阅读说明：本技术 一种高压水地区深大取水沉井结构及施工方法 (Open caisson structure for deep and large water intaking in high-pressure water area and construction method ) 是由 王安辉 罗如平 柳黎鑫 倪娇娇 赵亮 庄桂成 陈豪 左涛生 倪立 张艳芳 朱碧堂 于 2021-09-03 设计创作，主要内容包括：本发明公开了一种高水压地区深大取水沉井及其施工方法,包括沉井,所述沉井包括封底板、支撑短桩、取水管、外包混凝土、填充芯料及高压旋喷加固体,所述支撑短桩与封底板用于提供沉井竖向承载力,所述取水管用于取沉井内的水,所述外包混凝土及填充芯料用于包裹取水管,以保证其长期正常使用,所述高压旋喷加固体用于在取水管与沉井侧壁交汇处进行水泥高压旋喷加固,本发明能有效增强高水压地区深大取水沉井施工效率,避免发生沉井难以下沉的问题,同时沉井结构对取水管道具有较强的保护作用,可满足取水管道的长期正常使用要求。(The invention discloses a deep and large water intake open caisson in a high water pressure area and a construction method thereof, wherein the open caisson comprises a sealing bottom plate, a supporting short pile, a water intake pipe, outer concrete, a filling core material and a high-pressure rotary spraying reinforcing body, the supporting short pile and the sealing bottom plate are used for providing vertical bearing capacity of the open caisson, the water intake pipe is used for taking water in the open caisson, the outer concrete and the filling core material are used for wrapping the water intake pipe so as to ensure long-term normal use of the water intake pipe, and the high-pressure rotary spraying reinforcing body is used for carrying out cement high-pressure rotary spraying reinforcement at the intersection of the water intake pipe and the side wall of the open caisson.)

1. The utility model provides a deep big water intaking open caisson structure in high pressure water area which characterized in that: the open caisson comprises an open caisson body, wherein the open caisson body comprises a sealing bottom plate, a supporting short pile, a water taking pipe, outsourcing concrete, a filling core material and a high-pressure rotary spraying reinforcing body, the supporting short pile and the sealing bottom plate are used for providing vertical bearing capacity of the open caisson, the water taking pipe is used for taking water in the open caisson, the outsourcing concrete and the filling core material are used for wrapping the water taking pipe so as to ensure long-term normal use of the water taking pipe, and the high-pressure rotary spraying reinforcing body is used for carrying out cement high-pressure rotary spraying reinforcement at the junction of the water taking pipe and the side wall of the open caisson;

the open caisson is internally provided with an overwater floating platform, the overwater floating platform is provided with a high-pressure rotary spraying power device, and the high-pressure rotary spraying power device is used for quickly crushing and stripping soil bodies on the inner side of the open caisson through high-pressure air and high-pressure liquid sprayed out of a drill rod and extracting the crushed soil bodies.

2. The open caisson structure for deep and large water intaking in high-pressure water area according to claim 1, wherein: the periphery of the open caisson is provided with a circle of dewatering wells, and the dewatering wells are used for reducing the height of the underground water level in the sinking process of the open caisson and increasing the sinking load.

3. The open caisson structure for deep and large water intaking in high-pressure water area according to claim 2, wherein: the outer diameter of the open caisson is gradually reduced from bottom to top, and the outer wall of the open caisson is coated with wax.

4. The open caisson structure for deep and large water intaking in high-pressure water area according to claim 3, wherein: and a gravel cushion is laid on the top of the open caisson, and the laying range of the cushion is more than 500mm larger than the outer diameter of the open caisson.

5. The open caisson structure for deep and large water intaking in high-pressure water area according to claim 4, wherein: the floating platform comprises a plurality of floating boxes, a plurality of floating platform plates, a drawknot plate and a fixing rod, wherein the plurality of floating boxes are used for adjusting the height of the floating platform, the drawknot plate is used for connecting the plurality of floating platform plates into a whole, and the fixing rod is used for drawknot of the floating platform and the open caisson so as to ensure the stability of the floating platform plates.

