AU2020101047A4 - Method for filling underground cavity in bedrock by grouting and hydraulic filling device - Google Patents
Method for filling underground cavity in bedrock by grouting and hydraulic filling device Download PDFInfo
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- AU2020101047A4 AU2020101047A4 AU2020101047A AU2020101047A AU2020101047A4 AU 2020101047 A4 AU2020101047 A4 AU 2020101047A4 AU 2020101047 A AU2020101047 A AU 2020101047A AU 2020101047 A AU2020101047 A AU 2020101047A AU 2020101047 A4 AU2020101047 A4 AU 2020101047A4
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- 238000000034 method Methods 0.000 title claims abstract description 49
- 239000004576 sand Substances 0.000 claims abstract description 54
- 239000002689 soil Substances 0.000 claims abstract description 48
- 238000005553 drilling Methods 0.000 claims abstract description 41
- 239000002002 slurry Substances 0.000 claims description 85
- 239000004568 cement Substances 0.000 claims description 48
- 238000011010 flushing procedure Methods 0.000 claims description 35
- 238000005065 mining Methods 0.000 claims description 11
- 238000007789 sealing Methods 0.000 claims description 11
- 239000002245 particle Substances 0.000 claims description 10
- 239000011268 mixed slurry Substances 0.000 claims description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract description 25
- 235000019994 cava Nutrition 0.000 abstract description 16
- 230000000694 effects Effects 0.000 abstract description 10
- 239000000463 material Substances 0.000 abstract description 10
- 239000000945 filler Substances 0.000 description 15
- 235000019353 potassium silicate Nutrition 0.000 description 10
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 description 10
- 238000005429 filling process Methods 0.000 description 9
- 238000013461 design Methods 0.000 description 8
- 239000010881 fly ash Substances 0.000 description 8
- 239000011230 binding agent Substances 0.000 description 7
- 238000010586 diagram Methods 0.000 description 4
- 238000011161 development Methods 0.000 description 3
- 238000009792 diffusion process Methods 0.000 description 3
- 239000011440 grout Substances 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 239000012752 auxiliary agent Substances 0.000 description 2
- 229910000278 bentonite Inorganic materials 0.000 description 2
- 239000000440 bentonite Substances 0.000 description 2
- SVPXDRXYRYOSEX-UHFFFAOYSA-N bentoquatam Chemical compound O.O=[Si]=O.O=[Al]O[Al]=O SVPXDRXYRYOSEX-UHFFFAOYSA-N 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 239000003673 groundwater Substances 0.000 description 2
- 238000002347 injection Methods 0.000 description 2
- 239000007924 injection Substances 0.000 description 2
- 238000007689 inspection Methods 0.000 description 2
- 238000009434 installation Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 229910001570 bauxite Inorganic materials 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 238000009933 burial Methods 0.000 description 1
- 239000011083 cement mortar Substances 0.000 description 1
- 239000004927 clay Substances 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 239000004567 concrete Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000012634 fragment Substances 0.000 description 1
- 239000004570 mortar (masonry) Substances 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 239000011435 rock Substances 0.000 description 1
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Classifications
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D3/00—Improving or preserving soil or rock, e.g. preserving permafrost soil
- E02D3/12—Consolidating by placing solidifying or pore-filling substances in the soil
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D11/00—Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
- E21D11/04—Lining with building materials
- E21D11/10—Lining with building materials with concrete cast in situ; Shuttering also lost shutterings, e.g. made of blocks, of metal plates or other equipment adapted therefor
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- Engineering & Computer Science (AREA)
- Structural Engineering (AREA)
- Mining & Mineral Resources (AREA)
- Life Sciences & Earth Sciences (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Civil Engineering (AREA)
- Architecture (AREA)
- Geochemistry & Mineralogy (AREA)
- Geology (AREA)
- Agronomy & Crop Science (AREA)
- Environmental & Geological Engineering (AREA)
- Soil Sciences (AREA)
- Paleontology (AREA)
- General Engineering & Computer Science (AREA)
- Consolidation Of Soil By Introduction Of Solidifying Substances Into Soil (AREA)
Abstract
METHOD FOR FILLING UNDERGROUND CAVITY IN BEDROCK BY GROUTING
AND HYDRAULIC FILLING DEVICE
ABSTRACT
The present invention relates to the technical field of karst cave filling, and provides a
method for filling an underground cavity (8) (especially a karst cave and a roadway with a
large buried depth of greater than 30.0 m or with a large space) in bedrock (17) by grouting.
