CN102607943A - Clamp for measuring creep deformation of geo-grid material, and using method thereof - Google Patents

Abstract

The invention relates to a fixture for measuring the creep of geogrid materials and a method for using the fixture. The fixture includes an upper fixture and a lower fixture. The ruler and the inner measuring ruler are nested and slidably connected, and a dial is provided at the joint between the inner measuring ruler and the lower fixture, and the lower fixture is movably connected to the load bar through a rotating shaft, and the load bar is connected to the pallet. The invention overcomes the deficiencies in the previous creep experiment process, successfully reduces the experimental error, makes the grid force more balanced, the load application is more standardized, has higher accuracy, and greatly avoids the human factors. The experimental error is small, and the operation is convenient, which improves the experimental efficiency and is more practical.

Description

Fixture for measuring creep of geogrid material and method of use thereof

technical field

The invention relates to a device for measuring material creep in geotechnical material property experiments. the

Background technique

The phenomenon that the deformation of a material increases slowly over time under the action of constant stress is called creep. Creep test refers to the test to detect the creep deformation and creep speed of materials under the action of certain temperature and force. the

With the continuous development of civil engineering in my country, the performance requirements of geotechnical materials are gradually improved, and various new geosynthetic materials have been developed one after another. The performance test of new geosynthetic materials has become a direction that people pay close attention to. The performance test experiment of the material has been carried out in depth, and the efficient and accurate determination of the properties of the material has become the mainstream development trend. the

At present, many scholars have carried out many experimental studies on the creep characteristics of geosynthetics including geogrids. The creep experiments are roughly divided into two categories: one is the creep test under long-term load; the other is the creep test under long-term load. It is an accelerated creep test using the time-temperature equivalent principle and the load-time equivalent principle. For the former, according to the current regulations of most national standards, a long-term load creep test of more than 1000h should generally be carried out. For the latter, it is considered that the creep that occurs in a relatively short period of time under a relatively high load at a certain temperature is equivalent to the creep that occurs within a relatively long period of time under a relatively low load at the same temperature, so that The long-term creep properties of geosynthetics are obtained in a relatively short period of time. By controlling the temperature of the creep experiment process to be constant, measuring the slight deformation of the geotechnical material after a certain time interval, and finally obtaining the creep curve and creep rate of the material for reference in engineering and scientific research. the

At present, the process of grid creep test is basically mature, but it is insufficient in accuracy and is cumbersome. Since the parallel use of fixtures cannot be guaranteed, the length of each grid unit is not equal and the force is unbalanced; the suspension rod and The fixed connection method of the fixture cannot guarantee the vertical application of the load, and the slight lateral force formed has a great influence on the accuracy of the experimental results; Improperness will affect the experimental results. Therefore, traditional creep fixtures have been difficult to meet the needs of high-precision grid creep experiments. the

Contents of the invention

In view of the above problems, the present invention provides a fixture for measuring the creep of geogrid materials and its use method, which is easy to operate, efficient and convenient. the

The present invention is achieved through the following technical solutions:

A fixture for measuring the creep of geogrid materials, including an upper fixture and a lower fixture. The upper fixture and the lower fixture are respectively vertically connected to the outer measuring ruler and the inner measuring ruler on the same side, and the outer measuring ruler and the inner measuring ruler can be nested. Sliding connection, a dial is provided at the connection between the inner measuring scale and the lower fixture, the lower fixture is movably connected with the load bar through the rotating shaft, and the load bar is connected to the pallet. the

Fixing screws for tightening the grid material are respectively provided on the upper clamp and the lower clamp. the

The use method of the fixture for measuring the creep of geogrid material includes the following steps:

(1) Place the inner and outer measuring scales of the device horizontally, loosen the fixing screws of the upper and lower fixtures, place the grille to be tested between the upper and lower fixtures, keep the grille material naturally elongated without bending, and then tighten it Fix the screws to ensure that there will be no relative slippage between the grille and the fixture;

(2) Stand up the device, fix the upper fixture on the test bench, use a hydraulic jack to lift the tray under the load bar, and ensure that the tray does not pull downward on the grid at this time, and then fine-tune the distance between the upper and lower fixtures , confirm that the grille is in a natural straight state, adjust the zero adjustment knob of the dial, and set it to the initial zero scale;

(3) After a certain load is applied on the pallet and stabilized, lower the hydraulic jack slowly, and record it as zero time at the same time, and then observe and record the reading on the dial at regular intervals. the

The invention overcomes the deficiencies in the previous creep experiment process, successfully reduces the experimental error, makes the grid force more balanced, the load application is more standardized, has higher accuracy, and greatly avoids the human factors. The experimental error is small, and the operation is convenient, which improves the experimental efficiency and is more practical. Compared with traditional experimental devices, this device has the following advantages:

1. Fixtures are vertically fixed to the measuring scale to ensure the parallel placement of the upper and lower fixtures, further ensuring that the lengths of each unit of the grid are equal and evenly stretched, avoiding uneven force and reducing experimental errors. the

2. This device successfully avoids the cumbersome operation of fixing the fixture first and then placing the caliper between the upper and lower fixtures in the traditional test, and eliminates the phenomenon that the caliper slides and loses alignment midway. Real-time zero adjustment makes the experimental data more accurate and intuitive. the

