Tangential strain measuring device for drill hole

Abstract

The utility model discloses a drilling tangential strain measuring device which comprises a base which is of a hollow cylindrical structure. The strain gauge fixing device comprises a pre-pressing piece arranged in the base and a plurality of sets of elastic supporting pieces connected with the pre-pressing piece in a sliding mode, one ends of the elastic supporting pieces are arranged in the sliding ways in a sliding mode, the other ends of the elastic supporting pieces extend out of the base, the elastic supporting pieces are pressed, the elastic supporting pieces retract towards the interior of the base, and the elastic supporting pieces are fixed to the base. The strain gauge is arranged at the other end of the elastic supporting piece; the limiting device comprises a limiting rod and an elastic limiting pin, one end of the limiting rod is connected with the pre-pressing piece, the elastic limiting pin is matched with the limiting rod, a plurality of limiting grooves are formed in the outer wall of the limiting rod, the elastic limiting pin is clamped in the limiting grooves to limit the pre-pressing piece, the other end of the limiting rod extends out of the base, and the elastic limiting pin is limited on the base; and the strain gauge is electrically connected with the strain gauge. According to the utility model, the strain gauge does not need to be pasted on the inner wall of the drill hole during testing, and the strain gauge can adapt to drill holes with different sizes.

Description

Technical Field

[0001] The utility model belongs to the technical field of rock mechanics testing, and particularly relates to a device for measuring tangential strain of a borehole. Background Art

[0002] In-situ stress measurement is a very important issue in major construction projects. Correctly measuring the in-situ stress of rock mass is the basis for correctly and reasonably calculating the excavation load of underground projects. Therefore, in-situ stress measurement is very important. The on-site in-situ stress testing methods can be divided into two types: the stress relief method and the hydraulic fracturing method. Among them, the stress relief method is to drill a small hole (with a scale of about dozens of centimeters) along the axis of the borehole at the bottom of the borehole, lower the measuring device into the small hole (there are many different types of devices), and then continue to drill a core along the borehole downward to relieve the stress of the core surrounding rock at the bottom of the hole. The existing stress detection equipment applicable to the local wall stress relief method uses glue to paste the stress gauge on the sampling section, relieve the stress of the core in the sampling section, and measure the in-situ stress by recording the change of the strain data of the strain gauge. However, it has the following defects: (1) It cannot directly perform continuous sampling: Facing different sampling sections, the stress gauge needs to be re-pasted, which is time-consuming and laborious; (2) The stress gauge is easily damaged: As a precision electronic component, a high-precision strain gauge is easily damaged mechanically during the process of being re-pasted and removed, especially when drilling for oil, it is extremely easy to be damaged by the rock debris and irregular hole walls existing in the drilling fluid; (3) It is difficult to paste the stress gauge on the surface of the well wall under complex drilling conditions, and its success rate of adoption is low. Therefore, it is necessary to develop a device for measuring tangential strain of a borehole with a more firmly fixed strain gauge and without the need to remove it when changing the test section. Summary of the Utility Model

[0003] The purpose of the utility model is to provide a device for measuring tangential strain of a borehole aiming at the deficiencies of the prior art. This device does not need to paste the strain gauge on the inner wall of the borehole during testing, and it can be adapted to boreholes of different sizes for testing.

[0004] To solve the above technical problems, the utility model adopts the following technical scheme:

[0005] A device for measuring tangential strain of a borehole includes a base, a strain gauge fixing device, a strain gauge, a limiting device, and a strain gauge;

[0006] The base is a hollow cylindrical structure;

[0007] A strain gauge fixing device, which includes a preloading member disposed in a base and multiple groups of elastic support members slidably connected to the preloading member. The preloading member is frustum-shaped, and its diameter gradually increases as it approaches the limiting device. A plurality of slideways extending along its length direction are provided on the outer wall of the preloading member. One end of the elastic support member is slidably disposed in the slideway, and the other end of the elastic support member extends out of the base. By pressing the elastic support member, the elastic support member retracts into the base. The strain gauge is disposed on the other end of the elastic support member. During testing, the strain gauge is closely attached to the inner wall of the drill hole to be tested under the action of the elastic support member;

[0008] A limiting device, which includes a limiting rod with one end connected to the preloading member and an elastic limiting pin cooperating with the limiting rod. A plurality of limiting grooves are provided on the outer wall of the limiting rod, and the elastic limiting pin is clamped in the limiting groove to limit the preloading member. The other end of the limiting rod extends out of the base, and the elastic limiting pin is limited on the base;

[0009] A strain gauge, which is electrically connected to the strain gauge and is used to collect the strain data measured by the strain gauge.

