Method for directional drilling through broken rock strata based on trajectory prediction and roadway pre-grouting

Abstract

The present application relates to the directional drilling construction technology field, especially to a kind of method for directional drilling crossing broken rock strata based on trajectory pre-judgment and roadway pre-grouting, comprising the positional relationship of analyzing directional drilling design trajectory and roadway, identifying broken roof area needing reinforcement;Corresponding to the position intersecting with directional drilling design trajectory in roadway, the identified broken roof area is constructed grouting hole, and reinforcement material is injected into broken roof area through grouting hole to carry out pre-grouting;After the reinforcement material injected solidifies, directional drilling construction is carried out.The present application fundamentally solves the problems of drilling backflow anomaly, pump pressure rise, sticking and burying accidents caused by broken roof by active, advanced and accurate pre-reinforcement means, significantly improves the safety and success rate of directional drilling construction, can effectively avoid economic loss and construction delay caused by drilling accidents, and also reduces the material waste and effect discount caused by direct grouting in directional drilling of traditional method.

Description

Technical Field

[0001] This invention relates to the field of directional drilling technology, and in particular to a method for directional drilling through fractured rock strata based on trajectory prediction and tunnel pre-grouting. Background Technology

[0002] Coal mines have complex rock formations. Due to the need to pass through multiple rock strata and roadways during directional drilling, if encountering rock strata with poor geological conditions or areas with fractured roadway roofs, drilling water may escape from the fractured roof or along the anchor cables and bolts when the drilling trajectory crosses the roadway and encounters a fractured roof. This can result in no return water or abnormal return water in the borehole, increased pump pressure, and accidents such as drill bit pressure, stuck drill bit, and buried drill bit are likely to occur, causing the inability to drill normally and significant economic losses. Summary of the Invention

[0003] This invention provides a method for directional drilling through fractured rock strata based on trajectory prediction and roadway pre-grouting. This method addresses the shortcomings of existing technologies where directional drilling traverses roadways and encounters fractured roofs is prone to backflow anomalies that prevent normal drilling. The method enables pre-grouting reinforcement of the fractured roof, improving the stability of drilling operations and ensuring drilling safety.

[0004] This invention provides a method for directional drilling through fractured rock strata based on trajectory prediction and tunnel pre-grouting, comprising: Analyze the relationship between the directional drilling design trajectory and the location of the roadway to identify areas of fractured roof that require reinforcement.

[0005] In the tunnel, grouting holes are constructed at the locations corresponding to the intersection with the directional drilling design trajectory for the identified fractured roof area. Reinforcing material is injected into the fractured roof area through the grouting holes for pre-grouting.

[0006] After the injected reinforcing material has cured, directional drilling is carried out.

[0007] According to the present invention, a method for directional drilling through fractured rock strata based on trajectory prediction and pre-grouting of tunnels includes the following steps: constructing grouting holes in the identified fractured roof area, and injecting reinforcing material into the fractured roof area through the grouting holes for pre-grouting. Mark the drilling locations of all grouting holes in the fractured top plate area.

[0008] A drilling rig was set up in the tunnel and its angle was adjusted to drill grouting holes at all marked locations.

[0009] Connect the grouting pipe and the orifice grouting pipe, and insert the connected grouting pipe and the orifice grouting pipe into the drilled grouting hole, with the threaded end of the orifice grouting pipe protruding at least 150mm from the orifice opening.

[0010] The grouting pipe at the grouting hole opening is fixed with cement and the hole is sealed. A stop valve is installed at the outer end of the grouting pipe.

[0011] Connect the grouting system to the orifice shut-off valve and perform grouting until grout flows back into the grouting hole. Then stop grouting and close the orifice shut-off valve.

[0012] According to the present invention, a method for directional drilling through fractured rock strata based on trajectory prediction and pre-grouting of tunnels includes, wherein marking the drilling locations of all grouting holes in the fractured roof area comprises: Based on the tunnel roof, multiple rows of grouting hole location markers are arranged in the identified broken roof area. Each row of location markers includes at least two grouting holes, and the distance between two adjacent grouting holes is no more than 2000 mm.

[0013] According to the present invention, a method for directional drilling through fractured rock strata based on trajectory prediction and tunnel pre-grouting is provided, wherein the depth of the grouting hole is between 4000 mm and 8000 mm.

