Offshore multi-pile foundation integrated pile testing system and pile testing method

Abstract

The invention discloses an offshore multi-pile foundation integrated pile testing system and method in the technical field of pile foundations. The offshore multi-pile foundation integrated pile testing system comprises a counter-force loading system, a reference system and a data acquisition module. The counter-force loading system comprises a test pile, a main beam, a supporting beam, a pressing beam, a compression-resistant jack and an anti-pulling jack, the main beam is supported above the supporting beam, the pressing beam is supported above the main beam, the compression-resistant jack is installed between the test pile and the main beam, and the anti-pulling jack is installed between an upper pile cap of the test pile and the main beam; the reference system comprises reference piles, and two reference beams are arranged on the two sides of the arrangement direction of the test piles. The data acquisition module comprises an oil pressure detection unit, a pile top displacement detection unit and a pile body stress-strain detection unit. According to the in-situ double-bridge static cone penetration test device, high-strain initial redriving detection, a compression-resistant static load test, an anti-pulling static load test, a pile body stress-strain test and an in-situ double-bridge static cone penetration test of a plurality of test piles can be completed through one-time erection, and free switching between different test piles and different test methods is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of pile foundations, and in particular to an integrated pile testing system and a pile testing method for offshore multi-pile foundations. Background Art

[0002] In recent years, offshore projects such as large deep-water port terminals and offshore wind farm projects have developed rapidly. These offshore structures are mainly distributed in the delta areas of estuaries and seaports. The soil is mainly clay, silt, sand and weathered rock. Pile foundations are mainly used to bear the deadweight of the superstructure and other external loads. Therefore, pile foundations are one of the core parts of offshore projects. The quality of their construction directly affects the overall performance and operational safety of offshore structures, and is crucial to the quality of the project. In addition, the difficulty of maintenance and reinforcement after completion is much greater than that of land projects.

[0003] With the large-scale development of deep-water ports and offshore wind power, and the gradual development towards deep water and offshore, the requirements for driven piles are becoming higher and higher, requiring larger single pile bearing capacity, penetrating hard interlayers, withstanding higher impact stress, and rapid construction, etc. However, the successful use of driven piles is restricted by many factors such as engineering geological conditions, pile driving equipment, and design control standards. It is necessary to select relevant parameters through preliminary pile tests to determine the suitability of the pile driving construction process and the site strata.

[0004] In the prior art, due to the complex offshore environment and limitations of loading equipment, in the case of testing multiple pile foundations at sea, it is necessary to set up complex loading systems and reaction systems for each pile for vertical compressive static load test and vertical tensile static load test respectively. During the test, multiple disassembly and reinstallation are required to change the test format. The process is cumbersome and consumes a lot of ship lifting costs. During the installation of the test equipment, the requirements for sea conditions are also high, and the work efficiency is low, which often leads to delays in the test progress and increases the safety risks of offshore operations. Summary of the invention

[0005] In view of this, an object of the present invention is to provide an integrated pile testing system for offshore multi-pile foundations in order to solve the above technical problems.

[0006] The technical solution adopted by the present invention is: an integrated pile test system for offshore multi-pile foundations, including a reaction force loading system, a reference system and a data acquisition module; The reaction force loading system includes a test pile, a support pile, an anchor pile, a main beam, a support beam, a pressure beam, a compression jack, an anti-pulling jack and a reversing oil pump. A plurality of the test piles are arranged at intervals in the transverse direction, and a plurality of the support piles and the anchor piles are distributed on both sides of the test pile arrangement direction. The support beam and the pressure beam are arranged in the longitudinal direction, and the longitudinal ends of the support beam are connected to the support piles. The main beam is supported and fixed above the support beam in the transverse direction, and the pressure beam is supported and fixed above the main beam, and the two ends of the pressure beam are fixedly connected to the anchor piles; a lower pile cap of the test pile is installed on the top of the test pile, an upper pile cap of the test pile is arranged above the main beam, and the upper pile cap of the test pile and the lower pile cap of the test pile are fixedly connected by a first vertical connecting rod, the compression jack is installed between the lower pile cap of the test pile and the main beam, and the anti-pulling jack is installed between the upper pile cap of the test pile and the main beam, and the reversing oil pump is respectively connected to the compression jack and the anti-pulling jack through an oil supply pipeline; The reference system includes reference piles and reference beams, at least two of the reference piles are arranged at both ends of the test pile arrangement direction, two reference beams are arranged one-to-one at both sides of the test pile arrangement direction, and both ends of the reference beams are connected to the reference piles; The data acquisition module includes an oil pressure detection unit, a pile top displacement detection unit and a pile body stress and strain detection unit. The oil pressure detection unit is connected to the reversing oil pump and is used to obtain real-time output oil pressure information of the reversing oil pump. The pile top displacement detection unit is connected to the reference beam and is used to obtain real-time pile top displacement information of the test pile. The pile body stress and strain detection unit is installed on the test pile and is used to obtain pile body stress and strain information of the test pile.

[0007] Preferably, a lower pile cap is fixedly installed on the top of the anchor pile, and upper pile caps are arranged above both ends of the compression beam. The lower pile cap and the upper pile cap are fixedly connected by a second vertical connecting rod.

[0008] Preferably, the compression beams and the support beams are alternately arranged along the transverse direction.

[0009] Preferably, a first limiting steel plate for laterally limiting the support beam is fixedly connected to both sides of the top of the support pile, a second limiting steel plate for longitudinally limiting the main beam is fixedly connected to the support beam, and a third limiting steel plate for laterally limiting the compression beam is fixedly connected to the main beam.

[0010] Preferably, a steel plate is placed on the top of the pile cap under the test pile, a plurality of the compression jacks are symmetrically distributed above the steel plate around the axis of the test pile, a gasket is placed on the top of the compression jack, and a steel plate is placed between the gasket and the main beam; a steel plate is placed on the main beam, a plurality of the pull-out jacks are symmetrically distributed above the steel plate around the axis of the test pile, and a steel plate is placed between the top of the pull-out jack and the pile cap on the test pile.

[0011] Preferably, steel corbels are installed on both longitudinal sides of the reference pile, one end of the reference beam is fixedly connected to the steel corbels, and the other end of the reference beam is placed on the steel corbels.

