A cylindrical rock sample sealing device and method suitable for true triaxial test

Abstract

A sealing device and method for a columnar rock sample suitable for a true triaxial test, the device comprises a cylindrical pressure head, a heat shrink sleeve and a clamping nut; the cylindrical pressure head is provided with an annular boss, the annular boss is provided with an external thread; the rock sample is clamped between two cylindrical pressure heads; the clamping nut is provided with an annular convex edge, the clamping nut is screwed with the annular boss; the heat shrink sleeve is coated on the cylindrical pressure head and the outer side of the rock sample, and the heat shrink sleeve sleeve mouth is sealed and pressed between the axial side end face of the annular boss and the annular convex edge. The method is: place the rock sample on the bottom pressure head, insert the heat shrink sleeve, insert the clamping nut through the heat shrink sleeve, place the top pressure head on the top of the rock sample, so that the top pressure head is also located in the heat shrink sleeve, heat the heat shrink sleeve to shrink it, until the cylindrical pressure head and the rock sample are all tightly wrapped, cut off the heat shrink sleeve coated on the external thread surface of the annular boss, and screw the two clamping nuts onto the corresponding annular bosses respectively until the heat shrink sleeve sleeve mouth is compressed and sealed.

Description

Technical Field

[0001] The invention belongs to the technical field of true triaxial testing, and in particular relates to a rock sample sealing device and method suitable for true triaxial testing. Background Art

[0002] At present, when conducting true triaxial tests on rocks, the sealing effect of rock samples has never satisfied scientific researchers, because the rock sample and the pressure head need to be sealed with a heat shrink sleeve, and the heat shrink sleeve and the pressure head also need to be sealed to prevent the hydraulic oil in the pressure chamber from entering the rock sample through the gap between the heat shrink sleeve and the pressure head. Once the hydraulic oil enters the rock sample, the physical properties of the rock sample will change, and the test data obtained at this time will be distorted, and therefore will lose practical application value.

[0003] At present, the sealing of the heat shrink sleeve and the pressure head is mainly achieved by wrapping electrical tape, but this sealing method has the highest probability of sealing failure. This sealing method is mainly used in short-term true triaxial tests, because once the time is too long, the probability of sealing failure will increase exponentially. There is another more commonly used sealing method, which is to use a metal hoop to tighten the sleeve of the heat shrink sleeve on the pressure head. The timeliness of this sealing method will be slightly longer than the electrical tape wrapping sealing method, but it can only meet the short-term true triaxial test. With the continuous expansion of test subjects, the true triaxial test that needs to be carried out under long-term aging has received more and more attention. Some long-term tests can even last for several months. During such a long period of time, the rock sample needs to be in ultra-high pressure hydraulic oil all the time, and sealing failure is not allowed. However, the sealing method using metal hoops cannot meet the reliability requirements of sealing under long-term aging. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a columnar rock sample sealing device and method suitable for true triaxial testing, which effectively overcomes the disadvantage that the probability of rock sample sealing failure is high under traditional sealing methods and effectively improves the sealing reliability of rock samples.

