CN109339079B - Foundation pit water stopping system adjacent to river permeable stratum and construction process thereof - Google Patents
Foundation pit water stopping system adjacent to river permeable stratum and construction process thereof Download PDFInfo
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 107
- 238000010276 construction Methods 0.000 title claims abstract description 43
- 238000000034 method Methods 0.000 title claims abstract description 26
- 230000008569 process Effects 0.000 title claims abstract description 21
- 239000004927 clay Substances 0.000 claims abstract description 67
- 239000004567 concrete Substances 0.000 claims abstract description 67
- 239000011150 reinforced concrete Substances 0.000 claims abstract description 53
- 230000001681 protective effect Effects 0.000 claims abstract description 27
- 239000004744 fabric Substances 0.000 claims abstract description 3
- 238000005553 drilling Methods 0.000 claims description 18
- 230000002787 reinforcement Effects 0.000 claims description 13
- 239000002689 soil Substances 0.000 claims description 13
- 238000005520 cutting process Methods 0.000 claims description 4
- 239000004746 geotextile Substances 0.000 claims description 4
- 230000008595 infiltration Effects 0.000 claims description 3
- 238000001764 infiltration Methods 0.000 claims description 3
- 238000002156 mixing Methods 0.000 claims description 2
- 230000000979 retarding effect Effects 0.000 claims description 2
- 230000015572 biosynthetic process Effects 0.000 claims 1
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- 241000968069 Asterolecaniidae Species 0.000 abstract 1
- 101150054854 POU1F1 gene Proteins 0.000 description 19
- 239000010410 layer Substances 0.000 description 17
- 230000000694 effects Effects 0.000 description 10
- 239000003673 groundwater Substances 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 238000001556 precipitation Methods 0.000 description 4
- 230000009471 action Effects 0.000 description 3
- 238000004364 calculation method Methods 0.000 description 3
- 230000035699 permeability Effects 0.000 description 3
- 239000011241 protective layer Substances 0.000 description 3
- 238000009412 basement excavation Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000003204 osmotic effect Effects 0.000 description 2
- 230000000149 penetrating effect Effects 0.000 description 2
- 238000005086 pumping Methods 0.000 description 2
- 230000002411 adverse Effects 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 238000009435 building construction Methods 0.000 description 1
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- 238000005516 engineering process Methods 0.000 description 1
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- 230000009467 reduction Effects 0.000 description 1
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- 239000004576 sand Substances 0.000 description 1
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- 239000013049 sediment Substances 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000004575 stone Substances 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
- E02D19/00—Keeping dry foundation sites or other areas in the ground
- E02D19/02—Restraining of open water
- E02D19/04—Restraining of open water by coffer-dams, e.g. made of sheet piles
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D19/00—Keeping dry foundation sites or other areas in the ground
- E02D19/06—Restraining of underground water
- E02D19/10—Restraining of underground water by lowering level of ground water
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D19/00—Keeping dry foundation sites or other areas in the ground
- E02D19/06—Restraining of underground water
- E02D19/12—Restraining of underground water by damming or interrupting the passage of underground water
- E02D19/18—Restraining of underground water by damming or interrupting the passage of underground water by making use of sealing aprons, e.g. diaphragms made from bituminous or clay material
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D31/00—Protective arrangements for foundations or foundation structures; Ground foundation measures for protecting the soil or the subsoil water, e.g. preventing or counteracting oil pollution
- E02D31/02—Protective arrangements for foundations or foundation structures; Ground foundation measures for protecting the soil or the subsoil water, e.g. preventing or counteracting oil pollution against ground humidity or ground water
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Abstract
The invention provides a foundation pit water stop system adjacent to a river permeable stratum and a construction process thereof, wherein the foundation pit water stop system comprises a cofferdam, a protective wall, a waterproof wall, a second dewatering well, a clay occluding pile group and a first occluding pile group which are sequentially arranged; the bottoms of all the dewatering wells, the clay occluding piles, the plain concrete piles and the reinforced concrete piles enter the impermeable layer. Determining the range and scale of the cofferdam according to the foundation pit scale, engineering geology and hydrogeology conditions; piling up the protective wall, paving waterproof geotechnical cloth, piling up cofferdams, piling up dewatering wells, and arranging water suction pumps in all dewatering wells to enable the water level in the dewatering well at the far river side to be higher than the water level in the dewatering well at Yu Lin river side; building clay occlusion pile groups; constructing an engaged pile group of the reinforced concrete pile and the plain concrete pile; and wrapping the unidirectional grouting sleeve valve pipes by the adjacent reinforced concrete piles and plain concrete piles to build a foundation pit water stop system adjacent to the river permeable stratum. The water stopping system forms 'blocking and blocking' to water through a plurality of water stopping and preventing lines, and effectively meets the engineering water stopping requirement.
