Indonesian J
ournal of Ele
c
trical Engin
eering and
Computer Sci
e
nce
Vol. 2, No. 1,
April 201
6, pp. 215 ~ 22
0
DOI: 10.115
9
1
/ijeecs.v2.i1.pp21
5-2
2
0
215
Re
cei
v
ed
Jan
uary 9, 2016;
Re
vised Feb
r
uary
13, 201
6
;
Accepte
d
Febru
a
ry 28, 2
016
Nonlinear Dynamics Research between Drill Pipe
and Coal Hole Wall during Gas Extraction Drilling
Han Xiao-Ming, Luo Che
n
-Xu
*
, Zhan
g
Qiang-Qia
ng
Schoo
l of Mechan
ical a
nd Po
w
e
r Eng
i
ne
eri
n
g, Hena
n Pol
y
t
e
chn
i
c Univ
ersi
t
y
, Jiaoz
uo 4
5
4
000, Ch
in
a
*Corres
p
o
ndi
n
g
author, e-ma
i
l
: xzh
q
in
gtin
g
@
16
3.com
A
b
st
r
a
ct
Th
i
s
p
a
p
e
r
a
n
a
l
y
z
es the
imp
a
c
t o
f
ga
s dra
i
na
g
e
b
o
r
e
h
o
l
e
d
r
i
l
l
i
n
g
rod vi
b
r
a
t
io
n
p
h
en
om
ena
stability.Taki
ng
100
m
hol
e d
epth i
n
un
der
grou
nd co
al
mi
ne as
an
e
x
ampl
e, the d
y
na
mic si
mula
tio
n
ana
lysis
of the
und
ergr
oun
d
gas dr
ai
nag
e d
r
illi
ng r
od w
a
s
carried
o
u
t by
usin
g the A
N
S
YS finite
ele
m
en
t
dyna
mic ana
ly
sis mo
du
le LS
-DYNA metho
d
.Accordi
ng to
the collis
ion c
ourse b
e
tw
een
the drill p
i
pe
an
d
the coa
l
ho
le
w
a
ll, the La
gra
nge
alg
o
rith
m i
s
introd
uced to
analy
z
e
the st
ress chan
ge
of drill
pip
e
in th
e
collis
io
n
co
urs
e
of 98
mm, 10
8mm, 11
8
m
m and
1
2
8
m
m.
T
he fa
ilur
e
mec
han
is
m of
dril
l
pip
e
fati
gue
fra
c
ture
and
hol
e w
a
ll i
n
stabi
lity caus
ed by th
e col
l
i
s
ion b
e
tw
een
drill
pip
e
a
nd c
oal h
o
l
e
is a
n
a
l
y
z
e
d
. The res
u
lt
s
show
that the
stress caus
ed
by the
i
m
p
a
ct
of dril
lin
g s
pee
d, dril
lin
g
pr
es
sure a
n
d
coa
l
hol
e d
i
a
m
eter
is
larg
er than that
caused by th
e collis
io
n betw
een dri
ll pi
pe a
n
d
coal w
a
ll.
Ke
y
w
ords
:
dri
l
l
pip
e
; gas dra
i
nag
e; torsion
a
l
vibratio
n; hol
e w
a
ll instab
ility
Copy
right
©
2016 In
stitu
t
e o
f
Ad
van
ced
En
g
i
n
eerin
g and
Scien
ce. All
rig
h
t
s reser
ve
d
.
