Influence of sand content on the flow characteristics of soft soil under cyclic and high-f
植被混凝土边坡土壤团聚体的稳定性与可蚀性
湖南农业大学学报(自然科学版)2023，49(6)：702–707．DOI：10.13331/ki.jhau.2023.06.011Journal of Hunan Agricultural University(Natural Sciences)引用格式：马佳鑫，夏栋，艾尚进，舒倩，马悦阳，刘芳，闫书星．植被混凝土边坡土壤团聚体的稳定性与可蚀性[J]．湖南农业大学学报(自然科学版)，2023，49(6)：702–707．MA J X，XIA D，AI S J，SHU Q，MA Y Y，LIU F，YAN S X．Soil aggregate stability and erodibility ofvegetation concrete slope[J]．Journal of Hunan Agricultural University(Natural Sciences)，2023，49(6)：702–707．投稿网址：植被混凝土边坡土壤团聚体的稳定性与可蚀性马佳鑫1,2，夏栋2,3*，艾尚进2，舒倩1,2，马悦阳2，刘芳2,3，闫书星2,3(1.三峡大学生物与制药学院，湖北宜昌443002；2.水泥基生态修复技术湖北省工程研究中心，湖北宜昌443002；3.三峡大学水利与环境学院，湖北宜昌 443002)摘要：以湖北省宜昌市内恢复年限为1、3、5、18 a的植被混凝土生态修复边坡土壤为研究对象，采用Le Bissonnais法分析快速湿润(FW)、慢速湿润(SW)和机械扰动(WS)等3种处理条件下土壤团聚体的稳定性和可蚀性。
结果表明：SW处理下土壤团聚体以≥5.00 mm粒径为主，WS处理下土壤以≥5.00 mm粒径团聚体的占比最高，但其值低于SW处理的，FW处理下<0.25 mm的土壤团聚体粒径占比最高，说明土壤团聚体经FW处理后破碎程度大，SW处理后破碎程度小；土壤团聚体平均质量直径(MWD)和几何平均直径(GMD)值均表现为SW 处理中的最高，FW处理中的最低，而土壤可蚀性值(K)则与其相反，同一恢复年限的边坡土壤的相对消散指数均大于其相对机械破碎指数，说明快速湿润引起的消散作用是土壤团聚体破碎的主要机制；SW和WS处理下已恢复18 a的边坡土壤的粒径≥2.00 mm的团聚体占比最高，<0.25 mm的占比最低，MWD和GMD值最大，K值最小。
表面粗糙度对离心压气机气动性能影响分析
航空发动机Aeroengine收稿日期：2020-06-09基金项目：中国民航大学科研启动基金（2017QD01S ）资助作者简介：史磊（1988），男，博士，讲师，研究方向为轴流叶轮机械气动热力学；E-mail ：。
引用格式：史磊，刘嘉琦，黄晨雷.表面粗糙度对离心压气机气动性能影响分析[J].航空发动机，2022，48（3）：13-19.SHI Lei ，LIU Jiaqi ，HUANG Chenlei.Influence analysis of surface roughness on aerodynamic performance of centrifugal compressor[J].Aeroengine ，2022，48（3）：13-19.表面粗糙度对离心压气机气动性能影响分析史磊1，刘嘉琦2，黄晨雷1（1.中国民航大学中欧航空工程师学院，天津300300；2.上海飞机客户服务有限公司客户培训与运行事业部，上海200241）摘要：为探究叶片表面粗糙度的变化对压气机气动特性的影响，以某小型GTF 涡扇发动机离心压气机为研究对象，在假设粗糙度均匀分布的前提下分析了离心压气机内部流动细节，数值计算了以30μm 为间隔从30~270μm 共9种不同表面等效砂粒粗糙度k s 下的流动特性。
结果表明：当叶片表面从光滑状态增大到k s =270μm 时，峰值效率降低4.8%，对应的总压比降低9.4%。
通过对离心压气机内部流场分析可知，粗糙度逐步增大使叶片表面附面层厚度增加，诱导吸力面出现流动分离，使叶片尾迹区范围扩大，叶片流动损失增加等。
在数值研究的基础上，根据计算结果拟合并校验了离心压气机的总压损失系数ϖ、效率损失系数ζ与叶片表面粗糙度k s 的关系式，预测了其性能衰退规律。
关键词：离心压气机；表面粗糙度；气动性能；数值计算；衰退规律中图分类号：V231.3文献标识码：Adoi ：10.13477/ki.aeroengine.2022.03.003Influence Analysis of Surface Roughness on Aerodynamic Performance of Centrifugal CompressorSHI Lei 1，LIU Jia-qi 2，HUANG Chen-lei 1（1.Sino-European Institute of Aviation Engineering ，Civil Aviation University of China ，Tianjin 300300，China;2.Customer Training and Operation Business Unit ，Shanghai Aircraft Customer Service Co.，Ltd ，Shanghai 200241，China ）Abstract ：In order to investigate the influence of blade surface roughness on the compressor aerodynamic performance ，a centrifugal compressor of a small GTF turbofan engine was taken as the research object ，and the flow details in the centrifugal compressor were ana⁃lyzed under the assumption of uniform surface roughness distribution.The flow characteristics under 9different surface equivalent grit roughness ks from 30μm to 270μm at 30μm intervals were numerically calculated.The results show that when the blade surface rough⁃ness increases from smooth state to k s =270μm ，the peak efficiency decreases by 4.8%and the corresponding total pressure ratio decreases by 9.4%.Through the analysis of the internal flow field of centrifugal compressor ，it can be seen that the gradual increase of roughness in⁃creases the thickness of the boundary layer on the blade surface ，causes flow separation on the suction surface ，expands the range of the blade wake area ，and increases the blade flow loss.On the basis of numerical study ，the total pressure loss coefficient of centrifugal com⁃pressor is fitted and verified according to the calculation results ϖ、efficiency loss coefficient ζand blade surface roughness k s ，and the per⁃formance degradation law is predicted.Key words ：centrifugal compressor ；surface roughness ；aerodynamic performance ；numerical calculation ；degradation law0引言由于在运行过程中接触到的腐蚀性物质以及沙石颗粒等异物的吸入，航空发动机及地面燃气轮机的压气机叶片表面粗糙度将会逐渐增大，进而使其气动性能降低。
土壤水分运动
量纲:取决于水头梯度。如果水头梯度取长度比长度则导水率的量纲完全与 通量相同，也是速度的量纲（LT-1），经常使用。其它量纲不直观，应用很 少。
一、饱和土壤中水分运动 Flow of water in saturated soils
影响导水率因素： （1）土壤性质： A.质地： Ks（sand）=10-2~10-3（cm/秒） Ks（clay）=10-4~10-7 （cm/秒） B.结构：饱和导水率取决于能够导水的大孔隙的孔度，并不是取 决于土壤总孔度；田间裂隙、根孔和虫孔都是饱和导水的主要通 道(这些孔道往往在灌水入渗期间成为发生优先流的地方。有结 构土壤饱和导水率大于无结构的土壤。 总孔隙度大的土壤未必是饱和导水率最高的土壤 注意： 由于土壤基模特性的不稳定性，导致实际上土壤饱和 导水率往往不是常数。如土壤中离子代换作用、土壤胀缩过程、 以及封闭气体作用等。饱和导水率是一个常数是理论概念，它建 立在土壤基模特性稳定的基础上。实际上却并不是一个常数。 （2）环境温度：温度会影响到土壤中封闭空气的溶解度、会影响 到土壤中溶质离子溶解度，同样影响到水分的物理性状。所以， 影响到土壤导水率。 （3）流体性质：液体的粘滞系数（viscosity）和密度（fluid density） 也是影响导水率的主要因素。
一、饱和土壤中水分运动 Flow of water in saturated soils
2.达西定律（Darcy’s law) 1856年法国工程师Henri Darcy在Dijon城解决城市人口用水问题时总结发表 了达西定律，他指出：细沙过滤器中水流的速度与其所受的压力差成正比例，而 与过滤器的长度成反比。（达西定律诞生背景） 达西定律表达式： 一维情况下: Q q = A⋅t = − K ∆H ∆Z q : 流速（ flux density ; LT -1） Q ：流量 ( quantity of water ; m 3 ) A：土柱横截面积 ( cross − sec tional area ; m 2 ) t：时间（ time ; s） K ：导水率 ( hydraulic conductivi ty; m/s) ∆H ：压力差（ hydraulic head; m） ，水分移动的驱动力 ∆Z：土柱长度 (column length; m) ∆H ：水势梯度 ( hydraulic gradient ; m / m ) ∆Z “ −”：表示水流的方向由 水势高出流向水势低处
浅沟侵蚀
Soil detachment is defined as the dislodgment of soil particles from the soil mass at a particular location on the soil surface. The dislodgment is caused by the forces applied on the soil particles by erosive agents, which occurs primarily by the processes of splash from raindrop impact and scour by overland flow (Owoputi and Stolte, 1995). Detachment by splash under controlled laboratory conditions has been studied in detail, but detachment of cohesive soils by shallow clear–water flow under controlled laboratory conditions has received less attention (Nearing et al., 1991).
