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

Abstract

The present invention relates to the field of rock drilling, and particularly to a method for directional drilling and slotting of surrounding rock in underground engineering based on stress transfer, comprising the following steps: S1: Conduct directional drilling operations on the surrounding rock of the underground engineering, and set the drill hole at a distance from the contour of the underground engineering s meters, where s = (1 ± 10%) ( r p - r 0 ), r p is the radius of the loosening zone of the underground engineering, and r 0 is the equivalent radius of the underground engineering; S2: Based on the drill hole, conduct directional slotting operations on the surrounding rock of the underground engineering, and set the slot perpendicular to the direction of the principal stress of the in-situ stress field of the surrounding rock to cut off the stress transfer path. The present invention changes the continuity of the original rock and the stress transfer path through the gaps formed by original rock directional drilling and hydraulic directional slotting. Under the action of high in-situ stress, the original rock stress will redistribute around the drill hole and the gap, reducing the surrounding rock load acting on the underground engineering, being able to targetedly adjust the stress distribution, avoid excessive damage to the shallow surrounding rock, and retain the self-bearing capacity of the shallow surrounding rock to the greatest extent.

Description

Technical Field

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

[0002] Deep rock masses are in an environment of "three highs and one disturbance", changing from the steady-state small deformation in the shallow part to the high stress, dilatancy and strong rheology in the deep part. The deformation and failure behavior of the surrounding rocks shows complex non-steady-state and non-linear characteristics. The problem of large deformation of high in-situ stress soft rocks is likely to cause collapses, structural damages, construction delays, intrusion, increased costs, etc., seriously affecting the safety of engineering construction.

[0003] Currently, some treatment measures for the large deformation problem have been formed, such as advanced stress release, multi-layer ductile support, yielding support, etc. Each technology has its own advantages and disadvantages.

[0004] Advanced stress release method: This method can reduce the load of the surrounding rock acting on the support structure by drilling holes in advance within the cross-section of the tunnel to be excavated, but it causes greater disturbance to the surrounding rock, reducing the self-bearing capacity of the surrounding rock. Its advantage is that it has a greater impact on the bearing capacity of shallow surrounding rocks.

[0005] Multi-layer ductile support method: It can release part of the stress of the surrounding rock through the delayed construction between layers, reducing the force finally acting on the support. However, the difficulty of this method lies in the lack of a theory for scientifically and reasonably determining the construction timing of each layer of support, and the cost of multi-layer ductile support is very high.

[0006] Yielding support method: Yieldable arch frames, constant resistance large deformation anchor cables, yielding support systems. This type of method can release the stress of the surrounding rock well and control the development of the deformation of the surrounding rock at the same time, but the process is relatively complex and the on-site construction is more difficult.

[0007] Generally speaking, the current treatment technologies for large deformation of soft rocks lack quantitative control methods, cannot fully mobilize and exert the strength of the surrounding rock itself, and require multi-layer support or arch replacement, etc. The treatment cost is too high, and there is an urgent need to study more advanced and efficient large deformation pre-control technologies. Summary of the Invention

[0008] The object of the present invention is to overcome the deficiencies in the prior art that the advanced stress release method for treating large deformations of soft rock has a large disturbance and damage to the surrounding rock, reducing the self-bearing capacity of the surrounding rock; the multi-layer delayed support method is difficult to determine the construction timing of each layer of support and has too high a cost; the yielding support method and the rigid support method are inconvenient to construct and have a relatively high cost, and to provide a method for directional drilling and slotting of surrounding rock in underground engineering based on stress transfer, which can pre-reduce the load acting on the support structure before the excavation of the underground engineering. At the same time, it can transfer the in-situ stress of the shallow surrounding rock adjacent to the underground engineering to the deep surrounding rock, thereby greatly preserving the integrity of the shallow surrounding rock around the structure, giving full play to the self-bearing capacity of the surrounding rock, significantly reducing the load acting on the support structure, and reducing the support cost of the underground engineering.