1. Introduc
tion
The nonli
nea
r dynamic a
n
a
lysis of the drill stri
n
g
be
gan in the 19
60s, main o
n
resea
r
ch
and analysi
s
of
the
axial a
nd
torsio
nal vibration of
the d
r
ill
string
, the re
se
arch metho
d
i
s
t
he
differential
m
e
thod. Fi
nnie
and
Bailey t
h
rou
g
h
the
e
x
perime
n
t an
d the
metho
d
of trial
an
d
e
rro
r
in the case of
negle
c
ting
d
a
mping
cal
c
u
l
ated natu
r
al
freque
ncy of
drill st
ring i
n
1960.Millh
ei
m K
and Ap
osstal
M u
s
ing
D’Al
embe
rt’s
prin
ciple, i
n
the
case
of in
ertia
force
and
fri
c
tion to
con
s
i
der
the static an
alysis, a
nd th
e esta
blishm
ent of a
th
re
e-dim
e
n
s
iona
l finite eleme
n
t model
of
BHA
dynamics in t
he 198
0s [1
-3]. 1984 to 1
985 Dunay
cv
sky V et al st
udy the co
ndi
tion and
stabi
lity
of precession
in di
re
ctional
well
s
of the
drill
strin
g
, an
d dete
r
min
e
t
he
relation
shi
p
bet
wee
n
d
r
i
ll
string vibratio
n param
eters of re
son
ance
area and d
r
ill
pipe drilling
spe
ed, provid
es a theo
retical
basi
s
for [4-5] for the study of drill string lateral
vibration. Gao Yan [7] et al a
c
cordi
ng to the
wave the
o
ry, the mathem
a
t
ical mod
e
l of
drill pip
e
lon
g
itudinal vib
r
ation is
esta
b
lishe
d, and th
e
cha
nge
of the natural fre
q
uen
cy with th
e length
of the drill pi
pe i
s
studie
d
an
d a
nalyze
d
. Zha
ng
Yanglie et al to study the kinem
atics a
nd dynami
cs
of drill string
and so o
n
to do a lot of work,
and m
a
ke a
great
co
ntrib
u
tion. Zh
ou
Yong, Li
Zife
ng [8
-9] a
n
d
othe
rs sum
m
ed u
p
a
lot
of
pra
c
tical e
ngi
neeri
ng case, study the dril
l pipe in a
variety of stress situation
s
, an
d the cau
s
e o
f
the failure of
the drill pipe all kinds of vibration
m
ode to establi
s
h
a set of num
erical model, for
the furth
e
r re
sea
r
ch
wo
rk i
n
the
future
establ
i
s
h
the
theoreti
c
al
fo
undatio
n [10
-
11]. Qiu
Liqio
ng
according to
the Lagrangi
an equatio
n, the three
-
dim
ensi
onal finite element m
odel of drill st
ring
system
wa
s e
s
tabli
s
he
d, a
nd t
he
kineti
c
energy, pote
n
tial ene
rgy, dampin
g
mat
r
ix, mass mat
r
ix,
stiffness matrix and load m
a
trix
of the element we
re
calcul
ated
by usin
g the ene
rgy method.
The
numerical cal
c
ulation method of
wa
s used to
simulat
e
the vibration
of drill
stri
ng [12]. From
the
dome
s
tic
and
foreig
n p
ubli
s
he
d a
c
a
dem
ic p
ape
rs, th
e
literatu
r
e o
n
the vibratio
n
analysi
s
of th
e
soft outbu
rst
coal
seam
ga
s is still relati
vely sma
ll, the above cont
ent is t
he
re
search status o
f
drill pip
e
strin
g
vibration
in
petrole
um a
n
d
geol
ogi
cal
exploratio
n, b
u
t the ga
s d
r
ainag
e pip
e
a
n
d
the exploration drill pipe in some as
pect
s of the stress situation has
the similar, t
he research
of
gas drill
pipe
is al
so
ha
s t
he very
big
referen
c
e
fun
c
tion. Thi
s
pa
per i
n
tend
s t
o
u
s
e the
wa
y of
theory analy
s
is and nu
meri
cal sim
u
lation
, combine
d
with the rock breaki
ng theo
ry and nonlin
ea
r
dynamics th
eory, the dri
lling ope
ratio
n
s in so
ft coal se
ams
whe
n
the n
online
a
r dyn
a
mic
characteri
stics of
drill
pipe, hole wall
is impa
cted
by the tool
colli
sion
sim
u
lation m
odel is
establi
s
h
ed, t
he
cau
s
ed
by
colli
sion
of
coal an
d
ro
ck
stre
ss chan
g
e
rul
e
of
hole
wall i
s
studi
e
d
,
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ISSN: 25
02-4
752
IJEECS
Vol.
