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（5 ） Strength criteria for isotropic rock material（1）Types of strength criterionA peak strength criterion is a relation between stress components which will permit the peak strengths developed under various stress combinations to be Similarly, a residual strength criterion may be used to predict residual strengths under varying stress In the same way, a yield criterion is a relation between stress components which is satisfied at the onset of permanent Given that effective stresses control the stress-strain behaviour of rocks, strength and yield criteria are best written in effective stress However, around most mining excavations, the pore-water will be low, if not zero, and so For this reason it is common in mining rock mechanics to use total stresses in the majority of cases and to use effective stress criteria only in special The data presented in the preceding sections indicate that the general form of the peak strength criterion should be （8）This is sometimes written in terms of the shear, and normal stresses, on a particular plane in the specimen:（9）Because the available data indicate that the intermediate principal stress, has less influence on peak strength than the minor principal stress, all of the criteria used in practice are reduced to the form (10)2 Coulomb’s shear strength criterionIn one of the classic paper of rock and of engineering science, Coulomb(1977) postulated that the shear strengths of rock and of soil are made up of two part – a constant cohesion and a normal stress-dependent frictional (Actually, Coulomb presented his ideas and calculations in terms of forces; the differential concept of stress that we use today was not introduced until the ) Thus, the shear strength that can be developed on a plane such as ab in figure 22 is（11）Where c=cohesion and Ф= angle of internal Applying the stress transformation equation to the case shown in figure 22 givesAnd Substitution for and s = τ in equation 11 and rearranging gives the limiting stress condition on any plane defined by β as（12） There will be a critical plane on which the available shear strength will be first reaches as б1 is The Mohr circle construction of Figure 4023a given the orientation of this critical plane as （13）This result may also be obtained by putting d(s-τ)/dβ = 0 For the critical plane, sin2β = cosФ, cos2β = -sinФ, and equation 12 reduces to （14）This linear relation between and the peak value of is shown in Figure Note that the slope of this envelope is related to Ф by the equation（15）And that the uniaxial compressive strength is related to c and Ф by （16） If the Coulomb shown in Figure 23b is extrapolated to = 0, it will intersect the axis at an apparent value of uniaxial strength of the material given by （17）The measurement of the uniaxial tensile strength of rock is fraught with However, when it is satisfactorily measured, it takes values that are generally lower than those predicted value of