【作者】 王宏祥；

【导师】 闫澍旺；

【作者基本信息】 天津大学 ， 岩土工程， 2009， 博士

【摘要】 我国在内蒙古高寒地区存在大面积的湿地。由于经济开发和国防的需要,有些高速公路需要穿过湿地区域。由于湿地范围内的地基土表面为软粘土覆盖,需要经过处理才能高速公路的路基。高寒湿地路基的处理需要考虑的问题比较复杂,需要考虑当地的工程地质特点,冻胀影响,对环境的影响等因素,需要采用新的技术和方法。本文研究了利用强夯置换墩处治高寒湿地公路软基方法的技术机理与方法,并结合内蒙古海满一级公路二卡湿地实际工程建设中存在的一些关键技术问题,为强夯置换墩处治高寒湿地公路软基的设计和施工提供了依据及指导。工程实践已经验证了本文提出的方法的可行性和有效性。本文研究的主要成果如下:(1)采用数值分析、现场施工检测试验等手段,对强夯作用机理、强夯置换墩的成墩机制、强夯碎石墩复合地基的破坏形态、强夯碎石墩复合地基路堤稳定与变形影响因素等进行了分析,揭示了强夯开山石混合料置换墩处治湿地软基作用机理。(2)研究了强夯对软土地基的作用机理,得出了强夯冲击荷载和孔洞扩张作用使软土中产生高值超静孔隙水压力,造成软土发生水力劈裂作用,这种作用使软土的渗透性增加,使超静孔隙水压力迅速固结,达到了地基土强度增长的目的。(3)通过对复合地基承载力计算方法和路堤稳定性分析方法的对比分析,结合现有研究成果,推荐出了强夯置换墩复合地基承载力计算方法和路堤稳定性分析方法;基于极限平衡法,建立了散体材料变截面墩体极限承载力计算公式,为强夯置换墩这类散体材料变截面墩承载力计算提供了一种新的思路。(4)结合现场试验和依托工程施工,提出了强夯置换墩复合地基的施工工艺、质量检测手段、控制指标和要求。(5)通过数值分析和工程实践,得出强夯置换墩对地基渗透性没有影响,符合湿地保护要求。(6)基于对地温的实测分析,提出了高寒湿地路基冻胀防治措施,并通过实际工程检验了措施的有效性。(7)通过本文的研究提出强夯置换墩是处治高寒湿地软基的一种可行有效的方法。更多还原

【Abstract】 There lies a large amount of wetland in the alpine cold districts of the Inner Mongolia in our country. For the sake of economic development and the national defense, the expressway will extend through these areas. However, the soft clay foundation of the wetland cannot be used as the embankment only after appropriate treatment. Due to its complexity of the treatment , a series of issues need to be carefully studied, which include the local geological conditions, negative effect from the frost heave soil and environmemt destruction. New technique and method should be introduced to address these issues. Applying with the soft subgrade treatment mechanism and methodology on dynamic compacted piles in the alpine wetlands, this thesis is to provide theoretical data and guideline for soft subgrade design and construction in alpine wetlands replaced by the dynamic compaction methods. Some key technical issues have been illustrated for Erkar Wetland along Haiman Class I Highway in Inner Mogolia Autonomous Region. The study proposed in the thesis has been testified by some physical engineering works for its feasibility and efficiency. After the study, achievements have been made in the following aspects:(1) With the application of dynamic compaction, analysis is made on its functional mechanism, formation of dynamic compacted displacement piles, destructive pattern of macadam composite foundation and factors afftected the embankment stability and deformation of the macadam piles composite foundation. Soft subgrade treatment mechanism is envisaged for the alpine wetland replaced by dynamic compacted stone mixture piles.(2) Studies are made on the functional mechanism of soft subgrade treated by dynamic compaction. High-value and ultra-static pore water pressure is developed in the weak subgrade after impact load from dynamic compaction and the pore-cave expansion, which results in the hydraulic fracturing of the weak subgrade. Subgrade strength has thus been intensified with the increase of permeability of the soft soil and the instant solidation of the ultra-static pore water pressure.(3) Analysis is made to compare the calculation method of bearing on composite foundation and the analysed method of the embankment stability. Similar methodologies have been proposed by the replacement of dynamic compacted piles. Calculation method of ultimate bearing capacity of discrete material pile with variable cross-section is formulated by the application of limit equilibrium method. A new calculation method is developed for the afore-mentioned bearing capacity.(4) Construction technique, quality ensurance measures and indicators are proposed for quality control of the displaced pile composite foundation by dynamic compaction supported with the tests in-situ and an engineering works.(5) Data are analyzed and works investigated to prove that no negative effects have been shown to the permeability of the embankment by the application of dynamic compacted displacement.(6) Preventive measures for subgrade frost swelling in alpine wetlands are proposed after the test in-situ and analysis of the ground temperature. Its efficiency has been proved by an on-going engineering works.(7) The study shows that displacement by dynamic compaction is a practical and efficient measure for treatment of soft soil subgrade in alpine wetlands.更多还原