CN107869144B - Comprehensive construction method for pre-cut ring-sealed double-wall steel cofferdam deep water foundation - Google Patents
Comprehensive construction method for pre-cut ring-sealed double-wall steel cofferdam deep water foundation Download PDFInfo
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- CN107869144B CN107869144B CN201711147272.4A CN201711147272A CN107869144B CN 107869144 B CN107869144 B CN 107869144B CN 201711147272 A CN201711147272 A CN 201711147272A CN 107869144 B CN107869144 B CN 107869144B
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- E02D19/00—Keeping dry foundation sites or other areas in the ground
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Abstract
The invention discloses a comprehensive construction method of a pre-cut ring-sealed double-wall steel cofferdam deepwater foundation, which comprises the following steps: (1) setting up trestle and platform; (2) pile foundation construction; (3) Pre-cutting the riverbed at the cutting edge of the double-wall steel cofferdam by using a rotary drilling bit; (4) cofferdam assembly; (5) installing a cofferdam lowering system and a continuous jack; (6) lowering the cofferdam; and (7) sealing the bottom of the cofferdam. The comprehensive construction method of the pre-cut ring-sealed double-wall steel cofferdam deepwater foundation under complex geological conditions, disclosed by the invention, is perfect and improves the construction technical level, achieves the purposes of advanced, reasonable, economic and safe construction technology, provides experience for similar construction, and provides important guiding effects for deepwater foundation construction and cofferdam construction engineering.
Description
Technical Field
The invention relates to the field of construction of building bridges, in particular to a comprehensive construction method for a pre-cut ring-sealed double-wall steel cofferdam deep water foundation under complex geological conditions.
Background
Along with the rapid development of domestic and international bridge engineering, mankind starts bridge construction in rivers, lakes and seas, but along with the expansion of construction range, various technological innovations are brought about in deep water foundation construction.
At present, double-wall steel cofferdam construction bearing platforms are adopted for construction in water at home and abroad, and are common at home and abroad. The method mainly adopts a pile-first-weir-then-weir or a pile-first-weir-then-weir method for construction, and the assembly mode can select the processes of integral floating transportation, floating crane lifting, in-situ block assembly and the like. The descending process can adopt modes of a chain block, a jack matched with a steel strand and the like, and the bottom sealing mode is mostly fully sealed. The construction process is mature. But in the actual implementation process, quality safety accidents or hidden dangers occur to different degrees.
The cofferdam is smoothly lowered, and the completion of sealing the bottom and stopping water is a control procedure of the cofferdam deepwater construction process. Therefore, how to ensure the construction safety of the deepwater cofferdam, improve the construction quality, accelerate the construction progress, reduce the engineering cost and aim at the comprehensive construction of the deepwater foundation of the double-wall steel cofferdam under complex geological conditions to solve the main problem.
Disclosure of Invention
The invention aims to solve the technical problem of providing a comprehensive construction method for the pre-cut ring-sealed double-wall steel cofferdam deepwater foundation under complex geological conditions, which perfects and improves the construction technical level, achieves the purposes of advanced, reasonable, economic and safe construction technology, provides experience for similar construction, and provides important guidance for deepwater foundation construction and cofferdam construction engineering.
The technical problems to be solved by the invention are realized by the following technical scheme:
the comprehensive construction method of the pre-cut ring-sealed double-wall steel cofferdam deepwater foundation is characterized by comprising the following steps of: (1) setting up trestle and platform; (2) pile foundation construction; (3) Pre-cutting by rotary drilling of a double-wall steel cofferdam and assembling the cofferdam; (5) installing a cofferdam lowering system and a continuous jack; (6) lowering the cofferdam; and (7) sealing the bottom of the cofferdam.
Preferably, in the above technical solution, the step (3) includes:
1) Preparing for slitting construction: before slitting, removing the inner platform, and cleaning a sand egg layer along the cofferdam position by utilizing a grab bucket, a long arm hook machine and a sand pump;
2) And (3) grooving construction: and (3) adopting a rotary drilling bit to be matched with a spiral drill bit, and carrying out cofferdam lowering after the whole circumference of the cut is cut.
Preferably, in the above technical solution, in the slitting construction: the number of the cut is 130, the annular radius is 16.60m, and the adjusting space of 30cm outside the cofferdam is further ensured; positioning by measuring hole by hole in the cutting process; the cofferdam cutting edge can directly fall into the groove by 80cm, and then the rock stratum on the inner side of the cofferdam is removed by utilizing the self weight, a hydraulic grab bucket, a long arm excavator and the like, so that the cofferdam is ensured to continuously sink until reaching the designed elevation position; drilling to 29.0m elevation.
Preferably, in the above technical solution, the step (4) includes:
1) Setting a double-wall steel cofferdam lowering system;
2) Setting a pile planting anchoring in a reaction system of the lowering system;
3) The double-wall steel cofferdam lowering process comprises the following steps:
31 Hanging point setting): the lifting points are arranged at the tops of 8 anchor piles on the circumference of the cofferdam, so that lifting point components of the jack are reinforced, and 8 lifting points are adopted;
32 Upper hanging point structure): the hanging point adopts double I40b to form a stressed main beam; the main beam of the upper hanging point passes through the guide piles, the I-steel plates are provided with reinforcing front plates according to the interval of 30cm, and the I-steel bottoms are provided with reinforcing rib plates; reserving a 160mm hole between I-steel bars as a penetration space of a steel strand; a50 mm thick round steel plate is arranged at the top of the section steel, and a 150mm round hole is formed in the section steel and used as a steel strand passing space. 200 tons of continuous tensioning jack equipment is arranged at the top of the round steel plate. Filling the anchoring steel pipe with fine sand after the hanging point is installed, and pouring 1m high C30 concrete at the top to pour the steel pipe and the hanging point structure into a whole;
33 A lower hanging point structure): horizontally penetrating a cofferdam structure at a position 2m above a cofferdam blade foot, adopting I40b I-steel double roots as a horizontal main beam, arranging a reinforcing rib plate, and adopting a steel plate to be the same as an upper hanging point; a round hole of 15cm is formed at the position corresponding to the lower hanging point and the upper hanging point, so that a steel strand can conveniently pass through the round hole; in order to ensure that the stress length of the steel strand is more than 2m, a double I40b I-steel with the length of 70cm is additionally arranged under the main beam at the lower lifting point and is firmly welded on the main beam, and a round hole with the length of 15cm is formed; the bottom is provided with a 10cm thick steel plate opening or is regulated by adopting a round anchorage device; adopting an extruder to fix the steel strand Shan Duangui on the anchor;
34 Bearing bracket): two rows of double I20b work steel and steel pipe perforation are welded on the outer wall of the anchoring pile outside the cofferdam near the cofferdam side, and the two rows of double I20b work steel and the steel pipe perforation are connected by adopting a profile steel diagonal bracing to form a bearing bracket. The outer end of the bracket exceeds the steel cofferdam by 1m, and an operation platform is erected on the bracket.
