Weak weathered marble stratum wellbore ground pre-grouting slurry control method

Abstract

The application discloses a weak weathering marble stratum wellbore ground pre-grouting slurry control method, curtain rings are arranged in the space between shaft sinking facilities according to the diameter of a pre-excavated wellbore, the use of a site, the stratum trend, the tendency and the like, a plurality of grouting boreholes are arranged on the wellbore curtain ring, the borehole orifices are located on or near the curtain ring in combination with the arrangement of a site wellbore temporary construction facility, and the boreholes are drilled in a "double L" combined type in the stratum space track; the grouting layer section is drilled in sections from top to bottom in the outer curtain targeting area of the pre-excavated wellbore, so that the borehole bottom is located in the grouting curtain targeting area, the borehole orifice and the borehole bottom are different positions, and grouting is carried out through the multiple grouting holes distributed on the curtain line, so that an irregular closed thick-walled cylindrical water plugging curtain wall is formed in the stratum space outside the pre-excavated wellbore, and stratum water is blocked outside the curtain and flows around. The diffused slurry of each grouting hole on the curtain ring can be mutually connected to form a complete closed cylindrical wall, so that the water plugging effect of the curtain wall is ensured.

Description

Technical Field

[0001] This invention belongs to the field of wellbore water control technology, and relates to a method for controlling the slurry pre-grouting on the surface of wellbore in weakly weathered marble formations with large dip angles. Background Technology

[0002] Grouting technology originated in the early 19th century. With the advent of silicate cement in 1824, grouting was applied to projects such as tunnels, mines, dams, and foundations. Since the mid-to-late 20th century, with the development of grouting materials and methods, grouting technology has advanced rapidly, evolving from permeation grouting to composite grouting; from pressureless grouting to various forms of integrated grouting techniques, thus broadening the applicability of grouting methods.

[0003] When drilling shafts in high-altitude, cold mountainous areas, especially when the aquifer is thick and the groundwater recharge is high, a permanent closed water-tight curtain wall is formed around the shaft by pre-grouting on the surface before drilling or before entering the aquifer. This allows groundwater to flow around the shaft, and the shaft can be excavated and lined under the protection of the water-tight curtain, thus ensuring the safety of personnel and equipment at the working face. Research and analysis show that existing grouting and drainage technologies can control the direction of grout diffusion and actively divert water through drilling and pumping. However, the need to construct pumping and drainage equipment not only results in high construction costs but also wastes groundwater resources, limiting its applicability in high-altitude, cold mountainous areas.

[0004] To seize the "window of opportunity" for wellbore construction, temporary construction facilities such as wellhead equipment, stabilization units, winch rooms, and air compressor rooms are often set up first, followed by lock-in construction. This restricts the drilling rig's position, preventing the grouting section from being close to the well wall and evenly distributed around the wellbore. A curtain ring can only be set up in the gaps between the drilling facilities, with several grouting holes drilled on the curtain ring. However, for deeply buried, weakly weathered marble strata with steep inclinations, the fractures are relatively small, allowing water to pass through but with limited grout capacity, preventing sufficient grouting of the marble fractures. If the grout from adjacent injection holes cannot completely overlap, leaving water-conducting fractures, weak water outlets will appear in the curtain wall. Water from the outside of the curtain can penetrate through these fractures and enter the inside of the curtain. The larger the wellbore perimeter and the longer the curtain line perimeter, the more weak water outlets appear in the curtain wall, significantly reducing its seepage prevention capacity and failing to achieve the expected water-proofing effect.

[0005] The conventional method for controlling the grouting process of a watertight curtain is to adjust the grouting pressure and grout concentration in a timely manner based on the grout intake. However, due to the unevenness, complexity, and unpredictability of the fracture channels in weakly weathered marble, the pressurized grout often diffuses along the dominant fracture channels in the stratum being grouted. Blindly increasing the grouting pressure makes it difficult to ensure that the grout diffuses along the designed curtain line. Therefore, simply increasing the grouting pressure or changing the grout concentration cannot guarantee that the grout will form a complete closed watertight curtain wall along the curtain wall. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a method for controlling grouting slurry pre-injection on the surface of wellbore in weakly weathered marble formations. This method aims to solve the complexity and uncertainty of grout diffusion in weakly weathered marble formations, enabling the grout to effectively diffuse along the designed curtain ring and ensuring the water-blocking effect of the curtain wall.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A method for controlling the grouting slurry during surface pre-grouting in wellbore formations with weakly weathered marble includes the following steps:

[0009] Step 1: Based on the diameter of the pre-excavated shaft, the strike and dip of the strata, multiple curtain lines are laid around the pre-excavated shaft in the gap between the temporary construction facilities to form a curtain target area;

[0010] Step 2: Design multiple grouting borehole trajectories on the curtain line. The borehole openings are located on the curtain line or near the outside of the temporary well-drilling facility, and the bottom of the boreholes are located within the curtain target area. The borehole openings and bottoms are vertically displaced in the formation space, and the grouting borehole trajectories form a "double L" combination in the formation space.

