Improvement of the fluidity and setting time of grouting materials has been recognized as an effective approach of seepage prevention in foundation works, and it is quite common to be used for handling severe leakages...Improvement of the fluidity and setting time of grouting materials has been recognized as an effective approach of seepage prevention in foundation works, and it is quite common to be used for handling severe leakages in complex ground conditions, such as loose, broken and fully fissured stratum. For the purposed of better meeting the engineering requirements, experimental studies were conducted in this study with focus on the nanocomposite grouting materials and the related controlled grouting technology. As compared with the commonly used silicate-sulpho-aluminate composite cement, which is characterized by relatively poor rheological property, quick setting time and low strength, the most suitable nano-material with proper reactants were selected intentionally to improve the mentioned attributes of composite cement. Due to the setting time and strength of the targeted cement slurry behaving with poor performance of harmonization to engineering construction problems, hydration synergistic effect of these composites were investigated in our experiments. Results showed that the properties of grouting materials, including initial fluidity, setting time, ideal right-angle thickening, and early strength and late strength were sufficient to produce an expected grouting application. It is therefore advocated that the refined grouting material could provide a better solution to fix grouting problems in complex ground cementing operations.展开更多
The Weng’an Biota, a fossil KonservatLagerst?tte in South China that is c. 570 – 609 myr old, preserves the world’s oldest zoolite and provides a unique empirical record for studying animal origins and early evolut...The Weng’an Biota, a fossil KonservatLagerst?tte in South China that is c. 570 – 609 myr old, preserves the world’s oldest zoolite and provides a unique empirical record for studying animal origins and early evolution. Due to geological disasters caused by the exploitation of the local phosphate mine, part of the fossilized records and the geological sections of the Weng’an Biota have been seriously damaged. Protection of this unique fossil area is urgently required. In this research, an innovative scheme for the protection of the geological relics of the Weng’an Biota is proposed by backfilling the mine cavity with specially formulated grouting materials. In view of the shortcomings of the current grouting materials, such as the high proportion of water separation, the low stone percentage and high cost, newly developed grout materials consisting of mixtures of cement-fly ash-expansion agent(C-F-E) were systematically studied by a combined method of theoretical analysis and experimental study. Firstly, new grouting materials(C-F-E) were developed using selected proportions of(1) Portland cement(P·O 32.5),(2) external admixture(Fly ash),(3) expansion agent(NV) and(4) admixture(DFZ). Then, the properties of new grouting materials(C-F-E), such as stability, stone percentage, rheology, fluidity, setting time and compressive strength were evaluated by laboratory tests. Finally, a new model of the hydration process was proposed for these newly developed grouting materials based on a detailed scanning electron microscopy(SEM) study of their microstructural development. These research results will provide an effective solution to the protection of the geological relics of the Weng’an Biota. Additionally, these grouting materials may prove suitable for solving similar problems in the management of most mine cavities requiring stabilization in the future.展开更多
基金funded by National Natural Science of China (Grant Nos.41672362)Key Projects of Sichuan Provincial Department of Education (Grant No.16ZA0099)the State Key Laboratory of Geohazard Prevention & Geoenvironment Protection (Grant No.SKLGP2017Z011)
文摘Improvement of the fluidity and setting time of grouting materials has been recognized as an effective approach of seepage prevention in foundation works, and it is quite common to be used for handling severe leakages in complex ground conditions, such as loose, broken and fully fissured stratum. For the purposed of better meeting the engineering requirements, experimental studies were conducted in this study with focus on the nanocomposite grouting materials and the related controlled grouting technology. As compared with the commonly used silicate-sulpho-aluminate composite cement, which is characterized by relatively poor rheological property, quick setting time and low strength, the most suitable nano-material with proper reactants were selected intentionally to improve the mentioned attributes of composite cement. Due to the setting time and strength of the targeted cement slurry behaving with poor performance of harmonization to engineering construction problems, hydration synergistic effect of these composites were investigated in our experiments. Results showed that the properties of grouting materials, including initial fluidity, setting time, ideal right-angle thickening, and early strength and late strength were sufficient to produce an expected grouting application. It is therefore advocated that the refined grouting material could provide a better solution to fix grouting problems in complex ground cementing operations.
基金supported by the National Natural Science Foundation of China(Grant No.41672362)the Key projects of Sichuan Provincial Department of Education(Grant No.16ZA0099)the State Key Laboratory of Geohazard Prevention and Geoenvironment Protection(Grant No.SKLGP2017Z011)
文摘The Weng’an Biota, a fossil KonservatLagerst?tte in South China that is c. 570 – 609 myr old, preserves the world’s oldest zoolite and provides a unique empirical record for studying animal origins and early evolution. Due to geological disasters caused by the exploitation of the local phosphate mine, part of the fossilized records and the geological sections of the Weng’an Biota have been seriously damaged. Protection of this unique fossil area is urgently required. In this research, an innovative scheme for the protection of the geological relics of the Weng’an Biota is proposed by backfilling the mine cavity with specially formulated grouting materials. In view of the shortcomings of the current grouting materials, such as the high proportion of water separation, the low stone percentage and high cost, newly developed grout materials consisting of mixtures of cement-fly ash-expansion agent(C-F-E) were systematically studied by a combined method of theoretical analysis and experimental study. Firstly, new grouting materials(C-F-E) were developed using selected proportions of(1) Portland cement(P·O 32.5),(2) external admixture(Fly ash),(3) expansion agent(NV) and(4) admixture(DFZ). Then, the properties of new grouting materials(C-F-E), such as stability, stone percentage, rheology, fluidity, setting time and compressive strength were evaluated by laboratory tests. Finally, a new model of the hydration process was proposed for these newly developed grouting materials based on a detailed scanning electron microscopy(SEM) study of their microstructural development. These research results will provide an effective solution to the protection of the geological relics of the Weng’an Biota. Additionally, these grouting materials may prove suitable for solving similar problems in the management of most mine cavities requiring stabilization in the future.
