| Soil site is a kind of ancient site with soil quality as the main.It is the remains of human life and production activities preserved in history.Due to the special climatic conditions in arid and semi-arid areas in northwest China,soil sites are facing serious damage under the combined action of many factors,such as wind sand,concentrated rainfall,freeze-thaw,earthquake and so on.As an important cultural heritage,soil sites have a unique non-renewable nature,so the materials used for the reinforcement and restoration of earth-stone brick buildings have high requirements in durability,compatibility and appearance harmony.MICP method,as an emerging method of soil reinforcement in the field of bio-rock and soil in recent years,has the advantages of being green and sustainable and repairing the old as the old.In this study,we considered using the microbially induced calcium carbonate precipitation,a new green and environmentally friendly rock and soil reinforcement technology,to improve and reinforce the site soil.Taking the physical and mechanical characteristics of MICbially Induced Calcite Precipitation(Microbially Induced Calcite Precipitation)grouting for precipitation of the site as the research objective,based on the statics test and microscopic characteristic test,In this paper,the static properties and microstructural characteristics of the site soil reinforced by MICP grouting,such as compressive strength and shear strength,were studied,and the dynamic response characteristics of the wall model were numerically calculated by Midas GTS based on the example of the Shandan Ming Great Wall failure induced by the Menyuan earthquake.The main research results are as follows:(1)Considering the two parameters of the concentration of microbial grouting cement and the ratio of bacteria to cement,the orthogonal test was designed to explore the static characteristics of the site soil after reinforcement.The experimental results show that MICP technology can obviously improve the mechanical properties of soil at the site,and obtain a good reinforcement effect.When the nutrient concentration is 1.0 mol/L,the ratio of bacteria to cement is 1: When 1,the reinforcement effect is the best,the compressive strength of soil increases 2.6 times,the cohesion increases 6.2 times,the internal friction Angle increases 39%,and the mechanical properties of soil are significantly enhanced.(2)According to scanning electron microscope observation,calcium carbonate precipitates produced by inducing microbial metabolism not only effectively filled the soil pores,but also improved the cementation between soil particles and improved the strength of soil skeleton.Based on the statistical analysis of particle pores,it is concluded that,compared with plain soil samples,the apparent porosity of soil strengthened by MICP decreases,the average particle size increases,the probability entropy and fractal dimension of soil particles increase,the soil compactness increases,and the macroscopic mechanical properties of soil are improved.(3)Based on the dynamic response results obtained by numerical calculation,the seismic deformation response of the wall top after MICP repair and reinforcement is significantly weakened under the action of earthquake load,and the maximum principal stress and maximum shear stress in the cut zone at the bottom of the wall are also significantly reduced,effectively avoiding the instability of the wall and improving the stability of the wall.In addition,the compatibility between the reinforcement material and the soil mass is good.There is no obvious stress concentration on the contact surface between the filling material and the original wall.The overall deformation of the wall is more coordinated and uniform at the same height level. |
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