A device and method for measuring the direction of ground stress of a concrete precast product using hydraulic fracturing

Abstract

The application provides a water pressure fracturing ground stress direction measuring device and method for a concrete prefabricated part, relates to the technical field of ground stress direction measurement, and comprises a water pressure fracturing ground stress direction measuring device for a concrete prefabricated part, which comprises a concrete upper packoff section, a hollow columnar structure and a copper pipe inserted therein, and a drill rod threadedly connected to the copper pipe; a concrete fracturing section, a hollow columnar structure and in communication with the copper pipe; a concrete lower packoff section, an upper part being a solid columnar structure, a lower part being provided with a hollow copper column, and an electronic compass system being placed in the hollow copper column, the upper end of the concrete lower packoff section being connected with the concrete fracturing section, and the lower end being connected with a sealing bolt; and a method for measuring by using the water pressure fracturing ground stress direction measuring device for a concrete prefabricated part; the application is suitable for the measurement of the ground stress direction, improves the identification precision of the ground stress direction, and improves the passability of the measuring device.

Description

Technical Field

[0001] The present invention relates to the technical field of ground stress direction measurement, and in particular to a device and method for measuring the ground stress direction of a prefabricated concrete part caused by hydraulic fracturing. Background Art

[0002] In-situ stress, also known as in-situ rock stress, initial rock mass stress, or absolute stress, is generated over vast geological timescales due to tectonic movements and other factors. In-situ stress plays a crucial role in production practices such as mining, underground engineering, and energy development. Measuring in-situ stress is a prerequisite for determining the mechanical properties of engineering rock masses, analyzing surrounding rock stability, and enabling scientific excavation design and decision-making in geotechnical engineering. Therefore, selecting a reasonable and effective in-situ stress measurement method is of great significance.

[0003] Geostress measurement includes both magnitude and direction of geostress. For geostress direction measurement, the hydraulic fracturing impression method and borehole caving method are currently the main methods used.

[0004] Specifically, the hydraulic fracturing method for identifying the direction of principal stress involves: using hydraulic fracturing to create a vertical or nearly vertical crack in the borehole wall; then, sending an impression device into the hydraulic fracturing location downhole, and pressurizing and expanding the impression device so that the crack in the borehole wall is imprinted on the impression device; the impression device with the crack imprint is taken out to the ground, and the principal stress direction can be identified by analyzing the imprint on the outer surface of the impression device. The main problems with this method are: since it requires hydraulic fracturing to create a nearly vertical crack in the borehole wall, this process can only be achieved in a small number of hard and brittle rocks with good integrity, such as granite or marble. For a large number of boreholes with low compressive strength and broken formations, no cracks can be created or only chaotic cracks can be obtained, making it impossible to use the impression method to identify the principal stress direction. At the same time, when the impression device with the crack impression is removed from the surface, the outer surface of the impression device is easily rubbed by the hole wall, thereby wearing away the crack impression on the impression device surface. Therefore, when the impression device is removed from the surface, it is difficult to identify the principal stress direction by analyzing the cracks on the impression device surface. This phenomenon is particularly obvious when identifying the stress direction in deep holes.

[0005] The borehole collapse method for identifying the principal stress direction involves placing a downhole television in the borehole, imaging and observing the collapse of the rock in the borehole wall, and identifying the maximum principal stress direction based on the collapse direction. The main problems with this method are: since the collapse phenomenon occurs within a relatively large directional range, this range often has an angle of 20° to 50°, the collapse location distribution range is too wide, and occasionally even collapse occurs within the entire angle range of 0° to 360°. Therefore, it is difficult for the downhole television to accurately identify the exact collapse direction. Therefore, the accuracy of identifying the principal stress direction is very low, making it unsuitable for measurements requiring higher precision. At the same time, the collapse of the borehole wall can only occur in a few rock formations with good integrity and high hardness, such as granite and marble, and cannot occur in a large number of boreholes with low rock compressive strength and broken formations. Therefore, the scope of application of this method is relatively narrow.

[0006] In summary, the traditional method for measuring the direction of ground stress has the disadvantages of low accuracy in identifying the direction of ground stress and a small scope of application. Summary of the Invention

[0007] The object of the present invention is to provide a device and method for measuring the direction of hydraulic fracturing ground stress of precast concrete parts, which solves the problems of low recognition accuracy and small scope of application of traditional ground stress direction measurement methods.

