CN115032009A - Vertical cyclic loading simulation device and method for high-speed railway pile foundation of supergravity experiment cabin - Google Patents
Vertical cyclic loading simulation device and method for high-speed railway pile foundation of supergravity experiment cabin Download PDFInfo
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Abstract
The invention discloses a supergravity experimental cabin high-speed railway pile foundation vertical cyclic loading simulation device and a method, wherein the supergravity experimental cabin high-speed railway pile foundation vertical cyclic loading simulation device comprises the following steps: a model box; the bearing frame is fixedly arranged on the model box and used for bearing the reaction force during loading; the test model comprises a foundation model and a pile foundation model which are respectively used for simulating a prototype foundation soil body and a pile foundation; the loading device comprises a loading unit and a hydraulic source unit, wherein the loading unit applies vertical circulating load to the pile foundation, and the hydraulic source unit provides hydraulic pressure for the servo actuator; the data acquisition unit comprises a force sensor, a laser displacement meter, a pile body strain gauge and a data acquisition instrument and is used for measuring and recording the cyclic load borne by the pile top, the cyclic accumulated deformation of the pile top and the stress of the pile body; and the control unit comprises a computer and an action controller and is used for receiving the data and controlling the servo valve to work. The device and the method solve the equivalent simulation problem of the vertical circulation load of the high-speed railway pile foundation.
Description
Technical Field
The application relates to the technical field of high-speed railway foundation treatment, in particular to a vertical cyclic loading simulation device and method for a high-speed railway pile foundation of a supergravity test cabin.
Background
Compared with other foundation forms, the pile foundation has the characteristics of high bearing capacity, small and uniform deformation, material conservation, high construction mechanization degree and the like, and can be almost suitable for various geological conditions and various engineering constructions, so that the pile foundation is very widely applied to various industrial and civil building engineering. Particularly, when the upper structure load is complex and huge, the property of the foundation soil layer is poor, the requirement on foundation deformation is strict, and the earthquake-resistant grade is high, the pile foundation becomes a foundation treatment form which is the primary consideration in geotechnical engineering construction. In recent years, with the continuous development of national economy, more and more novel energy sources and high-speed traffic engineering are continuously built, such as wind power generation, offshore oil platforms, high-speed railways, expressways and the like. In these projects, the superstructure should bear the cyclic load with obvious periodicity such as wind, wave, traffic, etc. during the operation period, so the pile foundation should bear the constant load generated by the self-weight of the superstructure, and also bear the cyclic load in the vertical direction for a long time.
In these projects, the reasonable evaluation of the influence of the long-term cyclic loading effect on the bearing and deformation characteristics of the pile foundation is a very important content in the design of the pile foundation, and is more and more concerned by geotechnical engineering designers. Particularly for structures such as high-speed traffic and wind driven generators which are sensitive to uneven settlement of foundations, pile top accumulated deformation under long-term cyclic loading is often the most critical parameter to be controlled in the engineering design. However, the bearing deformation mechanism of the pile foundation under circulation is not sufficiently known in the academic world and the industrial world at present, the influence of the circulation load effect is not considered in the existing pile foundation design methods at home and abroad, and the related research needs to be carried out by further combining effective test means.
At present, scholars at home and abroad build a reduced scale model test device and a field test device by utilizing an actuator, but the vertical cyclic loading of an actual high-speed railway pile foundation cannot be simulated effectively due to technical limitation, particularly when a high-speed train runs at a high speed. Meanwhile, due to the reasons of stress loss or field condition limitation and the like, effective test research on the response of the soil body around the pile cannot be carried out. The geotechnical centrifuge can generate a supergravity field equivalent to a gravity field through rotation of the rotating arm, so that the model restores an actual stress strain condition under a limited size. Because the vertical cyclic loading test of the high-speed railway pile foundation developed in the centrifuge needs to improve the loading frequency corresponding to the prototype by multiple times, the test cannot equivalently simulate the loading frequency of the prototype under the influence of loading equipment, and has a great difference with the actual cyclic loading of the high-speed railway pile foundation.
Disclosure of Invention
The embodiment of the application aims to provide a device and a method for simulating vertical cyclic loading of a high-speed railway pile foundation of a supergravity test chamber, so as to solve the problem that the vertical cyclic loading of the high-speed railway pile foundation cannot be equivalently simulated in the prior art.
