CN108589694B - Subway protection method for unloading earthwork on tunnel by adopting vacuum preloading - Google Patents
Subway protection method for unloading earthwork on tunnel by adopting vacuum preloading Download PDFInfo
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- CN108589694B CN108589694B CN201810411603.9A CN201810411603A CN108589694B CN 108589694 B CN108589694 B CN 108589694B CN 201810411603 A CN201810411603 A CN 201810411603A CN 108589694 B CN108589694 B CN 108589694B
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D3/00—Improving or preserving soil or rock, e.g. preserving permafrost soil
- E02D3/02—Improving by compacting
- E02D3/10—Improving by compacting by watering, draining, de-aerating or blasting, e.g. by installing sand or wick drains
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- Excavating Of Shafts Or Tunnels (AREA)
Abstract
A subway protection method for unloading earthwork on a tunnel by adopting vacuum preloading comprises the steps of firstly, analyzing a geological survey report, and determining the thickness and the range of the earthwork needing to be unloaded in a field above the tunnel; secondly, calculating vertical and horizontal deformation of the tunnel and track facilities caused by unloading of the overlying earthwork; thirdly, performing vacuum preloading construction in the site, burying monitoring instruments in a proper time, and implementing informatization construction by monitoring the ground surface settlement and the deformation conditions of subway tunnels and track facilities during construction; and fourthly, unloading after the vacuum preloading meets the design requirement, and leveling the field to build the upper part. The invention mainly solves the problem of the safety influence on the tunnel in the construction process of excavating a sludge layer and reducing the elevation of a field when a building is built above a shallow tunnel near a sludge soft soil layer. The method has the advantages of mature process, information construction, reduction of excavation and abandonment of sludge earthwork, economy, environmental protection and strong safety guarantee for the subway tunnel.
Description
Technical Field
The invention relates to the field of geotechnical engineering and underground engineering, in particular to a subway protection method for unloading overlying earthwork of a tunnel by adopting vacuum preloading.
Background
The vacuum preloading is to form air pressure difference inside and outside a sealing film covered on the ground by vacuumizing the sealing film, and to form consolidation pressure in a soft soil layer, namely to increase the effective force by reducing the pore water pressure to enable the soft soil layer to drain and consolidate under the condition of unchanged total stress. The vacuum preloading method is widely applied to foundation treatment engineering in coastal soft soil areas. However, with the acceleration of subway construction in coastal soft soil areas, particularly coastal big cities, accidents are more and more affected by the construction above the subway on the safety of existing subway tunnel facilities, and particularly, when field level engineering is carried out above shallow tunnels in soft soil areas, earthwork needs to be excavated and unloaded, so that the tunnels are floated and deformed, and the safe operation of the subway is seriously affected.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a subway protection method for covering earthwork on a vacuum preloading unloading tunnel. The method aims to solve the problem of the safety influence on the tunnel in the construction process of excavating a sludge layer to reduce the elevation of a field when buildings are built above a shallow tunnel near a soft soil layer such as sludge.
The technical scheme adopted by the invention for solving the technical problems is as follows: the subway protection method for unloading the earthwork on the tunnel by adopting vacuum preloading is characterized by comprising the following steps of:
the method comprises the following steps: analyzing a geological survey report, finding out the buried depth of the subway tunnel, analyzing the requirement of site design elevation, and determining the thickness and range of earthwork needing to be unloaded of the site above the tunnel;
step two: calculating vertical and horizontal deformation of the tunnel and track facility caused by unloading of the overlying earthwork, and calculating design parameters and foundation settlement of an unloading field by adopting vacuum preloading;
step three: carrying out vacuum preloading construction in a field, embedding monitoring instruments in a proper time, and implementing informatization construction by monitoring surface subsidence and deformation conditions of subway tunnels and track facilities during construction;
step four: and unloading after the vacuum preloading meets the design requirements, and leveling the field to build the upper part.
