CN111910634A - Karst geological impact pore-forming construction method - Google Patents
Karst geological impact pore-forming construction method Download PDFInfo
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- CN111910634A CN111910634A CN202010732573.9A CN202010732573A CN111910634A CN 111910634 A CN111910634 A CN 111910634A CN 202010732573 A CN202010732573 A CN 202010732573A CN 111910634 A CN111910634 A CN 111910634A
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- 238000010276 construction Methods 0.000 title claims abstract description 40
- 239000002002 slurry Substances 0.000 claims abstract description 63
- 238000005553 drilling Methods 0.000 claims abstract description 47
- 238000000034 method Methods 0.000 claims abstract description 35
- 238000004080 punching Methods 0.000 claims abstract description 25
- 239000004575 stone Substances 0.000 claims abstract description 20
- 239000004567 concrete Substances 0.000 claims abstract description 18
- 239000011435 rock Substances 0.000 claims abstract description 17
- 238000013461 design Methods 0.000 claims abstract description 15
- 239000004927 clay Substances 0.000 claims abstract description 12
- 238000004140 cleaning Methods 0.000 claims abstract description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 12
- 238000012544 monitoring process Methods 0.000 claims abstract description 9
- 230000001681 protective effect Effects 0.000 claims abstract description 9
- 230000003116 impacting effect Effects 0.000 claims abstract description 7
- 230000002787 reinforcement Effects 0.000 claims abstract description 6
- 238000001514 detection method Methods 0.000 claims abstract description 5
- 239000002893 slag Substances 0.000 claims abstract description 5
- 229910000831 Steel Inorganic materials 0.000 claims description 34
- 239000010959 steel Substances 0.000 claims description 34
- 239000002689 soil Substances 0.000 claims description 19
- 239000000523 sample Substances 0.000 claims description 9
- 229910000278 bentonite Inorganic materials 0.000 claims description 8
- 239000000440 bentonite Substances 0.000 claims description 8
- SVPXDRXYRYOSEX-UHFFFAOYSA-N bentoquatam Chemical group O.O=[Si]=O.O=[Al]O[Al]=O SVPXDRXYRYOSEX-UHFFFAOYSA-N 0.000 claims description 8
- 238000011835 investigation Methods 0.000 claims description 8
- 230000003014 reinforcing effect Effects 0.000 claims description 8
- 239000004576 sand Substances 0.000 claims description 8
- 239000004568 cement Substances 0.000 claims description 6
- 239000011083 cement mortar Substances 0.000 claims description 6
- 230000005484 gravity Effects 0.000 claims description 6
- 230000000903 blocking effect Effects 0.000 claims description 5
- 239000000203 mixture Substances 0.000 claims description 5
- 238000009412 basement excavation Methods 0.000 claims description 4
- 239000004570 mortar (masonry) Substances 0.000 claims description 4
- 238000011161 development Methods 0.000 description 4
- 239000007788 liquid Substances 0.000 description 3
- 230000007547 defect Effects 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 235000019994 cava Nutrition 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000011178 precast concrete Substances 0.000 description 1
- 230000000246 remedial effect Effects 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
Classifications
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D7/00—Methods or apparatus for placing sheet pile bulkheads, piles, mouldpipes, or other moulds
- E02D7/26—Placing by using several means simultaneously
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
- E02D5/22—Piles
- E02D5/34—Concrete or concrete-like piles cast in position ; Apparatus for making same
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B1/00—Percussion drilling
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B21/00—Methods or apparatus for flushing boreholes, e.g. by use of exhaust air from motor
- E21B21/01—Arrangements for handling drilling fluids or cuttings outside the borehole, e.g. mud boxes
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B33/00—Sealing or packing boreholes or wells
- E21B33/10—Sealing or packing boreholes or wells in the borehole
- E21B33/13—Methods or devices for cementing, for plugging holes, crevices or the like
- E21B33/138—Plastering the borehole wall; Injecting into the formation
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D5/00—Lining shafts; Linings therefor
- E21D5/11—Lining shafts; Linings therefor with combinations of different materials, e.g. wood, metal, concrete
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- Engineering & Computer Science (AREA)
- Life Sciences & Earth Sciences (AREA)
- Mining & Mineral Resources (AREA)
- Geology (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Physics & Mathematics (AREA)
- Environmental & Geological Engineering (AREA)
- Fluid Mechanics (AREA)
