CN111927525A - Biogas static pressure exhaust construction method - Google Patents
Biogas static pressure exhaust construction method Download PDFInfo
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- CN111927525A CN111927525A CN202010713372.4A CN202010713372A CN111927525A CN 111927525 A CN111927525 A CN 111927525A CN 202010713372 A CN202010713372 A CN 202010713372A CN 111927525 A CN111927525 A CN 111927525A
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- 239000000523 sample Substances 0.000 claims abstract description 81
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21F—SAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
- E21F7/00—Methods or devices for drawing- off gases with or without subsequent use of the gas for any purpose
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21F—SAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
- E21F17/00—Methods or devices for use in mines or tunnels, not covered elsewhere
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21F—SAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
- E21F17/00—Methods or devices for use in mines or tunnels, not covered elsewhere
- E21F17/18—Special adaptations of signalling or alarm devices
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- Mining & Mineral Resources (AREA)
- Life Sciences & Earth Sciences (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Geology (AREA)
- Excavating Of Shafts Or Tunnels (AREA)
Abstract
The invention is suitable for the technical field of shield tunnel biogas discharge, and provides a construction method for static pressure biogas exhaust, which comprises the following steps: measuring and positioning, pipeline detection, static pressure probe rod, methane discharge and hole sealing, construction hole backfill and pavement restoration. The method creatively adopts the comprehensive construction technologies such as the static pressure pore-forming technology, the controlled discharge technology, the hole sealing backfill technology and the like, successfully reduces the air pressure of the interval methane layer to be below 0.05Mpa, well solves the problem that shallow methane causes harm to engineering construction and personnel, and obtains better social, economic and environmental benefits.
Description
Technical Field
The invention belongs to the technical field of shield tunnel biogas discharge, and particularly relates to a construction method for static pressure biogas discharge.
Background
In recent years, with the increase of subway lines, more and more subway planning lines in coastal cities and along rivers penetrate through a methane-containing stratum. The shallow marsh gas is mainly distributed in estuary and land frame sea area, and can be divided into two types according to the cause. One is the thermal methane formation, and organic matter below the seafloor of 2000m generally forms hydrocarbons at high temperature and pressure due to kerogen breakdown, the properties of which depend on the nature of the original organic matter and the geological environment. The other is a biological cause, when a large amount of land-source debris substances are deposited on the seabed, abundant biological debris and organic matters are brought, methane bacteria decompose methane from rotten organic matters to form gas-containing sediments, in several sea-going and sea-going retreats, the organic matters in a sludge layer are decomposed and fermented under the biochemical action of anaerobic bacteria, and are changed into gaseous products along with certain temperature and pressure, and when the generated shallow methane cannot be diffused into the atmosphere, the shallow methane is occasionally transported to and accumulated in the pores of the surrounding stratum, and the shallow methane is stored in the surrounding stratum to form a shallow methane reservoir (see the following formula).
When the engineering shield interval construction passes through the stratum, shallow methane can harm engineering construction and personnel:
1. in the shield tunneling process of the underground tunnel, when underground gas accumulated underground is suddenly released due to external factors, the pressure of the gas-containing layer is rapidly reduced, so that a gas-water interface moves towards a gas jet, the rapid gas flow has a strong scouring effect on the soil layer, the gas-containing soil layer is stirred in a large range, and meanwhile, the overlying or underlying stratum is severely disturbed. With the end of the strong air injection, the soil layer is inevitably subjected to rapid sedimentation, and then the soil body is consolidated again and sinks. Because the distribution of underground gas is uneven, the air pressure is unequal, and the difference of stratum bearing capacity is large, uneven settlement is often caused in the gas release process, so that the serious deformation of a tunnel structure is further induced, and even the segment is broken and damaged.
2. In the construction process, when shallow methane is gushed in a large area, the methane is accumulated in a certain range due to unsmooth ventilation. Because the main components of the shallow marsh gas are methane and nitrogen, when the gas concentration is too high, the oxygen content in the air is obviously reduced, and people suffocate. When the methane content in the air reaches 25-30%, headache, dizziness, hypodynamia, inattention, acceleration of respiration and heartbeat and ataxia can be caused. If the skin is not separated in time, asphyxia can occur, and the skin is liquefied by contact, which can cause frostbite. When the concentration is within the explosion limit range of 5-15%, severe explosion will occur when exposed fire occurs, and personal safety is seriously harmed.
