CN107178077B - karst area karst cave overburden grouting reinforcement structure and design method thereof - Google Patents
karst area karst cave overburden grouting reinforcement structure and design method thereof Download PDFInfo
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- CN107178077B CN107178077B CN201610135208.3A CN201610135208A CN107178077B CN 107178077 B CN107178077 B CN 107178077B CN 201610135208 A CN201610135208 A CN 201610135208A CN 107178077 B CN107178077 B CN 107178077B
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- 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
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- Consolidation Of Soil By Introduction Of Solidifying Substances Into Soil (AREA)
Abstract
the invention provides a karst area karst cave overburden grouting reinforcement structure and a design method thereof. The consolidation grouting layer is formed by grouting into gravel soil from a drill hole by using grouting equipment, and the thickness of the consolidation grouting layer is generally 5-8 m. The actual distribution length of the consolidation grouting layer is consistent with that of the karst cave, the width is calculated according to the width of the bottom of the roadbed, and the width influenced by collapse is accumulated. The grouting reinforcement structure for the soil layer on the karst cave in the karst region mainly has 3 advantages, and firstly, water is discharged, and the soil layer near the top plate of the karst cave is improved from a soft plastic state to a plastic hard plastic state, so that the erosion and corrosion resistance is improved; secondly, the seepage-proofing capacity is improved, so that the change speed of the underground water level is slowed down; thirdly, a thick liquid vein net is formed to compact the adjacent soil body, thereby improving the modulus of the soil body, reducing the Poisson ratio and improving the stress condition of the top plate of the karst cave.
Description
Technical Field
The invention relates to a foundation reinforcement technology in the field of rock and soil, in particular to a technology for processing an overlying soil layer of a karst cave in a karst region.
Background
The prior karst foundation treatment technology is dedicated to reinforcing the karst cave, mainly comprises measures such as blasting backfill, filling, dynamic compaction, grouting and the like, but is only suitable for the condition that the karst cave is buried shallowly. When the karst cave is deeply buried, if a drilling blasting mode is adopted, although the top plate of the karst cave can be exploded, the overlying soil layer is collapsed, and the blasting opening is easily buried. Even if blasting is successful, due to the deep burial, there is a great risk if backfilling is performed manually or mechanically. If a dynamic compaction mode is adopted, the effective compaction depth is limited, so that the dynamic compaction method can not be applied to the deep karst cave. If the karst caves are filled by grouting, the karst caves are often communicated with each other, so that excessive materials are consumed along with the loss of underground water, the effect is inconsistent, and the requirement of injecting hundreds of tons of cement slurry cannot be met.
Recent research shows that most of collapse of deep-buried karst caves is related to soil layer collapse caused by artificial pumping. Deep burying means that the soil layer near the bedrock surface (karst cave top plate) is in a plastic or even soft plastic state under the soaking of underground water, and deformation can be caused once disturbance. Because the underground water level of the manual pumping is rapidly reduced and runs off in the karst cave, the overburden layer on the karst cave is eroded and collapsed along with the artificial pumping. Therefore, the best mode for treating the deep-buried karst cave is neither blasting backfill nor dynamic compaction grouting. It is important to limit pumping to reduce the fluctuation of underground water level and to reinforce the overburden layer on the karst cave to prevent erosion by water. In consideration of the actual situation, the limitation of water pumping is not easy to realize, and based on the consideration, a new karst foundation treatment technology is very necessary to be provided, which aims to reinforce the soil layer on the karst cave, further improve the stability and reduce the collapse.
disclosure of Invention
Aiming at the problem that the existing karst area foundation treatment technology is difficult to treat the deep-buried karst cave, the invention provides a karst area karst cave overburden grouting reinforcement structure design and a calculation method. In order to achieve the purpose, the invention adopts the following technical scheme: a karst area karst cave overburden grouting reinforcement structure sequentially comprises limestone, a karst cave, a consolidation grouting layer, breccia soil, silty clay and roadbed filling from bottom to top, wherein the consolidation grouting layer is formed by grouting and consolidating in the breccia soil through drilling holes by using grouting equipment, and the thickness of the consolidation grouting layer is generally 5-8 m.
the actual distribution length of the consolidation grouting layer is consistent with that of the karst cave, the width is calculated according to the width of the bottom of the roadbed, and the collapse influence width d is accumulated.
the drilling depth is 2m above the earth-rock interface, the drilling depth is divided into two types of vertical holes and inclined holes, the mode of the vertical holes is still adopted in the roadbed range, the inclined holes are drilled outwards at the slope toe of the roadbed, and the inclined angles are calculated according to factors such as collapse influence width, grouting diffusion width and the like and a corresponding design method.
