Construction method of open caisson structure for composite terrain

Abstract

The invention provides a construction method of an open caisson structure for composite terrains, which comprises the following steps: measuring and positioning according to a design drawing, and releasing an open caisson position; an open caisson foundation pit sample position is released on the ground where the open caisson position is located, and an open caisson foundation pit is dug out; blade feet of the open caisson structure are manufactured according to design requirements; according to design requirements, an open caisson body of the open caisson structure is manufactured in a segmented mode, then the open caisson body sinks in a segmented mode, the open caisson structure comprises the open caisson body and a blade foot arranged at the bottom of the open caisson body, the open caisson body comprises an open caisson wall and a plurality of well bodies manufactured in a segmented mode, and manufacturing and sinking of the well bodies are alternately carried out; after the open caisson is about to sink in place, the bottom of the open caisson is sealed when the self-sinking speed is smaller than the first speed; and after the open caisson bottom sealing concrete construction is completed, bottom plate construction is conducted. The construction method is simple and easy to operate, the angle of the open caisson can be adjusted at any time, and the construction quality of the open caisson can be guaranteed.

Description

Technical Field

[0001] The present invention relates to the field of geotechnical and geological engineering technology, and in particular to a construction method of a caisson structure for composite terrain. Background Art

[0002] With the acceleration of urbanization, the number of pipeline projects for the transmission of liquid and gaseous media across roads, rivers, and buildings within and outside cities is increasing, and trenchless technology has been widely used. A caisson is a shaft-like structure. A pre-excavated shaft-shaped structure made of reinforced concrete on the ground serves as the support for the foundation pit wall. Under the protection of the shaft wall, soil is excavated within the shaft by machinery and manual labor. The structure, called a caisson, is sunk into the soil under its own weight, becoming the foundation for bridge piers or other structures. Caissons are widely used in foundation pits for large bridge piers, pumphouses for water intakes and sewage treatment plants, and the foundations of hydraulic facilities near rivers and lakes. They are generally used in the construction of foundation pits for large bridge piers, sewage pumping stations, large equipment foundations, civil air defense shelters, shield assembly shafts, and enclosures for the hydraulic foundations of underground driveways and stations.

[0003] The basic method of caisson construction is to first construct a shaft-shaped structure on the ground, and then use machinery and manual labor to dig the soil in the well. Under the protection of the well wall, the caisson relies on its own weight and other auxiliary measures to overcome the friction resistance of the well wall and sink to the designed elevation. Then the bottom is sealed and the internal structure is constructed. During the excavation process, as the soil in the well is excavated, there is a pressure difference between the soil inside and outside the well under the action of its own weight. The deeper the excavation, the easier it is for the soil outside the well to be squeezed inward, showing a phenomenon of pouring into the well, causing large-scale soil settlement in the vicinity, posing a safety hazard to the surrounding environment. The sand and soil that constantly surges in the well also cause trouble for construction. The difficulty of caisson construction is increased when constructing in composite formations.

[0004] Therefore, how to design a caisson structure with stable structure and applicable to ultra-deep excavation in composite strata and its construction method has become an important issue facing those skilled in the art. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a construction method of a caisson structure, which can be used for construction in composite formations and facilitates the operation of the caisson structure in composite formations and ultra-deep depths.

[0006] To achieve the above-mentioned object, the present invention provides a construction method for a caisson structure for composite terrain, the construction method specifically comprising the following steps:

[0007] 1) Measure and locate the caisson according to the design drawings and place it in the well;

[0008] 2) Place a sample caisson pit on the ground at the location of the caisson pit and dig out the caisson pit;

[0009] 3) Make the blade foot of the caisson structure according to the design requirements;

[0010] 4) manufacturing a caisson body of the caisson structure according to design requirements, manufacturing the caisson body of the caisson structure in sections according to the design requirements, and then sinking the caisson body in sections, wherein the caisson structure includes the caisson body and blade feet provided at the bottom of the caisson body, the caisson body includes a caisson wall and a plurality of well bodies manufactured in sections, and wherein the manufacturing and sinking of the plurality of well bodies are performed alternately;

[0011] 5) When the caisson sinks to the designed elevation by its own weight and is about to sink into place, when the self-sinking rate is less than the first speed, the bottom of the caisson is sealed;

[0012] 6) After the caisson bottom concrete construction is completed, the bottom plate construction shall be carried out; and

[0013] 7) Conduct quality inspection on caisson projects.

[0014] Furthermore, the position of the foundation pit is determined according to the coordinates in the design drawings, and the piles and center piles are controlled according to the axis of the caisson, and a caisson foundation pit sample is placed on the ground. The plane size of the foundation pit bottom is equal to the width of the blade foot sand cushion layer; the excavation depth of the foundation pit is about the first distance, and the slope is laid according to the first ratio. The distance from the edge of the foundation pit to the caisson wall is about the second distance; after the foundation pit is excavated, fixed guardrails are set around it for protection.

[0015] Furthermore, after the excavation of the foundation pit is completed, ensure that there is no water accumulation at the bottom of the pit, lay a sand cushion layer, and lay a plain concrete cushion layer on the sand cushion layer; the concrete cushion layer is 1.5m thick and 5.5m wide, and is laid in layers, with each layer not exceeding 30cm in thickness, and water is added layer by layer to ensure the optimal moisture content.

[0016] Furthermore, in order to prevent water seepage in the caisson wall, the bolt holes of the tension screws are waterproofed after the formwork is removed; small wooden blocks are chiseled out from the inner and outer ends of the bolt holes of the tension screws, and the recessed parts are smoothed with 1:2 cement mortar, and the outer layer is made into a 10mm thick waterproof mortar cake, and then two layers of waterproof glue are applied to cover it.

