外文翻译土的性质.docx

外文翻译土的性质1.2.2 Water in a Soil MassAs regards water in the soil,we differ among gravitational water or ground water,capillary water,bound water and interlayer water of a mineral.1.Gravitational waterThe gravitational water is mainly concentrated at contact point between grains that is in steady motion under the influence of gravitational forces.There is a regular water table for the water. Below the water table there exists a water-saturated zone and hydrostatic water within it,The gravitational water has a negative influence on foundation soil.This form of water exists in both coarse-grained soils and finer soils,following Darcy's law.It will be discussed in details in chapter 4.2.Capillary waterThe capillary water,above the gravitational water table,is held by capillary force (surface tension force) that is governed by the surface tension of grains and the diameter of voids.The height, Hc, to which water will rise in a capillary tube (void space) , is, theoretically,directly proportional to the surface tension force T, divided by the diameter of the tube d:Hc TdSo the height of the capillary zone (the occupied area of capillary water) will also be affected by the cleanness of the water; it could be much less for pollutes water. According to Terzaghi and Pech (1967) ,the Hc can be giver as:Hc ced10Where Hc ——maximum height of capillary size, in mm, relates to minimum pore size; e ——void ratio;d10 ——effective size, mm;2 c ——constant,10~20 mm (for clean water) .Capillary rising depends on grain size distribution. As always, the smaller the grain is, the higher the capillary rises, except for some of clay particles that is filled with bound water surrounding the grains. As a geotechnique engineer, you should be aware of a big difference between the capillary water and the gravitational water: the water-saturated zone filled with the gravitational water has hydrostatic pressure, while pore water pressure produced by the capillary water should be negative.3.Bound waterIn the fine-grained soils,the grain surface has an ionized layer around them, which is defined as bound water. More and more people have known that the cohesion force,which is against shearing stress, is to a large extent, resulted from the bound water. The plastic properties of clay soil such as swelling and shrinkage of clay, is mainly attached to the bound water. It is a very important factor considered in the design of a foundation. See Fig. 1-4.4.Interlayer waterThe interlayer water is hidden in a mineral. For example, the mineral,montmorillonitic has a layer structure, its interlayer space,is typically filled with water,originally filled, or filled later. Depending on the abundance or deficiency of water occupy this space, a montmorillonitic soil may exhibit its marked properties of swelling and shrinkage.The montmorillonitic soil, as a loadedfoundation, is very unstable when water is present. 1.2.3 Gas in a Soil MassAs always, gas basically exists in a soil mass. We differ between opened gas and closed gas. The opened gas is interconnected, and directly flows to atmosphere, while the closed gas retains.The former always takes place in the coarse-grained soil,which has little influence on the engineering properties of the soil. But the latter is so difficult to escape that there is a high compressibility and a low permeability for the soils.Geotechnical engineers should know that the presence of gas in the soil void is of great importance in the design of a foundation. 1.2.4 The Structural Features of a Soil Mass1.Different Layers of SoilFor the sedimentary formations, no matter whether they are wind-deposited,water-deposited or glacial-deposited, it is natural that there are different layers of soil,fine-grained soil or coarse-grained soil.Fine-grained layers are often embedded in coarse-grained layers and vice versa. We can also say,from the soil mechanics point of view, high bearing capacity (or Low compressive) layers are often embedding in low bearing capacity and vice versa. These different layers of soil will cause the problems as follows:〔1〕Long-term settlement if there are weak layers (existed).〔2〕Differential settlement of buildings (superstructure) due to the layers' thickness change in horizontal direction.〔3〕Landslide along a thin and weak layer (such as clay or silt) when deep excavating for foundation.It is emphasized that the weak layers of soil will be carefully studied in the building site for a successful foundation design.2.Non-homogeneities (Homogeneousness)Absolutely, soils are non-homogeneities materials that are different in deformation and strength in all directions. The non-homogeneities characteristics of soil are caused by not only the variation of deposit conditions, but also the effect of stress history. With a very large variations in size and shape, most of which are sharp-edged belonging to the former, while deep-going fissures and。