In order to achieve the purpose, the invention also provides a design method of the karst region karst cave overburden grouting reinforcement structure, which comprises the following steps:
1) calculating the collapse influence width d:
Assuming that the collapse affecting width is d, the following parameters are introduced:
H-karst cave overburden thickness, unit is m;
Alpha-collapse angle in degrees;
it is clear that there is d = Hcot alpha,
2) Calculating the inclination angle beta:
The depth of the drill hole (13) is 2m above the earth-rock interface, the drill hole is divided into a vertical hole and an inclined hole, the inclined hole is drilled outwards at the slope toe of the embankment in the mode of the vertical hole in the roadbed range, and the inclination angle beta is obtained by calculation according to the collapse influence width d, the grouting diffusion width w and the like;
for calculating the drill hole inclination angle beta at the slope toe of the embankment, the following parameters are introduced firstly:
h-drilling depth in m, from the ground;
w-slip casting diffusion width is m;
obviously with borehole inclination,
in summary, the inclination angle β of the drill hole at the toe of the embankment can be calculated according to the following formula:
The drilling depth h should be 2m above the earth-rock interface, i.e.:
h=H-2
Thus, the covering soil layer is consolidated into an artificial top plate by a grouting method, and the artificial top plate and the karst cave top plate form a composite top plate together, so that the bearing capacity of the karst cave is improved;
The breccia soil (17) and the silty clay (18) are typical karst cave covering soil, and considering the soil characteristics of the breccia soil (17) and the silty clay (18), the collapse angle alpha is 45 degrees, the grouting diffusion width w is 5m, and in sum, the calculation method of the drilling inclination angle beta at the slope toe of the embankment is simplified as follows:
。
under the general condition, the erosion cracks on the basal rock surface of the karst area are relatively developed, under the condition, the overlying soil layer, particularly near the basal rock surface, is easily eroded to form a soil cave under the influence of ground seepage and underground water level reduction, a water-resisting consolidation layer is formed by adopting a grouting method, and the consolidation thickness is generally 5-8 m.
the invention has the advantages that:
The karst area karst cave overburden grouting reinforcement structure is particularly suitable for deeply burying the karst cave, wherein the deep burying usually means that the top plate of the karst cave is subjected to smaller additional stress, and simultaneously means that the karst cave overburden is rich in underground water and is influenced by the underground water, the overburden of the karst cave is usually weak, and collapse is possible once the underground water level is greatly changed.
the soil layer on the reinforced karst cave is mainly 3 good, and firstly, the water is discharged, and the soil layer near the top plate of the karst cave is improved from a soft plastic state to a hard plastic state, so that the erosion and corrosion resistance is improved; secondly, the seepage-proofing capacity is improved, so that the change speed of the underground water level is slowed down; thirdly, a thick liquid vein net is formed to compact the adjacent soil body, thereby improving the modulus of the soil body, reducing the Poisson ratio and improving the stress condition of the top plate of the karst cave.
drawings
FIG. 1 is a schematic diagram of the grouting reinforcement structure of the overburden layer on the karst cave.
fig. 2 is a schematic structural view of a perforated pipe of the grouting equipment used in the invention.
Fig. 3 is a schematic view illustrating installation of construction equipment used in the present invention.
reference numerals: 1. a pulp inlet pipe; 2. a slurry return pipe; 3. a floral tube; 4. a pressure gauge; 5. a slurry inlet valve; 6. a slurry return valve; 7. a floral tube valve; 8. a fabric; 9. filling soil; 10. flower holes; 11. an adhesive tape; 12. a roadbed; 13. drilling; 14. limestone; 15. karst cave; 16. solidifying the grouting layer; 17. a gravel soil; 18. a powdery clay; 19. filling soil into the roadbed; 20. a soil-stone interface; 21. a hypothetical collapse pit; 22. the collapse affects the lines.