According to the first aspect of the embodiment of the application, a vertical circulation load-bearing simulation device for a high-speed railway pile foundation of a supergravity experimental cabin is provided, which is characterized by comprising:
a model box;
the bearing frame is fixedly arranged on the model box and used for bearing the reaction force during loading;
the test model comprises a foundation model and a pile foundation model, wherein the foundation model is arranged in the model box, and the bottom of the pile foundation model is inserted into the foundation model and is used for simulating a prototype foundation soil body and a pile foundation respectively;
the loading device comprises a loading unit and a hydraulic source unit, wherein the loading unit comprises a servo valve, a servo actuator and a servo valve block, the base end of the servo actuator is installed on the servo valve block, the driving end of the servo actuator acts on the pile foundation model, and the hydraulic source unit sequentially passes through the servo valve block and the servo valve to provide hydraulic pressure for the servo actuator;
the pile foundation model comprises a pile foundation, a data acquisition unit and a control unit, wherein the pile foundation is provided with a pile body stress gauge, the data acquisition unit comprises a force sensor, a laser displacement meter, a pile body strain gauge and a data acquisition instrument, the force sensor is used for monitoring the size of a vertical cyclic load applied to the pile foundation model, the laser displacement meter is used for monitoring the cyclic accumulated deformation of the pile foundation model, the pile body strain gauge is used for acquiring the pile body stress of the pile foundation model, and the force sensor, the laser displacement meter and the pile body strain gauge are all connected with the data acquisition instrument;
and the control unit comprises a computer and an action controller, the action controller is used for controlling the servo valve to work, and the action controller and the data acquisition instrument are connected with the computer.
Optionally, the pile foundation model includes a pile body model and a pile cap model, the pile body model is fixed on the pile cap model, and the driving end of the servo actuator acts on the pile cap model.
Optionally, the loading unit further includes a spherical hinge and a counter-force assembly, and the driving end of the servo actuator, the spherical hinge, the counter-force assembly, the force sensor and the pile foundation are sequentially connected.
Optionally, the servo valve block is mounted on the cross beam and can move transversely along the cross beam.
Optionally, the hydraulic source unit includes an oil source and an energy accumulator, and the oil source, the energy accumulator and the servo valve block are sequentially communicated.
Optionally, the hydraulic control system further comprises an energy accumulator base, a hydraulic valve block and a distributing valve, wherein the energy accumulator is installed on the hydraulic valve block through the energy accumulator base, the distributing valve is installed on the hydraulic valve block, the energy accumulator is communicated with the distributing valve through an internal channel of the hydraulic valve block, and the hydraulic valve block is communicated with the servo valve block through a pipeline.
According to a second aspect of the embodiment of the application, a vertical cyclic loading simulation method for a high-speed railway pile foundation of a supergravity experiment chamber is provided, and the method is realized under the vertical cyclic loading simulation device for the high-speed railway pile foundation of the supergravity experiment chamber in the first aspect, and comprises the following steps:
hoisting the model box into a hanging basket at one side of a rotating arm of the centrifuge, and pressing the pile foundation model into the foundation model to a first set depth;
gradually adjusting the height of the servo actuator to ensure that the counter-force component is just and effectively contacted with the pile cap model;
starting the centrifugal machine, and controlling the centrifugal machine to rotate to reach a set centrifugal acceleration ng;
under the ng condition, continuously pressing the pile foundation into the foundation model to a second set depth by using the loading device, simulating the pile pressing process under the prototype stress condition, and monitoring the pile foundation pressing depth through a laser displacement meter;
after pile pressing is finished, setting the loading waveform, the loading frequency, the load amplitude and the loading times of the servo actuator through the control unit;
applying a cyclic load equivalent to the vertical cyclic load of the high-speed railway pile foundation, comparing the input cyclic load after the data acquisition instrument obtains the numerical value of the force sensor, and automatically adjusting the cyclic load through the control unit under the condition of not meeting the input loading waveform, loading frequency and load amplitude until the output cyclic load is consistent with the set cyclic load;
the pile foundation cyclic accumulated deformation monitored can be fed back in real time through the laser displacement meter, the loading of the working condition is stopped when the loading times reach the set maximum loading times or the pile foundation cyclic accumulated deformation reaches the set maximum displacement value, and the loading of the next working condition is set through the computer and the action controller;
and after all the set working condition loading is finished, the test is finished, and the centrifuge is stopped.