uniaxial tensile stress, = Although it is widely used, Coulomb’s criterion is not a particularly satisfactory peak strength criterion for rock The reasons for this are:(a) It implies that a major shear fracture exist at peak Observations such as those made by Wawersik and Fairhurst(1970) show that is not always the (b) It implies a direction of shear failure which does not always agree with experimental (c) Experimental peak strength envelopes are generally non- They can be considered linear only over limited ranges of or For these reasons, other peak strength criteria are preferred for intact However, the Coulomb criterion can provide a good representation of residual strength conditions, and more particularly, of the shear strength of discontinuities in rock (section 7)3 Griffith crack theoryIn another of the classic papers of engineering science, Griffith (1921) postulated that fracture of brittle materials, such as steel and glass, is initial at tensile stress concentrations at the tips of minute, thin cracks (now referred to as Griffith based his determination of the conditions under which a crack would extend on his energy instability concept: A crack will extend only when the total potential energy of the system of applied forces and material decreases or remains constant with an increase in crack ROCK STRENGTH AND DEFORMABILITY For the case in which the potential energy of the applied forces is taken to be constant throughout, the criterion for crack extension may be written (19)Where c is a crack length parameter, We is the elastic energy stored around the crack and Wd is the surface energy of the crack Griffith (1921) applied this theory to the extension of an elliptical crack of initial length 2c that is perpendicular to the direction of loading of a plate of unit thickness subjected to a uniaxial tensile stress, б He found that the crack will extend when （20）Where α is the surface energy per unit area of the crack surfaces (associated with the rupturing of atomic bonds when the crack is formed), and E is the Young’s modulus of the uncracked It is important to note that it is the surface energy, α, which is the fundamental material property involved Experimental studies show that, for rock, a preexisting crack does not extend as a single pair of crack surface, but a fracture zone containing large numbers of very small cracks develops ahead of the propagating crack 9FIGURE 25) In this case, it is preferable to treat α as an apparent surface energy to distinguish it from the surface energy which may have a significantly smaller It is difficult, if not impossible, to correlate the results of different types of direct and indirect tensile test on rock using the average tensile stress in the fracture zone as the basic material For this reason, measurement of the ‘tensile strength’ of rock has not been discussed in this However, Hardy(1973) was to obtain good correlation between the results of a rang of tests involving tensile fracture when