CN113700018A

CN113700018A - Open caisson construction method for large-volume pump station

Info

Publication number: CN113700018A
Application number: CN202111050893.7A
Authority: CN
Inventors: 张显杨; 郭浩; 金玲玲; 金华
Original assignee: China MCC17 Group Co Ltd
Current assignee: China MCC17 Group Co Ltd
Priority date: 2021-09-08
Filing date: 2021-09-08
Publication date: 2021-11-26

Abstract

The invention discloses a large-volume pump station open caisson construction method, and relates to the technical field of open caisson construction. The open caisson construction method of the large-volume pump station mainly comprises the following construction steps: positioning and paying-off → well point dewatering → cutting edge earthwork → sand changing and filling cushion layer → cushion layer construction → cutting edge manufacturing → binding reinforcing steel bar, water stop steel plate adding → vertical mold → pouring concrete → binding well wall reinforcing steel bar → fixed reserved opening → water stop steel plate welding at joint → vertical mold → pouring well wall concrete → binding well wall reinforcing steel bar → water stop steel plate welding at joint → vertical mold → pouring well wall concrete → curing → template dismantling → soil in the open caisson → open caisson sinking → pouring bottom sealing concrete → binding bottom plate reinforcing steel bar → bottom plate pouring → curing → slope layer pouring, pump foundation pouring → maintenance platform construction → roof construction. According to the open caisson construction method of the large-volume pump station, the foundation construction difficulty of the large-volume pump station can be effectively reduced through the improvement of the construction structure and the construction process on the blade foot structure.

Description

Open caisson construction method for large-volume pump station

Technical Field

The invention relates to the technical field of open caisson construction, in particular to a large-volume pump station open caisson construction method.

Background

Along with the construction and development of urban rainwater and sewage pipe networks, the construction scale of a rainwater and sewage pump station is larger and larger, the difficulty of building a large-size pump station foundation is increased, and the pump station foundation construction is safe and reliable in a sunk well foundation form, so that the sunk well construction method for the large-size pump station is invented.

Therefore, the applicant inherits the abundant design development and actual manufacturing experience of the related industry for many years, researches and improves the existing structure and deficiency, and provides a large-volume pump station open caisson construction method so as to achieve the aim of higher practical value.

Disclosure of Invention

Technical problem to be solved

Aiming at the defects of the prior art, the invention provides a construction method of a large-volume pump station open caisson. The problem of the large-size pump station infrastructure degree of difficulty increase is solved.

(II) technical scheme

In order to achieve the purpose, the invention is realized by the following technical scheme: a construction method of a large-volume pump station open caisson comprises the following steps:

s1: manufacturing an open caisson structure;

s2: after the first section of the open caisson structure is manufactured, control points of the center and the axis of the open caisson structure are led to a bottom beam and a well wall of the structure, settlement observation points are arranged at four corners of the open caisson structure, and the upper structure of the open caisson is manufactured to measure the plane size of the open caisson structure and control the perpendicularity of the manufactured open caisson body by using the control points of the well body;

s3: laying a cushion layer on the foundation pit edge, and pouring a concrete cushion layer on the foundation pit edge;

s4: paving a sand cushion layer on the concrete cushion layer;

s5: after the first sand cushion layer is laid, water collecting wells are arranged on the sand cushion layer along the edge feet at the periphery, the sand cushion layer is connected with a vacuum pump, and water is continuously pumped during construction to prevent the sand cushion layer from being soaked in water;

s6: constructing a template;

s7: the inner and outer molds are supported vertically and horizontally in sections, and the reinforcing of the counter-pull screw rod can be adjusted according to the situation, but is not more than 80 cm. Each counter-pull screw is provided with a water-stopping steel sheet, and the outer counter-pull screw is cut off and leveled by cement mortar before the open caisson sinks, so that the sinking resistance of the open caisson is reduced; when the template is constructed, the size line of the template is required to be popped up according to the structure axis, so that the requirement on accurate size and tight abutted seam is met;

s8: before concrete pouring, all lantern rings of the reserved holes are propped up by cross steel pipes, the steel pipes are removed immediately after the templates are removed, and the holes are filled by cement mortar bricked;

s9: dismantling the template in the reserved hole, and avoiding vibration and damaging the hole wall when dismantling the template so as to ensure that the concrete surface does not collapse or crack;

s10: treating a construction joint;

s11: setting water-stop steel plates at construction joints between upper and lower sections of a well wall of the open caisson, wherein the two sections of concrete steel plates are buried by 15cm, the steel plate joints are firmly and compactly welded according to welding requirements, the construction joints are roughened and cleaned by water, the construction joints are fully wet and free from water accumulation, before the open caisson is connected high, the construction joints are roughened and cleaned, so that aggregates are exposed, cement mortar with the same label is used for connecting slurry, and the thickness is 1-2 cm;

s12: pouring concrete, when the pouring is started, in order to ensure that the bottom of the guide pipe is immediately surrounded and buried by a concrete pile, the slump can be properly reduced, the depth of the guide pipe inserted into the concrete is generally controlled to be more than 1m, when the funnel reaches the maximum height and can not be lifted, the short pipe at the upper part can be disassembled to shorten the length of the guide pipe, therefore, when the concrete in the guide pipe descends to the lower opening of the pipe joint to be disassembled, the guide pipe is quickly lowered, the concrete stops flowing out of the guide pipe, and then the disassembly work is carried out;

when the pouring is close to the end, concrete with larger fluidity can be adopted, and the depth of the conduit embedded in the concrete is properly increased. The elevation of the concrete surface reaches the designed elevation, and 10-20cm is poured in more. In the underwater concrete pouring process, the rising condition of the underwater concrete surface, the diffusion radius and the construction progress are measured constantly, and the embedding depth of the guide pipe is controlled according to the measurement data.

S13: dewatering at a well point;

s14: burying a mouth protecting pipe, wherein the bottom opening of the mouth protecting pipe is inserted into an undisturbed soil layer, filling and sealing the outside of the pipe by using cohesive soil to prevent the outside of the pipe from returning slurry during construction, and the upper part of the mouth protecting pipe is 30-50 cm higher than the ground; installing a drilling machine: the machine table is required to be installed stably and horizontally, the hook is aligned to the center of the hole, and three points of the hook, the turntable and the center of the hole form a vertical line; when drilling and tapping, the steel wire rope with the hook is tightly hung, the steel wire rope is slightly pressed and slowly rotated, the level of a drilling machine is ensured in the drilling process so as to ensure that the verticality of a drilled hole is less than 1%, the hole is naturally made into slurry in the hole, the specific gravity of the slurry is controlled to be 1.15-1.20 in the drilling process, and when the drilling tool is lifted or stopped, the slurry in the hole is fully pressed so as to prevent the hole wall from collapsing;

s15: cleaning holes and replacing slurry: in order to ensure that excessive mud skin is not formed at the aquifer part in the pore-forming process, when a drill hole is drilled to the top plate position of the aquifer, clear water is added for slurry mixing, after the drill hole is drilled to the designed elevation, the drill rod is lifted to 50cm away from the bottom of the hole before the drill is lifted, the hole is punched, impurities in the hole are removed, simultaneously, the density of slurry in the hole is gradually adjusted to be close to 1.05, the sediment of the bottom of the hole is less than 30cm, and the returned slurry does not contain mud blocks;

