CN103217345B - Device and method for measuring actual triaxial creep of geotechnical engineering test specimen - Google Patents

Abstract

The invention discloses a device for measuring the true triaxial creep of a geotechnical engineering test block, which includes a support structure, four surrounding pressure plates and upper and lower pressure plates to form a closed cavity for enclosing the test block The confining pressure plate includes two long confining pressure plates and two short confining pressure plates. The upper and lower pressure plates are rectangular top steel plates and bottom steel plates. ”-shaped long enclosure plate, and two “L”-shaped short enclosure plates bent outward on the remaining two sides, the bottom of the short enclosure plate is placed on the bottom steel plate; The steel plate is in close contact with the inner side of the two short surrounding pressure plates; the inside of the support structure is corresponding to the four surrounding pressure plates and the upper and lower pressure plates are vertically provided with pressure sensors, and the pressure sensors are equipped with grating scales. The invention also provides a method for measuring true triaxial creep of geotechnical engineering test blocks by using the device.

Description

Device and method for measuring true triaxial creep of geotechnical engineering test block

technical field

The invention relates to a device and method for measuring the true triaxial creep of a geotechnical engineering test block.

Background technique

Creep refers to the phenomenon that the strain of a solid material increases with time under the condition of keeping the stress constant. It is different from plastic deformation, which usually occurs after the stress exceeds the elastic limit, and creep can occur when the stress is less than the elastic limit, as long as the stress is applied for a long time.

Creep phenomenon is very common in geotechnical engineering, and many geotechnical engineering disasters are also closely related to rock and soil creep, such as landslides, landslides, foundation settlements, etc. Important guarantee.

In the past, creep tests in geotechnical engineering often stayed on uniaxial and pseudo-triaxial tests. The uniaxial test ignored the influence of the confining pressure of the test block, and the pseudo-triaxial test ignored the inequalities of the pressure in each direction of the test block. These cannot accurately reflect the real stress and creep behavior of rock and soil under actual conditions. True triaxial creep test instruments for rock and soil at home and abroad are very rare, with very complex structures, relatively large scale, cumbersome operations, and expensive prices, and are only used in high-strength creep tests. For triaxial creep tests under low-strength conditions Changes often lose accuracy. At present, the research on the creep phenomenon of rock and soil under the condition of low strength is relatively lacking.

Contents of the invention

The object of the present invention is to provide a device and method for measuring the true triaxial creep of a geotechnical engineering test block in order to overcome the above-mentioned deficiencies in the prior art.

To achieve the above object, the present invention adopts the following technical solutions:

A device for measuring the true triaxial creep of a geotechnical engineering test block includes a support structure, and the device also includes four surrounding pressure plates and upper and lower pressure plates to form a closed cavity that wraps the test block; the surrounding The pressing plate includes two long surrounding pressing plates and two short surrounding pressing plates. The upper and lower pressing plates are rectangular top steel plates and bottom steel plates. "L" shaped long enclosure, and two "L" shaped short enclosures bent outwards on the remaining two sides, the bottom of the short enclosure is placed on the bottom steel plate; the length of the long enclosure A top steel plate is set up at the top, and the top steel plate is in close contact with the inner surfaces of the two short surrounding pressure plates; the inside of the support structure is corresponding to the four surrounding pressure plates and the upper and lower pressure plates are vertically provided with pressure sensors, and the pressure There are grating rulers on the sensors.

The support structure includes a bottom plate and a "cross"-shaped top steel bracket, the four ends of the top steel bracket are respectively connected to the bottom plate through side steel brackets; the center of the bottom plate and the center of the side steel brackets are facing inward Equipped with hydraulic jack.

The lower end of the intersection of the top steel bracket is connected to the connecting steel sheet I, and the hydraulic jack is respectively connected to the connecting steel sheets II-VI through pressure sensors. The lower end of the connecting steel sheet I is provided with a top pulley, and the connecting steel sheet II The top of the top is provided with a bottom pulley, and the connecting steel sheets III～VI are all provided with lateral pulleys towards the inside; the top pulley supports the top steel plate, and the bottom pulley supports the bottom steel plate for placing the square test block. The four sides are closely attached to the two long surrounding pressure plates and the two short surrounding pressure plates respectively; the lateral pulleys support the outer surfaces of the four surrounding pressure plates.