Disclosure of Invention
The embodiment of the invention aims to provide a construction method for static pressure exhaust of biogas, aiming at solving the problems in the background art.
The embodiment of the invention is realized in such a way that a construction method for static pressure exhaust of methane comprises the following steps:
measurement and positioning: determining the spacing and planar position of the vent holes based on the survey report;
pipeline detection: detecting the position of the underground pipeline and determining whether to displace the discharge hole;
a static pressure probe rod: pressing the probe rod provided with the movable probe to a preset depth through a static pressure device; drilling a lead hole at the discharge port when the balance weight of the static pressure device is insufficient, and then pressing the probe rod provided with the movable probe to a preset depth by adopting the static pressure device;
discharging biogas: pulling up the probe rod to check whether methane exists; if the biogas escapes, discharging the biogas; and after the methane is discharged or when no methane escapes, pulling out the probe rod.
Preferably, the step of pipeline detection comprises:
collecting data of the underground pipeline;
according to the data of the underground pipeline, digging downwards at the discharge hole to reach the undisturbed soil or the digging depth is 2 m; if the pipeline or undisturbed soil is excavated to a depth greater than 2m, the discharge hole is displaced and re-excavated, otherwise, the discharge hole is not required to be displaced;
when the construction site can not be excavated, the position of the underground pipeline is determined by an ultrasonic detection mode.
Preferably, the step of pressing the probe rod with the movable probe to a predetermined depth by a static pressure device comprises:
firstly, a static pressure device is installed;
the center of the probe rod provided with the movable probe is aligned with the discharge hole, the static pressure device is adjusted to be horizontal, and then the probe rod and the movable probe are pressed to the designed depth through the static pressure device.
Preferably, the step of drilling a pilot hole comprises:
the casing wall is first lowered at the location of the drainage holes and then drilled into the casing wall by means of a drill to 5m above the gas bearing layer.
Preferably, the step of discharging biogas comprises:
testing the buried depth of the top plate and the bottom plate of the gas-containing layer: determining whether biogas exists or not by pulling up the rods one by one, if the biogas escapes, determining the depths of a top plate and a bottom plate of a biogas gas-containing layer by pulling up the probe rod, wherein the difference between the depths of the bottom plate and the top plate is the thickness of the gas-containing layer at the discharge hole; if no marsh gas exists, the probe rods are continuously pulled up meter by meter until the marsh gas exists or all the probe rods are pulled out;
air bleeding: pulling up the probe rod to separate the movable probe from the probe rod, gradually releasing methane through the probe rod under the condition of natural energy of a gas-containing layer by utilizing the pressure difference between the gas-containing layer and the probe rod, performing controlled deflation through a gate valve during methane release, and measuring the pressure and flow of methane discharge;
pulling up the probe rod: and after the air release step is finished, pulling all the rest probe rods away from the ground.
Preferably, the step of discharging the biogas is followed by steps of sealing holes, backfilling construction holes and restoring the pavement, wherein the steps of sealing holes, backfilling construction holes and restoring the pavement comprise:
firstly, filling the discharge hole with cement slurry from the bottom of the discharge hole upwards;
and then backfilling, tamping and rolling the construction holes excavated and explored manually according to municipal requirements, and restoring the pavement according to the original appearance.
Preferably, the pressure of the methane discharge is less than 0.05MPa, and the flow rate is less than 1.5m3And stopping methane discharge at the time of/h.