[0010] Further, an electronic compass is fixed on the end face of the preloading member, and the electronic compass is used to record the installation angle of the strain gauge.

[0011] Further, one end of the base away from the limiting rod is an open end, and a guiding member is provided at the open end of the base. The guiding member has an arc-shaped guiding surface.

[0012] Further, the elastic support member includes a first support rod slidably connected in the slideway, a first spring with one end connected to the first support rod, and a second support rod connected to the other end of the first spring. The strain gauge is fixed on the second support rod. Among them, when testing the strain in the drill hole to be tested, the first spring is in a compressed state.

[0013] Further, it also includes a limiting plate. The limiting plate is sleeved outside the base, and the limiting plate is a conical structure, and its diameter gradually decreases as it approaches the elastic support member. Among them, the minimum diameter of the limiting plate is smaller than the inner diameter of the drill hole to be tested, and the maximum diameter of the limiting plate is larger than the inner diameter of the drill hole to be tested.

[0014] Further, the elastic limiting pin includes a second spring limited in the side wall of the base and a limiting pin with one end connected to the second spring and the other end extending out of the base and clamped in the limiting groove.

[0015] Further, it also includes a mounting rod. During use, the mounting rod is connected to the limiting rod through a connecting member.

[0016] Compared with the prior art, the beneficial effects of the present utility model are as follows: First, the drilling tangential strain measuring device of the present utility model is fixed on the drilling to be tested through a limiting plate, and then the strain gauge is pressed against the inner wall of the drilling to be tested through a preloading member and an elastic support member, and a limiting device is used to lock the preloading member to lock the strain gauge, so that there is no need to paste the strain gauge, and there is no need to remove the strain gauge when replacing the tested drilling, improving the test efficiency and accuracy; In addition, the elastic support member can automatically adjust the length according to the inner diameter of the drilling to be tested. Therefore, the present utility model can be adapted to drillings of various sizes for use. Description of the Drawings

[0017] Figure 1 It is a schematic structural diagram of the drilling tangential strain measuring device according to an embodiment of the present utility model;

[0018] Figure 2 is Figure 1 the left view of Detailed Embodiments

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts shall fall within the protection scope of the present utility model.

[0020] It should be noted that, without conflict, the embodiments in the present utility model and the features in the embodiments can be combined with each other.

[0021] The present utility model will be further described below in conjunction with specific embodiments, but it is not limited to the present utility model.

[0022] Such as Figure 1 and Figure 2As shown in the figure, an embodiment of the present utility model discloses a drilling tangential strain measurement device, which includes a base 1, a strain gauge fixing device, a strain gauge 3, a limiting device, and a strain gauge. The base 1 is a hollow cylindrical structure with a cavity inside. One end of the base 1 is an open end, and the other end is provided with a first through hole for the limiting device to pass through. The strain gauge fixing device includes a preloading member 21 disposed in the cavity of the base 1 and a plurality of elastic support members slidably connected to the preloading member 21. In order to facilitate positioning the strain gauge 2 according to the inner diameter of the drilling to be tested, the preloading member 2 is provided in a frustum shape, and its diameter gradually increases as it approaches the limiting device. A slideway 22 is provided on the outer wall of the preloading member 21 along its length direction. In this embodiment, three slideways 22 are equally spaced on the outer wall of the preloading member 21. Correspondingly, three groups of elastic support members are slidably connected to the preloading member 21. One end of each group of elastic support members is slidably disposed in the slideway 22, and the other end of the elastic support member extends outside the base 1. By pressing the elastic support member, the elastic support member retracts into the base 1, and the strain gauge 3 is disposed at the other end of the elastic support member. The strain gauge 3 on each group of elastic support members is connected to the strain gauge through a cable, and the strain gauge is used to collect the strain data measured by the strain gauge 3.

