CN209745717U - triaxial hydraulic fracture test device - Google Patents

Abstract

the utility model belongs to the technical field of test equipment, and discloses a triaxial hydraulic fracture test device, which is provided with a triaxial apparatus; the triaxial apparatus is internally provided with a pressure chamber, the inside of the pressure chamber is fixed with a sample with a prefabricated crack inside, the lower end of the sample is communicated with a splitting pressure water inflow testing device on the left side of the triaxial apparatus through a first plastic pipe, and the bottom of the pressure chamber is communicated with a confining pressure ectosome variable measuring device on the right side of the triaxial apparatus through a second plastic pipe. The utility model discloses a left splitting pressure inflow testing arrangement of triaxial apparatus makes black ink slowly get into in the inside prefabricated crack of sample under certain pressure, form inner chamber pressure, the quality through measuring the ink changes and calculates the splitting inflow, become external air supply of measuring device through the confining pressure ectosome and exert certain pressure to the distilled water, make the sample consolidate under given pressure, through the change and the consolidation degree that the sample volume was measured to the change of throughput pressure measuring tank distilled water quality, the measuring accuracy is high.

Description

A three-axis hydraulic splitting test device

technical field

The utility model belongs to the technical field of test equipment, in particular to a three-axis hydraulic splitting test device.

Background technique

Currently, the closest existing technology in the industry:

Hydraulic fracturing is a physical phenomenon in which cracks occur and expand in rock or soil due to the rise of water pressure. Hydraulic fracturing is a general term for physical phenomena such as high-pressure water flow or other liquids that drive expansion, expansion, and interpenetration of existing cracks and pores in rock and soil.

The purpose of triaxial hydraulic splitting test is to study the law of hydraulic splitting of soil under confining pressure and understand the failure mode of hydraulic splitting. The effects of factors such as saturation, compaction, consolidation ratio, confining pressure, prefabricated joint size and hydraulic loading rate of clay core wall materials on hydraulic splitting pressure are mainly studied.

In summary, the problems in the prior art are:

(1) The hydraulic splitting test is carried out by using a drilled cylinder or a square sample. The cracks in actual engineering rarely have a circular cross-section. Use a hollow cylindrical specimen or a square specimen to study the law of hydraulic splitting. None of these simulation methods are suitable for the case where there are potential weak penetration surfaces in the core wall.

(2) The occurrence process of the hydraulic splitting of the sample was observed through the observation window on the side of the sample, but the simulated crack belongs to the plane strain problem, and the development of the crack direction cannot be simulated.

The difficulty of solving the above technical problems:

How to prefabricate a crack with a set size in the sample, and the size of the crack in the sample does not change under the stress state; track the expansion of the crack, and accurately obtain the amount of splitting water and the volume change of the sample, which is very important for the crack. Quantitative evaluation of development.

The significance of solving the above technical problems:

Tracking and quantitative description of the shape and evolution of triaxial hydraulic fracturing cracks, revealing the evolution mechanism of hydraulic fracturing on the weak surface of the clay core wall, and establishing a criterion to provide an analysis method for the hydraulic fracturing of the core wall material of earth-rock dams. The research results have Important theoretical significance and broad engineering application value.

Utility model content

Aiming at the problems existing in the prior art, the utility model provides a triaxial hydraulic splitting test device.

The utility model is achieved in that a triaxial hydraulic splitting test device is provided with:

Triaxial instrument;

A pressure chamber is arranged inside the triaxial instrument, and a sample with a prefabricated crack is fixed inside the pressure chamber, and the lower end of the sample communicates with the splitting pressure water inflow test device on the left side of the triaxial instrument through the first plastic tube. The bottom of the pressure chamber communicates with the confining pressure external volume variable measuring device on the right side of the triaxial instrument through the second plastic tube.

Further, the splitting pressure water inflow test device is provided with a first pressure tank filled with black ink, the upper end of the first pressure tank is provided with a sealing plug, the first plastic pipe extends into the bottom of the first pressure tank, and the first pressure tank Placed on the upper end of the first electronic balance, the upper end of the first pressure tank communicates with the first air source interface, and the first air source interface is provided with a regulating valve.

