CN110763569A - Geogrid creep test device and method considering soil mass constraint conditions - Google Patents

Abstract

The invention discloses a geogrid creep test device and a test method considering soil constraints, including a geogrid, a test frame, a test box, a creep detection mechanism and a load loading group. There are perforations on the side walls of the opposite sides of the test box, and the geogrid is penetrated in the two perforations, and the two ends extend out of the test box to connect with the fixed end and the movable end fixture respectively; the geogrid is buried in the test box. Inside, the packing is layered and compacted, and the detection end of the creep detection mechanism is connected to the corresponding preset detection point on the geogrid; the load loading group can output the vertical load and the horizontal load simultaneously or sequentially, among which the packing in the test chamber A vertical load is applied to the top, and a horizontal load is applied to either side of the geogrid; the other side of the geogrid opposite to the load-loading group is connected to the test frame or test box. The test device and the test method have a simple and practical structure, and are suitable for simulating the creep properties and strength change characteristics of a geogrid constrained by soil under different long-term loads.

Description

A geogrid creep test device and test method considering soil constraints

technical field

The invention relates to the technical field of geosynthetic material reinforced soil retaining walls, in particular to a geogrid creep test device and a test method considering soil constraints.

Background technique

In recent years, the research on the creep characteristics of geosynthetics at home and abroad has been increasing, but they are basically carried out for geotextiles or geomembranes; and most of the relevant tests on the short-term or long-term tensile strength of steel bars at home and abroad have been carried out. The standard stipulates that the reinforcement is stretched under unconstrained conditions and at a certain temperature and humidity, and the strength index obtained from this test condition is used as the material characteristic parameter. The creep characteristics of the reinforcement under the constraint conditions make the creep reduction coefficient of the reinforcement too large in engineering design, thus affecting the application of the reinforcement in the reinforced soil structure. In addition, as a thermo-viscoelastic material, geogrid will show its unique creep characteristics under certain temperature and long-term load. In order to understand the load-deformation behavior of the geogrid in the creep process under the action of temperature, some scholars have conducted a large number of temperature-accelerated creep tests on the geogrid under unconstrained conditions. Therefore, it is necessary to develop a geogrid creep test device and consider the influence of restrained conditions on creep through the geogrid creep test, and to explore the creep properties and strength variation characteristics of geogrids under different long-term loads.

SUMMARY OF THE INVENTION

The present invention aims to solve at least one of the technical problems mentioned above, and provides a geogrid creep test device and a test method considering soil constraints. The test device has a simple structure, is easy to build, and is suitable for indoor simulation. The creep properties and strength change characteristics of geogrids constrained by soil under different long-term loads; this test method is easy to operate and has high measurement accuracy.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A geogrid creep test device considering soil constraints, including a geogrid, a test frame, a test box set on the test frame, a creep detection mechanism and a load loading group, the test box on opposite sides is Each side wall is provided with perforations, and both ends of the geogrid can be perforated and extended out of the test box; the test box is filled with fillers on the upper and lower sides of the geogrid, and the detection end of the creep detection mechanism is provided with At least two, and they are respectively connected to the corresponding preset detection points on the geogrid; the load loading group can output vertical load and horizontal load simultaneously or sequentially; the load loading group can apply vertical load on the top of the filler in the test box, And can apply horizontal load to either side of the geogrid; the other side of the geogrid opposite the load loading group is connected to the test frame or the test box.

As an improvement of the above technical solution, the load loading group includes a stress mechanism capable of applying a vertical stress load and a force applying mechanism capable of applying a horizontal load; the stress mechanism can apply vertical stress to the top of the filler in the test chamber, so The output end of the force applying mechanism is connected with the geogrid, and exerts a horizontal pulling force on the geogrid.

As an improvement of the above technical solution, it also includes a clamping structure, the clamping structure includes a fixed clamp and a movable clamp, and the fixed clamp and the movable clamp are respectively clamped on both ends of the geogrid under horizontal force; The fixture is connected with the test frame or the test box, and the movable fixture is connected with the output end of the load loading group for applying the horizontal load.

