| The grouting technology behind the pile end is an important measure for the reinforcement and reinforcement of the bored pile.The slurry diffusion mechanism is of great significance to the grouting behind the pile end.At present,there are few studies on the Herschel-Bulkley fluid model at home and abroad.Therefore,this article will carry out the research,and the main research results are as follows:(1)Based on the time-invariant viscosity Herschel-Bulkley fluid constitutive equation and the uniform flow basic equation,the theoretical calculation formula of the Herschel-Bulkley rheological model slurry diffusion radius under split grouting is derived,and the formula and each Affecting the relationship between the parameters,the research results show that: the consistency coefficient and rheological index are positively correlated with the grouting pressure difference;the fracture height is negatively correlated with the grouting pressure difference.At the same time,with regard to the maximum diffusion radius of the slurry,the maximum diffusion radius of the slurry is positively correlated with the grouting pressure difference and the crack height;the maximum diffusion radius of the slurry is negatively correlated with the consistency coefficient and the rheological index.(2)Through the indoor model test,the test results are compared with the results calculated by the theoretical formula of Herschel-Bulkley slurry diffusion radius of viscosity-invariant viscosity.The verification results show that the relative error between the calculated value and the actual value-50% ～ 100%,and this range has been widely used in domestic experimental research.The research shows that the theoretical formula of Herschel-Bulkley slurry diffusion radius derived by this paper can reflect the slurry Diffusion law in injection medium.(3)Using the Herschel-Bulkley rheological model of slurry viscosity non-time-varying,the formula for calculating the upper return height of the slurry was derived.And analyzed the relationship between the formula and each parameter.(1)The upward return height of the slurry increases with the increase of grouting pressure,pile diameter and mud thickness,and the grouting pressure is positively related to the upward return height of the slurry;(2)The upward return height of the slurry increases with the burial depth and consistency The coefficient and rheological index increase and decrease;on this basis,the correctness of the back-grouting height after grouting is verified through engineering cases.(4)Using the time-varying viscosity of Herschel-Bulkley model,the theoretical formula of slurry diffusion radius was derived,and the relationship between the theoretical formula of diffusion radius and each parameter was analyzed.The analysis shows that the slurry diffusion radius increases with the increase of the grouting pressure difference and the height of the fracture,and the slurry diffusion radius decreases with the increase of the grouting time,slurry time-varying coefficient,slurry rheological index,and slurry initial consistency coefficient.(5)Based on the theory of column hole expansion,the lateral displacement calculation formula of the pile side soil is obtained;under certain assumptions,combined with the time-varying viscosity of the Herschel-Bulkley model and the basic equation of uniform flow,the post-injection of the pile end considering the time-varying viscosity is derived Highly analytic solution of the slurry.It can be seen from the calculation formula that grouting pressure,pile length,pile diameter,mud thickness,slurry rheological index,slurry initial consistency coefficient,slurry time-varying coefficient,and grouting time are important factors that affect slurry upflow.Through the analysis of engineering examples,it can be known that:(1)The upward return height of the slurry decreases with the increase of rheological index,and the upward return height of the slurry is closely related to the permeability coefficient of the soil;(2)The initial consistency coefficient of the slurry returns to the upward return of the slurry The change in height is significant,and the upward return of the slurry is basically not affected when it is greater than 30;(3)The maximum value range of the time-varying coefficient of the slurry affecting the upward return of the slurry is 0 ～ 0.015,and the clay is more conducive to the upward return of the slurry;The longer,the lower the height of the slurry.The reasonable selection of grouting time is very important for the effect of grouting behind the pile end;(5)The greater the grouting pressure,the greater the return height of the slurry;(6)The short pile is better than the long pile and the thick pile in the grouting effect behind the pile end Better than thin piles.(7)Increasing the thickness of the mud skin from 0.004 m to 0.02 m can increase the slurry return height by more than 10 times.Finally,the problems of time-varying viscosity of the slurry,comparison of calculated values of different theoretical formulas(slurry back-up),and grouting pressure loss are discussed.(6)Aiming at the upturning height of the slurry in the layered soil,the iterative calculation method of the final upturning height of the slurry is proposed by studying the soil layering around the pile body,and the pressure loss of the slurry during transportation and the upturning height of the slurry are discussed Further corrections are given,and the corresponding expressions of pressure reduction and slurry height correction are given.At the same time,the relationship between grouting pressure loss and pile length and the relationship between slurry viscosity and slurry hydration time are also discussed.The results show that the slurry viscosity increases with the increase of hydration time.(7)Using different theories to compare the research results of this paper,the results show that the calculation results of Dai Guoliang and this paper are less than the calculation results of Nan and Zhang Zhongmiao.Closer to the actual value of the project. |
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