Further:
the first step comprises the following steps:
a) analyzing a geological survey report, drawing a longitudinal section of the site, and noting the vertical distribution of the soil layer, the position of the tunnel, the designed elevation of the site and the thickness of the soil layer to be unloaded;
b) the physical and mechanical indexes of the silt soft soil layer are noted;
c) and determining the early consolidation pressure of the sludge according to the compression test, and analyzing the consolidation degree of the sludge.
The tunnel position in the step a) is that the top surface of the tunnel structure is positioned in the sludge soft soil layer or the distance between the top surface of the tunnel structure and the bottom surface of the sludge soft soil layer is less than 2.0 m; the thickness of the soil layer to be unloaded is 10% -20% of the thickness of the soft soil layer covered by the silt on the tunnel.
The second step comprises the following steps:
d) calculating vertical and horizontal deformation of the tunnel and track facilities caused by overlying earthwork unloading, and evaluating the influences of silt muck excavation, external volume of abandoned, engineering cost and tunnel deformation caused by the conventional earthwork unloading method on the safe operation of the subway;
e) calculating design parameters of the unloading site adopting vacuum preloading treatment, comprising the following steps: the arrangement distance and the arrangement depth of the plastic drainage plates, the thickness of the horizontal drainage sand cushion layer, the connection scheme of the vacuum piping and the plastic drainage plates, the arrangement number of vacuum pumps, the water depth on the sealing film and the full load time of vacuum preloading;
f) evaluating the safety influence of vacuum preloading construction on subway tunnels and track facilities, calculating the foundation settlement generated by vacuum preloading, comparing the foundation settlement with the elevation of a design site and the thickness of a soil layer to be unloaded, and determining the feasibility of covering earthwork on the tunnel by adopting vacuum preloading unloading.
The third step comprises:
g) the vacuum preloading construction in the field comprises the steps of flattening the field, paving a sand cushion layer (the thickness is less than 0.3m or not), driving a plastic drainage plate, laying a vacuum pipe system and connecting the drainage plate, arranging a sealing ditch, sealing a film field sealing system and laying a vacuum pump;
h) during vacuum preloading construction, bury monitoring instrument underground in good time according to the construction progress, include: deep settlement marks at the bottom ends of the drainage plates, pore water pressure meters in the sludge layers, vacuum degree measuring meters below the sealing films, surface settlement plates on the sealing films and deformation monitoring instruments in the tunnels;
i) during construction, when the deformation values of the subway tunnel and the track facilities exceed the warning values specified by the subway department, an alarm is immediately sent out, shutdown or vacuumizing is stopped, the deformation reason of the tunnel is found out, and the work is repeated after corresponding treatment measures are taken.
The fourth step comprises:
j) the total settlement of the earth surface during construction meets the design requirement and the vacuumizing can be stopped when the thickness of the earth to be unloaded is reached;
k) when the settlement rate of the foundation generated by vacuum preloading is less than 2mm/d for 1 month continuously, the vacuumizing can be stopped;
l) after vacuum unloading, leveling the field, and carrying out upper construction when the ground surface elevation meets the design elevation requirement.
On the basis of the conventional earthwork unloading method, the invention adopts the subway protection method for covering earthwork on the vacuum preloading unloading tunnel, which has mature process, can be constructed with information, reduces the excavation abandonment of silt earthwork, is economic and environment-friendly, and has strong safety guarantee on the subway tunnel, thereby solving the problems of difficult excavation of earthwork, especially silt soft soil, and large influence on tunnel deformation during engineering construction above a shallow tunnel in a coastal soft soil area.
Description of the drawings:
FIG. 1 is a schematic view of the present invention.
In the figure: 1-soft soil (silt) layer; 2-subway tunnel and deformation monitoring system; 3-a vacuum preloading system; 4-designing the ground elevation; and 5-unloading the soil layer (vacuum preloading settlement).