[0012] Preferably, the oil pressure detection unit is a pressure sensor, the pile top displacement detection unit is an electric displacement meter, the electric displacement meter is installed on the reference beam through a magnetic seat, the pile body stress and strain detection unit is a distributed sensing optical fiber, the distributed sensing optical fiber is pre-buried on both sides of the pile body of the test pile, and the distributed sensing optical fiber is electrically connected to the wireless transmission module at the top of the test pile, and the pressure sensor and the electric displacement meter are electrically connected to the static load automatic tester.

[0013] Preferably, the main beam, support beam and compression beam are all rectangular box beams with hollow structures.

[0014] The second object of the present invention is to provide an integrated pile testing method for an offshore multi-pile foundation, wherein the pile testing method uses the integrated pile testing system for an offshore multi-pile foundation, and the pile testing method comprises the following steps: S1: Distributed sensing optical fibers are buried on both sides of the test pile; S2: Conduct high-strain initial driving tests on test piles and anchor piles; S3: Conduct high-strain re-driving tests on test piles and anchor piles; S4: Build a test work platform on both sides of the test pile arrangement direction; S5: construct reaction force loading system, benchmark system and data acquisition module; S6: Conduct initial pressure test on the test pile; S7: Conduct a test pile compression test; S8: Conduct pull-out test on the test pile; S9: Conduct pile stress-strain test; S10: Conduct in-situ double bridge static penetration test.

[0015] Beneficial effects of the present invention: The integrated offshore multi-pile foundation test pile system of the present invention can complete various tests and inspections of multiple test piles in one erection, changing the traditional practice of having to assemble and disassemble the test piles one by one multiple times for testing, reducing the cost of large-tonnage ship machinery hoisting and labor costs at sea, shortening the construction period of the test reaction force device installation operation, and reducing the safety risks of multiple high-altitude hoisting operations at sea.

[0016] The integrated offshore multi-pile foundation test method of the present invention realizes high-strain monitoring and analysis of the whole process of pile driving of different pile lengths in the test area in one test, and compressive static load test (including initial pressure and re-compression), pull-out static load test, pile body stress-strain test and in-situ static penetration test of multiple test piles are completed at the same time. In this way, the in-situ test data of the interaction between the pile foundation and the soil body can be obtained more accurately, and the distribution law of the pile body stress-strain of the piles with different pile lengths during the hammering pile driving and static load process can be mastered, so as to provide scientific parameters for the selection of the hammer type of the engineering pile and the determination of the stop hammer standard, and the single pile compressive and pull-out ultimate bearing capacity of different pile types in the test area, the standard value of the compressive and pull-out pile side ultimate friction resistance of each soil layer and the standard value of the pile end ultimate resistance are measured, so as to improve the test efficiency and accuracy of offshore pile trials, ensure the construction period, quality and safety of offshore pile trials, and provide a scientific basis for selecting a reasonable bearing layer, an economical pile length and a reliable pile driving construction process for offshore pile foundations. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a three-dimensional schematic diagram of the integrated pile test system for offshore multi-pile foundations of the present invention; Figure 2 A top view of the integrated pile test system for offshore multi-pile foundations of the present invention; Figure 3 It is a front view of the integrated pile test system for offshore multi-pile foundations of the present invention; Figure 4 It is a three-dimensional schematic diagram of the reaction force loading system; Figure 5 It is the position relationship diagram between the benchmark system and the test pile; Figure 6 for Figure 3 A partial enlarged view of the Figure 7 This is a schematic diagram of the connection between the anchor pile and the pressure beam; Figure 8 The high strain initial driving test result of the test pile of the specific embodiment; Fig. 9 The high strain re-driving test result of the anchor pile of a specific embodiment; Fig.10 It is the initial pressure static load test curve of the test pile of a specific embodiment; Fig.11 It is the static load test curve of the test pile of the specific embodiment; Fig.12 It is the static load test curve of the pull-out resistance of the test pile of the specific embodiment; Fig.13 It is a comparison diagram of the double-bridge static penetration curve and the geological drilling hole of a specific embodiment.

[0018] Description of reference numerals in the figures: 100. Reaction loading system; 101, test pile; 102, support pile; 103, anchor pile; 104, main beam; 105, support beam; 106, pressure beam; 107, compression jack; 108, pull-out jack; 109, reversing oil pump; 110, lower pile cap of test pile; 111, upper pile cap of test pile; 112, first vertical connecting rod; 113, oil supply pipeline; 114, lower pile cap of anchor pile; 115, upper pile cap of anchor pile; 116, second vertical connecting rod; 117, first limit steel plate; 118, second limit steel plate; 119, third limit steel plate; 120, steel pad; 121, gasket; 200, benchmark system; 210, reference pile; 220, reference beam; 230, steel corbel; 300. Data acquisition module; 310, pressure detection unit; 320, pile top displacement detection unit; 330, pile body stress and strain detection unit; 340, static load automatic tester; 400. Experimental work platform. DETAILED DESCRIPTION

[0019] The specific embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. These embodiments are only used to illustrate the present invention, but not to limit the present invention.

[0020] In the description of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0021] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0022] Furthermore, in the description of the present invention, unless otherwise specified, “plurality” means two or more.

[0023] Examples, such as Figure 1-Figure 13 As shown, an integrated pile testing system for offshore multi-pile foundations includes a reaction force loading system 100 , a reference system 200 and a data acquisition module 300 .

