CN110905014A - Construction structure and construction method for underpinning pile foundation - Google Patents
Construction structure and construction method for underpinning pile foundation Download PDFInfo
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- 238000009424 underpinning Methods 0.000 title claims abstract description 131
- 238000010276 construction Methods 0.000 title claims abstract description 57
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- 241000972773 Aulopiformes Species 0.000 description 2
- 229910001294 Reinforcing steel Inorganic materials 0.000 description 2
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- 239000011888 foil Substances 0.000 description 1
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D35/00—Straightening, lifting, or lowering of foundation structures or of constructions erected on foundations
- E02D35/005—Lowering or lifting of foundation structures
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D33/00—Testing foundations or foundation structures
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
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- E02D5/64—Repairing piles
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Abstract
The invention discloses a construction structure and a construction method for underpinning a pile foundation, belonging to the technical field of underpinning and structural transformation of a pile foundation in building construction, wherein the construction structure comprises an original pile cap, an existing pile, a newly-built pile and a newly-built underpinning beam, the underpinned pile is a pile foundation at the edge part of the original pile cap, the newly-built pile cap and a pile embracing type pile cap, the newly-built pile cap is positioned at the top of the newly-built pile, and the pile embracing type pile cap is positioned on the existing pile at the adjacent side of the underpinned pile; the jacking devices are respectively arranged on the newly-built pile cap and the pile embracing type pile cap; the newly-built underpinning beam is connected with the original bearing platform, and the newly-built underpinning beam is positioned above the newly-built pile. The construction method of pile foundation underpinning utilizes the existing pile and newly-built pile as jacking platforms to underpin the pile foundation, the existing pile on the adjacent side of the underpinned pile is used, and the existing pile embracing pile type pile cap is constructed on the existing pile on the adjacent side; and constructing a newly-built pile, and constructing a newly-built pile cap on the newly-built pile. The method can save construction period and cost, reduce the influence on the surrounding environment, is suitable for the underpinning construction of the pile foundation of the abutment or the pile group, and is beneficial to popularization.
Description
Technical Field
The invention relates to the technical field of underpinning and structural transformation of a building construction pile foundation, in particular to a construction structure and a construction method for underpinning the pile foundation.
Background
Pile foundation underpinning is a method for underpinning a foundation by adopting a pile foundation form, is generally used for modifying an underground foundation of a building, and is a mode for treating and reinforcing the foundation. The pile foundation underpinning is mainly used for solving the problems that the foundation reinforcement of the existing building is realized, the underground engineering or the newly-built building engineering needs to be built under the foundation of the existing building to influence the safety of the existing building, and the existing pile conflicts during the construction of the newly-built building.
The existing piles are underpinned by utilizing the newly built piles, and the conventional underpinning scheme of 'removing one pile to build two piles and removing two piles to build four piles' is adopted, namely, four new pile foundations are required to be newly built for underpinning two existing piles to serve as jacking platforms. If conflict occurs with the pile foundation of the overpass bridge abutment in certain engineering construction, the two pile foundations at the east side under the bridge abutment need to be subjected to underpinning technology construction and then are treated and chiseled. If the newly-built pile foundation adopts the conventional underpinning scheme of removing one pile foundation and two pile foundations and removing four pile foundations, four pile foundations are required to be newly built as the jacking platform. Two newly-built piles can be constructed on the east side of the existing abutment, another newly-built pile is required to be constructed under the existing abutment, the space under the abutment is narrow, and the drilling machine and the reinforcement cage are limited by the space height, so that the construction difficulty is high; and the other pile is arranged on the overpass approach, and a road needs to be sealed during construction to carry out traffic guidance and improvement. By adopting the traditional construction mode, the construction difficulty, the organization difficulty and the coordination difficulty can be greatly increased.
