Research Of Development On Nano Soil Stabilizer And Properties Of Stabilized Soil

The production and construction engineerings were faced with the problems of high environmental cost of sand and gravel mining,difficult utilization of abandoned soil and slag,and the consolidation properties of traditional soil stabilizers need to be improved urgently in Loess Plateau and the vast areas without sand and gravel.In order to solve these problems,a new nano soil stabilizer was developed in this research,which could make full use of local soil and water resources,reduce the environmental harm caused by digging mountains and rivers.It could also meet the realistic needs of high-quality development of the Yellow River Basin and ecological and environmental protection in the Loess Plateau region The influence mechanism of the properties optimization of nano soil stabilizer was clarified through the method of combining laboratory mechanical test and field engineering practice,based on scanning electron microscope and energy spectrum analysis observation means.It also analyzed that the influence mechanism of nano soil stabilizer on the mechanical property and interface structure of soil,and established the uniaxial compression constitutive relation and model equation of nano stabilized soil.This research established the theory of soil stabilized by nano stabilizer based on the activation of inert minerals and ion reconstruction,and put forward the construction methods of new nano soil stabilizer and soil reconsolidation technology in different slope and gully ecological engineering,which could provide theoretical and technical supports for the further research and application of nano soil stabilizer in the area without sand and gravel.The main conclusions were as follows:1.Effect of nanomaterials on properties of soil stabilizer and development of nano soil stabilizer(N-MBER).In view of the defects of soil stabilizer in strength and durability and the performance advantages of nanomaterials,the improvement mechanism of mortar strength of nano soil stabilizer,ordinary soil stabilizer and grade 32.5 cement under different content of nano-Si O₂ and curing periods was discussed,by analyzing the variation rule of soil stabilized by nano soil stabilizer,influencing factors and microscopic particle morphology.The composite power exponential function model of compressive strength,content and curing period of nano soil stabilizer mortar sand was established,and the optimization mechanism of nano soil stabilizer on the micro geometry of soil particle interface was clarified.A new type of nano soil stabilizer named N-MBER was developed,which had an optimized formula of nano-Si O₂ content of 2.5%.The results of mortar tests showed that the strength of nano soil stabilizer with this content could be increased by more than 15%compared with the ordinary soil stabilizer,and by about 50%compared with grade 32.5cement.2.The influence mechanism of nano soil stabilizer on the mechanical property and interface structure of soil was revealed.It was found that the content and curing period of the N-MBER were significantly related to the mechanical properties of the nano stabilized soil,and the relationship between the content and the unconfined compressive strength of the nano stabilized soil was exponential function.In terms of mechanical properties,the unconfined compressive strength of nano stabilized soil at each period could be increased by 10%?30%compared with that of ordinary stabilized soil and grade 32.5cement soil.The influence mechanism of nano soil stabilizer on the mechanical property and interface structure of soil was revealed by comparing the change rule of water absorption,dry density and particle shape with curing periods of nano stabilized soil,ordinary stabilized soil and cement soil.Through the above research,the evolution mechanism of the microstructure and macroscopic mechanical properties of the soil stabilized by N-MBER was clarified.It provided a basis for further study of the stress-strain constitutive relationship of nano stabilized soil under stress condition.3.The elastoplastic constitutive model of nano stabilized soil under uniaxial compression was established.Three stages of nano stabilized soill stress-strain were clarified by analyzing the failure process of typical nano stabilized soil components under uniaxial compression,which named the early material internal pore closure stage,the linear elastic deformation stage before the peak stress and the material breaking stage after the peak stress.The elastoplastic constitutive model of uniaxial compression stress-strain for nano stabilized soil was proposed through model selection and parameter calculation,which was verified by experimental datas.The results of model verification indicated that this model could simulate the stress-strain curve of the nano stabilized soil material under uniaxial compression accurately.The above results showed reference for quantitatively calculating the stress-strain relationship of nano stabilized soil under one-dimensional compression,and provided a basis for the further study of anisotropic multiaxial force constitutive model of nano stabilized soil.4.Established the theory of stabilized soil by nano soil stabilizer basing on the activation of inert minerals and ion reconstruction.The effect of nano-Si O₂ in the hydration process of soil stabilizer was studied based on the mechanism of its hydration activity and ion composition and distribution,it was found that nano-Si O₂ could take advantage of its strong volcanic ash catalytic activity,small particles and high fluidity to activate soil inert minerals and chemical ion reconstruction,strengthen network cementation,and make the basic structural unit of the material closly aggregate and the phase interface tightly contact.At the same time,it could stimulate the potential activity of soil aluminate minerals,so that it can form firm polycrystalline clay aggregates at the phase interface and inside the soil unit,thereby improving the nature of the contact between the soil particles and producing higher strength and water stability.In addition,this research also found that the refinement rate of calcium hydroxide crystals by nano-Si O₂ in the early hydration process could reach more than 50%,and the nano soil stabilizer could increase the number of hydrated calcium silicate gels of different shapes in the soil colloid by up to 30%.Based on the above research,the basic theory of soil stabilized by N-MBER was constructed,that is,“Phase interface reconstruction theory based on activation of Soil inert minerals and regeneration of ion”.This theory can provide a theoretical basis for the further development and application of N-MBER.5.The construction technology of nano soil stabilizer in typical engineering was put forward.In this research,we applied the developed N-MBER and soil reconstruction technology to the practical projects of typical engineering in different soil quality areas basing independent research and development of soil stabilizer.The application results showed that the strength of the project built with the nano stabilized soil material was increased by more than 20%compared with that of the cement soil project at the same cost.The construction cost of using nano stabilized soil could be saved by more than 30%under the same engineering strength condition.Nano stabilized soil also had the advantages of local materials,simple construction and no pollution to the environment,which could be used as the main project to build warp dam retaining wall,road,reservoir and other facilities,while taking into account cost saving and environmental protection.The nano stabilized soil engineering and facilities could play a positive role in production construction and ecological restoration,and showed a good prospect of popularization and application in areas lacking of sand and gravel such as the Loess Plateau.