the apparent surface energy was used as the unifying material Griffith (1924) extended his theory to the case of applied compressive Neglecting the influence of friction on the cracks which will close under compression, and assuming the elliptical crack will propagate from the points of maximum tensile stress concentration (P IN Figure 26), Griffith obtained the following criterion for crack extension in plane compression:（20）Where is the uniaxial tensile strength of the uncracked material (a positive number) This criterion can also be expressed in terms of the shear stress, τ , and the normal stress, acting on the plane containing the major axis of the crack:（21） The envelopes given by equations and 21 are shown in Figure Note that this theory predicts that the uniaxial compressive compressive stress at crack extension will always be eight times the uniaxial tensile
国外著名土木工程相关期刊列表(SCI/EI)国际重要学术期刊推荐表序号 国际重要学术期刊名称（SCI、EI检索源）1 Advances in Structural Engineering2 ACI Journal of Materials3 ACI Structural Journal4 Automation in Construction5 Buildings and Structures6 Canadian Geotechnical Journal ISSN: 0008-36747 Canadian Journal of Civil Engineering8 Computational Mechanics9 Computers and Structures10 Computers and Geotechnics ISSN: 0266-352X11 Cement and Concrete Research12 Computer Methods in Applied Mechanics and Engineering13 Communications in Numerical Methods in Engineering14 Earthquake Engineering and Structural Dynamics15 Earthquake Spectrum16 Engineering Geology17 Engineering Analysis with Boundary Elements18 Engineering Structures19 Geotechnique ISSN:0016-850520 Ground Engineering21 Geotextiles and Geomembranes22 International Journal of Impact Engineering ISSN: 0734-743X23 International Journal for Numerical and Analytical Methods in Geomechanics ISSN: 0363-906124 International Journal for Numerical Methods in Engineering25 International Journal of Rock Mechanics and Mining Sciences ISSN: 1365-160926 International Journal of Solids and Structures27 International Journal of Steel Structures28 International Journal of Space Structures29 International Journal of the Geotechnical Structures30 Journal of Applied Mechanics, ASME31 Journal of Bridge Engineering , ASCE32 Journal of Computing in Civil Engineering, ASCE33 Journal of Composites for Engineering, ASCE34 Journal of Constructional Steel Research35 Journal of Engineering Mechanics, ASCE36 Journal of Geodynamics ISSN: 0264-370737 Journal of Geotechnical and Geoenvironmental Engineering, ASCE ISSN: 1019-24138 Journal of Sound and Vibration39 Journal of Steel & Composite Structures40 Journal of Structural Engineering, ASCE41 Journal of Wind Engineering & Industrial Aerodynamics Wind and Structures42 Journal of Construction and Management43 Preceding of Civil Engineering Bailing and Bridge Structures44 Reliability Engineering & System Safety ISSN: 0951-832045 Rock Mechanics and Rock Engineering ISSN: 0723-263246 Shock and Vibration ISSN: 1070-962247 Soils and Foundations ISSN: 0038-080648 Soil Dynamics and Earthquake Engineering49 Structural Engineers50 Structural Engineering and Mechanics51 The Structural Design of Tall Buildings52 Thin-walled Structures53 The Magazine of Concrete Research54 Tunnelling and Underground Space Technology55 Wind and Structures-An International Journal56 Finite Elements in Analysis and Design注：以上是否被SCI、EI检索期刊为准。 除以上学术期刊外，学科认为是国际重要学术期刊，且被SCI、EI检索，专家组可认定为国际重要学术期刊
