CN112730116B - In-situ testing device and method for dynamic stress-strain curve of soil body - Google Patents
In-situ testing device and method for dynamic stress-strain curve of soil body Download PDFInfo
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- G01N3/32—Investigating strength properties of solid materials by application of mechanical stress by applying repeated or pulsating forces
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Abstract
The invention discloses a dynamic stress-strain curve in-situ testing device, which comprises a movable system, a dynamic reaction system, a load servo system and a data acquisition system, wherein the device is powered by a hydraulic source, and can apply vertical dynamic load to a rigid plate of a vibrator under preset frequency, amplitude and loading cycle number so as to be spread into foundation soil. The invention also discloses a working method of the dynamic stress-strain curve in-situ test equipment, which provides a new method for the field test of the dynamic stress-strain curve of the soil body.
Description
Technical Field
The invention belongs to the technical field of civil engineering, and particularly relates to an in-situ testing device and method for a soil dynamic stress-strain curve.
Background
The high density of urban population, urban construction and urban traffic, and the rapidly evolving urban economy mean that the study of seismic problems faced by large, very large cities is a formidable task that seismic engineering researchers must currently face. Earthquakes are not only large energy releases, but also cause a large number of secondary disasters, and geotechnical related disasters are numerous, such as: debris flow, sand earthquake liquefaction, landslide, soft foundation collapse and the like, wherein the most serious is soil power damage.
The quantification of the dynamic stress-strain curve is indispensable in the analysis process of building the soil body dynamic constitutive model. At present, the test of the dynamic stress-strain curve mainly takes indoor test as a main part, and a dynamic triaxial apparatus is mainly used as equipment with more use and more reliable results. The main advantages of the dynamic triaxial test include: controllable test conditions, accurate results and the like. However, disturbance to the soil sample in the sampling process, difference between the indoor artificially prepared soil sample and the in-situ structure (soil sample size effect and the like), time effect and the like cause that the indoor test is influenced by difficult quantification in the aspect of reduction engineering reality, and four main influence factors for analyzing certain difference with the real stress environment of the on-site soil body are provided:
(1) the sample is anisotropic consolidated, and the natural soil layer is k0And (5) solidifying. The stress on the 45 ° face of the anisometric test specimen is the same as that of the natural soil layer if the test specimen is at k0After the solidification, the initial shear stress exists on the 45-degree surface and is inconsistent with the field condition;
(2) the main stress direction can only change 90 degrees in the vibration process, and actually a large main stress shaft swings left and right;
(3) the tensile stress and the compressive stress are different in damage, the hysteresis loops of the samples are asymmetric, the samples are firstly broken by pulling quickly, and the soil layer on site has no tensile stress;
(4) The sample is necked or protruded under the action of periodic loading, so that the pore redistribution is caused, and the strain and pore pressure measurement are influenced.
Disclosure of Invention
The purpose of the invention is as follows: in order to solve the technical problems in the prior art, the invention provides an in-situ test method for a soil body dynamic stress-strain curve.
In order to achieve the above object, the present invention provides an in-situ dynamic stress-strain curve testing device, which comprises a movable system, a dynamic reaction system, a load servo system and a data acquisition system, wherein,
the power reaction system comprises an electro-hydraulic servo actuator and a vibrator, the electro-hydraulic servo actuator comprises an electro-hydraulic servo hydraulic source, an oil delivery pipe and a guide post which are sequentially connected, the guide post comprises a piston rod and a guide sleeve arranged outside the piston rod, the bottom of the guide post is fixedly connected with an upper bearing plate, the middle part of the piston rod is provided with a displacement sensor, and the bottom of the piston rod is provided with a pressure sensor;
the vibrator comprises a lower bearing plate, a vertical damping air bag and a touch floor from top to bottom, and an air nozzle is arranged above the lower bearing plate;
the dynamic and static loads transmitted by the upper bearing plate of the electro-hydraulic servo actuator act on the lower bearing plate of the vibrator and are transmitted to the touch floor through the vertical damping air bag;
The load servo system is used for controlling the operation of the power reaction system, applying a vertical dynamic load under the preset frequency, amplitude and loading cycle number, and feeding back the results of the displacement sensor and the pressure sensor to the load private servo system;
the electro-hydraulic servo hydraulic source is electrically or wirelessly connected with the load servo system;
the data acquisition system comprises an acquisition instrument, and a vibration pickup and a soil pressure cell which are respectively connected with the acquisition instrument, wherein the soil pressure cell is embedded at the midpoint of the two vibration pickers, outputs the vertical stress of the point under the action of dynamic load in real time and transmits the vertical stress to the acquisition instrument;
the dynamic reaction system is arranged inside the movable system. The positions and the fixation of the components in the movable system can be planned according to actual conditions.
