Construction method for treating steep slope of karst area through grouting

Abstract

The invention discloses a construction method for treating a steep inclined slope in a karst area through grouting, and belongs to the field of karst area construction methods. S2, drilling is conducted; s3, a grouting pipe is installed; s4, preparing slurry; s5, performing grouting operation; and S6, hole sealing. According to the geological characteristics of a karst development area, the position of the engineering pile located on the abrupt slope surface is determined by combining a one-pile-one-exploration and karst survey report, then grouting holes are buried in the periphery of the engineering pile, the karst area is reinforced through grouting, the hidden karst cave abrupt slope surface is eliminated, the stability and perpendicularity of drilling holes are ensured, and the stability and perpendicularity of the drilling holes are improved. And the possibility of inclined drilling and drill rod breakage caused by uneven stress of the drill bit is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of construction methods in karst areas, and in particular to a construction method for grouting treatment of steep slopes in karst areas. Background Art

[0002] Karst development area refers to a special landform area formed by the long-term chemical dissolution of water in the distribution area of ​​soluble rocks (such as limestone, dolomite, gypsum, etc.). In these areas, groundwater and surface water form various karst landforms such as caves, karst depressions, stalagmites, stone pillars, stalactites, stone curtains, etc. through dissolution, erosion, and sedimentation.

[0003] As a special geological environment, the karst development area has diverse underground karst forms, widespread and irregular distribution, which brings many technical challenges to bored pile construction. Karst development areas usually have irregular geological structures such as cavities, cracks, steep slopes, etc. Due to uneven stress, the borehole may be deviated, the casing may not reach the bearing layer depth normally, and even the drill rod may break, resulting in the scrapping of the borehole, which seriously affects the overall construction quality and safety of the pile foundation project. Summary of the invention

[0004] In order to improve the problem of inclined drilling and drill rod breakage that are prone to occur during pile foundation construction in karst development areas, the present application provides a grouting treatment construction method for steep slopes in karst areas.

[0005] The present application provides a grouting treatment method for steep slopes in karst areas, which adopts the following technical solutions: A construction method for grouting treatment of steep slopes in karst areas, comprising the following steps: S1. Pretreatment area layout: Based on the geological survey report and the results of one pile and one exploration, a bedrock isovalue map is formed, and the karst development area with steep bedrock surface changes and large buried areas is selected to determine the engineering pile position in the grouting pretreatment area. With the engineering pile as the center point, grouting holes are set at intervals of 2m around; S2. Drilling: The grouting hole position is determined by on-site measurement and setting out, and the hole is drilled using a drilling rig. The steel casing is pressed into the hole while drilling until the steel casing enters the cave layer; S3, installing grouting pipes: after the four grouting holes of each pile foundation are drilled and the steel casing is installed, the grouting pipes are installed; S4. Slurry preparation: The grouting liquid mix ratio is water: cement = 0.8:1. According to the volume of the pre-prepared slurry, the required amount of cement and water is calculated according to the water-cement ratio. PO 42.5 ordinary Portland cement is used in the grouting construction; S5. Grouting operation: Use a high-pressure grouting pump to inject cement slurry into the cave through the grouting pipe. Grouting requires small amounts of multiple, repeated, and layered grouting. The layer height is preferably 1m. Each pile position has four grouting holes for cyclic grouting. The grouting speed is controlled at 50-100L / min. After each layer of grouting is completed, the grouting flower pipe is lifted to enter the next cycle; S6. Sealing: After the grouting of all grouting holes and inspection holes is completed, grouting and sealing will be carried out immediately. The "pressure grouting and sealing method" will be adopted. The slurry will be replaced with concentrated cement slurry with a water-cement ratio of 0.5:1. The grouting pressure can be determined according to the specific conditions of the project.