JINE Problem analysis on multi-layer frame construction in steel and [J]SichuanBuilding S18(06):13-Leung CKY Fiber optic sensorsconcrete: the future? NDT&EInternational 2001;34:85–
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童鞋你好！这个估计需要自己搜索了！网上基本很难找到免费给你服务的！我在这里给你点搜索国际上常用的外文数据库：----------------------------------------------------------❶ISI web of knowledge Engineering Village2❷Elsevier SDOL数据库 IEEE/IEE(IEL)❸EBSCOhost RSC英国皇家化学学会❹ACM美国计算机学会 ASCE美国土木工程师学会❺Springer电子期刊 WorldSciNet电子期刊全文库❻Nature周刊 NetLibrary电子图书❼ProQuest学位论文全文数据库❽国道外文专题数据库 CALIS西文期刊目次数据库❾推荐使用ISI web of knowledge Engineering Village2-----------------------------------------------------------中文翻译得自己做了，实在不成就谷歌翻译。弄完之后，自己阅读几遍弄顺了就成啦！学校以及老师都不会看这个东西的！外文翻译不是论文的主要内容！所以，很容易过去的！祝你好运！
知道几个，但英文不会写。
几年级的啊？
对土木工程的发展起关键作用的，首先是作为工程物质基础的土木建筑材料，其次是随之发展起来的设计理论和施工技术。每当出现新的优良的建筑材料时，土木工程就 会有飞跃式的发展。 人们在早期只能依靠泥土、木料及其它天然材料从事营造活动，后来出现了砖和瓦这种人工建筑材料，使人类第一次冲破了天然建筑材料的束缚。中国在公元前十一世纪 的西周初期制造出瓦。最早的砖出现在公元前五世纪至公元前三世纪战国时的墓室中。砖和瓦具有比土更优越的力学性能，可以就地取材，而又易于加工制作。 砖和瓦的出现使人们开始广泛地、大量地修建房屋和城防工程等。由此土木工程技术得到了飞速的发展。直至18～19世纪，在长达两千多年时间里，砖和瓦一直是土木工程的重要建筑材料，为人类文明作出了伟大的贡献，甚至在目前还被广泛采用。 钢材的大量应用是土木工程的第二次飞跃。 十七世纪70年代开始使用生铁、十九世纪初开始使用熟铁建造桥梁和房屋，这是钢结构出现的前奏。 从十九世纪中叶开始，冶金业冶炼并轧制出抗拉和抗压强度都很高、延性好、质量均匀的建筑钢材，随后又生产出高强度钢丝、钢索 。于是适应发展需要的钢结构得到蓬勃发展。除应用原有的粱、拱结构外，新兴的桁架、框架、网架结构、悬索结构逐渐推广，出现了结构形式百花争艳的局面。 建筑物跨径从砖结构、石结构、木结构的几米、几十米发展到钢结构的百米、几百米，直到现代的千米以上。于是在大江、海峡上架起大桥，在地面上建造起摩天大楼和高耸铁塔，甚至在地面下铺设铁路，创造出前所未有的奇迹。 为适应钢结构工程发展的需要，在牛顿力学的基础上，材料力学、结构力学、工程结构设计理论等就应运而生。施工机械、施工技术和施工组织设计的理论也随之发展，土木工程从经验上升成为科学，在工程实践和基础理论方面都面貌一新，从而促成了土木工程更迅速的发展。 十九世纪20年代，波特兰水泥制成后，混凝土问世了。混凝土骨料可以就地取材，混凝土构件易于成型，但混凝土的抗拉强度很小，用途受到限制。 十九世纪中叶以后，钢铁产量激增，随之出现了钢筋混凝土这种新型的复合建筑材料，其中钢筋承担拉力，混凝土承担压力，发挥了各自的优点。 二十世纪初以来，钢筋混凝土广泛应用于土木工程的各个领域。 从三十年代开始，出现了预应力混凝土。预应力混凝土结构的抗裂性能、刚度和承载能力，大大高于钢筋混凝土结构，因而用途更为广阔。土木工程进入了钢筋混凝土和预应力混凝土占统治地位的历史时期。混凝土的出现给建筑物带来了新的经济、美观的工程结构形式，使土木工程产生了新的施工技术和工程结构设计理论。这是土木工程的又一次飞跃发展。 建造一项工程设施一般要经过勘察、设计和施工三个阶段，需要运用工程地质勘察、水文地质勘察、工程测量、土力学、工程力学、工程设计、建筑材料、建筑设备、工程机械、建筑经济等学科和施工技术、施工组织等领域的知识 ，以及电子计算机和力学测试等技术。因而土木工程是一门范围广阔的综合性学科。随着科学技术的进步和工程实践的发展，土木工程这个学科也已发展成为内涵广泛、门类众多、结构复杂的综合体系。 土木工程是伴随着人类社会的发展而发展起来的。它所建造的工程设施反映出各个历史时期社会经济、文化、科学、技术发展的面貌，因而土木工程也就成为社会历史发展的见证之一。 远古时代，人们就开始修筑简陋的房舍、道路、桥梁和沟澶，以满足简单的生活和生产需要。后来，人们为了适应战争、生产和生活以及宗教传播的需要，兴建了城池、运河、宫殿、寺庙以及其他各种建筑物。 许多著名的工程设施显示出人类在这个历史时期的创造力。例如，中国的长城、都江堰、大运河、赵州桥、应县木塔，埃及的金字塔，希腊的巴台农神庙，罗马的给水工程、科洛西姆圆形竞技场(罗马大斗兽场)，以及其他许多著名的教堂、宫殿等。 产业革命以后，特别是到了20世纪，一方面社会向土木工程提出了新的需求；另一方面，社会各个领域为土木工程的前进创造了良好的条件。因而这个时期的土木工程得到突飞猛进的发展。在世界各地出现了现代化规模宏大的工业厂房、摩天大厦，核电站、高速公路和铁路、大跨桥梁、大直径运输管道长隧道、大运河、大堤坝、大飞机场、大海港以及海洋工程等等。现代土木工程不断地为人类社会创造崭新的物质环境，成为人类社会现代文明的重要组成部分。 土木工程是具有很强的实践性的学科。在早期，土木工程是通过工程实践，总结成功的经验，尤其是吸取失败的教训发展起来的。