- Structural Engineering (AREA)
- Mechanical Engineering (AREA)
- Civil Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Paleontology (AREA)
- Wood Science & Technology (AREA)
- Placing Or Removing Of Piles Or Sheet Piles, Or Accessories Thereof (AREA)
- Piles And Underground Anchors (AREA)
Abstract
The invention relates to a karst geological impact pore-forming construction method. According to the method, before pile foundation construction, advanced drilling treatment is carried out, a pile casing is embedded at a design hole position to a design depth, and reinforcement treatment is carried out on the pile casing; preparing slurry, punching the slurry into a rock stratum through a punching hammer of a punching drilling machine, maintaining the water level of the slurry to be stable through a slurry circulating system, and protecting walls through a protecting cylinder and filling mud stone clay; when the distance between the top plate and the karst cave is 0.8-1.2 m, adopting a small hammer to impact the top plate of the karst cave in a low stroke manner until the top plate of the karst cave is broken down, filling the karst cave with flaky clay to form a protective wall, and repeatedly impacting the protective wall in the low stroke manner by using the small hammer until the top plate of the karst cave is broken down; if the small hammer can not break the top plate of the karst cave, the big hammer is used for breaking the top plate of the karst cave by low-stroke impact; cleaning pile holes, carrying out geological detection, and transporting mud and drilling slag; and installing and positioning the reinforcement cage, installing a guide pipe for secondary hole cleaning, monitoring the performance of slurry, and pouring underwater concrete to a pile diameter which is one time of the design elevation. The invention can ensure the safety of pile-punching machinery and operators and the pile-forming quality of pile foundations.
Description
Technical Field
The invention relates to a karst geological impact pore-forming construction method, and belongs to the technical field of punching pile construction.
Background
The bored pile has the advantages of low construction noise, free control of the diameter of the pile body, suitability for various bottom layers, high bearing capacity, low construction cost, good earthquake resistance and the like, but the bored pile also has the defects that: through pipe method pouring concrete under water, pile shaft quality all is less than precast concrete pile, more because karst development area water resource is abundant, and strong development such as solution channel, solution tank and karst cave is difficult to accurate description in the geological survey before the construction, still in the work progress because the drilling is bored the operation of not normal of pouring, in case pile foundation quality defects such as laitance, double-layered mud, honeycomb, segregation appear very easily in case the problem appears.
The rock surface of the base in the karst area fluctuates, so that the stressed compression deformation of the foundation of the overlying soil layer is larger. In the horizontal direction, the thickness of the soil layer can reach 4-6 m, even more than ten meters at two points with the same distance (such as 1-2 m). The bottom of a thick soil layer generally has soft soil, so that the nonuniformity of the foundation is aggravated, and the phenomenon of hole deviation is caused when pile foundation construction is carried out and the pile foundation enters a bearing layer. Karst areas have shallow-buried, large-span and flat karst caves, and the upper soil layer is unstable or collapsed due to large disturbance to the soil layer in the construction process, or local damage of the foundation due to collapse is possible after engineering construction because the load stress of the stratum is changed by a building. The foundation soil cave is developed and can be kept relatively stable after being formed, but karst collapse is induced by artificial factors such as drilling, and a series of construction difficulties such as slurry leakage, drill jamming and drill dropping are easily caused when the drilling holes penetrate through the underground soil cave due to low bearing capacity of a karst area, and even collapse caused by hole collapse is caused.
Generally, the construction accidents of the cast-in-place pile foundation in the karst area can be mainly divided into two types: firstly, accidents such as slurry leakage, hole collapse, hole inclination, drill sticking and the like occur in the process of forming holes and piles; secondly, after pile forming, quality inspection finds that the quality of the pile foundation is unqualified, and even the accident of scrapping must be done if remedial measures such as pile breaking and the like are needed.