[0009] The present invention provides a method for directional drilling and slotting of surrounding rock in underground engineering based on stress transfer, comprising the following steps:

[0010] S1: Conduct directional drilling operations on the surrounding rock of the underground engineering, and set the drill holes at a distance of s meters from the contour of the underground engineering, where s = (1 ± 10%) ( r p - r 0 ), r p is the radius of the loosening zone of the underground engineering, and r 0 is the equivalent radius of the underground engineering;

[0011] S2: Based on the drill holes, conduct directional slotting operations on the surrounding rock of the underground engineering, and set the slots perpendicular to the direction of the principal stress of the in-situ stress field of the surrounding rock to cut off the stress transmission path.

[0012] Preferably, the calculation method of the radius r p of the loosening zone is:

[0013]

[0014] In the formula, r 0 is the equivalent radius of the underground engineering, and for a horseshoe-shaped or straight-wall arched section, it can be approximately taken as half of the structural height H or the structural width W , p 0 is the in-situ stress of the surrounding rock, p 1 is the design value of the support bearing capacity, c is the cohesion of the surrounding rock, is the internal friction angle of the surrounding rock.

[0015] Preferably, the boreholes are distributed on both sides and / or the top and / or the bottom outside the contour of the underground project.

[0016] Preferably, the hole spacing of the boreholes is 4 - 8 m, and the diameter of the boreholes is 90 - 150 mm.

[0017] Preferably, if the boreholes are arranged on both sides outside the contour of the underground project, the number of boreholes on one side of the side of the underground project is equal to the height of the underground project divided by the hole spacing of the boreholes, and is rounded up;

[0018] If the boreholes are arranged on the top or the bottom of the underground project, the number of boreholes on the top or the bottom of the underground project is equal to the width of the underground project divided by the hole spacing of the boreholes, and is rounded up;

[0019] If the boreholes are arranged on the top, the 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 the bottom.

[0020] Preferably, the length l of the slotted seam is calculated as follows: 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.

[0021] Preferably, the width t of the slotted seam is calculated as follows:

[0022] A finite element model is established, and the model size is not less than 10 times the size of the underground project;

[0023] According to the geological exploration data, the element parameters are set;

[0024] The boundary conditions are set, and the in-situ stress field boundary is set around the model according to the geological exploration data;

[0025] The borehole size, quantity, and the direction, length, and preset seam widths of the slotted seams are determined, where the preset seam widths include multiple ones;

[0026] The area where the slotted seam is to be cut is excavated, and calculation and analysis are carried out to obtain the distribution map of the in-situ stress field after the slotted seam pressure relief. Combining with the location of the underground project, the in-situ stress data of the underground project before and after the slotted seam pressure relief are analyzed. By comparing the calculation results under multiple preset seam widths, the final seam width is determined t .

[0027] Preferably, during the directional slotted seam operation, a single borehole is cut with a single direction or two directions.

[0028] Preferably, when performing the directional slitting operation, connect the slitting nozzle to the high-pressure pump through a high-pressure water pipe and lower it into the directional borehole until it reaches the predetermined slitting position. Real-time monitor the changes in pressure and flow rate through pressure sensors and flow sensors, and adjust the pressure and flow rate of the high-pressure pump in real time.

[0029] Preferably, it further includes step S3: After the slitting is completed, drill and excavate the surrounding rock of the underground project to form the engineering section of the underground project.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] Through the gaps formed by the original rock directional drilling and hydraulic directional slitting, the present invention changes the continuity of the original rock and the stress transmission path. Under the action of high in-situ stress, the original rock stress will redistribute around the borehole and the gaps, thereby reducing the surrounding rock load acting on the underground project. At the same time, since the slitting is carried out directionally, the stress distribution can be adjusted targeted, avoiding excessive damage to the shallow surrounding rock, and retaining the self-bearing capacity of the shallow surrounding rock to the greatest extent. When the subsequent underground project drilling and excavation construction is carried out, the shallow surrounding rock is free from the action of high in-situ stress, the integrity of the shallow surrounding rock is retained, the bearing capacity of the surrounding rock itself is greatly improved, the load acting on the support structure is reduced, and the support cost of the underground project is greatly reduced. Description of the Drawings

[0032] Figure 1 It is a schematic structural diagram of the directional drilling and hydraulic directional slitting described in Embodiment 1 of the present invention.