从17世纪开始，以伽利略和牛顿为先导的近代力学同土木工程实践结合起来，逐渐形成材料力学、结构力学、流体力学、岩体力学，作为土木工程的基础理论的学科。这样土木工程才逐渐从经验发展成为科学。 在土木工程的发展过程中，工程实践经验常先行于理论，工程事故常显示出未能预见的新因素，触发新理论的研究和发展。至今不少工程问题的处理，在很大程度上仍然依靠实践经验。 土木工程技术的发展之所以主要凭借工程实践而不是凭借科学试验和理论研究，有两个原因：一是有些客观情况过于复杂，难以如实地进行室内实验或现场测试和理论分析。例如，地基基础、隧道及地下工程的受力和变形的状态及其随时间的变化，至今还需要参考工程经验进行分析判断。二是只有进行新的工程实践，才能揭示新的问题。例如，建造了高层建筑、高耸塔桅和大跨桥梁等，工程的抗风和抗震问题突出了，才能发展出这方面的新理论和技术。在土木工程的长期实践中，人们不仅对房屋建筑艺术给予很大注意，取得了卓越的成就；而且对其他工程设施，也通过选用不同的建筑材料，例如采用石料、钢材和钢筋混凝土，配合自然环境建造了许多在艺术上十分优美、功能上又十分良好的工程。古代中国的万里长城，现代世界上的许多电视塔和斜张桥，都是这方面的例子。Plays a key role in the development of civil engineering, is the first civil construction materials as the basis for engineering material, followed by the subsequent development of the design theory and construction Whenever there is a fine new building materials, civil engineering will be a leap type People can only rely on the early Earth, wood and other natural materials in the construction activities, and later appeared in brick and tile that artificial materials, so that the first human to break the shackles of natural building Chinese in Eleventh Century BC in the early Western Zhou Dynasty created the The first brick in the fifth Century BC to the third Century BC, the tomb of the Warring States Brick and tile has superior mechanical properties,soil can obtain raw material locally, and easy to Emergence of brick and tile so that people began to widely, a large number of housing construction and urban flood control This civil engineering technology has been rapid Until 18 ~ nineteenth Century, as long as two thousand years, brick and tile has been a major civil engineering construction materials, made a great contribution to the human civilization, and was also widely used in the A large number of applications of steel products is the second leap in civil In seventeenth Century 70 time began using pig iron, the early nineteenth Century began to usewrought iron bridges and the construction of housing, which is a prelude to the emergence of From the beginning of the mid nineteenth Century, the metallurgical industry smelting and rolling out high tensile and compressive strength, good ductility, uniformity of the quality of construction steel, then produce high-strength steel wire, steel And meet the needs for development of steel structure has been In addition to the application of the original beam, arch structure, the new truss, frame, grid structure, and gradually promote the suspension structure,the form of the structure of a hundred flowers contend in beauty From the brick building long-span structure, stone structure, wood structure of a few meters, the development of tens of meters to 100 meters of steel structures, several hundred meters, 1000 meters until So the bridge in the river, channel, since the construction of skyscrapersand high-rise tower on the ground, even in the laying of underground railway, to create ahitherto To meet the development needs of the steel structure engineering, on the basis of