【作者】 周明涛；

【导师】 李建林； 许文年；

【作者基本信息】 武汉大学 ， 水工结构工程， 2010， 博士

【摘要】 在西部大开发战略的推动下,我国西部高寒地区的基础建设日益增多,众多基础设施在给人们生活及生产带来便利的同时也无情的毁损了沿途的陆地植被,并形成了大面积的无植被覆盖的裸露边坡。植被混凝土作为一种优良的人工生态基材,可修复陆地边坡受损植被并对其进行浅层防护,然而从其应用的地域范围来看,当前它仅实施在我国华南、华中及西南等气温条件较高的地区。考察国内边坡植被修复的其它常用人工基材,其应用区域工况与植被混凝土大致相仿,至今尚未发现成功修复高寒地区边坡植被的相关报道。基于此,本文以植被混凝土为研究对象,在试验研究其冻胀与融沉特性的前提下,结合水泥土抗冻改良措施,提出了高寒地区受损陆地边坡植被修复的适宜人工生态基材。论文的主要工作内容如下：(1)以冷端温度T、含水率ω、植生土土质为影响因素,对植被混凝土进行不同水平的单因素和三因素四水平正交冻胀试验,着重探讨植被混凝土在不同初始条件下单向冻结时冻胀率与各因素之间的变化关系。试验结果表明,植生土土质、含水率与冷端温度对植被混凝土的冻胀特性均有所影响,且其影响的强弱顺序为：植生土土质>含水率>冷端温度；含水率增大或冷端温度升高,植被混凝土的冻胀率均增大,但对于粘土配制的植被混凝土而言,含水率中间存在一个转折点,在转折点两边不同的范围内,冻胀率的变化幅度存在较大差异；其他条件都相同时,粘土配制的植被混凝土的冻胀效应明显强烈于砂土配制的植被混凝土；以上述结论为基础,建立植被混凝土冻胀预报综合模型。(2)在冻胀试验的基础上,以冷端温度T、含水率ω、植生土土质、融化温度T’为影响因素,对植被混凝土进行不同水平的单因素和四因素四水平正交融沉试验,着重探讨植被混凝土在不同初始条件下双向融化时融沉系数与各因素之间的变化关系。试验结果表明,植被混凝土的融沉特性受植生土土质、含水率与冷端温度的影响较大,而几乎不受融化温度的影响,且此四因素对其影响的强弱顺序为：植生土土质>含水率>冷端温度>融化温度；含水率增大或冷端温度升高,植被混凝土的融沉系数均增大,但对于粘土配制的植被混凝土而言,含水率中间存在一个转折点,在转折点两边不同的范围内,融沉系数的变化幅度存在较大差异；其他条件都相同时,粘土配制的植被混凝土的融沉效应明显强烈于砂土配制的植被混凝土；以上述结论为基础,建立植被混凝土融沉预报综合模型。(3)将植被混凝土冻胀与融沉试验结合在一起,探讨其冻融前后抗剪强度与体积变化状况。试验结果表明,冷端温度的变化对植被混凝土抗剪强度指标粘聚力及内摩擦角的影响均较大；含水率仅对植被混凝土粘聚力的影响较大,而对其内摩擦角的影响却比较小；融化温度对植被混凝土抗剪强度的几乎没有影响；植被混凝土在经历一个完整的冻胀与融沉过程后,其试样总体积变化不大,冻融作用仅对基材内部微观结构产生了强烈扰动。(4)借鉴上述研究成果,在不改变植被混凝土现有配比的前提下,以棕纤维、硅粉及表面活性剂为影响因素,对其进行单因素和三因素五水平正交抗冻改良试验,着重探讨不同因素与水平影响下植被混凝土的质量损失率及相对动弹性模量。试验结果表明,棕纤维、硅粉和表面活性剂均可影响植被混凝土的抗冻性能,且其影响的强弱顺序为：棕纤维>表面活性剂>硅粉；经过试验优化和验证,得出对植被混凝土抗冻性能增强效益最为显著的复合抗冻改良剂为棕纤维：硅粉：表面活性剂=11:3：0.05,且当掺入量为植生土干质量的1.5%时,改良植被混凝土的抗冻性能约是改良前的4倍；改良植被混凝土植物适应性分析结果显示,由棕纤维、硅粉和表面活性剂复合而成的抗冻改良剂不会对植物生长产生较大影响。本文针对植被混凝土这一常用人工生态基材,试验研究了其冻胀与融沉特性,并提出了最优抗冻改良剂配比方案及其掺入比,从而在国内首次得出了高寒地区边坡植被修复的适宜人工生态基材。论文研究成果除了对高寒地区陆地边坡植被的修复具有重要的实用价值和理论指导意义之外,其试验设计方法亦可为其它类似人工生态基材的冻融试验研究提供经验参考。更多还原