As an improvement of the above technical solution, the fixed fixture and the movable fixture are composed of three upper, middle and lower steel plates stacked in sequence. The upper steel plate is connected to the lower steel plate through a plurality of bolts through the middle steel plate. There are tooth-shaped occlusal grooves on the clamping surface of the tooth-shaped occlusion groove, and rubber gaskets are arranged on the tooth-shaped occlusion grooves to clamp the geogrid.

As an improvement of the above technical solution, the force applying mechanism includes a lever, an adjustment member, a counterweight arranged on one end of the lever, and a traction rope with one end connected to the other end of the lever. Both the lever and the adjustment member are installed on the test frame The other end of the pulling rope bypasses the adjusting member and is connected to the movable clamp on the geogrid; the adjusting member can adjust the levelness of the connecting end of the pulling rope and the geogrid.

As an improvement of the above technical solution, the creep detection mechanism includes a dial indicator and a steel wire with one end connected to the measuring end of the dial indicator, the dial indicator is provided with at least two, and the other end of the steel wire is fixed on the geogrid On the preset measuring point of the grid; the dial indicator is installed on the test stand or test box.

As an improvement of the above technical solution, the stress mechanism is a weight or a hydraulic mechanism with the output end set downward.

The invention also provides a geogrid creep test method considering soil constraints, comprising the following steps:

Step 1. Test preparation, prepare the test frame, test box, creep detection mechanism and load loading group for the test, and debug the equipment until it meets the test requirements, and measure the ultimate tensile strength UTS of the selected geogrid;

Step 2. Install the geogrid, fill the test box with filler, fill it in layers according to the preset pressure, and fill it up to the height of the plane where the perforations on both sides are located; then wear the preset specifications in the perforations on both sides. Geogrid, and fix one end of the steel wire at the preset measurement point position of the geogrid, and the other end of the steel wire is perforated from one side; fill the upper side of the geogrid in the test box, and divide it according to the preset pressure. layer filling;

Step 3. Install the test equipment, respectively clamp a fixed fixture and a movable fixture on both sides of the geogrid passing through the perforation, and the movable fixture is connected with the force-applying mechanism; and the fixed fixture is fixedly installed on the test box or test frame, and the fixed fixture is fixed. The geogrid on the side where the steel wire passes through; the end of the steel wire passing through the hole is connected to the measuring end of the dial indicator installed on the test frame or test box;

Step 4. Test loading, place the above-mentioned installed test equipment in a temperature of 18-22°C and a humidity of 40-60% and let it stand for 0.5-1 day; The vertical load of the grid is 10-18kPa; the horizontal tension applied by the force-applying mechanism to the movable fixture is M% of the ultimate tensile strength UTS of the geogrid, and the loading time is the time interval of 1min, 2min, 6min, 10min, 15min, 30min, 60min, 2h, 4h, 8h, 10h, 24h, 50h, 72h, 100h, 200h, 300h, 400h, 500h, 600h, 700h, 800h, 900h, 1000h and 1008h, when the creep loading time exceeds After 100h, the data collection time interval is 100h, the total creep test time is 42 days, and the values of the dial indicators corresponding to different preset detection points within the corresponding loading time are recorded;

Step 5. Repeat steps 2 to 4 at least twice. In each test, the horizontal tensile force applied by the force application mechanism to the movable fixture is increased by Δn% on the basis of the UTS horizontal tensile force value of the last geogrid ultimate tensile strength, and Δn is 6 to 10, and record the value of the dial indicator corresponding to different preset detection points within the corresponding loading time;

Step 6, calculation, calculate the strain value of the geogrid corresponding to the preset detection point by using the strain formula to calculate the values on different preset detection points recorded in steps 4 and 5:

ε=ΔL/L×100%

In the formula: ε is the strain of the bar; ΔL is the creep deformation of the bar, and its unit is mm; L is the effective length of the bar, that is, the net distance between the fixtures, and its unit is mm.