[0011] Step 3: Multiple grouting boreholes evenly distributed around the curtain line are designated as sequence I boreholes. Drilling of the non-grouting section I, non-grouting section II, and grouting section of the sequence I boreholes is completed from top to bottom. In the grouting section, the sequence I boreholes are drilled in sections from top to bottom within the target area of ​​the curtain outside the pre-excavated wellbore. When the initial grouting borehole in the sequence I borehole completes the drilling of the first section height of the grouting section, the sequence I borehole adjacent to the initial grouting borehole is designated as the strike-depression hole to complete the drilling of the same section. The sequence I borehole diagonally opposite the initial grouting borehole is designated as the dip-depression hole to complete the drilling of the higher section.

[0012] Step 4: Install orifice valves at the orifice openings of the strike-and-dimension pressure relief holes and open the orifice valves to bring the grouting borehole into a static pressure state. First, pressurize the grouting borehole with a large pump to clear the fissures in the weakly weathered marble, and observe the rise in water level and overflow in the grouting borehole to ensure the grouting effect. After the water pressurization is completed, start grouting. The grout should be diluted from thin to thick, flowing from the initial grouting hole along the strike of the stratum to the adjacent strike-and-dimension pressure relief hole in the same stratum, and along the dip of the stratum to the diagonally dip-and-dimension pressure relief hole in the higher stratum. When the grouting borehole reaches the grouting completion standard, the grouting work of the first layer is completed.

[0013] Step 5: Sequentially take the adjacent stress relief holes in Step 3 as the next grouting holes, the adjacent I-sequence drill holes of the grouting hole as the new stress relief holes, and the diagonal I-sequence drill holes of the grouting hole as the new directional stress relief holes. Repeat Steps 3 to 4.

[0014] Step 6: Repeat steps 3 to 5 above until the initial grouting hole in step 3 becomes the adjacent directional pressure relief hole, then the grouting work of the first section of the wellbore is completed.

[0015] Step 7: After the grout in the initial grouting hole solidifies, the grouting hole is swept and the drilling is extended to the second grouting layer. Repeat the above operation steps 3 to 6 until all I-sequence drill holes on the curtain line have completed the grouting work of the entire hole grouting layer.

[0016] Step 8: After the starting grouting hole has completed grouting of all layers in the segmented downward movement, there will be a blind zone in the diagonal grouting hole, which cannot guarantee the grouting effect. At this time, select the I-sequence borehole adjacent to the diagonal grouting hole of the starting grouting hole as the pressure relief hole, and use the same layer pressure relief method in step 4. Repeat steps 3 to 7 above until all I-sequence boreholes in the blind zone have completed the same layer grouting work of the remaining blind zone layers.

[0017] Step 9: The grouting holes that are interspersed between the first-order boreholes are used as second-order boreholes. Without pressure relief holes, the drilling is carried out in sections from top to bottom to complete the grouting of the same layer in sections.

[0018] Step 10: Complete grouting of all I-sequence and II-sequence boreholes. After the grout solidifies, an irregular, thick-walled, cylindrical, permanent closed water-tight curtain is formed in the steeply inclined, weakly weathered marble strata outside the pre-dug wellbore, preventing formation water from flowing around outside the curtain.

[0019] The present invention also includes the following technical features:

[0020] Specifically, in step 1, the distance between the inner curtain line and the pre-excavated well wall is D:

[0021] D=(2m-1)D e +2Hα-R h

[0022] In the above formula, m is the number of curtain coils counted from the center of the pre-excavated shaft;

[0023] H—Elevation of the grouting section, in meters;

[0024] α—Permissible borehole deviation rate;

[0025] R h —Rough diameter of the pre-excavated shaft, m;

[0026] D e —Thickness of the grouting hole junction, D e =1.2r, where r is the effective diffusion radius of the slurry.

[0027] Specifically, the effective diffusion radius r of the slurry is:

[0028]

[0029] In this formula: k—reciprocal of the slurry viscosity;

[0030] v—grout injection flow rate, m 3 min;

[0031] t—slurry gelation time, min;

[0032] n—Marble porosity, %.

[0033] Specifically, the distance between the inner curtain line and the pre-excavated shaft wall ranges from 1.5 to 2 meters, and the spacing between adjacent curtain lines is 1 meter.

[0034] Specifically, in step 2, based on the location of the pre-excavated well, a three-dimensional spatial coordinate system for the pre-grouting site is established, and the formula for calculating the spatial coordinates of the borehole trajectory is as follows:

[0035]

[0036]

[0037]

[0038] In the formula, For N i Point spatial coordinates; For N i With N i-1 Spatial distance between points, m; α is N i With N i-1 The angle between the line connecting the points and the z-axis is θ, where N is the z-axis. i With N i-1 Azimuth angle of the line connecting the points.

