冻融循环作用下某露天矿边坡稳定性研究.pdf

分类号 UDC 密级 学号1308140823 硕士学位论文硕士学位论文 冻融循环作用下某露天矿边坡稳定性研究冻融循环作用下某露天矿边坡稳定性研究 李李 国国 锋锋 学学 科科 名名 称称工工学学 学学 科科 门门 类类岩土工程岩土工程 指指 导导 教教 师师李李宁宁 教授教授 申申 请请 日日 期期2016 年年 4 月月 冻 融 循 环 作 用 下 某 露 天 矿 边 坡 稳 定 性 研 究 李 国 锋 西 安 理 工 大 学 摘要 1 论文题目论文题目冻融循环作用下某露天矿边坡稳定性研究冻融循环作用下某露天矿边坡稳定性研究 学科学科名称名称岩土工程岩土工程 研研 究究 生生李国锋李国锋签签 名名 指导教师李宁指导教师李宁 教授教授签签 名名 摘摘要要 本文以青海木里露天煤矿边坡的稳定性的影响因素分析和稳定性评价为最终目的。 首 先对圆柱岩样进行低温冻融试验模拟，确定出适用于 FLAC3D 的水冰相变简化算法和冻 融循环下的三场耦合算法，并对算法进行了验证；然后对理想边坡模型，基于屈服应变提 出相对安全系数的概念， 并以此研究了冻融循环作用下边坡稳定性影响因素； 最后对青海 木里露天煤矿边坡典型开挖断面进行了稳定性分析与评价。主要结论如下 （1）根据水冰相变能量阶段划分及含相变能量守恒平衡方程，将相变能量项用比热 项代换，依据相变时单元温度不变，确定出水冰相变简化算法。对“热流耦合” “热力耦 合” “流固耦合”进行串并联，并将其应用于一次冻胀模拟，对不同算法方案进行低温单 轴压缩试验和三场规律对比，确定出“热流力三场单开顺次串联”的三场耦合算法。通过 一次冻胀、一次冻融、冻融循环试验，对所确定的“含相变低温冻融循环三场耦合算法” 进行了验证。 （2）在冻融循环下，应用含相变的三场耦合算法，采用理想边坡模型，对“Z 型” 和“V 型”温度边界的边坡三场变化规律进行了对比研究。根据岩样屈服应变提出相对安 全系数概念，并以此为基准，对边坡稳定性影响因素进行分析。结果表明，冻融循环次数 和水分迁移是冻融循环下影响边坡稳定性最主要的两个因素。 （3）以木里露天煤矿边坡典型开挖断面为对象，通过含相变的三场耦合程序，对其 进行冻融循环下的边坡稳定性分析与评价。结果表明，在一次冻融中 10-11 月为最危险月 份，经过 13 次冻融循环，边坡将有破坏趋势。且此时边坡整体与局部相对安全系数分别 为 1.88 和 1.65，当考虑少量水分迁移时安全系数分别为 1.86 和 1.57。 （4）处于多年冻土层以下坡表，开挖后至少向坡内生成 5m 的冻结区，且厚度由高 向低逐渐减薄。温度降低后，位于多年冻土层外的坡表区域最先完全冻结。在坡顶和坡肩 一定范围内出现拉应力带， 在低中高程坡表形成剪应变增量带， 并有从坡角向内部软弱结 构面延伸的趋势。 关键字关键字水冰相变；三场耦合；冻融循环；露天矿边坡；影响因素；稳定性 西安理工大学硕士学位论文 2 Abstract 3 TitleResearch on slope stability of open-pit coal mine under freezing-thawing cycles MajorGeotechnicl Engineering NameGuofeng LISignature SupervisorProf. Ning LISignature Abstract The ultimate goal of this paper is slope stability influence factors analysis and stability uation of Qinghai Muli open-pit coal mine. Firstly, the simple algorithm is put forward and verified according to the thawing test of cylinder samples. And the way that is suitable for the FLAC3D is water-ice phase transition and THM coupling algorithm under freeze-thaw cycles. Then, by using ideal slope model, based on the term of relative safety factor, the influence factors of slope stability under freeze-thaw cycles are discussed. Finally, the stability of Muli slope typical section is analyzed and uated. The main conclusions are as follows 1 According to the phase change energy stage and energy balance equation containing phase change as well as unit temperature maintaining constant in phase transition, the energy of phase change is substituted by specific heat items so that the phase transation simple algorithm is ed. Based on series parallel of TH coupling, TM coupling or HM coupling, the THM coupling algorithm is put forward. Through once freezing, once freezing-thawing and freezing-thawing cycle tests, the feasibility of the algorithm is determined. 2 Under the freeze-thaw cycle, by using the ideal slope model, the “Z“ and “V“ type temperature boundary are comparative studied. According to the yield strain of the cylinder samples, the relative safety coefficient is proposed. On this basis, the slope stability influence factors are calculated. The results show that the number of freeze-thaw cycles and water migration are the main two factors affecting slope stability on freezing-thawing cycles. 3 Muli slope of open-pit coal mine excavation section as the object, by the THM coupling procedure, the slope stability is analyzed and uated under the freeze-thaw cycles. The results show that October and November is the most dangerous month during once freeze-thaw. After 13 times of freeze-thaw cycles, the slope will have destructive trend. The overall and local relative safety coefficients of slope are about 1.88 and 1.65, and when considering slight water transfer, the safety coefficients are about 1.86 and 1.57. 4 Below the permafrost layer of slope after excavation, the freezing zone at least 5m is generated. And the thickness is thinning from high to low. The lower temperature is located in 西安理工大学硕士学位论文 4 the area of permafrost slope surface layer outside the first completely frozen. In the top of the hill and slope shoulder within a certain range appear tensile stress zone. In low position of slope surface an area of shear strain increment with extending trend from the slope toe to the internal weak joint. Keywords Phase transition; THM coupling; Freezing-thawing cycles; Open-pit slope; Influence factors; Stability 目录 I 目 录 1 绪论...................................................................................................................................................................1 1.1 研究背景...................................................................................................................................................1 1.2 研究进展...................................................................................................................................................1 1.2.1 冻融循环理论...................................................................................................................................2 1.2.2 冻融循环试验...................................................................................................................................3 