consumption and voltage loss caused by interface resistance and electrode retention in traditional electro-osmotic method because of the use of metal electrodes,which seriously hinders the extensive development of electro-osmosis in engineering applications.The appearance of EKG materials which can be produced in large quantities can solve the problems of electrode corrosion and exhaust difficulties in the process of electro-osmosis.As an electrode for treating soft base,sludge and tailings by electro-osmosis,it has been gradually used in laboratory research and engineering practice,and the application and development of electroosmotic technology are pushed step by step.In order to study the resistance characteristics of the EKG electrode and the contact resistance between electrode and soil,and the potential of EKG electrode applied to electro-osmosis,the test methods of the EKG electrode resistivity and the contact resistance characteristic between the electrode and the soil were put forward on the basis of the predecessors,and a number of tests were carried out in the self-made model box,and indoor tests were carried out under different electrodes and different model sizes.The main work and research results are as follows:1.The research history and current situation of electro-osmosis were summarized,the basic mechanism and consolidation theory of electro-osmosis were described,and the influence factors of electro-osmotic effect were summarized.2.In view of the existing EKG electrode test method,the improvement scheme was proposed,and the test method of the new form of EKG electrode resistivity was proposed.The two test methods can be applied to the old form of the EKG electrode and the new form of the EKG electrode respectively.The test method of the new form of EKG electrode is verified in the laboratory test.The experimental results show that the resistivity measured by this method does not change with the length of electrode,it has good stability and can be easily applied to production practice.3.A method for measuring soil resistivity and contact resistance was proposed,which can avoid the shortcomings of the traditional method.The conjecture of the contact resistance between the soil and the electrode was proposed,and the traditional electric potential measurement and new method were used to verify the conjecture in the laboratory test.The experimental results show that the total electrical resistance in the electro-osmosis is roughly divided into soil resistance and the contact resistance between the electrode and the soil.The soil resistance basically does not change with the change of current in the circuit,and the contact resistance is closely related to the current,and it is approximately a power function relation with the current.When the current is small,the contact resistance is large,and it increases rapidly with the decrease of current.When the current is large,the contact resistance is small,and the amplitude of the current decreases with the increase of current4.The parameters can be estimated at the beginning of the on-site electro-osmosis by the laboratory test results of the new method.The calculation results show that the ratio of the effective potential of the soil is closely related to the potential gradient of the power supply.Reducing the electric potential gradient in the electro-osmosis will result in the decrease of the effective electric potential of the soil,so it is not suitable to use the low power supply voltage.On the other hand,the excessive increase of the power supply voltage has little effect on the effective electric potential of the soil.In the field of electro-osmosis,it is not necessary to pay too much attention to the electro-osmosis efficiency if the effective electric potential ratio of the soil is satisfied,so the suitable potential gradient should be selected according to the requirements of the time period and the field conditions to achieve the ultimate goal of the project.5.The aluminum,copper,iron and EKG electrode were used to carry out the indoor electro-osmotic test on the silt of the river bed of the Xunsi river.The test results show that the overall current of the electro-osmosis under the EKG electrode is the highest and the drainage amount is the largest.Under the potential gradient of 1.5V/cm,the treatment effect of EKG electrode on the silt of Xunsi river is better than that of metal electrode,considering the characteristics that EKG electrode is difficult to produce electrode corrosion,EKG electrode has great superiority in sludge dewatering.6.With the electro-osmosis evolved,the potential drop near the anode of the metal electrode increases gradually,and the potential drop near the anode of the copper electrode is particularly significant.The potential drop near the anode of the EKG electrode is basically unchanged.This may be due to the electrochemical passivation of the copper electrode in the electro-osmosis,and the electrochemical passivation makes the anode electrode.The contact resistance increases with the soil,resulting in the increase of the potential drop at the anode.7.The energy consumption per unit water decreases with time and then gradually increases in electro-osmosis.The energy reduction section is caused by the gradual decrease of the current when the drainage speed is basically kept unchanged.With the experiment evolved,the energy consumption per unit water is gradually increased,which indicates that a certain amount of water is expected to be discharged.The required energy consumption will be greatly increased.The unit mass energy consumption and the unit volume of the drainage ratio is basically linear,that is,the same proportion of water discharged,the basic need to consume the same proportion of energy,this linear relationship continues to a certain water content,and then the condition of electroosmotic conditions can not be further discharged from the soil.8.Changing the potential gradient will affect the cost and dewatering effect at the same time.Increasing the potential gradient will reduce the time limit,but the energy consumption will be improved,and the cost will be improved.In practical engineering,the appropriate potential gradient should be selected according to the cost and the requirement of dewatering eflfect.Selecting the right time to stop electro-osmosis can significantly reduce the power consumption and reduce the construction period and cost without affecting the total displacement of electro-osmosis.9.Under the same potential gradient,the overall electric current of the large model is larger than that of the small model,and the longer the length of the model,the longer the drainage process of electro-osmosis will take.The proportion of electro-osmotic drainage in soil under small section(12×12×20cm)is smaller,and the proportion of other effects(water evaporation and water electrolysis)is larger.The dewatering ability of the electro-osmosis to the soil will increase with the increase of the length of the model under the same electric potential gradient and the same section area. |
PDF Full Text Request