The method includes determining a drilling position, drilling through overburden soil (16),
installing a conveying casing (7), drilling in a bedrock section (17), filling by a hydraulic
filling method and grouting. In the present invention, the underground cavity (8) is filled with
sand and gravel aggregates (10) by using the hydraulic filling method, and then grouted to
solidify the filled sand and gravel aggregates (10) to improve the integrity of the filling
material. The filled sand and gravel aggregates (10) occupy the space in the underground
cavity (8), greatly reducing the amount of grouting and reducing the treatment cost. The
filled sand and gravel aggregates (10) also block or reduce the connecting channel between the
underground cavity (8) and the outside of the cavity, improving the filling treatment effect of
the underground cavity (8). The present invention solves the filling treatment problem of
deep-buried, large-space karst caves and roadways. The present invention further provides a
hydraulic filling device (7). The hydraulic filling device (7) is used to fill sand and gravel
aggregates (10) into karst caves, which has fast filling speed and good filling effect.
1/2
3
Water flow direction
FIG. 1
6
Connect 3PNL pump
Water flow direction
7F
FIG 2
Description
1/2
3
Water flow direction
FIG. 1
6
Connect 3PNL pump
Water flow direction
7F
FIG 2
METHOD FOR FILLING UNDERGROUND CAVITY IN BEDROCK BY GROUTING AND HYDRAULIC FILLING DEVICE TECHNICAL FIELD The present invention relates to the technical field of underground cavity filling, in particular to a method for filling an underground cavity in bedrock by grouting and a hydraulic filling device. BACKGROUND In the karst development area, fissures in karst rocks are well developed. Soil caves are gradually formed in the overburden soil above the covered karst caves under certain hydrodynamic conditions. The development of the soil caves affects the stability of the foundation and the safe use of buildings (structures) thereon. In order to prevent the development of karst caves and soil caves from harming the buildings (structures) above, cement slurry, mortar, concrete and other materials are poured (injected) into the caves. These methods achieve the purposes of filling the karst caves, blocking the groundwater runoff channels, preventing collapse of karst cave ceilings and improving the stability of foundations above the karst caves. The strength of the filling material to achieve the above purpose is often not high, but the cavities should be filled as densely as possible. However, a series of problems occur in the filling treatment of covered karst caves that are developed on a large-scale, unfilled, semi-filled and well-connected, especially those with a large buried depth greater than m or with a large space. For example, the filling material is difficult to be filled into the cave, the amount of the material poured (injected) is large, the filling range is not effectively controlled, and the grouting pressure is difficult to meet the design requirements. These problems lead to high treatment cost of karst caves and unsatisfactory treatment effect. In addition, some roadways excavated in the deep stratum for mining underground mines have become permanent abandoned underground spaces. If these abandoned underground spaces are not treated, there will be huge hidden dangers and a series of environmental problems such as ground subsidence. Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field. OBJECT OF THE INVENTION It is the object of the present invention to substantially overcome or at least ameliorate one or more of the disadvantages of the prior art or to provide a useful alternative.
SUMMARY In view of this, the present invention provides a method for filling an underground cavity in bedrock by grouting and a hydraulic filling device. The method of the present invention is used to fill covered karst caves and abandoned mining roadways, which greatly reduces the amount of grouting, reduces the treatment cost, increases the grouting pressure and improves the filling treatment effect. In one aspect, the present disclosure provides a method for filling an underground cavity in bedrock by grouting includes the following steps: (1) determining a drilling position according to a position of the underground cavity, which is directly above the underground cavity; (2) drilling through overburden soil above the bedrock at the determined drilling position; (3) installing a conveying casing into a borehole, extending the bottom of the conveying casing into the bedrock section, and using cement slurry to seal between the bottom of the conveying casing and the overburden soil; (4) continuing to drill the bedrock section until the borehole penetrates a ceiling of the underground cavity; (5) filling sand and gravel aggregates into the underground cavity through the borehole by using a hydraulic filling method; and (6) grouting the underground cavity through the borehole. Preferably, the underground cavity in the bedrock is a covered karst cave or an abandoned mining roadway in the bedrock. Preferably, in step (2), a diameter of the borehole in the overburden soil is not less than 4 times a maximum particle size of the sand and gravel aggregates used forfilling. Preferably, in step (3), the depth of the bottom of the conveying casing extending into the bedrock section is not less than 0.5 m; the diameter of the conveying casing is 146-168 mm; the conveying casing is provided with a flange on the top. Preferably, the method of using cement slurry to seal between the bottom of the conveying casing and the overburden soil is: injecting 1.5-2 m deep cement slurry into the bottom of the conveying casing by using a drill pipe, then lifting the conveying casing for 0.5-1 m, and lowering the conveying casing to the original position. Preferably, in step (5), the sand and gravel aggregates are filled with a hydraulic filling device; the hydraulic filling device includes a flushing pipe and a filling funnel; the bottom of the filling funnel communicates with a body of the flushing pipe; a slurry pump adapter and a flange joint are respectively provided at both ends of the flushing pipe; an exhaust pipe is provided on a wall of the flushing pipe at one end close to the flange joint; the flushing pipe communicates with the conveying casing through the flange joint. Preferably, the method of filling the sand and gravel aggregates is specifically: connecting the slurry pump adapter to a water supply pipe of a