CN105178366A - Model test device for vertical long-time settling character test of pile foundation and application of model test device - Google Patents

Abstract

A model test device for testing long-term settlement characteristics of pile foundations, including a test model box, a loading system and a test system, wherein the test model box is the main body of the model test device and is used to simulate the object to be tested; the loading system is arranged in the test model box is used to simulate loading on the tested object; the test original of the test system is set on the tested original of the model box to test the response of the tested object under dynamic load; the test model box, the loading system and The test systems are connected to each other to realize the model test for the long-term settlement characteristic test of the pile foundation. The invention also discloses its use for simulating and testing the vertical long-term settlement characteristics of pile foundations in different soil bodies and under different train loads. The invention can realize the vertical dynamic loading of the model pile, can test the stress and strain of the pile body under the action of the dynamic load, and the contact condition of the pile-soil interface in the model is consistent with the actual situation.

Description

Model test device and its application for testing the vertical long-term settlement characteristics of pile foundation

technical field

The invention belongs to the field of high-speed railway engineering, and relates to a simulation experiment device, in particular to a simulation test device for testing the vertical long-term settlement characteristics of bridge pile foundations.

Background technique

In order to reduce the overall and uneven settlement of the line and improve the safety of trains, pile foundations have been widely used in high-speed railway projects. Compared with other projects, the pile foundation in this kind of project not only bears the upper structural load, but also bears the dynamic load generated by the train operation. Under the long-term dynamic load, the settlement and deformation characteristics of the pile foundation are gradually recognized by experts in the industry. concern.

For the research on the long-term vertical settlement characteristics of such pile foundations, the field test is usually difficult to realize, and the lack of field measured data restricts the research progress of the problem, so the indoor model test becomes particularly important.

At present, the model test devices used for the study of pile foundation settlement characteristics at home and abroad are generally composed of model piles, model soils, model tanks, data acquisition systems, and test loading systems. Among them, the model piles are mostly simulated by steel pipes or aluminum pipes, which can consider the similar proportional relationship between material strength and geometric dimensions. Because the outer surfaces of steel pipes and aluminum pipes are relatively smooth, the contact conditions of the pile-soil interface are far from reality; model soil Sandy soil, silt soil or cohesive soil can be selected according to the actual situation; the model tank is generally a hollow cuboid or cylindrical structure, which is spliced by steel frames and steel plates; the data acquisition system is generally composed of displacement gauges, strain gauges and signal acquisition instruments Most of the test loading devices are simple vertical or horizontal static loading, and it is difficult to simulate the load characteristics of high-speed trains for dynamic loading. A few test devices that realize dynamic loading of pile foundations are only simple displacement-controlled reciprocating loading. For example, the patent of East China Survey and Design Research Institute of China Hydropower Consulting Group (authorized announcement number CN203432852U) "Pile foundation indoor model test horizontal static load and cyclic load application device", the device includes a swing arm, fixedly connected to the center of the lower surface of the swing arm The roller, the rolling gear located directly below the roller, and the force transmission belt wound on the roller and the rolling gear to realize the transmission connection. At the same time, a translation dowel is connected under the rolling gear, and one end of the translation dowel is connected to the stress in turn. Sensors and test model piles reciprocally load the model piles through dowel bars. This mechanical loading system has a complex structure, low loading frequency, small cycle loading times for a single test, and difficult to guarantee loading accuracy.

In summary, there is still a lack of a model test device for studying the vertical long-term settlement characteristics of pile foundations under train loads, a model test device that can reflect the real pile-soil contact, and the load on the pile top is close to the train load. Model test device.

Contents of the invention

The purpose of the present invention is to provide a model test device for testing the vertical long-term settlement characteristics of pile foundations and its application, which can realize the vertical long-term settlement characteristics tests of pile foundations in different soils and under different train loads. The tested items Including pile top settlement and pile body stress.

In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is:

A model test device for testing the long-term settlement characteristics of pile foundations, including a test model box, a loading system and a test system, each of which has different functions. The test model box is the main body of the model test device and is used to simulate the object to be tested; The system is set on the test model box for simulating loading on the measured object; the test original of the test system is set on the tested original of the model box to test the response of the measured object under the action of dynamic load.

The model box includes model grooves, model piles, and model soil; the loading system includes a loading reaction frame, an air compressor, a function signal generator, an electric proportional valve, and a cylinder; the testing system includes an electromechanical percentage Table, electronic strain gauge, dynamic strain acquisition instrument.