Further, the external pressure measurement device is provided with a balance frame, the upper end of the balance frame is fixed with a turntable through a rotating shaft, and the outer side of the turntable is sleeved with steel strands, and the left end of the steel strands is hung with a second container filled with distilled water. Pressure tank, the upper end of the second pressure tank communicates with the second air source interface, the second air source interface is provided with a regulating valve, the bottom of the second pressure tank communicates with the second plastic pipe, and the other end of the steel strand is hung with a heavy object. The lower end of the object is connected with the tray containing iron sand, and the tray is placed on the upper end of the second level.

Further, the outer side of the sample is covered with a rubber film, the bottom edge of the sample is provided with a sealing groove, the sealing groove is filled with glass glue, the lower end of the sample is glued with a plastic plate, and the middle of the plastic plate is pierced with a The inside of the sample is prefabricated with a plastic tube connected by cracks, the upper end of the sample is glued with a sample cap, and the upper end of the sample cap is concavely provided with a groove that matches the triaxial instrument.

In summary, the advantages and positive effects of the present utility model are:

The utility model makes the black ink slowly enter the prefabricated crack inside the sample under a certain pressure through the splitting pressure water inflow test device on the left side of the triaxial instrument to form the inner cavity pressure, and calculate the splitting by measuring the mass change of the ink. The amount of cracked water, through the external air source of the external pressure measuring device, exerts a certain pressure on the distilled water, so that the sample is consolidated under a given pressure, and the volume of the sample is measured by measuring the change in the quality of the distilled water in the pressure tank Variation and degree of consolidation. The utility model has the advantages of simple structure and high testing precision.

Description of drawings

Fig. 1 is the schematic structural diagram of the triaxial hydraulic splitting test device provided by the embodiment of the present invention;

Fig. 2 is the sample structure schematic diagram that the utility model embodiment provides;

Fig. 3 is a schematic diagram of the structure of the sealing groove provided by the embodiment of the present invention;

Fig. 4 is the structural representation of the sample making mold that the utility model embodiment provides;

In the figure: 1. Triaxial instrument; 2. Pressure chamber; 3. Sample cap; 4. Sample; 5. Sample base; 6. The first plastic tube; 7. The first pressure tank; 8. The first electronic Balance; 9. First air source interface; 10. Regulating valve; 11. Second plastic pipe; 12. Balance frame; 13. Second electronic balance; 14. Tray; 15. Weight; 16. Steel strand; 17 , turntable; 18, second pressure tank; 19, second air source interface; 20, plastic plate; 21, plastic pipe; 22, prefabricated crack; 23, steel plate; Shaped nut; 27, sealing groove.

Detailed ways

In order to further understand the invention content, characteristics and effects of the present utility model, the following examples are given, and detailed descriptions are given below in conjunction with the accompanying drawings.

As shown in Figures 1 to 3, the triaxial hydraulic splitting test device provided by the embodiment of the present invention includes: a triaxial instrument 1, a pressure chamber 2, a sample cap 3, a sample 4, a sample base 5, a first Plastic pipe 6, first pressure tank 7, first electronic balance 8, first air source interface 9, regulating valve 10, second plastic pipe 11, balance frame 12, second electronic balance 13, tray 14, weight 15, Steel strand 16, turntable 17, second pressure tank 18, second air source interface 19, plastic plate 20, plastic pipe 21, prefabricated crack 22, steel plate 23, hexagon socket head screw 24, screw rod 25, wing nut 26, seal Slot 27.

There is a pressure chamber 2 inside the triaxial instrument 1, and a sample 3 with a prefabricated crack 22 is fixed inside the pressure chamber 2. The lower end of the sample 1 passes through the first plastic tube 6 and the splitting pressure water intake on the left side of the triaxial instrument 1 The test device is in communication, and the bottom of the pressure chamber 2 is in communication with the external pressure measurement device on the right side of the triaxial instrument 1 through the second plastic tube 11 . The splitting pressure water inflow test device is provided with a first pressure tank 7 filled with black ink, the upper end of the first pressure tank 7 is provided with a sealing plug, the first plastic pipe 6 extends into the bottom of the first pressure tank 7, the first pressure tank 7 is placed on the upper end of the first electronic balance 8, and the upper end of the first pressure tank 7 communicates with the first air source interface 9, and the first air source interface 9 is provided with a regulating valve 10.