As an improvement to the above technical solution, the steel wire is parallel to the direction in which the force applying mechanism applies force to the geogrid.

As an improvement to the above technical solution, the measuring end of the dial indicator in step 3 is set horizontally and is on the same level as the steel wire.

Compared with the prior art, the beneficial effects of the present application are:

A geogrid creep test device considering soil constraints uses load loading groups to apply horizontal and vertical stress to the geogrid buried in the test box, which can effectively simulate the service process of reinforced soil retaining walls in actual engineering. The design of the perforations on the opposite sides of the test box can avoid the influence of the test box on the geogrid when the load loading group pulls the geogrid horizontally; the creep detection mechanism can be used to measure the geogrid during the test. The force situation of different preset detection points during the loading process is convenient for the test personnel to observe the force situation of different measurement points in the test box more intuitively, and the accuracy of the simulation test is improved. The local geogrid creep test device can effectively simulate the creep of the reinforced earth retaining wall in the actual road after being loaded through a simple model design, which is convenient for the testers to better design the reinforced earth retaining wall. Improve the safety of engineering structures. The invention also provides a geogrid creep test method considering soil constraints. The method is simple to operate, easy to implement, can effectively simulate the creep of the geogrid in the actual engineering structure, and is convenient to measure. reliable.

Description of drawings

The specific embodiments of the present invention will be described in further detail below in conjunction with the accompanying drawings, wherein:

1 is a schematic structural diagram 1 of an embodiment of the present invention;

2 is a second structural schematic diagram of an embodiment of the present invention;

3 is a schematic diagram of creep loading force according to an embodiment of the present invention;

Fig. 4 is the assembly schematic diagram of the geogrid in the embodiment of the present invention;

Fig. 5 is the tensile property curve diagram of the test geogrid sample in the embodiment of the present invention;

Fig. 6 is the cumulative curve diagram of particle size of filler in the embodiment of the present invention;

Fig. 7 is the graph when the ultimate tensile strength UTS of the geogrid is equal to 62% in the embodiment of the present invention;

FIG. 8 is a graph when the ultimate tensile strength UTS of the geogrid is equal to 72% in the embodiment of the present invention;

FIG. 9 is a graph when the ultimate tensile strength UTS of the geogrid is equal to 82% in the embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

It should be noted that when a component is referred to as being "fixed to" another component, it can be directly on the other component or there may also be a centered component. When a component is considered to be "connected" to another component, it may be directly connected to the other component or there may be a co-existence of an intervening component. When a component is said to be "set on" another component, it can be set directly on the other component or there may be a centered component at the same time, when a component is said to be "set in the middle", not just in the middle , as long as it is not set in the range limited by the middle part at both ends. The terms "vertical," "horizontal," "left," "right," and similar expressions are used herein for illustrative purposes only.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terms used herein in the description of the present invention are for the purpose of describing specific embodiments only, and are not intended to limit the present invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

As shown in FIGS. 1 to 9 , the present invention provides a geogrid creep test device considering soil constraints, including a test frame 1 , a test box 2 arranged on the test frame 1 , and a creep detection mechanism 3 And the load loading group 4, the side walls on the opposite sides of the test box 2 are provided with perforations 21, and the two perforations 21 are provided with a geogrid 5, and the two ends of the geogrid 5 are movable to extend the test. Outside the box 2; the test box 2 is located on the upper and lower sides of the geogrid 5 and is filled with fillers 6, and the detection ends of the creep detection mechanism 3 are provided with at least two, and the corresponding presets on the geogrid 5 are respectively provided. The detection point is connected; the load loading group 4 can output vertical load and horizontal load at the same time or in sequence; the load loading group 4 can apply a vertical load to the top of the filler 6 in the test box 2; A horizontal load is applied on one side; the other side of the geogrid 5 opposite to the load loading group 4 is connected to the test frame 1 or the test box 2 . In an actual test, two load loading groups 4 can be used, and at this time, the load loading group 4 only needs to output a vertical load or a horizontal load, which reduces the complexity of the entire load loading group 4 . In this application, the vertical load is mainly to simulate the self-weight of the superstructure and the traffic load on the road surface when the reinforced earth retaining wall is in service, so the directional continuous output stress can be used. The horizontal load is mainly to bear the tensile force of the edge part of the reinforced earth retaining wall under the uneven force or long-term failure state, while in the actual situation, the probability of the pulling force in the failure state is relatively small, and the failure at the same time It is no longer necessary to carry out tests on the reinforced earth retaining wall. For the convenience of design, this application can default to the horizontal load, which is mainly the tensile force that the reinforced earth retaining wall bears in different areas when the force is uneven. The test box 2 adopts a structure design with four sides closed mainly to realize the structure of the entire reinforced soil retaining wall unit, and the perforation 21 mainly reduces the influence of the side walls of the test box 2 on the geogrid 5 during the test. In practice, the filler 6 is basically a soil or crushed stone structure. In this application, in order to achieve simplicity and facilitate data measurement, the filler 6 uses river sand of medium size.

