Method of repairing aquifer by segmented directional grouting after mining in mining area

Abstract

The present application provides a method for repairing aquifers by segmented directional grouting after mining in a mining area, comprising: drilling in the ground area corresponding to the water gushing position in the goaf area to obtain grouting holes; using the grouting holes to perform segmented grouting on the target grouting layer, the segmented grouting includes scouring and migration grouting, splitting and diffusion grouting and sedimentation and compaction grouting in sequence, the scouring and migration grouting uses a slurry of a first specific gravity to perform grouting according to a first pump volume, the splitting and diffusion grouting uses a slurry of a second specific gravity to perform grouting according to a second pump volume, and the sedimentation and compaction grouting uses a slurry of a third specific gravity to perform grouting according to a third pump volume, wherein the first specific gravity is less than the second specific gravity and less than the third specific gravity, and the first pump volume is greater than the second pump volume and greater than or equal to the third pump volume; after the segmented grouting, waiting for setting is performed to complete the repair of the aquifer. The method for repairing aquifers by segmented directional grouting after mining in a mining area provided by the present application can effectively block post-mining fissures, reduce maintenance costs, reduce the loss of shallow water resources, and maintain the stability of the aquifer.

Description

Technical Field

[0001] The present application relates to the technical field of grouting repair, and in particular to a method for repairing aquifers by segmented directional grouting after mining in a mining area. Background Art

[0002] Coal is an important natural resource. With the increasing mining and utilization of coal, numerous goafs have been formed underground. A large amount of continuous roof water gushing has formed in the goafs, causing serious loss of shallow water resources. Currently, grouting treatment is the most commonly used technical method to maintain the stability of aquifers. The fluidity or pumpability of the slurry itself is pumped to the water gushing area through drilling to effectively repair the aquifer.

[0003] However, during the underground grouting treatment process, large-flow, high-velocity moving water will be encountered. Under the action of moving water, the slurry is greatly diluted, especially under broken rock, and the retention rate is extremely low. It cannot be effectively condensed and sealed. It often takes a large amount of slurry to achieve the repair of the aquifer. Therefore, there is an urgent need for an aquifer repair method that can effectively reduce the grouting amount. Summary of the invention

[0004] In view of this, the purpose of this application is to propose a method for repairing aquifers by segmented directional grouting after mining in a mining area to solve the above-mentioned technical problems.

[0005] The present application provides a method for repairing an aquifer by segmented directional grouting after mining in a mining area, comprising: drilling a grouting hole in a ground area corresponding to a water gushing position in a goaf area; performing segmented grouting on a target grouting layer using the grouting hole, wherein the segmented grouting comprises scouring and migration grouting, splitting and diffusion grouting, and sedimentation and compaction grouting in sequence, wherein the scouring and migration grouting uses a slurry of a first specific gravity for grouting according to a first pump volume, the splitting and diffusion grouting uses a slurry of a second specific gravity for grouting according to a second pump volume, and the sedimentation and compaction grouting uses a slurry of a third specific gravity for grouting according to a third pump volume, wherein the first specific gravity is less than the second specific gravity and less than the third specific gravity, and the first pump volume is greater than the second pump volume and greater than or equal to the third pump volume; and after the segmented grouting, waiting for setting is performed to complete the repair of the aquifer.

[0006] Furthermore, the drilling in the ground area corresponding to the water gushing position in the goaf to obtain the grouting hole includes: obtaining mining data and hydrogeological data of the goaf, wherein the mining data include goaf size, water gushing position, water gushing amount, ore layer mining thickness, mining technology and mining face advancement rate, and the hydrogeological data include the distribution status of aquifers in the goaf, water content of aquifers, status of post-mining roof fracture zone and status of caving zone; determining the drilling position and target grouting layer according to the mining data and the hydrogeological data.

[0007] Furthermore, the method of drilling in the ground area corresponding to the water gushing position in the goaf to obtain the grouting hole includes: drilling to a first depth at the drilling position to obtain the grouting hole, the first depth being less than the depth of the target grouting layer; inserting a casing into the grouting hole, and using a slurry with a fourth specific gravity to fix the pipe and wait for setting, the fourth specific gravity being greater than the third specific gravity.

[0008] Furthermore, the use of the grouting holes to perform segmented grouting on the target grouting layer includes: after the pipe is fixed and waited for solidification, continuing to drill the grouting holes to the auxiliary grouting layer, wherein the auxiliary grouting layer is located above the target grouting layer; and grouting the auxiliary grouting layer and waiting for solidification.

[0009] Furthermore, the vertical distance between the auxiliary grouting layer and the target grouting layer is 10m to 15m.

[0010] Furthermore, the grouting and waiting for setting of the auxiliary grouting layer includes: grouting the auxiliary grouting layer with a slurry of a fifth specific gravity according to the second pump volume, wherein the fifth specific gravity is greater than the first specific gravity and less than the second specific gravity; when the grouting pressure remains stable and continues for a first preset time, stopping the grouting and starting the waiting for setting.

[0011] Furthermore, the use of the grouting holes to perform segmented grouting on the target grouting layer includes: continuing to drill the grouting holes to the target grouting layer after the grouting is set; performing horizontal multi-branch drilling at the target grouting layer to obtain branch holes, and performing segmented grouting on the multiple branch holes.

[0012] Furthermore, the flushing and transporting grouting includes: starting grouting the target grouting layer with the slurry of the first specific gravity according to the first pump volume; when the grouting pressure reaches a first preset pressure and lasts for a first preset time, stopping the grouting.