[0006] By adopting the above technical scheme, according to the geological characteristics of the karst development area, combined with the pile-by-pile exploration and karst investigation report, the position of the engineering pile on the steep slope is determined, and then grouting holes are buried around the engineering piles. The karst area is reinforced by grouting, the steep slope of hidden karst caves is eliminated, the stability and verticality of the borehole are ensured, and the possibility of oblique drilling and drill rod breakage due to uneven force on the drill bit is reduced. It can also effectively reduce emergencies during pile foundation construction in karst development areas, speed up the construction progress to a certain extent, and reduce construction costs.

[0007] Preferably, the drilling rig is a 100-type drilling rig, and the drill bit size of the drilling rig is 108 mm; the diameter of the steel casing is 110 mm, and the wall thickness of the steel casing is 5.6 mm.

[0008] By adopting the above technical solution and using drilling rigs and steel casing of specific specifications, the consistency and reliability of drilling are ensured, the stability of grouting holes is enhanced, and the risks of hole collapse and drill rod breakage are reduced.

[0009] Preferably, in S2, the basis for judging that the steel casing has entered the karst layer is that the drilling speed of the drilling rig suddenly increases, indicating that the drill bit of the drilling rig has broken through the upper soil layer of the karst cave and entered the karst cave layer.

[0010] By adopting the above technical solution, whether the steel casing has entered the cave layer can be judged by the change of drilling speed, which provides an intuitive and accurate method to determine the drilling depth and helps to improve the accuracy of grouting.

[0011] Preferably, in S2, detailed drilling records should be made during the drilling process, including a geological description of the borehole, the difficulty of drilling, and whether there are voids, etc., and compared with the original geotechnical engineering survey report, and the drilling depth should be adjusted in real time.

[0012] By adopting the above technical solution, detailed drilling records and geological descriptions help to adjust the construction plan in real time, ensure the adaptability and flexibility of grouting operations, and improve construction efficiency and safety.

[0013] Preferably, in S3, the grouting flower tube is made of a hard plastic tube with an inner diameter of 38 mm, and there are 60-80 holes within a length of 1 m at the bottom end of the grouting flower tube. The holes are arranged in a plum blossom shape in four rows along the center line of the grouting flower tube, and the diameter of the holes is 1 mm-3 mm.

[0014] By adopting the above technical solution, the special design and layout of the grouting flower tube optimizes the distribution of the slurry and ensures the uniformity and effectiveness of the grouting effect.

[0015] Preferably, in S3, after the grouting flower pipe is installed, a certain proportion of cement slurry and water glass diluted to a certain proportion are used to inject and seal the hole in the annular gap between the hole wall of the steel casing and the grouting flower pipe.

[0016] By adopting the above technical solution, cement slurry and water glass are used to seal the hole between the steel casing and the grouting flower pipe, which enhances the stability of the hole wall, prevents the slurry from flowing up and flowing, and improves the grouting quality.

[0017] Preferably, in S3, the top of the grouting flower pipe emerges 200mm-300mm above the ground.

[0018] By adopting the above technical solution, the design of the top of the grouting flower pipe protruding from the ground avoids the interference of debris and mud, ensuring the cleanliness of the grouting process and the smooth flow of the grouting pipe.

[0019] Preferably, in S4, if the space volume in the cave is large and the water permeability is strong, a certain amount of water glass is added to the grouting liquid, and the ratio of the grouting liquid is water: cement: water glass = 1:1:1.

[0020] By adopting the above technical solution, water glass is added to large-volume, highly permeable caves, which improves the stability and permeability of the grouting liquid and ensures the grouting effect, especially under complex geological conditions.

[0021] Preferably, in S5, when the grouting reaches one of the following criteria, the grouting of the hole is terminated: a. The grouting orifice pressure is maintained at 0.3Mpa-0.5MPa, and the grouting volume is not more than 40L / min, and it is maintained for 30min; b. When the bedrock of the grouting borehole is intact, or when grouting is repeated and the orifice pressure exceeds 1.5MPa; c. When the grouting point is 3m-5m outside the grouting range; d. When the single hole grouting volume reaches 1.5-2.0 times the average grouting volume, and the grouting volume is significantly reduced; When the grouting fails to reach the above-mentioned completion standard, the hole shall be cleaned and grouting shall be performed again.

