Drill hole sealing device and method suitable for in-situ penetration test of engineering rock mass

Abstract

The invention provides a drill hole sealing device and method suitable for an engineering rock mass in-situ permeability test, and belongs to the technical field of engineering rock mass in-situ gas permeability tests. Comprising a data recording device, a pressurizing valve, a gas injection valve, a first pressure detection meter, a second pressure detection meter, a first volume change controllable flexible sealing device, a second volume change controllable flexible sealing device and a gas injection perforated pipe. S2, sealing the test hole; s3, injecting gas into the test hole; the method has the beneficial effects that the roughness degree of the hole wall is brought into a derivation process, the drilling hole sealing problem is converted into the stress analysis problem, and a more accurate sealing pressure setting method is obtained by comparing the friction force provided by the hole wall with the thrust of the test section gas to the sealing device.

Description

Technical Field

[0001] The present invention relates to the technical field of in-situ gas permeability testing for engineering rock masses, and particularly to a borehole sealing device and method suitable for in-situ permeability testing of engineering rock masses. Background Art

[0002] Nowadays, in various deep geological engineering projects, accurate measurement of permeability is an important task for guiding engineering practice. At present, the testing of in-situ gas permeability of engineering rock masses is mainly achieved through borehole air injection tests or borehole water pressure tests based on the steady-state method. Among them, sealing the drilled test borehole is a key task. Currently, the sealing of test boreholes mainly uses an expandable double rubber plug hole sealer, whose structure is similar to the existing mine water injection and grouting plug hole sealer. It is pressurized and expanded by a manual hydraulic pump to achieve the purpose of sealing the test borehole. Subsequently, to ensure sealing, gas with a pressure less than 2 / 3 of the rubber plug expansion pressure is injected into the hole for the air injection test.

[0003] However, generally, a series of pressure gradients need to be set for borehole air injection tests based on the steady-state method. Assuming the pressure in the test borehole is Pg and the pressure in the expandable rubber plug is P1, simply ensuring Pg ≤ 2 / 3P1 cannot guarantee absolute sealing of the test section. And it is difficult to achieve dynamic regulation by using a manual hydraulic pump to pressurize the expandable rubber plug to meet the test sealing requirements. Secondly, the general mine water injection and grouting plug hole sealer is a sealing and grouting integrated device with a large size and inconvenient operation. Therefore, it is necessary to seek a more accurate method for setting the sealing pressure and a method for dynamically regulating the sealing pressure, and design relevant devices to reduce the device size and lighten the operation burden to a certain extent.

[0004] In summary, the current testing work for in-situ gas permeability of engineering rock masses has the following defects:

[0005] 1. The sealing pressure judgment standard is not strict enough. Only by injecting gas with a pressure less than 2 / 3 of the sealing pressure for the test, without considering the roughness of the hole wall, it is easy to cause gas leakage;

[0006] 2. In the prior art, a manual hydraulic pump is generally used to pressurize the sealing device, and it is impossible to achieve dynamic sealing of the test borehole to meet the experimental requirements;

[0007] 3. In the prior art, an expandable double rubber plug hole sealer is generally used, whose structure is similar to the existing mine water injection and grouting plug hole sealer. Its sealing device and air injection device are of an integrated structure and have a large size, making operation and carrying inconvenient. At the same time, for tests that require changing the length of the test section, the integrated structure cannot arbitrarily adjust the length of the test section, and different specifications of sealing devices need to be manufactured and carried, adding a burden to on-site tests. At the same time, for the expandable double rubber plug hole sealer generally used in the prior art, the outer wall of its flexible sealing device with controllable volume change is not soft enough, and the sealing effect is poor for relatively broken holes. Summary of the Invention

[0008] The object of the present invention is to overcome the problems in the background art and provide a borehole sealing device and method suitable for in-situ permeability testing of engineering rock masses. The borehole sealing device achieves the purpose of reducing the device size and lightening the operation burden by designing a detachable flexible sealing device with a controllable volume change of a small size and an air injection pipe; the borehole sealing method obtains a more accurate sealing pressure setting method by performing a mechanical analysis and comparison of the sealing pressure and the test hole pressure; the test hole pressure and the pressure of the flexible sealing device with a controllable volume change are simultaneously acquired through a data recording system to realize the dynamic regulation of the sealing pressure.