[0024] The reaction force loading system includes a test pile 101, a support pile 102, an anchor pile 103, a main beam 104, a support beam 105, a compression beam 106, a compression jack 107, an anti-pulling jack 108 and a reversing oil pump 109; wherein, the number of the test piles 101 is multiple, and the multiple test piles 101 are arranged at intervals in the transverse direction, the number of the support piles 102 and the anchor piles 103 are both multiple, and the multiple support piles 102 and the anchor piles 103 are distributed on both sides of the test pile arrangement direction, that is, the multiple support piles 101 02 and anchor piles 103 are distributed on both sides of the longitudinal direction of the test pile 101; the number of the support beam 105 and the pressure beam 106 is multiple, and the multiple support beams 105 and the pressure beam 106 are arranged along the longitudinal direction, and the two longitudinal ends of the support beam 105 are fixedly connected with the two support piles 102 in a one-to-one correspondence, the main beam 104 is supported and fixed above the support beam 105 in the transverse direction, and the pressure beam 106 is supported and fixed above the main beam 104, and the two ends of the pressure beam 106 are fixedly connected with the two anchor piles 103 in a one-to-one correspondence. A lower pile cap 110 of the test pile is fixedly installed on the top of the test pile 101, and an upper pile cap 111 of the test pile is arranged above the main beam 104. The upper pile cap 111 of the test pile is located directly above the lower pile cap 110 of the test pile, and the upper pile cap 111 of the test pile and the lower pile cap 110 of the test pile are fixedly connected by a first vertical connecting rod 112; the compression jack 107 is installed between the lower pile cap 110 of the test pile and the main beam 104, and the pull-out jack 108 is installed between the upper pile cap 111 of the test pile and the main beam 104, and the reversing oil pump 109 is respectively connected to the compression jack 107 and the pull-out jack 108 through an oil supply pipeline 113; The reference system 200 includes reference piles 210 and reference beams 220. The number of the reference piles 210 is at least two, and the reference piles 210 are arranged at both ends of the test pile arrangement direction. The number of the reference beams 220 is two, and the two reference beams 220 are arranged one-to-one on both sides of the test pile arrangement direction. The reference beams 220 are spaced apart from the test piles 101, and both ends of the reference beams 220 are connected to the reference piles 210. The data acquisition module 300 includes an oil pressure detection unit 310, a pile top displacement detection unit 320 and a pile body stress and strain detection unit 330. The oil pressure detection unit 310 is connected to the reversing oil pump 109 and is used to obtain real-time output oil pressure information of the reversing oil pump 109. The pile top displacement detection unit 320 is connected to the reference beam 220 and is used to obtain real-time pile top displacement information of the test pile 101. The pile body stress and strain detection unit 330 is installed on the test pile 101 and is used to obtain pile body stress and strain information of the test pile 101.

[0025] The integrated offshore multi-pile foundation test pile system of the present application realizes that various tests and inspections of multiple test piles can be completed in one erection, which changes the traditional practice that offshore test piles must be assembled and disassembled multiple times for testing. It not only reduces the offshore large-tonnage ship machinery lifting costs and labor costs, shortens the construction period of the test reaction device installation operation, reduces the safety risks of multiple offshore high-altitude lifting operations, improves the offshore test pile testing efficiency and accuracy, and ensures the offshore test pile construction period, quality and safety.

[0026] It should be noted that the horizontal direction in this application refers to Figure 2 The double arrow direction in the vertical direction refers to Figure 2 The single arrow direction.

[0027] Specific embodiment 1, as Figure 1-Figure 7 As shown, an integrated pile testing system for offshore multi-pile foundations includes a reaction force loading system 100 , a reference system 200 and a data acquisition module 300 .

[0028] The reaction force loading system includes a test pile 101, a support pile 102, an anchor pile 103, a main beam 104, a support beam 105, a compression beam 106, a compression jack 107, an anti-pulling jack 108 and a reversing oil pump 109; wherein, the number of the test piles 101 is four, and the four test piles 101 are linearly arranged at equal intervals in the transverse direction, the number of the support piles 102 is four, the number of the anchor piles 103 is six, and the four support piles 102 and the six anchor piles 103 are distributed in two rows on both sides of the test pile arrangement direction, that is, the support piles 102 and the anchor piles 103 are distributed on both sides of the longitudinal direction of the test pile 101, and in the transverse direction, the anchor piles 103 and the support piles 102 are alternately arranged, that is, the support pile 102 is located between two adjacent anchor piles 103.

[0029] The number of the support beams 105 is two, the number of the compression beams 106 is three, and the support beams 105 and the compression beams 106 are both arranged along the longitudinal direction, the longitudinal ends of the support beam 105 are fixedly connected to the two support piles 102 in a one-to-one correspondence, and the longitudinal ends of the compression beam 106 are fixedly connected to the two anchor piles 103 in a one-to-one correspondence, so that the three compression beams 106 and the two support beams 105 are alternately arranged in the transverse direction, wherein the two compression beams 106 located at the transverse ends of the main beam 104 are also called side beams, and the compression beam 106 located between the two support beams 105 is also called a middle beam.

[0030] The main beam 104 is supported and fixed on the top of the support beam 105 in the transverse direction, and the pressure beam 106 is supported and fixed on the top of the main beam 104, and in the projection of the horizontal plane, the main beam 104 is located in the middle of the support beam 105 and the pressure beam 106; at the same time, the first limiting steel plates 117 are fixedly connected to both sides of the top of the support pile 102, and the two ends of the support beam 105 are placed on the top of the support pile 102. The first limiting steel plates 117 are located on both sides of the support beam 105 in the transverse direction, which are used to limit the support beam 105 in the transverse direction to prevent the support beam 105 from lateral sliding or overturning; 05 is fixedly connected with a second limiting steel plate 118 in the middle part, the main beam 104 is placed above the middle part of the supporting beam 105, and the second limiting steel plates 118 are located on both sides of the longitudinal direction of the main beam 104, for limiting the longitudinal position of the main beam 104 to prevent the main beam 104 from lateral sliding or overturning; a third limiting steel plate 119 is fixedly connected with the main beam 104, the compression beam 106 is placed above the middle part of the main beam 104, and the third limiting steel plates 119 are located on both sides of the lateral direction of the compression beam 106, for limiting the lateral position of the compression beam 106 to prevent the lateral sliding or overturning of the compression beam 106.

[0031] A lower pile cap 110 of the test pile is fixedly installed on the top of the test pile 101 in a one-to-one correspondence, and an upper pile cap 111 of the test pile is arranged above the main beam 104. The upper pile cap 111 of the test pile is located directly above the lower pile cap 110 of the test pile, and the upper pile cap 111 of the test pile and the lower pile cap 110 of the test pile are fixedly connected by a first vertical connecting rod 112; a lower pile cap 114 of the anchor pile is fixedly installed on the top of the anchor pile 103 in a one-to-one correspondence, and an upper pile cap 115 of the anchor pile is arranged above the two ends of the pressure beam 106, and the lower pile cap 114 of the anchor pile and the upper pile cap 115 of the anchor pile are fixedly connected by a second vertical connecting rod 116.