In one embodiment, the movable system is a special engineering vehicle, and the power reaction system is arranged in the special engineering vehicle and can extend out of the special engineering vehicle through a hole formed in the bottom of the special engineering vehicle.
In order to realize the vertical position change of the movable system, the bottom of the movable system is provided with a retractable support leg. When the movable system needs to be lifted, the supporting legs collected at the bottom are propped open to be corresponding to the wood piers arranged on the corresponding position on the ground, and the oil pressure is lifted to enable the supporting legs to be in contact with the wood piers arranged on the ground, so that the movable system is lifted.
Preferably, a hook is arranged in the engineering truck, a corresponding hook is arranged at the top end of the guide post, and the guide post and the corresponding hook are hung when the guide post is lifted to the highest position.
Preferably, the vertical shock absorbing air bag comprises 4 sets.
Preferably, the vibration pickups are arranged at a position which is 0.5-1m away from the bottom of the grounding plate in the vertical direction, the soil pressure cell is embedded at the middle point of the two vibration pickups, and the vertical stress of the point under the action of dynamic load is output in real time.
The invention further provides an in-situ test method for the dynamic stress-strain curve, which comprises the following steps:
1) the movable system enters a field, a relatively flat field is selected, and the positions of the movable system (1) and the vibrator are planned;
2) directly behind the mobile system, a 1.5 by 0.5(m) pit was dug;
3) after the pit is dug, marking the embedding positions of the vibration pickup and the soil pressure cell, and then adopting a hydraulic cylinder of a field pressure sensor to drill at the marking position until the vibration pickup and the soil pressure cell are embedded; after the vibration pickup and the soil pressure box are placed at the designated positions, firstly, a layer of sandy soil is scattered around the vibration pickup and the soil pressure box, and then, the original soil is backfilled and compacted;
4) placing the vibrator into the pit, wherein the direction of the vehicle body of the movable system is vertical to the direction of the grounding plate, and the grounding plate of the vibrator is tightly attached to the original soil layer;
5) After the vibrator is placed, the special engineering truck is driven in place, so that the upper bearing plate 10 of the actuator is superposed with the lower bearing plate of the vibrator;
6) connecting a load servo system and an electro-hydraulic servo hydraulic source, and opening control software to input engineering site information;
7) connecting joints of the embedded vibration pickup and the soil pressure cell with a data acquisition system, and preparing to acquire and store data;
8) connecting the air pipe with corresponding air nozzles at four corners of the vibrator to ensure that the air pipe cannot be pressed and opening the air valve;
9) a power supply is switched on, a vehicle key is inserted, the power system is started by ignition, then the oil pressure is increased, so that each supporting leg (2) is in contact with a wood pier placed on the ground, and the movable system is lifted; after ignition is started, the air pipe automatically inflates the air bag of the vibrator, and the inflation pressure can be monitored by a barometer;
10) and the upper bearing plate of the guide post driving actuator is lifted by the load servo system to complete unhooking.
