第11单元翻译

11 Geotechnical Engineering and Underground EngineeringUnit

11 岩土工程和地下工程

Soil

土

Loadings in buildings consist of the combined dead and imposed loads which exert a downward pressure upon the soil on which the structure is founded and this in turn promotes a reactive force in the form of an upward pressure from the soil. The structure is in effect sandwiched between these opposite pressures and the design of the building must be able to resist the resultant stresses set up within the structural members and the general building fabric. The supporting subsoil must be able to develop sufficient reactive force to give stability to the structure to prevent failure due to unequal settlement and to prevent failure of the subsoil due to shear. To enable a designer to select, design and detail a suitable foundation he (she) must have adequate data regarding the nature of the soil on which the structure will be founded and this is normally obtained from a planned soil investigation programmer.

作用在建筑物上的恒荷载和外加荷载，会给建筑结构所处的地基土体施加一个向下的力，反过来，地基土也会产生一个向上的反作用力（作用到建筑结构上）建筑结构在反作用力的作用下必须是（完好的）有效的，建筑设计（必须考虑）能够抵抗来自建筑结构构件和普通房屋结构的合应力。为了防止由于不均匀沉降而导致的结构破坏，为了避免地基土发生剪切破坏，为上部结构提供支撑的天然地基必须具有足够的承载力来保证上部结构的稳定性。设计师必须要掌握大量的建筑物所在位置的土体性质的资料，当然，这些资料是从初步土质勘察说明中获得的 ，只有这样，设计师才能更顺利地对基础进行选型，设计并能绘出所选合适基础的详图。

Although they are closely related, soil mechanics and foundation engineering are not synonymous. Foundation engineering as a profession is a subtle combination of soil mechanics and engineering geology with the intuitive art of judgment and innovation where experience exercises an important role. Soil mechanics, on the other hand, is a study of the behavior of a material whose most important characteristic is its particulate composition. Since this characteristic is not unique to soils, the principles and techniques of soil mechanics may find application to a variety of problems in geophysics, materials processes, and most recently, lunar exploration.

尽管土力学和基础工程中有很多东西是相关的，但是他们是不一样的。基础工程作为一个专业，与土力学和工程地质学有着微妙的关系，它需要具有一种直观的判断力和以经验为基础的创新能力。从另一方面看，土力学是一个来研究具有重要特征的颗粒组成的材料的性状的学科。既然这种特征并不只是土所特有的，那么，土力学的原则和技术则可以用来解决在地球物理学，材料加工工艺和最近的月球探测方面的各种问题。

The science of soil mechanics began its rapid growth with the pioneering studies of Karl Terzaghi during the early part of this century. Terzaghi developed many of the theories of soil mechanics out of the practical necessity of providing solutions to the many difficult foundation problems introduced by modern construction.

在本世纪初，太沙基在土力学方面开始了首创性研究，从此以后，土力学理论得到快速发展。太沙基发展了许多土力学理论，这些理论用来解决现代建筑中许多令人头痛的基础问题。

1 Characteristic of soils

1 土的性质

Soils are aggregates of mineral particles that cover extensive portions of the earth’s surface. In soil engineering, the force applied to soil masses very frequently produce relative displacements between particles. Hence a study of soil mechanics requires an appreciation of the particulate nature of the material. Another characteristic of soils is that they are three-phase systems: they are composed of solid particles, water, and air. Since air is very compressible, and water may flow into or out of a soil, the relative proportions of three components change with time and load. Hence these components often form the basis for the quantitative description of soil behavior.

覆盖在地球大部分表面的土是一种矿物颗粒的聚合体，在岩土工程中，在力的作用下

土壤体中的颗粒间经常发生相对位移，因此，一项土力学方面的研究必须是建立在对材料的颗粒性质足够了解的基础上，土的另一个重要特征是它们的三相体系，三相体系包括固相、液相和气相。因为气相是很容易压缩的，而液相则很容易进入或离开土体。所以三相组成的相对比例是随着时间和荷载相对变化的，因此，三相组成了土的性状和定量描述的一个标准。

2 Structure of soils

2 土的结构

The structure of natural soils is the net product of the interaction between the forces of sedimentation, surface forces of the soil particles, and subsequent geologic forces. If particles of sand are allowed to settle from a suspension in water, the particles tend to take up stable positions to form a single-grained structure. Very loose sand or silt may have a honeycomb structure. If the fine particles consist of clay materials, the surface forces play an important part. If strong attractive forces exist between the edge or corner and the face of clay plates, a flocculent develops.

