Application of deep - hole displacement monitoring
technology in landslide investigation
Wu Xianggen1
Pu Xingru2
Xing Zhihui 1
（1, Yunnan Geological Engineering the Second Investigation Institute
Kunming 650051
2, Yunnan surveying and Mapping Science and technology
consulting service center）
Abstract: Displacement monitoring of deep hole was introduced by this article to determine
sliding surface, and describes the applicability of the method. The application of this method can
greatly improve the quality of landslide investigation under complex geological conditions and
reduce project risk.
Key Word: Displacement monitoring of deep hole; landslide investigation; landslide investigation
1 Introduction
Determine sliding surface is not easy
for engineers in the landslide investigation,
especially in thick and thick layer of
bedding landslide investigation. At present,
the commonly used means such as well
drilling, exploration and geophysical
exploration, but they have some limitations.
For example, the mechanical core
interference is serious in the drilling process,
and not easy to find. Therefore, geological
structure and polished surface scratches can
easily be mistaken for the sliding surfacein
the area of development of geological
structures. And such as the use of well
drilling, excavation is very difficult and
posed a security risk to construction workers
when landslide deep, or the existence of
boulder. In geophysical exploration, it is
difficult to determine sliding surface when it
is very thin. This paper will discuss how to
use the new technology quickly and
accurately determine sliding surface.
At present, the deep hole displacement
monitoring technology is mainly used in the
landslide and the slope early warning and
forecasting. And it is not more common to
solve some difficult problems in landslide
investigation and design. In this article, the
western slope landslide of Changpo
opencast of Chuxiong Luhe colliery as an
example to help illustrate its application in
landslide reconnaissance.
2 Engineering survey
Changpo opencast of Chuxiong Luhe
colliery located in the Northwest of
Chuxiong city of Yunnan province, about 26
km away from chuxiong, 10 km away from
Nanhua ， Administrative divisions under
nanhua running, geographical coordinates
longitude 101 ° 18 ′ ~101 ° 22 ', North
latitude 25 ° 09 ' ~25 ° 11 '.
Changpo opencast rounded area
1.3km2, a depth of about 80m, opencast
slope sector by job slope, slope and platform
between ramps composition level. the
western slope landslide in the west of the
opencast. Landslide formation, the terrain is
messy.
Luhe colliery and surrounding exposed
the tertiary coal bearing construction and the
"Yunnan red layer". Construction line NW
Wu Xianggen, 1957.05, male, han ethnic group, xinyu jiangxi, senior engineer, engaged in geological hazard
survey and control design ,E-mail:sylwsq@163.com
trending. Into the coal strata upper Tertiary
Pliocene ciying (N2C), thickness of 57 ~
1072m, lithology is gray and black
argillaceous half cemented sandstone、sandy
mudstone conglomerate、basalt、oil shale,
upper clip lignite 15 layer, like a bowl
stacked output. Geological structure is a
short axis syncline, mining pit by syncline
core to expand the two wings, rock mining
pit, western slope Angle of 23 ° ~
24 °.Western slope deformation and sliding
when mining depth 60m in 1985, The
landslide in sharp slide again in 2001 when
mining depth 80m.
The landslide material including spoil,
silty clay and third Pliocene Ciying
formation (N2C) mudstone, sandstone and
lignite.spoil scattered in old mines soil
ground ,thickness 1～17 m. residual silty
clay layer only distributed in the part
area, ,thickness 1 ～ 12m. The N2C
formation is gray, dark gray thin mudstone,
with thin layers of sandstone and coal seam.,
Due to the formation of bedding, coal seam
relatively weak, there are many sliding
surfaces in this landslide. Because the
sliding surface and the original level
difficult to
distinguish, the landslide
investigation is very difficult.
3 The problems of preliminary
investigation
①Looking for sliding surface is very
difficult, only 30% of the borehole sliding
surface can be found .
②Because there are multiple sliding
surface, the corresponding relationship
between them is not clear.
③ The deepest sliding surface is
difficult to determine, so most likely leak
recognition.
Although able to draw a sliding surface
based on the experience , the above problem
makes the lack of strong evidence, but also
poses a risk for subsequent landslides
design.
