Model Test Of Shield Tunnel Backfill Grouting Using Synthetic Transparent Soil

This dissertation, based on the advantage that synthetic transparent soil being able to observe the internal soil deformation, utilizes this characteristic to make the transparent soil as the model soil material in the experiment, and adopts the PIV technology for imaging by laser irradiating transparent soil layer, and the CCD industrial camera to capture images, and uses PIVview2C software to extract and analyze the image information. This dissertation productively integrates the abovementioned theory and technology and physical model experiment and applies it to the model test of shield tunnel backfilling grouting. It conducts preliminary exploratory research on the influence of backfilling grouting on stratum settlement as well as on the filling and diffusion range of the grouting slurry.The main content and the research conclusions of this model experiment research are as follows:1) This dissertation makes a brief introduction to the theoretical basis, material, components and the specific compounding methods for artificial synthesizing the transparent soil. The author synthesized transparent soil used in this model experiment by using melted quartz sand as the granular material and making the solute dissolving in the solvent. The transparency effect of the soil turns worse as the particle size of the melted quartz sand narrows down.2) This dissertation has done a series of experiments on conventional soil property such as the screen test, compression test, direct shear test and triaxial test It studies the basic physical and mechanical property of transparent soil and makes comparison with the standard sand of corresponding grading. Transparent soil of different grading is subject to the same change trend as the frictional angle and compressibility of standard sand soil, with the only difference appearing in the cohesion force as it is bigger in the cohesion force triaxial test than in the direct shear test. The compressibility of transparent soil of different soil is smaller than the standard soil of corresponding grading.3) The dissertation makes a brief introduction to similar theories of physical modelling experiment and PIV technical principle. Based on the research in the abovementioned theories, this dissertation researches and designs the model experiment system, including the test chamber, propelling system, grouting system, laser irradiation, CCD camera imaging information collection system, PIVview2C software information extraction and Origin software reprocessing analysis and other analytical systems.4) This model test, based on the transparent soil, conducts the comparison experiment between the grouted sections of shield tunnel and non-grouted sections and the comparison experiment on grouting pressure. It analyses the sedimentation of the transparent soil layer and the filling and diffusion of the grouting slurry. Subsidence displacement of the grouting layer is much smaller than that of non-grouting slurry. Increased grouting pressure will cause a smaller degree of subsidence of the soil layer but too big grouting pressure will lead to the upheaval of the soil layer. The bigger the grouting pressure is, the better the filling of the grouting and larger diffusion will be. The diffusion under the same grouting pressure, however, hardly changes with the alteration of the depth of the tunnel.