[0014] According to the present invention, a method for directional drilling through fractured rock strata based on trajectory prediction and tunnel pre-grouting is provided. If cross-grouting occurs between adjacent grouting holes during the grouting process, the adjacent grouting holes experiencing cross-grouting are alternately grouted or grouted simultaneously in separate paths.

[0015] According to the present invention, a method for directional drilling through fractured rock strata based on trajectory prediction and tunnel pre-grouting is provided, wherein the reinforcing material injected into the fractured roof area based on the grouting hole is malathion.

[0016] According to the present invention, a method for directional drilling through fractured rock strata based on trajectory prediction and tunnel pre-grouting is provided. The reinforcing material injected into the fractured roof area through the grouting hole is a two-component slurry formed by mixing cement slurry and water glass solution. The volume ratio of the cement slurry and the water glass solution in the two-component slurry ranges from 1:0.4 to 1:0.6.

[0017] According to the present invention, a method for directional drilling through fractured rock strata based on trajectory prediction and tunnel pre-grouting is provided, wherein the cement slurry in the dual-liquid slurry is a slurry formed by silicate cement and water, and the water-cement ratio of the cement slurry is between 0.6:1 and 0.8:1.

[0018] According to the present invention, a method for directional drilling through fractured rock strata based on trajectory prediction and tunnel pre-grouting is provided, wherein the water glass solution in the dual-liquid grout is a water glass solution with a concentration range of 48 to 55 Baume degrees and a modulus range of 2.8 to 3.2.

[0019] According to the present invention, a method for directional drilling through fractured rock strata based on trajectory prediction and tunnel pre-grouting is provided. If leakage occurs in the grouting hole during the directional drilling process, aggregate is added to the bottom of the grouting hole for grouting and leakage plugging.

[0020] This invention provides a method for directional drilling through fractured rock strata based on trajectory prediction and pre-grouting of the tunnel. First, by accurately analyzing the spatial relationship between the designed directional drilling trajectory and the tunnel, areas of roof fracture that may cause drilling accidents are identified. Then, grouting holes are constructed in these areas according to specific parameters, and reinforcing materials such as mortar or cement-water glass grout are injected for pre-grouting to fill fissures and cement the fractured rock mass. After the grout solidifies to form a high-strength reinforced layer, directional drilling is then carried out. This method, based on trajectory prediction and pre-grouting of the tunnel, fundamentally solves the problems of abnormal borehole backflow, increased pump pressure, and frequent drill jamming and burial accidents caused by roof fracture through proactive, advanced, and precise pre-reinforcement measures. It significantly improves the safety and success rate of directional drilling, effectively avoiding economic losses and project delays caused by drilling accidents, and reducing material waste and reduced effectiveness caused by direct grouting in traditional directional drilling methods. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 This is a schematic flowchart of the method for directional drilling through fractured rock strata based on trajectory prediction and tunnel pre-grouting provided by the present invention.

[0023] Figure 2 This is a schematic diagram showing the relationship between the directional drilling design trajectory and the location of the roadway in the directional drilling method for traversing fractured rock strata based on trajectory prediction and roadway pre-grouting provided by the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0025] The following is combined with Figure 1 and Figure 2 The present invention describes the specific process of a method for directional drilling through fractured rock strata based on trajectory prediction and tunnel pre-grouting.

[0026] One embodiment of the present invention provides a method for directional drilling through fractured rock strata based on trajectory prediction and tunnel pre-grouting, see [link to relevant documentation]. Figure 1 As shown, the method for directional drilling through fractured rock strata based on trajectory prediction and tunnel pre-grouting includes the following steps S1 to S3.

[0027] S1. Analyze the relationship between the directional drilling design trajectory and the location of the roadway to identify the fractured roof area that needs reinforcement.

[0028] S2. In the tunnel, at the location corresponding to the intersection with the directional drilling design trajectory, construct grouting holes in the identified fractured roof area, and inject reinforcement material into the fractured roof area through the grouting holes for pre-grouting.

[0029] S3. After the reinforcing material to be injected has cured, directional drilling is carried out.