s16: a well pipe is lowered: the well pipe can be a sand-free concrete pipe, and a set of centralizer or centering device with the diameter less than 5cm is respectively arranged at the upper end and the lower end of the strainer pipe during pipe descending so as to ensure that the strainer pipe can be centered and the process of descending the pipe into the well is continuously carried out; filling gravel: before gravel filling, measuring the depth inside and outside the well pipe by using a measuring rope, wherein the depth values of the measuring rope and the depth value of the well pipe cannot be 50cm above the depth of the settling pipe, and the height of a gravel measuring material is required to be measured along with filling in the gravel filling process;

s17: well flushing: removing mud skin on the well wall, cleaning mud penetrating into the aquifer, and recovering pores of the aquifer; the well washing is carried out immediately after the well pipe is put down and the filter material is filled;

s18: the open caisson is divided into three stages of primary settling, intermediate settling and final settling from the beginning of settling to the end of settling;

s19: the sinking coefficient of the well is large during initial sinking, the gravity center is high, the stability is poor, therefore, the soil is to be fetched evenly and symmetrically, when fetching the soil, the middle soil is fetched firstly, then the peripheral soil is fetched, the soil body is fetched into a shallow pot bottom with the depth of 0.5-1.0 m in the well, then the peripheral soil body is fetched, the soil below the blade leg is always higher than the middle soil surface, the height difference of the control point is easy to be larger at the stage, the correction is timely carried out, the soil is fetched more at the high position, the soil is fetched less at the low position, the soil counter-force distribution condition of the blade leg tread in the well is adjusted, so that the sunk well changes the inclined state, and the sunk well gradually transits to the vertical direction. The measurement in the primary sinking stage requires once measurement every 30 minutes, the plane displacement is measured once every 2 hours, when the measurement report reflects that the deviation of the open caisson exceeds the limit, the soil sampling part is adjusted in time, but the soil sampling depth in the well is controlled, generally, the height difference of the soil sampling bottom surface is not more than 50cm, when the height difference of four corners of the measurement report is better, the symmetrical soil sampling is continued to be sunk in a normal state, but the depth of the soil digging pan bottom is limited not to exceed 1.0m, so that the open caisson is prevented from sudden sinking accidents, the duty taking, the duty measurement, the duty correction and the soil sampling are uniform, the height difference is controlled, and the open caisson can be ensured to enter the correct plane position in the primary sinking stage;

s20: at the end of the initial sinking stage, because a certain soil plug is formed after the sinking of the sinking well, the lateral resistance is large, the deviation correction is difficult, the height difference of control points at four corners is large by 10cm, namely the deviation correction is required, the height difference of the soil dug in the sinking well is preferably smaller than 1m during the deviation correction, the soil plug under the blade foot must be well controlled, particularly the soil plug under the blade foot of the outer side well wall must be well controlled, the soil body is broken and easy to generate soil surging, therefore, when the sinking well wall is close to the well wall, the position of the bottom of the pan should be well controlled, the soil body on the outer ring of the well wall is well stabilized, and the soil body lost on the outer ring of the well wall should be backfilled in time;

s21: the sinking well is sunk about 2m from the designed elevation and then enters the final sinking stage, the height difference of the soil in the well is strictly controlled at the moment to prevent the soil in the well from being dug and removed excessively to cause sudden sinking and excessive sinking of the well, the shape of the soil taking pan bottom gradually transits to the shape of a convex pan bottom from a concave surface, the soil taking speed and the soil taking quantity are properly slowed down, the soil taking range is strictly arranged according to the uniform and symmetrical principle, the deviation is basically corrected mainly, the sinking trend and the self-sinking inertia are measured and marked, the measurement is carried out once for 30 minutes, the height difference is controlled within 10cm, as the sinking well continues to sink, big stones can be adopted to fill the blade feet, soil squeezing sinking is gradually formed, the sinking is stopped and observed for 6 hours when the sinking well is 50cm from the designed elevation, the sinking well is generally slowly enters the designed elevation at the speed of about 1cm per hour to ensure the stability of the sinking well, the observation is continued after the sinking well enters the designed elevation, the well is completely stabilized, sinking the open caisson within 8 hours to be not more than 1cm, and sealing the bottom of the open caisson;

s22: preparing a back cover: the upper part of the conduit is formed by applying 2-3 short pipes with the length of about 1m, the conduit is convenient to disassemble after being lifted, the rest part of the conduit is formed by long conduits for reducing the water leakage phenomenon of a joint, the bottom end of the lowest section of the conduit is not provided with a flange plate so as to avoid damaging the water-proof effect of underwater concrete and the end part of the conduit, the surface stress of the inner wall of the conduit is smooth, the error is less than +/-2 mm, the conduit has enough tensile strength and can bear the self weight of the conduit and the total weight of the filled concrete, and the test tensile force after splicing is not less than 2 times of the total weight;

s23: clearing the base: when the sinking distance of the open caisson is 2m from the designed elevation, the height of the bottom sealing soil plug is combined to ensure the thickness of the concrete bottom sealing, the air suction dredge is used for removing the floating mud at the bottom of the pot in the open caisson, and the contact parts of the well wall, the bottom beam and the like and the bottom sealing concrete are washed clean.

Preferably, the thickness, backfill height and bearing capacity requirements of the sand cushion layer in the step S5 are determined through calculation.

Preferably, the supporting of the cutting edge can adopt a brick pad seat, the upper part of a concrete cushion layer is provided with a cutting edge template, cement mortar is smeared between the cutting edge and the brick pad seat, a layer of asphalt felt is laid in a dry mode, then reinforcing steel bars can be bound, and concrete can be poured.

Preferably, should single face hang line during S6 construction, will use the guiding rule to rectify roughness, straightness that hangs down at any time along with the increase of concreting: checking whether the relation between the root of the template and a control line meets the requirement, wherein the control line is generally 30cm to 50cm away from the wall edge; the thread drop is picked out by steel bars or battens, so that the thread drop hangs to the control line; and measuring the distance from the upper opening and the middle of the template to the vertical line by using a box ruler, wherein the template is vertical when the distance is equal to the lower distance.

Preferably, after the plain concrete cushion layer on the sand cushion layer reaches a certain strength, the blade foot brick laying forming die accurately measures and places the plane position of the open caisson on the cushion layer according to the well position, low-grade cement mortar is used during brick laying, the slope of the blade foot is ensured to be flat, lime and a small amount of cement mixture powder are used for brushing the brick laying forming die, and hole positions of pull rod screws of the open caisson wall template are reserved in the brick laying forming die.

Preferably, the structural concrete is poured to spread to the periphery from the center of the axis or the center of the bottom beam, and finally a well wall is poured; in the position where the pump pipe cannot stretch down in the reinforced bar dense area, the reinforced bars of the surface layer can be shifted firstly, so that the pump pipe stretches down, and then the pump pipe is recovered after the concrete surface rises to a certain height; the concrete material is required to be reasonably distributed, uniform and symmetrical, and cold seams are prevented from being generated in the pouring and tamping process.

Preferably, the concrete pouring adopts a layering method for construction, the thickness of each layer is not more than 50cm, the upper layer concrete and the lower layer concrete are in a step shape, and the time interval between the upper layer concrete and the lower layer concrete is not more than the initial setting time of the concrete; when the concrete is vibrated, the insertion time and the insertion position interval of the vibrating rod are controlled, the vibrating rod is required to be quickly inserted, slowly pulled and uniformly arranged, and the vibrating rod is required to be inserted into the lower layer by about 15cm when the upper layer concrete is vibrated so as to eliminate the seam between the two layers.

Preferably, when the structural concrete is poured and tamped, a settlement observation point is arranged on the well wall, observation is carried out in the pouring and tamping process and the maintenance period, and the sinking amount and the inclination amount of the open caisson are mastered in time.