[0032] Specifically, one main beam 104 and three compression beams 106 are all processed into a rectangular box beam structure using steel plates, and the pile caps 110 under the four test piles are all processed into a hollow circular ring box beam structure using steel plates, with the inner diameter of the hollow slightly larger than the inner diameter of the pile core cage, and the outer diameter slightly larger than the long side length of the pile cap 111 on the test pile. The pile caps 111 on the four test piles and the pile caps 115 on the six anchor piles are all processed into a rectangular box beam structure using steel plates. Since the box beam has large bending rigidity, stable performance and is relatively easy to process, the above components are preferably in the form of a box beam structure. The pile caps 114 under the six anchor piles are circular steel pipes with a wall thickness of not less than 2 cm, and the inner ring diameter is slightly smaller than the inner diameter of the pile core cage, so that each main reinforcement of the pile core cage can be single-sided / double-sidedly welded to the outside of the steel pipe. The length of the steel pipe can be customized and adjusted according to the sum of the heights of the support beam 105 and the main beam 104, so that the top elevation of the pile caps 114 under the six anchor piles is consistent with the top elevation of the main beam 104.

[0033] When the anchor pile 103 is a steel pipe pile, the diameter of the steel pipe used in the pile caps 114 under the six anchor piles is consistent with the diameter of the anchor pile 103; when the test pile 101 is a steel pipe pile, the hollow inner diameter of the hollow annular box beam structure of the pile caps 110 under the four test piles is consistent with the diameter of the test pile 101.

[0034] The core cages of the test piles and anchor piles should be processed with steel cages according to the inner diameters of the test piles 101 and anchor piles 103. The diameter, quantity and length of the main bars should meet the requirements that the sum of the tensile strengths of all the main bars configured for the core cages should not be less than 1.3 times the maximum pull-out bearing capacity required for a single test pile. The steel cages extend from the top of the pile into the pile to a certain depth and concrete is poured. The main bars are exposed 80cm above the top of the pile, and the friction between the core cage concrete and the inner wall of the foundation pile is used to ensure the overall pull-out resistance.

[0035] When the test pile 101 and the anchor pile 103 are steel pipe piles, there is no need to set up a pile core steel cage. The test pile 101 and the pile cap 110 under the test pile, as well as the anchor pile 103 and the pile cap 114 under the anchor pile can be directly welded and connected through multiple connecting steel plates. The sum of the tensile strengths of all connecting steel plates of a single pile should not be less than 1.3 times the maximum pull-out bearing capacity required for a single test pile 101 or anchor pile 103.

[0036] The four upper pile caps 111 of the test piles and the four lower pile caps 110 of the test piles are fixedly connected by welding through the first vertical connecting rod 112. The first vertical connecting rod 112 is a connecting steel bar. The single-sided welding length is not less than 10 times the diameter of the connecting steel bar, and the double-sided welding length is not less than 5 times the diameter of the connecting steel bar. The diameter, quantity and length of the selected connecting steel bar should meet the requirement that the sum of the tensile strength of all main bars is not less than 1.3 times the maximum pull-out test load required for a single test pile 101. It can also be connected by screws, but the structures of the upper pile cap 111 and the lower pile cap 110 of the test pile need to be modified respectively, and corresponding screw connection holes need to be added.

[0037] The six anchor pile upper caps 115 and the six anchor pile lower caps 114 are welded and fixedly connected through the second vertical connecting rod 116. The second vertical connecting rod 116 is a connecting steel bar. The single-sided welding length is not less than 10 times the diameter of the connecting steel bar, and the double-sided welding length is not less than 5 times the diameter of the connecting steel bar. The selected connecting steel bar diameter, quantity and length should meet the requirement that the sum of the tensile strength of all main bars is not less than 1.3 times the maximum pull-out bearing capacity required by a single anchor pile 103. It can also be connected by screws, but the structures of the lower pile cap 114 and the upper pile cap 115 of the anchor pile need to be modified respectively, and the corresponding screw connection holes need to be added.

[0038] There are multiple compression jacks 107, and the multiple compression jacks 107 are respectively placed on the pile caps 110 under the test piles. The main beam 104 is placed in the middle of the span of the two support beams 105 and is just above the pile caps 110 under the four test piles. A steel pad 120 is placed on the top of the pile caps 110 under the test piles. Multiple compression jacks 107 are placed on the steel pad 120 according to the load required for the test. The multiple compression jacks 107 are symmetrical about the central axis of the test pile 101, and the multiple compression jacks 107 are connected in parallel with each other. A gasket 121 is placed on the top of the compression jack 107, and another steel pad 120 is placed on the gasket 121. A steel pad 120 is placed on the main beam 104 directly below the pile caps 111 on the four test piles. A plurality of pull-out jacks 108 are placed on the steel pad 120 according to the load required for the test. The plurality of pull-out jacks 108 are symmetrical about the central axis of the test pile 101, and the plurality of pull-out jacks 108 are connected in parallel with each other, and are controlled successively by a reversing oil pump 109 (preferably an automatic reversing ultra-high pressure oil pump) and a correspondingly connected oil supply pipeline 113. The steel pad 120 mainly plays the role of load distribution and transmission of the jack, and the thickness of the steel pad 120 is about 8cm to 10cm. If the load of a single jack is too large, the steel pad 120 should be replaced with a load distribution box to avoid damage to the box beam due to local concentrated load stress; the role of the gasket 121 is mainly to reserve the travel space for the pull-out displacement of the test pile 101 by pulling out the gasket 121 when converting the pull-out test.

[0039] The reference system 200 includes reference piles 210 and reference beams 220. The number of the reference piles 210 is two, and the two reference piles 210 are arranged one-to-one at both ends of the test pile arrangement direction. The number of the reference beams 220 is two, and the two reference beams 220 are arranged one-to-one at both sides of the test pile arrangement direction. The reference beams 220 are arranged at a distance from the test piles 101, and the two ends of the reference beams 220 are connected to the reference piles 210.