6. The open caisson structure for deep and large water intaking in high-pressure water area according to claim 5, wherein: and the floating platform plate is provided with a circumferential or longitudinal and transverse guide channel, and the guide channel is matched with the drill rod.

7. The open caisson structure for deep and large water intaking in high-pressure water area according to claim 6, wherein: the number of the supporting short piles is multiple.

8. The open caisson structure for deep and large water intaking in high-pressure water area according to claim 7, wherein: the position that intake pipe and open caisson intersect sets up the reservation hole, the hoop strengthening rib and the distribution strengthening rib are arranged to the hole periphery, just the distribution strengthening rib includes horizontal muscle and vertical muscle.

9. The open caisson structure for deep and large water intaking in high-pressure water area according to claim 8, wherein: the water intake pipe is arranged in a Z shape.

10. The construction method of the open caisson structure for deep and large water intaking in the high-pressure water area according to claim 9, characterized in that: the method comprises the following steps:

construction preparation: the construction site 'tee joint one-level' work is well done, measurement setting is carried out according to design requirements, the actual position of the open caisson is determined, a gravel cushion layer is laid on the construction site, the laying range of the cushion layer is larger than the outer diameter of the open caisson by more than 500mm, and a stable and reliable operation surface is provided for subsequent open caisson construction and material stacking;

and (3) dewatering well construction: arranging a circle of precipitation well around the open caisson, wherein the depth of the precipitation well is greater than the maximum sinking depth of the open caisson, the bottommost part of the precipitation well is a precipitation pipe, the upper part of the precipitation pipe is a filter pipe with a hole, the upper part of the precipitation pipe is a common well pipe, the gap part of the precipitation pipe, the filter pipe and the open caisson is backfilled by medium coarse sand, and the gap part of the common well pipe and the open caisson is backfilled by common cohesive soil filling materials;

and (3) open caisson pouring construction: the outer wall of the open caisson adopts a step-type design, the outer diameter of the bottommost end is largest, the outer diameter is gradually reduced upwards along the depth, meanwhile, wax coating construction is carried out on the outer wall of the open caisson and thixotropic slurry resistance reduction is matched, the construction process of the open caisson mainly comprises erecting an inner die, binding steel bars, erecting an outer die and pouring concrete, the excavation process in the open caisson is matched, the pouring work of the open caisson can be completed by repeating the processes, meanwhile, a reserved hole is arranged at the position where a water taking pipe and the open caisson meet, the hole is blocked by a concrete thin plate, and annular reinforcing ribs and distributed reinforcing ribs are arranged at the periphery of the hole;

sinking construction of the open caisson: because the stratum of the water-taking open caisson is usually higher in underground water level, the underground water level is difficult to be completely reduced below the designed depth even if precipitation is adopted, the water-taking open caisson usually needs to be constructed by sinking the underwater open caisson, then the construction of the water-floating platform is adopted to carry out the excavation construction of the soil body in the underwater well, the water-floating platform is arranged at the inner side of the open caisson, the height of the water-floating platform is adjusted by the water tank at the lower part of the water-floating platform, a high-pressure rotary spraying power device is arranged on the platform, a high-pressure rotary spraying drill rod is connected below the platform and extends into the soil body to be excavated in the open caisson, the soil body at the inner side of the open caisson is quickly crushed and cut by the high-pressure air and high-pressure liquid sprayed by the drill rod, and further the crushed soil body is pumped out by a mud sucking device, the drill rod is moved on the floating platform through a guide channel, the omnibearing crushing and cutting of the soil body in the open caisson is realized, thereby the soil body in the open caisson is completely excavated, ensuring smooth sinking of the deep and large open caisson;

and (3) bottom sealing and water intake pipe hole high-pressure rotary spraying reinforcement: after the open caisson is sunk to the designed depth, firstly removing sludge at the bottom of the open caisson, driving a series of supporting short piles to improve the overall vertical bearing capacity of the open caisson, determining the number and the arrangement positions of the supporting short piles according to the design requirements, further laying a concrete sealing bottom plate reinforcing steel mesh and carrying out underwater concrete sealing bottom plate construction, after the open caisson bottom plate is poured, carrying out cement high-pressure rotary spraying reinforcement at the junction of a water intake pipe and the open caisson wall, wherein the reinforcement range of the cement high-pressure rotary spraying is determined according to the design requirements;