The model pile is prefabricated by concrete, and the model pile is filled in the model groove layer by layer with model soil. The model pile has a diameter of 4cm, a pile length of 50cm to 60cm, and a concrete grade of C30. A plexiglass plate with a length of 6cm, a width of 4cm, and a thickness of 0.8cm is attached to the top of the model pile as a pile cap, and a smooth round steel bar is equipped in the middle of the model pile. , an electronic strain gauge is pasted at every interval of 15cm on the light round steel bar, and the electronic strain gauge is connected with a metal wire and is drawn from one end of the light round steel bar, and the metal wire is connected with the acquisition port of the dynamic strain acquisition instrument at Together.

The model tank is placed in the middle of the bottom plate of the loading reaction frame, and the model tank is assembled from a steel frame and a plexiglass plate. It is characterized in that: the size of the model tank is 800×800×800 (cm), and the steel The frame is welded by ∠30×30×3 angle steel, and the thickness of the plexiglass plate is 1cm.

The loading reaction frame includes a base plate, a reaction beam and a connecting rod, and is characterized in that the reaction beam and the base plate are connected through a connecting rod, and the connecting rods are 4 threaded rods with a diameter of 3.2 cm and a length of 1.5 m. The height of the force beam can be adjusted by the nut on the connecting rod.

The reaction beam is formed by connecting the main beam and the secondary beam through bolts, the main beam is welded into a "mouth" shape by four I-beams, and the size is 840×840 (cm), and the secondary The beam is two 840cm long I-beams, which are connected to the main beam by bolts. The main beam is provided with multiple sets of bolt holes, and the position of the secondary beam on the main beam can be adjusted.

The loading system includes an air compressor. The air compressor is connected to the air inlet of the electric proportional valve through a high-pressure air pipe. The adjustable air pressure range of the electric proportional valve is 0-1MPa, the maximum flow rate is 5000L/min, and the input voltage range is 0-10VDC, the air outlet of the electrical proportional valve is connected to the cylinder through a high-pressure air pipe, the minimum operating pressure of the high-pressure air pipe is ≥2MPa, the electrical proportional valve is connected to a function signal generator through a metal wire, and the function signal generator The frequency range of the output signal is 0.1-100Hz. The cylinder is fixed on the secondary beam of the loading reaction frame through bolts, so that the piston rod of the cylinder is in contact with the pile cap of the model pile. Multiple sets of bolt holes are set on the secondary beam, and the cylinder The position on the secondary beam can be adjusted. The characteristics of the cylinder are: the cylinder diameter is 5cm, the working air pressure range is 0-5MPa, and the stroke of the piston rod is 8cm.

The electromechanical dial indicator is fixed on the secondary beam of the reaction beam through the table base, the hands of the electromechanical dial indicator are in contact with the pile cap of the model pile, and the electromechanical dial indicator is connected with the dynamic strain acquisition connected to the acquisition port of the instrument, the measurement range of the electromechanical dial indicator is 0-5cm, and the measurement accuracy is 0.01mm.

The purpose of the above-mentioned model test device is to simulate and test the long-term vertical settlement characteristics of pile foundations in different soils and under different train loads.

The items tested include pile top settlement (eg 0-5cm) and pile body stress.

The loading frequency range reaches 0.1-100Hz, and the number of loading times in a single test reaches 20,000 times.

Due to the adoption of the above scheme, the beneficial effects of the present invention are: the vertical dynamic loading of the model pile can be realized, and the vertical long-term settlement characteristics of the pile foundation under the train load conditions with different characteristics can be tested; the model pile is prefabricated with concrete reinforcement, and the upper reinforcement Strain gauges are attached to test the stress and strain of the pile body under dynamic load, and the contact condition of the pile-soil interface in the model is consistent with the actual situation, which can truly simulate the vertical settlement characteristics of the pile foundation under the long-term train load.

Description of drawings

Fig. 1 is a general installation schematic diagram of an embodiment of the device of the present invention.

Fig. 2 is a schematic structural view of the loading reaction frame in the embodiment of the present invention.

Fig. 3 is a schematic diagram of the structure of the reaction beam in the embodiment of the present invention.

Fig. 4 is a schematic diagram of the structure of the model pile in the embodiment of the present invention.