Wherein the earth pressureThe force box is embedded in the middle point of the two vibration pickups and outputs the vertical stress of the point under the action of dynamic load in real time; the dynamic strain is defined as the average dynamic strain between the two vibration pickups, if the displacement is linearly changed along with the distance between the two sensors, the value is considered to be equal to the dynamic strain at the midpoint of the two vibration pickups, the displacement-based method is used for calculation, the recorded speed-time history is subjected to numerical integration to obtain the displacement-time history, and the peak displacement of the displacement time history of the adjacent sensors is calculated; at the same time, the difference between the output larger peak displacement and the displacement recorded by another sensor is the total deformation between the adjacent sensors, and the displacement difference is divided by the distance between the two sensors to obtain the dynamic strain epsilon d：
In the formula u1Is the maximum displacement, u, in the displacement-time waveform diagram of the output of the vibration pickup at a certain vibration frequency2The displacement output by another vibration pickup at the same moment; Δ x is the distance between the two pickers.
Has the advantages that: compared with the prior art, the invention has the following advantages and positive effects:
(1) the interference to the soil layer is small, and the natural structure of the soil and the characteristics under natural stress can be reflected more truly;
(2) the size of the related soil is much larger than that of an indoor sample, so that the influence of the macroscopic structure of the soil on the property of the soil can be reflected more effectively, and the soil is more representative than a soil sample;
(3) the test can be repeatedly carried out, and the test period is shortened;
(4) the method is suitable for in-situ testing of dynamic stress-strain curves of various foundations, and has the characteristics of controllable frequency, amplitude, loading cycle frequency and the like, wide application range, strong controllability, high reliability and the like.
Drawings
FIG. 1 is a schematic diagram of a field test of a dynamic stress-strain curve in-situ test apparatus;
FIG. 2 is a front view of an electro-hydraulic servo actuator;
FIG. 3 is a cross-sectional view of an electro-hydraulic servo actuator;
FIG. 4 is a front view of the vibrator;
FIG. 5 is a top view of the vibrator;
FIG. 6 is a left side view of the vibrator;
FIG. 7 is a graph of displacement time-course;
FIG. 8 is a graph of dynamic strain versus cycle frequency;
FIG. 9 is a dynamic stress-strain curve;
wherein:
1-special engineering vehicle; 2, supporting legs; 3-load servo system; 4-electro-hydraulic servo hydraulic source; 5-an oil delivery pipe; 6, a guide post; 7, fixing a bracket; 8-a displacement sensor; 9-a pressure sensor; 10-upper bearing plate; 11-a vibrator; 12-air tap; 13-lower bearing plate; 14-vertical shock-absorbing air bags; 15-touching the floor; 16-a data acquisition system; 17-a vibration pickup; 18-earth pressure cell; 19-pressing the sensor hydraulic cylinder on site.
Detailed Description
The present invention will be described in further detail with reference to specific examples. The examples will help to understand the present invention given the detailed embodiments and the specific operation procedures, but the scope of the present invention is not limited to the examples described below.
The invention provides a dynamic stress-strain curve in-situ testing device. The system consists of a movable system, a load servo system, a power reaction system and a data acquisition system.
(1) Mobile system
The special engineering vehicle 1: diesel engine (250 kW power), 4 wheel drive.
(2) And the load servo system is loaded with microcomputer control electro-hydraulic servo dynamic test control software LETRY Trier 6200/6210.
The load servo system compares the command signal with the feedback signal, and then controls the whole system by using the difference signal to enable the system to complete the expected action. The system has two control modes of stress control (force control) and displacement control, the test generally adopts force control to apply dynamic load, vertical dynamic load can be applied under preset frequency, amplitude and loading cycle number, and the working principle of the system is introduced as follows:
1) test control software
The microcomputer-controlled electro-hydraulic servo dynamic and static test control software runs in various Windows environments, is friendly in interface and simple to operate, can complete setting of test conditions, sample parameters and the like and test data processing, can store test data in various file formats, can reproduce test courses and replay test data after the test is finished, can import the test data into various software such as Word, Excel, Access, MATLAB and the like, and can perform statistics, editing, classification, fitting test curves and the like, and can print a test report after the test is finished.