4 Deep hole displacement testing and the
introduction of the landslide thrust
testing technology ［2］
To solve the above problems, the
introduction of the Chinese academy of
geological sciences institute of prospecting
technology development QXY - 5 storage
type
borehole
inclinometer
and
corresponding software system.
QXY - 5 storage type borehole
inclinometer measuring principle is: in the
geotechnical
engineering
construction
drilling inclined tube, install, test, when the
rock mass deformation, by measuring the
Angle between the vertical and inclined tube
axis measurement variation, to monitor soil
and the lateral displacement of the rock.
As shown in Figure 1, with a guide
pulley inclinometer tube tilt meter gauge by
piecewise angle θi measured inclinometer
and plumb line, then the following formula
were determined at different elevations
horizontal displacement di
di=Lsinθi ………………………… （1）
According to the following formula,
start from point at the bottom of the dip tube
piecewise accumulative, available at any
height in the actual horizontal displacement
bn
2
n
bn=
 di ……………………………（2）
i 1
Sets the horizontal displacement of dip
tube tube mouth accumulation to B: full hole
section,
after
the
completion
of
measurement can draw along the dip tube
axis of different changes of the hole deep
horizontal displacement
N
B=
 di
……………………………（2）
i 1
In type :
di--Horizontal displacement of the
measuring section；
L--Section length of measuring points,
that is, the standard distance of the
instrument；
θi---The angle measuring section of
inclinometer and plumb line；
following advantages: 1. The instrument
using wire rope raising or lowering the
detector, enhance the weight of up to 2.2t
(4mm in diameter wire rope)，overcome the
weakness of the cable is not revisit;
compared to traditional tiltmeter, traditional
instruments must be divided into don't
measured slip direction and perpendicular to
the sliding direction twice each, and the
instrument only measuring A direction
(sliding direction and reverse direction) two
times, thus saving the operation time. But
the instrument also has some disadvantages:
once the instrument is repaired, the data can
not be used continuously, can only be used
in time.
According to the mine pit Lu Chang Po
west slope landslide, and made a special
monitoring design. In the landslide is
arranged on the 4 drill holes, is“十”shape,
monitoring hole layout in the original
exploration line. As shown in figure 2.
bn-- Horizontal displacement of the first
N measuring point at the bottom of the hole；
B--The measurement of horizontal
displacement of pipe；
N--Monitoring hole section number，
N=H/L，H is depth of hole。
Qxy-5 type memory borehole tiltmeter
using biaxial sensor, measuring direction for
second level, for a monitoring hole, just
rotating apparatus 180 degree can measure
the value of A0, a180, B0, B180, and the
instrument can automatically identify A0,
a180, B0, B180 value without artificial
record.
The detector of this instrument is
automatically stored, and the same time, the
inclination angle parameters are obtained by
the computer.
Through the practical application, the
author believes that the instrument has the
5 Monitoring results and Applications［1］—
［3］
Monitoring and installation work in
April 2, 2007, installation and grouting in
May 20, 2007 all over. The deep hole
displacement monitoring of the landslide
began in June 8, 2007, because the landslide
displacement is fast, to October 15, 2007,
the first is that the JK2 hole detector can not
be down to the end of the hole, the hole is
suspended. By November 30, 2007, the
remaining 3 were not detected in drilling
3
hole bottom, only in the sliding body
measuring secondary sliding surface.
5.1 Determination of the slip surface
Monitoring holes in the original
preliminary investigation between the holes
in dense arrangement, determined by the
Table 1
original preliminary investigation profile
check Jk1 sliding surface depth 37m,
JK2,46m; Jk3. 59M JK4,46.8m. The biggest
difference
of 6.3m
surface depth
determination and monitoring instrument,
such as table 1.
The displacement monitoring data table of the western slope landslide of
Changpo opencast of Chuxiong Luhe colliery
Monitor
The depth of
The depth of the
the surface error
Deformation zone
Orifice
hole NO
sliding surface
monitoring
between two
position/thickness
displacement
drilling
sliding surface
kinds of methods
of the sliding zone
(
logging （m）
（m）
（m）
（m）
JK1
33.6
36.7
3.1
32～36.7/4.7
JK2
45～46
52.5
6.5
JK3
57.9～58.5
52.7
JK4
45.4～46.3
44
total
Orifice
Orifice
displacement
Angle
average speed
displacem
（㎜/d）
ent （°）
174/(6.8～10.29)
1.23
107.9
51～52.5/ 1.5
134/(6.8～7.26)
2.92
139.37
5.2
51.34～52.7/1.36
79.14/(6.9～7.1)
3.77
143.3
1.4
43～44/ 1.0
80.16/(6.9～7.17)
2.11
146.8
㎜
)/start-stop
time(month.day).