In order to better apply loads, in another embodiment of the present application, the load loading group 4 includes a stress mechanism 41 capable of applying a vertical stress load and a force applying mechanism 42 capable of applying a horizontal load; the stress mechanism 41 can A vertical stress is applied to the top of the filler 6 in the test box 2 , and the output end of the force applying mechanism 42 is connected to the geogrid 5 . By applying the force separately, the whole test device can be effectively designed, and the load application in different directions can be easily controlled. In order to better clamp the geogrid 5, the test device of the present application further includes a clamping structure 7, and the clamping structure 7 includes a fixed fixture 71 and a movable fixture 72, and the fixed fixture 71 and the movable fixture 72 are respectively clamped The fixed fixture 71 is connected to the test frame 1 or the test box 2, and the movable fixture 72 is connected to the output end of the load loading group 4 for applying horizontal load. In practice, the movable clamp 72 is connected to the output end of the force applying mechanism 42, and the movable clamp 72 can realize large-area clamping, avoiding the stress concentration when the output end of the force applying mechanism 42 is directly connected to the geogrid 5. For better clamping without damaging the structure of the geogrid 5 , rubber gaskets 73 are provided on the clamping surfaces of the fixed clamp 71 and the movable clamp 72 . In another embodiment of the present application, the fixed fixture 71 and the movable fixture 72 are composed of three upper, middle, and lower steel plates stacked in sequence, and the upper steel plate is connected to the lower steel plate through a plurality of bolts through the middle steel plate. There are tooth-shaped occlusion grooves on the matching clamping surfaces of the steel plate and the lower layer of the steel plate, and rubber gaskets 73 are arranged on the tooth-shaped occlusion grooves to clamp the geogrid 5 .

1 to 4 , in order to better increase or decrease the magnitude of the horizontal load, the force applying mechanism 42 includes a lever 421, an adjustment member 422, a counterweight 423 arranged on one end of the lever 421, and another end connected to the lever 421. Pull cord 424 on one end. The lever 421 and the adjustment member 422 are both installed on the test frame 1, and the other end of the traction rope 424 bypasses the adjustment member 422 and is connected to the movable clamp 72 on the geogrid 5; the adjustment member 422 can adjust the traction pull. The level of the end of the rope 424 connected to the geogrid 5 . Using the lever 421 can effectively reduce the demand of the overall counterweight 423. In the test, the torque ratio at both ends of the lever 421 is 1:6, that is, the moment of the lever 421 at one end of the counterweight 423 is 6 times that of the other end of the lever 421. In addition, such a design can effectively reduce the situation that it is difficult for conventional equipment to persist in applying loads for a long time. In another embodiment of the present application, in actual use, the middle of the lever 421 is installed on the test frame 1 through a rotating sleeve, and the lever 421 itself can slide in the rotating sleeve, thereby adjusting the ratio of the torque at both ends. The main purpose of the adjustment member 422 is to adjust the levelness of the connecting end of the pulling rope 424 and the geogrid 5, so that the geogrid 5 is subjected to horizontal tension for later calculation, and at the same time, it reduces the tension between the geogrid 5 and the geogrid 5 during the stress process. The influence of the contact of the test chamber 2. However, due to the long test loading time, the stress mechanism 41 in this application is a weight or a hydraulic mechanism with the output end set downward. It is easier to use weights and can maintain a constant load for a long time, while selecting a hydraulic mechanism is convenient for later stages. load.

