基础及基础工程外文翻译河北建筑工程学院毕业设计（论文）外文资料翻译系别：土木工程专业：土木工程班级： ********* 姓名： ********** 学号： ************** 外文出处：GEOLOGLCAL AND GEOTECHNICAL ENGINEERING附件：1、外文原文；2、外文资料翻译译文。
指导教师评语：签字：年月日1、外文原文（复印件）Foundation And Foundation EngineeringStrucures or other constructed works are supported on the earth by foundation. The word “foundation” may mean the earth itself, something placed in or on the earth to provide support, or a combinnation of the earth and the elements placed on it. The foundation for a multistory office building could be a combination for an earth-fill dam would be the natural soil or rock on which the dam is placed. Concrete footings or which or in which they are placed. The installed elements and the natural soil or rock of the earth form a foundation system; the soil and rock provide the ultimate support of the system. Foundation that are installed may be either soil-bearing or rock –bearing. The reactions of the soil or rock to the imposed loads generally determined how well the foundation system functions. In designing the installed portions, the designer must determine the safe pressue which can be used on the soil or rock and the amount of total settlement and differential settlement which the structure can withstand.The installed parts of the foundation system may be footings, mat foundations, slab foundations, and caissons or piles, all of which are used to transfer load from a supersteucture into the earth. These parts, which transmit load from the superstructure to the earth, are called the substructure.Footing Footing or spread foundations are used to spread the loads from columns or walls to the underlying soil or rock. Normally, footings are constructed of reinfored concrete. However, under some circumstances they may be constructed of plain concrete or masonary, when each footing supports only one column, it is square. Footings supporting two coumns are called combined footings and may be either rectangular or trapezoidal. Cantilever footings are used to building line or exterior wall. Footings supportsing walls are continuous footings.The sizes of footings are determined by dividing the loads to be imposed at the base of the footings by the allowable bearing pressure which can be imposed on the soil or rock of the earth. Most building codes and textbooks on foundations contain tables listing allowable bearing pressures for various types of soil and rock; however , these tables give only general classifications and descriptions of the soil or rock must be used with caution. More specific information about the soil or rock is normally obtained by drilling test borings, extracting soil or rock samples, performing laboratory tests on the samples, and making engineering must be given to the amount of settlement which may occur and the capability of the structure to withstand such settement. If settlement is problem it may be necessary to use an alternatefoundation type rather than footings or to enlarge the footings and decrease the bearing pressure.Grade beams may be used between exterior column footings to support walls, with the beams transferring the weight of the walls to the column footings. Beams are also used between interior column footings to act as braces or to support interior walls. Retaining walls are those walls subject to horizontal earth pressures due to the retention of earth behind them. The foundation for these will not slide when subjected to the horizontal earth pressure. In addition,retaining walls must be designed so they will not overturn. In frost-susceptible areas, footings must be placed below the frost line.Mat foundations Mat or raft foundations are large, thick, and usually heavily reinforced concrete mats which transfer loads from a number or colums and walls to the underlying soil or rock. Mats are also combined footings.,but are much larger than a footing uniform pressure to the underlying soil or rock. Mats are rigid and will act as a bridge over discontinuities in the soil or rock on which they are founded. Mats founded several meters below the ground surface, when combined with external walls, are termed floating foundations. The weight of the soil excavated from the ground surface to the bottom of the mat may be equal to approach the total weight of the structure. In this case, little or no new load is applied to the underlying supporting soil, and settlements of a structure may be minimal after construction.Slab foundations Slab foundations are used for light structures wherein the columns and walls are supportes directly on the floor slab. The floor slab is thickened and more heavily reinforced at the places where the column and wall loads are imposed.Special problems Groundwater is a major problem in connection with the design and installation of foundations where a substructure is to be placed below the groundwater level. Well points, pumping from deep wells, or pumping from sumps are methods used to dewater construction sites during foundation installation. Other methods which are less often used are freezing of the water in the soul, removal of water by electroosmosis, and the installation of cutoff walls made of pilling or grout around the periphery from within the excavation. If dewatering operations are perfromed in an area surrounded by existing structures, precautions must be taken to project them, as the lowering of the geoundwater may cause the soil on which they are supported to subside.If a basement is partially or totally below the groundwater level, its walls must be