[0033] Figure 2 For Figure 1 Partial schematic diagram.

[0034] Markings in the figure:

[0035] 1 - Underground project, 2 - Borehole, 3 - Slitting. Detailed Embodiments

[0036] The present invention will be further described in detail below in conjunction with specific embodiments. However, this should not be construed as limiting the scope of the above-mentioned subject matter of the present invention to the following embodiments. All technologies implemented based on the content of the present invention belong to the scope of the present invention.

[0037] Unless otherwise specified, in the description of the specific embodiments of the present invention, the expression terms indicating the orientation or positional relationship such as "upper", "lower", "left", "right", "center", "inner", "outer", etc. are all based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship when the invention product / device / installation is in its usual use. These terms of orientation or positional relationship are only for the convenience of describing the solution of the present invention or simplifying the description in the specific embodiments, so as to facilitate technicians to quickly understand the solution, rather than indicating or implying that a specific device / component / element must have a specific orientation, or be constructed and operated in a specific positional relationship. Therefore, it should not be construed as a limitation to the present invention.

[0038] In addition, if terms such as "horizontal", "vertical", "hanging", "parallel" appear, it does not mean that the corresponding device / component / element is required to be absolutely horizontal or vertical or hanging or parallel, but it can be slightly inclined or have a deviation. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but it can be slightly inclined. Or, it can be simply understood that the corresponding device / component / element is arranged in the directions of "horizontal", "vertical", "hanging", "parallel", etc., and can have an error / deviation of ±10% relative to the corresponding direction setting, more preferably within ±8%, more preferably within ±6%, more preferably within ±5%, more preferably within ±4%. As long as the corresponding device / component / element is within the error / deviation range, it can still play its role in the solution of the present invention.

[0039] In addition, the expressions such as "first", "second", "third", etc. in the terms are only used to distinguish the description of the same or similar components, and should not be construed as emphasizing or implying the relative importance of a specific component.

[0040] In addition, in the description of the embodiments of the present invention, "several", "multiple", "a number of" represent at least 2. It can be any situation such as 2, 3, 4, 5, 6, 7, 8, 9, etc., and even can be more than 9.

[0041] In addition, in the description of the technical solution of the present invention, unless otherwise clearly specified / defined / restricted, where terms such as "set", "installed", "connected", "connected", "provided with", "laid", "arranged" appear, they should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection. It can be connection means commonly used in the art such as welding, riveting, bolting, threaded connection, etc. This connection can be a mechanical connection, an electrical connection or a communication connection; it can be directly connected, or indirectly connected through an intermediate medium, and can be the communication inside two elements.

[0042] Example 1

[0043] A method for directional drilling and slotting of surrounding rock in underground engineering based on stress transfer, comprising the following steps:

[0044] S1: Conduct directional drilling operations on the surrounding rock of the underground project, and set the borehole 2 at a distance of s meters from the contour of the underground project 1, where s = 1 ± 10% ( r p - r 0 ), r p is the radius of the loosened zone of the underground project, r 0 is the equivalent radius of the underground project, as shown in Figure 1 - Figure 2 . Specifically, it includes the following steps:

[0045] S11: Determine the position and quantity of the borehole 2. According to the distribution of the in-situ stress field of the deep underground project 1 and the structural design scheme, combined with the geological exploration data, set the borehole 2 at a certain distance s outside the contour of the underground project 1, distributed on both sides, the top, the bottom outside the structural contour, or both sides and the top and the bottom are set. The distance s between the borehole 2 and the contour line of the underground project 1 needs to be determined by calculation according to the structural section size and the surrounding rock conditions, generally taken at the radius of the loosened zone r p (the position deviation can be controlled within 10%), and the specific process is as follows:

