The research of rail transit engineering third-party monitoring
Jun-Jie GE1,a,
1
NO.388Xuefu Road,Kunming,Yunnan,P.R.China
axinyechgp@gmail.com
Abstract: the third party monitoring is aim to improving the orbit transportation construction
quality and ensure safety, which forecasts and monitors potential dangerous timely, accurately to
prevent major accidents occurrence. This paper takes the third-party monitoring first bid project of
Kunming metro rail transit construction as instance, combined with the engineering practice, this
paper discusses the main content of the third party monitoring, monitoring methods and technical
requirements. Finally, it discussed the processing and analysis of data.
Key words: third party monitoring, monitoring content, data analysis
1 introduction
With the rapid development of our social economy and urbanization, the subway construction
entered a rapid development period. Urban rail transit is closely related to people's daily life and
work. At present china has more than 40 cities are planning or constructing subway. Since 2010
Kunming has stepped in subway construction peak, until today it still have heavily construction
dynamic. But Kunming geological conditions is complex and engineering construction period is
urgent. Local site conditions is poorer. With the mutual influence of surrounding buildings,
pipelines and complex geological conditions, the risk of rail transit project construction is relative
bigger compared with other cities. Therefore, in the process of rail transit construction must take
on different monitoring measures and methods as to different levels risk.
This paper takes the third-party monitoring first bid project (line 2) of Kunming metro rail
transit construction as instance as an example. The first bid project from PanLong district planed
north bus passenger station to south round road station, which has 27 worksite, including 14
stations, 13 sections. Combining the rail transit subway construction mainly used method: cutting
and covering method, shield method, mining method, etc., it performs deformation monitoring
like fracture, dislocation, settlement, tilt, underground water level that appears in the construction
such. According to monitoring data, it strengthen forecasting work to avoid collapse, surface
subsidence, which ensures the safety of ground traffic and around buildings. So the
implementation of subway construction third party monitoring is very important and necessary.
2 the third party monitoring
Third-party subway construction monitoring is a new management mode, which ensures
construction quality and environment safety. Metro third-party monitoring are qualified third party
monitoring firm that entrusted by the owners according to China production safety law of the
People's Republic to monitor projection construction. It is independent from metro design,
construction and supervision party. It contrasts and tests deformation monitor of ground and road
subsidence, building and underground pipeline that along the subway construction. It use the
mathematical statistics modern theory to deal with monitoring data, trough analysis and forecast
result to prevent and avoid the tunnel collapse, surrounding buildings damage. So it prevent
tremendous accidents effectively and ensure subway construction production safety. Monitoring
scope: open cutting foundation trench, mining method tunnel construction, shield method tunnel
construction, and objects within tunnel 2.0 H surrounding scope and open cutting foundation
trench surface and supporting system, mining method tunnel excavation face five times the hole
diameter supporting structure, shield method five times the hole diameter construction scope of
the segment structure.
2.1 subsidence monitoring
Subsidence monitoring items include: pile top subsidence; surface subsidence; building
foundation settlement; underground pipeline settlement; vault sink; supporting pillar settlement;
relative and absolute sink that ground fissure corresponded.
2.1.1 Layout principle of measuring point
The project settlement deformation monitoring control network (or points), were established
with Kunming first period rail transit engineering construction elevation system, which started with
suitable control network second-class leveling point for subway construction. Control points is
composed by datum point and work basis points. According to the distribution condition of station,
building at interval for monitoring, bridge and, road surface, Control net was setting to local
independent network, using observation point, it sets into a closed loop network, connecting
network or connecting traverse form. It uses artificial excavation or drill a hole to produce ground
reference point and work basis points. As to different monitoring objects using different way to
produce measure point. Framework, brick structure object uses borehole embedded measuring point,
Steel structure adopts welded measuring point, special decorate object uses concealment measuring
point. Subsidence monitoring measuring point should avoid drainage pipe, window sill lines,
electric switch and obstacles. Positioned leveling rod should leave wall surface and ground some
distance and 0.2 ~ 0.5 m higher than floor.
