CN110763569A - Geogrid creep test device and method considering soil mass constraint conditions - Google Patents
Geogrid creep test device and method considering soil mass constraint conditions Download PDFInfo
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- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
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Abstract
The invention discloses a geogrid creep test device and a geogrid creep test method considering soil mass constraint conditions. The side walls of two opposite sides of the test box are respectively provided with a through hole, the geogrid is arranged in the two through holes in a penetrating way, and two ends of the geogrid extend out of the test box and are respectively connected with the fixed end clamp and the movable end clamp; burying the geogrid in a test box, compacting the filler in layers, and connecting the detection end of the creep detection mechanism with a corresponding preset detection point on the geogrid; the load loading group can output a vertical load and a horizontal load simultaneously or sequentially, wherein the vertical load is applied to the top of the filler in the test box, and the horizontal load is applied to any side of the geogrid; the other side of the geogrid opposite to the load loading group is connected with a test frame or a test box. The test device and the test method have simple and practical structures, and are suitable for simulating the creep property and the strength change characteristic of the geogrid constrained by the soil body under different long-term loads.
Description
Technical Field
The invention relates to the technical field of geosynthetic reinforced retaining walls, in particular to a geogrid creep test device and a geogrid creep test method considering soil mass constraint conditions.
Background
In recent years, the creep characteristics of geosynthetics have been increasingly studied at home and abroad, but they are basically developed for geotextiles or geomembranes; at present, most relevant test standards for short-term or long-term tensile strength of the reinforcement materials at home and abroad specify that the reinforcement materials are stretched under an unconstrained condition and a certain temperature and humidity are kept, strength indexes obtained under the test conditions are used as material characteristic parameters, and the creep property obtained in a creep test under the unconstrained condition is stronger than that of the reinforcement materials under the constrained condition, so that the creep reduction coefficient of the reinforcement materials during engineering design is overlarge, and the application of the reinforcement materials in a reinforced soil structure is influenced. In addition, geogrid, a thermal bonding elastic material, will necessarily exhibit its characteristic creep characteristics under a certain temperature and long-term load. In order to understand the load-deformation behavior of geogrids during creep under the action of temperature, a large number of temperature-accelerated creep tests are carried out by scholars on the geogrids under the unconstrained condition. Therefore, it is necessary to develop a geogrid creep test device and consider the influence of constraint conditions on creep through the geogrid creep test, and to study the creep property and strength change characteristic of the geogrid under different long-term loads.
Disclosure of Invention
The invention aims to at least solve one of the above technical problems and provides a geogrid creep test device and a geogrid creep test method considering soil mass constraint conditions, wherein the test device has a simple structure, is easy to build and is suitable for simulating the creep property and strength change characteristic of the geogrid constrained by the soil mass under different long-term loads indoors; the test method is convenient to operate and high in measurement accuracy.
In order to achieve the purpose, the invention adopts the technical scheme that:
a geogrid creep test device considering soil mass constraint conditions comprises a geogrid, a test frame, test boxes arranged on the test frame, a creep detection mechanism and a load loading group, wherein through holes are respectively formed in the side walls of two opposite sides of each test box, and two ends of the geogrid can pass through the through holes and extend out of the test boxes; the upper side and the lower side of the geogrid of the test box are filled with fillers, and at least two detection ends of the creep detection mechanism are arranged and are respectively connected with corresponding preset detection points on the geogrid; the load loading group can output a vertical load and a 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 on any side of the geogrid; the other side of the geogrid opposite to the load loading group is connected with a test frame or a test box.
As an improvement of the above technical solution, the load loading group comprises a stress mechanism capable of applying a vertical stress load and a force application mechanism capable of applying a horizontal load; the stress mechanism can apply vertical stress to the top of the filler in the test box, and the output end of the force application mechanism is connected with the geogrid to apply horizontal tension to the geogrid.
As an improvement of the above technical scheme, the geogrid clamp further comprises a clamping structure, wherein the clamping structure comprises a fixed clamp and a movable clamp, and the fixed clamp and the movable clamp are respectively clamped at two ends of the geogrid which are horizontally stressed; the fixed clamp is connected with the test frame or the test box, and the movable clamp is connected with the output end of the load loading group for applying horizontal load.
