Underground engineering surrounding rock directional drilling and slotting method based on stress transfer

Abstract

The invention relates to the field of rock drilling, in particular to an underground engineering surrounding rock directional drilling and slotting method based on stress transfer, which comprises the following steps: S1, carrying out directional drilling operation on underground engineering surrounding rock, arranging a drill hole at a position s meters away from an underground engineering outline, s = (1 + / -10%) (rp-r0), rp is the radius of a loose circle of the underground engineering, and r0 is the equivalent radius of the underground engineering; and S2, directional slotting operation is conducted on the underground engineering surrounding rock based on the drilled hole, a slot is arranged to be perpendicular to the main stress direction of a surrounding rock crustal stress field, and a stress transfer path is cut off. According to the method, the continuity and the stress transfer path of the protolith are changed through a gap formed by protolith directional drilling and hydraulic directional slotting. Under the action of high ground stress, primary rock stress can be redistributed around drill holes and gaps, the surrounding rock load acting on underground engineering is reduced, stress distribution can be adjusted in a targeted mode, excessive damage to shallow surrounding rock is avoided, and the self-bearing capacity of the shallow surrounding rock is reserved to the maximum extent.

Description

Technical Field

[0001] The invention relates to the field of rock drilling, and in particular to a directional drilling and slitting method for surrounding rocks of underground engineering based on stress transfer. Background Art

[0002] The deep rock mass is in a "three highs and one disturbance" environment, changing from a shallow steady-state small deformation to a deep high stress, crushing expansion and strong rheology. The surrounding rock deformation and failure behavior is characterized by complex non-steady-state and nonlinear characteristics. The large deformation of high-stress soft rock is prone to cause collapse, structural damage, construction delays, encroachment, cost increases, etc., which seriously affects the safety of engineering construction.

[0003] At present, some treatment measures for large deformation problems have been developed, such as advanced stress release, multi-layer ductile support, and pressure-yielding support. Each technology has its own advantages and disadvantages.

[0004] Advance stress release method: This method can reduce the load of surrounding rock on the support structure by pre-drilling holes in the planned tunnel section to relieve pressure, but it has a greater disturbance to the surrounding rock and reduces the self-bearing capacity of the surrounding rock. The advantage is that it has a greater impact on the bearing capacity of shallow surrounding rock.

[0005] Multi-layer ductile support method: Part of the surrounding rock stress can be released by delaying the construction between each layer, so that the final force acting on the support can be reduced. However, the difficulty of this method lies in the lack of a scientific and reasonable theory to determine the timing of construction of each layer of support, and the cost of multi-layer ductile support is very high.

[0006] The compression support method: retractable arch frame, constant resistance large deformation anchor cable, compression support system. This method can effectively release the stress of the surrounding rock and control the deformation development of the surrounding rock. However, the process is relatively complicated and on-site construction is relatively difficult.

[0007] In general, the current soft rock large deformation treatment technology lacks quantitative control methods, cannot fully mobilize and exert the strength of the surrounding rock itself, requires multi-layer support or arch replacement, etc., and the treatment cost is too high. There is an urgent need to study more advanced and efficient large deformation pre-control technology. Summary of the invention

[0008] The purpose of the present invention is to overcome the shortcomings of the prior art that the advanced stress release method used to treat large deformation of soft rock causes great disturbance and damage to the surrounding rock, and reduces the self-bearing capacity of the surrounding rock; the multi-layer delayed support method is difficult to determine the timing of the application of each layer of support, and the cost is too high; the compression support method and the rigid support method are inconvenient to construct and have a high cost. A directional drilling and slitting method for the surrounding rock of an underground project based on stress transfer is provided, which can reduce the load acting on the support structure in advance before the excavation of the underground project, and at the same time, can transfer the ground stress of the shallow surrounding rock adjacent to the underground project to the deep surrounding rock, thereby retaining the integrity of the shallow surrounding rock around the structure to a great extent, giving full play to the self-bearing capacity of the surrounding rock, greatly reducing the load acting on the support structure, and reducing the support cost of the underground project.