2) Function of test measurement control system
The full digital microcomputer control electro-hydraulic servo multi-channel control system is a distributed full digital closed loop microcomputer control system, and comprises a computer at the upper level, a plurality of single chips capable of independently completing multi-parameter control, data acquisition and preprocessing tasks and the like. The upper computer and the six channel control single-chip microcomputers transmit data in an asynchronous parallel and master-slave mode, each single-chip microcomputer independently completes preset and random instruction tasks and simultaneously transmits the data to the computer in a digital mode in time, the computer performs centralized processing and unified management on test set parameters, control parameter adjustment and the like of each channel, random control parameters of a test system are transmitted to each single-chip microcomputer, and comparison and coordination are performed through preset and designated control parameters of the system to realize coordination control loading.
(3) Dynamic reaction system
The power reaction system consists of an electro-hydraulic servo actuator and a vibrator.
1) Electro-hydraulic servo actuator
The electro-hydraulic servo actuator comprises an electro-hydraulic servo hydraulic source 4, an oil delivery pipe 5 and a guide post 6 which are sequentially connected, wherein the guide post 6 comprises a piston rod and a guide sleeve arranged outside the piston rod, the bottom of the guide post is fixedly connected with an upper bearing plate 10, a displacement sensor 8 is arranged in the middle of the piston rod 6, and a pressure sensor 9 is arranged at the bottom of the piston rod. The fixed support 7 is sleeved outside the guide sleeve and can be used for fixing an oil path, and results of the displacement sensor 8 and the pressure sensor 9 are fed back to the load servo system.
The working principle of the electro-hydraulic servo actuator is as follows: the system pressure oil provided by the hydraulic source enters the oil inlet cavity of the oil cylinder through the high-pressure energy accumulator, the precise oil filter and the electro-hydraulic servo valve by the oil inlet pipeline. The hydraulic oil in the oil return cavity returns to the oil tank through the electro-hydraulic servo valve, the oil return pipe, the cooler and the oil return oil filter. The energy accumulator is arranged on the oil inlet and return pipeline, so that pressure fluctuation can be eliminated, the effect of stabilizing the system pressure is achieved, and the control precision of the system is improved. The position and the stroke of the movement of a piston of the actuator are measured by a high-precision displacement sensor (8) arranged on the actuator, so that the position control of the electro-hydraulic servo actuator is realized. In the motion process of the actuator, the pressure sensor (9) connected to the end of the piston rod of the actuator can measure the acting force of the actuator on the test piece in real time, and the acting stroke of the load control actuator can meet the displacement of 1000mm soil body settlement through the electric control system. According to the load requirement required to be applied in the vertical direction in the test, the frequency and the amplitude of the dynamic load are adjustable under the control of the electro-hydraulic servo system, the static maximum test load is 100kN, and the dynamic maximum test load is 80 kN.
2) Vibration device
The vibrator comprises a lower bearing plate 13, a vertical damping air bag 14 and a grounding plate 15 from top to bottom, wherein an air nozzle 12 is arranged above the lower bearing plate 13.
The vertical vibration working principle is as follows: the dynamic and static loads transmitted by the upper bearing plate of the electro-hydraulic servo actuator act on the lower bearing plate of the vibrator and are transmitted to the ground contact plate contacted with the ground through 4 sets of vertical damping air bags, the applying work of the vertical dynamic and static test loads is realized, and a sensor is buried at a certain position below the vibrator.
4) Data acquisition system
The data acquisition system 16 includes a data acquisition instrument, a sensor, signal acquisition and analysis software, and the like.
1) The acquisition instrument: the DH5902 data acquisition instrument is used for acquiring the dynamic response test data.