Disclosure of Invention
The technical task of the invention is to provide a construction structure and a construction method for underpinning a pile foundation, aiming at the defects, so that the construction period can be shortened, the manufacturing cost can be reduced, and the influence on the surrounding environment can be reduced.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a construction structure for underpinning pile foundation includes original bearing platform, existing pile, newly-built pile and newly-built underpinning beam, the underpinned pile is the pile foundation of original bearing platform edge portion, said structure also includes newly-built pile cap and pile-holding type pile cap,
the newly-built pile cap is positioned at the top of the newly-built pile, and the pile-embracing type pile cap is positioned on the existing pile at the adjacent side of the underpinned pile; the jacking devices are respectively arranged on the newly-built pile cap and the pile embracing type pile cap;
the newly-built underpinning beam is connected with the original bearing platform, the area of the original bearing platform is enlarged, the whole underpinning beam is formed, and the newly-built underpinning beam is positioned above the newly-built pile.
This structure utilizes existing stake and newly-built stake to make jacking platform and carries out pile foundation underpin, supports the underpin roof beam through arranging the jacking device on newly-built pile cap and pile embracing formula pile cap, supports the construction of cuting of underpin stake under this, realizes pile foundation underpin, and more conventional "go one to build two, go two to build four" construction structures and practice thrift time limit for a project and cost greatly, and can reduce the influence to the surrounding environment.
Preferably, the number of the underpinned piles is two, and the number of the newly-built piles is two; newly-built pile caps are constructed on the two newly-built piles; two existing piles on the adjacent sides of the two underpinned piles are used for constructing pile embracing type pile caps respectively. And jacking devices are respectively arranged on the two newly-built pile caps and the two pile holding type pile caps, and the four pile caps are used as jacking platforms to realize jacking of the underpinned beam.
Preferably, the jacking device comprises a hydraulic jack, a self-locking device and an auxiliary support, 3 hydraulic jacks, 3 auxiliary supports and 3 self-locking devices are respectively arranged on the newly-built pile cap and the pile-embracing type pile cap in a delta shape, the jacks at the same end adopt parallel oil ways, and the oil pressure of each jack at the same end is ensured to be consistent.
Preferably, newly-built underpinning roof beam includes extension and bottom connecting portion, and the extension links to each other with original cushion cap tip, is located the top of newly-built stake, and extension bottom and original cushion cap bottom are connected to bottom connecting portion, make extension bottom and original cushion cap bottom become an organic whole, form the underpinning roof beam wholly, realize the jacking of newly-built stake.
Preferably, the structure further comprises a displacement meter, a strain gauge and an inclinometer, wherein the displacement meter, the strain gauge and the inclinometer are installed on the newly-built pile cap, the pile-embracing type pile cap and the underpinning beam. At least 1 displacement meter is respectively arranged on each newly-built pile cap and each pile embracing type pile cap, and the settlement displacement of the pile foundation is monitored; displacement meters are arranged on the top surfaces of the original bearing platform and the newly-built underpinning beam at intervals, and the settlement displacement of the underpinning beam is monitored; arranging inclinometers at four corners of the top surfaces of the original bearing platform and the newly-built underpinning beam, and monitoring the inclination deformation of the beam body; and strain gauges are installed on the side surfaces of the original bearing platform and the newly-built underpinning beam and connected with a strain gauge, and the longitudinal stress of the maximum bending moment section of the beam body is tested.
Preferably, the original bearing platform is an abutment, and the underpinned pile is a pile foundation at the end part of the abutment. The existing piles and the newly-built piles are jointly used as jacking platforms for active underpinning, and underpinning of the existing piles at the end portions of the bridge abutment is achieved.
The newly-built pile and the underpinned pile are equal-diameter piles, the cross section of the newly-built pile cap is square, and the side length is not less than 5/3 of the diameter of the existing pile; the cross section of the pile-embracing type pile cap is rectangular, the length of the short side is not less than 5/3 of the diameter of the existing pile, and the length of the long side is not less than 7/3 of the diameter of the existing pile.
The invention also claims a construction method for underpinning pile foundation, the underpinned pile is the pile foundation at the edge part of the original bearing platform, the underpinned beam is newly built and the newly built pile is used for underpinning the underpinned pile, the method is characterized in that the pile foundation underpinning is carried out by using the existing pile and the newly built pile as jacking platforms,
an existing pile on the adjacent side of the underpinning pile is imposed, and an existing pile embracing pile type pile cap is constructed on the existing pile on the adjacent side; constructing a newly-built pile, and constructing a newly-built pile cap on the newly-built pile; constructing a newly-built underpinning beam above the corresponding newly-built pile, and forming an underpinning beam whole with the original bearing platform;
and (3) installing jacking devices on the pile-embracing type pile cap and the newly-built pile cap, and respectively arranging displacement monitoring points on the pile-embracing type pile cap, the newly-built pile cap and the underpinning beam.