Detailed Description
embodiments of the present invention are described in detail below with reference to the accompanying drawings:
As shown in fig. 1, a karst region karst cave overburden grouting reinforcement structure comprises, from bottom to top, limestone 14, a karst cave 15, a consolidation grouting layer 16, breccia soil 17, silty clay 18 and roadbed filling 19. The consolidation grouting layer 16 is formed by grouting and consolidating the drilling holes 13 into the gravel soil 17 by using grouting equipment, and the thickness is generally 5-8 m.
the actual distribution length of the consolidation grouting layer 16 is consistent with that of the karst cave 15, the width is calculated according to the width of the bottom of the roadbed, and the collapse influence width d is accumulated. The depth of the drill hole 13 is more than 20 m of the earth-rock interface, the drill hole is divided into a vertical hole and an inclined hole, the mode of the vertical hole is still adopted in the roadbed range, the inclined hole is drilled outwards at the slope foot of the embankment, and the inclination angle beta is obtained by calculation according to the collapse influence width d, the grouting diffusion width w and the like.
a design method of a karst region karst cave overburden grouting reinforcement structure comprises the following steps:
1) Calculating the collapse influence width d:
Assuming that the collapse affecting width is d, the following parameters are introduced:
h-karst cave overburden thickness, unit is m;
Alpha-collapse angle in degrees;
It is clear that there is d = Hcot alpha,
2) Calculating the inclination angle beta:
the depth of the drill hole (13) is 2m above the earth-rock interface, the drill hole is divided into a vertical hole and an inclined hole, the inclined hole is drilled outwards at the slope toe of the embankment in the mode of the vertical hole in the roadbed range, and the inclination angle beta is obtained by calculation according to the collapse influence width d, the grouting diffusion width w and the like;
for calculating the drill hole inclination angle beta at the slope toe of the embankment, the following parameters are introduced firstly:
h-drilling depth in m, from the ground;
w-slip casting diffusion width is m;
obviously with borehole inclination,
In summary, the inclination angle β of the drill hole at the toe of the embankment can be calculated according to the following formula:
the drilling depth h should be 2m above the earth-rock interface, i.e.:
h=H-2
thus, the covering soil layer is consolidated into an artificial top plate by a grouting method, and the artificial top plate and the karst cave top plate form a composite top plate together, so that the bearing capacity of the karst cave is improved;
the breccia soil (17) and the silty clay (18) are typical karst cave covering soil, and considering the soil characteristics of the breccia soil (17) and the silty clay (18), the collapse angle alpha is 45 degrees, the grouting diffusion width w is 5m, and in sum, the calculation method of the drilling inclination angle beta at the slope toe of the embankment is simplified as follows:
。
As shown in fig. 2 and 3, a grouting device for grouting and reinforcing an overburden layer on a karst cave in a karst region comprises a grout inlet pipe 1, a grout return pipe 2, a perforated pipe 3, a pressure gauge 4 and a hole sealing device.
the pulp inlet pipe 1 is provided with a pulp inlet valve 5, the pulp return pipe 2 is provided with a pulp return valve 6, and the perforated pipe 3 is provided with a valve 7.
The lowest precision of the pressure gauge 4 can reach 0.01MPa, and the maximum measuring range can reach 2 MPa.
The bottom of the perforated pipe 3 is provided with a perforated hole 10, and the outer side of the perforated hole 10 is wound with an adhesive tape 11 in advance. The tape 11 can remain intact during placement of the floral tube 3 in the borehole 13 without being punctured by the drill cuttings.
the upper part of the perforated pipe 3 is exposed for 0.5-1.5 m in length so as to be conveniently connected with the slurry inlet pipe 1, the slurry return pipe 2, the pressure gauge 4, the valve and other components. The hole sealing device is formed by tamping the fabric 8 and the pad soil 9 in a layering manner.
the fabric 8 and the pad 9 must have certain pores to be used as exhaust channels and stop the slurry rather than the air.
the construction method for grouting and reinforcing the overburden layer on the karst cave in the karst region comprises the following steps:
S1) installing grouting pipe
And after drilling, checking the depth of the drilled hole 13, and placing the perforated pipe 3 under the condition that no hole collapse is confirmed, otherwise, cleaning the hole by using a drilling machine. Some holes 13 are not grouted later, and are often left for one or more days, during which the possibility of hole collapse is very high if rainfall is encountered again. Therefore, the depth of the borehole 13 should be checked before placing the floral tube 3 to avoid poor grouting.