As an improvement of the technical scheme, the fixed clamp and the movable clamp are formed by sequentially stacking three upper, middle and lower steel plates, the upper steel plate penetrates through the middle steel plate and is connected with the lower steel plate through a plurality of bolts, tooth-shaped occlusion grooves are formed in the middle steel plate and the lower steel plate on the matched clamping surfaces, and rubber gaskets are arranged on the tooth-shaped occlusion grooves and used for clamping the geogrid.
As an improvement of the technical scheme, the force application mechanism comprises a lever, an adjusting component, a balance weight arranged at one end of the lever and a traction pull rope with one end connected to the other end of the lever, the lever and the adjusting component are both arranged on the test frame, and the other end of the traction pull rope bypasses the adjusting component and is connected with a movable clamp on the geogrid; the adjusting component can adjust the levelness of the connecting end of the traction pull rope and the geogrid.
As an improvement of the technical scheme, the creep deformation detection mechanism comprises a dial indicator and at least two steel wires with one ends connected to the measuring ends of the dial indicator, and the other ends of the steel wires are fixed on a preset measuring point of the geogrid; the dial indicator is arranged on the test frame or the test box.
As an improvement of the technical scheme, the stress mechanism is a weight or a hydraulic mechanism with a downward output end.
The invention also provides a geogrid creep test method considering the soil mass constraint condition, which comprises the following steps:
step 1, preparing a test frame, a test box, a creep deformation detection mechanism and a load loading group for the test, debugging equipment until the equipment meets the test requirement, and measuring the ultimate tensile strength UTS of the selected geogrid;
and 6, calculating, namely calculating the values recorded in the steps 4 and 5 at different preset detection points through a strain formula to obtain strain values corresponding to the geogrids at the preset detection points:
ε＝ΔL/L×100％
in the formula: epsilon is strain of the rib material; delta L is creep deformation of the rib material, and the unit of delta L is mm; l is the effective length of the bar, i.e. the clear distance between the clamps, and is in mm.
As an improvement of the above technical scheme, the steel wire is parallel to the force application direction of the force application mechanism to the geogrid.
As an improvement of the technical scheme, in the step 3, the measuring end of the dial indicator is horizontally arranged and is positioned on the same horizontal plane with the steel wire.
Compared with the prior art, the beneficial effects of this application are:
a geogrid creep test device considering soil body constraint conditions applies horizontal and vertical stress to a geogrid buried in a test box by adopting a load loading group respectively, and can effectively simulate the load condition borne by a reinforced retaining wall in the service process in actual engineering; due to the design of the through holes on the two opposite sides of the test box, the influence of the test box on the geogrid can be avoided when the geogrid is horizontally pulled by the load loading group; the stress conditions of different preset detection points of the geogrid in the test loading process can be measured by the creep detection mechanism, so that testers can observe the stress conditions of different measurement points in the test box more visually, and the accuracy of a simulation test is improved. This geogrid creep test device can effectively simulate out the creep condition of geogrid after receiving the load with muscle retaining wall in the actual road through simple model design, and the tester of being convenient for designs better the muscle retaining wall, improves the security of engineering structure. The invention also provides a geogrid creep test method considering the soil body constraint conditions, the method is simple to operate and convenient to realize, the creep condition of the geogrid in the actual engineering structure can be effectively simulated, and the measurement is convenient and reliable.
Drawings
The following detailed description of embodiments of the invention is provided in conjunction with the appended drawings, in which:
FIG. 1 is a first schematic structural diagram according to an embodiment of the present invention;
FIG. 2 is a second schematic structural diagram according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of creep loading stress according to an embodiment of the present invention;
fig. 4 is a schematic view of the assembly of a geogrid according to an embodiment of the present invention;
fig. 5 is a graph of tensile properties of a test geogrid specimen according to an embodiment of the present invention;
FIG. 6 is a cumulative particle size plot of fillers in accordance with an embodiment of the present invention;
fig. 7 is a graph of geogrid ultimate tensile strength UTS equal to 62% in an embodiment of the present invention;
fig. 8 is a graph of geogrid ultimate tensile strength UTS equal to 72% in an embodiment of the present invention;
fig. 9 is a graph showing the ultimate tensile strength UTS of the geogrid equal to 82% in the example of the present invention.
