阅读说明：本技术 一种适用于富水地层深大沉井开挖及压沉施工方法 (Construction method suitable for excavation and pressure sinking of deep and large open caisson of water-rich stratum ) 是由 王安辉 罗如平 张艳芳 倪娇娇 朱碧堂 赵亮 庄桂成 陈豪 施发杰 袁灯 柳黎鑫 于 2021-09-03 设计创作，主要内容包括：本发明公开了一种适用于富水地层深大沉井开挖及压沉施工方法,涉及沉井施工技术领域,深大沉井开挖采用水上浮式平台开挖方法：在沉井内设置水上漂浮平台,水上漂浮平台通过浮箱调节施工高度,在平台上设置破泥装置将沉井内土体快速破碎切削,并采用吸泥装置将破碎土体抽出,可实现水下沉井快速开挖施工,在沉井外侧布置配重块,采用钢绞线连接配重块和沉井内侧壁,并在沉井顶部设置穿心千斤顶,通过穿心千斤顶反力作用对沉井施加向下作用力,促使沉井下沉。本发明能有效提高富水地区深大沉井水下开挖施工效率,同时所提出的沉井压沉方法构造简便,施工效率高,反压荷载大,可较好地解决深大沉井下沉困难问题。(The invention discloses a construction method suitable for deep and large open caisson excavation and pressure sinking of a water-rich stratum, which relates to the technical field of open caisson construction, wherein the deep and large open caisson excavation adopts an overwater floating platform excavation method: set up the floating platform on water in the open caisson, floating platform on water passes through the flotation pontoon and adjusts the construction height, set up broken mud device on the platform and with the quick broken cutting of soil body in the open caisson, and adopt and inhale mud device and take out broken soil body, can realize the quick excavation construction of open caisson under water, arrange the balancing weight outside the open caisson, adopt steel strand wires to connect balancing weight and open caisson inside wall, and set up the center-penetrating jack at the open caisson top, exert downward effort to the open caisson through center-penetrating jack counter-force, make the open caisson sink. The invention can effectively improve the underwater excavation construction efficiency of the deep and large open caisson in the water-rich area, and the open caisson sinking method has simple structure, high construction efficiency and large back pressure load, and can better solve the problem of difficult sinking of the deep and large open caisson.)

1. The utility model provides a construction method suitable for deep big open caisson excavation of rich water stratum and pressure sinking which characterized in that: the construction method comprises the following steps:

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 sand and plain concrete cushion layers are laid on the construction site, so that the ground surface forms certain supporting strength, the stability of the open caisson (1) in the sinking process is ensured, and the over-allowable differential settlement is avoided;

and (3) dewatering well construction: a circle of dewatering wells (9) are arranged on the periphery of the open caisson (1) by a drilling machine, the depth of the dewatering wells (9) is greater than the maximum designed sinking depth of the open caisson (1), to ensure that the underground water level in the well body can be effectively reduced, the dewatering well (9) mainly comprises a settling pipe (4), a filter pipe (8) with holes and a common well pipe (7), the settling pipe (4) is arranged at the bottom, used for preventing impurities and foreign matters in the precipitation process from clogging the precipitation well (9), the upper part of the settling pipe (4) is provided with a filter pipe (8) with a hole which is the main water pumping part of the precipitation well (9), a common well pipe (7) is arranged on the filter tube, the depth value of the filter tube with holes (8) is changed mainly according to the permeability of the ground stratum soil body, the ground stratum soil body is a sandy soil stratum, the depth of the filter tube with holes (8) takes a small value, otherwise, the ground stratum soil body is a sticky soil stratum, and the depth of the filter tube with holes (8) takes a large value;

pouring construction of a well body: the construction method comprises the following steps of carrying out wax coating construction on the outer wall of a well body and matching with thixotropic slurry for resistance reduction so as to further reduce the frictional resistance value of a well wall, carrying out drainage construction through a dewatering well (9) on the outer side of the open caisson (1), reducing the underground water level height in the well body, increasing the effective weight of the structure, effectively improving the sinking load of the open caisson (1), wherein the construction process of the side wall of the well body mainly comprises the steps of erecting an inner mold, binding steel bars, erecting an outer mold and pouring concrete, and the pouring work of the well body can be completed by matching with the excavation process in the well body and repeating the processes;