35 Limit): the displacement preventing device is arranged on the steel casing at the four inner corners, and consists of I-steel with the length of 2.5m and I40b, and is used for preventing the cofferdam from being deviated due to uneven stress, water flow impact and the like;
36 Checking and assembling the cofferdam;
37 A) lowering the cofferdam.
Preferably, in the above technical solution, the step 32) setting the pile-planting anchoring measure by the reaction system of the lowering system includes: and (3) lowering the counterforce pile, namely adopting a steel pipe pile with the diameter of phi 1000 multiplied by 10mm, vibrating and driving sandy cobbles into a bedrock layer, punching a hole by adopting a percussion drill in the steel pipe pile, hanging an anchoring reinforcement cage, and planting the pile for anchoring in an underwater concrete pouring mode, wherein the anchoring depth of the gravel layer is 2.5m below the steel pipe, so that the root stability of the steel pipe pile is improved, and the anti-overturning capacity of a trestle is enhanced.
Preferably, in the above technical solution, the 36) cofferdam inspection and assembly includes:
and (3) checking: after the cofferdam segments are processed, firstly, numbering each block; then checking the size, radian, truss and weld quality one by one, and transporting to the site after the detection is qualified; welding an assembly seam between two steel sleeve cofferdams, fully welding two sides, and detecting the penetration condition by using kerosene;
assembling: the sequence is assembled from one side to two ends section by section according to the block.
Preferably, in the above technical solution, the step 37) of lowering the cofferdam specifically includes:
the method comprises the steps of adopting a grab bucket and a long-arm hook machine to clean a riverbed in a cofferdam range, checking cleaning conditions by a diver, circularly assembling a first two-section crane of the cofferdam, checking weld quality, setting a lowering system, measuring and correcting the position of the cofferdam, the cofferdam level, debugging a jack, fully stressing the jack, observing and dismantling an operation platform, lowering the jack, entering water into the cofferdam, measuring and monitoring the position and level, lowering the cofferdam, self-floating the cofferdam, locking the jack, injecting water, lowering again, contacting the riverbed by the cofferdam, pouring concrete on the edge of the cofferdam, checking the relationship between the cofferdam and the riverbed by the diver, measuring and measuring the position and level, assembling a third section of cofferdam, starting a sand pump, hydraulic grab bucket, cleaning by the long-arm digger, cooperating and cleaning, lowering the cofferdam, entering the riverbed, checking the surrounding condition by the diver, splicing a fourth section of the cofferdam, continuously injecting and putting the cofferdam into a foundation, clearing residual sand and stones in a cofferdam groove by a suction machine, completely exposing the foundation rock face, and stopping the edge of the cofferdam, and sealing the edge by sealing by the water.
Preferably, in the above technical scheme, the cofferdam back cover in step (5) includes back cover cleaning construction:
restoring the platform in the cofferdam after the cofferdam is lowered to the riverbed; firstly, removing a sand pebble layer of a covering layer by using a long-arm excavator and a grab bucket; when the long arm excavator and the hydraulic grab bucket cannot be cleaned, the hydraulic grab bucket is adoptedThe steel pipe is inserted into the river bed and is composed of 2 pieces of 22m 3 Air is supplied by a single-screw air compressor for sucking mud and sand eggs; and cleaning at any time along with the sinking of the cofferdam.
After the cofferdam enters the riverbed, marking scales on the periphery of the cofferdam, measuring the height difference by adopting a level gauge along 8 lifting points of the cofferdam every 30cm, and adjusting the deviation by a jack when the error of two points exceeds 5 cm; when the cofferdam cutting edge is close to the bedrock surface, the diver drains, and the position of the suction dredger is adjusted, so that the suction dredger can timely clear a gap with the width of 1m between the cofferdam and the sandy pebble, and the process is repeated until the cofferdam is lowered to the bedrock surface; the suction dredge should continue to pump sand for 30 minutes, observe whether the sand outlet has river sand to appear, then follow the circumference and remove the sand pump, guarantee that the cofferdam inslot sand ovum is totally clear.
A deep water double-wall steel cofferdam lowering system applied to a comprehensive construction method of a deep water foundation of a pre-cut ring-sealed double-wall steel cofferdam.
Preferably, in the above technical scheme, the system comprises a cofferdam, descending piles, continuous tensioning jacks and steel strands, wherein 8 descending piles are arranged on the outer wall of the cofferdam in an equidistant annular mode, the bottom ends of the descending piles are anchored and solidified with a river bed by adopting reinforced concrete, the continuous tensioning jacks adopt 8 lifting points, and the lifting points correspond to the descending piles one by one.
The technical scheme of the invention has the following beneficial effects:
1) And adopting a rotary digging drill matched with a spiral drill bit to stir and lift out the bed bedrock, wherein the cutting depth is 2m below the elevation of the weir bottom. The cofferdam lowering blade feet cut into the groove, and then the annular sealing concrete construction is carried out in the groove according to the underwater concrete pouring process, so that the construction difficulty and risk are reduced, the construction period is shortened, the materials are saved, and the environmental hazard is reduced.
2) And the construction technology of the double-wall steel cofferdam is realized by utilizing the anchoring spiral pipe pile as a counterforce structure and using a continuous jack. After the preset independent spiral pipe and the river bed rock layer are anchored and solidified by reinforced concrete, fine sand is filled in the spiral pipe, a lowering bracket is arranged at the top of the spiral pipe, the pipe is filled with concrete and solidified, continuous jacks are symmetrically arranged on the lowering bracket according to the total weight of the cofferdam, and the lowering is controlled by steel strand suspension. The plurality of continuous jacks are supplied with oil by one oil pump, and the computer controls the single jack to adjust at any time so as to finish the lowering construction. The process is simple and convenient to operate, has high lowering speed, and reduces the number of operators and the operation intensity.
3) The lowering piles are arranged outside the cofferdam, 8 piles are annularly and equidistantly arranged along the outer wall of the cofferdam, the bottom ends of the spiral pipes are anchored with a river bed, and the tops of the spiral pipes are connected with the lowering hanging points into a whole through concrete, so that a counter-force supporting effect is provided for the lowering of the cofferdam; the top is consolidated with the upper hanging point through concrete. The structure is stable, the construction is convenient, the space in the cofferdam is not occupied, and the construction of the bearing platform pier body is facilitated.
4) According to the hydrogeology condition of a river channel, the trestle platform is supported by adopting a spiral steel pipe bent pier, the spiral pipe is sunk into a riverbed covering layer by adopting a vibrating hammer for enhancing the bearing capacity, stability and water flow impact resistance of the bent pier, and then a percussion drill is adopted to impact a hole from the inner side of the spiral pipe, so that the spiral pipe is followed. After the depth of the impact hole is more than 4m, a steel reinforcement cage is arranged in the spiral pipe, underwater concrete is poured into the spiral pipe by a conduit method, and the spiral pipe is anchored on a river bed. The structural stability of the trestle is improved, the bearing capacity of the trestle is improved, and meanwhile, the trestle can resist part of impact load for the cofferdam.