Description
Technical Field
The invention belongs to the technical field of building construction, relates to a waterproof and water-stopping engineering measure for a foundation pit, in particular to a waterproof and water-stopping measure for a foundation pit engineering with high water permeability, such as a layer being a sand pebble, which is close to a river, can be widely applied to water stopping in the foundation pit engineering, and can also be applied to other foundation pits and building (construction) waterproof engineering with high waterproof requirements.
Background
In engineering construction, waterproof engineering is always the focus of engineering constructor, from construction of beginning to later operation, and waterproof engineering's quality has great influence to each link of engineering construction. Especially in deep foundation pit engineering, the engineering effect of the waterproof measures directly influences the safety of the foundation pit engineering, so that in the foundation pit engineering, effective waterproof measures are needed to be adopted especially for the foundation pit engineering close to a water area, and the safety of the foundation pit is ensured.
In order to ensure the safety of the foundation pit, a guard pile and an inner supporting structure are generally adopted in the foundation pit engineering, waterproof measures such as precipitation outside the pit, underground continuous walls and the like are generally adopted in the foundation pit, but when the stratum is in close proximity to a river and is a high-permeability stratum such as sandy pebble, the underground water osmotic pressure is larger, the permeability is strong, and the general waterproof measures can reduce the waterproof effect even lose efficacy under the larger osmotic pressure. The underground diaphragm wall measures need grooving construction, the mud retaining wall is needed to be carried out in the area close to the river, but in the areas with abundant groundwater and pebble soil in the stratum, the problems of difficult grooving, slurry leakage of the mud retaining wall and the like exist, the stable groove wall of the underground diaphragm wall is not facilitated, the construction difficulty is high, the construction quality cannot be guaranteed, and the water stopping effect is affected.
Disclosure of Invention
The invention aims to provide a foundation pit water stop system suitable for a stratum with high water permeability close to a river, so that construction quality is ensured, and meanwhile, construction difficulty is reduced.
The invention further aims to provide a construction process of the foundation pit water stop system.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: a foundation pit water stopping system adjacent to a river permeable stratum comprises a cofferdam, a protective wall, a waterproof wall, a second water collecting facility, a second occluding pile group, a first occluding pile group) and a first water collecting facility which are sequentially arranged;
the cofferdam is formed by piling reinforced gabions, and the lower part of the cofferdam is positioned below the water surface of the river; the protective wall is built by stacking clay bags; the waterproof layer is paved by waterproof geotextile and is positioned between the protective wall and the river levee; the second water collecting facility is composed of at least one second dewatering well arranged side by side; the second engagement pile group consists of a plurality of clay engagement piles; the first occlusion pile group consists of a plurality of plain concrete piles and a plurality of reinforced concrete piles, the plain concrete piles and the reinforced concrete piles are arranged at intervals, and the adjacent plain concrete piles and the adjacent reinforced concrete piles are occluded with each other; the bottoms of the second dewatering well, the clay occluding pile, the plain concrete pile and the reinforced concrete pile all extend below the bottom surface of the foundation pit and enter the impermeable layer.