sinking the well body for construction: the construction method comprises the following steps that an overwater floating platform is adopted for construction to carry out soil body excavation construction in an underwater well, so that construction efficiency is improved, and construction risks are reduced, wherein the overwater floating platform comprises a floating box (11), a floating platform plate (16), a tie plate (13) and fixing rods (14), the floating platform plate (16) is arranged on the inner side of the open caisson (1), different construction heights of the platform are adjusted through the filling water quantity of the floating box (11) at the lower part of the floating platform plate (16), the tie plate (13) mainly connects all the dispersed floating platform plates (16) into a whole, the platform and the side wall of the open caisson (1) are tied through the fixing rods (14) so as to ensure the stability of the platform plates, a mud breaking device is arranged on the floating platform plate (16) to quickly break and cut a soil body (17), and further the broken soil body (17) is extracted through the mud sucking device;

and (3) deep and large open caisson pressure sinking construction: the deep and large open caisson (1) is assisted to sink by adopting a back pressure mode of a through jack (23), a steel frame reaction platform (22) is arranged at the top of the open caisson (1), the steel frame reaction platform (22) is connected to the well wall, the stress stability of the structure can be effectively ensured, the through jack (25) is anchored in the well wall at the top of the open caisson (1), the anchor jack (25) is fixed in the open caisson (1), two through jacks (23) are arranged on the steel frame reaction platform (22), the two through jacks (23) are connected in series through a steel strand (21), one end of the steel strand (21) is anchored on the steel frame reaction platform (22) at the inner side of the well wall, the other end is anchored on a balancing weight (20) at the outer side of the well wall, the balancing weight (20) is arranged on a bearing plate (24) on the ground surface, a supporting short pile (19) is arranged under the bearing plate (24) to ensure that the bearing plate (24) does not generate excessive deformation, in the actual construction engineering, the number of proper jacks can be determined according to the required magnitude of the sinking load, in the process of sinking, an oil cylinder of a penetrating jack (23) props against a steel strand (21) at the upper end, upward reaction force is applied to a counter weight block (20) on the outer side of a well wall through the steel strand (21), and according to the force action and reaction force principle, the counter weight block (20) generates downward reaction pressure on the structure of the sinking well (1) to promote the sinking well (1) to sink, so that the continuous sinking of the structure of the sinking well (1) is realized until the designed depth is reached;

bottom sealing construction of a well bottom: after the open caisson (1) sinks to the designed depth, firstly removing sludge at the bottom of the open caisson (1), pouring bottom sealing concrete (2), and preferably adopting a conduit method for pouring the underwater bottom sealing concrete (2) to construct so as to ensure that the poured bottom sealing concrete (2) does not have fillers such as segregation, sludge and the like, and laying a reinforcing mesh and carrying out concrete pouring construction on the bottom sealing plate (3) after the strength of the bottom sealing concrete (2) reaches the design requirement;

and (3) recovering the open caisson construction site: after sinking of the open caisson (1), pouring of bottom sealing concrete (2) and pouring of the bottom sealing plate (3) are completed, the construction site of the open caisson (1) is subjected to original state recovery, the structure of the open caisson (1) is well protected, and the well body is prevented from being damaged and endangering related personnel during use.

2. The excavation and pressure sinking construction method suitable for the deep and large open caisson of the water-rich stratum as claimed in claim 1, wherein: the concrete strength of the plain concrete cushion layer in the construction preparation step is not lower than C20.

3. The excavation and pressure sinking construction method suitable for the deep and large open caisson of the water-rich stratum as claimed in claim 2, wherein: the thickness of the cushion layer of the plain concrete cushion layer is more than 200mm, and the laying range is more than 500mm of the outer diameter of the open caisson (1).

4. The excavation and pressure sinking construction method suitable for the deep and large open caisson of the water-rich stratum as claimed in claim 1, wherein: the diameter of the filter holes in the filter tubes with holes (8) is larger than 3mm, and the periphery of the filter tubes with holes (8) is coated with filter cloth.