The construction method for static pressure methane exhaust provided by the embodiment of the invention is suitable for methane exhaust construction under various soft geological conditions such as silt layers, sand layers, silt stratums, backfill layers and the like; the method is mainly applied to the methane discharge construction of shield interval tunnels, underground excavated tunnels by a mining method and open-cut station projects passing through or adjacent to methane gas-bearing layers, and has the following advantages:
1. the device is simple, portable, convenient, rapid, economic and labor-saving to operate, not only can measure the pressure and flow of the biogas by connecting other instruments in the discharge process, but also can realize layered and segmented discharge and test at different depths in the stratum through operation steps;
2. the construction process is complete, the pore diameter of the formed hole is smaller (the pore diameter is 42mm) compared with that of a traditional drilling hole-forming casing method, and the collapse of the pore wall is not easily caused for the stratum mainly containing silt and sandy soil; in addition, the process does not need to adopt a slurry protection wall, the pressure difference between the air pressure of a gas-containing layer and the water pressure in the drilled hole is increased, and the discharge of methane is facilitated; meanwhile, the drilling and hole-forming casing method also has the defects of fixed hole depth, high cost, complex process, long construction period and the like;
3. the static pressure exhaust method can not cause the problems that solid particles of soil are easy to carry out by a negative pressure air exhaust method, the soil structure is damaged, the soil settlement is overlarge and the like.
Drawings
Fig. 1 is a process flow diagram of a construction method for static pressure exhausting of biogas according to an embodiment of the present invention;
fig. 2 is a schematic structural view of construction equipment for a biogas static pressure exhaust construction method according to an embodiment of the present invention;
fig. 3 is a process flow diagram for drilling a via according to an embodiment of the present invention.
In the drawings: 1. a movable probe; 2. a probe rod; 3. a counterforce device; 4. crossties; 5. a tee assembly; 6. a gate valve; 7. a rubber gas delivery pipe; 8. a gas-liquid separator; 9. a pressure gauge; 10. a flow meter; 11. adjusting a valve; 12. a water tank; 13. a gas sample collection bag; 14. a static pressure device; 15. drilling holes; 16. and (4) a filter screen.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Specific implementations of the present invention are described in detail below with reference to specific embodiments.
Example 1
As shown in fig. 1 and 2, a construction method for static pressure methane exhaust according to an embodiment of the present invention includes the following steps:
1. measurement and positioning:
firstly, collecting coordinates in an electronic topographic map according to specific positions of various biogas discharge holes determined by design, and then measuring by a measurer on the basis of a ZJCORS platform in a GPS-RTK mode according to the requirements of the real-time kinematic (RTK) specification of a global positioning system (CH/T2009-2010), wherein a local coordinate system is adopted as a coordinate result, and a 1985 national elevation standard is adopted; because the engineering point is located on land, the point sign adopts red paint-spraying marks, thereby preventing artificial damage; if the biogas discharge hole needs to be moved, the biogas discharge hole is approved by project managers, headquarters, supervision, design and owners; after the biogas treatment construction is finished, retesting is uniformly carried out; the elevation of each methane discharge hole orifice is measured according to a control system provided by Party A, a closed circuit such as II is formed between a measured point and a reference point, the initial value of each measured point is the average value of three tests, the observation result is subjected to strict adjustment calculation by a computer,
(N is the number of stations);
2. pipeline detection:
a. gathering pipeline data
Before construction, a detailed investigation scheme is formulated, on-site survey is carried out, suspicious points are found out, then pipeline position diagrams are called in relevant departments and units, and relevant pipeline data are collected; according to the data of the pipeline, on-site exploration and confirmation (manual exploration) are carried out on the methane discharge hole and the vicinity thereof before construction, the conditions of the type, the burial depth, the trend, the material and the like of the pipeline are found out, and the pipeline is clearly marked on a drawing and verified with a supervisory person of a pipeline ownership unit in the field;
b. manual digging probe