自然土壤的结构是沉降力、土壤颗粒的表面力、和随后的地质力量之间的相互作用的净产品。如果砂的颗粒在水中被允许从悬浮到沉降，颗粒朝着可以占用稳定位置的方向发展，最后形成一个单一的粒状结构。非常松散砂或淤泥可能有蜂窝状结构。如果细颗粒是粘土材料，表面力发挥重要作用。如果粘土板的边缘或角落和表面之间存在很强的吸引力，一种絮状发展。

Otherwise, the clay plates may occupy nearly parallel positions as they settle from suspension.This is called a dispersed structure.

否则，粘土板可能占据在从悬浮到沉淀之间的*行的位置。这被称为一种分散结构。

Soils with flocculent and honeycomb structures have large voids between soil particles and are held together by surface forces at the contact points. Such structures are generally not very stable. When a load is applied to the soil，the contacts may be broken and part of the structure destroyed, thus compressing the voids to form a more stable structure that can withstand the load. Some soil may be so unstable that the structure collapses with small disturbances. If the void space is filled with water, the soil-water mixture may lose all stability and flow as a viscous liquid. Occasionally very loose deposits of fine sand or silt have been observed to flow after small disturbances such as a seismic tremor, an adjacent slide, or even tidal action.

带有絮状和蜂窝状的土壤，土壤颗粒间有大的空隙和通过接触点表面力黏在一起。这样的结构通常不是很稳定。当负载被施加到土壤中时，连接处被断开和部分结构被毁坏，从而压缩一个更稳定能承受负载的结构的空隙。如果该空间内充满水，土壤和水的混合物可能失去作为一种粘稠的液体全部的稳定性和流动性。偶尔非常松散的细沙土的沉淀物已经被发现，随着如一场地震震动、一个相邻的滑落物、潮汐作用这类微小的扰动所带走。

3 Classification of soils

3 土的分类

Many soil descriptions and classifications are based on the size of the soil particles. This is the simplest criteria for soil description. Soils are commonly named gravel, sand, silt, and clay on the basis of the particle size. The dividing line between these categories is arbitrary, and，as is common to arbitrary definitions, there are several systems in current use. These systems were initiated independently by various agencies that worked with soils.

许多土壤描述和分类是基于土壤颗粒的大小。这是最简单的标准土壤描述。土壤通常命名为砾石，沙，淤泥和粘土上颗粒尺寸的基础。这些类别之间的分界线是任意的，并且，由于是常见任意定义，有几个系统在当前的使用。这些系统通过与土壤中各工作机构独立发起的。

Soils may be classified by any of the following methods: (1) Physical properties; (2) Geological origin; (3) Chemical composition; (4) Particle size.

土壤可通过任何以下方法进行分类：（1）物理性质，（2）地质起源，（3）化学成分（4）粒度。

It has been established that the physical properties of soils can be closely associated with their particle size both of which are of importance to the foundation engineer, architect or designer. All soils can be defined as being coarse-grained or fine-grained each resulting in different properties.

它已经确定土壤的物理性质可以被密切相关 其颗粒大小这两者都是重要的基础工程师，建筑师或设计师。所有土壤中可被定义为是粗粒度或细粒度的每个产生不同的属性。

Coarse-grained soils: these would include sands and grovels having a low proportion of voids, negligible cohesion when dry, high permeability and slight compressibility, which takes place almost immediately upon the application of load.

粗粒土：这将包括沙滩和grovels具有空隙的比例较低， 可以忽略不计的凝聚力干燥时，高磁导率和轻微的压缩，其中发生几乎紧随负载的应用。

Fine-grained sails: these include the cohesive silts and clays having a high proportion of voids, high cohesion, very low permeability and high compressibility which takes place slowly over a long period of time.