[0009] The present invention provides a method for directional drilling and cutting of surrounding rocks in underground engineering based on stress transfer, comprising the following steps: S1: Directional drilling is carried out on the surrounding rock of underground projects, and the boreholes are set at a distance from the contour of the underground project. s Meters, where s = (1 ± 10%) ( r p - r 0 ), r p is the radius of the loosening zone of underground engineering, r 0 is the equivalent radius of underground engineering; S2: Directional cutting of the surrounding rock of the underground project is performed based on the drilling, and the cutting is set to be perpendicular to the principal stress direction of the surrounding rock ground stress field to cut off the stress transfer path.

[0010] Preferably, the radius of the loose circle r p The calculation method is: In the formula, r 0 is the equivalent radius of underground engineering. For horseshoe-shaped or straight-walled arch sections, the structural height can be approximated as H or structure width W half of p 0 is the original rock stress of the surrounding rock, p 1 is the design value of support bearing capacity, c is the cohesion of the surrounding rock, is the internal friction angle of the surrounding rock.

[0011] Preferably, the drill holes are distributed on both sides and / or the top and / or the bottom outside the underground engineering contour.

[0012] Preferably, the hole spacing of the drill holes is 4-8 m, and the diameter of the drill holes is 90-150 mm.

[0013] Preferably, if the boreholes are arranged on both sides outside the outline of the underground project, the number of single-side boreholes on the side of the underground project is equal to the height of the underground project divided by the borehole spacing, and the number is rounded off; If the boreholes are arranged at the top or bottom of the underground project, the number of boreholes at the top or bottom of the underground project is equal to the width of the underground project divided by the spacing between the boreholes, rounded to the nearest integer; If the boreholes are set at the top, bottom and both sides of the underground project, the number of boreholes is the sum of the number of boreholes on the sides of the underground project and the number of boreholes on the top and bottom.

[0014] Preferably, the length of the slit l The calculation method is: l = (1 ± 10%) W, or l =(1±10%)H, where W is the width of the underground project and H is the height of the underground project.

[0015] Preferably, the slit width t The calculation method is: Establish a finite element model with a size no less than 10 times the size of the underground project; Set unit parameters according to geological survey data; Set boundary conditions and set the original rock stress field boundary around the model according to geological survey data; Determine the size and quantity of the drilling holes, as well as the direction, length, and preset slit width of the slits, wherein the preset slit widths include multiple ones; Excavate the proposed slot area, perform calculation and analysis, obtain the distribution diagram of the ground stress field after slot unloading, and analyze the ground stress data of the underground project before and after slot unloading in combination with the location of the underground project. Determine the final slot width by comparing the calculation results under multiple preset slot widths. t .

[0016] Preferably, when performing directional slitting operations, a single drill hole is slit unidirectionally or bidirectionally.

[0017] Preferably, when performing directional slitting operations, the slitting nozzle is connected to a high-pressure pump through a high-pressure water pipe and lowered into the directional borehole until it reaches the predetermined slitting position. The changes in pressure and flow are monitored in real time through pressure sensors and flow sensors, and the pressure and flow of the high-pressure pump are adjusted in real time.

[0018] Preferably, the method further comprises step S3: after the cutting is completed, drilling and excavating the surrounding rock of the underground project to form an engineering section of the underground project.

[0019] Compared with the prior art, the present invention has the following beneficial effects: The present invention changes the continuity and stress transfer path of the original rock through the gaps formed by directional drilling of the original rock and hydraulic directional cutting. Under the action of high ground stress, the original rock stress will be redistributed around the borehole and the gap, thereby reducing the surrounding rock load acting on the underground project. At the same time, since the cutting is carried out in a directional manner, the stress distribution can be adjusted in a targeted manner to avoid excessive damage to the shallow surrounding rock and retain the self-bearing capacity of the shallow surrounding rock to the greatest extent. During the subsequent drilling and excavation construction of the underground project, the shallow surrounding rock is protected from the high ground stress, and the integrity of the shallow surrounding rock is retained, which greatly improves the bearing capacity of the surrounding rock itself, reduces the load acting on the support structure, and greatly reduces the support cost of the underground project. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of directional drilling and hydraulic directional cutting described in Example 1 of the present invention.

[0021] Figure 2 for Figure 1 A partial schematic diagram of .