[0030] It is understood that the method for directional drilling through fractured rock strata based on trajectory prediction and roadway pre-grouting in this embodiment includes the following specific implementation process: First, by accurately analyzing the spatial relationship between the directional drilling design trajectory and the roadway, the fractured roof area that may cause drilling accidents is identified; then, grouting holes are constructed in this area according to specific parameters, and reinforcing materials such as malathion or cement-water glass double-liquid grout are injected for pre-grouting to fill cracks and cement the fractured rock mass; after the grout solidifies to form a high-strength reinforced layer, directional drilling is then carried out. This method for directional drilling through fractured rock strata based on trajectory prediction and roadway pre-grouting in this embodiment, through proactive, advanced, and precise pre-reinforcement methods, fundamentally solves the problems of abnormal borehole backflow, increased pump pressure, and frequent drill jamming and burying accidents caused by roof fracture. It significantly improves the safety and success rate of directional drilling construction, effectively avoids economic losses and project delays caused by drilling accidents, and also reduces material waste and reduced effectiveness caused by direct grouting in directional drilling using traditional methods.

[0031] In some embodiments of the method for directional drilling through fractured rock strata based on trajectory prediction and tunnel pre-grouting of the present invention, the construction of grouting holes in the identified fractured roof area and the injection of reinforcing material into the fractured roof area based on the grouting holes for pre-grouting include the following steps S21 to S25.

[0032] S21. Mark the drilling locations of all grouting holes in the fractured roof area. This step is based on the preliminary analysis of the relationship between the directional drilling trajectory and the roadway space, and involves scientifically laying out the holes in the identified fractured roof area. Typically, using the roadway roof as a reference, multiple rows of grouting hole location markers are arranged in the identified fractured roof area. Each row of location markers includes at least two grouting holes, and the distance between two adjacent grouting holes is no greater than 2000mm. Using specialized measuring tools and spray paint for precise layout and marking, this step ensures that the grouting holes cover the entire potentially fractured area, forming an effective reinforcement curtain and providing a precise spatial positioning basis for subsequent grouting operations.

[0033] S22. Set up the drilling rig in the roadway and adjust its angle. Drill grouting holes at all marked locations, with a depth between 4000mm and 8000mm. This step uses a drilling rig suitable for underground coal mine operations (such as the MQT series pneumatic anchor drill), equipped with a φ36mm drill bit. A wet drilling method is used at each marked point. During drilling, the stability of the drilling rig and the drilling angle must be strictly controlled to ensure the drilling direction is perpendicular to the roof rock surface or constructed at the designed angle. The drilling depth is usually selected between 4000mm and 8000mm, depending on the degree of roof fragmentation and reinforcement requirements. The entire drilling process requires standardized operation, real-time observation of rock strata changes and water return, and proper drilling records.

[0034] S23. Connect the grouting pipe and the orifice grouting pipe, and insert the connected grouting pipe and orifice grouting pipe into the drilled grouting hole, ensuring that the threaded end of the orifice grouting pipe protrudes at least 150mm from the hole opening. This step is performed immediately after drilling is completed, installing the grouting system. Reliably connect the rigid plastic grouting pipe (with several grouting holes in its wall) to the threaded metal orifice grouting pipe. Then insert this connector into the drilled grouting hole, ensuring that the threaded end of the orifice grouting pipe protrudes at least 150mm from the hole opening to facilitate subsequent connection of the grouting pipeline and installation of control valves.

[0035] S24. Secure the grouting pipe at the grouting hole opening with cement and seal the hole. Install a shut-off valve at the outer end of the grouting pipe. This step involves sealing the opening and installing the valve. Specifically, use pre-prepared quick-setting cement grout or a special sealing agent to tightly fill and seal the annular gap between the grouting pipe and the hole wall, ensuring it can withstand the high pressure generated during grouting (typically 2-5 MPa) to prevent grout leakage from the hole, which could lead to grouting failure or insufficient pressure. After the sealing material has cured, install a high-pressure shut-off valve at the exposed threaded end. The shut-off valve serves three purposes: first, it acts as a grout channel during grouting; second, it can be immediately closed after grouting to prevent grout backflow and pressure release, ensuring the grout fully penetrates the cracks under pressure; and third, it provides an interface for potential secondary grouting.

