Directional drilling apparatus for protecting coal pillars and control method

Abstract

The application relates to a directional drilling device and control method for protecting a coal pillar, which forms a protective cover outside the coal pillar in a full-spraying grouting mode, improves the strength of the coal pillar, realizes long-term effective support of the coal pillar to the overlying strata, and ensures the safety and stability of the surface building; in addition, the application has the advantages of small investment, low cost, small engineering quantity, short construction period, and the like while improving the strength and creep resistance of the coal pillar, and the nozzle assembly sprays at the target position point, so that the effectiveness of the spraying can be ensured.

Description

Technical Field

[0001] This application relates to the field of coal mine subsidence prevention and control, specifically to a directional drilling device and control method for protecting coal pillars. Background Technology

[0002] Coal mining primarily employs two methods: room-and-pillar mining and strip mining. Both are considered incomplete mining methods and are designed to prevent roof collapse and surface deformation. However, when structures are constructed on the surface above the goaf, detailed surveys reveal that partial roof collapse occurs over time, indicating that the goaf cannot remain stable indefinitely. This study also found that the safety and stability of the coal pillar are threatened by factors such as creep and groundwater erosion. Furthermore, the coal pillar deteriorates over time, potentially leading to fracturing of the overlying strata and impacting surface stability.

[0003] Currently, the main method for preventing coal mine subsidence is backfilling mining, which involves using slurry to replace coal pillars during mining, thereby protecting the roof and increasing the coal extraction rate. However, there are currently no solutions to address the problem of coal pillars gradually deteriorating after mining, leading to a shrinking core area, an expanding plastic zone, and a decreasing overlying support capacity. At present, we can only watch as the coal pillars gradually deteriorate over time until they become completely unstable and the ground subsides. But with the scarcity of surface land resources, population growth, and increased surface utilization, people need to build railways, highways, or houses above the goaf. Therefore, there is an urgent need for an effective method to prevent ground subsidence.

[0004] Currently, the main method for treating ground subsidence is to fill the underground voids by grouting. However, this method has drawbacks such as high cost, large workload, and long construction period. Summary of the Invention

[0005] In order to overcome at least one deficiency in the prior art, this application provides a directional drilling device and control method for protecting coal pillars.

[0006] In a first aspect, a control method for directional drilling equipment used to protect coal pillars is provided, comprising:

[0007] The drill rod of the directional drilling equipment drills holes from the surface through the strata and goaf to the location of the coal pillar end;

[0008] When the drill bit of the drill rod contacts the end of the coal pillar, record the position of the contact point, and control the drill rod to run the target distance along the target straight line so that the drill bit reaches the target position point; the target straight line is a straight line perpendicular to the plane where the end of the coal pillar is located and passes through the contact point;

[0009] The nozzle assembly on the drill bit is controlled to spray slurry onto the end of the coal pillar at the target location point to form a protective layer of the target thickness on the surface of the end of the coal pillar.

[0010] In one embodiment, the target distance is determined in the following manner:

[0011] Determine the target thickness of the protective layer;

[0012] Determine the target distance based on the target thickness and the spraying distance of the slurry.

[0013] In one embodiment, the method further includes:

[0014] Determine the surface area at the end of the coal pillar;

[0015] Determine the target thickness of the protective layer;

[0016] Based on the surface area and target thickness, the amount of grout injected into the directional drilling equipment is calculated to form a protective layer of the target thickness on the surface of the coal pillar end.

[0017] In one embodiment, the target thickness is:

[0018]

[0019] Where c is the target thickness, ρ is the density of the overlying strata, g is the gravitational acceleration, H is the thickness of the overlying strata, a is the width of the coal pillar, b is the distance between coal pillars, and σ s E represents the strength of the coal pillar. S E represents the elastic modulus of the coal pillar. c r is the elastic modulus of the protective layer. s This refers to the width of the shaping zone of the coal pillar.

[0020] In one embodiment, controlling a nozzle assembly mounted on a drill bit to spray slurry onto the end of a coal pillar at a target location includes:

[0021] After the nozzle assembly on the drill bit completes one spraying operation of slurry to the end of the coal pillar, the drill rod of the directional drilling equipment is controlled to move vertically so that the nozzle assembly sprays slurry evenly in the vertical direction at the end of the coal pillar.

