-
Lesson 1
Compression Members
New Words
1. achieve
achievement
2.
eccentricity
center,
中心
;
ec
centric
偏心的；
ec
centricity
偏心，偏心距
3.
inevitable
evitable
可避免的
avoidable;
in
evitable
不可避免的
unavoidable
4. truss
桁架
triangular truss, roof truss, truss
bridge
5. bracing
brace
支柱，支撑；
bracing,
支撑，撑杆
6. slender
细长，苗条；
stout; slenderness
7. buckle
压曲，屈曲；
buckling load
8. stocky
stout
9.
convincingly
convince,
convincing, convincingly
10. stub
树桩，
短而粗的东西；
stub column
短柱
11. curvature
曲率；
curve,
curvature
12. detractor
detract
draw or
take away; divert; belittle
，
贬低，诽谤；
13.
convince
14. argument
dispute, debate, quarrel, reason,
论据（理由）
15.
crookedness
crook
钩状物，
v
弯曲，
crooked
弯曲的
16. provision
规定，条款
Phrases and
Expressions
1. compression
member
2. bending moment
shear force,
axial force
3. call upon (on)
要求，请求，需要
4.
critical buckling load
临界屈曲荷载
critical
关键的，临界的
5. cross-sectional area
6.
radius of gyration
回转半径
gyration
7. slenderness ratio
长细比
8. tangent modulus
切线模量
9. stub
column
短柱
10. trial-and-
error approach
试算法
11. empirical formula
经验公式
empirical
经验的
12. residual stress
残余应力
residual
13. hot-rolled
shape
热轧型钢
hot-rolled bar
14. lower bound
下限
upper bound
上限
16. effective length
计算长度
Definition
（定义）
Compression
members
are
those
structural
elements
that
are
subjected
only
to
axial
compressive forces:
that is, the loads are applied along a
longitudinal axis through the centroid of
the
member
cross
section,
and
the
stress
can
be
taken
as
f
a
=P/A,
where
f
a
is
considered
to
be
uniform over the entire cross section.
受压构件是仅受轴向压力作用的构件，即：荷载是沿纵
轴加在其
截面形心上的，
其应力可表示为
…
，<
/p>
式中，
假定
f
a
在整个截面上均匀分布。
This
ideal
state is never achieved in
reality, however, and some
eccentricity
of the load is
inevitable.
然而，
现实中从来都不可能达到这种
理想状态，
因为荷载的一些偏心是不可避免的。
This
will result
in
bending,
but
it
can
usually
be
regarded
as
secondary
and
can
be
neglected
if
the
theoretical
loading condition is closely
approximated.
这将导致弯曲，但通常认为它是次要的，如果理论
工况是足够近似的，就可将其忽略。
This cannot
always be done if there is a computed bending
moment, and situation of this type will
be considered in
Beam-Columns.
< br>但这并非总是可行的，
如有计算出的弯矩存在时，这种情形将在梁柱
理论
中加以考虑。
The
most
common
type
of
compression
member
occurring
in
buildings
and
bridges
is
the
column
, a vertical member
whose primary function is to support vertical
loads.
在建筑物和桥梁
中最常见的受压构件就是柱，<
/p>
其主要功能就是支承竖向荷载。
In many
instances these members
are
also
called
upon
to
resist
bending,
and
in
these
cases
the
member
is
a
beam-column
.
Compression members can also be found
in trusses and as components of bracing systems. <
/p>
在许
多情况下，
它们也需要抵抗弯曲，在
此情况下，将它们称为梁柱。
受压构件也存在于桁架和
支撑系统
中。
Column Theory
（柱理论）
Consider the long, slender compression
member shown in Fig.1.1a.
考虑如图
1.1.a
所示的
长柱
If
the axial load P is slowly applied, it will
ultimately reach a value large enough to cause the
member to become unstable
and
assume
the shape
indicated by the dashed line.
如果慢慢增加轴
向荷载
P
，它最终将达到一个足够大的值使
该柱变得不稳定
(
失稳
)
，如图中虚线所示。
The
member is said to have buckled, and the
corresponding load is called th
e
critical buckling load
.
这时认为构件已经屈曲，相应的荷载称为临界屈曲荷载。
If
the member is more
stocky
,
as the
one in Fig.1.1b, a larger load
will be required to bring the member to the point
of instability.