[0040] Steel corbels 230 are installed on both longitudinal sides of the reference pile 210, and one end of the reference beam 220 is fixedly connected to the steel corbels 230, and the other end of the reference beam 220 is placed on the steel corbels 230 to reduce the flexural deformation of the two reference beams 220 caused by temperature changes.

[0041] Preferably, when one of the test piles 101 is being tested, a small steel plate can be used to temporarily raise the steel corbels 230 of the other test piles 101 to ensure that the two reference beams 220 are suspended above the steel corbels 230 of the test pile 101 being tested.

[0042] The data acquisition module 300 includes an oil pressure detection unit 310 , a pile top displacement detection unit 320 , a pile body stress and strain detection unit 330 and a static load automatic tester 340 .

[0043] The oil pressure detection unit 310 is a wireless pressure sensor, and the wireless pressure sensor is installed on the reversing oil pump 109, which is used to measure the real-time output oil pressure information and feed it back to the static load automatic tester 340. The static load automatic tester 340 automatically calculates the real-time vertical load value of the top of the test pile 101 according to the signal fed back by the pressure sensor and the calibration curves of multiple compression jacks 107 and multiple tension jacks 108, automatically records and adjusts the vertical load applied to the top of the test pile 101 by the high-pressure oil pump and the jack accordingly, thereby realizing remote control automatic step-by-step loading or unloading. The working pressure of the selected hydraulic jack and wireless pressure sensor at the maximum load of the test should be between 20% and 80% of the rated working pressure. After each compression test or pull-out test of a group of test piles 101 is completed, the reversing oil pump 109 and the wireless pressure sensor and the corresponding oil supply pipeline 113 need to be switched and connected to the multiple compression jacks 107 or multiple pull-out jacks 108 above the next test pile 101 that needs to be tested.

[0044] The pile top displacement detection unit 320 is an electric displacement meter, and there are four electric displacement meters, with a measuring range of 100 mm and an accuracy of 0.01 mm. The four electric displacement meters are symmetrically arranged around the steel brackets 50 cm below the top of the test pile 101. The four electric displacement meters are placed on two reference beams 220 through magnetic bases. The four electric displacement meters are connected to a wireless transmission device and connected to a static load automatic tester 340 to realize automatic collection and testing of the displacement information of the top of the test pile 101.

[0045] The pile stress and strain detection unit 330 is a distributed sensing optical fiber, which is symmetrically pre-buried on both sides of the test pile 101, with a measurement point spacing of 1m, forming a U-shaped loop, and a redundancy of 5m; all lines are connected from the pile top to the wireless transmission device and connected to the dense distributed optical fiber demodulator, and the automatic collection and testing of the stress and strain information of the test pile 101 is synchronously realized. After each compression test or pull-out test of a group of test piles 101 is completed, the pile top displacement detection unit 320 and the pile body stress and strain detection unit 330 need to be switched and installed at the next test pile 101 that needs to be tested.

[0046] After all the compression tests are completed, the four test pile upper caps 111 and the four test pile lower caps 110 are welded and fixed through the first vertical connecting rod 112. The compression test load of the four test piles 101 is provided by the six anchor piles 103 of the reaction loading system 100, and the pull-out test load of the four test piles 101 is provided by the four supporting piles 102 of the reaction loading system 100.

[0047] Embodiment, a method for integrated pile testing of offshore multi-pile foundation, the method for pile testing uses the above-mentioned integrated pile testing system for offshore multi-pile foundation, the method for pile testing comprises the following steps: S1: Distributed sensing optical fibers are buried on both sides of the pile body of the test pile 101.

[0048] Specifically, two dense distributed sensing optical fibers are symmetrically arranged on both sides of each test pile 101, with a distance of 1m between two adjacent strain measurement points, and a "U"-shaped transition is adopted at the bottom of the pile body, with a redundancy of 5m. After the pile body sensing optical fiber is laid, the lead optical cable at the pile head is reinforced with casings such as hard corrugated tubes and armored tubes to prevent the lead optical cable from being damaged during the transportation and driving of the pile. After the pile is buried, the single pile needs to be maintained for at least 3 days before the pile can be sunk. If the diameter of the test pile 101 is large, four dense distributed sensing optical fibers can also be symmetrically arranged along the pile body to obtain more accurate pile body stress and strain data.

[0049] S2: Perform high strain initial driving test on test piles and anchor piles.

[0050] Specifically, when the pile-driving ship is sinking the test pile 101 and the anchor pile 103, a high-strain initial driving test is carried out simultaneously. By setting the test piles 101 and the anchor piles 103 with different pile lengths in the test pile area, the whole driving process is monitored and analyzed by high-strain process, and the hammer force, hammer energy, maximum compressive stress and maximum tensile stress of the pile body are measured. The static soil resistance value of the single pile is obtained every 1m for the last 5m of each pile. The Case method is used to calculate the static soil resistance value of the single pile, and the pile driving parameters such as the drop hammer height, penetration, and number of hammer blows are summarized and compared and analyzed simultaneously. Based on this, scientific parameters for the selection of hammers and the stopping of hammers for the foundation pile sinking construction in the test area are proposed.

[0051] S3: Carry out high-strain re-driving test on test piles and anchor piles.

[0052] Specifically, after all the test piles 101 and anchor piles 103 are sunk, and after the rest time interval of the soil body that needs to be re-driven meets the requirements, the pile-driving ship cooperates to carry out high-strain re-driving detection of the test piles 101 and anchor piles 103. The curve fitting method is used to numerically calculate the wave problem, assuming the pile and soil mechanical models and model parameters of each pile unit, using the measured velocity (or force, upgoing wave, downgoing wave) curve as the input boundary condition, numerically solving the wave equation, inversely calculating the force (or velocity, downgoing wave, upgoing wave) curve at the top of the pile, inversely determining the mechanical model of the pile and soil and its parameter values, and obtaining the vertical compressive bearing capacity of a single pile, the pile body integrity coefficient, the theoretical analysis of the soil resistance at the pile side and pile end, and the simulated Qs curve. By comparing and analyzing the high-strain re-driving of the test piles 101 and anchor piles 103 with the initial driving and static load test results, the time effect coefficients of the foundation pile bearing capacity such as the vertical compressive bearing capacity of a single pile, the initial re-driving comparison coefficient, and the dynamic and static comparison coefficient can be further obtained.