[0022] In one embodiment, the method further includes:

[0023] The process of drilling a hole in the drill rod of the directional drilling equipment toward the end of the coal pillar and controlling the nozzle assembly on the drill bit to spray slurry onto the end of the coal pillar at the target location is performed multiple times.

[0024] After the previous process of spraying slurry to the end of the coal pillar is completed, the drill rod is controlled to retract and the drilling direction of the drill rod is changed so that the drill bit of the drill rod can reach another position along the width direction of the end of the coal pillar, and the nozzle assembly set on the drill bit is controlled to spray slurry to the end of the coal pillar at the target position point.

[0025] In one embodiment, the distance between the previous drill rod drilling trajectory and the subsequent drill rod drilling trajectory along the width direction of the coal pillar end is 0.8 times the diameter of the circular area formed by the slurry sprayed by the nozzle assembly.

[0026] In one embodiment, the strength of the protective layer satisfies the following formula:

[0027]

[0028] Where, σ c The strength of the protective layer is given by ρ, the density of the overlying strata is given by g, the acceleration due to gravity is given by H, the thickness of the overlying strata is given by a, the width of the coal pillar is given by b, the spacing between coal pillars is given by c, and the target thickness is given by r. s E represents the width of the plastic zone of the coal pillar. S E represents the elastic modulus of the coal pillar. c This is the elastic modulus of the protective layer.

[0029] Secondly, a directional drilling device for protecting coal pillars is provided, comprising: a main control unit, a drill rod, a drill bit at the end of the drill rod, and a nozzle assembly installed on the drill bit;

[0030] The main control unit is used to implement the above-mentioned control method for directional drilling equipment used to protect coal pillars.

[0031] In one embodiment, the nozzle assembly includes multiple nozzle bodies with different orientations and a valve body, the valve body being used to control the opening and closing of each nozzle body.

[0032] In one embodiment, the nozzle body is movably mounted on the drill bit so that the spacing between two adjacent nozzle bodies can be adjusted.

[0033] Compared with the prior art, this application has the following beneficial effects: The directional drilling equipment and control method for protecting coal pillars in this application form a protective cover around the coal pillar through full-jet grouting, thereby improving the strength of the coal pillar and achieving long-term effective support of the coal pillar for the overlying strata, thus ensuring the safety and stability of surface buildings. In addition, while improving the strength and creep resistance of the coal pillar, this application has the advantages of low cost, low workload, and short construction period. Furthermore, the nozzle assembly sprays at the target location, ensuring the effectiveness of the spraying. Attached Figure Description

[0034] This application can be better understood by referring to the description given below in conjunction with the accompanying drawings, which, together with the detailed description below, are incorporated in and form part of this specification. In the drawings:

[0035] Figure 1 A schematic diagram of a directional drilling device for protecting coal pillars according to an embodiment of this application is shown;

[0036] Figure 2 A schematic diagram of the nozzle assembly is shown.

[0037] Figure 3 A schematic diagram is shown of the first nozzle body AA performing horizontal spraying when the first opening and closing actuator aa is in the open state.

[0038] Figure 4 A schematic diagram is shown of the second nozzle body BB performing oblique upward spraying when the second opening and closing actuator bb is in the open state.

[0039] Figure 5 A schematic diagram is shown of the third nozzle body CC performing downward diagonal spraying when the third opening and closing actuator cc is in the open state.

[0040] Figure 6 A flowchart illustrating a control method for a directional drilling equipment for protecting coal pillars according to an embodiment of this application is shown.

[0041] Figure 7 A schematic diagram shows the spraying of slurry from the drill pipe to the end of the coal pillar;

[0042] Figure 8 A schematic diagram of the drill pipe's drilling trajectory is shown.

[0043] Figure label:

[0044] 1-Sediment, 2-Coal pillar, 3-Goaf, 4-Directional drilling equipment, 5-Main control unit, 6-Drill rod, 7-Drill bit, 8-Nozzle assembly, 9-Protective layer. Detailed Implementation

[0045] Exemplary embodiments of the present application will be described below with reference to the accompanying drawings. For clarity and brevity, not all features of the actual embodiments are described in the specification. However, it should be understood that many embodiment-specific decisions can be made in the development of any such actual embodiment to achieve the developer’s specific objectives, and these decisions may vary as the embodiments differ.

