No construction material has both engineering and physical properties which are more variable than the ground. These properties vary both laterally and vertically and often by large orders of magnitude. Those properties of particular interest to the foundation engineer include:

(1) Strength parameters ( stress-strain modulus, shear modulus,?Poison's ratio, cohesion, and angle of internal friction)

(2) Compressibility indexes (for deformation/settlement)

(3) Permeability

(4) Gravimetric-volumetric data ( unit weight, specific gravity;?void ratio, water content, etc.)

Some knowledge about these properties allows the engineer to make estimates for:

(1) Bearing capacity

(2) Settlements including both the amount and rate

(3) Earth pressures (both vertical and lateral)

(4) Pore pressures and dewatering quantities

沒(méi)有任何一種建筑材料的工程性質(zhì)和物理性質(zhì)像土那樣不均勻。而且土的這些性質(zhì)在橫向和豎向都不相同，其變化的數(shù)量級(jí)往往比較大?；A(chǔ)工程師特別感興趣的那些性質(zhì)包括：

1.?強(qiáng)度參數(shù)（應(yīng)力－應(yīng)變模量、剪切模量、泊桑比、內(nèi)聚力和內(nèi)摩擦角）；

2. 壓縮性指數(shù)（變形/沉降）；

3. 滲透性；

4. 重量－體積方面的數(shù)據(jù)（容重、比重、孔隙比、含水量等等）。

掌握了關(guān)于上述這些性質(zhì)的知識(shí)可以使工程師能夠?qū)σ韵赂鞣矫孀龀龉浪悖?/p>

1. 承載能力；

2.?沉降，包括數(shù)量和速率兩方面；

3.?土壓力（豎向和側(cè)向）；

4. 孔隙壓力和抽水量。

Much laboratory work in the area of soil behavior has been done and reported in geotechnical literature in recent years. Most of this work has been done on samples prepared under ideal conditions in the laboratory.?This tends to produce samples which are rather?homogeneous, uniform, and generally lacking in geological aging so that those properties of anisotropy and cementation are often not produced. A few laboratories attempt to reproduce anisotropy, but the?practice does not seem to be widespread at present. Reproducing aging and environmental processes in the laboratory to obtain natural cementation effects is generally too time-consuming to be practical.?Tests on laboratory samples, however, constitute a large part of the data base on which empirical correlations and field predictions are made. When one takes into account the actual soil makeup, its geologically obtained properties, and the difficulties of obtaining samples which have sufficiently small amounts of disturbance that the resulting test data are reliable, test data on laboratory prepared samples may bear little resemblance to field performance.

近年來(lái)，在實(shí)驗(yàn)室內(nèi)進(jìn)行了許多土的性質(zhì)方面的研究工作，并已經(jīng)在巖土工程文獻(xiàn)中發(fā)表。在這些工作中，大多數(shù)是采用在實(shí)驗(yàn)室中的理想條件下制備的土樣進(jìn)行的。這樣容易制成頗為各向同性、均質(zhì)的試樣，通常缺乏地質(zhì)時(shí)效的影響，因此一般不會(huì)形成各向異性和膠結(jié)作用這些性質(zhì)。少數(shù)實(shí)驗(yàn)室試圖仿制各向異性，但是這種做法日前看來(lái)并不廣泛。在實(shí)驗(yàn)室內(nèi)再現(xiàn)時(shí)效和環(huán)境過(guò)程，以獲取自然膠結(jié)效果，通常會(huì)因?yàn)榛ㄙM(fèi)太多的時(shí)間而不切實(shí)際。然而大量的經(jīng)驗(yàn)關(guān)系和進(jìn)行現(xiàn)場(chǎng)預(yù)測(cè)所依據(jù)的數(shù)據(jù)庫(kù)，主要是來(lái)自采用實(shí)驗(yàn)室試樣所做的試驗(yàn)。當(dāng)考慮到實(shí)際土層的組成、其地質(zhì)因素得到的性質(zhì)以及取得小到足以使試驗(yàn)數(shù)據(jù)可靠的試樣的困難，所以實(shí)驗(yàn)室制備的土樣的試驗(yàn)數(shù)據(jù)同現(xiàn)場(chǎng)的土樣很少有相似之處。

Several problems are involved with laboratory testing or field samples, including:

(1) Recovery of undisturbed samples

(2) Small quantity of samples relative to the volume of soil involved

(3) Limitations on laboratory test equipment ( and sometimes of qualified personnel)

實(shí)驗(yàn)室試驗(yàn)或者現(xiàn)場(chǎng)土樣涉及幾個(gè)問(wèn)題，其中包括：

1.未擾動(dòng)土樣的取得；

2.相對(duì)所涉及的土地體積而言，土樣數(shù)量較少；

3.室內(nèi)試驗(yàn)設(shè)備的限制（有時(shí)受到缺少合格的人員的限制）。

It is not difficult to see that "engineering judgment" will play a significant role in the practice of foundation engineering. The proper application of engineering judgment requires that the foundation engineer have available a site profile, soil property data, and sufficient geological information to arrive at a safe, economical, and practical decision. In cases such as one-story load-bearing wall construction used for buildings of the department store, office, and service station type where the soil is relatively homogeneous, the necessary information may comprise only the boring logs from four or five relatively shallow exploratory borings. For a 10-story building the necessary information would normally have to be more. Where a 100-story building is involved, the amount of information would be very?considerable and might cost on the order of 0. 5 to 1 percent of the total construction cost. It should be obvious that in any of the examples cited it would be helpful if the foundation engineer had provided recommendations and/or designs for previous projects near the current site.

在基礎(chǔ)工程實(shí)踐中，不難看出“工程判斷”起著重要的作用。正確地運(yùn)用工程判斷要求基礎(chǔ)工程師要有場(chǎng)地的地質(zhì)剖面、土地性質(zhì)數(shù)據(jù)和足夠的地質(zhì)資料，以便于作出一個(gè)安全、經(jīng)濟(jì)和實(shí)際的決策。在某些情況下，例如單層的商店、辦公室和服務(wù)站等建筑物的承重墻處的土質(zhì)比較均勻，則需要的資料可僅限于由四五個(gè)比較淺的勘探孔得出的鉆探記錄。一個(gè)十層的建筑物則需要更多的資料。如果涉及一個(gè)一百層的建筑物，則所需要的資料會(huì)相當(dāng)大，并且可能會(huì)花費(fèi)整個(gè)建筑物成本的0.5%～1%。顯然在上述任何一個(gè)例子中，如果基礎(chǔ)工程師曾經(jīng)對(duì)現(xiàn)場(chǎng)附近的以往的工程提供過(guò)建議和/或進(jìn)行過(guò)設(shè)計(jì)，則對(duì)目前的工程將是有幫助的。

A thorough understanding of the principles of soil mechanics in terms of stability, deformations, and water flow is a necessary ingredient to the successful practice of foundation engineering. Of nearly equal importance is an understanding of the geological processes involved in the formation of soil masses. It is now recognized that both soil stability and deformation are dependent on the stress history of the mass. It has been common until recently to associate foundation engineering solely with soil mechanics concerns, leaving the interfacing elements to the structural (or other) designer.

全面地掌握土力學(xué)中關(guān)于穩(wěn)定、變形和水流等各項(xiàng)原理是基礎(chǔ)工程成功的必要條件。了解土體形成所涉及的各種地質(zhì)過(guò)程也幾乎同相當(dāng)重要?，F(xiàn)在已經(jīng)認(rèn)識(shí)到土體的穩(wěn)定和變形都依賴于土體所受應(yīng)力的歷史。直到不久之前，僅僅將基礎(chǔ)工程與土力學(xué)相聯(lián)系，而將交界面構(gòu)件讓給結(jié)構(gòu)（或其他）工程師去處理的現(xiàn)象還很常見(jiàn)。

The science of soil mechanics and its relationship to geological processes has progressed considerably over the past fifty years.?However, because of the natural variability of soil and the resulting problems associated with testing, the design of a foundation still depends to a large degree upon the application of engineering judgment.

在過(guò)去的50 年中，土力學(xué)這門科學(xué)及其與地質(zhì)過(guò)程的關(guān)系取得了很大的進(jìn)展。然而，由于土的自然變異性以及因此而造成的測(cè)試問(wèn)題，使基礎(chǔ)的設(shè)計(jì)在很大程度上仍然靠運(yùn)用工程判斷。