CN101200898A - Construction Method of Bored Pile Foundation in Bare Slate and Shallow Overburden - Google Patents

Abstract

The invention relates to a construction method of a bored pile foundation, in particular to a construction method of a bare slate and shallow covering layer bored pile foundation which adopts jacket group jackets and steel cofferdams. It manufactures the cofferdam side plate, conduit and casing into a high and low leg structure, and then manufactures the high and low leg structure as a whole into a steel casing group and a jacket structure, welds the cofferdam side plate into a steel cofferdam and combines it with the casing group The jacket is welded into a whole, and the casing group jacket is hoisted and accurately positioned by a lifting device and lowered to the pier position. After the casing group jacket is leveled, concrete is used to seal the inside of the cofferdam with concrete to stabilize the casing group conduits The holes at the bottom of the casing and the plugging are installed, and the construction platform is installed on the jacket of the casing group to carry out the construction of bored piles. The invention effectively resists the effects of water flow, wind wave and wind load, ensures the stability of the steel casing and the platform, avoids the phenomena of slurry leakage and hole channeling during drilling construction, and ensures the smooth construction of bored piles at pier positions in bare slate and shallow overburden layers.

Description

Construction Method of Bored Pile Foundation in Bare Slate and Shallow Overburden

technical field

The invention relates to a construction method of a bored pile foundation, in particular to a construction method of a bare slate and shallow covering layer bored pile foundation which adopts jacket group jackets and steel cofferdams.

Background technique

With the continuous development of society, more and more bridges are being built, the difficulty of construction is increasing, and the quality requirements of construction are getting higher and higher. In the past, bridges were generally built on rivers and lakes with relatively thick soil layers. Under such geological conditions, the construction of bored pile foundation generally adopts the traditional positioning pile platform method or the construction method of inserting positioning piles and steel casing after the jacket is lowered. However, there are many rivers, lakes and marine formations with bare slate or shallow overburden. If these methods are used for construction, the stability of the steel casing and the tightness of the bottom opening of the casing cannot be guaranteed due to the effects and influences of water flow, wind waves and wind loads. Guaranteed, thus affecting the construction progress and quality. Therefore, on the bare slate or shallow overburden on rivers, lakes and oceans, the traditional positioning pile platform method or the construction method of inserting positioning piles and steel casings after the jacket is lowered cannot be used for the construction of pier position bored piles. So finding a new construction method to solve the above technical problems has always been a problem to be solved urgently by those skilled in the art.

Contents of the invention

The purpose of the present invention is to provide a light slate and shallow concrete casing using casing group jackets and steel cofferdams for the defects of the traditional positioning pile platform method or the construction method of inserting positioning piles and steel casings after the jacket is lowered. The new construction method of the overburden pile foundation can effectively resist the effects of water flow, wind wave and wind load, so that the construction can be carried out safely and reliably.

The technical solution of the present invention is achieved in the following way: it is to manufacture the cofferdam side plate, conduit and casing into a high and low leg structure, and then the high and low leg structure is integrally manufactured into a steel casing group and a jacket structure, and the cofferdam side plate The steel cofferdam is welded into a steel cofferdam and integrally welded with the casing group jacket, and the casing group jacket is hoisted and accurately positioned by a lifting device and lowered to the pier. After the casing group jacket is leveled, the cofferdam is fixed with concrete Carry out concrete back sealing inside, stabilize the casing group jacket and plug the loopholes at the bottom of the casing, and install a construction platform on the casing group jacket for bored pile construction.

The preferred technical solution of the present invention is to use a multi-beam sounding ship to accurately measure the elevation of the pier seabed rock surface, and to manufacture the cofferdam side plate, compartment plate, each conduit and casing into a form of high and low legs according to the measured elevation, and The rock surface is consistent; the steel cofferdam is provided with a partition board; the conduit is inserted with piles, and the construction platform is installed on the piles.

According to the construction characteristics of bare slate and shallow overburden pier bored piles on rivers, lakes and oceans, the present invention adopts the construction method of "casing group jacket + steel cofferdam", which can effectively resist water flow, wind waves and wind loads. Under the action of wind, waves and water flow, it can ensure the stability of the steel casing and the platform, avoid the phenomenon of slurry leakage and hole channeling during drilling construction, and ensure the smooth construction of bored piles in bare slate and shallow overburden piers.

Description of drawings

Fig. 1 is the overall layout plan of light slate and shallow overburden pier construction of the present invention

Fig. 2 is another overall layout diagram of light slate and shallow overburden pier construction of the present invention

Fig. 3 overall elevation layout of light slate and shallow overburden pier construction of the present invention

Fig. 4 overall side layout of the pier construction of light slate and shallow overburden layer of the present invention

In the figure: 1-high and low leg casing, 2-casing, 3-steel cofferdam side plate, 4-connecting casing, 5-positioning steel wire rope, 6-construction platform, 7-underwater bottom sealing concrete, 8-gravel Bags and concrete bags, 9-stakes.