Preferably, jacking comprises an existing pile jacking stage, a newly-built pile and an existing pile synchronous jacking stage, wherein the existing pile jacking stage only pressurizes the existing pile end; and in the stage of synchronously jacking the newly built pile and the existing pile, synchronously pressurizing the existing pile and the newly built pile at two ends of the underpinning beam.
And (4) entering the existing pile jacking stage after normal monitoring and debugging of the equipment, determining the optimal truncation jacking force of the existing pile and truncating the existing pile. And when the existing pile is cut off and the structure is stable and has no obvious change, entering a newly-built pile and existing pile synchronous jacking stage, determining the optimal pile-breaking jacking force of the underpinned pile in the stage, and cutting the underpinned pile.
The main purpose of the existing pile jacking stage is as follows:
analyzing and determining the actual best pile-breaking top lift force by only gradually loading and stabilizing the existing pile end; and (4) carrying out theoretical overpressure on the underpinning system to check the structural safety, in particular to a pile-embracing type pile cap.
The main purpose of the new pile construction and the existing pile synchronous jacking stage is as follows:
at the moment, the existing pile is cut off, and the early-stage settlement of the pile foundation is eliminated by synchronously and gradually loading and stabilizing the pressure at two ends; monitoring the displacement of the underpinning beam in the step-by-step pressurizing process, and determining the optimal jacking force of the underpinned pile during pile breaking; and (4) verifying the safety of the structure by using partial uplift resistance overpressure of the underpinned pile.
Further, the construction method comprises the following concrete construction steps:
1) constructing a new pile;
2) excavating the foundation pit to the designed elevation while supporting;
3) constructing a newly-built pile cap, an existing pile-holding pile cap and a underpinning beam;
4) respectively calculating the values of the jacking forces of the newly-built pile end and the existing pile end, and installing a jacking device after the underpinning beam and the pile cap concrete are equal in strength, wherein the jacking device comprises a self-locking device, an auxiliary support and a jack;
5) respectively arranging displacement monitoring points, stress strain monitoring points and inclination monitoring points on the pile cap and the underpinning beam, and collecting original detection data;
6) jacking the existing pile, synchronously detecting and cutting off the existing pile;
7) jacking and synchronous detection of the newly-built pile;
8) synchronously jacking the newly-built pile and the existing pile;
9) the pile is cut off by the underpinned pile;
10) the jack returns oil and withdraws, and the load is transferred to the self-locking device and the auxiliary support;
11) and pouring concrete at the underpinning node, and completing underpinning of the pile foundation by using the existing pile and the newly-built pile as the jacking platform.
Preferably, the newly-built pile end and the existing pile end are jacked up and pressurized step by step according to calculated values of 30%, 20%, 15%, 10%, 5%, 3% and 2%, theoretical overpressure inspection is carried out, the pressure is stabilized for 5 minutes after each step of loading, each data is monitored, and comprehensive analysis is carried out.
Compared with the prior art, the construction structure and the construction method for underpinning the pile foundation have the following advantages
Has the advantages that:
the construction structure and the construction method have the advantages that the existing pile and the newly-built pile are used as the jacking platform together, the construction period and the construction cost are greatly saved compared with the conventional pile foundation underpinning scheme of 'removing one pile and two piles and removing two piles and four piles', the influence on the surrounding environment is reduced, the construction structure and the construction method are suitable for pile foundation underpinning construction of bridge abutments or pile groups, and the use and popularization values are good.
Drawings
FIG. 1 is a schematic cross-sectional view of an embodiment of pile underpinning of a jacking platform using existing piles and newly-built piles;
fig. 2 is a BIM effect diagram for underpinning a pile foundation of a jacking platform by using an existing pile and a newly-built pile.
1. Original cushion cap, 2, newly-built underpinning roof beam, 3, newly-built stake, 4, existing stake, 5, by the underpinning stake, 6, newly-built pile cap, 7, embrace stake formula pile cap, 8, jacking device, 9, displacement meter, 10, foil gage, 11, inclinometer, 12, underpinning node.
