Study On Physical And Mechanical Properties And Economics Of Stone Powder Modified Superfluidity Cement Soil

With the continuous promotion of urbanization in coastal cities,soft ground is difficult to meet the bearing capacity and settlement requirements,and the traditional soft ground treatment scheme is increasingly uneconomical in the background,there is an urgent need to propose a safe,economic and green treatment scheme for soft ground.In order to respond to the national low-carbon environmental protection call,the city construction,natural mining construction generated waste stone powder as a substitute for part of the cement into the soft soil for modification,on the one hand to turn waste into treasure;on the other hand to improve the economy of its engineering use.Considering that the field construction of stone powder modified cement soil is mostly based on manual paving,and the pumping construction can be achieved by improving its flow degree to superfluid state,but the application of both to cement soil is less studied and the mechanism of influence is not clear,so it is necessary to systematically study the influence of stone powder and superfluid state on the physical and mechanical properties and economy of cement soil.The main research contents of this thesis are shown as follows:(1)By changing the main influencing factors(water-cement ratio,stone powder substitution,and fiber admixture)of the cement soil ratio,the parameters of flowability(224 mm to 259 mm),compressive strength(28 d strength between 0.84 MPa to 2.76 MPa)and water stability coefficient(28 d water stability coefficient between 0.815 to 0.845)of different ratios were obtained,and the result was that the way to improve the flowability of cement soil was to increase the water-cement ratio and increase the stone powder substitution,the way to improve the water stability of cement soil was to decrease the water-cement ratio and decrease the stone powder substitution,and the way to improve the water stability of cement soil was to increase the water-cement ratio and increase the stone powder substitution.The flow rate of the cement soil is increased by increasing the water-cement ratio and increasing the amount of stone powder substitution,the compressive strength of the cement soil is increased by decreasing the water-cement ratio and reducing the amount of stone powder substitution,and the water stability of the cement soil is increased by increasing the amount of stone powder substitution,and the effect of stone powder substitution on the parameters of the shear strength of the cement soil is investigated by the preliminary matching ratio,and the trend of increasing the cohesion of the cement soil and decreasing the angle of internal friction is obtained with the increase of stone powder substitution;The maximum compressive strength was obtained through the orthogonal experiments of extreme difference and analysis of variance(ANOVA),which corresponded to a water-cement ratio of 1.5,a stone powder substitution of 15% and a fiber doping of 0.4%;(2)Using scanning electron microscopy(SEM)and digital photographic deformation measurement(DPDM)to microscopic analysis and fine deformation measurement of stone powder modified superfluidic cement soil,it is concluded that the increase of hydration products with the increase of age leads to the increase of strength and the decrease of appearance damage displacement;with the increase of stone powder substitution the total number of hydration products decreases leading to the decrease of strength,but the appearance damage displacement increases,indicating that the modification of stone powder and the addition of fiber will improve the plasticity of cement soil;(3)Use ABAQUS numerical simulation software to investigate the foundation bearing capacity and stress diffusion angle of replacement cement foundation,and get the foundation bearing capacity of different replacement materials and replacement thickness,and get the ultimate bearing capacity of foundation with different amount of stone powder replacement materials,and the greatest influence of replacement thickness on the ultimate bearing capacity of foundation,and the maximum and minimum value of stress diffusion angle of foundation decreases with the increase of stone powder replacement;use python language for secondary development,randomly generate fiber model and test stress-strain curve for comparison,and get the simulation and test results are similar,which has reference value;(4)Using the hierarchical analysis method,the nine functional indicators of the foundation treatment program are scored to calculate the weights,and the value formula is used to calculate the value coefficients of three foundation treatment programs,namely,cement-infilled pile method,reinforced bedding method and replacement cement soil method,to conclude that the replacement cement soil method has value advantages and its application prospects;for the replacement cement soil site construction process and steps,a series of construction processes and operational precautions are formulated,which provide reference and suggestions for the actual application of future projects.There are 100 figures,37 tables and 85 references in this thesis.