[0023] In this embodiment, the elastic support member includes a first support rod 23 slidably connected in the slideway, a first spring 24 connected to one end of the first support rod 23, and a second support rod 25 connected to the other end of the first spring 24. A second through hole is provided on the side wall of the base 1, and the second support rod 25 extends outside the base 1 through the second through hole. The strain gauge 3 is disposed on the second support rod 25. When measuring the strain of the drilling to be tested, the first spring 24 is in a compressed state, and the strain gauge 3 is pressed against the inner wall of the drilling to be tested by the elastic action of the first spring 24. In order to record the installation angles of the strain gauges 3, an electronic compass 5 is installed on the end side of the preloading member. In addition, a guiding member 11 is provided at the open end of the base 1, and the guiding member 11 has an arc-shaped guiding surface. The arc-shaped guiding surface of the guiding member 11 can help the device to be advanced when the drilling tangential strain measurement device is placed into the drilling.

[0024] The limiting device includes a limiting rod 41 connected to one end of the preloading member 21 and an elastic limiting pin cooperating with the limiting rod. A plurality of limiting grooves are provided on the outer wall of the limiting rod 41, and the end of the elastic limiting pin is clamped in the limiting groove to limit the preloading member 21. In this embodiment, a screw rod is used as the limiting rod, and the other end of the limiting rod 41 extends outside the base 1 through the first through hole. The elastic limiting pin includes a second spring 42 limited in the side wall of the base 1 and a limiting pin 43 connected to one end of the second spring 42 and extending out of the base 1 and clamped in the limiting groove. Specifically, a clamping groove is provided on the side wall of the base 1, the second spring is limited in the clamping groove, and after the limiting pin 43 is connected to the second spring 42, it extends out of the side wall of the base 1 and is clamped in the limiting groove.

[0025] To facilitate the positioning of the drilling tangential strain measuring device, a conical positioning plate 6 is sleeved outside the base 1, and its diameter gradually decreases as it approaches the elastic support. Among them, the minimum diameter of the positioning plate 6 is smaller than the inner diameter of the drilling to be tested, and the maximum diameter of the positioning plate 6 is larger than the inner diameter of the drilling to be tested. During the test, the drilling tangential strain measuring device is fixed in the drilling to be tested by clamping the positioning plate 6 at the orifice of the drilling to be tested.

[0026] The drilling tangential strain measuring device further includes an installation rod 7. Before sending the drilling tangential strain measuring device into the drilling, the installation rod 7 and the positioning rod 41 are fixedly connected through an installation pin, and the drilling tangential strain measuring device is sent to the specified depth in the drilling to be tested through the installation rod 7. When testing the drilling stress, the installation pin is removed, so as to separate the installation rod 7 and the positioning rod 41.

[0027] When testing the stress during the process of relieving the drilling stress by applying the drilling tangential strain measuring device of this embodiment, the following steps are included:

[0028] Step 1: Fix the positioning rod 41 and the installation rod 7, and send the drilling tangential strain measuring device to the test depth in the pre-drilled small drilling 8 to be tested through the installation rod 7, and position the drilling tangential strain measuring device in the small drilling 8 to be tested through the positioning plate 6 on the base 1;

[0029] Step 2: Connect the cables 30 on each strain gauge 3 to the strain gauge.

[0030] Step 3: Push the installation rod 7 to apply pressure to the preloading member 21. The preloading member 21 is pressed to move forward into the drilling. At the same time, the elastic support sliding on the preloading member 21 slides in the slideway 22 in the opposite direction until the strain gauge 3 located at the end side of the elastic support is pressed against the inner wall of the small drilling 8 to be tested. During the process of pushing the installation rod 7, the preloading strain value of the strain gauge can be read to determine whether to continue applying preloading; when there is no need to continue pressurizing, at this time the strain gauge 3 is positioned, stop pushing the installation rod 7, and the positioning rod 41 also stops moving forward. The positioning pin 43 on the base 1 positions the positioning rod 41, so that the strain gauge 3 is locked on the inner wall of the small drilling 8 to be tested;

[0031] Step 4: After the strain gauge 3 is locked, remove the installation pin, withdraw the installation rod 7, record the installation angle of each strain gauge 3 at this time through the electronic compass 5, and record the initial strain value of each strain gauge 3 through the strain gauge.