[0046] 1) Determine the cohesion c of the surrounding rock, the internal friction angle , and the in-situ ground stress p 0 according to the geological exploration data;

[0047] 2) Obtain the design value of the support bearing capacity p 1 , the equivalent radius of the underground project r 0 according to the design data. For a horseshoe-shaped or straight-wall arched section, it can be approximately taken as half of the section width W;

[0048] The calculation method of the radius of the loosened zone r p is:

[0049]

[0050] In the formula, r 0 is the equivalent radius of the underground project, p 0 is the in-situ ground stress of the surrounding rock, p1 is the design value of the support bearing capacity, c is the cohesion of the surrounding rock, is the internal friction angle of the surrounding rock.

[0051] For underground projects mainly under horizontal ground stress, the positions of the boreholes 2 are set on both sides outside the contour of the underground project 1. Generally, one borehole is set on each side, and the number of boreholes on one side n can be increased according to the structural height H. Generally, the borehole spacing s 1 is 4 - 8m, and specifically it needs to be determined according to the rock conditions and the slotting length l Single borehole 2 can be slotted unidirectionally or bidirectionally.

[0052] For underground projects mainly under vertical ground stress, the positions of the boreholes 2 are mainly set in the top area outside the contour of the underground project 1. Generally, one borehole is set. Specifically, the number of boreholes at the top or bottom of the underground project 1 n can be increased according to the width W dimension of the underground project 1. Generally, the borehole spacing s 1 is 4 - 8m. The diameter D of the borehole 2 is generally 90 - 150 mm.

[0053] 1) If the boreholes are set on both sides of the underground project 1, the number of boreholes on one side of the side of the underground project 1 n is equal to the height H of the underground project 1 divided by the borehole spacing s 1 , and rounded to the nearest integer;

[0054] 2) If the boreholes are set at the top or bottom of the underground project 1, the number of boreholes at the top or bottom of the underground project 1 n is equal to the width W of the underground project 1 divided by the borehole spacing, and rounded to the nearest integer;

[0055] 3) If the boreholes are set at the top, bottom and both sides of the underground project 1, the number of boreholes n is the sum of the number of boreholes on the side of the underground project 1 and the number of boreholes at the top and bottom.

[0056] S12: Positioning and installation of the directional drilling equipment. Select a directional drilling equipment suitable for the underground project 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 that the equipment can operate normally.

[0057] S13: Drilling construction. Start the directional drilling equipment and carry out borehole operations according to the predetermined positions. During the drilling process, monitor the depth and axis trajectory of the borehole in real time to ensure that the borehole meets the requirements. It is recommended to control the deviation of the borehole depth within ±1m and the axis deviation within 1‰.

[0058] S2: Based on the borehole 2, conduct directional slotting operations on the surrounding rock of the underground project, set the slot 3 perpendicular to the main stress direction of the surrounding rock stress field, and cut off the stress transmission path, as Figure 1 - Figure 2 shown. Specifically, it includes the following steps:

[0059] S21: Determine the slot 3 parameters, including the direction, length l , and width t of the slot 3. The direction of the borehole slot 3 needs to be adjusted according to the main direction of stress distribution. The direction of the slot 3 should be as perpendicular as possible to the main stress direction, with the error controlled within 10%, to ensure that the slot 3 can effectively cut off the stress transmission path. The length l of the slot 3 should be determined according to the width or height of the structure. Generally, the length l of the slot 3 is close to the width and height of the underground project 1, and the length l of the slot 3 is controlled within plus or minus 10% of the width or height of the underground project 1. The width t of the slot depends on the engineering geological environment. Since the stress field distribution of the surrounding rock of the underground project 1 is complex, it is difficult to deal with the actual complex situation using the analytical analysis method. Generally, through numerical simulation analysis and calculation, the most reasonable slot width t is determined to ensure the pressure relief effect. The specific simulation process is as follows:

[0060] 1) Establish a finite element model, and the model size should not be less than 10 times the size of the underground project;

[0061] 2) Set the element parameters according to the geological exploration data;

[0062] 3) Set the boundary conditions, and set the in-situ stress field boundary around the model according to the geological exploration data;

[0063] 4) Determine the borehole size D, quantity n , and the direction, length l , width t of the slot, etc. The width t of the slot can be preset as multiple values to determine the optimal slot width size;

[0064] 5) Excavate the area to be slotted and conduct calculation and analysis to obtain the in-situ stress field distribution map after slotting pressure relief. Combining with the location of the underground project, the in-situ stress data of the underground project before and after slotting pressure relief can be analyzed. By comparing the calculation results under multiple preset slot widths, the final slot width t can be determined.

[0065] S22: Install pressure sensors and flow sensors at positions near the outlet of the high-pressure pump and the slotted nozzle to monitor the changes in pressure and flow in real time. The sensors can transmit the measured data to the control system so that the operator can timely understand the parameter conditions during the slotted operation. According to the monitored data and the slotted effect, adjust the pressure and flow of the high-pressure pump in real time. If it is found that the slotted depth is insufficient or the slotted width does not meet the requirements, the pressure or flow can be appropriately increased; if it is found that the rock is overly broken, that is, when the particle size and production of the cuttings returned from the borehole during slotted operation increase significantly, the pressure and flow need to be reduced. During the slotted operation, closely monitor the operating status of the equipment and the slotted quality, and make timely adjustments to ensure the best slotted effect.

[0066] S23: Hydraulic directional slotted construction. Select high-pressure hydraulic slotted equipment, including a high-pressure pump, a slotted nozzle, high-pressure water pipes, etc. Inspect and debug the equipment to ensure that the equipment can provide sufficient pressure and flow to meet the requirements of hydraulic directional slotted operation. Connect the slotted nozzle to the high-pressure pump through the high-pressure water pipe and slowly lower it into the directional borehole until it reaches the predetermined slotted position. During the lowering process, pay attention to protecting the nozzle and the water pipe to avoid damage. Start the high-pressure pump to spray high-pressure water through the slotted nozzle to form a high-speed jet. According to the pre-designed slotted direction and length, control the rotation and advancement of the slotted nozzle so that the high-speed jet cuts out a slit with a predetermined shape and size on the borehole wall. During the slotted operation, install high-precision pressure sensors near the outlet of the high-pressure pump and the slotted nozzle to monitor the pressure value in real time, and adjust the pressure of the high-pressure pump and the motion parameters of the slotted nozzle according to the actual situation; install a high-precision motion encoder on the driving device of the slotted nozzle to accurately measure parameters such as the position, speed, and acceleration of the nozzle, so as to precisely control the quality and effect of the slotted operation. After the slotted operation is completed, stop the high-pressure pump and take out the slotted nozzle from the borehole. During the slotted operation, strictly control the construction accuracy to ensure that the slotted operation meets the designed angle, length, and width.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] Example 2

[0073] Based on Example 1, this example illustrates the solution of the present invention through a specific case:

[0074] A certain highway tunnel has a two-way four-lane design. The tunnel cross-section width W is 12.4 m, the height H is 9.2 m, and the maximum buried depth is approximately 357 m. The tunnel site is located in a region with interbedded soft rocks of variable sandstone and slate. Affected by tectonic movements, the rock mass is extremely fragmented, with strong local folding and poor self-stabilization ability. The groundwater is extremely abundant, making the surrounding rock more prone to softening. According to the rock test results, the saturated compressive strength of moderately weathered variable sandstone is 35.01 MPa, and the saturated compressive strength of moderately weathered slate is 7.62 MPa. Affected by complex tectonic movements, the maximum horizontal principal stress is 7.00 - 11.15 MPa, with an average value of 9.2 MPa. The principal stress intersects the tunnel alignment at a large angle of 70°. Under the action of high in-situ stress and water-rich soft rock, large squeezing deformations are likely to occur, with large deformation pressures, high deformation speeds, and long durations.