slurry pump, turning on the slurry pump to send water, and filling the sand and gravel aggregates into the filling funnel, so that the sand and gravel aggregates are flushed into the underground cavity under the action of a hydraulic force; during the filling process, a mass ratio of the water to the sand and gravel aggregates is :1 to 10:1. Preferably, in step (6), the method of grouting is specifically: inserting a grouting pipe into the borehole, and extending a bottom end of the grouting pipe into the underground cavity; sealing a gap between the top of the grouting pipe and the borehole with mixed slurry; and starting grouting after the mixed slurry is solidified for at least 24 h. Preferably, the grouting is stopped when the pressure at a mouth of the borehole is greater than 1.0 MPa. In a further aspect, the present disclosure provides a hydraulic filling device, including a flushing pipe 2 and a filling funnel 3, wherein the bottom of thefilling funnel communicates with a body of the flushing pipe; a slurry pump adapter 1 and a flange joint 5 are respectively provided at both ends of the flushing pipe 2; an exhaust pipe 4 is provided on a wall of the flushing pipe at one end close to the flange joint 5. In a further aspect, the present disclosure provides a method for filling an underground cavity in bedrock by grouting, including determining a drilling position, drilling through overburden soil, installing a conveying casing, drilling in a bedrock section, filling by a hydraulic filling method and grouting, where the underground cavity is a karst cave or an abandoned mining roadway. In the present disclosure, the underground cavity is filled with sand and gravel aggregates by using a hydraulic filling method, and then grouted to solidify the filled sand and gravel aggregates to improve the integrity of the filling material. The filled sand and gravel aggregates occupy the space in the underground cavity, greatly reducing the amount of grouting and reducing the treatment cost. The filled sand and gravel aggregates also block or reduce the connecting channel between the underground cavity and the outside of the cavity, increasing the grouting pressure, controlling the slurry diffusion range, and improving the filling treatment effect of the underground cavity. The hydraulic filling device provided by the present disclosure is used to fill sand and gravel aggregates into karst caves or abandoned mining roadways, which has fast filling speed, convenient operation and good filling effect.
Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to". BRIEF DESCRIPTION OF DRAWINGS A preferred embodiment of the present invention will now be described by way of specific embodiments with reference to the examples and accompanying drawings in which: FIG. 1 is a structural diagram a hydraulic filling device; FIG. 2 is a diagram of filling by a hydraulic filling method; and FIG. 3 is a diagram of grouting. In the drawings, the following reference numbers are used to identify the corresponding features as follows: 1. slurry pump adapter; 2. flushing pipe; 3. filling funnel; 4. exhaust pipe; 5. flange joint; 6. hydraulic filling device; 7. conveying casing; 8. underground cavity; 9. filler in underground cavity; 10. sand and gravel aggregates filled in underground cavity; 11. grouting pipe; 12. cement/water glass slurry solidified mass; 13. high-pressure hose; 14. pressure gauge; 15. exhaust pipe (pressure gauge installation pipe); 16. overburden soil; and 17. bedrock. DETAILED DESCRIPTION The present invention provides a method for filling an underground cavity in bedrock by grouting, including the following steps: (1) determine a drilling position according to a position of the underground cavity, which is directly above the underground cavity; (2) drill through overburden soil above the bedrock at the determined drilling position; (3) install a conveying casing into a borehole, extend the bottom of the conveying casing into a bedrock section, and use cement slurry to seal between the bottom of the conveying casing and the overburden soil; (4) continue to drill the bedrock section until the borehole penetrates a ceiling of the underground cavity; (5) fill sand and gravel aggregates into the underground cavity through the borehole by using a hydraulic filling method; and (6) grout the underground cavity through the borehole. The present invention first determines a drilling position according to a position of the underground cavity. In the present invention, the underground cavity is located in the bedrock covered with overburden soil. The underground cavity in the bedrock is preferably a covered karst cave or an abandoned mining roadway in the bedrock. The method of the present invention is suitable for filling deep-buried (> 30 m), large-space karst caves and abandoned mining roadways. In the present invention, the location of the underground cavity is preferably determined according to a karst survey, the location of the borehole is determined according to the location of the underground cavity, and the borehole is directly located above the underground cavity. In a specific example of the present invention, a survey hole used for the karst survey can be used directly. After the location of the borehole is determined, the present invention drills through overburden soil above the bedrock at the determined drilling position. The present invention preferably adopts a survey drilling rig to drill, and the diameter of the borehole is determined based on the maximum particle size of the sand and gravel aggregates to be filled and the design diameter of the borehole to be drilled in the bedrock section. In the present invention, the diameter of the borehole in the overburden soil is preferably not less than 4 times the maximum particle size of the sand and gravel aggregates used for filling, and more preferably 4-6 times the maximum particle size of the sand and gravel aggregates. In a specific example of the present invention, in order to ensure the smooth progress of the filling, the diameter of the borehole in the overburden soil is preferably 146 mm to 168 mm, and may specifically be 146 mm or 168 mm. In a specific example of the present invention, the drilling is preferably carried out with a slurry wall, and the deviation of the verticality of the borehole is preferably not more than 1%. When a survey hole is used, it is preferably expanded according to the design diameter of karst treatment. After the overburden soil is drilled through, the present invention