如果
该构件更粗短些，如图
1.1b
所示，则需要更大的荷载才能使其屈曲。
For
extremely
stocky
members, failure may be by compressive
yielding rather than buckling.
对特别粗短的构件
，
破坏
可能是由受压屈服引起而非由屈曲引起。
For
these
stocky
members
and
for
more
slender
columns before they buckle, the
compressive stress P/A is uniform over the cross
section at any
point along the length.
对这些短柱以及更细长的柱，在其屈曲前，在其长度方向上任意点处
横截面上的压应力
P/A
都是均匀的。
As
we
shall
see,
the
load
at
which
buckling
occurs
is
a
function of
slenderness
, and for very
slender members this load could be quite small.
我们将会看
到，屈曲发生时的荷载是
长细程
度
的函数，非常细长的构件的屈曲荷载将会很低。
If the member is so slender
(a precise definition of slenderness will be given
shortly) that the
stress just before
buckling is below the proportional
limit
—
that is, the member is
still elastic
—
the
critical buckling load is given by
如果构件如此细长（随后将会给出细长程度的精确定义）以
致即将屈曲时
的应力低于比例极限—即，构件仍是弹性的，临界屈曲荷载如下式给出：
2
P
cr
?
?
2
EI<
/p>
L
2
(1.1)
where
E
is
the
modulus
of
elasticity
of
the
material,
I
is
the
moment
of
inertia
of
the
cross-sectional area with respect to
the minor principal axis, and L is the length of
the member
between points of support. <
/p>
式中
E
为材料弹性模量，
I
为关于截面副主轴的惯性矩，
L
为支座
间的距离。
For Eq1.1
to be valid, the member must be elastic, and its
ends must be free to rotate
but not
translate laterally. This end condition is
satisfied by hinges or pins.
要使方程
1.1
成立，
构
件必须是弹
性的，且其两端必须能自由转动，但不能侧向移动。
This
remarkable
relationship
was
first
formulated
by
Swiss
mathematician
Leonhard
Euler
and
published
in
1975.
此著名公式是瑞士数学家欧拉于
< br>1975
年提出的。
The
critical
load
is
sometimes referred to as the Euler load
or the Euler buckling load. The validity of Eq.1.1
has been
demonstrated
convincingly
by
numerous tests.
因此有时将临界荷载称为欧拉荷载或欧拉临界
荷载。欧拉公式的有效性（正确性）已由许多试验
充分
证实。
It will
be convenient to rewrite Eq.1.1 as follows:
方程
1.1
可方便地写为
P
cr
?<
/p>
?
2
EI
L
2
?
?
2
EAr
2
L
2
?
?
2
EA
(
L
/
r
)
2
(1.1a)
where
A
is
the
cross-sectional
area
and
r
is
the
radius
of
gyration
with
respect
to
the
axis
of
buckling.
The
ratio
L/r
is
the
slenderness
ratio
and
is
the
measure
of
a
compression
member
’
s
slenderness, with large values
corresponding to slender members.
式中
A
为截面面积，
r
为关于
屈曲轴的回转半径，
L/r
为长细比，它是对受压构件细长程度的一种度量，该值越大，构件
越细长。
If
the
critical
load
is
divided
by
the
cross-sectional
area,
the
critical
buckling
stress
is
obtained:
如果将屈曲荷载除以截面面积，便可得到以下屈曲应力：
P
cr
?<
/p>
2
E
F
cr
?
?
A
(
L
/
r
)
2
(1.2)
This is the compressive stress at which
buckling occur about the axis corresponding to r.
这便是
绕相应于
r
的轴发生屈曲时的压应力。
Since buckling will take
place as soon as the load reaches
the
value by Eq.1.1, the column will become unstable
about the principle axis corresponding to the
largest slenderness ratio. This usually
means the axis with the smaller moment of inertia.
由于一
旦荷载达到式
1.1
之值，柱将在与最大长细比对应的主轴方向变得不稳定
（失稳）
，通常该
轴是惯性矩较小的轴。
Thus,
the minimum moment of inertia and radius of
gyration of the cross
section should be
used in Eq.1.1 and 1.2.
因此，应在方程
< br>1.1
和
1.2
中采用截面的最
小惯性矩
和最小回转半径。
Early researchers soon found that
Euler
’
s equation did not
give reliable results for stocky, or
less slender, compression members.