On the premise of aiming at advanced, reasonable, economic and safe construction technology, the construction technology level of the foundation is improved and perfected, so that the foundation construction is successfully completed by engineering.
Drawings
FIG. 1 is a flow chart of the comprehensive construction method of the pre-cut ring-sealed double-wall steel cofferdam deepwater foundation.
Fig. 2 is a front view of the submerged double-wall steel cofferdam lowering system of the present invention.
FIG. 3 is a plan view of a cofferdam lowering pile and a lifting point of the deep water double wall steel cofferdam lowering system of the present invention.
FIG. 4 is a plan view of a cofferdam lowering system for double-wall steel cofferdam of the present invention.
Fig. 5 is an elevation view of the double-wall steel cofferdam lowering system of the present invention.
Detailed Description
Specific embodiments of the invention are described in detail below to facilitate a further understanding of the invention.
All experimental methods used in the following examples are conventional methods unless otherwise specified.
Example 1
The invention takes Mongolian to Huazhong railway coal transportation channel project as an example. The Jian Ganjiang extra large bridge site is located 9.6km downstream of Jian Gangshan large bridge and 4.6km downstream of Jian Gangshan large bridge. Start-stop mileage: DK1867+993.480 to DK1870+863.300, center mileage: DK1869+428.39, full length 2869.82m.
The bridge site spans the Ganjiang at DK 1868+350.8-DK 1869+350, the intersection angle of the river and the line is 95 degrees, the river banks are not arranged on both sides of the river, the river is navigable, the current situation is a V-class channel, the III-class channel is planned, the navigable net height is 10m, 1000t ships can be navigable, and the highest navigable water level takes H=50.59m. Crossing Ganjiang bridge site, H1% = 52.16m, Q1% = 23347m3/s, H2% = 51.53m, Q2% = 21400m3/s, H5% = 50.59m, Q5% = 18600m3/s, H10% = 50.01m, H0% = 48.59m, water level 40.08m when designed.
The spanned Ganjiang is a first large river in Ganjiang province, the bridge site area is positioned at the middle reaches of Ganjiang, subtropical wet monsoon climate areas are arranged at the positions in the river basin, the climate is mild, the rainfall is full, the four seasons are clear, the annual change of the rainfall in the year is large, the spatial distribution is uneven, and the storm is easy to cause flood. The water level of the bridge site area is 1015m wide, the highest historical water level is 52.57 (6 months in 1962), the lowest historical water level is 40.4m (12 months in 2008), and the water level amplitude is 12.17m.
The upper structure of the main span of the bridge span river section is designed as a 90+180+90m prestressed reinforced concrete continuous rigid frame arch, the rest hole spans are L=32m simply supported beams, and the lower structure is designed as a double-line solid pier and a bored pile group pile foundation. Wherein 11# -33# piers are organized according to construction in water, trestle bridges are respectively arranged on two sides, 13# -14# piers reserve channels, and the channel width is more than 100m. Each pier is provided with an overwater drilling operation platform, and is erected by adopting a crawler crane and a barge to cooperate with a vibrating hammer.
The bridge deck of the drilling platform is a 12mm thick patterned steel plate, and an I10I-steel longitudinal beam and an I20b I-steel cross beam are arranged below the bridge deck to form a bridge deck system; the main longitudinal beam adopts double-row single-layer 3X 1.5m Bailey beam, the cross beam adopts double I56 or three I40I-beams, and the abutment isOr->The individual parts of the spiral pipe foundation adopt pile planting technology. The casing adopts an inner diameterThe wall thickness of the steel casing is 16mm, and the casing needs to follow up to the bedrock layer. The pile foundation pore-forming adopts impact drilling pore-forming, the weight of the hammer is 10t, and the requirement on slurry wall protection is high. The pore-forming detection adopts an ultrasonic pore-forming quality detector. The pile is formed by pouring underwater concrete by a conduit method. The pile forming detection adopts an ultrasonic method.
The construction is performed by adopting a pile-first and weir-last method. The # 13 pier bearing platforms and the # 14 pier bearing platforms adopt round double-wall steel cofferdams, and are assembled in situ and lowered in sections. The inner diameter of the double-wall steel cofferdam is 30.5m; the full width of the cofferdam is 1.5m; the total height of the steel cofferdam is 21.5m, the elevation of the top surface is +48.6m, and the elevation of the bottom surface is +27.1m. The double-wall steel cofferdam steel adopts Q235B steel, is divided into 5 sections vertically, is divided into 16 blocks in each water-saving square direction, and has the total weight of 497t for a single cofferdam, and the steel consumption per square meter is as follows: 268.78 Kg/square meter.
Before cofferdam assembly, an XR360 rotary drilling drill is needed, a double-wall steel cofferdam is arranged on an outer side platform, a cutting is dug downwards, steel pile casing guide with the diameter of 2.8m is adopted, and a jump groove is dug. After the slitting is completed, the discharging facilities are arranged on 8 guide piles uniformly distributed on the outer side of the cofferdam along the circumferential direction, the cofferdam is assembled block by block, the cofferdam is discharged section by section, and 8 continuous jacks with 200t are adopted to match with steel strands for discharging. And (5) placing the cofferdam down after entering the river bed and pumping sand. The bottom sealing adopts a groove inner ring sealing technology, and the technology of pouring underwater concrete by a conduit method is adopted, wherein the height of C30 concrete entering bedrock is not less than 2.5m.
In detail:
1. trestle and platform construction
(1) Trestle bridge arrangement
According to meteorological hydrologic data: the trestle is arranged according to 48.59m (five years of flood level), and the main structure is 1.8m, so the height of the top surface of the trestle is set to be +50.4m. But 11# -13# piers (Ganjiang western coasts) have higher topography, and in order to meet the traffic requirement, 11# -13# piers trestle is provided with the top surface elevation of +52.0m.
The main bridge crossing the Ganjiang is provided with trestle bridges respectively at 10# to 13# piers on the west shore (small mileage side) and 14# to 33# piers on the east shore (large mileage side), a channel is reserved between the 13# to 14# piers for passing, and the trestle bridges on the two sides are both arranged at the upstream of the bridge position. The east landing stage is 735.6m long and the west landing stage is 182.1m long. The trestle is a double-lane steel bridge, the net width of the bridge deck is 5.7m, the full width is 6.0m, the western shore is 17 spans, the eastern shore is 58 spans, the trestle is arranged at equal span intervals, the shore sides of the western shore trestle are all 9m, and the shore sides of the western shore trestle are 15m between 12# -13# piers. The east-shore trestle is arranged according to 15m spans, and expansion joints are arranged every 10 spans.
(2) Construction platform design
The construction platform is a construction machine frequently stayed and working place, and when the construction platform is designed, the operation, the walking space and various load conditions of the implementation stage of equipment are fully considered according to the position and the function of the platform, so that the design of trestle is inconsistent. The platform has the main functions of providing working places for installing the steel cofferdam and the steel pile casing, drilling and subsequent bearing platform and pier body construction, and the main construction machinery on the platform comprises a drilling machine, a crane, a concrete transport vehicle and the like.