installs a conveying casing into a borehole, extends the bottom of the conveying casing into a bedrock section, and uses cement slurry to seal between the bottom of the conveying casing and the overburden soil. In the present invention, the diameter (outer diameter) of the conveying casing is preferably 146 mm to 168 mm, and specifically may be 146 mm or 168 mm. In a specific example of the present invention, the diameter of the conveying casing is preferably selected according to the diameter of the borehole in the overburden soil, and the conveying casing is preferably provided with a flange on the top for connecting a hydraulic filling device. In the present invention, the depth of the bottom of the conveying casing extending into the bedrock section is preferably not less than 0.5 m, and more preferably 0.5-1 m. In the present invention, the method of using cement slurry to seal between the bottom of the conveying casing and the overburden soil is preferably: inject 1.5-2 m deep cement slurry into the bottom of the conveying casing by using a drill pipe, then lift the conveying casing for 0.5-1 m, and lower the conveying casing to the original position. In this way, the casing is filled with the cement slurry inside and outside to ensure that the bottom of the casing and the overburden soil are effectively sealed after the cement slurry is solidified (the sealing length is 1.5-2 m). In the present invention, the cement slurry is preferably prepared from water and cement, and the water-cement ratio (weight ratio) of the cement slurry is preferably 0.6 to 0.8, more preferably 0.6. In the present invention, the drilling in the bedrock section is preferably performed after the cement slurry is solidified. In the present invention, the conveying casing is used to protect the overburden soil and prevent the borehole from collapsing during filling by using the hydraulic filling method. After the conveying casing and the overburden soil are sealed, the present invention preferably continues to drill the bedrock section until the borehole penetrates a ceiling of the underground cavity. In the present invention, a bedrock bit is preferably used to drill the bedrock section, and the diameter of the borehole in the bedrock section is preferably smaller than the diameter of the borehole in the overburden soil. In the art, the diameters of commonly used survey drills are 89 mm, 108 mm, 127 mm, 146 mm, 168 mm and 219 mm. When the diameter of the borehole in the overburden soil is 146 mm, the diameter of the borehole in the bedrock section is preferably 127 mm. When the diameter of the borehole in the overburden soil is 168 mm, the diameter of the borehole in the bedrock section is preferably 146 mm. The present invention sets the diameter of the borehole in the bedrock section to be smaller than the diameter of the borehole in the overburden soil by one order, which increases the drilling speed. In the present invention, the drilling in the bedrock section is preferably performed with water, and the drilling is preferably underbalanced drilling (UBD) to ensure the verticality of the borehole. After drilling through the ceiling of the underground cavity, the present invention preferably places the drill pipe at the bottom of the underground cavity, verifies the parameters of the underground cavity determined by a karst survey, and then lifts the drill pipe. The parameters of the underground cavity include the height of the cavity, the presence or absence of a filler, and the type of the filler. After the drill pipe is lifted, the present invention fills sand and gravel aggregates into the underground cavity through the borehole by using a hydraulic filling method. In the present invention, the sand and gravel aggregates are preferably filled with a hydraulic filling device. The structural diagram of the hydraulic filling device is shown in FIG. 1, which includes a flushing pipe 2 and a filling funnel 3. The bottom of thefilling funnel communicates with a body of the flushing pipe. A slurry pump adapter 1 and a flange joint 5 are respectively provided at both ends of the flushing pipe. An exhaust pipe 4 is provided on a wall of the flushing pipe at one end close to the flange joint. The flushing pipe communicates with the conveying casing through the flange joint. In the present invention, the inner diameter of the flushing pipe is preferably 127 mm, and the thickness of the wall is preferably 8 mm. The size of a filler inlet (where the flushing pipe communicates with the filling funnel) on the flushing pipe is preferably 500 x 500 mm. The inner diameter of the exhaust pipe is preferably 50 mm, and the distance between the exhaust pipe and the flange joint is preferably 200 mm. In the present invention, the method of filling the sand and gravel aggregates is specifically: connect a slurry pump adapter of the hydraulic filling device with a water supply pipe of a slurry pump; turn on the slurry pump to send water, and fill the filling funnel with the sand and gravel aggregates, and flush the sand and gravel aggregates into the underground cavity under the action of a hydraulic force. The slurry pump is preferably a 3PNL pump, and the flow rate of the slurry pump is preferably 108 m 3/h. In the present invention, in order to prevent clogging of the borehole, the flushing of water is started before the filling of the sand and gravel aggregates and stopped after the stop of the filling of the sand and gravel aggregates. In a specific example of the present invention, it is preferable to have someone to monitor the mouth of the borehole and stop filling immediately for analysis and treatment once finding that the aggregates accumulate at the filling funnel, the mouth of the borehole ejects a gas or water, or the inside of the borehole sounds abnormally. During the filling process, attention should be paid to the height of the filler in the underground cavity. The height of the filler preferably does not exceed the ceiling of the underground cavity. In a specific example of the present invention, the filling is preferably stopped when the height of the filler is 0.5 m away from the ceiling of the underground cavity. In the present invention, the filling by the hydraulic filling method is shown in FIG. 2. The reference numerals in FIG. 2 include: 6. hydraulic filling device, 7. conveying casing, 8. underground cavity, 9. filler in the underground cavity, 10. sand and gravel aggregates filled in the underground cavity, 16. overburden soil, and 17. bedrock. In the present