CN112900264A

CN112900264A - Suspension bridge major diameter secant pile gravity type anchorage foundation enclosure structure and construction method

Info

Publication number: CN112900264A
Application number: CN202110171198.XA
Authority: CN
Inventors: 贾利强; 吴明远; 李玉彬; 张伟; 何锦章; 王树华; 蒋树勤; 过超; 付佰勇; 黄月超; 班富理; 覃浩; 何潇
Original assignee: Guangxi Xingang Transportation Investment Co ltd; CCCC Highway Consultants Co Ltd; CCCC Highway Long Bridge Construction National Engineering Research Center Co Ltd
Current assignee: Guangxi Xingang Transportation Investment Co ltd; CCCC Highway Consultants Co Ltd; CCCC Highway Long Bridge Construction National Engineering Research Center Co Ltd
Priority date: 2021-02-08
Filing date: 2021-02-08
Publication date: 2021-06-04

Abstract

The invention discloses a gravity type anchorage foundation enclosure structure for large-diameter secant piles of a suspension bridge and a construction method of the gravity type anchorage foundation enclosure structure. The design structure is simple, and the lining construction is realized without adopting a reverse construction method in the excavation process, so that the construction procedures are reduced, the construction period is shortened, the damage of the enclosure structure caused by lining construction is prevented, and the application range of the suspension bridge is expanded. The invention also discloses a corresponding construction method for the suspension bridge large-diameter secant pile gravity type anchorage foundation enclosure.

Description

Suspension bridge major diameter secant pile gravity type anchorage foundation enclosure structure and construction method

Technical Field

The invention relates to the technical field of bridge engineering, in particular to a gravity type anchorage foundation enclosure structure of a large-diameter secant pile of a suspension bridge and a construction method.

Background

The anchorage is one of the most important structures for anchoring the main cable of the ground anchor type suspension bridge, and has the functions of transmitting the tension of the main cable to an anchorage block, transmitting the force to an anchorage foundation through the anchorage block and finally transmitting the force to the foundation, so that the tension of the main cable is balanced and the effect of providing anchoring force for the main cable is achieved. Common anchorage forms include gravity anchors, tunnel anchors and rock anchors. In the aspect of adaptability, different foundation forms are considered, the gravity type anchorage is almost suitable for all occasions, the anchorage foundation envelope structure commonly used in the circular diaphragm wall envelope structure, the space arch effect can control the lateral displacement in a very small range, in addition, because of the space symmetry of the circular enclosure structure, the soil pressure acting on the arch ring is mainly balanced in the diaphragm wall, the circular foundation pit enclosure structure mainly bears the circumferential axial force, the advantage of high compressive strength of concrete is fully exerted by the compressive property, so that the circular envelope structure is more and more applied to the engineering practice, but due to the limitation of the milling groove equipment, the diameter of the underground diaphragm wall enclosure structure mostly adopts a wall body with the thickness of 1.5m, because the excavation depth of the foundation pit is larger, and the water and soil pressure value behind the wall is larger, the lining needs to be constructed by adopting a reverse construction method in the excavation process, and the thickness of the diaphragm wall and the lining reaches 2 m-5 m.

When the circular underground continuous wall is constructed, the embedded connecting steel bars of the steel reinforcement cage are connected with the lining steel bars, so that the lining and the underground continuous wall form a whole, in order to ensure the connecting effect between the lining and the underground continuous wall, the enclosing structure is required to be subjected to scabbling treatment in the excavation process, the exposed site of the wall steel bars frequently appears due to misoperation in the scabbling process, the construction process of the lining is increased, and the wall structure is damaged in the wall scabbling process. Therefore, a novel supporting structure needs to be researched, the size of the supporting structure is increased, the lining needs to be constructed additionally in the excavation process, the construction procedures are reduced, the construction period is shortened, and the enclosure structure damage caused by lining construction is prevented.

Disclosure of Invention

In order to solve the problems, the invention provides a gravity type anchorage foundation enclosure structure of a large-diameter secant pile of a suspension bridge, which realizes that a lining does not need to be constructed by a reverse construction method in the excavation process, thereby reducing construction procedures, shortening construction period, preventing the enclosure structure from being damaged due to lining construction and expanding the application range of the suspension bridge.

The technical scheme adopted by the invention for solving the technical problems is as follows: the utility model provides a suspension bridge major diameter secant pile gravity type anchorage basis envelope, includes a plurality of I phase secant piles and a plurality of II phase connecting pile, I phase secant pile and II phase connecting pile interval cyclic connection in proper order and enclose and cover formation circular shape enclosure, foundation ditch in the enclosure is equipped with a plurality of precipitation wells, the outer wall junction department of I phase secant pile and II phase connecting pile is equipped with the stagnant water curtain.