[0005] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a cylindrical rock sample sealing device suitable for true triaxial test, comprising a first cylindrical pressure head, a second cylindrical pressure head, a heat shrink sleeve, a first clamping nut and a second clamping nut; the first cylindrical pressure head and the second cylindrical pressure head have the same structure and size, a first annular boss is provided in the axial middle part of the first cylindrical pressure head, a second annular boss is provided in the axial middle part of the second cylindrical pressure head, and external threads are provided on the outer peripheral surfaces of the first annular boss and the second annular boss; the first cylindrical pressure head is located at the bottom end of the rock sample, and the second cylindrical pressure head is located at the top end of the rock sample; the first clamping nut and the second clamping nut have the same structure and size, and the inner surfaces of the first clamping nut and the second clamping nut are provided with internal threads, and the internal threads of the first clamping nut are connected with the external threads of the first annular boss. The screw connection is carried out in a screw manner, and the internal thread of the second clamping nut is screwed with the external thread of the second annular boss; a first annular convex edge is provided on one side of the first clamping nut facing inward, and a second annular convex edge is provided on one side of the second clamping nut facing inward, the inner diameters of the first annular convex edge and the second annular convex edge are the same, and the inner diameters of the first annular convex edge and the second annular convex edge are larger than the diameter of the rock sample and smaller than the outer diameters of the first annular boss and the second annular boss; the heat shrink sleeve is covered on the outer surfaces of the first cylindrical pressure head, the rock sample and the second cylindrical pressure head, but the outer circumferential surfaces of the first annular boss and the second annular boss with external threads are not covered with the heat shrink sleeve; the bottom sleeve opening of the heat shrink sleeve is sealed and pressed between the axial end face of the first annular boss and the first annular convex edge, and the top sleeve opening of the heat shrink sleeve is sealed and pressed between the axial end face of the second annular boss and the second annular convex edge.

[0006] A method for sealing a columnar rock sample suitable for a true triaxial test, using the columnar rock sample sealing device suitable for a true triaxial test, comprises the following steps:

[0007] Step 1: Place the first cylindrical indenter vertically on the workbench;

[0008] Step 2: vertically place the rock sample on the top of the first cylindrical indenter;

[0009] Step 3: Put the heat shrink sleeve onto the rock sample and the outer side of the first cylindrical indenter in sequence;

[0010] Step 4: insert the first clamping nut into the rock sample through the heat shrink sleeve, with the first annular convex edge on the first clamping nut facing upward;

[0011] Step 5: Insert the second clamping nut into the rock sample through the heat shrink sleeve, with the second annular convex edge on the second clamping nut facing downward;

[0012] Step 6: vertically place the second cylindrical indenter on the top of the rock sample so that the second cylindrical indenter is also in the heat shrink sleeve;

[0013] Step 7: Use a heat shrink gun to heat the heat shrink sleeve to shrink the heat shrink sleeve until the heat shrink sleeve tightly wraps the first cylindrical indenter, the rock sample and the second cylindrical indenter;

[0014] Step 8: Use a tool to cut off the heat shrink sleeves covering the external thread surfaces of the first annular boss and the second annular boss respectively, so that the external threads of the first annular boss and the second annular boss are completely exposed;

[0015] Step nine: screw the first compression nut onto the first annular boss until the bottom sleeve opening of the heat shrink sleeve is sealed and pressed between the axial end surface of the first annular boss and the first annular convex edge;

[0016] Step 10: Screw the second clamping nut onto the second annular boss until the top sleeve opening of the heat shrink sleeve is sealed and compressed between the axial end surface of the second annular boss and the second annular convex edge, and the sealing of the rock sample is completed.

[0017] Beneficial effects of the present invention:

[0018] The columnar rock sample sealing device and method suitable for true triaxial testing of the present invention effectively overcomes the disadvantage of high probability of rock sample sealing failure under traditional sealing methods, effectively improves the sealing reliability of rock samples, greatly simplifies the operation process compared with traditional sealing methods, can quickly and efficiently complete the sealing of rock samples, and effectively saves test preparation time. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of a cylindrical rock sample sealing device suitable for true triaxial test of the present invention;

[0020] Figure 2 for Figure 1 Middle AA section view;