[0046] It should also be noted that, in order to avoid obscuring this application with unnecessary details, only the device structure closely related to the solution according to this application is shown in the accompanying drawings, while other details that are not closely related to this application are omitted.

[0047] It should be understood that this application is not limited to the described embodiments by virtue of the following description with reference to the accompanying drawings. In this document, embodiments may be combined with each other, features may be substituted or borrowed between different embodiments, and one or more features may be omitted in one embodiment, where feasible.

[0048] This application provides a directional drilling device for protecting coal pillars. Figure 1 A schematic diagram of a directional drilling device for protecting coal pillars according to an embodiment of this application is shown. See also: Figure 1 The directional drilling equipment 4 includes a main control unit 5 and a drill rod 6. A drill bit 7 is mounted at the end of the drill rod 6, and a nozzle assembly 8 is installed on the drill bit 7. The main control unit 5 controls the drill rod 6 of the directional drilling equipment 4 to drill from the surface, through the stratum 1 and the goaf 3, towards the location of the coal pillar end. It also controls the nozzle assembly 8 to spray slurry onto both ends of the coal pillar 2, forming a protective layer at the ends to improve the strength and creep resistance of the coal pillar, thereby protecting it. Here, the coal pillar is a strip coal pillar, and one side of each end of the coal pillar 2 is a goaf 3. In this embodiment, based on the coal mine design drawings and methods such as drilling, geophysical exploration, and electrical resistivity tomography, the location of the coal pillar during insufficient mining and the location of the goaf formed after mining can be determined.

[0049] In one embodiment, the nozzle assembly includes multiple nozzle bodies with different orientations and a valve body, the valve body being used to control the opening and closing of each nozzle body.

[0050] Here, the valve body includes multiple switching structures, each controlling the opening and closing state of a different nozzle body. The valve body can be located inside the nozzle body. In this embodiment, by setting multiple nozzle bodies with different orientations, the spraying area can be increased, the number of spraying passes can be reduced, and the spraying efficiency can be improved, thereby greatly shortening the construction period.

[0051] Specifically, the switching structure includes a valve body control unit and an opening / closing execution structure. By controlling the opening / closing execution structure through the valve body control unit, the nozzle body can be switched between the spraying state and the closed state. Figure 2 A schematic diagram of the nozzle assembly is shown; see [link / reference]. Figure 2The valve body has three opening / closing actuators: aa (first), bb (second), and cc (third). The nozzle body also has three components: AA (first), BB (second), and CC (third). The nozzle bodies can be fixedly mounted on the drill bit or movably mounted. When movably mounted, for example, a guide rail mounting method can be used to adjust the spacing between adjacent nozzle bodies. The open / closed state of the first actuator aa determines whether the first nozzle body AA is in the spraying / closing state; the open / closed state of the second actuator bb determines whether the second nozzle body BB is in the spraying / closing state; and the open / closed state of the third actuator cc determines whether the third nozzle body CC is in the spraying / closing state.

[0052] Figure 3 The diagram shows a schematic of the first nozzle body AA performing horizontal spraying when the first opening and closing execution structure aa is in the open state. When performing horizontal spraying, the first opening and closing execution structure aa is controlled to open the first nozzle body AA, and the second opening and closing execution structure bb and the third opening and closing execution structure cc are controlled to close, that is, the second nozzle body BB and the third nozzle body CC are both in the closed state. Figure 4 The diagram shows a schematic of the second nozzle body BB performing upward diagonal spraying when the second opening / closing actuator bb is in the open state. Figure 5 This diagram illustrates the third nozzle body CC performing downward diagonal spraying when the third opening / closing actuator cc is in the open state. During vertical spraying, as... Figure 4 As shown, the second opening / closing actuator bb opens the second nozzle body BB. At this time, both the first nozzle body AA and the third nozzle body CC are in the closed state. Or, as... Figure 5 As shown, the third opening / closing actuator cc opens the third nozzle body CC, while the first nozzle body AA and the second nozzle body BB are both in the closed state. Alternatively, the second opening / closing actuator bb opens the second nozzle body BB, and the third opening / closing actuator cc opens the third nozzle body CC, while the first nozzle body AA is in the closed state.