[0039] Specifically, the starting grouting hole in step 3 is any I-sequence borehole selected along the dip angle of the stratum on the side with the greatest burial depth in the same stratum.

[0040] Specifically, in step 4, when observing the rise in water level and overflow in the grouting borehole, if thick grout flows out of the pressure relief hole and the tendency pressure relief hole, the borehole valve should be closed immediately and grouting should continue in the grouting hole.

[0041] Specifically, in step 4, after the grouting work of the first layer is completed, the hole is swept after an interval of 10 hours, and the water pressure test is carried out on the grouting section. If the water absorption of the grouting section is greater than 60L / min, low pump rate re-grouting is required until the final hole standard is reached.

[0042] Specifically, in step 10, after forming an irregular thick-walled cylindrical permanent closed water-proof curtain, the "cross-core" method is used to arrange two inspection boreholes outside the curtain line. The inspection borehole trajectory passes through the pre-excavated well core to check the leakage points of the I-sequence borehole and II-sequence borehole, and grouting is added to the leakage points.

[0043] Specifically, after completing the inspection of the leak points and supplementary grouting, grouting is carried out on the inspection boreholes.

[0044] Compared with the prior art, the present invention has the following technical effects:

[0045] (1) This invention adopts a passive static pressure placement and pressure relief drainage method for boreholes, which is different from the existing active borehole pumping and drainage and dynamic water diversion mechanism. Existing drainage grouting requires drilling on the ground or at the working face for drainage. Both pumping and drainage require the formation water to flow, and the grout is forced to diffuse along the curtain ring by using the water head pressure difference. Its mechanism is to actively work from the drainage borehole to make the aquifer water flow. This invention adopts vertical displacement of the borehole opening and bottom in the formation space, segmented downward directional drilling, and the trajectory is a "double L" shaped borehole in the formation space. The borehole adjacent to the starting grouting hole is used as the strike pressure relief hole, and the diagonal borehole is used as the dip pressure relief hole. After the starting grouting hole has completed the grouting of all layers in the segmented downward drilling, there is a blind zone in the diagonal grouting hole, which cannot guarantee the grouting effect. Therefore, the blind zone adopts pressure relief at the same layer. The method of placing boreholes allows the grout to diffuse along the curtain ring direction. This passively utilizes the boreholes to relieve pressure, creating a greater pressure difference between the grouting holes and the pressure relief holes in the curtain ring. This indirectly increases the grouting pressure, causing the grout in the aquifer to flow towards the pressure relief holes, which can effectively improve the curtain grouting effect.

[0046] (2) This invention can effectively interfere with the grout diffusion direction, causing the grout to move along the curtain wall direction, thereby improving the impermeability of the curtain wall:

[0047] Under high grouting pressure, the grout is in a free-diffusion state, capable of spreading long distances in the advantageous channels of the grouting stratum, but its diffusion distance is very limited in the disadvantageous channels. Due to the complexity of weakly weathered marble strata and the human element of curtain engineering, the design direction of the curtain line is difficult to align with the advantageous channels of the grouting section. If the grout is not disturbed, although it may spread far, it may not be able to overlap along the curtain ring to form a complete anti-seepage cylinder wall. Therefore, simply increasing the grouting pressure is unlikely to achieve the expected water control effect of the well casing.

[0048] In a shallowly weathered marble aquifer with a steep dip angle, a pressure relief port is opened. Under the grouting pressure, the grout propels water flow within the aquifer. Formation water naturally flows along fracture channels towards the free face of the pressure relief port. Because the diameter of the pressure relief port is generally larger than the fracture opening at the injection site and the port is unobstructed, under continuous high grouting pressure, the aquifer water can flow upwards along the borehole wall to the borehole opening, drawing the grout towards the free face of the pressure relief port. This effectively guides the free movement of the grout. When thick grout overflows from the pressure relief port, it inevitably travels along the curtain ring direction from the injection port to the pressure relief port, increasing the grout diffusion distance in the curtain ring direction. Finally, through subsequent denser, interlaced grouting of the curtain injection ports, a permanently closed curtain wall is formed, significantly improving the wellbore's impermeability.

[0049] Due to the complexity of the grouting layers in the weakly weathered marble, it is possible that the grouting holes may have reached the completion criteria, but no thick grout may still flow out of the pressure relief holes. Because the curtain grouting layer and the pressure relief layer are in the same aquifer, the distance between the grouting holes and the pressure relief holes is small, and there is a uniform water level after the holes are formed. Under the grouting pressure, the water level in the pressure relief holes will naturally rise. Therefore, although no thick grout flows out of the pressure relief holes, the grout will also be subject to a certain amount of traction when the water level in the pressure relief holes is pushed up by the high grouting pressure. This is conducive to the grout flowing along the curtain ring towards the pressure relief holes, improving the effective diffusion distance of the grout and the curtain grouting effect.