Detailed Description
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, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It will be understood that when an element is referred to as being "secured to" another element, it can be directly on the other element or intervening elements may also be present. When a component is referred to as being "connected" to another component, it can be directly connected to the other component or intervening components may also be present. When a component is referred to as being "disposed on" another component, it can be directly on the other component or there can be intervening components, and when a component is referred to as being "disposed in the middle," it is not just disposed in the middle, so long as it is not disposed at both ends, but rather is within the scope of the middle. The terms "vertical," "horizontal," "left," "right," and the like as used herein are for illustrative purposes only.
Unless defined otherwise, 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 terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the 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 fig. 1 to 9, the invention provides a geogrid creep test device considering a soil mass constraint condition, which comprises a test frame 1, a test box 2 arranged on the test frame 1, a creep detection mechanism 3 and a load loading group 4, wherein through holes 21 are arranged on the side walls of two opposite sides of the test box 2, geogrids 5 are arranged in the two through holes 21, and two ends of the geogrids 5 movably extend out of the test box 2; the upper side and the lower side of the geogrid 5 of the test box 2 are filled with fillers 6, and at least two detection ends of the creep detection mechanism 3 are arranged and are respectively connected with corresponding preset detection points on the geogrid 5; the load loading group 4 can output a vertical load and a horizontal load simultaneously or sequentially; the load loading group 4 can apply vertical load to the top of the filler 6 in the test box 2; the load loading group 4 can apply horizontal loads to either side of the geogrid 5; the other side of the geogrid 5 opposite to the load loading group 4 is connected with the test frame 1 or the test box 2. In practical experiments, two load loading groups 4 can be adopted, and the load loading groups 4 only need to output vertical loads or horizontal loads, so that the complexity of the whole load loading group 4 is reduced. In this application, vertical load mainly is that the simulation reinforced earth barricade bears superstructure dead weight and combines the traffic load on the road surface under the in service state, consequently can adopt the stress of directional continuous output. The horizontal load mainly bears the pulling force of the reinforced retaining wall to the inside in the uneven stress state or the damaged state for a long time, in practical conditions, the probability that the pulling force appears relatively in the damaged state is small, the damaged reinforced retaining wall does not need to be tested, and the horizontal load can be acquiescent mainly by the pulling force borne by the reinforced retaining wall in different regions when the stress is uneven for the purpose of simple design. The test box 2 is designed to have a structure with four closed sides, mainly to realize the structure of the whole reinforced retaining wall unit, and the through holes 21 mainly reduce the influence of the side walls of the test box 2 on the geogrid 5 in the test process. The filler 6 is basically a soil body or a gravel structure under the actual condition, and in order to realize the simplicity and facilitate the data measurement, the filler 6 adopts river sand with medium specification.
In order to better apply the load, the load loading group 4 in another embodiment of the present application includes a stress mechanism 41 capable of applying a vertical stress load and a force application mechanism 42 capable of applying a horizontal load; the stress mechanism 41 can apply vertical stress to the top of the filler 6 in the test box 2, and the output end of the force application mechanism 42 is connected with the geogrid 5. By adopting a split force application mode, the whole test device can be effectively designed, and meanwhile, the load application conditions in different directions can be conveniently controlled. In order to better clamp the geogrid 5, the test device further comprises a clamping structure 7, wherein the clamping structure 7 comprises a fixed clamp 71 and a movable clamp 72, and the fixed clamp 71 and the movable clamp 72 are respectively clamped at two horizontally stressed ends of the geogrid 5; the fixed clamp 71 is connected with the test frame 1 or the test box 2, and the movable clamp 72 is connected with 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 application mechanism 42, and the movable clamp 72 can realize large-area clamping, so that the situation of stress concentration when the output end of the force application mechanism 42 is directly connected to the geogrid 5 is avoided. In order to better hold and not damage the structure of the geogrid 5, rubber gaskets 73 are arranged on the holding action surfaces of the fixed clamp 71 and the movable clamp 72. In another embodiment of the present application, the fixed clamp 71 and the movable clamp 72 are formed by stacking three upper, middle and lower steel plates in sequence, the upper steel plate passes through the middle steel plate and is connected with the lower steel plate through a plurality of bolts, the middle and lower steel plates have tooth-shaped engaging grooves on the matched clamping surfaces, and the tooth-shaped engaging grooves are provided with rubber gaskets 73 for clamping the geogrid 5.