5. The excavation and pressure sinking construction method suitable for the deep and large open caisson of the water-rich stratum as claimed in claim 1, wherein: gaps among the settling pipes (4), the filter pipes (8) with holes and the well holes of the open caisson (1) in the dewatering well construction step are backfilled by medium coarse sand fillers (5), and gaps among the common well pipes (7) and the well holes of the open caisson (1) are backfilled by common cohesive soil fillers (6).

6. The excavation and pressure sinking construction method suitable for the deep and large open caisson of the water-rich stratum as claimed in claim 1, wherein: the outside of the open caisson (1) adopts a step design, the outer diameter of the bottommost end of the open caisson is largest, the outer diameter is gradually reduced upwards along the depth of the open caisson, the section height of the open caisson is not less than 6m, and the step width is not less than 20 mm.

7. The excavation and pressure sinking construction method suitable for the deep and large open caisson of the water-rich stratum as claimed in claim 1, wherein: the mud breaking device in the well sinking construction step comprises a high-pressure rotary spraying power device (12) arranged on a floating platform plate (16) and a high-pressure rotary spraying drill rod (10) connected to the lower end of the high-pressure rotary spraying power device (12), wherein one end of the high-pressure rotary spraying drill rod (10) extends into a soil body (17).

8. The excavation and pressure sinking construction method suitable for the deep and large open caisson of the water-rich stratum as claimed in claim 7, wherein: a series of wireless deformation sensors (15) used for collecting inclination and settlement of open caisson monitoring points are arranged on the outer side wall of the open caisson (1), a series of guide channels (18) which are distributed annularly or longitudinally and transversely are arranged on the floating platform plate (16), and the high-pressure rotary spraying drill rod (10) is connected into the guide channels (18) in a sliding mode.

9. The excavation and pressure sinking construction method suitable for the deep and large open caisson of the water-rich stratum as claimed in claim 1, wherein: the steel frame reaction platform (22) is supported and connected on the well wall by a bracket, a fixed pulley is arranged on the upper portion of the center penetrating jack (23), and the steel strand (21) is movably arranged on the fixed pulley.

10. The excavation and pressure sinking construction method suitable for the deep and large open caisson of the water-rich stratum as claimed in claim 1, wherein: the anchoring pull rod (25) is fixed in the well wall through an expansion bolt, the steel frame counter-force platform (22) is a detachable platform and is detachably connected to the top of the open caisson (1) through an anchoring bolt.

Technical Field

The invention relates to the technical field of open caisson construction, in particular to a construction method suitable for excavation and pressure sinking of a deep and large open caisson of a water-rich stratum.

Background

With the vigorous development of infrastructure construction of bridges, municipal works, water conservancy and the like in China, the size of open caisson foundations gradually develops towards a great direction. For example, in the Yangtze river diversion project of the full-capacity water plant, in order to meet the requirement of long-distance water taking, 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 well body is 15m, so that the deepest constructed open caisson is the deepest constructed open caisson in China at present. For the foundation of a deep and large open caisson, the open caisson has larger diameter and deeper sinking depth, and the sinking resistance which needs to be overcome in the sinking process is larger, so that the problems of difficult sinking of the open caisson and the like are more easily caused.

In current engineering practice, open caisson sinking construction methods mainly include a top loading method and an anchorage/anchor pile method, and for example, patent CN201410261230.3 and patent CN201810679366.4 propose corresponding open caisson sinking promotion construction methods based on the idea of anchorage counter force. However, it should be noted that the construction method of promoting sinking by using the anchorage or the anchor pile needs to estimate sinking resistance of the open caisson more accurately to determine the size of the corresponding anchorage or anchor pile, and the construction is complicated and needs special construction machinery. The top stacking method is mainly suitable for small-size open caisson, has great construction safety risk for the overlarge upper stacking of deep and large open caisson foundations, and needs to prevent the integral overturn of the open caisson structure; and when the piling method is adopted for sinking construction of the open caisson, when the number of sinking rings needs to be increased, the sinking construction needs to be carried out again according to the unloading-piling process, so that the construction efficiency is low. In addition, for open caisson in water-rich area, the open caisson needs to be excavated, and how to improve the construction efficiency of excavation of underwater soil is also a problem to be faced by engineering personnel. Aiming at the defects, a deep and large open caisson excavation and pressure sinking construction method which can effectively solve the problem that the deep and large water taking open caisson is difficult to sink and is suitable for water-rich strata needs to be designed.

