Study On The Reinforcement Effect Of Nano-materials On Electro-osmotic Modified Soft Soil

Soft soil foundations are widely distributed in China.With the continuous advancement of urbanization,the demand for land resources is increasing.Treating soft soil foundations is the key to improving the utilization rate of land resources.Due to the high moisture content,compressibility and sensitivity of soft soil,low shear strength and permeability coefficient,the traditional treatment method of soft soil foundation has the limitations of long construction period and high economic cost,while the electro-osmosis method for low permeability soft soil has the advantages of short treatment time,uniform reinforcement effect,etc.In recent years,it has gradually become one of the research focuses of domestic and foreign scholars.At the same time,with the development of materials science,the advantages of nano-materials in soil improvement have also begun to be reflected,as they can significantly improve the physical and mechanical properties of soil at low dosages,gradually attracting attention in the field of geotechnical engineering.In this thesis,based on the characteristics of nano-materials and electro-osmosis,they are applied to soft soil foundation treatment.Through a series of laboratory tests,such as the influence of different types and incorporation ratios of nano-materials on the electro-osmosis effect,the influence of APAM and nano-materials on the electro-osmosis effect,and the influence of nano-materials on the flocculation-chemical electro-osmosis solidified soft soil,the reinforcement effect of the incorporation of nano-materials on the electro-osmosis modification of soft soil was discussed,in order to provide a new idea for the reinforcement of soft soil foundation.It can provide some reference for practical engineering application.The main research contents are as follows:(1)The one-dimensional electro-osmotic model system was designed by ourselves,and the three nano-materials,namely nano magnesium oxide,nano ferric oxide and nano alumina,were combined with the electro-osmotic method to carry out the ratio selection and proportion ratio test of nano-materials.During the test,the displacement,drainage rate,water content,current,settlement,bearing capacity,shear strength,microstructure and so on were analyzed.The results show that the nano-materials can significantly improve the efficiency of electro-osmotic drainage and improve the soil strength.Although the reinforcement effect of 1‰ nanometer magnesium oxide,1‰ nanometer ferric oxide and3‰ nanometer alumina is better,the total energy consumption is also increased,and the settlement of soil is not uniform.The anode and the middle area are better strengthened,but the water content of the cathode area is still higher.The bearing capacity and shear strength are low.(2)In order to improve the consolidation strength,a new organic polymer material,anionic polyacrylamide(APAM),was introduced into the mixture of nano-materials and soft soil under the optimal dosage ratio to modify the soft soil,and flocculation-electro-osmosis test was carried out on the soil sample.The results show that the addition of anionic polyacrylamide is helpful to further improve the electro-osmotic drainage effect,enhance the soil strength,and improve the soil settlement,but at the same time,the efficiency of flocculation-electro-osmotic treatment in the middle and late stage is low,the EKG electrode plate is easy to detangle from the soil in the electro-osmotic process,and the total energy consumption and energy consumption coefficient of the electro-osmotic treatment of soft soil are increased to some extent.The moisture content of the cathode region of soft soil is still relatively high,and the strength improvement is not obvious.(3)Chemical grouting was introduced on the soft soil foundation modified by nano-materials and APAM.Calcium chloride solution and sodium silicate solution were used to inject the test soil from anode and cathode respectively to study the effect of nano-materials on the flocculation-chemoelectro-osmotic soft soil.The results show that the injection of chemical grout can further improve the reinforcement effect of soft soil and alleviate the problem of insufficient strength of soil in the cathode region.Under the action of electric field,the slurry reacts chemically with the original ions in the soil,forming colloidal substances and minerals to cement the soil particles,and filling the pores between the soil particles,reducing the soil settlement and improving the uniformity of settlement.However,due to the high content of nano-alumina,combined with the flocculation of APAM,the electro-osmotic drainage of soil is blocked.