The specific implementation mode is as follows:
the invention discloses a subway protection method for covering earthwork on a vacuum preloading unloading tunnel, which is a specific implementation mode and is characterized by comprising the following steps of:
the method comprises the following steps: firstly, determining the field plane range, the unloading thickness, the thickness of a sludge layer and the tunnel burial depth of the earthwork to be unloaded according to a geological survey report and field level design elevation basic data, wherein the following two indexes are taken as applicability bases: the top surface of the tunnel structure is positioned in the silt and soft soil layer of the silt soil or the distance between the top surface of the tunnel structure and the bottom surface of the silt soft soil layer is less than 2.0m, and the thickness of the soil layer to be unloaded is 10-20% of the thickness of the silt soft soil layer coated on the tunnel;
step two: calculating vertical and horizontal deformation of the tunnel and track facilities caused by overlying earthwork unloading, and evaluating the influences of silt muck excavation, external volume of abandoned, engineering cost and tunnel deformation caused by the conventional earthwork unloading method on the safe operation of the subway; calculating design parameters of the unloading site adopting vacuum preloading treatment, comprising the following steps: the arrangement distance and the arrangement depth of the plastic drainage plates, the thickness of the horizontal drainage sand cushion layer, the connection scheme of the vacuum piping and the plastic drainage plates, the arrangement number of vacuum pumps, the water depth on the sealing film and the full load time of vacuum preloading; evaluating the safety influence of vacuum preloading construction on subway tunnels and track facilities, calculating the foundation settlement generated by vacuum preloading, comparing the foundation settlement with the elevation of a design site and the thickness of a soil layer to be unloaded, and determining the feasibility of covering earthwork on the tunnel by adopting vacuum preloading unloading;
step three: the vacuum preloading construction in the field comprises the steps of flattening the field, paving a sand cushion layer (the thickness is less than 0.3m or not), arranging a plastic drainage plate, arranging a vacuum pipe system and connecting the drainage plate, arranging a sealing ditch and a sealing film field sealing system and arranging a vacuum pump; during vacuum preloading construction, bury monitoring instrument underground in good time according to the construction progress, include: deep settlement marks at the bottom ends of the drainage plates, pore water pressure meters in the sludge layers, vacuum degree measuring meters below the sealing films, surface settlement plates on the sealing films and deformation monitoring instruments in the tunnels; during construction, when the deformation values of the subway tunnel and the track facility exceed the warning values specified by a subway department, immediately giving an alarm, shutting down or stopping vacuumizing, finding out the deformation reason of the tunnel and taking corresponding treatment measures and then re-working;
step four: the total settlement of the earth surface during construction meets the design requirements and reaches the thickness of the earth to be unloaded, or the vacuumizing can be stopped when the settlement rate of the foundation generated by vacuum preloading is less than 2mm/d for 1 month continuously; and after vacuum unloading, leveling the field, and carrying out upper construction when the ground surface elevation meets the design elevation requirement.
Claims (5)
1. A subway protection method for unloading earthwork on a tunnel by adopting vacuum preloading is characterized by comprising the following steps:
the method comprises the following steps: analyzing a geological survey report, finding out the buried depth of the subway tunnel, analyzing the requirement of site design elevation, and determining the thickness and range of earthwork needing to be unloaded of the site above the tunnel;
step two: calculating vertical and horizontal deformation of the tunnel and track facility caused by unloading of the overlying earthwork, and calculating design parameters and foundation settlement of an unloading field by adopting vacuum preloading;
step three: carrying out vacuum preloading construction in a field, embedding monitoring instruments in a proper time, and implementing informatization construction by monitoring surface subsidence and deformation conditions of subway tunnels and track facilities during construction;
step four: and unloading after the vacuum preloading meets the design requirements, and leveling the field to build the upper part.
2. A subway protection method using vacuum preloading unloading tunnel overburden earthwork as claimed in claim 1, wherein said step one includes:
a) analyzing a geological survey report, drawing a longitudinal section of the site, and noting the vertical distribution of the soil layer, the position of the tunnel, the designed elevation of the site and the thickness of the soil layer to be unloaded;
b) the physical and mechanical indexes of the silt soft soil layer are noted;
c) determining the early consolidation pressure of the sludge according to a compression test, and analyzing the consolidation degree of the sludge;
the tunnel position in the step a) is that the top surface of the tunnel structure is positioned in the sludge soft soil layer or the distance between the top surface of the tunnel structure and the bottom surface of the sludge soft soil layer is less than 2.0 m; the thickness of the soil layer to be unloaded is 10% -20% of the thickness of the soft soil layer covered by the silt on the tunnel.