invention, the weight ratio of the water to the sand and gravel aggregates during the filling process is preferably 5:1 to 10:1, more preferably 6:1 to 8:1. The maximum particle size of the sand and gravel aggregates preferably does not exceed 30 mm. The present invention has no special requirement for the composition of the sand and gravel aggregates, and graded sand and gravel aggregates known to those skilled in the art can be used. In the present invention, the underground cavity is filled with the sand and gravel aggregates by using the hydraulic filling method. The filled sand and gravel aggregates occupy the space in the underground cavity, greatly reducing the amount of grouting and reducing the treatment cost. The filled sand and gravel aggregates also block or reduce the connecting channel between the underground cavity and the outside of the cavity, increasing the grouting pressure, controlling the slurry diffusion range, and improving the filling treatment effect of the underground cavity. After the filling is completed, the present invention grouts the underground through the borehole. The present invention preferably removes the hydraulic filling device before grouting. In the present invention, the method of grouting is preferably: insert a grouting pipe into the borehole, and extends the bottom end of the grouting pipe into the underground cavity; seal the gap between the top of the grouting pipe and the borehole with mixed slurry; and start grouting after the mixed slurry is solidified for at least 24 h. In the present invention, the grouting pipe is preferably a steel pipe with an outer diameter of 1-1.5 inches. The mixed slurry is preferably a mixture of cement slurry and water glass slurry. The water-cement ratio (weight ratio) of the cement slurry is preferably 0.6. The water glass slurry is preferably 300 B6 water glass. The cement slurry and the water glass slurry are preferably stirred separately, and are poured into the sealing part at the same time according to a volume ratio of 1:0.5 between the cement slurry and the water glass slurry. In the present invention, the sealing length is preferably not less than 2.0 m, and more preferably 2.0-3.0 m. The present invention preferably provides an exhaust pipe at the sealing part. The bottom of the exhaust pipe extends below the sealing part, and the top of the exhaust pipe is exposed above the sealing part. The exhaust pipe is used to exhaust the gas in the underground cavity during the grouting process, and to install a pressure gauge to monitor the pressure at the mouth of the borehole during grouting. In the present invention, the grouting is preferably started after the mixed slurry has solidified for at least 24 h, and more preferably after the mixed slurry has solidified for 24-48 h. The slurry for grouting is preferably prepared from a cementing material and water. The cementing material preferably includes a main agent and an auxiliary agent. The main agent is preferably cement, and the auxiliary agent is preferably fly ash and/or bentonite. In a specific example of the present invention, the mixing ratio of the fly ash and/or bentonite is preferably determined according to the design strength of the slurry solidified mass, and is preferably not more than 50 wt% of the added amount of cement. The water-to-binder ratio (weight ratio) of the slurry is preferably 0.6-1.2, and more preferably 0.8-1. In a specific example of the present invention, it is preferable to connect the grouting pipe with a grouting pump, and then perform grouting in the order of thin slurry first and thick slurry second. The water-to-binder ratio (weight ratio) of the thin slurry is preferably 0.8-1.2, and more preferably 1.0-1.2. The water-to-binder ratio (weight ratio) of the thick slurry is preferably 0.6- 0.8, and more preferably 0.6-0.7. The present invention has no special requirement for the specific injection volume of the thin slurry and the thick slurry, and an empirical injection volume can be used. In a specific example of the present invention, when the grouting volume reaches 50-80% of the design volume but the grouting pressure is very small or the grouting pressure is not significantly increased, intermittent grouting is preferably performed subsequently. If necessary, 2-5wt% of water glass is added to the slurry to reduce the solidification time of the slurry and control the diffusion range of the slurry. In the present invention, the pressure gauge is preferably not installed to the nozzle of the exhaust pipe at the beginning of grouting, but installed to the nozzle when there is no gas discharged at the nozzle of the exhaust pipe. The grouting of the present invention is shown in FIG. 3. The reference numerals in FIG. 3 include: 9. filler in the underground cavity; 10. sand and gravel aggregates filled in the underground cavity; 11. grouting pipe; 12. cement/water glass slurry solidified mass; 13. high-pressure hose; 14. pressure gauge; 15. exhaust pipe (pressure gauge installation pipe); 16. overburden soil; and 17. bedrock. The present invention stops grouting when the pressure at the mouth of the borehole is preferably greater than 1.0 MPa, and more preferably 1.5 MPa. In a specific example of the present invention, before stopping grouting, the pressure at the mouth of the borehole is preferably kept stable for 15 min after reaching the required pressure. After the grouting is stopped, the filling of the underground cavity is completed. After the grouting is completed, the present invention preferably takes out the grouting pipe and uses cement mortar to seal the borehole. The present invention has no special limit on the sealing method, and a conventional method can be used. The present invention further provides a hydraulic filling device, as shown in FIG. 1. The hydraulic filling device includes a flushing pipe 2 and a filling funnel 3. The bottom of the filling funnel communicates with a body of the flushing pipe. A slurry pump adapter 1 and a flange joint 5 are respectively provided at both ends of the flushing pipe. An exhaust pipe 4 is provided on a wall of the flushing pipe at one end close to the flange joint. The flushing pipe communicates with the conveying casing through the flange joint. The dimensions of the components are consistent with those in the above solution, and will not be repeated here. The hydraulic filling device provided by the present invention is used to fill karst caves or abandoned mining roadways, which has fast filling speed and convenient operation.