2, No. 1, April 2016 : 215 –
220
216
to reveal the
drill hole
wall
instability ca
use
d
by colli
sion, drill pip
e
fatigue dam
a
g
e and fractu
re
mech
ani
sm.
2.
Running State Description of Drill Pipe
Analysis of drill pipe and the coal hole wa
ll contact
key is the problem of nonlinear
dynamics re
search of drill pipe,
the colli
sion p
r
o
c
e
ss
of the drill pipe and the co
al hole wall a
nd
other contact impact probl
e
ms are quit
e
differ
ent, because the drill rod is a root connect
e
d
throug
h the scre
w thre
ad
hollow sl
en
der rod.
Because of the compl
e
xity of the geologi
c
al
con
d
ition
s
of
coal
se
am
co
al se
am d
r
illi
ng en
gine
erin
g drillin
g is m
o
re
com
p
licated than
othe
rs,
in the p
r
o
c
e
s
s of d
r
illing
bit
will e
n
counte
r
with th
e g
e
o
l
ogical rock in
coal
seam, it
will le
ad to th
e
drill pipe drilli
ng di
rection deviating from
the expe
cted trajectory
di
rection,
namely
drill pi
pe bend
in the
co
al
hole
drillin
g, hole
will
fo
rm ful
c
rum
and
drill
pip
e
si
milar form of "pe
ndu
lum"
movement, t
h
is
kind of games ca
use
drill pi
pe and coal wall of
ho
le
intense multipoint contact
friction
colli
si
on o
c
curs. Fi
gure
1
sho
w
s the finite
ele
m
ent mod
e
l
of the bo
reh
o
l
e wall
of the
drill
pipe.
Figure 1. Finite element model of drill pipe and coal hole wall
The impa
ct of
the drill pip
e
and the
coal
hole wall is v
e
ry sh
ort, whi
c
h is
com
p
let
ed in a
few tens
of milliseconds. T
he impact force caused
by the impact i
s
the main cause of the failure
of the coal
hole wall. From
a large number of drilling operat
i
ons found in some of the
phen
omen
a and the expe
rimental resul
t
s obtaine
d
can be foun
d, in the drill pi
pe and the h
o
le
wall of the
collision
process in the
drill
pipe joint
s
and the hol
e wall of the colli
sion i
s
the m
o
st
[13-14]. F
o
llo
wing
the
Lag
rangia
n
meth
o
d
a
s
the
theo
retical
gui
dan
ce, the
collisi
on b
e
twe
e
n
d
r
ill
pipe a
nd
coa
l
wall i
s
studi
ed, and th
e n
online
a
r dy
n
a
m
ic cha
r
a
c
teristics of the i
m
pact fo
rce
of
drill pipe a
r
e
analyzed un
d
e
r the conditi
on of the ch
a
n
ge of the dia
m
eter of the coal hole.
3.
D
y
namic Si
mulation Anal
y
s
is of Collis
ion bet
w
e
e
n Drill Pipe and Coal Wall
In the
co
urse
of the
collisi
on b
e
twe
e
n
the d
r
ill
pipe
and th
e
co
al
wall, the
h
o
le
wall
i
s
see
n
as a rig
i
d body and is fixed. At a
spe
ed of
v=5
.