Detailed Description
The invention is further described with reference to the following figures and specific examples.
The utility model provides a construction structures of pile foundation underpin, includes original cushion cap 1, existing stake 4, newly-built stake 3 and newly-built underpin roof beam 2, is underpinned stake 5 for original cushion cap 1 limit portion pile foundation, and this structure still includes newly-built pile cap 6 and pile-embracing formula pile cap 7. The newly-built pile cap 6 is positioned at the top of the newly-built pile 3, and the pile-embracing type pile cap 7 is positioned on the existing pile 4 on the adjacent side of the underpinned pile 5.
The jacking device 8 is respectively arranged on the newly-built pile cap 6 and the pile embracing type pile cap 7, the newly-built underpinning beam 2 is connected with the original bearing platform 1, the area of the original bearing platform is enlarged, the whole underpinning beam is formed, and the newly-built underpinning beam 2 is positioned above the newly-built pile 3.
The original bearing platform 1 is an abutment, and the underpinned pile 5 is a pile foundation at the end part of the abutment. The existing pile 4 and the newly-built pile 3 are jointly used as a jacking platform to carry out active underpinning, and underpinning of the existing pile at the end part of the abutment is realized.
Two underpinned piles 5 are adopted, two newly-built piles 3 are adopted, two newly-built piles are adopted, and newly-built pile caps 6 are constructed on the newly-built piles 3; two existing piles 4 on the adjacent sides of two underpinned piles 5 are levitated, and pile embracing type pile caps 7 are respectively constructed. And jacking devices 8 are respectively arranged on the two newly-built pile caps 6 and the two pile holding type pile caps 7, and the four pile caps are used as jacking platforms to realize jacking of the underpinned beam. Newly-built underpinning roof beam 2 includes extension and bottom connecting portion, and the extension links to each other with 1 tip of original cushion cap, is located the top of newly-built stake 4, and extension bottom and 1 bottoms of original cushion cap are connected to bottom connecting portion, make extension bottom and 1 bottoms of original cushion cap become an organic whole, form the underpinning roof beam wholly, realize the jacking of newly-built stake 3.
Jacking device 8 includes hydraulic jack, self-lock device and auxiliary stay, is the article font respectively and arranges 3 hydraulic jack, 3 auxiliary stay and 3 self-lock device on newly-built pile cap 6 and pile-embracing formula pile cap 7, and same end jack adopts the parallel oil circuit, guarantees that every jack oil pressure of same end is unanimous.
The structure further comprises a displacement meter 9, a strain gauge 10 and an inclinometer 11, wherein the displacement meter 9, the strain gauge 10 and the inclinometer 11 are installed on the newly-built pile cap 6, the pile-embracing type pile cap 7 and the underpinning beam. At least 1 displacement meter 9 is respectively arranged on each newly-built pile cap 6 and each pile embracing type pile cap 7, and the settlement displacement of the pile foundation is monitored; displacement meters 9 are arranged on the top surfaces of the original bearing platform 1 and the newly-built underpinning beam 2 at intervals, and the settlement displacement of the underpinning beam is monitored; the four corners of the top surfaces of the original bearing platform 1 and the newly-built underpinning beam 2 are provided with inclinometers 11, and the inclination deformation of the beam body is monitored; and strain gauges 10 are arranged on the side surfaces of the original bearing platform 1 and the newly-built underpinning beam 2, the strain gauges 10 are connected with strain gauges, and the longitudinal stress of the maximum bending moment section of the beam body is tested.
A pile foundation underpins the construction method, underpins the pile for the original pile foundation of 1 edge of cushion cap, newly build underpin roof beam 2 and newly build 3 pile to underpin the said pile foundation, this method utilizes existing pile 4 and newly build 3 pile as the platform of jacking to carry on the underpin of the pile foundation.
