Piles are structural members of timber, concrete, and/or steel, used to transmit surface loads to lower levels in the soil mass. This may be by vertical distribution of the load along the pile shaft or a direct application of load to the lower stratum through the pile point.?A vertical distribution of the load is made using a friction, or?"floating, " pile and a direct load application is made by a point, or?"end-bearing," pile. This distinction of piles is purely one of?convenience since all piles function as a combination of side resistance and point bearing except when the pile penetrates an extremely soft soil to a solid base.

樁是木、混凝土或鋼制的結(jié)構構件，用來把地面上的荷載傳遞到土體的較深處。荷載傳遞可以通過沿樁身豎向分布或通過樁尖使荷載直接作用到下面的土層。采用摩擦樁時荷載為豎向分布，采用樁尖時荷載直接作用的是“端承樁”。把樁做這種區(qū)別完全是為了方便，因為除了樁是穿過一個極軟的士層而到達一個剛性層的情況，所有樁的功能都是由側(cè)阻力和端承力共同構成的。

Piles are commonly used:

(1) To carry the superstructure loads into or through a soil stratum. Both vertical and lateral loads may be involved.

(2) To resist uplift, or overturning, forces as for basement mats below the water table or to support tower legs subjected to overturing.

(3) To compact loose, cohesionless deposits through a combination of pile volume displacement and driving vibrations. These piles may be later pulled.

(4) To control settlements when spread footings or a mat is on a marginal soil or is underlain by a highly compressible stratum.

(5) To stiffen the soil beneath machine foundations to control both amplitudes of vibration and the natural frequency of the system.

(6) As an additional safety factor beneath bridge abutments and/ or piers, particularly if scour is a potential problem.

(7) In offshore construction to transmit loads above the water surface through the water and into the underlying soil. This is a case of partially embedded piling subjected to vertical (and buckling) as well as lateral loads.

樁通常用于下列情況：

(1)把上部結(jié)構的荷載傳到或傳給土層。包括垂直荷載和側(cè)向荷載。

(2)抵抗上拔或傾預，例如在地下水位以下的地下室筏基的受力或支承受傾覆作用的塔架。

(3)在樁體排土和打樁振動的共同作用下，使松散的非粘性土被壓實。這些樁以后也可以被拔出。

(4)當擴展式基腳或筏基位于邊緣性土層或者其下面有可壓縮性較高的地層時，用以控制沉降。

(5)提高機器基礎下面士的剛度，以控制該系統(tǒng)的振幅和固有頻率。

(6)作為橋臺和/或橋墩的一個附加安全系數(shù)，特別是當沖刷成為一個潛在的問題時。

(7)在海上工程結(jié)構中，把水面以上的荷載經(jīng)過水傳到下面土層內(nèi)。這是一種部分埋入樁，它既要承受垂直荷載（和壓曲）又要承受側(cè)向荷載。

Piles are sometimes used to control earth movements (as landslides) . The reader should note that power poles and many outdoor sign poles may be considered as partially embedded piles subject to lateral loads. Vertical loads may not be significant, although buckling may require investigation for very tall members.

樁有時亦用來控制土體移動（例如滑坡）。讀者應該注意到電線桿和許多戶外標志桿都可以看作是承受側(cè)向荷載的部分埋入樁。垂直荷載可能不大，但構件很高時可能需要考慮壓曲。

A pile foundation is more expensive than spread footings and likely to be more expensive than a mat. In any case great care should be exercised in determining the soil properties at the site for the depth of possible interest so that it can be accurately determined that a pile foundation is needed and, if so, that neither an excessive number nor lengths are specified. A cost analysis should be made to determine whether a mat or piles, in particular the type ( steel, concrete, etc.), are more economical. In those cases where piles are used to control the settlement at marginal soil sites, care should be taken to utilize both the existing ground and the piles in parallel so that a minimum number are required.