早期的研究者很快发现对短柱或不太细长的受压构件，
欧
拉公式并不能给出可靠的结果，
This is because of
the small slenderness ratio for members of
this type, which results in a large
buckling stress (from Eq.1.2).
这是因为这种构件
的长细比较
小，从而产生较高的屈曲应力。
If
the
stress
at
which
buckling
occurs
is
greater
than
the
proportional
limit
of
the
material,
the
relation
between
stress
and
strain
is
not
linear,
and
the
modulus of elasticity E
can no longer be used.
如果屈曲发生时的应力大于材料的比
例极限，
应
力应变关系就不再是线性的，也不能再用弹性模量<
/p>
E
。
3
This difficulty was
initially
resolved by
Friedrich Engesser, who proposed in
1889 the use of a
variable tangent
modulus E
t
in Eq.1.1.
这一困难最初由
Friedrich Engesser
所克服，他在
1889
年将可变的切线模量
用于方程
1.1.
For
a
material
with
a
stress-strain
curve
like
the
one
in
Fig.1.2, E is not a
constant for stress greater than the proportional
limit F
pl
. The tangent
modulus
E
t
is
defined as the slope of the tangent to the stress-
strain curve for values of
f
between F
pl
and
F
y
.
对于如图
1.2
所示的应力应变曲线
(
的材
料
)
，当应力超过比例极限时，
E
并非常数，当应力
处于
F
< br>pl
和
F
y
之间时，
将切线模量定义为应力应变曲线的切线的斜率，
I
f the compressive stress
at buckling,
P
cr
/A, is in this region, it
can be shown that
如果屈曲时的压应力在此范围时，
可以
证明
P
cr
?
?
2
E
t
I
L
2
(1.3)
This is identical to the Euler
equation, except that E
t
is
substituted for E.
除公式中将
E
代之以
E
t
外，上式
与欧拉公式完全相同。
Effective
Length
（计算长度）
Both
the Euler and tangent modulus equations are based
on the following assumptions:
欧拉和切
线模量方程都是基于如下假定：
1. The
column is perfectly straight, with no initial
crooked
ness.
柱完全竖直，无初始弯曲。
2.
The load is axial, with no eccentricity.
荷载是轴向加载，无偏心。
3.
The column is pinned at both ends.
柱在两端铰结。
The
first
two
conditions
mean
that
there
is
no
bending
moment
in
the
member
before
buckling.
前两
(
假定
)
条件意味着在屈曲前无弯矩存在。
As
mentioned
previously,
some
accidental moment will be present, but
in most cases it can be neglected.
如前所述
，可能偶然会
存在一些弯矩，
但在大多数情况下都可被忽略。<
/p>
The requirement for pinned ends,
however, is a
serious limitation, and
provisions must be made for other support
conditions.
然而，铰结要求是
一个严重的局限，
必须对其它支撑条件作出规定。
The pinned-end
condition is one that
requires
that the member
be
restrained
from lateral translation,
but not rotation, at the ends.
铰结条件要求
约束构件两端不发生侧移，但并不约束转动。
Since
it
is
virtually
impossible
to
construct
a
frictionless pin connection, even this
support condition can only be closely approximated
at best.
由于实际上不可能构造无摩擦铰连接，
即使
这种支撑条件最多也只能是非常近似。
Obviously,
all
columns
must
be
free
to
deform
axially.
显然，所有柱必须在轴向自由变形。
In
order
to
account for other end conditions, the
equations for critical buckling load will be
written as
为了
考虑其它边界条件，将临界荷载写
为如下形式
P
cr
< br>?
?
2
EA
(
KL
/
r
)
2
or
P
c
r
?
?
2
E<
/p>
t
A
(
KL
/
r
)
2
(1.4)
where
KL
is
the
effective
length,
and
K
is
called
the
effective
length
factor.
Values
of
K
for
different
cases can be determined with the aid of the
Commentary to the AISC Specification.
式
中
KL
为计算长度，
< br>K
称为计算长度系数，各种情况下的
K
< br>值可借助于
AISC
（美国钢结构
学会
American Institute of Steel
Construction
）规范的条文说明加以确定。
4
Lesson 2
Introduction to structural
design
New words
1.
framework
2. constraint
3.
collaborate
4. evaluation
5. fixture
6. partition
7. overlook
8. crane
9. fatigue
10. drift
11. enumerate
12. plumbing
13. ventilation
14. accessibility
15. code
16. administer
17. metropolitan
18. consolidate
19.
prescription
20. municipality
21. specification
22. mandate
frame+work=frame
构架，框架
; frame
structure,
框架结构
vt. constrain
约束，强迫；
n. constraint
约束
vt.
