Goaf grouting process method based on negative pressure drainage

Abstract

The invention relates to the technical field of goaf grouting, in particular to a goaf grouting process method based on negative pressure drainage, which comprises the following steps: S1, according to a grouting and filling sequence, constructing N central drill holes in a to-be-filled area, and respectively constructing M circumferential drill holes around each central drill hole at proper intervals; s2, after construction of all the drill holes is completed, hole opening grouting devices are installed at hole openings of the grouting holes; an orifice air extractor is mounted at the orifice of the negative-pressure air extraction hole; s3, after preparation is completed, a pumping and drainage test is started; s4, performing grouting operation; s5, at the last stage of grouting, when the orifice air extractor detects the grouting slurry, the negative pressure pumping and drainage operation is ended; and when the grouting completion standard is reached, the grouting operation of the grouting drilling hole is completed. According to the method, multi-channel synchronous grouting can be achieved, the flowing and diffusing speed of grout in the goaf is increased, the flowing speed of the grout in the goaf is increased through negative pressure drainage while it is guaranteed that the grout is diffused evenly and orderly, and the grouting and filling efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of goaf grouting, in particular to a goaf grouting process method based on negative pressure drainage. Background Art

[0002] Goaf grouting is an engineering technology used to treat the hollow areas formed during underground mining. It is particularly important in coal mining and other types of mining. Goaf grouting mainly injects specific slurries, such as cement, fly ash slurry, etc., into the goaf to fill these spaces, thereby enhancing ground stability and mitigating surface collapse and other geological disasters.

[0003] After searching, a patent document with patent publication number CN202310401404.0 disclosed a method for grouting treatment of compacted goaf areas of coal mine solid waste. The method mainly selects a suitable position in the side or top of the tunnel adjacent to the working face according to the calculated drilling position to drill the first hole, and drills a directional hole obliquely upward at this position in the direction of the compacted goaf. The drilling direction is perpendicular to the direction of the tunnel, and the directional hole is drilled until it passes through the working face. After the drilling is completed, the drilling grouting pipeline is installed and the borehole is reinforced.

[0004] It can be seen from the records in the above patent documents that the grouting operation in the goaf is achieved by drilling a directional hole obliquely upward at the drilling position and then drilling into the penetrating working face and injecting grout.

[0005] However, goaf grouting is a concealed project. Under conditions such as goaf grouting filling, broken rock grouting reinforcement and curtain grouting, when grouting from the ground to the deep goaf strata, the anisotropic distribution of the goaf cracks leads to uncertainty in the diffusion of the slurry. The above method cannot control the diffusion range and direction of the slurry.

[0006] To this end, the present invention optimizes and improves the problems existing in the prior art, and hereby proposes a goaf grouting process method based on negative pressure drainage to better solve the problems existing in the prior art. Summary of the invention

[0007] The present invention solves one of the above technical problems, and the technical solution adopted is: a goaf area grouting process method based on negative pressure drainage, comprising the following steps: S1: According to the grouting filling sequence, N central boreholes are constructed in the area to be filled, and M circumferential boreholes are constructed around each central borehole at appropriate intervals; Each central drill hole is used in combination with the peripheral drill holes around it, and the central drill hole and the peripheral drill holes are used as negative pressure exhaust holes and grouting holes respectively, or the central drill hole and the peripheral drill holes are used as grouting holes and negative pressure exhaust holes respectively; S2: After the construction of each drilling hole is completed, a hole grouting device is installed at the hole mouth of the grouting hole, and a negative pressure gauge is installed on the hole mouth grouting device; a hole mouth exhaust device is installed at the hole mouth of the negative pressure exhaust hole (the hole mouth exhaust device has a replaceable filter element built in to prevent gravel and debris from entering the vacuum pump), and the exhaust equipment is connected to the hole mouth exhaust device through the exhaust pipe; S3: After the above preparations are completed, the drainage test is started: determine the formal drainage pressure P and flow rate Q, close the grouting valve on the orifice grouting device, start the exhaust equipment, and start to exhaust air through the negative pressure exhaust hole to gradually form a negative pressure. During the drainage, record the reading value of the negative pressure gauge on the orifice grouting device, and dynamically adjust the drainage flow rate. When the negative pressure gauge reading reaches 0.5MPa, specifically, when the negative pressure gauge reading on the grouting borehole orifice grouting device always fails to reach 0.5MPa, and the negative pressure gauge reading on the exhaust device on the exhaust borehole exceeds 2.0MPa, the drainage test should be stopped. It is judged that the fracture connectivity between the two boreholes is poor and the borehole spacing is too large. One more borehole should be added between the two boreholes, the exhaust equipment should be closed, the drainage test should be ended, and the appropriate drainage flow rate Q and pressure P should be determined; S4: Formal grouting operation: connect the grouting pump to the borehole through the grouting pipe; start the air extraction equipment, and when the negative pressure gauge on the orifice grouting device reaches 0.5MPa, open the grouting valve on the orifice grouting device, start the grouting pump, and start the grouting filling operation; observe the changes in the negative pressure gauge on the orifice grouting device of the negative pressure extraction hole; S5: At the end of grouting, the filling slurry diffuses to the vicinity of the negative pressure exhaust hole and enters the negative pressure exhaust hole along with the exhaust gas flow. When the hole mouth exhaust device detects the grouting slurry, it indicates that the slurry has diffused to the drilling area and the negative pressure exhaust operation can be ended.

[0008] In actual working conditions, one grouting hole can be constructed and multiple negative pressure exhaust holes can be configured at the same time; one negative pressure exhaust hole can also be constructed and multiple grouting holes can be configured, or multiple grouting holes can be constructed and multiple negative pressure exhaust holes can be configured at the same time; the specific selection depends on the on-site usage requirements.

[0009] In any of the above schemes, preferably, N is an integer ≥ 1, M is an integer ≥ 3; and two adjacent central drill holes are arranged at intervals.

[0010] In any of the above schemes, it is preferred that each of the central drilled holes is used in combination with the circumferential drilled holes around it, and the central drilled hole is used as a grouting hole, and each of the circumferential drilled holes is used as a negative pressure exhaust hole.

[0011] In any of the above schemes, it is preferred that each of the central drill holes is used in combination with the circumferential drill holes around it, and the central drill hole is used as a negative pressure exhaust hole, and each of the circumferential drill holes is used as a grouting hole.

[0012] In any of the above schemes, it is preferred that the grouting pump is selected according to the type of grouting slurry; when the grouting slurry type is Newtonian fluid, the grouting pump selects a piston pump, and when the grouting slurry type is a paste, the grouting pump selects a plunger pump.

[0013] In any of the above solutions, it is preferred that the vacuum equipment is a high-flow, high-pressure vacuum pump.

[0014] In any of the above schemes, preferably, the borehole spacing between adjacent two directional boreholes is set to 15 meters to 30 meters, and the borehole spacing is dynamically adjusted according to the connectivity of the grouting layer.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. This method adopts a combined negative pressure grouting process, which can guide the diffusion range and direction of the slurry, realize precise control of grouting, and avoid slurry waste caused by disorderly diffusion of slurry.

[0016] 2. This technical process can effectively improve grouting efficiency, reduce grouting costs, and also shorten the grouting period.

[0017] 3. The grouting process method of the present invention can realize multi-channel synchronous grouting. First, it accelerates the flow and diffusion speed of the slurry in the goaf, improves the grouting filling efficiency, shortens the grouting treatment period, and reduces the construction cost; second, it ensures that the slurry is diffused and filled in all directions synchronously, avoids weak grouting areas, and improves the grouting treatment quality.

[0018] 4. By vacuuming to form negative pressure, the slurry is guided to flow and diffuse preferentially in the direction of poor connectivity, eliminating quality risks in areas where grouting is difficult, and then large-scale grouting is started in areas with good connectivity, thereby ensuring that all grouting areas achieve better grouting filling effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for the specific embodiments or the description of the prior art. In all the drawings, similar elements or components are generally identified by similar reference numerals. In the drawings, the elements or components are not necessarily drawn according to the actual scale.

[0020] Figure 1 Schematic diagram of the top view of the drilling layout of Example 1 of the present invention.

[0021] Figure 2 Schematic diagram of the top view of the drilling layout of Example 2 of the present invention.

[0022] Figure 3 Schematic diagram of the top view of the drilling layout of Example 3 of the present invention.

[0023] Figure 4 Schematic diagram of the top view of the drilling layout of Example 4 of the present invention.

[0024] Figure 5 It is a schematic diagram of the grouting cross-section structure of the present invention.

[0025] In the figure, 1, central drill hole; 2, peripheral drill holes; 3, ground surface; 4, goaf; 5, negative pressure exhaust hole; 6, grouting hole; among which, the arrow indicates the slurry drainage direction. DETAILED DESCRIPTION

[0026] The following is a detailed description of the embodiments of the technical solution of the present invention in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present invention. Figure 1-Figure 5 as shown in .

[0027] A goaf grouting process method based on negative pressure drainage comprises the following steps: S1: According to the grouting filling sequence, N central boreholes are constructed in the area to be filled, and M circumferential boreholes are constructed around each central borehole at appropriate intervals; Each central drill hole is used in combination with the peripheral drill holes around it, and the central drill hole and the peripheral drill holes are used as negative pressure exhaust holes and grouting holes respectively, or the central drill hole and the peripheral drill holes are used as grouting holes and negative pressure exhaust holes respectively; S2: After the construction of each drilling hole is completed, a hole grouting device is installed at the hole mouth of the grouting hole (a replaceable filter element is built into the hole mouth exhaust device to prevent gravel and debris from entering the vacuum pump). The hole mouth grouting device can use the grouting equipment (hole mouth device) in the prior art, which is used to be installed at the hole mouth position and complete the grouting operation, and a negative pressure gauge is installed on the hole mouth grouting device; a hole mouth exhaust device is installed at the hole mouth of the negative pressure exhaust hole, and the hole mouth exhaust device can use the grouting equipment (hole mouth device) in the prior art, which is used to be installed at the hole mouth position and complete the grouting operation, and the exhaust device is connected to the hole mouth exhaust device through an exhaust pipe; in addition, the exhaust drilling and grouting drilling positions can be flexibly switched as needed during the actual construction process; S3: After the above preparations are completed, the pumping test is started: determine the pressure P and flow Q of the formal pumping, close the grouting valve on the orifice grouting device, start the air extraction equipment, and start to pump out air through the negative pressure air extraction hole to gradually form a negative pressure. During the pumping period, the reading value of the negative pressure gauge on the orifice grouting device is recorded, and the pumping flow rate is dynamically adjusted. When the negative pressure gauge reading reaches 0.5MPa, the air extraction equipment is closed, the pumping test is ended, and the appropriate pumping flow rate Q and pressure P are determined; S4: Formal grouting operation: connect the grouting pump to the borehole through the grouting pipe; start the vacuum equipment, and wait until the negative pressure gauge on the orifice grouting device reaches 0.5MPa. Specifically, when the reading of the negative pressure gauge on the orifice grouting device of the grouting borehole always fails to reach 0.5MPa, and the reading of the negative pressure gauge on the orifice vacuum device of the vacuum borehole exceeds 2.0MPa, the vacuum test should be stopped. It is judged that the connectivity of the cracks between the two boreholes is poor and the distance between the boreholes is too large. One more borehole should be added between the two boreholes, the grouting valve on the orifice grouting device is opened, the grouting pump is started, and the grouting filling operation is started; observe the changes in the negative pressure gauge on the orifice vacuum device of the negative pressure vacuum hole; S5: At the end of grouting, the filling slurry diffuses to the vicinity of the negative pressure exhaust hole and enters the negative pressure exhaust hole along with the exhaust gas flow. In order to prevent the grouting slurry from entering the vacuum pump, it is necessary to reasonably control the hole mouth exhaust device and determine that the slurry has diffused to the negative pressure exhaust borehole before the grouting slurry enters the matching vacuum pump; when it is shown that the slurry has diffused to the borehole area, the negative pressure exhaust operation can be ended.