[0021] In the figure, 1 is the first cylindrical pressure head, 2 is the second cylindrical pressure head, 3 is the heat shrink sleeve, 4 is the first clamping nut, 5 is the second clamping nut, 6 is the first annular boss, 7 is the second annular boss, 8 is the rock sample, 9 is the first annular flange, and 10 is the second annular flange. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] like Figure 1 , 2As shown, a cylindrical rock sample sealing device suitable for true triaxial test includes a first cylindrical pressure head 1, a second cylindrical pressure head 2, a heat shrink sleeve 3, a first clamping nut 4 and a second clamping nut 5; the first cylindrical pressure head 1 and the second cylindrical pressure head 2 have the same structure and size, a first annular boss 6 is provided in the axial middle part of the first cylindrical pressure head 1, and a second annular boss 7 is provided in the axial middle part of the second cylindrical pressure head 2, and external threads are provided on the outer circumferential surfaces of the first annular boss 6 and the second annular boss 7; the first cylindrical pressure head 1 is located at the bottom end of the rock sample 8, and the second cylindrical pressure head 2 is located at the top end of the rock sample 8; the first clamping nut 4 and the second clamping nut 5 have the same structure and size, and internal threads are provided on the inner surfaces of the first clamping nut 4 and the second clamping nut 5, the internal threads of the first clamping nut 4 are threadedly matched with the external threads of the first annular boss 6, and the second clamping nut 5 is threadedly engaged with the external thread of the second annular boss 7; a first annular convex edge 9 is provided on one side of the first clamping nut 4 facing inward, and a second annular convex edge 10 is provided on one side of the second clamping nut 5 facing inward, the inner diameters of the first annular convex edge 9 and the second annular convex edge 10 are the same, and the inner diameters of the first annular convex edge 9 and the second annular convex edge 10 are larger than the diameter of the rock sample 8 and smaller than the outer diameters of the first annular boss 6 and the second annular boss 7; the heat shrink sleeve 3 is coated on the outer surfaces of the first cylindrical pressure head 1, the rock sample 8 and the second cylindrical pressure head 2, but the outer peripheral surfaces of the first annular boss 6 and the second annular boss 7 with external threads are not coated with the heat shrink sleeve 3; the bottom sleeve opening of the heat shrink sleeve 3 is sealed and pressed between the axial end face of the first annular boss 6 and the first annular convex edge 9, and the top sleeve opening of the heat shrink sleeve 3 is sealed and pressed between the axial end face of the second annular boss 7 and the second annular convex edge 10.

[0024] A method for sealing a columnar rock sample suitable for a true triaxial test, using the columnar rock sample sealing device suitable for a true triaxial test, comprises the following steps:

[0025] Step 1: Place the first cylindrical indenter 1 vertically on the workbench;

[0026] Step 2: vertically place the rock sample 8 on the top of the first cylindrical indenter 1;

[0027] Step 3: insert the heat shrink sleeve 3 into the rock sample 8 and the outer side of the first cylindrical indenter 1 in sequence;

[0028] Step 4: insert the first clamping nut 4 into the rock sample 8 through the heat shrink sleeve 3, with the first annular convex edge 9 on the first clamping nut 4 facing upwards;

[0029] Step 5: Insert the second clamping nut 5 into the rock sample 8 through the heat shrink sleeve 3, with the second annular convex edge 10 on the second clamping nut 5 facing downward;

[0030] Step 6: vertically place the second cylindrical indenter 2 on the top of the rock sample 8 so that the second cylindrical indenter 2 is also in the heat shrink sleeve 3;

[0031] Step 7: Use a heat shrink gun to heat the heat shrink sleeve 3 to shrink the heat shrink sleeve 3 until the heat shrink sleeve 3 tightly wraps the first cylindrical indenter 1, the rock sample 8 and the second cylindrical indenter 2;

[0032] Step 8: Use a tool to cut off the heat shrink sleeve 3 covering the external thread surfaces of the first annular boss 6 and the second annular boss 7, respectively, so that the external threads of the first annular boss 6 and the second annular boss 7 are completely exposed;

[0033] Step nine: screw the first compression nut 4 onto the first annular boss 6 until the bottom sleeve opening of the heat shrink sleeve 3 is sealed and pressed between the axial end surface of the first annular boss 6 and the first annular convex edge 9;

[0034] Step 10: Screw the second clamping nut 5 onto the second annular boss 7 until the top sleeve opening of the heat shrink sleeve 3 is sealed and pressed between the axial end surface of the second annular boss 7 and the second annular ridge 10, and the sealing of the rock sample 8 is completed.