[0009] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is specifically as follows: A borehole sealing device suitable for in-situ permeability testing of engineering rock masses, including a data recording device, a pressure regulating valve, an air injection valve, a pressure gauge one, a pressure gauge two, a flexible sealing device one with a controllable volume change, a flexible sealing device two with a controllable volume change, and an air injection perforated pipe. The flexible sealing device one with a controllable volume change and the flexible sealing device two with a controllable volume change are provided with mounting holes penetrating up and down. The flexible sealing device one with a controllable volume change and the flexible sealing device two with a controllable volume change can both adopt expansion plugs. The air injection perforated pipe can slide through the mounting holes on the flexible sealing device one with a controllable volume change and the flexible sealing device two with a controllable volume change. An air storage cavity is arranged inside each of the flexible sealing device one with a controllable volume change and the flexible sealing device two with a controllable volume change. Ports communicating with the air storage cavity are respectively arranged at the upper and lower ends of the flexible sealing device one with a controllable volume change. One end of the flexible sealing device two with a controllable volume change is also provided with a port communicating with its internal air storage cavity. After external gas enters the air storage cavity from the port, the corresponding flexible sealing device with a controllable volume change can expand outwards to strengthen the seal with the hole wall, and can also expand inwards to reduce the aperture of the mounting hole, thereby strengthening the connection seal with the air injection perforated pipe; the flexible sealing device one with a controllable volume change and the flexible sealing device two with a controllable volume change are made of flexible materials;

[0010] The air inlet of the pressure valve and the air inlet of the gas injection valve are respectively connected to the air outlet of the external gas injection device. The air outlet of the pressure valve is detachably connected to one port of the flexible sealing device I with controllable volume change through the first air pipe. The other port of the flexible sealing device I with controllable volume change is detachably connected to the air inlet of the flexible sealing device II with controllable volume change through the second air pipe. The air inlet of the gas injection perforated pipe is detachably connected to the air outlet of the gas injection valve through the third air pipe. The gas injection perforated pipe penetrates through the flexible sealing device I with controllable volume change and the flexible sealing device II with controllable volume change. A plurality of air holes are arranged on the gas injection perforated pipe, and the air holes are located between the flexible sealing device I with controllable volume change and the flexible sealing device II with controllable volume change. The data recording device, the pressure valve, the gas injection valve, the first pressure detection table, the second pressure detection table, the flexible sealing device I with controllable volume change, the flexible sealing device II with controllable volume change and the gas injection perforated pipe can be disassembled and assembled with each other, so as to overcome the technical problems in the prior art that the sealing device and the gas injection device are of an integrated structure, have a large size, and are inconvenient to operate and carry;

[0011] The first pressure detection table is installed on the pressure valve, and the second pressure detection table is installed on the gas injection valve. The signal output ends of the first pressure detection table and the second pressure detection table are respectively connected to the signal input end of the data recording device. The first pressure detection table and the second pressure detection table respectively transmit the detected gas pressure to the data recording device.

[0012] The present invention also provides a drilling sealing method, which includes the following steps:

[0013] S1, device installation;

[0014] S1.1 Drill a test hole with the required hole diameter on the rock mass to be measured;

[0015] S1.2 Pass the gas injection perforated pipe through the flexible sealing device I with controllable volume change and the flexible sealing device II with controllable volume change, so that the air holes are located between the flexible sealing device I with controllable volume change and the flexible sealing device II with controllable volume change;

[0016] S1.3 After the gas injection perforated pipe and the flexible sealing device I with controllable volume change and the flexible sealing device II with controllable volume change are installed, the whole is installed in the test hole on the rock mass to be measured, that is, the installed gas injection perforated pipe, the flexible sealing device I with controllable volume change and the flexible sealing device II with controllable volume change are integrally placed in the test hole. If it is necessary to change the test section length, only the distance between the flexible sealing device I with controllable volume change and the flexible sealing device II with controllable volume change needs to be adjusted during the installation process to change the test section length, enhancing the applicability;

[0017] S1.4. The inlet of the pressure valve is connected to an external gas injection device. The outlet of the pressure valve is connected to a flexible sealing device I with controllable volume change through a first air pipe. The flexible sealing device I with controllable volume change is connected to a flexible sealing device II with controllable volume change through a second air pipe. The inlet of the injection valve is connected to an external gas injection device, and the outlet of the injection valve is connected to the inlet of the injection perforated pipe through a third air pipe.

[0018] S1.5. The first pressure detection gauge and the second pressure detection gauge are respectively connected to the data recording device in signal.

[0019] S2. Seal the test hole.