water intake pipe communication construction: breaking a thin plate at the opening of the water taking pipe, connecting a water taking top pipe with a water taking pipe in the open caisson, connecting an upper water taking top pipe and a lower water taking top pipe in the open caisson by adopting a Z-shaped pipe, and directly conveying the two top pipes to a water plant through the water taking pipe for further treatment;

backfilling of open caisson core filling materials and site recovery: after the water intake pipes are communicated, firstly, the Z-shaped water intake pipes are wrapped by plain concrete filler along the depth direction to form a first protective layer of the water intake pipes, further, core filling materials are filled outside the concrete wrapping layers to compact and fill the inner wall of the whole open caisson to form a second protective layer of the water intake pipes, after the open caisson core filling materials are backfilled, original state recovery is carried out on the open caisson construction site, protection work of the open caisson structure is well carried out, and damage to the open caisson and the water intake pipes during use is prevented.

Technical Field

The invention relates to the technical field of open caisson construction, in particular to a deep and large water intake open caisson in a high water pressure area and a construction method thereof.

Background

In recent years, along with the vigorous promotion of urbanization construction, the problem of shortage of water resource supply in cities and towns is more and more prominent, and the rapid development of long-distance pipe-jacking diversion engineering construction in China is promoted. As an important component of water diversion engineering, the open caisson structure is widely applied to water taking engineering and can be used as a jacking reaction force supporting structure and a water taking temporary receiving structure. Compared with the open caisson foundation adopted in the field of traditional foundation engineering, in the field of municipal water diversion engineering, the difference between the elevation of the water taking point and the elevation of the ground surface outside the water body is large, the downward penetration depth of the water taking jacking pipe is large, the open caisson depth is generally large, and the diameter of the open caisson is also large due to the requirement of meeting the space requirement of the jacking pipe reverse thrust operation. Therefore, the sinking resistance of the water intake open caisson structure is larger, and the problem of difficult sinking is easy to occur. For example, in the Yangtze river diversion project of the full-capacity water plant, in order to meet the water taking requirement, two circular open caissons are arranged in the dam of the Yangtze river to serve as starting wells of a water taking pipeline of the Yangtze river, the depth of each open caisson is about 48m, and the inner diameter of each open caisson is 15m, so that the open caisson is the deepest constructed open caisson in China at present. In addition, because the open caisson setting position is nearer from the water intaking point, place groundwater often with water intaking point surface water intercommunication, the water level is higher, the water pressure that the open caisson receives is great, at the in-process that sinks easy emergence soil body gush, has great construction risk.

In the current engineering practice, in order to reduce the frictional resistance in the sinking process of the open caisson, a thixotropic slurry drag reduction method is usually adopted, but for municipal open caisson taking water with large depth, the construction requirement is often difficult to meet only by the thixotropic slurry. Particularly, when the stratum is a water-rich sand layer, the self-stability of sand is poor, and the sand is mixed into thixotropic slurry in the sinking process of the open caisson, so that the drag reduction effect of the slurry is greatly reduced, and the problem that the open caisson is difficult to sink is easily caused.

Disclosure of Invention

The invention aims to provide a deep and large water intake open caisson structure in a high-pressure water area and a construction method, which solve the problems mentioned in the technical background. In order to achieve the purpose, the invention provides the following technical scheme: the open caisson comprises an open caisson body, wherein the open caisson body comprises a sealing bottom plate, a supporting short pile, a water taking pipe, outsourcing concrete, a filling core material and a high-pressure rotary spraying reinforcing body, the supporting short pile and the sealing bottom plate are used for providing vertical bearing capacity of the open caisson, the water taking pipe is used for taking water in the open caisson, the outsourcing concrete and the filling core material are used for wrapping the water taking pipe so as to ensure long-term normal use of the water taking pipe, and the high-pressure rotary spraying reinforcing body is used for carrying out cement high-pressure rotary spraying reinforcement at the intersection of the water taking pipe and the side wall of the open caisson.

