Lesson 15 soil mechanical(土木工程專業(yè)英語)

1、Lesson 15 Text: Soil Mechanics教學(xué)要求:1、掌握有關(guān)Soil Mechanics的專業(yè)術(shù)語；2、 熟悉一些常見的表達(dá)方式；3、 延伸了解一些土力學(xué)歷史和名人；4、 能正確、流暢地翻譯1 Soil mechanics is concerned with the use of the laws of mechanics and hydraulics in engineering problems related to soil. Soil is a natural aggregate of mineral grains, with or without organic

2、 constituents, formed by the chemical and mechanical weathering of rock. It consists of three phases: solid mineral matter, water, and air or other gas. Soils are extremely variable composition, and it was this heterogeneity that long discouraged scientific studies of these deposits.hydraulics haidr

3、:liks 水力學(xué) aggregate grigeit 集合體phase feiz 階段,相heterogeneity .hetrudini:iti 異質(zhì)性,多相性 土力學(xué)研究的是在工程問題中與土相關(guān)的力學(xué)和水力學(xué)定律的應(yīng)用。土是礦物粒的天然集合物，這些礦物粒是巖石經(jīng)過化學(xué)或物理風(fēng)化而形成，含或者不含有機(jī)成分。土包含有三個(gè)相：固態(tài)的礦物質(zhì)，水，空氣或其他氣體。土的組成極其復(fù)雜，正是這種異質(zhì)性，長(zhǎng)期以來阻礙了對(duì)這個(gè)堆積物的研究。 2(生物體,有機(jī)體) 3Gradually, the investigation of failures of retaining walls, foundations

4、, embankments, pavement, and other structures resulted in a body of knowledge concerning the nature of soils and their behavior sufficient to give rise to soil mechanics as branch of engineering science.retaining wall :擋土墻 embankments imbkmnt 堤防, 筑堤pavement peivmnt 路面 逐漸地，通過對(duì)那些失敗的擋土墻、基礎(chǔ)、堤壩、路面及其他結(jié)構(gòu)的調(diào)

5、查研究，人們積累了大量的有關(guān)土的類型及其性質(zhì)的知識(shí)，從而形成了工程學(xué)科的分支土力學(xué)。 4 History. Little progress was made in dealing with soil problems on a scientific basis until the latter half of the 18th century, when the French physicist Charles-Augustin de Coulomb published his theory of pressure (1773). In 1857 the Scottish engineer W

6、illiam Rankine developed theory of equilibrium of earth masses and applied it to some elementary problems of foundation engineering. These two classical theories still form the basis of current methods of estimating earth pressure, even though they were based on the misconception that all soils lack

7、 cohesion, as does dry sand. Twentieth-century advances have been in the direction of taking cohesion into account; understanding the basic physical properties of soils in general and of a the plasticity of clay in particular; and systematically studying the shearing characteristics of soilthat is,

8、their performance under conditions of sliding. 5cohesion kuhi:n 內(nèi)聚力,粘聚力 ;plasticity plstisiti 塑性; 歷史。18世紀(jì)后葉之前，人們?cè)谘芯坑嘘P(guān)土的科學(xué)理論方面進(jìn)展很小，直到法國(guó)物理學(xué)家查里.奧古斯丁.庫侖（Charles-Augustin de coulomb）在1773年出版了他的土壓力學(xué)說。1857年，蘇格蘭工程師朗肯（William Rankine）發(fā)展了土的平衡理論，并將其用于基礎(chǔ)工程的基本問題中。盡管這兩個(gè)經(jīng)典理論是建立錯(cuò)誤的假設(shè)上，即認(rèn)為土和干燥的沙子一樣是缺乏粘聚力的，但仍然形成了當(dāng)前估算

9、土壓力方法的理論基礎(chǔ)。這方面的研究，在21世紀(jì)有了突破，粘聚力計(jì)入計(jì)算，了解了一般情況土的物理性質(zhì)和特殊情況下土的塑性，還系統(tǒng)地研究了土的剪切性質(zhì)也就是土滑動(dòng)時(shí)的性能。6 Charles Augustin de Coulomb (17361806) was a French physicist. He is best known as the discoverer of Coulombs law, which defines the force of electrostatic attraction and repulsion. The SI unit of charge, the coulo

