The edge of the cofferdam shall be 1m away from the edge of the pile foundation.
(2) Correction of end rectangular ratio: cut the pile end with oxyacetylene to keep it perpendicular to the axis, and then grind and repair the cutting surface with grinding wheel.
The construction starts from one end away from the main trestle, and the closure position is selected near the positioning steel pipe pile on one side of the supporting trestle, so as to facilitate the use of the positioning pile to provide reaction force, and the inverted chain is used to pull the closure mouth to speed up the closure speed.
The corbel shall be welded on the steel sheet pile to place the support on it.
During welding, butt weld first, then weld the reinforcing plate, and make pile lifting holes for new piles or lengthened piles at the pile end.
In order to prevent the support from arching upward when stressed, the reverse corbel shall be welded on the support.
During pile sinking, the steel sheet pile shall be inserted and driven stably, and the locking port shall be strictly aligned when inserting the pile.
When the amount of repair is small, the grinding wheel can also be directly used for correction.
Steel sheet pile cofferdam shall be set on the whole section of the corresponding pile foundation.
DZ60 vibration pile driver is selected for pile sinking and pulling machinery, and 50t crawler crane is used for purlin, support and sheet pile hoisting.
(2) After the steel sheet pile is transported to the material storage site in the operation area, the crawler crane shall be lifted and inserted, and then the vibrating hammer shall be started to vibrate and drive at the same time.
(6) Correction of lock mouth deformation: use standard steel plate as the lock mouth shaping mould, use slow winch to pull and adjust, or use oxyacetylene flame hot drying and sledgehammer to knock the mould for straightening.
Because the construction season is autumn and winter, the pile top elevation is designed as H = + 4m.
(3) Pile deflection correction: abdominal bending correction is to fix both ends of the bending section of the steel sheet pile on the support point, and use the jack set on the gantry top beam frame to push the concave convex part of the steel sheet pile for cold bending correction; Lateral bending correction is usually carried out on a special correction platform.
When installing the guide frame, first carry out positioning measurement.
During installation, the steel sheet pile shall not be dragged obliquely to avoid torsion and damage of the steel sheet pile.
After the total station is used to calibrate the sheet pile attitude in two directions, turn on the vibrating pile hammer, conduct low amplitude and light vibration to make the pile tip penetrate into the soil for about 1.0m, and then correct the sheet pile attitude again, and then apply normal excitation force to sink the pile in place.
When lengthening and welding, clamp it flat with a solid fixture to avoid deformation.
(3) According to the position of pile foundation and drilling platform, trestle and trestle, it is necessary to carry out inserting and driving operation in a certain order and reasonably arrange the construction.
400X170X15.5 U-shaped steel sheet pile II.
All steel sheet piles with bending, damage and non-conforming lock mouth shall be returned.
The steel sheet pile shall be fsp-iv steel sheet pile finalized in Germany, and the steel sheet pile cofferdam shall be constructed before the construction of pile foundation.
(4) Pile distortion correction: according to the distortion of steel sheet pile, the method in (3) can be used for correction.
Measures to prevent the inclination of steel sheet piles in the process of inserting and driving steel sheet piles.
In the whole process of steel sheet pile cofferdam driving, one steel sheet pile can be inserted and driven at the beginning, that is, each steel sheet pile can be driven to the design position.
Steel sheet pile layout plan (unit: cm) steel sheet pile layout elevation (unit: cm) 4、 The soil in the steel sheet pile of cofferdam foundation clearing shall be removed underwater.
The guide frame is fabricated in sections on site, assembled on the platform and fixed on the positioning pile.
The already driven steel sheet piles will be inclined under the influence of rising and falling tide, especially the impact of the tide facing surface is more serious, In order to prevent the front and back inclination caused by rising tide and falling tide during the insertion and driving of steel sheet pile, which will lead to the deformation of steel sheet pile, and more seriously, it will lead to the loosening of soil at the pile bottom and the back surge of foundation base, temporary tension and support facilities shall be adopted during the construction of steel sheet pile.
After the construction of bored piles, the drilling rig and platform shall be removed first, and then the first purlin support shall be placed before underwater foundation cleaning.
Because the first and second sheet piles have a vertical guiding effect on the subsequent sheet piles, they shall be driven carefully and slowly during the driving process.