[0022] Markings in the figure: 1- Underground engineering, 2- Drilling, 3- Cutting. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below in conjunction with specific embodiments. However, this should not be understood as the scope of the above subject matter of the present invention being limited to the following embodiments, and all technologies realized based on the content of the present invention belong to the scope of the present invention.

[0024] Unless otherwise specified, in the description of the specific embodiments of the present invention, the terms indicating the orientation or position relationship such as "up", "down", "left", "right", "center", "inside", "outside", etc. are all based on the expression of the orientation or position relationship shown in the drawings, or are the orientation or position relationship when the invented product / equipment / device is usually used. These terms of orientation or position relationship are only for the convenience of describing the scheme of the present invention or simplifying the description in the specific embodiments, so as to facilitate the technicians to quickly understand the scheme, and do not indicate or imply that a specific device / component / element must have a specific orientation, or be constructed and operated in a specific position relationship, and therefore cannot be understood as a limitation on the present invention.

[0025] In addition, if the terms "horizontal", "vertical", "overhanging", "parallel" and the like appear, it does not mean that the corresponding devices / components / elements are required to be absolutely horizontal or vertical or overhanging or parallel, but may be slightly tilted or have deviations. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but may be slightly tilted. Alternatively, it can be simplified to mean that the corresponding devices / components / elements are set in directions such as "horizontal", "vertical", "overhanging", "parallel", etc., and can have an error / deviation of ±10% relative to the corresponding direction setting, more preferably an error / deviation within ±8%, more preferably an error / deviation within ±6%, more preferably an error / deviation within ±5%, and more preferably an error / deviation within ±4%. As long as the corresponding device / component / element is within the error / deviation range, it can still achieve its role in the scheme of the present invention.

[0026] In addition, the expressions “first”, “second”, “third”, etc., which appear in the terms, are merely used to distinguish the description of the same or similar components and should not be understood as emphasizing or implying the relative importance of specific components.

[0027] In addition, in the description of the embodiments of the present invention, "several", "plurality" and "a number" represent at least 2. It can be any number such as 2, 3, 4, 5, 6, 7, 8, 9, and even more than 9.

[0028] In addition, in the description of the technical solution of the present invention, unless otherwise clearly specified / defined / restricted, the terms "set", "install", "connect", "connected", "provided with", "laid", and "arranged" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection, and can be welding, riveting, bolting, threading, and other commonly used connection means in the field. This connection can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection, or an indirect connection through an intermediate medium, and it can be the internal connection of two elements.

[0029] Example 1 A method for directional drilling and cutting of surrounding rocks in underground engineering based on stress transfer comprises the following steps: S1: Directional drilling is performed on the surrounding rock of the underground project, and borehole 2 is set at a distance from the outline of underground project 1. s Meters, where s =1±10%( r p - r 0 ), r p is the radius of the loosening zone of underground engineering, r 0is the equivalent radius of underground engineering, such as Figure 1-Figure 2 As shown. Specifically including the following steps: S11: Determine the location and number of boreholes 2. According to the distribution of the original rock stress field of the deep underground project 1 and the structural design plan, combined with geological exploration data, the boreholes 2 are set at a certain distance s outside the outline of the underground project 1, distributed on both sides, top, bottom, or both sides and top and bottom outside the structural outline. The distance s between the borehole 2 and the outline of the underground project 1 needs to be determined by calculation based on the structural section size and surrounding rock conditions, and is generally taken within the radius of the loosening zone. r p (the position deviation can be controlled within 10%), the specific process is as follows: 1) Determine the cohesion c and internal friction angle of the surrounding rock based on geological survey data , in situ rock stress p 0 ; 2) Obtain the design value of support bearing capacity based on design data p 1 , underground engineering equivalent radius r 0 , for horseshoe-shaped or straight-walled arch sections, it can be approximately taken as half of the section width W; The radius of the loose circle r p The calculation method is: In the formula, r 0 is the equivalent radius of underground engineering, p 0 is the original rock stress of the surrounding rock, p 1 is the design value of support bearing capacity, c is the cohesion of the surrounding rock, is the internal friction angle of the surrounding rock.