3. A subway protection method using vacuum preloading unloading tunnel overlying earthwork according to claim 1, wherein said step two includes:
d) calculating vertical and horizontal deformation of the tunnel and track facilities caused by overlying earthwork unloading, and evaluating the influences of silt muck excavation, external volume of abandoned, engineering cost and tunnel deformation caused by the conventional earthwork unloading method on the safe operation of the subway;
e) calculating design parameters of the unloading site adopting vacuum preloading treatment, comprising the following steps: the arrangement distance of the plastic drainage plates, the arranging depth, the thickness of the horizontal drainage sand cushion layer, the connection scheme of the vacuum piping and the plastic drainage plates, the arrangement number of vacuum pumps, the water depth on the sealing film and the full load time of vacuum preloading;
f) evaluating the safety influence of vacuum preloading construction on subway tunnels and track facilities, calculating the foundation settlement generated by vacuum preloading, comparing the foundation settlement with the elevation of a design site and the thickness of a soil layer to be unloaded, and determining the feasibility of covering earthwork on the tunnel by adopting vacuum preloading unloading.
4. A subway protection method using vacuum preloading unloading tunnel overburden earthwork as claimed in claim 1, wherein said step three includes:
g) the vacuum preloading construction in the field comprises the steps of flattening the field, paving a sand cushion layer, arranging a plastic drainage plate, arranging a vacuum pipe system, connecting the drainage plate, arranging a sealing ditch, sealing a film field sealing system and arranging a vacuum pump;
h) during vacuum preloading construction, bury monitoring instrument underground in good time according to the construction progress, include: deep settlement marks at the bottom ends of the drainage plates, pore water pressure meters in the sludge layers, vacuum degree measuring meters below the sealing films, surface settlement plates on the sealing films and deformation monitoring instruments in the tunnels;
i) during construction, when the deformation values of the subway tunnel and the track facilities exceed the warning values specified by the subway department, an alarm is immediately sent out, shutdown or vacuumizing is stopped, the deformation reason of the tunnel is found out, and the work is repeated after corresponding treatment measures are taken.
5. A subway protection method using vacuum preloading unloading tunnel overburden earthwork as claimed in claim 1, wherein said step four includes:
j) the total settlement of the earth surface during construction meets the design requirement and the vacuumizing can be stopped when the thickness of the earth to be unloaded is reached;
k) when the settlement rate of the foundation generated by vacuum preloading is less than 2mm/d for 1 month continuously, the vacuumizing can be stopped;
and after vacuum unloading, leveling the field, and carrying out upper construction when the ground surface elevation meets the design elevation requirement.
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| CN113550293A (en) * | 2021-07-20 | 2021-10-26 | 中国铁道科学研究院集团有限公司 | Method for treating foundation above shallow shield tunnel through vacuum preloading |
| CN114278300B (en) * | 2022-01-28 | 2023-09-15 | 六盘水师范学院 | Method for repairing coal mining damaged water-proof soil layer through vacuum preloading of thin sand layer coverage area |
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Effective date of registration: 20190729 Address after: Great engineering prospecting No. 8 building, eight South Road 518000 South Science and technology in Guangdong province Shenzhen city Nanshan District high tech Park 22 Applicant after: Academy of Iron Sciences (Shenzhen) Research and Design Institute Co.,Ltd. Applicant after: CHINA ACADEMY OF RAILWAY SCIENCES Corp.,Ltd. Address before: Great engineering prospecting No. 8 building, eight South Road 518000 South Science and technology in Guangdong province Shenzhen city Nanshan District high tech Park 22 Applicant before: Academy of Iron Sciences (Shenzhen) Research and Design Institute Co.,Ltd. |
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