Experimental Study On Microstructure And Reinforcement Characteristics Of Newly Reclaimed Soil

Due to the shortage of land resources and the demand for dredging of ports,the reclamation has become an important means of access to land resources in coastal areas.The dredger fill which used in the reclamation is characterized by large pore ratio,high compressibility,high water content and low bearing capacity.So reinforcement of the artificial reclaimed ground was up against the unavoidable technical difficulties,while the existing foundation treatment methods can meet the needs of the project at a certain extent,but due to the limitations of the lack of theory of consolidation and the engineering technology,the investment of engineering is enormous.Considering the existing consolidation theory fails to fully consider the microstructure and non-continuity characteristics of the dredger fill,the prediction ability of calculation cannot meet the requirements of the actual project.The physical and mechanical properties of the soil are the concrete manifestation of the microstructure,and its macroscopic properties are influenced by the microstructure state and the change.Therefore,the calculation results have some deviation,so the previous calculation theory is not suitable for the newly reclaimed foundation.The problem of land resource shortage in China has been alleviated by the sea reclamation engineering,which has expanded the living space and played a positive role in the development of national economy.After reclaiming land from seawaters,most of the land belongs to the littoral facies sediments,underconsolidated soil,high water content,large void ratio,poor permeability and low bearing capacity,high compressibility,large deformation and long consolidation time under load.In some parts,,the content of organic matter in the dredger fill that used in reclamation changed greatly.Therefore,it is difficult to use the site as a direct application of construction foundation,or even meet the basic requirements of personnel and equipment construction work.At home and abroad,people have spread a lot of work on the study of the engineering properties of solidified soil,through indoor experiment,field test and theoretical analysis to find the curing of formula and hardening mechanism,microstructure,deformation characteristics and influence factors of strength,and have achieved some results.But at present,the research and application technology of soil solidification time level is still low.they are still mostly used lime,cement,industrial mineral edge to improved soils which are traditional curing materials.The use of new curing agent is less.specially on the relatively high organic matter content of reclaimed soil solidification.Research works were rare.In this dissertation,the following research is carried out on the theory of consolidation of newly hydraulic reclamation and the test of curing the dredger fill.1.This dissertation studied the porosity structure characteristics of soft clay were qualitative analyzed by SEM images.Three dimensional porosity calculation model was built based on Image-Pro Plus(IPP)software.The calculation method of three dimensional porosity was introduced through a large amount of data statistics,comparing the relationship between the three dimensional porosity and macro porosity,the size of the contact area ratio of soil wsa obtained,the statistical method of average contact area ratio of soft soil was introduced,the theoretical relationship and influence coefficient of the average contact area ratio of soft soil and macroscopic porosity was obtained through the microcosmic experiment of soft soil in Hangzhou,Ningbo and Wenzhou.2.On the basis of the research of traditional Terzaghi one-dimensional consolidation theory and Biot consolidation theory,the theory of relation between the average contact area ratio and the macro porosity was introduced,we believe that the influence of contact area of soil particles to the effective stress transfer in soil skeleton which cannot be neglected.Based on this,the expression of effective stress was deduced considered the impact of contact area and compared it with the traditional principle of effective stress.And the expression of the one-dimensional consolidation equation and the biot consolidation equation are obtained by considering the contact of soil particles.3.To validate the stabilization effect of stabilizing agent GX08 treating the dredger fill soil in coastal region,and investigate the adverse influence of organic matter on cementing soft soil,unconfined compressive strength(UCS)tests were performed on stabilized soils.Test results indicate that organic matter significantly hinder the growth of the strength of stabilized soil,whereas stabilizing agent GX08 can effectively enhance the strength of the stabilized soil.The result shows that the strength of stabilized soil is well correlated with organic matter content as a form of quadratic function,and correlated linearly with cement content,and both are correlated as the form of logarithmic function with stabilizing agent GX08 content and curing time.The total cement/water is applied to the establishment of the stabilized soil strength model.Based on the analysis of tests data,a predict model,considering the influences of organic matter content,cement content,stabilizing agent content and curing time on the strength of stabilized soil,is proposed to predict strength development.