Preferably, a circle of dewatering wells are arranged on the periphery of the open caisson and used for reducing the height of the underground water level in the sinking process of the open caisson and increasing the sinking load.

Preferably, the outer diameter of the open caisson is gradually reduced from bottom to top, and the outer wall of the open caisson is coated with wax.

Preferably, a sand cushion layer is paved on the top of the open caisson, and the paving range of the cushion layer is more than 500mm larger than the outer diameter of the open caisson.

Preferably, the floating platform includes a plurality of flotation tanks, polylith floating platform board, drawknot board and dead lever, a plurality of flotation tanks are used for adjusting floating platform's height, the drawknot board is used for connecting polylith floating platform board as a whole, the dead lever is used for drawknot with floating platform and open caisson to guarantee floating platform board's stability.

Preferably, the platform plate is provided with a circumferential or longitudinal and transverse guide channel, and the guide channel is matched with the drill rod.

Preferably, the number of the supporting short piles is multiple.

Preferably, the position that intake pipe and open caisson intersect sets up the reservation hole, the hoop strengthening rib and the distribution strengthening rib are arranged to the hole periphery, just the distribution strengthening rib includes horizontal muscle and vertical muscle.

Preferably, the water taking pipe is arranged in a Z shape.

Preferably, the method comprises the following steps:

construction preparation: the construction site 'tee joint one-level' work is well done, measurement setting is carried out according to design requirements, the actual position of the open caisson is determined, a gravel cushion layer is laid on the construction site, the laying range of the cushion layer is larger than the outer diameter of the open caisson by more than 500mm, and a stable and reliable operation surface is provided for subsequent open caisson construction and material stacking;

and (3) dewatering well construction: arranging a circle of precipitation well around the open caisson, wherein the depth of the precipitation well is greater than the maximum sinking depth of the open caisson, the bottommost part of the precipitation well is a precipitation pipe, the upper part of the precipitation pipe is a filter pipe with a hole, the upper part of the precipitation pipe is a common well pipe, the gap part of the precipitation pipe, the filter pipe and the open caisson is backfilled by medium coarse sand, and the gap part of the common well pipe and the open caisson is backfilled by common cohesive soil filling materials;

and (3) open caisson pouring construction: the outer wall of the open caisson adopts a step-type design, the outer diameter of the bottommost end is largest, the outer diameter is gradually reduced upwards along the depth, meanwhile, wax coating construction is carried out on the outer wall of the open caisson and thixotropic slurry resistance reduction is matched, the construction process of the open caisson mainly comprises erecting an inner die, binding steel bars, erecting an outer die and pouring concrete, the excavation process in the open caisson is matched, the pouring work of the open caisson can be completed by repeating the processes, meanwhile, a reserved hole is arranged at the position where a water taking pipe and the open caisson meet, the hole is blocked by a concrete thin plate, and annular reinforcing ribs and distributed reinforcing ribs are arranged at the periphery of the hole;

sinking construction of the open caisson: because the stratum of the water-taking open caisson is usually higher in underground water level, the underground water level is difficult to be completely reduced below the designed depth even if precipitation is adopted, the water-taking open caisson usually needs to be constructed by sinking the underwater open caisson, then the construction of the water-floating platform is adopted to carry out the excavation construction of the soil body in the underwater well, the water-floating platform is arranged at the inner side of the open caisson, the height of the water-floating platform is adjusted by the water tank at the lower part of the water-floating platform, a high-pressure rotary spraying power device is arranged on the platform, a high-pressure rotary spraying drill rod is connected below the platform and extends into the soil body to be excavated in the open caisson, the soil body at the inner side of the open caisson is quickly crushed and cut by the high-pressure air and high-pressure liquid sprayed by the drill rod, and further the crushed soil body is pumped out by a mud sucking device, the drill rod is moved on the floating platform through a guide channel, the omnibearing crushing and cutting of the soil body in the open caisson is realized, thereby the soil body in the open caisson is completely excavated, ensuring smooth sinking of the deep and large open caisson;