[0053] S4: Build a test work platform on both sides of the test pile arrangement direction.

[0054] Specifically, after the high-strain re-driving test of the test pile 101 and the anchor pile 103 is completed, the test work platform 400 is set up, the pile body steel bracket (also called the enclosure) is installed, and the pile core steel cage of the anchor pile 103 and the test pile 101 is made, lowered, and the pile core concrete is poured. The test work platform 400 set up must meet the bearing capacity requirements of temporary loads such as personnel and equipment during the test, and is independent of the test pile 101 and the reference pile 210. The length of the pile core steel cage should ensure that its bonding force with the inner wall of the test pile 101 is not less than 1.3 times the maximum test load. If the test pile 101 and the anchor pile 103 are steel pipe piles, the pile core steel cage can be eliminated and directly welded by connecting steel plates.

[0055] S5: construct the reaction force loading system 100 , the reference system 200 and the data acquisition module 300 .

[0056] After the concrete pouring of the core cage of the test pile 101 and the anchor pile 103 is completed, the lower pile cap 114 of the anchor pile and the lower pile cap 110 of the test pile are hoisted to the test pile 101 and the anchor pile 103 for welding, and the two reference beams 220 of the reference system 200, the two support beams 105 of the reaction loading system 100, and the multiple compression jacks 107 are installed in place simultaneously. After the welding of the lower pile cap 110 of the test pile is completed, the installation of the reaction loading system 100 can be started, and the main beam 104 and the compression beam 106 are installed in sequence, and then the upper pile cap 115 of the anchor pile, the multiple anti-pulling jacks 108, and the upper pile cap 111 of the test pile are installed in place in sequence, and the welding of the connecting steel bars between the upper pile cap 115 of the anchor pile and the lower pile cap 114 of the anchor pile should be carried out immediately. The upper pile cap 111 of each test pile 101 and the lower pile cap 110 of the test pile should not be connected together at this stage.

[0057] Four electric displacement meters are installed on the steel bracket / enclosure about 50 cm below the top of the test pile through magnetic bases, avoiding the stress concentration area on the top of the pile as much as possible, and small pieces of glass are pasted at the contact points of the displacement meters to ensure good contact between the displacement meters and the reference beam 220. The electric displacement meters are connected to the static load automatic tester 340 through a wireless transmission device. The distributed optical fiber pre-buried in the pile body is connected to the dense distributed optical fiber demodulator through a wireless transmission device.

[0058] After the reaction loading system 100 is installed and all data acquisition modules 300 are connected, a system check is performed. The method is to apply a small load on the test pile 101 for pre-compression, the purpose of which is to eliminate the non-pile body settlement caused by the gap between the entire measurement system and the test pile 101 itself due to installation, pile head processing and other human factors, eliminate the air in the jack and pipeline, and check whether the pipeline joints, valves, etc. are leaking. If everything is normal, unload to zero, wait for the reading displayed by the electric displacement meter to stabilize, record the initial reading, and then start the formal loading test.

[0059] S6: Carry out initial pressure test on the test pile.

[0060] The compression test is carried out on each test pile 101 one by one, and the stress and strain test of the pile body is carried out simultaneously. The test sequence is from left to right. The initial pressure test sequence of each test pile 101 can be adjusted at any time on site according to the test requirements. Considering the influence of wind and wave factors in offshore tests, it is recommended to adopt the rapid maintenance load method. The load increment of each level is first determined according to one-tenth of the estimated design ultimate bearing capacity standard value, and then loaded to the maximum load or foundation soil failure according to the design requirements. At the same time, the axial reaction coefficient k value of each test pile 101 can be determined according to the test requirements, that is, the reciprocating cycle of loading and unloading between the permanent load standard value and the combined value of the permanent load and the variable load standard value is repeated three times, and the first and last points of a stable cycle are taken for calculation. After each loading, the sampling time is 0, 5, 10, 15, 30, and 60 minutes, and the next level of loading is carried out. After each level of unloading, the reading is measured for 15 minutes, and sampling is performed at 0, 5, 10, and 15 minutes. Then the load of one level can be unloaded. The sampling time when the load is unloaded to zero is: 0, 5, 10, 15, 30, and 60 minutes. According to the measured displacement data of the test pile under various levels of load and the provisions of relevant specifications, a comprehensive analysis is performed to determine the ultimate vertical compressive bearing capacity of the single pile under initial pressure.

[0061] S7: Conduct a test pile re-compression test.

[0062] After the initial pressure test of each test pile 101 is completed, after meeting the requirements of the rest time interval of the re-pressure test, the re-pressure test of each test pile 101 can be carried out again, and the pile body stress strain test can be carried out simultaneously. The order and test time of the re-pressure test of each test pile 101 can be adjusted arbitrarily according to the actual test requirements on site, without being restricted by the time and sequence generated by the multiple disassembly and assembly of the reaction force equipment. The test method is consistent with the initial pressure test. According to the measured displacement data of the test pile 101 under various levels of load, in accordance with the provisions of relevant specifications, a comprehensive analysis is performed to determine the vertical compressive ultimate bearing capacity of a single pile under re-pressure, and compared with the results of the initial pressure test, thereby obtaining the time effect coefficient of the pile bearing capacity recovery under static load conditions.

[0063] S8: Conduct pull-out test on the test pile.