[0036] S25. Connect the grouting system to the borehole shut-off valve and begin grouting until grout flows back into the borehole. Stop grouting and close the borehole shut-off valve. In this step, securely connect the outlet of the grouting pump (such as a ZBQ series pneumatic grouting pump) to the installed borehole shut-off valve via a high-pressure pipeline. After verifying that the entire system connection is correct, start the grouting pump and inject the prepared reinforcing grout (such as malathion or cement-water glass dual-liquid grout) into the borehole according to the preset parameters (such as grouting pressure 2~4MPa, grouting speed 10~25L / min). During the grouting process, a designated person must closely monitor the pressure gauge reading and the borehole opening and surrounding rock wall conditions. Grouting continues until grout is observed to flow steadily from the grouting hole opening or closely adjacent fissures (i.e., "grout backflow at the opening"). This indicates that the fissures have been basically filled with grout. Once this state is reached, the grouting pump is stopped first, then the opening shut-off valve is immediately closed, and finally the grouting pipeline is disassembled. The opening shut-off valve is used to "maintain pressure," allowing the grout to further penetrate into the micro-fissures under residual pressure, thereby improving the density and integrity of the reinforced body.

[0037] In some embodiments of the method for directional drilling through fractured rock strata based on trajectory prediction and tunnel pre-grouting of the present invention, if cross-grouting occurs between adjacent grouting holes during the grouting process, the adjacent grouting holes experiencing cross-grouting are alternately grouted or grouted simultaneously in separate paths.

[0038] It is important to understand that "grout cross-flow" refers to the phenomenon where, during grouting into grouting hole A, the grout does not completely diffuse within the rock fissures surrounding grouting hole A, but instead flows out through interconnected fissure channels from adjacent grouting holes B and C, or from fissures on the surface of other roadways. During the grouting process, on-site personnel must conduct continuous inspections. If grout is found flowing from adjacent, yet-to-be-grouted, boreholes, or if grout seeps from visible fissures in the roof or walls of nearby roadways, "grout cross-flow" can be immediately identified. Once identified, the alternating grouting method or the simultaneous grouting method described in this embodiment must be used immediately to address the issue.

[0039] Alternating grouting utilizes the natural channels formed by grout flow, most effectively "pinching" and filling interconnected fractures, ensuring that large through fractures are fully filled. It is suitable for situations where the grout flow channels are relatively unobstructed and the grout flow volume is large. In some specific examples, when grouting into grouting hole A causes grout to flow out from grouting hole B, grouting into grouting hole A is immediately stopped, and the grouting pipeline is quickly switched to the shut-off valve at the orifice of grouting hole B. Grouting into grouting hole B then begins, using the established grout flow channels to fill the fractures around grouting hole B. Simultaneously, the orifice of grouting hole A is observed. When grout flows out from grouting hole A again or the grouting pressure reaches the design value, grouting into grouting hole B is stopped again, and grouting is switched back to grouting hole A. This cycle is repeated multiple times until the pressure in both holes rises steadily during grouting and grout flow no longer occurs, indicating that the common fracture network between the two holes has been essentially filled.

[0040] The simultaneous grouting method with branch lines offers high grouting efficiency and can quickly seal large fissure channels. It is suitable for situations where fissures are extremely well-developed, grout leakage is significant, and multiple pumps are available on-site. In some specific examples, a single dual-liquid grouting pump (with two independently controllable output pipelines) or two independent grouting pumps are used. The grout outlet pipelines of the two pumps are connected to grouting holes A and B, respectively, where cross-contamination occurs. Both pumps are started simultaneously, injecting grout into the two holes at the same or similar grouting pressure and flow rate. By artificially creating a pressure balance zone, the grout converges, settles, and solidifies in the fissure area between holes A and B, effectively sealing the connecting channel.

[0041] In some embodiments of the method for directional drilling through fractured rock strata based on trajectory prediction and tunnel pre-grouting of the present invention, the reinforcing material injected into the fractured roof area through the grouting holes is Marisan (a polyurethane-based chemical grout). It is understood that Marisan is a low-viscosity polyurethane chemical grouting material composed of two components (resin and catalyst). Its core characteristic is that it reacts with water and foams, forming a closed-cell foam-like solidified body. In this embodiment, the use of Marisan as a reinforcing material is mainly suitable for situations where there is significant water seepage or inrush in the fractured roof area, requiring immediate water stoppage. Marisan can expand to 15-25 times its original volume, generating enormous expansion pressure to effectively seal cracks, and is particularly suitable for sealing cracks caused by flowing water.