[0020] S2.1. Set the test pressure in the test hole as P g , First, keep the injection valve closed and turn on the external gas injection device to make the external gas injection device inject test gas into the injection valve. At this time, the test gas will not enter the injection perforated pipe through the injection valve. At this time, the pressure obtained by the data recording device is the initial pressure P between the external gas injection device and the injection valve ’ , The initial pressure P ’ is slightly greater than the test pressure P set in the test plan g , It has been calculated in advance that when the injection valve is opened, the pressure of the test gas will drop from P ’ to P g after entering the injection perforated pipe. According to formula (1) and the test pressure P g , calculate the sealing pressure P1 in the flexible sealing device I with controllable volume change and the flexible sealing device II with controllable volume change.

[0021] The said formula (1) is:

[0022]

[0023] Wherein, P1 is the sealing pressure, P g is the test pressure, r2 is the outer diameter of the flexible sealing device I with controllable volume change, r1 is the inner diameter of the flexible sealing device I with controllable volume change, u is the static friction coefficient of the hole wall, and h is the height of the flexible sealing device I with controllable volume change;

[0024] S2.2. Inject the sealing pressure P1 calculated in S2.1 into the flexible sealing device I with controllable volume change and the flexible sealing device II with controllable volume change through the external gas injection device. At this time, the sealing is completed, and the sealing pressure P1 can seal the test pressure P of the gas in the test hole after the injection valve is opened. g ;

[0025] S3. Inject gas into the test hole.

[0026] S3.1. Open the gas injection valve. The test gas enters the gas injection perforated pipe through the gas injection valve and enters the test section of the test hole from the air outlet holes of the gas injection perforated pipe. At this time, the initial pressure P ’ will drop to the test pressure P g set in the test plan. The first test starts. The test gas penetrates into the atmosphere through the rock mass, and the air pressure gradually drops. During this process, the data recording device detects and records the pressure change in the test hole through Pressure Detection Table 2. Wait until the test pressure P g drops to the atmospheric pressure value, and the first test ends;

[0027] S3.2. After the first test is completed, since the sealing pressure in the Flexible Sealing Device 1 with controllable volume change and the Flexible Sealing Device 2 with controllable volume change is sufficient to seal the test section at this time, there is no need to close the gas injection valve. Repeat step S3.1. Directly inject the test gas with a pressure higher than the previous pressure set in the test plan into the gas injection perforated pipe through the external gas injection device, that is, inject gas with a higher pressure again. The data recording device continues to detect and record the pressure change in the test hole, and at the same time, uses Equation (1) to calculate the required sealing pressure P1 in real time. The external gas injection device injects the sealing gas with the corresponding pressure into the Flexible Sealing Device 1 with controllable volume change and the Flexible Sealing Device 2 with controllable volume change according to the calculated sealing pressure P1, so as to realize the dynamic sealing of the test hole. In the actual drilling air injection test based on the steady-state method, after changing the injection flow rate, the sealing pressure of the Flexible Sealing Device with controllable volume change is adjusted in real time according to the measured pressure in the test hole to complete the dynamic regulation of the drilling sealing work.

[0028] Furthermore, the derivation process of Equation (1) is as follows:

[0029] S2.11. Assume that the test pressure in the test hole is P g , and the sealing pressure in the Flexible Sealing Device 1 with controllable volume change is P1. By analyzing the forces on the Flexible Sealing Device 1 with controllable volume change, it can be obtained that the mutual forces between the Flexible Sealing Device 1 with controllable volume change and the wall in the horizontal direction are P1 and P1'. These two forces are equal in magnitude and opposite in direction. Therefore, the Flexible Sealing Device 1 with controllable volume change is in force balance in the horizontal direction; in the vertical direction, the Flexible Sealing Device 1 with controllable volume change is subjected to an upward force F g given by the gas in the test hole, and a downward frictional force F f provided by the wall of the test hole. Therefore, whether the gas in the test hole leaks mainly depends on the balance in the vertical direction;

[0030] S2.12. Regarding the frictional force, the maximum static frictional force F f= u·F1, where u is the static friction coefficient of the test hole wall, and F1 is the extrusion force exerted by a pair of hole walls of the flexible sealing device with controllable volume change. Its magnitude is equal to the normal stress on the hole wall multiplied by the contact area between the flexible sealing device with controllable volume change and the hole wall, that is, the lateral area of the flexible sealing device with controllable volume change. Assuming that the inner diameter of the flexible sealing device with controllable volume change is r1, the outer diameter is r2, and the height is h. At this time, the lateral area S1 of the flexible sealing device with controllable volume change = 2πr2h. Therefore, the maximum static friction force F f = u·F1 = u·P1·S1 = 2uπr2hP1;

