【作者】 邹力；

【导师】 吴兴序；

【作者基本信息】 西南交通大学 ， 岩土工程， 2010， 博士

【摘要】 桩基后注浆包括桩端压力注浆和桩侧压力注浆。该项技术是土体加固技术和桩基工程技术的有机结合,它既克服了灌注桩成孔工艺的固有缺陷,又加固了桩端和桩侧附近的土体,从而大幅度提高了单桩承载力。大量工程实践表明,该技术具有承载力高、适用范围广、施工方法灵活、效益显著和便于普及的特点,是一项提高桩基竖向承载力和减小不均匀沉降的有效技术。本文依托铁道部科技研究开发计划重大课题(2008G032-3)：《京沪高速铁路桥梁桩基后注浆技术试验研究》开展研究。京沪高速铁路沿线大部为软土地区,表层第四系土层厚度20～75m,地质情况极为复杂。如何控制桩基的工后沉降量及沉降特性,保证桩基的承载力成为保证整个工程质量的控制因素。因此,进行桩基后注浆技术来减小桩基础沉降量以及缩短沉降稳定时间的研究非常必要。由于桩基后注浆技术的机理仍不明朗,尤其是关于注浆减小群桩沉降方面的研究更为鲜见。因此,进行桩基后注浆技术来减小群桩基础沉降量以及缩短沉降稳定时间的研究不仅具有重要的理论意义,还具有重要的工程应用价值。故本文针对后注浆群桩基础沉降性状这一课题展开相关研究工作。本文的主要研究工作及相关结论如下：开展了大规模的桥梁长大群桩后注浆现场试验,积累了丰富的实测数据资料,并对实测数据进行了分析研究,得出桩侧注浆与桩端注浆对群桩基础的沉降均起到明显的减小和控制作用,对于缩短固结沉降的时间方面,桩端压力注浆的效果更为稳定；基于现场试验数据,探讨了后注浆对群桩沉降性状的影响机理,运用Vesic理论,探讨了深厚软土层中后注浆桩的浆液对土体产生的影响,提出在深厚软土层中,桩侧注浆对桩周土体的影响较小,桩端注浆能更有效地加固桩周土体,对于长大群桩基础,桩端注浆控制沉降效果良好,甚至可以优于桩侧注浆；结合现场试验,提出了利用注浆后的单桩静载试验结果反推土的参数,然后运用剪切变形传递法计算注浆后群桩基础的沉降量这一方法,并结合当前规范进行了验证；使用FLAC3D程序,开展了后注浆群桩基础三维数值模拟静载试验研究,研究了深厚软土层中注浆后的群桩基础在设计荷载作用内的荷载-沉降规律,以及由注浆引起的桩侧与桩端条件的改变对群桩基础沉降量的影响,得出对于位于深厚软土层中的长大群桩基础,桩侧注浆与桩端注浆均可减小其在正常使用状态下的沉降量,桩端注浆效果更佳的结论；桩端注浆引起的群桩沉降量减小缘于桩端形成的注浆加固体有效地加固了桩端下卧层,同时由于高压浆液沿桩侧桩-土界面上涌,改善了桩端以上一定范围的桩侧界面条件,以及对桩侧土起到了一定的固化作用；采用非参数时间序列模型和多维核函数估计法对深厚软土层中的后注浆与未注浆群桩基础的沉降-时间数据进行了建模与沉降预测,并对时间序列模型进行了适用性分析；分析与预测结果表明,非参数时间序列模型预测效果良好,与传统参数时间序列模型相比,更具工程实用性。更多还原

【Abstract】 Pile foundation post grouting includes both pile end pressure grouting and pile side pressure grouting. This technique is an organic combination of the soil reinforcement technique and the pile foundation engineering techniques, which overcomes the inherent faults of pile foundation hole-making and reinforces the soil mass nearby pile end and pile side so as to substantially raise the pile bearing capacity. A great number of project practices show that this technique is featured by its high bearing capacity, wide application scope, flexible construction methods, significant benefits and easy popularization. It has been proved in practice that it is an effective technique to raise the vertical bearing capacity of bored pile and reduce the pile group differential settlement.The research of this paper is conducted under the Experimental Study of Bridge Pile Foundation Post Grouting Techniques of Beijing-Shanghai High-speed Railway, which is a major subject of science and technology R&D program of China’s Ministry of Railways (2008G032-3). Most areas along the Beijing-Shanghai High-speed Railway are of soft soil; the Quaternary System soil layer at the surface is 20 to 75m thick, with quite complicated geological conditions. It is a controlling factor for guaranteeing the entire project quality to control the settlement after construction and settlement characteristics of pile foundation and to guarantee the pile foundation bearing capacity. Therefore, it is necessary to conduct the research and study of pile foundation post grouting techniques to reduce the pile foundation settlement and shorten the settlement stability time. The mechanism of pile foundation post grouting techniques is still unclear, and the study of the grouting for reducing pile group settlement, in particular, is rare. Therefore, it is of important theoretical values as well as important project application values to conduct the research and study of pile foundation post grouting techniques to reduce the pile group foundation settlement and shorten the settlement stability time. Therefore, researches of the subject of post grouting pile group foundation settlement characteristics are conducted for this paper.The main research work and conclusions of this paper are as follows:a large-scale post grouting field test of long and large pile group has been conducted; abundant measurement data and documents have been accumulated, and measurement data have been analyzed and researched to come to the conclusion that the pile side grouting and pile end grouting have obviously reduction and controlling effects on the settlement of pile group foundation; the effect of pile end pressure grouting on shortening the consolidation settlement is more stable. Based on the field test data, the mechanism of the influence of post grouting on the pile group settlement characteristics is explored; adopting the Vesic theory, the influence of post grouting pile grout on the deep soft soil layer is expounded; it is proposed that the effect of pile side grouting on the soil around pile in deep soft soil layer is small, and the pile end grouting may more effectively reinforce the soil around pile; the effect of pile end grouting in controlling the settlement of long and large pile group is good, even better than the pile side grouting. With consideration given to the field test, it is proposed than soil parameters may be inverted from the results of single pile static load test after grouting, and then the settlement amount of pile group foundation after grouting may be calculated with the shear displacement method, which is verified according to the prevailing technical code. With the FLAC3D program, the research of the three-dimensional numerical simulation static load test of post grouting pile group foundation is conducted; the load-settlement regularities of the pile group foundation in the deep soft soil layer after grouting within the design load, and the influence of the changes of pile side and pile end conditions caused by grouting on the pile group foundation settlement are studied, and it is concluded that, as for the long and large pile group foundation in the deep soft soil layer, the pile side grouting and the pile end grouting may reduce its settlement during normal use conditions, and the pile end grouting is with better effects. The reduction of the pile group settlement caused by the pile end grouting is due to the effective reinforcement of pile end substratum by the grouting strengthening body formed at the pile end; moreover, the upward flow of high pressure grouting along the interface between pile and soil at the pile side improves the pile side interface conditions within a certain scope above the pile end and somewhat solidifies the pile side soil. Time series modeling and settlement prediction are conducted for the settlement-time data of the post grouting and non-grouting pile group foundation in the deep soft soil layer, based on nonparamatic time series model and multi-variate kernel function estimation. Applicability of time-series models is also analyzed. The analysis and results show that:the nonparametric time series model can achieve good prediction results, and is more practicable in engineering by contrast with the conventional parametric time series models.更多还原