The method commandeers the existing pile 4 at the adjacent side of the underpinned pile 5, and constructs an existing pile holding pile type pile cap 7 on the existing pile 4 at the adjacent side; constructing a newly-built pile 3, and constructing a newly-built pile cap 6 on the newly-built pile 3; and constructing a newly-built underpinning beam 2 above the newly-built pile 3, and forming an integral underpinning beam with the original bearing platform 1. And (3) installing a jacking device 8 on the pile-embracing type pile cap 7 and the newly-built pile cap 6, and respectively arranging displacement monitoring points on the pile-embracing type pile cap 7, the newly-built pile cap 6 and the underpinning beam.
The jacking comprises an existing pile jacking stage, a newly-built pile and an existing pile synchronous jacking stage, wherein the existing pile jacking stage only pressurizes the existing pile end; and in the stage of synchronously jacking the newly built pile and the existing pile, synchronously pressurizing the existing pile 4 and the newly built pile 3 positioned at the two ends of the underpinning beam.
And after the equipment and the monitoring and debugging are normal, the existing pile jacking stage is started, the best truncation jacking force of the existing pile 4 is determined, and the existing pile 4 is truncated. And when the existing pile 4 is cut off and the structure is stable and has no obvious change, entering a stage of synchronously jacking the newly-built pile and the existing pile, determining the optimal pile-breaking jacking force of the underpinned pile 5 in the stage, and cutting off the underpinned pile 5.
The main purpose of the existing pile jacking stage is as follows:
analyzing and determining the actual best pile-breaking top lift force by only gradually loading and stabilizing the existing pile end; and (3) carrying out theoretical overpressure on the underpinning system to check the structural safety, in particular to the pile-embracing type pile cap 7.
The main purpose of the new pile construction and the existing pile synchronous jacking stage is as follows:
at the moment, the existing pile 4 is cut off, and the early-stage settlement of the pile foundation is eliminated by synchronously and gradually loading and stabilizing the pressure at two ends; monitoring the displacement of the underpinning beam in the step-by-step pressurizing process, and determining the optimal jacking force of the underpinned pile during pile breaking; the safety of the structure is verified by overpressure with partial resistance to uplift of the underpinned pile 5.
The construction method comprises the following concrete construction steps:
1) constructing a new pile;
2) excavating the foundation pit to the designed elevation while supporting;
3) constructing a newly-built pile cap, an existing pile-holding pile cap and a underpinning beam;
4) respectively calculating the values of the jacking forces of the newly-built pile end and the existing pile end, and installing a jacking device after the underpinning beam and the pile cap concrete are equal in strength, wherein the jacking device comprises a self-locking device, an auxiliary support and a jack;
5) respectively arranging displacement monitoring points, stress strain monitoring points and inclination monitoring points on the pile cap and the underpinning beam, and collecting original detection data;
6) jacking the existing pile, synchronously detecting and cutting off the existing pile;
7) jacking and synchronous detection of the newly-built pile;
8) synchronously jacking the newly-built pile and the existing pile;
9) the pile is cut off by the underpinned pile;
10) the jack returns oil and withdraws, and the load is transferred to the self-locking device and the auxiliary support;
11) and pouring concrete at the underpinning node, and completing underpinning of the pile foundation by using the existing pile and the newly-built pile as the jacking platform.
Taking the first-stage project of No. 3 track traffic of Zhengzhou city as an example, the section of the Salmon station-Xinglong pavement station of the first-stage project of No. 3 track traffic of Zhengzhou city is constructed by a shield method, the right track tunnel conflicts with pile foundations (friction piles) NYT1-1 and NYT1-5 of a northern tricyclic overpass NYT-1 bridge abutment of the Nanyang road at the mileage DK7+930.0, and the soil covering depth of the conflict position is about 11.78 m. 8 bored piles with the diameter of 1500mm and the length of 23.5m are arranged below the NY1 bridge abutment, wherein two pile foundations NYT1-1 and NYT1-5 on the easterest side conflict with a right-line tunnel, and the two pile foundations need to be subjected to underpinning technology construction post-treatment and chiseled.
However, if the newly-built pile foundation adopts the conventional underpinning scheme of removing one pile foundation and two pile foundations and removing four pile foundations, four pile foundations are required to be newly built as the jacking platform. Two newly-built piles can be constructed on the east side of the existing abutment, another newly-built pile is required to be constructed under the existing abutment, the space under the abutment is narrow, and the drilling machine and the reinforcement cage are limited by the space height, so that the construction difficulty is high; and the other pile is arranged on the overpass approach, and a road needs to be sealed during construction to carry out traffic guidance and improvement. If the method is adopted to carry out underpinning of NYT1-1 and NYT1-5, the construction difficulty, the organization difficulty and the coordination difficulty are greatly increased.