Optionally, the applied equivalent cyclic load includes static load of the high-speed railway embankment and upper track structure and vertical cyclic load generated by the operation of the high-speed train; the applied equivalent cyclic load waveform is the same as the actual vertical cyclic load waveform of the high-speed railway pile foundation and is M wave.
Optionally, the equivalent cyclic load frequency conforms to a scale relationship under the supergravity condition, and is ω m ：ω p ＝n；
In the formula:
ω m loading frequency for equivalent cyclic load under the condition of supergravity;
ω p to a practical high speedVertical cyclic loading frequency of the railway pile foundation;
n is the value of n in the set centrifugal acceleration ng.
Optionally, the equivalent cyclic load size meets the scale relation under the supergravity condition, and is P m ：P p ＝
In the formula:
P m the equivalent circulating load under the condition of supergravity is obtained;
P p the vertical cyclic loading size of the actual high-speed railway pile foundation is obtained;
n is the value of n in the set centrifugal acceleration ng.
The technical scheme provided by the embodiment of the application can have the following beneficial effects:
according to the embodiment, the geostress condition of the deep soft soil foundation is reproduced by the aid of the supergravity field which is generated by the geotechnical centrifuge and is equivalent to the gravity field, the load with reasonable waveform, frequency, amplitude and frequency is applied to the pile foundation through the servo actuator, the problem that vertical cyclic load generated by operation of a high-speed train cannot be equivalently simulated in a laboratory is solved, and vertical cyclic loading of the high-speed railway pile foundation is truly restored. The driving end, the spherical hinge, the counter-force assembly, the force sensor and the pile foundation of the servo actuator are sequentially connected, so that the pile foundation is prevented from bearing an additional bending effect, and the cyclic load is guaranteed to be applied vertically downwards. The vertical cyclic load of the maximum 12Hz under the normal gravity can be simulated in the supergravity experiment chamber, the maximum load can reach 2250KN, the problem that the existing loading device cannot simulate the vertical cyclic load-bearing working condition of the pile foundation at the higher train running speed is solved, and the vertical cyclic load-bearing working condition of the pile foundation in the existing high-speed railway engineering in China and even all over the world is basically covered. The device and the method provide an important experimental means for reasonably evaluating the influence of long-term vertical cyclic load effect on the bearing and deformation characteristics of the high-speed railway pile foundation and researching the bearing deformation mechanism of the pile foundation under the cyclic condition.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and together with the description, serve to explain the principles of the application.
Fig. 1 is an oblique view illustrating a high-speed railway pile foundation vertical cyclic loading simulation device for a supergravity experiment chamber according to an exemplary embodiment.
Fig. 2 is a schematic sectional view along the direction a-a of the high-speed railway pile foundation vertical cyclic loading simulation device for the supergravity experiment chamber according to an exemplary embodiment.
Fig. 3 is a schematic diagram illustrating a loading device in a high-speed railway pile foundation vertical cyclic loading simulation device for a supergravity experiment chamber according to an exemplary embodiment.
Fig. 4 is a schematic diagram illustrating connection between an oil source and an energy accumulator in a vertical cyclic loading simulation device for a high-speed railway pile foundation of a supergravity experimental cabin according to an exemplary embodiment.
Fig. 5 is a schematic diagram of a loading unit in a high-speed railway pile foundation vertical cyclic loading simulation device for a supergravity experiment chamber according to an exemplary embodiment.
Fig. 6 is a schematic diagram illustrating a pile foundation model in a high-speed railway pile foundation vertical circulation load simulation device for a supergravity experimental cabin according to an exemplary embodiment.
The reference numbers in the figures have:
1. a model box; 2. a load-bearing frame; 3. an eye bolt; 4. a cross beam; 5. an accumulator; 6. a counter-force component; 7. a force sensor; 8. a servo valve; 9. a servo valve block; 10. a servo actuator; 11. a foundation model; 12. a pile body model; 13. a pile cap model; 14. a hydraulic valve block; 15. an accumulator base; 16. an accumulator coupling; 17. a distributing valve; 18. a source of oil; 19. an oil line; 20. spherical hinge; 21. a laser displacement meter; 22. a computer; 23, a data acquisition instrument; 24. an actuator controller; 25. a data line and a power line; 26. a control line and a power line; 27. a pile body strain gauge; 28. a pile body hole; 29. a threaded hole; 30 threads.