(3) Bridge deck system installation
After the bailey pieces are assembled and hoisted in place, transverse bridge distributing beams are paved on the bailey pieces, longitudinal distributing beams are paved on the bailey pieces, the transverse distributing beams I20 are distributed according to the interval of 50cm, and the longitudinal distributing beams are distributed according to the interval of 25cm by adopting I10b engineering steel. The transverse distribution I-steel and the bailey pieces are fixed by adopting phi 20U-shaped bolts, and a set of bolts are arranged at the intersection of each set of bailey pieces and the I-steel cross beam. And the welding between the longitudinal and transverse distribution beams is firm. And An Zhanqiao after the distribution beam is installed, performing platform system (bridge deck system) construction, installing a hoisting steel plate, and spot welding the contact point of the bridge deck and the distribution beam, wherein the quality of a welding seam is required to meet the requirement, and an expansion joint with the width of 1-2 cm is arranged between every two panels and is used for preventing the steel plate from warping and rolling caused by temperature change. Finally, installing a guardrail upright post and a guardrail handrail.
(4) Drilling platform construction
After the construction trestle is erected, namely an underwater drilling platform is erected at one side of the trestle at the pier position, the top height of the platform is consistent with that of the trestle, and the distance from the outer edge of the platform to the center of the drilling pile is required to be not less than 2m. The drilling platform is driven into the steel pipe pile by matching the crawler crane with the vibrating hammer to serve as a pile foundation. And erecting a drilling platform by adopting steel pipe piles, bailey beams, section steel and the like.
2. Pile foundation construction
(1) Pile foundation construction sequence arrangement
And during construction of trestle and platform, steel pipe piles in the cofferdam and near the periphery of the cofferdam are driven below the bottom of the bearing platform in a pile planting mode, so that the stability of the platform in the drilling machine operation process is ensured. And then a drilling operation platform is erected, and a drilling machine works on the drilling platform to finish the pile foundation construction task.
(2) Steel casing manufacturing and mounting scheme
Diameter of No. 13 and No. 14 pier drilled pileBy means of inner diameter->Steel casing with wall thickness of 16 mm. The steel pile casing is manufactured in sections in a processing plant, the length of each section is not more than 12m, the pile casing is formed by rolling A3 steel plates, every other transverse welding joint is additionally arranged at the welding joint to strengthen the steel belt with the thickness of 16mm and the width of 200 mm. The pile casing transverse joint at the position without steel belt adopts 12 steel plates with the thickness of 200 multiplied by 100 multiplied by 16mm for welding reinforcement except that the groove double-sided full welding is adopted, the reinforcing plate and the pile casing welding joint are disconnected at the crossing position with the pile casing main welding joint, and the 16Mn steel belt with the thickness of 16mm and the width of 500mm is additionally arranged at the pile casing foot to be used as a cutting edge. The two ends in the cylinder are provided with cross supports made of angle steel to keep the roundness of the protection cylinder.
(3) Construction of steel pile casing
In order to ensure the plane position and the verticality of the steel pile casing, a guide positioning frame is firstly installed, and then the steel pile casing is hung.
Firstly, measuring, positioning and paying off are carried out, and the center position of the pile is paid off by using a construction platform. The steel pile casing is uniformly processed on site, transported to the pier position by a transport box car, and inserted by adopting a 50t crawler crane matched with a 90KW vibrating hammer. And positioning the front surface and the side surface of the steel pile casing by using a total station, correcting the verticality of the steel pile casing when inserting and beating the pile casing, keeping the hammer and the steel pile casing at the same longitudinal axis, correcting the verticality of the steel pile casing once every 1-2 m, and continuing inserting and beating after adjustment until the steel pile casing is driven into bedrock and does not sink.
When the pile casing cannot sink under the action of the vibrating hammer and cannot reach the bottom of +28.818 m. The pile casing follow-up mode is adopted, the rotary drilling drill or the impact drill digs (impacts) downwards in the pile casing below the back cover, and then the vibration hammer vibrates the pile casing to enable the pile casing to reach the corresponding position.
(4) Drilling and pouring
Every main pierPile foundation 12 roots, wherein: each pile length of the # 13 pile is 54m, and each pile length of the # 14 pile is 49m. And (3) fixing the steel pile casing in place, and preparing slurry after the bottom sealing concrete pouring is completed. Drilling, emptying, placing a reinforcement cage and pouring concrete.
3. Rotary drilling and cutting
(1) Preparation for slitting construction
Before slitting, the inner platform needs to be dismantled, and the sand egg layer is cleaned as much as possible along the cofferdam position by utilizing a grab bucket, a long-arm hook machine and a sand pump. The cleaning condition is determined according to the effect, and the diver is launched to check the effect. The rotary drilling bit selects Xu Gong XR360 and the jump groove is excavated.
The accurate measurement position is required to be measured during the slitting operation, and the positioning is accurate; before slitting, the platform in the influence range is required to be divided into an inner part platform and an outer part platform, the structure of overhanging is forbidden when rotary drilling operation is performed, the relation between each beret sheet and the I-steel beam is carefully checked, and the overhanging part is found to be required to be removed.
The rotary drilling rig and the crawler crane cannot be close to each other, and other equipment cannot be uniformly arranged on the platform, so that accidents caused by local load concentration are avoided.
(2) Grooving construction
Geological survey is carried out according to main pier pile foundation sand samples and 12# and 15# riverbeds before double-wall steel cofferdam pre-cutting construction, the hardness degree of a base stratum is found to be far smaller than that of an expected base stratum, then XR360 rotary drilling is adopted to drill and match with a spiral drill bit, and cofferdam lowering is carried out after the whole circumference of cutting. 130 cuts are made, the annular radius is 16.60m, and the adjusting space of 30cm outside the cofferdam is ensured. And in the process of slitting, measuring and hole-by-hole positioning are adopted. The cofferdam cutting edge can directly fall into the groove by 80cm, and then the rock stratum on the inner side of the cofferdam is removed by utilizing the self weight, a hydraulic grab bucket, a long arm excavator and the like, so that the cofferdam is ensured to continuously sink until reaching the designed elevation position. In the process of rotary drilling and cutting, the actual riverbed elevation is found to be 34-36 m, the bedrock layer elevation is basically kept around 31.5m, the bedrock surface is not less than 1.5m for ensuring the pile foundation cutting depth, the effective height of the bottom sealing concrete is not less than 2m, the on-site cutting elevation is determined to be 29.0m, and the vertical drilling height of the rotary drilling and cutting is 23m.
4. Cofferdam lowering
(1) Lowering system
The cofferdam descending system adopts a continuous jack to cooperate with a steel strand for descending. The continuous jack is characterized in that according to stress, a computer is operated to directly input data, and the operation is simple and convenient; the automatic and continuous reciprocating descending can be realized, and the descending speed is high; only a plurality of people are needed to observe the deviation condition at regular time.
8 anchor spiral steel pipes are annularly and equidistantly arranged along the outer wall of the cofferdam 1 to serve as a lowering pile 2. The bottom end of the lowering pile 2 is anchored and consolidated with a river bed by adopting reinforced concrete.