[0064] After the compression test of each test pile 101 is completed, the two ends of the connecting steel bars between the upper pile cap 111 and the lower pile cap 110 of all the test piles 101 are welded and fixed, and after the pull-out test rest time interval requirements are met, the pull-out test of each test pile 101 can be started. Among them, for the two middle test piles 101, after the compression jack 107 is retracted to the bottom and the gasket 121 is pulled out, the pull-out loading can be directly carried out, and the pile body stress-strain test can be carried out simultaneously. For the test piles 101 at both ends, before the pull-out test of the two middle test piles 101, the multiple compression jacks 107 of the two test piles 101 at both ends are first raised to contact with the bottom of the main beam 104 and maintain pressure. The purpose is to use the two middle test piles 101 as the lever fulcrum during the pull-out test of the two test piles 101 at both ends. Then, after the compression jacks 107 of the two test piles 101 at both ends are retracted to the bottom and the gaskets 121 are pulled out, the pull-out test is carried out, and the pile body stress-strain test is carried out simultaneously. The test recommends the use of the rapid maintenance load method, the observation time is consistent with the compression test, and the vertical pull-out ultimate bearing capacity of the single pile is determined by comprehensive analysis based on the measured displacement data of the test piles under various levels of load and in accordance with the provisions of relevant specifications.

[0065] S9: Conduct pile body stress-strain test.

[0066] The axial strain of the optical fiber is obtained by testing the densely distributed optical fiber demodulator Since the distributed sensing optical fiber is pre-buried and fixed in the pile body of the test pile 101, under the action of static load, the axial deformation of the optical fiber is consistent with the axial deformation of the pile body, so the pile body strain is also the axial strain of the optical fiber. , then the pile stress is ,in: is the elastic modulus of the test pile. The axial force of the pile is: ,in: is the cross-sectional area of ​​the pile body.

[0067] The lateral friction of the pile body is calculated according to the soil layer. Two cross sections are taken from the pile body in the same soil layer. The axial force values ​​on the two cross sections are obtained using the above axial force calculation method. The ratio of the difference in axial force values ​​to the area around the pile in this section is the lateral friction. The lateral friction value is expressed in the form of a square wave with the soil layer as the boundary. The basic differential equation for pile load transfer is: ,in: The friction resistance of the pile side is is the pile axial force, is the circumference of the pile body, which can be further simplified as: ,in: is the change in axial force between two sections of the pile body in a certain soil layer, is the depth difference between the two sections of the pile body in the soil layer. Substituting the two equations into the equation, we can get: ,in: It is the change of axial strain between two sections of the pile body in a certain soil layer.

[0068] Through the pile body stress-strain test, the distribution law of pile side compressive friction resistance, pile side pullout friction resistance and pile end resistance of each soil layer in the test site and the pullout reduction coefficient of each soil layer are obtained, and the pile body axial force at different positions of the pile body, the distribution of pile side friction resistance and the performance of pile end resistance are determined, so as to study the load transfer mechanism of the test pile.

[0069] S10: Conduct in-situ double bridge static penetration test.

[0070] After all static load tests are completed, the static penetration test equipment is temporarily fixed on the two support beams 105. The support beams 105 and the support piles 102 are used to provide the reaction force required for the static penetration test. The cone tip resistance q of each test soil layer is measured by the double bridge static penetration test. c and side wall friction resistance f s , combined with the hammer pile driving records, high strain initial and repeated driving tests and static load test results, the measured pile side friction and pile end resistance recommended values ​​were compared and analyzed to further accurately divide the soil stratification in the test area.

[0071] The following test verification results demonstrate the implementation effect of an integrated offshore multi-pile foundation test pile system and test method involved in this application.

[0072] The test object is a preliminary test pile project in a certain sea area, and the piles are arranged in combination with the auxiliary platform pile foundation to save project investment. It consists of 4 test piles, 10 anchor piles and 2 reference piles. The test piles, anchor piles and reference piles are all Φ1000mmPHC piles + steel pile shoes, with pile lengths ranging from 41m to 47m, and steel pile shoes ranging from 1m to 3m. The estimated compressive ultimate bearing capacity standard value of the test pile is about 9000kN, and the actual maximum load is 9000kN to 13000kN. The estimated pull-out ultimate bearing capacity standard value is about 3750kN, and the actual maximum load is 4500kN. The test results of a certain test pile as an example are shown in Tables 1 to 8 and Figure 8 to Figure 13 .

[0073] Table 1 High strain test initial and repeated recovery coefficient

[0074] The high strain initial driving test results of a test pile (hammer force and pile stress) are shown in Figure 8 The high strain re-driving test results of a certain anchor pile (the vertical compressive bearing capacity of a single pile and the Qs curve simulated by the pile integrity coefficient) are shown in Fig. 9 .

[0075] Table 2 Test results of initial compression static load, repeated compression static load and anti-pulling static load of a test pile. Cyclic loading and unloading test was carried out during the initial compression test to determine the axial reaction coefficient k value. The test curve is shown in Figure 8 to Figure 11 .

[0076]

[0077] According to the provisions of "Technical Specifications for Testing and Inspection of Foundation Pile for Water Transport Engineering" (JTS240-2020), the ultimate bearing capacity of a single pile is determined through comprehensive analysis: the ultimate vertical compressive bearing capacity of the test pile under initial compression is 8000 kN, the ultimate vertical compressive bearing capacity of the test pile under repeated compression is 7000 kN, the ultimate vertical pull-out bearing capacity of the single pile is not less than 4500 kN, and the time interval between the initial and repeated compression tests is 3 days, that is, the recovery coefficient of the ultimate bearing capacity of the single pile under static load conditions for 3 days is 87.5%.

[0078] Table 3 Comparison of dynamic and static recovery coefficients of test piles

[0079] Table 4 Recommended values ​​of standard values ​​of ultimate friction resistance of compression pile side

[0080] Table 5 Recommended values ​​of standard values ​​of ultimate end resistance of compression pile ends

[0081] Table 6 Recommended values ​​of lateral friction and pull-out reduction coefficient of pull-out piles

[0082] Table 7 Standard value of ultimate side friction of compression pile f s and the standard value of the ultimate end resistance of the pile end f p Comparison table

[0083] Table 8 Comparative analysis of the differences in the bottom elevation division between geological drilling holes and two static exploration holes

[0084] According to the actual measurement of cone tip resistance q by double bridge static penetration c and side wall friction resistance f s Data, test curve see Fig.13 Combined with the hammer pile driving records, high strain initial and repeated driving tests and static load test results, it is recommended to move the bottom elevation of the ⑦2-1 layer near the test pile area downward by 2.6m, that is, adjust it from -31.20m to -33.80m.