The bottom of the perforated pipe 3 is provided with a perforated hole 13, and the outer side of the perforated hole 13 is wound with an adhesive tape 11 in advance so as not to be blocked by drilling slag in the placing process. In the process of injecting the grout, the adhesive tape 11 falls off under the action of the grout, so that the flower holes 10 are communicated, and the grouting is not influenced.
the traditional hydraulic and pneumatic grout stopping plug can only be used in a complete rock stratum, and the grout stopping effect is not ideal when the traditional hydraulic and pneumatic grout stopping plug is used in a loose soil layer. Therefore, a method for compacting the fabric 8 and the pad 9 in layers is provided, which is simple but not ineffective. In addition, because the fabric 8 and the pad 9 always have certain pores, the fabric can be used as an exhaust channel to stop slurry and not stop air, thereby better discharging air bubbles in cement slurry and further improving the grouting quality.
s2) grouting
And after the grout inlet pipe 1, the grout return pipe 2 and the perforated pipe 3 are completely installed, closing the grout return valve 6, and opening the perforated pipe valve 7 and the grout inlet valve 5 in sequence to start grouting. A pressure gauge 4 is installed at the orifice to control the final filling condition. The grouting pressure is noticed at any moment in the grouting process, and if the grouting pressure exceeds 0.35MPa, the slurry return valve 6 is opened in time to unload the slurry to within 0.25MPa so as to avoid the arch and crack of the roadbed caused by overlarge pressure.
S3) final note
In general, the following final-note conditions may be employed:
after the grouting pressure exceeds 0.35MPa and the slurry return valve 6 is opened to unload to 0.25MPa for 3 continuous times, the slurry return amount is already large, the slurry inlet amount is correspondingly reduced, and the final grouting condition can be met.
more preferably, if a flowmeter is further mounted on the slurry inlet pipe 1, the following final injection conditions can be adopted:
a. the final injection pressure reaches 0.25-0.35 MPa, the slurry suction amount is not more than 40L/min, and the final injection pressure is maintained for 30 min.
b. The single-hole grouting amount reaches 3m3and the pulp inlet amount is obviously reduced.
The perforated pipe 3 should be pulled out immediately after the grouting is finished to prevent the grout from solidifying in the perforated pipe 3. After the floral tube 3 is pulled out, the floral tube 3 is washed in time to keep clean and smooth. Holes left after the pipe is pulled out are sealed by cement paste or C15 concrete in time. The grouting must be continued and should be resumed early if interrupted for any reason, or else the borehole 13 should be flushed immediately and the grouting resumed thereafter.
s4) processing method for drilling through karst cave top plate
if the karst cave is exposed by penetrating through the karst cave top plate in the drilling process, the following technical measures of firstly carrying out sand and then carrying out slurry can be adopted:
a. and (3) tying and hanging a heavy object by using a lifting rope, fixing the free end of the lifting rope near the drilled hole, wherein the length of the lifting rope is preferably 2 meters longer than the depth of the drilled hole, the lifting rope is firmer as much as possible, the heavy object is tightly tied and hung, and meanwhile, the diameter of the heavy object is not more than 30 mm.
b. the end of the suspended weight is placed into the borehole so that the weight rests substantially at the bottom opening of the borehole and the lifting rope is re-secured. The lifting rope is shaken to enable the weight to be changed back and forth so as to confirm that the weight is bound and hung well and cannot fall off easily.
c. and (4) filling sand into the drill hole until the position of the bottom orifice of the drill hole is reached, and judging whether a heavy object hung by the lifting rope is buried by the sand or not and whether the heavy object can be lifted easily or not.
d. And taking out the lifting rope, grouting into the drill hole by adopting the grouting pressure of 0.1MPa, and subsequently adjusting the grouting pressure according to the grouting speed. If the volume of the karst cave is too large, materials such as sand, silt, fly ash and the like can be mixed into the slurry.