1.2.3 冻融循环数值模拟...........................................................................................................................4 1.2.4 冻融循环作用下边坡稳定性..........................................................................................................4 1.3 研究思路...................................................................................................................................................5 2 圆柱试样冻融模拟试验.................................................................................................................................7 2.1 模型建立参数选取..................................................................................................................................7 2.1.1 试验模型............................................................................................................................................7 2.1.2 试验方法............................................................................................................................................8 2.1.3 试验参数............................................................................................................................................8 2.2 一次冻胀模拟...........................................................................................................................................9 2.2.1 水冰相变过程...................................................................................................................................9 2.2.2 水冰相变能量守恒.........................................................................................................................10 2.2.3 低温三场耦合算法.........................................................................................................................14 2.2.4 一次冻胀模拟.................................................................................................................................16 2.2.5 一次冻胀下不同耦合算法比较....................................................................................................18 2.3 一次冻融模拟.........................................................................................................................................23 2.3.1 温度特性..........................................................................................................................................23 2.3.2 变形特性..........................................................................................................................................25 2.3.3 渗流特性..........................................................................................................................................27 2.3.4 一次冻融各场历时云图................................................................................................................30 2.4 冻融循环模拟.........................................................................................................................................34 2.5 小结..........................................................................................................................................................37 3 理想边坡模型下的冻融循环模拟试验......................................................................................................39 3.1 低温冻融循环作用下影响边坡稳定性的因素..................................................................................39 3.2 影响因素试验方案................................................................................................................................41 西安理工大学硕士学位论文 II 3.3 模型建立参数选取................................................................................................................................42 3.4 一次冻融下各场变化规律....................................................................................................................45 3.4.1 V 型温度边界一次冻融场分析.....................................................................................................45 3.4.2 Z 型温度边界一次冻融场分析.....................................................................................................51 3.4.3 V 型温度边界下一次融冻下各场分布规律图可动画演示................................................... 57 3.4.4 Z 型温度边界下一次融冻下各场分布规律图可动画演示....................................................62 3.5 一次冻融下安全系数分析....................................................................................................................67 3.5.1 相对安全系数的定义....................................................................................................................67 3.5.2 V 型温度边界安全系数分析.........................................................................................................67 3.5.3 Z 型温度边界安全系数分析.........................................................................................................70 3.6 冻融循环下边坡稳定性影响因素分析..............................................................................................73 3.6.1 温度边界形式影响.........................................................................................................................73 3.6.2 