[0013] Furthermore, the splitting diffusion grouting includes: starting grouting the target grouting layer after the scour migration grouting is completed for a second preset time; when the grouting pressure reaches the second preset pressure, continuing grouting with the slurry of the second specific gravity according to the second pump volume; when the grouting pressure reaches a third preset pressure and continues for the first preset time, stopping grouting, wherein the second preset pressure is less than the third preset pressure and less than the second preset pressure.

[0014] Furthermore, the deposition compaction grouting includes: starting grouting the target grouting layer after the splitting diffusion grouting completes the second preset time; when the grouting pressure reaches the first preset pressure, continuing grouting with the slurry of the third specific gravity according to the third pump volume; when the grouting pressure reaches a fourth preset pressure and continues for the first preset time, stopping grouting, wherein the fourth preset pressure is greater than the first preset pressure.

[0015] From the above, it can be seen that the present application provides a method for repairing an aquifer by segmented directional grouting after mining in a mining area, comprising: drilling a grouting hole in a ground area corresponding to a water gushing position in a goaf area; using the grouting hole to perform segmented grouting on a target grouting layer, the segmented grouting sequentially comprises scouring and migration grouting, splitting and diffusion grouting and sedimentation and compaction grouting, the scouring and migration grouting uses a slurry of a first specific gravity for grouting according to a first pump volume, the splitting and diffusion grouting uses a slurry of a second specific gravity for grouting according to a second pump volume, and the sedimentation and compaction grouting uses a slurry of a third specific gravity for grouting according to a third pump volume, wherein the first specific gravity is less than the second specific gravity and less than the third specific gravity, and the first pump volume is greater than the second pump volume greater than or equal to the third pump volume; after segmented grouting, waiting for setting is carried out to complete the aquifer repair; by adjusting the slurry specific gravity and pump volume, the influence of dynamic water on the slurry is weakened, and the segmented grouting operations of scouring and migration grouting, splitting and diffusion grouting and sedimentation and compaction grouting are carried out in sequence to improve the slurry retention rate, effectively block the cracks, effectively reduce the loss of shallow water resources, and maintain the stability of the aquifer. Compared with conventional grouting methods, the grouting volume can be greatly reduced. After experimental testing, the grouting volume can be reduced by up to 89%; the method of post-mining segmented directional grouting to repair the aquifer in this mining area is simple and convenient, which can effectively block post-mining cracks, reduce maintenance costs, reduce the loss of shallow water resources, and maintain the stability of the aquifer. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the present application or related technologies, the drawings required for use in the embodiments or related technical descriptions are briefly introduced below. Obviously, the drawings described below are only embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0017] Figure 1 It is a schematic flow chart of a method for repairing aquifers by segmented directional grouting after mining in a mining area in an embodiment of the present application;

[0018] Figure 2 It is a schematic diagram of the cross-sectional structure of the goaf;

[0019] Figure 3 This is a schematic diagram of the whole process test of segmented grouting;

[0020] Figure 4A test schematic diagram of a scour migration grouting process;

[0021] Figure 5 A test schematic diagram of a splitting diffusion grouting process;

[0022] Figure 6 A test schematic diagram of a sedimentation compaction grouting process;

[0023] Figure 7 This is a schematic diagram of the standby water pressure test;

[0024] Figure 8 This is a schematic diagram comparing the grouting volume of segmented grouting and conventional grouting;

[0025] Fig. 9 Schematic diagram of the comparison of grouting volumes for multiple branch holes using segmented grouting.

[0026] Figure numerals: 1. grouting hole; 2. branch hole; 3. target grouting layer; 4. auxiliary grouting layer. DETAILED DESCRIPTION

[0027] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0028] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the embodiments of the present application should be the usual meanings understood by people with ordinary skills in the field to which the present application belongs. The "first", "second" and similar words used in the embodiments of the present application do not represent any order, quantity or importance, but are only used to distinguish different components. "Including" or "comprising" and similar words mean that the elements or objects appearing in front of the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0029] Coal is an important natural resource. With the increasing mining and utilization of coal, numerous goafs have been formed underground. A large amount of continuous roof water gushing has formed in the goafs, causing serious loss of shallow water resources. Currently, grouting treatment is the most commonly used technical method to maintain the stability of aquifers. The fluidity or pumpability of the slurry itself is pumped to the water gushing area through drilling to effectively repair the aquifer.

[0030] However, during the underground grouting treatment process, large-flow, high-velocity moving water will be encountered. Under the action of moving water, the slurry is greatly diluted, especially under broken rock, and the retention rate is extremely low. It cannot be effectively condensed and sealed. It often takes a large amount of slurry to achieve the repair of the aquifer. Therefore, there is an urgent need for an aquifer repair method that can effectively reduce the grouting amount.

[0031] Grouting is an underground concealed project, and the diffusion of grouting materials is unpredictable under complex geological conditions. The main grouting theories currently include splitting grouting theory, compaction grouting theory, penetration grouting theory, electrochemical grouting theory and fissure grouting theory.

[0032] Split grouting is a grouting method that uses high pressure to inject slurry into rock and soil to increase its strength and reduce permeability. The reinforcement and anti-seepage effects of split grouting are the result of the combined action of slurry and rock and soil. The split grouting process includes stages such as bubbling and compaction, split flow, etc. At each stage, the slurry always exerts an effect on the rock and soil, including filling and diffusion, compaction, ion exchange, etc. After the grouting is completed, the slurry condenses in the rock and soil to form an intricate slurry vein network, which can also play a role in skeleton support.

