阅读说明：本技术 一种深水入岩条件下无封底双壁钢围堰深水基础施工方法 (Construction method of deepwater foundation of double-wall steel cofferdam without sealing bottom under deepwater rock entering condition ) 是由 刘昕炜 首京 许洪左 欧阳继平 许哲辉 王刚 王聪 黄清河 欧佳林 王伟 于 2021-07-23 设计创作，主要内容包括：本发明涉及一种深水入岩条件下无封底双壁钢围堰深水基础施工方法,在岩层质河床上预成槽,双壁钢围堰下放至槽内后灌注混凝土,双壁钢围堰在槽内通过浇筑混凝土与河床固结；双壁钢围堰就位后,围堰内无封底混凝土,抽水完成后采用机械进行清基。具体包括如下步骤：(1)桩基施工；(2)旋挖机引槽；(3)安装拼装支架；(4)双壁钢围堰拼装；(5)安装下放系统；(6)双壁钢围堰下放；(7)槽内浇筑混凝土；(8)抽水；(9)清基。本发明在河床地质坚硬、围堰内无封底混凝土条件下提供了一种工期短、安全可靠、施工环保、经济合理且质量满足要求,属于大型桥梁的深水基础施工技术领域。(The invention relates to a construction method of a deepwater foundation of a double-wall steel cofferdam without a sealing bottom under the condition of deepwater rock entering, wherein a groove is preformed on a rock stratum riverbed, a double-wall steel cofferdam is placed into the groove and then poured with concrete, and the double-wall steel cofferdam is consolidated with the riverbed in the groove by pouring the concrete; and after the double-wall steel cofferdam is in place, no bottom sealing concrete exists in the cofferdam, and the foundation is cleaned by adopting machinery after water pumping is finished. The method specifically comprises the following steps: (1) constructing a pile foundation; (2) a rotary digging machine guide groove; (3) mounting an assembling support; (4) assembling the double-wall steel cofferdam; (5) installing a lowering system; (6) lowering the double-wall steel cofferdam; (7) concrete is poured in the groove; (8) pumping water; (9) and (5) clearing the base. The invention provides a construction method which is short in construction period, safe, reliable, environment-friendly in construction, economical and reasonable and meets the requirements for quality under the conditions that riverbed geology is hard and bottom sealing concrete does not exist in cofferdams, and belongs to the technical field of deep water foundation construction of large bridges.)

1. A construction method of a deepwater foundation of a double-wall steel cofferdam without a back cover under the condition of deepwater rock entering is characterized by comprising the following steps: pre-forming a groove on a rock stratum riverbed, pouring concrete after the double-wall steel cofferdam is put into the groove, and solidifying the double-wall steel cofferdam with the riverbed in the groove by pouring concrete; and after the double-wall steel cofferdam is in place, no bottom sealing concrete exists in the cofferdam, and the foundation is cleaned by adopting machinery after water pumping is finished.

2. The construction method of the deepwater foundation of the double-wall steel cofferdam without the back cover under the deepwater rock-entering condition as claimed in claim 1, wherein the construction method comprises the following steps: the method comprises the following steps: (1) constructing a pile foundation; (2) a rotary digging machine guide groove; (3) mounting an assembling support; (4) assembling the double-wall steel cofferdam; (5) installing a lowering system; (6) lowering the double-wall steel cofferdam; (7) concrete is poured in the groove; (8) pumping water; (9) and (5) clearing the base.

3. The construction method of the deepwater foundation of the double-wall steel cofferdam without the back cover under the deepwater rock-entering condition as claimed in claim 2, characterized by comprising the following steps: in the step (2), a rotary drilling is adopted to separate holes and jump, and the measurement and hole-by-hole positioning are carried out in the groove guiding process, so that the width and the depth of the groove guiding are ensured.

4. The construction method of the deepwater foundation of the double-wall steel cofferdam without the back cover under the deepwater rock-entering condition as claimed in claim 2, characterized by comprising the following steps: in the step (3), an assembling support is welded on the outer side of the steel casing, and a lower inclined support is adopted below the assembling support as a main stress member; the steel protective cylinders are connected into a whole by steel pipes.

5. The construction method of the deepwater foundation of the double-wall steel cofferdam without the back cover under the deepwater rock-entering condition as claimed in claim 2, characterized by comprising the following steps: in the step (4), lofting an assembly contour line on the assembly support before assembly, welding a limiting block at the edge of an outer contour line, and controlling the plane position of a lower opening line of the double-wall steel cofferdam through the limiting block; the upper opening of the double-wall steel cofferdam is fixed outside the steel casing through welding temporary support; and meanwhile, controlling the verticality of the double-wall steel cofferdam.

