Indoor large-size fissure rock specimen preparation device and method

Abstract

The application provides a device and method for preparing large-size fissure rock samples in a laboratory, which comprises a fissure rock sample, a cuboid plastic net, a cuboid mold and a cement paste layer; the fissure rock sample is obtained by chiseling at a representative position; the fissure rock sample is put in the middle of the cuboid mold after being held by the cuboid plastic net; the cuboid mold is in the shape of a hollow cuboid; and the cement paste layer is formed by pouring the cement paste into the gap between the fissure rock sample and the cuboid mold. The application can guarantee the integrity of the fissure rock, effectively prepare large-size fissure rock samples, realize the laboratory test of large-size fissure rock, and change the current situation that only field rock mechanics test can be carried out.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of rock mechanics test, in particular to a large-size fractured rock test piece preparation device and method. BACKGROUND

[0002] Rock mechanics parameters are important parameters for stability analysis and design of rock engineering such as rock slope engineering and rock tunnel engineering. Rock mechanics parameters are mainly obtained through indoor rock mechanics test and field rock mechanics test. When carrying out field rock mechanics test, different types of rock mechanics test equipment must be transported to the field, and space is also needed for installation and debugging, so the cost of field rock mechanics test is high. In order to control the test cost, simple projects that do not require large test equipment are carried out on site, and complex projects that require large test equipment are carried out in the laboratory.

[0003] When carrying out indoor rock mechanics test, rock samples need to be transported from the field to the laboratory. For complete rock, it can be directly transported to the laboratory after simple treatment on site, and the rock test piece is not easy to damage. In recent years, in order to truly reflect the properties of rock, the size of rock samples has increased from a few centimeters to tens of centimeters, and even to meters. Therefore, large-size rock samples will contain a certain number of structural planes or fractures (referred to as fragile rock) that intersect each other. The external force generated during handling and transportation will damage the internal structure of the rock, and the test results will deviate seriously from the true value. More seriously, some fractured rock samples cannot be made into rock test pieces required by the test, so indoor rock mechanics test cannot be effectively carried out. This is also the difficulty and blank of domestic indoor rock mechanics test for fractured rock.

[0004] At present, in order to obtain the mechanical parameters of fractured rock, test researchers estimate the mechanical parameters of complete rock according to experience. Due to the complexity of the structure of fractured rock, the artificially estimated value often deviates greatly from the actual situation, and the estimated value is too small, which leaves a safety hazard to the project. This is also the main reason why some rock engineering projects still have engineering accidents despite reinforcement treatment. If the estimated value is too large, it will increase the cost of rock engineering treatment.

[0005] At present, rock mechanics test generally includes rock tensile strength test, compressive strength test, shear strength test and compression strength test under different water content. The various mechanical tests can be carried out smoothly, which mainly depends on whether the rock test piece can be successfully made. According to the international and domestic rock test regulations, it is clearly required that the rock sample should be representative, the surface of the test piece should be smooth, and there should be no obvious cracks and defects. When samples of different specifications and shapes are made, the rock test piece should be made by the consistent method and tool as far as possible, and the cutting, polishing and processing operations are carried out according to the test requirements, so as to ensure that the internal structure of the rock test piece is not affected. For small size complete rock, the rock test piece can easily meet the above requirements, but for large size fractured rock, if not properly treated, on-site sampling, transportation and indoor processing, the internal structure of the rock will be seriously damaged, which will lead to serious deviation of the test results from the true value, and more seriously, the sample cannot be successfully made, which will lead to the test cannot be carried out smoothly.

[0006] In view of the difficulties encountered in the rock mechanics test of large size fractured rock, the key problem to be solved is to effectively make the fractured rock test piece under the condition that the internal state of the fractured rock is not damaged, and the test results of the successfully made fractured rock test piece are less affected and can reflect the mechanical properties of the fractured rock itself. SUMMARY

[0007] The purpose of the present application is to provide an indoor large size fractured rock test piece preparation device and method, which solves the problem of effectively making the fractured rock test piece under the condition that the original mechanical properties of the large size fractured rock are slightly damaged, thereby realizing the indoor replacement of the field rock mechanics test. Through the indoor test, not only the mechanical parameters of the fractured rock under different water content can be obtained, but also the test cost is greatly reduced.