Disclosure of Invention

The invention aims to provide a construction method suitable for excavation and pressure sinking of a deep and large open caisson of a water-rich stratum, which aims to solve the problems in the technical background, and the method is characterized in that the assembly of an annular support is completed through main components, and uniformly distributed radial pressure is applied to the inner wall of a lining segment, so that the safety and stability of the whole shield tunnel and the convenience of personnel passing and material transportation in the process of opening the lower part of the segment and constructing a water collecting well of the tunnel are ensured; by adopting the water collecting well with the oval cross section, under the supporting action of the annular support, the bottom lining segment is subjected to cutting opening, soil body reinforcement, excavation, primary support, secondary support and maintenance of the molded concrete, and finally the construction of the water collecting well is completed. In particular, the annular support and the working method provided by the invention are also suitable for the general situation that the water collecting well is arranged in the communication channel.

In order to achieve the purpose, the invention provides the following technical scheme:

a construction method suitable for excavation and pressure sinking of a deep and large open caisson of a water-rich stratum comprises the following steps:

construction preparation: the construction site 'tee joint leveling' work is well done, measurement setting is carried out according to design requirements, the actual construction position of the open caisson is determined, and gravel and plain concrete cushion layers are laid on the construction site, so that the ground surface forms certain supporting strength, the stability of the open caisson sinking process is ensured, and over-allowable differential settlement is avoided;

and (3) dewatering well construction: the method is characterized in that a circle of precipitation well is arranged at the periphery of an open caisson by a drilling machine, the depth of the precipitation well is greater than the maximum designed sinking depth of the open caisson so as to ensure that the underground water level in the well can be effectively reduced, the precipitation well mainly comprises a settling pipe, a perforated filter pipe and a common well pipe, the settling pipe is arranged at the bottom and is used for preventing impurities and foreign matters in water from clogging the precipitation well in the precipitation process, the perforated filter pipe is arranged at the upper part of the settling pipe and is a main water pumping part of the precipitation well, the common well pipe is arranged at the upper part of the settling pipe, the depth value of the perforated filter pipe is mainly changed according to the permeability of a ground stratum soil body, the ground stratum soil body is a sandy soil stratum, the depth of the perforated filter pipe is small, otherwise, the ground stratum soil body is a sticky soil stratum, and the depth of the perforated filter pipe is large;

pouring construction of a well body: the construction method comprises the following steps of carrying out wax coating construction on the outer wall of a well body and matching with thixotropic slurry for resistance reduction so as to further reduce the well wall friction resistance value, simultaneously carrying out drainage construction through a dewatering well outside the open caisson, reducing the underground water level height in the well body, increasing the effective weight of the structure, effectively improving the sinking load of the open caisson, wherein the construction process of the side wall of the well body mainly comprises the steps of erecting an inner mold, binding steel bars, erecting an outer mold and pouring concrete, and matching with the excavation process in the well body, the pouring work of the well body can be completed by repeating the processes;

sinking the well body for construction: the construction of the water floating platform is adopted to carry out the excavation construction of the soil body in the underwater well, so as to improve the construction efficiency and reduce the construction risk, the water floating platform comprises floating boxes, floating platform plates, tie plates and fixing rods, the floating platform plates are arranged on the inner side of the open caisson, the floating platform plates adjust different construction heights of the platform through the filling water quantity of the floating boxes on the lower part of the floating platform plates, the tie plates mainly connect all the dispersed floating platform plates into a whole, the platform and the side wall of the open caisson are tied through the fixing rods so as to ensure the stability of the platform plates, a mud breaking device is arranged on the floating platform plates to quickly break and cut the soil body, and the broken soil body is further extracted out through a mud suction device;