2.1.2 Subsidence monitoring methods and technical requirements
Adopting geometric leveling method conducts leveling network observation. It uses Trimble
DINI12 electronic level owned record program to record field observation data file. According to
engineering measurement specification GB50026-2007 third-class vertical displacement
monitoring network technical requirements, the main technical indicators and requirements are
shown in table 1.
Table 1 Monitoring point main technical indicators and the requirements
serial
number
1
indicator
tolerance
Monitoring point and adjacent datum point
1.0mm
elevation difference in error mean square
error
2
3
4
Each station elevation difference mean
0.30mm
square error
Roundtrip mutual difference and loop
closure error
Measured station elevation difference
±0.6
n mm（n is station number）
±0.8
n mm（n is station number）
2.2 Slant monitoring
2.2.1 Layout principles of measuring-point
As to ordinary low-rise building, it can calculation based tilt according to the settlement
difference of observation data. The project tilt monitoring object is mainly refers to main body of
tall building tilt monitoring. It can use physical body tilt monitor Pitch point method, horizontal
Angle measurement method, the forward intersection method, laser scanner method, digital
photogrammetry observation method, and special tilt sensor test method to conduct High-rise
building tilt monitoring. Considering Kunming subway engineering environment conditions,
monitoring precision requirements, engineering cost comprehensively. Main body of tall building
project adopts forward intersection method to monitor tilt.
Measuring point should be fixed in slant building top and bottom., the principle of
measuring-point: (1) observation points were fixed in the place where can reflect the deformation
part accurately, and, in parallel to the main body of building vertical axis top and bottom
location;(2) top and bottom measuring point should be good visibility with control point, no
obstructions and refraction.
2.2.2The slant monitoring methods and technical requirements
Oblique observation adopts forward intersection method, using a Leica TCA1800 total
station, PDA to record the field observation data file.
It follows engineering measurement GB50026-2007 second-class horizontal displacement
monitoring network technical requirements to conduct forward intersection measurement of
building oblique observation. The main technical requirements are shown in table 2.
Table 2 main observation technical indicators and requirements
serial
number
item
Indicators or tolerance
1
Horizontal Angle observation
number
6
2
mean square error of angle
1.0 秒
3
side relative error
≤1/100000
4
measurement number of each side
roundtrip 4 times
2.3 horizontal displacement monitoring
Horizontal displacement monitoring items include: embosom pile top horizontal
displacement, building oblique, and relative and absolute horizontal displacement of ground
fissure.
2.3.1 Layout principles of measuring-point
It adopts traverse network to monitor embosom pile top horizontal displacement. It uses polar
coordinate method to perform measuring point monitoring. It uses Kunming rail transit first period
engineering construction plane control system to establish control points. It. adopt adhesion or
closure traverse, starting and closed on the subway precision transverse. It distributes control
points according to the embosom field condition and foundation ditch position reasonably.
Generally it has no less than three points in each foundation ditch, it consist monitoring network
with the observation point.
According to the third party monitoring design drawings it posits point on the top of
foundation ditch embosom wall around. Layout principles: (1) Measuring point should be
designed in foundation ditch ring beam and embosom wall or the top of the underground
continuous wall where is relatively fixed place. The place is easy to set and not easy to damage. It
can reflect lateral deformation of foundation embosom structure top pile (wall).(2) it fixes points
around the foundation ditch wall, pile top ,decorating1 point every 20 m;(3) measuring point set
centering sign .
2.3.2 Horizontal displacement monitoring method and technical
requirements
It adopts traverse network to monitor embosom pile top horizontal displacement. It uses polar
coordinate method to perform measuring point monitoring. It uses Leica TCA1800 total station to
monitor.
It follows engineering measurement GB50026-2007 second-class horizontal displacement
monitoring network technical requirements to conduct control network setting and the monitoring
point observation. The main technical requirements are shown in table 3.
Table 3 main technical indicators and requirements
serial
number
item
Indicators or tolerance
1
Horizontal Angle observation
number
6
2
mean square error of angle
1.0 秒
3
side relative error
≤1/100000
4
measurement number of each side
roundtrip 4 times
According to the actual work experience, as to reference point observation, traverse method
is easy to operate. Using high precision measuring instruments and according to the corresponding
operation technical specification, it is easy to achieve the monitoring accuracy.