6. The construction method of the deepwater foundation of the double-wall steel cofferdam without the back cover under the deepwater rock-entering condition as claimed in claim 2, characterized by comprising the following steps: in the step (5), the lowering system comprises a main beam, a continuous jack, a hydraulic oil pump and a high-strength steel strand; the main beam is arranged above the steel casing, and a plurality of continuous jacks form a plurality of lowering points on the main beam; and controlling the double-wall steel cofferdam to be lowered through the continuous jack.

7. The construction method of the deepwater foundation of the double-wall steel cofferdam without the back cover under the deepwater rock-entering condition as claimed in claim 2, characterized by comprising the following steps: in the step (6), the double-wall steel cofferdam comprises a bottom section, a middle section and an upper section from bottom to top, and the double-wall steel cofferdam is placed down twice; the first lowering is finished by assembling the bottom section cofferdam and the middle section cofferdam, and the two sections of double-wall steel cofferdams are lowered as a whole; the second time is that the three sections of double-wall steel cofferdams are integrally put down after being completely finished; the double-wall steel cofferdam helps sinking by pouring water into the double walls.

8. The construction method of the deepwater foundation of the double-wall steel cofferdam without the back cover under the deepwater rock-entering condition as claimed in claim 2, characterized by comprising the following steps: and (7) after the double-wall steel cofferdam is sunk to the position, pouring concrete in the groove, and filling concrete in the double walls to ensure that the concrete pressure of the inner wall and the concrete pressure of the outer wall are consistent.

9. The construction method of the deepwater foundation of the double-wall steel cofferdam without the back cover under the deepwater rock-entering condition as claimed in claim 2, characterized by comprising the following steps: and (8) pumping water in the double-wall steel cofferdam after the concrete reaches the strength, and installing an inner support of the double-wall steel cofferdam.

10. The construction method of the deepwater foundation of the double-wall steel cofferdam without the back cover under the deepwater rock-entering condition as claimed in claim 2, characterized by comprising the following steps: and (9) after the water pumping is finished, lowering the excavator with the gun head to a river bed to break the rock stratum.

Technical Field

The invention relates to a deep water foundation construction technology of a large bridge, in particular to a construction method of a deep water foundation of a double-wall steel cofferdam without a sealing bottom under a deep water rock entering condition.

Background

In recent years, with the construction of bridges spanning large rivers and rivers, large-span deepwater bridges have been rapidly developed, and the deepwater foundation construction of large bridges is usually carried out by means of cofferdams.

CN106638640A discloses a construction method of a bottom-sealing-free concrete combined cofferdam under rock stratum geological conditions, which comprises the following steps: firstly, welding a support piece and a guide frame on the outer side of a steel casing around a bearing platform to be built; then inserting and driving the locking steel pipe pile downwards along the guide frame, wherein the bottom opening reaches the surface of a strongly weathered rock stratum; carrying out rotary drilling downwards from the inside of the steel pipe pile by using a rotary drilling rig, and constructing a drilled pile at the bottom of the steel pipe pile after the drilled pile penetrates into the weakly weathered rock stratum; after all the drilled piles at the bottoms of all the steel pipe piles are completely constructed, forming a closed cofferdam; then pumping out river water in the cofferdam and installing an inner cofferdam support; arranging a submerged pump in the cofferdam for pumping seepage water, and excavating and cleaning the foundation to the bottom of the bearing platform by using an excavator; and finally, pouring a concrete cushion layer at the bottom of the bearing platform, and finishing the construction of the bearing platform in an anhydrous dry environment. The construction method utilizes the rock stratum structure to form the waterproof structure, however, the construction process is complex, the whole cofferdam structure needs to be constructed on site, the construction requirement is high, and the construction difficulty is high.

Compared with other cofferdam structural forms, the double-wall steel cofferdam has higher rigidity and stability, good water stopping performance and relatively wide application of the structural form, and can be used as a water surrounding structure for lower structure construction and a template for bearing platform concrete construction. However, the double-wall steel cofferdam has the defects of larger structural weight and size, longer prefabrication and processing time and more difficult downward placing. In the prior art, a technology for constructing a deepwater foundation by combining a double-wall steel cofferdam structure and a rock stratum structure to form a water-proof structure does not exist.