Preferably, the edge of the sunk well is generally provided with a soil dike with the width of lm, so that the edge of the sunk well extrudes soil and sinks, the disturbance degree to soil bodies around the well is reduced, only when the soil bodies in the middle of the sunk well are completely washed and do not sink or are corrected, the soil bodies at the edge can be properly washed, but the soil bodies outside the tread of the edge are strictly washed and brushed.

Preferably, the hopper in S12 is filled with concrete with larger slump, and then the ball plug is slowly lowered for a certain distance. When pouring, the rope or the thick iron wire is cut, concrete is rapidly and continuously poured into the funnel, at the moment, air and water in the guide pipe and the ball plug are extruded by the gravity of the concrete and are discharged from the pipe bottom, the concrete is piled into a cone shape around the pipe bottom, and the lower end of the half guide pipe is buried in the concrete.

Drawings

FIG. 1 is a flow chart of the open caisson construction process;

FIG. 2 is a schematic view of the pad layer and the blade;

fig. 3 is a schematic view of open caisson vertical mold.

In the figure: 1. a plain concrete cushion; 2. a sand cushion layer; 3. a well wall; 4. a blade foot; 5. oppositely pulling the screw rod; 6. and (5) template.

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. 1-3, a method for constructing a large-volume pump station open caisson includes the following steps:

after the first section of the open caisson structure is manufactured, control points of the center and the axis of the structure are led to a bottom beam and a well wall of the structure, settlement observation points are arranged at four corners of the structure, and the open caisson upper structure can be manufactured by using the control points of a well body to measure the plane size of the open caisson structure and control the perpendicularity of the well body.

In order to prevent the problems of well body cracks, deformation and the like caused by uneven sinking of the open caisson, laying a cushion layer on the edge foot of the foundation pit, and pouring a concrete cushion layer on the upper part of the cushion layer; in order to prevent the influence of underground water and rainwater on the quality of the sand cushion layer, after the first sand cushion layer is laid, water collecting wells are arranged on the sand cushion layer along the peripheral edge feet, and are connected with vacuum pumps; the thickness of the cushion layer, the backfill height and the bearing capacity requirement are determined by calculation.

The supporting of the cutting edge can adopt a brick pad seat, the upper part of a concrete cushion layer is provided with a cutting edge template, cement mortar is smeared between the cutting edge and the brick pad seat, a layer of asphalt felt is laid in a dry mode, then reinforcing steel bars can be bound, and concrete is poured.

The template construction process flow comprises the following steps: measuring and paying off → supporting of a template on the inner side of a cutting edge foot → erecting of a scaffold → binding of steel bars → installing of a template, reinforcement → checking of the size and the position of a beam mold, concrete pouring → curing → second section of steel bar binding → positioning of a screw rod → positioning of an inner mold → positioning of a fixed inner mold → positioning of an outer mold → positioning of the fixed outer mold → checking of the size and the position of the beam mold, concrete pouring → curing → third section, and the second-layer process is repeated.

The inner and outer molds are supported vertically and horizontally in sections, and the reinforcing of the counter-pull screw rod can be adjusted according to the situation, but is not more than 80 cm. Each counter-pull screw is provided with a water-stopping steel sheet, and the outer counter-pull screw is cut off and leveled by cement mortar before the open caisson sinks, so that the sinking resistance of the open caisson is reduced; when the template is constructed, the size line of the template is required to be popped up according to the structural axis, so that the requirement on accurate size and tight abutted seam is met.

In order to prevent the reserved holes from deforming, the cross-shaped steel pipes are used for supporting the lantern rings of all the reserved holes before concrete pouring, the steel pipes are removed immediately after the templates are removed, and the holes are filled with cement mortar bricks.

During construction, a single-side hanging wire is required, and the guiding rule is required to be used for correcting the flatness and the verticality at any time along with the increase of the poured concrete: checking whether the relation between the root of the template and a control line meets the requirement, wherein the control line is generally 30cm to 50cm away from the wall edge; the thread drop is picked out by steel bars or battens, so that the thread drop hangs to the control line; and measuring the distance from the upper opening and the middle of the template to the vertical line by using a box ruler, wherein the template is vertical when the distance is equal to the lower distance.

The removal of the inner template of the reserved hole can ensure that the concrete surface does not collapse or crack, and the vibration and the damage to the hole wall are avoided during the removal of the template.

After the plain concrete cushion layer on the sand cushion layer reaches a certain strength, the blade foot brick building tire mold accurately measures and places the plane position of the open caisson on the cushion layer according to the well position, low-grade cement mortar is applied during brick building, the slope of the blade foot is ensured to be smooth, lime and a small amount of cement are mixed and powdered to brush the brick building tire mold, and the hole position of a pull rod screw of the open caisson wall template is reserved in the brick building tire mold.

And (4) pouring the structural concrete to diffuse around from the axis center or the bottom beam center, and finally pouring the well wall. In the position where the pump pipe in the reinforcing steel bar dense area can not stretch down, the reinforcing steel bars on the surface layer can be firstly displaced, so that the pump pipe stretches down, and then the pump pipe is recovered after the concrete surface rises to a certain height. The concrete material is required to be reasonably distributed, uniform and symmetrical, and cold seams are prevented from being generated in the pouring and tamping process.

And (3) treating a construction joint, arranging a water stop steel plate between the upper section of the open caisson wall and the lower section of the caisson wall, burying two sections of concrete steel plates by 15cm, and firmly and compactly welding steel plate joints strictly according to welding requirements. And (3) roughening the construction joint, cleaning with water, fully wetting without water accumulation, and roughening and cleaning the construction joint before the open caisson is connected to the high position to expose the aggregate. And cement mortar with the same mark is used for mortar jointing, and the thickness is 1-2 cm.

The concrete pouring adopts a layering method for construction, the thickness of each layer is not more than 50cm, the upper layer concrete and the lower layer concrete are in a step shape, and the interval of the concrete pouring time of the upper layer and the lower layer concrete is not more than the initial setting time of the concrete; when the concrete is vibrated, attention should be paid to control the insertion time and the insertion position interval of the vibrating rods, and the vibrating rods need to be inserted quickly, pulled slowly and arranged uniformly. The lower layer should be inserted about 15cm when the upper layer concrete is vibrated to eliminate the seam between the two layers.

When the structural concrete is poured and tamped, settlement observation points are arranged on the well wall, observation is carried out in the pouring and tamping process and during maintenance, and the sinking amount and the inclination amount of the open caisson are mastered in time.

Well point dewatering: well point measuring and positioning → well head digging, a safety protection cylinder → drill rig installation, in place → drilling hole forming → bottom gravel cushion layer → well hanging and releasing → gravel filter layer between well pipe and hole wall → well washing → water pump arranged below the inside of well pipe, water pumping control circuit installation → water pumping test → normal work of water pumping well → well sealing after water pumping is finished.

Burying a mouth protecting pipe: the bottom opening of the mouth protecting pipe is inserted into an undisturbed soil layer, the outside of the pipe is tightly filled by using cohesive soil to prevent the outside of the pipe from returning slurry during construction, and the upper part of the mouth protecting pipe is 30-50 cm higher than the ground; installing a drilling machine: the machine table is required to be installed stably and horizontally, the hook is aligned to the center of the hole, and three points of the hook, the turntable and the center of the hole form a vertical line; when drilling and tapping, the steel wire rope with the hook is tightly hung, the steel wire rope is slightly pressed and slowly rotated, the level of the drilling machine is ensured in the drilling process so as to ensure the verticality (less than 1%) of the drilled hole, the hole is naturally made into slurry in the hole forming construction, the specific gravity of the slurry is controlled to be 1.15-1.20 in the drilling process, and when the drilling tool is lifted or stopped, the hole is fully pressed with the slurry so as to prevent the hole wall from collapsing.