[0033] At present, the grouting splitting pressure Pd is the grouting pressure inside the splitting channel greater than the sum of the minimum principal stress δ3 and the tensile strength δt of the injected rock mass as the judgment condition for the crack to continue to split and expand forward, which can be expressed as formula (1):

[0034] P d =σ3+σ t (1)

[0035] The stress intensity factor generated by the grouting pressure on the inner wall of the entire crack and the ground stress on the outer wall at the crack tip is greater than or equal to the fracture toughness K IC As the judgment condition, as shown in formula (2):

[0036]

[0037] Where ΔP(x) is the net pressure in the crack, R is the half length of the crack, and when the slurry flows in shear, the grouting pressure presents a decaying non-uniform load distribution inside the crack channel, and the movement of the slurry and the expansion of the cleavage crack are carried out synchronously. On the one hand, it must follow the movement law of the slurry, and on the other hand, the diffusion of the slurry must also satisfy the diffusion law of the cleavage crack.

[0038] Compression grouting refers to injecting a slurry with a larger specific gravity into the target layer and squeezing it to fill the cracks between the holes, forming slurry bubbles at the grouting site, and the diffusion of the slurry produces compression under the stress resistance of the surrounding rock mass. The slurry completely replaces the crack space within the grouting range. Due to the high viscosity of the slurry, it is difficult for the slurry to flow freely in the cracks, and external pressure is required to assist the grouting. As the degree of compression and compaction increases, the mechanical strength and structural stability of the injected rock layer also increase.

[0039] According to the law of slurry diffusion, the greater the initial pressure, the better the slurry diffusion performance, but increasing the initial grouting pressure needs to rely on the grouting pump volume adjustment. Generally, the greater the grouting pump volume, the more slurry is released. With the increase of grouting time, the diffusion distance and diffusion rate of the slurry in the initial stage increase when the pump volume is stable. As the grouting process proceeds, the diffusion distance continues to increase on this basis, but due to the increase in the initial grouting pressure, the volume strain of the slurry in the fracture body of the grouting layer will produce a sudden change in volume strain at the initial moment. When the volume strain reaches a certain degree, the mechanical strength of the rock formation decreases, the rock mass is broken, causing the rock mass fracture to further expand, resulting in a splitting effect, and achieving the purpose of slurry diffusion.

[0040] Secondly, the pump volume and pressure also have different reaction rules in the middle and late stages of grouting. In order to ensure that the grouting material is fully filled in the fracture development body, it is particularly important to further control the pump volume. With the splitting effect generated by the initial grouting pressure, the final slurry diffusion distance has been roughly determined. At this time, the slurry volume strain in the rock body will be blocked by the surrounding rock, and the pump volume will be fed back along the delivery pipeline, resulting in increased pressure and increased grouting pump load. Therefore, the pressure increase rate can be reduced by appropriately adjusting the pump volume and slurry specific gravity.

[0041] Typical water-rich sand layer penetration grouting is essentially a process of using slurry to displace substances in the pores of the injected medium. During the penetration grouting process, as the pump volume and the slurry pressure in the rock mass constantly affect the changes in the slurry and fracture channels, the transverse fractures that penetrate between adjacent longitudinal fractures are the slurry flow channels of the adjacent longitudinal fractures. When the slurry flow position in the dominant fracture is greater than that in the adjacent fracture, replenishment occurs. However, due to its complex pore channels, the slurry migration is hindered to a certain extent, resulting in adsorption and precipitation during migration, and then blocking the pore channels of the sandstone fracture body. In addition, due to the intricate pore channels of the sand layer, the impurities scattered between the pores under post-mining stress disturbance and the dilution under hydraulic conditions profoundly affect the slurry diffusion range and slurry pressure attenuation law in the grouting project.

[0042] There are a certain amount of primary fractures in the rock mass. When the coal seam is disturbed by mining, these primary fractures will be disturbed and further developed and expanded, and a more complex secondary fracture network will be generated. However, under the long-term gravity settlement of the overlying rock, the rock mass destroyed by mining disturbance will be compacted and re-cemented into rock, and the broken fractures will gradually close, producing a self-repairing effect. This process will reduce the development range and opening degree of the overburden water-conducting fractures, but this short-term bridging will still face accidents such as water inrush and sand burst under the scouring, expansion and strengthening of the water passage of dynamic water.

[0043] Below, through specific embodiments and combined Figures 1 to 9 To describe the technical solution of this application in detail.

[0044] Some embodiments of the present application provide a method for repairing an aquifer by segmented directional grouting after mining in a mining area, such as Figure 1 As shown, the following steps are included:

[0045] S1. Drilling is performed in the ground area corresponding to the water gushing position in the goaf to obtain grouting holes.

[0046] The ground area corresponding to the water gushing position can be determined based on experience or relevant water gushing data. For example, the water gushing amount, water level and water pressure of the water gushing point of the closed wall of the underground tunnel are obtained, and the distribution area of ​​the water-filled channel of the underground water gushing and the distribution of the water-rich area of ​​the aquifer are determined in combination with the development law of the mining-induced overburden fractures and the geophysical exploration results of the water-rich property of the roof. Finally, the ground area corresponding to the water gushing position is divided; or the ground position directly corresponding to the water gushing point is the ground area, which is not limited here; grouting holes are drilled in the ground area for subsequent grouting operations.

[0047] S2. Use the grouting holes to perform segmented grouting on the target grouting layer, and the segmented grouting includes scour migration grouting, splitting diffusion grouting and sedimentation compaction grouting in sequence. The scour migration grouting uses a slurry with a first specific gravity to perform grouting according to a first pump volume, the splitting diffusion grouting uses a slurry with a second specific gravity to perform grouting according to a second pump volume, and the sedimentation compaction grouting uses a slurry with a third specific gravity to perform grouting according to a third pump volume, wherein the first specific gravity is less than the second specific gravity and less than the third specific gravity, and the first pump volume is greater than the second pump volume and greater than or equal to the third pump volume.