The measuring device for the external body change of confining pressure is provided with a balance frame 12, and the upper end of the balance frame 12 is fixed with a turntable 17 through a rotating shaft. The second pressure tank 18, the upper end of the second pressure tank 18 communicates with the second air source interface 19, the second air source interface 19 is provided with a regulating valve, the bottom of the second pressure tank 18 communicates with the second plastic pipe 11, and the steel strand 16 The other end is hung with heavy object 15, and the lower end of heavy object 15 is connected with the tray 14 that iron sand is housed, and tray 14 is placed on the second day level 13 upper end.

The outer side of sample 4 is covered with a rubber film, the bottom edge of sample 4 is provided with a sealing groove 27, and the sealing groove is filled with glass glue. 4. The plastic pipe 21 connected by the internal prefabricated crack 22. The upper end of the sample 4 is glued with the sample cap 3. The upper end of the sample cap 3 is concavely provided with a groove matching the triaxial instrument 1.

The working principle of the utility model is:

Open a small circular hole in the middle of a plastic plate with a thickness of 5mm, and stick a plastic tube with a length of 15mm and an outer diameter of 8mm to the small hole of the plastic plate with AB glue, and bond the bottom of the sample to the plastic plate through AB glue , the plastic pipe passes through the small hole and inserts a small amount into the standard sand in the prefabricated crack, and sticks a filter paper to prevent the standard sand from leaking out. Wrap the sample with a rubber film and put it in a moisture tank for 12 hours until the AB glue is completely cured. Then place the sample on the base of the triaxial instrument. A certain thickness of glass glue is applied between the base and the plastic plate, between the top of the sample and the sample cap, and between the rubber film and the sample base and the sample cap. Also apply a little glass glue, and tie the two ends of the sample tightly with rubber bands to prevent water and air leakage. The plastic tube at the bottom of the sample is connected to the split pressure water inflow test device, and the ink can enter the inside of the sample along the plastic tube. Let it stand for 12 hours, and the test can be carried out after the glass glue is cured. After the AB glue and glass glue are cured, the pressure chamber is installed, and a certain confining pressure is applied to the sample through the external body variable measuring device (gas-water conversion device) to make it consolidate. Read the reading of the high-precision electronic balance at regular intervals. When the reading is basically unchanged (such as the rate of change is less than 0.1g/h), it is considered to be stable.

Split pressure water inflow test device The pressure chamber filled with black ink is connected to the crack filled with sand at the bottom of the sample through a conduit, and the air inside is exhausted before the test. Open the pressure regulating valve on the splitting pressure water inflow test device, first apply an inner chamber pressure of 20kPa to the sample, and you can see that the black ink slowly enters the inside of the sample along the plastic tube. After each pressure is applied, this value remains unchanged. When the reading change rate of the high-precision electronic balance on the splitting pressure water inflow testing device is less than 0.05g/min, the test is considered to be balanced, and the next level of pressure can be applied. By analogy, until the sample splits, the reading of the electronic balance decreases sharply at this time, and a large amount of ink gushes out from the inside of the sample.

Each ink pressure increase amplitude is 20kPa, record each pressure reading and the reading of the electronic balance after stabilization. The pressure at which the final sample splits is the hydraulic splitting pressure of the sample under this test condition. After the test, the sample was removed from the base of the triaxial instrument and scanned on a CT scanner to observe the distribution of cracks inside the sample and compare it with the sample before the test.

As shown in Figure 4, the sample making mold is made of three steel plates spliced together, and the two right-angle steel plates are connected by six M6 inner hexagonal screws to form a frame, and then two movable M6 screws and Two wing nuts are connected with the bottom plate to form a cuboid box with a size of 240mm×240mm×120mm (length×width×height). The thickness of the steel plate is 10mm, which is a high-strength steel plate, which can ensure that no deformation occurs during the sample preparation process.

The specific sample making process is as follows:

(1) Use hexagon socket screws and wing nuts to form a square mold, and use a hexagon wrench and a common wrench to tighten each screw and nut, and each contact surface is in a state of tight fit to prevent deformation due to lack of tightening during the sample preparation process . Apply a layer of lubricating oil evenly on the inner wall of the mold to facilitate sample preparation and demoulding.