Cleaning holes and replacing slurry: in order to ensure that excessive mud skin is not formed at the aquifer part in the pore-forming process, clear water is added for size mixing when the drill hole is drilled to the top plate position of the aquifer. And after drilling to a designed elevation, lifting the drill rod to be 50cm away from the bottom of the hole before lifting the drill, punching, removing impurities in the hole, and simultaneously gradually adjusting the density of the slurry in the hole to be close to 1.05, wherein the sediment at the bottom of the hole is less than 30cm, and the returned slurry does not contain a mud block.

A well pipe is lowered: the well pipe can be a sand-free concrete pipe, and a set of centralizers (centralizers) with the diameter smaller than the aperture 5cm are respectively arranged at the upper end and the lower end of the strainer during pipe descending so as to ensure that the strainer can be centered. The process of running the well pipe is continuously carried out; filling gravel: before gravel filling, the depth inside and outside the well pipe is measured by using a measuring rope, the depth value of the measuring rope and the depth value of the well pipe cannot be 50cm above the depth of the settling pipe, and the height of a gravel measuring material is required to be measured along with filling in the gravel filling process.

Well flushing: removing mud skin on the well wall, cleaning mud penetrating into the aquifer, and recovering pores of the aquifer; the well washing is carried out immediately after the well pipe is put down and the filter material is filled;

the open caisson is divided into three stages of primary settling, intermediate settling and final settling from the beginning of settling to the end of settling.

The well has large sinking coefficient, high gravity center and poor stability during initial sinking, so that soil taking needs to be uniform and symmetrical. When taking soil, taking the middle soil firstly, then taking the peripheral soil, taking the soil body into a shallow pot bottom with the depth of 0.5-1.0 m in the well, and then taking the peripheral soil body, wherein the soil below the blade leg is always higher than the middle soil surface. The height difference of the control point is easy to be larger at the stage, the deviation is corrected in time, more soil is taken at the high position, less soil is taken at the low position, the soil reaction force distribution condition of the blade tread in the open caisson is adjusted, so that the open caisson changes the inclined state and gradually transits to the vertical direction. The measurement in the initial setting stage requires once every 30 minutes, the plane displacement is measured once every 2 hours, and when the measurement report reflects that the deviation of the open caisson exceeds the limit, the soil sampling position is adjusted in time. However, the soil taking depth in the well is controlled, the height difference of the soil taking bottom surface is generally not larger than 50cm, when the height difference of four corners of a measurement report is good, the soil is symmetrically taken, the normal state is kept for sinking, but the depth of the soil digging pan bottom is limited not to exceed 1.0m, so that the sunk well is prevented from sudden sinking accidents, the frequent taking, the frequent measurement, the frequent correction and the uniform soil taking are realized, the height difference is controlled well, and the sunk well can enter the correct plane position in the primary sinking stage.

In the final stage of the initial sinking stage, because the open caisson sinks to form a certain soil plug, the lateral resistance is large, the deviation correction is difficult, and the height difference of the control points at four corners is large by 10cm, namely the deviation correction is required. When the deviation is corrected, the difference of the soil excavation height in the well is preferably less than 1m, and the difference is not too large. The soil plug under the blade foot must be well controlled, particularly the soil plug under the blade foot of the outside well wall must be well controlled, the soil body is broken and easy to generate soil gushing, so when the well wall is dug, the position of the pot bottom should be well controlled, the soil body on the outer ring of the well wall is well stabilized, and meanwhile, the soil body lost on the outer ring of the well wall should be timely backfilled.

And entering a final sinking stage when the sinking well sinks about 2m away from the designed elevation, wherein the height difference of the soil body in the well is strictly controlled. To prevent the soil in the well from being dug too much, resulting in the sudden sinking and the excessive sinking of the well. The shape of the soil taking pot bottom gradually transits from a concave surface to a convex reverse pot bottom, the soil taking speed and the soil taking quantity are properly slowed down, the soil taking range is strictly arranged according to the principle of uniform symmetry, and basically the correction is mainly carried out. And measuring the subsidence trend and the self-subsidence inertia once in 30 minutes, controlling the height difference within 10cm, and gradually forming soil squeezing subsidence by adopting large stones to fill the space under the blade along with the continuous subsidence of the open caisson. Stopping taking the open caisson when the open caisson is 50cm away from the designed elevation and observing for 6 hours, and generally slowly entering the open caisson into the designed elevation at the speed of about 1cm per hour to ensure the stability of the open caisson. And (4) continuously observing after the open caisson enters the designed elevation, and sealing the bottom of the open caisson when the open caisson is completely stable and sinks to be not more than 1cm within 8 hours.

The edge of the sunk well generally keeps a soil dike with the width of lm, so that the edge of the sunk well extrudes soil to sink, and the disturbance degree to soil around the well is reduced. Only when the soil mass in the middle of the open caisson is completely removed and does not sink or the deviation is corrected, the soil mass at the blade foot can be properly removed, but the soil mass outside the tread of the blade foot is strictly prevented from being removed and brushed.

Preparing a back cover: the upper part of the conduit is composed of 2-3 short pipes with the length of about 1m, the conduit is convenient to disassemble after being lifted, the conduit of the rest part can be composed of long conduits for reducing the water leakage phenomenon of joints, the bottom end of the lowest section of the conduit is not provided with a flange plate so as to avoid damaging the water-proof effect of underwater concrete and the end part of the conduit, the surface stress of the inner wall of the conduit is smooth, the error is less than +/-2 mm, the conduit has enough tensile strength and can bear the dead weight of the conduit and the total weight of the filled concrete, and the test tensile force after splicing is not less than 2 times of the total weight.

Clearing the base: when the sinking distance of the open caisson is 2m from the designed elevation, the height of the bottom sealing soil plug is combined to ensure the thickness of the concrete bottom sealing, the air suction dredge is used for removing the floating mud at the bottom of the pot in the open caisson, and the contact parts of the well wall, the bottom beam and the like and the bottom sealing concrete are washed clean.

When the precipitation effect is not good, an underwater bottom sealing is adopted, the distance between the bottom of the guide pipe and the soil surface at the bottom of the well is 30-40cm during construction, and a funnel with the length of about 3m3 is arranged at the top of the guide pipe to ensure the requirement of pouring blanking. A ball plug is placed in the neck of the funnel and secured with a rope or thick wire. When the ball plug is placed, the center of the ball plug is above the water surface, a layer of thick cement mortar is firstly paved on the upper part of the ball plug, and after the ball plug is lubricated, concrete is poured.

The funnel is filled with concrete with larger slump, and then the ball plug is slowly lowered for a certain distance. When pouring, the rope or the thick iron wire is cut, concrete is rapidly and continuously poured into the funnel, at the moment, air and water in the guide pipe and the ball plug are extruded by the gravity of the concrete and are discharged from the pipe bottom, the concrete is piled into a cone shape around the pipe bottom, and the lower end of the half guide pipe is buried in the concrete.