Large area dredging by excavator is used for underwater foundation cleaning, and the foundation cleaning mud pump is used to suck out at the corner of pile head and steel sheet pile cofferdam..
Guide frame installation.
When the water is gradually pumped to 20cm below the support, the bracket shall be welded and the support shall be placed.
The vibration shall be suspended after every 1m of pile sinking, and the pile body attitude shall be corrected and adjusted to ensure the accurate position, direction and perpendicularity of sheet piles.
Before driving steel sheet pile, insert and drive positioning pile first, and then install the guide frame.
(2) The pile driving shall be horizontal and vertical.
When inserting and driving steel sheet piles, the first steel sheet pile must be inserted and driven correctly to avoid affecting the subsequent steel sheet piles.
For the sequence of inserting and driving steel sheet piles, because there are two flow directions in tidal rivers, in order to reduce the flow resistance, insert and drive from the side to the upstream and downstream, and close the dragon on the other side.
If the underwater guide frame is far from the shore or the completed Pier (or construction temporary bridge), the forward intersection method shall be used for positioning.
Since the first pile is the reference pile of subsequent piles, it shall be installed carefully, and its correct position shall be determined with a total station without inclination.
Correction method of steel sheet pile (1) surface defect correction: first clean the rust and oil stain on the surface near the defect, then repair it by welding, and then grind it with grinding wheel.
2.
Inserting and driving steel sheet piles 3.
Fix both ends of the bending section of the steel sheet pile on the support of the correction platform, and press the convex part of the steel sheet pile with the jack set on the side correction platform of the bending section of the steel sheet pile for cold bending correction.
In order to facilitate the lifting of steel sheet pile, a hole with a diameter of about 5cm shall be cut at the center 10 cm below the top of steel sheet pile by gas cutting.
If the closure is wrong, it shall be pulled together by chain fall or pulley group.
2.
(3) When the closure is difficult due to the inconsistency of modulus between the corner and the closed closure, the special-shaped pile or the method of correcting the axis direction and length shall be adopted to ensure the closure.
If the lock mouth cannot pass through or the pile body has defects such as bending, distortion and dead bending, it shall be repaired by cold bending, hot knocking (temperature not exceeding 800 ~ 1000 ℃), welding, riveting, cutting, lengthening and other methods.
During lifting, the lifting wire and steel sheet pile shall be firmly connected by snap ring, and rope shall be tied at the lower part of steel sheet pile to ensure that it will not shake violently during lifting.
At the same time, the strength of the joint is equal to that of other sections.
The construction method of sheet pile cofferdam is guided by guide frame and driven one by one.
1、 Construction method 1.
When it reaches the last closure position, it shall be inserted first and then driven.
3、 The internal support of steel sheet pile is set according to the depth of foundation pit and water pressure, and the support adopts double splicing 32A I-beam.
Steel sheet pile driving method steel sheet pile is required to be driven with small lock mouth, as shown in the figure (1) before driving, the lock mouth of steel sheet pile shall be coated with butter mixture ointment (weight mix ratio: butter: asphalt: dry sawdust: dry clay = 2:2:1) to reduce friction during driving and strengthen anti-seepage performance.
Inserting and driving steel sheet pile (1) for the qualified steel sheet pile, in order to ensure the smooth insertion and removal of steel sheet pile during construction and increase the anti-seepage performance of steel sheet pile during use, the lock mouth of each steel sheet pile must be evenly coated with mixed oil.
After sinking to the predetermined position, the plate pile head and the guide frame shall be welded and fixed immediately.
Schematic diagram of installation preparation 1.
The measures are to use steel wire rope to connect with steel trestle or steel platform and set wind rope.
If the tide cycle of the project location is semi diurnal tide, the tide range of rising and falling tide is large and the tide is rapid, the inserting and driving of steel sheet piles can only be carried out in the flat tide.
(5) Correction of local deformation of pile section: the local deformation shall be corrected by the combination of Jack pressing, sledgehammer knocking and oxyacetylene flame hot drying.
The plane section size of the steel cofferdam is 16.5m × 3.5m。 The number of steel sheet piles for a single steel cofferdam is 86 plus 4 corner piles.
In order to make the support closely contact with the steel sheet pile, short support or wooden wedge shall be welded between the support and the steel sheet pile.
In order to facilitate the construction of column, the support shall avoid the position of column body and formwork.
After the steel sheet piles are transported to the construction site, the length must be checked and measured one by one.