4
Through the analysis of the
displacement monitoring hole depth
variation (see Figure 3, 4) and found that
curve in the sliding surface was obvious
gently dipping, deformation length 1 ~
1.74m, sliding surface depth for 36.7 to
52.7m (see Table 1). Due to the landslide
is bedding landslide, the potential slip
surface is difficult to find, according to
the broken degree of cores to determine
the position of slip surface error is
relatively large, and not necessarily is the
sliding surface. Both the error, in addition
to close to the JK4 and other monitoring
hole difference of a few meters, Jk1
difference 3.1m, core logging surface
depth is too shallow, jk3 difference 6.6 ~
5.8m and core logging surface depth
darker. Cause of this error is the main
reason: 1.strata in the middle between
tectonic breccia and layer between sliding
mud development, fault tectonic breccia
and layer between sliding mud as sliding
belt;2.along to the structure development,
slip zone along the smooth development,
smooth and level are indistinguishable.
of modified (see Figure 5). It's to improve
the quality of the survey results, reducing
the risk of landslide control.
Based on the deep displacement
monitoring data to the depth of the surface
5.2 Determination of displacement direction
and displacement velocity of landslide
At the same time, the site of the deep hole
displacement monitoring is carried out, and the
5
monitoring and measuring of the total station is
also carried out. Monitors both the general trend is
the same, but monitoring of surface error is
relatively large, because of the limitation of terrain
visibility conditions, to stay away from 1km to the
monitoring station to see monitoring points. The
error is so in more than 1 cm, for the slow speed
and displacement of landslide will lose its
significance.
According to the deep displacement
monitoring data, calculate the orifice and at any
depth slip direction and slip velocity. After
calculation, the slip velocity of each point is
different, between 1.23 to 3.77 mm /d, hole slip
direction between 107.9 °to 146.8 °. This is
consistent with the actual situation of the landslide.
7 Conclusions and recommendations
Deep hole displacement monitoring has
been used in our country for 8 years, as
technical maturity, result reliable, it is a new
method for the investigation of landslide and
slope. In some complex geological
conditions, exploration is in the slow sliding
and has a plurality of sliding surface of
landslide, significant effect. Through the
landslide investigation and monitoring work
of many years of experience: 1. the landslide
monitoring results, especially the deep
displacement monitoring results, the main
conclusions of the investigation report of
landslide is the basis, can directly determine
the status of the stability of landslide; 2. The
displacement monitoring deep hole of
investigation stage is reserved to the
landslide treatment and operation stage, and
the dynamic changes of the landslide in the
construction stage and the engineering effect
can be kept at any time;3. For the important
landslide, the monitoring unit should at least
spare one instrument, and the standby
instrument and standby instrument to
establish
the
corresponding
error
relationship (through the same hole for a
time to get the data comparison); 4.the
method of operation simple, and dynamic
monitoring work together, less investment,
quick effect, greatly improves the quality of
landslide investigation, reduce project risk,
greatly reduces the difficulty of surface field
catalog personnel identification, worthy of
promotion.
In this paper, the application of a
monitoring method in landslide investigation
is carried out. In fact, the same as the
landslide thrust monitoring can be used for
the investigation of landslide.
References:
［1］Wang Aijun, Yang Xiuyuan, etc. The
Fujiayan landslide deformation monitoring
and analysis of Chongqing District of
Wanzhou city. Hydrogeological engineering
geology (J), 2008, (2), 104-108.
［2］Wang Dianmin, etc.. Development and
application of QXY-5 type memory borehole
tiltmeter. Chinese Journal of geological
hazard and control (J), 2007, (18):54-57.
［3］Liang Longlong, etc.. Application of
deep - hole monitoring in the treatment of
the landslide of the tang. Subgrade
Engineering (J), 2008, (5):201-202.
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