Referring to FIG. 4 , in order to better measure the deformation of the geogrid 5 , the creep detection mechanism 3 includes a dial indicator 31 and a steel wire 32 connected to the measuring end of the dial indicator 31 . There are at least two dial indicators 31 , the other end of the steel wire 32 is fixed on a preset measurement point on the geogrid 5 , and the dial indicators 31 are installed on the test frame 1 or the test box 2 . Dial indicator 31 is often used for shape and position error and length measurement of small displacement. Due to the large number of scales set inside, the design similar to micrometer can effectively ensure the accuracy of measurement. The steel wire 32 is used to conduct the deformation of each measuring section of the geogrid 5, the overall idea is novel, and the deformation transmission is accurate. In the actual measurement, after the geogrid 5 is subjected to the combined action of the vertical load and the horizontal load, it will inevitably deform to the side of the output end of the horizontal load, while the dial indicator 31 is in the opposite direction of the horizontal load. The deformation amount of 5 is directly transmitted to the dial indicator 31 through the steel wire 32, and the dial indicator 31 displays the deformation value of the preset detection point on the geogrid 5, and the strain value can be obtained through the deformation calculation formula, and then the creep deformation value can be determined. subtraction factor.

The local geogrid creep test device uses the load loading group 4 to apply horizontal and vertical stress to the geogrid 5 buried in the test box 2, which can effectively simulate the load in the actual reinforced earth retaining wall structure. The design of the opposite side wall perforations 21 on the test box 2 can avoid the influence of the test box 2 on the geogrid 5 when the load loading group 4 pulls the geogrid 5 horizontally; the creep detection mechanism 3 can be used to measure the geogrid 5. The force of the grid 5 at different preset detection points during the test loading process is convenient for the test personnel to observe the deformation of different measurement points in the test box 2 more intuitively, and the accuracy of the test simulation is improved. The local geogrid creep test device can effectively simulate the creep of the reinforced earth retaining wall in the actual road after being loaded through a simple model design, which is convenient for the testers to better design the reinforced earth retaining wall. Improve the safety of engineering structures.

In addition, the present invention also provides a geogrid creep test method considering soil constraints, comprising the following steps:

Step 1. Test preparation, prepare the test frame 1, test box 2, creep detection mechanism 3 and load loading group 4 for the test, and debug the equipment until it meets the test requirements, and measure the ultimate tensile strength UTS of the selected geogrid 5;

Step 2. Install geogrid 5, fill filler 6 in test box 2 below the plane where perforations 21 on both sides are located, and fill in layers according to the preset pressure; Grid 5, and fix one end of the steel wire 32 at the preset measurement point position of the geogrid 5, and the other end of the steel wire 32 passes through the perforation 21 on one side; the test box 2 is located on the upper side of the geogrid 5. Filling 6, according to Preset pressure for layered filling;

Step 3. Install the test equipment, clamp a fixed fixture 71 and a movable fixture 72 on the two side walls of the geogrid 5 passing through the hole 21 respectively, and the movable fixture 72 is connected with the force applying mechanism 42; the fixed fixture 71 is fixedly installed in the test box 2 Or on the test frame 1, and the fixing fixture 71 clamps the end of the geogrid 5 on the side where the steel wire 32 passes through; measuring end connection;