软土地层中压入式沉井下沉的土塞效应及其影响
DOI: 10.3785/j.issn.1008-973X.2020.07.017软土地层中压入式沉井下沉的土塞效应及其影响易琼1，廖少明1，朱继文2，徐伟忠2(1. 同济大学 地下建筑与工程系，上海 200092；2. 上海城建市政工程（集团）有限公司，上海 200065)摘 要：针对软土地层中压入式沉井的下沉稳定性控制问题，基于土塞形成机理推导出土塞高度的计算表达式，采用耦合欧拉-拉格朗日法（CEL ）模拟沉井的动态压入过程，分析下沉中的土塞演化过程及土体应力、应变场，探讨土塞效应对沉井侧摩阻力和刃脚阻力的影响. 结果表明：在软土地层中，土塞高度的计算表达式能够较准确地得到下沉时的井内土塞高度；沉井压入下沉时土塞效应逐渐增大，在下沉深度约为25 m 时变化趋势放缓，土塞率(PLR)约为0.56，土塞增量填充率(IFR)约为0.41，土塞为不完全闭塞；土塞效应引起的井内土体水平和竖向应力激增及土体等效塑性应变主要集中于有效土塞高度范围内；土塞效应会使沉井侧摩阻力尤其是内壁侧摩阻力显著增大；土塞效应会使沉井刃脚阻力增大，尤其在软弱地层中最明显.关键词： 压入式沉井；软土地层；土塞效应；有效土塞高度；耦合欧拉-拉格朗日法（CEL ）中图分类号： U 445 文献标志码： A 文章编号： 1008−973X （2020）07−1380−10Effect of soil plugging during press-in caisson sinking in soft groundYI Qiong 1, LIAO Shao-ming 1, ZHU Ji-wen 2, XU Wei-zhong 2(1. Department of Geotechnical Engineering , Tongji University , Shanghai 200092, China ; 2. Shanghai Urban ConstructionMunicipal Engineering (Group ) Limited Company , Shanghai 200065, China )Abstract: An analytical calculation formula of soil plug’s height was deduced based on the generating mechanism of soil plug in order to analyze the control of press-in caisson ’s sinking stability in soft ground. Then the coupled Eulerian-Lagrangian (CEL) method was used to simulate the sinking process of a press-in caisson. The influence of soil plugging effect on lateral friction force and blade feet resistance force was discussed based on the analysis of the developing process of soil plug and stress and strain field of soil. Results show that the analytical calculation formula can precisely predict the soil plug’s height in soft ground. The soil plugging effect gradually increases during the caisson’s press-in sinking procedure, but the pace of change slows down around the depth of 25 m. The plug length ratio (PLR) is about 0.56 at the end of sinking, and the incremental filling ratio (IFR) is about 0.41, which means that the soil plug is still incomplete occlusive. The increase in horizontal and vertical soil stress as well as the equivalent plastic strain caused by soil plugging effect mainly concentrated in the range of the effective soil plug’s height. Then the lateral friction force increases, but lateral friction force of inner wall grows more remarkable compared with outer wall. The blade feet resistance force increases owing to soil plugging effect, and the increase becomes significant especially in soft ground.Key words: press-in caisson; soft ground; soil plugging effect; effective soil plug’s height; coupled Eulerian-Lagrangian (CEL)压入式沉井工法[1]施工时通过由千斤顶组成的反力控制装置提供下压力，在尽量减少井内取土的情况下将沉井平稳地压入土层内，可以克服竖向地层差异性的不利影响并保证下沉的稳定收稿日期：2019−06−09. 网址：/eng/article/2020/1008-973X/202007017.shtml基金项目：国家“973”重点基础研究发展规划资助项目（2015CB057806）；上海市科委资助项目（18DZ1205404）.作者简介：易琼（1996—），男，硕士生，从事盾构隧道及沉井等地下工程的研究. /0000-0003-1425-6640.E-mail ：******************.cn通信联系人：廖少明，男，教授，博导. /0000-0001-6448-2086. E-mail ：**************第 54 卷第 7 期 2020 年 7 月浙 江 大 学 学 报(工学版)Journal of Zhejiang University (Engineering Science)Vol.54 No.7Jul. 2020性. 该工法施工时压入式沉井周边及底部土体会挤入井内形成土塞，并随着沉井下沉逐渐增高，使得井壁侧摩阻力和刃脚阻力增大，即产生土塞效应.目前，国内外对于土塞效应的研究主要是以开口管桩为研究对象.在理论分析方面，Paikowsky等[2]研究发现，土塞高度在桩内土体闭塞后不随入土深度的增加而增大；Randolph等[3]建立土塞的一维静力平衡方程，引入“有效土塞高度”的概念；杜来斌[4]研究指出，桩内土中楔体的形成是产生土塞的一个关键因素；赵明华等[5]基于太沙基极限承载力理论，推导出管桩沉桩时的土塞高度计算公式. 在数值模拟方面，詹永祥等[6]采用颗粒流程序PFC2D模拟开口管桩的沉桩过程，发现土塞效应随着管桩直径的增大迅速减小；肖勇杰等[7]建立有限元-无限元耦合模型，模拟灌注桩护壁套管高频振动贯入的全过程；董译之等[8]建立耦合欧拉-拉格朗日(CEL)模型，对超长大单桩的高频振动贯入过程进行模拟；王腾等[9]基于CEL模拟发现，钢管桩的土塞效应随着桩-土摩擦系数增大、桩径减小而增强. 在试验研究方面，朱合华等[10]对软土超长PHC桩打桩进行现场试验，发现影响土塞高度的主要因素是土性；周健等[11]通过模型试验，在细观上研究砂土中开口管桩沉桩时土塞的形成机制；张忠苗等[12-13]对淤泥质黏土互层及粉土层静压预应力混凝土管桩进行试验研究，分析土塞效应影响下的径向及桩端土压力变化情况；Tan[14]对比分析了一系列钢管桩静压贯入试验，发现管内土塞完全闭塞后外侧摩阻力约占总摩阻力的2/3. Liu等[15]通过开展粉土地层中开口管桩的沉桩试验，研究沉桩过程中桩内的土塞效应及其影响.当前关于土塞效应的研究大多局限于开口管桩，对压入式沉井的针对性不足. 本文以压入式沉井为研究对象，采用CEL有限元方法对下沉过程进行数值模拟，分析压入下沉产生的土塞效应，探讨下沉时井内土塞的发展情况及土塞效应对下沉阻力的影响.1 压入式沉井概况浙江省温州市南塘街北入口改造工程中，采用压入式沉井工法施工一超深地下立体停车库，以满足周边停车的需求. 其中作为车库主体结构的沉井采用矩形断面，尺寸为21.125 m×17.2 m，高度为34.05 m，长、短边各设一道中隔墙，将沉井分为4个井隔舱. 沉井结构布置如图1所示，施工场地平面情况如图2所示.温州是我国沿海的典型深厚软土地区，根据中隔墙.125 m17.2m34.5mBBAA刃脚(a) 沉井结构三维示意图图 1 沉井结构图Fig.1 Structure profile of press-in caisson锦绣路住宅区施工场地南塘街钻孔灌注桩ϕ600@900152.9 m6.3m28.27m1 40014146464161 40050021 1258 912.58 912.5配电室垃圾中转站1F3F硂11硂11硂11硂2硂11北比例01020m单位：mm图 2 施工场地平面图Fig.2 Plan of construction site第 7 期易琼, 等：软土地层中压入式沉井下沉的土塞效应及其影响[J]. 浙江大学学报：工学版,2020, 54(7): 1380–1389.1381地质勘察结果可知，施工场地自上而下主要由杂填土、淤泥、粉质黏土、黏土等工程地质层组成.其中，①1杂填土层的均匀性差，压缩性低；②1、②2淤泥层为流塑性，压缩性及灵敏度高，整个淤泥层厚度近25 m ，承载能力差，属典型的软弱地基土；④11、④12粉质黏土层为可塑性，中压缩性；④2、⑤2黏土层呈软~可塑状，中~高压缩性. 场地内的平均地下水位约为1.5 m. 施工前，将场地内的①1杂填土层换填为砂垫层. 场地的地质剖面如图3所示，各土层的物理力学参数根据地勘报告取值，如表1所示. 表中，d 为层厚，γ为重度，c 为黏聚力，φ为内摩擦角，E s1-2为压缩模量，f k 为单位摩阻力，f ak 为地基承载力.2 土塞效应的形成机理与力学分析压入式沉井下沉中周边土体涌入井内不代表井内土体闭塞产生土塞效应，土塞闭塞程度通常用土塞率（plug length ratio ，PLR ）和土塞增量填充率（incremental filling ratio ，IFR ）这2个指标[16]来描述：式中：h 为井内土塞高度，H 为沉井下沉深度，d h 为井内土塞高度增量，d H 为沉井下沉深度增量.PLR 、IFR 的取值一般为0~1.0，且其值越小，土塞闭塞程度越高：0表示土塞完全闭塞；1.0表示土塞完全不闭塞；0~1.0时表示不完全闭塞. 由于刃脚的切削作用，实际下沉过程中有些沉井的井内有可能出现细长的土柱，使得井内土塞高度大于下沉深度，即P L R 、I F R 有可能大于1.0.PLR 计算容易但仅能反映土柱高度的变化；IFR 虽然能够直观地反映土塞闭塞程度的变化，但计算相对复杂.土塞高度和闭塞程度的变化情况取决于土塞所受的竖直向下的总荷载与底部地基极限承载力之间的相对大小. 当竖直向下总荷载等于底部地基极限承载力时，土塞处于临界平衡状态；当竖直向下总荷载大于底部地基极限承载力时，周边土体无法进入井内，土塞高度不再变化，土塞达到闭塞状态；当竖直向下总荷载小于底部地基极限承载力时，周边土体可以进入井内，土塞高度继续增加，土塞处于非闭塞状态. 随着沉井下沉深度的增加，井壁摩擦力和底部地基极限承载力会不断变化，井内土塞有可能在闭塞与不闭塞状态之间切换，因此土塞的演变过程实质上是土塞平衡状态的不断形成和被打破的过程.压入式沉井下沉过程中井内土塞的受力情况④粉质黏土④黏土④粉质黏土②淤泥②淤泥砂垫层图 3 施工场地地质剖面图Fig.3 Geological profile of construction site表 1 土层的主要物理力学参数Tab.1 Physico-mechanical parameters of soil layers土层名称d /m γ/（kN·m −3）直剪E s1-2/MPaf k /kPaf ak /kPac /kPaφ/（°）砂垫层 3.120.010.030.013.820120②1淤泥12.715.08.98.2 1.451040②2淤泥10.015.711.39.221150④11粉质黏土 3.519.325.119.4 5.7321140④12粉质黏土 6.017.714.629.98.3523150④2黏土15.217.825.611.1 3.9318120⑤2黏土19.518.129.414.24.96201301382浙 江 大 学 学 报（工学版）第 54 卷可以简化，如图4所示. 借鉴Randolph 等[3]引入的“有效土塞高度”概念，假定有效土塞以上的土体未被挤密而处于松散状态，其所受摩擦力相比有效土塞内土体可以忽略，因而这部分土体可以简化为超载作用在下方的有效土塞上. 以井内土塞表面为原点，向下为z 轴正向，则有效土塞的静力极限平衡方程为式中：G 为有效土塞自重，γh ′A 其中为土体天然重度，为有效土塞高度，为土塞横断面面积；p 为上方土体自重超载，τz L q u 为土塞深度z 处所受井壁单位摩擦力；为土塞横断面周长；为刃脚底地基极限承载力.τz 土塞深度z 处所受井壁单位摩擦力为σv ητz σv φ′δη式中：为土塞中深度z 处的竖向应力；为深度z 处与的比值，其值取决于该位置水平与竖向应力之比，但其大小在土体受到压入破坏后难以确定. 保守考虑，可以假定土塞边缘土体主动破坏时的内摩擦角为，土塞与井壁之间的摩擦角为，则由图4（d ）极限莫尔圆得到的最小值[5]：sin ∆=sin δ/sin φ′式中：. 根据经验，参考典型的桩η土表面粗糙度，一般可取0.15~0.23[5].η将式（4）~（6）代入式（3），并假设沿深度不变，求解积分得到定义有效土塞高度比如下：将式（9）代入式（8），可以解得土塞高度为ξξ=0.7理论上可以通过式（10）预先求得沉井下沉过程中井内的土塞高度，然而实际情况下式（10）中的参数往往较难取得. 如土塞所受的摩擦力除了与土体的物理力学性质有关外，还与土塞的挤密程度、土塞和井壁间的摩擦角等因素有关. 在工程实践中，可以简单地以地质勘察得到的地基承载力进行深度修正后作为刃脚底地基承载力，并假定随下沉深度线性增长且下沉至设计深度时[12]. 认为土塞与井壁充分接触，假定内侧井隔舱横断面面积、周长即为土塞横断面面积、周长. 在以上假定下，可以计算得到下沉过程中土塞高度的近似值，用以指导设计施工.3 土塞效应数值分析模型建立3.1 模型及边界条件采用ABAQUS/Explicit 中的CEL 有限元方法，建立压入式沉井下沉过程的数值模型，如图5所示. 沉井尺寸同图1，模型长150 m 、宽120 m 、高70 m. 