[0028] In actual working conditions, one grouting hole can be constructed and multiple negative pressure exhaust holes can be configured at the same time; one negative pressure exhaust hole can also be constructed and multiple grouting holes can be configured, or multiple grouting holes can be constructed and multiple negative pressure exhaust holes can be configured at the same time; the specific selection depends on the on-site usage requirements.

[0029] In any of the above schemes, preferably, N is an integer ≥1, M is an integer ≥3; and two adjacent central drill holes are arranged at intervals.

[0030] In any of the above schemes, it is preferred that each of the central drilled holes is used in combination with the circumferential drilled holes around it, and the central drilled hole is used as a grouting hole, and each of the circumferential drilled holes is used as a negative pressure exhaust hole.

[0031] In any of the above schemes, it is preferred that each of the central drill holes is used in combination with the circumferential drill holes around it, and the central drill hole is used as a negative pressure exhaust hole, and each of the circumferential drill holes is used as a grouting hole.

[0032] In any of the above schemes, it is preferred that the grouting pump is selected according to the type of grouting slurry; when the grouting slurry type is Newtonian fluid, the grouting pump selects a piston pump, and when the grouting slurry type is a paste, the grouting pump selects a plunger pump.

[0033] In any of the above solutions, it is preferred that the air extraction device is a large-flow high-pressure air compressor.

[0034] In any of the above schemes, preferably, the borehole spacing between adjacent two directional boreholes is set to 15 meters to 30 meters, and the borehole spacing is dynamically adjusted according to the connectivity of the grouting layer.

[0035] Example 1: When the central drill hole is used as the grouting hole and the circumferential drill holes are used as negative pressure exhaust holes: A grouting hole is constructed in the treatment area, with it as the center and four negative pressure adsorption boreholes are arranged around it. Five boreholes constitute a grouting unit. The spacing between boreholes is generally 15-30 meters, which is adjusted dynamically according to the adsorption effect.

[0036] After the construction of each drilling hole is completed, a hole mouth grouting device is installed at the hole mouth of the grouting hole, and a negative pressure gauge is installed on the hole mouth grouting device; a hole mouth exhaust device is installed at the hole mouth of the negative pressure exhaust hole, and the exhaust equipment is connected to the hole mouth exhaust device through an exhaust pipe.

[0037] After the preparation work is completed, the extraction test begins.

[0038] Close the grouting valve on the grouting device at the mouth of the grouting hole, start the exhaust equipment on the negative pressure exhaust hole 1, and begin to exhaust air outwards through the negative pressure exhaust hole to gradually form a negative pressure in the goaf around the borehole. During the exhaust, record the negative pressure gauge on the grouting device at the mouth of the grouting hole, dynamically adjust the exhaust flow of the negative pressure exhaust hole 1, and when the negative pressure gauge reads 0.5MPa, close the exhaust equipment of the negative pressure exhaust hole 1, and record the exhaust flow Q1 at this time; follow this cycle, and start the exhaust equipment on the negative pressure exhaust holes 2, 3, and 4 respectively, and when the negative pressure gauge reads 0.5MPa, close the exhaust equipment, and record the exhaust flow Q2, Q3, and Q4 at this time.

[0039] Analyze and determine the size of the drainage flow Q1, Q2, Q3, and Q4 of each negative pressure exhaust hole. The larger the drainage flow, the worse the connectivity between the negative pressure exhaust hole and the grouting hole, and the larger the drainage flow required for actual grouting. By adjusting the drainage flow of the negative pressure exhaust holes in different directions, the slurry can be evenly diffused around the grouting holes to avoid grouting blind spots and improve the grouting treatment effect.

[0040] In the initial grouting stage, the initial drainage flow rate of each negative pressure drainage hole can be set to Q1 / 4, Q2 / 4, Q3 / 4, and Q4 / 4 according to the drainage test results.

[0041] During the grouting process, dynamic adjustments are made according to the actual situation. The vacuum hole where the slurry or groundwater first reaches the negative pressure stops pumping.

[0042] Example 2: When the central drill hole is used as the negative pressure exhaust hole and the circumferential drill holes are used as the grouting holes: A negative pressure adsorption borehole is constructed in the treatment area, with it as the center and four grouting holes arranged around it. Five boreholes constitute a grouting unit. The spacing between boreholes is generally 15-30 meters, which is adjusted dynamically according to the adsorption effect.

[0043] After the construction of each drilling hole is completed, a hole mouth grouting device is installed at the hole mouth of the grouting hole, and a negative pressure gauge is installed on the hole mouth grouting device; a hole mouth exhaust device is installed at the hole mouth of the negative pressure exhaust hole, and the exhaust equipment is connected to the hole mouth exhaust device through an exhaust pipe.

[0044] After the preparation work is completed, the extraction test begins.

[0045] Close the grouting valve on the grouting device at the orifice of grouting hole 1, start the exhaust equipment on the negative pressure exhaust hole, and begin to exhaust air outwards through the negative pressure exhaust hole to gradually form a negative pressure in the goaf around the borehole. During the exhaust, record the negative pressure gauge on the grouting device at the orifice of grouting hole 1, dynamically adjust the exhaust flow of the negative pressure exhaust hole, and when the negative pressure gauge reading reaches 0.5MPa, close the exhaust equipment of the negative pressure exhaust hole, and record the exhaust flow Q1 at this time; repeat this cycle, and when the negative pressure gauge readings at the orifices of grouting holes 2, 3, and 4 reach 0.5MPa, close their exhaust equipment, and record the exhaust flow rates Q2, Q3, and Q4 at this time, respectively.

[0046] Analyze and determine the corresponding drainage flow rates Q1, Q2, Q3, and Q4 when the negative pressure at the mouth of each grouting hole reaches 0.5 MPa. The larger the drainage flow rate, the worse the connectivity between the negative pressure extraction hole and the grouting hole, and the larger the drainage flow rate required for actual grouting.

[0047] When the sizes of Q1, Q2, Q3, and Q4 are relatively close, after turning on the vacuum pump, grouting can be started simultaneously for grouting holes 1, 2, 3, and 4. The grouting flow rates of the grouting holes are q1, q2, q3, and q4 respectively. The larger the required pumping flow rate Q is, the smaller the corresponding grouting flow rate q is, and the pressure P is appropriately increased.

[0048] When the slurry or groundwater in a grouting hole reaches the negative pressure exhaust hole, stop pumping; continue grouting until the end hole standard is reached and then stop grouting.

[0049] Note that when one of the Qi is significantly larger than the others, the grouting hole corresponding to the Qi should be filled first, and the negative pressure exhaust hole should be used to exhaust the air synchronously. When the slurry or groundwater reaches the negative pressure exhaust hole, the exhaust should be stopped; then the grouting of other boreholes can be started.

[0050] By vacuuming to form negative pressure, the slurry is guided to flow and diffuse preferentially in the direction of poor connectivity, eliminating quality risks in areas where grouting is difficult. Then, large-scale grouting is started in areas with good connectivity, ensuring that all grouting areas achieve better grouting filling effects.

[0051] Example 3: When there are multiple peripheral boreholes, and when the central borehole is used as a grouting hole and the circumferential boreholes are used as negative pressure exhaust holes: The difference in internal pressure values ​​of each negative pressure exhaust hole is controlled to achieve synchronous multi-channel grouting.

[0052] When one grouting hole is equipped with four air extraction holes, the difference in the internal pressure values ​​of each borehole is controlled mainly by controlling the extraction flow Q of the four negative pressure air extraction holes to adjust the internal pressure values ​​of the four negative pressure air extraction holes. The size of Q is set in the same way as above. The four air extraction holes are equipped with four vacuum pumps, which can be independently regulated in four directions.

[0053] Embodiment 4: When there are multiple central drill holes, and when the central drill hole is used as a negative pressure exhaust hole and the circumferential drill holes are used as grouting holes: An exhaust hole is set in the center of the four grouting holes to control the difference in internal pressure values ​​of each borehole. The pressure values ​​inside the four grouting holes are mainly adjusted by controlling the grouting flow rate q and grouting pressure P of the four grouting holes.