Referring to fig. 1 to 4, in order to increase or decrease the magnitude of the horizontal load, the forcing mechanism 42 includes a lever 421, an adjusting member 422, a weight 423 disposed at one end of the lever 421, and a pull rope 424 having one end connected to the other end of the lever 421. The lever 421 and the adjusting member 422 are both installed on the test frame 1, and the other end of the traction pull rope 424 is connected with the movable clamp 72 on the geogrid 5 by bypassing the adjusting member 422; the adjusting member 422 can adjust the levelness of the end of the pulling rope 424 connected with the geogrid 5. The lever 421 can effectively reduce the demand of the integral counterweight 423, and the torque ratio of the two ends of the lever 421 in the test is 1: 6, i.e., the moment of the lever 421 at one end of the weight 423 is 6 times the moment at the other end of the lever 421. In addition, the design can effectively reduce the situation that the conventional equipment is difficult to insist on applying load for a long time. In another embodiment of the present application, the middle of the lever 421 is mounted on the test frame 1 through a rotating sleeve in practical use, and the lever 421 itself can slide in the rotating sleeve, so that the ratio of the moments at the two ends can be adjusted. The adjusting member 422 is mainly used for adjusting the levelness of the end of the whole pulling rope 424 connected with the geogrid 5, so that the geogrid 5 is pulled horizontally to facilitate later calculation, and meanwhile, the influence of contact between the geogrid 5 and the test box 2 in the stress process is reduced. And because the test loading time is long, stress mechanism 41 is the hydraulic pressure mechanism that weight or output set up downwards in this application, and it is then more simple and convenient to utilize the weight, can keep constant load for a long time, and the later stage loading of being convenient for is then selected hydraulic pressure mechanism.
Referring to fig. 4, in order to better measure the deformation amount of the geogrid 5, the creep detection mechanism 3 includes a dial indicator 31 and a steel wire 32 having one end connected to the measuring end of the dial indicator 31. The dial indicator 31 is provided with at least two, the other end of the steel wire 32 is fixed on a preset measuring point on the geogrid 5, and the dial indicator 31 is installed on the test frame 1 or the test box 2. The dial indicator 31 is often used for measuring the length of shape, position error and small displacement, and the design similar to a micrometer can effectively ensure the measuring accuracy due to the fact that a large number of scales are arranged in the dial indicator. Utilize steel wire 32 to carry out each measurement section deformation of conduction geogrid 5, whole thinking is novel, and deformation conduction is accurate, and the influence that self deformation caused to percentage table 31 measurement in the conduction process can effectively be avoided to tiny and the rigidity of steel wire 32 is big. In actual measurement, after the geogrid 5 is subjected to the comprehensive action of vertical load and horizontal load, deformation towards one side of the output end of the horizontal load is inevitably generated, the dial indicator 31 is in the opposite direction of the horizontal load, the deformation quantity of the geogrid 5 is directly transmitted into the dial indicator 31 through the steel wire 32, the dial indicator 31 displays the deformation value of the preset detection point on the geogrid 5, the strain value can be obtained through a deformation calculation formula, and then the creep reduction coefficient is determined.