针对该工程的地质特点，将地层简化为3层土，用欧拉网格模拟，即：换填后的砂垫层，厚3.1 m ；②1淤泥、②2淤泥合并成的淤泥层，厚H hh ′有效土塞总土塞(a) 土塞模型有效土塞受力情况G超载 pq uτγσvτd z 图 4 井内土塞受力分析图Fig.4 Force analysis diagram of soil plug in press-in caisson空物质层欧拉土体6沉井刚体70 m 10 m120 m 150 m图 5 CEL 有限元模型示意图Fig.5 Sketch of CEL finite element model第 7 期易琼, 等：软土地层中压入式沉井下沉的土塞效应及其影响[J]. 浙江大学学报：工学版,2020, 54(7): 1380–1389.138312.7 m；④11粉质黏土、④12粉质黏土、④2黏土、⑤2黏土合并成的黏土层，厚44.2 m. CEL法模型中除了欧拉土体外，还需在其上方设一个厚度为10 m的空物质层，以容纳地表土体可能发生的隆起变形. 沉井初始位置位于模型的欧拉土体表面正中心.针对该工程的特点及地质条件，为了实现对沉井下沉过程的合理模拟，采用如下基本假定.1）由于沉井刚度远大于周边土体刚度，可将其近似视作刚体，采用拉格朗日网格建模，单元类型为R3D4单元.2）土体选用DP（Drucker-Prager）弹塑性本构模型并采用欧拉网格建模，单元类型为EC3D8R.3）采用耦合欧拉-拉格朗日（CEL）方法考虑土体的大变形问题，沉井与土体的接触耦合按罚函数约束来考虑.4）CEL方法的收敛性对网格密度的依赖较大，参考文献[9]，网格尺寸选为沉井壁厚/6.5）采用位移贯入法，给沉井施加匀速变化的位移曲线进行加载，模拟整个下沉过程，在下沉过程中井内不挖土，且整个过程中沉井结构保持垂直姿态.由于在CEL方法中欧拉网格不发生变形，实际运动的是网格中的材料，材料的运动趋势体现为通过欧拉网格节点的速度方向和大小. 对于该模型而言，边界条件取为约束模型底面X、Y、Z方向的速度和模型4个侧面X、Y方向的速度.3.2 计算参数选取cφ沉井结构按刚体进行模拟，无需设置材料参数. 地层对应的部分物理力学参数可以由原地层的物理力学参数转换得到. 数值模拟中，DP弹塑性本构模型参数可以由土体抗剪强度参数、计算得到[17]：βφσccκ式中：为DP模型内摩擦角，为内摩擦角，为三轴受压下的屈服应力，为黏聚力，为流动应力比.土体弹性模量E根据文献[18]，对软土统一取为E=3E s. 砂垫层泊松比ν取0.2，淤泥层、黏土层泊松比ν取0.49. 沉井结构与土体间的界面摩擦系数μ取0.3. 由此得到的土体计算参数见表2.表中，ψ为剪胀角，E为弾性模量.表 2 CEL法的土体计算参数Tab.2 Calculation parameters of soils in CEL method土层γ/(kN·m−3)c/kPaφ/（°）β/（°）κψ/（°）σc/kPa E s1−2/kPa E/kPaν砂垫层20.010.03050.20.778034.6413 80041 4000.20淤泥层15.310.08.617.50.905023.25 1 692 5 0760.49黏土层18.025.415.931.10.833067.29 5 12715 3810.493.3 数值模型验证为了验证本文CEL数值分析计算结果的正确性，采用同样的参数选取方法、计算假定及网格密度，对张忠苗等[12]实施的萧山试验建立CEL数值模型进行计算. 以沉桩过程中的管壁端阻为例，将CEL数值模型得到的结果与张忠苗等[12]的现场试验结果进行对比，如图6所示.图中，p ann为管壁端阻.从图6可以看出，虽然数值模拟得到的端阻波动较大，但经过平滑处理后的结果与现场试验结果在变化趋势上是较吻合的，表明CEL法的数值模拟结果是比较合理的. 采用CEL法研究压入式沉井下沉过程中的土塞效应是可行的.图 6 数值模型与现场试验得到的端阻对比Fig.6 Comparison of tip resistance between numerical model and field test1384浙江大学学报（工学版）第 54 卷4 土塞效应及其影响的数值分析4.1 土塞演化规律γηA L 为了分析压入式沉井下沉过程中土塞的演化规律，分别采用式（10）及数值模拟方法，对背景工程计算得到的结果绘制出PLR 、IFR 随下沉深度的变化情况，如图7所示. 其中，采用式（10）计算土塞高度时，取下沉深度范围内加权平均值16.48 kPa ，取0.2，土塞横断面面积、周长分别为60.14 m 2、31.24 m ，其他参数见表1. 从图7可以发现，在压入下沉初期，由于土体处于较松动的状态，土塞高度增长较快，PLR 、IFR 均较大，土塞闭塞程度低；从砂垫层进入淤泥层时，P L R 、IFR 急剧减小，土塞高度的增长速度大大减慢，土塞闭塞程度显著提高；随后曲线迎来拐点，即当沉井主体在淤泥层中下沉时，PLR 减小趋势大大减缓，IFR 略有增大，土塞闭塞程度缓慢增大；当沉井下沉至黏土层时，PLR 减小趋势稍有增大，IFR 快速减小，土塞闭塞程度进一步提高；沉井下沉至设计深度后，井内土塞的PLR 约为0.56，IFR 约为0.41，可见此时土塞为不完全闭塞，但闭塞程度较高.淤泥土质软弱、流动性大，加上刃脚的切削作用，使得单一淤泥层时初始贯入阶段井内形成的土柱较高，甚至会超过下沉深度，PLR 增加；砂垫层土质较硬、摩擦力大，淤泥上覆砂土垫层井内土塞更容易闭塞，使得初始贯入阶段PLR 开始降低. 与仅考虑淤泥层单一土层情况下的PLR 变化情况相比，考虑了砂垫层、淤泥层、黏土层多层土层后整个下沉过程的PLR 都偏小，这说明软弱淤泥层上覆较硬的砂层会使土塞闭塞程度提高，土塞效应增大. 这一点与王腾等[9]研究发现的上硬下软地层中土塞闭塞情况相符. 在下沉深度达到一定程度后，仅考虑淤泥层单一土层的PLR 与考虑砂垫层、淤泥层、黏土层3类土层时的PLR 相近. 这表明上覆较硬砂层对土塞效应的影响只是在浅层较显著，在下沉深度较深（约25 m 处）时，只考虑淤泥层的土体挤密效果足够使得侧摩阻力大到阻碍周边土体进入井内，井内土塞会达到一定的闭塞程度.与数值模拟相比，采用本文推导的式（10）计算得到的PLR 变化趋势基本一致，尤其在单一土层情况下十分接近，仅数值上偏大. 说明本文推导的土塞高度计算公式具有一定的合理性. 以下沉至设计深度时为例，采用式（10）计算得到的PLR 约为0.64，稍大于数值模拟结果. 这是因为通过土塞静力平衡计算土塞高度时，假定土塞所受到的井壁摩擦力仅与竖向应力有关，未考虑挤土效应所引起的土体挤密对井壁摩擦力的影响，导致井壁摩擦力比实际情况偏小.4.2 土塞效应对土体运动场的影响αα在下沉过程中，土塞效应会对沉井内部及周边土体的运动产生一定的影响. 如图8所示为压入式沉井下沉过程的地层运动速度场分布图，定义下沉深度比=下沉深度/沉井总高度，选取分别为0.25、0.50、0.75、1.00的几个关键阶段进行分析. 在压入下沉初期，由于土体颗粒较松散，沉井内土体的速度矢量相对杂乱，井壁附近土体受摩图 7 土塞率、土塞增量填充率随下沉深度的变化Fig.7 Variation of PLR and IFR along sinking depth(a) α=0.25(b) α=0.50(c) α=0.75(d) α=1.00图 8 下沉过程中的土体速度场分布Fig.8 Typical distribution of soil velocity field during sinking pro-cedure第 7 期易琼, 等：软土地层中压入式沉井下沉的土塞效应及其影响[J]. 浙江大学学报：工学版,2020, 54(7): 1380–1389.1385擦带动有一定向下的速度，周边地表有一定向上的运动速度，刃脚底土体主要被向下挤压而产生较大的竖直向下的运动速度. 随着沉井的不断下沉，井壁摩擦力逐渐增大，可带动的土体范围增大，带动向下的速度接近刃脚底土体竖向向下的速度，于是井壁在摩擦力作用下带动着土塞上部土体向下运动，同时周边土体从底部向上运动进入井内. 当上下两部分土体在某一界面达到平衡后，土体向两边井壁散开并被井壁摩擦带动向下.这种土塞中土体颗粒的循环运动模式在下沉深度比为0.75时体现得最明显. 当土塞闭塞程度较大（PLR=0.56）时，在自重和井壁摩擦力作用下土塞内土体整体向下，周边土体几乎不再进入井内.可见，土塞的形成演变过程实质上是随着下沉深度的增大，井内土体逐渐被挤密，井壁与土塞的摩擦力随之增大，摩擦力增大到一定程度后和自重一起阻碍周边土体进一步进入井内的过程. 这种对土体进入井内的运动趋势的阻碍越大，土塞闭塞程度越高.α由于CEL 方法中网格与材料相互独立，无法直接得到准确的地层变形情况. 采用示踪粒子（tracer particle ）技术对地层进行标记，追踪土体颗粒的变形趋势. 如图9所示为压入式沉井下沉各阶段的土体颗粒变形趋势，选取分别为0.25、0.50、0.75、1.00的几个关键阶段进行分析，其中的白色方框表示所追踪的土体颗粒. 由土体颗粒变形趋势可知，压入式沉井下沉引起的土体变形情况大致为靠近沉井处的土体受到井壁摩擦力作用向下运动，地表处体现为沉降；稍远一点的土体由于被挤压发生向上运动，地表处体现为隆起；井内土塞区的土体由于越靠近井壁被带动向下运动的趋势越明显，中间的土体会发生一定的向上运动，因而会形成拱起状的土拱，随着沉井下沉深度的增加，这种拱起越来越明显.4.3 土塞效应对土体应力应变的影响为了分析考虑土塞效应后的压入式沉井下沉过程中沉井周边土体的应力应变情况，绘制下沉时的典型水平应力云图、竖向应力云图及等效塑性应变云图，分别如图10~12所示. 选取α分别为0.25、0.50、0.75、1.00的几个关键阶段进行分析，重点对井内土塞周边的土体进行分析.从图10可以看出，压入式沉井下沉时对土体的挤压效应会使得周边土体的水平应力增大，水(a) α=0.25(b) α=0.50(c) α=0.75(d) α=1.00图 10 典型水平应力云图Fig.10 Typical horizontal stress contours(a) α=0.25(b) α=0.50(c) α=0.75(d) α=1.00图 11 典型竖向应力云图Fig.11 Typical vertical stress contours(a) α=0.25(b) α=0.50(c) α=0.75(d) α=1.00图 9 下沉过图程中的土体颗粒变形趋势Fig.9 Typical deformation trend of soil particles during sinkingprocedure1386浙 江 大 学 学 报（工学版）第 54 卷平应力增大越多说明这种挤土效应越明显. 在压入下沉初期，刃脚底面及下方一定范围的土体水平应力增加；随着下沉深度的增加，井内土体的水平应力也有所增加；井内形成土塞后，土塞下部的土体水平应力增加较明显，且土塞闭塞程度越高，水平应力增大的部分越往下.从图11可以看出，由于挤土效应的存在，压入式沉井下沉对竖向应力的主要影响表现为刃脚底及下方一定范围内土体的竖向应力激增. 井内土塞产生后，刃脚底还会产生向下凸的应力拱，阻碍了周边土体涌入井内. 土塞闭塞程度越高、土塞效应越大，刃脚底的应力拱越大，竖向应力增大越明显. 在沉井下沉至最终深度时，刃脚底应力拱最大的向下应力达到2.8 MPa ，远远超过了原先该深度的土体天然自重应力场，土体难以进一步涌入井内，说明此时土塞较闭塞.由图12可以发现，在压入下沉初期，土体发生的塑性应变主要集中在刃脚底面；当土体挤密到一定程度使得井壁摩擦力增大后，井壁附近土体被带动向下发生变形，产生了一定程度的塑性应变. 从塑性应变的发展趋势来看，井壁附近土体塑性应变不沿着井壁全高度发展，而是主要集中在土塞下部的一定范围. 这说明这部分土塞中的土体比上方的土体所受的井壁摩擦力较大，相应发生的向下运动变形也大，因此该部分的土塞可以视作为有效土塞. 有效土塞占整个土塞的比例越小，表明土塞闭塞程度越高.4.4 土塞效应对侧摩阻力的影响压入式沉井下沉过程中所产生的土塞效应会由图13可知，内壁侧摩阻力随下沉深度的增加呈不断增大趋势. 考虑土塞效应下数值模拟所得的内壁侧摩阻力比不考虑土塞效应计算得到的内壁侧摩阻力大，这种差距在下沉到底时最明显，增大了约242.1%. 当土塞达到一定闭塞程度(a) α=0.25(b) α=0.50(c) α=0.75(d) α=1.00图 12 等效塑性应变云图Fig.12 Typical equivalent plastic strain contours数值模拟与规范[19]方法的差值水平应力图 13 内壁侧摩阻力随下沉深度的变化Fig.13 Variation of lateral friction force of inner wall along sinkingdepth水平应力数值模拟与规范[19]方法的差值淤泥层图 14 外壁侧摩阻力随下沉深度的变化Fig.14 Variation of lateral friction force of outer wall along sinkingdepth水平应力发现，井壁内侧土体的水平应力相对较大，表明内侧井壁与土体间产生了较大的挤压应力. 土塞效应对内壁侧摩阻力的影响较明显.由图14可知，外壁侧摩阻力随下沉深度的增加呈不断增大的趋势. 当下沉深度较小时，考虑土塞效应下数值模拟所得的外壁侧摩阻力与不考虑土塞效应计算得到的外壁侧摩阻力相差不大，只有在下沉深度较大时考虑土塞效应的外壁摩阻力才会明显大于不考虑土塞效应的情况，下沉到底时考虑土塞效应后的外壁摩阻力比不考虑土塞效应时增大了约200%. 通过数值模拟所得的外壁侧摩阻力变化曲线的拐点出现在下沉深度25 m 左右，之后外壁侧摩阻力开始快速增大. 分析此时井壁周边土体的水平应力发现，井壁外侧土体的水平应力相比内侧较小. 相比内壁侧摩阻力，土塞效应对外壁侧摩阻力的影响较小，仅在土塞闭塞程度较高、土塞效应较大之后才会对外壁侧摩阻力产生显著影响.4.5 土塞效应对刃脚阻力的影响压入式沉井下沉时的土塞效应在竖向上会在刃脚底部产生一个向下的应力拱，阻碍周边土体进入井内. 土塞效应除了会对侧摩阻力产生影响外，还会对刃脚阻力产生影响. 为了分析土塞效应对刃脚阻力的影响，选取数值模拟所得的刃脚阻力F Rb随下沉深度的变化情况，与未考虑土塞效应的刃脚极限阻力进行对比，得到F Rb随下沉深度的变化关系，如图15所示. 未考虑土塞效应的刃脚极限阻力采用太沙基地基极限承载力乘上刃脚面积进行计算.的刃脚阻力大. 土塞效应引起的刃脚阻力增大在软弱地层如淤泥层中尤为明显，整体上增大了将近1倍. 下沉到底时考虑土塞效应后的刃脚阻力比不考虑土塞效应时增大了约61.9%. 通过数值模拟所得的刃脚阻力变化曲线的拐点出现在下沉深度25 m左右，之后刃脚阻力的增大趋势略有加快，但不如侧摩阻力显著. 分析此时刃脚底部土体的竖向应力发现，刃脚底部的应力拱十分明显.土塞效应产生后会使得刃脚阻力增大，在软弱地层中尤为明显.5 结 论（1）基于土塞受力机理推导得到土塞高度的理论计算公式，并与数值模拟进行对比，发现在软土地层且各层土之间差异不大时，两者结果基本一致. 该公式能够为现场工程师预估沉井下沉过程中的土塞高度提供一定的计算依据.（2）在下沉初期，PLR、IFR均较大，土塞闭塞程度低；进入淤泥层瞬间，PLR、IFR急剧减小，土塞闭塞程度显著提高；在淤泥层中下沉时，PLR 的减小趋势大大缓和，IFR略有增大；下沉至最终指定深度后，井内土塞的PLR约为0.56，IFR约为0.41. 与单一软弱淤泥层情况相比，上覆较硬砂层会增大土塞效应.（3）在沉井下沉过程中，作用在井壁上的土体水平应力增加，但主要集中在有效土塞高度范围，刃脚附近的土体竖向应力激增并同时形成一个向下的应力拱. 土体的等效塑性应变主要发生在有效土塞高度范围内，表明这部分的土体所受摩擦力较大，相应产生的滑移变形大.（4）土塞效应会使得井壁所受的侧摩阻力增大，对内壁侧摩阻力的影响尤为显著，对外壁侧摩阻力的影响仅在土塞效应较大（下沉深度约为25 m）时较明显. 沉井下沉至设计深度后，相比不考虑土塞效应的情况，考虑土塞效应后的内壁侧摩阻力增大约242.1%、外壁侧摩阻力增大约200.1%.（5）土塞效应会使得刃脚底部产生一个向下的应力拱，阻碍周边土体进一步涌入井内，从而导致刃脚阻力增大. 土塞效应对刃脚阻力的影响在软弱地层（淤泥层）更明显，整体上增大将近竖向应力数值模拟与太沙基法的差值图 15 刃脚阻力随下沉深度的变化Fig.15 Variation of blade feet resistance force along sinking depth。