(2) Prepare Lianghekou clay samples according to the optimum water content. After the soil material is prepared, put it in a closed plastic bucket and let it stand for 24 hours to make the moisture content uniform. Measure its moisture content before the test, and the moisture content of the final test shall prevail. The compaction degree of the sample is 98%, and the sample is divided into four layers, and the thickness of each layer after compaction is 30mm. Strictly control the height of each layer of soil material before and after compaction to ensure the uniformity of the entire sample. After each layer of soil material is hammered, the surface is shaved, and then poured into the next layer of soil material for compaction.

(3) When the height of the sample reaches 60mm, scrape the surface of the sample, fill the next layer and half of the soil material surface is flat, put two plastic plates of a certain size coated with Vaseline on the surface of the sample, Use a ruler to measure the distance so that it is in the correct position, then fill in the other half of the soil, making sure that the plastic plate does not move when adding soil. Continue to prepare samples according to the above steps until complete.

(4) After the sample is made, unscrew the inner hexagon nut and wing nut, and take off the mold, as shown in Figure 2(3). Stand the sample after demoulding on the table, divide it evenly from the middle with a wire saw, and divide it into two cuboid samples with dimensions of 120mm×120mm×240mm (length×width×height). Locate the center of the cuboid sample so that the plastic plate is just in the middle of the sample, put it on the soil cutter, and cut the cuboid sample into a cylindrical sample of Φ101mm×H200mm with tools such as soil repair knife and wire saw , and put into a circular mold of the corresponding size.

(5) Fix the round mold with a cage, carefully pull out the plastic plate with pliers, and the prefabricated gap is formed. Fill a certain amount of white standard sand into the prefabricated gap, and insert and tamp with a steel wire while filling to make it evenly compacted. Then dig a sealing groove with a width of about 5mm and a depth of about 3mm around the sample. When installing the sample, fill the sealing groove with glass glue to seal and stop water. Paste a wet filter paper on the bottom of the sample after sand filling.

The above descriptions are only preferred embodiments of the present utility model, and are not intended to limit the present utility model in any form. Any simple modifications made to the above embodiments according to the technical essence of the present utility model are equivalent to changes and modifications. All belong to the scope of the technical solution of the utility model.

Claims (4)

1. A triaxial hydraulic splitting test device is characterized in that, the triaxial hydraulic splitting test device is provided with: Triaxial instrument; A pressure chamber is arranged inside the triaxial instrument, and a sample with a prefabricated crack is fixed inside the pressure chamber, and the lower end of the sample communicates with the splitting pressure water inflow test device on the left side of the triaxial instrument through the first plastic tube. The bottom of the pressure chamber communicates with the confining pressure external volume variable measuring device on the right side of the triaxial instrument through the second plastic tube. 2. triaxial hydraulic splitting test device as claimed in claim 1, is characterized in that, described splitting pressure water inflow test device is provided with the first pressure tank that black ink is housed, and the first pressure tank upper end plug is provided with The sealing plug, the first plastic tube extends into the bottom of the first pressure tank, the first pressure tank is placed on the upper end of the first electronic balance, the upper end of the first pressure tank communicates with the first air source interface, and the first air source interface is provided with a regulating valve. 3. triaxial hydraulic splitting test device as claimed in claim 1, is characterized in that, described confining pressure outer body variable measuring device is provided with balance frame, and the balance frame upper end is fixed with rotating disk by rotating shaft, and the disk of rotating disk is sleeved along the outer side. There is a steel strand, and the left end of the steel strand is hung with a second pressure tank filled with distilled water. The upper end of the second pressure tank is connected to the second air source interface. It communicates with the second plastic pipe, and a heavy object is hung on the other end of the steel strand, and the lower end of the heavy object is connected with a tray containing iron sand, and the tray is placed on the upper end of the second level. 4. The triaxial hydraulic splitting test device as claimed in claim 1, wherein a rubber film is set on the outside of the sample, a sealing groove is provided on the bottom edge of the sample, and glass glue is filled in the sealing groove The lower end of the sample is glued with a plastic plate, and the middle of the plastic plate is provided with a plastic tube communicating with the prefabricated crack inside the sample. The upper end of the sample is glued with a sample cap, and the upper end of the sample cap is recessed with three Axis fits the groove.