合作，通敌；
collaboration,
collaborative
vt. evaluate,
value; assess, assessment
vt. fix,
fixture
固定设备，固定物，夹具
vt. n
分割，划分，
make apart; partition wall
n.
超重机，鹤
.n
疲劳
fatigue strength, fatigue failure
v.n
漂流，漂移，
雪堆
v. list
列举
n. (
卫生，自来水
)
管道，
plumber
管道工
n.
通风，
ventilate,
ventilate a room, a well-ventilated room, vent
通风口
n.
可达性，
access, n.
vt.
通道，接近；
accessible
易接近的，可达到的
n. vt
代码，编码，规范
v.
管理，执行；
administrate,
管理
a.
大城市，
of metropolis
v.
巩固，
strengthen
，
reinforce;
consolidation
n.
规定，命令，药方；
prescribe
n.
市政当局，直辖市，
municipal government
n.
详述，规格
,
规范；
specify
n.
书面命令，委托，
Phrases and expressions
1. functional design
2. bending
moment
3. dead
load
4. live load
5.
nonstructural components
6.
force due to gravity
7. gravity load
8. building code
功能设计
弯矩
非结构构件
5
9. design specifications
设计规程
10.
nonprofit organization
非赢利组织，弄
non-government
organization
11. the
National Building Code
12. the Uniform
Building Code
13. the Standard Building
Code
14. Building Officials and Code
Administrators International (BOCA)
国际建筑公务员与法规管
理人员联合会
15. AISC
美国钢结构学会
American Institute of Steel
Construction
16. AASHTO
美国公路和运输工作者协会
American Association of
State Highway and Transportation
Officials
17. AREA
18. AISI
美国铁道工程协会
美国钢铁学会
the American Railway Engineering
Association
American Iron
and Steel Institute
Introduction to
Structural Design
Structural design
The structural design of
building, whether of structural steel or
reinforced concrete, requires the
determination
of
the
overall
proportions
and
dimensions
of
the
supporting
framework
and
the
selection
of the cross sections of individual members.
建筑结构设计，
不论是钢结构还是钢筋混
凝土结构
，都需要确定其支承结构的整体比例和尺寸以及各构件的截面尺寸。
In most
cases
the functional design, including
the establishment of the number of stories and the
floor plan, will
have
been
done
by
an
architect,
and
the
structural
engineer
must
work
within
the
constraints
imposed by this
design.
在大多数情况下，
功能设计，
包括楼层层数和楼层平面的确定，
将要
由建筑师来完成
，
因而结构工程师必须在此约束条件下工作。
Ideally,
the engineer and architect
will
collaborate
throughout
the
design
process
so
that
the
project
is
completed
in
an
efficient
manner.
在理想状态下，
工程师和建筑师将在整个设计过程中协同工作从而高效地完成设计
工作。
In effect, however, the
design can be summed up as follows:
然而，
事实上，设计过程可
概括如下：
The architect
decides how the building should look; the engineer
must make sure that it
doesn
’
t fall
down.
建筑师确定建筑物的外观，
工程师必须确保其不会
倒塌。
Although this is an
oversimplification, it affirms the
first priority of
the structural
engineer: safety. Other important
considerations include serviceability
(how well the structure performs in terms of
appearance and
deflection) and economy.
尽管这样说过分简单，但它明确了工程师的第一个主要任务，即，
确保安全。其它要考虑的因素包括适用性（就外观和挠曲而言其工作性能如何）
。
An
economical structure
requires an efficient use of materials and
construction labor. Although this
can
usually be accomplished by a design that requires
a minimum amount of material, savings can
often be realized by using slightly
more material if it results in a simpler, more
easily constructed
projects.
经济的结构要求对材料和人工的有效使用，
尽管这通常都能通过要求最少材料来取
得，但通过采用稍多的材料，但能使建筑物更简单和更容易建造常常会实现节约的目的。
6
Loads
The forces the act on
a structure are called
loads
. They belong to one of
two broad categories,
dead load and
live load
.
作用在结构物上的各种力称为荷载，它
们属于一两种广义类型，恒
载和活载。
Dead loads
are those that are permanent, including the weight
of the structure itself,
which is
sometimes called the
self-
weight
.