36m/s drill (drill rotation
speed
)
alon
g the
radial
direction of coal hol
e
wa
ll
impact
coal
wall.According to
the diam
eter
of drill pi
pe,
coal
hole
wall
hol
e diameter and drill
shaft speed
computing collisi
on
ve
locity of dri
ll pipe and the
hole wall. This pap
er mai
n
ly analyze
s
the drill pip
e
in 98 mm, 10
8 mm, 118 m
m
and 128 m
m
coal
hol
e in t
he pi
pe
at th
e same
point,
the
stre
ss
va
riation i
n
the
different time.
Thu
s
reveal
ed
colli
sion
coal
wall of hole drill pipe's in
fluence on the stability of hole wall.
Evaluation Warning : The document was created with Spire.PDF for Python.
IJEECS
ISSN:
2502-4
752
Nonli
near Dynam
ics Research between
Drill Pipe and Coal
Hole
Wall …
(LUO C
h
en-x
u)
217
(a)
(b)
Figure 2. Stress analysi
s
of
the 98mm pore wall
coal drill pipe and hole wall
collisi
o
n
In figure 2, the figure
(a) and
(b) is
drill
pipe in the
coal with a
diameter of 98
mm hole
colli
sion
wall
unde
r the a
c
tion of stre
ss
distrib
u
tion of
different time
, the initial co
ndition
s for d
r
ill
pipe rotatio
n
of linear velo
city of
5.36 m/s colli
sion wit
h
the coal wal
l
in the radial
dire
ction. In the
first to break
the coal i
n
the process of drilling
bit can produce a l
o
t of broken
coal in the coal
hole
clea
ran
c
e, d
r
ill pip
e
and
coal
ho
le wall i
n
the
pro
c
e
s
s of
colli
sion
bre
a
k
ing th
ese coal
further squee
ze, alo
ng
wit
h
the hi
gh
pressure ai
r fl
o
w
of p
u
mp
st
ation to p
r
ovi
de di
scha
rge
hole,
in the
process, as a resul
t
of the
drill
pipe
drillin
g
speed faster, drill
pipe
dril
ling pressure is
bigger. In the drill rod el
ast
i
c deformation energy
and mutual
superposition of vibration
wave
by
drill pip
e
vibration (stre
s
s), unde
r the j
o
int acti
o
n
o
f
collisi
on
with the hol
e
wall, the stress
cha
nge
s as
shown in figure 2. Impose a
fter initial
con
d
itions on d
r
ill
pipe, drill pipe and co
al ho
l
e
wall alon
g the radial di
re
ction is touch, at ti
me t = 0.0098
s, dril
l pipe and coal wall of h
o
le
colli
sion
stress valu
e in
cre
a
se
rapidly to
89M
pa, th
e
stre
ss of
drill
pipe
in
the
subsequ
ent ti
me
increa
se
s u
n
c
ea
sin
g
ly, at time t =
0.0
735
s
stre
ss value
rea
c
h
e
d 22
0Mp
a
.
From th
e a
b
o
ve
analysi
s
resul
t, the drill stri
ng collisio
n wall of hole of
t
i
me is very
short, the colli
sion
of drill pi
pe
prod
uced by
stre
ss value i
s
la
rge, the
reason i
s
be
cause the
sm
all co
al hol
e
clea
ran
c
e, hi
gh
drilling
rat
e
a
nd d
r
illing
pre
s
sure
is big
g
e
r, d
r
ill pi
pe
b
endin
g
d
e
formation of t
he
elasti
c e
n
erg
y
is
absorbed by drill pipe
and
the hole wall.
(c
)
(d)
Figure 3. Stress analysi
s
of
the 108mm pore
wall coal drill pipe and
hole wall colli
sion
In Figure
3, figure
(c) an
d (d) is th
e drill
pipe un
de
r wi
th a diamete
r
of 108mm
coal hole
wall colli
sio
n
effects at different times of stress
distributio
n an
d initial cond
itions for drill
rod
rotating
move
ment of lin
e speed i
s
5.36
m/s in th
e
ra
dial di
re
ction
and th
e coal
wall
colli
sion.