Disclosure of Invention
Aiming at the technical problem of difficult construction of karst geological impact hole forming, the invention provides the karst geological impact hole forming construction method which can ensure the safety of pile punching machinery and operators and the pile forming quality of pile foundations.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a karst geological impact pore-forming construction method comprises the following specific steps:
(1) before pile foundation construction, advance drilling treatment is carried out: measuring and lofting the pile position, tamping the area around an excavation point, adopting a core drilling machine to drill a hole in advance at the pile position, and prejudging the karst cave position and the slurry leakage condition according to the soil property parameters and the integrity of the core sample;
(2) embedding a pile casing at a design hole position to a design depth, and reinforcing the pile casing;
(3) preparing a slurry pool and a slurry circulating system, and preparing slurry;
(4) the rock stratum is flushed by a punching hammer of the punching drilling machine, the water level of the slurry is kept stable by a slurry circulating system, and the wall is protected by a protecting cylinder and filled with mud stone clay; when the distance between the top plate and the karst cave is 0.8-1.2 m, adopting a small hammer to impact the top plate of the karst cave in a low stroke manner until the top plate of the karst cave is broken down, filling the karst cave with flaky clay to form a protective wall, and repeatedly impacting the protective wall in the low stroke manner by using the small hammer until the top plate of the karst cave is broken down; if the small hammer can not break the top plate of the karst cave, the big hammer is used for breaking the top plate of the karst cave by low-stroke impact;
(5) cleaning pile holes, carrying out geological detection, and transporting mud and drilling slag;
(6) and installing and positioning the reinforcement cage, installing a guide pipe for secondary hole cleaning, monitoring the performance of slurry, and pouring underwater concrete to a pile diameter which is one time of the design elevation.
The concrete method for prejudging the position of the karst cave and the slurry leakage condition in the step (1) is
1) The first stage is as follows: surveying the geology in the field in the early construction period, arranging drilled holes at intervals of 2 x 2m to find the boundary position of a karst cave, and surveying the position of the karst in the field;
2) and a second stage: the advanced geological drilling during the construction of the bored pile carries out karst investigation of a karst area of a field according to the position of karst, wherein the investigation parameters are the type of the karst, the thickness and the elevation of a top plate and a bottom plate, and the drilling depth is below 1m when the advanced geological drilling is drilled into a weathered bearing stratum or 5m when the advanced geological drilling is drilled into the bottom of the pile.
And (2) performing advanced drilling treatment in the step (1) to form a pile and multiple probes.
In the step (2), the wall thickness of the pile casing is 10-15 mm, the length of the pile casing is 5-8 m, the inner diameter of the pile casing is 0.5-1.0 mm larger than the diameter of the punched pile, and a supporting piece is embedded outside the pile casing in the pile casing reinforcing treatment method.
The slurry in the step (3) is bentonite slurry, and the mass concentration of bentonite in the slurry is 50-60%.
And (4) the impact hammer is impacted into a rock stratum, if a non-open type fracture karst cave is met, large stones with the diameter not less than 500mm are thrown into the pile hole until the stacking height of the large stones exceeds 50-100 cm of the top surface of the karst cave, then the large stones are impacted to the position 30cm away from the top surface of the karst cave, then a mixture of broken stones and soil or cement is thrown until the stacking height of the broken stones and the soil or the cement exceeds 5-10 cm of the top surface of the karst cave, and the impact is carried out after the mixture is solidified.
Further, in the impact process of the impact hammer, if the water level in the hole is unstable, pouring cement mortar or underwater concrete at the position of the non-open type fracture karst cave to block the non-open type fracture karst cave, standing for more than 24 hours, removing the mortar layer or the underwater concrete layer, and continuously adopting the impact hammer to impact the hole; when the non-open type fracture caverns are continuously encountered within a distance of 5m, the non-open type fracture caverns are separately blocked or continuously blocked, wherein the continuous blocking is realized by treating two or more non-open type fracture caverns together.
And (4) the impact hammer is impacted into the rock stratum, if the rock stratum meets the open type fracture karst cave, the stability of the hole wall is monitored, if the hole wall is stable, the impact hammer continuously impacts, meanwhile, the rolled steel casing is tightly held, the steel casing is put to a preset position by a loosening method, wherein the thickness of the steel casing is more than 4mm, the outer diameter of the steel casing is the same as or 1-2 cm smaller than the hole diameter of the pile, and the length of the steel casing is 3-4 m larger than the depth of the karst cave.
And (3) monitoring the slurry performance in the step (6) to ensure that the sand content is less than 4%, the specific gravity of the slurry is 1.1-1.2, and the viscosity is 18-23 s.