[0030] For underground projects dominated by horizontal ground stress, borehole 2 is set on both sides outside the outline of underground project 1. Generally, one borehole is set on each side. The number of boreholes on one side is n Can be increased according to the structure height H, generally the drilling spacing s 1 4~8m, depending on the rock conditions and cutting length l A single borehole 2 can be cut in one direction or in two directions.

[0031] For underground projects dominated by vertical geostress, the location of borehole 2 is mainly set at the top area outside the outline of underground project 1. Generally, one borehole is set. The number of boreholes at the top or bottom of underground project 1 is nIt can be increased according to the width W of underground engineering 1. Generally, the drilling spacing is s 1 At 4~8m, the diameter D of borehole 2 is generally 90~150mm.

[0032] 1) If the boreholes are set on both sides of the underground project 1, the number of single-side boreholes on the side of the underground project 1 is n Equal to the height H of the underground project 1 divided by the drilling spacing s 1 , and round it off; 2) If the boreholes are located at the top or bottom of the underground project 1, the number of boreholes located at the top or bottom of the underground project 1 n It is equal to the width W of underground project 1 divided by the drilling spacing, and rounded to the nearest integer; 3) If the boreholes are set at the top, bottom and both sides of the underground project 1, the number of boreholes n It is the sum of the number of side holes drilled in underground project 1 and the number of top and bottom holes drilled.

[0033] S12: Positioning and installation of directional drilling equipment. Select directional drilling equipment suitable for underground engineering environment to ensure the performance and reliability of the equipment. Transport the equipment to the construction site, and install and debug it according to the operating procedures to ensure the normal operation of the equipment.

[0034] S13: Drilling construction. Start the directional drilling equipment and perform drilling operations according to the predetermined position. During the drilling process, monitor the depth and axis trajectory of the drilling hole in real time to ensure that the drilling meets the requirements. It is recommended that the drilling depth deviation be controlled within ±1m and the axis deviation be controlled within 1‰.

[0035] S2: Based on the borehole 2, the surrounding rock of the underground project is cut in a directional manner, and the cut 3 is set to be perpendicular to the principal stress direction of the surrounding rock ground stress field, so as to cut off the stress transfer path, such as Figure 1-Figure 2 As shown. Specifically including the following steps: S21: Determine the parameters of slit 3, including the direction and length of slit 3 l , seam width t The direction of the drilling slit 3 needs to be adjusted according to the main direction of stress distribution. The direction of the slit 3 should be as perpendicular to the main stress direction as possible, and the error should be controlled within 10% to ensure that the slit 3 can effectively cut off the stress transfer path. l It should be determined according to the width or height of the structure. Generally, the length of the slit is 3 l The width and height of the underground project 1 are similar, and the length of the cut 3 is l Control within plus or minus 10% of the width or height of the underground project 1. tIt depends on the engineering geological environment. Due to the complex distribution of the surrounding rock stress field of underground engineering 1, it is difficult to use analytical analysis methods to deal with the actual complex situation. Generally, the most reasonable crack width is determined by numerical simulation analysis and calculation. t , to ensure the pressure relief effect. The specific simulation process is as follows: 1) Establish a finite element model, the model size should be no less than 10 times the size of the underground project; 2) Set unit parameters according to geological survey data; 3) Set boundary conditions and set the original rock stress field boundary around the model according to geological survey data; 4) Determine the drilling size D and quantity n And the direction and length of the cutting l , seam width t Wait, seam width t Can be preset to multiple values ​​to determine the best seam width; 5) Excavate the proposed cutting area and perform calculation and analysis to obtain the distribution diagram of the ground stress field after the cutting is unloaded. Combined with the location of the underground project, the ground stress data of the underground project before and after the cutting is unloaded can be analyzed. By comparing the calculation results under multiple preset joint widths, the final joint width can be determined. t .

[0036] S22: Install pressure sensors and flow sensors at the outlet of the high-pressure pump and near the slitting nozzle to monitor the changes in pressure and flow in real time. The sensor can transmit the measurement data to the control system so that the operator can timely understand the parameters during the slitting process. According to the monitoring data and the slitting effect, the pressure and flow of the high-pressure pump are adjusted in real time. If it is found that the slitting depth is not enough or the slitting width does not meet the requirements, the pressure or flow can be appropriately increased; if it is found that the rock is excessively broken, that is, the particle size and output of the rock cuttings returned from the drilling during the slitting process increase significantly, the pressure and flow need to be reduced. During the slitting process, pay close attention to the operating status of the equipment and the slitting quality, and make adjustments in time to ensure the best slitting effect.