3. The rotating shaft is connected to the loading rod, and the natural vertical state is achieved by gravity, which ensures the vertical application of the load, eliminates the lateral force caused by the non-vertical loading rod, and greatly improves the accuracy of the experiment. the

The following is a comparison of creep experiments of a new type of geogrid material: (each group of experiments measures the co-extension of two grid materials) 

Data analysis: It can be seen from the above table that the final reading of the instrument panel with this patented fixture is equal to the actual elongation, and the measurement is simple. The error caused by artificial calculation is avoided; because the load applied by the new device is more uniform, the biased pull effect caused by the non-vertical load application is avoided, and the two grid materials are balanced in force, so that the grid material is not affected by a single load. The force is large and elongated, so the measurement result is smaller than the original method, and the experimental accuracy has been improved. the

Description of drawings

Fig. 1 is a structural schematic diagram of the device of the present invention. the

1. Upper fixture; 2. Lower fixture; 3. Fixing screw of upper fixture; 4. Fixing screw of lower fixture; 5. Dial; 6. Adjusting knob; 7. Shaft; 8. Loading bar; 9. Tray; 10. Outside measuring stick; 11. Inside measuring stick. the

Detailed ways

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

A fixture for measuring the creep of geogrid materials, comprising an upper fixture 1 and a lower fixture 2, and the upper fixture 1 and the lower fixture 2 are vertically connected to the outer measuring ruler 10 and the inner measuring ruler 11 respectively on the same side, and the outer measuring ruler 10 Nested and slidably connected with the inner measuring ruler 11, a dial 5 is provided at the joint between the inner measuring ruler 11 and the lower fixture 2, the lower fixture 2 is movably connected with the load bar 8 through the rotating shaft 7, and the load bar 8 is connected to the pallet 9. the

The upper fixture 1 and the lower fixture 2 are respectively provided with fixing screws for tightening the grid material. the

The dial 5 is placed on the inner scale 11, and after the grid material is clamped, it is set to the initial zero scale by adjusting the knob 6, and the relative displacement of the inner and outer scales is accurately displayed during the creep process, thereby reflecting the creep of the grid material. change the situation. the

The pallet 9 is vertically connected to the load bar 8, and the other end of the load bar 8 is provided with a rotating shaft 7, which is assembled with the lower clamp 2 and can swing freely to ensure the vertical application of the load. the

Example 1

The creep experiment of a new type of geogrid material is measured by the new measurement device, and the experimental steps are as follows: 

A Place the whole device horizontally, loosen the fixing screws 3 and 4 of the upper and lower fixtures, place the grid to be tested between the fixtures, keep the grid material stretched naturally without bending, and then tighten the fixing screws 3 and 4 to ensure that the grid is in contact with the fixture There will be no relative slippage between them. the

B erect the device, fix the upper fixture 1 on the test bench, use a hydraulic jack to lift the lower tray 9 of the load bar, and ensure that the tray 9 has no downward pulling force on the grille at this time, and then fine-tune the upper and lower fixtures 1 and 2 Make sure that the grille is in a natural straight state, adjust the zero adjustment knob 6 on the scale dial 5, and set it as the initial zero scale. the

C After applying a certain load on the pallet 9 and stabilizing it, lower the hydraulic jack slowly, and record it as zero time at the same time, then observe and record the reading on the lower dial 5 at regular intervals, and carry out the next experiment. the

The measurement results are shown in the table below:

The test results show that this experiment meets the requirements of the creep experiment, and the operation is simple, the accuracy is improved, and the uneven force caused by the partial tension is successfully avoided. the

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Claims (3)

1. anchor clamps that are used to measure the geo-grid material creep; It is characterized in that it comprises anchor clamps, lower clamp, last anchor clamps, lower clamp be vertical respectively outside gage and the inboard gage of connecting in the same side; The external pelivimetry chi slidably is connected with inboard gage is nested; Inboard gage and lower clamp junction are provided with index dial, and lower clamp flexibly connects through rotating shaft and load-carrying bar, and the load-carrying bar connects pallet.

2. a kind of anchor clamps that are used to measure the geo-grid material creep according to claim 1 is characterized in that, described going up on anchor clamps, the lower clamp is respectively equipped with the fixed screw that steps up grid material.

3. claim 1 or 2 described a kind of method of application that are used to measure the anchor clamps of geo-grid material creep is characterized in that, comprise that step is following:

(1) the medial and lateral gage with device is horizontal positioned; Loosen the fixed screw of upper and lower anchor clamps, grid to be measured is placed between the upper and lower anchor clamps, keep grid material to extend not crooked naturally; Tighten fixed screw afterwards, guarantee not slippage relatively between grid and anchor clamps;

(2) device is holded up; On test-bed, use hydraulic jack that the pallet under the load-carrying bar is held up clamps on it, guarantee that pallet is not to the downward pulling force of grid at this moment; Trickle afterwards adjustment is spacing jig up and down; Confirm that grid is in the nature straight configuration, adjustment index dial zeroing knob is made as initial zero graduation;

(3) apply on the pallet constant load stable after, slowly fall hydraulic jack, be designated as zero simultaneously constantly, whenever afterwards observe reading and record on the index dial down at a distance from regular time.

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