The invention has the beneficial effects that:
according to the invention, through advanced drilling treatment, the karst cave position and the slurry leakage condition can be pre-judged through the soil property parameters and the integrity of the core sample, and when the distance is 0.5-1.5 m m away from the top plate of the karst cave, a low-speed drilling mode is adopted, so that the phenomenon that the liquid level in the hole suddenly drops to cause hole collapse when the karst cave is met in the drilling process is avoided; the method comprises the steps of punching a punching hammer into a rock stratum, when the punching hammer meets an unopened fracture karst cave, throwing large stones with the diameter not less than 500mm into a pile hole until the stacking height of the large stones exceeds 50-100 cm of the top surface of the karst cave, then impacting until the stacking height of the large stones exceeds 30cm of the top surface of the karst cave, then throwing a mixture of broken stones and soil or cement until the stacking height of the broken stones and the soil or the cement exceeds 5-10 cm of the top surface of the karst cave, impacting after solidification to block passages of the karst fractures or the karst cave at pile foundation positions, and blocking or reducing the water passing road surface of.
The specific implementation mode is as follows:
the present invention will be further described with reference to the following embodiments.
Example 1: a karst geological impact pore-forming construction method comprises the following specific steps:
(1) before pile foundation construction, advance drilling treatment is carried out: measuring and lofting the pile position, tamping the area around an excavation point, and adopting a core drilling machine to drill a hole in advance at the pile position, wherein the hole drilling process is one pile and multiple probes so as to improve the accuracy of judging the position, the size, the distribution condition of karst cave cracks and the slurry leakage degree of the karst cave, and the position and the slurry leakage condition of the karst cave are pre-judged according to the soil property parameters and the integrity of the core sample;
the concrete method for pre-judging the position of the karst cave and the slurry leakage condition comprises
1) The first stage is as follows: surveying the geology in the field in the early construction period, arranging drilled holes at intervals of 2 x 2m to find the boundary position of a karst cave, and surveying the position of the karst in the field;
2) and a second stage: the advanced geological drilling during the construction of the bored pile carries out karst investigation of a karst area of a field according to the position of karst, wherein the investigation parameters are the type of the karst, the thickness and the elevation of a top plate and a bottom plate, and the drilling depth is below 1m when the drilling is carried out to a middle weathering bearing stratum or 5m when the drilling is carried out to the designed elevation of the pile bottom;
(2) embedding a pile casing at a design hole position to a design depth, and reinforcing the pile casing; the wall thickness of the pile casing is 10-15 mm, the length of the pile casing is 5-8 m, the inner diameter of the pile casing is 0.5-1.0 mm larger than the diameter of the punched pile, and a supporting piece is embedded outside the pile casing in the pile casing reinforcing treatment method;
(3) preparing a slurry pool and a slurry circulating system, and preparing slurry; wherein the slurry is bentonite slurry, and the mass concentration of the bentonite in the slurry is 50-60%;
(4) the rock stratum is flushed by a punching hammer of the punching drilling machine, the water level of the slurry is kept stable by a slurry circulating system, and the wall is protected by a protecting cylinder and filled with mud stone clay; when the distance between the top plate and the karst cave is 0.8-1.2 m, adopting a small hammer to impact the top plate of the karst cave in a low stroke manner until the top plate of the karst cave is broken down, filling the karst cave with flaky clay to form a protective wall, and repeatedly impacting the protective wall in the low stroke manner by using the small hammer until the top plate of the karst cave is broken down; if the small hammer can not break the top plate of the karst cave, the big hammer is used for breaking the top plate of the karst cave by low-stroke impact;