Step 4. Test loading, place the above-mentioned installed test equipment in a temperature of 18 to 22° C. and a humidity of 40 to 60% for 0.5 to 1 day; The vertical load perpendicular to the geogrid 5 is 10-18kPa; the horizontal tension applied by the force applying mechanism 42 to the movable fixture 72 is M% of the ultimate tensile strength UTS of the geogrid 5, and the loading time is time The interval is 1min, 2min, 6min, 10min, 15min, 30min, 60min, 2h, 4h, 8h, 10h, 24h, 50h, 72h, ..., 1000h, 1008h. When the creep loading time exceeds 100h, the data acquisition time interval is 100h, measure the change in the length of the grid sample, the total creep test time is 1008h, and record the value of the dial indicator 31 corresponding to different preset detection points within the corresponding loading time;

Step 5. Repeat steps 2 to 4 at least twice. In each test, the horizontal tensile force applied by the force applying mechanism 42 to the movable fixture 72 is increased by Δn% on the basis of the UTS horizontal tensile force value of the last geogrid 5 ultimate tensile strength. , Δn is 6-10, and record the value of the dial indicator 31 corresponding to different preset detection points within the corresponding loading time;

Step 6, calculation, calculate the strain value of the geogrid 5 on the corresponding preset detection point by calculating the recorded values of the different preset detection points recorded in steps 4 and 5 through the strain formula:

ε=ΔL/L×100%

In the formula: ε is the strain amount of the reinforcement in %; ΔL is the creep deformation of the reinforcement in mm; L is the effective length of the reinforcement, that is, the net distance between the fixtures, and its unit is mm.

In the method of this application, three groups of specific tests are listed. The set environmental conditions are carried out under the conditions of indoor temperature of 20°C and humidity of 50%. The geogrid 5 of this test adopts bidirectional geogrid, and its model can be selected as TGSG-3030, and according to the corresponding standard of "Geosynthetics Testing Regulations" SL235-2012, the conventional tensile test under unconstrained conditions was carried out. The ultimate tensile strength is about 29.5kN/m, and the peak failure strain is about 10.3 %. The tensile properties of the test geogrid are shown in Figure 5. Filler 6 is medium sand with good particle gradation, the uniformity coefficient Cu=8.44, the curvature coefficient Cc=1.15, the relative density of soil particles is 2.65, the maximum dry density is 1.69g/cm3, the internal friction angle is 39°, and the particle gradation is The curves are shown in Figure 6. In addition, before the test is loaded, the resting time is preferably 1 day. At this time, the stress mechanism 41 does not apply stress to the top of the filler 6 in the test box 2. The purpose is to maintain the environment and display of the geogrid 5 and the filler 6. Consistent, improving the measurement accuracy later.

In addition, in the above step 4, the M of the ultimate tensile strength UTS is 62, that is, the horizontal tensile force of the first test is 62% of the ultimate tensile strength UTS, and Δn is selected as 10 in this embodiment, that is, each test is in the previous test. On the basis of the 10% tensile load, the test was carried out under the environment of room temperature of 20 °C and humidity of 50%. This test consists of three groups, that is, the ultimate tensile strength UTS of each group is 62%, 72%, and 82%, respectively. When cutting the geogrid 5 sample, the length of the geogrid 5 sample is longer than the length of the entire test box 2 in order to be better able to be clamped by the movable clamp 72 and the fixed clamp 71 at both ends. In this way, it is convenient for both sides of the geogrid 5 to pass through the perforations 21 on both sides of the test box 2. The operator clamps the corresponding end of the geogrid 5 through the movable fixture 72 and the fixed fixture 71, and then the fixed fixture 71 is fixed. The movable clamp 72 is connected to the input end of the traction rope 424, and finally, the counterweight 423 on one end of the lever 421 is rapidly increased within a specified time. The tensile force of the grid 5, so that the creep test can be realized. The ultimate tensile strength UTS of each group of tests is different at different preset detection points. Please refer to Figure 7, Figure 8 and Figure 9; Figure 7 shows different measurement points when the ultimate tensile strength UTS is equal to 62%. Figure 8 is the creep curve at different measurement points when the ultimate tensile strength UTS is equal to 72%, and Figure 9 is the creep curve at different measurement points when the ultimate tensile strength UTS is equal to 82%. In addition, the geogrid 5 sample is provided with 5 preset detection points, namely A, B, C, D, E five preset detection points, through the shape between adjacent two preset detection points It can be seen from the variables that under different load levels, the creep deformation of different measuring sections of the geogrid has a similar development trend with time. From the analysis of different measurement sections of the geogrid sample, the 5AB section of the geogrid is close to the position of the movable end fixture, and each curve increases almost linearly with time. The tensile modulus of the geogrid 5 gradually decreases, and the curve develops gradually. It is flattened, indicating that the geogrid 5 has significant viscoelastic deformation characteristics. While the BC section and CD section of the geogrid continue to increase with the grid load holding time, the creep deformation decreases in turn, and the peak value is about 64% and 21% of the deformation peak value of the AB section. The above phenomenon is mainly due to the friction between the built-in reinforcement and the filler interface of the reinforced earth retaining wall and the occlusal effect when the overlying load is applied to the composite of the reinforced earth retaining wall. The material property is high polymer, so that the tensile force in the horizontal direction under the constraint of filler 6, namely sand soil, is unevenly distributed, so that the grid creep deformation mainly occurs near the tensile end, that is, the AB section. Conclusion: With the increase of creep load level under sand confinement, the creep phenomenon of geogrid 5 is more obvious, and the creep strain and creep rate are larger. When the geogrid 5 is under low stress, the creep rate first increases and then decreases, and tends to stabilize quickly; when the stress is high, the creep rate is faster, and it takes a long period of time to basically stabilize.

