Hole wall strain relief ground stress test patch device and test method

Abstract

The invention belongs to the technical field of geotechnical engineering, and provides a hole wall strain relief ground stress test patch device and a test method.The hole wall strain relief ground stress test patch device comprises an air bag, at least three sets of strain rosettes are arranged on the outer wall of the air bag in the axis direction of the air bag, and each strain rosette is composed of four strain gauges in different directions; the strain gauge is clamped in a bracket arranged on the outer wall of the air bag; the air bag is inflated or deflated through the air guide piece, so that the air bag is switched between a relaxed state and an expanded state; when the air bag is in a loose state, a gap exists between the outer wall of the air bag and the surrounding rock; when the air bag is in an expansion state, the strain gauge and the bracket are adhered to the surrounding rock through an adhesive. Measurement failures caused by various factors are effectively avoided, and the success rate and the result accuracy of single-point primary rock stress testing and the drilling utilization rate are greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of geotechnical engineering, in particular to a hole wall strain releasing in-situ stress test patch device and a test method. BACKGROUND

[0002] In the process of excavation construction of underground engineering, various methods are often used to evaluate the stability of the engineering rock mass, and the original rock stress is the premise and basis for the overall stability analysis of the engineering rock mass. The size and direction of the original rock stress have a decisive role in the overall planning of underground engineering, the design of supporting structure and the selection of construction technology, and effective methods must be taken to test the original rock stress of the rock mass in the engineering range. The commonly used original rock stress test method at home and abroad is the hollow inclusion sleeve hole stress relief method, the basic principle of which is to first stick and install a hollow inclusion containing multi-angle strain gauges in the undisturbed area of the borehole, and then sleeve a borehole coaxial with the small hole outside the hollow inclusion. The strain change of the hollow inclusion in different directions and the elastic parameters of the rock are used to calculate the three-dimensional original rock stress components in the borehole coordinate system. This method is widely used in in-situ stress measurement due to its simple construction.

[0003] Although the hollow inclusion sleeve hole stress relief original rock stress test method is theoretically complete, in the process of relieving the thick-walled cylindrical core drilled, the core often breaks due to cracks, disturbance and other reasons, and the area to be pasted between the hollow inclusion and the hole wall is large, which makes it difficult to ensure that the two are tightly pasted in water or water-rich strata. Therefore, a hollow inclusion sensor without thickness is needed to effectively control the orientation angle of the strain gauge, directly measure the hole wall strain change during the hole wall relief process, and calculate the in-situ stress, in order to overcome the problem that the conventional hollow inclusion in-situ stress test is prone to failure due to core breakage or eccentricity. SUMMARY

[0004] The purpose of the present application is to provide a hole wall strain releasing in-situ stress test patch device and a test method to solve the problems existing in the prior art and effectively avoid measurement failure caused by factors such as core breakage and non-dense pasting, greatly improving the success rate and accuracy of original rock stress testing.

[0005] To achieve the above-mentioned purpose, the present application provides the following solution: the present application provides a hole wall strain releasing in-situ stress test patch device, comprising:

[0006] The gas bag has at least three groups of strain flowers arranged around the gas bag axis direction on the outer wall of the gas bag, the strain flowers are composed of four strain gauges in different directions, and the strain gauges are clamped in the grooves arranged on the outer wall of the gas bag.

[0007] A gas guide, through which the gas bag is inflated or deflated to switch between the relaxed state and the inflated state; when the gas bag is in the relaxed state, there is a gap between the outer wall of the gas bag and the surrounding rock; when the gas bag is in the inflated state, the strain gauge and the bracket are adhered to the surrounding rock by an adhesive.

[0008] Preferably, the gas guide comprises:

[0009] A seal, which is fixed to the open end of the gas bag;

[0010] A gas guide tube, which penetrates the seal, the gas inlet end of the gas guide tube communicates with the inner cavity of the gas bag, and the gas bag is inflated through the gas guide tube to make the gas bag in the inflated state, and the gas bag is deflated through the gas guide tube to make the gas bag in the relaxed state.

