Abstract
Diffusion radius is an important construction parameter, because it can significantly influence the grouting effectiveness. Theoretical models in predicting diffusion radius have been practiced, but there are still significant discrepancies between theoretical calculations and realistic results in the practical construction. One of the critical reasons for the misprediction is the time-dependent behavior of the cement grout, which is significantly affected by the water-cement ratio (W/C). Therefore, this paper experimentally and numerically studies the influence of W/C on the viscosity variation of the grout and grouting process. Firstly, the apparent viscosity of the cement grout under different W/C is tested by a rotational viscometer in a laboratory experiment. Subsequently, based on the laboratory tests, numerical models are established to investigate the influence of W/C on the diffusion process of cement grout in sand layers. According to the laboratory results, the apparent viscosity of cement grouts decreases with the increase of W/C. Besides, the apparent viscosity increases with time, while the increasing range of apparent viscosity firstly increases and then decreases as W/C increases. Based on the simulated results, when W/C changes from 0.8 to 1.1, the diffusion radius at 60 min experiences a less and less obvious increase under the given grouting pressure for permeation grouting in the sand layer. When W/C is 0.9, the relative error reaches to 37.65% at 60 min, which is slightly lower than that of 0.8. However, when W/C changes from 0.9 to 1.0, the relative error becomes very narrow (21.36%), and this figure is much lower than that of 0.8 or 0.9. The simulation results are verified by field test, and the relative error is 6%, which proves the effectiveness of the analysis. Therefore, the cement permeation model considering viscosity variation of the grout is a reasonable alternative in the real project. At the same time, the time-dependent behavior of cement grouts should be considered, especially when using cement grouts with a low water-cement ratio in the practical engineering.
Highlights
Unfavorable foundation is a common problem in civil engineering and transport engineering
It is found that the average error of the slurry diffusion radius between the simulation results and the field test results is 6%, and the simulation results are in good agreement with the test results, which verifies the analysis conclusions in this paper
In order to investigate the viscosity variation of cement grouts under different water-cement ratio (W/C) and the influence of W/C on the permeation grouting process in the sand layer, this paper carried out laboratory experiments and numerical simulations
Summary
Unfavorable foundation is a common problem in civil engineering and transport engineering. Permeation grouting with cement grouts has been widely utilized for foundation improvement because of its simple construction and high efficiency [1,2,3]. A reasonable estimation of grouting parameters before practical engineering will help grouting construction meet requirements at a relatively low price. In order to improve the accuracy of calculation, scholars have investigated permeation grouting from different points of view. Yang et al [5] and Ye et al [6] established theoretical models based on different constitutive models of flow pattern and deduced the calculation formulas for diffusion range or grouting pressure for permeation grouting. Celik [7] investigated the features of cement-based permeation grout based on some important grout parameters, such as the rheological properties, coefficient of permeability to grout, and injectability of cement
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