According to the geogrid creep test device, the load loading group 4 is adopted to apply horizontal and vertical stress to the geogrid 5 embedded in the test box 2 respectively, so that the load condition borne in the actual reinforced earth retaining wall structure can be effectively simulated; the design of the opposite side wall through holes 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 horizontally pulls the geogrid 5; the creep detection mechanism 3 can be used for measuring the stress conditions of different preset detection points of the geogrid 5 in the test loading process, so that testers can observe the deformation of different measurement points in the test box 2 more intuitively, and the accuracy of test simulation is improved. This geogrid creep test device can effectively simulate out the creep condition of geogrid after receiving the load with muscle retaining wall in the actual road through simple model design, and the tester of being convenient for designs better the muscle retaining wall, improves the security of engineering structure.
In addition, the invention also provides a geogrid creep test method considering the soil mass constraint condition, which comprises the following steps:
step 1, preparing a test, namely preparing a test frame 1, a test box 2, a creep deformation detection mechanism 3 and a load loading group 4 for the test, debugging equipment until the equipment meets the test requirement, and measuring the ultimate tensile strength UTS of the selected geogrid 5;
and 6, calculating, namely calculating recorded values on different preset detection points recorded in the step 4 and the step 5 through a strain formula to obtain strain values corresponding to the geogrid 5 on the preset detection points:
ε＝ΔL/L×100％
in the formula: epsilon is strain capacity of the reinforcement; delta L is creep deformation mm of the rib material; l is the effective length of the bar, i.e. the clear distance between the clamps, and is in mm.
Three specific tests are given in the method, the set environmental conditions are that the indoor temperature is 20 ℃ and the humidity is 50%, the geogrid 5 of the test adopts a bidirectional geogrid, the type of the bidirectional geogrid can be selected from TGSG-3030, and a conventional tensile test under an unconstrained condition is carried out according to the corresponding standard of specification 'geosynthetic material test procedure' SL235-2012, the ultimate tensile strength of the test is about 29.5kN/m, and the peak failure strain is about 10.3%. The tensile properties of the test geogrid are shown in fig. 5. The filler 6 is medium sand with good grain composition, the uniformity coefficient Cu is 8.44, the curvature coefficient Cc is 1.15, the relative density of soil grains is 2.65, the maximum dry density is 1.69g/cm3, the internal friction angle is 39 degrees, and the grain composition curve is shown in figure 6 in detail. In addition, the standing time is preferably 1 day before the test loading, and the stress mechanism 41 does not apply stress to the top of the filler 6 in the test box 2, so that the aim of keeping the environment and the display of the geogrid 5 and the filler 6 consistent is mainly achieved, and the measurement accuracy in the later period is improved.
In addition, M of the ultimate tensile strength UTS in the above step 4 is 62%, i.e., the first test horizontal tensile force is 62% of the ultimate tensile strength UTS, and Δ n is 10 selected in this example, i.e., 10% of tensile load is added to each test based on the previous test, and the test is performed at room temperature of 20 ℃ and humidity of 50%. The test is carried out in three groups, namely the ultimate tensile strength UTS of each group is respectively 62%, 72% and 82%. When shearing geogrid 5 sample, in order to be able to be better by the both ends of movable clamp 72 and the centre gripping of mounting fixture 71, the length of geogrid 5 sample of shearing compares whole test box 2 and wants long, be convenient for geogrid 5 both sides to wear out from the both sides perforation 21 of test box 2 like this, the operation workman presss from both sides the one end that geogrid 5 corresponds respectively through movable clamp 72 and mounting fixture 71, then fix mounting fixture 71, movable clamp 72 connects on the input of pulling the stay cord 424, increase promptly at the final counter weight 423 on one end of lever 421 promptly in the stipulated time promptly, counter weight 423 turns into the dead weight through the moment coefficient of lever to the pulling force of movable clamp 72 and geogrid 5, can realize creep test like this. The ultimate tensile strengths of different preset detection points of the ultimate tensile strength UTS of each set of tests are different, and can be seen in fig. 7, 8 and 9; fig. 7 is a creep curve diagram of different measurement points when the ultimate tensile strength UTS is equal to 62%, fig. 8 is a creep curve diagram of different measurement points when the ultimate tensile strength UTS is equal to 72%, and fig. 9 is a creep curve diagram of different measurement points when the ultimate tensile strength UTS is equal to 82%. In addition, 5 samples of the geogrid are provided