【Abstract】 The infrastructure constructions through or located in alpine area of our country are gradually increasing for the promotion of the western development strategy. These infrastructure constructions are benefit for human life and production, but at the same time they have damaged vegetations and led to a large amount of bare slopes too. As an excellent artificial ecological material, the main function of the vegetation-growing concrete is to restore vegetations by shallow layer protection. At present it was only implemented in part of the high temperature areas, such as the south China, the central China and the southwest of China. There were few reports about the successful ecological restoration through the common artificial ecological materials in domestic which have the similar working condition with vegetation-growing concrete.For the reason above, the vegetation-growing concrete is chosen as the research object to study the frost-heave and thaw-settlement properties of vegetation-growing concrete firstly. As well, it is tested for the anti-freeze and improvement combined with the measures of cement soil. The specific works and main research achievements are as follows:(1)Taken cold-end temperature, water content and plant generate as the influence factors, frost-heave experiments are carried out by different levels of single factor and orthogonal four levels of three factors for the vegetation-growing concrete, and it emphatically discusses the relationship between the frost-heave ratios and various factors in different initial conditions in the course of unidirectional freezing. Result shows that cold-end temperature, water content, plant generate all influence the frost-heave properties of the vegetation-growing concrete. The order of influence intensity by various factors is as follows:plant generate> water content> cold-end temperature. The frost-heave ratios of the vegetation-growing concrete will increase with the raising of the water content and cold-end temperature. But for the vegetation-growing concrete composed with clay, there is a turning point for water content. And in the two sides of this point, the frost-heave ratio takes on a large difference. Under the same conditions, the frost-heave effect of vegetation-growing concrete composed with clay is greater than that composed with sand. Then, the paper makes prediction models of frost-heave for vegetation-growing concrete.(2)On the basis of the frost-heave test, taken cold-end temperature, water content, plant generate and thawing temperature as influence factors, thaw-settlement experiments are carried out by different levels of single factor and orthogonal four levels of four factors for the vegetation-growing concrete, and it emphatically discusses the relationship between the thaw-settlement coefficients and various factors in different initial conditions in the course of bidirectional thawing. Result suggests that cold-end temperature, water content and plant generate all obviously influence the thaw-settlement characters of vegetation-growing concrete, while thawing temperature almost has no influence on them, and the order is as follows:plant generate> water content> cold-end temperature> thawing temperature. The thaw-settlement coefficients of the vegetation-growing concrete will increase with the raising of water content and cold-end temperature. But for the vegetation-growing concrete composed with clay, there is a turning point for water moisture too. And the thaw-settlement coefficient has a large difference in the two sides of this point. Under the same conditions, the thaw-settlement effect of vegetation-growing concrete composed with clay is greater than that composed with sand. Then, the paper makes prediction models of thaw-settlement for vegetation-growing concrete.(3)Combined with experiments of the frost-heave and the thaw-settlement for vegetation-growing concrete, the paper discusses the changes of shear strength and volume. Result indicates that the change of cold-end temperature has great influence on the shear strength indexes. Water content only has great influence on the cohesion, while the influence on the internal friction angle is not obvious. Thawing temperature almost has no influence on the shear strength indexes. There are little changes in volume after a complete process of frost-heave and thaw-settlement, while the micro structure of the material is disturbed obviously by the freezing and thawing action.(4)In the premise of without altering the proportions of raw materials, taken palm fiber, silica powder and surfactant as influence factors, anti-frost and improvement experiments are carried out by different levels of single factor and orthogonal five levels of three factors for the vegetation-growing concrete, and it emphatically discusses the mass loss and relative dynamic elastic modulus of the vegetation-growing concrete influenced by various factors under different conditions. It shows that the palm fiber, silica powder and surfactant all influence the frost resistance property of the vegetation-growing concrete. The order of the influence is as followed:the palm fiber> surfactants> silica powder. It also indicates that the best additive agent to improve the frost resistance property of the vegetation-growing concrete as followed:palm fiber:silica powder:surfactant=1:3:0.05. While the additive amount reaches 1.5% by weight of the dry plant generate, the frost resistance property of the vegetation-growing concrete can be improved about three times. It also shows that this additive agent hardly influences on plant’s growth though the plant adaptability analysis of improved vegetation-growing concrete.Basis on the artificial ecological material of vegetation-growing concrete, the paper obtains the frost-heave and the thaw-settlement characteristics, and puts forward an optimal method and mixing proportion of the additive agent to improve the frost resistance property of the vegetation-growing concrete, firstly reporting the proper ecological material for slope vegetation restoration in alpine region. Research not only has important theoretical and practical significance for slope ecology restoration in alpine region, but also provides reference value to the research of similar ecological material.更多还原