and (3) bottom sealing and water intake pipe hole high-pressure rotary spraying reinforcement: after the open caisson is sunk to the designed depth, firstly removing sludge at the bottom of the open caisson, driving a series of supporting short piles to improve the overall vertical bearing capacity of the open caisson, determining the number and the arrangement positions of the supporting short piles according to the design requirements, further laying a concrete sealing bottom plate reinforcing steel mesh and carrying out underwater concrete sealing bottom plate construction, after the open caisson bottom plate is poured, carrying out cement high-pressure rotary spraying reinforcement at the junction of a water intake pipe and the open caisson wall, wherein the reinforcement range of the cement high-pressure rotary spraying is determined according to the design requirements;

water intake pipe communication construction: breaking a thin plate at the opening of the water taking pipe, connecting a water taking top pipe with a water taking pipe in the open caisson, connecting an upper water taking top pipe and a lower water taking top pipe in the open caisson by adopting a Z-shaped pipe, and directly conveying the two top pipes to a water plant through the water taking pipe for further treatment;

backfilling of open caisson core filling materials and site recovery: after the water intake pipes are communicated, firstly, the Z-shaped water intake pipes are wrapped by plain concrete filler along the depth direction to form a first protective layer of the water intake pipes, further, core filling materials are filled outside the concrete wrapping layers to compact and fill the inner wall of the whole open caisson to form a second protective layer of the water intake pipes, after the open caisson core filling materials are backfilled, original state recovery is carried out on the open caisson construction site, protection work of the open caisson structure is well carried out, and damage to the open caisson and the water intake pipes during use is prevented.

In conclusion, the invention has the following beneficial effects:

the step type high water pressure area deep and large water taking open caisson structure and the construction method thereof can greatly reduce the frictional resistance applied to the sinking construction of a well body, and meanwhile, the water taking pipe in the well body is provided with sufficient protection measures, so that the long-term normal use of the water taking pipe in the well body can be effectively ensured; the construction method reduces the height of the underground water level in the sinking process of the open caisson by arranging a circle of dewatering wells at the periphery of the wall of the open caisson pipe, can effectively increase the sinking load, adopts an above-water platform type excavation mode, and crushes and cuts the soil body on the inner side of the open caisson through a high-pressure rotary jet drill rod, thereby greatly improving the sinking efficiency of the open caisson and reducing the risk of underwater excavation construction.

Drawings

FIG. 1 is a schematic view of a structure of a water intake open caisson;

FIG. 2 is a flow chart of water intake open caisson construction

FIG. 3 is a schematic view of a dewatering well arrangement;

FIG. 4 is a schematic illustration of soil excavation within a floating platform well;

fig. 5 is a schematic plan view of a floating platform;

fig. 6 is a schematic diagram of the arrangement of reinforcing ribs of the reserved holes.

