The trench excavation depth of this contract section is around 4 meters. As the construction area is located in the main street and the water table is high. There is no condition for sloping excavation. It is proposed to use the method of straight trench excavation supported by well-point precipitation and driven sheet piles to carry out the construction.
The first step is to remove the structures, roadway slabs and pavement within the pipeline route. The old pavement and concrete structures are removed mechanically. Sidewalk slabs are removed manually, and the old slabs are protected for reuse.
1. Construction of well-point precipitation
(1) equipment:
①, well-point pipe: φ60, wall thickness of 3.0mm seamless steel pipe or galvanized pipe, 6m long
around 6m
, one end of the thickness of 4.0mm welded to the steel plate, in this end of the 1.4m-long range, the wall of the pipe drilling φ15mm small round holes, the distance between holes for 25mm, the outside of two layers of filters, the filter is made of steel plate with the thickness of 4.0mm. Two layers of filter screen, the filter screen using woven cloth, and then wrapped in a layer of larger mesh nylon wire mesh, every 50 ~ 60mm with No. 10 lead wire tied together, the other end of the filter pipe and the well point pipe for connection.
②, connecting pipe: transparent pipe and well point pipe and the main pipe connection, using No. 8 lead wire tied, should be tightened to prevent air leakage.
③, the main pipe: φ100 ~ 120 steel pipe, wall thickness of 4.0mm, with a flange plus rubber gasket connection to prevent air and water leakage.
④, pumping equipment: according to the design of the vacuum pump, as well as unit fittings and water tank.
⑤, water gun: φ60 × 5 seamless steel pipe, the lower end of the welded a φ16 gun nozzle, the upper end is bent at about a right angle, and out of the impact pipe, and high-pressure hose connection.
(2) Materials:
Coarse sand shall not be used in the sand, and the use of fine sand is strictly prohibited to prevent clogging of the mesh of the filter pipe.
(3) technical preparation:
①Detailed review of the engineering geological survey report, understand the engineering geological situation, analyze the technical problems that may arise in the process of precipitation and the measures taken.
②, hole drilling equipment and pumping equipment inspection.
(4) well point installation
①, installation procedures: well point positioning → installation of high-pressure pumps → drilling holes for installation of buried well point pipe → layout and installation of the main pipe → connection of the well point pipe and the main pipe → installation of pumping equipment → test pumping and inspection → formally put into the descending procedure.
②, well point pipe buried: according to the construction unit to provide the measurement of the control point, measurement and placement of the line to determine
define the location of the well point, and then in the well position first dug a small pit, about 500mm deep, in order to facilitate the impact of the hole when the collection of water, buried pipe when the filling of sand, and the use of guttering will be connected to the pit and the collection of pit, in order to drain the excess water.
③, the steel pipe water gun aligned with the location of the well point, start the high-pressure water pump, water pressure control at 0.4 ~ 0.8MPa, in the water gun high-pressure water jets under the impact of the steel pipe began to sink, and constantly raise and lower the steel pipe and the water gun. General sandy clay, according to experience, the steel pipe fall within 1000mm, in the water jet and steel pipe under the action of the punch, about 20 ~ 30min time, the well point tube can be sunk 5m or so, if you encounter a thicker pure clay, sinking time to be prolonged, at this time you can increase the pressure of the high-pressure pump to accelerate the sinking speed of the tube. Impact hole diameter should be 100 ~ 150mm, to ensure that there is a certain gap between the pipe wall and the well point pipe, in order to fill the gravel,
Punching depth should be lower than the design depth of the filter pipe placement of more than 500mm, in order to prevent the impact of the steel pipe lifting
Pulling out part of the soil collapsed, and so that the bottom of the filter pipe there is enough gravel.
The impact pipe should be kept vertical when moving up and down, so as to keep the wall of the well point precipitation well vertical, if encountered in the impact of larger stones and bricks, there will be tilted phenomenon, at this time into the diameter of the hole should try to keep the same up and down.
After the well hole impact molding, the upper end of the well point pipe should be plugged, between the well point pipe and the hole wall filled with gravel filter layer. Sand and gravel must be coarse sand to prevent clogging of the mesh of the filter tube, the sand and gravel filter layer filled with quality directly affects the effect of light well point precipitation.