Firstly, fencing is carried out according to requirements, day and night warning lamps and warning boards are arranged at the periphery of the fencing or road safety signs such as warning lines are arranged, then the fencing is manually excavated to original state soil or the depth is 2m, the original state soil is excavated to the depth which is more than 2m or special conditions are analyzed in time, and project responsible persons are reported to research scheme countermeasures again; the shallow part 10m is drilled by adopting a press-in method, the construction is stopped immediately when abnormality occurs, and the excavation is carried out again after the ownership unit is confirmed;
c. ultrasonic detection
For the area where the pipeline cannot be confirmed in a manual excavation mode, an ultrasonic radar can be used for detection, detection data are analyzed by a computer to form a detection report, and whether the pipeline exists underground or not is confirmed according to the report result;
3. a static pressure probe rod:
a. reaction device mounting
Firstly, installing a counterforce device 3, a sleeper 4 and a static pressure device 14; for a relatively spacious and thick filling section around the project, the ground anchor can be directly adopted as the counterforce device 3; for sections which cannot be anchored in the ground, a crawler-type static pressure device 14 can be adopted to use self weight or add a counterweight as a counterforce device 3;
b. static pressure probe and probe rod
Before the discharge construction, geological data of a discharge hole position and the depth, pressure and reserve size of the methane embedment are carefully checked;
the static pressure device 14 generally adopts double-oil-cylinder full hydraulic transmission equipment, the center of a probe rod 2 provided with a movable probe 1 is aligned with a discharge hole, the diameter of the probe rod 2 is 42mm, the wall thickness is 5mm, and the middle part is hollow, when the probe 2 is pulled up, the movable probe 1 is separated from the probe rod 2, and a drilling hole 15 and a filter screen 16 are arranged at the connecting part of the probe rod 2 and the movable probe 1, so that methane can conveniently enter the probe rod 2 from the drilling hole 15 and the filter screen 16; adjusting the static pressure device 14 to be horizontal by adjusting the sleepers 4 and the foot pads of the base of the static pressure device 14, rechecking by using a leveling rod, and connecting the static pressure device 14 with a ground anchor or paving a heavy object by using a high-strength bolt; then checking whether the equipment instrument is normal, and making all preparation work; then the probe rod 2 and the movable probe 1 are pressed to the designed depth by a static pressure device 14;
c. drilling a lead hole:
when the engineering filling is thick or the static pressure resistance is large and the static pressure cannot reach a section with a preset depth, excavating and exploring, and then constructing by adopting a drilling hole leading static pressure method, wherein compared with the static pressure method, the method increases the hole leading process of a drilling machine;
1) drilling process flow
In the biogas treatment construction, mechanical drilling is adopted as an auxiliary means, the drilling is mainly used for leading holes and casing running, the specific process flow is shown in figure 3, the construction site is leveled after the discharge holes are measured and positioned, then a drilling machine is installed at a drilling point, a mud pit is manufactured at the drilling point, then the drilling machine drills underground from the mud pit, elevation retesting is carried out through a level gauge to determine the depth of the drilling hole, the drilled hole diameter is cleaned after the drilling is finished, then the drilling machine moves to the next hole turning point, and the site is cleaned after the drilling is finished;
2) drilling process
The drilling method and the drilling process are determined according to the rock and soil type, the rock and soil drillability classification and the drilling technical requirements;
adopting a rotary drilling machine for construction, and selecting an adaptive drilling machine (XY-100 type) according to the requirements of the hole depth and the hole diameter;
soft soil layer, silt and sandy soil below the underground water level need to be drilled by adopting high-quality slurry to protect the wall;
3) drilling construction requirements
The following preparation work is done before construction:
enough personnel and equipment are input to ensure the construction period;
carrying out underground pipeline investigation, carrying out construction process protection, and ensuring that all underground pipelines are not damaged by drilling;
various kinds of on-site materials must be put neatly, so that the on-site civilization, sanitation and tidiness are kept;
4) drilling and leading process
