Soil Mechanics in Foundation Engineering
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
没有任何一种建筑材料的工程性质和物理性质像土那样不均匀。而且土的这些性质在横向和竖向都不相同，其变化的数量级往往比较大。基础工程师特别感兴趣的那些性质包括：
1. 强度参数（应力－应变模量、剪切模量、泊桑比、内聚力和内摩擦角）；
2. 压缩性指数（变形/沉降）；
3. 渗透性；
4. 重量－体积方面的数据（容重、比重、孔隙比、含水量等等）。
掌握了关于上述这些性质的知识可以使工程师能够对以下各方面做出估算：
1. 承载能力；
2. 沉降，包括数量和速率两方面；
3. 土压力（竖向和侧向）；
4. 孔隙压力和抽水量。
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.
近年来，在实验室内进行了许多土的性质方面的研究工作，并已经在岩土工程文献中发表。在这些工作中，大多数是采用在实验室中的理想条件下制备的土样进行的。这样容易制成颇为各向同性、均质的试样，通常缺乏地质时效的影响，因此一般不会形成各向异性和胶结作用这些性质。少数实验室试图仿制各向异性，但是这种做法日前看来并不广泛。在实验室内再现时效和环境过程，以获取自然胶结效果，通常会因为花费太多的时间而不切实际。然而大量的经验关系和进行现场预测所依据的数据库，主要是来自采用实验室试样所做的试验。当考虑到实际土层的组成、其地质因素得到的性质以及取得小到足以使试验数据可靠的试样的困难，所以实验室制备的土样的试验数据同现场的土样很少有相似之处。
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)
实验室试验或者现场土样涉及几个问题，其中包括：
1.未扰动土样的取得；
2.相对所涉及的土地体积而言，土样数量较少；
3.室内试验设备的限制（有时受到缺少合格的人员的限制）。
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.
在基础工程实践中，不难看出“工程判断”起着重要的作用。正确地运用工程判断要求基础工程师要有场地的地质剖面、土地性质数据和足够的地质资料，以便于作出一个安全、经济和实际的决策。在某些情况下，例如单层的商店、办公室和服务站等建筑物的承重墙处的土质比较均匀，则需要的资料可仅限于由四五个比较浅的勘探孔得出的钻探记录。一个十层的建筑物则需要更多的资料。如果涉及一个一百层的建筑物，则所需要的资料会相当大，并且可能会花费整个建筑物成本的0.5%～1%。显然在上述任何一个例子中，如果基础工程师曾经对现场附近的以往的工程提供过建议和/或进行过设计，则对目前的工程将是有帮助的。
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.
全面地掌握土力学中关于稳定、变形和水流等各项原理是基础工程成功的必要条件。了解土体形成所涉及的各种地质过程也几乎同相当重要。现在已经认识到土体的稳定和变形都依赖于土体所受应力的历史。直到不久之前，仅仅将基础工程与土力学相联系，而将交界面构件让给结构（或其他）工程师去处理的现象还很常见。
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.
在过去的50 年中，土力学这门科学及其与地质过程的关系取得了很大的进展。然而，由于土的自然变异性以及因此而造成的测试问题，使基础的设计在很大程度上仍然靠运用工程判断。