天大化工原理-英文版课件-Chapter 3-11流体流动现象
Quicksand 流 沙 and some sand-filled emulsions乳状液
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3. Time-dependent flow
• Thixotropic（触变性） liquids break down under continued shear and on mixing give lower shear stress for a given shear rate; that is, their apparent viscosity decreases with time.
18
2. Laminar flow层流
• At low velocities fluids tend to flow without lateral mixing, and adjacent layers slide past one another as playing cards do. There are neither cross-currents nor eddies. This regime is called laminar flow. (p45)
2
3.1 INTRODUCTION
• • • • 1. Ideal fluid and actual fluid(viscous fluid ) 2. Potential flow 势流 3. Viscous flow 粘性流 4. Velocity field 速度场
3
1. Ideal fluid and actual fluid(viscous fluid )
6
2. Potential flow(or irrotational flow) 势流(或无漩流)
• (1) Neither circulations nor eddies can form within the stream, so that potential flow is also called irrotational flow; • (2) friction cannot develop, so that there is no dissipation of mechanical energy into heat. •理想流体的无漩流动
水流星实验教学设计
水流星实验教学设计水流星实验是一种常见的物理实验，旨在通过观察水流的运动来研究液体的流动特性。
该实验可以帮助学生更好地理解流体力学的基本原理，以及液体在管道中的流动规律。
以下是针对水流星实验的教学设计：一、实验设备与材料准备：1. 实验装置：玻璃管、水槽、水流星装置（包括出水孔、加压泵等）2. 实验材料：水、比色皿、计时器等二、实验目的：1. 观察水流的运动特性；2. 研究流体的运动规律；3. 探讨液体在管道中的流动原理；三、实验步骤：1. 搭建实验装置：将玻璃管置于水槽内，并连接水流星装置；2. 准备实验材料：准备比色皿和计时器；3. 进行实验：通过操作水流星装置，使水流经玻璃管，落入比色皿中，观察水流的运动轨迹，并记录实验数据；4. 实验记录：记录水流的流速、流量等数据，并进行图表分析；5. 实验分析：根据实验数据和观察结果，讨论水流的运动规律和液体在管道中的流动原理；四、实验内容：1. 观察水流的流动状态：通过操作水流星装置，可以观察到水流自上而下流经玻璃管，在落入比色皿中时，形成不同的水流状态，如直线流动、旋涡流动等；2. 流速与流量的测量：通过计时器可以测量水流通过管道的时间，从而计算出水流的平均流速和流量；3. 实验数据分析：根据实验数据，可以制作图表，分析水流速度随时间的变化规律，以及不同管道直径对水流速度的影响等；五、实验总结和讨论：1. 总结实验结果：根据实验数据和观察结果，总结水流的运动规律和液体在管道中的流动特性；2. 讨论液体流动的应用：讨论液体流动规律在工程和生活中的应用，如水流动力学在水利工程、管道输送等方面的应用；3. 提出问题与展望：根据实验过程中的发现，提出相关问题并展望未来的研究方向。
六、实验注意事项：1. 遵守实验操作规程，确保实验安全；2. 注意实验装置的搭建和调试，确保实验顺利进行；3. 认真记录实验数据，准确分析实验结果；4. 注意水流星装置的使用方法，避免浪费水资源；5. 实验结束后，做好实验装置的清洁和维护。
《工程地质专业英语》
《工程地质专业英语》教学大纲课程代码：课程名称：工程地质专业英语学时安排：总学时36学分：2适合专业：工程地质先修课程：《大学英语》，《工程地质学》，《工程岩土学》等教材：〈工程地质专业英语〉郑孝玉编，吉林大学校内讲义，2005，7参考书：编写人：郑孝玉➢教学目的和要求工程地质专业英语是工程地质专业4年级学生的选修课，是在学生学习和掌握了基础理论课，专业课及大学英语之基础上为培养和提高学生专业英语能力而设置的。
通过讲授和与学生交流为他们灌输一些相关专业词汇，表述方式及科学文献的翻译、课程写作技巧和规范等。
为将来学习和工作储备一些相关知识。
➢课程内容概要1．本课程教学内容●The Engineering Properties of Rocks1）rock index propertiesCertain index properties of rocks are of particular importance to the engineering, which are defined below.Specific gravity (G s and G b). G b is the specific gravity of the solid mineral material of the rock by itself. G b is the specific gravity of the complete rock, grain plus voids, with the voids empty except for air. Both are defined as a weight per unit volume.Saturation moisture content (i s). This is the total amount of water present in a rock with the voids full. The ratio of weight of water to dry weight of rock sample, expressed as a percentage, is the saturation moisture content (i s).Moisture content (W). This is the amount of water normally present in the voids of a rock , again expressed as a percentage (see i s) above. Rocks are rarely saturated with water, thus in normal circumstances w is less than is.Porosity (n). This is the ratio of volume of voids in a rock total volume of the sample. It is expressedas a percentage; 10% average, 5% is low and more than 15% is high.The factors that control the porosity of terrigenous sedimentary rocks and soils are as follows:(a)The degree of cementation(b)The sorting of the sediment(c)The packing of the grains(d)The shape of the grainsWater-yielding capacity. Not all of the water in a rock can be removed from it by flow under the force of gravity. Some is held as a film on the surface of the grains by capillary forces.Permeability(k). This is a measure of the fluid conductivity of the rock for a given hydraulic gradient.2）basic characteristics of soils2.1 the nature of soilsThe destructive process in the formation of soil from rock may be either physical or chemical. The physical process may be erosion by the action of wind, water or glaciers, or disintegration caused by alternate freezing and thawing m in cracks in the rock.The chemical process results in changes in the mineral form of the parent rock due to the action of water (especially if it contains traces of acid or alkali), oxygen and carbon dioxide. Chemical weathering results in the formation of groups of crystalline particles of colloidal size (<0.002 mm) known as the clay minerals.Particle sizes in soils can vary from over 100 mm to less than 0.001 mm. Most types of soil consist of a graded mixture of particles from two or more size ranges. All clay size particles are not necessarily clay mineral particles: the finest rock flour particles may be of clay size. If clay mineral particles are present they usually exert a considerable influence on the properties of a soil, an influence out of all proportion to their percentage by weight in the soil.2.2 particle size analysisThe particle size analysis of a soil sample involves determining the percentage by weight of particles within the different size ranges. The particle size distribution of a coarse-grained soil can be determined by the method of sieving. The soil sample is passed through a series of standard test sieves having successively smaller mesh sizes. The weight of soil retained in each sieve is determined and the cumulative percentage by weight passing each sieve is calculated. If fine-grained particles are present in the soil, the sample should be treated with a flocculating agent and washed through the sieves.The particle size distribution of a soil is presented as a curve on a semi-logarithmic plot, the ordinates being the percentage by weight of particles smaller than the size given by the abscissa. The flatter the distribution curve the larger the range of particle sizes in the soil; the steeper the curve the smaller the size range. A coarse-grained soil is described as well graded if there is no excess of particles in any size range and if no intermediate sizes are lacking. In general a well graded soil is represented by a smooth, concave distribution curve. A coarse-grained soil is described as poorly graded (a)if particles of both large and small sizes are present but with a relatively low proportion of particles of intermediate size (a gap-graded soil). Particle size is represented on a logarithmic scale so that two soils having the same degree of uniformity are represented by curves of the same shape regardless of their positions on the particle size distribution plot. The particle size corresponding to