Study On The Performance Deterioration Of Filling Slurry And Mechanism Of Freezing Pipe Sinking Blocked During Freezing Hole Sealing

With whole depth freeze sinking technology is widely used in shaft construction of watery strata, further research about the technology of freezing hole sealing needs to be done to reduce the loss caused by failure of freezing pipe sinking. In this thesis, a method combining indoor experiment, numerical simulation, physical simulation and theoretical analysis was applied to study on the performance deterioration of filling slurry and mechanism of freezing pipe sinking blocked during freezing hole sealing.Firstly, based on the existing formulation of retarding grout and drilling slurry, taking apparent viscosity as the deterioration index, indoor experiment has been done to study the performance degradation process of retarding grout and mixing slurry. The increase of the viscosity of retarding grout is mainly influenced by curing temperature initially and time afterwards. The viscosity of slurry increases faster under permeable environment, including three periods, respectively mainly influenced by curing time, permeable environment and curing time. The viscosity of mixed slurry increases initially and decreases afterwards along with the increasing of curing temperature when the time is less than 20 h. With the increase of curing time, the viscosity of mixed slurry and retarding grout increases linearly. Compared with retarding grout, the mixed slurry is influenced more significantly by time and permeability. With the increase of volume fraction of retarding grout, the change of the viscosity of mixed slurry is complicated. Put at 40 degrees celsius for 10 hours without dehydration, the apparent viscosity of the mixing slurry consisting of 1/3 regarting grout and 2/3 drilling mud is 1251.18 m Paï¹'s, and the apparent viscosity of regarting grout is 243.68 m Paï¹'s. On the basis of significance from large to low, the influencing factors of performance degradation of the retarding grout are in turn as follow: permeable environment, curing time, curing temperature. Similarly the factors of performance degradation of the retarding grout are as follow: permeable environment, mixing volume fraction, curing time, curing temperature.Secondly, through the numerical simulation of the change regulation of mixing height when the mud is being replaced by cement slurry in annular space, it is found that along with the increasing of slurry injection flow, cement slurry height in annular space, roughness of freezing hole wall and freezing hole diameter, the mixing height respectively presents the trend of increasing initially decreasing afterwards, increasing, decreasing initially increasing afterwards flatting finally and increasing initially decreasing afterwards. Compared with mud viscosity, the change of the retarding grout viscosity has greater impact on mixing height. When the mud is being replaced by cement slurry in annular space, on the basis of significance from large to low, the influencing factors of mixing height are in turn as follow: cement slurry height in annular space, slurry injection flow, freezing hole diameter, and roughness of freeze hole wall. The distribution law of the mixed segment can be got through physical simulation on the replacement process. The results of numerical simulation are smaller comparing to that of physical simulation.Thirdly, numerical simulation of the process how the slurry in annular space flows upward when freezing pipe is sinking has been conducted to get the flowing regulation of the slurry. Along with the increasing of inking velocity of freezing pipe, external diameter of freezing pipe, diameter of freezing hole, slurry viscosity and density, the shear rate of slurry in annular space to freezing pipe respectively presents the trend of increasing, increasing, decreasing, increasing and decreasing. With the increasing of eccentricity, the shear rate to the pipe of the widest and narrowest gap in annular space respectively presents the trend of increasing initially decreasing afterwards, decreasing initially increasing afterwards. When the eccentricity is greater than 0.6, the narrowest gap becomes stagnating flow region. The main influencing factors of the shear rate of the slurry in annular space are as follow: sinking velocity of freezing pipe, external diameter of freezing pipe, diameter of freezing hole.Fourthly, on the basis of previous studies, the mechanical model for sinking process of freezing pipe is built to analyze whether the pipe can sink to the bottom of the freezing hole for the typical engineering example. The analysis results are in agreement with the actual engineering results. The mechanism of freezing pipe sinking blocked is achieved. The fundamental reason is that the mixing slurry is widespread and serious, meanwhile it reacts thickening and flocculation. The most important reason is that the annulus space outside the freezing pipe is too small, which causing the shear rate to be too large, producing large viscous resistance, finally resulting in difficuty for slurry to flow upward. In order to sinking the pipe successfully, some technical measures are proposed.The grouting speed shuold be reduced appropriately to decrease the mixed height and degree. The aperture diameter and pipe size should be matched reasonably to provide enough annular space. Last but not least, the eccentricity ratio of the pipe should be reduced.Finally, through indoor experiment, the existing formulation of retarding grout has been improved, to reduce viscosity of retarding grout.