[0017] Furthermore, before the caisson sinks, a first number of vertical lines are symmetrically popped out on the inner and outer walls of the caisson to measure the inclination of the caisson when sinking; and a plumb bob is hung at the top of the first number of vertical lines on the inner wall of the caisson, and a mark plate is set at the blade foot. During the caisson sinking construction, the caisson deflection is observed at any time so that it can be corrected in time; and on the outer wall of the caisson, a horizontal measuring ruler is drawn along the first number of vertical lines to measure the sinking amount and sinking deviation of the caisson.

[0018] Furthermore, when the caisson sinks, the cushion concrete is first broken, and then a long-arm excavator is used to dig the soil. When digging, the surrounding areas are dug first and then the middle. The excavation is carried out in layers, and the thickness of each layer is 40 cm. The soil surface in the middle part should always be higher than the soil surface around it, in the shape of an inverted pot, so that it cuts the soil and sinks, and each sinking is controlled at about 20 cm.

[0019] Furthermore, during the initial sinking stage of the caisson, the position, elevation or settlement value, and verticality of the caisson should be measured in a timely manner, at least twice every 8 hours and once every 3 meters of sinking, and records should be kept. Continuous observation should be carried out and corrections should be made in a timely manner if necessary.

[0020] Furthermore, during the final sinking stage of the caisson, measurements should be taken at least once every hour. If the caisson still cannot stop after excavation has stopped, measures should be taken immediately to control the sinking of the caisson.

[0021] Furthermore, when the caisson sinks close to the design elevation, observation should be strengthened. When the cumulative settlement of the caisson within 8 hours is no more than the third distance, the bottom should be sealed.

[0022] Furthermore, after the caisson sinks to the designed elevation, a shaped guardrail is set at a position 1m outside the caisson. Through the technical solution provided by the present invention, the construction method of the caisson structure for composite terrain provided by the present invention has at least the following technical effects:

[0023] (1) The caisson structure provided by the present invention is simple in structure and easy to construct, and can be used for construction on complex terrains, making operations convenient;

[0024] (2) The caisson structure provided by the present invention adopts a segmented design, and the height, thickness and other parameters of different sections of the well body can be flexibly designed according to different terrain conditions, which is conducive to the progress of construction.

[0025] (3) The caisson structure provided by the present invention includes multiple well bodies and is suitable for ultra-deep caisson construction.

[0026] The present invention provides a construction method for a caisson structure for complex terrains. The method utilizes a segmented construction and sinking process, resulting in simple operation and ease of adjustment based on the caisson's conditions, ensuring smooth construction. Furthermore, the method allows for on-the-spot corrections during construction, facilitating adjustment of the caisson's angle to ensure high-quality construction. Furthermore, a guardrail is installed after the caisson is sunk to provide safety during subsequent construction.

[0027] Moreover, the caisson structure using the construction method of the caisson structure for composite terrain provided by the present invention is simple in structure and easy to construct, and is suitable for ultra-deep caisson construction and composite terrain construction; and the construction method provided by the present invention is simple and easy to operate, and the angle of the caisson can be adjusted at any time during the construction process, which is conducive to ensuring the quality of the caisson construction.

[0028] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a general plan view of a project example using the construction method according to an embodiment of the present invention.

[0030] Figure 2 It is a flow chart of a construction method of a caisson structure for composite terrain according to an embodiment of the present invention.

[0031] Figure 3 Schematic diagram of the arrangement of longitudinal horizontal bars of a scaffold according to an embodiment of the present invention

[0032] Figure 4 It is a schematic diagram of the installation of the side formwork of the caisson wall according to an embodiment of the present invention.

[0033] Figure 5 Schematic diagram of an underwater bottom sealing platform for a rectangular caisson according to an embodiment of the present invention.

[0034] Figure 6 It is a structural schematic diagram of an embodiment of the caisson structure provided by the present invention.

[0035] Figure 7 It is a structural schematic diagram of another embodiment of the caisson structure provided by the present invention.

[0036] Figure 8 It is a structural schematic diagram of another embodiment of the caisson structure provided by the present invention. DETAILED DESCRIPTION

[0037] The following describes the specific implementation of the embodiment of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific implementation described herein is only used to illustrate and explain the embodiment of the present invention and is not used to limit the embodiment of the present invention.

[0038] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0039] In the present invention, unless otherwise specified, the directional words used, such as "up, down, top, bottom", are usually used to describe the relative positional relationships of the components in the directions shown in the drawings or in the vertical, perpendicular or gravity directions. The transverse direction used refers to the direction consistent with the length of the transverse steel bars, and the longitudinal direction refers to the direction consistent with the length of the longitudinal steel bars.

[0040] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0041] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0042] For the engineering that the present invention is particularly applicable to, for example Figure 1 As shown in the Civil Engineering Section III of a certain road's integrated pipeline corridor project, four shield tunneling shafts and three shield section pipeline branching points were constructed using caissons. Additionally, two power pipe jacking tunnels were constructed on the north and south sides of the station shaft, connecting to the No. 7 shield tunneling shaft. The north pipe jacking tunnel is 22 meters long, and the south pipe jacking tunnel is 100 meters long. Both tunnels are constructed using double pipe jacking tunnels with an inner diameter of 3.5 meters.

[0043] Let's combine Figure 2 The construction method of the caisson structure for composite terrain provided by the present invention is specifically described, and the method comprises:

[0044] 1) After measuring and locating according to the design drawings, the caisson position is set. Before excavating the foundation pit, the site is leveled, and then the well position is set according to the designed well coordinates. The well position control points are protected by using the surrounding environment. At the same time, the leveling points provided by the design are re-measured. According to the construction needs, multiple leveling control points are set and protected.

