Foundation pit online monitoring
1 Monitoring content
The main impact scope of foundation pit construction is as follows:
|
Foundation pit project influence area |
range |
|
main area of influence |
Around the foundation pit 0.7H or H tan (45 ° -time φ /2) |
|
secondary area of influence |
Around the foundation pit 0.7H-(2.0~3.0)H or tan(45°-timeφ/2)- ( 2.0~3.0 ) within the range of H |
|
area of possible influence |
Outside the range of H ( 2.0~3.0 ) around the foundation pit |
2 Monitoring programs
The schematic diagram of the monitoring plan is as follows:
The specific monitoring plan is as follows:
|
Monitoring content |
Monitoring instruments |
Measuring point arrangement |
|
|
answer Measurement item target |
Vertical displacement of retaining pile (wall) |
level |
The monitoring level should not be greater than 20m , the number of monitoring points on each side should not be less than 3 , the top of the enclosure wall should be arranged, and the horizontal and vertical points should be shared. |
|
Horizontal displacement of supporting pile (wall) body |
Inclinometer |
Arrange one place every 10-20 meters, and each side should not be less than one inside the enclosure wall and inside the soil |
|
|
Anchor tension |
Anchor gauge |
Monitoring points should be arranged in the middle of each side of the foundation pit, at the outer corner and in the section with complex geological conditions |
|
|
Support shaft force |
Axial Dynamometer |
support end |
|
|
groundwater level |
Pore pressure gauge |
The groundwater level in the foundation pit should be arranged in the center of the foundation pit and in the middle of two adjacent dewatering wells; The groundwater level outside the foundation pit is arranged along the surrounding buildings and pipelines at a distance of 20-50 meters |
|
|
subsidence |
level |
It should be arranged at the nodes, corner points and parts with large deformation curvature of the pipeline |
|
|
Column settlement |
level |
It is arranged on the pillars in the middle of the foundation pit, at the intersection of multiple supports, and at places with complex geological conditions |
Key monitoring projects:
Automatically monitor the horizontal displacement of the enclosure piles in key areas, such as the outer corner of the foundation pit, the area where the soil quality changes abruptly, etc.; perform automatic monitoring of the axial force of the support, the axial force of the anchor cable, and the soil pressure behind the enclosure piles, saving manpower and material resources; Automatic monitoring of some groundwater levels.
|
Monitoring items |
Location or monitoring object |
test element |
Measuring point arrangement |
|
Horizontal displacement of enclosure pile |
Inside the enclosure structure of key areas (the positive angle of the foundation pit or the geological abrupt place) |
Inclinometer Tube Inclinometer |
Hole spacing 20~40 meters |
|
Support axial force, anchor cable axial force, soil pressure behind retaining pile |
Support, end of anchor cable |
Axial Force Gauge Strain Gauge |
Not less than 1%~3% of the number of bolts in each layer , and shall not be less than 3 and the measuring points shall be consistent in the vertical direction by 1%~3% , and shall not be less than 3 and the measuring points shall be maintained in the vertical direction. consistent |
|
groundwater level |
Around the foundation pit (automatic monitoring of some groundwater levels) |
water level gauge |
The hole spacing is 15~25 meters , the area near the river is encrypted 15~25 meters , and the area near the river is encrypted |
3 system advantages
Ø 24 -hour real-time monitoring: Through real-time online monitoring of supporting structure, surface settlement, and the inclination of retaining piles, the structural changes of the building foundation pit can be grasped in real time. Report push: The monitoring results are displayed and released in real time, and the monitoring reports are regularly pushed to users.
ØMulti -level early warning: establish a three-level alarm mechanism, when the detected data is abnormal, the user will be notified in the form of text message, fax, broadcast, etc. at the first time, so as to realize the comprehensive early warning function.
Ø Emergency plan processing: directly extract the corresponding processing methods from the expert system, and take measures such as personnel intervention and road blockade in a timely manner to eliminate potential safety hazards in the bud.
ØStructural trend analysis: Through the monitoring data analysis and safety evaluation of the foundation pit construction period, the structural stability trend analysis can be achieved.
ØStorage of historical data: The storage of monitoring data provides an analogy basis for the design and construction of similar projects in the future.
4 Monitoring basis
( 1 ) Project-related survey and design materials and bidding documents;
( 2 ) "Urban Rail Transit Engineering Measurement Specification" ( GB50308-2008 );
( 3 ) "Urban Measurement Specification" ( CJJ/T8-2011 );
( 4 ) "Technical Specification for Surveying of New Railway Engineering" ( TB10101-2009 );
( 5 ) "Engineering Measurement Specification" ( GB50026-2007 );
( 6 ) "Code for Measurement of Building Deformation" ( JGJ8-2007 );
( 7 ) "Technical Regulations for Building Foundation Pit Support" ( JGJ120-2012 );
( 8 ) "National First- and Second-Class Leveling Standards" ( GB/T12897-2006 );
( 9 ) "Code for Construction and Acceptance of Underground Railway Projects" ( GB50299-2003 );
( 10 ) "Detailed Rules for Safety and Quality Management of Construction Division";
( 11 ) "Code for Design of Building Foundation" ( GB50007-2011 );
( 12 ) "Technical Specifications for Urban Rail Transit Engineering Monitoring" ( GB 50911-2013 );
( 13 ) "Technical Specification for Construction Foundation Pit Engineering Monitoring" GB50497-2009 ;
( 14 ) Design drawings and other relevant technical specifications;