[0048] It takes a certain amount of time for the fractured rock strata to self-repair after mining, but it is impossible to guarantee safe coal mining during this period. Therefore, during the period from mining to the implementation of treatment, the disturbed fractures are not completely healed and in the process of dynamic water migration, the fine particles carried by the water flow and the original impurities in the channel are scattered and attached to the inner wall of the water channel, directly hindering the migration of slurry, causing blockage at the front end of the fracture, stagnation and accumulation of slurry, and unable to meet the needs of diffusion treatment. Therefore, it is necessary to use a grouting pump to inject a small specific gravity slurry into the borehole in a capping manner, replace the drilling fluid on the inner wall of the borehole, and flush and move the impurities between the larger fractures through a large pumping volume. Therefore, the flushing and migration grouting mainly focuses on the "small specific gravity, large pumping volume" method to flush the attachments at the front end of the fracture and the migration of the channel.

[0049] During the scouring and migration grouting stage, not only the attachments and impurities in the fissure channel are scoured and migrated, but also the unbridged fissures are expanded and split and pried. The first specific gravity is, for example, 1.5g / cm 3 , the first pump volume is, for example, 390L / min, which is not specifically limited; Figure 3 As shown in the figure, in the water pressure test 12 hours after the scouring and migration grouting, compared with the pressure before injection, the pressure rises faster and the subsequent pressure tends to be stable, indicating that the front-end crack reinforcement effect is good and the channel impurities are scour more thoroughly.

[0050] According to previous construction experience, it is easier to reach the crack splitting pressure under the action of higher specific gravity and external force. However, the slurry viscosity is high under high specific gravity, and it is difficult to migrate in the front tiny cracks. Therefore, the splitting diffusion grouting focuses on continuous splitting diffusion under "medium specific gravity and medium pumping volume". The second specific gravity is, for example, 1.75g / cm 3 The second pump volume is, for example, 250L / min, which is not specifically limited. Under the action of dynamic water, less slurry remains in the water channel, but a water pressure test is still required to verify the grouting effect of the splitting diffusion grouting stage. Another function is to flush and replace the solidified slurry on the inner wall of the borehole to dredge the water channel.

[0051] Sediment compaction grouting uses "high specific gravity, medium pump volume or small pump volume" to fill and reinforce the water channel and further compact the slurry filling at the front end of the crack to achieve sediment compaction. The third specific gravity is, for example, 2.0g / cm 3 The third pump volume is, for example, 250L / min or 160L / min, without specific limitation; as the degree of compression and compaction increases, scour is further reduced, and the mechanical strength and structural stability of the grouting layer are also enhanced, thereby improving the retention and consolidation of the slurry in the pore channels under dynamic water dilution.

[0052] By adjusting the slurry specific gravity and pump volume, the impact of dynamic water on the slurry is weakened. The segmented grouting operations of scouring and migration grouting, splitting and diffusion grouting and sedimentation and compaction grouting are carried out in sequence to improve the slurry retention rate, effectively seal the cracks, effectively reduce the loss of shallow water resources, and maintain the stability of the aquifer. Compared with conventional grouting methods, the grouting volume can be greatly reduced. According to experimental tests, the grouting volume can be reduced by up to 89%.

[0053] S3. After segmented grouting, wait for setting to complete the repair of the aquifer.

[0054] After the segmented grouting, wait for 12 hours to solidify in order to stabilize the grout solidification skeleton. Figure 3 As shown in the figure, the water pressure test is carried out immediately after the sedimentation compaction grouting is completed. The water pressure rises rapidly, and the curve is steep and straight, which meets the grouting end standard and continues to wait for setting. In the waiting for setting stage, the solidification is formed into a body, and the crack space is gradually filled with slurry. As the waiting time increases, the crack consolidation becomes stronger, and the front end of the crack becomes denser and forms a whole.

[0055] The method of post-mining segmented directional grouting to repair the aquifer in this mining area is simple and convenient. It can effectively seal post-mining cracks, reduce maintenance costs, reduce the loss of shallow water resources, and maintain the stability of the aquifer.

[0056] In some embodiments, step S1 includes:

[0057] S01. Obtain mining data and hydrogeological data of the goaf, wherein the mining data include goaf size, water gushing location, water gushing volume, ore layer mining thickness, mining technology and mining face advancement rate; the hydrogeological data include the distribution status of aquifers in the goaf, water content of aquifers, status of post-mining roof fracture zone and status of caving zone.

[0058] S02. Determine the drilling position and target grouting layer according to the mining data and the hydrogeological data.

[0059] Based on the mining data and hydrogeological data, the density and distribution characteristics of the mining-induced cracks in the roof after mining are determined through numerical simulation and theoretical analysis, so as to select the drilling location and target grouting layer, which will not be elaborated here.

[0060] In some embodiments, step S1 includes:

[0061] S101, drilling at the drilling position to a first depth to obtain the grouting hole, wherein the first depth is less than the depth of the target grouting layer.

[0062] S102, inserting a casing into the grouting hole, and using slurry with a fourth specific gravity to fix the pipe and wait for solidification, wherein the fourth specific gravity is greater than the third specific gravity.