[0008] The embodiments of the present invention are implemented through the following technical solutions: a device for measuring the direction of hydraulic fracturing stress of a precast concrete part, comprising an upper concrete isolation section, which is a hollow cylindrical structure and is plugged with a copper tube, which is threadedly connected to a drill rod; a concrete fracturing section, which is a hollow cylindrical structure and is connected to the copper tube; a lower concrete isolation section, which is a solid cylindrical structure at the top and is provided with a hollow copper column at the bottom, in which an electronic compass system is placed; the upper end of the lower concrete isolation section is connected to the concrete fracturing section, and the lower end is connected to a sealing bolt;

[0009] Furthermore, the concrete fracturing section is provided with several layers of longitudinal toughness reinforcement bars;

[0010] Furthermore, the longitudinal toughness reinforcement rib is made of non-magnetic material and has a diameter of 1-3 mm;

[0011] Furthermore, the longitudinal toughness reinforcement ribs are evenly spaced circumferentially;

[0012] Furthermore, the copper tube wall thickness is 3-10 mm;

[0013] Furthermore, the drill pipe is connected to a ground high-pressure water pressurization system.

[0014] A method for measuring the direction of hydraulic fracturing stress of a precast concrete part using a device for measuring the direction of hydraulic fracturing stress of the precast concrete part comprises:

[0015] Step S1: Drilling a hole into the ground and filling the test section where the ground stress direction measurement is required with concrete mortar;

[0016] Step S2: Place the entire prefabricated concrete component, including the upper concrete isolation section, the concrete fracturing section, and the lower concrete isolation section, into the test section concrete mortar, and thread the upper drill rod to connect it to the surface high-pressure water pressurization system.

[0017] Step S3: After the concrete mortar in the test section is completely solidified, the entire system is placed underground for 7 to 28 days to allow the rock on the borehole wall to creep and squeeze, so that the crustal stress is gradually applied to the outer wall of the concrete fracturing section;

[0018] Step S4: The surface high-pressure water pressure system adds high-pressure water from low to high pressure into the hollow space inside the fracturing section through the drill pipe, thread and copper pipe until the concrete is fractured. At this time, longitudinal fracturing cracks will be generated in the concrete;

[0019] Step S5: After the concrete is fractured, a drilling rig is used to drill in and remove the upper concrete isolation section, the concrete fracturing section, and the lower concrete isolation section to the surface;

[0020] Step S6: reading the direction data in the electronic compass system and calculating the direction of the longitudinal compression crack in the concrete; the direction of the longitudinal compression crack in the concrete is the direction of the maximum horizontal principal stress component in the ground stress components;

[0021] Furthermore, the length of the test section is greater than the sum of the lengths of the upper concrete isolation section, the concrete fracturing section, and the lower concrete isolation section.

[0022] The technical solution of the present invention has at least the following advantages and beneficial effects: first, by analyzing the longitudinal fracturing cracks in the concrete fracturing section and using the direction data of the electronic compass system, the ground stress direction can be accurately obtained, which has the advantage of high ground stress direction measurement accuracy; second, it has the advantage of a wide range of applicability, and can be applied to the ground stress direction measurement of rock formations with good integrity and high hardness, as well as the ground stress direction measurement of formations with low rock compressive strength and easily broken formations; finally, the measurement accuracy of the present invention is not affected by the drilling depth. Compared with traditional technologies, it is very suitable for deep drilling ground stress direction measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 A schematic structural diagram of a device for measuring the direction of hydraulic fracturing stress of a precast concrete component provided in Example 1 of the present invention;

[0025] Figure 2 A schematic cross-sectional view of a longitudinal reinforcement of a device for measuring the direction of hydraulic fracturing stress of a precast concrete part provided in Example 1 of the present invention;

[0026] Figure 3 A longitudinal schematic diagram of the longitudinal reinforcement of the device for measuring the direction of hydraulic fracturing stress of a precast concrete part provided in Example 1 of the present invention;

[0027] Figure 4 Schematic diagram of the use scenario of the device for measuring the direction of hydraulic fracturing stress of precast concrete parts provided in Example 2 of the present invention.