细粒土：这些包括凝聚力粉砂和具有高比例的粘土 空隙，高内聚，非常低的渗透性和高压缩其中发生缓慢以上的很长一段时间。

There are of course soils which can be classified in between the two extremes described above. BS 1377 deals with the methods of testing soils and divides particle sizes into follows:

当然也有可以描述这两个极端之间进行分类的土壤以上。 BS1377处理测试土壤的方法和划分的粒度如下：

The silt, sand and gravel particles are also further subdivided into fine, medium and coarse with particle sizes lying between the extremes quoted above.

淤泥，砂石颗粒也进一步细分为细，中，粗 与粒径躺在上面引述的两个极端之间

Grain size is the basis of soil mechanics, since it is this which decides whether a soil is frictional or cohesive, a sand or a clay. Every large civil engineering job starts with a soil mechanics surrey in its early stages.

晶粒尺寸为土力学的基础，因为它是这样，其确定土壤是否是摩擦或凝聚力，沙或泥土。每一个大型民用工程作业开始带土力学萨里在其早期阶段。

4 Mechanical property of soils

4土的力学性能

The resistance which can be offered by a soil to the sliding of one portion over another or its shear strength is of importance to the designer since it can be used to calculate the bearing capacity of a soil and the pressure it can exert on such members as capacity of a soil . Resistance to shear in a soil under load depends mainly upon its particle composition. If a soil is granular in form, the frictional resistance between the particles increases with the load applied and consequently its shear strength also increases with the magnitude of the applied load. Conversely clay particles being small develop no frictional resistance and therefore its shear strength will remain constant whatever the magnitude of the applied load. Intermediate soils such as sandy clays normally give only a slight increase in shear strength as the load is applied.

土壤提供的阻力是由可滑动的部分作用另一部分产生的，也可以说其抗剪强度设计非常重要,因为它可以用来计算土壤压力等性能，从而可以在发掘支架等发挥作用。土壤的抵抗剪切载荷主要取决于其粒子组成。土是由颗粒构成的，颗粒之间的摩擦力与负载有关，它的抗剪强度随负载的增加而增加。粘土颗粒被分开后摩擦力就没有或很小，因此它的抗剪强度不随负载的改变而变化。中间土壤例如沙粘土随负载的增加抗剪强度也只稍微有所增加。

Compressibility is the characteristic of the reduction of the volume of soils in the pressure (weight of additional stress or stress). Another important property of soils which must be ascertained before a final choice of foundation type and design can be made is compressibility, and two factors must be taken into account: (1) rate at which compression takes place; (2) total amount of compression when full load is applied.

土壤的压缩性是指土壤体积随压力（附加应力或应力）的变化而发生改变的性质。土壤的基础类型的选择和设计的另一个重要属性可压缩性的确定要考虑两个因素(1)压缩速率(2)满荷载的压缩量

When dealing with non-cohesive soils such as sands and grovels the rate of compression will keep pace with the construction of the building and therefore when the structure is complete there should be no further settlement if the soil remains in the same state. A soil is compressed when loaded by the expulsion of air and/or water from the voids and by the natural rearrangement of the particles. In cohesive soils the voids are very often completely saturated with water which in itself is nearly incompressible and therefore compression of the soil can only take

place by the water moving out of the voids thus allowing settlement of the particles. Expulsion of water from the voids within cohesive soils can occur but only at a very slow rate due mainly to the resistance offered by the plate-like particles of the soil through which it must flow. This gradual compressive movement of a soil is called consolidation. Uniform settlement will not normally cause undue damage to a structure but uneven settlement can cause progressive structural damage.

对于其上建设建筑的非粘性土壤砂等的压缩率，随建筑的完成土壤基本保持不变的状态，因此不必做进一步的检测等。土壤的压缩是在加载的作用下将空气和水排出的过程。粘性土土壤孔隙完全饱和时几乎不能压缩，因为土壤的压缩只发生在有移动空间的条件下。土壤孔隙水的排出可能发生但速度非常慢，主要是平板状的颗粒土壤因抵抗运动发生。这种渐变的压缩运动称为固结。通常压缩量不会过度，但不均匀沉降会引起建筑结构的损坏从而引起建筑结构性的破坏。