[0063] According to the design coordinates, a 215mm carbide drill bit was used to drill a hole to 90m, i.e. the first depth (the depth of the top interface of the target grouting layer), and a 168mm casing was inserted. Single-liquid cement slurry was used to fix the pipe. The fourth specific gravity of the slurry was 2.10g / cm 3 , inject the pressure cap until the slurry returns to the hole mouth, wait for 48 hours to set, and then carry out the pipe sealing and water-stop test. When the pump volume is not less than 48L / min and the pressure is not less than 7MPa within 10 minutes, it means that the test meets the standard. If it does not meet the standard, reopen the hole and insert the casing or pull out the casing to fix the pipe again.

[0064] In some embodiments, the step of performing segmented grouting on the target grouting layer by using the grouting holes comprises:

[0065] S103, after the pipe is solidified, continue drilling into the grouting hole to the auxiliary grouting layer, wherein the auxiliary grouting layer is located above the target grouting layer.

[0066] S104, grouting the auxiliary grouting layer and waiting for setting.

[0067] After the pipe is solidified, continue drilling the grouting hole to the auxiliary grouting layer. Figure 2 As shown in the figure, the auxiliary grouting layer is located above the target grouting layer. The auxiliary grouting layer is grouted before the target grouting layer is grouted in sections to fully fill and reinforce the cracks on the top of the target grouting layer, forming a grouting dome on the plane. For the shallow aquifer, the overlying aquifer of the overflowing recharge coal seam can be recharged once, and the dynamic water interference in the subsequent section grouting can be reduced. It is also easier to drill the subsequent branch holes, solving the problem of branch hole collapse. After the auxiliary grouting layer is grouting reinforced and the branch hole is grouting-transformed to the aquifer, the slurry can be prevented from running upward and bubbling out from the ground. At the same time, the slurry can be promoted to spread horizontally and downward, solving the problem of slurry running randomly during the grouting process.

[0068] When the grouting end standard is met, that is, the auxiliary grouting layer is allowed to solidify, drilling is carried out to the target grouting layer. Under the staged grouting method, the cracks are sealed, the recharge is reduced to the greatest extent, the grouting rock layer is transformed, the ecological water level of the shallow aquifer is protected, and the interference with the mine is reduced.

[0069] In some embodiments, the vertical distance between the auxiliary grouting layer and the target grouting layer is 10m to 15m.

[0070] Avoid vertical spacing that is too short, which will first block some cracks in the target grouting layer and affect the diffusion of subsequent segmented grouting slurry; also avoid vertical spacing that is too large, which will fail to effectively block the top of the target grouting layer and cause the subsequent segmented grouting slurry to run upward.

[0071] In some embodiments, step S104 includes:

[0072] S1041. Grouting the auxiliary grouting layer with slurry of fifth specific gravity according to the second pump volume, wherein the fifth specific gravity is greater than the first specific gravity and less than the second specific gravity.

[0073] S1042. When the grouting pressure remains stable and lasts for the first preset time, stop grouting and start waiting for setting.

[0074] The auxiliary grouting layer is mainly used to plug the top cracks and inhibit the unstable upward diffusion of the slurry in the target grouting layer. Therefore, the slurry can be made of ordinary silicate P.O42.5 cement, water, and clay (5000 mesh). Under the aforementioned broken rock layer, the crack opening is large, the crack communication is complex, and the crack space particles are obvious. Therefore, the impurities between the holes are continuously and stably flushed with a constant specific gravity and pump volume. The fifth specific gravity is, for example, 1.55g / cm 3 The second pump volume is, for example, 250L / min. When the pressure rises to 1 to 1.5 times the hydrostatic pressure, the pump volume can be adjusted appropriately to stabilize the grouting pressure. The first preset time is, for example, 40 minutes. After the grouting pressure is stable for 40 minutes, the auxiliary grouting layer grouting end standard is met, and the grouting is stopped and waited for 24 hours to achieve the purpose of reducing the overflow recharge of the shallow aquifer and controlling the horizontal diffusion of the slurry in the target grouting layer.

[0075] In some embodiments, the step of performing segmented grouting on the target grouting layer by using the grouting holes includes:

[0076] S201, after the grouting is allowed to set, continue drilling into the grouting hole to the target grouting layer.

[0077] S202, performing horizontal multi-branch drilling at the target grouting layer to obtain branch holes, and performing segmented grouting on the plurality of branch holes.

[0078] By performing segmented grouting through multiple branch holes, the grouting range can be expanded and the sealing effect can be improved.

[0079] In some embodiments, the flushing migration grouting comprises:

[0080] S203, starting grouting at the target grouting layer using the slurry with the first specific gravity according to the first pump volume.

[0081] S204. When the grouting pressure reaches a first preset pressure and lasts for a first preset time, stop grouting.

[0082] like Figure 2 As shown in the figure, during the scouring and migration grouting stage, the slurry density is mainly adjusted to 1.5 g / cm 3, and the grouting parameters of 390L / min are used to inject the grouting to ensure unimpeded migration of the diluted slurry in the pores and to strengthen the fracture channel under large pumping volume, which serves as the basis for the next stage of splitting and expansion.

[0083] Therefore, the grouting pressure in this section increases slowly and lasts for a long time. When the grouting pressure reaches about 1Mpa, it means that the slurry density at this time is difficult to meet the further migration of attachments, and the grouting pump is difficult to load after increasing the density. At this time, the density can be adjusted to 1.75g / cm 3 , the pump volume is 250L / min, the grouting pressure enters a short decline after adjustment, and then the pressure continues to rise rapidly under the crack splitting and diffusion. The first preset pressure is, for example, 2MPa, and the first preset time is, for example, 30min. When the grouting pressure stabilizes at above 2MPa for 30min, the scouring and migration grouting stage is ended to ensure the filling and reinforcement of the front space of the crack.

