【作者】 王宏贵；

【导师】 徐林荣；

【作者基本信息】 中南大学 ， 道路与铁道工程， 2011， 博士

【摘要】 在深厚软基上修建高等级铁路是世界性难题,沿海地区多条在建及待建的客运专线与高速铁路的软土层厚度超过复合地基处理方法质量可控制的深度范围内。为此,提出长板-短桩复合地基新方法,并依托国家自然科学基金项目“高速铁路无碴轨道桩-筏复合地基固结特性与沉降控制机理研究(51078358)”以及铁路科技研究开发计划项目“客运专线复合加固深层软土技术研究(2008G005-C)”,以甬台温客运专线温州南站大面积深厚软土层处理加固工程为工程背景,采用了模型试验、工艺性试桩试验、现场试验依次递进的试验研究手段,结合理论分析与数值模拟方法,对长板-短桩复合地基的加固机理与工程应用进行了深入系统研究。主要创新成果如下：1.基于相似理论,开展了长板-短桩复合地基大型室内模型试验研究,全面获取了复合地基的变形规律与力学性状；结合数值分析成果,为试验段地基处理方案设计拟定了合理的桩长及桩间距,有效指导了长板-短桩复合地基工程实践。2.实测数据表明试验段路基一直处于稳定状态,工后沉降在规范容许值范围内。这说明采用长板-短桩复合地基处理大面积深厚软土技术上是可行的,为沿海地区铁路客运专线地基处理提供了一种新方法。3.综合分析模型试验及现场测试成果,明确了长板-短桩复合地基加固机理：搅拌桩在减小地基总沉降量的同时,有效的提高了地基稳定性,从而确保施工期的填筑速率；塑料排水板显著提高了地基土固结排水速率与沉降速率,从而可缩短工期或减小工后沉降。4.通过模型试验首次系统测试了长板-短桩复合地基桩土界面荷载传递规律。测试结果表明桩侧摩阻力分布形状基本呈三段直线,桩顶区域承受负摩擦力,中性点约位于L/10处；桩底处桩身轴力很小,即长板-短桩复合地基中的桩可视为纯摩擦桩。5.首次完整测试了填筑期间长板-短桩复合地基桩土沉降差、桩顶及桩底刺入量的发展规律,获取了桩-土-褥垫层承载变形机理。测试结果表明在柔性荷载作用下,长板-短桩复合地基桩顶区域存在负摩擦力,加固区沉降以桩底刺入为王。6.基于长板-短桩复合地基荷载传递规律与变形性状,采用Boussinesq-Mindlin联合求解法计算复合地基下卧层附加应力,建立了长板-短桩复合地基复合层沉降解析计算方法；提出了长板-短桩复合地基复合层固结度解析计算方法。7.采用大型有限差分软件FLAC3D,基于流固耦合理论,考虑桩土相互作用,对长板短桩复合地基开展了数值分析研究,系统验证了本文的试验成果与理论分析成果,全面对比塑料排水板地基、搅拌桩复合地基与长板-短桩复合地基工程性状的差异,并深入研究了搅拌桩长度及置换率对长板-短桩复合地基工程性状的影响作用。更多还原

【Abstract】 It is a global problem to construct high class railway on deep soft soil subgrade, especially for those under or pending construction projects of high-speed passenger railway and high speed railway in coastal areas, which are usually located in soft soil with the thickness exceeding the quality control depth range of composite-foundation treatment method. As a result, the PVD-DMM composite foundation Method is proposed. Based on the project of "High-speed Railway Ballastless Track Pile Raft Consolidation of Composite Foundation Characteristics and Settlement Control Mechanism Research" supported by National Natural Science Foundation, and project of "PDL Composite Reinforcement Deep Soft Soil Technology Research" supported by Railway Technology Research and Development Program, this paper sets engineering background in "Ningbo-Taizhou-Wenzhou" passenger special line located in Wenzhou South Railway Station, featuring large area of deep soft soil, and adopts model testing, workmanship tests of piles, filed tests in turn by experimental research methods. Combining theoretical analysis and numerical simulation method, this paper digs deeper into the reinforcement mechanism and engineering properties of PVD-DMM composite foundation. With major innovation results show as follows:1. Based on the similarity theory, it conducted a large indoor model study of PVD-DMM composite foundation, and gained the deformation and mechanical properties for composite foundation comprehensively; Combined with the testing results of numerical analysis, it worked out reasonable pile lengths and pile spacing for the design of foundation treatment, and guided the engineering practice in PVD-DMM composite foundation effectively.2. The measured data shows that the testing roadbed has been in a stable state constantly, and the post-construction settlement is in the allowed range of regulation. This shows that it is technically feasible to use PVD-DMM composite foundation in dealing with large deep soft soil, which provides a new method for subgrade treatment in coastal high-speed passenger railway.3. Synthesizing the analytical results of the model and field test, it clarifies the reinforcement mechanism for PVD-DMM composite foundation:when the mix pile foundation is reducing total settlement, it improves the foundation stability effectively at the same time, thus, which ensures the filling velocity during the construction period; Plastic drainage plate enhances the rate of the drainage consolidation and sedimentation for foundation soil remarkably, thus, which can shorten the construction period or reduce the post-construction settlement.4. Through model test, the pile-soil interface load transfer law of PVD-DMM composite foundation is system tested first time. Results show that the distribution shape of Skin friction are three straight line, the area of pile top bear negative friction, neutral point located in L/10 position; the axial force of pile body is small in the bottom, which proof pile of PVD-DMM composite foundation can be regarded as the pure friction pile.5. the compaction during the differential settlement between pile and soil of PVD-DMM composite foundation, the development law of pile top and pile bottom stroke amount are First completely tested, obtained the bearing deformation mechanism of pile-soil-cushion. Test results showed that there are negative friction in the pile top area of PVD-DMM composite foundation under the flexible loads, settlement of reinforced area pile primarily contain bottom pierce.6. Based on load transfer law and deformation characters of PVD-DMM composite foundation, Boussinesq-Mindlin joint solving method is used to calculate underlying soil layer additional stress of composite foundation, and a composite layer settlement analytical calculation of PVD-DMM composite foundation is established; a Composite foundation consolidation degree analytic calculation method of PVD-DMM composite foundation is advised.7. Based on the fluid-structure interaction theory, Using a large-scale finite difference software FLAC3D,considering pile-soil interaction, carried out numerical analysis to long board short pile composite foundation, systemic test the result proved in this paper and the theoretical analysis results, comprehensive contrast difference properties among plastic drainage plate foundation, mixing pile composite foundation and long board-short pile composite foundation, and take deeply research on the effect of mixing pile length and replacement rate of long board-short pile composite foundation engineering properties.更多还原