and (3) deep and large open caisson pressure sinking construction: the method is characterized in that a penetrating jack counter-pressure mode is adopted to assist the sinking of the deep and large sinking well, a steel frame counter-force platform is arranged at the top of the sinking well, the steel frame counter-force platform is connected to the well wall, the force stability of the structure can be effectively ensured, the steel frame counter-force platform is anchored in the well wall at the top of the sinking well through an anchoring pull rod, the end part of the anchoring pull rod is fixed in the sinking well, two penetrating jacks are arranged on the steel frame counter-force platform, the two penetrating jacks are connected in series through steel strands, one end of each steel strand is anchored on the steel frame counter-force platform at the inner side of the well wall, the other end of each steel strand is anchored on a balancing weight at the outer side of the well wall, the balancing weight is arranged on a bearing plate on the ground surface, a supporting short pile is arranged below the bearing plate to ensure that the bearing plate does not generate excessive deformation, the proper number of the jacks can be determined according to the required magnitude of the compressive load in the actual construction engineering, an oil cylinder of the penetrating jacks supports the steel strands at the upper end, and exerts upward counter-force on the balancing weight at the outer side of the well wall through the steel strands, according to the force action and reaction force principle, the counter weight block generates downward counter pressure on the open caisson structure to promote the open caisson to sink, so that continuous pressure sinking of the open caisson structure is realized until the design depth is reached;

bottom sealing construction of a well bottom: after the open caisson is sunk to the designed depth, firstly removing sludge at the bottom of the open caisson, pouring bottom sealing concrete, and preferably constructing the underwater bottom sealing concrete by adopting a conduit method so as to ensure that the poured bottom sealing concrete does not have fillers such as segregation, sludge and the like, and after the strength of the bottom sealing concrete reaches the design requirement, laying a reinforcing mesh and carrying out concrete pouring construction of the bottom sealing plate;

and (3) recovering the open caisson construction site: after sinking of the open caisson, bottom sealing concrete pouring and bottom sealing plate pouring are completed, the original state of the construction site of the open caisson is restored, the protection work of the open caisson structure is well done, and the well body is prevented from being damaged and endangering related personnel during use.

As a further scheme of the invention: the concrete strength of the plain concrete cushion layer in the construction preparation step is not lower than C20.

As a further scheme of the invention: the thickness of the cushion layer of the plain concrete cushion layer is more than 200mm, and the laying range is more than 500mm of the outer diameter of the open caisson.

As a further scheme of the invention: the diameter of the filter holes in the filter tube with the holes is larger than 3mm, and the periphery of the filter tube with the holes is coated with filter cloth.

As a further scheme of the invention: and gaps among the settling pipes, the filter pipes with holes and the open caisson hole in the dewatering well construction step are backfilled by medium coarse sand filling materials, and gaps among the common well pipe and the open caisson hole are backfilled by common viscous soil filling materials.

As a further scheme of the invention: the open caisson outside adopts the step design, and its bottom external diameter is the biggest, upwards reduces gradually along its degree of depth, and its merogenesis height is not less than 6m, and the step width is not less than 20 mm.

As a further scheme of the invention: the mud breaking device in the well sinking construction step comprises a high-pressure jet grouting power device arranged on the floating platform plate and a high-pressure jet grouting drill rod connected to the lower end of the high-pressure jet grouting power device, wherein one end of the high-pressure jet grouting drill rod extends into a soil body.

As a further scheme of the invention: the high-pressure jet grouting drill pipe is characterized in that a series of wireless deformation sensors used for collecting inclination and settlement of open caisson monitoring points are arranged on the outer side wall of the open caisson, a series of guide channels distributed annularly or longitudinally and transversely are arranged on the floating platform plate, and the high-pressure jet grouting drill pipe is connected in the guide channels in a sliding mode.

As a further scheme of the invention: the steel frame counter-force platform is supported and connected on the well wall by a bracket, the upper part of the center penetrating jack is provided with a fixed pulley, and the steel strand is movably arranged on the fixed pulley.

As a further scheme of the invention: the anchoring pull rod end is fixed in the well wall through an expansion bolt, the steel frame counter-force platform is a detachable platform and is detachably connected to the top of the open caisson through an anchoring bolt.