Disclosure of Invention

Aiming at the technical problems in the prior art, the invention aims to: the construction method of the deepwater foundation of the double-wall steel cofferdam without the sealing bottom under the deepwater rock-entering condition is short in construction period, safe, reliable and environment-friendly.

In order to achieve the purpose, the invention adopts the following technical scheme:

a construction method of a bottom-sealing-free double-wall steel cofferdam deepwater foundation under deepwater rock entering conditions comprises the steps of pre-forming a groove on a rock stratum riverbed, pouring concrete after a double-wall steel cofferdam is placed into the groove, and solidifying the double-wall steel cofferdam with the riverbed in the groove through pouring concrete; and after the double-wall steel cofferdam is in place, no bottom sealing concrete exists in the cofferdam, and the foundation is cleaned by adopting machinery after water pumping is finished.

A construction method of a deepwater foundation of a double-wall steel cofferdam without a back cover under the condition of deepwater rock entering comprises the following steps: (1) constructing a pile foundation; (2) a rotary digging machine guide groove; (3) mounting an assembling support; (4) assembling the double-wall steel cofferdam; (5) installing a lowering system; (6) lowering the double-wall steel cofferdam; (7) concrete is poured in the groove; (8) pumping water; (9) and (5) clearing the base.

Preferably, in the step (2), a rotary drilling and hole-separating jumping drill is adopted, measurement is carried out in the groove guiding process, hole-by-hole positioning is carried out, and the width and the depth of the groove guiding are ensured.

Preferably, in the step (3), an assembling support is welded on the outer side of the steel casing, and a lower inclined support is adopted below the assembling support as a main stress member; the steel protective cylinders are connected into a whole by steel pipes.

Preferably, in the step (4), lofting an assembly contour line on the assembly support before assembly, welding a limiting block at the edge of an outer contour line, and controlling the plane position of a lower opening line of the double-wall steel cofferdam through the limiting block; the upper opening of the double-wall steel cofferdam is fixed outside the steel casing through welding temporary support; and meanwhile, controlling the verticality of the double-wall steel cofferdam.

Preferably, in the step (5), the lowering system comprises a main beam, a continuous jack, a hydraulic oil pump and a high-strength steel strand; the main beam is arranged above the steel casing, and a plurality of continuous jacks form a plurality of lowering points on the main beam; and controlling the double-wall steel cofferdam to be lowered through the continuous jack.

Preferably, in the step (6), the double-wall steel cofferdam comprises a bottom section, a middle section and an upper section from bottom to top, and the double-wall steel cofferdam is lowered twice; the first lowering is finished by assembling the bottom section cofferdam and the middle section cofferdam, and the two sections of double-wall steel cofferdams are lowered as a whole; the second time is that the three sections of double-wall steel cofferdams are integrally put down after being completely finished; the double-wall steel cofferdam helps sinking by pouring water into the double walls.

Preferably, in the step (7), after the double-wall steel cofferdam is sunk to the position, concrete is poured in the groove, and meanwhile, the double walls are filled with concrete, so that the pressure of the concrete on the inner and outer walls is consistent.

Preferably, in the step (8), after the strength of the concrete is reached, pumping water in the double-wall steel cofferdam, and installing an inner support of the double-wall steel cofferdam.

Preferably, in step (9), after the water pumping is completed, a digging machine with a cannon head is used for descending to a river bed to break the rock stratum.

The invention is suitable for the following environments: the method has strong adaptability to construction conditions that a bearing platform is hard to enter rock and a riverbed rock stratum, underwater blasting is not allowed, and the method is suitable for the middle-weathered and strong-weathered hard impervious rock stratum where steel sheet piles cannot be inserted and driven.

The invention has the following advantages:

(1) compared with a steel sheet pile and a steel pipe pile cofferdam, the construction in a medium weathering rock stratum or a strong weathering rock stratum usually needs to be conducted with hole leading, and the construction cost is high. And compare two kinds of cofferdams in the front, the double-walled steel cofferdam water stopping nature is better, and structural rigidity is bigger, and the construction is safer.

(2) The rotary drilling and spiral drill bit are adopted to pre-form the groove on the riverbed, the grooving depth of the riverbed is about 6.7 meters, the cofferdam is put down in place and then the construction is carried out in the groove according to the underwater concrete pouring process, the pre-grooving process reduces the construction difficulty and risk, and the height of the cofferdam can be controlled relatively. The steel cofferdam goes into the rock, has increased the anti-scouring ability of cofferdam, has increased antidumping ability, and structural security is better, and the cofferdam has better stability.