[0008] An indoor large size fractured rock test piece preparation device, comprising a size fractured rock test piece preparation device and method, comprising a fractured rock sample, a cuboid plastic net, a cuboid mold and a cement slurry layer.

[0009] The fractured rock sample is a cuboid, which is obtained by artificial chiseling at a representative position according to the requirements of rock mechanics test;

[0010] The strength of the cuboid plastic net is lower than that of the fractured rock sample, and the cuboid plastic net is opened at one end along the length direction, and the cuboid plastic net is placed in the middle of the cuboid mold after the fractured rock sample is put in the cuboid plastic net.

[0011] The cuboid mold shape is an empty cuboid, one of the rectangular alloy plates of the cuboid mold is a free alloy plate which can be freely detached, a small hole is left at the end position along the length direction of the free alloy plate for grouting, exhaust and drainage, the other three rectangular alloy plates are an integral whole, one of the two square faces perpendicular to the rectangular face is open without an alloy cover plate, and the other square alloy plate is an integral whole with the three rectangular alloy plates;

[0012] The cement paste layer is formed by pouring the cement paste into the gap between the fractured rock sample and the cuboid mold.

[0013] Further, the fractured rock sample specification is high x wide x long = 30 cm x 30 cm x 60 cm.

[0014] Further, the cuboid plastic net inner space size is high x wide x long = 32 cm x 32 cm x 62 cm, the wall thickness is 0.2 cm, and the grid size is 1-2 cm.

[0015] Further, the cuboid mold inner space size is high x wide x long

[0016] = 34 cm x 34 cm x 64 cm, the material is an alloy material, and the wall thickness is 1-2 cm.

[0017] Further, the free alloy plate is freely detachable from the other abutting face of the cuboid mold through a lock buckle.

[0018] Further, the other one of the two square alloy plates perpendicular to the rectangular face leaves a cylinder with a height of 1 cm and a radius of 2 cm at the inner four corner positions.

[0019] Further, the water-cement ratio in the cement paste is 0.6:1, the cement grade is 325#, and the consistency is 70 mm.

[0020] An indoor large-size fractured rock test piece preparation method, which uses the device, comprises the following steps:

[0021] Step 1: on-site field investigation is carried out to determine the position of the fractured rock sample to be chiseled and to mark the position;

[0022] Step 2: the fractured rock sample is artificially chiseled at the specified position according to the test requirements, and the size of the fractured rock sample is measured;

[0023] Step 3: the plastic net is used to hold the fractured rock sample;

[0024] Step 4: remove the free alloy plate from the cuboid mold, place it on the flat ground, and then place the fissured rock sample covered with a plastic net on the free alloy plate, cover the other part of the cuboid mold, and buckle the detachable free alloy plate, then turn it over so that the alloy plate is on the bottom of the cuboid mold, and the end with the small hole is on the bottom, adjust the position of the fissured rock sample (1) so that it is centered in the cuboid mold;

[0025] Step 5: mix the cement paste according to the test mix ratio and consistency, stir it evenly, open the small hole of the free alloy plate, and slowly pour the mixed cement paste into the gap between the fissured rock sample and the cuboid mold, and then vibrate and stir to form; at the same time, use conventional concrete pouring methods to make a pure cement paste test piece;

[0026] Step 6: after 7 days of aging, remove the composite structure composed of fissured rock, plastic net, and cement paste layer from the cuboid mold, and then transport the composite structure and pure cement test piece back to the indoor laboratory.

[0027] Further, it also includes:

[0028] Step 7: without any polishing and processing, the composite structure and pure cement test piece are directly cured according to the test method conditions, and then different indoor rock mechanics tests are carried out; the pure cement test piece and the composite structure carry out the same type of mechanical test, and through the mechanical test of the pure cement test piece, the pressure and deformation curve of the cement solidified paste layer are obtained;

[0029] Step 8: according to the pressure and deformation curve variation characteristics obtained by the composite structure test, read the pressure F and the corresponding deformation μ of the fissured rock when it breaks from the curve, and then find the pressure value corresponding to the deformation μ in the pressure and deformation curve of the pure cement test piece according to the obtained deformation μ, calculate the strength σ0 of the cement paste layer, set the strength of the fissured rock as σ, the bottom area or side area of the mold as S1, and the bottom area or side area of the fissured rock test piece as S2, and according to the limit equilibrium theory and the test results comparison analysis, the fissured rock strength σ is calculated according to the rock strength correction formula:

[0030]

[0031] The calculated rock mechanics parameter values can accurately reflect the mechanical properties of the rock.