[0037] S23: Hydraulic directional slotting construction. Use high-pressure hydraulic slotting equipment, including high-pressure pumps, slotting nozzles, high-pressure water pipes, etc. Check and debug the equipment to ensure that the equipment can provide sufficient pressure and flow to meet the requirements of hydraulic directional slotting. Connect the slotting nozzle to the high-pressure pump through a high-pressure water pipe, and slowly lower it into the directional borehole until it reaches the predetermined slotting position. During the lowering process, pay attention to protecting the nozzle and water pipe to avoid damage. Start the high-pressure pump and spray high-pressure water through the slotting nozzle to form a high-speed jet. According to the pre-designed slotting direction and length, control the rotation and propulsion of the slotting nozzle so that the high-speed jet cuts a slot of a predetermined shape and size on the borehole wall. During the slotting process, install high-precision pressure sensors at the outlet of the high-pressure pump and near the slotting nozzle to monitor the pressure value in real time, and adjust the pressure of the high-pressure pump and the motion parameters of the slotting nozzle according to the actual situation; install a high-precision motion encoder on the drive device of the slotting nozzle to accurately measure the position, speed, acceleration and other parameters of the nozzle, so as to accurately control the quality and effect of the slotting. After the slitting is completed, stop the high-pressure pump and remove the slitting nozzle from the drill hole. During the slitting, the construction accuracy must be strictly controlled to ensure that the slitting reaches the designed angle, length and width.

[0038] Through the above steps, the gaps formed by directional drilling and hydraulic directional slitting change the continuity and stress transfer path of the original rock. Under the action of high ground stress, the stress will be redistributed around the borehole and the gap, thereby reducing the surrounding rock load acting on the underground project. At the same time, since the slitting is carried out in a directional manner, the stress distribution can be adjusted in a targeted manner to avoid excessive damage to the shallow surrounding rock and retain the self-bearing capacity of the shallow surrounding rock to the greatest extent. Generally, for horizontal high ground stress underground projects, holes can be drilled on both sides of the structure by directional drilling equipment, and then high-pressure hydraulic directional slitting technology is used in the borehole to cut up and down on both sides of the structure. Through this arrangement, the horizontal ground stress of the original rock is greatly unloaded after slitting, and the ground stress acting on the shallow surrounding rock of the underground project is greatly reduced, so that during the subsequent excavation and construction of the underground project, the shallow surrounding rock is protected from the high ground stress, and the integrity of the shallow surrounding rock is retained, which greatly improves the bearing capacity of the surrounding rock itself, reduces the load acting on the support structure, and greatly reduces the support cost of the underground project.

[0039] In a preferred solution, the method further comprises step S3: after the cutting is completed, drilling and excavating the surrounding rock of the underground project to form an engineering section of the underground project 1.

[0040] The present invention can specifically regulate the original rock stress field of deep underground engineering through directional drilling and hydraulic directional cutting, effectively reduce the surrounding rock load acting on the underground engineering, improve the stability and safety of the underground engineering, and facilitate drilling into the surrounding rock of the underground engineering to form the engineering section of the underground engineering 1.

[0041] The present invention adopts directional cutting technology, which can retain the self-bearing capacity of shallow surrounding rock to the greatest extent, reduce damage to shallow surrounding rock, reduce later support costs, and combine with conventional anchor spraying support to greatly improve the economy of the project.

[0042] The technology of the present invention is relatively simple to operate, the drilling and cutting construction does not interfere with the underground engineering excavation, does not affect the normal excavation construction, improves the construction efficiency, and has broad application prospects.

