季冻区沼泽草炭土冻胀机理研究

The study on frost heave is always a hot subject in the frozen soil research field, it has great difference in frost heave characteristics to each kind of soil. With the high speed development of our country economic, much many new-constructed highways inevitably pass through turfy soil areas. Through investigation on behavior to the completed and used highway in turfy soil district, it has been discovered that roadbed has been great settlement and engendered a great deal of disease caused by the extruded the basis of roadbed such as lateral sticking out or cutting crack to squeeze out, roadbed sliding caves in, heave frost, road surface net crack and so on. Therefore, it may be necessary to analyze the mechanics of frost heave of turfy soil on the basis of laboratory experiments. The study according to the geological environment of swamp turfy soil in seasonal frozen region, combine with the characteristic of engineering construction. Base on the winter freeze-thaw turfy soil field experiment outside, that getting the physical mechanical properties index, thermodynamic parameter and chemical property. Though the laboratory of turfy soil frost heave by different degree of decomposition, organic matter content, moisture content, temperature, the frost heave characteristics under different influencing factors can be get. Experiments of frost heave under different conditions are tested in laboratory to get index of each sample which can show the degree of frost heave, namely, the ratio of frost heave. Microstructure parameters of each sample are selected and quantitative analysed by WD-5 SEM before tests. From the perspective of macro and micro, frost heave mechanism of turfy soil in the season frozen can be summed up. Combined with the macroscopic and microscopic parameters, establish frost heave prediction model of turfy soil in season frozen zone.It may be provided the reasonable grounds and design consideration for line engineering construction of turfy soil in season frozen zone.

土体冻胀一直是冻土研究领域的热门课题，不同性质土的冻胀特性有很大差异。沼泽草炭土是一种富含植物纤维的具有特殊性质的土，其工程特性与其他类型土有着本质的区别，这些特性导致季冻区沼泽草炭土地区的路基经常出现一系列的病害问题，从而影响到其安全与正常使用，因此有必要对草炭土冻胀特性进行研究。本项研究主要以现场地质调研及室内外试验为前提，测试和分析研究区草炭土的物理力学性质指标、化学性质指标和热力学参数；通过对不同分解度、有机质含量、含水率、温度的草炭土进行室内冻胀试验，研究草炭土在不同影响因素下的冻胀特性；利用扫描电镜及分析软件对图片进行定量分析，揭示季冻区沼泽草炭土产生冻胀的微观本质，从宏观和微观角度总结出季冻区沼泽草炭土冻胀机理，结合宏观及微观参数，建立季冻区沼泽草炭土冻胀预测模型，为季冻区沼泽草炭土地区的线路工程建设提供较为合理的理论基础与设计依据。

沼泽草炭土是一种富含植物纤维的具有特殊性质的土，其工程特性与其他类型土有着本质的区别，这些特性导致季冻区沼泽草炭土地区的路基经常出现一系列的病害问题，从而影响到其安全与正常使用，有必要对草炭土冻胀特性进行研究。因此，本项目采用理论分析，室内试验和模型模拟结合的方法，对季冻区沼泽草炭土的冻胀特性展开研究，主要研究成果如下：.（1）研究了季冻区沼泽草炭土的工程性质。测试和分析了研究区草炭土的物质组成、物理性质指标、化学性质指标和热力学参数。.（2）研究了季冻区沼泽草炭土的冻胀特性。采用冻胀试验，分析草炭土在不同有机质含量、不同含水率、不同温度下的冻胀特性, 不同有机质含量草炭土的冻胀率总体上是随着含水量的增加而提高，随着温度逐渐降低，在相同有机质含量范围内，草炭土的冻胀率随冻结温度降低而增大。通过扫描电镜分析了沼泽草炭土冻结前后的微观结构特点，利用图片分析软件，从微观角度对草炭土冻胀机理进行了揭示。通过对宏观试验所测数据的整理分析，利用SPSS统计分析软件，建立了各因素与冻胀率的回归方程。.（3）建立了草炭土冻胀的神经网络预测模型。利用粗糙集理论和基于灰色关联分析理论，采用灰色关联度分析孔隙率、含水量、温度、有机质含量4 个因素对草炭土冻胀率的敏感性，结果发现，季冻区沼泽草炭土冻胀率敏感性影响大小的因子依次为含水量、温度、有机质含量和孔隙率，即土体冻胀率受土体自身特性的影响最大。结合宏观影响因素及微观结构参数，用神经网络方法代替数学方法建立了草炭土冻胀预测模型, 避免了数学建模确定复杂的函数参数和建立一系列假设条件,更真实地反映了草炭土的冻胀特征。通过模拟可以看出，考虑有机质含量的自适应神经模糊系统的季冻区草炭土冻胀预测模型具有良好的泛化能力和容错能力，通过预测数据与试验数据对比分析表明该预测模型能够很好的描述草炭土各参数对冻胀的影响。