[0054] Through the air extraction test to test the direction with poor connectivity, small flow and high pressure grouting is adopted in the borehole; through the air extraction test to test the direction with good connectivity, large flow and low pressure grouting is adopted in the borehole. At the same time, the intermittent grouting process can be optimized for the boreholes with excessive grouting volume, and the slurry diffusion range can be adjusted. The required filling slurry is calculated according to the filling range to avoid the slurry spreading outside the treatment area and causing unnecessary losses, while ensuring that the final filling effects in all directions meet the treatment requirements.

[0055] Realizing multi-channel simultaneous grouting can accelerate the flow and diffusion speed of the slurry in the goaf, improve the grouting filling efficiency, shorten the grouting treatment period, and reduce construction costs.

[0056] The second is to ensure that the slurry diffuses and fills in all directions simultaneously, avoid weak grouting areas, and improve the quality of grouting management.

[0057] In the method of the present invention, the connectivity of the voids in different directions can be tested by a gas extraction test to determine the injectability of the goaf; then the diffusion range of the slurry can be controlled by controlling the gas extraction flow or grouting flow q, grouting pressure P, etc. in different directions, thereby ensuring that the filling is not excessive and the treatment requirements can be met.

[0058] In addition, clean water is used to clean the broken porous rock in the goaf before grouting to improve the connectivity of the voids.

[0059] The following is an addition to the post-grouting treatment effect detection method: the air-exhaust borehole can be used as an effect detection hole during the grouting process to determine the slurry diffusion range, carry out well logging and other work, and detect the treatment effect during grouting, which helps to guide the adjustment of the grouting process and optimize the design.

[0060] After the grouting is completed, the grouting treatment effect is generally evaluated comprehensively through the method of drilling + geophysical exploration. The specific methods and steps are as follows: 1. First, select 3-5% of the grouting holes in the treatment area as test holes. The layout of the test holes should take into account the principle of overall and key areas. Drill holes should also be arranged in areas with abnormal grouting. Observe whether there is drill drop or water leakage through drilling holes, and take cores to test the strength of the filling body.

[0061] 2. Use the detection borehole to conduct borehole observation, observe the filling of cracks in the borehole wall, calculate the filling rate, and determine whether it meets the design requirements.

[0062] 3. Carry out coalfield logging in the inspection borehole to test the resistivity, volume density, acoustic wave and other parameters in the borehole, compare them with the logging parameters of the exploration borehole before grouting, and qualitatively analyze the grouting effect.

[0063] 4. You can also select seismic method, VSP method, electrical method, etc. for qualitative analysis according to the depth of goaf, water accumulation, geological conditions, etc.

[0064] 5. After the geophysical exploration is completed, a grouting test is carried out on the test borehole, the filling rate is calculated based on the grouting volume of the test borehole, and the grouting effect is quantitatively evaluated.

[0065] 6. Based on the surface displacement observation, the probability integral method and numerical calculation method are used to estimate the residual settlement of the goaf site, and the site stability and suitability for engineering construction are evaluated in combination with the filling situation.

[0066] The grouting method designed in the present invention has the following advantages: first, by guiding the slurry flow, the diffusion distance of the slurry in the area is increased, the number of holes drilled is reduced, the drilling period and the cost of treatment are reduced; second, the slurry is spread more evenly to avoid the existence of grouting blind areas.

[0067] When the slurry diffuses in the fractured formation, according to the principle of least resistance, it often diffuses in a single direction with the least resistance, or is affected by factors such as the formation inclination and the direction of the fracture, which can easily cause the slurry to diffuse too far in a certain direction, beyond the effective treatment area, resulting in slurry waste, and create grouting weak areas in other directions, posing quality risks.

[0068] The use of negative pressure adsorption combined grouting can improve the grouting efficiency, avoid the existence of weak grouting areas, and ensure the quality of grouting management.

[0069] It should be noted that in the grouting process, the negative pressure exhaust hole is used as a slurry observation borehole, or a new observation borehole is added, a tracer is added to the slurry, and water samples are taken from the borehole at regular intervals to detect and analyze the slurry diffusion direction and range.