The shoulder inner side and the bottom of the surrounding pressure plate are respectively provided with a shoulder pulley of the surrounding pressure plate and a bottom pulley of the surrounding pressure plate.

The method for measuring the true triaxial creep of the geotechnical engineering test block by using the above-mentioned device, the specific steps are as follows:

1) Assemble the test device to form a closed cavity to wrap the test block;

2) Pre-compression, so that the inside of the support structure is in contact with the four surrounding pressure plates and the upper and lower pressure plates, and keeps them stable;

3) Adjust the indication of the pressure sensor corresponding to the bottom steel plate to make it zero, and record the initial reading of the corresponding grating scale;

4) Adjust the hydraulic jacks in the x-axis, y-axis, and z-axis directions respectively, so that the readings of the pressure sensors in the three directions reach the set values respectively and keep them stable; the set values range from 0 to 5 MPa;

5) Measure the creep displacement in the x-direction and y-direction, and take the rising distance of the bottom steel plate as the axial creep displacement of the test piece.

The specific method of step 1) is as follows: set up the support structure, set the bottom steel plate on the bottom of the support structure, set up two long enclosure pressure plates on the adjacent sides of the bottom steel plate; place the test block on the bottom steel plate, And close to the long confining compression plate, place the two short confining compression plates on the bottom steel plate, and contact with the test block; place the top steel plate on the long confining compression plate, contact with the sides of the two short confining compression plates, forming a closed cavity to wrap the test block .

The specific method of setting up the supporting structure is: connecting the four ends of the "ten"-shaped top steel bracket to the bottom plate through the side steel brackets; the center of the bottom plate and the center of the side steel brackets are respectively installed hydraulic jacks towards the inside; The lower end of the intersection of the top steel bracket is connected to the connecting steel sheet I, and the hydraulic jack is respectively connected to the connecting steel sheets II~VI through pressure sensors. Bottom pulleys are installed on the top of sheet II, and lateral pulleys are installed on the connecting steel sheets III-VI towards the inside; the top pulley supports the top steel plate, the bottom pulley supports the bottom steel plate, and the lateral pulley supports the outer sides of the four surrounding pressure plates.

In the step 5), the specific method of measuring the creep displacement in the x-direction and the y-direction is: measure once every 30 minutes within 1 day, and measure once every 2 hours after 1 day.

Working principle of the present invention:

1 The square test block is surrounded by four sets of surrounding steel plates, and the confining pressure is approximated by the extrusion of the four steel plates;

2. The four groups of steel plates adopt the "windmill" overlapping method, and the relative position can be changed freely within a certain range when the lateral force is applied;

3 Ball pulleys are placed between the contact surfaces of the four groups of steel plates to reduce frictional resistance and overcome the bias effect at the same time;

4 The upper and lower sets of baffles of the test block are misplaced and overlapped, and each covers two sets of surrounding steel plates to ensure the free deformation of the test block when axial force is applied;

5 The pressure sensor is connected to the outer side of the steel plate through a ball pulley, and the lateral stress is applied by hydraulic jack pressure, and the sensor can accurately control the pressure;

6 Gravity loading cannot realize the axial pressurization of this device. This device adopts the method of extruding the test block from bottom to top, which ensures the stability of the whole device.

The present invention realizes the three-way loading of the test block through the slidable overlapping of four groups of surrounding pressure plates and the upper and lower pressure plates. The four sets of surrounding pressure plates adopt the "windmill" lap joint method, and the relative positions can be changed freely within a certain range when the lateral force is applied, ensuring the independence of the force in the x and y directions; the upper and lower pressure plates are connected with the two groups The staggered lap connection of the lateral steel plates ensures the independence of the z-axis force of the test block; the "windmill" surrounding structure can make the test block receive unequal confining pressure laterally, and can ensure that the test block is laterally Free deformation ensures the independence of lateral pressure.

Ball pulleys are placed between the contact surfaces of the four sets of surrounding pressure plates, which reduces frictional resistance and can slide freely relative to each other. The four sets of confining pressure plates adopt an "L"-shaped design shape, which overcomes the bias effect of the confining pressure plates during the movement process. The outer side of the pressure plate is in contact with the pressure sensor in the form of a pulley, which ensures that the axial pressure is along the axial direction of the specimen, and at the same time ensures the independence of the axial pressure.