In order to further improve the accuracy of the entire test data, the steel wire 32 is parallel to the direction in which the force applying mechanism 42 applies force to the geogrid 5 , thereby reducing the influence of the steel wire 32 on the test box 2 during measurement. In addition, in step 3, the measuring end of the dial indicator 31 is set horizontally and is on the same horizontal plane as the steel wire 32, so as to avoid a force component in other directions when the measuring end of the dial indicator 31 is stressed, which improves the measurement accuracy.

The invention provides a geogrid creep test method considering soil constraints. The method is simple to operate, easy to implement, can effectively simulate the creep condition of the geogrid 5 in the actual engineering structure, and is convenient to measure. reliable.

The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be included within the scope of the technical solutions of the present invention.

Claims (10)

1. a geogrid creep test device considering soil constraints is characterized in that, comprising geogrid, test frame, test box, creep detection mechanism and load loading group arranged on the test frame, described There are perforations on the side walls on the opposite sides of the test box, and both ends of the geogrid can be perforated and extended out of the test box; the test box is filled with fillers on the upper and lower sides of the geogrid, and the creep detection There are at least two detection ends of the mechanism, and they are respectively connected with the corresponding preset detection points on the geogrid; the load loading group can output vertical load and horizontal load simultaneously or sequentially; A vertical load is applied on the top, and a horizontal load can be applied to either side of the geogrid; the other side of the geogrid opposite the load-loading group is connected to a test frame or a test box. 2 . A geogrid creep test device considering soil constraints according to claim 1 , wherein the load loading group comprises a stress mechanism capable of applying vertical stress loads and a stress mechanism capable of applying horizontal loads. 3 . A force applying mechanism; the stress mechanism can apply vertical stress to the top of the filler in the test box, and the output end of the force applying mechanism is connected with the geogrid. 3. A geogrid creep test device considering soil constraints according to claim 1 or 2, characterized in that, further comprising a clamping structure, the clamping structure comprising a fixed clamp and a movable clamp, the The fixed fixture and the movable fixture are respectively clamped on both ends of the geogrid under horizontal force; the fixed fixture is connected with the test frame or the test box, and the movable fixture is connected with the output end of the load loading group which applies the horizontal load. 4. A geogrid creep test device considering soil constraints according to claim 3, wherein the fixed fixture and the movable fixture are formed by stacking three upper, middle and lower steel plates in turn The upper steel plate is connected to the lower steel plate through a plurality of bolts through the middle steel plate. The middle and lower steel plates have tooth-shaped occlusion grooves on the matching clamping surfaces, and the tooth-shaped occlusion grooves are provided with rubber gaskets to clamp the geogrid . 5. A geogrid creep test device considering soil constraints according to claim 2, wherein the force applying mechanism comprises a lever, an adjusting member, a counterweight arranged on one end of the lever and one end A traction rope connected to the other end of the lever, the lever and the adjustment member are both installed on the test frame, and the other end of the traction rope bypasses the adjustment member and is connected to the movable clamp on the geogrid; the adjustment member can Adjust the level of the connection end between the traction rope and the geogrid. 