[0028] Icons: 1-concrete upper isolation section, 2-concrete fracturing section, 3-concrete lower isolation section, 4-copper pipe, 5-drill pipe, 6-hollow copper column, 7-electronic compass system, 8-longitudinal toughness reinforcement, 9-stratum, 10-test section, 11-sealing bolt. DETAILED DESCRIPTION

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0030] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but rather merely represents selected embodiments of the present invention. The embodiments of the present invention and all other embodiments derived by persons of ordinary skill in the art without inventive effort are intended to fall within the scope of protection of the present invention.

[0031] Example 1

[0032] This embodiment provides a device for measuring the direction of hydraulic fracturing stress of a prefabricated concrete part. The device has a completely axisymmetric structure and includes an upper concrete isolation section 1, which is a hollow cylindrical structure and is plugged with a copper tube 4. The copper tube 4 is threadedly connected to a drill rod 5, and the drill rod 5 is connected to a ground high-pressure water pressurization system; a concrete fracturing section 2, which is a hollow cylindrical structure with a diameter of 10 mm to 30 mm and is connected to the copper tube 4. The wall thickness of the copper tube 4 is 3 to 10 mm; a lower concrete isolation section 3, which has a solid cylindrical structure at the top and a hollow copper column 6 at the bottom. An electronic compass system 7 is placed in the hollow copper column 6. The upper end of the lower concrete isolation section 3 is connected to the concrete fracturing section 2, and the lower end is connected to a sealing bolt 11. The upper concrete isolation section 1, the concrete fracturing section 2, and the lower concrete isolation section 3 are integrally formed by concrete pouring.

[0033] Several layers of longitudinal toughness reinforcement ribs 8 are provided in the concrete of the concrete fracturing section 2; the longitudinal toughness reinforcement ribs 8 generally have 4 layers, and in some embodiments, more or fewer layers can be provided as needed; the longitudinal toughness reinforcement ribs 8 are made of non-magnetic material, for example, copper wire or aluminum wire, and have a diameter generally of 1-3 mm; the longitudinal toughness reinforcement ribs 8 are generally placed evenly on the circumference and cast with concrete, and their placement density is set according to the required measurement accuracy. If the required directional measurement accuracy is less than 10 radians, one longitudinal toughness reinforcement rib 8 is provided every 10 radians. If the required directional measurement accuracy is less than 5 radians, one longitudinal toughness reinforcement rib 8 is provided every 5 radians.

[0034] Example 2

[0035] This embodiment provides a method for measuring the direction of hydraulic fracturing stress of a precast concrete part using a device for measuring the direction of hydraulic fracturing stress, including:

[0036] Step S1: Drilling a hole in the stratum 9 and filling a test section 10 where the in-situ stress direction measurement is required with concrete mortar; the length of the test section 10 must be greater than the sum of the lengths of the upper concrete isolation section 1, the concrete fracturing section 2, and the lower concrete isolation section 3;

[0037] Step S2: Place the entire prefabricated concrete component, including the upper concrete isolation section 1, the concrete fracturing section 2, and the lower concrete isolation section 3, into the concrete mortar of the test section 10, and thread the upper drill rod 5, which is connected to the surface high-pressure water pressurization system;

[0038] Step S3: After the concrete mortar in the test section 10 is completely solidified, the entire system is placed underground for 7 to 28 days to allow the rock on the borehole wall to creep and squeeze, so that the crustal stress is gradually applied to the outer wall of the concrete fracturing section 2;

[0039] Step S4: The surface high-pressure water pressure system adds high-pressure water from low to high pressure into the hollow space inside the fracturing section through the drill pipe 5, the thread and the copper tube 4 until the concrete is fractured. At this time, longitudinal fracture cracks will be generated in the concrete.

[0040] Step S5: After the concrete is fractured, a drilling rig is used to drill in and remove the upper concrete isolation section 1, the concrete fracturing section 2, and the lower concrete isolation section 3 to the ground;

[0041] Step S6: reading the direction data in the electronic compass system 7 and calculating the direction of the longitudinal concrete compression crack; the direction of the longitudinal concrete compression crack is the direction of the maximum horizontal principal stress component in the ground stress components.