[0042] If the grouting effect of Marisan is unsatisfactory, in other embodiments of the method for directional drilling through fractured rock strata based on trajectory prediction and tunnel pre-grouting of the present invention, the reinforcing material injected into the fractured roof area through the grouting hole can also be a two-component grout formed by mixing cement slurry and water glass solution. It is understood that the two-component grout used in this embodiment consists of two components: cement slurry and water glass solution. After meeting at the borehole or mixer, a rapid gelation reaction can occur. By changing the water-cement ratio of the cement slurry, the water glass concentration (Baumé degree Be'), and the volume ratio of the two liquids, its gelation time can be precisely controlled within tens of seconds to several minutes to adapt to the grouting requirements of different fracture sizes. After solidification, the two-component grout forms a solidified body with cement hydration products as its framework, exhibiting high later-stage strength and good durability, significantly improving the bearing capacity and structural strength of the fractured rock mass.

[0043] In some specific examples, the volume ratio of cement slurry to water glass solution in the two-component grout ranges from 1:0.4 to 1:0.6; the cement slurry in the two-component grout is a slurry prepared from silicate cement and water, with a water-cement ratio ranging from 0.6:1 to 0.8:1; the water glass solution in the two-component grout is a water glass solution with a concentration ranging from 48 to 55 Baume degrees and a modulus ranging from 2.8 to 3.2.

[0044] Understandably, the volume ratio of cement slurry to water glass solution in a two-component grout is crucial for controlling gelation speed and early strength; a higher proportion of water glass solution results in faster gelation. Experiments have shown that when the volume ratio of cement slurry to water glass solution is less than 1:0.4, the water glass is insufficient to quickly coat cement particles and initiate their reaction, leading to an excessively long gelation time. In water-rich formations, the grout is easily dispersed or diluted by groundwater, resulting in reinforcement failure or extremely low strength. When the volume ratio of cement slurry to water glass solution is greater than 1:0.6, the reaction accelerates dramatically, and the gelation time is too short (usually only a few seconds). This makes it prone to solidification during pumping or before sufficient penetration into fractures, causing blockages in the grouting pipeline or only forming shallow seals, preventing deep reinforcement. Furthermore, an excessively high proportion of silica gel in the product increases the brittleness of the solidified body, potentially reducing long-term strength and unnecessarily increasing material costs. The volume ratio range (1:0.4 to 1:0.6) provided in this embodiment ensures sufficient working time (typically tens of seconds to several minutes) for pumping and penetration, while also enabling rapid gelation to form early strength and effectively seal cracks.

[0045] The water-cement ratio of cement grout determines its consistency and final strength. A low water-cement ratio results in a thicker grout with higher strength, but poor injectability; conversely, a high water-cement ratio requires fine-tuning on-site based on crack size. When the water-cement ratio is less than 0.6:1, the grout is too viscous, with extremely poor fluidity, high pumping resistance, and difficulty in injecting into fine cracks, easily leading to excessively high grouting pump pressure and pipeline blockage. When the water-cement ratio is greater than 0.8:1, the grout is too thin. Although it has good fluidity, excess water evaporates, leaving pores and making the solidified body loose. Furthermore, the grout has poor stability, and excess water will precipitate before solidification, affecting the reinforcement effect and potentially eroding the injected grout. After solidification, significant volume shrinkage may occur, potentially causing detachment from the crack wall and creating new cracks. This embodiment uses cement grout with a water-cement ratio between 0.6:1 and 0.8:1 to maximize the density and final strength of the two-component grout solidification while ensuring good injectability.

[0046] The modulus of a water glass solution represents the molar ratio of SiO2 to Na2O, affecting its chemical activity. The concentration of the water glass solution directly affects the content of substances participating in the reaction; both factors jointly determine the reactivity of water glass with cement slurry. When the concentration of the water glass solution is below 48 Baume, the effective components are few, and the water content is high, which is equivalent to diluting the reactants, leading to a slower reaction rate with cement slurry and a decrease in strength. When the concentration of the water glass solution is above 55 Baume, the solution viscosity increases significantly, its own fluidity deteriorates, making it difficult to mix with cement slurry and reducing its injectability, which is also unfavorable for pumping and penetration. When the modulus of the water glass solution is less than 2.8, the Na2O content is relatively high, and the alkalinity is too strong. Although the reaction is fast, the stability of the products is poor, making them susceptible to water erosion and resulting in poor long-term strength. When the modulus of the water glass solution is greater than 3.2, it tends to be neutral, its chemical activity decreases, the reaction rate with cement is slow, and it is prone to silica gel precipitation and deterioration when left to stand. The water glass solution in this embodiment uses a concentration of 48~55Be' and a modulus range of 2.8~3.2, which is the golden range that balances the activity, stability and injectability of water glass when used as a grouting material, ensuring that it reacts quickly, stably and effectively with cement grout.