According to the force analysis condition of the continuous jack 3 and the empirical data requirement that the stressed length of the steel strand 4 is not smaller than 2m. The lifting point parts of the jack 3 are reinforced, 8 lifting points are adopted, and the lifting points are divided into two types. The main difference is that the distance between the two-wall steel cofferdam and the outer wall of the double-wall steel cofferdam is 40cm and 50cm respectively, and the two-wall steel cofferdam is provided with a first-type lifting point 2 and a second-type lifting point 6.
The two types of hanging points are distributed on the plane, the hanging points are arranged one by one according to the numbers of the on-site guide piles, and the accuracy of the position model is ensured. Wherein two first type suspension points are separated by one second type suspension point.
The hanging point adopts double I40b to form a stressed main beam; the main beam of the upper suspension point 5 passes through the guide piles, the I-steel is provided with reinforcing front plates (sigma=20mm) according to the interval of 30cm, and the I-steel bottom is provided with reinforcing rib plates (sigma=20mm). And a 160mm hole is reserved between the I-shaped steels and is used as a penetration space of a steel strand. A50 mm thick round steel plate (diameter 1.0 m) is arranged at the top of the section steel, and a 150mm round hole is formed in the section steel as a steel strand passing space. 200 tons of continuous tensioning jack equipment is arranged at the top of the round steel plate.
In order to enhance the stability of the stressed structure of the guide pile steel pipe, and evenly distribute the whole stress. And after the hanging point is set, filling the steel pipe with fine sand, and pouring 1m high C30 concrete at the top to pour the steel pipe and the hanging point structure into a whole.
The lower hanging point 6 is set: the 2m position on the cofferdam blade foot horizontally passes through the cofferdam structure, I40b I-steel double roots are adopted as a horizontal main beam, a reinforcing rib plate is arranged, and a steel plate is adopted to be the same as an upper hanging point. The corresponding part of the lower hanging point and the upper hanging point is provided with a 15cm round hole, so that a steel strand can conveniently pass through the round hole. In order to ensure that the stress length of the steel strand is more than 2m, a double I40b I-steel with the length of 70cm is additionally arranged under the main beam at the lower lifting point and is firmly welded on the main beam, and a round hole with the length of 15cm is formed. The bottom is provided with a 10cm thick steel plate hole or is regulated by adopting a round anchor. The steel strand Shan Duangui is secured to the anchor using an extruder.
(2) Bearing bracket
Two rows of double I20b work steel and steel pipe perforation are welded on the outer wall of the guide pile on the outer side of the cofferdam near the cofferdam side, and the two rows of double I20b work steel and the steel pipe perforation are connected through a profile steel diagonal bracing to form a bearing bracket. The outer end of the bracket exceeds the steel cofferdam by 1m, and an operation platform is erected on the bracket. The bracket is assembled at 16 positions.
(3) Limiting device
The limit is arranged on steel casings at four inner corners, I40b I-steel spacing is adopted for 2m arrangement, and 2.5m I-steel 40b is vertically placed near the cofferdam and used as limiting equipment for preventing the cofferdam from shifting due to uneven stress, water flow impact and the like.
(4) Cofferdam inspection
After the cofferdam segment is processed, firstly, each block is numbered, and the number range is as follows: 0-1-5-16; numbering scheme: spraying paint; then checking the size, radian, truss and weld quality one by one, and the detection method comprises the following steps: ruler amount, visual inspection, kerosene penetration method, and the like. After the detection is qualified, the prescription can be transported to the site.
(5) Cofferdam transportation
The No. 13 pier adopts steam transportation, the No. 14 pier adopts a steam transportation matched barge to transport to the pier platform position, and then 50 tons of crawler cranes are discharged on the platform.
And after other materials on the platform are cleaned, the cofferdam is placed under the space without any obstacle. And (3) hoisting by adopting a 50-ton crawler crane, wherein each section of each cofferdam is 656cm long, and 4 hoisting points are arranged in total. And measuring and lofting out the plane contour line of the cutting edge of the first sleeve box cofferdam and the block segment line on the bearing bracket and the assembly platform by using a total station. The installation of the first block cofferdam is to strictly control the deviation of the plane position size and the verticality, and the first block cofferdam can be fixed after being detected to meet the requirements.
(6) Cofferdam assembly
When a certain block is assembled, when errors of the plane position size, the perpendicularity and the design position are found to be larger, the block is adjusted to be at the design position by cutting joints as much as possible, so that larger accumulated errors are reduced when the folding sections are assembled. Welding the assembly seam between two steel sleeve cofferdams, requiring double-sided full welding, and detecting penetration condition by kerosene, wherein measures should be taken to reduce deformation of the panel during welding, such as symmetrical jump welding of sections, and then repair welding to reach full welding.
50 ton crawler crane is adopted for assembly, the working radius of the crawler crane is 12m, the length of a main arm is 16.0m, and the maximum hoisting weight is 9.5t > the maximum weight of the section is 8.8t. With different assembling positions, the occupied position of the crane is also adjusted.
And the two ends are assembled section by section from one side according to the blocks. And the assembling position of the first block is 2 blocks symmetrical along the bridge direction. Because of certain errors in the installation process, when the last 2 blocks are spliced, the error accumulation is large, and in order to ensure smooth installation, the compartment plate is recovered by 10cm in the length direction during the last processing, and the original length of the two side wall plates is kept. And cutting the redundant wall plates according to the final assembly condition. Eliminating the influence of accumulated errors.
(7) Cofferdam lowering procedure
The water level elevation is 44m when the cofferdam is lowered, the bearing bracket top elevation is 45.5m, the river bed elevation is 35m, and the cofferdam welding height is required to be 1.5m from the water surface. Therefore, only 44m+1.5m-35 m=10.5 m is needed, the cofferdam is in contact with the river bed. The sectional heights of the cofferdam designed in the prior art from bottom to top are as follows: 4.8m,6m,4.8m,2.8m, 3.1m, and a total height of 21.5m. In order to reduce the influence of water flow on the assembly of the cofferdam segments as much as possible, the first section and the second section are decided to be put down together after the assembly is completed. The main controls were as follows: the weight 117t of the first section cofferdam, pouring blade foot concrete after self-floating, and pouring the total weight 351t, namely under the self-floating state of the first section cofferdam, the jack is stressed 351t; if the total weight of the two sections of cofferdam is 349t after being completely assembled, the total weight is basically equivalent to the descending stress of the two sections. Therefore, the welding head and the welding two sections are adjusted to be put down once after the welding is finished. The top standard height of the assembled cofferdam is as follows: 56.3m, 4.3m above the platform.