Newton's mechanics, material mechanics, structural mechanics, structural engineering design theory would emerge as the times Theoretical design of machinery, construction technology and organization construction also development, civil engineering from the experience of rising to become science, both in engineering practice and theoretical basis for a new, which led tomore rapid development of civil In nineteenth Century 20, Portland cement concrete was Concrete aggregate can obtain raw material locally, easy to concrete structures forming, but the tensile strength of concrete is very small, limited By the middle of the nineteenth Century, the surge in steel production,followed by a composite building material of this new type of reinforced concrete, which bear the tension steel, concrete bear the pressure, to play their respective Since the beginning of twentieth Century, each field of reinforced concrete is widely used in From the beginning of the thirty's, the prestressed The crack resistance, stiffness and bearing capacity of prestressed concrete structure, much higher than the reinforced concrete structure, which uses Civil engineering into the reinforced concrete and prestressed concrete dominant historical Concrete brings the structural form of new economic,aesthetic to the building, civil engineering so that a theory of new construction technology and engineering structure This is a leap in the development of civil A project to build the facilities in general to go through investigation, design and construction in three stages, need to discipline the use of geological prospecting projects, hydro geological survey, engineering survey, soil mechanics, engineering mechanics, engineering design,building materials, construction equipment, engineering machinery, building the economy, and the construction technology, construction and other fields of knowledge, as well as the computer and mechanical testing Civil engineering is therefore a broad range of integrated With the development of science and technology development and engineering practice, the civil engineering disciplines have also been developed into a comprehensivesystem of broad connotation, category numerous, complicated Civil engineering is accompanied by the development of human society and the development It works in the construction of facilities reflect the face of social and economic development,technology, science, culture in every historical period, so the civil engineering has become one of the social and historical development of the In ancient times, people began to build simple houses, roads, bridges and water channel, to meet the simple life and production Later, people in order to adapt to the war, productionand dissemination of religious life and the need to build the city, canals,, palaces, temples and other Many well-known works shown in this historical period of human For example, Chinathe Great Wall, Dujiangyan, the Grande Canale, the Zhaozhou Bridge, the Yingxian