[0032] Step 5: Conduct a stress relief test, and record the strain value of each strain gauge 3 during the relief process through the strain gauge.

[0033] Step 6: After completely relieving the test small borehole 8 equipped with the borehole tangential strain measurement device, obtain the final strain value after relief through the strain gauge and the strain gauge 3. By comparing the strain values of each strain gauge 3 before and after relief, the strain change amount of each strain gauge 3 before and after relief can be obtained. Combining the previously obtained elastic modulus E and Poisson's ratio μ of the rock, substituting the strain change amount obtained after relieving each strain gauge 3, the installation angle of each strain gauge, and the elastic modulus E and Poisson's ratio μ of the rock into the following formula, the two-dimensional stress value on the cross-section of the borehole can be calculated:

[0034]

[0035] In the formula, ε i represents the strain value of the i-th strain gauge, k i represents the calibration coefficient of the i-th strain gauge, α i represents the installation angle corresponding to the i-th strain gauge, E represents the elastic modulus of the rock, μ represents the Poisson's ratio of the rock, σ x represents the stress value in the X direction, σ y represents the stress value in the Y direction.

[0036] The above is only a preferred embodiment of the present utility model, and does not limit the implementation manners and protection scope of the present utility model. For those skilled in the art, it should be able to realize that the solutions obtained by equivalent substitution and obvious changes made by using the content of the specification of the present utility model should all be included in the protection scope of the present utility model.

Claims

1. A drilling tangential strain measurement device, characterized in that It includes a base, a strain gauge fixing device, a strain gauge, a limiting device and a strain gauge instrument; The base is a hollow cylindrical structure; The strain gauge fixing device includes a preloading member arranged in the base and multiple groups of elastic support members slidably connected to the preloading member. The preloading member is frustum-shaped, and its diameter gradually increases as it approaches the limiting device. A plurality of slideways extending along its length direction are arranged on the outer wall of the preloading member. One end of the elastic support member is slidably arranged in the slideway, and the other end of the elastic support member extends out of the base. By pressing the elastic support member, the elastic support member retracts into the base. The strain gauge is arranged on the other end of the elastic support member. During testing, the strain gauge is closely attached to the inner wall of the drill hole to be tested under the action of the elastic support member; The limiting device includes a limiting rod with one end connected to the preloading member and an elastic limiting pin cooperating with the limiting rod. A plurality of limiting grooves are arranged on the outer wall of the limiting rod, and the elastic limiting pin is clamped in the limiting groove to limit the preloading member. The other end of the limiting rod extends out of the base, and the elastic limiting pin is limited on the base; The strain gauge instrument is electrically connected to the strain gauge and is used to collect the strain data measured by the strain gauge.

2. The drilling tangential strain measuring device according to claim 1, wherein An electronic compass is fixed on the end face of the preloading member, and the electronic compass is used to record the installation angle of the strain gauge.

3. The drilling tangential strain measuring device according to claim 1, characterized in that, One end of the base away from the limiting rod is an open end, and a guiding member is arranged at the open end of the base. The guiding member has an arc-shaped guiding surface.

4. The drilling tangential strain measuring device according to claim 1, wherein The elastic support member includes a first support rod slidably connected in the slideway, a first spring with one end connected to the first support rod, and a second support rod connected to the other end of the first spring. The strain gauge is fixed on the second support rod. Among them, when testing the strain in the drill hole to be tested, the first spring is in a compressed state.

5. The drilling tangential strain measuring device according to claim 1, characterized in that, It further includes a limiting plate. The limiting plate is sleeved outside the base, and the limiting plate is a conical structure, and its diameter gradually decreases as it approaches the elastic support member. Among them, the minimum diameter of the limiting plate is smaller than the inner diameter of the drill hole to be tested, and the maximum diameter of the limiting plate is larger than the inner diameter of the drill hole to be tested.

6. The drilling tangential strain measuring device according to claim 1, characterized in that, The elastic limiting pin includes a second spring limited in the side wall of the base and a limiting pin with one end connected to the second spring and the other end extending out of the base and clamped in the limiting groove.

7. The drilling tangential strain measuring device according to claim 1, characterized in that It further includes an installation rod. During use, the installation rod is connected to the limiting rod through a connecting piece.

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