[0050] (3) This invention eliminates the need for drilling drainage holes, resulting in a simple and low-cost process. Actively diverting grout into the stratum being grouted can interfere with grout flow and improve the curtain's impermeability. Drainage grouting can be divided into two types: one utilizes the working face space for drainage, and the other involves pumping water through the curtain holes on the ground. Drainage at the working face requires the construction of dedicated drainage holes, increasing the drilling workload and necessitating forced discharge of overflowing water. While the drainage holes in ground-based drainage grouting are also located at the curtain grouting hole locations, pumping requires the use of a pumping device and external power for extended periods. Compared to face-based drainage and surface pumping, this invention eliminates the need for drilling at the face for drainage and the installation of surface pumping equipment with drainage power. Depending on site conditions, stratum dip, and strike, pressure relief holes can be arranged along the curtain line or around the perimeter, either uniformly or non-uniformly, forming a vertical "double L" shape in the geological space. Holes adjacent to the initial grouting hole serve as strike-based pressure relief holes, while diagonal holes serve as dip-based pressure relief holes. After the initial grouting hole completes grouting for all layers in segments, the diagonal grouting holes will have blind spots, compromising grouting effectiveness. Pressure relief in these blind spots will be implemented at the same stratum level. The entire curtain wall construction process involves minimal drilling, resulting in simple procedures and low costs.

[0051] (4) The slurry diversion control principle of this invention is simple, requires no extra operations, and is highly practical. This invention adopts the principle of directional pressure relief and diversion in the aquifer with "double L-shaped" boreholes at the same strike level, higher dip level, and same blind zone level, supplemented by high grouting pressure stabilization grouting. Under grouting pressure, if there is a pressure relief point on the free face of the grouting stratum, the groundwater in the corresponding section will flow towards the pressure relief point, guiding the slurry to move towards that point along the curtain design direction. Utilizing this principle, in the implementation of this invention, it is only necessary to construct pressure relief holes at a certain distance from the grouting hole at the same strike level, higher dip level, and same blind zone level, then place the borehole, observe the borehole, and close the borehole valve when thick slurry flows out, thereby achieving the purpose of increasing the effective diffusion distance of the slurry. Compared with surface pumping and face drainage, this invention is simple in principle, convenient to operate, and has very strong practicality. Attached Figure Description

[0052] Figure 1 A schematic diagram showing the layout of existing temporary facilities on the surface of the well shaft;

[0053] Figure 2 A schematic diagram of the spatial trajectory coordinate model of a "double L" combined borehole;

[0054] Figure 3 Schematic diagram of the first and second sequence boreholes on the wellbore curtain ring;

[0055] Figure 4 This is a schematic diagram showing the diffusion of grout from the injection hole to the pressure relief hole;

[0056] Figure 5 This is a schematic diagram of a borehole for well inspection.

[0057] The meanings of the labels in the diagram are as follows:

[0058] 1.1. Derrick foundation; 1.2. Derrick; 1.3. Pre-excavated shaft; 1.4. Locking shaft wall;

[0059] 2.1. Hole apex angle; 2.2. Hole azimuth angle; 2.3. Drilling trajectory; 2.4. Coordinates of trajectory control points;

[0060] 1-1. First borehole opening of sequence I, 1-2. Second borehole opening of sequence I, 1-3. Third borehole opening of sequence I, 1-4. Fourth borehole opening of sequence I, 2-1. First borehole opening of sequence II, 2-2. Second borehole opening of sequence II, 2-3. Third borehole opening of sequence II, 2-4. Fourth borehole opening of sequence II, 3. Final borehole position of sequence I, 4. Final borehole position of sequence II, 5. Drilling trajectory, 6. Bottom curtain drainage blind section area;

[0061] 4.1. Wellbore lock section; 4.2. Working face; 4.3. Pre-excavated wellbore strata; 4.4. Grouting hole; 4.5. Pressure relief hole; 4.6. Curtain target area; 4.7. Grouting section; 4.8. Drainage and pressure relief section; 4.9. Curtain drainage blind section area at the bottom of the stratum dip angle.

[0062] 5.1. Inspect the opening of Hole I; 5.2. Inspect the opening of Hole II; 5.3. Inspect the final hole position of Hole I; 5.4. Inspect the final hole position of Hole II; 5.5. Inspect the hole trajectory. Detailed Implementation

[0063] This invention, based on the pre-dug well diameter, site conditions, and geological strike and dip, sets up a curtain ring in the space between well drilling facilities. Several grouting boreholes are then installed on the curtain ring. Considering the layout of temporary well facilities, the borehole openings are positioned on or near the curtain ring, and the borehole trajectories in the geological space form a "double L" shape. The grouting sections are drilled segmentally from top to bottom within the curtain target area outside the pre-dug well, ensuring the bottom of the borehole is within the grouting curtain target area, while the borehole opening and bottom are displaced. Grout is injected through multiple grouting holes distributed along the curtain line, forming an irregular, closed, thick-walled cylindrical water-blocking curtain wall in the geological space outside the pre-dug well, preventing formation water from flowing around the curtain. The key to the pre-grouting water-blocking curtain at the well surface is controlling the grouting process to ensure the diffusion distance of the grout, allowing the diffused grout from each grouting hole on the curtain ring to overlap and form a complete closed cylindrical wall.