Detailed Description
Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present application, as detailed in the appended claims.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this application and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.
It is to be understood that although the terms first, second, third, etc. may be used herein to describe various information, such information should not be limited to these terms. These terms are only used to distinguish one type of information from another. For example, first information may also be referred to as second information, and similarly, second information may also be referred to as first information, without departing from the scope of the present application. The word "if," as used herein, may be interpreted as "when or" responsive to a determination, "depending on the context.
Referring to fig. 1 to 6, an embodiment of the present invention provides a supergravity experimental cabin high-speed railway pile foundation vertical cyclic loading simulation apparatus, including: the device comprises a model box 1, a bearing frame 2, a lifting eye bolt 3, a test model, a loading device, a data acquisition unit and a control unit; the bearing frame 2 is fixedly arranged on the model box 1 through the lifting eye bolt 3 and is used for bearing the reaction force during loading; the test model comprises a foundation model 11 and a pile foundation model, the foundation model is arranged in the model box, and the bottom of the pile foundation model is inserted into the foundation model and is used for simulating a prototype foundation soil body and a pile foundation respectively; the loading device comprises a loading unit and a hydraulic source unit, the loading unit comprises a servo valve 8, a servo valve block 9 and a servo actuator 10, the base end of the servo actuator 10 is installed on the servo valve block 9, the driving end of the servo actuator acts on the pile foundation model, and the hydraulic source unit sequentially passes through the servo valve block 9 and the servo valve 8 to provide hydraulic pressure for the servo actuator 10; the data acquisition unit comprises a force sensor 7, a laser displacement meter 21, a pile body strain gauge 27 and a data acquisition instrument 23, wherein the force sensor 7 is used for monitoring the size of a vertical cyclic load applied to the pile foundation model, the laser displacement meter 21 is used for monitoring the cyclic accumulated deformation of the pile foundation model, the pile body strain gauge 27 is used for monitoring the pile body stress of the pile foundation model, and the force sensor 7, the laser displacement meter 21 and the pile body strain gauge 27 are all connected with the data acquisition instrument 23; the control unit comprises a computer 22 and an action controller 24, the action controller 24 is used for controlling the servo valve 8 to work, and the action controller 24 and the data acquisition instrument 23 are both connected with the computer 22.
According to the embodiment, the geostress condition of the deep soft soil foundation is reproduced by the aid of the supergravity field which is generated by the geotechnical centrifuge and is equivalent to the gravity field, the load with reasonable waveform, frequency, amplitude and frequency is applied to the pile foundation through the servo actuator, the problem that vertical cyclic load generated by operation of a high-speed train cannot be equivalently simulated in a laboratory is solved, and vertical cyclic loading of the high-speed railway pile foundation is truly restored. The vertical cyclic load of the maximum 12Hz under the normal gravity can be simulated in the supergravity experiment chamber, the maximum load can reach 2250KN, the problem that the existing loading device cannot simulate the vertical cyclic load-bearing working condition of the pile foundation at the higher train running speed is solved, and the vertical cyclic load-bearing working condition of the pile foundation in the existing high-speed railway engineering in China and even all over the world is basically covered.
In this embodiment, the pile foundation model includes a pile body model 12 and a pile cap model 13, the pile body model 12 is fixed on the pile cap model 13, and the driving end of the servo actuator 10 acts on the pile cap model 13.
Specifically, the upper end of the pile body model 12 is provided with a thread 30 with a set length, the pile cap model 13 is provided with a threaded hole 29 at a set position, and the pile body model 12 is rigidly connected with the pile cap model in a manner of fixing the thread 30 and the threaded hole 29; the pile body model 12 comprises a pile body hole 28 drilled at a set position, and a lead of the pile body strain gauge 27 is led out from the inside of the pile body model 12 upwards through the pile body hole 28.