After the first section and the second section are welded, performing weld inspection, lifting the cofferdam by 10cm by a jack, holding the load for 12 hours, observing stress deformation conditions of the cofferdam, lifting points and the like, then cutting off weighing brackets, starting the cofferdam to be released, observing deformation and deviation correction in the process, and placing 2.225m downwards, namely, the elevation of the top of the cofferdam is as follows: 52.575m, the cofferdam reaches self-floating, water is injected into the cofferdam for 2.5m height, the cofferdam is lowered again for 1.827m, the accumulated total lowering height is 4.052m, the elevation of the cofferdam top is 50.748m, the self-floating is achieved, the water injection is 1.7 m, the cofferdam is lowered again for 1.715 m, the self-floating is achieved, 1.6m high concrete is poured at the edge, the dead weight of the concrete is 351t, the cofferdam is continuously lowered, when the cofferdam is lowered again for 2.333m, and the total lowering height is 8.1m, the elevation of the cofferdam top is: 46.8m, the elevation of the cofferdam bottom is: 36.0m, and the cofferdam floats again; at the moment, the cofferdam is not contacted with the riverbed yet, the cofferdam top is higher than the riverbed, water is added for 1m, the cofferdam is placed down to the implantation, the third section of cofferdam is assembled for 4.8m, the elevation of the cofferdam top is 50.6m, equipment such as a long arm digger on an inner side platform is used for cleaning the contact position of cutting edges, a mud suction machine is used for sucking mud, sand pumping and placing down are carried out, water is injected into the cofferdam in the process, the water is injected for 6.4m, the cofferdam is placed down for 3.6m, the elevation of the cofferdam top is 47m, the elevation of the cofferdam bottom is 31.4m, concrete is poured for 2.3 m again, the cofferdam is placed down for 2.4m, the cofferdam bottom is placed in place for 29m, the digger, the hydraulic grab is used for grabbing pebbles and bedrock layer, and annular bottom sealing is carried out, and the top cofferdam is used for determining whether the fourth section is arranged according to the water level condition.
(8) Riverbed cleaning
After the cofferdam is lowered to the riverbed, the sand and pebbles in the cofferdam are cleaned synchronously with the lowering of the cofferdam, the sand and pebbles layer of the cover layer is cleaned by means of a long-arm excavator, a grab bucket and the like, and meanwhile water is injected into the cofferdam by a water pump, so that the height difference between the inner water surface and the outer water surface of the cofferdam is not more than 50cm. After the cover layer is removed, the sand and pebbles in the cofferdam are ensured not to be silted up, and the sand and pebbles in the pre-digging groove are pumped out along with the sinking of the cofferdam. The sand pump specifications are shown in the following table, and the minimum specifications are: NSQ200-15-22 model sand pump totally 8, symmetrically arrange. The theoretical flow rate of the sand pump is 140m 3 And/h, the estimated riverbed cleaning engineering amount is about 3621m 3 In order to ensure synchronous cofferdam lowering, 8 sand pumping pumps are uniformly arranged along the circumference, and the sand pumping speed is predicted: 1120m 3 ×0.6＝672m 3 And/h. The total amount of sand eggs in the groove is about 820m 3 Considering continuous dredging of river beds in the cofferdam, the sand and pebbles are required to be cleaned up about 1801m when the cofferdam is lowered 3 The lowering speed of the cofferdam is estimated to be 1.8m/h (without splicing time), and sand pebbles are required to be cleaned: 432.4m 3 Therefore, the lowering speed requirement of the cofferdam can be met.
Under the condition that the cofferdam is temporarily locked, the inner part is welded with the upper and lower climbing ladders, so that workers can reach the water surface, and 1m long-distance steel is horizontally welded at the position of the water surface of the cofferdam to serve as a sand pump hanging part. Then the sand pump is put down to the river bed surface and lifted up by 10 cm. The sand discharge port is fixed at the top of the platform and discharges the extracted sand to Ganjiang. And then synchronously starting a sand pump, slowly lowering the cofferdam, marking scales on the periphery of the cofferdam, measuring the height difference by adopting a level gauge along 8 lifting points of the cofferdam every 30cm, and adjusting the deviation by a jack when the two-point error exceeds 5 cm. If the heights of the top surfaces or the lowering depths are still different, the fact that the heights of the river sand at the bottom are not uniform is proved, the friction resistance is increased, and the sand pump at the position where the cofferdam is submerged less is turned on singly, and the river sand at the position is extracted independently. Until the lowering is uniform. Along with the lowering of the cofferdam, the sand pump falls along with the cofferdam. When the sand pumping approaches the bedrock surface, the diver drains, the relation between the sand pumping pump and the groove is checked, and the position of the sand pumping pump is adjusted, so that the sand pumping pump can smoothly fall into the groove along with the cofferdam, and the process is repeated until the cofferdam is lowered to the design position. At the moment, the sand pump should continue pumping sand for 30 minutes, whether river sand is still present at the sand outlet is observed, and then the sand pump is moved along the circumference, so that the sand eggs in the cofferdam groove are completely cleared.
The lowering speed should be slowed down, and the position and the horizontal state of the plane should be checked every 30cm of lowering, and the diver should check underwater if necessary.
(9) Attention points when cofferdam is put down
Before the cofferdam is put down, the four symmetrical directions of the cofferdam are required, the paint spraying interval is 30cm, the graduation marks are checked once when 60cm is put down, and after the deviation exceeds 10cm, the jack is adjusted in one direction.
Before lowering, checking and recording the plane position, the horizontal state and the like of the cofferdam; every 2 meters is measured again and compared with the initial value, and deviation is found to be corrected in time. The deviation rectifying measure adopts a single side or a single jack to start and adjust.
The descending process needs special personnel to instruct, and a plurality of persons measure the number of the report so as to avoid the deviation of the cofferdam caused by inconsistent descending speed.
When the cofferdam is lowered, no matter the jack or the sand pump is adjusted, the offset and the inclination of the cofferdam can not be corrected, and the existence of the drifting stone at the bottom is proved. After the cofferdam is lifted to a certain height through the reverse process of the jack, a diver is used for launching, and equipment such as a hand drill, an air compressor and the like is used for breaking the boulder.
The sand pumping in the cofferdam groove is carried out in the cofferdam, and because the depth of the groove is 2.0m, the minimum distance between the cofferdam and the groove is only 40cm, and the sand pumping is difficult to clean. The sand and pebbles in the groove are not thoroughly cleaned, the cofferdam cannot be put in place, and the following measures are adopted for treatment:
when the cofferdam is lowered to the position where the cofferdam cannot be lowered, the cofferdam is attached to the inner wall of the cofferdam, the hydraulic grab bucket is utilized in the circumferential direction, the long arm digger is used for directly cutting, the cutting forms an integral empty slot with the original cutting, the working space in the inner slot of the cofferdam is increased, the minimum width is increased to 1.4m, the cutting depth enters the foundation rock 2.0m deep main pier position, the riverbed needs to be cleaned, the cleaning position needs to be at the height of +31.818m, the cleaning depth is 4.8m, and the cleaning area is as follows: (30.5 m x 30.5 m/4) x pi= 730.25 square meters, the cleaning work amount is: 3505m 3 。
5. Cofferdam back cover
(1) Plugging before bottom sealing
The diver is launched to check individual suspended conditions of the cofferdam, the diver uses mould bag concrete (or intestine bags phi 100-150) to stop leakage, the mould bag concrete uses woven bags to contain 1:1 dry-mixed cement mortar, after the mould bag concrete is filled, the diver is immersed into the bottom of the cofferdam, the diver is placed to the corresponding position, and the gap of the edge foot of the cofferdam is blocked.