[0047] In some embodiments of the method for directional drilling through fractured rock strata based on trajectory prediction and tunnel pre-grouting of the present invention, if leakage occurs in the grouting hole during the directional drilling construction process, aggregate is added to the bottom of the grouting hole for grouting and leakage plugging.

[0048] It is important to understand that the bottom grouting and plugging process in this embodiment is a targeted dynamic plugging technique. It does not refer to leakage from previously pre-grouted holes, but rather to a situation where, during subsequent directional drilling, a new, unexplored, or fractured formation outside the pre-grouted area is encountered, resulting in a significant loss of drilling fluid (or water) from the borehole. When the directional drilling rig operator observes a sharp decrease or complete interruption in the return water volume within the borehole, along with a sudden drop in the injection pump pressure and potential fluctuations in the drilling rig torque, this indicates that the borehole has encountered a significant fracture or fracture zone at a certain depth, and drilling fluid is leaking into the formation in large quantities. The current borehole depth, i.e., the depth (H) of the lost layer, is accurately calculated using the measurement while drilling (MWD) system on the drilling rig or in conjunction with the drill string descent depth. The on-site technical supervisor determines, based on the severity of the leakage, whether to initiate the "bottom aggregate grouting" procedure (this embodiment's solution is required when the leakage rate exceeds the pumping capacity and normal circulation cannot be maintained).

[0049] The specific implementation process of bottom hole grouting for leak sealing in this embodiment is as follows: Material preparation: Select flexible and fibrous materials such as fine sawdust, rice husks, shredded hemp fibers, and nut shell powder to prepare aggregates (the role of aggregates is to quickly enter the fracture channels, intertwine with each other to form "plugs", creating conditions for subsequent grout bridging and sealing); prepare cement grout (usually using 425# or 525# ordinary Portland cement), the water-cement ratio can be slightly higher than the normal value (such as 0.8:1~1:1) to ensure its good fluidity and permeability.

[0050] Implement bottom-hole aggregate grouting for leak sealing: Lower the drill string assembly (without drill bit rotation) to the leakage zone (hole depth H) or 1-2 meters above it. Pump pre-mixed aggregate grout (a mixture of aggregate and water) into the leakage point at the bottom of the hole through the center hole of the drill pipe (or the annulus between the drill pipe and the hole wall). The amount of aggregate added depends on the leakage situation, aiming to allow the fibrous aggregate to preferentially enter the large fractures, forming a preliminary plugging network. Immediately afterwards, without lifting the drill, switch to pumping cement grout. The cement grout will push the aggregate grout in front into the deeper fractures and penetrate into the network formed by the aggregate bridging. After injecting the predetermined amount of cement grout, slowly raise the drill rod to above the grout column, close the borehole sealing device, and continue to pump a small amount of clean water into the hole to apply pressure. The pressure is generally controlled at 2~4MPa to promote better grout penetration into the fracture. Maintain the pressure for a period of time (e.g., 10~30 minutes) until the pressure stabilizes, indicating that the leakage channel has been initially blocked. Stop pumping, completely pull the drill rod out of the hole, and wait for the cement grout to solidify (usually requires 8~24 hours of standing).

[0051] After the cement slurry reaches sufficient strength, lower the drilling tool (with drill bit) again to drill through the solidified cement plug in the hole, clear the channel, and complete the hole cleaning process. After cleaning the hole to the original leakage layer, resume pumping drilling fluid and carefully observe whether the return water has returned to normal and whether the pressure is stable. If there is still slight leakage, consider performing a second small-scale grouting to seal it; if the leakage disappears or is significantly reduced, it indicates that the leak has been successfully plugged, and normal drilling can continue.