In this embodiment, the loading unit further includes a spherical hinge 20 and a reaction assembly 6, the driving end of the servo actuator 10, the spherical hinge 20, the reaction assembly 6, the force sensor 7 and the pile foundation model are sequentially connected, and the application of the spherical hinge 20 avoids the pile foundation from bearing an additional bending effect, and ensures that the applied cyclic load is vertically downward.
In the embodiment, the device further comprises a cross beam 4, wherein the cross beam 4 is installed on the bearing frame 2, and the servo valve block 9 is installed on the cross beam 4 and can move transversely along the cross beam 4.
In this embodiment, the hydraulic source unit includes an oil source 18 and an accumulator 5, the oil source 18, the accumulator 5 and the servo valve block 9 are sequentially communicated, and the application of the accumulator 5 can improve the load output capacity of the loading device.
In particular, with reference to fig. 4, the oil source 18 is connected to the accumulator 5 via the oil line 19 and the accumulator connection 16.
In the embodiment, the hydraulic servo valve further comprises an energy accumulator base 15, a hydraulic valve block 14 and a distribution valve 17, wherein the energy accumulator 5 is installed on the hydraulic valve block 14 through the energy accumulator base 15, the distribution valve 17 is installed on the hydraulic valve block 14, the energy accumulator 5 is communicated with the distribution valve 17 through an internal channel of the hydraulic valve block 14, and the hydraulic valve block 14 is communicated with the servo valve block 9 through a pipeline; the energy accumulator 5 is directly connected with the distributing valve 17 and the hydraulic valve block 14, so that stable pressure output can be realized, and the output load stability under the high-frequency loading condition is ensured; the application of the hydraulic valve block 14 ensures the stability of oil pressure and loss.
In this embodiment, the servo valve 8 preferably selects the micro high frequency response servo valve 8, and the micro high frequency response servo valve 8 can still meet the requirement of large amplitude load output in the supergravity experiment chamber and meet the requirement of doubling the loading frequency after time reduction.
In this embodiment, the data acquisition instrument 21 is connected with the laser displacement meter 21, the force sensor 7 and the pile body strain gauge 27 through a data line and a power line 25, and collects sensor data in the test process in real time, so as to monitor the size of the load borne by the pile foundation and the stress of the pile body, and judge whether to adjust and correct the waveform, amplitude and frequency of the applied cyclic load; the laser displacement meter 21 can feed back the monitored pile foundation cycle accumulated deformation in real time, judge whether the pile foundation cycle accumulated deformation reaches a set maximum value, and control the loading device to stop applying vertical cyclic load through the action controller 24 if the pile foundation cycle accumulated deformation reaches the set maximum value.
In this embodiment, the action controller 24 is connected to the servo actuator 10 and the computer 22 respectively, and is used for controlling the application and the stop of the cyclic load in real time, the computer 22 inputs the waveform, the amplitude, the frequency and the loading frequency of the cyclic load in the action controller 24 to realize equivalent simulation of the vertical cyclic load of the pile top under different high-speed train operation conditions, and the action controller 24 automatically corrects the waveform, the amplitude and the frequency of the input load to achieve an input value when the pile foundation bears the load and the input cyclic load is different.
The installation process of the high-speed railway pile foundation vertical circulation load simulation device for the supergravity experimental cabin provided by the embodiment of the invention is as follows:
(1) preparing a foundation model 11 in said model box 1;
specifically, in this embodiment, as shown in fig. 2, a soil body required for the test is filled in the mold box 1 and compacted layer by layer according to the set moisture condition. After filling, the model box 1 and the foundation model 11 are hoisted in a hanging basket at the side of a rotating arm of the centrifugal machine, the centrifugal machine rotating machine reaches a set centrifugal acceleration ng to finish consolidation of the foundation model 11, and g is a gravity acceleration.
(2) Stopping the centrifuge;
(3) pressing the pile foundation model into the consolidated foundation model 11 to a first set depth, and rigidly connecting the pile body model 12 and the pile cap model 13; the pile body model 12 and the pile cap model 13 are prepared according to the reduced scale requirement under the centrifugal acceleration ng under the set supergravity environment;
(4) hoisting the bearing frame 2 to the model box 1 and fixing the bearing frame by using an eyebolt 3;
(5) mounting the loading device on the carrying frame 2;
specifically, in the present embodiment, as shown in fig. 1, the loading device is hoisted above the bearing frame 2, and the cross beam 4 and the bearing frame 2 are fixed by bolts; at the same time, the reaction force assembly 6 is ensured to be positioned right above the center of the pile cap model 13.