The other technical scheme adopted by the invention is as follows: the construction process of the foundation pit water stop system adjacent to the river permeable stratum comprises the following steps:
1) Determining the range and the scale of the cofferdam according to the scale of the foundation pit, engineering geology and hydrogeological conditions;
2) Clay is put into the woven bag to form a clay bag; laying the clay bags along the river levee to form a protective wall, and laying waterproof geotextiles on one side of the protective wall facing the river levee to form a waterproof layer;
3) A cofferdam formed by piling reinforced gabions is arranged on one side of the protective wall away from the river levee,
4) At least one second dewatering well is arranged between the river levee and the delimited foundation pit area, water pumps are arranged in all the dewatering wells, and the water level in the second dewatering well is controlled so that the water level at the far river side in the second dewatering well is higher than the water level at the near river side;
5) Determining the diameter and the occlusion amount of the clay occlusion pile according to engineering geology and hydrogeology conditions, and determining the position of an interception axis outside the determined foundation pit fender pile; constructing a guide wall by taking the infiltration intercepting axis as a center; then, determining the pile position of the clay occluding pile along the guide wall, and drilling holes in the determined pile position of the clay occluding pile by adopting a full-rotation sleeve drilling method, so that the lower end of the sleeve enters a water-impermeable layer; in the drilling process, drilling and soil taking are carried out along the inner wall of the sleeve, and the sleeve is drilled into a final hole after the elevation of the pile hole is designed; placing a guide pipe in the drilled hole, backfilling clay layer by layer through the guide pipe, hammering and tamping, and lifting the guide pipe while backfilling to build a clay occluding pile; repeating the drilling and clay backfilling processes on adjacent pile positions of the built clay occluding pile to build a second clay occluding pile; and so on until a second occluding pile group is built, and the occluding part of the previous clay occluding pile is cut off before the construction from the construction of the second clay occluding pile;
6) Construction reinforced concrete and plain concrete engaged pile
a. And determining pile positions, pile diameters and biting amount in the second biting pile group on site according to the design data, and binding a reinforcement cage for the reinforced concrete piles.
According to the preset retarding time, determining the blending amount of retarder in plain concrete through a test;
b. piling a pile hole of the plain concrete pile, pouring concrete mixed with retarder into the pile hole of the plain concrete pile, and stopping pouring after reaching a designed elevation; continuing to construct the next plain concrete pile until the construction of all the plain concrete piles is completed;
c. cutting the engaged parts of plain concrete piles at two sides of a pile hole of the reinforced concrete pile to be driven; then, constructing a reinforced concrete pile, wherein the reinforced concrete pile is meshed with the plain concrete pile; after all the reinforced concrete piles are built, downwards drilling holes on the top surfaces of the meshed parts of all the reinforced concrete piles and plain concrete piles, penetrating one-way grouting sleeve valve pipes into all the drilled holes, and exposing the upper ends of the one-way grouting sleeve valve pipes out of the pile tops to build a foundation pit water stop system adjacent to a river permeable stratum.
The foundation pit water stop system can play a good role in protecting foundation pit safety, and has the following advantages:
1) The reinforced gabion cofferdam is arranged after the clay bags are built on the river levee piles close to the side of the foundation pit, so that groundwater seepage can be controlled at the source, and adverse effects of external water sources on the foundation pit after excavation are greatly reduced.
2) The cofferdam adopts the reinforced gabion, the material price is low, pollution-free, the construction of being convenient for, and after the construction is accomplished, can carry out recycle to the reinforced gabion according to the engineering needs, the clay bag adopts general braided bag, installs clay material in, and the waterproof performance is good, pollution-free, and the low price, clay can reuse, reduces engineering cost.
3) The dewatering well intercepts groundwater on the seepage channel, which intercepts and guides water permeated by the first defense line, directly discharges potential safety hazards of the water out of the engineering range, and greatly improves the safety of the foundation pit. The scheme is simple in construction and good in water stopping effect, and drainage can be continuously performed during construction. The depth of the dewatering well is larger than that of the foundation pit, so that groundwater can infiltrate from the foundation pit to the dewatering well under the action of hydraulic gradient.
4) The two sides of the foundation pit adopt unequal pressure dewatering, so that the trend of dumping the foundation pit at the side of the river under the action of lateral water pressure after the foundation pit is excavated is reduced, and the axial force of the support in the foundation pit is reduced to a certain extent.