Furthermore, still include the ground back up coat, the ground back up coat set up in the bottom of I phase secant pile and II phase connecting pile.

Furthermore, a milling joint is formed at the joint of the stage I occlusive pile and the stage II connecting pile, so that the post-poured stage II connecting pile and the stage I occlusive pile are mutually occluded at the joint to form a tight joint.

Furthermore, the stage I occlusive piles adopt round piles or oval piles, and the stage II connecting piles adopt square piles.

Furthermore, a plurality of sound measuring tubes are respectively arranged in the stage I occlusive pile and the stage II connecting pile.

The invention also provides a construction method for the suspension bridge large-diameter secant pile gravity type anchorage foundation enclosure, which comprises the following construction steps:

s1.0, firstly, carrying out foundation reinforcement treatment on a soft foundation at the top by adopting a stirring pile to form a foundation reinforcement layer; the slurry conveying pipeline is not longer than 50m during foundation stabilization construction, the pressure at the tail end of the pipeline is kept at 0.25-0.4 MPa during normal construction, the horizontal slurry spraying distance of a slurry outlet is not less than 2m, the cement slurry is sieved after being fully stirred, the slurry is stored and is continuously stirred to prevent segregation, the stirring head is lifted after the slurry is stirred for 30s, when the construction is stopped due to reasons, if the shutdown is not more than 3 hours, 1m is drilled to carry out lap joint construction, otherwise, piles must be supplemented beside.

S1.1, excavating a guide wall groove, binding guide wall reinforcing steel bars, erecting a template, pouring guide wall concrete to complete the manufacture of the guide wall, ensuring accurate positioning of an occlusive pile, ensuring that a drilling machine is stable and bearing construction load.

S2, adopting a rotary drilling rig to drill a pile foundation hole, checking that slurry indexes and hole bottom sediment thickness in the hole meet design and standard requirements, completing the manufacturing and the lowering of a steel reinforcement cage of the secant pile in the first stage, and then pouring pile body concrete to complete the construction of the secant pile in the first stage. After the drilled hole reaches the design elevation, the hole depth and the hole diameter are checked, and the hole cleaning can be carried out if the hole depth and the hole diameter meet the standard requirements. The hole cleaning process adopts a gas lift reverse circulation method, a water head in a hole must be kept during hole cleaning to prevent hole collapse, and the hole cleaning cannot be replaced by a mode of deepening the drilling depth. And if the thickness of the sediment at the bottom of the hole can not meet the design requirement, secondary hole cleaning is carried out.

And S3, after the I-stage occlusive pile is poured and solidified, grooving the II-stage groove section by using a groove milling machine, manufacturing and grooving the reinforcing cage of the II-stage groove section, and then pouring concrete to complete construction of the II-stage connecting pile. The horizontal distance between the guide pipes and the end part of the groove section is not more than 3m and not more than 1.5m in the concrete pouring process. The lower end of the guide pipe is 0.3-0.5 m away from the bottom of the groove, and a water-proof plug is hung in the position close to the slurry surface in the guide pipe before concrete is poured. In order to ensure the bottom cleaning quality, concrete pouring is carried out within 4 hours after the reinforcement cage is sunk in place. The concrete reserves in each conduit storage hopper should guarantee that the buried pipe depth is not less than 0.5m when the concrete begins to be poured. After the water-insulating bolt suspension wires are cut off from the guide pipes, concrete should be uniformly and continuously poured at the same time, and the pouring speed of the concrete should not be lower than 2 m/h. The conduits are gradually lifted along with the concrete pouring, the depth of embedding the conduits in the concrete is 1.5-3 m, the height difference of concrete between every two adjacent conduits is not more than 0.5m, and the concrete pouring height is preferably 0.3-0.5 m higher than the designed height.

And S4.0, grouting the pile bottom after the supporting construction is completed. The grouting holes enter 10m below the wall bottom or enter bedrock with the rock permeability less than 1Lu, and the cement paste mixing ratio, the grouting depth and the grouting mode are determined through tests before construction. And (4) grouting qualification standard: the water permeability checked by pressurized water is not more than 3 Lu.

S4.1, after the construction of the enclosure structure is finished, detecting the enclosure structure by adopting ultrasonic waves, and if the wall quality is found to have general defects through ultrasonic wave detection, adopting measures such as grouting and the like for treatment; if a large defect is found, a groove section diaphragm wall is constructed by clinging the original structure at the outer side of the position, and a jet grouting pile is adopted between the pile foundation and the groove in the stage II for water sealing treatment.

