CN116591476A - Inverted siphon prestressed anchor cable construction method - Google Patents

Abstract

The invention discloses an inverted siphon prestressed anchor cable construction method, which comprises the following steps: when the anchor cable sleeve is installed, firstly installing anchor cable sleeves pre-embedded in the press piers, and then installing anchor cable sleeves between the press piers, wherein the anchor cable sleeves are welded; the anchor cable pipeline positioned in the ballast is fixed by adopting positioning steel bars, the grid of the positioning steel bars is square, and the clearance size is 2-3 mm greater than that of the prestressed reinforcement pipeline; cutting by adopting a grinder when the anchor cable is fed, carding and straightening according to the number of the prestressed duct steel bundles after feeding, tightly wrapping one end penetrated by the steel bundles by using a transparent adhesive tape, manually matching a winch for penetrating the steel bundles, penetrating the steel bundles from one end wrapped by the adhesive tape, checking whether the lengths of the exposed beam bodies of the steel bundles at two ends meet the working length of a jack by 55cm after the anchor cable is penetrated, and numbering the penetrated anchor cable after meeting the requirements; and then tensioning the prestressed anchor cable and grouting the sealing anchor.

Description

Inverted siphon prestressed anchor cable construction method

Technical Field

The invention relates to the field of building construction, in particular to a construction method of an inverted siphon prestressed anchor cable.

Background

The length of the steel pipe arch prestressed anchor cable of the No. 1 inverted siphon suspension section reaches 157 meters, and the inverted siphon prestressed tensioning is performed by adopting common and conventional tensioning equipment, but the length of the inverted siphon prestressed anchor cable is longer, and secondary inverted jacking (limited by the tensioning stroke of a jack) is performed in the tensioning process.

Disclosure of Invention

In order to solve the problems, the invention provides a construction method of an inverted siphon prestressed anchor cable.

In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:

the construction method of the inverted siphon prestressed anchor cable comprises the following steps:

s1, installing anchor cable sleeve

The 1# inverted siphon anchor cable sleeve is made of Q345D steel pipes, the wall thickness is 12mm, the diameter of the sleeve is 150mm, installation is carried out according to the construction progress section by section during installation, the anchor cable sleeves pre-buried in the 27# anchor cable sleeve, the 28# anchor cable sleeve and the 29# anchor cable sleeve are firstly installed, and then the anchor cable sleeve between the anchor cables is installed, and the anchor cable sleeve is welded;

the anchor cable pipeline positioned in the ballast is fixed by adopting positioning steel bars, the grid of the positioning steel bars is square, and the clearance size is 2-3 mm greater than that of the prestressed reinforcement pipeline;

the installed pipe must meet the following requirements: the allowable deviation of the pipeline coordinates in the long direction is 30mm, the allowable deviation in the high direction is 10mm, and the allowable deviation of the pipeline spacing in the same row is 10mm;

s2, blanking and beam penetrating of steel strand

Removing moisture-proof package of the bundled anchor cable outside the anchor cable in a flat field, covering the anchor cable with a special anchor cable cage, wedging the end face of the coiled anchor cable with the cage by square timber and wooden wedges, removing steel strips bound on the anchor cable, and beginning to withdraw the inner core;

Cutting by adopting a grinder when the anchor cable is fed, carding and straightening according to the number of the prestressed duct steel bundles after feeding, and tightly wrapping one end penetrated by the steel bundles by using a transparent adhesive tape to prevent the pipeline from being damaged when passing through;

the wire harness is threaded by adopting a manual winch, one end of the adhesive tape is threaded, the prestress rib passes through the pipeline with uniform force and consistent rhythm, and the wire harness is prevented from impacting the pipe wall when the prestress rib is in large and small force, and the wire harness is prevented from damaging the pipeline, so that the wire harness is difficult to continue; after the anchor cable is penetrated, checking whether the lengths of the exposed beam bodies of the steel bundles at two ends meet the working length of the jack by 55cm or not, numbering the penetrated anchor cable after meeting the requirements, and ensuring that the anchor cable does not cross and wind when penetrating the anchor cable in the pipeline during the later stretching;

s3, installing an anchor backing plate and a working anchor plate

Before installing the anchor backing plate, removing the rubberized fabric wrapped on the end part of the steel strand, checking whether the lengths of the exposed steel strands of the pore channels are equivalent, and ensuring that the lengths of the exposed steel strands of the pore channels at each end meet the working length of the jack;

when the anchor backing plate is installed, according to the arrangement of hole sites on the anchor backing plate, penetrating into the anchor backing plate holes from bottom to top in batches, and ensuring the consistent numbering sequence of the two tensioning ends during installation;

s4, tensioning the prestressed anchor cable

Calculating the relation between the tension under the anchor and the reading of the pressure gauge and the relation between the tension under the anchor and the elongation of the steel bundle according to a < calibration certificate > issued by a detection unit, a steel strand mechanical property test report, design control stress, the number of the steel strands of a pore canal and related data, and compiling a tensioning calculation book, wherein the tensioning calculation book can be implemented after review and confirmation by a master engineer;

According to the tensioning calculation book, jack numbers, pressure gauge numbers, steel bundle numbers, initial tensioning stress and control stress are used for compiling a small form in a simplified text expression mode, and a transparent adhesive tape is used for being attached to the center position of the front face of the oil gauge, so that tensioning operators can conveniently use the pre-stressed anchor cable to tension the steel pipe arch rib concrete cube until the strength reaches 100% of the designed concrete strength level, and the tensioning operation is carried out after the age is not less than 28 days;

before tensioning, the jack after verification, a matched pressure gauge, a ZB4-500 piezoelectric oil pump and a high-pressure oil pipe are installed, and each interface part is cleaned and filled with a copper sealing ring; adding a proper amount of L-HM32 hydraulic oil into the oil pump, cleaning the oil tank, pump body pipelines and the like before adding the hydraulic oil, and filtering the hydraulic oil; recheck each connection site: whether the oil pipe has cracks, whether the joint is firm, whether the screw thread specification of the joint is consistent, whether an oil delivery nozzle connected with a main pressure gauge is consistent with the ejection direction of a jack piston, and the like; after the connection state is confirmed to be correct, the oil pump is started, and the air in each oil accommodating space of the oil pump and the air in the jack oil cylinder are removed under the idle state through each control valve so as to avoid the phenomena of unstable pressure, insufficient flow, sudden jump of the piston and the like caused by the air;

Before the jack is in place, carefully checking whether the anchor backing plate is vertical to the pore canal, the grouting holes of the anchor backing plate are smooth, the working clamping pieces are normally installed, the number of steel bundles and the working length are equal, and installing the jack and the tool anchor assembly after the jack is correctly confirmed; the jack stretches the prestressed steel bundles in sequence: mounting left N1-right N1 in place; firstly, an anchor cable sequentially penetrates into a limiting plate, and a 100mm position at the tail end of the anchor cable is bound into a bundle by a binding wire, so that the steel hinge wire ends are prevented from being scattered due to the fact that the steel hinge wire ends prop against connecting positions such as an inner cylinder of a jack when an installation jack penetrates in;

when the tool anchor is installed, the hole position of the tool anchor corresponds to the hole position of the limiting plate, the dislocation and twisting of the prestressed tendons between the limiting plate and the tool anchor are strictly prevented, finally, the clamping piece and the baffle are installed, the tool clamping piece is uniformly pushed into the tool anchor and lightly squeezed, the position of the jack is adjusted through a chain block on the hanger, the jack, the tool anchor and the like are vertical to the stretching section at the plate end, and the axes of the pore canal, the anchor and the jack are basically coincident;

in the operation process, two jacks are adopted for symmetrical and synchronous tensioning, a tensioning operator mutually reports oil meter reading and oil cylinder elongation through an interphone, the allowable error of synchronous tensioning force of the two jacks is controlled to be +/-2%, the oil cylinder elongation error is controlled to be within 10mm, the holding time is kept for 5 minutes until the two ends are tensioned to the under-anchor control stress, and the anchoring can be realized after the stress is stable; the anchoring is realized by opening an oil return valve, retracting the steel hinge wire inwards and bringing the steel hinge wire into a working clamping piece; when the unloading valve is opened, the strength is slow, the oil return is uniform, and when the pointer of the pressure gauge returns to 2MPa, the extension of the oil cylinder is measured, so that the retraction of the tapping beam is calculated;

