| With the rapid development of the world economy,the level of urbanization in our country has been deepening,which makes the pressure of large and medium-sized urban traffic increase and land resources become increasingly scarce,which directly restricts the process of urban development.Therefore,the development and utilization of underground space and the strengthening of urban rail transit construction have become an important means of improving urban construction at this stage,but the construction of underground works will inevitably have a certain impact on existing buildings and surface facilities,while the injection behind the underground space wall Pulp and filling can effectively improve the sedimentation of the earth's surface.The new grouting material is a double-slurry underground filling material with excellent characteristics such as rapid setting,early strength and easy transportation.It is widely used in foundation treatment,rock mass reinforcement,port engineering,mine environment and back wall grouting.With the extensive use of grouting materials,domestic and foreign scholars are also committed to the in-depth study of the performance and mechanism of underground grouting materials.Based on the research of the project group,the hydration reaction mechanism of 5h,1d,3d,7d and 28 d of the new grouting material with water cement ratio of 1.5:1 was analyzed and studied by XRD diffraction pattern.Based on the CEMHYD3 D program,the computer software program is used to complete the compilation of image processing program,autocorrelation function calculation program,particulate phase dispensing program and hydration model program in the three-dimensional hydration model of new grouting material,which can be used to construct the three-dimensional micro-hydration model of new grouting material and simulate its hydration reaction process,and a new grouting material was established on the basis of the strength model of "glue-air ratio".Strength prediction model of different age of material achieves the purpose of predicting its compressive strength.The main research contents and conclusions are as follows:By studying the hydration reaction of sulphoaluminate cement,the hydration products of each component were obtained,and the XRD test was carried out on a new grouting material with a water-cement ratio of 1.5:1.The hydration products of different ages were analyzed,and the hydration reaction equation of each stage was written.The results show that the hydration products of the new grouting materials for 5h and 1d are mainly ettringite and hydrated calcium sulphoaluminate hydrate,while the hydration products of 3d have low-sulfur hydrated sulphoaluminate.The main reason is that as the hydration reaction deepens,the hydrated calcium sulphoaluminate hydrate formed by the reaction gradually forms low-sulfur hydrated calcium sulphoaluminate,so that the compressive strength of the stone body is continuously increased.The hydration products of 7D and 28 d are mainly ettringite and garnet.The reason is that in the gypsum lime environment,the tricalcium aluminate contained in the new grouting material first converts into calcium aluminate hydrate,and then gradually reacts to form hydrogarnet.At the same time,in the environment of gypsum,hydrogarnet will react with it to form ettringite,so that the strength of the stone body will still increase after 28 days.The new grouting material was made into a SEM sample by epoxy resin,and the phase distribution of the material during hydration was simulated.After cutting and grinding,the test was carried out to obtain a two-dimensional image of the initial hydration.Through the low vacuum mode image acquisition + energy spectrum analysis(surface analysis mode)test of the sample of the new grouting material,the SEM electron microscopy image and the phase distribution information of each element in the region was obtained,and the initial two-dimensional images are the basis of image processing.The area fraction and circumference fraction of phase particles used in three-dimensional hydration model of new grouting materials were obtained by phase recognition and image processing of two-dimensional images.The volume fraction and surface area fraction of phase particles used to construct three-dimensional microstructure were obtained based on stereological principle.Based on the CEMHYD3 D hydration program,the image processing program,autocorrelation function calculation program,particle phase placement program and hydration model program for the new grouting material were programmed by computer program,and the 3D microscopic hydration simulation model was established.The particle size distribution of the phase particles of the new grouting material was measured.Based on this,the phase particles were placed in the three-dimensional hydration model,and the hydration model was adjusted by calculating the hydraulic radius and the autocorrelation coefficient between the phases.The volume fraction and surface area fraction of the phase were simulated according to the experimental environmental conditions,and the hydration reaction of the new grouting material was obtained.The hydration degree of each age provides experimental basis for the establishment of strength prediction model of new grouting material.Using the hydration degree of each grouting material obtained in the threedimensional hydration model at various ages,the strength prediction formula was established by using the “glue-to-air ratio” model,and the compressive strength value was predicted.At the same time,according to the strength value measured by compressive strength test,Matlab numerical fitting was applied to the strength prediction model,which corrected the effect of the early aging of the new grouting material due to the addition of early strength agent,and obtained new grouting.The strength prediction formula of the material can more accurately predict the compressive strength values of the new grouting materials at different ages.There are 27 figures,12 tables and 87 references in the thesis. |
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