And S4.2, constructing the crown beam after the construction of the enclosure structure is finished. The crown beam is of a reinforced concrete circular structure, the outer side of the crown beam is flush with the pile foundation, and the height of the crown beam is 2.0 m.

And S4.3, after the crown beam concrete reaches 90% of the design strength, carrying out dewatering well excavation on the foundation pit in the enclosure. And excavating all layers of soil bodies in the foundation pit by adopting an island method, excavating peripheral soil bodies in a partition symmetry mode, and excavating middle soil bodies. And (3) before each layer of soil is excavated, the soil in the foundation pit is subjected to layered pre-drainage and dewatering. The precipitation water level in the pit should be controlled to be 1-1.5 m below the excavation surface. When the foundation pit is excavated, the allowable overload at the periphery of the foundation pit is not more than 20kN/m²。

And S4.4, if water leaks from the supporting structure in the excavation process, performing rotary spraying reinforcement treatment on the peripheral soil body.

And S5, after the foundation is excavated, arranging blind ditches and water collecting wells to drain the seepage water of the foundation.

Further, before the stage i occlusive pile steel reinforcement cage is lowered in the step S2, a plurality of acoustic pipes are bound to the side portion of the stage i occlusive pile steel reinforcement cage, the acoustic pipes are connected by using screw threads, welding is avoided, smoothness of the acoustic pipes is guaranteed, and each acoustic pipe needs to be compacted by grouting after detection is finished.

Further, in step S2, the first stage secant pile cage may be processed by segmentation, and lengthened when being hoisted, the main reinforcement of the first stage secant pile cage should be mechanically connected, and the joint position should meet the specification. Effective positioning and transferring measures are adopted when the I-stage secant pile reinforcement cage is placed, and accurate positioning of the reinforcement is ensured, and influence on the hole wall is prevented. After the steel reinforcement cage of the secant pile at the stage I is in place, the steel reinforcement cage is reliably fixed, so that the steel reinforcement cage is prevented from floating upwards when concrete is poured.

Furthermore, the pouring of the pile body concrete in step S2 should be completed once without interruption. The pile body adopts C40 underwater concrete, the indexes of the concrete such as strength, slump and the like should be strictly controlled in the construction, and the pouring quality of the concrete is ensured. The maximum particle size of the concrete coarse aggregate is not more than 25 mm. Two adjacent piles must not be simultaneously formed with holes or poured with concrete so as to avoid disturbing the hole wall and causing the accidents of hole crossing and pile breaking.

Further, in the grooving process of the step S3, the grooving perpendicularity deviation is not larger than 1/400 wall height, the deviation of the adjacent groove section at the joint and the center line of the pile foundation at any depth is not larger than 60mm, the wall thickness error is 0-30 mm, the plane error is smaller than +/-30 mm, the slurry liquid level in the groove is kept higher than the underground water level by more than 1m, the relative density of fresh slurry is 1.05-1.1, the bottom is carefully cleaned after the grooving, the bottom cleaning thickness is smaller than 20cm, and secondary hole cleaning after the steel reinforcement cage is lowered is avoided. And after the concrete of the connecting pile in the second stage reaches 80% of the design strength, constructing the wall bottom waterproof curtain.

Furthermore, in step S3, in order to ensure the stability and rigidity of the steel reinforcement cage of the second-stage groove section during the hoisting process, the steel reinforcement cage of the second-stage groove section is required to be integrally manufactured or pre-assembled on the same platform, the steel reinforcement connection adopts straight thread sleeve connection, the joint positions are staggered, and the connection at the intersection of the longitudinal steel reinforcement and the transverse steel reinforcement meets the design requirements. And in order to ensure the thickness of the steel bar protective layer, positioning cushion blocks are welded on two sides of the steel bar cage, two columns are arranged on each side of the horizontal direction of the steel bar cage, and the distance between every two columns of positioning cushion blocks is 4 m. The length tolerance of the reinforcement cage is +/-50 mm, the width tolerance is +/-20 mm, the thickness tolerance is 0-10 mm, the interval tolerance of the main reinforcements is +/-10 mm, and the center tolerance of the embedded part is +/-10 mm.

The invention has the beneficial effects that:

1. the design utilizes the large-diameter secant pile as an anchorage foundation enclosure structure, and is different from a circular diaphragm wall enclosure structure, the large-diameter secant pile is a groove section I, a groove milling machine is adopted to mill grooves between pile foundations after construction is completed, a groove section of a connecting pile in a phase II is formed, the groove section is in lap joint with the pile foundations, a milled joint is formed, the measure that the rigidity of the enclosure structure is enhanced by adopting a reverse construction method to construct a lining when the circular diaphragm wall enclosure structure is constructed is overcome, a steel bar connecting piece is not required to be pre-embedded when building enclosure structure steel bars are manufactured, the construction procedures are reduced, the construction period is shortened, and the enclosure structure damage caused by lining construction is prevented.

