土木专业英语课件Lesson

Lesson 3New words1. colloidal胶状的，胶体的，colloid 胶体2. sieven,v. 筛，过筛，过滤3. samplen.vt. 样品，取样 specimen4. meshn.v 网孔，网格，分网格5. cumulative a. 积累的；cumulate, cumulation 6. gradingn. 级配，等级；grade7. sedimentationn. 沉淀; sediment 8. suspensionn. 悬浮；suspend bridge cable-stayed bridge 9. agitatev. 搅动，混合；disturb10. hydrometern. （液体）比重计11. viscosityn. 黏性；viscoidal 12. flakyn. 薄片状的，of flake 13. pipetten. 吸液管14. irrecoverablea. 不可恢复的 irretrievable 15. concave a. 凹的；convex 凸的16. permeabilityn. 渗透性; permeate, permeable seep seepage Phrases and expressions1. frost susceptibility霜冻敏感性2. sieving method筛分法3. semi-logarithmic curve半对数曲线4. grading curve级配曲线 5. wet sieving湿法筛分6. dispersing agent分散剂7. Stokes law斯托克定律8. unit weight重度 9. coefficient of grading级配系数10. sedimentation method沉降法11. particle-size distribution粒径分布Text Particle Size Analysis 粒径分析The range of particle sizes encountered in soils is very wide: from around 200mm down to the colloidal size of some clays of less than 0.001mm. 在各种土中所遇到的粒径范围很大，大到200mm小到小于0.001mm的一些粘土胶粒。Although natural soils are mixtures of various-sized particles, it is common to find a predominance occurring within a relatively narrow band of sizes. 尽管天然土都是由各种粒径的颗粒组成，但通常可发现其主要组成颗粒出现在一个比较小的粒径范围内。When the width of this size band is very narrow the soil will be termed poorly-graded, if it is wide the soil is said to be well-graded. 当这一粒径范围非常小时，称这种土级配较差，而当其较大时，称这种土级配良好。A number of engineering properties, e.g. permeability, frost susceptibility, compressibility, are related directly or indirectly to particle-size characteristics. 土的许多工程特性，如渗透性、霜冻敏感性、可压缩性等都直接或间接的与土的级配特性有关。Fig.3.1 shows the British Standard range of percentage of particle sizes. 图3.1为粒径百分数的英国标准范围。The particle-size analysis of a soil is carried out by determining the weight percentage falling within bands of size represented by these divisions and sub-divisions. 通过确定落入由这些粒径分组和子组所代表的粒径范围的重量百分比，对土进行粒径分析。In the case of a coarse soil, from which fine-grained particles have been removed or were absent, the usual process is a sieve analysis. 对于粗粒土，它里面的细粒土被除去或本身就无细颗粒，常用的方法就是筛分法。A representative sample of the soil is split systematically down to a convenient sub-sample size and then oven-dried. 此法是将要分析土的一代表样本系统地分为方便的子样本，然后烘干。This sample is then passed through a nest of standard test sieves arranged in descending order of mesh size. 再使烘干的土样通过一组筛孔尺寸由大至小放置的标准试验筛。The weight of soil retained on each sieve is determined and the cumulative percentage of the sub-sample weight passing each sieve calculated. 称量每个筛中剩下的土样的重量，并计算出通过每个筛的累计百分数。From these figures the particle-size distribution for the soil is plotted as a semi-logarithmic curve (Fig.3.2) known as grading curve. 根据这些数据，以半对数曲线的形式描出该土的粒径分布图，即所谓的级配曲线。细粒粗粒非常粗大颗粒粘土胶粒粉土砂砾石石块细中粗细中粗细中粗卵石块石Where the soil sample contains fine-grained particles, a wet sieving procedure is first carried out to remove these and to determine the combined clay/silt fraction percentage. 在土样中含有细土粒的场合，首先用湿筛分法将其除去，并确定粘粒/粉粒总共所占的分数。A suitable-sized sub-sample is first oven-dried and then sieved to separate the coarsest particles (>20mm). 将一适量的分土样烘干，并过筛分开最粗的颗粒（>20mm的颗粒）The sub-sample is then immersed in water containing a dispersing agent and allowed to stand before being washed through a 63mm(micron) mesh sieve. 然后将土样浸入含有分散剂的水中，并在将其用63微米筛过筛前搁置起来（并将其搁置一会，再用63micron的筛子过筛）。The retained fraction is again oven-dried and passed through a nest of sieves. 将筛中保留的部分烘干，并用一组筛子过筛。After weighing the fractions retained on each sieve and calculating the cumulative percentage passing each sieve, the grading curve is drawn. 称量落在每个筛中土重，并计算出通过每个的累计百分数后，就可描出级配曲线。