Comprehensively considering the field environment, considering factors such as construction period, construction cost and safety, finally determining that two underpinning piles with the pile length of 35m and the diameter of 1500mm are newly built on the east side of the original bearing platform to be respectively used as pile caps, additionally adopting pile caps of existing bridge abutment pile foundations NYT1-2 and NYT1-6 to be used as a jacking platform together, and enlarging the upper original bridge abutment to be used as an underpinning beam to form the bridge abutment pile foundation underpinning system.
Construction method
A tunnel between a No. 3 line first-stage engineering salmon station of Zhengzhou track traffic and a Xinglong paving station area passes through a south-yang road and a northern-tricyclic overpass, a right line tunnel passes through NY1 abutment NYT1-1 and NYT1-5 piles, pile foundation underpinning is needed to be carried out on the right line tunnel, and a mode that the existing pile and a newly-built pile are jointly used as a jacking platform for active underpinning is designed. Firstly constructing and newly building underpinning piles XZ-1 and XZ-2, then excavating a foundation pit to 2.2m below an old pile cap, respectively constructing pile caps of 2500 multiplied by 1500mm and 2500 multiplied by 3500 multiplied by 1500mm on the underpinning piles and the existing piles as jacking platforms, and after the pile caps are finished, as shown in figure 1, enlarging the size of the original pile cap to be used as an underpinning beam to form the underpinning system of the time, as shown in figure 2.
The load that passes for the underpinning beam bottom according to abutment and superstructure that the design institute provided is 18795.36KN, redistribute the load, consider the burden frictional resistance and the safe deposit of original pile foundation, the load coefficient takes 1.2 to carry out the mechanics checking calculation, it is 14903.388KN, 7695.044KN to calculate respectively to get the jacking force theoretical value of existing pile end and newly-built pile end, jacking platform both ends are according to theoretical design value 30%, 20%, 15%, 10%, 5%, 3%, 2% pressurization jacking step by step.
And after the newly added structural concrete has equal strength, the die carrier is removed, the jacking device is installed, and monitoring points are arranged. 3 320T hydraulic jacks, 3 auxiliary supports and 3 self-locking devices are respectively arranged on each pile cap in a shape like a Chinese character pin, and the jacks at the same end adopt parallel oil ways to ensure that the oil pressure of each jack at the same end is consistent. The main parts of the monitoring point arrangement are a pile cap and a underpinning beam. 1 displacement monitoring point is arranged at the upper part of each pile cap respectively to monitor the settlement displacement of the pile foundation; grinding the north side surface of the underpinning beam by using an angle grinder, pasting a strain gauge after the position of the flat fixed point is polished, connecting a strain gauge to test the longitudinal stress of the maximum bending moment section of the beam body, and arranging 15 strain gauges in total; 4 displacement meters are arranged on the top surface of the underpinned beam concrete at intervals to monitor the settlement displacement of the underpinned beam, and inclinometers are arranged at four corners to monitor the inclination deformation of the beam body. And debugging the equipment and collecting and recording original monitoring data after the jacking equipment and the monitoring points are completely installed.
And after the equipment and the monitoring and debugging are normal, entering the existing pile jacking stage. The main purpose is as follows: 1. analyzing and determining the actual best pile-breaking top lift force by only gradually loading and stabilizing the existing pile end; 2. theoretical overpressure is performed on the underpinning system to verify structural safety (especially the outer pile cap).