The solutions provided by the present invention are described in detail below with reference to the examples, but these examples may not be understood as a limitation to the protection scope of the present invention. Example 1 Tangshan, an industrial city in China's north Hebei province, is located where karst fissures are developed in a shallow burial area. The dynamic changes of groundwater have caused the Quatemary overburden structure to be damaged to varying degrees, resulting in many karst collapses. "Geological Disaster Treatment Project on Karst Collapse of Tangshan Stadium" adopted the method of the present invention to implement karst collapse treatment, and the J2 karst treatment borehole is taken as an example to illustrate the implementation process of the method for filling a covered karst cave by grouting according to the present invention. A karst survey showed that at the J2 borehole, the Quaternary overburden soil above the bedrock was 39.8 m in thickness, and an unfilled karst cave was at a depth of 45.1-55.7 m. (1) Determine a drilling position. This project used the karst survey hole as a borehole, which was located directly above the karst cave. (2) Drill in the overburden soil. A survey drilling rig was used to drill the overburden soil with a slurry wall, and the deviation of the verticality of the borehole was not more than 1%. Considering that the maximum particle size of the sand and gravel aggregates to be filled was mm, the design diameter of the borehole was 127 mm in the bedrock section and 168 mm in the overburden soil. During the treatment, the survey hole was expanded to make the diameter of the borehole reach 168 mm. The overburden soil section of the borehole was as thick as 39.8 m, and the drilling was stopped at 40.3 m to get ready to install a conveying casing. (3) Install the conveying casing. The conveying casing was installed to protect the overburden soil and prevent the borehole from collapsing during filling by using a hydraulic filling method. After drilling through the overburden soil above the bedrock surface, aCD146 mm conveying casing was inserted into the borehole. The conveying casing had a length of 40.5 m and a wall thickness of 4.5 mm, and the bottom of the casing extended into the bedrock for 0.5 m. After the casing was installed, 2.0 m deep cement slurry was injected to the bottom of the borehole by using a drill pipe. The conveying casing was lifted for 0.5-1.0 m and then lowered to the original position. In this way, the casing was filled with the cement slurry inside and outside to ensure that the casing and the overburden soil were effectively sealed after the cement slurry was solidified. The water-cement ratio of the cement slurry was 0.6. The drilling in the bedrock section was performed after the cement slurry was solidified.
