Study On The Whole Process And Ground Lift Effect Of Fracture Grouting By Cement Based Slurry In Undisturbed Soft Soil

With the continuous increase in the number and speed of infrastructure construction in my country,the disasters and diseases encountered in the process of project construction and operation have become increasingly prominent.Among all kinds of diseases,engineering disasters caused by uneven settlement and leakage are particularly prominent.Undisturbed soft soil layers are more prone to engineering safety problems due to the characteristics of high water content,low soil strength,and significant rheology.Numerous engineering practices have shown that grouting can effectively control disasters and diseases in the entire life cycle of infrastructure projects,among which split grouting has the effect of strengthening the stratum and uplifting.This paper aims at fracture grouting process of cement-based grout in undisturbed soft soil strata.Considering the properties of undisturbed soil,pore tortuosity effect in porous media soil,and properties of cement-based grout.The fracture pressure caused by fracture grouting,the change of the expansion crack width of the slurry vein path,the influence of grouting slurry on the diffusion and the analysis of the effect of grouting on the ground displacement and lifting were analyzed.Mainly carried out the following research work:(1)Considering the undisturbed soil properties of soft soil strata,the transformed stress method is used to combine the Wheeler model with the SMP strength criterion.Establishment of an elastic-plastic analysis model for undisturbed undrained soil expansion problem.Analysis of the fracture grouting mechanism of cement-based grout in undisturbed soft soil.Derivation of analytical expressions for splitting pressure and soil deformation in split grouting.On this basis,the influence of parameters such as internal friction angle,Poisson’s ratio and elastic modulus on the splitting and grouting initiation is discussed.It is clear that the splitting pressure increases nonlinearly with the increase of internal friction angle,elastic modulus and initial stress of soil.(2)Consideration of compressive properties of undisturbed soft soil strata during split grouting by using double logarithmic curve.The compressive deformation of soil in the process of slurry diffusion is divided into: elastic-elastic compression region,elastic-plastic compression region and plastic-plastic compression region.Theoretical analytical formulas for the width of the pulp veins and the radius of diffusion of the pulp in the three compression regions are established.On this basis.The effects of grouting amount,rheological coefficient of grouting,grouting gradient and other factors on the width and expansion radius of the grouting are discussed.It is clear that the width of the pulp vein increases nonlinearly with the increase of grouting time,the width of the pulp vein has a positive correlation with the unit grouting amount and a negative correlation with the rheological coefficient of the slurry.(3)Consideration of pore tortuosity effect and time-varying slurry viscosity in undisturbed porous medium soil.The properties of cement-based slurries were described using H-B fluids.Based on the fractal theory,the diffusion mechanism of the split grouting slurry in the formation was analyzed.Derive the theoretical analytical formula of cement-based grout grouting amount.On this basis,the influence of the properties of the grout and the tortuosity effect of soil pores on the diffusion of split grouting is discussed.It is clear that the properties of the grout are closely related to the grouting diffusion and the average flow rate of the grouting amount of the multishaped single-hole pore conforms to: equilateral triangle>semicircle>square>circle;It is determined that the actual grouting amount is related to the difference between the maximum pore area and the minimum pore area.(4)Using random medium theory and horizontal radial circular grouting model to analyze various grouting conditions such as uniaxial single hole,uniaxial porous,and multi-axial porous.The theoretical calculation model of ground lift generated by split grouting under various working conditions is deduced.On this basis,the influence of parameters such as grouting diffusion radius,grouting vein width,grouting hole radius,grouting depth,and formation uplift influence angle on formation uplift by split grouting is analyzed.It is clear that grouting diffusion radius,grouting pulse width and formation uplift influence angle are positively correlated with displacement uplift;grouting hole radius and grouting depth are negatively correlated with displacement uplift.