The stretching adopts double control of stretching force and stretching amount, the stretching force is controlled in a main control mode, the proportion and control of stretching stress and stretching amount are paid attention to in real time in the stretching process, when the prestress steel beam reaches the designed stretching force, the error between the actual stretching amount and the theoretical stretching amount is controlled to be within +/-6%, the stretching operation is stopped in time when the middle is abnormal, the reason is found out, and the operation can be performed after the problem is solved;

the cable tensioning procedure is as follows:

0 → initial stress 20% σk → 25% σk → 50% σk → 75% σk → 100% σk holding for 10min → anchoring; the prestressed tendons can be anchored after the tension control stress is stable, the top surfaces of the clamping pieces after anchoring are flush, the mutual dislocation of the prestressed tendons is not more than 2mm, and the exposed height is not more than 4mm;

after tensioning, checking the conditions of broken wires and sliding wires of the anchor cable, wherein the number of the broken wires and the sliding wires in the same component is not more than 1% of the total number of the steel wires, filling a pre-stressed anchor cable tensioning field quality inspection report sheet after inspection and confirmation, sawing redundant anchor cables at the end part by using a grinding wheel saw, and ensuring that the exposed length of the anchor cable is more than 50mm after cutting;

s5, sealing anchor grouting

After tensioning and anchoring the prestressed tendons, finishing grouting engineering, pressing slurry into the anchor cable sleeve from one section to the other end according to the principle of 'low in and high out', namely arranging a grouting hole at a lower position of an anchor backing plate at one end, arranging an exhaust and slurry outlet hole at a higher position of the anchor backing plate at the other end, and plugging the grouting hole and the slurry outlet hole in time after grouting is finished when slurry with the same concentration as the grouting hole is fresh Kong Maochu in the grouting process, and indicating that grouting in the whole pore canal is finished;

1) Flushing duct

Before grouting, the pore canal is flushed by using pressurized water, sundries such as powder slag and the like in the pore canal are removed, the smoothness of the pore canal is ensured, accumulated water in the pore canal is blown off by using an air compressor air pipe after flushing, but the pore canal is kept moist to ensure that cement paste is well combined with the pore wall, and in the flushing process, if phenomena of water leakage and water leakage are found, the blocking leak is treated;

2) Cement paste mixing

(1) The cement paste has enough fluidity, and the fluidity is 150-200mm, so that the grouting requirement can be met;

(2) the water for the water mortar is clean water, does not contain substances harmful to cement or prestressed anchor cables, and does not contain more than 500mg of chloride ions per liter of water;

(3) additive agent

In order to prevent the cement slurry in the pore canal from generating volume shrinkage, an expanding agent-aluminum powder is permeated into the cement slurry, wherein the permeation amount of the aluminum powder is 0.01 percent of the cement dosage, or the expanding agent of the UEA is permeated into the cement slurry, and the permeation amount of the UEA is 10-12 percent of the cement dosage;

3) Stirring of cement paste

Firstly adding water into a stirrer, starting the stirrer, then adding cement and an expanding agent, and calculating the water quantity and the additive quantity by taking the weight of the cement as a base number in material metering; the stirring time should ensure the uniform mixing of the cement paste, generally not less than 2min, the stirring of the cement paste should be uninterrupted in the grouting process, and the cement paste should be circulated in the stirrer and the grouting machine when the grouting process is short-paused, so as to prevent the pipeline and the switch valve from being blocked after precipitation;

4) The main technical indexes of the cement slurry are as follows:

(1) the cement mark is not lower than 42.5, and the water-cement ratio is 0.38-0.45;

(2) the bleeding rate is controlled at 2% after the cement paste is mixed for 3 hours, and the whole bleeding is absorbed after the cement paste is supplemented in 24 hours;

(3) the free expansion rate of the expanding agent added into the cement slurry is less than 10%;

(4) the consistency of the cement paste is controlled between 14 and 18 seconds;

(5) more than 500mg of chloride ions or any other organic matters are not needed in each liter of water;

5) Pressure injection of cement paste

After the prestressed anchor cable is tensioned, grouting the pore canal within 3 days, wherein the grouting of the pore canal is to utilize a grouting pump to press and pour cement paste into the pore canal of the prestressed anchor cable so as to fill the gap between the prestressed anchor cable and the pore canal, and the prestressed anchor cable and the concrete are firmly bonded into a whole; grouting the pore canal in time, wherein the grouting adopts a piston grouting pump, the grouting pressure is based on ensuring that cement paste pressed into the hole is compact, the maximum grouting pressure is controlled to be 0.3-0.4MPa, and when the grouting is adopted for one time, the pressure is properly increased, but the maximum grouting pressure is not more than 1.0MPa;

grouting is carried out slowly and uniformly without interruption, the starting pressure is small, the pressure is gradually increased, the grouting is carried out until the exhaust holes at the other end of the pore canal are full and the thick slurry is discharged, and then a bolt plug is adopted to block a slurry outlet; in order to ensure that the pore canal is filled with mortar, when the weight of the slurry discharged from the slurry outlet is the same as that of the injected slurry, the slurry can be shielded, the slurry shielding pressure is preferably 0.4MPa, the slurry shielding time is preferably 25min, the slurry inlet valve is closed, the slurry is returned by a slurry pressing machine, and after the cement slurry is solidified, the connecting joint is disassembled and cleaned immediately;

In order to check the actual density of cement slurry in the pore canal, checking the compaction condition of the cement slurry from a checking hole after grouting, if not, performing secondary grouting in time;

after grouting is completed, the strength of the reserved slurry test piece reaches 35MPa, and then the next working procedure construction can be carried out.

Further, in step S4, in the working process, the loading and unloading stress of the oil pump and the jack is stable, so as to avoid impact, and the oil pump and the jack are strictly controlled according to the oil meter readings reached in each stage in the < tensioning calculation book >.