In the figure: 1. sinking a well; 2. a water intake pipe; 3. sealing the bottom plate; 4. supporting the short piles; 5. concrete is coated outside; 6. filling a core material; 7. high-pressure rotary spraying to reinforce the body; 8. a settling tube; 9. medium coarse sand; 10. cohesive soil filler; 11. a well pipe; 12. a filter tube; 13. dewatering wells; 14. a drill stem; 15. a buoyancy tank; 16. a soil body; 17. a high-pressure rotary jet power device; 18. a drawknot plate; 19. fixing the rod; 20. a floating platform deck; 21. a guide channel; 22. circumferential reinforcing ribs; 23. a hole; 24. and reinforcing ribs are distributed.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1 to 6, the open caisson for deep and large water intake in high water pressure areas and the construction method thereof comprise an open caisson 1, wherein the open caisson 1 comprises a sealing bottom plate 3, a supporting stub 4, a water intake pipe 2, an outer concrete 5, a filling core material 6 and a high-pressure rotary spraying reinforcing body 7, the supporting stub 4 and the sealing bottom plate 3 are used for providing vertical bearing capacity of the open caisson 1, the water intake pipe 2 is used for taking water in the open caisson 1, the outer concrete 5 and the filling core material 6 are used for wrapping the water intake pipe 2 so as to ensure long-term normal use of the open caisson, the high-pressure rotary spraying reinforcing body 7 is used for carrying out cement high-pressure rotary spraying reinforcement at the junction of the water intake pipe 2 and the side wall of the open caisson 1, the long-term durability of the water intake pipe 2 can be effectively improved through the outer concrete 5 and the filling core material 6, the corrosion and deformation of the water intake pipe 2 in the use process are avoided, the outer diameter of the open caisson 1 is gradually reduced from bottom to top, the outer wall of the open caisson 1 is coated with wax. An overwater floating platform is arranged in the open caisson 1, a high-pressure rotary spraying power device 17 is arranged on the overwater floating platform, and the high-pressure rotary spraying power device 17 sprays high-pressure air and high-pressure liquid through a drill rod 14 to quickly break and strip soil bodies on the inner side of the open caisson and extract the broken soil bodies. The floating platform comprises a plurality of floating boxes 15, a plurality of floating platform plates 20, tie plates 18 and fixing rods 19, wherein the floating boxes 15 are used for adjusting the height of the floating platform, the tie plates 18 are used for connecting the floating platform plates 20 into a whole, and the fixing rods 19 are used for tying the floating platform and the open caisson 1 so as to ensure the stability of the floating platform plates 20. The floating platform plate 20 is provided with a circumferential or longitudinal and transverse guide channel 21, and the guide channel 21 is matched with the drill pipe 14. The number of the support short piles 4 is multiple. The position that intake pipe 2 and open caisson 1 intersect sets up and reserves hole 23, hoop strengthening rib 22 and distribution strengthening rib 24 are arranged to the hole 23 periphery, just the distribution strengthening rib includes horizontal muscle and vertical muscle. The water intake pipe 2 is arranged in a Z shape, a water source is led out of the open caisson 1 through the Z-shaped water intake pipe 2, and the height value of the floating platform can be adjusted by filling box pressing water with different volumes into the floating box 15, so that cutting and pumping drainage of soil bodies on the inner side of the open caisson 1 with different depths can be realized, and the construction operation efficiency is improved. In order to ensure that the heavy water intake open caisson can smoothly sink to a designed position in a high water pressure area, a circle of precipitation wells are arranged on the periphery of the pipe wall of the open caisson 1 so as to reduce the height of the underground water level in the sinking process of the open caisson 1 and increase the sinking load; further, in order to improve the sinking rate of the open caisson 1, an overwater platform type excavation mode is adopted, and the soil body on the inner side of the open caisson 1 is broken and stripped by arranging the high-pressure rotary spraying drill rod 14 on the platform, so that the excavation rate on the inner side of the open caisson 1 can be greatly improved, and meanwhile, the danger of traditional underwater operation construction can also be avoided. The invention can effectively enhance the construction efficiency of the open caisson for deep and large water intake in high water pressure areas, avoid the problem that the open caisson is difficult to sink, and meanwhile, the open caisson structure has stronger protection effect on the prop of the water intake pipe 2, thereby meeting the long-term normal use requirement of the water intake pipe 2

Construction preparation: the construction site 'tee joint leveling' work is well done, the measurement and setting-out are carried out according to the design requirements, the actual construction position of the open caisson 1 is determined, and a gravel or plain concrete cushion (the preferable strength is not lower than C20) is laid on the construction site, so that the ground surface forms a certain supporting strength, the stability of the sinking process of the open caisson 1 is ensured, and the over-allowable differential settlement is avoided; the thickness of the cushion layer is more than 200mm, the laying range is more than 500mm of the outer diameter of the open caisson, and a stable and reliable operation surface is provided for the subsequent open caisson construction and material stacking;