[0042] It is worth mentioning that, firstly, by analyzing the longitudinal fracturing cracks in the concrete fracturing section 2 and using the direction data of the electronic compass system 7, the ground stress direction can be accurately obtained, which has the advantage of high ground stress direction measurement accuracy; secondly, it has the advantage of a wide range of applicability, and can be applied to ground stress direction measurement of rock strata 9 with good integrity and high hardness, as well as ground stress direction measurement of strata 9 with low rock compressive strength and easily broken; finally, the measurement accuracy of the present invention is not affected by the drilling depth. Compared with traditional technologies, it is very suitable for deep drilling ground stress direction measurement.

[0043] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for measuring the direction of hydraulic fracturing stress of precast concrete parts using a device for measuring the direction of hydraulic fracturing stress of precast concrete parts, characterized in that: The device for measuring the direction of hydraulic fracturing stress of a prefabricated concrete part comprises: The upper concrete sealing section (1) is a hollow columnar structure and is plugged with a copper tube (4), wherein the copper tube (4) is threadedly connected to a drill rod (5); The concrete fracturing section (2) is a hollow columnar structure and is connected to the copper tube (4). The concrete fracturing section (2) can add high-pressure water from low to high pressure through the internal hollow until the concrete is fractured and longitudinal fracturing cracks are generated in the concrete. The concrete lower sealing section (3) has a solid columnar structure at the top and a hollow copper column (6) at the bottom. The hollow copper column (6) is provided with an electronic compass system (7). The upper end of the concrete lower sealing section (3) is connected to the concrete fracturing section (2), and the lower end is connected to a sealing bolt (11); The concrete fracturing section (2) is provided with several layers of longitudinal toughness reinforcement bars (8); A method for measuring the direction of hydraulic fracturing stress of a precast concrete component using a device for measuring the direction of hydraulic fracturing stress of the precast concrete component comprises: Step S1: Drilling a hole in the ground layer (9) and filling a test section (10) where the ground stress direction measurement is required with concrete mortar; Step S2: placing the entire prefabricated concrete component, including the upper concrete isolation section (1), the concrete fracturing section (2) and the lower concrete isolation section (3), into the concrete mortar of the test section (10), and threading the upper drill rod (5) to connect the drill rod (5) to the ground high-pressure water pressurization system; Step S3: After the concrete mortar of the test section (10) is completely solidified, the entire system is placed underground for 7 to 28 days to wait for the rock on the borehole wall to creep and squeeze, so that the crustal stress is gradually applied to the outer wall of the concrete fracturing section (2); Step S4: The surface high-pressure water pressurization system adds high-pressure water from low to high pressure into the hollow space inside the fracturing section through the drill rod (5), the thread and the copper tube (4) until the concrete is fractured. At this time, longitudinal fracture cracks are generated in the concrete. Step S5: After the concrete is fractured, a drilling rig is used to drill in and remove the upper concrete sealing section (1), the concrete fracturing section (2) and the lower concrete sealing section (3) to the ground; Step S6: reading the direction data in the electronic compass system (7) and calculating the direction of the longitudinal concrete fracture; the direction of the longitudinal concrete fracture is the direction of the maximum horizontal principal stress component in the ground stress components.

2. The method for measuring the stress direction of precast concrete parts by using the hydraulic fracturing stress measuring device as claimed in claim 1, characterized in that: The longitudinal toughness reinforcement rib (8) is made of non-magnetic material and has a diameter of 1-3 mm.

3. The method for measuring the stress direction of precast concrete parts by using the hydraulic fracturing device as claimed in claim 2, characterized in that: The longitudinal toughness reinforcement ribs (8) are evenly spaced in the circumferential direction.

4. The method for measuring the stress direction of precast concrete parts by using the hydraulic fracturing device as claimed in claim 3, characterized in that: The copper tube (4) has a wall thickness of 3-10 mm.

5. The method for measuring the stress direction of precast concrete parts by using the hydraulic fracturing stress measuring device as claimed in claim 4, characterized in that: The drill rod (5) is connected to a ground high-pressure water pressurization system.

6. The method for measuring the stress direction of a precast concrete component by using a hydraulic fracturing device according to claim 1, wherein: The length of the test section (10) is greater than the sum of the lengths of the upper concrete isolation section (1), the concrete fracturing section (2) and the lower concrete isolation section (3).

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