[0031] S2.13. For the upward force exerted by the gas in the test hole on the flexible sealing device with controllable volume change, the test pressure F g is equal to the normal stress on the bottom of the flexible sealing device with controllable volume change multiplied by the contact area S2 between the gas and the flexible sealing device with controllable volume change. S2 = π(r2 2 - r1 2 ), so there is F g = P g ·S2 = π(r2 2 - r1 2 )P g ;

[0032] Therefore, when F g ≤ F f , the gas will not leak, that is, π(r2 2 - r1 2 )P g ≤ 2uπr2hP1. By simplification, we can get:

[0033]

[0034] S2.14. Considering that in some cases, there is an incomplete contact area between the flexible sealing device with controllable volume change and the test hole wall, and its expansion mainly occurs in the middle section. Select 80% of the actual lateral area of the flexible sealing device with controllable volume change to ensure the effective sealing area, that is, F g ≤ 0.8F f , and after simplification, we get

[0035]

[0036] Therefore, when the pressure of the flexible sealing device with controllable volume change and the test hole pressure satisfy equation (1), it is considered that the sealing is effective.

[0037] Compared with the prior art, the beneficial effects of the present invention are:

[0038] 1. The present invention provides a borehole sealing method for in-situ gas permeability testing of engineering rock masses achieved by combining mechanical analysis. By incorporating the roughness of the borehole wall into the derivation process, the borehole sealing problem is transformed into a force analysis problem. By comparing the frictional force that the borehole wall can provide with the thrust of the gas in the test section on the sealing device, a more accurate sealing pressure setting method is obtained, solving the problems in traditional sealing methods that the sealing pressure setting lacks a scientific basis and it is difficult to ensure the sealing of test holes with different roughnesses, and achieving effective sealing of test holes in different scenarios.

[0039] 2. The present invention provides a real-time monitoring and dynamic regulation mechanism for the sealing pressure and the pressure in the test hole. By adding corresponding pressure sensors in the test device and connecting them to a data recording system, the sealing pressure and the pressure in the test hole can be monitored in real time, and the sealing effect can be evaluated in real time using the sealing pressure setting method mentioned in formula (1). According to the change of the pressure in the hole, the required sealing pressure in real time is given, solving the problem that traditional borehole sealing is difficult to achieve dynamic sealing of boreholes and improving the sealing effect under different test schemes.

[0040] 3. In the present invention, a flexible sealing device made of a detachable flexible material with controllable volume change is adopted. By reducing the device volume and making the sealing device and the gas injection device detachable, the length of the test section can be adjusted arbitrarily, solving the problems of traditional integrated expandable double rubber plug hole sealers with large size, easy to increase the test burden, and inability to flexibly change the length of the test section, greatly improving the test efficiency; at the same time, by using flexible materials and increasing the flexibility of the sealing device, the gap between the broken rock mass and the sealing device can be appropriately filled during the sealing process, solving the problems of traditional sealing devices with hard outer walls and poor sealing effect on broken rock masses, and greatly ensuring the sealing effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The drawings are used to provide a further understanding of the present invention and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the present invention and do not constitute a limitation to the present invention.

[0042] Figure 1 It is a schematic diagram of the principle of sealing pressure analysis in the present invention.

[0043] Figure 2 It is a schematic diagram of the structure of the test device of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0044] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. Of course, the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0045] Embodiment