2. This design is consolidated the soft soil foundation through the ground back up coat, prevents that the grooving in-process from appearing the hole phenomenon of collapsing. Two sides of the underground continuous wall are respectively reinforced by adopting 2 rows of three-axis stirring piles with the diameter of 85cm and the interval of 1.8 m; the rest are stirring piles with the diameter of 80cm and the distance of 2 m.

3. This design adopts precipitation well and stagnant water curtain to carry out precipitation to the foundation ditch, the guarantee construction safety. Arranging a certain number of dewatering wells at the periphery of an anchorage foundation pit, carrying out dewatering treatment in the foundation pit before excavating a rock-soil body, controlling the dewatering water level to be not less than 2m below an excavation surface, excavating a first level and protecting a first level, carrying out grouting water-stopping curtain construction, and setting a proper amount of water level monitoring holes outside the foundation pit when the water level in the foundation pit is reduced to an excavation base surface so as to monitor the influence of the dewatering in the pit on the water level outside the foundation pit.

4. The design directly excavates the foundation pit by an island method, and is safe and quick;

5. the design carries out water stopping by a method of grouting at the bottom of the pile bottom, and is stable and reliable.

Drawings

FIG. 1 is a schematic view of the overall construction of the enclosure of the present invention;

fig. 2 is a schematic connection diagram of a stage i occlusive pile and a stage ii connecting pile of the building envelope.

Detailed Description

The invention will be further described with reference to the accompanying drawings.

As shown in fig. 1 and 2, the gravity type anchorage foundation enclosure structure of the large-diameter secant pile of the suspension bridge and the construction method thereof comprise a plurality of stage-I secant piles 10 and a plurality of stage-II connecting piles 20, wherein the stage-I secant piles 10 and the stage-II connecting piles 20 are sequentially and circularly connected and enclosed to form a circular anchorage foundation enclosure structure, foundation reinforcing layers are arranged at the bottoms of the stage-I secant piles 10 and the stage-II connecting piles 20, the stage-I secant piles 10 adopt circular piles or elliptical piles, rotary drilling and drilling are adopted for construction to form holes, the holes are cleaned after the holes reach a designed height, a groove section reinforcing cage 11 at the stage I is placed down after the holes are cleaned, and then the groove section at the stage I is poured to form a pile; the second-stage connecting pile 20 is a square pile, a slot milling machine is used for hole forming 20 in the construction process, hole cleaning is conducted after the design elevation is achieved, a second-stage slot section reinforcement cage 21 is placed after the hole cleaning, then the pile is formed through pouring, and a milling joint is formed at the position where the first-stage occlusive pile 10 and the second-stage connecting pile 20 are connected, so that the second-stage connecting pile 20 and the first-stage occlusive pile 10 which are poured later are mutually occluded at a joint, and a tight joint is formed. After the stage I secant pile 10 and the stage II connecting pile 20 are poured into the anchorage foundation enclosing structure, the island construction method is adopted to excavate the foundation pit in the enclosure, a dewatering well 30 is adopted to carry out layering pre-dewatering on the soil body in the foundation pit before each layer of soil body is excavated, in order to prevent water seepage from the wall side, the joint of the outer walls of the stage I secant pile 10 and the stage II connecting pile 20 is subjected to rotary spraying reinforcement to form a waterproof curtain 40 in the excavating process.

After the excavation is finished, in order to prevent the water seepage of the substrate, a plurality of acoustic pipes 12 bound on the steel reinforcement cage 11 of the groove section I and a plurality of acoustic pipes 22 bound on the square pile steel reinforcement cage 21 of the groove section II are respectively adopted for grouting and bottom sealing, so that the groundwater seepage is prevented.

And S5, after the foundation is excavated to the base, arranging a blind ditch and a water collecting well to drain seepage water of the base, and completing the integral construction of the suspension bridge large-diameter secant pile gravity type anchorage foundation enclosure structure.

The above description is only a preferred embodiment of the present invention, and the scope of the present invention should not be limited thereby, and all the simple equivalent changes and modifications made in the claims and the description of the present invention are within the scope of the present invention.

Claims

1. The utility model provides a suspension bridge major diameter secant pile gravity type anchorage basis envelope, its characterized in that includes a plurality of I phase secant piles and a plurality of II phase connecting pile, I phase secant pile and II phase connecting pile interval cyclic connection in proper order and enclose and cover formation enclosure, foundation ditch in the enclosure is equipped with a plurality of precipitation wells, the outer wall junction department of I phase secant pile and II phase connecting pile is equipped with the stagnant water curtain.

