毕业设计外文翻译(5)

vicinity of the face

for a tunnel in the Mingtam Power Cavern Project．The measured data are plotted as dots in

Fig．4．Based on this data，Hock(1999)suggested the following empirical best-fit relationship

between Ur and distance X from the face： Ur

rITlax - l+expl l·Iul j it 喜’： l — 。

一一——广一一——— 一—百 E— xc — avatin— f ； 耋 f g dir

Fig．3 Profile of radial displacements U for an unsuppo~ed tunnel 90 Van·hung DAO．Water Sconce and Engineering，Sep．2009，Vo1．2，No．3，87—95

● ， ● ， 1．00 O．75 0．50 0．25 0 广— ＼口 E

xcavating direc~ ?

Pan et 995 “ “ ( 1 ) ‘ ＼ 、：

8 6 4 2 0 —2 _4

Fig．4 profiles derived from elastic models(Panet 1 995)，measurements in tunnel(Chem et a1．1 998)，and

best fit tO measurements(Hoek 1 999)

2．3 Characteristic curve of supporting structure

The characteristic curve shows the working capacity of the supporting structures

(concrete，gunite，rock anchor or form stee1)．It is based on the linear relation between

supporting pressure Pi and radial displacement“，，and it is applied to a supporting section for

a unit length along the tunnel axis．

Assuming the stifness of supporting stru ctures to be ，the elastic section of the

support characteristic curve can be calculated using the following formula：

= U (8)

The stiffness of concrete or gunite stru ctures iS K s = 1+Vc

ri 一(ri— ) (1—2vc)ri +( 一 )

where is the elastic modulus of gunite(concrete)，Vc is the Poisson coeficient of gunite

(concrete)，and tc is the lining thickness．

The stiffness of a steel support stru cture is calculated with the following form ula：

： ( +sinOcos0) Is

2sin 0 + E (10。 )

where S iS the distance between the supports along the tunnel axis(m)， is the half of：：the

angle between the tamping bars(。)，W is the width of the tamping blocks(m)，A is the

cross-sectional area of the section(m )，I iS the moment of inertia of the section(m4)，巨iS

the Young’S modulus for the steel(MPa)，tB is the thickness of the block(m)，and EB is the

Young’S modulus for the block matedal(MPa)．

The stiffness of a supporting structure using a mechanical anchor or chemical bonding

anchor with a length of lh and a diameter of d can be calculated as follows：

1 一 S f ’

where S is the distance between the anchors 石 ：Eb along +Q] (11)

the tunnel circumference，Sl is the

Van。hung DAO．Water Science and Engineering,Sep．2009，Vo1．2，No．3

， 87—95 9 1

distance between the anchors along the tunnel axis，a is the anchor pulling force，Eb is the

elastic modulus of anchor materials，and，is the free length of the bolt or cable．

W hen composite supporting structures are used，the components of the composite

supporting structures are all assumed to be installed at the same time，and the stifness of the

composite supporting structures is assumed to be the sum of the stifness of each of the

structure’S components： Ks= l+ K s2 (12)

where 1 is the stifness of the first supporting structure，and Ks2 is the stifness of the

second supporting structure．

Therefore，the characteristic curve of the supporting structure is specified by the

following equation： 罢 (13)

where“p is the displacement component of supporting structures and compressed rock，and

U0 is the initial displacement component of the tunnel before the lining is installed(defined by

means of the stress release efect)． 3 Example study

3．1 Description of example and design parameters

A survey of the intake tunnel of the Ban Ve Hydroelectric Power Plant(Nghe An

Province，Vietnam)was carried out．The material parameters ofthe tunnel are shown inTable 1．

Table I Physical and mechanical parameters of tunnel

Th e applied supporting structure was a combination of Gunite M 300 with a thickness of

10 cm an d steel anchors with diameters of 20 mm and lengths of 2 m．Anchor spacing along

the tunnel circumference an d along the tunnel axis was 1．5 m．The Matlab programming

language was used for the computation． 3．2 Calculation results and analysis

The stress value of the ground base P0：7．300 8 MPa．Figs．5 and 6 show the stresses

within the plastic an d elastic regions，respectively．It can be seen from Fig．5 that the

maximum plastic region radius =1．145 1 m．Therefore，the stress at the elasto—plastic

boundary ：4．019 5 MPa．This iS the maximum pressure value that the supporting structure

is able to bear．Th e maximum displacement“ ：0．111 8 m，which corresponds to Pi=0

(without support)．Fig．7 shows the stress release coeficient of the tunnel boundary without

support along the tunnel axis．The interactive curves between the ground base and supporting

structures at diferent initial displacements are shown in Fig．8．