恒载是那些永久荷载，包括结构自身的重量，
有时
也称为自重。
Other dead loads in
a building include the weight of nonstructural
components such
as floor coverings,
suspended ceilings with light fixtures, and
partitions.
其它建筑物恒载包括非
结构构件的重
量，
如楼面面层、
带有灯具的吊顶以及隔墙。
< br>All of the loads mentioned thus far
are forces due to gravity and are
referred to as gravity loads.
至此所提的各种荷载
都是由重力
所引起，
因而称为重力荷载。
Live loads, which can also be gravity loads, are
those that are not as
permanent as dead
loads.
活载也可以是重力荷载，
它们是那些不如恒载那
样永久的荷载。
This
type may or may
not be acting on the structure as any given time,
and the location may not be
fixed.
这类荷载可能也可能不总是作用在结构物上，且作用位置也可能不是固定的。
Examples of live load include furniture, equipment, and occupants of buildings.
活荷载包括家
具、
设置和建筑物的居住者。
In general, the magnitude of a live load is not as well defined as that
of a dead load,
and it usually must be estimated. In many cases, a
given structural member must be
investigated
for
various
positions
of
the
live
load
so
that
a
potential
failure
situation
is
not
overlooked.
通常，活荷载的大小不如恒载那样确
定，常常必须估计。在许多情况下，必须
研究活荷载作用在一给定的结构构件的各个位置
以便不会漏掉每个可能的破坏情形。
Building
codes
Building must be designed and
constructed according to the provisions of a
building codes, which
is a legal
document containing requirements related to such
things as structural safety, fire safety,
plumbing, ventilation, and
accessibility to the physically disabled.
< br>建筑物必须根据各种建筑规
范的条款设计和建造，规范是一种法律文件，包含各种
要求，如建筑安全、防火安全、上下
水、通风和体残人的可达性等。
A building code has the force of law and is administered by a
governmental entity
such as a city, a county, or, for some large
metropolitan areas, a consolidated
government.
建筑规范具有法律效力，由政府部位
发布，如城市、县、对于大的城区，如联
合政府。
Buildi
ng codes do not give design provisions, but they
do specify the design requirements
and
constraints that must be satisfied.
建筑规
范并不给出设计规定，但却规定设计必须满足的
各种要求和约束条款。
< br>Of particular importance to the structural engineer is the prescription of
minimum
live
loads
for
buildings.
对结构工程师特别重要的是建筑物的最
小活荷载规定。
Although the engineer is
encouraged to investigate the actual loading
conditions and attempt to
determine
realistic values, the structure must be able to
support these specified minimum loads.
尽管鼓励工程师研究实际荷载工况以确定真实的荷载值，
结构必须能支承这些规定的最小
荷
载。
Design
specifications
In contrast to building
codes, design specifications give more specific
guidance for the design of
7
structural members and
their connections.
与建筑规范不同，设计规程给出结构构件及其
连接
的更具体的指南。
They
present
the
guidelines
and
criteria
that
enable
a
structural
engineer
to
achieve the objectives
mandated by a building code.
它们给出各种方针和标
准，使结构工程师
能建筑规范所规定的目标。
Design
specifications
represent
what
is
considered
to
be
good
engineering practice
based on their latest research.
根据其最新研究
，
设计规程结出认为是好的
工程作法。
They
are
periodically
revised
and
updated
by
supplements
or
by
completely
new
editions.
它们通过补充或通过发布新版本得到定期修订和更新。
As
with model building codes,
design
specifications
are
written
in
a
legal
format
by
nonprofit
organizations.
如同一般建筑规
范，设计规程由非赢利组织编写。
They have no legal standing on their own, but by presenting
design
criteria
and
limits
in
the
form
of
legal
mandates
and
prohibitions,
they
can
easily
be
adopted, by reference, as
part of a building code.
尽管它们本身并无法律地位，<
/p>
但却以法令和禁
令的形式给出设计准则和限制，
< br>以参考文献的形式，
它们可容易地被录入，
并作为建筑规
范
的一部分。
8
Lesson 3
New
words
1. col`loidal
胶状的，胶体的，
`colloid
胶体
2. sieve
n,v.
筛，过筛，过滤
3. sample
.
样品，取样
specimen
4. mesh
n.v
网孔，网格，分网格
5. `cumulative
a.