[0032] The present application aims at the problem that large-size indoor fissure rock is not easy to be formed, develops a slurry layer material with low strength and high permeability, and uses the developed cement slurry layer and high-flexibility plastic net composite structure which has certain compressive and tensile resistance to seal, protect and reinforce the fissure rock sample, so that the fissure rock is not easy to be damaged and destroyed during transportation and preparation, the integrity of the fissure rock is ensured, the large-size fissure rock test piece is effectively prepared, the large-size fissure rock indoor test is realized, and the status that only field rock mechanics test can be carried out is changed; the uniaxial compressive strength of the cement slurry layer composite structure is far lower than the uniaxial compressive strength of the rock, which is beneficial to effectively identifying the rupture pressure of the slurry layer and the rupture pressure of the rock test piece from the test pressure and deformation curve, and ensures the accuracy of the rock strength parameters obtained by the test; the high permeability of the cement slurry layer composite structure is beneficial to realizing the hydraulic connection between the rock test piece and the outside, and the preparation of the rock test piece in different water content states such as dry, natural and saturated. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is a structural schematic view of an indoor large-size fissure rock test piece preparation device according to an embodiment of the present application, wherein (a) is a top plan view, and (b) is an elevation view;

[0034] Figure 2 is a schematic view of stress in an indoor rock mechanics test according to the present application.

[0035] In the figure: 1 - rock sample, 2 - plastic net, 3 - cuboid mold, 4 - formed cement slurry layer DETAILED DESCRIPTION

[0036] To make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0037] Please refer to Figure 1 and Figure 2 The embodiments of the present application provide an indoor large-size fissure rock test piece preparation device, which comprises a fissure rock sample 1, a cuboid plastic net 2, a cuboid mold 3 and a cement slurry layer 4.

[0038] The rock sample 1 is artificially chiseled at a representative position according to the requirements of rock mechanics test, and has a size of about 30cm×30cm×60cm.

[0039] The cuboid plastic net 2 has low material strength, good flexibility and is not easy to break, has an inner space of about 32cm*32cm*62cm, a wall thickness of about 0.2cm, a grid size of 1-2cm, is open at one end along the length direction, is installed between the fissure rock sample 1 and the cuboid mold 3, and plays a role of reinforcing when the cement mortar is poured, so that the cement mortar is not easy to disperse and the bonding force is increased.

[0040] The cuboid mold 3 has an inner space of 34cm*34cm*64cm and a wall thickness of about 1-2cm, an alloy plate of one of the rectangular faces of the cuboid mold 3 can be removed as a free alloy plate, a small hole is left at the center of the alloy plate end along the length direction, one hole is left at a position 1.5cm away from the edge of the free alloy plate in the embodiment, and the hole is used for air and water drainage when the cement mortar is poured. The other hole is used for air and water drainage when the cement mortar is poured, one of the two square faces is open and has no alloy plate, the other square face has a cylinder with a height of 2cm and a radius of 1-2cm left at the four corners inside the alloy plate, the three rectangular alloy plates and the one square alloy plate are integrated, the free alloy plate and the integrated whole formed by the other faces are connected by a lock buckle, and the cuboid mold 3 plays a role of cement mortar forming and protection.

[0041] In order to make the cement mortar layer 4 have low strength and good permeability after forming, the mixing ratio obtained through experiments is as follows: the water-cement ratio is 0.6:1, and the consistency is about 70mm.

[0042] The embodiment of the application also provides a preparation method of an indoor large-size fissure rock test piece, which is prepared by using the device.

[0043] Step 1: field investigation is carried out on site, the position of the fissure rock sample is determined, and the position is marked, and the mark should be clear.

[0044] Step 2: the fissure rock sample 1 is manually chiseled at the specified position, and the sample size is measured.

[0045] Step 3: the free alloy plate in the cuboid mold 3 is removed, the free alloy plate is placed on the flat ground, the fissure rock sample 1 is stably placed on the free alloy plate by using the cuboid plastic net 2, the other parts of the cuboid mold 3 are sleeved, one end of the free alloy plate with the small hole is connected to one end of the square alloy plate, the lock buckle is buckled, the cuboid mold 3 is turned over with the open face without the alloy plate upward, the positions of the cuboid plastic net 2 and the fissure rock sample 1 are adjusted, and the fissure rock sample 1 is centrally placed in the cuboid mold 3.