[0052] The following describes in detail the specific implementation process of the method for directional drilling through fractured rock strata based on trajectory prediction and roadway pre-grouting in the 12220 working face ventilation roadway of the Qinxin Coal Mine in Shanxi Province. When performing hydraulic fracturing technology in the directional long borehole area of ​​the 12220 and 12218 stop-mining lines at the working face, refer to... Figure 2 As shown, borehole #3 in the design trajectory needs to traverse a rock stratum approximately 12m above the roof of ventilation roadway 12220. Geological analysis and preliminary exploration revealed a fractured area in the roof of this section of the roadway. Direct drilling would likely cause water to seep through the roof fractures along the anchor cables, leading to abnormal water return within the borehole, increased pump pressure, and a serious risk of stuck or buried drill bit. Therefore, it was decided to implement the pre-grouting reinforcement process described in this invention in the fractured roof area of ​​the roadway below the design trajectory before drilling borehole #3.

[0053] S1. Analyze the relationship between the directional drilling design trajectory and the location of the roadway to identify the fractured roof area that needs reinforcement.

[0054] First, based on the design trajectory diagram of directional drilling hole #3 (see...) Figure 2 The exact location of its intersection with the 12220 ventilation roadway was calculated, determining that it would cross within a 5-meter range before and after the 80-meter mark in the ventilation roadway. Subsequently, technical personnel conducted a detailed survey of the 10-meter-long roof of the roadway. Through methods such as tapping on the roof and walls, observing the loosening of existing anchor cables and bolts, and assessing the water seepage from the roof, they determined that the roof section was a fractured area with developed cracks and was identified as a target area requiring advanced reinforcement.

[0055] S2. At the locations within the roadway corresponding to the intersection with the directional drilling design trajectory, construct grouting holes in the identified fractured roof area. Inject reinforcing material into the fractured roof area through these holes for pre-grouting. This step specifically includes the following sub-steps: S21. Marking Borehole Locations: Using the tunnel roof as a reference, arrange grouting holes within a 5m radius around the 80m mark. Use three rows with a row spacing of 2000mm, two grouting holes per row, and a hole spacing of 1800mm (not exceeding 2000mm) within the same row. Clearly mark all hole locations with red spray paint and verify with a measuring tape to ensure the hole location error is controlled within ±200mm.

[0056] S22. Drilling Grouting Holes: An MQT-120 pneumatic anchor drill rig with a φ36mm drill bit was used for wet drilling. The operator firmly set up the drill rig below the marked hole position, adjusted the drill rod angle to make it perpendicular to the top rock surface, and then advanced the drill at a constant speed to drill grouting holes. Given the severe fracture of the top slab in this area, the grouting hole depth was determined to be 8000mm to ensure reinforcement depth. During the drilling process, a designated person observed the operation of the drill rig and the color of the returned water to make a preliminary assessment of the rock strata condition.

[0057] S23. Installation of Grouting Pipe and Sealing: After drilling is completed, remove the drill rod and connect the φ20mm outer diameter rigid plastic grouting pipe to the metal orifice grouting pipe. Insert them together into the drilled grouting hole, ensuring that the threaded end of the orifice grouting pipe protrudes 150mm from the orifice opening. Use 425# ordinary silicate cement to prepare a quick-setting cement grout, and tightly fill and seal the gap between the orifice grouting pipe and the hole wall to prevent grout from overflowing from the orifice during pressure grouting. After the sealing cement has cured, install a high-pressure orifice shut-off valve on the exposed threaded end of the orifice grouting pipe.

[0058] S24. Connection System and Grouting: The outlet pipeline of the ZBQ-10 / 6 pneumatic grouting pump is reliably connected to the orifice shut-off valve via a high-pressure hose. Cement-water glass dual-liquid grout is selected as the reinforcing material for this grouting. Cement grout preparation: 425# ordinary Portland cement is used, and the cement grout is prepared in a mixing tank at a water-cement ratio of 0.7:1 (within the range of 0.6:1 to 0.8:1 required by this invention). Water glass preparation: A water glass solution with a concentration of 50Be' and a modulus of 3.0 (both within the range of 48-55Be' and 2.8-3.2 required by this invention) is used. Dual-liquid grout mixing: The cement grout and water glass are mixed at a volume ratio of 1:0.5 (within the range of 1:0.4 to 1:0.6 required by this invention) using the dual-liquid grouting pump in the orifice mixer and then injected into the grouting hole.

