Строкова Л.А. Soil Mechanics. Практикум для занятий на английском языке по дисциплине Механика грунтов - файл n1.docСтрокова Л.А. Soil Mechanics. Практикум для занятий на английском языке по дисциплине Механика грунтовскачать
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TOMSK POLYTECHNIC UNIVERSITYENGLISH LANGUAGE PRACTICE Soil Mechanics
L.A. StrokovaRecommended for publishing as a study aid by the Editorial Board of Tomsk Polytechnic University
Tomsk Polytechnic University Publishing House
Федеральное агентство по образованию
Государственное образовательное учреждение высшего профессионального образования «НАЦИОНАЛЬНЫЙ ИССЛЕДОВАТЕЛЬСКИЙ ТОМСКИЙ ПОЛИТЕХНИЧЕСКИЙ УНИВЕРСИТЕТ» Л.А. Строкова
Профессиональный английский язык
Практикум для занятий на английском языке
по дисциплине «Механика грунтов»
Томского политехнического университета
ББК 26.3Строкова Л.А.
Практикум для занятий на английском языке по дисциплине «Механика грунтов». – Томск: Изд-во Томского политехнического университета, 2010. – 48с.
Работа содержит методические материалы, направленные на отработку и закрепление как аспектов английского языка, так и профессиональной лексики, и предназначено для студентов 4 курса, обучающихся в Институте геологии и нефтегазового дела по направлению 130100 «Геология и разведка полезных ископаемых». Предлагаемые материалы способствуют знакомству с терминами, используемыми в инженерной практике в англоязычных странах. УДК 624.131 ББК 26.3 Рецензент
Доцент кафедры иностранных языков в области геологии и
нефтегазового дела (ИЯГН) Болсуновская Людмила Михайловна
© ГГОУ ВПО «Национальный исследовательский Томский политехнический университет», 2010
© Строкова Л.А., 2010
© Оформление. Издательство Томского
политехнического университета, 2010
1. Some Basic Soil Properties
Most soils are produced by the breakdown (“weathering”) of rocks. The principal exceptions are those of biological origin – e.g. offshore soils often consist of the remains of the skeletons of tiny marine organisms, or of the shells of such organisms, and are hence composed largely of calcium carbonate (CaCO3
), and are called calcareous
soils or carbonate
soils (these two terms are almost, but not completely, synonymous). In some offshore regions influenced by deposition from major river systems (e.g. in the Gulf of Mexico, around the mouth of the Mississippi, or off Brazil, around the mouth of the Amazon, the soils can consist of clays of terrestrial origin, washed out by the river).
1.2. Rock “weathering”
The process of rock breakdown to form soil is termed rock “weathering”. This is either:
Mechanical weathering – the physical breakdown that occurs due to mechanical forces (ice expanding in cracks, rocks grinding together, erosion by action of water, heating-cooling cycles, etc). The rock is broken into smaller and smaller particles, but the original rock minerals are not changed. This produces (in order of decreasing size) cobbles (> 60mm), gravel (60mm – 2 mm), sand (2 mm to 60 m) and silt (60 m to 2 m). It is very difficult to break down soil to finer than silt size by mechanical breakdown.
Chemical weathering – where the actual minerals in the parent rock are changed, by chemical “rotting” – e.g. by the action of oxygen and water, particularly in warm humid climates. This forms completely new minerals – called clay. Clay particles are “platey” in structure (much smaller in one dimension than in the other two – like cornflakes), but silts, sands, gravels, etc are more rounded in aspect ratio (not that much difference between maximum and minimum dimensions). Clays are actually quite complex, with complex electro-chemical forces between the grains. They have very high “specific surface area” – the surface area per unit weight (e.g. the clay mineral montmorillonite can have hundreds of m2 in surface area per gram of material). Since many of the particle interactions are surface effects, these are very important for clay minerals.
1.3. Soil Classification
Soils are classified on the basis of:
Size (as above). Determined using a series of sieves of decreasing mesh size (down to 60 m) and sedimentation methods (from about 100 m down to about 2m; below m, the material is defined as clay, and, for clay, size does not mean much.
Fine grained soils (silts and clays) are also classified according to plasticity properties (effectively, how well they absorb water). The plasticity properties are called the Atterberg Limits, which are water contents at which the soil changes from a viscous liquid state to a plastic solid state (the “liquid limit”, wL), and from a plastic solid state to a brittle solid state (the “plastic limit”, wp). The difference between these is the “plasticity index”, Ip = wL – wp.
1.4. Soil “density”
The density of the soil particles themselves is denoted s (the soil particle density)
, and for many soils, this is between 2.6 and 2.7 t/m3
. The density of water w
is 1 t/m3
. The relative density of the soil particles is therefore Gs = s/w
(being a ratio, this is just a dimensionless number).
As we are generally dealing with soil on the earth’s surface (and not on the moon, or in a centrifuge with elevated g
-level), we are usually interested in the forces
in soil, and hence we are more interested in weight than density, where weight is simply .g (and g, the acceleration due to the earth’s gravity, is 9.81 m/s2
). Thus, instead of using density all the time, we use unit weight (where = .g, and has units of kN/m3
). The unit weight of water, w
, is therefore 9.81 kN/m3
. The unit weight of quartz (the mineral that many sands are comprised of) is about 26 kN/m3
(that is, a solid 1 m3
block of silica would weigh 26 kN.)
If a 1 m3
container is filled with dry silica sand, the weight would be considerably less than the weight of a solid block of silica, due to the air-filled voids
between the particles.
The basic means of expressing the density of packing is to use the voids ratio (e):
is the volume of the voids, and Vs
is the volume of the “solids” (soil particles). Note that e
can be greater than 1 (it very often is for clay soils).
So, for our 1 m3
box of dry sand, the total weight of the soil in this state is the dry unit weight
If the voids are now completely filled with water, the box will of course be heavier. The weight would now correspond to the saturated unit weight (sat
The “wetness” of a soil is described (in civil engineering) by on a weight basis:
(often expressed as %)
(i.e. as the weight of water divided by the weight of the dry soil. This is found by weighing the wet sample first, then drying it in the oven, then weighing the dry soil).
From these relationships, we can see that: