The Study On Mechanics Properties And Reinforcement Mechanism Of Pumice-cement Composite Soil

Cement and the composite pile-soil are widely applied in engineering practice, particularly in the projects including soft soil foundation treatment, maintenance of foundation pit, slope reinforcement, and preventing water by grouting. Due to the extensive application of cement, cement additives that are able to strengthen early, to enhance and to reinforce anti-permeation in practice are also in wide use in cement to improve the engineering characteristics of cement. But influenced by the regional differences of soil, the engineering characteristics of cement with additives vary differently. Thus it will lead to the problems of piling difficulty , less solidarity ,and great increase of the handling cost,Therefore, based on the local natural resources --- natural pumice in the western district of Inner Mongolia, a new type of building material --- natural pumice powder cement-soil is developed in this paper. This thesis also does research on the mechanical characteristics of cement through laboratory work , analyses the evolution of the mechanical properties and establishes relevant constitutive model, which has practical significance in both theory and engineering in the process of wide application of cement in Inner Mongolia. Firstly ,we did the unconfined compressive strengh test of cement soil by different proportions of cement,different soil raw moisture content and different curing time respectively.Through the analysis of the experimental results,we can discover the main facts which can affect the strengh of cement.The experimental results obtained from the laboratory tests show that along with the proportion of cement increasing,the strengh of cement soil also appears a linear increase.In the pace with the soil raw moisture content increasing,the strengh of cement appears a reduction after the increase,just as a parabolic change.Along with the increase of the curing time and the strengh of cement soil,the both parties appeared a quite good linear relationship.According to the different proportions of pumice powder,cement,soil raw moisture content, the unconfined compressive strengh test by different curing times and the common triaxial test,we can get the corresponding measure and data of strengh under the different proportions.The experimental results shows:when the proportion of cement is 16%, the proportion of pumice powder is 8%, the strengh is the best in any curing time.At the same time,based on those data,we can get the most suitable proportion of the new type building material as we introduced in this paper.Secondly, this paper established strength prediction model under the action of many factors taken into account, suitable for the soil in Inner Mongolia ordinary cement soil and pumice cement composite soil , based on a large number of pilot test data collection. It also analysed the deformation characteristics of the ordinary cement and pumice cement soil in uniaxial and triaxial state respectively, deducing the stress of ordinary cement soil and pumice cement soil—strain constitutive equation.Lastly, this paper analyzed the microstructural features of pumice composite cement soil, combined with analysis of soil microstructure and unconfined compression test of the pumice cement composite soil, using SEM test. It also studied curing mechanism and loss characteristics of pumice cement composite soil, and preliminarily obtained damage prediction model of pumice cement composites soil. It essentially studied the strength formation mechanism of pumice cement composite soil.