After a pit is manually excavated and no pipeline or other facilities are arranged at a hole position, firstly, a steel protective pipe with an orifice of 127mm in diameter is arranged, a hammering method is adopted until the pipe wall is stable and does not shake, then an XY-100 type drilling machine is adopted to lead the hole to be 5m above an air source layer, and then a static pressure process is adopted to discharge the methane at the lower part until the design depth is reached; the lead hole drilling adopts an XY-100 type oil pressure drilling machine, and adopts construction processes such as rotary drilling, slurry wall protection and the like;
4. discharging biogas:
a. testing the buried depth of the top and bottom plates of the gas-bearing layer
Determining whether biogas exists or not by pulling up the rods one by one, if the biogas escapes, determining the depths of a top plate and a bottom plate of a biogas gas-containing layer by pulling up the probe rod 2, wherein the difference between the buried depths of the bottom plate and the top plate of the gas-containing layer is the thickness of the gas-containing layer at the hole position, and if the biogas does not exist, continuously pulling up the probe rod 2 meter by meter until the biogas exists or all the probe rods 2 are pulled out;
b. measuring pressure and flow
Aiming at a discharge hole for detecting the existence of methane, in the process of pulling up after the bottom plate of a gas-containing layer is detected to be buried deeply, when the methane escapes from the end head of the upper part of a probe rod 2, a three-way component 5 is connected with the probe rod 2 through threads, gas reaches a gas-liquid separator 8 through a rubber gas pipe 7 by adjusting the opening or closing state of each gate valve 6, the gas-liquid separator 8 is used for separating mud, fine sand and gas, when the whole system is in balance, a pressure value can be directly read from a pressure gauge 9, and when the flow is measured, the flow value of a flowmeter 10 is read by adjusting the opening or closing state of each gate valve 6 and the state of an adjusting valve 11; the gas passing through the flowmeter 10 enters a water tank 12 and is collected by a gas sample collection bag 13;
c. air release
When the probe and the probe rod 2 are statically pressed to the depth of a gas-containing layer, the probe and the probe rod 2 are slightly pulled upwards, the movable probe 1 is thrown into the soil, and gas is gradually released through the probe rod 2 under the crustal pressure of the gas-containing layer by utilizing the pressure difference between the gas-containing layer and the probe rod 2, so that the gas amount is reduced, and the pressure is reduced; when the air pressure and the flow in the discharge hole are extremely large, if the conditions of mud and sand spraying occur when the sand blasting air column occurs, the gas-liquid separator 8 is connected in time to measure the air pressure, the flow, the methane concentration and the like; adjusting the pressure reducing valve and the air outlet gate valve 6 when necessary, reducing the flow of the air outlet, closing the air outlet gate valve 6 when necessary, standing for a period of time, and then slowly opening the air outlet gate valve 6; if no gas is sprayed out, the probe rod 2 is retracted to carry out the construction of the next hole; during the deflation process, controlled deflation can be performed through the gate valve 6; observing the air pressure state, controlling the discharge flow and continuously recording related parameters; photographing is needed in the whole deflation process, and the initial time of gas release, the attenuation rule of the change of the deflation air pressure and the eruption characteristics are recorded; debugging a gate valve 6, wherein the air pressure is weakened after a period of time, and the air release stage is stopped when the measured air pressure is less than 0.05 MPa; when the biogas is difficult to be released through the pressure of the earth crust, an air compressor can be used for supplying air and pressing air to send outside air into the gas-containing layer, so that the pressure of the gas-containing layer is increased, and the biogas is completely released;
d. pull-up probe rod
After all tests are finished, pulling all the rest probe rods 2 off the ground at a constant speed;
5. hole sealing, construction hole backfilling and pavement restoration:
after the construction of the methane discharge holes is finished, effective hole sealing is carried out, the hole sealing material adopts 32.5MPa of pure cement slurry, the water cement ratio is 0.5-0.7, and the cement dosage is determined according to the hole depth; controlling cement slurry to be uniformly stirred per 5kg/m, feeding the cement slurry into the bottom of a hole by a slurry pump with BW (250) through a drill rod, wherein the pressure of the slurry pump is 0.3-0.5 MPa, recharging the cement slurry from the bottom of the hole upwards, observing for 10 minutes after the cement slurry is filled, and stopping grouting after the slurry surface is stable; and after hole sealing, backfilling, tamping and rolling construction holes excavated and detected manually according to municipal requirements, and restoring the pavement according to the original appearance.