[0053] In this embodiment, by alternating the operation of each nozzle body, spraying can be performed in multiple directions, including horizontal, upward, and downward, thereby forming a mesh structure in an all-round and uniform manner. This embodiment does not specifically limit the opening angle of each nozzle in the nozzle body; it can be reasonably set according to actual needs. The nozzle body may include two nozzles, each of which can be movably mounted on the drill bit, meaning the nozzles can rotate. In other embodiments, a camera can be placed near the nozzle assembly. The smoothness of the coal pillar end surface is determined by the image captured by the camera, and the nozzle angle is then controlled by the valve control unit. This allows for reasonable setting of the nozzle angles even on rough coal pillar surfaces, ensuring a uniform coating of the protective layer and effectively avoiding slurry waste. To ensure good imaging results, this embodiment can also place supplementary lighting near the nozzle assembly to increase brightness in dark environments.

[0054] This application also provides a control method for directional drilling equipment for protecting coal pillars. This method is applied to the main control unit in the above embodiment. Figure 6 A flowchart illustrating a control method for directional drilling equipment for protecting coal pillars according to an embodiment of this application is shown. Here, a specific description is given using the example of spraying slurry to one end of the coal pillar. See [link to relevant documentation]. Figure 6 The methods include:

[0055] Step S1: The drill rod of the directional drilling equipment drills a hole from the surface through the strata and goaf to the location of the coal pillar end.

[0056] Step S2: When the drill bit of the drill rod contacts the end of the coal pillar, record the position of the contact point, and control the drill rod to move the target distance along the target straight line so that the drill bit reaches the target position point; the target straight line is a straight line perpendicular to the surface where the end of the coal pillar is located and passes through the contact point. Here, when the drill rod reaches the goaf, the main control unit controls the drill bit to rotate, making it close to the edge of the coal pillar, and uses the drill bit to find the edge of the coal pillar. After finding the edge of the coal pillar, record the position of the contact point; the target distance is the retraction distance of the drill rod in the goaf, and the target position point is the position where the nozzle assembly sprays the slurry.

[0057] Step S3: Control the nozzle assembly on the drill bit to spray slurry onto the end of the coal pillar at the target location point to form a protective layer of the target thickness on the surface of the coal pillar end. Here, the slurry is delivered to the nozzle assembly through the drill pipe. The nozzle assembly sprays two different components of slurry onto the end of the coal pillar sequentially, forming a high-pressure jet grouting method. The first component of the slurry forms a mesh structure, which uniformly wraps around the end of the coal pillar from top to bottom. Then, the second component of the slurry is injected into the mesh structure. The second component of the slurry is a fast-setting slurry, which solidifies within the mesh structure. The mesh structure can prevent the second component of the slurry from diffusing outward, ensuring that the second component of the slurry remains within the mesh structure, so that the formed protective layer adheres to the surface of the coal pillar end. The grout injected in jet grouting is a liquid that condenses upon contact with air, and it condenses even faster upon contact with solids. During the jet grouting process, when the grout touches the coal pillar, its condensation rate is higher than that of grout in the air, so the grout is sprayed onto the end of the coal pillar to form a mesh structure of a certain thickness.

[0058] Here, the quick-setting grout, also known as quick-setting high-strength grout, can be cement grout, a mixed grout composed of cement and mortar, etc. As described above, the mesh structure formed by the grout injection acts as a grouting skeleton. Once a complete mesh structure has been constructed on the sidewall of the coal pillar to be protected (i.e., the edge of the coal pillar), quick-setting high-strength grout is injected into the mesh structure using a drill rod. This allows the injected grout to quickly solidify within the mesh structure, thereby forming a high-strength protective shield of a certain thickness around the coal pillar. Furthermore, the formed high-strength protective shield can, on the one hand, withstand pressure, thus reducing the stress on the coal pillar, and on the other hand, prevent further creep and deterioration of the coal pillar.

[0059] In the above embodiments, directional drilling technology is used to first form a mesh structure on the surface of the coal pillar end to be protected using jet grouting. Then, a high-strength, fast-setting grout is injected into the mesh structure using a directional drill rod, thereby forming a protective cover around the coal pillar. This improves the strength of the coal pillar, prevents creep and deterioration, and ensures long-term effective support of the coal pillar for the overlying strata, thus ensuring the safety and stability of surface structures. Simultaneously, the overall construction process has the advantages of low cost, minimal workload, and short construction period. This method is even more advantageous when existing buildings exist in the area to be treated, as it bypasses building construction without demolition.