[0022] By adopting the above technical solution, clear grouting completion standards help construction personnel to accurately judge the completion of the grouting process, ensure the adequacy and uniformity of grouting, and improve the reliability and safety of construction; when these standards are not met, the measures of cleaning the hole and re-grouting ensure that the grouting effect meets the standards and ensure the quality of the project.

[0023] In summary, the present application includes at least one of the following beneficial technical effects: 1. According to the geological characteristics of the karst development area, combined with the pile-by-pile exploration and karst investigation report, the location of the engineering pile on the steep slope is determined, and then grouting holes are buried around the engineering piles. The karst area is reinforced by grouting, the steep slope of the hidden karst cave is eliminated, the stability and verticality of the borehole are ensured, and the possibility of oblique drilling and drill rod breakage due to uneven force on the drill bit is reduced. It can also effectively reduce emergencies during the pile foundation construction process in the karst development area, speed up the construction progress to a certain extent, and reduce the construction cost; 2. The change in drilling speed is used to determine whether the steel casing has entered the cave layer, providing an intuitive and accurate method to determine the drilling depth, which helps to improve the accuracy of grouting; 3. Use cement slurry and water glass to seal the hole between the steel casing and the grouting flower pipe, which enhances the stability of the hole wall, prevents the slurry from flowing up and flowing, and improves the grouting quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a method flow chart of the grouting treatment method for steep slope construction in karst areas according to an embodiment of the present application. DETAILED DESCRIPTION

[0025] The following is combined with Figure 1 This application is described in further detail.

[0026] The present application embodiment discloses a construction method for grouting treatment of steep slopes in karst areas. Figure 1 The construction method of grouting treatment of steep slopes in karst areas includes the following steps: S1. Staking out the pretreatment area: Based on the geological survey report and the record of pile-by-pile exploration results, a bedrock contour map is formed, and the karst development area with steep bedrock surface changes and large buried areas is selected to determine the engineering pile positions in the grouting pretreatment area; with the engineering pile as the center point, grouting holes are set at intervals of 2m around it.

[0027] S2. Drilling: The grouting hole position is determined by on-site measurement and setting out. A 100-type drilling rig is used to drill holes with a drill bit size of 108mm. The holes are drilled to 0.2m from the bottom of the cave. When drilling, the steel casing is pressed in while drilling until it enters the cave layer. The steel casing has a diameter of 110mm and a wall thickness of 5.6mm. The steel casing is used to support the hole wall, prevent the hole from collapsing, and ensure the smooth entry of the grouting flower pipe.

[0028] The judgment basis for the steel casing to enter the cave layer is: the drilling speed of the drilling rig suddenly increases, which means that the drill bit has broken through the upper soil layer of the cave and entered the cave layer. After the drill bit is lifted above the ground, the steel casing is fixed and the drilling rig moves to the next hole position.

[0029] During the drilling process, detailed drilling records should be kept, including geological description of the borehole, difficulty of drilling, and whether there are voids, etc., and compared with the original geotechnical engineering survey report, the drilling depth can be adjusted in real time, which will help improve the effect of the next grouting operation.

[0030] S3. Install grouting pipe: After the four grouting holes of each pile foundation are drilled and the casing is installed, install the grouting pipe. The grouting pipe is made of a hard plastic pipe with an inner diameter of 38mm. There are 60-80 holes within a length of 1m at the bottom of the grouting pipe. The holes are arranged in four rows in a plum blossom shape along the center line of the grouting pipe, and the hole diameter is 1mm-3mm.

[0031] After the grouting flower tube is installed, a certain proportion of cement slurry and water glass diluted to a certain proportion are used to fill and seal the annular gap between the hole wall and the grouting flower tube to prevent the slurry from flowing upward along the hole wall and the tube wall during grouting, and to prevent the slurry from flowing between the grouting hole sections.