Has the advantages that:

1. the invention provides a construction method suitable for excavation and pressure sinking of a deep and large open caisson in a water-rich stratum, which can effectively increase sinking load by arranging a circle of precipitation wells at the periphery of the wall of the open caisson pipe to reduce the height of the underground water level in the sinking process of the open caisson; an overwater platform type soil excavation mode is adopted, soil bodies on the inner side of the open caisson are crushed and cut through a soil crushing device, and the sinking efficiency of the open caisson is greatly improved; the counter weight block is arranged on the outer side of the open caisson, the steel strand is adopted to connect the counter weight block and the inner side wall of the open caisson, the penetrating jack is arranged at the top of the open caisson, downward acting force is applied to the open caisson through the counter-force action of the penetrating jack, the open caisson is promoted to sink, the risk of traditional pressure-sinking construction is greatly reduced, and meanwhile, the open caisson pressure-sinking method is simple and convenient in structure, high in construction efficiency and large in counter pressure load, and the problem of difficulty in sinking of the deep and large open caisson can be well solved.

Drawings

FIG. 1 is a construction flow chart of the present invention;

FIG. 2 is a schematic sectional view of a dewatering well according to the present invention;

FIG. 3 is a schematic top plan view of the dewatering well according to the present invention;

FIG. 4 is a schematic diagram of the excavation of the soil in the water floating platform well according to the present invention;

FIG. 5 is a schematic top plan view of the water platform of the present invention;

FIG. 6 is a schematic diagram of the sinking well pressure and sinking construction of the present invention;

FIG. 7 is a schematic plan view of a crush-and-sink structure of the present invention;

in the figure: 1. sinking a well; 2. sealing bottom concrete; 3. sealing the bottom plate; 4. a settling tube; 5. filling medium coarse sand; 6. cohesive soil filler; 7. a plain well pipe; 8. a perforated filter tube; 9. dewatering wells; 10. high-pressure rotary spraying drill pipes; 11. a buoyancy tank; 12. a high-pressure rotary jet power device; 13. a drawknot plate; 14. fixing the rod; 15. a wireless deformation sensor; 16. a floating platform deck; 17. a soil body; 18. a guide channel; 19. supporting the short piles; 20. a balancing weight; 21. steel strand wires; 22. a steel frame counter-force platform; 23. a center-penetrating jack; 24. a bearing plate; 25. and anchoring the pull rod.

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.

The invention provides the following technical scheme:

as shown in fig. 1-7, a construction method for excavation and pressure sinking of a deep and large open caisson in a water-rich stratum comprises the following steps:

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 sand and plain concrete cushion layers are laid on the construction site, so that a certain supporting strength is formed on the ground surface, the stability of the open caisson 1 in the sinking process is ensured, the over-allowable differential settlement is avoided, and a stable and reliable operation surface is provided for the subsequent open caisson 1 construction and material stacking;

and (3) dewatering well construction: as shown in figure 3, a circle of precipitation wells 9 are arranged on the periphery of the open caisson 1 by a drilling machine, the depth of the precipitation wells 9 is greater than the maximum designed sinking depth of the open caisson 1 so as to ensure that the underground water level in the well body can be effectively reduced, the distance between the precipitation wells 9 and the outer wall of the open caisson 1 is not more than 3m so as to improve the precipitation efficiency of the precipitation wells 9, as shown in figure 2, the precipitation wells 9 mainly comprise precipitation pipes 4, perforated filter pipes 8 and common well pipes 7, the precipitation pipes 4 are arranged at the bottoms and are used for preventing impurities and foreign matters in water from clogging the precipitation wells 9 in the precipitation process, the perforated filter pipes 8 are arranged at the upper parts of the precipitation pipes 4 and are main water pumping parts of the precipitation wells 9, the common well pipes 7 are arranged on the upper parts of the well walls without water pumping holes, the depth values of the perforated filter pipes 8 are mainly changed according to the permeability of the soil body of the ground stratum, the ground soil body is a sandy soil body, the depth of the perforated filter pipes 8 is a small value, otherwise, the ground body is a sticky soil body, the depth of the filter tube with the hole 8 is a large value;

