【正文】 s possible in the drawing office by drawing cross sections of the earthwork. On the site when further information bees available he can make changes in jis sections and layout,but the drawing lffice work will not have been lost. It will have helped him to reach the best solution in the shortest time.The cheapest way of moving earth is to take it directly out of the cut and drop it as fill with the same machine. This is not always possible, but when it canbe done it is ideal, being both quick and cheap. Draglines, bulldozers and face shovels an do this. The largest radius is obtained with the dragline,and the largest tonnage of earth is moved by the bulldozer, though only over short disadvantages of the dragline are that it must dig below itself, it cannot dig with force into pacted material, it cannot dig on steep slopws, and its dumping and digging are not accurate.Face shovels are between bulldozers and draglines, having a larger radius of action than bulldozers but less than draglines. They are anle to dig into a vertical cliff face in a way which would be dangerous tor a bulldozer operator and impossible for a dragline. Each piece of equipment should be level of their tracks and for deep digs in pact material a backacter is most useful, but its dumping radius is considerably less than that of the same escavator fitted with a face shovel.Rubbertyred bowl scrapers are indispensable for fairly level digging where the distance of transport is too much tor a dragline or face shovel. They can dig the material deeply ( but only below themselves ) to a fairly flat surface, carry it hundreds of meters if need be, then drop it and level it roughly during the dumping. For hard digging it is often found economical to keep a pusher tractor ( wheeled or tracked ) on the digging site, to push each scraper as it returns to dig. As soon as the scraper is full,the pusher tractor returns to the beginning of the dig to heop to help the nest scraper.Bowl scrapers are often extremely powerful machines。many makers build scrapers of 8 cubic meters struck capacity, which carry 10 m 179。 heaped. The largest selfpropelled scrapers are of 19 m 179。 struck capacity ( 25 m 179。 heaped )and they are driven by a tractor engine of 430 horsepowers.Dumpers are probably the monest rubbertyred transport since they can also conveniently be used for carrying concrete or other building materials. Dumpers have the earth container over the front axle on large rubbertyred wheels, and the container tips forwards on most types, though in articulated dumpers the direction of tip can be widely varied. The smallest dumpers have a capacity of about m 179。, and the largest standard types are of about m 179。. Special types include the selfloading dumper of up to 4 m 179。 and the articulated type of about m 179。. The distinction between dumpers and dump trucks must be remembered .dumpers tip forwards and the driver sits behind the load. Dump trucks are heavy, strengthened tipping lorries, the driver travels in front lf the load and the load is dumped behind him, so they are sometimes called reardump trucks. 土方工程的施工 由于和土木工程中任何其他工種的施工方法與費用相比較，土方挖運的施工方法與費用的變化都要快得多，因此對于有事業(yè)心的人來說，土方工程是一個可以大有作為的領域。在1935年，目前采用的利用輪胎式機械設備進行土方挖運的方法大多數還沒有出現。那是大部分土方是采用窄軌鐵路運輸，在這目前來說是很少采用的。當時主要的開挖方式是使用正鏟、反鏟、拉鏟或抓斗等挖土機，盡管這些機械目前仍然在廣泛應用，但是它們只不過是目前所采用的許多方法中的一小部分。因此，一個工程師為了使自己在土方挖運設備方面的知識跟得上時代的發(fā)展，他應當花費一些時間去研究現代的機械。一般說來，有關挖土機、裝載機和運輸機械的唯一可靠而又最新的資料可以從制造廠商處獲得。土方工程或土方挖運工程指的是把地表面過高處的土壤挖去（挖方），并把它傾卸到地表面過低的其他地方（填方）。為了降低土方工程費用，填方量應該等于挖方量，而且挖方地點應該盡可能靠近土方量相等的填方地點，以減少運輸量和填方的二次搬運。土方設計這項工作落到了從事道路設計的工程師的身上，因為土方工程的設計比其他任何工作更能決定工程造價是否低廉。根據現有的地圖和標高，道路工程師應在設計繪圖室中的工作也并不是徒勞的。它將幫助他在最短的時間內獲得最好的方案。費用最低的運土方法是用同一臺機械直接挖方取土并且卸土作為填方。這并不是經常可以做到的，但是如果能夠做到則是很理想的，因為這樣做既快捷又省錢。拉鏟挖土機。推土機和正鏟挖土機都能做到這點。拉鏟挖土機的工作半徑最大。推土機所推運的圖的數量最多，只是運輸距離很短。拉鏟挖土機的缺點是只能挖比它本身低的土，不能施加壓力挖入壓實的土壤內，不能在陡坡上挖土，而且挖。卸都不準確。正鏟挖土機介于推土機和拉鏟挖土機的之間，其作用半徑大于推土機，但小于拉鏟挖土機。正鏟挖土機能挖取豎直陡峭的工作面，這種方式對推土機司機來說是危險的，而對拉鏟挖土機則是不可能的。每種機械設備應該進行最適合它的性能的作業(yè)。正鏟挖土機不能挖比其停機平面低很多的土，而深挖堅實的土壤時，反鏟挖土機最適用，但其卸料半徑比起裝有正鏟的同一挖土機的卸料半徑則要小很多。在比較平坦的場地開挖，如果用拉鏟或正鏟挖土機運輸距離太遠時，則裝有輪胎式的斗式鏟運機就是比不可少的。它能在比較平的地面上挖較深的土（但只能挖機械本身下面的土），需要時可以將土運至幾百米遠，然后卸土并在卸土的過程中把土大致鏟平。在挖掘硬土時，人們發(fā)現在開挖場地經常用一輛助推拖拉機（輪式或履帶式），對返回挖土的鏟運機進行助推這種施工方法是經濟的。一旦鏟運機裝滿，助推拖拉機就回到開挖的地點去幫助下一臺鏟運機。斗式鏟運機通常是功率非常大的機械，許多廠家制造的鏟運機鏟斗容量為8 m179。，滿載時可達10 m179。最大的自行式鏟運機鏟斗容量為19立方米（滿載時為25 m179。），由430馬力的牽引發(fā)動機驅動。翻斗機可能是使用最為普遍的輪胎式運輸設備，因為它們還可以被用來送混凝土或者其他建筑材料。翻斗車的車斗位于大橡膠輪胎車輪前軸的上方，盡管鉸接式翻斗車的卸料方向有很多種，但大多數車斗是向前翻轉的。，179。特殊型式的翻斗車包括容量為4 m179。的自裝式翻斗車， m179。的鉸接式翻斗車。必須記住翻斗車與自卸卡車之間的區(qū)別。翻斗車車斗向前傾翻而司機坐在后方卸載，因此有時被稱為后卸卡車。