Fig. 5 is a first structural schematic diagram (plan view) of the bottom plate in the embodiment of the present invention.

Fig. 6 is a second structural schematic view (side elevation view) of the bottom plate in the embodiment of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the embodiments shown in the accompanying drawings.

As shown in Figure 1, a model test device for testing the vertical long-term settlement characteristics of pile foundations, including: model tank 1, model pile 2, model soil 3, loading reaction frame 4, air compressor 5, and electric proportional valve 6. DC power supply 7, function signal generator 8, dynamic strain acquisition instrument 9, cylinder 10, electromechanical dial indicator 11, table base 12, high pressure air pipe 13, metal wire 14; In the middle of the lower floor, the model pile 2 is filled in the model groove 1 with model soil 3 in layers; the air compressor 5, the electric proportional valve 6 and the cylinder 10 are connected in sequence with the high-pressure air pipe 13, and the cylinder 10 is connected to the Load the secondary beam of the reaction force frame 4, make the piston rod of the cylinder 10 contact with the pile cap of the model pile 2, and make the piston rod carry out dynamic loading on the model pile 2 through air pressure mediation; The terminals of the generator 8 and the electrical proportional valve 6 are connected sequentially; the loading waveform is controlled by the function signal generator 8, and the wires of the electromechanical dial gauge 11 and the wires drawn from the electronic strain gauges in the model pile 2 are connected to the dynamic strain acquisition on the data acquisition port of instrument 9.

As shown in FIG. 2 , the model pile 2 is prefabricated by concrete, and a steel bar 201 with a diameter of 0.6 cm is arranged in the middle, and an electronic strain gauge 202 is pasted on the steel bar, and the electronic strain gauge is used to test the stress of the pile body.

As shown in Figure 3, it includes: a loading reaction beam 401, a base plate 402, a connecting rod 403, and a nut 404. The loading reaction beam 401 and the base plate 402 are connected by four connecting rods 403, and the loading reaction beam 401 and the base plate 402 are connected. The bottom plate 402 is fixed by a nut 404 , and the height of the loading reaction beam 401 can be adjusted by the nut 404 .

As shown in Figure 4, it includes: main beam 401a, secondary beam 401b, small bolt hole 401c, large bolt hole 401d, main beam 401a is welded by I-beam, square shape, said small bolt hole 401c A total of eight groups of 32, eight groups of small bolt holes 401c on the main beam 401a are used to fix the secondary beam 401b, three groups of small bolt holes 401c on the secondary beam 401b are used to fix the cylinder 10, and the large bolt holes 401d is used to connect the loading reaction beam 401 and the connecting rod 403 .

Fig. 5 is a structural diagram one (plan view) of the bottom plate 402 of the loading reaction force frame 4, as shown in Fig. 5, the bottom plate 402 is a lattice plate form, the surface is a steel plate 402a, and the middle is a lattice structure welded by the steel plate 402a , there are large bolt holes 402b at the four corners, and the large bolt holes 402b are used to connect the bottom plate 402 and the connecting rod 403 .

Fig. 6 is the second structure diagram (side elevation view) of the bottom plate 402 of the loading reaction force frame 4. As shown in Fig. 6, the bottom plate 402 is welded by steel plates 402a, and the corners of the bottom plate are provided with large bolt holes 402b.

The connection and test steps of the test device of the present invention are:

Fix the model tank 1 on the base plate 402 of the loading reaction force frame 4, set the model pile 2 in the model tank 1 and fill the model soil 3, after the filling is completed, the electromechanical dial indicator 11 is fixed on the load by the table base 12 Make it contact with the pile cap 203 of the model pile 2 on the reaction force beam 401;

Adopt high-pressure air pipe 13 to connect air compressor 5, electric proportional valve 6, cylinder 10 in sequence, and cylinder 10 is fixed on the secondary beam 401b of loading reaction beam 401 as power output device, and make it connect with model pile 2 pile cap 203 contact, and then connect the DC power supply 7, the function signal generator 8, the electrical proportional valve 6 and other electronic components with metal wires 14 in turn;

Lead out the electronic strain gauge 202 and the electromechanical dial indicator 11 and connect it with the dynamic strain acquisition instrument 9;

Open the power switch of air compressor 5, dynamic strain acquisition instrument 9 and function signal generator 8;

Set the output signal waveform to the function signal generator 8, start loading and measure the pile top displacement and pile body strain.