[0046] As Figure 1 - Figure 2 shown, this embodiment provides a borehole sealing device applicable to in-situ permeability testing of engineering rock masses, including a data recording device, a pressure regulating valve, an air injection valve, a pressure gauge I, a pressure gauge II, a flexible sealing device I with controllable volume change, a flexible sealing device II with controllable volume change, and an air injection perforated pipe. The flexible sealing device I with controllable volume change and the flexible sealing device II with controllable volume change are vertically penetrated with mounting holes. The air injection perforated pipe can slide through the mounting holes on the flexible sealing device I with controllable volume change and the flexible sealing device II with controllable volume change. The flexible sealing device I with controllable volume change and the flexible sealing device II with controllable volume change can both adopt expansion plugs. An air storage cavity is arranged inside both the flexible sealing device I with controllable volume change and the flexible sealing device II with controllable volume change. Ports communicating with the air storage cavity are respectively arranged at the upper and lower ends of the flexible sealing device I with controllable volume change. A port communicating with the internal air storage cavity is also arranged at one end of the flexible sealing device II with controllable volume change. After external gas enters the air storage cavity from the port, the corresponding flexible sealing device with controllable volume change can expand outwards to strengthen the seal with the hole wall, and can also expand inwards to reduce the aperture of the mounting hole, thereby strengthening the connection seal with the air injection perforated pipe. The flexible sealing device I with controllable volume change and the flexible sealing device II with controllable volume change are made of flexible materials. The air inlet of the pressure regulating valve and the air inlet of the air injection valve are respectively connected to the air outlet of an external air injection device. The air outlet of the pressure regulating valve is detachably connected to one of the ports of the flexible sealing device I with controllable volume change through an air pipe I. The other port of the flexible sealing device I with controllable volume change is detachably connected to the air inlet of the flexible sealing device II with controllable volume change through an air pipe II. The air inlet of the air injection perforated pipe is detachably connected to the air outlet of the air injection valve through an air pipe III. The air injection perforated pipe penetrates through the flexible sealing device I with controllable volume change and the flexible sealing device II with controllable volume change. A plurality of air outlet holes are arranged on the air injection perforated pipe, and the air outlet holes are located between the flexible sealing device I with controllable volume change and the flexible sealing device II with controllable volume change. The data recording device, the pressure regulating valve, the air injection valve, the pressure gauge I, the pressure gauge II, the flexible sealing device I with controllable volume change, the flexible sealing device II with controllable volume change, and the air injection perforated pipe can be disassembled and assembled with each other, thereby overcoming the technical problems in the prior art that the sealing device and the air injection device are of an integrated structure, with large size, inconvenient operation and carrying. The pressure gauge I is installed on the pressure regulating valve, and the pressure gauge II is installed on the air injection valve. The signal output end of the pressure gauge I and the signal output end of the pressure gauge II are respectively connected to the signal input end of the data recording device. The pressure gauge I and the pressure gauge II respectively transmit the detected gas pressure to the data recording device.

[0047] To better achieve the above-mentioned inventive effects, the present invention also provides a drilling sealing method, including the following steps:

[0048] S1. Device installation;

[0049] S1.1 Drill a test hole with the required hole diameter on the rock mass to be measured;

[0050] S1.2 Pass the gas injection perforated pipe through the flexible sealing device one with controllable volume change and the flexible sealing device two with controllable volume change, so that the air outlet holes are located between the flexible sealing device one with controllable volume change and the flexible sealing device two with controllable volume change;

[0051] S1.3 After the gas injection perforated pipe, the flexible sealing device one with controllable volume change and the flexible sealing device two with controllable volume change are installed, then the whole is installed in the test hole on the rock mass to be measured, that is, the installed gas injection perforated pipe, the flexible sealing device one with controllable volume change and the flexible sealing device two with controllable volume change are put into the test hole as a whole. If it is necessary to change the length of the test section, just adjust the distance between the flexible sealing device one with controllable volume change and the flexible sealing device two with controllable volume change during the installation process to change the length of the test section and enhance the applicability;

[0052] S1.4 Connect the air inlet of the pressure regulating valve to the external gas injection device, connect the air outlet of the pressure regulating valve to the flexible sealing device one with controllable volume change through the first air pipe, connect the flexible sealing device one with controllable volume change and the flexible sealing device two with controllable volume change through the second air pipe, connect the air inlet of the gas injection valve to the external gas injection device, and connect the air outlet of the gas injection valve to the air inlet of the gas injection perforated pipe through the third air pipe;

[0053] S1.5 Connect the first pressure detection gauge and the second pressure detection gauge to the data recording device through signals respectively;

[0054] S2. Test hole sealing;

[0055] S2.1 Set the test pressure in the test hole as P g , First, keep the gas injection valve closed, turn on the external gas injection device, so that the external gas injection device injects test gas into the gas injection valve. At this time, the test gas will not enter the gas injection perforated pipe through the gas injection valve. At this time, the pressure obtained by the data recording device is the initial pressure P between the external gas injection device and the gas injection valve ’ , the initial pressure P ’ is slightly greater than the test pressure P set in the test plan g , It has been calculated in advance that when the gas injection valve is opened, the pressure of the test gas will drop from P ’ to P g after entering the gas injection perforated pipe. According to formula (1) and the test pressure P g, calculate the sealing pressure P1 in the flexible sealing device 1 with controllable volume change and the flexible sealing device 2 with controllable volume change.