[0084] In some embodiments, the splitting diffusion grouting comprises:

[0085] S205: After the flushing and transporting grouting is completed for a second preset time, grouting is started on the target grouting layer.

[0086] S206. When the grouting pressure reaches the second preset pressure, continue grouting using the slurry of the second specific gravity according to the second pump volume.

[0087] S207. When the grouting pressure reaches a third preset pressure and lasts for the first preset time, stop grouting, wherein the second preset pressure is less than the third preset pressure which is less than the second preset pressure.

[0088] The second preset time is, for example, 12 hours. After the flushing and transporting grouting is completed for the second preset time, the target grouting layer is started to be grouted. The solidified slurry of the previous stage can be quickly flushed and transported with the slurry of "large pump volume and small specific gravity"; the second preset pressure is, for example, 1MPa. When the grouting pressure rises rapidly to 1MPa, the specific gravity of the slurry is adjusted to 1.75g / cm 3 , the pump volume is 250L / min for main grouting, and the injection crack channel is filled for a long time under this grouting parameter, and the rock and soil body is exerted through slurry bubbling, compaction and splitting flow to overcome the dilution under dynamic water and complete the splitting and diffusion. The third preset pressure is, for example, 1.5MPa. When the grouting pressure is stable at more than 1.5MPa for 30 minutes, the splitting and diffusion grouting stage is ended. This stage can also play a role in skeleton support and promote the subsequent grouting.

[0089] In some embodiments, the deposition compaction grouting comprises:

[0090] S208, after the splitting diffusion grouting completes the second preset time, starting grouting for the target grouting layer.

[0091] S209. When the grouting pressure reaches the first preset pressure, continue grouting using the slurry with the third specific gravity according to the third pump volume.

[0092] S210. When the grouting pressure reaches a fourth preset pressure and lasts for the first preset time, stop grouting, wherein the fourth preset pressure is greater than the first preset pressure.

[0093] After the second preset time of splitting diffusion grouting, grouting is started at the target grouting layer with a specific gravity of 2.0g / cm 3 , with a pump volume of 250L / min, the water channel is filled and reinforced, and the slurry filling at the front end of the crack is further compacted to achieve sedimentation and compaction.

[0094] In this stage, the fracture channel can be further flushed and the front end accumulated by the method of "small specific gravity and large pump volume". When the pressure reaches about 1Mpa, the specific gravity is adjusted to 1.75g / cm 3 , the pump volume is 250L / min, to achieve rapid deposition of slurry in the water channel. The first preset pressure is, for example, 2Mpa. When the grouting pressure rises to 2Mpa, the main "large specific gravity, medium pump volume", that is, specific gravity 2.0g / cm 3 , grouting is performed at a pump volume of 250L / min to cover and compact the previous slurry. Due to the large specific gravity of the slurry, it is difficult for the slurry to flow freely in the cracks. When the grouting pressure is stable at above 2.8MPa, the pump volume can be adjusted to 160L / min to assist in grouting. As the degree of compression and compaction increases, scouring is further reduced, and the mechanical strength and structural stability of the grouting layer are also enhanced, which improves the retention and consolidation of the slurry in the pore channel under dynamic water dilution. The fourth preset pressure is, for example, 3MPa. When the grouting pressure is stable at above 3MPa for 30 minutes, the sedimentation compaction grouting is completed.

[0095] In some embodiments, the method of post-mining segmented directional grouting to repair aquifers in the mining area is applied to the weak or missing red soil area in the west wing of the 12th plate of Shaanxi Coal Caojiatan Coal Mine. The treatment layer is the upper part of the weathered bedrock after mining. The overlying rock layer of the coal seam in this area is 287m, and the treatment layer is less than 100m from the ground. Clay cement slurry is selected. The grouting process is described in order of scouring migration, splitting diffusion, and deposition compaction.

[0096] like Figure 4As shown, it is scour migration grouting. Taking the Z1-7-3 branch hole in the treatment area as an example, the hole is 135m long and the drilling point is the upper part of the weathered bedrock. When drilling to 103m, the drilling fluid in the hole does not return, and the hole is completely lost. The same row of holes Z1-4 have signs of slurry flowing to the adjacent holes (in order to eliminate the interference of slurry flow, grouting and drilling shall not be carried out simultaneously), and in the water pressure test after the completion of the hole, the pump volume gradually increases to 160L / min. From this, it can be indirectly judged that the formation where the hole is located is broken and the water channel has a horizontal penetration.

[0097] In the case of concentrated development of water-conducting channels, it is particularly important to carry out scouring and migration first. Unbridged cracks or micro-particle impurities carried by gravity collapse and dynamic water will greatly affect the subsequent diffusion of slurry. The hole is slowly pressurized under the grouting method of "small specific gravity, large pumping volume", focusing on splitting the front end of the crack and scouring the channel. After the specific gravity is increased, the grouting pressure is stabilized at more than 2MPa.

[0098] like Figure 5 The figure shows the splitting diffusion grouting. Taking the Z1-5-1 branch hole in the treatment area as an example, the hole is 130m long and the drilling point is the upper part of the weathered bedrock. The hole has a leakage of 0.8m at 95.71m to 110m. 3 , the drilling fluid loss was 2.4m at 110.9m to 122.9m 3 , which indicates that there are large crack channels in these two places. After the scouring and migration grouting is completed, the pressure curve of the water pressure test shows that the pressure rises quickly and the final pressure reaches 1.5MPa. At this stage, relying on "medium specific gravity and medium pump volume", the grouting pressure rises steadily, and the slurry bubbles, squeezes, pushes, splits and diffuses.