any specified value on the percentagesmaller scale can be read from the particle size distribution plot.2.3 plasticity of fine-grained soilsPlasticity is an important characteristic in the case of fine-grained soils, the term plasticity describing the ability of a soil to undergo unrecoverable deformation at constant volume without cracking or crumbling. Plasticity is due to the presence of clay minerals or organic material.Most fine-grained soils exist naturally in the plastic state. The upper and lower limits of therange of water content over which a soil exhibits plastic behaviour are defined as the liquid limit (LL or w L) and the plastic limit (PL or w P) respectively.2.4 soil compactionCompaction is the process of increasing the density of a soil by packing the particles closer together with a reduction in the volume of air: there is no significant change in the volume of water in the soil. In the construction of fills and embankments, loose soil is placed layers ranging between 75 mm and 450 mm in thickness, each layer being compacted to a specified standard by means of rollers, vibrators or rammers. In general the higher the degree of compaction the higher will be the shear strength and the lower will be the compressibility of the soil.The degree of compaction of a soil is measured in terms of dry density, i.e. the mass of solids only per unit volume of soil.The dry density of a given soil after compaction depends on the water content and the energy supplied by the compaction equipment (referred to as the compactive effort).The compaction characteristics of a soil can be assessed by means of standard laboratory tests. After compaction using one of the three standard methods, the bulk density and water content of the soil are determined and the dry density calculated. For a given soil the process is repeated at least five times, the water content of the sample being increased each time. At low values of water content most soils tend to be stiff and are difficult to compact. As the water content is increased the soil becomes more workable, facilitating compaction and resulting in higher dry densities. At high water contents, however, the dry density decreases with increasing water content, an increasing proportion of the soil volume being occupied by water.In Situ Testing1. penetrometersPenetrometer test evolved from the need to acquire data on subsurface soils which could not be obtained by other means. Basically a penetrometer consists of a conical point attached to a drive rod which is forced into the ground either by hammer blows or by jacking. Hence two types of penetrometer tests are recognized, the dynamic and the static. Both methods measure the resistance to penetration offered by the soil at any particular depth. Penetration of the cone forces the soil aside, creating a complex shear failure and thus provides an indirect measure of the in situ shear strength of the soil.Dynamic penetrometers were originally designed to determine the relative density of cohesionless soils but their use has been extended to include the design of pile foundations by determining the load and the required embedment of piles into the bearing strata.2．shear vane testBecause soft clays, may suffer disturbance when sampled and therefore give unreliable results whentested for strength in the laboratory, a vane test is often used to measure the in situ undrained shear strength. Vane tests can be used in clays which have a consistency varying from very soft to firm.3．plate load and jacking testsLoading tests can be carried out on loading plates. However, just because the ground immediately beneath a plate is capable of carrying a heavy load without excessive settlement, this does not necessarily mean that the ground will carry the proposed structural load. This is especially the case where a weaker horizon occurs at depth but is still within the influence of the bulb of pressure which will be generated by the structure.4．Pressure testsHydrostatic pressure chambers are used to measure the reaction of a rock mass to stress over large areas, giving values of Young’s modulus, elastic recovery, inelastic deformation and creep. The results are used to evaluate the behaviour of dam foundations and related strain distribution in the structure and to help estimate the behaviour of pressure tunnel linings. Hydrostatic chambers cover a much larger surface area than other test methods and so provide better results of mass behaviour. However, because of their cost these tests are used sparingly. A dilatometer can be used in a borehole to obtain data relating to the deformability of a rock mass. These instruments range up to about 300 mm in diameter and over 1 m in length and can exert pressures of up to 20 MN/m2 on the borehole walls.5．In situ shear testIn an in situ shear test a block of rock is sheared from the rock surface whilst a horizontal jack exerts a vertical load. It is advantageous to make the tests inside galleries, where reactions for the jacks are readily available. The tests are performed at various normal loads and give an estimate of the angle of shearing resistance and cohesion of the rock. In situ shear tests are usually performed on blocks, 700 ×700 mm, cut in the rock. These tests can be made on the same rock where it shows different degrees of alteration and along different directions according to the discontinuity pattern. The factor of safety against strain due to sliding may depend on a limited zone and it is therefore essential to find and investigate the weakest zones. It is sometimes difficult to obtain sufficiently undisturbed, as in the case of shales, to perform tests. This is also the case when the rocks are affected by residual stresses.Consolidation TheoryConsolidation is the gradual reduction in volume of a fully saturated soil of low permeability due to drainage of some of the pore water, the process continuing until the excess pore water pressure set up by an increase in total stress has completely dissipated: the simplest case is that of one-dimensional consolidation, in which a condition of zero lateral strain is implicit. The process of swelling, the reverse of consolidation, is the gradual increase in volume of a soil under negative excess pore water pressure. 1．the oedometer testThe characteristics of a soil during one-dimensional consolidation or swelling can be determined by means of the oedometer test. The test procedure has been standardized in Standards which specifies that the oedometer shall be of the fixed ring type. The void ratio at the end of each increment period can be calculated from the dial gauge readings and either the water content or dry weight of the specimen at the end of the test.2．