10、mb, was so named in his honour. William John Macquorn Rankine (1820-1872) was a Scottish engineer and physicist. Rankine 被后人譽(yù)為那個(gè)時(shí)代的天才，他在熱力學(xué)、流體力學(xué)及土力學(xué)等領(lǐng)域均有杰出的貢獻(xiàn)。 7 Both Coulombs and Rankines theories assumed that the surface of rupture of soil subjected to a shearing force is a plane. While this is a

11、reasonable approximation for sand, cohesive soils tend to slip along a curved surface. In the early 20th century, Swedish engineers proposed a circular arc as the surface of slip. During the last half century considerable progress has been made in the scientific study of soil and in the application

12、of theory and experimental data to engineering design. rupture rpt(r) 斷裂a(bǔ)pproximation 接近、近似值cohesive kuhi:siv 粘性的(有結(jié)合性的,有粘聚性的)8 A significant advance was made by the German engineer Karl Terzaghi, who in 1925 published a mathematical investigation of the rate of consolidation of clays under applied

13、pressure. His analysis, which was confirmed experimentally, explained the time lag of settlements on fully waterlogged clay deposits. Terzaghi coined the term soil mechanics in 1925 when he published the book Erdbaumenchanik (“Earth-. BuildingKarl Terzaghi （ 1883 1963 ）卡爾特扎吉 consolidation kn.slidein

14、 固結(jié)waterlogged w:tlgd 浸滿水的mechanics”)9Karl TerzaghiThe Father of Soil Mechanics. Born: October 2, 1883 in Prague Died: October 25, 1963 in Winchester, Massachusetts He was married to Ruth D. Terzaghi, a geologist. He won the Norman Medal of ASCE four times (1930, 1943, 1946, and 1955). He was given

15、nine honorary doctorate degrees from universities in eight different countries. He started modern soil mechanics with his theories of consolidation, lateral earth pressures, bearing capacity, and stability. nutshell: 10 Researching on subgrade materials, the natural foundation under pavements, was b

16、egun about 1920 by the U.S. Bureau of Public Roads. Several simple tests were correlated with the properties of natural soils in relation to pavement design. In England, the Road Research Board was set up in 1993. In 1936 the first international conference on soils was held atsubgrade 路基 U.S. Bureau

17、 of Public Roads 美國(guó)公路局 Road Research Board 公路研究部Harvard University.11 Today, the civil engineer relies heavily on the numerical results of tests to reinforce experience and correlate new problems with established solutions. Obtaining truly representative samples of soils for such tests, however, is

18、extremely difficult; hence there is a trend toward testing on the site instead of in the laboratory, and many important properties are now evaluated in this way. . 今天，土木工程師都會(huì)借重于試驗(yàn)的數(shù)據(jù)來加強(qiáng)經(jīng)驗(yàn)，把新問題和已確定的解決方法聯(lián)系起來。但是，要獲得具有代表性的土樣做測(cè)試，是非常困難的，因此，現(xiàn)在傾向于用在現(xiàn)場(chǎng)做測(cè)試來取代實(shí)驗(yàn)室的試驗(yàn)?，F(xiàn)在，大多數(shù)重要的土特性采用這種方法來評(píng)定。 12 Engineering proper

19、ties of soils. The properties of soil that determine their suitability for engineering use include internal friction, cohesion, compressibility, elasticity, permeability, and internal friction 內(nèi)摩擦力cohesion kuhi:n 粘聚力compressibility km.presibiliti 壓縮性permeability .p:mibiliti 滲透性capillarity kpilriti 毛

20、細(xì)性Capillarity.13 Internal friction is the resistance to sliding offered by the soil mass. Sand and gravel have higher internal friction than clays; in the latter an increase in moisture lowers the intern friction. The tendency of a soil to slide under the weight of a structure may be translated into

21、 shear; that is , a movement of a mass of soil in plans, either horizontal, vertical, or other. Such a shearing movement involves a danger of 內(nèi)摩擦力土體是抵抗滑動(dòng)的力。沙子和沙礫比粘土的內(nèi)摩擦力大，后者的內(nèi)摩擦力隨著濕氣的增加而降低。土在結(jié)構(gòu)的重力下，其滑動(dòng)的趨勢(shì)可能會(huì)轉(zhuǎn)換成剪切，也就是土的平面的，水平的、豎向的或者其他方向的運(yùn)動(dòng)。這種剪切運(yùn)動(dòng)會(huì)造成危險(xiǎn)的建筑事故。 building failure. 14 Also resisting the dan

22、ger of shear is the property of cohesion, which is the mutual attraction of soil particles due to molecular forces and the existence of moisture between them. Cohesion is generally very high in clays but almost nonexistent in sands or silts. Cohesion values range from zero for dry sand to 2,000 poun