with 5 preset detection points which are A, B, C, D, E five preset detection points respectively, and the development situation that the creep deformation of different detection sections of the geogrid changes along with time is basically similar under different load levels can be seen through the deformation amount between every two adjacent preset detection points. From different section angle analyses of survey of geogrid sample, geogrid 5AB section is close to the expansion end anchor clamps position promptly, and each curve increases nearly linearly along with the time growth, and geogrid 5's tensile modulus reduces gradually, and the curve development situation is gradually gentle, shows that geogrid 5 has apparent viscoelasticity deformation characteristic. And the BC section and the CD section of the geogrid are continuously increased along with the load holding time of the geogrid, the creep deformation of the geogrid is sequentially reduced, and the peak values of the creep deformation are sequentially about 64 percent and 21 percent of the deformation peak value of the AB section. The phenomenon is mainly caused because when the reinforced retaining wall complex is acted with overlying load, the reinforced retaining wall is internally provided with friction force between the ribs and the filler interface and has an embedding and meshing effect, and meanwhile, because the material attribute of the geogrid 5 is high polymer, the geogrid is subjected to uneven distribution of horizontal tension under the restraint of the filler 6, namely sandy soil, so that the creep deformation of the geogrid is mainly generated near the stretching end, namely an AB section. And (4) conclusion: with the increase of creep load level under the restriction of sandy soil, the more obvious the creep phenomenon of the geogrid 5 is, and the larger the creep strain and creep rate are. When the geogrid 5 is under lower stress, the creep rate is increased and then decreased, and the geogrid quickly tends to be stable; at higher stresses, the creep rate is higher and tends to be substantially stable over a long period of time.
In order to further improve the accuracy of the whole test data, the steel wire 32 is parallel to the force applying direction of the force applying mechanism 42 on the geogrid 5, so that the influence of the steel wire 32 on the test box 2 during measurement is reduced. In addition, the measuring end of the dial indicator 31 in the step 3 is horizontally arranged and is positioned at the same horizontal plane with the steel wire 32, so that component force in other directions is avoided when the measuring end of the dial indicator 31 is stressed, and the measuring precision is improved.
The geogrid creep test method considering the soil body constraint conditions is simple to operate and convenient to implement, can effectively simulate the creep condition of the geogrid 5 in a practical engineering structure, and is convenient and reliable to measure.
The above embodiments are only for illustrating the technical solutions of the present invention and are not limited thereto, and any modification or equivalent replacement without departing from the spirit and scope of the present invention should be covered within the technical solutions of the present invention.
Claims (10)
1. A geogrid creep test device considering soil mass constraint conditions is characterized by comprising a geogrid, a test frame, test boxes arranged on the test frame, a creep detection mechanism and a load loading group, wherein through holes are respectively formed in the side walls of two opposite sides of each test box, and two ends of the geogrid can pass through the through holes and extend out of the test boxes; the upper side and the lower side of the geogrid of the test box are filled with fillers, and at least two detection ends of the creep detection mechanism are arranged and are respectively connected with corresponding preset detection points on the geogrid; the load loading group can output a vertical load and a 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 on any side of the geogrid; the other side of the geogrid opposite to the load loading group is connected with a test frame or a test box.
2. The geogrid creep test device considering the soil mass constraint conditions, according to claim 1, wherein the load loading group comprises a stress mechanism capable of applying a vertical stress load and a force application mechanism capable of applying a horizontal load; the stress mechanism can apply vertical stress to the top of the filler in the test box, and the output end of the force application mechanism is connected with the geogrid.
3. The geogrid creep test device considering the soil mass constraint conditions according to claim 1 or 2, characterized by further comprising a clamping structure, wherein the clamping structure comprises a fixed clamp and a movable clamp, and the fixed clamp and the movable clamp are respectively clamped at two ends of the geogrid which are horizontally stressed; the fixed clamp is connected with the test frame or the test box, and the movable clamp is connected with the output end of the load loading group for applying horizontal load.