(3) The cofferdam is transported and assembled without large-scale ship hoisting equipment, thereby reducing the use of large-scale machinery such as a transport ship and obtaining good economic benefit.

(4) The cofferdam construction has no back cover concrete, saves materials, has economic advantages, saves the rising time of the strength of the back cover concrete, shortens the construction period and reduces the influence on the environment.

(5) For harder rock stratum of underwater geology, the base cleaning operation is generally carried out by adopting directional blasting, and the method has larger environmental pollution. The invention is relatively more economical and more environment-friendly in a way of cleaning the foundation. And after water pumping, the foundation is cleaned, the construction is controllable, the speed is high, and compared with directional blasting, the method is more economical, more environment-friendly and safer.

Drawings

Fig. 1 is a flow chart of a construction method.

Fig. 2 is a schematic view of a sequence of a guide groove of the rotary drilling machine.

Fig. 3 is a schematic diagram of assembly of cofferdams after pre-grooving.

Fig. 4 is a schematic view of concrete in the tank and the double wall after the cofferdam is lowered.

Fig. 5 is a schematic view of the cofferdam cross section after the cofferdam is lowered.

In fig. 2, the order of the guide slots and the jump holes is from (i) to (b). a is 2000mm, b is 300mm, and c is 1000 mm.

In fig. 3 to 5, 1 is the wall body of the double-walled steel cofferdam, 2 is the continuous jack of transferring the system, 3 is the girder of transferring the system, 4 is the high strength steel strand wires of transferring the system, 5 is the hoisting point support of transferring the system, 6 is the stopper, 7 is for assembling the support, 8 is the steel casing, 9 is the pre-grooving, 10 is the in-groove concrete, 11 is the in-double-walled concrete, 12 is the internal stay.

Detailed Description

The present invention will be described in further detail with reference to specific embodiments.

A construction method of a deepwater foundation of a double-wall steel cofferdam without a back cover under the condition of deepwater rock entering mainly comprises the following two parts: firstly, pre-forming a groove on a rock stratum riverbed, pouring concrete after a double-wall steel cofferdam is put into the groove, and solidifying the double-wall steel cofferdam with the riverbed in the groove through pouring concrete; and secondly, after the double-wall steel cofferdam is in place, no bottom sealing concrete exists in the cofferdam, and the foundation is cleaned by adopting machinery after water pumping is finished. The construction method has strong applicability to construction conditions such as a hard rock stratum riverbed surface underwater embedded bearing platform, no bottom sealing concrete in a cofferdam, no underwater blasting, and the like, provides experience for similar construction, and provides an important guiding function for deep water foundation construction of complex geology.

The method comprises the following specific steps:

(1) pile foundation construction

The construction method is characterized in that the construction is carried out by adopting a pile-first weir method, the pile foundation of the main tower is constructed by adopting a punching pile machine, the pile diameter is 2m, the diameter of the steel casing is 2.3m, and the pile machine is arranged on a construction platform to carry out pile foundation construction.

(2) Rotary drilling machine guide groove

After the pile foundation is finished, the construction platform needs to be dismantled before cofferdam grooving, and a rotary drilling rig is adopted for construction. The drill bit of 1.5m diameter is cooperated, 1.7m leading hole protects a section of thick bamboo, and each protects a section of thick bamboo and vertically overlaps 30cm, and transversely overlaps 100cm, separates the hole and jumps and bores, measures and advances the hole location one by one at the time of leading the groove in-process, observes the condition of leading the groove through the camera under water simultaneously, guides machinery to maintain the groove limit, ensures to lead the groove width 2m, leads the groove to the design depth, and the grooving degree of depth is about 6.7 meters.

(3) Mounting and assembling support

The assembly support of the cofferdam is welded on the outer side of the steel pile casing, the assembly support is formed by welding a double-assembly I45b I-shaped steel and a lower inclined strut, and the steel pile casings are horizontally connected into a whole by steel pipes. The splicing support is made of 2I45b I-steel, and the parallel steel pipe is made of a steel pipe with the diameter of 30. Aiming at the problem of overlarge local stress of the lower diagonal bracing bracket, a circle of 50cm arc reinforcing steel plate with the height and the wall thickness of 12mm is additionally welded at the intersection point of the lower diagonal bracing bracket and the steel casing.