designed to withstand the hydrostatic pressure of the water on the outside in addition to the pressure from the soil backfill. An alternate procedure is to install a permanent system to remove watet outside the walls. Some substructure below groundwater level may at times besubjected to hydrostaic uplift forces which are greater than the downward forces imposed by the structures. In these cases, provisions must be to anchor the structures to prevent them from floating upward.Groundwater also causes problems by infiltrating though basement walls., slabs, and joints into the basement itself. This can be prevented or reduced by providing an external permanent drainage system that carries water away from the basenment, by encasing the walls and slabs in an permeability. Combinations of the foregoing are also used. Retaining walls and abutments ofen abutments can escape. The water pressure behind the walls is relieved as the water flows though the walls into an open external drainage system.Foundations placed on expansive soil are often subjected to distressing movement unless special precautions are taken. Expansive soil are those which swell and contract excessively with varying amounts of moissture. Problems can be overcome by installing foundations below the zone of significant change in moisture content and backfilling with nonexpansive materials, by altering the soil with an admixture such as lime or cement so that volumn changes do not occur, or by providing flexibility in the structure to accommodate movements.Underpinning of foundation is often necessary, and it may be either remedial or precautionary. Remedial underpinning is used to correct defects in existing froundations which may have settled excessively. If the structure is to be saved or returned to its original state, additional foundation support must be provided. Precautionary underpinning is used when new structure are to be installed adjacent to or beneath existing structures, as in the construction of city subways. Underpinning of foundation is a specialized construction technique. The work is generally performed in a confined space, such as the basement of a building, or in small pits excavated outside a building area. It is necessary to provide support for the loads of the existing structure while new foundations are installed. The new foundations may be footings which are placed deeper in the ground than the original foundations, or they may be piles or caissons.Underpinning of a wall footing may be performed by excavating pits adjacent to and beneath existing foundations. The pits are small, some 0.9m wide by 1.2m long. Horizontal sheeting is placed in the pits as excavation proceeds to prevent caving of the walls and undermining of the structure being underpinned. When the new bearing stratum is reached, forms are placed in the pit, and concrete is poured from the new bearing stratum up to within 76mm of the bottom of the old footing. After the new concrete has hardened, the 76mm space is packed by hand with a mixture of sand, cement, and a small amount of water. Called grout, themixture is packed very tightly into the space between the top of the new footing and the underside of the old footing. The pit underpinning process is repeated throughout the entirelength of the wall footing. The resulting new foundation may be a continuous wall or intermittent piers.One indisputable face is this: whatever the shape of a building or structure and whatever the nature and number of its supports, the whole weight of the building must come down to, and be supported by the ground. It is therefore essential that, for any propose structure, sufficient knowledge be obtained of the nature of the supporting soil and its load-bearing capacity.The purpose of a foundation is to convey the weight of a building to the soil in such a manner:(1)That excessive settlement will not occur;(2)That differential settlement of various sections of the building, which causescracks in the structure, will not occur;(3)That the soil will not fail under its load, thus causing no collapse of thebuilding.Compared with structural materials, such as steel and timber, soil is difficult to investigate scientifically. It can vary considerably in its properties on one building site both in horizontal and vertical directions.Until the 20th century, foundations were constucted mainly on the basis of experience. For important structures, deep trial pits were dug so that the soil could be examined for some distance below the surface, and sometimes loading tests on small area at the botton of the pits, were made to estimate the safe-bearing capacity of the soil.Some time about 1920 there began a more scientific approach to the behavior of soil. One of the earliest names, and a most important one, connected with this new science, is Dr. Karl Terzaghi, who made an extensive study of the properties of soils. Since 1920 much research has been carried out in many countries; many tests (site and laboratory) have been devised, and there is now a considerable literature on the subject of soil mechanics. Modern site investigations for important structures are carried out by specialist firms who have trained persomnel, equipment for drilling and boring and for extracting samples of soil, and facilities for making site and laboratory tests.All the material foeming the crust of the earth likely to be affected by the pressure of strutures is dicided by engineers into two major geoups: rocks and soils. The term “rock” is reserved for hard , rigid, and strongly cemented material, while “soil” is applied to the comparatively soft and loose materials.Soils without of organic deposits such as peat are broadly divided into two groups: cohesive and non-cohesive. Silts and clays are cohesive, while granular materials such assands and gravels are non-cohesive.Owing to the weight of a building or other structure, there is bound to be a certain amount of settlement. It was stated previously that force cannot be applied to any material without causing deformation. The total settlement of a building takes place in two stages:(1)Immediate settlement, as the building is being erected, due to elastic and plasticdeformation of the soil.