[0099] like Figure 6 The figure shows the sedimentation compaction grouting. Taking the Z3-10-3 branch hole in the treatment area as an example, the hole is 141m long and the drilling point is the upper part of the weathered bedrock. When drilling the horizontal section of the hole, the drilling fluid returns to the clay cement slurry. After the grouting of the hole is completed, the drilling continues. In addition, the drilling fluid loss at 95.15m to 100m of the Z3-10 straight hole consumes 1.3m 3 ; Branch hole Z3-10-1 lost 0.7m between 105.09m and 106.09m 3 , Z3-10-3 lost 2.8m between 106.79m and 137.61m 3 It can be inferred that the horizontal stratum strength in this area is fragile and the cracks are connected. From the splitting diffusion grouting water pressure curve, the line growth trend is stable and the filling effect after splitting is significant. Under the adjustment of "high specific gravity and small pump volume", the grouting pressure once rose to 3.7MPa, which supplemented the compaction deposition effect and further improved the slurry retention and consolidation.

[0100] like Figure 7As shown in the figure, it is a solidified body after segmented grouting. Taking the Z3-3-2 branch hole in the treatment area as an example, the hole is 130m long and the drilling point is the upper part of the weathered bedrock. The hole has a serious loss of 8.45m in the straight hole section from 78.35m to 100m. 3 ; The branch holes of Z3-3 straight hole have leakage at 104.21m to 110m, 110.42m to 122.4m, and 108.7m to 128.4m. The leakage location is in the fracture zone at the top of the weathered bedrock. The fractures are concentrated and connected in the lateral direction. The hole was tested for water pressure after deposition and compaction, and at intervals of 1 day and 3 days. As time goes by, the pressure slope and final pressure increase with time. The slurry expands after stagnation, tightens the fracture wall, and consolidates into a body, realizing the repair of the aquifer.

[0101] Conventional grouting technology generally adopts the in-hole plugging and segmented downward cement filling grouting. The cement slurry is evenly injected into the borehole through the grouting pump and grouting pipeline to displace the moisture and gas in the rock cracks or between soil particles by filling, penetrating and compacting. After hardening, the rock and soil in the diffusion range are cemented into a whole to form a rock body with high strength, low compressibility, high permeability and good stability, so that the grouting treatment layer is reinforced to prevent or reduce infiltration and uneven settlement.

[0102] For example, in the specific process, in the second section of the borehole (the borehole channel after the casing is inserted and waited for setting), the segmented downward grouting with in-hole plugs is adopted. The preliminary design of the unit grouting section length is 10m to 20m. Simple hydrological observation is carried out, and finally the borehole is grouted with high pressure.

[0103] A water pressure test is carried out before injection. After the casing is lowered and waited for solidification, the grouting borehole is drilled downward with a section length controlled at 10m to 20m. One or two drill rods are lifted and connected with a grouting stop plug. The drill rods are lowered to the initial drilling point and clean water is pumped into the grouting pump through the grouting pipeline and drill rod. The grouting flow rate and specific gravity are determined based on the water pressure test results.

[0104] The plug in the hole is grouting in sections. The original drill pipe connection remains unchanged. The cement slurry is injected through the grouting pipeline and the drill pipe without drilling. After reaching the grouting end standard (generally 2 to 3 times the hydrostatic pressure, water pressure stabilization for 30 minutes), the drill is lifted and waited for setting for 24 hours. After the section waiting is completed, the hole is swept to the end of the previous grouting section and drilling is continued for 10m to 20m. The previous steps are repeated until the section grouting is completed and the hole is sealed.

[0105] The main grouting materials are water and ordinary silicate P.O42.5 cement, and the specific gravity of cement slurry is 1.1-1.3g / cm 3 .

[0106] A comparative experiment of grouting repair was conducted using conventional grouting technology and the method of post-mining directional grouting to repair aquifers in the mining area of ​​this scheme. The experimental results are as follows Figure 8As shown, 1-1-1 and 1-1-2 are different branch holes of the same grouting hole 1-1, 1-2-1 and 1-2-2 are different branch holes of the same grouting hole 1-2, and 1-3-1 and 1-3-2 are different branch holes of the same grouting hole 1-3. It can be seen that the grouting amount used in the grouting by this method is significantly lower than the grouting amount of the conventional grouting method. This scheme can reduce the grouting amount by up to 89%. In addition, the grouting of different branch holes is also compared by this method, as shown in FIG. Fig. 9 As shown, 2-3-1 and 2-3-2 are different branch holes of the same grouting hole 2-3, and 3-2-1, 3-2-2 and 3-2-3 are different branch holes of the same grouting hole 3-2. It can be seen that the grouting amounts are not much different, indicating that the grouting effect is stable.

[0107] It should be noted that the above describes some embodiments of the present application. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recorded in the claims can be performed in an order different from that in the above embodiments and still achieve the desired results. In addition, the processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0108] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present application (including the claims) is limited to these examples. In line with the concept of the present application, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the embodiments of the present application as described above, which are not provided in detail for the sake of simplicity.

[0109] In addition, to simplify the description and discussion, and in order not to make the embodiment of the present application difficult to understand, the known power supply / ground connection with other components may or may not be shown in the provided drawings. In addition, the device can be shown in the form of a block diagram to avoid making the embodiment of the present application difficult to understand, and this also takes into account the following fact, that is, the details of the implementation method of these block diagram devices are highly dependent on the platform to be implemented in the embodiment of the present application (that is, these details should be completely within the scope of understanding of those skilled in the art). In the case of elaborating specific details to describe the exemplary embodiments of the present application, it is obvious to those skilled in the art that the embodiment of the present application can be implemented without these specific details or when these specific details are changed. Therefore, these descriptions should be considered to be illustrative rather than restrictive.