[0011] Preferably, the inner wall of the gas bag opposite to the bracket is fixed to the outer wall of the gas guide tube by an extension support.

[0012] Preferably, the outer wall of the seal abuts against the surrounding rock by a limiting rubber ring.

[0013] Preferably, the wire electrically connected with the strain gauge penetrates the inner cavity of the gas guide tube and is connected with an external test device.

[0014] A hole wall stress relief method, comprising the following steps:

[0015] S1, a large hole is opened, and a concentric small hole is drilled after the large hole drilling, and a drilling column coordinate system is determined;

[0016] S2, the gas bag is sent into the small hole, the gas bag is inflated, the gas bag is inflated and adhered to the surrounding rock, the strain gauge is adhered to the surrounding rock of the small hole by an adhesive, and the wire is connected;

[0017] S3, data acquisition and hole casing relief are performed synchronously, the change amount of each strain gauge in the stress relief process is tested, and the core is taken out after the reading is stable;

[0018] S4, the elastic modulus and Poisson's ratio of the test point position surrounding rock are tested by modulus determination or conventional uniaxial compression test, and the in-situ stress test result is calculated according to the circular hole wall surrounding rock stress solution.

[0019] Preferably, the in-situ stress of the to-be-tested point position comprises:

[0020] The deviation value in the in-situ stress test result is removed;

[0021] Based on the in-situ stress test result after removing the deviation value, an in-situ stress solution statically indeterminate model is constructed;

[0022] Solve the ground stress solution undetermined model based on the least square method, and obtain the ground stress.

[0023] Preferably, the stress relief process needs to be carried out after the strain gauge is completely cured and attached to the hole wall by the adhesive when the air bag is inflated, and the air bag is released and kept in a relaxed state.

[0024] Preferably, the large hole opening depth is at least 2-4 times the spatial span or height of the test position, and the hole wall is cleaned after drilling.

[0025] The present application discloses the following technical effects:

[0026] (1) Suitable for stress measurement of broken thick-walled cylindrical core in sampling process, solves the problem of low success rate of test results and difficult to guarantee accuracy caused by objective reasons such as core disturbance, local broken of surrounding rock, incomplete sticking of hollow inclusion and surrounding rock, etc.

[0027] (2) The strain gauge can be well attached to the hole wall by using air bag expansion during the pasting process, the patching device can be reused, the strain gauge is firmly and reliably pasted to the surrounding rock, the patching efficiency is high, the installation process is simple, the waste hole rate is low, and the test cost is low. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings:

[0029] Figure 1 It is a structural schematic diagram of the hole wall strain relief ground stress test patching device of the present application;

[0030] Figure 2 It is a sectional view of the patching device in the present application;

[0031] Figure 3 It is a distribution schematic diagram of the strain rosette and the strain gauge in the present application.

[0032] Figure 4 It is an angle schematic diagram of the strain rosette in the present application;

[0033] Figure 5 It is a structural schematic diagram of the telescopic support in the present application;

[0034] Among them, 1, strain gauge; 2, wire; 3, limiting rubber ring; 4, seal; 5, bracket; 6, air guide pipe; 7, air bag; 8, telescopic support. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only 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 work fall within the protection scope of the present application.

[0036] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0037] With reference to Figures 1-5 The present application provides a hole wall strain relief stress test patch device, comprising:

[0038] The gas bag 7 is provided with at least three groups of strain flowers around the axis direction of the gas bag 7 on the outer wall of the gas bag 7, and the strain flower is composed of four strain gauges 1 in different directions, and the strain gauge 1 is clamped in the holding groove 5 provided on the outer wall of the gas bag 7;

[0039] The gas guide member is used for inflating or deflating the gas bag 7, so that the gas bag 7 is switched between the relaxed state and the inflated state; when the gas bag 7 is in the relaxed state, there is a gap between the outer wall of the gas bag 7 and the surrounding rock; when the gas bag 7 is in the inflated state, the strain gauge 1 and the holding groove 5 are pasted to the surrounding rock through the adhesive.