积累的；
cumulate,
cumulation
6. grading
n.
级配，等级；
grade
7.
sedimentation
n.
沉淀
; sediment
8. suspension
n.
悬浮；
suspend ~bridge cable-
stayed bridge
9. agitate
v.
搅动，混合；
disturb
10.
hydro
meter
n.
（液体）比重计
11.
viscosity
n.
黏性；
viscoidal
12. flaky
n.
薄片状的，
of flake
13. pipette
n.
吸液管
14.
ir
recoverable
a.
不可恢复的
ir
retrievable
15.
con
cave
a.
凹的；
con
vex
凸的
16.
permeability
n.
渗透性
; permeate, permeable
seep
seepage
Phrases and
expressions
1. frost susceptibility
2. sieving method
3. semi-
logarithmic curve
4. grading curve
5. wet sieving
6.
dispersing agent
7. Stoke
’
s law
8.
unit weight
9. coefficient of grading
10. sedimentation method
11.
particle-size distribution
霜冻敏感性
筛分法
半对数曲线
级配曲线
湿法筛分
分散剂
斯托克定律
重度
级配系数
沉降法
粒径分布
9
Text
Particle Size Analysis
粒径分析
The range of particle sizes encountered
in soils is very wide: from around 200mm down to
the colloidal size of some clays of
less than 0.001mm.
在各种土中所遇到的粒径范围很大，大
到
200mm
小到小于
0.001mm
的一些粘土胶粒。
Although
natural
soils
are
mixtures
of
various-sized particles, it is common
to find a predominance occurring within a
relatively narrow
band of sizes.
尽管天然土都是由各种粒径的颗粒组成，
但通常可发现其主要组成颗粒出现在
一个比较小的粒径范围内。
When
the
width
of
this
size
band
is
very
narrow
the
soil
will
be
termed poorly-graded, if
it is wide the soil is said to be well-graded.
当这一粒径范围非常小时，
称这种土级配较差，
而当其较大时，
称这种土级配良好。
A number of
engineering properties, e.g.
permeability, frost susceptibility,
compressibility, are related directly or
indirectly to particle-size
characteristics.
土的许多工程特性，如渗
透性、霜冻敏感性、可压缩性等都直接或间接的与
土的级配特性有关。
< br>
Fig.3.1 shows the
British Standard range of percentage of particle
sizes.
图
3.1
为粒径百分<
/p>
数的英国标准范围。
The particle-size
analysis of a soil is carried out by determining
the weight
percentage falling within
bands of size represented by these divisions and
sub-divisions.
通过确
定落入由这些粒径分组
和子组所代表的粒径范围的重量百分比，对土进行粒径分析。
In
the
case
of
a
coarse
soil,
from which
fine-grained
particles
have
been
removed
or
were
absent,
the
usual process is a sieve analysis.
对于粗粒土，它里面的细粒土被除去或本身就无细颗粒，常
用的方法就是
筛分法。
A
representative
sample
of
the
soil
is
split
systematically
down
to
a
convenient
sub-sample size and then oven-dried.
此法
是将要分析土的一代表样本系统地分为
方便的子样本，然后烘干。
This
sample
is
then
passed
through
a
nest
of
standard
test
sieves
arranged
in
descending
order
of
mesh
size.
再使烘干的土样通过一组筛孔尺寸由大至小放置<
/p>
的标准试验筛。
The
weight
of
soil
retained
on
each
sieve
is
determined
and
the
cumulative
percentage of the sub-sample weight
passing each sieve calculated.
称量每个筛中剩下
的土样的
重量，并计算出通过每个筛的累计百分数。
From
these figures the particle-size distribution for
the soil is plotted as a semi-
logarithmic curve (Fig.3.2) known as grading
curve.
根据这些数据，
以半对数曲线的形式描出该土的
粒径分布图，即所谓的级配曲线。
细粒
粘
土
胶粒
粉土
细
中
粗
粗粒
砂
细
中
粗
砾石
细
中
粗
非常粗大颗粒
石块
卵石
块石
Where the soil
sample contains fine-grained particles, a wet
sieving procedure is first carried
out
to remove these and to determine the combined
clay/silt fraction percentage.
在土样中含有
细土粒的场合，
首先用湿筛分法将其除去，
并确定粘粒
/
粉粒总共所占的分数。
A
suitable-sized
sub-sample is first
oven-dried and then sieved to separate the
coarsest particles (>20mm).