(4) Drill in the bedrock section. The drill bit was replaced to drill in the bedrock section, and the diameter of the borehole in the bedrock section was 127 mm. The drilling in the bedrock section was performed with water, and the drilling was UBD to ensure the verticality of the borehole. The drilling was progressed until the borehole penetrated the ceiling of the underlying karst cave. After the ceiling of the cave was drilled through, the drill pipe was continuously lowered to the bottom of the karst cave. Then the parameters of the karst cave determined by the karst survey were verified. It was verified that the height of the karst cave was 10.0 m, and there was a 0.6 m filler at the bottom of the cave, which was red clay with bedrock fragments. (5) Fill by using a hydraulic filling method. A hydraulic filling device was installed on the top of the conveying casing. The tail of the hydraulic filling device was connected to a water supply pipe of a 3PNL pump. The 3PNL pump was turned on to fill a filling funnel with sand and gravel aggregates, which were washed into the cave under the action of a hydraulic force. In order to prevent clogging of the borehole, the flushing of the water was started first before the filling of the sand and gravel aggregates and stopped after the filling of the sand and gravel aggregates was stopped. During the filling process, the ratio of the water to the sand and gravel aggregates was controlled to 5:1 to 10:1, and the maximum particle size of the sand and gravel aggregates was 30 mm. During the filling process, a special person was assigned to monitor the mouth of the borehole. Once it was found that the aggregates accumulated at the filling funnel, the mouth of the borehole ejected a gas or water, or the inside of the borehole sounded abnormally, the filling was stopped immediately, and the situation was dealt with promptly. During the filling process, attention was paid to the height of the filler in the karst cave, and when the filler was 0.5 m away from the ceiling of the karst cave, the filling was stopped. Finally, the borehole was filled with totally 150.3 m 3 of graded aggregates. (6) Grout. The hydraulic filling device was removed, and then a grouting pipe was installed into the borehole. The grouting pipe extended into the karst cave for 0.5 m. A 2.0 m deep part at the top of the grouting hole was sealed by cement/water glass slurry. An exhaust pipe was installed at the sealing part, and the grouting was started after the slurry was solidified for 24 h. The cementing material in the injected slurry included cement and fly ash, and the mixing ratio of the fly ash was 50% by weight of cement. The grouting was performed in the order of thin slurry first and thick slurry second. The water-to-binder ratio of the thin slurry was 1.0, and the water-to-binder ratio of the thick slurry was 0.7. A total of 578.71 m3 of cement/fly ash slurry was injected into this borehole. At the end of the grouting, the pressure of the grouting pipe at the mouth of the borehole was 1.5 MPa, and the grouting was stopped after the pressure was stabilized for 15 min. After the completion of the treatment project, the standard penetration test (SPT) and the Rayleigh wave method were used for inspection. The results showed that the number of SPT blow counts increased from 4-6 to 18-38, the wave speed in the treatment area significantly increased, and there was no low-speed area, indicating that the treatment effect was significant. Example 2 The goaf roadway treatment area of Senze Coal and Aluminum Co., Ltd is located in Liulin County, Shanxi Province, China. The treatment area is about 150 m long from east to west and 45 m wide from north to south. The roadway was excavated for private mining of bauxite in the 1990s. The collapse of the roadway has caused ground subsidence, leading to road rupture and mountain cracking. The treatment was implemented by using the method of the present invention. According to the design scheme, the identified treatment area was to be filled by grouting (preliminarily 14 boreholes were arranged at designated positions and 3 arranged at non-designated positions). The Z3 treatment hole is taken as an example to illustrate the implementation process of the method of the present invention. The mining roadway that the borehole Z3 reached was basically north-south. The cross section of the roadway was horseshoe-shaped, with a height of about 2.0 m, a width of about 2.0 m and a buried depth of 31.5 m to 33.5 m. The two ends of the roadway led to a mountain (south side) and the outside of a road (north side), respectively. The roadway was well preserved and there was almost no filling in the roadway. (1) Determine a drilling position. The borehole was located directly above the roadway based on survey data. (2) Drill in the overburden soil. An XY-150 survey drilling rig was used to drill the overburden soil with a slurry wall, and the deviation of the verticality of the borehole was not more than 1%. Considering that the maximum particle size of the sand and gravel aggregates to be filled was 30 mm, the design diameter of the borehole was 127 mm in the bedrock section and 146 mm in the overburden soil. The overburden soil section of the borehole was as thick as 18.3 m, and the drilling was stopped at 18.8 m to get ready to install a conveying casing. (3) Install the conveying casing. The conveying casing was installed to protect the overburden soil and prevent the borehole from collapsing during filling by using a hydraulic filling method. After drilling through the overburden soil above the bedrock surface, aCD146 mm conveying casing was installed into the borehole. The conveying casing had a length of 19 m and a wall thickness of 4.5 mm, and the bottom of the casing extended into the bedrock for