The jacking operation at the stage only loads the existing pile end step by step, and the stable self-locking device of the newly built pile end does not load. Loading according to ten levels, pressurizing in a grading way, stabilizing the pressure for 5 minutes after each level of loading, monitoring each data and comprehensively analyzing. When the pressure is increased to a certain level, the underpinning beam is monitored to have a lifting trend, the optimal truncation jacking force of the existing pile 4 can be determined to be near the jacking force of the upper level, at the moment, the settlement displacement data of the underpinning beam and the pile embracing type pile cap 7 are analyzed, and if the existing pile 4 does not slide relative to the pile embracing type pile cap 7, the appearance of the structure is checked, the analysis and monitoring data are normal, and the bearing capacity of the structure can be further loaded and tested. When the pile-embracing pile cap is loaded to a higher level, monitoring that the displacement of the underpinning beam is lifted within 1mm, the edge displacement of the pile-embracing pile cap 7 sinks, checking the appearance of the structure, analyzing monitoring data, and if the displacement is normal, indicating that the bearing capacity of the structure meets the requirement without continuous loading. Returning oil to the optimal jacking force, and cutting off the existing pile 4 by using a rope saw after stabilizing the pressure.
And when the structure is stable and has no obvious change, entering a stage of synchronously jacking four piles at two ends of the underpinning beam, namely a stage of synchronously jacking a newly-built pile and an existing pile. The main purpose is as follows: 1. at the moment, the existing pile 4 is cut off, and the early settlement of the pile foundation is eliminated by synchronously loading and stabilizing pressure step by step at the two ends; 2. monitoring the displacement of the underpinning beam in the step-by-step pressurizing process to determine the optimal jacking force of the underpinned pile 5 during pile breaking; 3. the safety of the structure is verified by overpressure with partial resistance to uplift of the underpinned pile 5.
At the moment, the pressure of the existing pile 4 is stabilized to the optimal jacking force before pile breaking, and the newly-built pile end is pressurized to the optimal jacking force before pile breaking of the existing pile 4 in a grading manner, so that synchronous jacking with the existing pile 4 end is realized. Then, the two ends are synchronously pressurized step by step, when the pressure is pressurized to a certain level, the underpinning beam is monitored to have the upward lifting trend, at the moment, in order to prevent the upper structure from rebounding after pile breaking, the upper-level jacking force can be judged to be the optimal pile breaking jacking force, the structure appearance is checked, and the monitoring data is analyzed and monitored if the upper-level jacking force is normal. In order to further check the structural safety, the pressure is continuously and synchronously increased to a higher level, and the uplifting condition of the underpinning beam and the sinking condition of the pile cap are monitored after the pressure is stabilized. The uplift of the underpinning beam is controlled within 1mm, the subsidence of the pile cap is controlled within 5mm, the change of the underpinning beam is taken as the main point, if the uplift of the underpinning beam is close to 1mm, and the subsidence of the pile cap is overlarge, the friction force of the soil body around the pile is small, the pile circumference needs to be properly grouted and reinforced to increase the friction force around the pile, and when the subsidence of the pile cap is small, the friction force around the pile meets the requirement. And when the structural appearance is checked and the monitoring data are analyzed normally, the final jacking force can be judged as the final jacking force. And returning the oil to the optimal pile-breaking jacking force by the jack, and cutting the underpinned pile 5 after pressure stabilization.
And (3) grouting and locking by a synchronous self-locking device along with the cutting of the underpinned pile 5 during jacking, welding and reinforcing by auxiliary support, and gradually returning oil by the jack after the monitoring is stable to finish load transfer. And after the jack is completely withdrawn, grouting the broken pile opening of the existing pile, recovering the reinforcing steel bars of the existing pile, and binding the reinforcing steel bars of the underpinning nodes to finish concrete pouring. And (5) utilizing the existing pile and the newly-built pile to make a jacking platform pile foundation underpinning construction process.
The present invention can be easily implemented by those skilled in the art from the above detailed description. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the basis of the disclosed embodiments, a person skilled in the art can combine different technical features at will, thereby implementing different technical solutions.
In addition to the technical features described in the specification, the technology is known to those skilled in the art.
Claims (10)
1. A construction structure for underpinning pile foundation includes original bearing platform, existing pile, newly-built pile and newly-built underpinning beam, and the underpinned pile is the pile foundation on the edge of original bearing platform, and is characterized by that said structure also includes newly-built pile cap and pile-holding type pile cap,
the newly-built pile cap is positioned at the top of the newly-built pile, and the pile-embracing type pile cap is positioned on the existing pile at the adjacent side of the underpinned pile; the jacking devices are respectively arranged on the newly-built pile cap and the pile embracing type pile cap;
the newly-built underpinning beam is connected with the original bearing platform, and the newly-built underpinning beam is positioned above the newly-built pile.