[0064] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0065] Example 1:

[0066] like Figures 1 to 5 As shown in the figure, this embodiment provides a method for controlling the grouting slurry during surface pre-grouting in wellbore formations with weakly weathered marble, including the following steps:

[0067] Step 1: Due to the construction "window period" at the construction site, the shaft locking section is generally constructed first. The construction "window period" is determined comprehensively based on site climate conditions and past meteorological data, including air temperature, rainfall, snowfall thickness, and surface temperature. In conjunction with the layout of temporary well-drilling facilities at the site, and according to the diameter of the pre-drilled shaft and the dip angle of the strata, a curtain target zone is set in the strata outside the shaft. The curtain target zone consists of multiple curtain lines, with the inner curtain line being D' away from the pre-drilled shaft wall.

[0068] Based on the diameter of the pre-excavated shaft, the direction and dip of the strata, multiple curtain lines are laid around the pre-excavated shaft to form a curtain target area in the space between the temporary construction facilities for shaft drilling. Figure 1This is a schematic diagram of the existing temporary facilities on the surface of the well shaft, showing the locations of the derrick foundation 1.1, the derrick 1.2, the pre-excavated well shaft 1.3, and the lock-entry well wall 1.4.

[0069] In step 1, the distance between the inner curtain line and the pre-excavated shaft wall is D:

[0070] D=(2m-1)D e +2Hα-R h

[0071] In the above formula, m is the number of curtain coils counted from the center of the pre-excavated shaft;

[0072] H—Elevation of the grouting section, in meters;

[0073] α—Permissible borehole deviation rate;

[0074] R h —Rough diameter of the pre-excavated shaft, m;

[0075] D e —Thickness of the grouting hole junction, D e =1.2r, where r is the effective diffusion radius of the slurry:

[0076]

[0077] In this formula: k—reciprocal of the slurry viscosity;

[0078] v—grout injection flow rate, m 3 min;

[0079] t—slurry gelation time, min;

[0080] n—Marble porosity, %.

[0081] Due to the different degrees of fracture development, fracture opening and communication conditions in marble strata at different locations, the distance between the inner curtain line and the pre-excavated well wall ranges from 1.5 to 2 meters, and the spacing between adjacent curtain lines is 1 meter.

[0082] Step 2: Design multiple grouting borehole trajectories along the curtain line. The borehole openings are located on the curtain line or near the outer side of the temporary well-drilling facility, and the bottom of the boreholes are located within the curtain target area. The grouting boreholes can be evenly or unevenly arranged along the curtain line. The borehole openings and bottoms are vertically displaced in the formation space. The drilling is carried out in a segmented downward directional manner, and the trajectory forms a "double L" combination in the formation space. Multiple grouting boreholes can be arranged outside the wellbore, and grouting can be carried out simultaneously in different curtain circles.

[0083] In step 2, based on the location of the pre-dug well, a three-dimensional spatial coordinate system for the pre-grouting site is established. The drilling rig's computer program measures the borehole inclination angle, azimuth, and tool face angle in real time. The calculation program calculates the spatial trajectory coordinates of the "double L" combined borehole according to the following formula, so that the borehole extends as far as possible along the designed trajectory. The formula for calculating the spatial coordinates of the borehole trajectory is as follows:

[0084]

[0085]

[0086]

[0087] In the formula, For N i Point spatial coordinates; For N i With N i-1 Spatial distance between points, m; α is N i With N i-1 The angle between the line connecting the points and the z-axis is θ, where N is the z-axis. i With N i-1 The azimuth of the line connecting the points. For example... Figure 2 This is a schematic diagram of the spatial trajectory coordinate model of the "double L" combined type borehole, which is marked with the borehole apex angle 2.1, borehole azimuth angle 2.2, borehole trajectory 2.3, and trajectory control point coordinates 2.4.