2) Signal acquisition and analysis software: the dynamic reaction test data acquisition and analysis system is a DHDAS dynamic signal acquisition and analysis system for Donghua test. The system software has a measurement mode and an analysis mode. The measurement mode is used to operate real-time data sampling and basic analysis of the acquired data. The measurement mode can perform operations such as setting parameter files, sampling setting, measurement, graphic region design and the like. The analysis mode is used for off-line analysis of the measured data. The analysis mode can perform data file processing, test course review, test result output, printing and other operations.
3) The sensor: the magneto-electric velocity transducer DH610V of the vibration pickup 17, it converts the vibration velocity quantity into the voltage quantity to output by using the electromagnetic induction principle, the measuring range is 0.125 m/s; DMTY type soil pressure cell, measuring range 150 kPa.
The invention is further explained and verified by combining practical engineering. The specific embodiments described herein are merely illustrative and not restrictive of the scope of the invention.
The test aims at a blank site foundation soil of a Duan test base of Nanjing Water conservancy science research institute, the base is located in Duan county of Maanshan city, and the in-situ test equipment of the dynamic stress-strain curve and the working method thereof provided by the invention are adopted to carry out the field test.
The test aims at a blank site foundation soil of a Ducheng test base of Nanjing Water conservancy science research institute, the base is located in Ducheng county of Maanshan city, and 5 meters below the ground surface is a homogeneous soil body according to a field survey result. The site foundation soil is clay which is yellow brown, and the site soil sample is taken back to carry out the basic physical property test of the indoor soil, so that all the parameters are shown in table 1.
TABLE 1 basic physical Properties of the soil
Preparation work of field test:
the operation process is as follows:
1) and (3) the special engineering truck 1 enters the site, a relatively flat site is selected, and the positions of the special engineering truck 1 and the vibrator 11 are planned.
2) And digging a pit with the length of 1.5-0.5 m right behind the special engineering truck.
3) After the pit is dug, the sensor 17/18 is marked, then the sensor 17 and the sensor 18 are embedded after the sensor is drilled to a specified depth by adopting the hydraulic cylinder 19 for pressing the sensor on site, and then the sensor 17 and the sensor 18 are placed at specified positions, a layer of sandy soil is scattered around the sensor, and then the original soil is backfilled and compacted.
4) The vibrator 11 is placed in the pit, and the direction of the vehicle body is perpendicular to the direction of the touch floor 15. The ground plate 15 of the vibrator should be as close to the original soil layer as possible.
5) After the vibrator 11 is placed, the special engineering vehicle 1 is driven to the position actuator upper bearing plate 10 and the vibrator lower bearing plate 13 are overlapped.
6) And connecting the load servo system 3 with the electro-hydraulic servo hydraulic source 4, and opening control software to input engineering site information.
7) The joints of the embedded sensors 17 and 18 are connected with a data acquisition system 16 to prepare for acquiring and storing data.
8) The air pipe is connected with corresponding air nozzles 12 at four corners of the vibrator to ensure that the air pipe cannot be pressed and the air valve is opened.
9) And (3) switching on a power supply, inserting a vehicle key, igniting to start a power system, and then increasing oil pressure to enable each supporting leg 2 to contact the wood pier to lift the special engineering vehicle. After ignition is started, the air pipe automatically inflates the air bag of the vibrator, and inflation pressure can be monitored by a barometer.
10) And under the control of the load servo system 3, the guide post 6 drives the upper bearing plate 10 of the actuator to rise to the position thereof, so as to complete unhooking.
Content of the experiment
After the preparation, the test was started.
1) Wave form: the vibration waveform selected by the test is a sine waveform.
2) Circulating for the times of the circulation: the test researches the change relationship among dynamic stress, dynamic strain and vibration frequency, and the loading cycle times set by the test are respectively 10, 20 and 40 times. And during field test, the interval from the end of the current setting cycle to the next loading is at least two hours. )
3) Loading frequency: the loading frequency was set to 1Hz, considering that the test did not investigate the effect of the loading frequency on the test results.