0.5 m. After the casing was installed, 2.0 m deep cement slurry was injected to the bottom of the borehole by using a drill pipe. The conveying casing was lifted for 0.5-1.0 m and then lowered to the original position. In this way, the casing was filled with the cement slurry inside and outside to ensure that the casing and the overburden soil were effectively sealed after the cement slurry was solidified. The water-cement ratio of the cement slurry was 0.6. The drilling in the bedrock section was performed after the cement slurry was solidified. (4) Drill in the bedrock section. The drill bit was replaced to drill in the bedrock section, and the diameter of the borehole in the bedrock section was 127 mm. The drilling in the bedrock section was performed with water, and the drilling was UBD to ensure the verticality of the borehole. The drilling was progressed until the borehole penetrated the ceiling of the underlying roadway. After the ceiling of the roadway was drilled through, the drill pipe was continuously lowered to the bottom of the roadway. Then the parameters of the roadway determined by a survey were verified. The inspection of a borehole television (TV) showed that the roadway was 2.0 min height and well preserved, there was almost no filling in the roadway, and the roadway extended to both sides long. (5) Fill by using a hydraulic filling method. A hydraulic filling device was installed on the top of the conveying casing. The tail of the hydraulic filling device was connected to a water supply pipe of a 3PNL pump. The 3PNL pump was turned on to fill a filling funnel with sand and gravel aggregates, which were washed into the roadway under the action of a hydraulic force. In order to prevent clogging of the borehole, the flushing of the water was started first before the filling of the sand and gravel aggregates and stopped after the filling of the sand and gravel aggregates was stopped. During the filling process, the ratio of the water to the sand and gravel aggregates was controlled to 5:1 to 10:1, and the maximum particle size of the sand and gravel aggregates was 20 mm. During the filling process, a special person was assigned to monitor the mouth of the borehole. Once it was found that the aggregates accumulated at the filling funnel, the mouth of the borehole ejected a gas or water, or the inside of the borehole sounded abnormally, the filling was stopped immediately, and the situation was dealt with promptly. During the filling process, attention was paid to the height of the filler in the roadway, and when the filler was 0.2 m away from the ceiling of the roadway, the filling was stopped. Finally, the borehole was filled with totally 122.6m3 of graded sand and gravel aggregates. (6) Grout. The hydraulic filling device was removed, and then a grouting pipe was installed into the borehole. The grouting pipe extended into the roadway for 0.5 m. A 2.0 m deep part at the top of the grouting hole was sealed by cement/water glass slurry. An exhaust pipe was installed at the sealing part, and the grouting was started after the slurry was solidified for 24 h. The cementing material in the injected slurry included cement and fly ash, and the mixing ratio of the fly ash was 30% by weight of cement. The grouting was performed in the order of thin slurry first and thick slurry second. The water-to-binder ratio of the thin slurry was 1.0, and the water-to-binder ratio of the thick slurry was 0.7. A total of 128.5 m 3 of cement/fly ash slurry was injected into the borehole. At the end of the grouting, the pressure of the grouting pipe at the mouth of the borehole was 1.2 MPa, and the grouting was stopped after the pressure was stabilized for 15 min. After the treatment was completed, the grouting effect was detected by means of drilling and geophysical exploration. A cement slurry solidified mass and a cement slurry/roadway filler mixture were drilled directly from the detection borehole, and then a cement slurry/bedrock solidified mass was drilled from the construction treatment borehole. The geophysical survey found that the grouting treatment and crack filling caused significant changes in the physical and electrical characteristics of the goaf roadway, indicating that the grouting treatment effect was significant. The above described are merely preferred implementations of the present invention. It should be noted that a person of ordinary skill in the art may further make several improvements and modifications without departing from the principle of the present invention, but such improvements and modifications shall also be deemed as falling within the protection scope of the present invention.
Claims (5)
1. A method for filling an underground cavity in bedrock by grouting, comprising the following steps: (1) determining a drilling position according to a position of the underground cavity, which is directly above the underground cavity; (2) drilling through overburden soil above the bedrock at the determined drilling position; (3) installing a conveying casing into a borehole, extending the bottom of the conveying casing into the bedrock section, and using cement slurry to seal between the bottom of the conveying casing and the overburden soil; (4) continuing to drill the bedrock section until the borehole penetrates a ceiling of the underground cavity;
(5) filling sand and gravel aggregates into the underground cavity through the borehole by using a hydraulic filling method; and (6) grouting the underground cavity through the borehole.
2. The method according to claim 1, wherein the underground cavity in the bedrock is a covered karst cave or an abandoned mining roadway in the bedrock.
3. The method according to claim 1, wherein in step (2), a diameter of the borehole in the overburden soil is not less than 4 times a maximum particle size of the sand and gravel aggregates used for filling; wherein in step (3), the depth of the bottom of the conveying casing extending into the bedrock section is not less than 0.5 m; the diameter of the conveying casing is 146-168 mm; the conveying casing is provided with a flange on the top; wherein in step (5), the sand and gravel aggregates are filled with a hydraulic filling device; the hydraulic filling device comprises a flushing pipe and a filling funnel; the bottom of the filling funnel communicates with a body of the flushing pipe; a slurry pump adapter and a flange joint are respectively provided at both ends of the flushing pipe; an exhaust pipe is provided on a wall of the flushing pipe at one end close to the flange joint; the flushing pipe communicates with the conveying casing through the flange joint.
4. The method according to claim 1, wherein in step (6), the method of grouting is specifically: inserting a grouting pipe into the borehole, and extending a bottom end of the grouting pipe into the underground cavity; sealing a gap between the top of the grouting pipe and the borehole with mixed slurry; and starting grouting after the mixed slurry is solidified for at least 24 h.
5. A hydraulic filling device, comprising a flushing pipe and a filling funnel, wherein the bottom of the filling funnel communicates with a body of the flushing pipe; a slurry pump adapter and a flange joint are respectively provided at both ends of the flushing pipe; an exhaust pipe is provided on a wall of the flushing pipe at one end close to the flange joint.
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| CN202010422625.2A CN111535297A (en) | 2020-05-19 | 2020-05-19 | Method for filling underground cavity of foundation rock stratum by filler grouting and hydraulic filling device |
| CN202010422625.2 | 2020-05-19 |
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| AU2020101047A4 true AU2020101047A4 (en) | 2020-07-23 |
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