[0045] 2) Lay out a sample caisson pit on the ground at the location of the caisson pit and excavate the caisson pit. The location of the pit is determined according to the coordinates in the design drawings. The control piles and center pile are aligned along the caisson axis. The planar dimensions of the pit bottom are equal to the width of the blade foot sand cushion.

[0046] Based on site conditions, the excavation depth of the foundation pit is set at a first distance, for example, approximately 2 meters. The slope is set at a first ratio, for example, 1:1. The distance from the pit edge to the caisson wall is set at a second distance, for example, approximately 4 meters. The excavation is carried out using a crawler excavator, which moves backward along the perimeter of the caisson. The excavated soil is then transported directly off the construction site by dump trucks. After the excavation is complete, a fixed guardrail is installed around the pit for protection.

[0047] Open drainage of the collection pit: dig drainage ditches with a width of 30 cm and a depth of 50 cm around the bottom of the foundation pit and connect them to the collection well in the foundation pit. The collection well should be at least 50 cm deeper than the collection ditch. Use a drainage pump to drain the water in the collection well to the nearby rainwater manhole or river. The lowest water level should always be maintained in the collection well until the collection well is abolished.

[0048] 3) Fabricate the caisson's blade footing according to design requirements. The load on the caisson's blade footing surface exceeds the bearing capacity of the underlying foundation soil, so a sand cushion of appropriate width and thickness must be laid. A plain concrete cushion layer is then placed on top of the sand cushion to expand the bearing area. After excavation, ensure there is no water accumulation at the bottom of the pit and lay the sand cushion.

[0049] In one embodiment of the present invention, the cushion layer is 1.5m thick and 5.5m wide, laid in layers, with each layer no thicker than 30cm. Water is added layer by layer to ensure optimal moisture content. The sand cushion layer is compacted using a flat vibrator, with a 1 / 3 overlap required.

[0050] To expand the supporting area of the caisson's blades and reduce pressure on the sand cushion, a C20 plain concrete cushion was laid on top of the sand cushion. The concrete cushion was 30cm thick and 1.5m wide. When setting up the scaffolding, the concrete was appropriately widened based on on-site construction conditions to facilitate formwork assembly and the construction of the formwork support during shaft wall construction.

[0051] 4) Manufacturing a caisson body of the caisson structure according to the design requirements, manufacturing the caisson body of the caisson structure in sections according to the design requirements, and then sinking the caisson body in sections, wherein the caisson structure includes a caisson body and a blade foot arranged at the bottom of the caisson body, the caisson body includes a caisson wall and a plurality of well bodies manufactured in sections, and the manufacturing and sinking of the plurality of well bodies are performed alternately, for example Figure 2 shown.

[0052] Specifically, taking 5 well bodies as an example, after the first well body is made, the first well body is sunk first and then the second well body is made; after the second well body is sunk, the third well body is made; after the third well body is sunk, the fourth well body is made; after the fourth well body is sunk, the fifth well body is made and sunk.

[0053] Here, the production of the caisson body according to the embodiment of the present invention is first described.

[0054] In the embodiments of the present invention, multiple shafts of the caisson body are first fabricated in sections according to the design requirements. The following example uses the fabrication and sinking of the first shaft of the caisson body as an example. The fabrication and sinking processes for the second, third, and other shafts are similar or identical.

[0055] In the example of the present invention, the production of the caisson body includes at least scaffolding engineering, formwork engineering, well wall and middle partition wall formwork construction, top plate and top beam formwork design, support acceptance, steel bar construction, concrete pouring construction, as well as formwork removal and maintenance.

[0056] In the scaffolding project of the embodiment of the present invention, a scaffolding (for example, double rows) needs to be set up when making the caisson body. The inner and outer operating brackets (non-load-bearing) of the scaffolding are all socket-type steel pipe brackets. The brackets are made of, for example, The steel pipe fastener structure is a knotted structure, and the vertical pipe of the outer support must be located on the sand cushion layer in the well foundation, and the lower end of the vertical pipe is covered with wooden boards. Special cast iron fasteners are used to connect the steel pipes, and the screw torque is, for example, 40-50N / m. In order to ensure the overall stability of the outer support, diagonal braces are set along the well wall, for example, within a length of about 2m, and the upper end of the support is fastened to the inner support with a connecting rod, with a spacing of, for example, 2m. The scaffolding must be connected as a whole at the corners, and the outer and inner supports of the caisson must also be connected as a whole at the highest point. A safety net must be set up when the distance between the caisson wall and the support exceeds, for example, 60cm. Specifically, in the scaffolding project, there are three processes: ① erection of vertical poles and horizontal poles; ② setting of scissors braces; ③ implementation of support erection.

[0057] In the above-mentioned ① erection of vertical poles and horizontal poles in the embodiment of the present invention, before erecting the vertical poles of the support, the plan should be accurately laid out and the construction should be strictly in accordance with the drawing. Figure 3 As shown, the bottom longitudinal and transverse horizontal bars serve as sweeping bars, and the height from the ground should be, for example, 300mm. An adjustable base or a fixed base should be provided at the bottom of the vertical pole. In the above-mentioned ② scissors brace setting of the embodiment of the present invention, during the erection of the support vertical pole, as the upper caisson is gradually raised, diagonal braces, horizontal scissors braces, and vertical scissors braces are synchronously set, and the density of the scissors braces is 1 / 4 of the support vertical pole, to avoid deflection and tipping during the erection process and increase the stability of the support vertical pole. The vertical scissors braces should be set continuously from the bottom to the top of the support around, and the middle horizontal and longitudinal vertical scissors braces should also be set continuously from the bottom to the top, and the spacing between them should be, for example, less than or equal to 4.5m. The horizontal scissors braces must be set at both the top and bottom of the support, and the spacing between the middle horizontal scissors braces should be, for example, less than or equal to 4.8m. At the corners of the scaffolding and the ends of the open-type scaffolding, diagonal bars should be set continuously from the bottom to the top of the frame.