4. The geogrid creep test device considering the soil mass constraint condition according to claim 3, wherein the fixed clamp and the movable clamp are formed by sequentially stacking three upper, middle and lower steel plates, the upper steel plate penetrates through the middle steel plate to be connected with the lower steel plate through a plurality of bolts, toothed meshing grooves are formed in the middle and lower steel plates on the matched clamping surfaces, and rubber gaskets are arranged on the toothed meshing grooves to clamp the geogrid.
5. The geogrid creep test device considering the soil mass constraint conditions is characterized in that the force application mechanism comprises a lever, an adjusting component, a balance weight arranged at one end of the lever and a traction pull rope with one end connected to the other end of the lever, the lever and the adjusting component are both arranged on a test frame, and the other end of the traction pull rope bypasses the adjusting component and is connected with a movable clamp on the geogrid; the adjusting component can adjust the levelness of the connecting end of the traction pull rope and the geogrid.
6. The geogrid creep test device considering the soil mass constraint conditions is characterized in that the creep detection mechanism comprises at least two dial indicators and steel wires, one ends of the steel wires are connected to the measuring ends of the dial indicators, and the other ends of the steel wires are fixed to preset measuring points of the geogrid; the dial indicator is arranged on the test frame or the test box.
7. The geogrid creep test device considering the soil mass constraint conditions is characterized in that the stress mechanism is a weight or a hydraulic mechanism with a downward output end.
8. A geogrid creep test method considering soil mass constraint conditions is characterized by comprising the following steps:
step 1, preparing a test frame, a test box, a creep deformation detection mechanism and a load loading group for the test, debugging equipment until the equipment meets the test requirement, and measuring the ultimate tensile strength UTS of the selected geogrid;
step 2, installing geogrids, filling fillers in the test box, performing layered filling according to preset pressure, and filling until the fillers are flush with the plane where the through holes on the two sides are located; then, inserting geogrids with preset specifications into the through holes on the two sides, fixing one end of a steel wire at a preset measuring point position of the geogrids, and enabling the other end of the steel wire to penetrate through the through hole on one side; filling filler on the upper side of the geogrid in the test box, and performing layered filling according to preset pressure;
step 3, mounting test equipment, respectively clamping a fixed clamp and a movable clamp at two sides of the geogrid penetrating through the through hole, wherein the movable clamp is connected with a force application mechanism; the fixing clamp is fixedly arranged on the test box or the test frame, and clamps the geogrid at one side through which the steel wire penetrates; one end of the steel wire penetrating through the through hole is connected with a measuring end of a dial indicator arranged on the test frame or the test box;
step 4, loading a test, namely standing the mounted test equipment for 0.5-1 day under the conditions that the temperature is 18-22 ℃ and the humidity is 40-60%; the stress mechanism applies a vertical load perpendicular to the geogrid to the filler in the test box, and the vertical load is 10-18 kPa; the horizontal tension applied to the movable clamp by the force application mechanism is M% of the ultimate tensile strength UTS of the geogrid, 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 the numerical values of the dial indicators corresponding to different preset detection points in the corresponding loading time are recorded;
step 5, repeating the steps 2 to 4 at least twice, increasing the horizontal tension applied to the movable clamp by the force application mechanism in each test by delta n% on the basis of the last geogrid ultimate tensile strength UTS horizontal tension value, wherein the delta n is 6-10, and recording the numerical values of corresponding dial indicators of different preset detection points in corresponding loading time;
and 6, calculating, namely calculating the values recorded in the steps 4 and 5 at different preset detection points through a strain formula to obtain strain values corresponding to the geogrids at the preset detection points:
ε＝ΔL/L×100％
in the formula: epsilon is strain of the rib material; delta L is creep deformation of the rib material, and the unit of delta L is mm; l is the effective length of the bar, i.e. the clear distance between the clamps, and is in mm.
9. The geogrid creep test method considering the soil mass constraint condition according to claim 8, wherein the steel wire is parallel to the force application direction of the force application mechanism to the geogrid.
10. The geogrid creep test method considering the soil mass constraint conditions according to claim 8, wherein the measuring end of the dial indicator in the step 3 is horizontally arranged and is positioned at the same horizontal plane with the steel wire.
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