The above list is only one embodiment of the present invention. Obviously, the structural design and calculation method of the present invention are not limited to the above embodiments, and many variations are possible. All modifications which can be derived or suggested by a person skilled in the art from the disclosure of the present invention are to be considered within the scope of the invention.
Claims (1)
1. the utility model provides a karst area solution cavity coats soil layer slip casting reinforced structure which characterized in that: the cement-based gravel-gravel combined road bed sequentially comprises limestone (14), a karst cave (15), a consolidation grouting layer (16), breccid soil (17), silty clay (18) and road bed filling soil (19) from bottom to top, wherein the consolidation grouting layer (16) is formed by grouting and consolidating through a drilling hole (13) into the breccid soil (17) by using grouting equipment, the depth of the drilling hole (13) is 2m above an earth-stone interface (20) and is divided into a vertical hole and an inclined hole, the range of the road bed (12) still adopts the mode of the vertical hole, the slope foot of the road bed (12) outwards drills the inclined hole, and the inclined hole is obtained by calculating according to a collapse influence width and a grouting diffusion width and a corresponding design method; if the top plate of the karst cave is drilled through carelessly in the drilling process, firstly filling sand and then grouting, and adopting a lifting rope to bind and hang a heavy object to judge the sand filling condition;
the design method of the karst area karst cave overburden grouting reinforcement structure comprises the following steps:
1) Calculating the collapse influence width d:
Assuming that the collapse affecting width is d, the following parameters are introduced:
h-karst cave overburden thickness, unit is m;
Alpha-collapse angle in degrees;
it is clear that there is d = Hcot alpha,
2) Calculating the inclination angle beta:
The depth of the drill hole (13) is 2m above the earth-rock interface, the drill hole is divided into a vertical hole and an inclined hole, the inclined hole is drilled outwards at the slope toe of the embankment in the mode of the vertical hole in the roadbed range, and the inclination angle beta is obtained by calculation according to the collapse influence width d and the grouting diffusion width w;
For calculating the drill hole inclination angle beta at the slope toe of the embankment, the following parameters are introduced firstly:
h-drilling depth in m, from the ground;
w-slip casting diffusion width is m;
Obviously with borehole inclination；
In summary, the inclination angle β of the drill hole at the toe of the embankment is calculated according to the following formula:
；
the drilling depth h should be 2m above the earth-rock interface, i.e.:
h=H-2；
Thus, the covering soil layer is consolidated into an artificial top plate by a grouting method, and the artificial top plate and the karst cave top plate form a composite top plate together, so that the bearing capacity of the karst cave is improved;
The breccia soil (17) and the silty clay (18) are typical karst cave covering soil, and considering the soil characteristics of the breccia soil (17) and the silty clay (18), the collapse angle alpha is 45 degrees, the grouting diffusion width w is 5m, and in sum, the calculation method of the drilling inclination angle beta at the slope toe of the embankment is simplified as follows:
。
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| CN108842754B (en) * | 2018-07-05 | 2020-03-17 | 浙江科技学院 | Grouting reinforcement method and device in gravel layer rich in flowing underground water |
| CN111305027B (en) * | 2020-03-04 | 2021-04-27 | 桂林电子科技大学 | Rapid repairing construction method and repairing structure for subsidence of karst area pavement |
| CN111393102A (en) * | 2020-03-24 | 2020-07-10 | 王新文 | Grouting material for reinforcing silty cohesive soil karst caves, preparation method and application thereof |
| CN111501424A (en) * | 2020-05-08 | 2020-08-07 | 中铁二院工程集团有限责任公司 | Comprehensive treatment method for subgrade karst collapse |
| CN112626950B (en) * | 2020-11-24 | 2022-09-30 | 山东省交通规划设计院集团有限公司 | Treatment method for karst roadbed by combining soil arch effect |
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| US5256004A (en) * | 1990-07-31 | 1993-10-26 | Fondazioni Speciali, S.R.L. | Method of forming consolidated earth columns by injection and the relevant plant and column |
| CN102071607B (en) * | 2011-01-26 | 2013-12-18 | 北京中铁瑞威基础工程有限公司 | Railroad bed repair method without affecting existing running conditions |
| CN105297736B (en) * | 2015-10-13 | 2017-05-03 | 长安大学 | Sequential deepening grouting construction technology and device for soil covering layer on karst cave in karst area |
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