Wood Tower, the Pyramid of Egypt, Greece's Parthenon, Rome's water supply project, Kolo Sim Arena(Rome Coliseum), and many other famous churches, After the industrial revolution, especially in twentieth Century, on one hand, the society puts forward new requirements to the civil engineering; on the other hand, each field of the society to create good conditions for the advancement of civil Thus this period of civil engineering has make a spurt of progress of In the rest of the world in the modern large-scale industrial plants, skyscrapers, nuclear power plants, highways and railways, long-span bridge, large diameter pipelines long tunnel, the Grande Canale, big dams, big airport, port and marine engineering Modern civil engineering to create a new physical environment for the human society, has become an important part of modern civilization of human Civil engineering is a very practical In the early days, through the civil engineering practice, summing up successful experience, especially draw lessons from the failure of From the beginning of seventeenth Century, with Galileo and Newton as a combination of pilot with the mechanics of the modern civil engineering practice, gradually formed the mechanical material mechanics, structural mechanics, fluid mechanics, rock mass, as the basis of the theory of civil engineering This experience in civil engineering from the gradually developed into a In the process of the development of civil engineering, engineering practice often first experience in theory, engineering accidents often show a new unforeseen factors, triggering a new theory of research and Yet many engineering problems, still rely on practical experience in the very great
1钢筋混凝土 素混凝土是由水泥、水、细骨料、粗骨料（碎石或；卵石）、空气，通常还有其他外加剂等经过凝固硬化而成。将可塑的混凝土拌合物注入到模板内，并将其捣实，然后进行养护，以加速水泥与水的水化反应，最后获得硬化的混凝土。其最终制成品具有较高的抗压强度和较低的抗拉强度。其抗拉强度约为抗压强度的十分之一。因此，截面的受拉区必须配置抗拉钢筋和抗剪钢筋以增加钢筋混凝土构件中较弱的受拉区的强度。 由于钢筋混凝土截面在均质性上与标准的木材或钢的截面存在着差异，因此，需要对结构设计的基本原理进行修改。将钢筋混凝土这种非均质截面的两种组成部分按一定比例适当布置，可以最好的利用这两种材料。这一要求是可以达到的。因混凝土由配料搅拌成湿拌合物，经过振捣并凝固硬化，可以做成任何一种需要的形状。如果拌制混凝土的各种材料配合比恰当，则混凝土制成品的强度较高，经久耐用，配置钢筋后，可以作为任何结构体系的主要构件。 浇筑混凝土所需要的技术取决于即将浇筑的构件类型，诸如：柱、梁、墙、板、基础，大体积混凝土水坝或者继续延长已浇筑完毕并且已经凝固的混凝土等。对于梁、柱、墙等构件，当模板清理干净后应该在其上涂油，钢筋表面的锈及其他有害物质也应该被清除干净。浇筑基础前，应将坑底土夯实并用水浸湿6英寸，以免土壤从新浇的混凝土中吸收水分。一般情况下，除使用混凝土泵浇筑外，混凝土都应在水平方向分层浇筑，并使用插入式或表面式高频电动振捣器捣实。必须记住，过分的振捣将导致骨料离析和混凝土泌浆等现象，因而是有害的。 水泥的水化作用发生在有水分存在，而且气温在50°F以上的条件下。为了保证水泥的水化作用得以进行，必须具备上述条件。如果干燥过快则会出现表面裂缝，这将有损与混凝土的强度，同时也会影响到水泥水化作用的充分进行。 设计钢筋混凝土构件时显然需要处理大量的参数，诸如宽度、高度等几何尺寸，配筋的面积，钢筋的应变和混凝土的应变，钢筋的应力等等。因此，在选择混凝土截面时需要进行试算并作调整，根据施工现场条件、混凝土原材料的供应情况、业主提出的特殊要求、对建筑和净空高度的要求、所用的设计规范以及建筑物周围环境条件等最后确定截面。钢筋混凝土通常是现场浇注的合成材料，它与在工厂中制造的标准的钢结构梁、柱等不同，因此对于上面所提到的一系列因素必须予以考虑。 对结构体系的各个部位均需选定试算截面并进行验算，以确定该截面的名义强度是否足以承受所作用的计算荷载。由于经常需要进行多次试算，才能求出所需的 3 截面，因此设计时第一次采用的数值将导致一系列的试算与调整工作。 选择混凝土截面时，采用试算与调整过程可以使复核与设计结合在一起。因此，当试算截面选定后，每次设计都是对截面进行复核。手册、图表和微型计算机以及专用程序的使用，使这种设计方法更为简捷有效，而传统的方法则是把钢筋混凝土的复核与单纯的设计分别进行处理。 2土方工程 由于和土木工程中任何其他工种的施工方法与费用相比较，土方挖运的施工方法与费用的变化都要快得多，因此对于有事业心的人来说，土方工程是一个可以大有作为的领域。