Further, in step S4, the in-situ tensile elongation value is measured:

1) Starting oil pumps at two ends, closing a main oil delivery valve, supplying oil to an oil cylinder of a jack, opening the main oil delivery valve after the oil cylinder exposes out of a cylinder body for about 20mm, stopping the oil pump, installing a limiting plate, the jack and a tool anchor assembly, installing the jack after the oil cylinder exposes out of 20mm, and ensuring accurate measurement of the elongation of the oil cylinder when the tensile force reaches initial stress, and simultaneously, preventing the problem of easy disassembly of the jack due to tensile sliding wires;

2) Starting the oil pump again, closing the main oil feeding valve, feeding oil to the jack oil cylinder, stopping feeding oil to the jack oil cylinder when the pressure gauge reads the initial stress (20% sigma k), measuring the length L1 from the shell at the end part of the jack to the scale, and marking the position of the clamping piece of each steel strand tool so as to more intuitively observe any slippage of each steel strand;

3) Continuously supplying oil to the jack cylinder, stopping supplying oil to the jack cylinder when the pressure gauge reads 25% sigma k, and measuring the length L2 from the shell at the end part of the jack to the scale;

4) Continuously supplying oil to the jack cylinder, stopping supplying oil to the jack cylinder when the pressure gauge reads to 50% sigma k, and measuring the length L3 from the shell at the end part of the jack to the scale;

5) Continuously supplying oil to the jack cylinder, stopping supplying oil to the jack cylinder when the pressure gauge reads 75% sigma k, and measuring the length L4 from the shell at the end part of the jack to the scale;

6) Continuously supplying oil to the jack cylinder, when the reading of the pressure gauge reaches 100% sigma k, holding the load (keeping the reading of the pressure gauge unchanged) for 10min, and measuring the length L5 from the shell at the end part of the jack to the scale;

7) Stopping the oil pump, opening the unloading valve, and measuring the length L6 from the end shell of the jack to the scale when the pointer of the pressure gauge returns to 2 MPa;

8) Each parameter was calculated according to the following formula:

20% tensile force to 100% tensile force elongation value Δl1=l5-L1;

an initial stress 20% tensile elongation Δl2=l2-L1;

the actual stretching value Deltals=DeltaL1+DeltaL2 of the prestressed tendon stretching;

anchoring retraction = L5-L6-L, where L is jack working length extension;

9) And filling in a prestress tensioning original record form according to the description, and mastering double control by a field tensioning construction technician.

The invention has the following beneficial effects:

compared with the traditional anchor cable process, the anchor device used in the construction method can replace fixed oblique iron and anchors in the traditional anchor cable process, the two processes are optimized into one process, and meanwhile, the device can realize secondary inverted jacking adjustment through a jack, so that the purpose of meeting stretching elongation is achieved; and the anchor cable is convenient and practical to stretch.

Drawings

Other features, objects and advantages of the present invention will become more apparent upon reading of the detailed description of non-limiting embodiments, given with reference to the accompanying drawings in which:

fig. 1 is a flowchart of a process for pre-stressing a steel pipe arch in a suspension segment according to an embodiment of the present invention.

Detailed Description

The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the present invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications could be made by those skilled in the art without departing from the inventive concept. These are all within the scope of the present invention.

1.1 engineering overview

Three branches are dry 1 st standard section (pile number 0+000-8+238.32), total length 8.238km, wherein the underdrain 4 seat (1 # underdrain length 57.74m, 2# underdrain length 22.40m, 3# underdrain length 22.17m, 4# underdrain length 7.62 m), tunnel 3 seat (1 # tunnel length 1081.8m, 2# tunnel length 343.52m, 3# tunnel length 2927.08 m), aqueduct 2 seat (1 # aqueduct length 65m, 2# aqueduct length 101 m), inverted siphon 1 seat (pile number: K4+ 620.71-K8+ 238.82).

The total tension of the prestressed anchor cable of the standard section is 1# inverted siphon 27# to 29# pier section steel pipe arch suspension section, the prestressed anchor cable is 2 bundles of 15 phi s15.2, the total tension force under the anchor is 3000KN, the control tension under the anchor cable of a single bundle is 1500KN, and the two ends of the steel pipe arch suspension section are symmetrically tensioned.

2 the basis for programming

(1) And (5) designing a drawing.

(2) Anchor rope for prestressed concrete (GB/T5224-2003)

(3) Anchor, clamp and connector for tendons (GB/T14370-2007)

(4) Anchor, clamp and connector application technical Specification for prestressed tendons (JGJ 85-2002)

(5) Construction Specification of prestressed anchor rope for Water and electricity Hydraulic engineering (DLT 5083-2010)

(6) Construction Specification for concrete Structure engineering (GB 50666-2011)

(7) Grouting material (agent) for highway engineering prestressed duct (JTT 946-2014)

3. Preparation for construction

3.1 Raw material and tensioning equipment preparation

(1) Anchor cable

The prestress system adopts II-level low-relaxation high-strength prestress ribs, and the product meets the GB/15224-2003 standard. Standard strength fpk =1860 Mpa, nominal diameter Φ=15.2 mm, nominal cross-sectional area 140mm2; ep=1.95×105Mpa.

(2) Anchor device

The anchoring system adopts a self-anchored wire drawing system. The anchorage device is M15-15 which accords with the regulations of anchorage devices, clamps and connectors for prestressed tendons (GB/T14370-2007) and anchorage devices for prestressed anchor cables for highway bridges, connector test methods and inspection rules (JT 329.2-1997).

(3) Jack and oil pressure gauge preparation

The prestress tensioning equipment adopts 2 YDC4000 penetrating hydraulic jacks (the numbers are 110# and 112# respectively), is provided with 2 oil pressure gauges (the numbers are 037391191# and 037399191# respectively), and is entrusted to detection, calibration and determination by engineering detection limited company of Lanzhou traffic university, and an oil pump linear regression equation is determined.

3.2 inspection and storage of raw materials

(1) Prestressed anchorage cable (Steel strand)

1) The number of the prestressed tendons is same as the number of the furnace and the tank, the specification of the prestressed tendons is same as the specification of the furnace and the tank, the production process of the prestressed tendons and the delivery state of the prestressed tendons are same as one batch every 60t, and less than 60t is counted by one batch, and each batch is subjected to sampling inspection once.

2) After the pre-stressed anchor cable enters the field, the material part informs a laboratory to sample and test, 3 discs are taken from each batch of anchor cables, a group of samples are intercepted from the normal part of the end part of the anchor cable selected by each disc to carry out surface quality, diameter deviation and mechanical property tests, and if each batch is less than 3 discs, the test is carried out disc by disc.

3) The appearance of the anchor cable is checked by a tensioning shift disc by disc, and the surface of the anchor cable cannot be provided with cracks, thorns, mechanical damages, iron scales and oil marks.

4) The anchor cable should prevent rust, pollution and bending in the transportation and storage processes, and must not be thrown from high positions when the anchor cable is assembled and disassembled, pollution and electric spark damage are avoided when the anchor cable is manufactured and installed, and the exposed part of the anchor cable is wrapped by a canvas sleeve after tensioning, so that rain is prevented from being poured. This item is jointly responsible by the material part and the tensioning work.

5) The anchor cable should be deposited on the bar-shaped concrete table in the movable steel bar shed according to the factory name, specification and grade in batches, the platform is 30cm higher than the ground, the water-proof and drainage facilities are arranged around, and the product identification and the inspection test state identification are made.

6) The elastic modulus difference of the anchor cables in different batches is directly used for the same pore canal within the range of 5GPa, and the average elastic modulus of the pore canal is used for calculating the elongation. Elastic modulus exceeding 5GPa prohibits use in the same tunnel. When the residual quantity of the anchor cable in the batch is less than the required quantity of a hole, the residual anchor cable in the batch is treated as a waste material.

(2) Anchor and clamp

1) The anchor and the clamp are subjected to the technical identification and the product identification of the above levels, before leaving the factory, the anchor and the clamp are inspected by a supplier according to the regulations, and a quality certificate is provided, so that the products in the same kind, the same material and the same production process condition and in the same batch can be regarded as the same inspection batch. The number of the anchor devices per acceptance batch is not more than 1000. The number of the inspection batches of the clamp is not more than 500.

2) When the anchor clamps enter the field, appearance inspection should be carried out one by one, cracks, flaws and rust cannot be caused, and the size cannot exceed the allowable deviation.

3) The anchor devices and the clamps are orderly stacked in a warehouse with good ventilation according to different specifications. During stacking, transporting, loading and unloading and construction of finished products, collision, stepping, throwing and dragging are strictly forbidden.

4) The same hollow slab should be manufactured by the same manufacturing plant, and the working anchors are not proper. The limit plate, the tool anchor and the working anchor are matched with the same production plant.