5) The clay material used for the clay occluding piles has good water-proof performance, the piles are in an occluding state, the seepage channels of water are closed, and the water-proof and water-stopping effects are good. And the clay can not cause dust and pollute the environment.
6) The clay material has relatively stable performance, is not easy to be corroded by harmful ions in water, and can play a role in stopping water for a long time.
7) The clay pile forming process is convenient for mechanical construction, improves efficiency, saves time, has high pile forming efficiency and good effect, and is easy to ensure engineering quality.
8) The guard piles are supported by adopting reinforced concrete piles and plain concrete piles in a meshed mode, a final water stop barrier is formed, a one-way grouting sleeve valve pipe is buried after holes are drilled in meshed positions, grouting reinforcement is carried out when water leakage occurs in meshed positions in the later period, and reserved conditions are reserved for later period repair and reinforcement.
9) The concrete and plain concrete occluding structure not only can play a role in water resistance, but also can form the foundation pit supporting structure integrally, the rigidity is obviously improved, and the stability of a foundation pit can be greatly improved.
10 In the calculation of the foundation pit support structure, the contribution of part of plain concrete piles to the rigidity of the reinforced concrete piles is considered, so that the section normal stress of the reinforced concrete piles can be reduced, a certain reinforcement is reduced, and the manufacturing cost is saved.
Drawings
FIG. 1 is a schematic illustration of the foundation pit water stop system of the present invention.
Fig. 2 is a top view of fig. 1.
FIG. 3 is a schematic diagram of the unequal pressure precipitation on both sides of the foundation pit.
In the figure: 1. the foundation pit comprises a first dewatering well, a first occlusion pile group, a second dewatering well, a waterproof layer, a protective wall, a cofferdam, a clay occlusion pile, a plain concrete pile, a reinforced concrete pile and a one-way sealing sleeve valve pipe.
Detailed Description
The invention will be described in detail below with reference to the drawings and the detailed description.
As shown in fig. 1 and 2, the foundation pit water stop system of the invention comprises a cofferdam 8, a protective wall 7, a waterproof layer 6, a second water collecting facility, a second occluding pile group 4, a first occluding pile group 3 and a first water collecting facility which are sequentially arranged;
the cofferdam 8 is formed by piling reinforced gabions, and the lower part of the cofferdam 8 is below the water surface of the river. The protective wall 7 is built by stacking clay bags. The waterproof layer 6 is paved by waterproof geotechnical cloth, and the waterproof layer 6 is positioned between the protective wall 7 and the river levee. The second water collecting facility is composed of at least one second dewatering well 5, and all the second dewatering wells 5 are positioned between the protective wall 7 and the second occlusion pile group 4. The second set of engagement piles 4 consists of a plurality of clay engagement piles 9. The first occlusion pile group 3 is composed of a plurality of plain concrete piles 10 and a plurality of reinforced concrete piles 11, the plain concrete piles 10 and the reinforced concrete piles 11 are arranged at intervals, the adjacent plain concrete piles 10 and the adjacent reinforced concrete piles 11 are occluded with each other, and unidirectional grouting sleeve valve pipes 12 are buried in the occlusion parts of the plain concrete piles 10 and the reinforced concrete piles 11. The first water collecting facility is composed of at least one first dewatering well 2, all the first dewatering wells 2 are located in the range of the foundation pit 1 on the inner side of the first occlusion pile group 3, and the first dewatering wells 2 are gradually removed along with excavation of the foundation pit.
The bottoms of the first dewatering well 2, the second dewatering well 5, the clay occluding pile 9, the plain concrete pile 10 and the reinforced concrete pile 11 all extend below the bottom surface of the foundation pit 1 and enter the impervious layer. The first dewatering well 2 is located in the foundation pit 1.