(2) Cofferdam annular bottom sealing
The inner diameter size of the main pier double-wall steel cofferdam is D=30.5m, the elevation of the bottom of the cofferdam is designed to be 29m, the bottom sealing is realized by adopting ring sealing, and the bottom sealing is realized in the depth of the dug groove. The total area of the back cover concrete is 197.8 square meters, and the thickness of the back cover is 2.5m, so the back cover concrete is 413m 3 . In order to ensure smooth bottom sealing and reliable concrete quality, a method of pouring underwater concrete is adopted for bottom sealing.
The pouring guide pipe in the cofferdam is fixed, after the cofferdam is put in place, 32 pipes are fixedly placed on the inner wall of the cofferdamCatheters with the length of 24m and each catheter needs to be infused with 12.9m 3 The flow radius R of the concrete is about 50m. And (5) strictly checking the connection quality of the guide pipes before assembling, and using the guide pipes after the guide pipes are checked to be qualified. And 2 guide pipes are symmetrically poured at the same opening.
The conduit is connected with 3m 3 The bottom sealing funnel is hung on the upper platform by a 20t guide chain. The lower end of the catheter was placed 20cm above the top of the back cover and checked with a measuring cable.
In order to increase the connectivity between the cofferdam and the concrete, a plurality of the inclined plates of the blade feet are welded vertically and horizontallyReinforcing steel bars.
The bottom sealing concrete is respectively supplied with No. 14 and No. 13 main piers by a Tianyu mixing station and a Zhangshan mixing station, transported to the site by a tank truck, and poured into a hopper for underwater bottom sealing concrete.
(3) Pumping water and cleaning river bed
After the cofferdam bottom sealing is completed for 4 days, the concrete strength (the co-culture test piece) reaches a design value C35, and then classified water pumping is started. After water pumping is completed, observing for one day, and if the cofferdam is stable, cleaning the riverbed in the cofferdam to the position of 30cm below the bearing platform. The manual and small-sized excavators are used for cleaning, and the crane is matched with the lifting. The local bottom sealing concrete is cleaned according to whether the construction condition of the bearing platform is influenced or not. In order to ensure that pumping can be successfully completed, 3 (500 m) 3 And/h) pumping water by using the water pump, and simultaneously, 4 water pumps are reserved for standby; the clear bottom in the cofferdam is arranged at a larger position of the circular arc, a 1m multiplied by 0.5m water collecting pit is arranged, and a water pump is arranged in the water collecting pit to pump water at any time.
In order to ensure the safety of the cushion layer structure, a 20cm multiplied by 20cm reinforcing steel bar net is arranged in the cushion layer, and reinforcing steel bars with phi 12mm are adopted; the concrete adopts C30 concrete.
When water pumping is finished, the steel cofferdam is subjected to larger buoyancy, and the stress condition of the internal structure of the steel cofferdam changes, so that the water level of the bulkhead is kept when the water in the cofferdam is discharged, if the water is not enough, the water is injected in time, and the water injection height in the bulkhead is lower than the cofferdam top by 6 m.
The invention has the advantages that:
(1) The safety is good. During construction of trestle and platform, steel pipe piles of special geology around the cofferdam are punched by a percussion drill, anchored steel reinforcement cages are hung and placed, pile planting anchoring is carried out in a mode of underwater concrete pouring, anti-capsizing capacity is improved, and construction safety is guaranteed.
(2) The construction period is shortened. The double-wall steel cofferdam is lowered by adopting a continuous jack and steel strand lowering technology, and an annular bottom sealing technology is adopted during bottom sealing, so that the work efficiency is improved, and the construction period is shortened.
(3) Protecting the environment. The double-wall steel cofferdam is cut by adopting a rotary drilling annular cutting technology, the conventional blasting technology is not selected, and the environment is protected to the greatest extent.
(4) The double-wall steel cofferdam is assembled by adopting an in-situ assembling technology without large equipment, so that the use of large machinery such as a transport ship is reduced, and good economic benefit is obtained.
Although the present invention has been described with reference to the above embodiments, it should be understood that the present invention is not limited thereto, and that various changes and modifications may be made by those skilled in the art without departing from the spirit and scope of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.
Claims (7)
1. The comprehensive construction method of the pre-cut ring-sealed double-wall steel cofferdam deepwater foundation is characterized by comprising the following steps of: (1) setting up trestle and platform; (2) pile foundation construction; (3) double-wall steel cofferdam rotary drilling pre-cutting; (4) cofferdam assembly; (5) installing a cofferdam lowering system and a continuous jack; (6) lowering the cofferdam; and (7) cofferdam back cover;
the step (3) comprises:
1) Preparing for slitting construction: before slitting, removing the inner platform, and cleaning a sand egg layer along the cofferdam position by utilizing a grab bucket, a long arm hook machine and a sand pump;
2) And (3) grooving construction: adopting a rotary drilling bit to be matched with a spiral drill bit, and carrying out cofferdam lowering after the whole circumference of the cut is cut;
in the slitting construction: the number of the cut is 130, the annular radius is 16.60m, and the adjusting space of 30cm outside the cofferdam is further ensured; positioning by measuring hole by hole in the cutting process; the cofferdam cutting edge can directly fall into the groove by 80cm, and then the rock stratum on the inner side of the cofferdam is removed by utilizing the self weight, the hydraulic grab bucket and the long arm excavator, so that the cofferdam is ensured to continuously sink until reaching the designed elevation position; drilling to 29.0m elevation;
the step (6) comprises:
1) Setting a double-wall steel cofferdam lowering system;
2) Setting a pile planting anchoring in a reaction system of the lowering system;
3) The double-wall steel cofferdam lowering process comprises the following steps:
31 Hanging point setting): the lifting points are arranged at the tops of 8 anchor piles on the circumference of the cofferdam, so that lifting point components of the jack are reinforced, and 8 lifting points are adopted;
32 Upper hanging point structure): the hanging point adopts double I40b to form a stressed main beam; the main beam of the upper hanging point passes through the guide piles, the I-steel plates are provided with reinforcing front plates according to the interval of 30cm, and the I-steel bottoms are provided with reinforcing rib plates; reserving a 160mm hole between I-steel bars as a penetration space of a steel strand; a 50mm thick round steel plate is arranged at the top of the section steel, and a 150mm round hole is formed in the section steel as a steel strand passing space; 200 tons of continuous tensioning jack equipment is arranged at the top of the round steel plate; filling the anchoring steel pipe with fine sand after the hanging point is installed, and pouring 1m high C30 concrete at the top to pour the steel pipe and the hanging point structure into a whole;
33 A lower hanging point structure): horizontally penetrating a cofferdam structure at a position 2m above a cofferdam blade foot, adopting I40b I-steel double roots as a horizontal main beam, arranging a reinforcing rib plate, and adopting a steel plate to be the same as an upper hanging point; a round hole of 15cm is formed at the position corresponding to the lower hanging point and the upper hanging point, so that a steel strand can conveniently pass through the round hole; in order to ensure that the stress length of the steel strand is more than 2m, a double I40b I-steel with the length of 70cm is additionally arranged under the main beam at the lower lifting point and is firmly welded on the main beam, and a round hole with the length of 15cm is formed; the bottom is provided with a 10cm thick steel plate opening or is regulated by adopting a round anchorage device; adopting an extruder to fix the steel strand Shan Duangui on the anchor;
34 Bearing bracket): two rows of double I20b work steel of each row are welded with the perforation of the steel pipe by adopting a profile steel diagonal bracing to connect the outer walls of the anchoring piles on the outer sides of the cofferdam close to the cofferdam side, so as to form bearing brackets; the outer ends of the brackets exceed the steel cofferdam by 1m, and an operation platform is erected on the brackets;
35 Limit): the method is completed by arranging an anti-displacement device on steel casings at four inner corners, wherein the device consists of I-steel with the length of 2.5m and I40b and is used for preventing the cofferdam from being deviated due to uneven stress and water flow impact;