6 . A geogrid creep test device considering soil constraints according to claim 1 , wherein the creep detection mechanism comprises a dial indicator and one end connected to the dial indicator measuring end. 7 . Steel wire, the dial indicator is provided with at least two, the other end of the steel wire is fixed on the preset measurement point of the geogrid; the dial indicator is installed on the test frame or the test box. 7 . A geogrid creep test device considering soil constraints according to claim 2 , wherein the stress mechanism is a weight or a hydraulic mechanism with the output end set downward. 8 . 8. A geogrid creep test method considering soil constraint conditions, is characterized in that, comprises the following steps: Step 1. Test preparation, prepare the test frame, test box, creep detection mechanism and load loading group for the test, and debug the equipment until it meets the test requirements, and measure the ultimate tensile strength UTS of the selected geogrid; Step 2. Install the geogrid, fill the test box with filler, fill it in layers according to the preset pressure, and fill it up to the height of the plane where the perforations on both sides are located; then wear the preset specifications in the perforations on both sides. Geogrid, and fix one end of the steel wire at the preset measurement point position of the geogrid, and the other end of the steel wire is perforated from one side; fill the upper side of the geogrid in the test box, and divide it according to the preset pressure. layer filling; Step 3. Install the test equipment, respectively clamp a fixed fixture and a movable fixture on both sides of the geogrid passing through the perforation, and the movable fixture is connected with the force-applying mechanism; and the fixed fixture is fixedly installed on the test box or test frame, and the fixed fixture is fixed. The geogrid on the side where the steel wire passes through; the end of the steel wire passing through the hole is connected to the measuring end of the dial indicator installed on the test frame or test box; Step 4. Test loading, place the installed test equipment at a temperature of 18 to 22 °C and a humidity of 40 to 60% for 0.5 to 1 day; The vertical load of the grid, the vertical load is 10 ~ 18kPa; the horizontal tensile force applied by the force application mechanism to the movable fixture is M% of the ultimate tensile strength UTS of the geogrid, and the loading time is 1min, 2min, 6min, 10min. , 15min, 30min, 60min, 2h, 4h, 8h, 10h, 24h, 50h, 72h, 100h, 200h, 300h, 400h, 500h, 600h, 700h, 800h, 900h, 1000h and 1008h, and record different preset detection points The value of the corresponding dial indicator in the corresponding loading time; Step 5. Repeat steps 2 to 4 at least twice. In each test, the horizontal tensile force applied by the force application mechanism to the movable fixture is increased by Δn% on the basis of the UTS horizontal tensile force value of the last geogrid ultimate tensile strength, and Δn is 6 to 10, and record the value of the dial indicator corresponding to different preset detection points within the corresponding loading time; Step 6, calculation, calculate the strain value of the geogrid corresponding to the preset detection point by using the strain formula to calculate the values on different preset detection points recorded in steps 4 and 5: ε=ΔL/L×100% In the formula: ε is the strain of the bar; ΔL is the creep deformation of the bar, and its unit is mm; L is the effective length of the bar, that is, the net distance between the fixtures, and its unit is mm. 9 . The method for creep testing of a geogrid considering soil constraints according to claim 8 , wherein the steel wire is parallel to the direction in which the force exerting mechanism applies force to the geogrid. 10 . 10 . The method for creep testing of geogrid considering soil constraints according to claim 8 , wherein the measuring end of the dial indicator in step 3 is set horizontally and is at the same level as the steel wire. 11 .

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