When pouring is started, in order to ensure that the bottom of the guide pipe is immediately surrounded and buried by the concrete pile, the slump can be properly reduced. The depth of the guide pipe inserted into the concrete is preferably controlled to be more than 1m, and when the funnel reaches the maximum height and can not be lifted any more, the short pipe at the upper part can be detached to shorten the length of the guide pipe. Therefore, when the concrete in the conduit descends to the lower opening of the pipe joint to be disassembled, the conduit is quickly lowered, so that the concrete stops flowing out of the conduit, and then the disassembly work is carried out.

And after the open caisson concrete bottom plate reaches the designed strength, stopping pumping water, filling the water collecting well with plain concrete, covering the water collecting well with a steel cover plate with bolt holes and a rubber gasket, screwing all bolts on the flange plate, wherein the elevation of the upper opening of the water collecting well is 20-30cm lower than the elevation of the top surface of the reinforced concrete bottom plate, and leveling with the plain concrete after the bottom plate is finished.

The open caisson is preferably made at a height that does not make the center of gravity too high above the ground, preferably not more than the short side or diameter of the open caisson.

Controlling the height difference of the cutting edge: before sinking, the elevation of the blade foot of the sinking well is led to the stable place at the upper part of the sinking well, and the soil taking sequence and depth are controlled according to the height difference during sinking so as to control the height difference of the blade foot

In order to ensure the precision of the measurement and positioning work of the engineering structure, a total station and a level gauge are adopted for measurement lofting and rechecking. The open caisson structure is lofted according to design coordinates, the center lines of the edge legs and the bottom beams are determined, the side line of the caisson wall is determined according to the center line lofting, and the side line is popped up by using ink lines. Checking whether the structural size and the diagonal size of each bin meet the requirements or not, and performing the next procedure after determining that the structural size and the diagonal size of each bin do not meet the requirements. After the first section of the open caisson structure is manufactured, control points of the center and the axis of the structure are led to a bottom beam and a well wall of the structure, settlement observation points are arranged at four corners of the structure, and the open caisson upper structure can be manufactured by using the control points of a well body to measure the plane size of the open caisson structure and control the perpendicularity of the well body.

Well point dewatering construction: 1. measuring the well placement: the dewatering wells are uniformly distributed around the open caisson, and the well mouth is higher than the ground. If the site construction process encounters obstacles or is influenced by construction conditions, the site can be properly adjusted. 2. Burying a mouth protecting pipe: the bottom opening of the mouth protecting pipe is inserted into an undisturbed soil layer, the outside of the pipe is tightly filled by using cohesive soil to prevent the outside of the pipe from returning slurry during construction, and the upper part of the mouth protecting pipe is 30-50 cm higher than the ground. 3. Installing a drilling machine: the machine table is required to be installed stably and horizontally, the hook is aligned to the center of the hole, and the hook, the turntable and the center of the hole form a vertical line. 4. Drilling to form a hole: drilling construction description records are made, and effective water inlet of the placement position of the water filter pipe is guaranteed. When drilling, the steel wire rope with the hook is tightly hung, the steel wire rope is slightly pressed and slowly rotated, the level of the drilling machine is ensured in the drilling process so as to ensure the verticality of the drilled hole, the hole is naturally made into slurry in the hole during hole forming construction, and when the drilling tool is lifted or stopped, the hole is fully pressed with slurry so as to prevent the hole wall from collapsing. 5. Cleaning holes and replacing slurry: the hole cleaning and slurry changing work before the well casing is lowered is a key process for ensuring the well quality, and in order to ensure that excessive thick mud skin is not formed at the aquifer part in the hole forming process, clean water is added for slurry mixing when a drill hole is drilled to the top plate position of the aquifer. And after drilling to a designed elevation, lifting the drill rod to be 50cm away from the bottom of the hole before lifting the drill, punching, removing impurities in the hole, wherein the sediment at the bottom of the hole is less than 30cm, and the returned slurry does not contain mud blocks. The first hole cleaning and slurry changing is the key for ensuring the quality of the finished well, and the first hole cleaning and slurry changing directly influences the quality of the finished well, so that the hole cleaning and slurry changing work during construction does not meet the specified requirements and the construction of the next procedure is not allowed to enter. 6. A well pipe is lowered: the hole depth must be measured before the pipe is lowered, after the hole depth meets the design requirements, the well pipe starts to be lowered, and a set of centralizers with the diameter smaller than the aperture 5cm is respectively arranged at the upper end and the lower end of the strainer during pipe lowering so as to ensure that the strainer can be centered. The process of lowering the well pipe should be continuously carried out, and the well pipe should be stopped in the middle, for example, the well pipe should be pulled out again when the hole collapses or the sediment is too thick due to mechanical failure, etc., and the well pipe should be lowered again after hole sweeping and hole cleaning, and the well pipe should be prevented from being forcibly inserted into the bottom of the collapsed hole. 7. Filling gravel: before gravel filling, the depth inside and outside the well pipe is measured by using a measuring rope, and the depth value of the measuring rope and the depth value of the well pipe cannot be shallower than the depth of the settling pipe by 50 cm. The height of the gravel material is measured along with the gravel filling in the gravel filling process. The gravel packing process should be continued until the gravel is dropped into a predetermined position. 8. Well flushing: removing mud skin on the well wall, cleaning mud penetrating into the aquifer, and recovering pores of the aquifer; the well washing is carried out immediately after the well pipe is put down and the filter material is filled, so that the problem that the water seepage effect is influenced because the protective wall mud skin is aged gradually and is difficult to damage after too long time is avoided. It is never allowed to sit for too long or to centrally flush after drilling is completed. 9. Installing a pump for trying pumping: after the well completion construction is finished, the submersible pump is timely put in, drainage pipelines, cables and the like are laid, and the water pumping and drainage system can be started to pump water in a trial mode after the water pumping and drainage system is installed. 10. And (3) draining, namely, during well washing and dewatering operation, water is drained into open ditches around the field by using pipelines, the water is drained into drainage ditches preset outside the field through the drainage ditches, and the drainage pipelines around the field are cleaned regularly to ensure the smoothness of a drainage system.

After the excavation of foundation ditch is ended, experience receipts are closed the check, and in time the grit bed course is paved, and in order to guarantee the grit bed course quality, the grit bed course adopts medium coarse sand, and the layering is paved, is compacted with flat vibrator.

Before the templates are assembled, a scaffold is firstly put up, a base plate is laid at the bottom of the support, the maximum distance between the adjacent side of the support and the well wall is 40cm, and the cross braces are strengthened to ensure the stability of the support, ensure tight splicing and no slurry leakage, and control the verticality and the flatness of the templates in real time. Before the mold is erected, the sizes of structural side lines of a well wall and a frame beam need to be checked, the relative positions of all parts of the structure need to be checked, and the mold is erected after the requirements are met.

The open caisson is divided into a plurality of sections, and the open caisson is symmetrically and uniformly poured in layers so as to avoid uneven sinking or inclination of the foundation, the concrete is continuously poured once, and the second section can be poured when the first section of concrete reaches 80% of the designed strength.

The sinking construction is carried out according to the principle of 'first middle and back, layered symmetrical soil breaking, first high and then low and timely deviation rectifying', a soil dike with the width of about 1m is generally reserved at the edge of the sinking well blade, so that the sinking well blade is squeezed to sink soil, and the disturbance degree to soil around the well is reduced. Only when the soil body in the middle of the open caisson is completely flushed but does not sink or is corrected, the soil body at the blade foot position can be properly flushed, but the soil body on the outer side of the tread of the blade foot is strictly prevented from being flushed and brushed, a mechanical cooperation manual soil discharging mode is adopted in the open caisson process, the excavator works in a relatively spacious place, manual excavation is adopted at the edge position, and the muck is conveyed to the ground by using a truck crane and a winch during soil discharging.