In
the
drilli
ng p
r
ocess of
d
r
i
ll
pipe, drill bro
k
en
coal
and
guid
e
th
e drilli
ng, in
normal
drilli
ng
con
d
ition
s
, the coal hol
e diameter shoul
d is slight
ly large
r
than th
e diameter d
r
ill bit, drill pip
e
and th
e
coal
hole
of the a
n
nular spa
c
e i
s
n
o
t large,
b
u
t in fro
n
t of t
he d
r
ill pi
pe v
i
bration
an
alysis
shows that,
the drill
pipe vibration of
elas
ti
c deformation and drilling pressure under t
h
e
combi
ned
a
c
t
i
on of
drill
pip
e
an
d th
e
co
al hol
e
wall
contact
occu
rs. The
stress
gene
rated
by
the
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02-4
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IJEECS
Vol.
2, No. 1, April 2016 : 215 –
220
218
colli
sion
is sh
own
in
Figu
re
4. Th
e
drill
rod i
s
applie
d
initial conditio
n
s, in
the
coll
ision
of th
e d
r
ill
rod
of this p
e
riod
of time
t=0s ~
0.07
1s, d
r
ill pip
e
along th
e co
al hole
diam
eter a
nd h
o
le
wall
colli
sion, the drill pipe in this pe
riod of
time should
force valu
e gradu
ally incre
a
se
d from 0 to
80MPa. The drill pipe in t=0.01
13
s wh
en the st
ate of freedom o
f
movement to the bendi
ng
deform
a
tion and po
re wal
l
collisio
n of the equivale
nt
stress in
cre
a
se
d rapi
dly to 38MPa. Fro
m
coal
and
ro
ck mechani
cs rese
arch
kn
o
w
, co
al rock i
s
a
kin
d
of b
r
ittle hard
mat
e
rial
s, no
wat
e
r
dry coal
seam drilli
ng process,
the dril
l bit to drill t
h
rough th
e
coal experience
has a lot
o
f
fractu
red
zon
e
(b
ro
ke
n re
gion),
wh
ere
the
coal
ex
perie
nce i
s
v
e
ry un
stabl
e
, with th
e viol
ent
vibration of t
he drill pipe,
coal
began t
o
coll
apse, pi
pe extrusio
n pressure
unde
r the
action o
f
coal
pa
rticle
s be
com
e
s b
r
oke
n
exh
a
u
s
t hole
coal
.
At this time
coal
hol
e
di
ameter furth
e
r
increa
se
s. From the drill pi
pe and
coal h
o
le wall
conta
c
t colli
sion d
u
r
ing this
peri
o
d, when
rea
c
h
maximum co
ntact stre
ss, the
equival
e
n
t
stre
ss
va
lue
and
red
u
ce
soo
n
, this i
s
becau
se in t
he
event of a severe vibrat
ion reduces the
drilling
rate,
while it
s im
pact stress drops
rapidly, the
drill
operators d
e
pendi
ng o
n
th
e situatio
n
wil
l
be repe
ated
back to d
r
ill, to
re
du
ce the
violent vibrati
on
and impa
ct.
(e)
(f)
Figure 4. Impact stress of drilling pi
pe a
nd co
al hole
wall un
der th
e con
d
ition of
118mm
Drill pi
pe under with
a diameter of 118mm coal
hol
e
wall
colli
sion effects
at different
times of
stress di
stribution,
bec
ause the
diameter of t
he hol
e
wa
ll i
n
creases
so t
he drill pipe and
the coal h
o
le
wall in the ra
dial dire
ction
on the colli
sio
n
velocity is redu
ced to 3.5
8
m/s in Figu
re 4
Diag
ram e a
nd f. From applying initial
condition
s a
nd to the dril
l pipe and th
e coal hol
e wall
colli
sion of thi
s
pe
riod of ti
me t=0
s
~ 0.