the method comprises the following steps that a punching hammer is punched into a rock stratum, if an open-type crack karst cave is met, the stability of a hole wall is monitored, if the hole wall is stable, the punching hammer continues to impact, a rolled steel casing is gripped, the steel casing is put to a preset position by a loosening method, wherein the thickness of the steel casing is more than 4mm, the outer diameter of the steel casing is the same as the diameter of a pile or smaller than the diameter of the pile by 1-2 cm, and the length of the steel casing is 3-4 m larger than the depth of the karst cave; in the impact process of the impact hammer, if the water level in the hole is unstable, pouring cement mortar or underwater concrete at the position of the non-open type fracture karst cave to block the non-open type fracture karst cave, standing for more than 24 hours, removing the mortar layer or the underwater concrete layer, and continuously adopting the impact hammer to impact the hole; when the non-open type fracture caverns are continuously encountered within a distance of 5m, the non-open type fracture caverns are separately blocked or continuously blocked, wherein the continuous blocking is that two or more than two non-open type fracture caverns are treated together;
the method comprises the following steps that a punching hammer is punched into a rock stratum, if an open-type crack karst cave is met, the stability of a hole wall is monitored, if the hole wall is stable, the punching hammer continues to impact, a rolled steel casing is gripped, the steel casing is put to a preset position by a loosening method, wherein the thickness of the steel casing is more than 4mm, the outer diameter of the steel casing is the same as the diameter of a pile or smaller than the diameter of the pile by 1-2 cm, and the length of the steel casing is 3-4 m larger than the depth of the karst cave;
when the karst cave is constructed in the drilling process, if the karst cave is not filled compactly, slurry in the hole can be quickly lost to form slurry leakage, the liquid level in the hole can be quickly reduced or the duration time is too long when the hole is serious, so that the hole collapse phenomenon is caused by overlarge pressure difference between the inside and the outside of the hole, a steel pile casing or a double sleeve is selected, wherein the outer diameter of the first pile casing of the double sleeve is 2-3 grades larger than the pile diameter and is placed into a clay layer, and the outer side of the bottom of the pile casing is solidified and stopped by adopting cement mortar; the second casing is 1 grade larger than the pile diameter and is put on bedrock in a karst fissure strong development zone to prevent the hole wall from collapsing;
(5) cleaning pile holes, carrying out geological detection, and transporting mud and drilling slag; and tracking and measuring the slurry performance in the hole cleaning process, wherein the slurry performance is that the sand content is less than 8%, the specific gravity of the slurry is 1.15-1.20 (the specific gravity of a sand layer is 1.2-1.4), and the viscosity is as follows: the bottom layer is 16-25 s, and the loose bottom layer is 19-28 s;
(6) installing and positioning a steel reinforcement cage, installing a guide pipe for secondary hole cleaning, monitoring mud performance, and pouring underwater concrete to a pile diameter which is one time of a design elevation, wherein the monitoring mud performance is that the sand content is less than 4%, the mud proportion is 1.1-1.2, and the viscosity is 18-23 s.
Example 2: the embodiment is a karst geological impact pore-forming method in certain highway engineering in Yunnan;
a karst geological impact pore-forming construction method comprises the following specific steps:
(1) before pile foundation construction, advance drilling treatment is carried out: measuring and lofting the pile position, tamping the area around an excavation point, and adopting a core drilling machine to drill a hole in advance at the pile position, wherein the hole drilling process is one pile and multiple probes so as to improve the accuracy of judging the position, the size, the distribution condition of karst cave cracks and the slurry leakage degree of the karst cave, and the position and the slurry leakage condition of the karst cave are pre-judged according to the soil property parameters and the integrity of the core sample;
the concrete method for pre-judging the position of the karst cave and the slurry leakage condition comprises
1) The first stage is as follows: surveying the geology in the field in the early construction period, arranging drilled holes at intervals of 2 x 2m to find the boundary position of a karst cave, and surveying the position of the karst in the field;
2) and a second stage: the advanced geological drilling during the construction of the bored pile carries out karst investigation of a karst area of a field according to the position of karst, wherein the investigation parameters are the type of the karst, the thickness and the elevation of a top plate and a bottom plate, and the drilling depth is below 1m when the drilling is carried out to a middle weathering bearing stratum or 5m when the drilling is carried out to the designed elevation of the pile bottom;