[0046] Step 4: Mix the cement paste according to the mixing ratio and consistency, stir uniformly, open the small holes on the free alloy plate, slowly pour the mixed cement paste into the gap between the fractured rock sample 1 and the cuboid mold 3, and oscillate and stir to form a pure cement paste test piece in a conventional concrete pouring manner.

[0047] Step 5: After the age reaches 7 days, the composite structure composed of the fractured rock sample 1, the plastic net 2 and the cement paste layer 4 is taken out of the cuboid mold 3 and transported back to the indoor laboratory.

[0048] Step 6: Without any processing and polishing, the transported composite structure is cured according to the requirements of the test method, and indoor rock mechanics tests can be carried out. The pure cement test piece and the composite structure carry out the same type of mechanical test, and through the mechanical test of the pure cement test piece, the pressure and deformation curve of the cement paste layer 4 after cement solidification can be obtained.

[0049] Step 7: According to the pressure and deformation curve variation characteristics obtained by the mechanical test of the composite structure, the pressure F and the corresponding deformation amount μ of the rock rupture are read from the curve, and the pressure value corresponding to the deformation amount μ is found from the pressure and deformation curve of the pure cement test piece, and the strength σ0 of the deformation amount μ corresponding to the cement paste layer is calculated, assuming that the fractured rock strength is σ, S2 is the bottom area or side area of the fractured rock sample, S1 is the bottom area or side area of the empty cuboid mold 3, and the limit equilibrium theory and test results are compared and analyzed, and the rock strength correction formula is as follows:

[0050]

[0051] The fractured rock strength is calculated, so that the calculated fractured rock strength has excluded the influence of the cement paste layer, and the obtained rock mechanics parameter value directly reflects the mechanical properties of the rock itself.

[0052] The indoor test replaces the field test, which reduces the test cost and can obtain rock mechanics parameters under different water conditions, breaking through the difficulty that the field test can only obtain rock mechanics parameters under a certain water condition. In the past, the fractured rock test piece directly uses the uniaxial compression load-displacement curve to calculate the compression strength parameter, ignoring the influence of the protective mortar strength, and the calculated parameter value is an approximate value. The calculation formula proposed in the present application eliminates the load borne by the mortar in the mortar-protected fractured rock test piece, and the calculated uniaxial compression strength of the fractured rock test piece is the true strength value of the fractured rock, and the calculation result is more accurate.

[0053] The cement slurry layer material with low strength and good permeability is developed, and is used for protecting and reinforcing fissured rock, preventing the fissured rock from being damaged or destroyed during transportation, solving the problem that large-size fissured rock cannot be prepared into a shape in a laboratory, and realizing the indoor rock mechanics test of large-size fissured rock; the large-size fissured rock test piece prepared by using the device is not easy to break under the action of external force, the composite structure formed does not need to be treated after curing under the test conditions stipulated in the test method; the indoor rock mechanics test replaces the field rock mechanics test, which reduces the test cost and can obtain rock mechanics parameters under different water content states, and breaks through the predicament that the field test can only obtain rock mechanics parameters under a certain water content state; the fissured rock strength calculation formula eliminates the influence of the cement slurry layer strength, and the calculation result can reflect the mechanical properties of the rock itself.

[0054] The contents not described in detail in the specification belong to the prior art known by the person skilled in the art.

[0055] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited to this, any change or replacement easily thought of by the person skilled in the art within the technical range disclosed by the present application should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An indoor apparatus for preparing large-size fractured rock specimens, characterized in that: The sample includes a fractured rock sample (1), a cuboid plastic mesh (2), a cuboid mold (3), and a cement slurry layer (4). The fractured rock sample (1) is a cuboid, which was obtained manually from a representative location according to the requirements of rock mechanics test; The cuboid plastic mesh (2) has a lower strength than the fractured rock sample (1), and is open at one end along its length. The cuboid plastic mesh (2) holds the fractured rock sample (1) and places it in the middle of the cuboid mold (3). The rectangular mold (3) is a hollow rectangular prism. One of the rectangular alloy plates of the rectangular mold (3) is a free alloy plate that can be freely disassembled. A small hole is left at the end along the length of the free alloy plate for grouting, venting and drainage. The other three rectangular alloy plates are a whole. One of the two square faces perpendicular to the rectangular face is open and has no alloy cover plate. The other square alloy plate and the three rectangular alloy plates form a whole. The cement slurry layer (4) is formed by pouring cement slurry into the gap between the fractured rock sample (1) and the cuboid mold (3); The rectangular plastic mesh (2) is flexible, with a wall thickness of 0.2cm and a mesh size of 1~2cm; the water-cement ratio in the cement slurry is 0.6:1, the cement grade is 325#, and the consistency is 70mm.