[0058] In the implementation of the above-mentioned ③ bracket erection in the embodiment provided by the invention, when erecting the bracket poles, first measure and lay out the lines, pop out the center and side lines of the structure on the plain concrete cushion layer (or the structural bottom plate), and pop out the ink lines according to the vertical and horizontal spacing of the poles, then place the base at the intersection of the vertical and horizontal ink lines (the position of the poles), and then erect the bracket poles. The bracket poles are symmetrically erected on both sides with the center line of the structure as the axis and perpendicular to the center point of the structure. They are fixed with a coupler-type steel pipe scaffold at the intersection. Before erection, the position of the bracket poles is laid out. The load-bearing bracket is the load-bearing bracket, and the pole is the direct load-bearing pole. Therefore, the distance and verticality between the poles must be strictly controlled. The height of the sweeping rod from the ground is, for example, 30 cm. In places with high and low terrain, a stepped setting is performed to keep the height of the sweeping rod no higher than, for example, 30 cm from the ground. The side walls (well walls) are connected to the top supports with coaxial parts, and the top supports are tightened with horizontal top supports when they meet the middle partition wall. If the distance between the adjustable top support and the topmost horizontal bar is greater than or equal to, for example, 0.7 meters, add another horizontal bar to ensure that the free end of the vertical pole below the top support is no more than, for example, 70 cm to ensure the stability of the top support of the extension. The top elevation of the vertical pole is adjusted using the top support screws on the vertical pole.

[0059] The construction passage must be kept basically consistent with the progress of the scaffolding erection. The passage shall not be erected after all the scaffolding has been erected to ensure the safety of the scaffolding construction. When erecting, the support frame and scaffolding should be erected separately.

[0060] In the formwork engineering in the embodiment of the present invention, for example, 15mm bamboo plywood (or bamboo fence board) is used for the caisson formwork, and the formwork on the blade foot pad should be installed in sections for easy removal. Taking into account the pouring speed and the height of the well wall poured at one time, a large lateral pressure is generated on the formwork, and the formwork is fixed with, for example, M14 tension bolts. The lower half of the tension bolts of each pouring are fixed with, for example, double nuts. The tension bolts must be kept flexible for assembly and disassembly, and it is strictly forbidden to connect the bolts with steel bars to reinforce the formwork. For example, the horizontal and vertical spacing of the bolts is 40cm×40cm, and a 60mm×60mm×3mm steel plate water stop is set in the middle, for example, and is fully welded to the screw rod. Keep the formwork stable, and use the next section of the caisson formwork to fix the previous section of the caisson formwork.

[0061] To prevent water seepage from the well wall, waterproof the tension bolt holes after removing the formwork. Remove the small wood blocks at the inner and outer ends of the tension bolt holes. Smooth the recessed areas with, for example, 1:2 cement mortar. Apply, for example, a 10mm thick waterproof mortar cake on the outside, and then apply, for example, two layers of waterproof glue to cover it.

[0062] Generally, no earlier than 5 days after the completion of concrete pouring (depending on the temperature at the time), the tie bolts of the caisson wall panels can be loosened, and the formwork and fastener-type steel pipes can be removed. The order of operation is to remove the formwork and fastener-type steel pipes from top to bottom and from the inside to the outside. Be careful not to hit hard or damage the surface of the newly poured concrete when removing the steel formwork. After the formwork is removed, the concrete surface should be promptly chiseled at the root of the bolt to form a pit with a radius of 3 cm and a circular depth of 3 cm, for example. Then the tie bolts should be cut off, the pit should be filled with waterproof mortar, and waterproof material should be applied twice. For the suspended part of the larger hole, the concrete bottom formwork should be removed as required when the concrete strength reaches more than 70% of the design strength. The removed formwork, steel pipe scaffolding pipe, and hardware accessories should be cleaned and stacked neatly in time. After the formwork is removed, the measuring level mark should be sprayed on the well wall, and the measuring caisson displacement mark should be sprayed at the midpoint of the well mouth.

[0063] In the construction of the well wall and middle partition wall formwork in the embodiment of the present invention, the well wall and partition wall inner and outer side formwork adopts, for example, 15mm bamboo plywood formwork, and the vertical back rib adopts, for example, 40×60mm square wood, with a spacing of, for example, 20cm; the square well adopts tensioning screws and φ48 double-piece steel pipes for support, and the round well adopts two φ20 threaded steel bars for formwork fixation; the caisson formwork is erected by first erecting the inner formwork and then the outer formwork, and a 60×60×3mm water stop plate is set in the middle of the tensioning screws. After the square caisson formwork is installed, the inner formwork is supported by steel pipes or threaded steel bars. Formwork installation and support diagram, for example, Figure 4 The diagram shown is a schematic diagram of the installation of the side formwork of the caisson wall.

[0064] In the roof and top beam formwork designs of the embodiments of the present invention, the maximum erection height of the caisson formwork, for example, is approximately 4.6 meters (measured from the top of the base plate to the bottom of the roof plate, for the north caisson). Construction places high demands on the rigidity, stability, and integrity of the support system. Considering both construction safety and operability while also taking into account cost-effectiveness, this project's load-bearing formwork utilizes a scaffolding system.