compressibility characteristicsTypical plots of void ratio (e) after consolidation, against effective stress (σ/) for a saturated clay are shown that an initial compression followed by expansion and recompression. The shapes of the curves are related to the stress history of the clay.The compressibility of the clay can be represented by one of the following coefficients.The coefficient of volume compressibility (m v ), The compression index (C c ).3. Preconsolidation pressureWhenever possible the preconsolidation pressure for an overconsolidated clay should not be exceeded in construction. Compression will not usually be great if the effective vertical stress remains below /c σ:only if /c σis exceeded will compression be large.4. 1-D consolidation settlement5. degree of consolidation6. Terzaghi ’s theory of one-dimensional consolidationThe assumptions made in the theory are:1. The soil is homogenous.2. The soil is fully saturated.3. The solid particles and water are incompressible.4. Compression and flow are one-dimensional (vertical).5. Strains are small.6. Darcy ’s law is valid at all hydraulic gradients.7. The coefficient of permeability and the coefficient of volume compressibility remain constant throughout the process.8. There is a unique relationship, independent of time, between void ratio and effective stress.7. Second compressionSecondary compression is thought to be due to the gradual readjustment of the lay particles into a more stable configuration following the structural disturbance caused by the decrease in void ratio, especially if the clay is laterally confined. An additional factor is the gradual lateral displacements which take place in thick clay layers subjected to shear stresses. The rate of secondary compression is thought to be controlled by the highly viscous film of adsorbed water surrounding the clay mineral particles in the soil..Bearing CapacityIn order to avoid shear failure or substantial shear deformation of the ground, the foundation pressures used in design should have an adequate factor of safety when compared with the ultimate bearing capacity of the foundation. The ultimate bearing capacity is the value of the loading intensity which causes the ground to fail suddenly in shear. If this is to be avoided then a factor of safety must be applied to the ultimate bearing capacity, the value obtained being the maximum safe bearing capacity.1. stress distribution in soilA reasonable approximation of how stress is distributed in soil uponloading can be obtained by assuming that the soil behaves in an elastic manner as if it was a homogenous material.2. Foundation failureThere are usually three stages in the development of a foundation failure.The weight of the material in the passive zones resists the lifting forces and provides the reaction through the other two zones which counteract downward motion of the foundation structure. Thus the bearing capacity is a function of the resistance to uplift of the passive zone. A surcharge placed on the passive zone or increasing the depth of the foundation therefore increase the bearing capacity.3. bearing capacity factorsA number of bearing capacity factors are used to determined the influence of the various characteristics of a soil and formation structure on the ultimate bearing capacity.4. contact pressureThe pressure acting between the bottom of a foundation structure and the soil is the contact pressure. The assumption that a uniformly loaded foundation structure transmits the load uniformly so that the ground is uniformly stressed is by on means valid. In fact, of course, the clay yields slightly and so reduces the stress at the edges. As the load is increased more and more local yielding of the ground material takes place until, then the loading is close to that which would cause failure, the distribution is probably very nearly uniform. Therefore at working loads a uniformly loaded foundation structure on clay imposes a widely varying contact pressure.5. allowable contact pressure for rock massesIf the rock mass contains few defects the allowable contact pressure at the surface may be taken conservatively as the unconfined compressive strength of the intact rock. Most rock masses, however, are affected by joints or weathering which may significantly affect their strength and engineering behaviour.●The stability of slopes1 the stability of slopes in soilsThe stability of slopes is critical factor in open excavation. This stability is usually expressed in terms of factor of safety (F), the design of potential stability increasing as the value of F increases above unity. A soil mass under given loads should have an adequate factor of safety will respect to shear failure, and deformation under given loads should not exceed certain tolerable limits.There are several methods available for analysis of the stability of slopes in soils. Most of theses may be classed as limit equilibrium methods in which the basic assumption is that coulomb’s failure criterion is satisfied along the assumed path of failure.1.1 analysis of stability in cohesive soil1.2 the Swedish method slices2 the stability of slopes in rocksThe design for a slope excavated in rock necessitates a well planned site investigation, indeed no design can be better than the quality of the geological input data. Such a site investigation must obtain as much information as possible on the character of the discontinuities within the rock mass in question, since the stability of a rock mass is frequently dependent upon the nature of the discontinuities. Information relating to the spatial relationships between discontinuities affords some indication of the modes of failure which may occur and information relating to the shear strength of the rock mass, or more particularly the shear strength along discontinuities, is required for use in the stability analysis. Furthermore data should be collected from all newly excavated faces in order to confirm or amend the original assumption made during design and, if necessary, to provide a basis for re-design.2.1 factors influencing rock slope stability2.2 types of failure in rock slopes●Methods of slope control and stabilizationIt is rarely economical to design a rock slope so that no subsequent rock falls occur, indeed many roads in rough terrain could not be constructed with the finance available without accepting some such risk. Therefore except there absolute security is essential, slopes should be designed to allow small falls ofrock under controlled conditions. For an economical design, about 10% of the slope area may require some treatment at a later date. Subsequent slope treatment may take the form of a reduction in the overall slope angle so as to increase the