Bottom sealing: the distance between the bottom of the conduit and the soil surface at the bottom of the well is 30-40cm, and the top of the conduit is provided with 3m³The left and right funnels ensure the blanking requirement of pouring. A ball plug is placed in the neck of the funnel and secured with a rope or thick wire. When the ball plug is placed, the center of the ball plug is above the water surface, a layer of thick cement mortar is firstly paved on the upper part of the ball plug, and after the ball plug is lubricated, concrete is poured. The funnel is filled with concrete with larger slump, and then the ball plug is slowly lowered for a certain distance. Cutting rope or thick iron wire while pouring, and pouring into funnel rapidly and continuouslyWhen the concrete is filled, the air and water in the conduit and the ball plug are extruded by the gravity of the concrete and discharged from the bottom of the conduit, the concrete is piled up in a conical shape around the bottom of the conduit, and the lower end of the half conduit is embedded into the concrete. At the beginning of casting, the slump can be reduced properly in order to ensure that the bottom of the guide pipe is immediately buried by the concrete pile. In the underwater concrete pouring process, the lifting of the guide pipe is also a key problem, the guide pipe is lifted slowly and falls quickly, the depth of the guide pipe inserted into the concrete is preferably controlled to be more than 1m, and when the funnel reaches the maximum height and cannot be lifted any more, the short pipe at the upper part can be detached to shorten the length of the guide pipe. Therefore, when the concrete in the conduit descends to the lower opening of the pipe joint to be disassembled, the conduit is quickly lowered, so that the concrete stops flowing out of the conduit, and then the disassembly work is carried out. After the funnel is filled with the leaked concrete continuously, the guide pipe can be improved to restore the pouring work. When the pouring operation is about to end, concrete with larger fluidity can be adopted, the water cement ratio is not required to be changed, and the depth of the conduit buried in the concrete is properly increased. And (3) pouring 10-20cm more when the elevation of the concrete surface reaches the designed elevation, then pulling out the guide pipe from the concrete, and washing the guide pipe clean. In the underwater concrete pouring process, the rising condition of the underwater concrete surface, the diffusion radius and the construction progress are measured constantly, and the embedding depth of the guide pipe is controlled according to the measurement data

A bottom plate: after the bottom sealing concrete reaches the designed strength, water can be pumped. The method comprises the following steps of cleaning floating ash on the contact surface of bottom sealing concrete and a bottom plate slot opening before bottom plate construction, then carrying out reinforcement binding construction according to design requirements, cleaning a pre-buried connector, shaping a reserved inserted bar of the bottom plate, straightening, welding, binding and the like. When the reinforcing bars are bound, the connection between the edge foot reinforcing bars and the bottom plate reinforcing bars and the distance between the upper layer of reinforcing bars and the lower layer of reinforcing bars are ensured, and the surface of the edge foot concrete is roughened to expose stones, so that the edge foot concrete and the bottom plate concrete are combined conveniently. After the bottom plate steel bar project is qualified through inspection, pouring the bottom plate, and timely maintaining the bottom plate after concrete pouring is finished to ensure that the surface of the bottom plate is not exposed to the white and prevent severe change of sunlight and temperature difference so as to prevent the bottom plate from generating shrinkage cracks and influencing the construction quality and the use function of the open caisson

The well point dewatering process comprises the following specific steps:

A. measuring the well placement: the dewatering wells are uniformly distributed around the open caisson and are 8 meters away from the outer wall of the open caisson. The well head is higher than the ground. If the site construction process encounters obstacles (such as pile positions) or is influenced by construction conditions, the site can be properly adjusted.

B. Burying a mouth protecting pipe: the bottom opening of the mouth protecting pipe is inserted into an undisturbed soil layer, the outside of the pipe is tightly filled by using cohesive soil to prevent the outside of the pipe from returning slurry during construction, and the upper part of the mouth protecting pipe is 0.30-0.50 m higher than the ground.

C. Installing a drilling machine: the machine table is required to be installed stably and horizontally, the hook is aligned to the center of the hole, and the hook, the turntable and the center of the hole form a vertical line.

D. Drilling to form a hole: the aperture of the dewatering well is 400mm, and the aperture is the bottom. Drilling construction description records are made, designers need to be informed in time in the drilling process if actual geological conditions are inconsistent with data provided in exploration, the structure of the well is adjusted in time, and the arrangement position of the water filter pipe can be ensured to be capable of effectively feeding water. When drilling and tapping, the steel wire rope with the hook is tightly hung, the steel wire rope is slightly pressed and slowly rotated, the level of the drilling machine is ensured in the drilling process so as to ensure the verticality (less than 1%) of the drilled hole, the hole is naturally made into slurry in the hole forming construction, the specific gravity of the slurry is controlled to be 1.15-1.20 in the drilling process, and when the drilling tool is lifted or stopped, the hole is fully pressed with the slurry so as to prevent the hole wall from collapsing.

E. Cleaning holes and replacing slurry: the hole cleaning and slurry changing work before the well casing is lowered is a key process for ensuring the well quality, and in order to ensure that excessive thick mud skin is not formed at the aquifer part in the hole forming process, clean water is added for slurry mixing when a drill hole is drilled to the top plate position of the aquifer. And after drilling to a designed elevation, lifting the drill rod to be 0.50m away from the bottom of the hole before lifting the drill, punching, removing impurities in the hole, and simultaneously gradually adjusting the density of the slurry in the hole to be close to 1.05, wherein the sediment at the bottom of the hole is less than 30cm, and the returned slurry does not contain a mud block. The first hole cleaning and slurry changing is the key for ensuring the quality of the finished well, and the first hole cleaning and slurry changing directly influences the quality of the finished well, so that the hole cleaning and slurry changing work during construction does not meet the specified requirements and the construction of the next procedure is not allowed to enter.

F. A well pipe is lowered: the well pipe is a phi 400mm sand-free concrete pipe, and after the well pipe enters the field, whether the gap of the filter meets the design requirement or not is checked. The hole depth must be measured before the pipe is lowered, after the hole depth meets the design requirements, the well pipe is started to be lowered, and a set of centering device (centering device) with the diameter smaller than 5cm is respectively arranged at the upper end and the lower end of the strainer pipe during pipe lowering so as to ensure that the strainer pipe can be centered. The process of lowering the well pipe should be continuously carried out, and the well pipe should be stopped in the middle, for example, the well pipe should be pulled out again when the hole collapses or the sediment is too thick due to mechanical failure, etc., and the well pipe should be lowered again after hole sweeping and hole cleaning, and the well pipe should be prevented from being forcibly inserted into the bottom of the collapsed hole.

G. Filling gravel: before gravel filling, the depth inside and outside the well pipe is measured by using a measuring rope, and the depth value of the measuring rope and the depth value of the well pipe cannot be shallower than the depth of the settling pipe by 50 cm. The height of the gravel material is measured along with the gravel filling in the gravel filling process. The gravel packing process should be continued until the gravel is dropped into a predetermined position. The amount of filter material finally charged should not be less than 95% of the calculated amount.

H. Well flushing: removing mud skin on the well wall, cleaning mud penetrating into the aquifer, and recovering pores of the aquifer; the well washing is carried out immediately after the well pipe is put down and the filter material is filled, so that the problem that the water seepage effect is influenced because the protective wall mud skin is aged gradually and is difficult to damage after too long time is avoided. It is never allowed to sit for too long or to centrally flush after drilling is completed.