After filling the well point with sand, 1.0~1.5m below the mouth of the well is sealed and compacted with clay to prevent air leakage and reduce the effect of precipitation.
④, pipeline installation
First along the well point pipeline outside, laying water collection hair pipe, and with rubber pad bolts to connect the dry pipe, the trunk pipe connected to the water tank pump, and then pull out the well point pipe on the end of the cork, with the hose and the main pipe connected to the main pipe, and then 10 # lead wire tied to prevent pipeline is not tight leakage and reduce the vacuum of the entire pipeline. The slope of the main water flow according to the slope to the pump room 5 ‰ slope and brick will be the main pipe pad. And do a good job of winter precipitation frost insulation.
⑤, check the pipeline
Check the collection of water under the tube and well point tube connected to the hose of the various joints in the test pumping whether there is a leakage phenomenon, found that this situation should be reconnected or plugged with putty, re-tighten the flange bolts and the hose of the lead wire until there is no air leakage. In the formal operation of the pumping must be carried out before the test pumping, in order to check whether the pumping equipment operation is normal, whether there is air leakage in the pipeline. Install a vacuum gauge on the water pump inlet pipe and a pressure gauge on the water pump outlet pipe. In order to observe the depth of precipitation, whether to achieve the depth of precipitation required by the construction organization design, set up an observation well point in the center of the pit, in order to measure the water level through the observation well point, and depict
the precipitation curve.
During the trial pumping, the vacuum degree of the whole pipe network should be checked, and it should reach 550mmHg (73.33kPa) before it can be officially put into pumping.
6, pumping
Trial pumping after all the installation of light well point pipe network. When the pumping equipment operation is normal, the entire pumping pipeline without air leakage, can be put into normal pumping operations. Earthwork can be excavated after 3d of precipitation.
2. Excavation trench
(1) The width of the bottom of the trench should be the outer diameter of the pipe +0.4m.
(2) When the trench is excavated, the elevation of the basement should be strictly controlled, and it should not be over-excavated or the base surface should not be disturbed. Excavator digging to 20cm from the base, using manual continue to excavate until the elevation.
(3) The bottom of the trench shall not be flooded.
(4) Excavation trench quality standards:
1) loose soil, silt, large stones and other debris must be removed from the bottom of the trench, to keep the bottom of the trench is not flooded.
2) allowable deviation of the trench see table:
item item allowable deviation inspection frequency inspection method
scope points
1 elevation of the bottom of the trench-30mm between the two wells 3 with a level meter measurements
2 bottom of the trench centerline is not less than the provisions of the centerline of the two wells between the 6 hung with a ruler,
each side of the width of each side of the counting 3 points
3 trench slope is not steeper than specified between the two wells 6 with a slope ruler test,
3 points per side
3. Pipeline foundation (20cm thick dry paving gravel foundation)
(1) pipeline foundation materials and thickness should be in line with the design of the design of the project design requirements of the construction drawings.
(2) The foundation shall be compacted and the surface shall be flat. Pipeline foundation in the interface parts, should be reserved groove. In order to interface operation, interface is completed, then fill with the same material.
(3) Pipeline foundation quality standards
1) Pipeline foundation shall not be laid on silt or loose fill.
2) Pipeline foundation should have a flat surface and be straight between two wells.
3) Pipeline foundation
Allowable deviation is shown in the table:
Order Item Allowable Deviation Inspection Frequency Inspection Method
Scope Points
1 Foundation centerline +10mm10m2 Hanging the centerline with a ruler,
Width of each side of the 0mm per side counted as 1 point
2 Foundation thickness +10mm10m2 Measurement with a ruler,
0mm each side of 1 point
3 foundation elevation +10mm10m2 measured with a level meter,
-20mm each side of 1 point
4. Pipeline Laying
(1) Laying Pipe
1) to be used in the pipe section should be carried out in accordance with product standards for section-by-section quality inspection, and those that do not meet the standards shall not be used. Those who do not meet the standard shall not be used, and should be well marked, and dealt with separately.
2) Pipe section on-site handling is generally available for manual handling, handling must be gently lifted and put down. It is strictly prohibited to drag the pipe on the ground.