(6) Hoisting the model box 1, the test model and the loading device into a hanging basket at one side of a rotating arm of the centrifuge;
(6) connecting the oil source 18 and the accumulator 5;
specifically, in the present embodiment, as shown in fig. 4, the oil source 18 and the accumulator joint 16 are connected by the oil line 19, and whether or not the oil leakage and oil leakage phenomenon occurs in the line is observed by passing high-quality hydraulic oil at a certain pressure.
(7) Connecting the action controller 24 and the servo valve 8, and adjusting the telescopic state of the servo actuator 10 by controlling the output command of the action controller 24 to adjust the servo actuator 10 to the maximum telescopic state;
(8) connecting the force sensor 7 and the laser displacement meter 21 to the data acquisition instrument 23, and gradually adjusting the servo actuator 10 to ensure that the counter force component 6 is just and effectively contacted with the pile cap model 13;
specifically, the force sensor 7 and the laser displacement meter 21 are respectively connected to the data acquisition instrument 23, and whether the output value of the sensor is matched with the current state or not and whether the display value is stable or not is observed; and (3) gradually extending the servo actuator 10 until the value of the force sensor 7 just starts to respond, and judging whether the pile foundation begins to deform or not through the laser displacement meter 21 to ensure that the counter-force component 6 just and effectively contacts with the pile cap model 13.
(9) Starting the centrifugal machine, and controlling the centrifugal machine to rotate to reach a set centrifugal acceleration ng;
(10) and under the ng condition, continuously pressing the pile foundation model into the foundation model 11 to a second set depth by using the loading device, simulating the pile pressing process under the prototype stress condition, and monitoring the pressing depth of the pile foundation model by using a laser displacement meter 21 arranged above the pile cap model 13.
The embodiment of the invention also provides a vertical cyclic loading simulation method of the high-speed railway pile foundation for the supergravity test chamber, which is realized in the vertical cyclic loading simulation device of the high-speed railway pile foundation for the supergravity test chamber and specifically comprises the following steps:
(1) hoisting the model box 1, the test model and the loading device into a hanging basket at the side of a rotating arm of the centrifuge, and pressing the pile foundation model into the foundation model to a first set depth;
(2) the telescopic state of the servo actuator 10 is adjusted through the output command of the control and manufacturing controller 24, and the height of the servo actuator 10 is gradually adjusted to enable the counter-force component 6 to be just and effectively contacted with the pile cap model 13;
(3) starting the centrifugal machine, and controlling the centrifugal machine to rotate to reach a set centrifugal acceleration ng;
(4) under the ng condition, continuously pressing the pile foundation model into the foundation model 11 to a second set depth by using a loading device, simulating the pile pressing process under the prototype stress condition, and monitoring the pile foundation pressing depth by using a laser displacement meter 21;
(5) after pile pressing is finished, according to a scale relation under the centrifugal acceleration ng under the set supergravity environment, setting the loading waveform, the loading frequency, the load amplitude and the loading times of a loading device through a computer 22 and an action controller 24, and simulating the vertical cyclic loading of the high-speed railway pile foundation during different operating conditions of the actual high-speed train;
(6) applying a cyclic load equivalent to the vertical cyclic load of the high-speed railway pile foundation, comparing the input cyclic load after the data acquisition instrument 23 obtains the measured value of the force sensor 7, and automatically adjusting the cyclic load through the control unit under the condition of not meeting the input loading waveform, loading frequency and load amplitude until the output cyclic load is consistent with the set cyclic load;
(7) the laser displacement meter 21 can feed back the monitored pile foundation cyclic accumulated deformation in real time, stop the loading of the working condition when the loading times reach the set maximum loading times or the pile foundation cyclic accumulated deformation reaches the set maximum displacement value, and set the loading of the next working condition through the computer 22 and the action controller 24;
(8) and after all the set working condition loading is finished, the test is finished, and the centrifuge is stopped.
In this embodiment, the applied equivalent cyclic load waveform is the same as the actual vertical cyclic load waveform of the high-speed railway pile foundation, and is an M wave.