[0075] 1. Set the drilling positions and quantities

[0076] Based on the engineering geological conditions of the tunnel, the principal stress of the surrounding rock stress field is the horizontal stress, which forms an angle of 70° with the tunnel axis. Therefore, the drill holes are set on both sides outside the tunnel structure contour line, with one drill hole on each side. The drill hole diameter is 150 mm, the drill hole depth is 100 m, and the drill holes are set at the springing of the arch.

[0077] 1) Determine the cohesion of the surrounding rock according to the geological exploration data c It is 0.3 MPa, and the internal friction angle is 34°, and the in-situ rock stress p 0 is 9.2 MPa;

[0078] 2) Obtain the design value of the support bearing capacity according to the design data p 1 It is 0.35 MPa, and the equivalent radius of the underground project r 0 , for a horseshoe-shaped cross-section, it can be approximately taken as half of the cross-section width W, that is r 0 is 6.2 m;

[0079] 3) Calculate the radius of the loosening zone according to the following formula r p :

[0080]

[0081] Therefore, the drill holes are set at a distance of 10.1 m from the center of the structure, that is: 10.1 - 6.2 = 3.9 m outside the structure contour line.

[0082] 2. Determine the slotting parameters

[0083] The direction of the slotted seam forms a 90-degree angle with the direction of the maximum principal stress of the original rock. Therefore, in this example, the direction of the slotted seam is set to the vertical direction. The length of the slotted seam is determined according to the height of the underground project, taking 9 meters (4.5 meters above and below the borehole). The width of the slotted seam is taken as 5 centimeters.

[0084] 3. Positioning and installation of the directional drilling equipment.

[0085] According to the pre-set drilling parameters, select the directional drilling equipment and transport it to the construction site for installation and commissioning.

[0086] 4. Drilling construction. Start the drilling construction according to the pre-set drilling parameters. During the drilling process, monitor the depth, angle, and trajectory of the borehole in real time to ensure that the borehole meets the design requirements. After the drilling is completed, clean and inspect the borehole.

[0087] 5. Real-time monitoring and adjustment of construction parameters.

[0088] Install pressure sensors and flow sensors at positions such as the outlet of the high-pressure pump and near the slotted nozzle to monitor the changes in pressure and flow in real time. According to the monitoring data and the slotted seam effect, adjust the pressure and flow of the high-pressure pump in real time.

[0089] 6. Hydraulic directional slotted seam construction.

[0090] Select a high-pressure hydraulic slotted seam equipment, the rated pressure of its high-pressure pump is 50 MPa, and the flow rate is 150 L / min. Connect the slotted nozzle to the high-pressure pump through a high-pressure water pipe and lower it into the directional borehole.

[0091] Start the high-pressure pump, spray the high-pressure water through the slotted nozzle at a pressure of 40 MPa to form a high-speed jet. Cut slotted seams with a length of 4 meters and a width of 50 millimeters on the upper and lower parts of the borehole wall. After the slotted seam is completed, stop the high-pressure pump and take out the slotted nozzle from the borehole.

[0092] According to the analysis results, after the tunnel structure is treated by slotted seams through boreholes, the original rock principal stress between the tunnel structure and the borehole is reduced by 30%. At the same time, due to stress regulation by slotted seams through boreholes outside the tunnel contour, after the in-situ stress is reduced, the load borne by the surrounding rock between the borehole and the tunnel structure is also reduced, and the integrity of the surrounding rock is retained, thus greatly reducing the surrounding rock load acting on the tunnel support structure, reducing the deformation of the primary support of the tunnel, and the deformation can be reduced by more than 50%, thereby greatly reducing the support cost of high in-situ stress and large deformation tunnels.