[0060] In one embodiment, the target distance is determined in the following manner:

[0061] Determine the target thickness of the protective layer;

[0062] The target distance is determined based on the target thickness and the spraying distance of the slurry. Here, the target distance = target thickness of the protective layer + spraying distance of the slurry. The spraying distance of the slurry is approximately 0.8m to 1.4m.

[0063] Specifically, the target thickness is:

[0064]

[0065] Where c is the target thickness, ρ is the density of the overlying strata, g is the gravitational acceleration, H is the thickness of the overlying strata, a is the width of the coal pillar, b is the distance between coal pillars, and σ s E represents the strength of the coal pillar. S E represents the elastic modulus of the coal pillar. c r is the elastic modulus of the protective layer. s This refers to the width of the shaping zone of the coal pillar.

[0066] In the above embodiments, the following method is used to determine the target thickness c:

[0067] The first step is to sample the coal pillar and test its uniaxial compressive strength, using the uniaxial compressive strength as the parameter information of the coal pillar.

[0068] The second step is to conduct graded load creep tests based on the uniaxial compressive strength. During the test, each grade is loaded with 5% to 10% of the uniaxial compressive strength.

[0069] The third step is to determine the load σ at the point of creep failure based on the creep test curve. s As a stable creep load, that is, under the action of this load, the coal pillar will not deform and become unstable due to creep.

[0070] Fourth, after protective backfilling on both sides of the strip coal pillar, the backfill and the coal pillar jointly bear the upper load. Considering the deformation coordination of the load, the load borne by the coal pillar (i.e., the load borne by the target coal pillar mentioned above) is given by the following formula:

[0071]

[0072] Among them, S s Let ρ be the load borne by the coal pillar, g be the density of the overlying strata, H be the thickness of the overlying strata, a be the width of the coal pillar, b be the spacing between coal pillars (i.e., the width of the strip coal pillar mining, which can be obtained from the coal mine design drawings), c be the thickness of the protective layer, and E be the thickness of the protective layer. S E represents the elastic modulus of the coal pillar. c r is the elastic modulus of the protective layer. s The width of the plastic zone of the coal pillar, and p is the coal wall constraint stress of the coal pillar, in MPa. Since the constraint force of the stripping body on the coal pillar is small, it can be ignored, i.e., p = 0. p′ is the unconstrained coal wall strength, in MPa; for example, p′ = 0.1, in MPa. h is the height of the coal pillar, in meters. G is the internal friction angle with the coal pillar. The relevant coefficients, specifically: in,

[0073] The load S borne by the filling body c (i.e., the load borne by the protective layer) is:

[0074]

[0075] Fifth, to ensure the coal pillar does not fail due to creep instability, the two sides of the coal pillar are reinforced to ensure that the coal pillar can withstand the load S. s Not greater than σ s The following formula is obtained:

[0076]

[0077] Transforming the above formula, we obtain the following formula:

[0078]

[0079] The above formula represents the conditions that the thickness of the protective layers on both sides of the coal pillar must meet to ensure its stability. In the embodiments of this application, if a ratio is formed... While a thicker protective layer can achieve the desired protection, it also increases material costs and lengthens the construction period. Therefore, this application's embodiments prioritize the use of... As the target thickness.

[0080] In one embodiment, to ensure the stability of the protective layer, the strength σ of the protective layer is... c The following condition σ must be met. c ≥S c ,Right now:

[0081]

[0082] Where, σ c The strength of the protective layer is given by ρ, the density of the overlying strata is given by g, the acceleration due to gravity is given by H, the thickness of the overlying strata is given by a, the width of the coal pillar is given by b, the spacing between coal pillars is given by c, and the target thickness is given by r. s E represents the width of the plastic zone of the coal pillar. S E represents the elastic modulus of the coal pillar. c This is the elastic modulus of the protective layer.

[0083] In one embodiment, the method further includes:

[0084] Determine the surface area at the end of the coal pillar; here, a is the width of the coal pillar and h is the height of the coal pillar. Therefore, when the target coal pillar is a strip coal pillar, the surface area is represented as ah.

[0085] Determine the target thickness of the protective layer;

[0086] Based on the surface area and target thickness, the amount of grout injected into the directional drilling equipment is calculated to form a protective layer of the target thickness on the surface of the coal pillar end.