2. A pile underpinning construction structure as claimed in claim 1 wherein there are two underpinned piles and two newly constructed piles; newly-built pile caps are constructed on the two newly-built piles; two existing piles on the adjacent sides of the two underpinned piles are used for constructing pile embracing type pile caps respectively.
3. The construction structure for underpinning a pile foundation as claimed in claim 1, wherein the jacking device comprises hydraulic jacks, self-locking devices and auxiliary supports, and 3 hydraulic jacks, 3 auxiliary supports and 3 self-locking devices are respectively arranged on the newly-built pile cap and the pile-embracing type pile cap in a delta shape.
4. A pile underpinning construction structure as claimed in claim 1 wherein said new underpinning beam includes an extension portion connected to the end of the original platform above the new pile and a bottom connecting portion connecting the bottom of the extension portion to the bottom of the original platform to integrate the bottom of the extension portion with the bottom of the original platform.
5. The structure of claim 1, wherein at least 1 displacement gauge is disposed on each of the new pile cap and the pile embracing type pile cap, the displacement gauges are spaced apart from the top surfaces of the original pile cap and the new underpinning beam, the inclinometers are disposed at four corners of the top surfaces of the original pile cap and the new underpinning beam, and strain gauges are mounted on the side surfaces of the original pile cap and the new underpinning beam and connected with the strain gauges.
6. A pile foundation underpinning construction structure as claimed in any one of claims 1 to 5, wherein said original cap is an abutment and the underpinned pile is an abutment end pile.
7. A construction method for underpinning pile foundation features that the underpinned pile is the pile foundation on the edge of original pile cap, the underpinned beam is newly built and the newly built pile is used to underpin the underpinned pile, and features that the existing pile and newly built pile are used as lifting platform to underpin the pile foundation,
an existing pile on the adjacent side of the underpinning pile is imposed, and an existing pile embracing pile type pile cap is constructed on the existing pile on the adjacent side; constructing a newly-built pile, and constructing a newly-built pile cap on the newly-built pile; constructing a newly-built underpinning beam above the corresponding newly-built pile, and forming an underpinning beam whole with the original bearing platform;
and (3) installing jacking devices on the pile-embracing type pile cap and the newly-built pile cap, and respectively arranging displacement monitoring points on the pile-embracing type pile cap, the newly-built pile cap and the underpinning beam.
8. The method of claim 7, wherein the jacking comprises an existing pile jacking phase and a newly-built pile and existing pile synchronous jacking phase, wherein the existing pile jacking phase only pressurizes the existing pile end; and in the stage of synchronously jacking the newly built pile and the existing pile, synchronously pressurizing the existing pile and the newly built pile at two ends of the underpinning beam.
9. A method of pile foundation underpinning as claimed in claim 7 or 8, characterised in that the concrete steps are as follows:
1) constructing a new pile;
2) excavating the foundation pit to the designed elevation while supporting;
3) constructing a newly-built pile cap, an existing pile-holding pile cap and a underpinning beam;
4) respectively calculating the values of the jacking forces of the newly-built pile end and the existing pile end, and installing a jacking device after the underpinning beam and the pile cap concrete are equal in strength, wherein the jacking device comprises a self-locking device, an auxiliary support and a jack;
5) respectively arranging displacement monitoring points, stress strain monitoring points and inclination monitoring points on the pile cap and the underpinning beam, and collecting original detection data;
6) jacking the existing pile, synchronously detecting and cutting off the existing pile;
7) jacking and synchronous detection of the newly-built pile;
8) synchronously jacking the newly-built pile and the existing pile;
9) the pile is cut off by the underpinned pile;
10) the jack returns oil and withdraws, and the load is transferred to the self-locking device and the auxiliary support;
11) and pouring concrete at the underpinning node, and completing underpinning of the pile foundation by using the existing pile and the newly-built pile as the jacking platform.
10. A method according to claim 7, wherein the newly-built pile end and the existing pile end are progressively pressurised by a calculated amount of 30%, 20%, 15%, 10%, 5%, 3%, 2%.
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