[0043] Example 2 Based on Example 1, this example illustrates the solution of the present invention through a specific case: A highway tunnel is a two-way four-lane tunnel with a cross-sectional width W of 12.4m, a height H of 9.2m, and a maximum burial depth of about 357m. The area where the tunnel is located is a soft rock with interlayers of metamorphic sandstone and slate; affected by the structure, the rock mass is extremely broken, with strong local wrinkles and poor self-stabilization ability; the groundwater is extremely abundant, which makes the surrounding rock itself more easily softened. According to the results of rock tests: the saturated compressive strength of moderately weathered metamorphic sandstone is 35.01MPa. The saturated compressive strength of moderately weathered slate is 7.62MPa. Affected by the complex structure, the maximum horizontal principal stress is 7.00~11.15MPa, with an average value of 9.2MPa; the principal stress intersects with the tunnel at a large angle of 70°. Under the action of high-stress water-rich soft rock, it is easy to undergo large extrusion deformation, with large deformation pressure, fast deformation speed, and long duration.

[0044] 1. Set the drilling position and quantity According to the engineering geological conditions of the tunnel, the principal stress in the surrounding rock stress field is horizontal stress, and the angle with the tunnel axis is 70°. Therefore, the drilling holes are set on both sides outside the tunnel structure contour line, with one drilling hole on each side. The drilling diameter is 150 mm, the drilling depth is 100 m, and the drilling holes are set at the arch waist.

[0045] 1) Determine the cohesion of the surrounding rock based on geological survey data c is 0.3MPa, internal friction angle is 34°, the original rock stress p 0 9.2MPa; 2) Obtain the design value of support bearing capacity based on design data p 1 0.35MPa, equivalent radius of underground engineering r 0 For a horseshoe-shaped section, it can be approximated as half of the section width W, that is, r 0 6.2m; 3) Calculate the radius of the loose circle according to the following formula r p : Therefore, the drilling hole is set at a distance of 10.1m from the center of the structure, that is, 10.1-6.2=3.9m outside the structural outline.

[0046] 2. Determine the cutting parameters The cutting direction is at a 90-degree angle to the direction of the maximum principal stress of the original rock, so the cutting direction is set to the vertical direction in this example. The cutting length is determined according to the height of the underground project, which is 9 meters (4.5 meters above and below the borehole). The cutting width is 5 centimeters.

[0047] 3. Positioning and installation of directional drilling equipment.

[0048] According to the pre-set drilling parameters, directional drilling equipment is selected and transported to the construction site for installation and commissioning.

[0049] 4. Drilling construction. Start drilling construction according to the pre-set drilling parameters. During the drilling process, monitor the depth, angle and trajectory of the drilling in real time to ensure that the drilling meets the design requirements. After the drilling is completed, clean and inspect the drilling hole.

[0050] 5. Real-time monitoring and adjustment of construction parameters.

[0051] Install pressure sensors and flow sensors at the outlet of the high-pressure pump and near the slitting nozzle to monitor the changes in pressure and flow in real time. Adjust the pressure and flow of the high-pressure pump in real time based on the monitoring data and slitting effect.

[0052] 6. Hydraulic directional cutting construction.

[0053] Use high-pressure hydraulic slotting equipment, the rated pressure of its high-pressure pump is 50MPa, and the flow rate is 150L / min. Connect the slotting nozzle to the high-pressure pump through a high-pressure water pipe and lower it into the directional borehole.

[0054] Start the high-pressure pump and spray high-pressure water at a pressure of 40MPa through the slotting nozzle to form a high-speed jet. Cut a 4-meter-long and 50-mm-wide slot on the upper and lower sides of the borehole wall. After the slotting is completed, stop the high-pressure pump and remove the slotting nozzle from the borehole.

[0055] According to the analysis results, after drilling and cutting, the original rock principal stress between the tunnel structure and the borehole was reduced by 30%. At the same time, due to the stress regulation by drilling and cutting outside the tunnel contour, the load on the surrounding rock between the borehole and the tunnel structure was reduced after the ground stress was reduced, and the integrity of the surrounding rock was preserved, thereby greatly reducing the surrounding rock load acting on the tunnel support structure and reducing the deformation of the tunnel primary support. The deformation can be reduced by more than 50%, thereby greatly reducing the support cost of tunnels with high ground stress and large deformation.