0121
s, dr
ill pi
pe alon
g the
diamete
r
dire
ction of the
coal
hole unifo
rm
motion. At this time the
co
ntacts
sh
oul
d be forc
e to 0.
In time t=
0.0123s
.
Due to
the
colli
sion
cont
act drill
pipe
and the
wal
l
of the coal
hole, at the
collisi
on p
o
i
n
t sho
u
ld force
increa
se
s ra
p
i
dly and at the point
of con
t
act stre
ss qu
ickly reac
hed
38Mpa. After the collisi
on
of
the drill pi
pe
and the
coal
hole
wall 0.0
539
s time of
drill pip
e
sho
u
ld force rea
c
hes th
e maxi
mum
value of 8
9
.6
MPa. From
th
e above
an
al
ysis, it c
an
b
e
known that
the stress
ch
ange
of d
r
ill p
i
pe
and the
colli
sion spee
d is
a nonli
nea
r relation
ship. F
r
om
within th
e co
ntact im
pact of d
r
ill p
i
pe
and the
coal
hole wall of this p
e
rio
d
of time, wh
e
n
th
e co
ntact
stre
ss
rea
c
h
ed a
maximum val
ue,
and then, the
equivalent
stress value an
d decrea
s
e
s
quickly. This i
s
be
cau
s
e m
o
st of the ene
r
gy
wa
s ab
sorbe
d
coal b
o
re
ho
le wall an
d dri
ll pipe.
Evaluation Warning : The document was created with Spire.PDF for Python.
IJEECS
ISSN:
2502-4
752
Nonli
near Dynam
ics Research between
Drill Pipe and Coal
Hole
Wall …
(LUO C
h
en-x
u)
219
(g)
(h)
Figure 5. Impact stress of drilling pi
pe a
nd co
al hole
wall un
der th
e con
d
ition of
128mm
In the drill pipe and the coal hole wall
conti
nuo
us
collision p
r
o
c
e
ss, coal co
ntinuou
sly
from the
coal
hole wall st
ri
pping down the drill
pi
pe and the
coal hole wall of the annular
space
is m
o
re and
more big,
at t
h
is
point, the
drill pi
pe because of it
s vi
brat
ion
over speed makes
the
hole
drillin
g
rig d
r
illing
sp
eed i
s
l
o
we
red, the
dr
ill pipe bendi
ng
ela
s
tic defo
r
mation
can be
d
e
c
r
e
as
ed
as w
e
ll. As
s
how
n
in
F
i
g
u
r
e
5
,
w
h
en
the
pore
si
ze i
s
1
28mm, the
st
ress val
u
e
s
a
r
e
signifi
cantly lowe
r than th
o
s
e of the first
three. A
fter a
pplying the in
itial con
d
ition
s
, we
obtain t
he
maximum stress value of 74Mpa and 76Mpa. With
drill pipe st
ress valu
e decreases
graduall
y
,
the pip
e
b
u
rst failure
an
d fa
tigue fra
c
tu
re
phe
nome
n
o
n
will
de
crea
se. In this case the
stability
of
hole wall is very helpful, is benefici
a
l to
the gas d
r
ain
age drilli
ng proce
s
s smo
o
thly.
In order to more
c
l
early
with the force of t
he in
crease
of the
co
al h
o
le di
amete
r
the drill
pipe, we will
drill pipe with
diamete
r
cha
nge of stre
ss cha
nge data l
i
st, as sho
w
n
in Table 1, an
d
dra
w
the grap
h, as sh
own in Figure 6.