The invention also provides a construction process of the foundation pit water stop system, which comprises the following steps:
1) Determining the range and the scale of the cofferdam 8 according to the scale of the foundation pit 1, engineering geology and hydrogeological conditions;
2) Filling clay into the woven bag to form a clay bag; building the clay bags along river levees to form a protective wall 7, paving waterproof geotextiles on one side of the protective wall 7 facing the river levees to form a waterproof layer 6, and positioning the waterproof layer 6 between the protective wall 7 and the river levees;
3) Arranging a reinforced concrete cage on one side of the protective wall 7 away from the river levee to pile up a cofferdam 8, and determining the diameter of the reinforced concrete used by the reinforced concrete cage according to calculation; hoisting the manufactured reinforced gabion to a designed position, placing the reinforced gabion into a river to pile up the part of the cofferdam 8 positioned below the water surface, wherein the part of the cofferdam 8 positioned above the water surface can be constructed by adopting two methods: firstly, directly piling up the reinforced gabion; firstly hoisting the reinforcement cage to the position, and then filling the stone into the reinforcement cage;
4) At least one second dewatering well 5 is arranged between the river levee and the foundation pit 1, when the number of the second dewatering wells 5 exceeds two, connecting lines of all the second dewatering wells 5 and the protective wall 7 are arranged in the same direction, at least one first dewatering well 2 is arranged in the delimited area of the foundation pit 1, and when the number of the first dewatering wells 2 exceeds two, connecting lines of all the first dewatering wells 2 and the protective wall 7 are arranged in the same direction; the distance between two adjacent first dewatering wells 2 and the distance between two adjacent second dewatering wells 5 are determined according to hydrogeological survey data, water suction pumps are arranged in all dewatering wells so as to lead the water collected in the dewatering wells to a drainage system, sediment purification is carried out first, emission standards are ensured to be met,
controlling the water levels of the river facing side and the river far side in the second dewatering well 5, keeping the water level of the river far side higher than the water level of the river facing side, keeping certain lateral water pressure difference at two sides of the foundation pit 1, and reducing the tendency of dumping in the river facing side of the foundation pit 1 after the foundation pit 1 is excavated as shown in fig. 3;
the lateral soil pressure of the cofferdam is E1, the lateral soil pressure of the far river side is E2, the construction of the cofferdam at the river side can increase the lateral soil pressure, the stratum at the far river side has completed consolidation settlement, the lateral soil pressure is smaller than the lateral soil pressure of the cofferdam, and E2<E1, after the foundation pit is excavated, under the action of E1, the enclosure system has a tendency of tilting integrally to the far river side, and the water level H at the far river side is reduced by utilizing the unequal pressure precipitation at the two sides 2 Is higher than the water level H at the side of the river 1 Lateral water pressure（γ w Severe in water), in satisfying ∈>In the equation, the tendency of the foundation pit 1 to topple inward can be greatly reduced.
5) According to engineering geology and hydrogeology conditions, determining the diameter and engagement amount of the clay engagement pile 9, and determining the position of an intercepting axis outside the foundation pit guard pile; constructing a guide wall by taking the infiltration intercepting axis as a center; then, determining the pile position of the clay occlusion pile 9 along the guide wall; drilling holes at the determined pile positions, drilling holes by adopting full-rotation casing pipes, pressing down the casing pipes when driving the casing pipes in a rotation mode, connecting the casing pipes by adopting threads, and enabling the lower ends of the casing pipes to enter a water-impermeable layer; in the drilling process, drilling and soil taking are carried out along the inner wall of the sleeve, and the sleeve is drilled into a final hole after the elevation of the pile hole is designed; placing a guide pipe in the drilled hole, backfilling clay layer by layer through the guide pipe, hammering and tamping, and lifting the guide pipe while backfilling to build a clay occluding pile 9; repeating the drilling and clay backfilling processes on adjacent pile positions of the built clay occluding pile 9 to build a second clay occluding pile 9; and so on until the second occluding pile group 4 is built, and from the construction of the second clay occluding pile 9, the occluding part of the previous clay occluding pile 9 is needed to be cut off before construction, so that the next clay occluding pile 9 and the previous clay occluding pile 9 form new occlusion;
the second set of engagement piles 4 formed by the plurality of clay engagement piles 9 fully considers engineering geological and hydrogeological conditions to determine pile diameter and engagement amount. The construction machinery is a full-rotation full-casing drilling machine, the process technology is mature, and the water stopping effect can be exerted for a long time after one-time construction is completed.