[0088] Step 3: Multiple grouting boreholes evenly distributed circumferentially along the curtain line from the grouting boreholes designed in Step 2 are designated as Sequence I boreholes. Following the dip angle of the strata, first select any Sequence I borehole on the side with the greatest burial depth within the same stratum as the starting grouting hole. Then, select the Sequence I borehole adjacent to the starting grouting hole in a clockwise or counterclockwise direction as the strike-type pressure relief hole. Select the Sequence I borehole diagonally opposite the starting grouting hole as the dip-type pressure relief hole. The grouting boreholes complete the non-grouting section I (isolation and anti-collapse section) from top to bottom. Drilling of the non-grouting section II (solid pipe anti-collapse section) and the grouting section; grouting boreholes are drilled in sections from top to bottom within the pre-excavated wellbore curtain target area in the grouting section. When the initial grouting borehole completes the drilling of the first section height of the grouting section, the adjacent I-sequence boreholes serve as strike-restraining holes to complete the drilling of the same section. The diagonally opposite I-sequence boreholes serve as dip-restraining holes to complete the drilling of the higher sections. Specifically, in this embodiment, four I-sequence boreholes are evenly distributed within the wellbore curtain target area, such as... Figure 3 The boreholes shown are the first borehole (1-1), the second borehole (1-2), the third borehole (1-3), and the fourth borehole (1-4) of the I-sequence borehole sequence. Following the dip angle of the strata, the borehole at the greater burial depth within the same stratum was first selected as the starting grouting hole for the I-sequence borehole sequence. Figure 3 The first borehole of the I-sequence drilling sequence, 1-1, is located in a clockwise direction. The I-sequence drilling hole adjacent to the starting grouting hole is the pressure relief hole. Figure 3 The second borehole in the first-order drilling sequence, borehole 1-2, is a deflection hole opposite to the initial grouting hole. Figure 3 The third borehole in the I-sequence drilling sequence is borehole 1-3. Grouting holes are used to complete drilling of the non-grouting section I (isolation and anti-collapse section), non-grouting section II (solidification and anti-collapse section), and grouting section from top to bottom. Grouting sections are drilled in segments from top to bottom within the target area of ​​the pre-excavated wellbore curtain. When a grouting borehole completes drilling of the first section height of the grouting section, a strike-type pressure relief hole completes drilling of the same section, and a dip-type pressure relief hole completes drilling of higher sections.

[0089] Step 4: Install orifice valves at the orifice openings of the strike-and-dipping pressure relief holes, and open the valves to bring the grouting boreholes to a static pressure state. First, pump water at a high flow rate to clear fissures in the weakly weathered marble, and observe the water level rise and overflow in the grouting boreholes to ensure grouting effectiveness. After the water pumping is completed, grouting begins. The grout gradually thickens, flowing from the initial grouting hole along the strike of the strata to adjacent strike-and-dipping pressure relief holes in the same stratum, and then along the dip of the strata to diagonally dipping pressure relief holes in higher strata. When the grouting borehole reaches the grouting completion standard, the grouting work of the first layer is ended; after 10 hours, the borehole is swept and the grouting section is pressure tested. If the water absorption of the grouting section of the borehole is greater than 60L / min, low pump rate re-grouting is required until the final borehole standard is reached; in step 4, when observing the rise in water level and overflow of the directional pressure relief hole and the inclined pressure relief hole, if thick slurry flows out of the directional pressure relief hole and the inclined pressure relief hole, the borehole valve is immediately closed and the grouting hole continues to be grouted.

[0090] Step 5: Sequentially using the adjacent stress relief holes from Step 3 as the next grouting holes, the adjacent I-sequence drill holes of this grouting hole become new stress relief holes, and the diagonal I-sequence drill holes of this grouting hole become new trend stress relief holes. Steps 3 to 4 are repeated. Specifically, in this embodiment, using... Figure 3 In the first sequence of drilling, the second hole is a grouting hole, the third hole is a directional pressure relief hole, and the fourth hole is a diagonal pressure relief hole. Steps 3 to 4 are repeated.

[0091] Step 6: Repeat steps 3 to 5 above until the initial grouting hole in step 3 becomes an adjacent pressure relief hole, thus completing the grouting work for the first section of the wellbore. Specifically, in this embodiment, using... Figure 3 The third borehole in the I-sequence drilling is a grouting hole, and the fourth borehole in the I-sequence drilling is a directional pressure relief hole. The above steps are repeated until the initial grouting hole in step 3 becomes an adjacent directional pressure relief hole, thus completing the grouting work for the first section of the wellbore.

[0092] Step 7: After the grout in the initial grouting hole solidifies, the grouting hole is swept and the drilling is extended to the second grouting section. Steps 3 to 6 above are repeated until all I-sequence grouting holes on the curtain line complete the grouting work of the entire hole grouting section. Specifically, in this embodiment, the above steps are repeated until the fourth borehole of the I-sequence is used as the grouting hole and the first borehole of the I-sequence is used as the directional pressure relief hole, to complete the grouting work of the first section of the wellbore.

[0093] Step 8: After the starting grouting hole has completed grouting of all layers in the segmented downward movement, there will be a blind zone in the diagonal grouting hole, which cannot guarantee the grouting effect. At this time, select the I-sequence borehole adjacent to the diagonal grouting hole of the starting grouting hole as the pressure relief hole, and use the same layer pressure relief method in step 4. Repeat steps 3 to 7 above until all I-sequence boreholes in the blind zone have completed the same layer grouting work of the remaining blind zone layers.