(2) embedding a pile casing at a design hole position to a design depth, and reinforcing the pile casing; the wall thickness of the pile casing is 12mm, the length of the pile casing is 8m, the inner diameter of the pile casing is 0.8mm larger than the diameter of the punched pile, and a supporting piece is embedded outside the pile casing in the pile casing reinforcing treatment method;
(3) preparing a slurry pool and a slurry circulating system, and preparing slurry; wherein the mud is bentonite mud, and the mass concentration of the bentonite in the mud is 55 percent;
(4) the rock stratum is flushed by a punching hammer of the punching drilling machine, the water level of the slurry is kept stable by a slurry circulating system, and the wall is protected by a protecting cylinder and filled with mud stone clay; when the distance is 1.1m from the top plate of the karst cave, adopting a small hammer to impact the top plate of the karst cave in a low stroke manner until the top plate of the karst cave is broken down, then adopting rubble clay to fill the karst cave to form a protective wall, and repeatedly impacting the karst cave top plate in a low stroke manner by using the small hammer to break the karst cave top plate; if the small hammer can not break the top plate of the karst cave, the big hammer is used for breaking the top plate of the karst cave by low-stroke impact;
the method comprises the following steps that a punching hammer is punched into a rock stratum, if an open-type crack karst cave is met, the stability of a hole wall is monitored, if the hole wall is stable, the punching hammer continues to impact, a rolled steel casing is gripped, the steel casing is put to a preset position by a loosening method, wherein the thickness of the steel casing is more than 4mm, the outer diameter of the steel casing is the same as the diameter of a pile or smaller than the diameter of the pile by 1-2 cm, and the length of the steel casing is 3-4 m larger than the depth of the karst cave; in the impact process of the impact hammer, if the water level in the hole is unstable, pouring cement mortar or underwater concrete at the position of the non-open type fracture karst cave to block the non-open type fracture karst cave, standing for more than 24 hours, removing the mortar layer or the underwater concrete layer, and continuously adopting the impact hammer to impact the hole; when the non-open type fracture caverns are continuously encountered within a distance of 5m, the non-open type fracture caverns are separately blocked or continuously blocked, wherein the continuous blocking is that two or more than two non-open type fracture caverns are treated together;
the method comprises the following steps that a punching hammer is punched into a rock stratum, if an open-type crack karst cave is met, the stability of a hole wall is monitored, if the hole wall is stable, the punching hammer continues to impact, a rolled steel casing is gripped, the steel casing is put to a preset position by a loosening method, wherein the thickness of the steel casing is more than 4mm, the outer diameter of the steel casing is the same as the diameter of a pile or smaller than the diameter of the pile by 1-2 cm, and the length of the steel casing is 3-4 m larger than the depth of the karst cave;
when the karst cave is constructed in the drilling process, if the karst cave is not filled compactly, slurry in the hole can be quickly lost to form slurry leakage, the liquid level in the hole can be quickly reduced or the duration time is too long when the hole is serious, so that the hole collapse phenomenon is caused by overlarge pressure difference between the inside and the outside of the hole, a steel pile casing or a double sleeve is selected, wherein the outer diameter of the first pile casing of the double sleeve is 2-3 grades larger than the pile diameter and is placed into a clay layer, and the outer side of the bottom of the pile casing is solidified and stopped by adopting cement mortar; the second casing is 1 grade larger than the pile diameter and is put on bedrock in a karst fissure strong development zone to prevent the hole wall from collapsing;
(5) cleaning pile holes, carrying out geological detection, and transporting mud and drilling slag; and tracking and measuring the slurry performance in the hole cleaning process, wherein the slurry performance is that the sand content is less than 8%, the specific gravity of the slurry is 1.15-1.20 (the specific gravity of a sand layer is 1.2-1.4), and the viscosity is as follows: the bottom layer is 16-25 s, and the loose bottom layer is 19-28 s;
(6) installing and positioning a steel reinforcement cage, installing a guide pipe for secondary hole cleaning, monitoring mud performance, and pouring underwater concrete to a pile diameter which is one time of a design elevation, wherein the monitoring mud performance is that the sand content is less than 4%, the mud proportion is 1.1-1.2, and the viscosity is 18-23 s.
While the present invention has been described in detail with reference to the specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.