[0070] In addition, considering that the air extraction holes and grouting holes are close to each other, the air extraction holes and grouting holes can be treated as a group of boreholes, and the cross-hole CT geophysical method can be used to judge the grouting effect by using the difference in test parameters before and after grouting.

[0071] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments may still be modified, or some or all of the technical features may be replaced by equivalents. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention. For those skilled in the art, any replacement, improvement or change made to the implementation mode of the present invention falls within the protection scope of the present invention.

[0072] The matters not described in detail in the present invention are all known technologies to those skilled in the art.

Claims

1. A method for grouting in goaf based on negative pressure drainage, characterized in that: The steps include: S1: According to the grouting filling sequence, N central boreholes are constructed in the area to be filled, and M circumferential boreholes are constructed around each central borehole at appropriate intervals; Each central drill hole is used in combination with the peripheral drill holes around it, and the central drill hole and the peripheral drill holes are used as negative pressure exhaust holes and grouting holes respectively, or the central drill hole and the peripheral drill holes are used as grouting holes and negative pressure exhaust holes respectively; S2: After the construction of each drilling hole is completed, a hole grouting device is installed at the hole mouth of the grouting hole, and a negative pressure gauge is installed on the hole mouth grouting device; a hole mouth exhaust device is installed at the hole mouth of the negative pressure exhaust hole, and the exhaust equipment is connected to the hole mouth exhaust device through an exhaust pipe; S3: After the above preparations are completed, the pumping test is started: determine the pressure P and flow Q of the formal pumping, close the grouting valve on the orifice grouting device, start the air extraction equipment, and start to pump out air through the negative pressure air extraction hole to gradually form a negative pressure. During the pumping period, the reading value of the negative pressure gauge on the orifice grouting device is recorded, and the pumping flow rate is dynamically adjusted. When the negative pressure gauge reading reaches 0.5MPa, the air extraction equipment is closed, the pumping test is ended, and the appropriate pumping flow rate Q and pressure P are determined; S4: Formal grouting operation: connect the grouting pump to the borehole through the grouting pipe; Start the air extraction equipment, and when the negative pressure gauge on the orifice grouting device reaches 0.5MPa, open the grouting valve on the orifice grouting device, start the grouting pump, and start the grouting filling operation; Observe the changes in the negative pressure gauge on the vacuum device at the vacuum hole; S5: At the end of grouting, the filling slurry diffuses to the vicinity of the negative pressure exhaust hole and enters the negative pressure exhaust hole along with the exhaust gas flow. When the hole mouth exhaust device detects the grouting slurry, it indicates that the slurry has diffused to the drilling area and the negative pressure exhaust operation can be ended.

2. The method for grouting a goaf area based on negative pressure drainage according to claim 1, characterized in that: N is an integer ≥1, M is an integer ≥3; and two adjacent center drill holes are arranged at intervals.

3. The method for grouting a goaf area based on negative pressure drainage according to claim 2, characterized in that: Each of the central drilled holes is used in combination with the circumferential drilled holes around it, and the central drilled hole is used as a grouting hole, and each of the circumferential drilled holes is used as a negative pressure exhaust hole.

4. The method for grouting a goaf area based on negative pressure drainage according to claim 2, characterized in that: Each of the central drilled holes is used in combination with the circumferential drilled holes around it, and the central drilled hole is used as a negative pressure exhaust hole, and each of the circumferential drilled holes is used as a grouting hole.

5. The method for grouting in goaf based on negative pressure drainage according to claim 4, characterized in that: The grouting pump is selected according to the type of grouting slurry; when the grouting slurry type is Newtonian fluid, the grouting pump is selected as a piston pump, and when the grouting slurry type is a paste, the grouting pump is selected as a plunger pump.

6. The method for grouting in goaf based on negative pressure drainage according to claim 5, characterized in that: The air extraction device is a high-pressure vacuum pump with a large flow rate.

7. The method for grouting in goaf based on negative pressure drainage according to claim 6, characterized in that: The drilling spacing between adjacent two directional boreholes is set to 15 meters to 30 meters, and the drilling spacing is dynamically adjusted according to the connectivity of the grouting layers.

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