[0094] Step 9: The grouting boreholes interspersed between the first-sequence boreholes are designated as second-sequence boreholes. Without pressure relief holes, drilling proceeds in sections from top to bottom, completing grouting at the same layer in each section. In this embodiment, as... Figure 3 As shown, the second-order drilling includes the first borehole opening 2-1, the second borehole opening 2-2, the third borehole opening 2-3, and the fourth borehole opening 2-4. The figure also marks the end hole position 3 of the first-order drilling, the end hole position 4 of the second-order drilling, the drilling trajectory 5, and the bottom curtain drainage blind section 6.

[0095] Figure 4 This diagram illustrates the diffusion of grout from the injection hole to the pressure relief hole. From top to bottom, the diagram shows the wellbore lock section 4.1, the working face 4.2, and the pre-excavated wellbore formation 4.3. The diagram also marks the injection hole 4.4, the pressure relief hole 4.5, the curtain target area 4.6, the injection section 4.7, the diversion and pressure relief section 4.8, and the curtain diversion blind section area at the bottom of the formation dip angle 4.9.

[0096] Step 10: Complete grouting of all I-sequence and II-sequence boreholes. After the grout solidifies, an irregular, thick-walled, cylindrical, permanent closed water-tight curtain is formed in the steeply inclined, weakly weathered marble strata outside the pre-dug wellbore, preventing formation water from flowing around outside the curtain.

[0097] After forming an irregular, thick-walled, cylindrical, permanently closed water-tight curtain in the steeply dipped, weakly weathered marble strata outside the pre-excavated shaft, the "cross-core drilling method" is applied. Two inspection boreholes are arranged outside the curtain line, with the borehole trajectory passing through the "core" of the pre-excavated shaft. Figure 5The diagram shows a schematic of the boreholes for well inspection. Two inspection boreholes are designated Inspection Hole I and Inspection Hole II. The diagram labels the borehole openings of Inspection Hole I (5.1) and II (5.2), the final borehole positions of Inspection Hole I (5.3) and II (5.4), and the borehole trajectory (5.5). Through conventional water pressure and pumping tests, the permeability coefficient of the grouting curtain was calculated. Combined with methods such as fiber optic grating monitoring of the heat exchange rate within the borehole and cross-hole CT testing of the grouting curtain resistivity, the effectiveness of the leaks at the I and II sequence boreholes was checked. Supplementary grouting was then performed at the leak points to further improve the impermeability of the steeply inclined, weakly weathered marble aquifer in the well. In this invention, the final boreholes of both the I and II sequence boreholes must fall within the curtain target area. Inspection of the inspection boreholes is conducted initially, followed by grouting.

Claims

1. A weak weathered marble formation wellbore ground pre-grouting slurry control method, characterized in that, The method comprises the following steps: Step 1, according to the pre-excavated wellbore diameter, the stratum trend and the inclination, a plurality of curtain lines are arranged around the pre-excavated wellbore to form a curtain target area in the space between the shaft sinking temporary construction facilities; Step 2, a plurality of grouting drill hole trajectories are designed on the curtain lines, the drill hole orifice is located on or close to the outside of the shaft sinking temporary construction facilities, the drill hole bottom is located in the curtain target area, the drill hole orifice and the bottom are vertically located in the stratum space, and the grouting drill hole trajectory is in a "double L" combination in the stratum space; Step 3, a plurality of grouting drill holes uniformly distributed along the curtain line are taken as I sequence drill holes, and the non-grouting layer section I, the non-grouting layer section II and the grouting layer section are drilled from top to bottom respectively; in the grouting layer section, the I sequence drill holes are drilled from top to bottom in the curtain target area outside the pre-excavated wellbore, when the starting grouting drill hole in the I sequence drill hole completes the drilling of the first section of the grouting layer section, the I sequence drill hole adjacent to the starting grouting drill hole is taken as a strike pressure relief hole, the drilling of the same layer section is completed, and the I sequence drill hole opposite to the starting grouting drill hole is taken as an inclination pressure relief hole, and the drilling work of the high position layer section is completed; Step 4, the orifice valve is installed at the orifice of the strike pressure relief hole and the inclination pressure relief hole, the orifice valve is opened, and the grouting drill hole is in a static pressure state; the grouting drill hole is first subjected to large-pump-amount water pressure to dredge the fissures of the weakly weathered marble, the water level rise and overflow of the grouting drill hole are observed to ensure the grouting effect; after the water pressure is ended, grouting is started, the grout is from dilute to thick, flows to the adjacent strike pressure relief hole in the same layer along the stratum trend from the starting grouting hole, and flows to the opposite inclination pressure relief hole in the high layer along the stratum inclination, when the grouting drill hole reaches the grouting end standard, the grouting work of the first layer section is ended; Step 5, the adjacent strike pressure relief hole in step 3 is sequentially taken as the next grouting hole, the adjacent I sequence drill hole of the grouting hole is taken as a new strike pressure relief hole, and the opposite I sequence drill hole of the grouting hole is taken as a new inclination pressure relief hole, and steps 3 to 4 are repeated; Step 6, steps 3 to 5 are repeated until the starting grouting hole in step 3 becomes the adjacent strike pressure relief hole, and then the grouting work of the first section of the wellbore is completed; Step 7, after the grout in the starting grouting hole is solidified, the grouting hole is swept and drilled to the second grouting layer section, and steps 3 to 6 are repeated until all the I sequence drill holes on the curtain line complete the grouting work of the full-hole grouting layer section; Step 8, when the starting grouting hole completes the grouting of all the layer sections by descending in sections, the opposite grouting hole has a blind section and cannot guarantee the grouting effect, at this time, the I sequence drill hole adjacent to the opposite grouting hole of the starting grouting hole is taken as a pressure relief hole, the same layer pressure relief is adopted according to step 4, and steps 3 to 7 are repeated until all the I sequence drill holes in the blind section complete the same layer grouting work of the remaining blind section layer; Step 9, the grouting drill hole arranged between the I sequence drill holes is taken as a II sequence drill hole, and the grouting of the same layer is completed by descending in sections from top to bottom without pressure relief hole; Step 10, after the grouting of all the I sequence drill holes and the II sequence drill holes is completed, the grout is solidified, an irregular thick-walled cylindrical permanent closed water isolation curtain is formed in the large-inclination weakly weathered marble stratum outside the pre-excavated wellbore, and the stratum water is blocked outside the curtain.