3.3 tensioning tool, pressure gauge and grouting tool

(1) The application of the prestress to the steel pipe arch of the suspension section is implemented and completed through a jack and an ultra-high pressure oil pump, a pressure gauge, an anchor, a steel beam and the like which are matched with the jack, and the tensioning of the prestress of the post-tensioning hollow slab is preferably realized by adopting a penetrating double-acting self-anchoring jack. The rated tensioning force of the tensioning jack is preferably 1.5 times the required tensioning force and must not be less than 1.2 times. The pressure gauge is preferably in a vibration-proof type, the maximum reading of the surface is 1.5-2.0 times of the tensile force, and the precision is not lower than one level. The oil tank capacity of the oil pump is preferably 1.5 times of the total oil delivery quantity of the tensioning jack, and the rated oil pressure is preferably 1.4 times of the oil pressure used. The working anchor of the steel pipe arch of the suspension section of the standard is an anchor with M15-15 specification, two YCQ4000 jacks and two ZB4-500 electric oil pumps are selected for tensioning, and a 1.5-level 0-50 MPa shockproof pressure gauge is adopted as the pressure gauge. The tensioning tool equipment is matched with an anchor product for use, and correction, inspection and calibration are carried out before use.

(2) The jack for tensioning and the pressure gauge are matched for calibration, and the running direction of the jack piston during calibration is consistent with the actual tensioning working state. Calibration should be re-performed when in one of the following cases.

1) The service time exceeds six months.

2) The number of stretching times exceeds 300.

3) During the use process, abnormal conditions occur to the jack or the pressure gauge.

4) After the jack overhauls or the fittings are replaced.

4 construction process and construction method

4.1 construction method and construction points

(1) Mounting anchor cable sleeve

The 1# inverted siphon anchor cable sleeve is made of Q345D steel pipes, the wall thickness is 12mm, the diameter of the sleeve is 150mm, the sleeve is installed according to the construction progress section during installation, the anchor cable sleeves pre-buried in 27#, 28#, 29# press piers are installed firstly, and then the anchor cable sleeve between the press piers is installed, and the anchor cable sleeve is welded.

The anchor cable pipeline that the prestressing force sleeve pipe should carry out careful visual inspection before the installation, the position should be accurate, round in order, is located the anchor rope pipeline of pier adopts the locating reinforcement fixed, and the locating reinforcement net is square, and the headroom size is greater than prestressing force reinforcement pipeline 2 ~ 3mm, and the locating net sets up according to the prestressing force reinforcing bar arrangement requirement, and the locating net is firmly connected with the pier reinforcing bar net, adopts spot welding to connect if necessary.

The installed pipe must meet the following table requirements.

Prestressed pipeline installation allowance deviation meter

(2) Blanking and bundling steel strand

The surface of the anchor cable must not be provided with substances such as lubricant, oil stain and the like for reducing the binding force of the anchor cable and concrete, the blanking length of the anchor cable is accurately calculated, and the factors such as the length of a pipeline, the length of an anchor clamp, the length of a jack, the exposed length after the anchor is anchored by a tool and the like are considered during calculation. The prestressed anchor cable of the standard section is symmetrically tensioned by two YCQ4000 jacks, and the blanking length of the anchor cable is +60cm multiplied by 2 of the length of the anchor cable sleeve pipeline.

The anchor cable should be laid in a flat field. Removing the moisture-proof package outside the bundled anchor cable, covering the bundled anchor cable by a special anchor cable cage, wedging the end face of the coiled anchor cable with the cage by square timber and wooden wedges, and removing steel strips bound on the anchor cable. The anchor cable is uncoiled from the inner core to be pulled out, and the anchor cable is prevented from being ejected out to hurt people when the anchor cable is uncoiled to be tapped.

And cutting by adopting a grinder during the blanking of the anchor cable, and strictly forbidding the cutting by adopting arc welding. In order to prevent uneven stress caused by disturbance of intertwining and stretching of the anchor cable during beam penetration and stretching, carding and straightening are carried out according to the number of prestressed duct steel beams after discharging. One end penetrated by the steel bundle is tightly wrapped by a transparent adhesive tape so as to prevent the pipeline from being damaged when passing through.

The wire harness is carried out by adopting a manual winch, one end of the self-winding adhesive tape penetrates, the prestress rib is uniform and consistent in strength when passing through the pipeline, the wire harness is prevented from impacting the pipe wall when being large and small, and the wire harness is prevented from impacting the pipe wall when being strong, so that the wire harness is damaged, and the wire harness is difficult to continue. After the anchor cable is penetrated, checking whether the lengths of the exposed beam bodies of the steel bundles at the two ends meet the working length of the jack by 55cm. And numbering the penetrated anchor cables after meeting the requirements, so that the anchor cables cannot cross and wind when penetrating through the anchorage device in the pipeline in the later stretching process.

(3) Installing anchor backing plate and working anchor plate

Before the anchor backing plate is installed, the rubberized fabric wrapped on the end part of the steel hinge line is removed, whether the lengths of the exposed steel hinge lines of the pore channels are equivalent or not is checked, and the lengths of the exposed steel hinge lines of the pore channels at the ends are ensured to meet the working length of the jack.

When the anchor backing plate is installed, the anchor backing plate penetrates into the anchor backing plate holes from bottom to top in batches according to the arrangement of hole sites on the anchor backing plate, and the serial numbers at the two ends of tensioning are ensured to be consistent during installation.

(4) Tensioning of prestressed anchor cable

The prestressed anchor cable of the standard section is 2 bundles of 15 phi s15.2, the total tension force under the anchor is 3000KN, the control tension force under the anchor of the single-bundle anchor cable is 1500KN, and the super-tension coefficient of the anchor cable of the concrete structure is 1.03-1.05 according to the standard requirement.

The stretching operation is implemented after the project department calculates the relation between the stretching force under the anchor and the reading of the pressure gauge, the relation between the stretching force under the anchor and the elongation of the steel bundle and the programming of the stretching calculation book according to the < calibration certificate > issued by the detection unit, the steel strand mechanical property test report, the design control stress, the number of the steel strands of the pore canal and the related data, and the total engineer reviews and signs. According to the tensioning calculation book, jack numbers, pressure gauge numbers, steel bundle numbers, initial tensioning stress and control stress are used for compiling a small form in a simplified text expression mode, and a transparent adhesive tape is used for being attached to the center position of the front face of the oil gauge, so that tensioning operators can conveniently use the pre-stressed anchor cable to tension the steel pipe arch rib concrete cube until the strength reaches 100% of the designed concrete strength level, and the tensioning operation is carried out after the age is not less than 28 days.

Before tensioning, the jack after verification, the matched pressure gauge, the ZB4-500 piezoelectric oil pump and the high-pressure oil pipe are installed, and each joint part is cleaned and filled with a copper sealing ring. An appropriate amount of L-HM32 hydraulic oil is added into the oil pump, and the oil tank, pump body pipelines and the like are cleaned before the hydraulic oil is added, so that the hydraulic oil needs to be filtered. Recheck each connection site: whether the oil pipe has cracks, whether the joint is firm, whether the joint screw thread specification is consistent, whether the oil delivery nozzle connected with the main pressure meter is consistent with the ejection direction of the jack piston, and the like. After the connection state is confirmed to be correct, the oil pump is started, and the air in each oil accommodating space of the oil pump and the air in the jack oil cylinder are discharged under the idle state through each control valve, so that the phenomena of unstable pressure, insufficient flow, sudden jump of the piston and the like caused by the air are avoided.