2. The indoor large-size fractured rock specimen preparation device as described in claim 1, characterized in that: The dimensions of the fractured rock sample (1) are 30cm × 30cm × 60cm (height × width × length).

3. The indoor large-size fractured rock specimen preparation device as described in claim 2, characterized in that: The internal dimensions of the rectangular plastic mesh (2) are height × width × length = 32cm × 32cm × 62cm.

4. The indoor large-size fractured rock specimen preparation device as described in claim 3, characterized in that: The internal dimensions of the rectangular mold (3) are 34cm × 34cm × 64cm (height × width × length), and the material is alloy material with a wall thickness of 1~2cm.

5. The indoor large-size fractured rock specimen preparation device as described in claim 1, characterized in that: The free alloy plate can be freely disassembled from other adjacent surfaces of the cuboid mold (3) via a latch.

6. The indoor large-size fractured rock specimen preparation device as described in claim 1, characterized in that: Another square alloy plate, which is perpendicular to the rectangular face, has a cylinder with a height of 1cm and a radius of 2cm at each of its four inner corners.

7. A method for preparing large-size fractured rock specimens indoors, characterized in that... The method, performed using the apparatus according to any one of claims 1-6, comprises the following steps: Step 1: Conduct an on-site investigation to determine the location where fractured rock samples can be extracted and mark it; Step 2: According to the test requirements, manually chisel out a fractured rock sample (1) at the designated location and measure the size of the fractured rock sample (1); Step 3: Wrap the fractured rock sample (1) with the plastic net (2); Step 4: Remove the free alloy plate from the cuboid mold (3), place it stably on a flat ground, and then place the fractured rock sample (1) held in the plastic net (2) stably on the free alloy plate. Cover the other parts of the cuboid mold (3), and after fastening the free and detachable free alloy plate, flip it over so that the side of the cuboid mold (3) without the alloy plate is facing up and the end of the free alloy plate with the small hole is facing down. Adjust the position of the fractured rock sample (1) so that the fractured rock sample (1) is centered in the cuboid mold (3). Step 5: Mix the cement slurry according to the mix ratio and consistency obtained from the experiment, stir evenly, open the small hole of the free alloy plate, slowly pour the mixed cement slurry into the gap between the fractured rock sample (1) and the cuboid mold (3), and vibrate and stir to form the shape; at the same time, use the conventional concrete pouring method to make pure cement slurry specimens of the same specifications. Step 6: After the curing period reaches 7 days, the composite structure consisting of the fractured rock sample (1), plastic mesh (2) and cement slurry layer (4) is taken out from the cuboid mold (3), and the composite structure and the pure cement specimen are transported back to the indoor laboratory.

8. The method for preparing large-size fractured rock specimens indoors as described in claim 7, characterized in that: Also includes: Step 7: Without any grinding or processing, the composite structure and the pure cement specimen are cured directly according to the test method conditions and then different indoor rock mechanics tests are carried out; the pure cement specimen and the composite structure are subjected to the same type of mechanical test. Through the mechanical test of the pure cement specimen, the pressure and deformation curves of the cement paste layer (4) after cement curing are obtained. Step 8: Based on the pressure and deformation curves obtained from the composite structure test, read the pressure F and the corresponding deformation μ when the fractured rock breaks from the curves. Based on the obtained deformation μ, find the pressure value corresponding to the deformation μ in the pressure and deformation curve of the pure cement specimen, and calculate the strength of the cement paste layer (4). Let the strength of the fractured rock be σ, the bottom area or side area of ​​the cuboid mold (3) be S1, and the bottom area or side area of ​​the fractured rock sample (1) be S2. Based on the limit equilibrium theory and comparative analysis of experimental results, the strength of the fractured rock σ is calculated according to the rock strength correction formula: ； The calculated rock mechanical parameters can accurately reflect the mechanical properties of the rock.

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