边界温度值影响.............................................................................................................................74 3.6.3 初始温度影响.................................................................................................................................76 3.6.4 冻结温度影响.................................................................................................................................77 3.6.5 初始含水量影响.............................................................................................................................79 3.6.6 相变水分迁移量影响.....................................................................................................................81 3.6.7 冻融循环次数影响.........................................................................................................................83 3.6.8 坡高影响..........................................................................................................................................85 3.6.9 坡角影响..........................................................................................................................................87 3.7 小结..........................................................................................................................................................90 4 木里煤矿边坡冻融循环作用下稳定性分析.............................................................................................91 4.1 木里煤矿边坡概况................................................................................................................................91 4.2 边坡模型及相关参数............................................................................................................................92 4.2.1 计算模型..........................................................................................................................................92 4.2.2 计算参数..........................................................................................................................................93 4.3.边坡冻融循环稳定性分析....................................................................................................................96 4.3.1 无水分迁移边坡安全系数分析....................................................................................................96 4.3.2 有水分迁移边坡安全系数分析....................................................................................................98 4.3.3 无水分迁移边坡场分析..............................................................................................................101 4.4 小结....................................................................................................................................................... 107 目录 III 5 结论与展望..................................................................................................................................................109 5.1 结论....................................................................................................................................................... 109 5.2 展望....................................................................................................................................................... 110 致谢..................................................................................................................................................................111 参考文献..........................................................................................................................................................113 笔者攻读硕士学位期间从事的实践工作和主要成果..............................................................................117 参加课题..................................................................................................................................................... 117 参加会议..................................................................................................................................................... 117 发表论文..................................................................................................................................................... 117 西安理工大学硕士学位论文 IV 1 绪论 1 1 绪论绪论 1.1 研究背景研究背景 随着煤炭工业的快速发展和开采技术的进步，且在区域经济需求的推动下，煤炭开采 的脚步已跨入到高海拔和高纬度的多年冻土区。木里煤田地处青海省西北部，祁连山南麓， 属于青藏高原多年冻土区的一部分。该区海拔 4000 m 以上，年最低气温-34℃，最高气温 19.8℃，平均气温- 5.1℃，是青海省最大的煤炭资源分区之一。但是，该区煤碳资源多赋存 于多年冻土岩层以下，且地质构造发育、水文地质条件复杂，使得煤矿安全高效开采严重 受阻[1]。 木里聚乎更四井田位于聚乎更矿区南向斜的西段，东侧以 F3 断层为界与一井田相接， 西侧以 F7 断层与哆嗦公马井田为界。 井田总体构造形态为一倾向南西的单斜构造， 浅部较 陡 25～40向深部逐渐变缓 5～20[2]。 该处多年冻土层厚约 58～60 m， 季节性冻土 层厚度约 5～6 m。四井田首采区于 2011 年正式开始采剥，露天矿非工作帮边坡设计高度 为 280 m，综合坡角为 31。木里冻土区边坡岩土体在反复冻胀融沉作用下边坡已出现多 处蠕滑、热融滑塌现象。露天矿边坡经过开挖，不仅改变了原地层的应力场，还改变了坡 表一定深度地层的温度场和水分场，致使坡体裂隙扩张，结构更加松散，边坡的稳定性遭 到了扰动和破坏。边坡裂隙岩体受冻融产生的损伤变形、破坏与裂隙岩体内部自由水、重 力水以及孔隙水的冻融变化、水热交换以及水分、温度变化这一复杂过程有关。该变化过 程使岩体变形演化范围扩大，岩体强度降低进而威胁采场边坡安全。 林宏志[3]认为地下水分场、温度场以及变形场成为控制冻土边坡变形的关键要素。 曹伟 等[4]认为煤矿开采会加剧多年冻土区面积的退缩，植被破坏，边坡滑塌等。牛富俊等[5-6]认 为，煤层开采影响冻土层分布，在坡表一定范围内形成季节性冻土层，当地表温度升高、 地下冰融化时，易产生溯源滑塌现象。 随着露天矿爆破开采的继续进行，已扰动的坡体将会处于温度更替、冷热交换、水分 迁移、冻胀融沉、裂隙扩张等状态中，坡体不断的累积损伤，致使边坡岩体不断的发生滑 移、崩塌和剥落等灾害，对矿坑中施工人员和机械构成严重的安全威胁。因此，研究冻