[0056] Equation (1) is:

[0057]

[0058] where P1 is the sealing pressure, P g is the test pressure, r2 is the outer diameter of the flexible sealing device 1 with controllable volume change, r1 is the inner diameter of the flexible sealing device 1 with controllable volume change, u is the static friction coefficient of the hole wall, and h is the height of the flexible sealing device 1 with controllable volume change;

[0059] S2.2, inject the sealing pressure P1 calculated in S2.1 into the flexible sealing device 1 with controllable volume change and the flexible sealing device 2 with controllable volume change through an external gas injection device. At this time, the sealing is completed. This sealing pressure P1 can seal the test pressure P of the gas in the test hole after opening the gas injection valve. g ;

[0060] S3, inject gas into the test hole;

[0061] S3.1, open the gas injection valve. The test gas enters the gas injection perforated pipe through the gas injection valve and enters the test section of the test hole from the air outlet holes of the gas injection perforated pipe. At this time, the initial pressure P ’ will drop to the test pressure P set in the test plan. g , the first test starts. The test gas penetrates through the rock mass into the atmosphere, and the air pressure gradually drops. During this process, the data recording device detects and records the pressure change in the test hole through the pressure detection table 2. Wait until the test pressure P g drops to the atmospheric pressure value, and the first test ends;

[0062] S3.2. After the first test is completed, since the sealing pressures in the flexible sealing device I with controllable volume change and the flexible sealing device II with controllable volume change are sufficient to seal the test section at this time, there is no need to close the gas injection valve. Repeat step S3.1. Directly inject the test gas with a pressure higher than the previous pressure set in the experimental plan into the gas injection perforated pipe through the external gas injection device, that is, inject gas with a higher pressure again. The data recording device continues to detect and record the pressure change in the test hole, and at the same time, the required sealing pressure P1 is calculated in real time using Equation (1). The external gas injection device injects the sealing gas with the corresponding pressure into the flexible sealing device I with controllable volume change and the flexible sealing device II with controllable volume change according to the calculated sealing pressure P1, so as to realize the dynamic sealing of the test hole. In the actual drilling gas injection test based on the steady-state method, after changing the injection flow rate, the sealing pressure of the flexible sealing device with controllable volume change is adjusted in real time according to the measured pressure in the test hole to complete the dynamic regulation of the drilling sealing work.

[0063] As Figure 1 shown, the derivation process of Equation (1) is as follows:

[0064] Assume that the test pressure in the test hole is P g , and the sealing pressure in the flexible sealing device I with controllable volume change is P1. By analyzing the forces on the flexible sealing device I with controllable volume change, it can be obtained that the mutual forces between the flexible sealing device I with controllable volume change and the wall in the horizontal direction are P1 and P1', and these two forces are equal in magnitude and opposite in direction. Therefore, the flexible sealing device I with controllable volume change is in force balance in the horizontal direction; in the vertical direction, the flexible sealing device I with controllable volume change is subject to an upward force F g given by the gas in the test hole, and a downward frictional force F f provided by the wall of the test hole. Therefore, whether the gas in the test hole leaks mainly depends on the balance in the vertical direction;

[0065] Regarding the frictional force, the maximum static frictional force F f that the wall of the test hole can provide = u·F1, where u is the static friction coefficient of the wall of the test hole, and F1 is the extrusion force of the flexible sealing device I with controllable volume change on the hole wall, and its magnitude is equal to the normal stress on the hole wall multiplied by the contact area between the flexible sealing device I with controllable volume change and the hole wall, that is, the lateral area of the flexible sealing device I with controllable volume change. Assume that the inner diameter of the flexible sealing device I with controllable volume change is r1, the outer diameter is r2, and the height is h. At this time, the lateral area S1 of the flexible sealing device I with controllable volume change = 2πr2h. Therefore, the maximum static frictional force F f = u·F1 = u·P1·S1 = 2uπr2hP1;

[0066] For the upward force applied to the flexible sealing device I with controllable volume change of the gas in the test hole, the test pressure F g is equal to the normal stress received at the bottom of the flexible sealing device I with controllable volume change multiplied by the contact area S2 between the gas and the flexible sealing device with controllable volume change, and S2 = π(r2 2 - r1 2 ), so there is F g = P g ·S2 = π(r2 2 - r1 2 )P g ;

[0067] Therefore, when F g ≤ F f , the gas will not leak, that is, π(r2 2 - r1 2 )P g ≤ 2uπr2hP1, and through simplification, we can get:

[0068]

[0069] S2.14. Considering that in some cases, there is an incomplete contact area between the flexible sealing device with controllable volume change and the test hole wall, and its expansion mainly occurs in the middle section. To ensure the sealing effect, we believe that the effective sealing area is 80% of the side area of the actual flexible sealing device with controllable volume change. At this time, F g ≤ 0.8F f , and after simplification, we get

[0070]

[0071] Therefore, when the pressure of the flexible sealing device I with controllable volume change and the test hole pressure satisfy equation (1), it is considered that the sealing is effective.