6) Construction reinforced concrete and plain concrete engaged pile
a. According to design data, determining pile positions, pile diameters and biting amount in the second biting pile group 3 on site, binding reinforcement cages used for reinforced concrete piles 11 in advance, performing retarder doping amount tests, and determining retarder doping amount in plain concrete according to preset retarder time;
b. constructing plain concrete piles by adopting a bored pile method or other construction methods: piling a pile hole of the plain concrete pile, pouring prepared concrete into the pile hole of the plain concrete pile, and stopping pouring after reaching a designed elevation; continuing to construct the next plain concrete pile 10 until all of the plain concrete piles are constructed;
c. the reinforced concrete pile 11 is constructed by adopting a bored pile or other methods: piling up pile holes of the reinforced concrete piles, cutting the engaged parts of plain concrete piles 10 on two sides of the pile holes of the reinforced concrete piles to be piled up according to the determined engaged amount, and adding retarder into the plain concrete to facilitate the cutting at the moment, hoisting a reinforcement cage after the pile holes are finished, placing the reinforcement cage to meet the requirement of vertical perpendicularity, pouring concrete, gradually completing the construction of the reinforced concrete piles 11 and forming engagement with the plain concrete piles 10; until all the reinforced concrete piles 11 are built; drilling holes downwards on the top surfaces of the engaged parts of all reinforced concrete piles 11 and plain concrete piles 10, wherein the depth of each hole is the same as the pile length of the reinforced concrete pile 11, penetrating one-way grouting sleeve valve pipes 12 into all drilled holes, exposing the upper ends of the one-way grouting sleeve valve pipes 12 outside the pile tops, facilitating later grouting construction, and blocking the pipe orifice caps of the one-way grouting sleeve valve pipes 12 to prevent sundries from entering the grouting pipes; building a foundation pit water stop system adjacent to a river permeable stratum.
The foundation pit guard pile is combined with a plain concrete engaged pile by adopting a reinforced concrete pileIs a building envelope. The guard pile is mainly used for resisting lateral soil pressure, the individual concrete piles can be equivalently used as rectangular beams for calculation, and the section resisting moment isConsidering the rigidity of the plain concrete pile, the plain concrete pile and the reinforced concrete piles on two sides are respectively combined into an integral component from the center of the section, and the section resisting moment after combination is as follows:
b=0.8d，h=0.8d，b 1 =r-c，h 1 =r；
wherein: b is the section width of the guard pile equivalent rectangular beam; h is the section height of the guard pile equivalent rectangular beam; d is the diameter of the fender post; b 1 Equivalent width of plain concrete piles; h is a 1 Equivalent height of the plain concrete pile; r is the radius of the plain concrete pile; c is the width of the occlusal part.
Under the same lateral soil pressure, the bending moment M of the soil at two sides of the foundation pit to the guard piles is generated 1 =M 2 Normal stress of cross sectionBecause of W 2 >W 1 So the section normal stress sigma 2 <σ 1 Reduced reinforcement dosage->The purpose of saving the manufacturing cost is achieved.