I. Installing a pump for trying pumping: after the well completion construction is finished, the submersible pump is timely put in, drainage pipelines, cables and the like are laid, and the water pumping and drainage system can be started to pump water in a trial mode after the water pumping and drainage system is installed. The cabling and piping system is arranged with care to avoid damage during the pumping process, and therefore identification is made on these devices on site.

J. And (3) draining, namely, during well washing and precipitation operation, water is drained into open ditches (channels) around the field by using pipelines, the water is drained into drainage channels preset outside the field through the drainage channels (channels), and the drainage pipelines around the field are cleaned at regular time to ensure the smoothness of a drainage system.

Plugging of dewatering well

A. Stopping the pump

And before the well is sealed, the pump of the deep well is stopped in sequence according to the sequence of the sealing cover.

B. Deep well recharge and micro-expansion concrete construction

After the construction of the steel pipe sleeve is finished, the deep well is recharged with stones and medium sand (the mixing ratio of the stones and the sand is 3:7), C20 dry-mixed concrete is poured within the range of 1m below the bottom plate, the upper part of the deep well is poured to the well mouth with C25 concrete 200mm, and then the well mouth is closed.

C. Installation of flange covers

Derusting the pre-buried steel plate and the bolts, polishing the pre-buried steel plate and the bolts to the surface of the steel plate by using an angle grinder, and brushing polyurethane waterproof paint once.

Secondly, manufacturing a rubber gasket according to the size of the pipe flange cover plate and the bolt hole, wherein the thickness of the rubber gasket is 5 mm. Thirdly, sleeving the rubber gasket which is manufactured in advance on the bolt of the steel sleeve, then placing the pipe flange cover, and symmetrically and alternately screwing the nuts (double nuts) by using a socket wrench. The flange cover plate is ensured to be tightly sealed and air-tight.

D. Micro-expansion concrete construction

Firstly, after confirming that the flange cover plate is sealed tightly and qualified, cleaning the steel sleeve, and pouring C45P8 micro-expansion concrete in the upper part of the cover plate

The template construction process comprises the following steps:

(1) the process flow comprises the following steps: measuring and paying off → supporting of a template on the inner side of a cutting edge foot → erecting of a scaffold → binding of steel bars → installing of a template, reinforcement → checking of the size and the position of a beam mold, concrete pouring → curing → second section of steel bar binding → positioning of a screw rod → positioning of an inner mold → positioning of a fixed inner mold → positioning of an outer mold → positioning of the fixed outer mold → checking of the size and the position of the beam mold, concrete pouring → curing → third section, and the second-layer process is repeated.

(2) All the templates and the supporting steel pipes are manually transported to each construction point.

(3) When the template is constructed, the size line of the template is required to be popped up according to the structural axis, so that the requirement on accurate size and tight abutted seam is met.

(4) In order to prevent the reserved holes from deforming, the lantern rings of all the reserved holes are propped up by cross steel pipes (phi 48 multiplied by 2.7mm) before concrete is poured, the steel pipes are removed immediately after the templates are removed, and the holes are filled by cement mortar bricks.

(5) The method of formwork removal is conventional and generally carried out after 12 hours after the concrete has been poured.

(6) The detached templates, wood ridges, supporting steel pipes, fasteners and the like are sorted, maintained and stacked according to specifications so as to be used next time.

Template fabrication and processing

The templates used in the whole project are all made into shaped templates in a woodworking processing field, and are conveyed to a field for assembly after being uniformly numbered and coated with the separant. Before the template is processed, the materials entering the field are checked and accepted, the thickness of the boards is consistent, the board surface is smooth and flat, and the battens are subjected to double-side press polishing by a thicknesser to enable the thickness of the battens to be consistent; the cut of the panel is straight and smooth, and is coated with waterproof glue for sealing.

In the template course of working, template long edge direction wooden tree stretches out template thickness of template, and unified 150mm staggers with the template during back of the body rib installation to the staggered overlap joint of upper and lower joint improves the assembly precision, reduces and assembles the gap.

Cutting and assembling are carried out according to the turnover pattern, plates with degumming, hollowing, uneven corners, warped plate surfaces and incomplete plate surfaces and peritoneum cannot be used, and the plates are cut and molded at one time after being subjected to line snapping by a plate cutting machine during cutting so as to enable the splicing seams to be flat and close during installation.

Formwork installation

After the template is processed in a processing field, the template is transported to a use place according to the number and needs to be installed by paying attention to the following points:

(1) the surface of the template is coated with a release agent, and the selected release agent does not influence the beauty of the exposed surface of the structure.

(2) The surface of the template is required to be flat and clean, the requirement on the geometric dimension is accurate, the splicing is tight, and slurry leakage cannot occur. Sponge strips are adhered to all the abutted seams, so that joints at the overlapped parts of the abutted seams are tight, and slurry leakage is prevented.

(3) Before the template is reused, the concrete residues on the surface are removed, the damaged template is trimmed and replaced, and the sponge strips are adhered again.

(4) For the template project with complex structure and high installation difficulty, the sample turning work is required to be done, and a schematic diagram with installation numbers, sizes and assembly positions is drawn.

(5) The installed formwork must have sufficient strength, rigidity and stability to ensure the precision prescribed by the overall dimensions of the structure and the accuracy of the structure in spatial position.

(6) The embedded parts and the reserved holes fixed on the template are not omitted, a plurality of M4 bolts are adopted to be fixed on the template according to the size of the embedded parts, the embedded parts on other non-template surfaces can be fixed on the main bars by using additional steel bars or the embedded steel is used for fixing the embedded parts, the position, the surface flatness and the elevation of the embedded parts need to meet the requirements of design and specification, and the requirements of smoothness, flatness, regularity and first-class appearance quality are met.

(7) All forms of formwork will be made fixed according to design dimensions.

(8) Installation of embedded parts

Firstly, mounting small embedded parts: in the structure construction, the embedded small embedded part is positioned by connecting two phi 12 screw rods on the embedded part, penetrating through a template and then fixing by using a screw cap.

Secondly, large embedded part installation: the equipment installation requires that large-scale embedded iron pieces need to be installed, and a large-scale auxiliary frame is adopted for installing and positioning the large-scale embedded iron pieces.

Thirdly, installing the embedded bolts: the embedded bolt is installed by adopting the auxiliary shaping steel frame fixing and bolt fine-tuning process.

(9) The formwork support adopts a fastener steel pipe support system for construction.

(10) Control measure for template verticality

1) The measurer structurally emits the axis and the horizontal marking line, and the constructor plays a sideline according to the drawing and the axis.

2) During construction, a single-side hanging wire is required, and the guiding rule is required to be used for correcting the flatness and the verticality at any time along with the increase of the poured concrete. The method for checking the perpendicularity and the flatness of the template comprises the following steps:

checking whether the relation between the root of the template and a control line meets the requirement (the control line is generally 300mm or 500mm away from a wall side line);

picking out the thread drop by using a steel bar or a batten to lead the thread drop to hang on the control line;

thirdly, measuring the distance from the upper opening and the middle of the template to the vertical line by using a box ruler, wherein the template is vertical when the distance is equal to the lower distance;

form removal

(1) The formwork dismantling time is determined according to concrete marks, pouring sequence and stress conditions, the concrete strength when the formwork and the support are dismantled is required to meet design requirements, and when no specific requirements exist in design, the concrete strength is required to meet the standard regulations, namely: the non-bearing side formwork can be disassembled when the concrete strength can ensure that the surface and edges are not damaged by the disassembly of the formwork; the reinforced concrete structure bearing template can be disassembled when the concrete strength reaches over 75 percent of the design strength; the time for stripping the concrete members poured on site in the underwater and water level fluctuation areas is properly prolonged.