[0065] During the inspection of the scaffolding in the embodiments of the present invention, the following key aspects should be examined: The following should be checked: The diagonal bars, vertical bars, and scissor braces are properly installed to ensure geometrical deformation of the frame; Whether there is uneven foundation settlement, and whether the contact between the vertical bar base and the foundation surface is loose or hanging; Whether the vertical bar connecting pins and scissor braces are installed in accordance with requirements, and whether the fasteners are tightened to the required level. The engagement length between the adjustable support screw and the adjusting nut must be no less than, for example, 6 turns, and the length of insertion into the vertical bar must be no less than, for example, 150 mm.

[0066] In the steel bar construction in the embodiment of the present invention, the caisson steel bars in the embodiment of the present invention all adopt HPB300 and HRB400 steel bars, including: on-site storage of steel bars, processing of steel bars, and connection of steel bars.

[0067] In the concrete pouring construction in the embodiment of the present invention, for example, the concrete strength grade of the caisson structure is C35, the anti-seepage grade is P8, and the concrete is poured by commercial concrete pumping. Concrete pouring is a key link in caisson construction. Under the premise of ensuring the quality of concrete, the pouring procedure must be reasonably arranged and the pouring time of concrete must be controlled. The pouring height of each layer is, for example, not more than 30 cm, and the secondary concrete mixture must be vibrated before the previous layer of concrete reaches initial setting. The insert vibrator is arranged to vibrate according to an effective diameter of, for example, 30 cm in the plane, and should be inserted into the previous layer of concrete, for example, 5 cm. The concrete is not allowed to slide directly down the inclined surface or flow to its final pouring position. The vibrator should avoid colliding with the steel formwork or embedded parts. When pouring concrete from a height, its unloading height should not exceed, for example, 2 m.

[0068] Before pouring concrete, settlement observation points are set up on the four corner formworks of the well to promptly detect uneven settlement of the caisson due to its own weight during the pouring process; guide the location and sequence of concrete pouring during the pouring process, and promptly correct deviations caused by the caisson during the pouring process.

[0069] Treatment of the concrete construction joints of the caisson wall: When pouring concrete, the concrete at the construction joints of the caisson wall should be fully tamped to facilitate dense adhesion of the concrete; the construction joints should be set in a V shape, and the surface of the construction joints should be roughened before the caisson is raised, and the exposed stones at the floating slurry position should be removed. It should be cleaned and fully moistened, and cement mortar should be used to connect the mortar before pouring the upper layer of concrete.

[0070] In the demoulding and maintenance of the embodiment of the present invention, generally 48 hours after the concrete pouring is completed, the tension bolts of the caisson wall can be loosened, and the formwork and fastener-type steel pipes can be removed. The caisson straight wall formwork should not be removed until the concrete reaches more than 25% of the design strength. The operation sequence is to remove the formwork and fastener-type steel pipes from top to bottom and from the inside to the outside. After the lower section is made, the formwork cannot be completely removed. For example, more than 1m must be left to support the upper section formwork. After the formwork is removed, the concrete surface is promptly chiseled into a pit with a diameter of, for example, 5cm and a depth of 2cm at the root of the tension screw, and then the tension bolts are cut off, the pit is filled with waterproof mortar for the second time, and waterproof material is applied twice. For the concrete bottom formwork of the suspended part of the larger hole, it should be removed as required when the concrete strength reaches, for example, 80% of the design strength. After the formwork is removed, the measuring level marks are sprayed at the four corners of the well, and the measuring caisson displacement marks are sprayed at the top of the well. After the side formwork of the well wall is removed, straw bags should be hung in time and water should be sprinkled for maintenance to keep the concrete surface moist, and the maintenance time should not be less than 7 days.

[0071] Next, the method for sinking a segmented caisson according to an embodiment of the present invention is described. After the first well body is made in sections, the first well body is sunk first, and then the second well body is made. After the second well body is sunk, the third well body is made, and then the third well body is sunk... The Nth section of the well body is made, and then the Nth sinking is performed, for example, Figure 2 As shown, the fabrication and sinking of multiple wellbores are carried out alternately.

[0072] The following is a detailed description of the sinking of a caisson.

[0073] First, the preparation work for sinking according to the embodiment of the present invention is explained. Before the caisson is sunk, all the reserved holes on the caisson wall are blocked. For larger holes, cement mortar bricks can be used to block them, and cement mortar is used to plaster the side close to the soil. The strength of the mortar used to block the holes should meet the requirements of resisting soil pressure and water pressure during sinking, and it should also be easy to dismantle. Before the caisson is sunk, a first number, such as 4 vertical lines, are symmetrically popped out on the inner and outer walls to measure the inclination of the caisson when it sinks. Hang a plumb bob at the top of the 4 vertical lines inside the caisson, and set a mark plate at the blade foot. During the caisson sinking construction, observe the caisson deflection at any time so that it can be corrected in time. Draw a horizontal measuring ruler along the 4 vertical lines on the outer wall of the caisson to measure the sinking amount and sinking deviation of the caisson. Check whether the machinery, equipment and tools used for the sinking of the caisson are intact and whether the quantity meets the requirements.

[0074] Before removing the concrete cushion layer, all concrete cushion layers should be grouped and numbered symmetrically at intervals. When removing the concrete, work should be carried out in groups, symmetrically and synchronously. Only after the concrete cushion layer with the same number has been removed and backfilled can the next group of numbered concrete cushion layers be removed. Each group of concrete cushion layers must be backfilled in time after being chiseled out, and the backfill material should be medium-coarse sand.