and (3) dewatering well construction: as shown in fig. 3, a circle of precipitation well 13 is arranged on the periphery of the open caisson 1 by a drilling machine, and the depth of the precipitation well 13 is larger than the maximum designed sinking depth of the open caisson 1 so as to ensure that the underground water level in the open caisson 1 can be effectively reduced; the distance between the dewatering well 13 and the outer wall of the open caisson is not more than 3m, so that the dewatering efficiency of the dewatering well 13 is improved. As shown in fig. 1, the precipitation well 13 mainly comprises a settling pipe 8, a filter pipe 12 and a common well pipe, wherein the settling pipe 8 is arranged at the bottommost part and is used for preventing impurities and foreign matters in the precipitation process from clogging the precipitation well 13; the upper part of the settling pipe 8 is provided with a filter pipe 12 with a hole (the diameter of the filter hole is preferably larger than 3mm and is wrapped by filter cloth), which is the main water pumping part of a dewatering well 13, and the upper part of the settling pipe is provided with a common well pipe 11 (the well wall is not provided with a water pumping hole); the depth value of the filter pipe 12 is mainly related to the permeability of the soil body of the field stratum, the filter pipe 12 can take a small value in the sandy soil stratum, and otherwise, the depth value of the filter pipe 12 in the viscous soil stratum can take a large value. Correspondingly, the gap parts of the settling pipe 8, the filter pipe 12 and the open caisson 1 hole are backfilled by medium coarse sand 9, and the gap parts of the common well pipe 11 and the open caisson 1 hole can be backfilled by common cohesive soil filling materials;

pouring construction of the open caisson 1: in order to reduce the frictional resistance in the sinking process of the deep and large open caisson, the outer wall of the open caisson 1 is designed in a stepped mode, the outer diameter of the bottom end is largest, the outer diameter is gradually reduced upwards along the depth, and the heights of all sections and the heights of the steps are determined according to the stratum characteristics and the design depth. Under the condition of meeting the design condition, the preferred segmental height is not less than 6m, and the step width is not less than 20 mm. Meanwhile, wax coating construction is carried out on the outer wall of the open caisson 1, and thixotropic slurry is matched for resistance reduction, so that the well wall friction resistance value is further reduced; further, drainage construction is carried out through the dewatering well 13 on the outer side of the open caisson, the underground water level height in the open caisson 1 is reduced, the effective weight of the structure is increased, and the sinking load of the open caisson is effectively improved. The construction process of the side wall of the open caisson 1 mainly comprises erecting an internal mold, binding steel bars, erecting an external mold and pouring concrete; and (5) repeating the above processes in coordination with the excavation process in the open caisson to complete the pouring work of the open caisson. As shown in fig. 6, in order to ensure that the water intake pipe 2 can smoothly pass through the borehole wall, a reserved hole 23 is arranged at the intersection position of the water intake pipe 2 and the open caisson 1, the hole 23 is sealed by a concrete thin plate, and a circumferential reinforcing rib 22 and a distributed reinforcing rib 24 (the distributed reinforcing ribs include transverse ribs and longitudinal ribs) are arranged at the periphery of the hole 23;

sinking construction of the open caisson 1: since the stratum where the water taking open caisson 1 is located is generally high in ground water level, even if precipitation is performed by the precipitation well 13, it is difficult to completely reduce the ground water level to below the designed depth, and therefore the water taking open caisson 1 generally needs to be constructed by sinking the open caisson 1. The construction of the water floating platform is preferably adopted for soil body excavation construction in the underwater open caisson 1, so that the construction efficiency is improved, and the construction risk is reduced. As shown in fig. 4, the water floating platform comprises buoyancy tanks 15, a floating platform plate 20, a drawknot plate 18 and fixing bars 19. An over-water floating platform is arranged on the inner side of the open caisson 1, and the platform height is adjusted by a floating platform plate 20 through a lower floating box 15 of the floating platform plate. As shown in fig. 5, the tie plates 18 essentially connect a plurality of floating platform plates 20 together as a unit; further, the platform is tied with the wall of the open caisson 1 through the fixing rods 19, so that the stability of the platform plate is guaranteed. As shown in fig. 4, a high-pressure jet grouting power device 17 is arranged on a floating platform plate 20, a high-pressure jet grouting drill pipe 14 is connected below the high-pressure jet grouting power device, and the drill pipe 14 is provided with a high-pressure nozzle and extends into a soil body 16 to be excavated in the open caisson 1; the soil 16 inside the open caisson 1 is quickly crushed and cut by high-pressure air and high-pressure liquid sprayed out of the drill pipe 14, and the crushed soil 16 is further pumped out by a mud suction device.

