CN101666722B - An Electroosmotic Consolidation Method for Large Triaxial Test of Gravel Mixed Materials - Google Patents

Abstract

The invention discloses an electroosmotic consolidation method for a large triaxial test of gravel-mixed materials. Electric geosynthetic electrodes are respectively arranged at both ends of a sample in a large triaxial apparatus, and are connected with an external power supply through wires. The lower sample undergoes electroosmotic consolidation. The method of the invention can greatly shorten the sample consolidation time of the large triaxial test, improve the work efficiency, and meanwhile, the sample is uniformly consolidated. The invention only adds electrodes, wires and a power supply to the triaxial instrument, has low application cost, and is convenient to operate, and is a fast and effective method for consolidating gravel-mixed materials in large triaxial tests.

Description

An Electroosmotic Consolidation Method for Large Triaxial Test of Gravel Mixed Materials

technical field

The invention relates to a consolidation method for a large triaxial test, in particular to an electroosmotic consolidation method for a large triaxial test with gravel.

Background technique

There are many high-core rockfill dams under construction or to be built in Southwest my country, and the height of many dams reaches more than 200m, or even 300m. The traditional method of using cohesive soil core wall as anti-seepage body can no longer meet the strength and deformation requirements of super-high earth-rockfill dam core wall. After rolling, gravel soil can generally obtain higher density and strength, lower compressibility and better anti-seepage performance. This kind of gravel mixed material has been widely used as core wall anti-seepage in high earth-rock dam engineering seepage material.

In the design and calculation of high core wall dams, it is necessary to understand the strength and deformation characteristics of gravel core wall materials, so triaxial tests are required. Due to the large particle size of the gravel material, a triaxial test of a conventional size cannot be carried out, so a large triaxial test is required, and the sample diameter is generally 300mm×600mm. In the large triaxial strength-deformation test of gravel-mixed core wall materials, the specimen first needs to be consolidated.

Before the present invention, the method of consolidating under the action of confining pressure was adopted for the consolidation of samples. Due to the large diameter of the specimen (300mm) and the long drainage path, the consolidation time was very long. The consolidation time is related to the amount of gravel mixed, the less gravel mixed, the longer the consolidation time. For example, for a sample mixed with 50% gravel, the consolidation time takes about one week. If the amount of gravel is less, the consolidation time will be as long as several weeks. During the consolidation of the sample, the test equipment is occupied and precious test resources are wasted. Dozens of large triaxial tests are often required for an earth-rock dam. If calculated according to this consolidation time, the required test period will be very long, which is a waste of time and low test efficiency.

Contents of the invention

The purpose of the present invention is to overcome the defects of long consolidation time and low test efficiency of the above-mentioned large triaxial test sample, and propose an electroosmotic consolidation method for large triaxial test of gravel material.

Technical scheme of the present invention is:

A kind of electroosmotic consolidation method of large triaxial test of gravel material, comprising the following steps:

(1) Reserve drain holes and wire passing holes on the base and cover of the large triaxial instrument;

(2) Place the insulating plate, the electrode plate and the filter paper in sequence on the base;

(3) Pass the lower wire through the base and the insulating plate, and connect with the lower electrode plate;

(4) Make a gravel-mixed sample on the base;

(5) Place filter paper, electrode plate and insulating plate in sequence on the sample;

(6) Pass the upper wire through the cover plate and the insulating plate, and connect with the upper electrode plate;

(7) Connect the drain pipe;

(8) Lead the upper and lower wires out of the pressure chamber and connect them to the external power supply;

(9) Turn on the power, and the sample undergoes electroosmotic consolidation.

In steps (2) and (6), the electrode plate is made of electrodynamic geosynthetics (EGK for short). Electric geosynthetics have been woven into conductive materials, such as graphite, metal wire, etc., which can conduct electricity, and there are many needle-like holes that penetrate up and down to facilitate drainage. The diameter of the electrode plate is the same as that of the sample; the insulating plate is made of insulating hard plastic, the diameter is the same as that of the electrode plate, and holes for wires are reserved on the insulating plate.

The method of the present invention can also perform electrode switching during the electroosmotic consolidation process in step (9).

In the method of the invention, confining pressure can be added to the sample while electroosmosis is being consolidated, so that the sample is consolidated under the joint action of confining pressure and electroosmosis.

Advantage and effect of the present invention are:

The electroosmotic method is used to consolidate the large triaxial test sample mixed with gravel, which overcomes the shortcomings of the traditional consolidation method due to the large size of the sample and the long drainage path, which leads to the slow consolidation of the sample. The time required has changed from several days or even weeks to several hours, which greatly shortens the consolidation time and improves work efficiency.

The present invention uses EGK as the electrode, which solves the problem of electric corrosion caused by the traditional use of metal electrodes, and the EGK electrode can be used as both the cathode and the anode, which is convenient for electrode conversion. The EGK material itself also has drainage performance, and no additional drainage body.

The method of the present invention can be realized on the original test instrument, only electrodes, wires and power supply are added on the basis of the existing triaxial instrument, and the application cost is low; the present invention is easy to operate, and the large triaxial test steps can basically be carried out according to the original steps, Only during consolidation, the original confining pressure consolidation is changed to electroosmotic consolidation, without increasing the difficulty of operation.

The present invention is a very effective method for quickly consolidating gravel-mixed materials by electroosmotic method in a large triaxial test, and the technical effect is very good. Other advantages of the present invention will continue to be described below in conjunction with specific embodiments.

Description of drawings

Fig. 1 - structural schematic diagram of the present invention.