In this embodiment, the equivalent cyclic load frequency conforms to the scale relationship under the supergravity condition, and is ω m ：ω p ＝n；
In the formula:
ω m loading frequency for equivalent cyclic load under the condition of supergravity;
ω p the vertical cyclic loading frequency is the actual high-speed railway pile foundation;
n is the value of n in the set centrifugal acceleration ng.
In this embodiment, the equivalent cyclic load magnitude meets the scale relation under the supergravity condition, and is P m ：
In the formula:
P m the equivalent circulating load under the condition of supergravity is obtained;
P p the vertical cyclic loading size of the actual high-speed railway pile foundation is obtained;
n is the value of n in the set centrifugal acceleration ng.
According to the embodiment of the invention, the earth stress condition of the deep soft soil foundation is reproduced by using the supergravity field which is generated by the geotechnical centrifuge and is equivalent to the gravity field, so that the actual stress-strain condition of the pile foundation model is restored under the limited size. The loading waveform, the loading frequency, the load amplitude and the loading times of the servo actuator are set by the action controller 24, the problem that the vertical cyclic load generated by the operation of a high-speed train cannot be equivalently simulated in a laboratory is solved, and the vertical cyclic load of the high-speed railway pile foundation is really restored.
In conclusion, the device realizes the simulation of the vertical cyclic loading of the high-speed railway pile foundation in the supergravity experimental cabin through the accurate control of the action controller 24 and the servo valve 8, and truly reproduces the stress-strain condition when the actual vertical cyclic loading of the high-speed railway pile foundation is carried out. By utilizing the shrinkage response under the supergravity, the device and the method are suitable for researching the long-term service performance of the pile foundation under the combined action of static loads of the embankment, the superstructure and the like and vertical cyclic loads generated by the operation of a high-speed train in the engineering of the high-speed railway and the like, are also suitable for researching the influence of the long-term cyclic loads on the bearing and deformation characteristics of the pile foundation in the large-span time process, and provide related technical support for the design of structures sensitive to uneven settlement of the foundation, such as the high-speed railway and the like.
Other embodiments of the present application will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the application and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the application being indicated by the following claims.
It will be understood that the present application is not limited to the precise arrangements described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the application is limited only by the appended claims.
Claims (10)
1. The utility model provides a vertical circulation load analogue means of hypergravity experiment cabin high speed railway pile foundation which characterized in that includes:
a model box;
the bearing frame is fixedly arranged on the model box and used for bearing the reaction force during loading;
the test model comprises a foundation model and a pile foundation model, wherein the foundation model is arranged in the model box, and the bottom of the pile foundation model is inserted into the foundation model and is used for simulating a prototype foundation soil body and a pile foundation respectively;
the loading device comprises a loading unit and a hydraulic source unit, wherein the loading unit comprises a servo valve, a servo actuator and a servo valve block, the base end of the servo actuator is installed on the servo valve block, the driving end of the servo actuator acts on the pile foundation model, and the hydraulic source unit sequentially passes through the servo valve block and the servo valve to provide hydraulic pressure for the servo actuator;
the pile foundation model comprises a pile foundation, a data acquisition unit and a control unit, wherein the pile foundation is provided with a pile body stress gauge, the data acquisition unit comprises a force sensor, a laser displacement meter, a pile body strain gauge and a data acquisition instrument, the force sensor is used for monitoring the size of a vertical cyclic load applied to the pile foundation model, the laser displacement meter is used for monitoring the cyclic accumulated deformation of the pile foundation model, the pile body strain gauge is used for acquiring the pile body stress of the pile foundation model, and the force sensor, the laser displacement meter and the pile body strain gauge are all connected with the data acquisition instrument;
and the control unit comprises a computer and an action controller, the action controller is used for controlling the servo valve to work, and the action controller and the data acquisition instrument are connected with the computer.
2. The hypergravity experimental cabin high-speed railway pile foundation vertical cyclic loading simulation device of claim 1, wherein the pile foundation model comprises a pile body model and a pile cap model, the pile body model is fixed on the pile cap model, and a driving end of the servo actuator acts on the pile cap model.