[0035] The solutions in the embodiments are not intended to limit the patent protection scope of the present invention. All equivalent implementations or changes that do not deviate from the present invention are included in the patent scope of this case.

Claims

1. A cylindrical rock sample sealing device suitable for true triaxial testing, characterized in that: The invention comprises a first cylindrical pressure head, a second cylindrical pressure head, a heat shrink sleeve, a first clamping nut and a second clamping nut; the first cylindrical pressure head and the second cylindrical pressure head have the same structure and size, a first annular boss is provided in the axial middle part of the first cylindrical pressure head, a second annular boss is provided in the axial middle part of the second cylindrical pressure head, and external threads are provided on the outer peripheral surfaces of the first annular boss and the second annular boss; the first cylindrical pressure head is located at the bottom end of the rock sample, and the second cylindrical pressure head is located at the top end of the rock sample; the first clamping nut and the second clamping nut have the same structure and size, internal threads are provided on the inner surfaces of the first clamping nut and the second clamping nut, the internal threads of the first clamping nut are threadedly matched with the external threads of the first annular boss, and the internal threads of the second clamping nut are threadedly matched with the external threads of the second annular boss The external thread of the boss is threadedly engaged; a first annular flange is provided inwardly on one side of the first clamping nut, and a second annular flange is provided inwardly on one side of the second clamping nut, the inner diameters of the first annular flange and the second annular flange are the same, and the inner diameters of the first annular flange and the second annular flange are larger than the diameter of the rock sample and smaller than the outer diameters of the first annular flange and the second annular flange; the heat shrink sleeve is covered on the outer surfaces of the first cylindrical pressure head, the rock sample and the second cylindrical pressure head, but the outer circumferential surfaces of the first annular boss and the second annular boss with external threads are not covered with the heat shrink sleeve; the bottom sleeve opening of the heat shrink sleeve is sealed and pressed between the axial end face of the first annular boss and the first annular flange, and the top sleeve opening of the heat shrink sleeve is sealed and pressed between the axial end face of the second annular boss and the second annular flange.

2. A method for sealing a columnar rock sample suitable for true triaxial testing, using the columnar rock sample sealing device suitable for true triaxial testing as claimed in claim 1, characterized in that The steps include: Step 1: Place the first cylindrical indenter vertically on the workbench; Step 2: vertically place the rock sample on the top of the first cylindrical indenter; Step 3: Put the heat shrink sleeve onto the rock sample and the outer side of the first cylindrical indenter in sequence; Step 4: insert the first clamping nut into the rock sample through the heat shrink sleeve, with the first annular convex edge on the first clamping nut facing upward; Step 5: Insert the second clamping nut into the rock sample through the heat shrink sleeve, with the second annular convex edge on the second clamping nut facing downward; Step 6: vertically place the second cylindrical indenter on the top of the rock sample so that the second cylindrical indenter is also in the heat shrink sleeve; Step 7: Use a heat shrink gun to heat the heat shrink sleeve to shrink the heat shrink sleeve until the heat shrink sleeve tightly wraps the first cylindrical indenter, the rock sample and the second cylindrical indenter; Step 8: Use a tool to cut off the heat shrink sleeves covering the external thread surfaces of the first annular boss and the second annular boss respectively, so that the external threads of the first annular boss and the second annular boss are completely exposed; Step nine: screw the first compression nut onto the first annular boss until the bottom sleeve opening of the heat shrink sleeve is sealed and pressed between the axial end surface of the first annular boss and the first annular convex edge; Step 10: Screw the second clamping nut onto the second annular boss until the top sleeve opening of the heat shrink sleeve is sealed and compressed between the axial end surface of the second annular boss and the second annular convex edge, and the sealing of the rock sample is completed.

Images