In the figure, 1-pressure chamber; 2-cover plate; 3-base; 4-sample; 5-filter paper; 6-electrode plate; 7-insulating plate; 11-power supply; 12-water stop bolt.

Detailed ways

The method of the present invention is used for the large triaxial test of the gravel-mixed core wall material, and its instrumentation is shown in Figure 1.

A large triaxial test electroosmotic rapid consolidation method for gravel-mixed core wall materials, the specific technical steps are:

(1) On the base 3 and the cover plate 2 of the large-scale triaxial instrument, drain holes 9 and passages for wires to pass through are respectively reserved.

(2) Place the insulating plate 7 on the base 3. The insulating plate 7 is located on the top surface of the base 3. The diameter is the same as that of the sample 4, which is 300 mm, and the thickness is 1-2 mm. The insulating plate 7 is reserved for the wire 8 to pass through. Aperture, insulating plate 7 is made of insulating hard plastic, requires small deformation, and the effect of insulating plate 7 is to insulate between the lower electrode plate 6 and the base 3 to prevent leakage.

Place the electrode plate 6 on the insulating plate 7. The diameter of the electrode plate 6 is the same as that of the sample 4, which is 300mm. The thickness of the electrode plate 6 is 1-2cm. Inserted metal wire, it can conduct electricity, and there are many needle-like holes that penetrate up and down to facilitate drainage. On the one hand, it plays the role of electrifying the electrode, and on the other hand, it can replace the permeable stone in the traditional triaxial test as a drainage channel.

The filter paper 5 is placed on the electrode plate 6. The filter paper 5 has a circular shape with a diameter of 300 mm. On the one hand, it prevents soil particles from directly entering the electrode, and on the other hand, it makes the bottom surface of the sample 4 drain evenly.

(3) Pass the lower lead wire 8 through the small hole reserved on the base 3 and the insulating plate 7, and contact and connect with the lower electrode plate 6. When connecting, it can be directly wound on the wire of the electrode plate 6, and it can be energized immediately Can. The wire 8 requires insulation on the outer surface.

(4) Fabricate the gravel-mixed core wall material sample 4 on the base 3, and the fabrication method is the same as the general triaxial test.

(5) Place the filter paper 5, the electrode plate 6 and the insulating plate 7 sequentially on the top surface of the sample 4; except that the placing order is reversed, the others are the same as step (3).

(6) Pass the upper lead 8 through the small hole reserved on the cover plate 2 and the insulating plate 7, and the lead 8 is connected to the upper electrode plate 6;

(7) Connect the drain pipe 10 well.

(8) Pass the two wires 8 through the small holes on the top surface of the pressure chamber 1, and the wires 8 must be provided with water-stop bolts 12 at the outlets of the base 3, cover plate 2, and pressure chamber 1 to prevent water from infiltrating and infiltrating out.

Connect the two wires 8 leading out of the pressure chamber 1 with an external power supply 11, the power supply 11 adopts a DC power supply, and the voltage can be adjusted.

(9) Turn on the power supply 11, and the sample 4 begins to undergo electroosmotic consolidation, and select an appropriate voltage according to the amount of gravel mixed in the sample and the required consolidation time. .

During electroosmotic consolidation, the pore water moves up and down the cathode in the electrode plate 6, and the water is discharged through the drainage channel of the cathode. In the present invention, drainage channels are provided at both ends of the sample 4, so the electrode plates at both ends of the sample 4 can be used as anodes or cathodes. Another benefit of using the EGK material as the electrode plate 6 is that it can be used as both an anode and a cathode. During the consolidation process of the test, in order to make the top and bottom of the sample 4 uniformly consolidated, the electrode switching can be performed every certain time, such as 15MIN, 30MIN, 45MIN, 60MIN, 1.5 hours or 2 hours, even if two wires 8 and the connection of the positive and negative poles of the power supply 11 are interchanged, that is, the electrode conversion is completed. Through the electrode conversion technology, the sample 4 is drained through the upper and lower ends respectively, which not only speeds up the consolidation speed, but also ensures uniform consolidation.

At the same time of electroosmotic consolidation, confining pressure can also be added around sample 4, so that sample 4 can be consolidated under the combined action of confining pressure and electroosmosis, which can give full play to the strengths of the two consolidation methods, and consolidate Faster, better consolidation.

The protection scope of the present invention is not limited only to the description of the embodiment, but is defined according to the claims.

Claims (3)

1. A method for electroosmotic consolidation of gravel-mixed large triaxial tests, comprising the following steps: (1) Reserve drain holes and wire passing holes on the base and cover of the large triaxial instrument; (2) Place the insulating plate, the electrode plate and the filter paper in sequence on the base; (3) Pass the lower wire through the base and the insulating plate, and connect with the lower electrode plate; (4) Make a gravel-mixed sample on the base; (5) Place filter paper, electrode plate and insulating plate in sequence on the sample; (6) Pass the upper wire through the cover plate and the insulating plate, and connect with the upper electrode plate; (7) Connect the drain pipe; (8) Lead the upper and lower wires out of the pressure chamber and connect them to the external power supply; (9) Turn on the power supply, the sample undergoes electroosmosis consolidation, and performs electrode conversion during the electroosmosis consolidation process; The electrode plates are made of electrodynamic geosynthetic materials. 2. The electroosmotic consolidation method of gravel-mixed large triaxial test according to claim 1, characterized in that: the diameters of the electrode plates and insulating plates are the same as the sample. 3. the electroosmotic consolidation method of gravel-mixed large triaxial test according to claim 1, is characterized in that: sample adds confining pressure while electroosmotic consolidation, makes sample in confining pressure-electroosmosis Consolidation occurs under combined action.

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