Before the jack is in place, whether the anchor backing plate is vertical to the pore canal or not is carefully checked, grouting holes of the anchor backing plate are smooth, working clamping pieces are installed normally, the number of steel bundles and working length are increased, and the jack and the tool anchor assembly are installed after the jack is correctly confirmed. The jack stretches the prestressed steel bundles in sequence: left N1→right N1 are installed in place. Firstly, an anchor cable sequentially penetrates into a limiting plate, and a 100mm position at the tail end of the anchor cable is bound into a bundle by a binding wire, so that when an installation jack penetrates in, a steel hinge wire head is prevented from propping against connecting positions such as an inner cylinder of the jack, and the like, so that the steel hinge wire head is prevented from being scattered.

When the tool anchor is installed, the hole position of the tool anchor corresponds to the hole position of the limiting plate, and the dislocation and twisting of the prestressed tendons between the limiting plate and the tool anchor are strictly prevented. And finally, installing clamping pieces and baffle plates, uniformly pushing the tool clamping pieces into the tool anchors and lightly squeezing the tool clamping pieces, and adjusting the positions of the jacks through the chain blocks on the hanging frame, so that the jacks, the tool anchors and the like are vertical to the stretching sections at the plate ends, and the axes of the pore canal, the anchorage device and the jacks are basically coincident.

In the operation process, two jacks are adopted for symmetrical and synchronous tensioning, a tensioning operator mutually reports oil meter reading and oil cylinder elongation through an interphone, the allowable error of synchronous tensioning force of the two jacks is controlled to be +/-2%, the oil cylinder elongation error is controlled to be within 10mm, the holding time is kept for 5 minutes until the two ends are tensioned to the under-anchor control stress, and the anchoring can be achieved after the stress is stable. The anchoring is realized by opening an oil return valve, retracting the steel hinge wire inwards and bringing the steel hinge wire into the working clamping piece. When the unloading valve is opened, the force is slow, and the oil return is uniform. When the pointer of the pressure gauge returns to 2MPa, the extension of the oil cylinder is measured, so that the retraction of the tapping beam is calculated.

In the working process of the oil pump and the jack, the loading and unloading stress aims at stability, and the impact is avoided. Strictly in terms of the oil meter readings reached at each stage in < stretch-draw calculation >.

The stretching adopts double control of stretching force and stretching amount. And (3) stretching force is controlled in a main control mode, and proportion and control of stretching stress and stretching amount are paid attention to in the stretching process. When the prestress steel beam reaches the design tensile force, the error between the actual extension and the theoretical extension is controlled within +/-6 percent. When abnormality occurs in the middle, the tensioning operation is stopped in time, the reason is found out, and the operation can be performed after the problem is solved.

Because the jack stroke used in the tensioning is 200mm, the actual tensioning elongation is about 270mm, the jack needs to be subjected to secondary cylinder pouring, the tensioning can be stopped when the jack cylinder body is exposed for 180mm for the first time, the oil gauge reading is recorded, the oil return anchor is subjected to cylinder pouring, then the secondary tensioning is performed, the oil gauge tensioning reading is read when the tensioning is stopped for the first time, the exposed length of the jack cylinder body starts to be recorded at the moment, and the tensioning is stopped when the oil gauge reading reaches the tensioning control force.

The cable tensioning procedure is as follows:

0→initial stress (20% σk) →25% σk→50% σk→75% σk→100% σk (10 min under load) →anchoring (p=1500kn is the design tension control force)

The prestressed tendons can be anchored after the tension control stress is stable. The top surfaces of the clamping pieces after anchoring are flush, the dislocation of the clamping pieces is not more than 2mm, and the exposed height is not more than 4mm.

After the tensioning is finished, the broken wire and the sliding wire condition of the anchor cable are checked, and the number of broken wires and sliding wires in the same component is not more than 1% of the total number of the steel wires. Filling in a pre-stressed anchor cable tensioning field quality inspection report sheet after inspection and confirmation, sawing redundant anchor cables at the end part by using a grinding wheel, and enabling the exposed length of the anchor cables to be more than 50mm after the cutting is finished.

In-situ tensile elongation value measurement (taking a two-end tensioning jack as an example):

1) And starting the oil pumps at two ends, closing the main oil delivery valve, supplying oil to the jack oil cylinder, and opening the main oil delivery valve after the oil cylinder exposes the cylinder body for about 20mm to stop the oil pump. And installing a limiting plate, a jack and a tool anchor assembly. The jack is arranged after the oil cylinder is exposed for 20mm, so that the oil cylinder elongation measurement is accurate when the tensile force reaches the initial stress, and meanwhile, the problem of jack treatment for easily disassembling the tensile sliding wire is solved.

2) And starting the oil pump again, closing the main oil feeding valve, feeding oil to the jack oil cylinder, stopping feeding oil to the jack oil cylinder when the pressure gauge reads the initial stress (20% sigma k), measuring the length L1 from the shell at the end part of the jack to the scale, and marking the position of the clamping piece of each steel strand tool so as to more intuitively observe any slippage of each steel strand.

3) And continuously supplying oil to the jack cylinder, stopping supplying oil to the jack cylinder when the pressure gauge reads to 25% sigma k, and measuring the length L2 from the shell at the end part of the jack to the scale.

4) And continuously supplying oil to the jack cylinder, stopping supplying oil to the jack cylinder when the pressure gauge reads to 50% sigma k, and measuring the length L3 from the shell at the end part of the jack to the scale.

5) And continuously supplying oil to the jack cylinder, stopping supplying oil to the jack cylinder when the pressure gauge reads to 75% sigma k, and measuring the length L4 from the shell at the end part of the jack to the scale.

6) And continuously supplying oil to the jack cylinder, when the reading of the pressure gauge reaches 100% sigma k, holding the load (keeping the reading of the pressure gauge unchanged) for 10min, and measuring the length L5 from the shell at the end part of the jack to the scale.

7) Stopping the oil pump, opening the unloading valve, and measuring the length L6 from the end shell of the jack to the scale when the pointer of the pressure gauge returns to 2 MPa.

8) 20% tensile force to 100% tensile force elongation value Δl1=l5-L1

An initial stress 20% tensile elongation Δl2=l2-L1;

actual stretching value Deltals=DeltaL1+DeltaL2 of prestressed tendon stretching

Anchoring retraction = L5-L6-L (jack working length extension)

9) And filling in a prestress tensioning original record form according to the description, and mastering double control by a field tensioning construction technician.

(5) Sealing anchor grouting

After the prestressed reinforcement is tensioned and anchored, grouting engineering should be completed as soon as possible. When the anchor cable sleeve is grouted, slurry is pressed from one section to the other end, namely, a grouting hole is arranged at the lower position of the anchor backing plate at one end, an exhaust hole and a slurry outlet hole are arranged at the higher position of the anchor backing plate at the other end, and when the slurry with the same concentration as the grouting hole is fresh in the slurry outlet Kong Maochu in the grouting process, the grouting in the whole pore canal is finished. And (5) plugging the grouting holes and the grouting outlet in time after grouting is completed.

1) Flushing duct

The pore canal is washed by pressurized water before grouting to remove impurities such as powder slag in the pore canal, so as to ensure the smoothness of the pore canal, and the accumulated water in the pore canal is blown off by an air compressor after washing, but the pore canal is kept moist so as to ensure that cement paste and the pore wall are well combined, and in the washing process, if water leakage and water leakage phenomena are found, the leak is blocked in time for treatment.

2) Cement paste mixing

(1) The cement paste has enough fluidity, and the fluidity is 150-200mm, so that the grouting requirement can be met.

(2) The water for the water mortar should be clean water, and does not contain substances harmful to cement or prestressed anchor cables, and the water per liter should not contain more than 500mg of chloride ions.