The above description of the embodiments is for those of ordinary skill in the art to understand and apply the present invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments, and apply the general principles described here to other embodiments without creative efforts. Therefore, the present invention is not limited to the embodiments herein. Improvements and modifications made by those skilled in the art according to the disclosure of the present invention without departing from the scope of the present invention should fall within the protection scope of the present invention.

Claims (10)

1. a model test apparatus for pile foundation long-term settlement characteristic test, is characterized in that: comprise test model case, loading system and test macro, and wherein, test model case is the main body of model test apparatus, for simulating measurand; Loading system is arranged on test model case, for carrying out simulation loading to measurand; The test original paper of test macro is arranged on the tested original paper of model casing, for testing the response of measurand under dynamic load function; Described test model case, loading system and test macro are interconnected the model testing realizing the characteristic test of pile foundation long-term settlement.

2. model test apparatus according to claim 1, is characterized in that: described test model case comprises model groove, Model Pile, model clay; Described loading system comprises reaction frame for loading, air compressor, high-pressure air pipe, function signal generator, electric Proportion valve, cylinder; Described test macro comprises dynamo-electric dial gage, electronics foil gauge, dynamic strain Acquisition Instrument; Wherein, described model groove is arranged at the lower shoe centre position of reaction frame for loading, described Model Pile with model clay placement in layers in model groove; Air compressor, electric Proportion valve and cylinder is connected successively by high-pressure air pipe; Cylinder is bolted on the secondary beam of reaction frame for loading, and the piston rod of cylinder is contacted with the pile cover of Model Pile, makes piston rod carry out power loading to Model Pile by air pressure adjustment; Connected successively by the terminals of wire by dc source, function signal generator, electric Proportion valve; The wire of being drawn by electronics foil gauge in the wire of dynamo-electric dial gage and Model Pile is connected on the data acquisition port of dynamic strain Acquisition Instrument.

3. model test apparatus according to claim 2, is characterized in that: described Model Pile is concrete precast pile; Preferably, Model Pile diameter 4cm, the long 50 ~ 60cm of being of stake, pile concrete label are C30; Or preferably, 6 × 4 × 0.8cm poly (methyl methacrylate) plate pile cover is posted on described Model Pile stake top; Or preferably, described Model Pile is furnished with a plain bar, described reinforcing bar posts an electronics foil gauge for testing pile body stress every 15cm.

4. model test apparatus according to claim 2, is characterized in that: described model groove by steel frame and poly (methyl methacrylate) plate assembled; Preferably, model groove is of a size of 800 × 800 × 800cm, poly (methyl methacrylate) plate thickness of slab 1cm; Preferably, the measurement range of described dynamo-electric dial gage is 0 ~ 5cm, and certainty of measurement is 0.01mm.

5. model test apparatus according to claim 2, it is characterized in that: described reaction frame for loading comprises base plate, reaction beam and connecting rod, reaction beam is connected by connecting rod with base plate, counter-force depth of beam can regulate, described connecting rod diameter 3.2cm, long 1.5m, threaded rod quantity is 4.

6. model test apparatus according to claim 1, is characterized in that: the air pressure adjustment scope of described electric Proportion valve is 0 ~ 1MPa, and maximum stream flow is 5000L/min, and signal input range is 0 ~ 10VDC; Or preferably, the output signal frequency scope of described function signal generator is 0.1 ~ 100Hz; Or, preferably, the cylinder diameter 5cm of described cylinder, the air pressure scope of application 0 ~ 5MPa; Or, preferably, piston rod stroke 8cm, the position on secondary beam can regulate; Or, preferably, the minimum use air pressure >=2MPa of described high-pressure air pipe.

7. model test apparatus according to claim 5, is characterized in that: described dynamo-electric dial gage is fixed on described reaction beam, and the described indicator of dynamo-electric dial gage contacts to test pile head settlement with the pile cover of Model Pile.

8. the purposes of arbitrary described model test apparatus in claim 1 to 7, is characterized in that: use it for the vertical long-term settlement characteristic of simulation pile foundation in various soil mass, under different High-speed Train Loads and tested.

9. purposes according to claim 8, is characterized in that: the project of testing comprises pile head settlement and pile body stress.

10. purposes according to claim 8, is characterized in that: loading frequency scope reaches 0.1 ~ 100Hz, and the loading number of times in single test reaches 20,000 times.