factor of safety. Obviously care must be taken to avoid damaging the slope when it is being trimmed by further blasting. Care also should be taken to maintain a constant slope line.1 reinforcement of slopesRock bolts may be used as reinforcement to enhance the stability of slopes excavated in jointed rock masses. They provide additional strength on critical planes of weakness within the rock mass.Reinforced earth walls are constructed by erecting a thin front skin at the face of the wall whilst at the same time the earth is placed. Strips of steel are fixed to the facing skin at regular intervals. They can be rapidly erected but only serve to support shallow translation slides. Gabions consists of strong wire mesh surrounding placed stones which are built to a given height. They provide a stable structure pervious to water.2 drainage of slopesDrainage is the most generally applicable method for improving the stability of slopes for the corrective treatment of slides, regardless of type, since it reduces the effectiveness of the principal causes of instability, namely, excess pore water pressure. In rock masses ground water also tends to reduce the shear strength along discontinuities. Moreover drainage is the only economic way of dealing with slides involving the movement of several million cubic metres.●Underground cavern1 location of underground cavernThe site investigation for an underground cavern has to locate a sufficiently large mass of sound rock in which the cavern can be excavated. Because caverns usually are located at appearance of weathering and consequently the chief considerations are rock quality, geological structure and ground water conditions. The orientation of an underground cavern is usually based on an analysis of the area and, where relevant, also on the basis of the stress distribution. It usually is considered necessary to avoid and orientation whereby the long axis is parallel to steeply inclined major joint sets.2 stability of underground caverns3 influence of joins4 excavation of underground caverns●Types of foundation structuresFootingsRafsPiersPiles●Dewatering●Some of the worst conditions are met in excavation which have to be taken below the water table. In such cases the water level must be lowered by dewatering. The method adopted for dewatering an excavation depends upon the permeability of the soil and its variation within the stratal sequence, the depth of base level below the water table, piezometric conditions in underlying horizons, the method ofproviding support to the sides of the excavation and of safeguarding neighbouring structures.●Methods of ground treatment1 grounting2 vibroflotation or vibrocompaction3 dynamic compaction●Geological factors in roof behaviorApart from the presence of high stress levels in relation to rock strength, strata behaviour in the roof of an underground mine is affected by a number of detailed geological features in the actual beds concerned among which the more significant factors are discussed below.1 presence of weak or unconsolidated materials2 deteroration with exposure3 bedding-plane discontinuities4 washout structures5 joint and fault pattern2．学生学习本课程的基本要求了解和掌握工程地质有关的专业词汇，规范的英语表达方式；通过教学是学生基本借助工具书可以流利阅读，翻译专业英语。
基于_RWEQ_模型的土壤颗粒含量与土壤可蚀性关系研究
Hans Journal of Agricultural Sciences 农业科学, 2023, 13(6), 619-626 Published Online June 2023 in Hans. https:///journal/hjas https:///10.12677/hjas.2023.136084基于RWEQ 模型的土壤颗粒含量与 土壤可蚀性关系研究刘 洋1，李 欣2，闫 晴1，张彩荣11北京林业大学水土保持学院，北京2陕西镇安抽水蓄能有限公司，陕西 商洛收稿日期：2023年5月26日；录用日期：2023年6月23日；发布日期：2023年6月30日摘 要本文为研究土壤颗粒含量与土壤可蚀性因子EF 值的关系，依据RWEQ 模型，构建了各土壤颗粒含量分别从1%到98%以及粉粒、粘粒和砂粒含量为1%、2%、10%、30%、50%、70%、90%的整数组合数据集，计算了有机质含量为2%的前提条件下的土壤可蚀因子EF 值，分析了不同土壤颗粒含量条件下土壤可蚀因子变化以及其两者间的相关性。
结果表明：1) 土壤砂粒含量越高，土壤可蚀性因子EF 值越大，说明砂粒含量与土壤可蚀性因子EF 值呈正相关；2) 当土壤粘粒含量较低时，向土壤中加入粘土颗粒，土壤可蚀性降低速度显著加快，说明粘粒含量越高，土壤抗侵蚀能力提升越快；3) 影响土壤可蚀性的主要因子为土壤砂粒含量与土壤粘粒含量的比值(Sa/Cl)，其比值越大，土壤可蚀性越低，控制好粘土与砂粒的比例，可有效提高土地抗侵蚀能力。
关键词RWEQ 模型，土壤颗粒含量，土壤可蚀性因子Study on the Relationship between Soil Particle Content and Soil Erodibility Based on RWEQ ModelYang Liu 1, Xin Li 2, Qing Yan 1, Cairong Zhang 11School of Soil and Water Conservation, Beijing Forestry University, Beijing 2Shaanxi Zhen’an Pumped Storage Co., Ltd., Shangluo ShaanxiReceived: May 26th , 2023; accepted: Jun. 23rd , 2023; published: Jun. 30th, 2023刘洋 等AbstractIn order to study the relationship between soil particle content and soil erodibility factor EF value, based on the RWEQ model, the integer combination data sets of soil particle content from 1% to 98% and silt, clay and sand content of 1%, 2%, 10%, 30%, 50%, 70% and 90% were constructed in this paper. The soil erodibility factor EF value under the premise of the organic matter content of 2% was calculated, and the changes in soil erodibility factor under different soil particle contents and the correlation between them were analyzed. The results showed that: 1 ) The higher the soil sand content, the greater the soil erodibility factor EF value, indicating that the sand content was positively correlated with the soil erodibility factor EF value; 2 ) When the soil clay content was low, adding clay particles to the soil, the soil erodibility decreased significantly faster, indicating that the higher the clay content, the faster the soil erosion resistance increased; 3 ) The main factor affecting soil erodibility is the ratio of soil sand content to soil clay content (Sa/Cl). The greater the ratio, the lower the soil erodibility. Controlling the ratio of clay to sand can effectively improve soil erosion re-sistance.KeywordsRWEQ Model, Soil Particle Content, Soil Erodibility FactorCopyright © 2023 by author(s) and Hans Publishers Inc.This work is licensed under the Creative Commons Attribution International License (CC BY 4.0). /licenses/by/4.0/1. 引言土壤侵蚀是土壤退化的一种表现形式。
废钢对转炉熔池流体流动影响研究