[0072] Therefore, the present invention proposes a drilling sealing method for in-situ gas permeability testing of engineering rock masses realized by combining mechanical analysis. By incorporating the roughness of the hole wall into the derivation process, the drilling sealing problem is transformed into a force analysis problem. By comparing the frictional force that the hole wall can provide with the thrust of the gas in the test section on the sealing device, a more accurate sealing pressure setting method is obtained, solving the problems in the traditional sealing method that the sealing pressure setting lacks scientific basis and it is difficult to ensure the sealing of test holes with different roughnesses, and realizing the effective sealing of test holes in different scenarios.

[0073] In summary, the test device reduces the device size and lightens the operation burden by designing a detachable flexible sealing device with a controllable small-size volume change and an air injection perforated pipe; the test method obtains a more accurate sealing pressure setting method by performing mechanical analysis and comparison on the sealing pressure and the test hole pressure; the data recording system simultaneously acquires the test hole pressure and the pressure of the flexible sealing device with controllable volume change to realize the dynamic regulation of the sealing pressure.

[0074] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A borehole sealing device applicable to in-situ permeability testing of engineering rock masses, characterized in that, It includes a data recording device, a pressure regulating valve, an air injection valve, a pressure gauge I, a pressure gauge II, a flexible sealing device I with controllable volume change, a flexible sealing device II with controllable volume change, and an air injection perforated pipe; The air inlet of the pressure regulating valve and the air inlet of the air injection valve are respectively connected to the air outlet of an external air injection device. The air outlet of the pressure regulating valve is detachably connected to one port of the flexible sealing device I with controllable volume change through an air pipe I. The other port of the flexible sealing device I with controllable volume change and the air inlet of the flexible sealing device II with controllable volume change are detachably connected through an air pipe II. The air inlet of the air injection perforated pipe is detachably connected to the air outlet of the air injection valve through an air pipe III. The air injection perforated pipe penetrates through the flexible sealing device I with controllable volume change and the flexible sealing device II with controllable volume change. A plurality of air holes are arranged on the air injection perforated pipe, and the air holes are located between the flexible sealing device I with controllable volume change and the flexible sealing device II with controllable volume change; The pressure gauge I is installed on the pressure regulating valve, the pressure gauge II is installed on the air injection valve, and the signal output end of the pressure gauge I and the signal output end of the pressure gauge II are respectively connected to the signal input end of the data recording device.

2. A borehole sealing method, which is based on the borehole sealing device for in-situ permeability testing of engineering rock masses described in claim 1, is characterized in that, It includes the following steps: S1. Device installation; S1.

1. Drill a test hole with the required hole diameter in the rock mass to be measured; S1.

2. Pass the air injection perforated pipe through the flexible sealing device I with controllable volume change and the flexible sealing device II with controllable volume change, so that the air holes are located between the flexible sealing device I with controllable volume change and the flexible sealing device II with controllable volume change; S1.

3. After the air injection perforated pipe is installed with the flexible sealing device I with controllable volume change and the flexible sealing device II with controllable volume change, the whole is installed in the test hole in the rock mass to be measured; S1.

4. Connect the air inlet of the pressure regulating valve to the external air injection device. Connect the air outlet of the pressure regulating valve to the flexible sealing device I with controllable volume change through an air pipe I. Connect the flexible sealing device I with controllable volume change and the flexible sealing device II with controllable volume change through an air pipe II. Connect the air inlet of the air injection valve to the external air injection device. Connect the air outlet of the air injection valve to the air inlet of the air injection perforated pipe through an air pipe III; S1.

5. Connect the pressure gauge I and the pressure gauge II to the data recording device respectively; S2. Seal the test hole; S2.1, Set the test pressure in the test hole to P g , First, keep the gas injection valve closed and open the external gas injection device to inject test gas into the gas injection valve by the external gas injection device. At this time, the test gas will not enter the gas injection perforated pipe through the gas injection valve. The pressure obtained by the data recording device at this time is the initial pressure P between the external gas injection device and the gas injection valve ’ , According to formula (1) and the test pressure P g , Calculate the sealing pressure P1 in the flexible sealing device one with controllable volume change and the flexible sealing device two with controllable volume change The formula (1) is: Among them, P1 is the sealing pressure, P g is the test pressure, r2 is the outer diameter of the flexible sealing device with controllable volume change, r1 is the inner diameter of the flexible sealing device with controllable volume change, u is the static friction coefficient of the hole wall, and h is the height of the flexible sealing device with controllable volume change; S2.