23、ds per square foot for very stiff clay.mutual mju:tjul共同的,相互的 particle p:tikl 粒子,點(diǎn),極小量 molecular mulekjul 分子的silt silt 淤泥15 Compressibility is an important soil characteristic because of the possibility of compacting the soil by rolling, tamping, vibration, or other means, thus increasing its densit

24、y and load-bearing strength. An elastic soil tends to resume its original condition after compaction. Elastic (expansible) soil are unsuitable as subgrades for flexible pavements since they compact and expand as a vehicle passes over them, causing failure of the pavement.rolling r:uli碾壓 tampingtmpi

25、夯實(shí)vibration vaibrein 振動(dòng)flexible pavements 柔性路面16Cross sections of modern pavement 17 Permeability is the property of a soil that permits the flow of the water through it. Freezing-thawing cycles in winter and wetting-drying cycles in summer alter the packing density of soil grains. Permeability Capi

26、llarity causes water to rise through the soil above the normal horizontal plane of free water. In most soil numerous channels for capillary action exist; in clays, moisture may be raised as much asthawing :i 融化 packing density 堆積密度numerous nju:mrs 許多can be reduced by compaction. 30 feet by capillari

27、ty.18 Density can be determined by weight and volume measurements or by special measuring devices. Stability of soils is measured by an instrument called a stabilometer, which specifically measures the horizontal pressure transmitted by a vertical load. Consolidation is the compaction or pressing to

28、gether of soil that occurs under a specific load condition; thatstability stbiliti 穩(wěn)定性 stabilometer .steibilmit 穩(wěn)定儀,穩(wěn)定性量測(cè)儀 密度可以通過測(cè)定重量和體積得到，或者用特殊的測(cè)量?jī)x器測(cè)得。土的穩(wěn)定性可用一種穩(wěn)定儀測(cè)得，穩(wěn)定儀可明確測(cè)出豎向荷載帶來的水平壓力。固結(jié)是土在一種特殊荷載下的發(fā)生的壓實(shí)或者擠壓，同樣也可以測(cè)試出來。 property is also tested. 19 Site Investigation. Soil surveys are conducted to g

29、ather data on the nature and extent of the soil expected to be encountered on a project. The amount of effort spent on site investigation depends on the size and importance of the project; it may range from visual inspection to elaborate subsurface exploration by boring and laboratory testing. Colle

30、ction of representative sample is essential for proper identification and classification of soils. survey s:vei 測(cè)量 elaborate ilbrt 精細(xì)的,詳盡的 boring b:ri 鉆孔identification ai.dentifikein 鑒定,確認(rèn)20The number of samples taken depends on previously available data, variation in soil types, and the size of the

31、 project. Generally, in the natural profile at a location, there is more variation in soil characteristics with depth than horizontal distance. It is not good practice to collect composite samples for any given horizon (layer),since this does not truly represent any one location and could prove misl

32、eading. Even slight variation in soil characteristics in a horizon should be duly noted. Classification of the soil in terms of grain size and the liquid and plastic limits are particularlyprofile prufail 剖面，側(cè)面plastic limit限important steps.21 An understanding of the eventual use of the data obtained

33、 during site investigation is important. Advance information on the site conditions is helpful in planning any survey program. Information on topography, geological features (outcrops, road and stream cuts, lake beds, weathered remnants, etc.), paleontological maps, aerial photographs, well logs, an

34、d excavations can prove invaluable. Geophysical exploration methods yield useful corroboratory data. Measurement of the electrical resistivity of soils provides an insight into several soiltopography tpgrfi 地形學(xué),地勢(shì)geological dildikl 地質(zhì)學(xué)的，地質(zhì)的outcrops autkrp 露頭paleontological古生物學(xué)的； geophysical地球物理學(xué)的；el

35、ectrical resistivity ：電阻 characteristics.22 Seismic techniques often are used to determine the characteristics of various subsurface strata by measuring the velocity of propagation of explosively generated shock waves through the strata. The propagation velocity varies widely for different types of soils. Shock waves also are utilized to determine the depth of bedrock by measuring the time required for the shock wave to travel to he bedrock and returnSeismic saizmik 地震的 strata streit pl層(地層,階層,薄片) stratum: streitm velocity vilsiti 速度propagation .prpgein 傳播 地震學(xué)技術(shù)通過測(cè)定激震波穿過地層的傳播速度來確定不同地層的性質(zhì)