[0075] Secondly, in the example embodiment of the present invention, regarding the sinking of the caisson, when the first shaft is lowered, the cushion concrete is first crushed, and then the soil is excavated using a long-arm excavator. The excavated soil is directly loaded onto trucks for transportation. A dedicated person is assigned to direct and coordinate the excavation process. Excavation is carried out in layers, starting with the perimeter and then digging in the center. Each layer is excavated, for example, 40 cm thick. The soil surface in the center should always be higher than the surrounding soil surface, forming an inverted pot shape, so that the soil is cut and sunk. Each sinking is controlled to approximately 20 cm, for example.

[0076] Excavation near and below the blade foot requires symmetry and balance, with consistent excavation speeds and consistent surface elevations (except when correcting deviations). Simultaneously, efforts are strengthened to complete excavation in the shortest possible time to ensure even sinking of the caisson. Throughout the entire caisson sinking process, guidance and flexible adjustments to the excavation range and methods are implemented based on variations in the subsidence coefficient and soil conditions to ensure a smooth and balanced sinking of the caisson.

[0077] Third, as the caisson sinks, it is necessary to control the sinking of the caisson. During the sinking process of the caisson according to the embodiment of the present invention, the inclination of the caisson and the elevation of the blade foot tread are frequently observed. When the caisson blade foot is buried less than, for example, 1 / 3 of the caisson height, the inclination of the caisson shaft is particularly observed. When the elevation of the caisson blade foot tread sinks to approximately 2 meters from the design elevation, the elevation and amount of sinking should be monitored more closely.

[0078] The method for observing the vertical inclination of a caisson shaft is to place, for example, four plumb bobbins on the shaft's perimeter. When the shaft deflects, the plumb bobbins' hanging lines deviate from the vertical line on the shaft's inner wall. Correction is then made based on the deviation. Observations are generally performed before and after each caisson sinking.

[0079] In an embodiment of the present invention, there are different sinking observation requirements for different sinking stages in the sinking process. Specifically, during the sinking process, in the initial sinking stage, the position, elevation (settlement value) and verticality of the caisson are measured in a timely manner, at least twice every 8 hours, and once every 3m of sinking, and records are kept. Continuous observation and timely correction should be made when necessary. In the final sinking stage, measurements should be taken at least once per hour. If the caisson still cannot stop after stopping excavation, measures should be taken immediately to control the sinking of the caisson. When the caisson sinks close to the design elevation, observations should be strengthened. When the cumulative settlement of the caisson within 8 hours is observed to be no more than a specific distance, such as 10 mm, preparations can be made for bottom sealing.

[0080] In particular, with respect to the final sinking control of the embodiment of the present invention, when the blade foot tread of the caisson structure sinks to a point where there is, for example, about 1m left from the design elevation, the caisson enters the final sinking stage. At this time, a "deep pot bottom" should be avoided, because an excessively deep pot bottom may cause a large amount of soil under the blade foot to flow into the well, making sudden sinking or over-sinking likely to occur. First, flush the soil near the blade foot to form an "inverted pot bottom", and then dig the soil in the center as appropriate, control the sinking speed, and stop sinking immediately when it sinks to 0.2 to 0.3m higher than the design elevation. Of course, during the caisson sinking process, it is necessary to keep a record of the caisson sinking construction. Furthermore, during the caisson sinking process, whether it is caisson pit excavation or caisson sinking, excavators and manual labor are used in conjunction with each other, and the parking positions of the excavators and earth-moving vehicles need to be considered. In this caisson construction, the excavators are planned to be parked around the caisson, at least 3 meters away from the caisson wall, to reduce the horizontal load on the caisson. Symmetrical parking is required for flexible operation, uniform construction, symmetrical excavation, human-machine coordination, reasonable deployment, and scientific implementation. The soil in the caisson is excavated mechanically, and the construction speed is reasonably controlled.

[0081] When the caisson is sunk and the concrete is raised, stabilization measures are also required. To elaborate, the caissons of the embodiments provided by the present invention all need to be raised. After the caisson sinks for the first time, the caisson will continue to be raised after the concrete reaches the design strength. At this time, since the top few meters of the caisson are above the ground, the outer side of the wall does not contact the stratum soil and there is no friction. This is a situation where the dead weight increases but the friction does not increase accordingly. Therefore, this working condition needs to consider preventing and avoiding the caisson from sinking or tilting on its own. Under normal circumstances, the sinking coefficient K1>1 of the caisson during the sinking period. When the wall of the caisson is raised, the sinking stability coefficient K2 must be less than 1. At this time, the sinking stability coefficient of the caisson is calculated. If the sinking stability coefficient of the caisson satisfies K2<1, it is considered that the foundation is stable and the caisson will not sink or tilt on its own. If the sinking stability coefficient of the caisson does not meet the condition of K2>1, temporary measures such as filling the well are needed to ensure the stability of the foundation when the caisson is raised.

[0082] After the caisson is sunk, it needs to be protected. In the post-sinking protection of the caisson in the embodiment of the present invention, after the caisson sinks to the designed elevation, a fixed guardrail is set at a specific distance outside the caisson, for example, 1m, and a green net and safety warning signs are hung as safety protection during the subsequent construction process.

[0083] 5) After the caisson sinks to the design elevation by its own weight and is about to sink into place, when the self-sinking rate is less than the first speed, for example, 10mm / 8h, the bottom of the caisson is sealed. To elaborate, the caisson sinking process is not carried out continuously. When the caisson sinks to a certain distance, the bottom of the caisson needs to be sealed. In the caisson bottom sealing of the embodiment of the present invention, since most of this project is soft soil, according to previous construction experience, when the caisson sinks to a distance of about 0.2 to 0.3m from the design elevation, it is necessary to stop digging and pay attention to observation. After the caisson sinks to the design elevation by its own weight and is about to sink into place, strengthen observation. When the self-sinking rate is less than 10mm / 8h, the bottom can be sealed.