[0040] The device uses the extension performance of the gas bag 7 and the principle that the gas bag 7 can be deformed after inflation to paste the strain gauge 1 to the hole wall of the test point drill hole for testing. The basic principle is to measure the strain difference of the strain gauge 1 before and after the strain relief, and to obtain the stress by calculation. The holding groove 5 plays a role of fixing and clamping the strain gauge 1, preventing the strain gauge 1 from moving out of position during pasting; the strain gauge 1 holding groove 5 has a certain curvature, and the size is the same as the curvature of the drill hole wall. The present application is suitable for stress measurement of broken thick-walled cylindrical core in the sampling process, and solves the problems of low success rate of test results and difficult to guarantee accuracy caused by objective reasons such as core disturbance, local fracture of surrounding rock, incomplete pasting of hollow inclusion and surrounding rock, etc. The strain gauge 1 can be well pasted to the hole wall by using the inflation of the gas bag 7 during pasting, the patch device can be repeatedly used, the pasting of the strain gauge 1 to the surrounding rock is firm and reliable, the patching efficiency is high, the installation process is simple, the waste hole rate is low, and the test cost is low.

[0041] When the strain gauge 1 is completely pasted and starts to test, the internal gas pressure of the gas bag 7 needs to be released to keep the relaxed state.

[0042] Further optimization scheme, the gas guide member comprises:

[0043] The sealing 4 is fixedly connected to the open end of the gas bag 7;

[0044] The air duct 6 penetrates the sealing 4, the air inlet end of the air duct 6 communicates with the inner cavity of the air bag 7, and the air bag 7 is inflated through the air duct 6, so that the air bag 7 is in an inflated state, and the air bag 7 is deflated through the air duct 6, so that the air bag 7 is in a relaxed state.

[0045] When the patch device is tested, the air bag 7 is inflated through the air duct 6, the air bag 7 is deformed radially and axially, and the air bag 7 drives the bracket 5 to tightly fit the hole wall. The bracket 5 and the hole wall are pasted by the adhesive on the outer side of the bracket 5.

[0046] The air duct 6 plays a role of inflation and guiding when the air bag 7 is delivered into the hole, so that the air bag 7 does not fold in the relaxed state to avoid test failure.

[0047] The air bag 7 needs to be made of a material with good ductility and not easy to break.

[0048] Further optimization scheme, the inner wall of the air bag 7 opposite to the bracket 5 is fixed to the outer wall of the air duct 6 through the telescopic support 8.

[0049] The telescopic support 8 can ensure that the bracket 5 moves radially, and the telescopic support is directly set as a rectangular cross section, which can avoid rotation of the telescopic support during extension or contraction, and ensure stability.

[0050] Further optimization scheme, the outer wall of the sealing 4 abuts against the surrounding rock through the limiting rubber ring 3.

[0051] The limiting rubber ring 3 can prevent the package body from moving and tearing the lead 2 during inflation.

[0052] Further optimization scheme, the lead 2 electrically connected with the strain gauge 1 penetrates the inner cavity of the air duct 6 and is connected with the external test equipment.

[0053] The strain signals measured before and after the strain gauge 1 is released are transmitted through the lead 2.