In addition, the following quality control measures should be noted in the operation of the construction method:
1. the methane discharge hole is positioned by adopting GPS measurement, the elevation measurement of the hole opening is carried out by an external leveling method, and the closed difference of a loop meets the requirement of measurement precision; measuring the hole site coordinates by a conventional lead measuring method, wherein the measuring precision at least meets the requirements of a map root point, and when holes are formed, owners and design approval are required to be obtained in advance if the hole sites need to be moved;
2. before shallow methane testing equipment enters a field, equipment instruments must be checked, a pre-instruction book (namely a single-hole task book) is formulated according to a construction organization scheme, and engineering requirement standards and a treatment method which possibly causes problems are indicated;
3. and (3) a balanced air bleeding principle: the methane release rate should not generate significant gathering to the stratum around the air release hole, slow and balanced air release is carried out, taking the sand without taking out mud as the control standard, and the dynamic balance of pressure is emphasized in the release process;
4. emission standard: meets the design requirements according to the drawing, the pressure of the common marsh gas is less than 0.05MPa, and the flow is less than 1.5m3And h, the risk of engineering accidents caused by the methane can be effectively reduced.
There are some additional security measures:
1. in the construction process, the construction is carried out strictly according to safety construction standard standards such as building construction safety inspection standard (JGJ59), construction site temporary electricity utilization safety technical specification (JGJ46), construction machinery use safety technical specification (JGJ33) and the like;
2. the erection of the operation rack of the drilling machine must be firm and reliable, and the operation rack is fixed on a site foundation so as to avoid the collapse and the overturn of the rack in the drilling process;
3. safety principle: measures such as a gas alarm instrument, a warning lamp, warning clothes and the like are provided, ventilation is increased, and fire prevention and blowout prevention are emphasized;
4. before the discharge construction, safety education is carried out on all people, prevention education of methane hazard such as methane is strengthened, and smoking is strictly prohibited;
5. a methane (methane type) monitoring alarm is required to be arranged, and measures are taken in time when an alarm is found;
6. during construction, fire prevention and poisoning prevention measures are required to be ensured in place, and air circulation is ensured;
7. the management of fire sources is enhanced, open fire is avoided, and other combustible substances are strictly forbidden;
8. the electric line connection and the use of equipment are standardized, and the spark is prevented;
9. constructors wear anti-static clothes to prevent static electricity;
10. preparing a fire extinguisher, a shovel and a fire-extinguishing water tap on site, connecting a water pump, and preparing at any time;
11. and a warning line is arranged at 10m outside the construction range, so that the situation that irrelevant personnel enter the field and are surrounded is avoided.
There are some other environmental protection measures:
1. in the construction process, the construction is carried out according to environmental protection construction standard standards such as ' noise emission standard of building construction site boundary ' (GB12523-2011), ' standards for protecting sanitary environment and protecting fire protection of safety protection site of construction engineering (DB 11/945-;
2. building wastes and waste materials generated in the construction process are intensively placed in a specified area and are timely recovered and cleaned;
3. oil stains generated in the construction process are removed in time;
4. the slurry must be stirred in a predetermined area, and a stirring area must not be provided at will.
The benefit generated by the method of the invention is analyzed as follows:
1. economic benefits are as follows:
a. construction indirect cost analysis
If biogas is not discharged in advance in engineering construction, the shield tunnel is always in a high-gas-risk area during construction, an effective gas monitoring, alarming and ventilating system needs to be established, construction mechanical equipment needs an anti-explosion device, and personnel are provided with anti-static clothes and the like, so that the shield construction progress is seriously influenced, and the construction risk is increased;
temporarily not considering related emergency expenses after gas construction supporting facilities and risks occur, only analyzing construction equipment lease and project management expenses, predicting that the construction progress is reduced to 8-10 rings/day from 15 rings/day, engineering accounts for 6000 rings, accumulating construction days is increased by about 1000 days, 5000 yuan is spent according to single-line shield tunnel equipment lease and personnel management expenses, and 5000 × 1000 is 5000000 yuan;
the cost of single methane treatment hole in the interval is 10000 yuan, 200 methane discharge holes are distributed in the whole shield interval line, and the cost of methane treatment is 10000 multiplied by 200 which is 2000000 yuan;
through comparative analysis, the cost can be saved by 3000000 yuan compared with the non-discharge treatment after the methane is discharged in advance.
b. Comparison of work period benefits
The biogas is not processed: shield tunneling is carried out for about 8-10 rings/day, 6000 rings are counted in total, and construction days are counted for about 667 days;
and (3) biogas treatment: shield tunneling is carried out for about 15 rings/day, 6000 rings are counted, and construction days are counted for about 400 days;
therefore, after the biogas is treated in advance, the total construction days are saved by 267 days.