2. The gravity type anchorage foundation envelope structure for large-diameter secant piles of a suspension bridge according to claim 1, which is characterized by further comprising a foundation reinforcing layer, wherein the foundation reinforcing layer is arranged at the bottom of the stage I secant pile and the stage II connecting pile.

3. The suspension bridge large-diameter secant pile gravity type anchorage foundation envelope structure as claimed in claim 1, wherein a plurality of sounding pipes are respectively arranged in the stage I secant pile and the stage II connecting pile.

4. A construction method for a suspension bridge large-diameter secant pile gravity type anchorage foundation enclosure is characterized in that the following construction steps are carried out on the basis of the suspension bridge large-diameter secant pile gravity type anchorage foundation enclosure structure of any one of claims 1 to 3:

s1, excavating a guide wall groove, binding guide wall reinforcing steel bars, erecting a template, and pouring guide wall concrete to finish the manufacture of a guide wall;

s2, adopting a rotary drilling pile foundation to form a hole, checking that the slurry index and the bottom sediment thickness in the hole meet the requirements, completing the manufacturing and the lowering of a steel reinforcement cage of the secant pile at the first stage, and then pouring pile body concrete to complete the construction of the secant pile at the first stage;

s3, after the stage I occlusive pile is poured and solidified, grooving the stage II groove section by using a groove milling machine, completing the manufacturing and grooving of the stage II groove section reinforcement cage, and then pouring concrete to complete the construction of the stage II connecting pile;

s4, carrying out dewatering well excavation on the foundation pit in the enclosure;

5. The construction method for a suspension bridge large-diameter secant pile gravity type anchorage foundation envelope as claimed in claim 4, wherein before the stage I secant pile reinforcement cage is lowered in step S2, a plurality of acoustic pipes are bound on the side of the stage I secant pile reinforcement cage.

6. The construction method for the suspension bridge large-diameter secant pile gravity type anchorage foundation enclosure according to claim 4, characterized in that the pile body concrete pouring in the step S2 is completed once without interruption, the pile body is C40 underwater concrete, and the maximum particle size of the concrete coarse aggregate is not more than 25 mm.

7. The construction method for the suspension bridge large-diameter secant pile gravity type anchorage foundation enclosure according to claim 4, is characterized in that in the grooving process of step S3, the grooving perpendicularity deviation is not more than 1/400 wall height, the deviation of any depth between the adjacent groove section at the joint and the center line of the pile foundation is not more than 60mm, the wall thickness error is 0-30 mm, the plane error is less than +/-30 mm, the slurry liquid level in the groove is kept higher than the underground water level by more than 1m, the relative density of fresh slurry is 1.05-1.1, and the bottom cleaning thickness is less than 20cm after grooving.

8. The construction method for the suspension bridge large-diameter secant pile gravity type anchorage foundation enclosure according to claim 4, wherein in the step S3, after the concrete of the connection pile in the stage II reaches 80% of the design strength, construction of a water-stop curtain is carried out.

9. The construction method for the suspension bridge large-diameter secant pile gravity type anchorage foundation enclosure according to claim 4, wherein the step S4 further comprises the following steps:

and S4.0, grouting the pile bottom after the supporting construction is completed.

10. The construction method for the suspension bridge large-diameter secant pile gravity type anchorage foundation enclosure according to claim 4 or 9, wherein the step S4 further comprises the following steps:

s4.1, after the construction of the enclosure structure is finished, detecting the enclosure structure by adopting ultrasonic waves, and if the wall quality is detected to have general defects by the ultrasonic wave detection, adopting a grouting measure to process; if a large defect is found, constructing a groove section diaphragm wall by clinging to the original structure at the outer side of the position, and sealing water between the pile foundation and the groove in the stage II by adopting a jet grouting pile;

s4.2, constructing a crown beam after the construction of the enclosure structure is finished;

s4.3, after the crown beam concrete reaches 90% of the design strength, carrying out dewatering well excavation on the foundation pit in the enclosure; excavating all layers of soil bodies in the foundation pit by adopting an island method, excavating peripheral soil bodies in a partition symmetry mode, and then excavating middle soil bodies; before each layer of soil body is excavated, carrying out layered pre-drainage dewatering on the soil body in the foundation pit, and controlling the level of the dewatering water in the pit to be 1-1.5 m below the excavation surface; when the foundation pit is excavated, the allowable overload at the periphery of the foundation pit is not more than 20kN/m²。