2. Inject the sealing pressure P1 calculated in S2.1 into the flexible sealing device with controllable volume change I and the flexible sealing device with controllable volume change II through an external gas injection device. At this time, the sealing is completed, and the sealing pressure P1 can seal the test pressure P of the gas in the test hole after the gas injection valve is opened. g ; S3. Inject air into the test hole; S3.

1. Open the gas injection valve. The test gas enters the gas injection perforated pipe through the gas injection valve and enters the test section of the test hole through the air outlet holes of the gas injection perforated pipe. At this time, the initial pressure P ’ will drop to the test pressure P g set in the test plan, and the first test starts. The test gas penetrates through the rock mass into the atmosphere, and the air pressure gradually drops. During this process, the data recording device detects and records the pressure change in the test hole through pressure detector two. Wait until the test pressure P g drops to the atmospheric pressure value, and the first test ends; S3.

2. After the first test is completed, since the sealing pressures in the flexible sealing device I with controllable volume change and the flexible sealing device II with controllable volume change are sufficient to seal the test section at this time, there is no need to close the gas injection valve. Repeat step S3.

1. Directly inject the test gas with a pressure higher than the previous one set in the experimental plan into the gas injection perforated pipe through the external gas injection device. The data recording device continues to detect and record the pressure change in the test hole, and at the same time, uses formula (1) to calculate the required sealing pressure P1 in real time. The external gas injection device injects the sealing gas with the corresponding pressure into the flexible sealing device I with controllable volume change and the flexible sealing device II with controllable volume change according to the calculated sealing pressure P1, so as to realize the dynamic sealing of the test hole.

3. The drilling sealing method according to claim 2, characterized in that, In step S2.1, the derivation process of formula (1) is as follows: S2.

11. Assume that the test pressure in the test hole is P g , and the sealing pressure in the flexible sealing device I with controllable volume change is P1. Conduct a force analysis on the flexible sealing device I with controllable volume change. That is, the mutual forces between the flexible sealing device I with controllable volume change and the wall in the horizontal direction are P1 and P1', and these two forces are equal in magnitude and opposite in direction. Therefore, the flexible sealing device I with controllable volume change is in force balance in the horizontal direction; in the vertical direction, the flexible sealing device I with controllable volume change is subjected to an upward force F from the gas in the test hole g , and the downward frictional force F provided by the wall of the test hole f . Therefore, whether the gas in the test hole leaks mainly depends on the balance in the vertical direction; S2.

12. For the frictional force, the maximum static frictional force F that the test hole wall can provide f = u·F1, where u is the static friction coefficient of the test hole wall, and F1 is the extrusion force of a pair of hole walls of the flexible sealing device with controllable volume change. Its magnitude is equal to the normal stress on the hole wall multiplied by the contact area between the flexible sealing device with controllable volume change and the hole wall, that is, the lateral area of the flexible sealing device with controllable volume change. Assuming that the inner diameter of the flexible sealing device with controllable volume change is r1, the outer diameter is r2, and the height is h. At this time, the lateral area S1 of the flexible sealing device with controllable volume change = 2πr2h. Therefore, the maximum static frictional force F f = u·F1 = u·P1·S1 = 2uπr2hP1; S2.13, for the upward force applied to the flexible sealing device I with controllable gas volume change in the test hole, the test pressure F g is equal to the normal stress on the bottom of the flexible sealing device I with controllable volume change multiplied by the contact area S2 between the gas and the flexible sealing device with controllable volume change. S2 = π(r2 2 - r1 2 ), so there is F g = P g ·S2 = π(r2 2 - r1 2 )P g ; Therefore, when F g ≤F f the gas will not leak, that is, π(r2 2 -r1 2 )P g ≤2uπr2hP1, which can be simplified to: S2.14, select 80% of the area on one side of the flexible sealing device with a controllable actual volume change to ensure the effective sealing area, i.e., F g ≤0.8F f , which simplifies to Therefore, when the pressure of the flexible sealing device I with controllable volume change and the pressure of the test hole satisfy formula (1), the sealing is effective.

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