2. Social benefits are as follows:
the static pressure exhaust method is adopted for methane discharge in a construction area, so that the construction risk can be effectively reduced, the pressure of a gas-containing layer is prevented from being rapidly reduced due to sudden release of underground gas caused by external action in the shield tunneling process of an underground tunnel, the overlying or underlying stratum is severely disturbed, even uneven settlement is caused in the gas release process, further, the serious deformation of a tunnel structure is induced, even, the segment is broken and damaged, the large-area collapse of the construction area is finally avoided, and the safety of pedestrians and passing vehicles is ensured.
3. Environmental benefits:
compared with a drilling hole-forming method, the static pressure exhaust method has smaller aperture and less backfill slurry amount, and reduces the pollution of chemical slurry to the stratum;
the static pressure exhaust method can effectively control the exhaust process and prevent the gushing accident caused by high air pressure, thereby avoiding the damage to the surrounding environment.
The method is suitable for methane discharge construction under various soft geological conditions such as silt layers, sand layers, silt stratums, backfill layers and the like; the method is mainly applied to the methane discharge construction of shield interval tunnels, underground excavated tunnels by a mining method and open-cut station projects passing through or adjacent to methane gas-bearing layers, and has the following advantages:
1. the device is simple, portable, convenient, rapid, economic and labor-saving to operate, not only can measure the pressure and flow of the biogas by connecting other instruments in the discharge process, but also can realize layered and segmented discharge and test at different depths in the stratum through operation steps;
2. the construction process is complete, the pore diameter of the formed hole is smaller (the pore diameter is 42mm) compared with that of a traditional drilling hole-forming casing method, and the collapse of the pore wall is not easily caused for the stratum mainly containing silt and sandy soil; in addition, the process does not need to adopt a slurry protection wall, the pressure difference between the air pressure of a gas-containing layer and the water pressure in the drilled hole is increased, and the discharge of methane is facilitated; meanwhile, the drilling and hole-forming casing method also has the defects of fixed hole depth, high cost, complex process, long construction period and the like;
3. the static pressure exhaust method can not cause the problems that solid particles of soil are easy to carry out by a negative pressure air exhaust method, the soil structure is damaged, the soil settlement is overlarge and the like.
Example 2
The biogas static pressure exhaust construction method in the embodiment 1 is applied to projects from a river station to a green six-way station, a green six-way station to a green fluffy station and a green fluffy station to a Yiliandong two-way station of the Hangzhou subway No. 8 line first-stage project.
Wherein, the section from the scenic road station to the green six road stations is an underground shield section, a village residential area and a small four-port direct river are mainly built downwards in the section, and the starting and ending mileage of the section is as follows: right DK10+ 738.712-right DK11+726.680, the right line is 987.968m in length; the device comprises a left DK10+ 738.712-a left DK11+726.678, a left linear long chain 2.223m, a left linear long chain 990.189m, and a communication channel is arranged between the left DK10+738.712 and the left DK11+ 726.678.
The section from the green six-way station to the green fluffy station is an underground shield section, the line extends to the east after going out of the green six-way station, deflects towards the south and the east after passing through a residential area, deflects towards the east after passing through a river and the residential area, enters the green fluffy station after passing through a straight river with a head, the residential area, a head fluffy middle bridge and a comprehensive pipe gallery, the starting and stopping mileage of the section is right K11+ 965.735-right K13+433.140, and two communication channels are arranged in the section.
The section from the Qingliang road station to the Yiliandong two-way station is a shield section, the shield section enters the Yiliandong two-way station after passing through the residences and rivers, the starting and stopping mileage of the section is right K13+ 662.28-right K15+187.72, and a communication channel is arranged in the section.