2. The weakly weathered marble formation wellbore ground pre-grouting slurry control method of claim 1, wherein, The distance between the inner circle curtain line and the pre-excavated shaft wall in step 1 is D: D = (2m - 1)D e + 2Hα-R h In the above formula, m is the number of curtain line loops from the center of the pre-excavated shaft; H is the elevation of the grouting section, m; Alpha is the allowable inclination rate of the borehole; R h — pre-excavated shaft ramp, m; D e — the intersection thickness of the grouting hole, D e = 1.2r, r is the effective diffusion radius of the slurry.

3. The weakly weathered marble formation wellbore ground pre- grouting slurry control method of claim 2, wherein, The effective diffusion radius r of the slurry is: In the formula: k is the reciprocal of the viscosity of the slurry; v - slurry injection flow rate, m 3 min; t is the gel time of the slurry, min; n is the porosity of marble, %.

4. The weakly weathered marble formation wellbore surface pre- grouting slurry control method of claim 3, wherein, The distance between the inner circle curtain line and the pre-excavated shaft wall is in the range of 1.5-2 m, and the distance between adjacent curtain lines is 1 m.

5. The weakly weathered marble formation wellbore ground pre- grouting slurry control method of claim 1, wherein, In step 2, according to the position of the pre-excavated shaft, a three-dimensional coordinate system of the pre-grouting site is established, and the spatial coordinate calculation formula of the borehole trajectory is as follows: wherein N i Point space coordinates; N i N i-1 Point space distance, m; a i N i-1 Point line and z-axis angle, θ i N i-1 Point line azimuth angle.

6. The weakly weathered marble formation wellbore ground pre-grouting slurry control method of claim 1, wherein, The starting grouting hole in step 3 is any I sequence borehole on the side of the same layer with large buried depth selected along the dip angle of the stratum.

7. The weakly weathered marble formation wellbore ground pre-grouting slurry control method of claim 1, wherein, In step 4, when observing the water level rise and overflow of the grouting borehole, if thick slurry flows out of the strike pressure-relief hole and the dip pressure-relief hole, the valve at the hole mouth is immediately closed, and the grouting hole continues to be grouted.

8. The weakly weathered marble formation wellbore ground pre-grouting slurry control method of claim 1, wherein, In step 4, after completing the grouting work of the first layer section, the hole is scanned after 10 hours, and the water absorption of the grouting section is detected. If the water absorption is greater than 60 L / min, low-pump-rate re-grouting is required until the final hole standard is reached.

9. The weakly weathered marble formation wellbore ground pre-grouting slurry control method of claim 1, wherein, In step 10, after forming the irregular thick-walled cylindrical permanent closed water-resisting curtain, the "cross-core" method is used to arrange two inspection boreholes outside the curtain line site. The inspection borehole trajectory passes through the "core" of the pre-excavated shaft, and the I sequence borehole and the II sequence borehole are checked for leakage points, and the leakage points are supplemented with grouting.

10. The weakly weathered marble formation wellbore surface pre- grouting slurry control method of claim 9, wherein, After completing the leakage point inspection and supplementary grouting, the inspection borehole is grouted.

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