2.4the underground water level monitoring
2.4.1 Layout principles of measuring-point
It should according to the hydrological data to bury water level monitoring pipe. It should
posit close to the foundation ditch or tunnel outside that parallel to the foundation ditch or
tunnel .It is in the same fracture surface of road and the surface subsidence pile (wall) top, strut
axial where the water content and water permeability is strong. In this project, it generally posits 3
~ 5 monitoring hole around station foundation ditch the, complicated geological conditions
interval posits 3 ~ 5 monitoring holes.
2.4.2 The underground water level monitoring method and technical
requirements
Near the monitoring foundation ditch or tunnel, it uses geological drilling rig to drill into required
depth (usually below perennial water level 10 m), casing filtering plastic into the hole, pipe
diameter is about 90 mm. it fills clean sand between casing and hole wall, and rinses, at the bore
hole bottom to prevent mud plugging. Tube should above the ground about 20 cm, adding a lid
don't let the rain in. some brick structure is built around the pipe to prevent damage.
Underground water level monitoring can use ruler to gauge, the principle of steel rule water
level gauge is putting water level indicator into buried pipes slowly, once the head of water level
indicator contacts the water, it start to make sounds, then readings measuring ruler top position
value .Every time readings position should be consistent to corresponding pipe top, and fixed the
personnel to read. According to the elevation of pipe top and the ground elevation difference, it
can calculate height and depth of underground water level.
3 the data processing and analysis
The main analysis content and rail transit engineering deformation monitoring object is
ground, road, building subsidence and underground pipeline spatial characteristics and dynamic
changes, which along the subway. This method selects some feature points to periodical repeated
observation. Through the data processing, it acquires data function relation that reflects the change
rule by monitoring group subsidence, horizontal displacement variation with time. It uses this data
function relation to forecast the next phase monitoring data, possibility of monitoring point
maximum displacement or stress value, which predicts monitor objects safety condition to
determine the engineering measures. Observation adjustment calculation requirements: (1) The
stability of the datum point be calculated and independent closure error and connecting traverse
error must satisfy the precision requirement, which ensure the initial data accuracy;(2) before the
adjustment ,it tests the stability of control points and compares the Angle and distance of the
periods adjacent control points, which ensures the data reliability; (3) Using huaxing survey
control net adjustment software, it checks observation data accuracy and reliability before the
adjustment. If checked data is qualified then it uses rigorous method to calculate (4) adjustment
data should be accurate to 0.1 mm. Through periodic deformation observation point elevation
value, it calculates periods phases subsidence, deformation rate, cumulative settlement data, etc.
The results are shown in table 4, table 5.
The first phase project of kunming rail transit
Device Name：Timble
data：2010.09.20~2010.09.26
last term
accumulat
ive
measureme
variation
measureme
initial
nt
value
nt num
value(mm)
position
(mm)
9.19
A~BInterval Ming dig period
DiNi0.3electronic level
ground surface settlement
Device number：732144
currentaccumulated variation(mm）
9.20
9.21
9.22
-16.6
-9.5
9.23
9.24
9.25
-19.2
-10.8
9.26
The third party monitoring report
check data：2010.07.02
report num:07-01-01
current
accumulat current
deformati
control value
initial
ed
displacem
on
observati conclusio
displacem
ent
rate(mm/d
on time
n
ent
change(mm
)
change(mm
)
accumulat
rate(mm/d
)
ed
)
value(mm)
-2.6
-19.2
-0.65
-25.0
10.07.24
warning
-1.3
-10.8
-0.33
-25.0
10.07.24
normal
D1-2
D1-3
0.0
0.0
D1-4
0.0
-3.2
-4.2
-1.0
-4.2
-0.11
-25.0
10.07.24
normal
D1-6
D1-7
D2-2
D2-3
D2-4
D2-6
D2-7
0.0
0.0
0.0
0.0
0.0
0.0
0.0
-11.6
-11.2
-17.4
-12.4
-8.7
-4.2
-4.9
-11.3
-11.2
-19.7
-14.4
0.3
0.0
-2.3
-2.0
0.07
0.00
-0.58
-0.50
-4.7
-5.5
-0.5
-0.6