将一适
< br>量的分土样烘干，并过筛分开最粗的颗粒（
>20mm
的
颗粒）
The sub-sample is then immersed
in
water
containing
a
dispersing
agent
and
allowed
to
stand
before
being
washed
through
a
63
?
m(micron) mesh
sieve.
然后将土样浸入含有分散剂的水中，
并在将其用
63
微米筛过筛前
搁置起来（并将其搁
置一会，再用
63micron
的筛子过筛）
< br>。
The
retained
fraction
is
again
oven-dried and passed through a nest of
sieves.
将筛中保留的部分烘干，并用一组筛子过筛。
After
weighing
the
fractions
retained
on
each
sieve
and
calculating
the
cumulative
percentage
10
passing each sieve, the grading curve
is drawn.
称量落在每个筛中土重，并计算出通过每个的
累计百分数后，就可描出级配曲线。
The
combined
clay/silt
fraction
is
determined
from
the
weight
difference
and
expressed
as
a
percentage
of
the
total
sub-sample
weight.
The
coarsest
fraction (>20mm)
can also be sieved and the results used to
complete the grading curve.
由重量
< br>差确定粘粒
/
粉粒的总重，并将其表示为子土样总重的百
分数。最粗的部分（即粒径
>20mm
的部分）也可被过筛，并
用其结果完成级配曲线的绘制。
A
further sub-division of particle-size distribution
in the fine-grained fraction is not possible
by
the
sieving
method.
不能用筛分法对细粒部分的粒径分布作进一步分组。
A
process
of
sedimentation
is
normally
carried
out
for
this
purpose.
通常必须用沉降法实现此目的。
A
small sub-sample of soil is
first treated with a dispersing agent and then
washed through a 63
?
m
sieve.
首先将一小子土样用分散剂进行处理，然后洗过
63
的筛子。
The
soil/water suspension
is then made up
to 500 ml, agitated vigorously for a short while
and then allowed to settle.
再从
中取出
500ml
的土
/
水悬浮液，
充分搅拌一会后让其沉降。
The
procedure is based on
Stoke
’
s law,
which states that the velocity at which
a spherical particle will sink due to gravity in a
suspension
is
given
by:
此方法是基于斯托克思定律，即在重力作用下球形颗粒
在某一悬浮液中下降的
速度为
Where d=diameter of particle
颗粒直径
?
s
=unit weight
of the grain of particle
颗粒重度
?
w
=unit weight
of the suspension fluid (usually water)
悬浮液的重度（通过为水的重度）
?
=
vescosity
of the
suspension fluid
（悬浮液的黏度）
The diameter of those particles that
will have settled a given distance in a given time
(t) may
be obtained by rearranging
Eq.3.1:
将式
3.1
变形得在
给定时间
t
内，
沉降一给定距离的那些
颗
粒的直径为
Usually h=100mm,
通常
h=100mm, giving
由此给出
Samples
taken
at
a
depth
of
100mm,
at
an
elapsed
time
of
t,
will
not,
therefore,
include
particles of greater size than the
diameter d given by Eq.3.2;
因此在，
在深度
100mm
处，
t <
/p>
时间
后所取的悬浮液中将不会有粒径大于式
3.2
所给出的土粒
;
but
the
proportions
of
particles
smaller than d in the suspension will
remain unchanged.
但悬浮液中小于
d
的颗粒所占的比例
仍保持不变。
The
procedure using a hydrometer consists of measuring
the suspension density at a
depth of
100mm at a series of elapsed-time intervals.
用液体比重计的方法包括以一系列时间
间隔在深度
100mm
处测定悬浮液的比重。
The
percentage-finer
values
corresponding
to
particular diameter (i.e. particle
sizes) are obtained from the density readings, and
thus a grading
curve for the fine-
grained fraction may be drawn.
通过比重读数得到
小于某一特定粒径的颗粒
的百分数，从而可画出细粒部分的级配曲线。
< br>
Grading Characteristics
The
grading
curve
is
a
graphical
representation
of
the
particle-size
distribution
and
is
therefore
useful in itself as a means of
describing the soil.
级配曲线是粒径分布的一种图形表达，<
/p>
因而可
用来作为描述土的手段。
For
this
reason
it
is
always
a
good
idea
to
include
copies
of
grading
11
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