[0054] A hole wall strain release stress test method, comprising the following steps:

[0055] S1, a large hole is opened, a concentric small hole is drilled after the large hole drilling is completed, and a borehole column coordinate system is determined;

[0056] A large hole is drilled into the rock mass through a hydraulic drilling machine and a guide device at a measurement point, the large hole is drilled to a specified position, the debris in the large hole is cleaned, and a concentric tapered hole is drilled at the bottom of the large hole to facilitate the drilling of the small hole. The drilling depth of the small hole is not less than the length of the air bag 7 in the inflated state, the small hole wall is cleaned and dried, and a borehole column coordinate system (ρ, θ, z) is determined;

[0057] S2, the air bag 7 is sent into the hole, the air bag 7 is inflated, the air bag 7 is expanded and attached to the surrounding rock, the strain gauge 1 is attached to the surrounding rock of the hole by the adhesive and is wired;

[0058] The patch air bag 7 is sent into the hole by a special tool containing a gyroscope, and the air guide pipe 6 serves as a guide; after being sent to the specified position and positioned, the air bag 7 is inflated, so that the air bag 7 is tightly attached to the hole wall, and the strain gauge 1 is tightly attached to the surrounding rock of the hole by the adhesive on the bracket 5.

[0059] S3, data acquisition and hole release are performed synchronously, the change amount of each strain gauge 1 during the stress release process is tested, and the core is taken out after the reading is stable;

[0060] The strain gauge wire is connected before coring, the adhesive is completely cured and attached to the hole wall, the air bag 7 is released and kept in a relaxed state, data acquisition and hole release are performed synchronously, the hole release drill bit diameter is R, the drilling speed is kept at 10-20 mm / min, the change amount of each strain gauge 1 of the hollow inclusion during the release process is tested, and the core is taken out after the reading is stable.

[0061] S4, the elastic modulus and Poisson's ratio of the surrounding rock at the test point position are tested by modulus determination or conventional uniaxial compression test, and the in-situ stress test results are calculated according to the stress release of the surrounding rock of the circular hole.

[0062] The specific calculation formula is as follows,

[0063] The strain change amount of the strain gauge 1 is:

[0064]

[0065] Let: Eε ij =A1σ x +A2σ y +A3σ z +A4τ xy +A5τ yz +A6τ zx , then

[0066]

[0067] In the formula, i=1~3 is the strain gauge number; j=1~4 is the strain gauge number; ΔE ij is the strain change amount of the strain gauge 1; θ i is the polar angle of the strain gauge (the polar angle of the strain gauge cannot be the same each time the release is performed); is the angle of the strain gauge 1; E is the elastic modulus of the rock; v is the Poisson's ratio of the rock; σ x , σ y , σ z , τ xy , τyz , τ zx are equation simplification coefficients.

[0068] The normal equation of the strain variation equation of the strain gauge 1 is constructed based on the least square principle as:

[0069]

[0070] In the formula, s is the number of observation value equations, and s = ij; i is the number of single hollow inclusion strain roses; j is the number of different direction strain gauges 1 contained in each strain rose; A k1 , A k2 ... A k6 are equation simplification coefficients; Δε k is the strain difference of the strain gauge 1 before and after the solution.

[0071] The in-situ stress value in the borehole cylindrical coordinate system is:

[0072]

[0073] Further optimization scheme, obtaining the in-situ stress of the to-be-measured in-situ stress point position includes:

[0074] Eliminate the deviation value in the in-situ stress test result;

[0075] Based on the in-situ stress test result after eliminating the deviation value, an in-situ stress solution over-determined model is constructed;

[0076] Based on the least square method, the in-situ stress solution over-determined model is solved to obtain the in-situ stress.

[0077] Further optimization scheme, the stress solution process needs to be carried out after the strain gauge 1 is completely cured and attached to the hole wall by the adhesive when the air bag 7 is inflated, and the air bag 7 air is kept in a relaxed state.

[0078] Further optimization scheme, the large hole opening depth is at least 2-4 times the spatial span or height of the test position, and the hole wall is cleaned after drilling.

[0079] Further optimization scheme, the stress test can be carried out on the broken thick-walled cylinder, but if the broken crack passes through the strain gauge 1 during the solution process, it is considered as a test failure, and the test needs to be carried out again after drilling.