Soil mass crushing and cutting need to be matched with deformation monitoring data of the open caisson 1 in real time, and the crushing and cutting position and speed are adjusted according to the inclination condition of the open caisson 1. Referring to fig. 5, the preferred method is to provide a series of circumferential or longitudinal/transverse guide channels 21 on the floating platform plate 20, and to move the drill pipe 14 through the guide channels 21 to the area to be excavated and to perform soil body breaking and cutting according to the real-time monitoring data of the inclination of the open caisson. By reasonably arranging the guide channel 21, the stable sinking of the open caisson 1 can be ensured, the soil in the open caisson 1 can be crushed and cut in all directions, the soil 16 in the wall of the open caisson 1 is completely excavated, and the smooth sinking of the deep and large open caisson 1 is ensured;

1, bottom sealing of the open caisson and high-pressure rotary spraying and reinforcing of the water intake pipe 2 pipeline opening: after the open caisson 1 sinks to the designed depth, firstly removing sludge at the bottom of the open caisson, pouring bottom sealing concrete, and driving a series of supporting short piles 4 (figure 1), wherein the number and the arrangement positions of the supporting short piles 4 are determined according to the design requirements; further, 3 reinforcing meshes of the concrete sealing bottom plate are arranged, the underwater concrete sealing bottom plate 3 is constructed, and the underwater concrete pouring preferably adopts a conduit method to ensure that the poured concrete sealing bottom plate 3 does not have fillers such as segregation and silt, and the construction quality of the sealing bottom plate 3 is influenced. After the sealing plate 3 of the open caisson 1 is poured, cement high-pressure rotary spraying reinforcement is carried out at the intersection of the water taking pipe 2 and the wall of the open caisson 1, the reinforcement range of the high-pressure rotary spraying reinforcement body 7 is determined according to design requirements, and the preferable suggestion is that the diameter of the water taking pipe 2 is more than 3 times. The high-pressure rotary spraying is preferably constructed by adopting triple-tube equipment, the pressure of high-pressure water is between 30 and 35MPa, the pressure of compressed air is between 0.6 and 0.8MPa, the pressure of cement slurry is between 25 and 30MPa, the cement is more than 32.5 common portland cement, the dosage of the cement per linear meter is more than 300kg, and the diameter of the formed high-pressure rotary spraying pile is more than 800mm so as to improve the water stopping and water resisting effects;

and (3) communicating and constructing a water taking pipe 2: and breaking the thin plate at the hole 23, and connecting the water taking jacking pipe with the water taking pipe 2. As shown in figure 1, a Z-shaped water taking pipe 2 is connected with a top pipe, so that the problem that the water taking top pipe is easily clogged by impurities in water under the action of self weight in the traditional water taking mode of the artesian well is solved; the Z-shaped water taking pipe 2 is connected with the water taking jacking pipe in a welding mode, and the quality of a welding seam needs to be ensured so as to ensure the reliability of pipeline connection under the impact of water flow pressure.

Backfilling a core filling material of the open caisson 1 and recovering a field: after the water taking pipe 2 is communicated, firstly, the Z-shaped water taking pipe 2 is wrapped by adopting outer concrete 5 along the depth direction, and the wrapping thickness is more than 20 cm; when the filler outer-coated concrete 5 is poured, a formwork is required to be erected on the outer side of the water intake pipe 2, and corresponding pouring is carried out. Furthermore, filling core material 6 is carried out outside the outer concrete 5, and the filling core material 6 can preferably adopt cohesive soil with the compactness of more than 95 percent. Through the double protection measures, the long-term durability of the water taking pipe 2 can be effectively improved, and the water taking pipe 2 is prevented from being corroded and deformed in the using process. After the open caisson 1 is filled with the core material 6 and backfilled, the construction site of the open caisson 1 is subjected to original state recovery, the protection work of the structure of the open caisson 1 is well done, and the open caisson 1 and the water taking pipe 2 are prevented from being damaged in the using period.

The present embodiment is only for explaining the present invention, and it is not limited to the present invention, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present invention.