[0087] Here, the target thickness of the protective layer is c. Therefore, the amount of grout required for a single strip coal pillar to achieve creep resistance protection can be calculated using the following formula:

[0088] V=2λahc

[0089] Where V represents the amount of grout required for a single strip coal pillar to achieve creep protection, in meters (m). 3 ; a is the width of the coal pillar in meters; h is the height of the coal pillar in meters; λ is a coefficient, the value of which is any value selected from the range of 0.25 to 0.40.

[0090] In practical applications, the surface of the coal pillar designed during coal mining is flat. However, over time, it may develop uneven local areas. Therefore, in calculating the grouting volume, this embodiment can first calculate based on a flat surface. After calculation, the grouting volume is obtained, which can be, for example, 20,000 cubic meters or 2 million cubic meters. Optionally, this embodiment can fine-tune the grouting volume based on this. Since this embodiment can install a camera at the end of the drill rod, local areas can be marked, and the dosage of grout can be increased when spraying local areas to ensure that the protective layer thickness reaches the target thickness, thereby ensuring safety.

[0091] In one embodiment, controlling a nozzle assembly mounted on a drill bit to spray slurry onto the end of a coal pillar at a target location includes:

[0092] After the nozzle assembly on the drill bit completes one spraying operation of slurry towards the end of the coal pillar, the drill rod of the directional drilling equipment is controlled to move vertically so that the nozzle assembly sprays slurry evenly in the vertical direction at the end of the coal pillar. Figure 7 A schematic diagram shows the spraying of slurry from the drill pipe to the end of the coal pillar, as shown. Figure 7 The arrow indicates that the purpose of controlling the drill rod of the directional drilling equipment to move vertically is to ensure that the vertical direction of the coal pillar end is completely covered by slurry.

[0093] In one embodiment, Figure 8A schematic diagram of the drill rod's drilling trajectory is shown. Since the area that the nozzle assembly can spray is not determined by the size of each nozzle in the nozzle body, due to the injection pressure during spraying, it forms a circular extended range (i.e., the spray range, which is actually a circular area) centered on the nozzle assembly, based on the material's properties. If only one spray is applied to the end of the coal pillar, the slurry cannot cover the entire width of the coal pillar end. Therefore, in this embodiment, the process of the drill rod of the directional drilling equipment drilling towards the coal pillar end and controlling the nozzle assembly on the drill bit to spray slurry onto the coal pillar end at the target location point is performed multiple times. After the previous slurry spraying process to the coal pillar end is completed, the drill rod is controlled to retract, and the drilling direction of the drill rod is changed, so that the drill bit of the drill rod can reach another position along the width direction of the coal pillar end, and the nozzle assembly on the drill bit is controlled to spray slurry onto the coal pillar end at the target location point.

[0094] In this embodiment, see Figure 8 , Figure 8 Each line in the diagram represents a drilling trajectory. The drill rod drills vertically from the surface into the strata to form a main hole. The drilling direction of the drill rod is controlled so that the drill bit reaches a position perpendicular to the end surface of the coal pillar. When the drill bit contacts the end of the coal pillar, the drill rod is controlled to move a target distance along a target straight line to reach the target position. The nozzle assembly on the drill bit is then controlled to spray slurry onto the end of the coal pillar at the target position to form a protective layer of the target thickness on the surface of the coal pillar. After performing this operation once, the drill rod is retracted to the main hole position, and then the drilling direction is changed. The above operation is performed again so that the drill bit reaches another position along the width direction of the coal pillar end, and the nozzle assembly on the drill bit is controlled to spray slurry onto the end of the coal pillar at the target position. Ultimately, the goal of uniformly spraying slurry along the width direction of the coal pillar end is achieved. This embodiment can reduce the number of main holes (i.e., reduce the number of surface drillings), save drilling workload, and prevent situations where drilling is impossible under surface structures; it can also improve spraying efficiency and shorten the construction period.

[0095] Furthermore, the distance between the previous drill pipe drilling trajectory and the subsequent drill pipe drilling trajectory along the width direction of the coal pillar end is 0.8 times the diameter of the circular area formed by the slurry sprayed by the nozzle assembly, that is... Figure 8 The spacing between two adjacent lines is 0.8 times the diameter of the circular area formed by the nozzle assembly spraying the slurry; this spacing can be adjusted adaptively according to the actual situation, and the specific value of this spacing is not specifically limited in the embodiments of this application.