Detailed ways

The present invention will be further described below in conjunction with accompanying drawing:

As shown in Figures 1 and 3, the present invention manufactures the cofferdam side plates, conduits and casings into high and low leg structures, and then manufactures the high and low leg structures as a whole into steel casing groups and jacket structures, and the cofferdam side plates The steel cofferdam is welded into a steel cofferdam and integrally welded with the casing group jacket, and the casing group jacket is hoisted and accurately positioned by a lifting device and lowered to the pier. After the casing group jacket is leveled, the cofferdam is fixed with concrete Carry out concrete back sealing inside, stabilize the casing group jacket and plug the loopholes at the bottom of the casing, and install a construction platform on the casing group jacket for bored pile construction. The steel cofferdam may be provided with partition boards; the conduit is inserted with piles, and the construction platform is installed on the piles.

Specific steps are as follows:

1. Topographic survey

The elevation of the river (sea) bed in the construction area is measured by a multi-beam sounding ship, and the measurement results are converted into a topographic map of the elevation of the river (sea) bed.

2. Fabrication, lowering and leveling of casing group jacket + steel cofferdam

Determine the relative height difference and position of each casing 1, casing 2 and steel cofferdam side plate 3 according to the measured topographic map of the river (sea) bed surface elevation, to ensure that the casing group jacket is lowered to a certain height above the construction water level . The high and low leg casing 1 is welded into a whole by the connecting sleeve 4 through the temporary copying pad to form a casing group, and several casings 2 are arranged around the casing group, and a large casing is formed by welding the connecting casing 4 and the casing 1. The jacket can be used to level the casing group jacket by inserting piles 9 in the casing when it is lowered, and the anti-overturning moment of the jacket has also been increased. Install steel cofferdam trusses and steel cofferdam side plates 3 around the large jacket, and install casing group jacket lifting points to complete the manufacture of casing group jackets.

After the casing group jacket is fabricated, the casing group jacket is hoisted to the construction pier by a large floating crane. Use the measurement and positioning system to locate and anchor the floating crane. Set up the working positioning ship at an appropriate position, install the winch, and the guiding and positioning wire rope 5 of the engineering ship is fixed on the top of the jacket. The lowering time of the jacket should try to avoid the time periods of fast flow such as rising and falling tides, tidal surges and astronomical spring tides, and choose to lower the jacket during low and flat tides. In order to overcome the inclination or instability of the jacket due to the force of the water flow, the positioning piles 9 at the four corners are temporarily fixed with the casing group jacket and lowered together, and are lowered under the auxiliary positioning of the positioning ship hoist, and the casing group jacket is lowered After it is in place, untie the four positioning corner piles 9, and immediately perform insertion, leveling, and deviation correction, so that the lowering deviation and verticality of the jacket meet the design requirements.

3. Back cover inside the cofferdam

After the casing group jacket is lowered into place, in flat tide weather with little wind and waves, use a concrete mixing ship or an onshore concrete factory to carry out concrete back sealing on the casing group jacket, and pour underwater bottom sealing concrete 7 to make the casing group and the foundation The rock is bonded into a whole to enhance the overall stability of the casing group jacket and prevent concrete leakage when pouring into piles. Before the back sealing, the floating crane can be used to throw and fill gravel bags and concrete bags 8 outside the cofferdam, and divers lightly dive inside the cofferdam to plug the leakage. In order to improve the success rate of back sealing, in addition to setting cofferdam side panels 3 around the jacket of the casing group, partition boards are also installed in the cofferdam to divide a large cofferdam into several small cofferdams. Progress from low to high elevations.

4. Install bored pile platform for drilling

After the back cover is successful, build a construction platform 6 on the casing group jacket, and install a drilling rig on the platform 6 to carry out bored pile construction.

Claims (4)

1. A construction method for bare slate and shallow overburden bored pile foundations, characterized in that it manufactures the cofferdam side plates, conduits and casings into high and low leg structures, and then makes the high and low leg structures integrally into steel protection The shell group and jacket structure, the side plate of the cofferdam is welded into a steel cofferdam and welded with the casing group jacket as a whole, and the casing group jacket is hoisted and accurately positioned by a lifting device and lowered to the pier position, and the casing After the jacket group is leveled, concrete is used to seal the inside of the cofferdam with concrete to stabilize the casing group jacket and seal the leaks at the bottom of the casing group, and install a construction platform on the casing group jacket to carry out bored pile construction. 2. The construction method of bare slate and shallow overburden pile foundations according to claim 1, characterized in that: the multi-beam sounding ship is used to accurately measure the pier seabed rock surface elevation, and the cofferdam is placed according to the measured elevation. Side panels, bulkheads, each conduit and casing are manufactured as high and low legs to conform to the rock face. 3. The construction method of bare slate and shallow overburden bored pile foundation according to claim 1, characterized in that: the steel cofferdam is provided with a partition board. 4. The construction method of bare slate and shallow overburden bored pile foundation according to claim 1, characterized in that: piles are inserted in the conduit, and the construction platform is installed on the piles.

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