Analysis Of Mechanical Properties Of Uplifted Foundation Grouted By Expansive Cement Slurry

At present,grouting lifting technology has been widely applied in engineering practice.However,theoretical studies and practices have shown that traditional grouting formations are significantly uplifted,the building foundation uplifting process is instable,and there are wave-like settlements.In order to make the building structure stable and uniform uplifting,therefore,the research on the uplifting of the building structure from the grouting material is considered in this paper.In view of the defects of traditional cement grouting material,a kind of composite slurry,expansive cement slurry,is prepared by adding clay,water glass and expansive agent in cement slurry.The expansion performance of expansive cement slurry was studied,and the expansion mechanism and the uplift effect of expansive cement slurry are studied based on the finite difference software system.The main research contents and results are as follows:1)Analysis of interaction mechanism of various components of the expansive cement slurry.Through the hydration and condensation hardening mechanism of cement slurry,the reason of the volume shrinkage of cement stone was analyzed.The crystallization law and volume deformation theory of the expansive cement slurry in the setting and hardening process were explored through the action mechanism of expansive agent,clay and water glass and cement.2)Experimental research on expansion properties of expansive cement paste.The effects of different water-binder ratios,expansion agent content,clay content,water glass content on the expansion rate and expansion stress of the slurry were analyzed by orthogonal test,and the optimal ratio was determined.The experimental results show that the limit expansion rate increases with the growth of the age and then decreases gradually,and the expansion rate reaches the maximum at 7d,while the 28d is stable.The limit expansion rate of expansive cement paste with different proportions follows3#>2#>4#>5#>1#>8#>9#>6#>7#,which shows that the effect of water-binder ratios on the expansion rate is the most,and the limit expansion rate gradually decreases with the increase of water-binder ratios.According to the range analysis and variance analysis,the degree of influence of water-binder ratio,clay content,water glass content,and expansion agent content on the limiting expansion rate is:water-binder ratio>expansion agent content>water glass content>clay content.The optimal mix ratio is A₁B₂C₂D₃,the water-binder ratio is 0.6,the clay content is 10%,the water glass content is 2%,and the expansion agent content is 12%.3)The establishment of a mathematical model for expansion of expansive cement paste.According to the orthogonal test results,the correlations between the limiting expansion rate and the water-binder ratio,the clay content,the water glass content,and the expansion agent content were first obtained.Then,through the regression analysis,the regression equation and the single-factor fitting curve between the limiting expansion rate and various factors were obtained.At the same time,Matlab software was used for regression analysis.A regression model was established for the limiting expansion rate to water-binder ratio,clay content,water glass content,and expansion agent content.4)The establishment of a numerical model for expansion of expansive cement paste.The expansion displacement of the expansive cement paste under the optimal ratio is selected,the rate of a given step corresponding to the preset displacement is calculated,and the expansion process is simulated by applying a radial velocity to the outer node of the pulp bubble to perform the expansion,which provides a powerful guarantee for the numerical simulation of the uplift of expansive cement soil.Based on the stochastic medium theory,a single-hole grouting uplift model was established.By applying radial pressure to the surface of the pulp bubble,the single-hole grouting uplift process of the expansive cement slurry under different grouting pressures was simulated,so as to provide reliable guarantee and reference for guiding the construction of engineering.5)Numerical simulation of uplifting process of expansive cement soil.Based on the analysis results of theory,test and expansive cement slurry expansion model,the soil uplift model is constructed,and the soil uplift mechanism under different mix ratio cement soil and different overburden loading conditions is simulated and analyzed.The comprehensive analysis shows that the uplift displacement of the cement soil of the test number 3#reaches the maximum,indicating that the matching ratio of the test number 3#is the optimal mix ratio;the overlying load and the uplift displacement have a significant negative correlation,and the uplift displacement gradually decreases with the increase of the overlying load,and the uplift displacement is reduced to zero when the overlying load reaches 0.5MPa.