[0080] In the description of the present application, it needs to be understood that the terms "longitudinal", "transverse", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, which are only for the convenience of describing the present application, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0081] The above-described embodiments are only to describe the preferred modes of the present application, and not to limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements to the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. A hole wall strain relief ground stress test patch device, characterized in that: include: An airbag (7), wherein at least three groups of strain gauges are arranged on the outer wall of the airbag (7) around the axis of the airbag (7), the strain gauges are composed of four strain gauges (1) in different directions, and the strain gauges (1) are clamped in brackets (5) arranged on the outer wall of the airbag (7); An air guide is used to inflate or deflate the airbag (7) so that the airbag (7) switches between a relaxed state and an expanded state; when the airbag (7) is in the relaxed state, a gap exists between the outer wall of the airbag (7) and the surrounding rock; when the airbag (7) is in the expanded state, the strain gauge (1) and the bracket (5) are adhered to the surrounding rock via an adhesive.

2. A hole wall strain relief ground stress test patch device according to claim 1, characterized in that: The air guide comprises: A seal (4), the seal (4) being fixed to the open end of the airbag (7); An air guide tube (6) is provided, wherein the air guide tube (6) passes through the sealing opening (4), an air inlet end of the air guide tube (6) is communicated with an inner cavity of the air bag (7), and the air bag (7) is inflated through the air guide tube (6) to put the air bag (7) in an expanded state, and the air bag (7) is deflated through the air guide tube (6) to put the air bag (7) in a relaxed state.

3. The hole wall strain relief ground stress test patch device according to claim 2, characterized in that: The inner wall of the air bag (7) opposite to the bracket (5) is fixedly connected to the outer wall of the airway tube (6) via a telescopic bracket (8).

4. The hole wall strain relief ground stress test patch device according to claim 2, characterized in that: The outer wall of the sealing opening (4) is in contact with the surrounding rock via a limiting rubber ring (3).

5. The hole wall strain relief ground stress test patch device according to claim 2, characterized in that: A wire (2) electrically connected to the strain gauge (1) passes through the inner cavity of the airway tube (6) and is connected to an external testing device.

6. A borehole wall strain relief ground stress testing method, according to the borehole wall strain relief ground stress testing patch device according to claim 1, characterized in that: The steps include: S1. Drill a large hole, drill concentric small holes after completing the drilling of the large hole, and determine the coordinate system of the drilling column; S2, inserting the airbag (7) into the small hole, inflating the airbag (7), causing the airbag (7) to expand and fit the surrounding rock, and adhering the strain gauge (1) to the surrounding rock of the small hole through an adhesive and performing wiring; S3, data acquisition and casing release are carried out simultaneously, and the change of each strain gauge (1) during the stress release process is tested, and the core is taken out after the reading is stable; S4. Test the elastic modulus and Poisson's ratio of the surrounding rock at the measuring point through elastic modulus calibration or conventional uniaxial compression test, and calculate the ground stress test results based on the stress solution of the surrounding rock of the circular hole wall.

7. A borehole wall strain relief ground stress testing method according to claim 5, characterized in that: Obtaining the in-situ stress at the in-situ stress point to be measured includes: Eliminate deviation values ​​in geostress test results; Based on the in-situ stress test results after eliminating the deviation value, an in-situ stress solution hyperstatic model is constructed; Based on the least square method, the statically indeterminate model of the ground stress solution is solved to obtain the ground stress.

8. The method for testing hole wall strain relief in-situ stress according to claim 5, characterized in that: The stress relief process needs to be carried out when the airbag (7) is inflated to ensure that the strain gauge (1) is completely cured and bonded to the hole wall through the adhesive, and the air in the airbag (7) is released to maintain a relaxed state.

9. The method for testing hole wall strain relief in-situ stress according to claim 5, characterized in that: The large hole opening depth should be at least 2-4 times the test location space span or height, and the hole wall should be cleaned after drilling is completed.

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