[0084] The concrete is pumped into the aggregate hopper and poured into the caisson through the conduit. The C20 concrete is poured underwater to seal the bottom. The thickness of the bottom seal is, for example, 1.8 to 2.2 meters. Before the conduit is used, it must be visually inspected and docked. Check whether the conduit has deformation, pits, bends, damage or cracks, etc., and check whether there is concrete adhesion and consolidation on its inner wall. The maximum particle size of the concrete aggregate is, for example, not greater than 1 / 6 of the inner diameter of the conduit, and the slump is controlled within, for example, 180 mm to 220 mm, and has a certain fluidity. When pouring concrete, the insertion depth of the conduit is not less than, for example, 1 meter, and the height of the conduit from the bottom surface of the base is, for example, 0.3 to 0.4 meters.

[0085] The pouring of bottom seal concrete should be symmetrical and even, starting from the bottom of the pot and ending at the surrounding areas. From the bottom seal to the time when the concrete reaches the design strength value, the water level inside and outside the well should be kept equal to prevent the bottom seal concrete from being subjected to water pressure. Only when the underwater bottom seal concrete strength reaches the design requirements can the water in the well be pumped out to pour the bottom plate concrete. During the entire pouring process, the rise of the underwater concrete surface should be measured frequently with a measuring rope. At the same time, the elevation of the lower end of the conduit can be calculated through the scale on the conduit and the water depth measured by the measuring rope, and the depth of the lower end of the conduit buried in the concrete can be grasped. According to the effective radius of the conduit, the caisson is evenly divided into 4 blocks, and 4 conduits are arranged in each well. During construction, the pouring is cyclical. The pouring time of each conduit is generally no more than 20 minutes, and the difference between the bottoms of adjacent pipes is no more than 20cm. The pouring radius of the conduit is 3.5m. For example, Figure 5 shown.

[0086] 6) After the caisson bottom concrete construction is completed, the base plate construction will be carried out. The base plate concrete strength grade is C35P10. Since pre-buried steel bars are installed during the construction of the caisson wall, when the base plate steel bars are tied, they need to be effectively connected with the pre-buried steel bars of the wall. Before tying the base plate steel bars, the base plate concrete surface needs to be cleaned and marked on the surface as the control point for the spacing of the base plate steel bars. After the steel bars are tied, the project department will conduct an inspection and acceptance. Only after the procedures are completed and meet the requirements can the concrete be poured. Concrete pouring and maintenance are carried out in accordance with the requirements of the shaft wall concrete construction.

[0087] 7) Finally, the caisson project needs to be quality inspected. In the embodiment of the present invention, the construction quality inspection of the sand cushion layer must be carried out in layers, and the upper layer should be laid after the compaction coefficient of each layer reaches 0.93. The inspection points for the construction quality of the sand cushion layer should be arranged such that when laying along the edge of the ring, there should be no less than 1 point for every 10m, and when laying the whole floor, there should be no less than 1 point for every 50m2, and there should be no less than 3 points for each single project. When inspecting the construction quality of the cushion layer by the ring knife method, the sampling point should be located at 2 / 3 of the thickness of each layer.

[0088] During caisson fabrication, the position, size, and tightness of the formwork, as well as the location of the reinforcement, embedded components, and reserved openings, should be inspected and accepted before concrete pouring. After formwork removal, the pouring quality should be visually inspected and strength tested. The allowable deviations for caisson and pneumatic caisson fabrication should comply with the requirements in Table 1 below.

[0089] Table 1 Permissible deviation of caisson structure production

[0090]

[0091]

[0092] Note:

[0093] 1) L1 is the designed caisson (box) length (mm), B is the designed caisson (box) width (mm), H1 is the designed caisson (box) height (mm), and D1 is the designed caisson (box) diameter (mm);

[0094] 2) When checking the center line position, measure in both the longitudinal and transverse directions and take the larger value.

[0095] During the sinking and bottom sealing of the caisson according to the embodiment of the present invention, the allowable deviation during the sinking of the caisson and the pneumatic caisson shall comply with the provisions of the following Table 2.

[0096] Table 2 Permissible deviations during the sinking phase of the caisson

[0097]

[0098] Note:

[0099] (1) L1 is the designed caisson length (mm), H2 is the sinking depth (mm);

[0100] (2) When the sinking speed is fast, increase the measurement frequency appropriately.

[0101] The allowable deviation after the final sinking of the caisson in the embodiment of the present invention should comply with the provisions of Table 3.

[0102] Table 3: Permissible deviation after caisson sinking

[0103]

[0104] Note: L2 is the distance between the two corners of a rectangular caisson, and the distance between two perpendicular diameters for a circular caisson (mm); H3 is the total sinking depth (mm).

[0105] In the caisson bottom sealing embodiment of the present invention, the construction inspection should comply with the following regulations: the working performance of the concrete should be inspected before bottom sealing, and the bottom sealing can be carried out only after it meets the requirements; when the caisson bottom is dry-sealed, the groundwater level in the well should be controlled below the bottom of the pit, for example 0.5m, and the strength and thickness of the concrete should be checked after the caisson bottom sealing is completed.