樁基礎要比擴展式基腳多花很多錢，也可能比筏基更加昂貴。在任何情況下，都應該對現(xiàn)場可能有影響的深度內(nèi)在的參數(shù)非常仔細地加以確定，以便決定是否需要采用樁基礎，如果需要，則不要采用過多的樁和過長的樁。應該先分析造價，然后決定采用筏基還是樁基，特別是要決定采用哪一種樁（鋼、混凝土等）更為經(jīng)濟。在那些邊緣性土層中為控制沉降而采用樁基時，應該注意要利用原有的地基和樁，以使所需要的樁數(shù)為最少。

Piles are inserted into the soil via a number of methods:

(1) Driving with a steady succession of blows on the top of the pile using a pile hammer. This produces both considerable noise and local vibrations which may be disallowed by local codes or environmental agencies and, of course, may damage adjacent property.

(2) Driving using a vibratory device attached to the top of the pile. This is usually a relatively quiet method and driving vibrations may not be excessive. The method is more applicable in soil deposits?with little cohesion.

(3) Jacking the pile. This is more applicable for short stiff members.

(4) Drilling a hole and either inserting a pile into it or, more common, filling the cavity with concrete which produces a pile upon hardening.

可以采用許多方法把樁置于土中：

(1)用樁錘對樁頂均勻地連續(xù)錘擊把樁打入，這種方法產(chǎn)生相當大的噪聲和現(xiàn)場振動。這兩項都可能是當?shù)胤ㄒ?guī)和環(huán)保機構禁止的，當然也可能損壞附近的財產(chǎn)。

(2)采用在樁頂上安裝振動器的方式使樁下沉。通常這是一種比較安靜的方法，而且沉樁振動也不太大。這種方法適用于黏聚力小的士層。

(3)用千斤頂壓樁，這種方法對剛度較大的短樁比較適用。

(4)鉆孔后將樁插入，或者更為常見的是向鉆出的孔洞內(nèi)澆筑混凝土，混凝土硬化后就形成樁。

When a pile foundation is decided upon, it is necessary to compute the required pile cross section and length based on the load from the superstructure, allowable stress in the pile material ( code value), and the in situ soil properties. This is so that the necessary number and lengths of piles can be ordered by the foundation contractor. Dynamic formulas, pile-load tests, or a combination are used on site to determine if the piles are adequately designed and placed. It is generally conceded that a load test is the most reliable means of determining the actual pile capacity.

在決定采用樁基時，必須根據(jù)上部結(jié)構傳來的荷載、樁體材料的允許應力（規(guī)范值）和現(xiàn)場土質(zhì)，來計算樁的截面和長度。這樣基礎承包商就能據(jù)此來訂購所需要的樁的數(shù)量和樁長。在現(xiàn)場使用動力學公式，荷載試驗或兩種方法結(jié)合來確定樁的設計和設置是否妥當。通常認為，荷載試驗是確定樁的實際承載力的最可靠方式。

Pile-capacity determinations are very difficult. A large number of different equations are used, and seldom will any two give the same computed capacity. Organizations which have been using a particular equation tend to stick with it -particularly if a successful data base has been established. In a design situation one might compute the pile capacity by several equations using the required empirical factors suitably adjusted (or estimated) and observe the computed capacity.?From a number of these computations some "feel" for the probable capacity will develop so that a design recommendation/ proposal can be made.

確定樁的承載力非常困難，雖然已經(jīng)有許多公式可以供使用，但很難有任何兩個公式會給出相同的計算結(jié)果。有些機構使用過某一特定的公式后便一直采用它，特別是在已經(jīng)成功地建立起數(shù)據(jù)庫以后。設計時要通過若干個公式計算樁的承載力并采用所需的經(jīng)驗系數(shù)加以適當調(diào)整（或估算），然后觀察計算得到的承載力。根據(jù)若干次這種計算，對樁可能有的承載力便有了“概念”，據(jù)此就能作出設計建議。

We should note that although all the pile-capacity equations are for a single pile, rarely is a single pile used, rather two or three or more piles are used in a group. We should further note that the soil properties which are used in the design are those from the initial soil-exploration program, and the soil properties which exist when the foundation is in service may be a little or considerably different depending on how the piles have been placed and the number of piles in the group.

應當注意雖然所有的樁承載力公式都是針對單樁的，但是在實際中很少使用單樁，而是采用兩根或三根（或更多）的樁成群使用。應該注意設計中采用的土質(zhì)性能是由最初土地勘察時得到的，而土的性質(zhì)在基礎使用時會發(fā)生一些或較大的變化，這與樁是如何設置的和樁群中的樁數(shù)有關。