[0059] S25. Start grouting, controlling the grouting pressure at 2-3 MPa and the grouting speed at 15 L / min. Closely monitor the pressure gauge readings and the surrounding roof and sidewall conditions during grouting. If cross-grouting is observed between adjacent grouting holes (the second hole in the second row and the first hole in the third row), immediately adopt an alternating grouting method: grout one hole first, pause, then grout the other hole experiencing cross-grouting, repeating this process until each hole meets the completion criteria. Continue grouting until thick grout flows out of the hole's shut-off valve (hole backflow), indicating that the fracture is essentially filled. At this point, stop the grouting pump and immediately close the hole's shut-off valve to prevent grout backflow. Dismantle the grouting pipeline and move to the next grouting hole to continue work.

[0060] S3. After the reinforcing material to be injected has cured, directional drilling is carried out.

[0061] After grouting was completed in all grouting holes, the mixture was left to stand for 24 hours to allow the two-component grout to fully solidify and reach its initial strength. Once the reinforcement material had cured, directional drilling was performed using a directional drilling rig along the original design trajectory for borehole #3. Throughout the directional drilling process, no water leakage, backflow, or severe pump pressure fluctuations occurred in the fractured section of the original roof slab. The borehole successfully traversed this area, effectively preventing drill bit burial accidents and demonstrating the excellent effect of pre-grouting reinforcement.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for directional drilling through fractured rock strata based on trajectory prediction and pre-grouting of tunnels, characterized in that, include: Analyze the relationship between the directional drilling design trajectory and the location of the roadway to identify areas of fractured roof that require reinforcement; In the tunnel, grouting holes are constructed at the locations corresponding to the intersection with the directional drilling design trajectory for the identified fractured roof area. Reinforcing material is injected into the fractured roof area through the grouting holes for pre-grouting. After the injected reinforcing material has cured, directional drilling is carried out. The step of pre-grouting by injecting reinforcing material into the identified grouting holes in the fractured roof area includes: Marking the drilling locations of all grouting holes in the fractured roof area includes: using the roadway roof as a reference, arranging multiple rows of grouting hole location markers in the identified fractured roof area, each row of location markers including at least two grouting holes, and the hole spacing between two adjacent grouting holes not exceeding 2000 mm; A drilling rig was set up in the tunnel and the angle of the drilling rig was adjusted. Grouting holes were drilled at all marked positions. The depth of the grouting holes was between 4000mm and 8000mm. Connect the grouting pipe and the orifice grouting pipe, and insert the connected grouting pipe and the orifice grouting pipe into the drilled grouting hole, with the threaded end of the orifice grouting pipe protruding at least 150mm from the orifice opening; The grouting pipe at the opening of the grouting hole is fixed with cement and the hole is sealed. A stop valve is installed at the outer end of the grouting pipe at the opening. Connect the grouting system to the orifice shut-off valve and perform grouting until grout flows back into the grouting hole. Then stop grouting and close the orifice shut-off valve.

2. The method for directional drilling through fractured rock strata based on trajectory prediction and tunnel pre-grouting according to claim 1, characterized in that, If cross-grouting occurs between adjacent grouting holes during the grouting process, the adjacent grouting holes experiencing cross-grouting shall be grouted alternately or simultaneously in separate channels.

3. The method for directional drilling through fractured rock strata based on trajectory prediction and tunnel pre-grouting according to claim 1, characterized in that, The reinforcing material injected into the fractured top plate area through the grouting hole is malissa.

4. The method for directional drilling through fractured rock strata based on trajectory prediction and tunnel pre-grouting according to claim 1, characterized in that, The reinforcing material injected into the fractured top plate area through the grouting hole is a two-component grout formed by mixing cement grout and water glass solution, wherein the volume ratio of the cement grout and the water glass solution in the two-component grout ranges from 1:0.4 to 1:0.

6.

5. The method for directional drilling through fractured rock strata based on trajectory prediction and tunnel pre-grouting according to claim 4, characterized in that, The cement slurry in the dual-liquid slurry is a slurry prepared from silicate cement and water, and the water-cement ratio of the cement slurry is between 0.6:1 and 0.8:

1.

6. The method for directional drilling through fractured rock strata based on trajectory prediction and tunnel pre-grouting according to claim 4, characterized in that, The water glass solution in the two-component slurry is a water glass solution with a concentration range of 48 to 55 Baume degrees and a modulus range of 2.8 to 3.

2.

7. The method for directional drilling through fractured rock strata based on trajectory prediction and tunnel pre-grouting according to claim 1, characterized in that, If leakage occurs in the grouting hole during directional drilling, aggregate is added to the bottom of the grouting hole for grouting to plug the leakage.

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