[0032] The top of the grouting pipe is 200-300mm above the ground to prevent debris and mud from drilling into the grouting pipe.

[0033] S4. Slurry preparation: The grouting liquid mix ratio is water: cement = 0.8:1. According to the volume of the pre-prepared slurry, the required amount of cement and water is calculated according to the water-cement ratio. P.O42.5 ordinary Portland cement is used in grouting construction.

[0034] If the space volume inside the cave is large and the water permeability is strong, a certain amount of water glass is added to form cement-water glass slurry in the ratio of water: cement: water glass = 1:1:1.

[0035] S5. Grouting operation: Use a high-pressure grouting pump to inject cement slurry into the cave through the grouting pipe. Grouting requires multiple, repeated, and layered grouting in small amounts. The layer height is preferably 1m. Each pile position has four grouting holes for cyclic grouting, and the grouting speed is controlled at 50-100L / min. After each layer of grouting is completed, lift the grouting flower pipe to enter the next cycle.

[0036] When water glass is added to the grouting liquid and if the grouting process needs to be suspended, the water glass grouting tube must be taken out and placed in a clean water bucket first, and then the cement pipe is taken out, and clean water is injected into the hole before stopping the grouting. While keeping the pipeline unobstructed, ensure that the grouting section is not affected by water injection.

[0037] When the grouting reaches one of the following standards, the grouting of the hole is terminated: a. The grouting hole pressure is maintained at 0.3Mpa-0.5MPa, the grouting volume is not more than 40L / min, and it is maintained for 30 minutes.

[0038] b. When the bedrock of the grouting borehole is intact, or when grouting is repeated multiple times and the hole pressure exceeds 1.5PMa.

[0039] c. When the slurry bubbling point is 3-5m outside the grouting range.

[0040] d. When the single-hole grouting volume reaches 1.5-2.0 times the average grouting volume, and the grouting volume is significantly reduced.

[0041] When the above-mentioned end standards are not met, the hole should be cleaned and grouting should be carried out again; S6. Sealing holes: After the grouting of all grouting holes and inspection holes is completed, grouting and sealing holes are carried out immediately. The "pressure grouting and sealing method" is adopted. The slurry is replaced by concentrated cement slurry with a water-cement ratio of 0.5:1. The grouting pressure can be determined according to the specific conditions of the project. Generally, a pressure of 0.8-1MPa can be used for deeper grouting holes. When the injection rate is not more than 1L / min, it will be stopped after 30min.

[0042] The implementation principle of a grouting construction method for treating steep slopes in karst areas in an embodiment of the present application is as follows: according to the geological characteristics of the karst development area, combined with one pile and one exploration and karst investigation reports, the position of the engineering piles located on the steep slope surface is determined, and then grouting holes are buried around the engineering piles. The karst area is reinforced by grouting, and the steep slope surface of hidden karst caves is eliminated, thereby ensuring the stability and verticality of the borehole, reducing the possibility of oblique drilling and drill rod breakage due to uneven force on the drill bit, improving the construction safety factor and ensuring the construction quality at the same time, and during the process, there is no need to backfill sand and gravel for the second time to treat the steep slopes of hidden karst caves in the karst development area, thus laying a good foundation for pile foundation construction in advance, accelerating the overall construction rhythm, and reducing construction costs.

[0043] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A construction method for grouting treatment of steep slopes in karst areas, characterized in that: The following steps are involved: S1. Pretreatment area layout: Based on the geological survey report and the results of one pile and one exploration, a bedrock isovalue map is formed, and the karst development area with steep bedrock surface changes and large buried areas is selected to determine the engineering pile position in the grouting pretreatment area. With the engineering pile as the center point, grouting holes are set at intervals of 2m around; S2. Drilling: The grouting hole position is determined by on-site measurement and setting out, and the hole is drilled using a drilling rig. The steel casing is pressed into the hole while drilling until the steel casing enters the cave layer; S3, installing grouting pipes: after the four grouting holes of each pile foundation are drilled and the steel casing is installed, the grouting pipes are installed; S4. Slurry preparation: The grouting liquid mix ratio is water: cement = 0.8:

1. According to the volume of the pre-prepared slurry, the required amount of cement and water is calculated according to the water-cement ratio. In the grouting construction, P.O42.5 ordinary Portland cement is used; S5. Grouting operation: Use a high-pressure grouting pump to inject cement slurry into the cave through the grouting pipe. Grouting requires multiple, repeated, and layered grouting in small amounts. The layer height is preferably 1m. Each pile position has four grouting holes for cyclic grouting. The grouting speed is controlled at 50-100L / min. After each layer of grouting is completed, the grouting flower pipe is lifted to enter the next cycle; S6. Sealing holes: After the grouting of all grouting holes and inspection holes is completed, grouting and sealing will be carried out immediately. The "pressure grouting and sealing method" will be adopted. The slurry will be replaced with concentrated cement slurry with a water-cement ratio of 0.5:

1. The grouting pressure can be determined according to the specific conditions of the project.

2. The grouting treatment method for steep slopes in karst areas according to claim 1 is characterized in that: The drilling rig is a 100-type drilling rig, and the drill bit size of the drilling rig is 108 mm; the diameter of the steel casing is 110 mm, and the wall thickness of the steel casing is 5.6 mm.

3. The grouting treatment method for steep slopes in karst areas according to claim 1 is characterized in that: In S2, the basis for judging that the steel casing has entered the karst cave layer is that the drilling speed of the drilling rig is suddenly accelerated, indicating that the drill bit of the drilling rig has broken through the upper soil layer of the karst cave and entered the karst cave layer.

4. The grouting treatment method for steep slopes in karst areas according to claim 3 is characterized in that: In S2, detailed drilling records should be made during the drilling process, including geological description of the borehole, drilling difficulty, and whether there are voids, etc., and compared with the original geotechnical engineering investigation report to adjust the drilling depth in real time.

5. The grouting treatment method for steep slopes in karst areas according to claim 1 is characterized in that: In S3, the grouting flower pipe is made of a hard plastic pipe with an inner diameter of 38 mm. There are 60-80 holes within a length of 1 m at the bottom end of the grouting flower pipe. The holes are arranged in four rows in a plum blossom shape along the center line of the grouting flower pipe. The diameter of the holes is 1 mm-3 mm.

6. A grouting treatment method for steep slopes in karst areas according to claim 5, characterized in that: In S3, after the grouting flower pipe is installed, a certain proportion of cement slurry and water glass diluted to a certain proportion are used to inject and seal the hole in the annular gap between the hole wall of the steel casing and the grouting flower pipe.

7. A grouting treatment method for steep slopes in karst areas according to claim 6, characterized in that: In S3, the top of the grouting flower pipe emerges 200mm-300mm above the ground.

8. A grouting treatment method for steep slopes in karst areas according to claim 1, characterized in that: In S4, if the space volume in the cave is large and the water permeability is strong, a certain amount of water glass is added to the grouting liquid, and the ratio of the grouting liquid is water: cement: water glass = 1:1:

1.

9. A grouting treatment method for steep slopes in karst areas according to claim 1, characterized in that: In S5, when the grouting reaches one of the following criteria, the grouting of the hole is terminated: a. The grouting hole pressure is maintained at 0.3Mpa-0.5MPa, the grouting volume is not more than 40L / min, and it is maintained for 30min; b. When the bedrock of the grouting borehole is intact, or when grouting is repeated and the orifice pressure exceeds 1.5MPa; c. When the grouting point is 3m-5m outside the grouting range; d. When the single hole grouting volume reaches 1.5-2.0 times the average grouting volume, and the grouting volume is significantly reduced; When the grouting fails to reach the above-mentioned completion standard, the hole shall be cleaned and grouting shall be performed again.

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