[0085] Compared with the prior art, this application has at least the following beneficial technical effects: One-time erection can not only complete the high-strain initial and repeated driving inspection of multiple test piles, compressive static load test, tensile static load test, pile body stress-strain test, and in-situ double-bridge static penetration test, but also facilitate free switching between different test piles and different test methods.

[0086] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. An integrated pile test system for offshore multi-pile foundations, characterized in that: It comprises a reaction force loading system (100), a reference system (200) and a data acquisition module (300); The reaction force loading system comprises a test pile (101), a support pile (102), an anchor pile (103), a main beam (104), a support beam (105), a pressure beam (106), a compression jack (107), an anti-pulling jack (108) and a reversing oil pump (109); a plurality of the test piles (101) are arranged at intervals in a transverse direction; a plurality of the support piles (102) and the anchor piles (103) are distributed on both sides of the test pile arrangement direction; the support beam (105) and the pressure beam (106) are arranged in a longitudinal direction; both longitudinal ends of the support beam (105) are connected to the support pile (102); the main beam (104) is supported and fixed above the support beam (105) in a transverse direction; and the pressure beam (106) is supported and fixed on the main beam (104), and both ends of the compression beam (106) are fixedly connected to the anchor pile (103); a lower pile cap (110) of the test pile is installed on the top of the test pile (101), an upper pile cap (111) of the test pile is arranged above the main beam (104), the upper pile cap (111) of the test pile and the lower pile cap (110) of the test pile are connected via a first vertical connecting rod (112), the compression jack (107) is installed between the lower pile cap (110) of the test pile and the main beam (104), the anti-pulling jack (108) is installed between the upper pile cap (111) of the test pile and the main beam (104), and the reversing oil pump (109) is respectively connected to the compression jack (107) and the anti-pulling jack (108) via an oil supply pipeline (113); The reference system (200) comprises reference piles (210) and reference beams (220), at least two of the reference piles (210) are arranged at two ends of the test pile arrangement direction, two of the reference beams (220) are arranged in a one-to-one correspondence at two sides of the test pile arrangement direction, and both ends of the reference beams (220) are connected to the reference piles (210); The data acquisition module (300) comprises an oil pressure detection unit (310), a pile top displacement detection unit (320) and a pile body stress and strain detection unit (330); the oil pressure detection unit (310) is connected to a reversing oil pump (109) and is used to obtain real-time output oil pressure information of the reversing oil pump (109); the pile top displacement detection unit (320) is connected to a reference beam (220) and is used to obtain real-time pile top displacement information of the test pile (101); and the pile body stress and strain detection unit (330) is installed on the test pile (101) and is used to obtain pile body stress and strain information of the test pile (101).

2. An integrated pile testing system for offshore multi-pile foundations according to claim 1, characterized in that: A lower pile cap (114) is fixedly mounted on the top of the anchor pile (103), and upper pile caps (115) are arranged above both ends of the compression beam (106). The lower pile cap (114) and the upper pile cap (115) are fixedly connected via a second vertical connecting rod (116).

3. The integrated pile testing system for offshore multi-pile foundation according to claim 2 is characterized in that: The compression beams (106) and the support beams (105) are arranged alternately along the transverse direction.

4. The integrated pile testing system for offshore multi-pile foundation according to claim 1, characterized in that: A first limiting steel plate (117) for laterally limiting the support beam (105) is fixedly connected to both sides of the top end of the support pile (102); a second limiting steel plate (118) for longitudinally limiting the main beam (104) is fixedly connected to the support beam (105); and a third limiting steel plate (119) for laterally limiting the pressure beam (106) is fixedly connected to the main beam (104).

5. The integrated pile testing system for offshore multi-pile foundation according to claim 1 is characterized in that: A steel pad (120) is placed on the top of the lower pile cap (110) of the test pile; a plurality of the compression jacks (107) are symmetrically distributed above the steel pad (120) around the axis of the test pile (101); a gasket (121) is placed on the top of the compression jack (107); a steel pad (120) is placed between the gasket (121) and the main beam (104); a steel pad (120) is placed on the main beam (104); a plurality of the pull-out jacks (108) are symmetrically distributed above the steel pad (120) around the axis of the test pile (101); a steel pad (120) is placed between the top of the pull-out jack (108) and the upper pile cap (111) of the test pile.

6. The integrated pile testing system for offshore multi-pile foundation according to claim 1, characterized in that: Steel corbels (230) are installed on both longitudinal sides of the reference pile (210), one end of the reference beam (220) is fixedly connected to the steel corbel (230), and the other end of the reference beam (220) is placed on the steel corbel (230).

7. The integrated pile testing system for offshore multi-pile foundation according to claim 1, characterized in that: The oil pressure detection unit (310) is a pressure sensor, the pile top displacement detection unit (320) is an electric displacement meter, the electric displacement meter is mounted on the reference beam (220) via a magnetic base, the pile body stress and strain detection unit (330) is a distributed sensing optical fiber, the distributed sensing optical fiber is pre-buried on both sides of the pile body of the test pile (101), and the distributed sensing optical fiber is electrically connected to a wireless transmission module at the top of the test pile (101), and the pressure sensor and the electric displacement meter are electrically connected to a static load automatic tester (340).

8. The integrated pile testing system for offshore multi-pile foundations according to claim 1, characterized in that: The main beam (104), the supporting beam (105) and the compression beam (106) are all rectangular box beams with hollow structures.

9. An integrated pile testing method for offshore multi-pile foundations, the pile testing method using the integrated pile testing system for offshore multi-pile foundations according to any one of claims 1 to 8, characterized in that: The pile testing method comprises the following steps: S1: Distributed sensing optical fibers are buried on both sides of the test pile (101); S2: Performing high-strain initial driving test on the test pile (101) and the anchor pile (103); S3: performing high strain re-driving testing on the test pile (101) and the anchor pile (103); S4: Building a test work platform (400) on both sides of the test pile arrangement direction; S5: constructing a reaction force loading system (100), a reference system (200) and a data acquisition module (300); S6: Conduct initial pressure test on the test pile; S7: Conduct a test pile compression test; S8: Conduct pull-out test on the test pile; S9: Conduct pile stress-strain test; S10: Conduct in-situ double bridge static penetration test.

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