-11.3
-11.2
-19.7
-14.4
-8.7
-4.7
-5.5
-25.0
-25.0
-25.0
-25.0
-25.0
-25.0
-25.0
10.07.24
10.07.24
10.07.24
10.07.24
10.07.29
10.07.24
10.07.24
normal
normal
warning
normal
resisted
normal
normal
D3-1
0.0
-2.5
-25.0
10.07.24
normal
D3-2
D3-3
D3-4
D3-6
0.0
0.0
0.0
0.0
-7.2
-8.4
-7.6
-7.6
-9.0
-10.2
-8.8
-8.2
-1.8
-1.8
-1.2
-0.6
-25.0
-25.0
-25.0
-25.0
10.07.29
10.07.24
10.07.24
10.07.24
normal
normal
normal
normal
±2.0
-0.13
-0.15
-2.5
-9.0
-10.2
-8.8
-8.2
-0.45
-0.45
-0.30
-0.15
备注
last
time9.14
last time
9.16
Table 5 the maximum value of monitoring data statistics
This period The maximum
The
measure
period
The average
monitoring
maximum accumulative
accumulative
monitoring
point
deformation
deformation
program
deformation deformation
deformation
state
number
rate (mm/d)
rate (mm/d)
(mm)
(mm)
values (mm)
surface
subsidence
D1-2
D2-2
-2.6
-19.7
-0.65
-25.0
±2.0
normal
-0.58
-25.0
±2.0
warning
Note: positive settlement deformation value is ridgy and negative is sinking; positive wall
deformation offsets into foundation ditch, negative is offsetting outside to foundation ditch,
Underground water level rising is positive and lowing is negative.
On the basis of monitoring data and statistics, it draws a graph (see figure 1) for predicting and
analyzing the stability of observation point. (1)Observation point stability analysis uses stable
datum point as reference point to calculate adjustment results; (2) Through comparing the
maximum deformation and maximum measurement error (twice mean square error), it analyzes
two phase observation point changes. When maximum deformation is less than maximum
measurement error, that means two periods observation points haven’t significant change or
change ;( 3) As to multiphase deformation observation results, when adjacent period deformation
is small, but the variation trend is obvious, it shall be deemed to have a change. If found abnormal
monitoring stations, it conducts warning judgment analysis. (1) Comparing the phase distortion
rate and the accumulative deformation value. If phase deformation rate or accumulative
deformation value less than warning value, it is normal state; If phase deformation rate or
accumulative deformation value one of them is bigger than warning value but less than the control
values ,it is warning state. If phase deformation rate or accumulative deformation value one of
them is bigger than control values, it is control state. (2) if data is warning state, it performs
comprehensive judgment according to inspect information, construction schedule, construction
measures condition, supporting palisade structure stability, surrounding environment condition
stability (3) confirmed analysis that abnormal situation, it should notify the relevant parties to take
measures promptly.
surface settlement
0
（mm）
Cumulative settlement
typical curve of
-10
-20
7/24
8/3
8/13
8/23
9/2
9/12
D1-2
D2-2
D2-3
D2-4
D2-6
D3-3
D3-6
D4-3
D4-6
D5-2
D5-4
9/22 data
Table 1 typical curve of surface settlement
4. Conclusion
Due to the different geological condition between Kunming Beijing, Shanghai, Shenzhen and
other places, it is more complex. So it uses different monitoring methods to conduct third party
monitoring of the first phase project of Kunming rail transit project bid. It monitors pile (wall) of
the foundation ditch deformation, pile (wall) top horizontal displacement, ground subsidence,
building inclined.it can be monitor subway construction surroundings timely. In the construction
critical period or abnormal situation, it adds frequencies appropriately. At abnormal situations, it
adjusts and strengthens monitoring plan dynamically. Monitoring solution improves engineering
quality and safety of subway construction, which ensures the subway construction smoothly.
Therefore, it plays a guiding role and significance to research and summary third party monitoring
rail transit project technology methods and data processing and analysis.
References
[1] Dengli. The third party monitoring application research in xi 'an subway construction.
Science and technology in western China，2013（1）
：1-3
[2] GB 50026-2007. Engineering surveying specification [S].
[3] JGJ/T 8-2007. Building deformation surveying specification [S].
[4] JGJ120-99. Construction of foundation ditch supporting technology regulation [S].