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for directional drilling and cutting of surrounding rocks in underground engineering based on stress transfer, characterized in that: The following steps are involved: S1: Directional drilling is performed on the surrounding rock of the underground project, and the borehole (2) is set at a distance from the outline of the underground project (1). s Meters, where s = (1 ± 10%) ( r p - r 0 ), r p is the radius of the loosening zone of underground engineering, r 0 is the equivalent radius of underground engineering; S2: Based on the borehole (2), a directional slotting operation is performed on the surrounding rock of the underground project, and the slotting (3) is set to be perpendicular to the principal stress direction of the surrounding rock ground stress field, thereby cutting off the stress transfer path.

2. The method for directional drilling and slitting of surrounding rocks in underground engineering based on stress transfer according to claim 1, characterized in that: The radius of the loose circle r p The calculation method is: In the formula, r 0 is the equivalent radius of underground engineering, p 0 is the original rock stress of the surrounding rock, p 1 is the design value of support bearing capacity, c is the cohesion of the surrounding rock, is the internal friction angle of the surrounding rock.

3. The method for directional drilling and slitting of surrounding rocks in underground engineering based on stress transfer according to claim 1, characterized in that: The boreholes (2) are distributed on both sides and / or the top and / or the bottom of the outline of the underground project (1).

4. The method for directional drilling and slotting of surrounding rocks in underground engineering based on stress transfer according to claim 3 is characterized in that: The hole spacing of the drill holes (2) is 4 to 8 m, and the diameter of the drill holes (2) is 90 to 150 mm.

5. The method for directional drilling and slotting of surrounding rocks in underground engineering based on stress transfer according to claim 3, characterized in that: If the boreholes (2) are arranged on both sides outside the outline of the underground project (1), the number of single-sided boreholes on the side of the underground project (1) is equal to the height of the underground project (1) divided by the distance between the boreholes, and the number is rounded off; If the boreholes (2) are arranged at the top or bottom of the underground project (1), the number of boreholes at the top or bottom of the underground project (1) is equal to the width of the underground project (1) divided by the distance between the boreholes, and the number is rounded up; If the boreholes (2) are arranged at the top, bottom and both sides of the underground project (1), the number of boreholes is the sum of the number of boreholes on the sides and the number of boreholes on the top and bottom of the underground project (1).

6. The method for directional drilling and slotting of surrounding rocks in underground engineering based on stress transfer according to claim 1, characterized in that: The length of the slit (3) l The calculation method is: l = (1 ± 10%) W, or l = (1 ± 10%) H, wherein W is the width of the underground project (1) and H is the height of the underground project (1).

7. The method for directional drilling and slotting of surrounding rocks in underground engineering based on stress transfer according to claim 6, characterized in that: The width of the slit (3) t The calculation method is: Establish a finite element model, the size of which is not less than 10 times the size of the underground project (1); Set unit parameters according to geological survey data; Set boundary conditions and set the original rock stress field boundary around the model according to geological survey data; Determine the size and quantity of the drilling holes, as well as the direction, length, and preset slit width of the slits, wherein the preset slit widths include multiple ones; Excavate the proposed slot area, perform calculation and analysis, obtain the distribution diagram of the ground stress field after slot unloading, and analyze the ground stress data of the underground project before and after slot unloading in combination with the location of the underground project. Determine the final slot width by comparing the calculation results under multiple preset slot widths. t .

8. The method for directional drilling and slotting of surrounding rocks in underground engineering based on stress transfer according to claim 1, characterized in that: When performing directional slitting operations, a single drill hole is slit in one direction or in two directions.

9. The method for directional drilling and slotting of surrounding rocks in underground engineering based on stress transfer according to claim 8, characterized in that: When performing directional cutting operations, the cutting nozzle is connected to the high-pressure pump through a high-pressure water pipe and lowered into the directional borehole until it reaches the predetermined cutting position. The pressure and flow changes are monitored in real time through pressure sensors and flow sensors, and the pressure and flow of the high-pressure pump are adjusted in real time.

10. A method for directional drilling and slotting of surrounding rocks in underground engineering based on stress transfer according to any one of claims 1 to 9, characterized in that: The step S3 is also included: after the cutting is completed, drilling and excavating the surrounding rock of the underground project to form the engineering section of the underground project (1).

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