宽级配砾石土强度、渗透特性与细观结构研究
文献类型：学位论文
| 作者 | 周小军 |
| 学位类别 | 博士 |
| 答辩日期 | 2012-05-20 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 北京 |
| 导师 | 崔鹏 |
| 关键词 | 泥石流 宽级配砾石土 强度特性 渗透特征 细颗粒运移 细观结构 |
| 其他题名 | Study on Strength and Permeability Characteristics and Meso-structure of Wide-grading Gravelly Soil in Triggering Area of Debris flow |
| 学位专业 | 岩土工程 |
| 中文摘要 | “宽级配砾石土”在自然界具有广泛的分布，特别在我国新构造运动强烈，地形起伏大，泥石流广泛发育的西南地区。论文针对我国泥石流灾害频发的现状，以形成泥石流的土源条件砾石土体为研究对象，分析该类土体的强度、渗透特征，模拟降雨条件下宽级配砾石土堆积体失稳过程，观测强度实验前后土体细观结构变化，取得了以下主要认识和成果。 1、在总结前人研究基础上，初步确定了泥石流源区砾石土粗细颗粒分界粒径；分析了泥石流源区砾石土的应力-应变特性，给出了不同干密度和含水率条件下强度指标变化规律。 2、利用量纲分析方法，提出了渗透系数满足k=RCuCc(γw/μ)dn2e/(1+e)关系；针对泥石流源区砾石土体的渗透沉降性，研制了一套砾石土渗透特性测试设备，获得实用新型专利（ZL 201120287503.3），并利用该设备进行实验，揭示了渗透系数与不同孔隙比、不均匀系数与曲率系数的变化规律；明确了渗透过程中砾石土细颗粒发生的运移和积聚现象。 3、基于正交原理，设计了16组人工降雨条件下的水槽实验。实验结果表明，①随着降雨持续入渗，土体细颗粒逐渐向斜坡坡角富集，土体内部含水率增加，孔隙水压力上升，局部形成饱水层（水膜），从而导致土体强度降低，松散堆积体失稳；②斜坡坡角细颗粒增量在8.4~30.02%，影响细颗粒增量的主次关系为降雨历时＞降雨强度＞斜坡坡度；给出了细颗粒增量与控制因素降雨强度和降雨历时的多元回归关系式；③砾石土堆积体失稳过程可以描述为降雨→水分下渗（非饱和向饱和转变）→土体组构变化（含水率、孔隙水压力变化和细颗粒迁移）→土体强度变化直至破坏（土体某一点发生破坏发展为更多点破坏形成塑性区）→砾石土堆积体稳定性破坏。 4、利用环境扫描电子显微镜和IPP图像处理技术，对泥石流源区天然土体和强度实验后土体的细观结构进行了初步的定性和定量分析：①天然土体结构单元和孔隙排列紊乱无序，未见颗粒集聚体和孔隙定向排列的趋势，结构单元存在点-边、点-面、边-边或边-面的多种连接方式；强度实验后结构单元连接向面-面方式转变，孔隙由起初较多的似圆状过渡为缝隙状，粗大孔隙明显变小、变少；②结构单元体和孔隙等效直径主要集中10~20 μm和20~50 μm两个区间，＜10 μm、50~100 μm、100~200 μm和＞200 μm四个区间内只有小比例分布，外力作用对10~50 μm的颗粒集聚体和孔隙影响最甚。 |
| 英文摘要 | “Wide-grading gravelly soil” is widely distributed in the nature, especially in southwest of China where the new tectonic is intense, topography changes great and debris flow develops extensively. Taking the gravelly soil in triggering area of debris flow as the object, strength charactristics and infiltration process are studied, the failure mechanism of “wide-grading gravelly soil” under intense rainfall are analyzed, the soil meso-structure property before and after strength tests are preliminary discussed. The main results are as follows. 1. Based on a large number of field investigation and experimental data, the particle size that is divided into fine and coarse is defined initially. Stress-strain curves of wide-graiding gravelly soil present strain-hardening phenomenon. The cohesion c and the friction angle φ increase with increasing dry density. With the increase of moisture content, the cohesion decreases sharply, while the friction angle φ first increases and then decreases. 2. In order to effectively obtain the permeability coefficient and settlement of gravelly soil of debris flow, a set of integrated test equipment is designed and developed（ZL 201120287503.3）. Based on dimensional analysis of permeability coefficient, the tests of seepage law under different void ratio, non-uniform coefficient and curvature coefficient are carried out respectively; then the calculation equation of permeability coefficient is established, which is and the physical meaning is clear and definite for the parameters; the penetration tests show that the fine grains in “wide-grading gravel soil” migrated and aggregated obviously. 3. A flow controlled and slope adjusted artificial rainfall flume system is designed and developed, 16 groups of artificial rainfall flume tests are designed using orthogonal theory. ① The results show that fine grains easily gather at the slope angle with the continuous rain, its content after the test is significantly higher than before, varying from 8.4% to 30.02%. The aggregation of fine particles may easily cause void plugging, and then pore water pressure increases, finally make the soil effective stress reduced. ② Among 3 influential factors to the effect of fine grain movement, the rainfall time is the most important one, followed by the rainfall intensity and slope gradient. And the rainfall time and intensity play a decisive role. The statistical relationship of increment of fine grains (y) and controlling factors rainfall intensity (x1) and time (x2) can be described as. ③ The process of wide-grading gravelly soil initiation can be described as follows, 1)starting rain→2)water infiltration (at this stage, the soil shift from unsaturated to saturated )→3)soil fabric change(including water content change and fine grains migration )→4)soil strength change until to the damage(the soil strength will be failure at a certain point, and then more points damaged, at last, plastic zone formed)→5)destruction of the overall stability of accumulation body. 4. Based on environmental scanning electron microscope (ESEM) and the IPP image processing technology, the soil meso-structure are preliminary qualitative and quantitative analyzed. ①The structure units and pores of undisturbed soil in triggering area of debris flow appears no orientation trend, and the arrangement is chaos. The structure units connect with each other by various ways, such as point to edge contacting, point to face contacting, edge to edge contacting, edge to face contacting and et al. The connection of structure units changes to face to face after the strength tests. And rounded pores in the soil transform to gaps link shape, big pores become smaller and fewer after the experiments. ② Pore size distribution between the undisturbed soil and after strength test are essentially similar. The equivalent diameter of structure units and pores are mainly in the range of 10~20 μm to 20~50 μm, but fewer scattered in ＜10 μm, 50~100 μm, 100~200 μm and ＞200 μm. The structure units and pores among 10~50 μm are affected most than other ranges when suffered external force. |
| 语种 | 中文 |
| 公开日期 | 2013-01-16 |
| 源URL | [http://192.168.143.20:8080/handle/131551/4818]  |
| 专题 | 成都山地灾害与环境研究所_山地灾害与地表过程重点实验室 |
| 推荐引用方式 GB/T 7714 | 周小军. 宽级配砾石土强度、渗透特性与细观结构研究[D]. 北京. 中国科学院研究生院. 2012. |
入库方式： OAI收割
来源：成都山地灾害与环境研究所
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