(3) Additive:

in order to prevent the cement slurry in the pore canal from generating volume shrinkage, the infiltration amount of the aluminum powder which is infiltrated into the cement slurry by the expanding agent (aluminum powder) is 0.01 percent of the cement dosage, or the infiltration amount of the UEA expanding agent is 10 to 12 percent of the cement dosage.

3) Stirring of cement paste:

the mixing proportion of cement paste is determined by trial and test before stirring, and can also be determined by the conventional mixing proportion. The cement paste is mixed, firstly, water is added into a stirrer, after the stirrer is started, cement and an expanding agent are added, and the water quantity and the additive quantity are calculated by taking the weight of the cement as the base number in material metering. The stirring time should ensure that the cement paste is uniformly mixed, generally not less than 2min, the stirring of the cement paste should be uninterrupted in the grouting process, and the cement paste should be circulated in a stirrer and a grouting machine when the grouting process is short-paused, so that the pipeline and a switch valve are prevented from being blocked after precipitation.

4) The main technical indexes of the cement slurry are as follows:

(1) the cement grade is not lower than 42.5, and the water-cement ratio is 0.38-0.45.

(2) The bleeding rate is controlled at 2% after the cement paste is mixed for 3 hours, and the whole bleeding is absorbed in the 24 hours.

(3) The free expansion rate of the expanding agent mixed in the cement slurry is less than 10 percent.

(4) The consistency of the cement paste is controlled between 14 and 18 seconds.

(5) More than 500mg of chloride ion or any other organic matter should not be contained in each liter of water.

5) Pressure injection of cement paste

After the prestressed anchor cable is stretched, the pore canal is grouted within 3 days. The grouting of the duct is to utilize a grouting pump to press and pour cement slurry into the duct of the prestressed tendon, so that the cement slurry fills up the gap between the prestressed anchor cable and the duct, and the prestressed anchor cable and the concrete are firmly bonded into a whole. The grouting process of the pore canal in time adopts a piston grouting pump, the grouting pressure is based on ensuring that cement paste pressed into the pore is compact, the maximum grouting pressure is controlled to be 0.3-0.4MPa, and the pressure is properly increased when the disposable grouting is adopted, but the maximum grouting pressure is not more than 1.0MPa.

Grouting should be performed slowly and uniformly without interruption, the starting pressure is small, the pressure is gradually increased, grouting should be performed until the other end of the pore canal is full in exhaust hole and thick slurry (cement slurry with the same specified consistency) is discharged, and then a bolt plug is used for blocking a slurry outlet. In order to ensure that the pore canal is filled with mortar, when the weight of the slurry discharged from the slurry outlet is the same as that of the injected slurry, the slurry can be screened, the pressure of the slurry is preferably 0.4MPa, and the slurry screening time is preferably 25min. And closing a slurry inlet valve, returning slurry by the slurry pressing machine, and disassembling the connecting joint after the cement slurry is solidified, so as to clean immediately.

In order to check the actual density of cement slurry in the pore canal, the compaction condition of the cement slurry should be checked after grouting from a checking hole, if the cement slurry is not treated in time, the treatment method can adopt secondary grouting. And (5) preparing a standard test block while mixing cement paste, and curing under the condition of Liang Tongdeng. The compressive strength of cement paste is not lower than 35MPa, and the cement paste test block is manufactured by using a cubic mortar test mold with the side length of 70.7 mm.

After grouting is completed, the construction of the next working procedure can be carried out after the strength of the reserved slurry test piece reaches 35 MPa.

6) Prestress tension safety operation rule

(1) The tensioning operation area should be provided with obvious warning marks to prohibit non-staff from entering the tensioning area.

(2) Personnel participating in stretching must carry out training and technical engagement before going on duty, and the operation of stretching is to divide work definitely, and fixed post obeys unified command, dresses work protection articles.

(3) Before the tensioning operation, whether tensioning equipment and tools (such as a jack, an oil pump, a pressure gauge, an oil pipe and the like) meet the construction and safety requirements or not is checked, and the tensioning operation can be performed after the checking is qualified. The oil pipe should be subjected to a comparison test before use, and unqualified oil pipe cannot be used; the stretching anchorage device is matched with a machine tool, when the anchorage device enters the field, appearance inspection is carried out in batches, cracks, flaws and rust cannot be generated, and the anchorage device can be used after the inspection is qualified; the jack and the pressure gauge should be matched and checked; the stretching machine should be used and managed by special personnel, and should be maintained frequently and checked regularly.

(4) When the oil pump is started, the oil inlet and return speeds and the pointer lifting of the pressure gauge are stable, uniform and consistent.

(5) The relief valve on the oil pump should be adjusted to a state where the maximum working oil pressure cannot be automatically opened. The safety valve should remain sensitive and reliable.

(6) The installation of the oil pressure gauge is required to be tightly and fully buckled, the high-pressure oil pipe used between the oil pump and the jack and all joints of the oil way are required to be complete and tight, the oil way is smooth, and the oil can not leak oil after being kept for more than 5 minutes under the maximum working oil pressure. If the damaged person is in time replaced.

(7) The connection point between the oil pump and the jack must be intact. The oil pump operator must wear protective eyes to prevent oil pipe breakage and joint oil spray from damaging eyes.

(8) The oil pumps at the two ends should be stable and matched with the mercy to have unified command of special people when pre-pressurizing. Before stretching, the operator determines the connection signal. When the two ends of the tension piece are far apart, communication equipment such as interphone and the like is arranged.

(9) When the tension is performed, the safety valve is adjusted to a specified value, and then the tension operation can be started. When the prestressed anchor cable is stretched, people do not stand on the front of the two ends of the beam, high-pressure oil pumps are placed on the two sides of the beam, and operators stand on the side surfaces of the prestressed anchor cable.

When abnormal conditions such as an oil pump oil jack anchor and the like are found during tensioning, the machine should be immediately stopped for inspection.

Tightly forbidding an impacting anchor, a steel bundle and a steel bar; before grouting, the beam end should be provided with a retaining wall and a baffle.

7 quality assurance measures

(1) The construction is strictly carried out according to the design drawing and the current construction acceptance standardization organization, and the concrete operation is strictly carried out according to the approved construction scheme and the prestress construction method.

(2) The self-checking, mutual checking and other checking works are carefully performed, the hidden engineering acceptance is performed in time, and the construction of the next working procedure cannot be performed without acceptance. A self-checking system is established, and the checking is carried out by technology, quality inspection and construction team captain, technology and team captain layer by layer, and the responsibility is put down to each worker.

(3) Before tensioning construction, the drawing and the construction condition are carefully rechecked, and after the pressure test strength of the concrete test block maintained under the same condition on site reaches the tensile strength allowed by design, the tensioning can be performed.

(4) All stretching personnel are trained before construction, and are allowed to go on duty.

(5) And (5) carrying out construction strictly according to the drawing requirements. The found problems should be reported to the relevant units in time, and construction is continued after verification by the relevant departments.

(6) Before the prestressed tendons are stretched, the bearing supports of important parts cannot be removed.

(7) Before tensioning, the appearance of the beam to be tensioned should be checked to confirm that the concrete pouring quality is qualified, no honeycomb, hollow cavity,

(8) Stretching can be performed after no abnormal cracks are found; if abnormal, the relevant units should be informed in time to find out the reasons, if necessary, the tensioning scheme is adjusted, and tensioning is performed after approval.

(9) The anchor cable is stored in a reinforced steel bar processing awning, covered with awning cloth and rust-proof.

(10) When the environmental temperature of the engineering is lower than-15 ℃, prestress tensioning is not suitable.