[0110] Although the present application has been described in conjunction with the specific embodiments of the present application, many replacements, modifications and variations of these embodiments will be apparent to those of ordinary skill in the art based on the foregoing description. The present application embodiments are intended to encompass all such replacements, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application embodiments should be included in the protection scope of the present application.

Claims

1. A method for repairing aquifers by segmented directional grouting after mining in a mining area, characterized in that: include: Drilling is performed in the ground area corresponding to the water inflow location in the goaf to obtain a grouting hole; The grouting holes are used to perform segmented grouting on the target grouting layer, and the segmented grouting includes flushing and transporting grouting, splitting and diffusion grouting and sedimentation and compaction grouting in sequence. The flushing and transporting grouting uses a slurry with a first specific gravity to perform grouting according to a first pump volume, the splitting and diffusion grouting uses a slurry with a second specific gravity to perform grouting according to a second pump volume, and the sedimentation and compaction grouting uses a slurry with a third specific gravity to perform grouting according to a third pump volume, wherein the first specific gravity is less than the second specific gravity and less than the third specific gravity, and the first pump volume is greater than the second pump volume and greater than or equal to the third pump volume; the flushing and transporting grouting includes: starting grouting the target grouting layer with the slurry with the first specific gravity according to the first pump volume; stopping grouting when the grouting pressure reaches a first preset pressure and lasts for a first preset time; the splitting and diffusion grouting includes: after the flushing and transporting grouting is completed for a second preset time , start grouting the target grouting layer; when the grouting pressure reaches the second preset pressure, continue grouting with the slurry of the second specific gravity according to the second pump volume; when the grouting pressure reaches the third preset pressure and lasts for the first preset time, stop grouting, wherein the second preset pressure is less than the third preset pressure and less than the first preset pressure; the sedimentation compaction grouting includes: after the splitting diffusion grouting completes the second preset time, start grouting the target grouting layer; when the grouting pressure reaches the first preset pressure, continue grouting with the slurry of the third specific gravity according to the third pump volume; when the grouting pressure reaches the fourth preset pressure and lasts for the first preset time, stop grouting, wherein the fourth preset pressure is greater than the first preset pressure; in the flushing and migration grouting stage, adjust the slurry specific gravity to 1.5g / cm 3 , the pump volume is 390L / min to ensure that the diluted slurry can migrate unimpeded in the pores and reach the enhanced fracture channel under large pump volume, which serves as the basis for the next stage of splitting and diffusion. When the grouting pressure reaches 1Mpa, the specific gravity is adjusted to 1.75g / cm 3 , the pump volume is 250L / min, the grouting pressure enters a short decline after adjustment, and then the pressure rises rapidly and continuously under the crack splitting and diffusion. The first preset pressure is 2MPa, and the first preset time is 30min. When the grouting pressure stabilizes above 2MPa for 30min, the flushing and migration grouting stage is ended; After the segmented grouting, the aquifer repair is completed by waiting for setting.

2. The method for repairing aquifers by segmented directional grouting after mining in a mining area according to claim 1, characterized in that: The drilling in the ground area corresponding to the water gushing position in the goaf to obtain the grouting hole comprises: Acquire mining data and hydrogeological data of the goaf, wherein the mining data include goaf size, water inflow location, water inflow volume, ore layer mining thickness, mining technology and mining face advancement rate, and the hydrogeological data include the distribution status of aquifers in the goaf, water content of aquifers, post-mining roof fracture zone status and caving zone status; The drilling position and the target grouting layer are determined according to the mining data and the hydrogeological data.

3. The method for repairing aquifers by segmented directional grouting after mining in a mining area according to claim 2, characterized in that: The method of drilling a grouting hole in a ground area corresponding to a water gushing position in the goaf includes: Drilling at the drilling position to a first depth to obtain the grouting hole, wherein the first depth is less than the depth of the target grouting layer; A casing is lowered into the grouting hole, and slurry with a fourth specific gravity is used to fix the pipe and wait for solidification, wherein the fourth specific gravity is greater than the third specific gravity.

4. The method for repairing aquifers by segmented directional grouting after mining in a mining area according to claim 3, characterized in that: The step of performing segmented grouting on the target grouting layer by using the grouting holes comprises: After the pipe is fixed and solidified, the grouting hole is continuously drilled to the auxiliary grouting layer, wherein the auxiliary grouting layer is located above the target grouting layer; The auxiliary grouting layer is grouted and allowed to set.

5. The method for repairing aquifers by segmented directional grouting after mining in a mining area according to claim 4, characterized in that: The vertical distance between the auxiliary grouting layer and the target grouting layer is 10m to 15m.

6. The method for repairing aquifers by segmented directional grouting after mining in a mining area according to claim 4, characterized in that: The step of performing grouting and waiting for setting on the auxiliary grouting layer comprises: Grouting the auxiliary grouting layer with slurry of a fifth specific gravity according to the second pump volume, wherein the fifth specific gravity is greater than the first specific gravity and less than the second specific gravity; When the grouting pressure remains stable and lasts for the first preset time, the grouting is stopped and waiting for setting begins.

7. The method for repairing aquifers by segmented directional grouting after mining in a mining area according to claim 4, characterized in that: The step of performing segmented grouting on the target grouting layer by using the grouting holes comprises: After the grouting is allowed to set, continue drilling the grouting hole to the target grouting layer; Horizontal multi-branch drilling is performed at the target grouting layer to obtain branch holes, and segmented grouting is performed on the multiple branch holes.

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