(2)Consolidation settlement caused by the sequeezing-out of water contained in thepores of the soil and thus compressing the soil to a smaller volume.From the settlement point of view, non-cohesive soils such as sands and geavels are not very troublesome since they are only moderately compressible and are evey permeable (a permeable material is one which allows water through it easily). Consolidation settlement due to sequeezing-out of pore water therefore occurs very quickly during and soon after the erection of the strycture, and is comparatively small. Special attention, however, must be given to loose sands, which can show appreciable settlement if subjected to vibration.Cohesive soils such as clay have very low permeability, which means that squeezing of water from the pores due to consoildation settlement of the building is a slow process. Furthermore, the compressibility of most calys and silts is appreciable and there is a compressibility volume reduction under pressure. The final settlement of a structure founded on clay may therefore not occur until some years after erection and must be allowed for in design calculations.Clay is aslo a troublesome material when encounterd in shallow foundations (for houses and other small buildings). Cohesive soils dry out in the summer and spring; surface cracks can occur which may extend to about 0.3m in britain.Precast Piles Precast piles, which are usually square or octagonal in cross-section, are driven into the soil by repeated blows from a falling weighted or from a steam hammer. The piles are driven in until a certain number of blows produce only a small further penetration which has been predetermined by zalculations in accordance with the loads , and the piles will be called upon to supports .A simple illustation is that of knocking a timber stake into soil. The deeper the stake is driven into the geound, the greater is the frictional resistance and the harder it is to drive the stake downwards. When a pile is driven a sufficient distance, the resultant load it has to carry is usually supported partly by frictional force on the sides of the pile and partly by the bearing resistance of the soil under the foot of the pile.If the strata are of such a nature that the soil can offer negligible frictional resistance, the pile must be drien until it meets a hard strtum such as rock capable of supporting the full load.Alternatively the soil may be of such a nature that most of the trsistance to the downward artion of the weight of the building is provided by frictional resistance.Inspporting their loads, piles act as columns, except that the soil provides lateral restraint.Another method, as used by the Franki Compressed Pile Co, consists in driving a steel tube to the required depth and filling it with in-situ concrete. First, the bottom of the tube is sealed by a temporary gravel plug. The tube is then driven to the required depth by blows on this plug from a long heavy cylindrical hammer. Concrete is then placed in the tube and rammed so that a bulbous foot is produced (thus increasing bearing resistance). As the rammed concrete approaches the ground surface, the tube is geadually withdrawn.Bored Piles Driven piles displace and compress the soil. Then piles are bored in situ, the soil is removed by special boring tools to form cylindrial holes equal to the depths of the prepared piles. Steel reinforcenment is then inserted and concreted rammed in to form the pile, which frequently has a bulbous base due to heary ramming of the frist batch of concrete. In addition, bored piles are useful where headroom is restricted so that it is impossible to have long lengths of precast piles projecting above ground level.Cylinder Piles Cylinder foundations, 2m or more in diameter, have been employed for many years, the holes being made by excavating soil with hand or mechanically operated geabs. During the last few years new methods have developed for forming these large diameter holes. In one system, first used in the United States, angles(drills), varying from 1m to 2.3m in diameter, are used for boring holes which may be as much as 25m deep or more. The bottoms of the 2.3m diameter cylinders, and 2.3m for the 1m diameter cylinders. Large bearing areas are thus obtained; one of these piles in the London clay was designed to supporting a load of 2000 tones. One advantage of a large-diameter cylinder pile is that cap, which is required when the column has to be supported by a number of small-diameter piles.Piles Caps When small-diameter driven or bored piles are used, the number of piles required to suppore one column must be transferred to the piles by means of a foundation called a pile cap. Reinforcement is required in the cap to resist bending stresses, etc.2、外文资料翻译译文基础及基础工程建筑物或是已建成的工程是由基础下的地基土支撑着的。