(11) When grouting construction is carried out under the condition that the ambient temperature is higher than 35 ℃ or the daily average ambient temperature is continuously lower than 5 ℃ for 5 days, the anchor cable sleeve is wound by adopting a self-temperature-control heat tracing belt, and the outside is wrapped by adopting heat preservation cotton.

The foregoing describes specific embodiments of the present invention. It is to be understood that the invention is not limited to the particular embodiments described above, and that various changes and modifications may be made by one skilled in the art within the scope of the claims without affecting the spirit of the invention.

Claims (3)

1. The construction method of the inverted siphon prestressed anchor cable is characterized by comprising the following steps of: the method comprises the following steps:

s1, installing anchor cable sleeve

The 1# inverted siphon anchor cable sleeve is made of Q345D steel pipes, the wall thickness is 12mm, the diameter of the sleeve is 150mm, installation is carried out according to the construction progress section by section during installation, the anchor cable sleeves pre-buried in the 27# anchor cable sleeve, the 28# anchor cable sleeve and the 29# anchor cable sleeve are firstly installed, and then the anchor cable sleeve between the anchor cables is installed, and the anchor cable sleeve is welded;

The anchor cable pipeline positioned in the ballast is fixed by adopting positioning steel bars, the grid of the positioning steel bars is square, and the clearance size is 2-3 mm greater than that of the prestressed reinforcement pipeline;

the installed pipe must meet the following requirements: the allowable deviation of the pipeline coordinates in the long direction is 30mm, the allowable deviation in the high direction is 10mm, and the allowable deviation of the pipeline spacing in the same row is 10mm;

s2, blanking and beam penetrating of steel strand

Removing moisture-proof package of the bundled anchor cable outside the anchor cable in a flat field, covering the anchor cable with a special anchor cable cage, wedging the end face of the coiled anchor cable with the cage by square timber and wooden wedges, removing steel strips bound on the anchor cable, and beginning to withdraw the inner core;

cutting by adopting a grinder when the anchor cable is fed, carding and straightening according to the number of the prestressed duct steel bundles after feeding, and tightly wrapping one end penetrated by the steel bundles by using a transparent adhesive tape to prevent the pipeline from being damaged when passing through;

the wire harness is threaded by adopting a manual winch, one end of the adhesive tape is threaded, the prestress rib passes through the pipeline with uniform force and consistent rhythm, and the wire harness is prevented from impacting the pipe wall when the prestress rib is in large and small force, and the wire harness is prevented from damaging the pipeline, so that the wire harness is difficult to continue; after the anchor cable is penetrated, checking whether the lengths of the exposed beam bodies of the steel bundles at two ends meet the working length of the jack by 55cm or not, numbering the penetrated anchor cable after meeting the requirements, and ensuring that the anchor cable does not cross and wind when penetrating the anchor cable in the pipeline during the later stretching;

S3, installing an anchor backing plate and a working anchor plate

Before installing the anchor backing plate, removing the rubberized fabric wrapped on the end part of the steel strand, checking whether the lengths of the exposed steel strands of the pore channels are equivalent, and ensuring that the lengths of the exposed steel strands of the pore channels at each end meet the working length of the jack;

when the anchor backing plate is installed, according to the arrangement of hole sites on the anchor backing plate, penetrating into the anchor backing plate holes from bottom to top in batches, and ensuring the consistent numbering sequence of the two tensioning ends during installation;

s4, tensioning the prestressed anchor cable

Calculating the relation between the tension under the anchor and the reading of the pressure gauge and the relation between the tension under the anchor and the elongation of the steel bundle according to a < calibration certificate > issued by a detection unit, a steel strand mechanical property test report, design control stress, the number of the steel strands of a pore canal and related data, and compiling a tensioning calculation book, wherein the tensioning calculation book can be implemented after review and confirmation by a master engineer;

according to the tensioning calculation book, jack numbers, pressure gauge numbers, steel bundle numbers, initial tensioning stress and control stress are used for compiling a small form in a simplified text expression mode, and a transparent adhesive tape is used for being attached to the center position of the front face of the oil gauge, so that tensioning operators can conveniently use the pre-stressed anchor cable to tension the steel pipe arch rib concrete cube until the strength reaches 100% of the designed concrete strength level, and the tensioning operation is carried out after the age is not less than 28 days;

Before tensioning, the jack after verification, a matched pressure gauge, a ZB4-500 piezoelectric oil pump and a high-pressure oil pipe are installed, and each interface part is cleaned and filled with a copper sealing ring; adding a proper amount of L-HM32 hydraulic oil into the oil pump, cleaning the oil tank, pump body pipelines and the like before adding the hydraulic oil, and filtering the hydraulic oil; recheck each connection site: whether the oil pipe has cracks, whether the joint is firm, whether the screw thread specification of the joint is consistent, and whether an oil delivery nozzle connected with a main pressure gauge is consistent with the ejection direction of a jack piston; after the connection state is confirmed to be correct, the oil pump is started, and air in each oil accommodating space of the oil pump and air in the jack oil cylinder are discharged through each control valve under the idle state so as to avoid unstable pressure, insufficient flow and sudden jump of the piston caused by the air;

before the jack is in place, carefully checking whether the anchor backing plate is vertical to the pore canal, ensuring that grouting holes of the anchor backing plate are smooth, installing working clamping pieces in a standard mode, installing the jack and the tool anchor assembly after the number and the working length of each steel beam are confirmed to be correct; the jack stretches the prestressed steel bundles in sequence: mounting left N1-right N1 in place; firstly, an anchor cable sequentially penetrates into a limiting plate, and a 100mm position at the tail end of the anchor cable is bound into a bundle by a binding wire, so that the steel hinge wire ends are prevented from being scattered due to the fact that the steel hinge wire ends prop against connecting positions such as an inner cylinder of a jack when an installation jack penetrates in;

When the tool anchor is installed, the hole position of the tool anchor corresponds to the hole position of the limiting plate, the dislocation and twisting of the prestressed tendons between the limiting plate and the tool anchor are strictly prevented, finally, the clamping piece and the baffle are installed, the tool clamping piece is uniformly pushed into the tool anchor and lightly squeezed, the position of the jack is adjusted through a chain block on the hanger, the jack, the tool anchor and the plate end are vertical in stretching section, and the axes of the hole, the anchor and the jack are basically coincident;

in the operation process, two jacks are adopted for symmetrical and synchronous tensioning, a tensioning operator mutually reports oil meter reading and oil cylinder elongation through an interphone, the allowable error of synchronous tensioning force of the two jacks is controlled to be +/-2%, the oil cylinder elongation error is controlled to be within 10mm, the holding time is kept for 5 minutes until the two ends are tensioned to the under-anchor control stress, and the anchoring can be realized after the stress is stable; the anchoring is realized by opening an oil return valve, retracting the steel hinge wire inwards and bringing the steel hinge wire into a working clamping piece; when the unloading valve is opened, the strength is slow, the oil return is uniform, and when the pointer of the pressure gauge returns to 2MPa, the extension of the oil cylinder is measured, so that the retraction of the tapping beam is calculated;

the stretching adopts double control of stretching force and stretching amount, the stretching force is controlled in a main control mode, the proportion and control of stretching stress and stretching amount are paid attention to in real time in the stretching process, when the prestress steel beam reaches the designed stretching force, the error between the actual stretching amount and the theoretical stretching amount is controlled to be within +/-6%, the stretching operation is stopped in time when the middle is abnormal, the reason is found out, and the operation can be performed after the problem is solved;

The cable tensioning procedure is as follows:

0 → initial stress 20% σk → 25% σk → 50% σk → 75% σk → 100% σk holding for 10min → anchoring; the prestressed tendons can be anchored after the tension control stress is stable, the top surfaces of the clamping pieces after anchoring are flush, the mutual dislocation of the prestressed tendons is not more than 2mm, and the exposed height is not more than 4mm;

after tensioning, checking the conditions of broken wires and sliding wires of the anchor cable, wherein the number of the broken wires and the sliding wires in the same component is not more than 1% of the total number of the steel wires, filling a pre-stressed anchor cable tensioning field quality inspection report sheet after inspection and confirmation, sawing redundant anchor cables at the end part by using a grinding wheel saw, and ensuring that the exposed length of the anchor cable is more than 50mm after cutting;

s5, sealing anchor grouting

After tensioning and anchoring the prestressed tendons, finishing grouting engineering, pressing slurry into the anchor cable sleeve from one section to the other end according to the principle of 'low in and high out', namely arranging a grouting hole at a lower position of an anchor backing plate at one end, arranging an exhaust and slurry outlet hole at a higher position of the anchor backing plate at the other end, and plugging the grouting hole and the slurry outlet hole in time after grouting is finished when slurry with the same concentration as the grouting hole is fresh Kong Maochu in the grouting process, and indicating that grouting in the whole pore canal is finished;

1) Flushing duct

The pore canal is washed by pressurized water before grouting, accumulated water in the pore canal is blown off by an air compressor after washing, but the pore canal is kept moist to ensure that cement paste is well combined with the pore wall, and in the washing process, if water leakage and water leakage phenomena are found, the blocking leak is treated;

2) Cement paste mixing

(1) The cement paste has enough fluidity, and the fluidity is 150-200mm, so that the grouting requirement can be met;

(2) the water for the water mortar is clean water, does not contain substances harmful to cement or prestressed anchor cables, and does not contain more than 500mg of chloride ions per liter of water;

(3) additive agent

In order to prevent the cement slurry in the pore canal from generating volume shrinkage, an expanding agent-aluminum powder is permeated into the cement slurry, wherein the permeation amount of the aluminum powder is 0.01 percent of the cement dosage, or the expanding agent of the UEA is permeated into the cement slurry, and the permeation amount of the UEA is 10-12 percent of the cement dosage;

3) Stirring of cement paste

Firstly adding water into a stirrer, starting the stirrer, then adding cement and an expanding agent, and calculating the water quantity and the additive quantity by taking the weight of the cement as a base number in material metering; the stirring time should ensure the uniform mixing of the cement paste, generally not less than 2min, the stirring of the cement paste should be uninterrupted in the grouting process, and the cement paste should be circulated in the stirrer and the grouting machine when the grouting process is short-paused, so as to prevent the pipeline and the switch valve from being blocked after precipitation;

4) The main technical indexes of the cement slurry are as follows:

(1) the cement mark is not lower than 42.5, and the water-cement ratio is 0.38-0.45;

(2) the bleeding rate is controlled at 2% after the cement paste is mixed for 3 hours, and the whole bleeding is absorbed after the cement paste is supplemented in 24 hours;

(3) the free expansion rate of the expanding agent added into the cement slurry is less than 10%;

(4) the consistency of the cement paste is controlled between 14 and 18 seconds;

(5) more than 500mg of chloride ions or any other organic matters are not needed in each liter of water;

5) Pressure injection of cement paste

After the prestressed anchor cable is tensioned, grouting the pore canal within 3 days, wherein the grouting of the pore canal is to utilize a grouting pump to press and pour cement paste into the pore canal of the prestressed anchor cable so as to fill the gap between the prestressed anchor cable and the pore canal, and the prestressed anchor cable and the concrete are firmly bonded into a whole; grouting the pore canal in time, and grouting process: the grouting adopts a piston grouting pump, the grouting pressure is based on ensuring that the cement paste in the pressing hole is compact, the maximum pressure of grouting is controlled to be 0.3-0.4MPa, and when the disposable grouting is adopted, the pressure is properly increased, but the maximum pressure is not more than 1.0MPa;

grouting is carried out slowly and uniformly without interruption, the starting pressure is small, the pressure is gradually increased, the grouting is carried out until the exhaust holes at the other end of the pore canal are full and the thick slurry is discharged, and then a bolt plug is adopted to block a slurry outlet; in order to ensure that the pore canal is filled with mortar, when the weight of the slurry discharged from the slurry outlet is the same as that of the injected slurry, the slurry can be shielded, the slurry shielding pressure is preferably 0.4MPa, the slurry shielding time is preferably 25min, the slurry inlet valve is closed, the slurry is returned by a slurry pressing machine, and after the cement slurry is solidified, the connecting joint is disassembled and cleaned immediately;

In order to check the actual density of cement slurry in the pore canal, checking the compaction condition of the cement slurry from a checking hole after grouting, if not, performing secondary grouting in time;

after grouting is completed, the strength of the reserved slurry test piece reaches 35MPa, and then the next working procedure construction can be carried out.

2. The inverted siphon prestressed anchorage cable construction method according to claim 1, wherein: in the step S4, in the working process of the oil pump and the jack, the stress of loading and unloading is stable, the impact is avoided, and the oil is strictly controlled according to the oil meter readings reached in each stage in the tensioning calculation book.

3. The inverted siphon prestressed anchorage cable construction method according to claim 1, wherein: in step S4, in-situ tensile elongation value measurement:

1) Starting oil pumps at two ends, closing a main oil delivery valve, supplying oil to an oil cylinder of a jack, opening the main oil delivery valve after the oil cylinder exposes out of a cylinder body for about 20mm, stopping the oil pump, installing a limiting plate, the jack and a tool anchor assembly, installing the jack after the oil cylinder exposes out of 20mm, and ensuring accurate measurement of the elongation of the oil cylinder when the tensile force reaches initial stress, and simultaneously, preventing the problem of easy disassembly of the jack due to tensile sliding wires;

2) Starting the oil pump again, closing the main oil feeding valve, feeding oil to the jack oil cylinder, stopping feeding oil to the jack oil cylinder when the pressure gauge reads the initial stress (20% sigma k), measuring the length L1 from the shell at the end part of the jack to the scale, and marking the position of the clamping piece of each steel strand tool so as to more intuitively observe any slippage of each steel strand;

3) Continuously supplying oil to the jack cylinder, stopping supplying oil to the jack cylinder when the pressure gauge reads 25% sigma k, and measuring the length L2 from the shell at the end part of the jack to the scale;

4) Continuously supplying oil to the jack cylinder, stopping supplying oil to the jack cylinder when the pressure gauge reads to 50% sigma k, and measuring the length L3 from the shell at the end part of the jack to the scale;

5) Continuously supplying oil to the jack cylinder, stopping supplying oil to the jack cylinder when the pressure gauge reads 75% sigma k, and measuring the length L4 from the shell at the end part of the jack to the scale;

6) Continuously supplying oil to the jack cylinder, when the reading of the pressure gauge reaches 100% sigma k, holding the load (keeping the reading of the pressure gauge unchanged) for 10min, and measuring the length L5 from the shell at the end part of the jack to the scale;

7) Stopping the oil pump, opening the unloading valve, and measuring the length L6 from the end shell of the jack to the scale when the pointer of the pressure gauge returns to 2 MPa;

8) Each parameter was calculated according to the following formula:

20% tensile force to 100% tensile force elongation value Δl1=l5-L1;

an initial stress 20% tensile elongation Δl2=l2-L1;

the actual stretching value Deltals=DeltaL1+DeltaL2 of the prestressed tendon stretching;

anchoring retraction = L5-L6-L, where L is jack working length extension;

9) And filling in a prestress tensioning original record form according to the description, and mastering double control by a field tensioning construction technician.