在1935年，目前采用的利用轮胎式机械设备进行土方挖运的方法大多数还没有出现。那是大部分土方是采用窄轨铁路运输，在这目前来说是很少采用的。当时主要的开挖方式是使用正铲、反铲、拉铲或抓斗等挖土机，尽管这些机械目前仍然在广泛应用，但是它们只不过是目前所采用的许多方法中的一小部分。因此，一个工程师为了使自己在土方挖运设备方面的知识跟得上时代的发展，他应当花费一些时间去研究现代的机械。一般说来，有关挖土机、装载机和运输机械的唯一可靠而又最新的资料可以从制造厂商处获得。 土方工程或土方挖运工程指的是把地表面过高处的土壤挖去（挖方），并把它倾卸到地表面过低的其他地方（填方）。为了降低土方工程费用，填方量应该等于挖方量，而且挖方地点应该尽可能靠近土方量相等的填方地点，以减少运输量和填方的二次搬运。土方设计这项工作落到了从事道路设计的工程师的身上，因为土方工程的设计比其他任何工作更能决定工程造价是否低廉。根据现有的地图和标高，道路工程师应在设计绘图室中的工作也并不是徒劳的。它将帮助他在最短的时间内获得最好的方案。 费用最低的运土方法是用同一台机械直接挖方取土并且卸土作为填方。这并不是经常可以做到的，但是如果能够做到则是很理想的，因为这样做既快捷又省钱。拉铲挖土机。推土机和正铲挖土机都能做到这点。拉铲挖土机的工作半径最大。推土机所推运的图的数量最多，只是运输距离很短。拉铲挖土机的缺点是只能挖比它本身低的土，不能施加压力挖入压实的土壤内，不能在陡坡上挖土，而且挖。卸都不准确。 正铲挖土机介于推土机和拉铲挖土机的之间，其作用半径大于推土机，但小于拉铲挖土机。正铲挖土机能挖取竖直陡峭的工作面，这种方式对推土机司机来说是危险的，而对拉铲挖土机则是不可能的。每种机械设备应该进行最适合它的性能的作业。正铲挖土机不能挖比其停机平面低很多的土，而深挖坚实的土壤时，反铲挖土机最适用，但其卸料半径比起装有正铲的同一挖土机的卸料半径则要小很多。在比较平坦的场地开挖，如果用拉铲或正铲挖土机运输距离太远时，则装有轮胎式的斗式铲运机就是比不可少的。它能在比较平的地面上挖较深的土（但只能挖机械本身下面的土），需要时可以将土运至几百米远，然后卸土并在卸土的过程中把土大致铲平。在挖掘硬土时，人们发现在开挖场地经常用一辆助推拖拉机（轮式或履带式），对返回挖土的铲运机进行助推这种施工方法是经济的。一旦铲运机装满，助推拖拉机就回到开挖的地点去帮助下一台铲运机。 斗式铲运机通常是功率非常大的机械，许多厂家制造的铲运机铲斗容量为8 m³，满载时可达10 m³。最大的自行式铲运机铲斗容量为19立方米（满载时为25 m³），由430马力的牵引发动机驱动。 翻斗机可能是使用最为普遍的轮胎式运输设备，因为它们还可以被用来送混凝土或者其他建筑材料。翻斗车的车斗位于大橡胶轮胎车轮前轴的上方，尽管铰接式翻斗车的卸料方向有很多种，但大多数车斗是向前翻转的。最小的翻斗车的容量大约为5立方米，而最大的标准型翻斗车的容量大约为5m³。特殊型式的翻斗车包括容量为4 m³的自装式翻斗车，和容量约为5 m³的铰接式翻斗车。必须记住翻斗车与自卸卡车之间的区别。翻斗车车斗向前倾翻而司机坐在后方卸载，因此有时被称为后卸卡车。 3结构的安全度 规范的主要目的是提供一般性的设计原理和计算方法，以便验算结构的安全度。就目前的趋势而言，安全系数与所使用的材料性质及其组织情况无关，通常把它定义为发生破坏的条件与结构可预料的最不利的工作条件之比值。这个比值还与结构的破坏概率（危险率）成反比。 破坏不仅仅指结构的整体破坏，而且还指结构不能正常的使用，或者，用更为确切的话来说，把破坏看成是结构已经达到不能继续承担其设计荷载的“极限状态”。通常有两种类型的极限状态，即： （1）强度极限状态，它相当于结构能够达到的最大承载能力。其例子包括结构的局部屈曲和整体不稳定性；某此界面失效，随后结构转变为机构；疲劳破坏；引起结构几何形状显著变化的弹性变形或塑性变形或徐变；结构对交变荷载、火灾和爆炸的敏感性。 （2）使用极限状态，它对应着结构的使用功能和耐久性。器例子包括结构失稳之前的过大变形和位移；早期开裂或过大的裂缝；较大的振动和腐蚀。 根据不同的安全度条件，可以把结构验算所采用的计算方法分成： （1）确定性的方法，在这种方法中，把主要参数看作非随机参数。 （2）概率方法，在这种方法中，主要参数被认为是随机参数。此外，根据安全系数的不同用途，可以把结构的计算方法分为： （1）容许应力法，在这种方法中，把结构承受最大荷载时计算得到的应力与经过按规定的安全系数进行折减后的材料强度作比较。 （2）极限状态法，在这种方法中，结构的工作状态是以其最大强度为依据来衡量的。由理论分析确定的这一最大强度应不小于结构承受计算荷载所算得的强度（极限状态）。计算荷载等于分别乘以荷载系数的活载与恒载之和。 把对应于不乘以荷载系数的活载和恒载的工作（使用）条件的应力与规定值（使用极限状态）相比较。根据前两种方法和后两种方法的四种可能组合，我们可以得到一些实用的计算方法。通常采用下面两种计算方法： 确定性的方法，这种方法采用容许应力。 概率方法，这种方法采用极限状态。 至少在理论上，概率法的主要优点是可以科学的考虑所有随机安全系数，然后将这些随机安全系数组合成确定的安全系数。概率法取决于： 1 Reinforced Concrete Plain concrete is formed from a hardened mixture of cement ,water ,fine aggregate, coarse aggregate (crushed stone or gravel),air, and often other The plastic mix is placed and consolidated in the formwork, then cured to facilitate the acceleration of the chemical hydration reaction lf the cement/water mix, resulting in hardened The finished product has high compressive strength, and low resistance to tension, such that its tensile strength is approximately one tenth lf its compressive Consequently, tensile and shear reinforcement in the tensile regions of sections has to be provided to compensate for the weak tension regions in the reinforced concrete It is this deviation in the composition of a reinforces concrete section from the homogeneity of 答题实属不易，请楼主谅解，求采纳~