Table 1. Ch
a
nge of stress
of drill pipe
Coal
hole
diamet
er(mm)
83
88
93
98
103
108 113 118
123 128
133
Max
i
mum stress of
dr
ill pipe (
M
pa)
307
271 253 243
189 117
106
94
82
76
43
The curve can be seen
from Figu
re
6, the
stre
ss value of dri
ll pipe is ob
viously
decrea
s
e
d
wi
th the cha
n
g
e
of the diam
eter of c
oal h
o
le. That in the sm
all coal
hole diam
eter,
drill pipe a
nd
the coal h
o
le
wall conta
c
t should forc
e i
s
large
r
, with the gra
dual ex
pan
sion of the
coal
hole
dia
m
eter, d
r
ill pi
pe conta
c
t st
ress i
s
redu
ced g
r
ad
ually, and
gra
d
uall
y beco
me m
o
re
stable state.
Figure 6. Maximum stress
cha
nge
curve
of drill pipe with diameter o
f
coal hole
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ISSN: 25
02-4
752
IJEECS
Vol.
2, No. 1, April 2016 : 215 –
220
220
Thro
ugh the i
m
pact in
different ap
ertu
re
of drill pipe
st
ress a
nalysi
s
sho
w
s that the coal
hole
diameter by 83mm i
n
creased to 133mm, dr
ill
pi
pe and the
wall of the hol
e
coal
maxim
u
m
impact
stress by the value of the
reduced to the 43Mpa. Thi
s
is
because in t
he initial drilli
ng
process of the drill
rod
stress
st
ate from unstable to stabl
e, cont
act impact
stress
reduction
can
effectively reduce the fatigue dama
ge of
drill pipe wh
i
c
h are ca
use
d
by the
collision. At the same
time, the d
e
crease of
the
contact
stress
of the
drill
p
i
pe
is a
l
s
o
b
ene
fic
i
a
l
to ma
inta
in
th
e s
t
ab
ilit
y
of the hole wall.
4. Conclu
sion
Takin
g
into a
c
count du
e to the drill pip
e
and the
co
al hole wall o
f
the conta
c
t colli
sion,
according to
dynamics i
s
widely u
s
e
d
in the
central
differen
c
e
method, co
mbined with the
colli
sion p
r
o
c
ess of drill p
i
pe drill pip
e
is con
s
tr
uct
ed by the force of the
co
llision b
ound
ary
conditions, using the
com
m
ercial
software A
N
SYS dynamic
module
of LS-DYNA
to drill pi
pe
and the
coal
hole wall to
uch hit a
nd l
oadin
g
pro
c
e
ss i
s
sim
u
lat
ed and
analy
z
ed, in a
ce
rtain
extent can in
stead
of the actual
experi
m
ent, red
u
ce
test co
st
an
d improve the efficien
cy of
sci
ent
if
ic re
se
arc
h
.
Found in the
analysi
s
of the pro
c
e
ss of colli
si
on is le
ad to instabili
ty of
the hole wall of
the mai
n
rea
s
on
s, the
d
r
ill
pipe
an
d th
e coal
hole
wall
colli
sio
n
make
s the
d
egre
e
of be
n
d
ing
deform
a
tion of the drill ro
d increa
se, a
l
so ma
ke the
vibration ph
enome
non al
so mo
re inte
nse
colli
sion
anal
ysis p
r
o
c
e
s
s i
s
mo
re
com
p
l
i
cated. T
he
collision
en
erg
y
wave (i.e.
stress
wave) b
y
the drill pip
e
and the coa
l
body part o
r
all of t
he
a
b
so
rption, wh
ich
is drill
pi
pe
limitation o
f
fatigue, fract
u
re an
d hol
e wall coll
ap
se, colla
pse
hole and pi
pe sticking
phen
omen
on
th
e
importa
nt rea
s
on.
Ackn
o
w
l
e
dg
ements
The autho
rs are g
r
ateful for the fundin
g
of
this work by the Hen
an provin
ce
edu
catio
n
depa
rtment
applie
d re
se
arch p
r
oje
c
t
fund (1
5A4
4000
4, 16A4
6000
5) a
nd
Hen
an p
r
ovi
n
ce
sci
en
ce an
d tech
nolo
g
y project (1
621
02
2102
29).
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eim KK
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