第21卷第4期 2021年4月过程工程学报The Chinese Journal of Process EngineeringVol.21 No.4Apr. 2021】流动与传递l DOI: 10.12034/j.issn. 1009-606X.220131 Influence of scrap on bath flow characteristics of converterXiaobin ZHOU1*,Shiheng PENG1,Yong LIU1,Duogang WANG21. School of Metallurgical Engineering, Anhui University of Technology, Ma'anshan, Anhui 243000, China2. Shanghai Meishan Iron and Steel Co., Ltd., Nanjing, Jiangsu 210039, fchinaAbstract: The current study focus on the flow characteristicsand the effects o f scrap on the bath flow with the help ofmathematical model which is built based on the physical modelof a 250 t converter.The results showed that the mixing timewas a decreasing function of the flow rate of bottom blowingwhen the flow rate was relatively low (<40 L/min).On thecontrary,excessive high flow rate of the bottom blowing wouldnot contribute on the decreasing of the mixing time whichdemonstrated that increasing flow rate was not favorable fordecreasing the mixing time if the flow rate was higher than thecritical value.With increasing the scrap volume,the plumeformed in the bottom blowing moved towards to the bath wall.Meanwhile,the maximum velocity of the plume increased from0.24 m/s to0.40 m/s when the bottom flow rate was50 L/min compared to the flow rate o f15 L/min.The kinetic energy of the bath was increased while the volume ratio o f the low-velocity zone was decreased when the scrap volume increased.The volume ratio of the low-velocity zone can be decreased89.46% when401scrap was added into the bath compared to that of no scrap addition.Specifically,compared to that of 15 L/min when 60 t scrap was added,the transfer indexes decreased 2.98%, 6.27% and 8.68% when the bottom flow rate increased to 25, 40 and 50 L/min, respectively.The effects o f the scrap volume on the energy transfer index was also investigated and the results showed that increasing the scrap volume was benefit to increase the energy transfer index for the bath and large volume o f the scrap greatly increased the energy transfer index.When the bottom flow rate was25 L/min,the energy transfer index increased2.48% and41.41% when the scrap volume increased to 10 and60 t,respectively.Key words: scrap;phisical simulation;numerial simulation;kinetic energy o f the bath;energy index o f bottom blowing收稿：2020-04-14，修回：2020-05-31,网络发表：2020-07-20，Received: 2020-04-14, Revised: 2020-05-31，Published online: 2020-07-20基金项目：国家自然科学基金资助项目(编号：51704006)作者简介：周小宾(1985-)，男，安漱省马鞍山市人，博士研宄生，讲师，冶金工程专业，E-mail: ******************.引用格式：周小宾，彭世恒，刘勇，等.废钢对转炉熔池流体流动影响研究.过程工程学报，2021，21(4): 410-419.Zhou X B, Peng S H, Liu Y, et a l. Influence of scrap on bath flow characteristics of converter (in Chinese). Chin. J. Process Eng., 2021,21(4): 410-419, DOI: 10.12034/j.issn.l009-606X.220131.第4期周小宾等：废钢对转炉熔池流体流动影响研究411废钢对转炉熔池流体流动影响研究周小宾”，彭世恒\刘勇、王多刚21.安徽工业大学冶金工程学院，安徽马鞍山2430002.上海梅山钢铁股份有限公司，江苏南京210039摘要：通过物理模拟和数值模拟，研宂某钢厂250吨转炉中废钢集中分布时熔池特征，以及废钢对转炉熔池流体流动的影响。
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Vol. 18, No. 3 EARTHQUAKE ENGINEERING AND ENGINEERING VIBRATION July, 2019Earthq Eng & Eng Vib (2019) 18: 487-496 DOI: https://doi.org/10.1007/s11803-019-0516-7
Infl uence of sand content on the fl ow characteristics of soft soil under cyclic and high-frequency vibration
Zhuang Zhongxun1†, Yin Deshun1‡, Bai Chunyu1† and Zhou Chao2†
1. College of Mechanics and Material, Hohai University, Nanjing 211100, China 2. China Machinery International Engineering Design & Research Institute Co. Ltd, East China Branch, Nanjing 214006, China
Abstract: The fl ow characteristics of foundation soils subjected to train loads can present engineering hazards in high-
speed railways. In order to verify the feasibility of blending coarse sand in modifying soft subsoil, undrained pulling sphere tests were carried out and the train loads were simulated through localized and cyclic vibration at various frequencies. Laboratory testing results indicate that the fl ow characteristics of soft soil can be signifi cantly enhanced by high-frequency vibration; meanwhile the continuous increase in fl ow characteristics caused by cyclic vibration may be an important reason for the long-term settlement of soft subsoil. The infl uence of sand content on fl ow characteristics is also studied in detail, and it is shown that the addition of coarse sand can weaken the fl ow characteristics of soft soil induced by sudden vibration at lower than 50 Hz. Under the condition of cyclic vibration, the growth of the fl ow characteristics of sand-clay mixtures is mainly caused by the fi rst-time vibration in the cycle, and the increase in sand content can make the fl ow characteristics present a faster convergent tendency.
Keywords: sand content; fl ow characteristics; pulling sphere tests; soft soil
Correspondence to: Yin Deshun, College of Mechanics and Material, Hohai University, Nanjing 211100, China Tel: +86-13675176567 E-mail: yindeshun@hhu.edu.cn†Undergraduate; ‡Professor Supported by: Natural Science Foundation of Jiangsu Province of China under Grant No. BK2012810Received June 21, 2017; Accepted August 25, 2018
1 IntroductionMany high-speed railways located in the eastern coastal areas of China are built on soft grounds due to the extensive distribution of soft soil. It is known that thick soft soil layers have brought great security risks to the construction and development of current Chinese rail transportation due to its high compressibility and natural water content, low shear resistance and low bearing capacity. Based on the results of previous investigations reported by Zhan et al. (2014), Madshus and Kaynia (2000), and Sheng et al. (2004), the foundation soil of railways are subjected to static loads of embankment and operational loads which is mainly shown as vibration. Currently, the continuous post-construction settlement that happens in high-speed railway tunnels and subways (Chen et al., 2002; Liu and Chen, 2008; Huang et al., 2015), is mainly attributed to the subsoil instead of the roadbed (Bian et al., 2010). Hence it is essential to characterize the behavior of foundation soil of high-
speed railways under cyclic and vibration loads in order to apply a simple and eff ective method to achieve soil improvement.The increase in the fl ow characteristics of soft soil caused by vibration is an important reason for subgrade settlement and structural failure, which are mainly shown as seismic liquefaction and damage to pile foundations, according to Tang et al. (2014), Zhou et al. (2014), Jafarian et al. (2014), Barlett and Youd (1995). How the dynamic properties of soft soil subjected to vibration loads change have been extensively investigated in the literature. Many researchers (Boulanger and Idriss, 2006; Lee and Sheu, 2007; Mortezaie and Vucetic, 2013; Vucetic and Dobry, 1988) have applied several theories and explanations to the changes in modulus degradation, permeability and liquefaction resistance from the point of view of solid mechanics. However, as a fl uid-like state, the motion and deformation properties of liquefi ed soil are similar to viscous fl uid instead of solid; thus it is more appropriate to investigate the fl ow characteristics of undermined soft soil based on hydrodynamics assumption in accordance with Hadush et al. (2000) and Uzuoka et al. (1998). Hwang et al. (2006) considered liquefi ed sand as a non-Newtonian fl uid, and found out its viscosity decreased with increasing shear strain rate through sinking ball tests and pulling bar tests. Montassar and de Buhan (2005) modeled liquefi ed ground as a viscoplastic material; they presented a comprehensive numerical method to simulate the incipient fl ow failure