3) Under the pipe can be carried out manually, by the ground personnel to pass the pipe to the bottom of the trench construction personnel. For large excavation trench, non-metallic rope can also be used to tie the ends of the pipe body, to maintain the balance of the pipe body at a constant speed slip, so that the pipe is placed smoothly in the trench, it is strictly prohibited to the pipe to the edge of the groove tumbling into the groove. Crane down the pipe, the application of non-metallic rope fastening, is strictly prohibited skewer lifting.
4) pipe should be socket in the direction of water flow, the socket against the direction of water flow installation, installation is generally carried out by the downstream to the upstream.
5) The pipe can be cut off by hand saw according to the required length, and the break should be trimmed.
(2) Rubber ring interface
1) The location of the rubber ring should be placed in the slot between the second and third bars of the pipe socket.
2) When interfacing, first clean the inner wall of the socket and apply lubricant on the inner wall of the socket and the rubber ring of the socket, then align the center axis of the socket end.
3) interface method: a person with cotton yarn rope hanging socket B pipe, another person with a long pry bar diagonally inserted into the foundation, and against the center of the end of the pipe end of the cross-file plate, and then force the B pipe socket slowly inserted into the socket of the A pipe to the intended position.
4) After the pipeline interface, the elevation and straightness of the pipeline should be reviewed to make it conform to the design requirements.
5) Quality standard of pipe laying and interface
①, the pipe should be straight, the slope of the bottom of the pipe should be in accordance with the design, and there should be no backwater. Allowable deviation of the pipeline laying line is shown in the table:
Item Item Allowable Deviation
1 centerline 20mm
2 bottom elevation +20mm, -10mm
3 socket socket outer gap between the amount of <9mm
②, the interface rubber ring in place, there are two ways to test:
One is the socket end, the rubber ring in place of two ways to test:
2, the interface rubber ring in place:
2, the interface rubber ring in place:
2, the pipe should be straight. p>One is in the socket end of a certain position (generally about 23cm long) to mark the line, the installation of the marking line to check whether it is in place.
The second is to listen to the sound, generally in place, the socket and socket contact will sound impact.
Three pounds of water test quality standards
Pressure piping must be based on the design of water pressure requirements for the pound of water test. Pound of water test using sampling methods.
5. check well construction
(1) sewage check wells of brick masonry must ensure that the mortar is full, straight gray joints, there shall be no through joints, the wall must be cleared of surface dirt, floating ash, etc. before treatment. Flow channel and well wall masonry at the same time, the height of the flow channel: sewage well and pipe top flat. Flow channel in the well should be smooth, there shall be no construction debris and other debris. The inner wall of the well is plastered with 20mm thick 1:2.5 cement mortar on D/2+200mm (D: pipe diameter) on the flow channel, and hooked with 1:2 waterproof cement mortar above. In case of groundwater, the outer wall of the well is plastered with 20mm thick 1:2 waterproof cement mortar to 500mm above the groundwater level. the well ring is made of C30 concrete, and the well cover and seat ring are installed with 1:2 cement mortar and plastered with triangular gray, and the top surface of the well cover is leveled with the road surface. The steel fiber well cover and seat ring must be intact, smoothly installed and correctly positioned. The inspection well of this project adopts closing type.
Mortar using mechanical mixing, mixing time shall not be less than 3 minutes, mortar should be mixed with the use of, generally within 3 hours, the use of overnight mortar is strictly prohibited.
The permissible deviation of inspection wells and inspection methods are shown in the following table:
Items of permissible deviation (mm) inspection frequency inspection method
Well body size ± 20 per seat / 2 points with a ruler
Well cover and the roadway elevation difference of the non-roadway ± 20 per seat / 1 point with a ruler
Roadway ± 5
Bottom of the elevation of the well D≤1000mm ± 10 per seat / 1 point with a level meter
D>1000mm ± 15 per seat / 1 point with a level meter
6. water closure (sewage pipeline requirements)
pipeline installation is completed before covering the soil, shall be required to carry out water closure test in accordance with the requirements of the acceptance specification for the construction of the leakage is confirmed in the specification allowable value range before covering the soil backfill. When the end of the pipeline interface work after the first release of water immersion 24 hours, visual inspection of no obvious leakage can be done before the water closure test, and should be carried out before the backfill, in order to observe the leakage of the pipeline and the interface and to take measures to plug the leakage, in order to save the test work, can also be selected a number of wells together with the water closure test, but it is appropriate to a section of a pipe with a well, it is not appropriate to test the pipe not to try the wells.