Through two sets of "L"-shaped long side pressure plates and two sets of "L"-shaped short side pressure plates overlapped up and down, the free deformation of the test block under axial force is realized, and the axial force of the test block is guaranteed at the same time. independence. The outer side of the "L"-shaped steel plate is in contact with the pressure sensor in the form of a pulley, which ensures that the device is pressurized along the axis of the test block, and at the same time ensures the independence of the axial pressure and lateral pressure of the test block. Pressurization is achieved by hydraulic jacks to ensure constant pressure. Precise and constant control of the pressure is achieved using a pressure sensor. The three-way displacement of the test block is measured by a grating ruler, which greatly improves the experimental accuracy.

The invention overcomes the difficulties encountered in the previous true triaxial creep. The "windmill" surrounding structure can make the test block receive unequal confining pressure laterally, and can deform freely. The use of ball pulleys reduces the surrounding steel plate. friction between them, and can move freely within a certain range; the electronic pressure sensor controls the pressurization method of the hydraulic jack to accurately and constantly pressurize the rock and soil test block, ensuring the accuracy of the experiment; the axial pressure adopts bottom-up The way of pressing up ensures the free deformation of the test block in the axial direction and ensures the stability of the whole device.

The beneficial effect of the present invention is,

1. The present invention solves many inconveniences in previous experiments, and realizes the simulation experiment of test block creep under low pressure conditions.

2. Hydraulic jack pressurization is simple and easy to implement, easy to adjust;

3. The deformation of the creep process is relatively slow, and the test period is long. The automatic regulation and pressure of the hydraulic jack ensures the accuracy of the experiment, which is sufficient to meet the needs of low-strength creep experiments;

4. The installation of the pressure sensor ensures the constant creep confining pressure and the accuracy of the low-intensity true triaxial creep experiment.

5. The method of extruding the test block from bottom to top ensures the stability of the whole device.

6. The grating ruler is used to measure the displacement of the test block, which improves the test accuracy.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is the structural representation of support structure;

Fig. 3 is a side view of the direction of the short enclosure pressure plate;

Fig. 4 is a side view of the direction of the long enclosure pressure plate;

Fig. 5 is the view before loading test block;

Fig. 6 is the view after loading test block;

Among them, 1 fixing screw 2. Top steel bracket 3. Side steel bracket 4. Grating ruler 5. Bottom plate 6. Hydraulic jack 7. Lateral pulley 8. Connecting steel sheet II9. Bottom pulley 10. Pressure sensor 11. Top steel plate 12. Short surrounding pressing plate 13. Long surrounding pressing plate 14. Bottom steel plate 15. Enclosing pressing plate shoulder pulley 16. Enclosing pressing plate bottom pulley.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and embodiments. It should be noted that the following description is only for explaining the present invention and not limiting its content.

The present invention includes a support structure, and the inside of the support structure slides and overlaps four confining pressure plates and upper and lower pressure plates to form a closed cavity for wrapping the test block; the confining pressure plates include two long confining pressure plates 13 and two short confining pressure plates 14. The upper and lower pressure plates are rectangular top steel plates 11 and bottom steel plates 14. Two "L" shaped long enclosure pressure plates 13 bent outwards are set up on the adjacent two sides of the bottom steel plate 14, and the remaining two Two "L" shaped short enclosures 12 bent outwards are set up on the side, and the bottom of the short enclosures 12 is placed on the bottom steel plate 14; the top of the long enclosure 13 is provided with a top steel plate 11, which is connected with two The inner side of the short confining pressure plate 12 is close to it; the inside of the support structure corresponds to the four confining pressure plates and the upper and lower pressure plates are vertically provided with pressure sensors 10, and the pressure sensors 10 are equipped with grating rulers 4.

The supporting structure includes a bottom plate 5 and a "ten"-shaped top steel bracket 2. The four ends of the top steel bracket 2 are respectively connected to the bottom plate 5 through side steel brackets 3, and the joints are fixedly connected by fixing screws 1; the center and side of the bottom plate 5 The central part of the steel bracket 3 is provided with a hydraulic jack 6 towards the inside respectively.