[0093] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for directional drilling and slotting of surrounding rock in underground engineering based on stress transfer, characterized in that It includes the following steps: S1: Conduct directional drilling operations on the surrounding rock of underground engineering, and set the borehole (2) at a distance from the contour of the underground engineering (1) s meters, where s = (1 ± 10%) ( r p - r 0), r p is the radius of the loosened zone of the underground engineering, r 0 is the equivalent radius of the underground engineering; S2: Based on the borehole (2), perform a directional slotting operation on the surrounding rock of the underground project, set the slot (3) perpendicular to the direction of the principal stress of the in-situ stress field of the surrounding rock, and cut off the stress transmission path; Neither the borehole (2) nor the slot (3) is connected to the underground project (1). The continuity of the original rock and the stress transmission path are changed through the slots formed by directional drilling and directional slotting, while retaining the self-bearing capacity of the shallow surrounding rock; The length of the slotted seam (3) l is calculated as follows: l = (1 ± 10%)W, or l = (1 ± 10%)H, where W is the width of the underground project (1) and H is the height of the underground project (1); The slit width of the slotted seam (3) t is calculated as follows: Establish a finite element model, and the model size is not less than 10 times the size of the underground project (1); Set the element parameters according to the geological exploration data; Set the boundary conditions, and set the in-situ stress field boundary around the model according to the geological exploration data; Determine the borehole size, quantity, and the direction, length, and preset slot width of the slot, where the preset slot width includes multiple values; Excavate the area where the slots are to be cut, conduct calculation and analysis to obtain the distribution map of the in-situ stress field after slot cutting for pressure relief, and combine with the location of the underground project to analyze and obtain the in-situ stress data of the underground project before and after slot cutting for pressure relief. By comparing the calculation results under multiple preset slot widths, determine the final slot width t .

2. The method for directional drilling and slotting of surrounding rock in underground engineering based on stress transfer according to claim 1, characterized in that, The radius of the loosening zone r p The calculation method is as follows: In the formula, r 0 is the equivalent radius of the underground project, p 0 is the initial in-situ stress of the surrounding rock, p 1 is the design value of the support bearing capacity, c is the cohesion of the surrounding rock, is the internal friction angle of the surrounding rock.

3. A method for directional drilling and slotting of surrounding rock 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 outside the contour of the underground project (1).

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

5. A method for directional drilling and slotting of the surrounding rock of an underground project based on stress transfer according to claim 3, characterized in that If the boreholes (2) are arranged on both sides outside the contour of the underground project (1), the number of boreholes on one side of the side of the underground project (1) is equal to the height of the underground project (1) divided by the hole spacing of the boreholes, and rounded up to the nearest integer; If the boreholes (2) are arranged on the top or the bottom of the underground project (1), the number of boreholes on the top or the bottom of the underground project (1) is equal to the width of the underground project (1) divided by the hole spacing of the boreholes, and rounded up to the nearest integer; If the boreholes (2) are arranged on 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 the bottom of the underground project (1).

6. The method for directional drilling and slotting of surrounding rock in underground engineering based on stress transfer according to claim 1, characterized in that, During the directional slotting operation, each borehole performs single-directional slotting or two-directional slotting.

7. A method for directional drilling and slotting of surrounding rock in underground engineering based on stress transfer according to claim 6, characterized in that During the directional slotting operation, connect the slotting nozzle to the high-pressure pump through a high-pressure water pipe, lower it into the directional borehole until it reaches the predetermined slotting position, and monitor the changes in pressure and flow rate in real time through a pressure sensor and a flow sensor, and adjust the pressure and flow rate of the high-pressure pump in real time.

8. A method for directional drilling and slotting of surrounding rock in underground engineering based on stress transfer according to any one of claims 1-7, characterized in that It further includes step S3: After slotting is completed, drill and excavate the surrounding rock of the underground project to form the engineering section of the underground project (1).

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