36 Checking and assembling the cofferdam;
37 A) lowering the cofferdam.
2. The comprehensive construction method of the pre-cut ring-sealed double-wall steel cofferdam deepwater foundation according to claim 1, wherein the step 2) of setting the pile planting anchoring measure by the reaction system of the lowering system comprises the following steps: and (3) lowering the counterforce pile, namely adopting a steel pipe pile with the diameter of phi 1000 multiplied by 10mm, vibrating and driving sandy cobbles into a bedrock layer, punching a hole by adopting a percussion drill in the steel pipe pile, hanging an anchoring reinforcement cage, and planting the pile for anchoring in an underwater concrete pouring mode, wherein the anchoring depth of the gravel layer is 2.5m below the steel pipe, so that the root stability of the steel pipe pile is improved, and the anti-overturning capacity of a trestle is enhanced.
3. The comprehensive construction method of the pre-cut ring-sealed double-wall steel cofferdam deepwater foundation according to claim 1, wherein the 36) cofferdam inspection and assembly comprises:
and (3) checking: after the cofferdam segments are processed, firstly, numbering each block; then checking the size, radian, truss and weld quality one by one, and transporting to the site after the detection is qualified; welding an assembly seam between two steel sleeve cofferdams, fully welding two sides, and detecting the penetration condition by using kerosene;
assembling: the sequence is assembled from one side to two ends section by section according to the block.
4. The comprehensive construction method of the pre-cut ring-sealed double-wall steel cofferdam deepwater foundation according to claim 1, wherein the step 37) of cofferdam lowering specifically comprises:
the method comprises the steps of adopting a grab bucket and a long-arm hook machine to clean a riverbed in a cofferdam range, checking cleaning conditions by a diver, circularly assembling a first two-section crane of the cofferdam, checking weld quality, setting a lowering system, measuring and correcting the position of the cofferdam, the cofferdam level, debugging a jack, fully stressing the jack, observing and dismantling an operation platform, lowering the jack, entering water into the cofferdam, measuring and monitoring the position and level, lowering the cofferdam, self-floating the cofferdam, locking the jack, injecting water, lowering again, contacting the riverbed by the cofferdam, pouring concrete on the edge of the cofferdam, checking the relationship between the cofferdam and the riverbed by the diver, measuring and measuring the position and level, assembling a third section of cofferdam, starting a sand pump, hydraulic grab bucket, cleaning by the long-arm digger, cooperating and cleaning, lowering the cofferdam, entering the riverbed, checking the surrounding condition by the diver, splicing a fourth section of the cofferdam, continuously injecting and putting the cofferdam into a foundation, clearing residual sand and stones in a cofferdam groove by a suction machine, completely exposing the foundation rock face, and stopping the edge of the cofferdam, and sealing the edge by sealing by the water.
5. The comprehensive construction method of the pre-cut ring-sealed double-wall steel cofferdam deepwater foundation according to claim 1, wherein the cofferdam bottom sealing in the step (7) comprises bottom sealing cleaning construction:
restoring the platform in the cofferdam after the cofferdam is lowered to the riverbed; firstly, removing a sand pebble layer of a covering layer by using a long-arm excavator and a grab bucket; when the long-arm excavator and the hydraulic grab bucket cannot be cleaned, a steel pipe with the diameter of 300mm is inserted into a riverbed, and 2 single-screw air compressors with the diameter of 22 m/s are used for supplying air to perform mud suction and sand egg suction operations; cleaning at any time along with the sinking of the cofferdam;
after the cofferdam enters the riverbed, marking scales on the periphery of the cofferdam, measuring the height difference by adopting a level gauge along 8 lifting points of the cofferdam every 30cm, and adjusting the deviation by a jack when the two points are found to be more than 5 cm; when the cofferdam cutting edge is close to the bedrock surface, the diver drains, and the position of the suction dredger is adjusted, so that the suction dredger can timely clear a gap with the width of 1m between the cofferdam and the sandy pebble, and the process is repeated until the cofferdam is lowered to the bedrock surface; the suction dredge should continue to pump sand for 30 minutes, observe whether the sand outlet has river sand to appear, then follow the circumference and remove the sand pump, guarantee that the cofferdam inslot sand ovum is totally clear.
6. A deep water double-wall steel cofferdam lowering system applied to the comprehensive construction method of the deep water foundation of the pre-cut ring-sealed double-wall steel cofferdam as set forth in any one of claims 1 to 5.
7. The deepwater double-wall steel cofferdam lowering system of claim 6, comprising: the cofferdam, pile, jack and steel strand wires of transferring down, the interval is annular to set up 8 pile down on the cofferdam outer wall, pile bottom end adopts reinforced concrete and riverbed anchor to consolidate down, the jack is continuous stretch-draw jack, adopts 8 hoisting points, the hoisting point with pile one-to-one down.
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| CN108532616A (en) * | 2018-05-04 | 2018-09-14 | 中国建筑第四工程局有限公司 | A kind of bridge Double-Wall Steel Boxed Cofferdam jack synchronization sinking construction engineering method |
| CN109371997A (en) * | 2018-12-04 | 2019-02-22 | 中铁六局集团有限公司 | A kind of double-wall cofferdam and pier construction method |
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| CN111119212A (en) * | 2019-12-18 | 2020-05-08 | 中建三局基础设施建设投资有限公司 | Construction method for sinking double-wall steel cofferdam under deep clay layer condition |
| CN111119213A (en) * | 2019-12-18 | 2020-05-08 | 中建三局基础设施建设投资有限公司 | Double-wall steel cofferdam with open edge feet and construction method thereof |
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| CN113550340A (en) * | 2021-07-23 | 2021-10-26 | 广州市市政工程机械施工有限公司 | Construction method of deepwater foundation of double-wall steel cofferdam without sealing bottom under deepwater rock entering condition |
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