According to the foundation pit water stopping system, firstly, after clay bags are piled up on river levees close to the side of a foundation pit 1, a cofferdam 8 formed by piling up reinforced gabions is arranged and is used as a first water stopping and preventing line; and then a second water collecting facility formed by at least two second dewatering wells 5 and a first water collecting facility formed by at least two first dewatering wells 2 are built and used as a second water stopping and preventing line, so that the underground water in the range of the foundation pit 1 is collected to the dewatering wells, accumulated water in the dewatering wells is pumped out by a water pump and is introduced into a foundation pit drainage system, and the distance between the dewatering wells is determined according to the underground hydrologic conditions. The water level of the far river side is kept higher than the water level of the near river side by adopting unequal pressure precipitation on the near river side and the far river side of the foundation pit 1, so that certain lateral water pressure difference is kept on two sides of the foundation pit 1, and the trend of dumping in the near river side of the foundation pit 1 after the foundation pit 1 is excavated is reduced; and (3) clay occluding piles are applied to the outer sides of the enclosure piles of the foundation pit 1 to form a second occluding pile group 4 serving as a third water stopping and preventing line. In order to ensure the water stopping effect of the foundation 1, a first occlusion pile group 3 formed by the reinforced concrete piles 11 and the plain concrete piles 10 at intervals is adopted for the foundation pit guard piles, so that a fourth water stopping and preventing line is formed. In the construction process of the occluding pile, the plain concrete pile 10 is firstly constructed, and a certain amount of retarder is doped in the plain concrete, so that the occluding part can be conveniently cut when the reinforced concrete pile 11 is subsequently constructed. The construction process is characterized in that a blocking position is a weak link, and due to construction errors, phenomena of insufficient blocking amount, occurrence of cracks at the blocking position and the like exist, and aiming at the quality problem of the blocking position, the construction process embeds the unidirectional grouting sleeve valve pipe 12 at the blocking position of the reinforced concrete pile 11 and the plain concrete pile 10, when the blocking position has quality defects, grouting can be carried out through the grouting sleeve valve pipe 12, the blocking position is reinforced, the quality defects of the blocking position are repaired, and therefore the water stopping effect of the blocking pile is ensured. The clay occluding pile 9 is of a flexible structure, a certain deformation is allowed without failure, the reinforced concrete pile 11 and the plain concrete pile 10 are of a rigid structure, the foundation pit 1 can be supported, the rigid structure and the flexible structure form a rigid and flexible structure, and the foundation pit 1 is well watered and supported. The water is blocked by the plurality of foundation pit water stopping and preventing lines, so that the engineering water stopping requirement can be effectively met.
In the water pumping process of the second dewatering well 5, along with the reduction of the water level, the seepage water head is gradually increased, and the pressure of a gap in the soil body is gradually reduced between the river levee and the second dewatering well 5, so that the protective layer 6 can be more tightly stuck to the river levee in the water pumping process, and the seepage of the river water is greatly weakened. The protective wall 7 is tightly pressed on the outer side of the protective layer 6 to prevent the protective layer 6 from being washed by water, and meanwhile, the protective wall 7 can also isolate the direct contact between an external water source and a river levee to a certain extent to play a role in isolating water from the source.
Claims (4)
1. The foundation pit water stopping system adjacent to the river water permeable stratum is characterized by comprising a cofferdam (8), a protective wall (7), a waterproof layer (6), a second water collecting facility, a second occluding pile group (4) and a first occluding pile group (3) which are sequentially arranged;
the cofferdam (8) is formed by piling reinforced gabions, and the lower part of the cofferdam (8) is positioned below the water surface of the river; the protective wall (7) is formed by stacking clay bags; the waterproof layer (6) is paved by waterproof geotextile, and the waterproof layer (6) is positioned between the protective wall (7) and the river levee; the second water collecting facility is composed of at least one second dewatering well (5) arranged side by side; the second engagement pile group (4) consists of a plurality of clay engagement piles (9); the first occlusion pile group (3) consists of a plurality of plain concrete piles (10) and a plurality of reinforced concrete piles (11), wherein the plain concrete piles (10) and the reinforced concrete piles (11) are arranged at intervals, and the adjacent plain concrete piles (10) and the adjacent reinforced concrete piles (11) are occluded with each other; the bottoms of the second dewatering well (5), the clay occluding pile (9), the plain concrete pile (10) and the reinforced concrete pile (11) all extend below the bottom surface of the foundation pit (1) and enter the impermeable layer.
2. Foundation pit water stop system in the immediate vicinity of river water permeable formation according to claim 1, characterized in that the engagement of plain concrete piles (10) and reinforced concrete piles (11) is buried with one-way grouting sleeve valve pipes (12).