pouring construction of a well body: the construction method comprises the following steps of carrying out wax coating construction on the outer wall of a well body and matching with thixotropic slurry for resistance reduction so as to further reduce the well wall friction resistance value, simultaneously carrying out dewatering construction through a dewatering well 9 on the outer side of the open caisson 1, reducing the underground water level height in the well body, increasing the effective weight of the structure, effectively improving the sinking load of the open caisson 1, wherein the construction process of the side wall of the well body mainly comprises the steps of erecting an internal mold, binding reinforcing steel bars, erecting an external mold and pouring concrete, matching with the excavation process in the well body, and repeating the processes to complete the pouring work of the well body;

sinking the well body for construction: because the stratum of the water taking open caisson 1 is usually higher in underground water level, even if the water is lowered by the precipitation well 9, the underground water level is difficult to be completely lowered below the designed depth, the water taking open caisson 1 usually needs to be constructed for sinking the underwater well body, the invention preferably adopts the construction of the water floating platform to carry out the excavation construction of the soil body 17 in the underwater well, so as to improve the construction efficiency and reduce the construction risk, as shown in figure 4, the water floating platform comprises floating boxes 11, floating platform plates 16, tie plates 13 and fixing rods 14, the floating platform plates 16 are arranged at the inner side of the open caisson 1, the floating platform plates 16 adjust the different construction heights of the platform through the water filling amount of the floating boxes 11 at the lower part of the floating platform, as shown in figure 5, the tie plates 13 mainly connect the dispersed floating platform plates 16 into a whole, and tie the platform and the side wall of the open caisson 1 through the fixing rods 14, so as to ensure the stability of the floating platform plates, arranging a mud breaking device on the floating platform plate 16 to quickly break and cut the soil body 17, and further extracting the broken soil body 17 through a mud suction device;

and (3) deep and large open caisson pressure sinking construction: for a deep and large open caisson 1, the sinking frictional resistance is large, the open caisson 1 is difficult to sink to the designed depth only by the dead weight of the caisson body, an additional sinking measure needs to be taken during construction, the deep and large open caisson 1 is assisted to sink by adopting a penetrating jack 23 back pressure mode, as shown in fig. 6, a steel frame counterforce platform 22 is arranged at the top of the open caisson 1, the steel frame counterforce platform 22 is connected to the well wall, the stress stability of the structure can be effectively ensured, and is anchored in the well wall at the top of the open caisson 1 through an anchoring pull rod 25, the end part of the anchoring pull rod 25 is fixed in the open caisson 1, two penetrating jacks 23 are arranged on the steel frame counterforce platform 22, the two penetrating jacks 23 are connected in series through a steel strand 21, one end of the steel strand 21 is anchored on the steel frame counterforce platform 22 at the inner side of the well wall, the other end is anchored on a counterweight 20 at the outer side of the well wall, the counterweight 20 is arranged on a bearing plate 24 on the ground surface, the supporting short piles 19 are arranged below the bearing plate 24 to ensure that the bearing plate 24 does not generate excessive deformation, the number of the proper jacks can be determined according to the required magnitude of the pressure-sinking load in the actual construction engineering, in the pressure-sinking process, the oil cylinders of the penetrating jacks 23 prop against the steel strands 21 at the upper ends, upward reaction force is applied to the counter weight block 20 at the outer side of the well wall through the steel strands 21, according to the principle of force action and reaction force, the counter weight block 20 generates downward counter pressure on the structure of the open caisson 1 to promote the open caisson 1 to sink, and thus the continuous pressure-sinking of the structure of the open caisson 1 is realized until the design depth is reached;

bottom sealing construction of a well bottom: after the open caisson 1 sinks to the designed depth, firstly removing sludge at the bottom of the open caisson 1, pouring the bottom sealing concrete 2, and preferably adopting a conduit method for pouring the underwater bottom sealing concrete 2 to ensure that the poured bottom sealing concrete 2 does not have fillings such as segregation and sludge, and after the strength of the bottom sealing concrete 2 reaches the design requirement, laying a reinforcing mesh and carrying out concrete pouring construction on the bottom sealing plate 3;

and (3) recovering the open caisson construction site: after sinking of the open caisson 1, pouring of bottom sealing concrete 2 and pouring of the bottom sealing plate 3 are completed, the construction site of the open caisson 1 is subjected to original state recovery, and the protection work of the structure of the open caisson 1 is well done, so that the well body is prevented from being damaged and endangering related personnel during use.

