【作者】 刘栋；

【导师】 崔溦； 迟守旭；

【作者基本信息】 天津大学 ， 水利工程， 2019， 硕士

【摘要】 注浆是改善不良地质条件的重要手段,砂土地层中普通水泥可灌性较差,化学灌浆可灌性好,凝结时间可以控制,但对环境有一定毒性。硅溶胶特别适应于孔隙率小的砂土地层,但加固后强度略低。改性硅溶胶可以避免上述缺陷,是近年来发展起来的一种性能优越的灌浆材料。岩土体中注浆需要特别关注的一个重要问题是注浆过程中的次生危害,由于改性硅溶胶浆材凝结时间很快,材料在较短时间内由液态变为固态,进而显著改变灌后复合地层性质,由此引起注浆压力、基础响应的改变必须引起重视。以室内材料性能试验、灌浆试验为基础,基于相变理论,采用数值模拟技术研究了灌浆过程中改性硅溶胶浆液相态变化以及由此引起的基础响应,包括变形及塑性破坏,以优化注浆工艺。主要研究内容如下:(1)从凝胶化学反应机理出发,研究改性硅溶胶凝胶时间影响因素,通过室内配比实验,初选符合指标要求的改性硅溶胶配比,并通过室内性能试验,研究了改性硅溶胶的加固性能和相变规律。(2)研发了室内二维砂土灌浆模拟试验装置,研究有无地下水影响改性硅溶胶在砂土介质中扩散规律和范围,研究了硅溶胶固砂体的成形机制和相变特性。(3)建立改性硅溶胶在砂土中灌浆的二维数值模型,基于相变理论和流固耦合,研究浆液在砂土中扩散的动态规律及应力场,渗流场与位移场的时空规律以及相变后复合地层性质的改变,由此引起后续注浆位移变形重分布。(4)通过改性硅溶胶在新疆输水工程引水隧洞中的应用,表明改性硅溶胶在与砂土介质性质类似的强风化岩地层中可灌性好,在异常条件下凝结时间可靠,浆液相变后复合地层渗透性等特性符合工程实践要求,应用前景广阔。理论分析和工程实践结果表明:改性硅溶胶浆液扩散性好,凝结时间可靠;地下水条件下浆材灌后在25min时间内发生相变,相变后复合地层特性发生明显变化,并显著影响后续注浆的基础变形和位移分布。更多还原

【Abstract】 Grouting is an important means to improve unfavorable geological conditions.Ordinary cement in sand layer can be poorly irrigated.Chemical grouting materials which has certain toxicity to the envronment have low viscosity,and condensation time can be controlled.Silica sol is especially suitable for sand and soil layers with low porosity.But the strength of silica sol is slightly lower after reinforcement.The modified silica sol can avoid the above defects and is a superior grouting material developed in recent years.An important issue that needs special attention in grouting in rock and soil is the secondary hazard during the grouting process.Due to the fast setting time of the modified silica sol slurry,the material changes from liquid to solid in a short time,which significantly changes properties of the composite stratum after grouting.Therefore,the changes of grouting pressure and foundation response have to be paid attention to.Based on the indoor material performance tests,grouting tests and the phase transition theory,the change of phase state of the modified silica sol slurry during the grouting process and the results in foundation response,including deformation and plastic damage,were studied by numerical simulation to optimize the grouting prcess.The main research contents are as follows:(1)Based on the mechanism of gel chemical reaction,the influencing factors of modified silica sol gel time were studied.Through the indoor mix ratio experiments,the mix ratio of modified silica sol meeting the requirements of the index was selected.The reinforcement performance and phase transformation rule of modified silica sol were studied through laboratory performance tests.(2)The indoor two-dimensional sand grouting simulation test device was developed to study the diffusion law and phase transformation range of modified silica sol in sand media with or without groundwater.The forming mechanism and phase transition characteristics of silica sol sand body were studied.(3)A two-dimensional numerical model for modified silica sol grouting in sand was established.Based on phase transition theory and fluid-solid coupling,the dynamic law of slurry diffusion in sand,space-time law of stress field,seepage field and displacement field were studied.And the property change of the composite formation after phase transformation were studied,thereby causing redistribution of subsequent grouting displacement and deformation.(4)The application of modified silica sol in diversion tunnel of water conveying project in Xinjiang shows that the modified silica sol has good potability in highly-weathered rock strata with properties similar to sand,reliable condensation time under abnormal conditions.The properties(like permeability)of the composite formation after phase change of slurry conform to engineering requirements,which has broad application prospects.The theoretical analysis and engineering practice results show that the modified silica sol slurry has good diffusibility and reliable setting time.The phase transformation occurs in the 25 min period after the slurry material is poured under ground water condition.The formation characteristics changes obviously after the phase transformation of slurry,which significantly affects the base deformation and displacement distribution during the subsequent grouting.更多还原