The combined clay/silt fraction is determined from the weight difference and expressed as a percentage of the total sub-sample weight. The coarsest fraction (>20mm) can also be sieved and the results used to complete the grading curve. 由重量差确定粘粒/粉粒的总重，并将其表示为子土样总重的百分数。最粗的部分（即粒径>20mm的部分）也可被过筛，并用其结果完成级配曲线的绘制。A further sub-division of particle-size distribution in the fine-grained fraction is not possible by the sieving method. 不能用筛分法对细粒部分的粒径分布作进一步分组。A process of sedimentation is normally carried out for this purpose. 通常必须用沉降法实现此目的。 A small sub-sample of soil is first treated with a dispersing agent and then washed through a 63mm sieve. 首先将一小子土样用分散剂进行处理，然后洗过63的筛子。The soil/water suspension is then made up to 500 ml, agitated vigorously for a short while and then allowed to settle. 再从中取出500ml的土/水悬浮液，充分搅拌一会后让其沉降。The procedure is based on Stokes law, which states that the velocity at which a spherical particle will sink due to gravity in a suspension is given by: 此方法是基于斯托克思定律，即在重力作用下球形颗粒在某一悬浮液中下降的速度为Where d=diameter of particle 颗粒直径gs =unit weight of the grain of particle 颗粒重度gw =unit weight of the suspension fluid (usually water) 悬浮液的重度（通过为水的重度）h=vescosity of the suspension fluid （悬浮液的黏度）The diameter of those particles that will have settled a given distance in a given time (t) may be obtained by rearranging Eq.3.1: 将式3.1变形得在给定时间t内，沉降一给定距离的那些颗粒的直径为Usually h=100mm, 通常h=100mm, giving 由此给出Samples taken at a depth of 100mm, at an elapsed time of t, will not, therefore, include particles of greater size than the diameter d given by Eq.3.2; 因此在，在深度100mm处，t 时间后所取的悬浮液中将不会有粒径大于式3.2所给出的土粒; but the proportions of particles smaller than d in the suspension will remain unchanged. 但悬浮液中小于d的颗粒所占的比例仍保持不变。The procedure using a hydrometer consists of measuring the suspension density at a depth of 100mm at a series of elapsed-time intervals. 用液体比重计的方法包括以一系列时间间隔在深度100mm处测定悬浮液的比重。The percentage-finer values corresponding to particular diameter (i.e. particle sizes) are obtained from the density readings, and thus a grading curve for the fine-grained fraction may be drawn. 通过比重读数得到小于某一特定粒径的颗粒的百分数，从而可画出细粒部分的级配曲线。Grading CharacteristicsThe grading curve is a graphical representation of the particle-size distribution and is therefore useful in itself as a means of describing the soil. 级配曲线是粒径分布的一种图形表达，因而可用来作为描述土的手段。For this reason it is always a good idea to include copies of grading curves in laboratory and other similar reports. 因此，人们总是认为在实验室报告或其它报告里附上几份级配曲线是一种好做法。 It should also be remembered that the primary object is to provide a descriptive term for the type of soil. 还应牢记的是我们的主要目的是提供对土的类型的描述性术语。This is easily done using the type of chart by estimating the range of sizes included in the most representative fraction of the soil. 这可容易地通过采用这种级配曲线做到，因为用它能估计出土中最有代表性的成分的粒径范围。For example, the steep curve may be taken to represent a poorly-graded medium sand, indicating a narrow range of sizes. 例如，陡峭的曲线可用来表示级配差的中砂，并表示其粒径范围比较小。A further quantitative analysis of grading curves may be carried out using certain geometric values known as grading characteristics. 通过采用某些称为级配特征的几何值，可进一步对级配曲线进行定量的分析。First of all, three points are located on the grading curve to give the following characteristic sizes: 首先，定出级配曲线上的三个点以给出以下特征粒径：D10=maximum size of the smallest 10 percent of the sample; 只有10%土样通过的最大粒径；D30= maximum size of the smallest 30 percent of the sample; 只有30%土样通过的最大粒径；D60= maximum size of the smallest 60 percent of the sample；只有60%土样通过的最大粒径；From these characteristic sizes, the following grading characteristics are defined: 根据这些特征粒径，定义出如下级配特征：Effective size 有效粒径Uniformity coefficient均匀系数Coefficient of gradation级配系数