The concrete strength of the plain concrete cushion layer in the construction preparation step is not lower than C20, so that the ground surface can form a certain supporting strength.

The thickness of the cushion layer of the plain concrete cushion layer is larger than 200mm, the laying range is larger than the outer diameter of the open caisson 1 by more than 500mm, and the construction can be carried out more stably in the subsequent construction process.

The diameter of the filtration pore in the perforated filter pipe 8 is larger than 3mm, and the periphery of the perforated filter pipe 8 is coated with filter cloth, so that various sizes of silt and gravel can be prevented from entering the perforated filter pipe 8.

In the dewatering well construction step, gaps among the settling pipes 4, the filter pipes 8 with holes and the open caisson 1 are backfilled by medium coarse sand fillers 5, and gaps between the common well pipe 7 and the open caisson 1 are backfilled by common cohesive soil fillers 6.

In order to reduce the frictional resistance in the sinking process of the deep and large open caisson 1, the outer side of the open caisson 1 is designed in a step manner, the outer diameter of the bottommost end of the open caisson is largest, the outer diameter is gradually reduced upwards along the depth of the open caisson, the height of each section and the height of the step need to be determined according to the stratum characteristics and the design depth, specifically, the height of each section is not less than 6m, and the width of the step is not less than 20 mm.

The mud breaking device in the well sinking construction step comprises a high-pressure jet grouting power device 12 arranged on a floating platform plate 16 and a high-pressure jet grouting drill rod 10 connected to the lower end of the high-pressure jet grouting power device 12, one end of the high-pressure jet grouting drill rod 10 extends into a soil body 17, and the soil body 17 on the inner side of the open caisson 1 is quickly broken and cut by high-pressure air and high-pressure liquid sprayed by the high-pressure jet grouting drill rod 10.

The outer side wall of the open caisson 1 is provided with a series of wireless deformation sensors 15 for acquiring the inclination and settlement of open caisson monitoring points, a floating platform plate 16 is provided with a series of guide channels 18 which are distributed annularly or longitudinally and transversely, a high-pressure rotary jet drill rod 10 is connected in the guide channels 18 in a sliding manner, the crushing and cutting of soil 17 need to be matched with the deformation monitoring data of the open caisson 1 in real time, and the crushing and cutting position and speed can be adjusted according to the inclination condition of the open caisson 1, as shown in figure 5, the wireless deformation sensors 15 can simultaneously acquire the inclination and settlement of the open caisson monitoring points, the inclination characteristic of the open caisson well structure can be reflected in real time by networking all the wireless deformation sensors 15, according to the real-time monitoring data of the inclination of the open caisson 1, the high-pressure rotary jet drill rod 10 is moved to an area which needs to be further excavated through the guide channels 18 and the soil 17 is crushed and cut, and the guide channels 18 are reasonably arranged, not only can guarantee that open caisson 1 steadily sinks, can realize the all-round broken cutting of the soil body in the well in addition, excavate the soil body in the wall of a well completely, guarantee the sinking smoothly of dark big open caisson 1.

Steelframe counter-force platform 22 adopts bracket formula support connection on the wall of a well, has guaranteed steelframe counter-force platform 22's support stability, and the center-penetrating jack 23 upper portion is equipped with the fixed pulley, and the activity of steel strand wires 21 sets up on the fixed pulley, can guarantee the stability that steel strand wires 21 passed power.

The tip of anchor pull rod 25 passes through expansion bolts to be fixed in the wall of a well, and steelframe reaction platform 22 is detachable platform, and its anchor bolt releasable connection is at open caisson 1 top, can demolish steelframe reaction platform 22 through dismantling anchor bolt to further install on the position of newly pouring, can realize the continuous pressure of open caisson 1 structure and sink, until reaching the design depth.

The preferred embodiments of the invention disclosed above are intended to be illustrative only. The preferred embodiments are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention. The invention is limited only by the claims and their full scope and equivalents.