The method is adopted for construction of methane discharge in the interval, 200 methane discharge holes are completed in the interval from 2019, 4 months to 2019, the pressure of the pressure final hole of the discharge holes is less than 0.05Mpa, the average ground surface settlement of a gas discharge area is less than 3mm, when the shield interval is constructed, harmful gases such as methane, carbon monoxide, hydrogen sulfide and the like are not found in gas monitoring in a tunnel, the shield construction is safe and stable, the construction speed is guaranteed, the construction safety coefficient is also improved, the approval of owners, headquarters, design and supervision units is obtained, and good social benefits are obtained.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (7)
1. A construction method for static pressure exhaust of methane is characterized by comprising the following steps:
measurement and positioning: determining the spacing and planar position of the vent holes based on the survey report;
pipeline detection: detecting the position of the underground pipeline and determining whether to displace the discharge hole;
a static pressure probe rod: pressing the probe rod provided with the movable probe to a preset depth through a static pressure device; drilling a lead hole at the discharge port when the balance weight of the static pressure device is insufficient, and then pressing the probe rod provided with the movable probe to a preset depth by adopting the static pressure device;
discharging biogas: pulling up the probe rod to check whether methane exists; if the biogas escapes, discharging the biogas; and after the methane is discharged or when no methane escapes, pulling out the probe rod.
2. The biogas static pressure exhaust construction method according to claim 1, wherein the pipeline detecting step comprises:
collecting data of the underground pipeline;
according to the data of the underground pipeline, digging downwards at the discharge hole to reach the undisturbed soil or the digging depth is 2 m; if the pipeline or undisturbed soil is excavated to a depth greater than 2m, the discharge hole is displaced and re-excavated, otherwise, the discharge hole is not required to be displaced;
when the construction site can not be excavated, the position of the underground pipeline is determined by an ultrasonic detection mode.
3. The biogas static pressure exhaust construction method as claimed in claim 1, wherein the step of pressing the probe rod equipped with the movable probe to a predetermined depth by the static pressure device comprises:
firstly, a static pressure device is installed;
the center of the probe rod provided with the movable probe is aligned with the discharge hole, the static pressure device is adjusted to be horizontal, and then the probe rod and the movable probe are pressed to the designed depth through the static pressure device.
4. A biogas static pressure exhaust construction method according to claim 1, wherein the step of drilling the pilot hole comprises:
the casing wall is first lowered at the location of the drainage holes and then drilled into the casing wall by means of a drill to 5m above the gas bearing layer.
5. The construction method of claim 1, wherein the step of discharging biogas comprises:
testing the buried depth of the top plate and the bottom plate of the gas-containing layer: determining whether biogas exists or not by pulling up the rods one by one, if the biogas escapes, determining the depths of a top plate and a bottom plate of a biogas gas-containing layer by pulling up the probe rod, wherein the difference between the depths of the bottom plate and the top plate is the thickness of the gas-containing layer at the discharge hole; if no marsh gas exists, the probe rods are continuously pulled up meter by meter until the marsh gas exists or all the probe rods are pulled out;
air bleeding: pulling up the probe rod to separate the movable probe from the probe rod, gradually releasing methane through the probe rod under the condition of natural energy of a gas-containing layer by utilizing the pressure difference between the gas-containing layer and the probe rod, performing controlled deflation through a gate valve during methane release, and measuring the pressure and flow of methane discharge;
pulling up the probe rod: and after the air release step is finished, pulling all the rest probe rods away from the ground.
6. The construction method for static pressure methane exhaust according to claim 1, wherein the step of discharging methane is followed by steps of sealing holes, backfilling construction holes and recovering pavement, and the steps of sealing holes, backfilling construction holes and recovering pavement comprise:
firstly, filling the discharge hole with cement slurry from the bottom of the discharge hole upwards;
and then backfilling, tamping and rolling the construction holes excavated and explored manually according to municipal requirements, and restoring the pavement according to the original appearance.
7. The construction method of biogas static pressure exhaust according to any one of claims 1 or 5, characterized in that the pressure of biogas discharge is less than 0.05MPa, and the flow rate is less than 1.5m3And stopping methane discharge at the time of/h.
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