4) Dynamic load amplitude: the test adopts a force control mode, in order to calculate and obtain a relation curve of dynamic stress-dynamic strain, the test adopts a mode of gradually increasing load, and the test load is respectively set to be 30kPa, 60kPa and 90 kPa. In the field test, the interval of applying the dynamic load of each group is one day. )
Test results and analysis
Relationship between dynamic strain and vibration frequency
The displacement u-time t output at a certain vibration frequency during the test is shown in FIG. 7, and the soil body dynamic strain ε at the local vibration frequency is calculated by using the formula (1)dIs 7.35X 10-4。
After the test is finished, calculating the dynamic strain corresponding to all the vibration times, and sequentially accumulating the deformation values under each group of dynamic loads to obtain the dynamic strain epsilon dThe variation with cycle number N is shown in fig. 8.
As can be seen from fig. 8, the dynamic strain of the soil increases with the number of vibrations during the dynamic load operation. The greater the dynamic stress, the greater the dynamic strain. Under the same dynamic load, the dynamic strain caused when the soil body is loaded to the previous cycle for the next time is less than the dynamic strain caused when the previous cycle is ended, such as sigmadWhen the pressure is 30kPa, the dynamic strain epsilon caused after the end of the test when N is 10 in the cycle number set for the first timedIs 1.07X 10-3And the dynamic strain epsilon caused when the 10 th load is loaded 20 timesdIs 0.89X 10-3The difference between the two is 0.18 multiplied by 10-3When σ isdThis difference is 0.51 × 10 at 90kPa-3. From the perspective of the loading process, although a time interval is set during the field test of two adjacent loads, the two adjacent loads are actually a loading-unloading-reloading process, which shows that the soil body has unrecoverable plastic deformation under the action of dynamic load, the increase of the follow-up load becomes more obvious, and the viscoelastic-plastic property of the soil is reflected. In addition, dynamic strain and vibrationThe change curve of the times is more and more gentle, which shows that the dynamic strain is more and more slowly increased along with the increase of the vibration times, and the reason for analyzing the change curve is that the soil body is gradually compacted in the vibration process, the soil particles are more compact, so that the effective stress is increased, and the capability of the soil body for resisting damage and deformation is enhanced.
Dynamic stress-strain curve
Under a certain vibration frequency, the relationship between the change of the trimming dynamic stress and the change of the dynamic strain is shown in fig. 9, and as can be seen from fig. 9, the dynamic stress-strain curve is close to a hyperbolic curve, which is generally called a backbone curve and reflects the nonlinearity of the soil. The method adopts a Duncan-Zhang hyperbolic model, the expression is shown in formula 2), and the dynamic stress-strain relation of the natural soil body is fitted to obtain the values of model parameters a and b under corresponding vibration times as shown in formula 2).
In the formula, a and b are experimental parameters.
From table 2, it can be found that the overall variation range of the model parameters a and b is small, a tends to increase with the increase of the vibration frequency, and the increasing amplitude is larger and larger, which indicates that a is greatly influenced by the cycle frequency N and is in a positive correlation; the value of b is not greatly influenced by N of the cycle times, and the analysis shows that the value of b is mainly influenced by the physical and mechanical properties of the soil body.
TABLE 2 model parameter values
In conclusion, the test curves measured by the device have good regularity, are consistent with actual conditions, and indicate that the in-situ test equipment for the dynamic stress-strain curve works normally, and has real and accurate test data and high reliability.
The invention provides a thought and a method of a soil dynamic stress-strain curve in-situ testing device, and a method and a way for implementing the technical scheme are many, the above description is only a preferred embodiment of the invention, and it should be noted that, for a person skilled in the art, a plurality of improvements and decorations can be made without departing from the principle of the invention, and the improvements and decorations should also be regarded as the protection scope of the invention. All the components not specified in the present embodiment can be realized by the prior art.