Claims (9)
1. A karst geology impact pore-forming construction method is characterized by comprising the following specific steps:
(1) before pile foundation construction, advance drilling treatment is carried out: measuring and lofting the pile position, tamping the area around an excavation point, adopting a core drilling machine to drill a hole in advance at the pile position, and prejudging the karst cave position and the slurry leakage condition according to the soil property parameters and the integrity of the core sample;
(2) embedding a pile casing at a design hole position to a design depth, and reinforcing the pile casing;
(3) preparing a slurry pool and a slurry circulating system, and preparing slurry;
(4) the rock stratum is flushed by a punching hammer of the punching drilling machine, the water level of the slurry is kept stable by a slurry circulating system, and the wall is protected by a protecting cylinder and filled with mud stone clay; when the distance between the top plate and the karst cave is 0.8-1.2 m, adopting a small hammer to impact the top plate of the karst cave in a low stroke manner until the top plate of the karst cave is broken down, filling the karst cave with flaky clay to form a protective wall, and repeatedly impacting the protective wall in the low stroke manner by using the small hammer until the top plate of the karst cave is broken down; if the small hammer can not break the top plate of the karst cave, the big hammer is used for breaking the top plate of the karst cave by low-stroke impact;
(5) cleaning pile holes, carrying out geological detection, and transporting mud and drilling slag;
(6) and installing and positioning the reinforcement cage, installing a guide pipe for secondary hole cleaning, monitoring the performance of slurry, and pouring underwater concrete to a pile diameter which is one time of the design elevation.
2. The karst geological impact pore-forming construction method according to claim 1, characterized in that: the concrete method for prejudging the position of the karst cave and the slurry leakage condition in the step (1) is
1) The first stage is as follows: surveying the geology in the field in the early construction period, arranging drilled holes at intervals of 2 x 2m to find the boundary position of a karst cave, and surveying the position of the karst in the field;
2) and a second stage: the advanced geological drilling during the construction of the bored pile carries out karst investigation of a karst area of a field according to the position of karst, wherein the investigation parameters are the type of the karst, the thickness and the elevation of a top plate and a bottom plate, and the drilling depth is below 1m when the advanced geological drilling is drilled into a weathered bearing stratum or 5m when the advanced geological drilling is drilled into the bottom of the pile.
3. The karst geological impact pore-forming construction method according to claim 1, characterized in that: and (2) performing advanced drilling treatment to form a pile with multiple probes.
4. The karst geological impact pore-forming construction method according to claim 1, characterized in that: in the step (2), the wall thickness of the pile casing is 10-15 mm, the length of the pile casing is 5-8 m, the inner diameter of the pile casing is 0.5-1.0 mm larger than the diameter of the punched pile, and a supporting piece is embedded outside the pile casing in the pile casing reinforcing treatment method.
5. The karst geological impact pore-forming construction method according to claim 1, characterized in that: and (3) the slurry is bentonite slurry, and the mass concentration of the bentonite in the slurry is 50-60%.
6. The karst geological impact pore-forming construction method according to claim 1, characterized in that: and (4) the impact hammer is impacted into a rock stratum, if a non-open type fracture karst cave is met, large stones with the diameter not smaller than 500mm are thrown into the pile hole until the stacking height of the large stones exceeds 50-100 cm of the top surface of the karst cave, then the large stones are impacted to a position 30cm away from the top surface of the karst cave, then a mixture of broken stones and soil or cement is thrown until the stacking height of the broken stones and the soil or the cement exceeds 5-10 cm of the top surface of the karst cave, and the impact is carried out after the mixture is solidified.
7. The karst geological impact pore-forming construction method according to claim 6, characterized in that: in the impact process of the impact hammer, if the water level in the hole is unstable, pouring cement mortar or underwater concrete at the position of the non-open type fracture karst cave to block the non-open type fracture karst cave, standing for more than 24 hours, removing the mortar layer or the underwater concrete layer, and continuously adopting the impact hammer to impact the hole; when the non-open type fracture caverns are continuously encountered within a distance of 5m, the non-open type fracture caverns are separately blocked or continuously blocked, wherein the continuous blocking is realized by treating two or more non-open type fracture caverns together.
8. The karst geological impact pore-forming construction method according to claim 1, characterized in that: and (4) the impact hammer is impacted into a rock stratum, if the rock stratum meets the open type fracture karst cave, the stability of the hole wall is monitored, if the hole wall is stable, the impact hammer continuously impacts, meanwhile, the rolled steel casing is tightly held, the steel casing is put to a preset position by a loosening method, wherein the thickness of the steel casing is more than 4mm, the outer diameter of the steel casing is the same as the diameter of the pile or smaller than the diameter of the pile by 1-2 cm, and the length of the steel casing is larger than the depth of the karst cave by 3-4 m.
9. The karst geological impact pore-forming construction method according to claim 1, characterized in that: and (6) monitoring the slurry performance in the step (6) that the sand content is less than 4%, the specific gravity of the slurry is 1.1-1.2, and the viscosity is 18-23 s.
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