(2) The removal of the inner template of the reserved hole can ensure that the concrete surface does not collapse or crack, and the vibration and the damage to the hole wall are avoided during the removal of the template.

(3) The structure of the template and the bracket is removed, and the concrete can bear all the use load after the strength of the concrete meets the requirement; when the effect of construction load is more unfavorable than the use of load, the temporary support must be added after accounting.

(4) The removed templates are cleaned of the bonded mortar and dirt in time, deformed and damaged templates are shaped and repaired, and the templates are maintained, stored in a classified mode, maintained, prevented from deforming and cracking and used for increasing the using times of the templates. The template is prohibited from continuing to be used without cleaning, repair, and maintenance.

3.6.6 template installation requirements

(1) Before the mold is erected, the sizes of structural side lines of a well wall and a frame beam need to be checked, the relative positions of all parts of the structure need to be checked, and the mold is erected after the requirements are met.

(2) After the plain concrete cushion layer on the sand cushion layer reaches a certain strength, the blade brick building moulding bed accurately measures the plane position of the sunk well (popping the well wall and the inner and outer side lines of the partition wall by using an ink fountain) on the cushion layer according to the designed well position, carries out brick moulding bed construction, applies low-grade cement mortar during brick building, ensures that the inclined plane of the blade is smooth, uses lime and a small amount of cement mixture powder to brush the brick building moulding bed, and needs to leave a hole site for a pull rod screw of the sunk well wall moulding bed plate.

(3) Erecting formwork

The template engineering takes care of the following points:

the template assembly is constructed according to a turning pattern of the template, the scaffold provides operation template erecting conditions for the template, the embedded parts and the wall-penetrating hole are finished after the inner template is erected, and the position, elevation and axis of the embedded parts and the wall-penetrating hole are ensured to be correct.

The template adopts 15mm thick high-strength plywood, adopts the wooden pattern in special positions such as reservation hole, wall of a well bottom plate position, its surface of wooden pattern assembled should be planed, and the piece is tight level and smooth, does not leak thick liquid, and all template surfaces are level and smooth, accord with the standard requirement. The purlin surrounding vertical rib is made of a phi 48 steel pipe, the pull rod bolt is made of phi 16mm round steel, the middle of the purlin surrounding vertical rib is provided with a water stop sheet, the periphery of the purlin surrounding vertical rib is welded, the pull rod screw is horizontally arranged at a distance of 35cm, and the vertical distance of 35-80 cm is unequal. In order to prevent the support from being strengthened by the mold explosion during concrete pouring and the detection of the joints of the templates, all the joints and the joints of the templates need to be detected and embedded one by one to prevent slurry leakage, the templates are erected and then checked and accepted by supervision, and the important items of checking and accepting are plane size, section size, flatness, embedded parts, wall through holes and the like.

In summary, the open caisson construction method of the large-volume pump station can effectively reduce the difficulty of foundation construction of the large-volume pump station through the improvement of the construction structure and the construction process on the blade foot structure.

It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. A construction method of a large-volume pump station open caisson is characterized by comprising the following steps: the method comprises the following steps:

s1: manufacturing an open caisson structure;

s4: paving a sand cushion layer on the concrete cushion layer;

s6: constructing a template;

s10: treating a construction joint;

S13: dewatering at a well point;

2. The construction method of the open caisson of the large-volume pump station according to claim 1, wherein: and in the step S5, the thickness, the backfill height and the bearing capacity of the sand cushion layer are determined by calculation.

3. The construction method of the open caisson of the large-volume pump station according to claim 1, wherein: the supporting of the cutting edge can adopt a brick pad seat, the upper part of a concrete cushion layer is provided with a cutting edge template, cement mortar is smeared between the cutting edge and the brick pad seat, a layer of asphalt felt is laid in a dry mode, then reinforcing steel bars can be bound, and concrete can be poured.

4. The construction method of the open caisson of the large-volume pump station according to claim 1, wherein: should single face hang line during S6 construction, will use the guiding rule to rectify roughness, straightness that hangs down at any time along with concreting' S increase: checking whether the relation between the root of the template and a control line meets the requirement, wherein the control line is generally 30cm to 50cm away from the wall edge; the thread drop is picked out by steel bars or battens, so that the thread drop hangs to the control line; and measuring the distance from the upper opening and the middle of the template to the vertical line by using a box ruler, wherein the template is vertical when the distance is equal to the lower distance.

5. The construction method of the open caisson of the large-volume pump station according to claim 1, wherein: after the plain concrete cushion layer on the sand cushion layer reaches a certain strength, the blade foot brick building tire mold accurately measures and places the plane position of the open caisson on the cushion layer according to the well position, low-grade cement mortar is applied during brick building, the slope of the blade foot is ensured to be smooth, lime and a small amount of cement are mixed and pulverized to brush the brick building tire mold, and hole positions of pull rod screws of the open caisson wall template are reserved in the brick building tire mold.

6. The construction method of the open caisson of the large-volume pump station according to claim 1, wherein: the structural concrete is poured to spread to the periphery from the center of the axis or the center of the bottom beam, and finally a well wall is poured; in the position where the pump pipe cannot stretch down in the reinforced bar dense area, the reinforced bars of the surface layer can be shifted firstly, so that the pump pipe stretches down, and then the pump pipe is recovered after the concrete surface rises to a certain height; the concrete material is required to be reasonably distributed, uniform and symmetrical, and cold seams are prevented from being generated in the pouring and tamping process.

7. The construction method of the open caisson of the large-volume pump station according to claim 1, wherein: the concrete pouring adopts a layering method for construction, the thickness of each layer is not more than 50cm, the upper layer concrete and the lower layer concrete are in a step shape, and the interval between the tamping time of the upper layer concrete and the tamping time of the lower layer concrete is not more than the initial setting time of the concrete; when the concrete is vibrated, the insertion time and the insertion position interval of the vibrating rod are controlled, the vibrating rod is required to be quickly inserted, slowly pulled and uniformly arranged, and the vibrating rod is required to be inserted into the lower layer by about 15cm when the upper layer concrete is vibrated so as to eliminate the seam between the two layers.

8. The construction method of the open caisson of the large-volume pump station according to claim 7, wherein: when the structural concrete is poured and tamped, settlement observation points are arranged on the well wall, observation is carried out in the pouring and tamping process and during maintenance, and the sinking amount and the inclination amount of the open caisson are mastered in time.

9. The construction method of the open caisson of the large-volume pump station according to claim 1, wherein: the edge of the blade leg of the sinking well is generally kept with a soil dike with the width of lm, so that the blade leg of the sinking well extrudes soil and sinks, the disturbance degree to soil bodies around the well is reduced, only when the middle soil body of the sinking well is completely flushed but not sunk or is corrected, the soil body at the blade leg can be properly flushed, but the soil body outside the tread of the blade leg is strictly prevented from being brushed.

10. The construction method of the open caisson of the large-volume pump station according to claim 1, wherein: in the S12, the funnel is filled with concrete with larger slump, and then the ball plug is slowly lowered for a certain distance. When pouring, the rope or the thick iron wire is cut, concrete is rapidly and continuously poured into the funnel, at the moment, air and water in the guide pipe and the ball plug are extruded by the gravity of the concrete and are discharged from the pipe bottom, the concrete is piled into a cone shape around the pipe bottom, and the lower end of the half guide pipe is buried in the concrete.