The lower end of the intersection of the top steel bracket 2 is connected with the connecting steel sheet I, and the hydraulic jack 6 is respectively connected with the connecting steel sheet II8, connecting steel sheet III, connecting steel sheet IV, connecting steel sheet V, and connecting steel sheet VI through the pressure sensor 10, The lower end of the connecting steel sheet I is provided with a top pulley, the top of the connecting steel sheet II8 is provided with a bottom pulley 9, and the connecting steel sheets III～VI are provided with a lateral pulley 7 towards the inside; the top pulley supports the top steel plate 11, and the bottom pulley 9 Support the bottom steel plate 14 for placing the square test block, the four sides of the test block are respectively closely attached to the two long surrounding pressure plates 13 and the two short surrounding pressure plates 12; the lateral pulley 7 supports the outer sides of the four surrounding pressure plates .

The inner side and bottom of the shoulder of the surrounding pressure plate are respectively provided with a shoulder pulley 15 of the surrounding pressure plate and a pulley 16 at the bottom of the surrounding pressure plate.

The method for measuring the true triaxial creep of the geotechnical engineering test block by using the above-mentioned device, the specific steps are as follows:

1) Assemble the test device to form a closed cavity to wrap the test block;

2) Pre-compression, so that the inside of the support structure is in contact with the four surrounding pressure plates and the upper and lower pressure plates, and keeps them stable;

3) Adjust the reading of the pressure sensor 10 corresponding to the bottom steel plate 14 to return to zero, and record the initial reading of the corresponding grating scale 4;

4) Adjust the hydraulic jacks 6 in the x-axis, y-axis, and z-axis directions respectively, so that the readings of the pressure sensors 10 in the three directions respectively reach the set values and keep them stable; the set values range from 0 to 5 MPa;

5) Measure the creep displacement in the x-direction and y-direction, and take the rising distance of the bottom steel plate 14 as the axial creep displacement of the test piece.

The specific method of step 1) is: set up the support structure, set up the bottom steel plate 14 on the bottom of the support structure, set up two long surrounding pressure plates 13 on the adjacent sides of the bottom steel plate 14; place the test block on the bottom steel plate 14 and close to the long enclosure compression plate 13, place the two short enclosure compression panels 12 on the bottom steel plate 14, and make contact with the test block; Contact to form a closed cavity to wrap the test piece.

The specific method of setting up the support structure is: connect the four ends of the "ten"-shaped top steel bracket 2 to the bottom plate through the side steel bracket 3 respectively; the center of the bottom plate 5 and the center of the side steel bracket 3 are respectively installed hydraulic pressure Jack 6; the lower end of the intersection of the top steel bracket 2 is connected to the connecting steel sheet I, and the hydraulic jack 6 is respectively connected to the connecting steel sheet II8, connecting steel sheet III, connecting steel sheet IV, connecting steel sheet V, and connecting steel sheet through the pressure sensor 10 VI connection, grating ruler 4 is installed on each pressure sensor 10, top pulley is installed on the lower end of connecting steel sheet I, bottom pulley 9 is installed on the top of connecting steel sheet II8, and lateral pulley 7 is installed on the inner side of connecting steel sheets III-VI; The top pulley supports the top steel plate, the bottom pulley 9 supports the bottom steel plate 14, and the lateral pulley 7 supports the outer surfaces of the four surrounding pressure plates.

In step 5), the specific method for measuring the creep displacement in the x-direction and y-direction is: measure once every 30 minutes within 1 day, and measure once every 2 hours after 1 day.

Although the specific implementation of the present invention has been described above in conjunction with the accompanying drawings, it does not limit the protection scope of the present invention. On the basis of the technical solution of the present invention, those skilled in the art can make various Modifications or variations are still within the protection scope of the present invention.