[0096] In summary, the coal pillar protection method of this application forms a protective cover around the coal pillar through full-jet grouting, thereby improving the strength of the coal pillar and achieving long-term effective support for the overlying strata, ensuring the safety and stability of surface buildings. In addition, this application has the advantages of low cost, low workload, and short construction period while improving the strength and creep resistance of the coal pillar. Furthermore, the nozzle assembly sprays at the target location, ensuring the effectiveness of the spraying.

[0097] The above descriptions are merely various embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A control method for directional drilling equipment used to protect coal pillars, characterized in that, include: The drill rod of the directional drilling equipment drills holes from the surface through the strata and goaf to the location of the coal pillar end; When the drill bit of the drill rod contacts the end of the coal pillar, the position of the contact point is recorded, and the drill rod is controlled to run a target distance along a target straight line so that the drill bit reaches the target position point; the target straight line is a straight line perpendicular to the plane where the end of the coal pillar is located and passes through the contact point; The nozzle assembly on the drill bit is controlled to spray slurry onto the end of the coal pillar at the target location point to form a protective layer of target thickness on the surface of the end of the coal pillar; The target thickness is: in, c For the target thickness, The density of the overlying rock strata. It is the acceleration due to gravity. The thickness of the overlying rock strata. The width of the coal pillar. This refers to the spacing between coal pillars. For the strength of the coal pillar, The elastic modulus of the coal pillar. The elastic modulus of the protective layer, The width of the plastic zone of the coal pillar; Controlling the nozzle assembly mounted on the drill bit to spray slurry onto the end of the coal pillar at the target location point includes: After the nozzle assembly on the drill bit completes one spraying operation of slurry towards the end of the coal pillar, the drill rod of the directional drilling equipment is controlled to move in the vertical direction so that the nozzle assembly sprays slurry evenly in the vertical direction at the end of the coal pillar. The process of drilling a hole in the drill rod of the directional drilling equipment toward the end of the coal pillar and controlling the nozzle assembly on the drill bit to spray slurry onto the end of the coal pillar at the target location point is performed multiple times. After the previous process of spraying slurry to the end of the coal pillar is completed, the drill rod is controlled to retract and the drilling direction of the drill rod is changed so that the drill bit of the drill rod can reach another position along the width direction of the end of the coal pillar, and the nozzle assembly set on the drill bit is controlled to spray slurry to the end of the coal pillar at the target position point.

2. The method as described in claim 1, characterized in that, The target distance is determined in the following way: Determine the target thickness of the protective layer; The target distance is determined based on the target thickness and the spraying distance of the slurry.

3. The method as described in claim 1, characterized in that, The method further includes: Determine the surface area at the end of the coal pillar; Determine the target thickness of the protective layer; Based on the surface area and the target thickness, the amount of grout injected into the directional drilling equipment is calculated to form a protective layer of the target thickness on the surface of the coal pillar end.

4. The method as described in claim 1, characterized in that, The distance between the previous drill rod drilling trajectory and the subsequent drill rod drilling trajectory along the width direction of the end of the coal pillar is 0.8 times the diameter of the circular area formed by the slurry sprayed by the nozzle assembly.

5. The method as described in claim 1, characterized in that, The strength of the protective layer satisfies the following formula: in, For the strength of the protective layer, The density of the overlying rock strata. It is the acceleration due to gravity. The thickness of the overlying rock strata. The width of the coal pillar. This refers to the spacing between coal pillars. c For the target thickness, The width of the plastic zone of the coal pillar. The elastic modulus of the coal pillar. This is the elastic modulus of the protective layer.

6. A directional drilling device for protecting coal pillars, characterized in that, include: The main control unit and the drill rod are provided with a drill bit at the end of the drill rod, and a nozzle assembly is installed on the drill bit. The main control unit is used to implement the directional drilling equipment control method for protecting coal pillars as described in any one of claims 1-5.

7. The directional drilling equipment as described in claim 6, characterized in that, The nozzle assembly includes multiple nozzle bodies with different orientations and a valve body, the valve body being used to control the opening and closing of each nozzle body.

8. The directional drilling equipment as described in claim 7, characterized in that, The nozzle body is movably mounted on the drill bit so that the spacing between two adjacent nozzle bodies can be adjusted.

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