(4) Double-wall steel cofferdam assembly

The double-wall steel cofferdam consists of three parts, namely a wall body, a blade foot and an inner support, wherein the wall body consists of an inner wall plate, an outer wall plate, a horizontal inclined support, a vertical stiffening rib, a horizontal annular plate and a communicating vessel. The inner wall plate and the outer wall plate are made of 10mm steel plates, the edge foot is reinforced by 12mm steel plates, the vertical ribs are made of 75X 50X 8 steel angles, the horizontal ring plate is made of 20mm steel plates, the horizontal inclined strut is made of 2X 125X 12 double-spliced steel angles, the enclosing purlin is made of 3 spliced 45b I-shaped steel, and the inner strut is made of 630X 10 round steel pipes. The cofferdam segment and the inner support are processed and manufactured in the field, are transported to the field for splicing and welding, and the communicating vessel is responsible for returning water to the inside of the cofferdam.

The cofferdam processed in a block mode in a factory is transferred to a construction site by a flat trailer, the cofferdam in the block mode is hoisted to an installation position by a 75t truck crane or a crawler crane, after a lower opening is in place, the cofferdam in the block mode is temporarily welded with a limiting block to be fixed, the upper portion of the cofferdam in the block mode is temporarily welded with section steel and a steel casing, the plane position and the verticality are checked and checked through a measuring instrument, and after the checking and checking meet the requirements, the blocks are welded. And (4) respectively assembling block by block from one side to two ends according to the drawing. The assembly is carried out for the first time, namely assembly of bottom sections and middle sections of cofferdams is carried out, after the assembly is finished, the two sections of steel cofferdams are lowered as a whole and float on the water surface, and assembly of upper sections of cofferdams is carried out after the cofferdams are stable.

(5) Installation lowering system

The cofferdam transferring system is a complete transferring system formed by a main beam, a continuous jack, a hydraulic oil pump and a high-strength steel strand as a flexible suspender and a hoisting point support, and the high double-wall steel cofferdam is controlled to be transferred by the continuous jack. The total weight of the cofferdam is about 680t, the lifting point girder adopts two double-spliced H45 steel to form the girder, totally 8 lowering points are arranged and are respectively positioned on the outside pile foundation steel casing, each lowering point adopts 200t continuous jacks, and each continuous jack is provided with 10 jacksThe lower end of a 1860 Mpa-grade high-strength steel strand is connected with a lifting point support, and the cofferdam is integrally and gradually put into water under a putting system.

(6) Lowering of double-wall steel cofferdam

And the cofferdam is placed downwards twice. And the first lowering is completed by assembling the bottom section cofferdam and the middle section cofferdam, and the two sections of steel cofferdams are lowered as a whole. And after the upper cofferdam is assembled, the upper cofferdam is integrally sunk after the three cofferdam systems are completely assembled for the second time. 2 centrifugal pumps are adopted for pumping water, and water is filled into the double walls to assist the sinking of the cofferdam.

(7) Concrete is poured in the groove

And concrete is poured in the groove, the cofferdam is poured in the groove after sinking in place, and the cofferdam is poured underwater until the cofferdam is level with the river bed surface. And filling concrete into the double walls, and pouring simultaneously to ensure that the concrete pressure of the inner wall and the outer wall is consistent, and when the concrete strength reaches 80%, coarse sand or water pressure in the double-wall filling is heavy to resist the buoyancy generated by pumping water in the subsequent cofferdam.

(8) Water pumping

And pumping water in the steel cofferdam when the strength of the concrete poured into the groove reaches 90 percent. 6-station 200m water pumping³The/h centrifugal pump. Before pumping water, the communicating vessel on the cofferdam wall body is closed, and the water is pumped to the river bed surface. And carrying out cofferdam internal bracing installation in the water pumping process.

(9) Cleaning base

After pumping water, a digging machine with a gun head is used for lowering the water to a riverbed to break rock strata, the truck is hung on the bridge floor of a trestle, earthwork in the cofferdam is transported ashore by matching with a hopper, and the bottom elevation is controlled according to the bottom elevation of the bearing platform.

The invention provides the construction method of the underwater foundation double-wall steel cofferdam with short construction period, safety, reliability, environmental protection, economy, reasonability and quality meeting the requirements under the conditions that the riverbed geology is hard and no bottom-sealing concrete exists in the cofferdam, and improves and perfects the construction technical level on the premise of taking advanced, reasonability, economy and safety as the construction technology, so that the engineering can smoothly complete the foundation construction.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.