Claims (8)
1. The dynamic stress-strain curve in-situ testing device is characterized by comprising a movable system, a dynamic reaction system, a load servo system (3) and a data acquisition system, wherein,
the power reaction system comprises an electro-hydraulic servo actuator and a vibrator, the electro-hydraulic servo actuator comprises an electro-hydraulic servo hydraulic source (4), an oil delivery pipe (5) and a guide post (6) which are sequentially connected, the guide post (6) comprises a piston rod and a guide sleeve arranged outside the piston rod, the bottom of the guide post is fixedly connected with an upper bearing plate (10), the middle part of the piston rod is provided with a displacement sensor (8), and the bottom of the piston rod is provided with a pressure sensor (9);
the vibrator comprises a lower bearing plate (13), a vertical shock absorption air bag (14) and a touch floor (15) from top to bottom, and an air nozzle (12) is arranged above the lower bearing plate (13);
the dynamic and static loads transmitted by the upper bearing plate (10) of the electro-hydraulic servo actuator act on the lower bearing plate (13) of the vibrator and are transmitted to the touch floor (15) through the vertical damping air bag;
the load servo system is used for controlling the operation of the dynamic reaction system, applying vertical dynamic load under the preset frequency, amplitude and loading cycle number, and feeding back the results of the displacement sensor (8) and the pressure sensor (9) to the load servo system;
The electro-hydraulic servo hydraulic source is electrically or wirelessly connected with the load servo system;
the data acquisition system comprises an acquisition instrument, and a vibration pickup (17) and a soil pressure box (18) which are respectively connected with the acquisition instrument, wherein the soil pressure box (18) is embedded at the midpoint position of the two vibration pickup (17), outputs the vertical stress of the point under the action of dynamic load in real time and transmits the vertical stress to the acquisition instrument;
the dynamic reaction system is arranged inside the movable system.
2. The dynamic stress-strain curve in-situ test device as claimed in claim 1, wherein the movable system is a special engineering vehicle, and the dynamic reaction system is arranged in the special engineering vehicle and can extend out of the special engineering vehicle through a hole arranged at the bottom of the special engineering vehicle.
3. The in-situ test device for dynamic stress-strain curves according to claim 2, characterized in that the bottom of the movable system is provided with retractable and telescopic supporting legs (2).
4. The dynamic stress-strain curve in-situ test device as claimed in claim 2, wherein a hook is arranged inside the engineering truck, the top end of the guide post is provided with a corresponding hook, and the guide post and the corresponding hook are hung when the guide post is lifted to the highest position.
5. The in-situ test device for the dynamic stress-strain curve of claim 1, wherein the vertical shock absorption air bag comprises 4 sets.
6. The dynamic stress-strain curve in-situ test device of claim 1, wherein the vibration pickers are arranged at a position which is 0.5 to 1m away from the bottom of the grounding plate in the vertical direction, the soil pressure box is embedded at the middle points of the two vibration pickers, and the vertical stress of the points under the action of dynamic load is output in real time.