3. The supergravity experiment chamber high-speed railway pile foundation vertical cyclic loading simulation device of claim 2, wherein the loading unit further comprises a spherical hinge and a reaction assembly, and the driving end of the servo actuator, the spherical hinge, the reaction assembly, the force sensor and the pile foundation are connected in sequence.
4. The supergravity experiment cabin high-speed railway pile foundation vertical cyclic loading simulation device of claim 1, further comprising a cross beam, wherein the cross beam is mounted on the bearing frame, and the servo valve block is mounted on the cross beam and can move transversely along the cross beam.
5. The supergravity experiment cabin high-speed railway pile foundation vertical cyclic loading simulation device of claim 1, wherein the hydraulic source unit comprises an oil source and an energy accumulator, and the oil source, the energy accumulator and the servo valve block are communicated in sequence.
6. The supergravity experiment cabin high-speed railway pile foundation vertical circulation load-bearing simulation device according to claim 5, further comprising an energy accumulator base, a hydraulic valve block and a distribution valve, wherein the energy accumulator is mounted on the hydraulic valve block through the energy accumulator base, the distribution valve is mounted on the hydraulic valve block, the energy accumulator is communicated with the distribution valve through an internal channel of the hydraulic valve block, and the hydraulic valve block is communicated with the servo valve block through a pipeline.
7. A vertical cyclic loading simulation method for a high-speed railway pile foundation of a supergravity experiment chamber is realized under the vertical cyclic loading simulation device for the high-speed railway pile foundation of the supergravity experiment chamber in claim 3, and comprises the following steps:
hoisting the model box into a hanging basket at one side of a rotating arm of the centrifuge, and pressing the pile foundation model into the foundation model to a first set depth;
gradually adjusting the height of the servo actuator to ensure that the counter-force assembly is just and effectively contacted with the pile cap model;
starting the centrifugal machine, and controlling the centrifugal machine to rotate to reach a set centrifugal acceleration ng;
under the ng condition, continuously pressing the pile foundation into the foundation model to a second set depth by using the loading device, simulating the pile pressing process under the prototype stress condition, and monitoring the pile foundation pressing depth by using a laser displacement meter;
after pile pressing is finished, setting the loading waveform, loading frequency, load amplitude and loading times of the servo actuator through the control unit;
applying a cyclic load equivalent to the vertical cyclic load of the high-speed railway pile foundation, comparing the input cyclic load after the data acquisition instrument obtains the numerical value of the force sensor, and automatically adjusting the cyclic load through the control unit under the condition of not meeting the input loading waveform, loading frequency and load amplitude until the output cyclic load is consistent with the set cyclic load;
the pile foundation cyclic accumulated deformation monitored can be fed back in real time through the laser displacement meter, the loading of the working condition is stopped when the loading times reach the set maximum loading times or the pile foundation cyclic accumulated deformation reaches the set maximum displacement value, and the loading of the next working condition is set through the computer and the action controller;
and after all the set working condition loading is finished, the test is finished, and the centrifuge is stopped.
8. The method for simulating vertical cyclic loading of the high-speed railway pile foundation of the supergravity experimental cabin according to claim 6, wherein the applied equivalent cyclic loads comprise static loads of a high-speed railway embankment and an upper track structure and vertical cyclic loads generated by running of a high-speed train; the applied equivalent cyclic load waveform is the same as the actual vertical cyclic load waveform of the high-speed railway pile foundation and is M wave.
9. The method for simulating vertical cyclic loading of the high-speed railway pile foundation of the supergravity experimental cabin according to claim 6, wherein the equivalent cyclic loading frequency meets the scale relation under the supergravity condition and is omega m ：ω p ＝n；
In the formula:
ω m loading frequency for equivalent cyclic load under the condition of supergravity;
ω p the vertical cyclic loading frequency is the actual high-speed railway pile foundation;
n is the value of n in the set centrifugal acceleration ng.
10. The high-speed railway pile foundation vertical direction of the supergravity experimental cabin according to claim 6The cyclic loading simulation method is characterized in that the equivalent cyclic loading magnitude meets the scale relation under the supergravity condition and is P m ：
In the formula:
P m the equivalent circulating load under the condition of supergravity is obtained;
P p the vertical cyclic loading size of the actual high-speed railway pile foundation is obtained;
n is the value of n in the set centrifugal acceleration ng.
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