According to the technical requirements of the water closure test test and timely record of water seepage, observation of leakage points, determination of water seepage time shall not be less than 30 minutes.
After passing the water closure test, backfill immediately:
7.trench backfill
(1) trench backfill should be in the pipeline after the acceptance of concealed works. Trench backfill should be timely, to prevent the pipeline exposure time is too long to cause damage.
(2) Trench backfilling should follow the following regulations:
1) Within 70cm of the top of the pipe, it must be backfilled manually, and mechanical bulldozing backfilling is strictly prohibited.
2) backfill from the bottom of the pipe and the foundation of the combination of parts, along the pipe chest cavity on both sides of the symmetrical layer backfill and tamping, each layer of backfill height of no more than 20cm, until the top of the pipe above 30cm. the quality of backfill material should be in line with the design requirements.
3) rolling machinery rolling, above the top of the pipe re soil thickness should not be less than 70cm.
(3) trench re soil compactness standards:
1) trench backfill coarse sand dry weight see table:
Order item dry weight test frequency test method
Range Points
1 thorax part of the ≥16KN/m3 Two wells each layer of a group with ∮16 steel 0.7m
(3 points) self-fall test from a height
2 Above the top of the pipe ≥16KN/m3 Two wells each layer of a group with #16 steel 0.7m
500mm (3 points) self-fall test from a height
2) trench backfill compactness:
①, thorax backfill compacted in the roadway under surface
In other soil surface area: 90%
②, ditch (pipe) above the top of the backfill, in the depth of 70cm immediately above the top of the pipe, in order not to cause damage to the ditch compaction machinery (pipe), can be divided into thin layers of manual tamping to the specified compactness.
8. Pipe
(1) general
1) pipe, rubber ring and other materials, should be in line with the current product standards, with the quality inspection department's product certification and product performance specifications, and should indicate the manufacturer, specifications and production date.
2) socket interface sealing rubber ring, must be with the pipe specifications.
(2) the quality of the pipe
1) the pipe requires the appearance of the same color, smooth and flat inner wall. Pipe body shall not have cracks, bar connection defects shall not exceed 2, the mouth of the pipe shall not be with broken, cracked, deformed defects.
2) The end face of the pipe should be flat, perpendicular to the axis of the center of the pipe, the axis shall not have obvious bending appears. Pipe socket outer diameter, socket inner diameter of the size and garden must comply with the provisions of product standards.
3) pipe internal pressure strength and stiffness should meet the design requirements.
4) pipe interface with rubber ring performance, size should meet the design requirements. Rubber ring appearance should be smooth and flat, there shall be no air holes, cracks, roll wrinkles, broken, heavy skin and seam phenomenon.
9. Loading and unloading, transportation and stacking
(1) pipe, pipe fittings in the loading and unloading, transportation and stacking should be avoided, and is strictly prohibited throwing.
(2) When the pipe is transported in batches, the socket, socket should be staggered in layers, and should be bundled securely.
(3) pipe stacking should be shaded, socket and socket should be spaced flush arrangement, the ends with wooden wedges plug secure.
(4) rubber ring in the preservation and transportation, shall not be damaged.
10. Removal of support
Removal of steel sheet pile support should comply with the following regulations:
(1) backfill reaches the required height before pulling out the steel sheet pile;
(2) backfill the pile hole in time after pulling out the steel sheet pile;
(3) take measures to fill the pile hole when backfilling, and when sand is used to fill the pile hole, it can be flushed to help the sinking; when there is a requirement to control the ground settlement, it is necessary to take measures to fill the pile hole. When it is required to control the ground settlement, it is appropriate to take measures of grouting while pulling out the pile.
11, road, road plate repair
Pipeline project after the end of the tight schedule for road repair work. The content of the repair work is mainly 150m2 of the two gray stone road base layer; 150m2 of asphalt concrete road surface layer; 100m of the side stones and 1360m2 of the sidewalk board paving. Sidewalk plate using the original demolition of the material, such as defects in addition to the purchase of the same type and color of the supplement.
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