7. The dynamic stress-strain curve in-situ test method is characterized by comprising the following steps of:
1) the movable system (1) enters a field, a relatively flat field is selected, and the positions of the movable system (1) and the vibrator (11) are planned;
2) digging a pit of 1.5m by 0.5m directly behind the mobile system (1);
3) after the pit is dug, marking the embedding positions of the shock pick-up device (17) and the soil pressure box (18), drilling holes to a specified depth at the marking positions by adopting a hydraulic cylinder (19) of a field pressure sensor, and then embedding the shock pick-up device (17) and the soil pressure box (18); after the vibration pickup (17) and the soil pressure box (18) are placed at the designated positions, a layer of sandy soil is scattered around the vibration pickup and then the original soil is backfilled and compacted;
4) placing the vibrator (11) into the pit, wherein the body direction of the movable system (1) is vertical to the direction of the touch floor (15), and the touch floor (15) of the vibrator is tightly attached to the original soil layer;
5) After the vibrator (11) is placed, the movable system (1) is opened in place, so that the upper bearing plate (10) of the actuator is superposed with the lower bearing plate (13) of the vibrator;
6) connecting a load servo system (3) with an electro-hydraulic servo hydraulic source (4), and opening control software to input engineering site information;
7) connecting joints of the pre-buried vibration pickup (17) and the soil pressure box (18) with a data acquisition system (16) to prepare for acquiring and storing data;
8) connecting the air pipe with corresponding air nozzles (12) at four corners of the vibrator to ensure that the air pipe cannot be pressed and opening the air valve;
9) turning on a power supply, inserting a vehicle key, igniting and starting a power system, then increasing oil pressure to enable each supporting leg (2) to contact a wood pier placed on the ground, and lifting the movable system (1); after ignition is started, the air pipe automatically inflates the air bag of the vibrator, and the inflation pressure can be monitored by a barometer;
10) the guide post (6) drives the upper bearing plate (10) of the actuator to lift the position of the upper bearing plate through the control of the load servo system (3), and unhooking is completed.
8. The method according to claim 7, wherein the earth pressure cell is embedded at the midpoint of the two vibration pickers, and outputs the vertical stress of the point under the action of dynamic load in real time; the dynamic strain is defined as the average dynamic strain between the two transducers, assuming that the displacement varies linearly with the distance between the two transducers, this value is considered equal to the dynamic strain at the midpoint of the two transducers, calculated using a displacement-based method, and the recorded velocity-time history is counted Integrating the values to obtain a displacement-time history, and calculating the peak displacement of the displacement time histories of the adjacent sensors; at the same time, the difference between the output larger peak displacement and the displacement recorded by another sensor is the total deformation between the adjacent sensors, and the displacement difference is divided by the distance between the two sensors to obtain the dynamic strain epsilond：
In the formula u1Is the maximum displacement in the displacement-time waveform diagram of the output of the vibration pickup at a certain vibration frequency, u2The displacement output by another vibration pickup at the same moment; Δ x is the distance between the two pickups.
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| CN105181498A (en) * | 2015-09-08 | 2015-12-23 | 中山大学 | Simple instrument method for test of internal stress of soil mass under cyclic loading |
| CN205898797U (en) * | 2016-08-15 | 2017-01-18 | 铁道第三勘察设计院集团有限公司 | Simulation train moves and carries testing arrangement of soil deformation characteristic down |
| CN108195684A (en) * | 2017-12-05 | 2018-06-22 | 同济大学 | Pilot system available for ground mechanical behavior under research loopy moving load action |
| CN110333148A (en) * | 2019-05-28 | 2019-10-15 | 江苏科技大学 | A kind of native dynamic shear modulus test method based on vibration attenuation curve fining analysis |
| CN111257113A (en) * | 2020-02-20 | 2020-06-09 | 东南大学 | Concrete uniaxial tensile stress strain full curve testing method and testing device |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105181498A (en) * | 2015-09-08 | 2015-12-23 | 中山大学 | Simple instrument method for test of internal stress of soil mass under cyclic loading |
| CN205898797U (en) * | 2016-08-15 | 2017-01-18 | 铁道第三勘察设计院集团有限公司 | Simulation train moves and carries testing arrangement of soil deformation characteristic down |
| CN108195684A (en) * | 2017-12-05 | 2018-06-22 | 同济大学 | Pilot system available for ground mechanical behavior under research loopy moving load action |
| CN110333148A (en) * | 2019-05-28 | 2019-10-15 | 江苏科技大学 | A kind of native dynamic shear modulus test method based on vibration attenuation curve fining analysis |
| CN111257113A (en) * | 2020-02-20 | 2020-06-09 | 东南大学 | Concrete uniaxial tensile stress strain full curve testing method and testing device |
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