Claims (8)

1. for measuring the device of Geotechnical Engineering test block true triaxial creep, comprising supporting construction, it is characterized in that, described device also comprises four confined pressure plates and upper and lower increased pressure board, to form the enclosed cavity of a parcel test block; Described confined pressure plate comprises two long confined pressure plates and two short confined pressure plates, described upper and lower increased pressure board is rectangular top steel plate and bottom steel plate, two long confined pressure plates of " L " shape bent laterally are set up in adjacent two sides of described bottom steel plate, two short confined pressure plates of " L " shape bent laterally are set up in remaining two sides, the long side guide of " L " shape and the upper and lower dislocation lap joint of short side guide of " L " shape; The bottom of described short confined pressure plate is placed on the steel plate of bottom; Top steel plate is set up on the top of described long confined pressure plate, and the medial surface of described top steel plate and two short confined pressure plates is close to; Four described confined pressure plates adopt the overlapping mode of " windmill type "; The overlapping mode that upper and lower increased pressure board and two groups of side direction steel plates stagger up and down; The inside of described supporting construction corresponds to four confined pressure plates and is provided with pressure transducer with upper and lower increased pressure board is all vertical, and described pressure transducer is equipped with grating scale.

2. device according to claim 1, is characterized in that, described supporting construction comprises the top steel bracket of base plate and " ten " font, and four ends of described top steel bracket are connected with base plate respectively by sidepiece steel bracket; The central authorities of described base plate and the central authorities of sidepiece steel bracket are inwardly provided with hydraulic jack respectively.

3. device according to claim 2, it is characterized in that, the infall lower end of described top steel bracket be connected steel disc I and connect, described hydraulic jack respectively by pressure transducer be connected steel disc II ~ VI and connect, the lower end of described connection steel disc I is provided with top pulleys, the top connecting steel disc II is provided with bottom pulley, connects steel disc III ~ VI and is equipped with side direction pulley towards inner side; Described top pulleys support, top steel plate, described bottom pulley supports the bottom steel plate for placing square test block, and long confined pressure plate and two short confined pressure plates fit tightly with two respectively in four sides of described test block; The lateral surface of described side direction pulley support four confined pressure plates.

4. device according to claim 1, is characterized in that, inside the shoulder of described confined pressure plate and bottom is respectively equipped with confined pressure plate shoulder pulley and confined pressure plate bottom pulley.

5. utilize the method for the measurement device Geotechnical Engineering test block true triaxial creep described in claim 1, it is characterized in that, concrete steps are as follows:

1) assembling test device, forms an enclosed cavity parcel test block;

2) precharge, makes the inside of supporting construction contact with four confined pressure plates and upper and lower increased pressure board, and keeps stable;

3) regulate the registration of the pressure transducer corresponding with bottom steel plate, make it zero, and record the initial reading of corresponding grating scale;

4) regulate the hydraulic jack 6 in x-axis, y-axis, z-axis direction respectively, make the reading of the pressure transducer 10 in three directions reach setting value respectively, and keep stable; The scope of described setting value is 0 ~ 5MPa;

5) measure the creeping displacement in x direction, y direction, get the climb of bottom steel plate as the displacement of test block Axial creep.

6. method according to claim 5, is characterized in that, the concrete grammar of described step 1) is: take and put supporting construction, by the bottom that bottom steel plate is set up in supporting construction, two long confined pressure plates is set up the adjacent side at bottom steel plate; Test block is positioned on the steel plate of bottom, and near long confined pressure plate, two short confined pressure plates is placed on the steel plate of bottom, and contacts with test block; Top steel plate is placed on long confined pressure plate, with the contacts side surfaces of two short confined pressure plates, forms the test block of enclosed cavity parcel.

7. method according to claim 6, is characterized in that, described in take the concrete grammar putting supporting construction and be: four ends of " ten " font top steel bracket are connected to base plate respectively by sidepiece steel bracket; Hydraulic jack is inwardly installed respectively by the central authorities of base plate and the central authorities of sidepiece steel bracket; The infall lower end of top steel bracket be connected steel disc I and connect, hydraulic jack respectively by pressure transducer be connected steel disc II ~ VI and connect, each pressure transducer all installs grating scale, top pulleys is installed in the lower end connecting steel disc I, bottom pulley is installed on the top connecting steel disc II, connect steel disc III ~ VI towards inner side equal installation side to pulley; Top pulleys support, top steel plate, bottom pulley support base steel plate, the lateral surface of side direction pulley support four confined pressure plates.

8. method according to claim 5, is characterized in that, in described step 5), the concrete grammar of the creeping displacement in measurement x direction, y direction is: measured once every 30 minutes in 1 day, measures once after 1 day every 2 hours.