3. A construction process of a foundation pit water stop system adjacent to a river water permeable stratum as claimed in claim 1, which is characterized by comprising the following steps:
1) Determining the range and the scale of the cofferdam (8) according to the scale of the foundation pit (1), engineering geology and hydrogeological conditions;
2) Clay is put into the woven bag to form a clay bag; the clay bags are piled up along the river levee to form a protective wall (7), and waterproof geotechnical cloth is paved on one side of the protective wall (7) facing the river levee to form a waterproof layer (6);
3) A cofferdam (8) formed by piling reinforced gabions is arranged on one side of the protective wall (7) away from the river levee,
4) At least one second dewatering well (5) is arranged between the river levee and the delimited foundation pit (1), water pumps are arranged in all dewatering wells, and the water level in the second dewatering well (5) is controlled so that the water level at the far river side in the second dewatering well (5) is higher than the water level at the near river side;
5) According to engineering geology and hydrogeology conditions, determining the diameter and the occlusion amount of a clay occlusion pile (9), and determining the position of an interception axis outside a determined foundation pit fender pile; constructing a guide wall by taking the infiltration intercepting axis as a center; then, determining the pile position of the clay occluding pile (9) along the guide wall, and drilling holes in the determined pile position of the clay occluding pile (9) by adopting a full-rotation sleeve drilling method so that the lower end of a sleeve enters a water-impermeable layer; in the drilling process, drilling and soil taking are carried out along the inner wall of the sleeve, and the sleeve is drilled into a final hole after the elevation of the pile hole is designed; placing a guide pipe in the drilled hole, backfilling clay layer by layer through the guide pipe, hammering and tamping, and lifting the guide pipe while backfilling to build a clay occluding pile (9); repeating the drilling and clay backfilling processes on adjacent pile positions of the built clay occluding pile (9) to build a second clay occluding pile (9); and so on until a second occluding pile group (4) is built, and before the construction, the occluding part of the previous clay occluding pile (9) is needed to be cut off from the construction of the second clay occluding pile (9);
6) Construction reinforced concrete and plain concrete engaged pile
a. According to the design data, determining pile positions, pile diameters and biting amount in the second biting pile group (4) on site, and binding reinforcement cages used for the reinforced concrete piles (11);
according to the preset retarding time, determining the blending amount of retarder in plain concrete through a test;
b. piling a pile hole of the plain concrete pile, pouring concrete mixed with retarder into the pile hole of the plain concrete pile, and stopping pouring after reaching a designed elevation; continuing to construct the next plain concrete pile (10) until the construction of all the plain concrete piles (10) is completed;
c. cutting the engaged parts of plain concrete piles (10) on two sides of a pile hole of the reinforced concrete pile to be driven; then, constructing a reinforced concrete pile (11), wherein the reinforced concrete pile (11) is meshed with the plain concrete pile (10); after all the reinforced concrete piles (11) are built, the top surfaces of the meshed parts of all the reinforced concrete piles (11) and the plain concrete piles (10) are downwards drilled, all the drilled holes are penetrated with one-way grouting sleeve valve pipes (12), and the upper ends of the one-way grouting sleeve valve pipes (12) are exposed out of the pile tops to build a foundation pit water stopping system adjacent to a river permeable stratum.
4. The foundation pit water stop system and construction process adjacent to the river water permeable stratum according to claim 3, wherein in the step 6), the requirement of vertical perpendicularity is satisfied for placing the reinforcement cage, then the clay bags are firstly laid on the river levee adjacent to the foundation pit side, and then the reinforcement cage cofferdam is arranged.
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| CN110258606A (en) * | 2019-06-26 | 2019-09-20 | 中国电建集团成都勘测设计研究院有限公司 | Projecting wall encloses well construction |
| CN110468860A (en) * | 2019-09-18 | 2019-11-19 | 南水北调中线干线工程建设管理局 | For the water sealing structure between underwater canopy cofferdam bottom panel and lining cutting |
| CN112195938A (en) * | 2020-09-04 | 2021-01-08 | 北京市轨道交通建设管理有限公司 | Treatment method for water seepage of occlusive pile |
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