[0106] Now, an application example of a project using the above-mentioned construction method of the caisson structure for composite terrain according to the embodiment of the present invention is described. Figure 1 and Figure 2As shown, the caisson applicable to the method of the present invention adopts reinforced concrete caisson, which is divided into north and south caissons. For example, the caisson is first made to the top elevation of the blade foot, and after reaching the design strength, the blade foot is sunk, and then a section of the well body is made and sunk one section at a time. The blade foot elevation of the bottom of the north caisson is -9.245m, which can be divided into two sinking constructions; the blade foot elevation of the bottom of the south caisson is -14.526, which can be divided into three sinking constructions; the blade foot elevation of the bottom of the 7# branch well is -33.261m, which can be divided into 8 sinking constructions; the blade foot elevation of the bottom of the 8# branch well is -20.691, which can be divided into 6 sinking constructions; the blade foot elevation of the bottom of the 9# branch well is -18.872m, which can be divided into 5 sinking constructions, and the height of a single well body is controlled within 5m. Branch shafts 7#, 8#, and 9# were sunk using the undrained excavation method, while the north and south caissons were sunk using the drained excavation method. After sinking to the designed elevation, bottom sealing was carried out. After the pipe jacking construction was completed, the well walls and roof were cast. The pipe jacking construction included the following: 1. Portal reinforcement: φ850@600 triaxial cement mixing piles were used, and φ800@600 high-pressure jet grouting piles were used for caulking and corner filling between the portal and the structure. 2. Construction of the main pipe jacking structure: Double pipe jacking pipes with an inner diameter of 3.5m were used. In addition, the strata involved in the caisson and pipe jacking construction are mainly: ①1a layer and ①1b layer of fill, ①2 layer of clay, ②1 layer of silty clay, ②1a layer of clay, ②2 layer of silty silty clay, ②2a layer of silt, ③1 layer of silt sand, ③2a layer of silty clay, ③2b layer of silty silty clay, ④1 layer of silty clayey silt, ④2 layers of clay and ⑤1 layer of clay, ⑤4 layer of silty clay.

[0107] In the construction method of the caisson structure of the embodiment of the present invention, Figure 2 As shown, concrete curing and formwork removal, caisson stability observation and quality inspection after bottom sealing are required.

[0108] Next, the present invention will describe different embodiments of caisson structures that can be formed in the above-mentioned caisson structure construction method.

[0109] As in the embodiment of the present invention Figure 6 As shown, the present invention provides a structural diagram of an embodiment (embodiment 1) of a caisson structure. Figure 6 As can be seen in the figure, the caisson structure provided in this embodiment includes a caisson body 1 and a blade foot 2 arranged at the bottom of the caisson body 1. The caisson body 1 includes a caisson wall, and the caisson wall includes an inner wall 101 and an outer wall 102. The inner wall 101 and the outer wall 102 are both reinforced concrete structures, and the space between the inner wall 101 and the outer wall 102 is also filled with a reinforced concrete structure.

[0110] The caisson body 1 provided by the present invention has a segmented structure. In this embodiment, the caisson body 1 is a five-section structure, comprising a first shaft 11, a second shaft 12, a third shaft 13, a fourth shaft 14, and a fifth shaft 15. Waterstop plates 3 measuring 60mm x 60mm x 3mm are installed at the junctions between the first shaft 11 and the second shaft 12, the second shaft 12 and the third shaft 13, the third shaft 13 and the fourth shaft 14, and the fourth shaft 14 and the fifth shaft 15. To prevent water seepage into the caisson body 1, the outer perimeter of the waterstop steel plates 3 is coated with a 10mm thick waterproof mortar cake and covered with waterproof adhesive.

[0111] The caisson body 1 is a rectangular parallelepiped structure, the blade foot 2 is a structure that is wide at the top and narrow at the bottom, the bottom 2 of the blade foot is a planar structure, and the thickness of the connection between the blade foot 2 and the caisson body 1 is greater than the thickness of the well wall of the caisson body 1. The well wall thickness of the caisson body 1 will be designed differently according to the actual construction conditions, and the well wall thickness of the caisson body 1 in different sections will be different. In this embodiment, the caisson body 1 has a height of 21.372 meters, a length of 9.2 meters, and a width w1 of 7.7 meters. The thickness d2 of the well wall of the first well body 11 is 1.1 meters; the thickness d1 of the well wall of the second well body 12, the third well body 13, and the fourth well body 14 is 0.9 meters. The height of the blade foot 2 is 3.7 meters, and the thickness d4 of the blade foot 2 is 1.7 meters.

[0112] During the actual construction process, the caisson body 1 is manufactured in sections. The caisson body of the caisson structure is manufactured according to the design requirements, and the first well body 11, the second well body 12, the third well body 13, the fourth well body 14 and the fifth well body 15 are manufactured in sections; then the caisson structure 1 is sunk in sections; after the first well body 11 is manufactured, the first well body 11 is sunk first and then the second well body 12 is manufactured; after the second well body 12 is sunk, the third well body 13 is manufactured; after the third well body 13 is sunk, the fourth well body 14 is manufactured; after the fourth well body 14 is sunk, the fifth well body 15 is manufactured and sunk.

[0113] The tread load on the caisson's blade foot 2 exceeds the bearing capacity of the underlying foundation soil, so a sand cushion layer 6 of appropriate width and thickness must be laid. A plain concrete cushion layer 7 is then placed on top of the sand cushion layer 6 to expand the pressure-bearing area. After excavation of the foundation pit is complete, ensuring that there is no water accumulation at the bottom of the pit, the sand cushion layer 6 is laid. The caisson structure 1 also includes a top plate structure 4, which is a reinforced concrete structure with a thickness of 50 cm.

[0114] Next, if Figure 7The figure shows a schematic diagram of the structure of another embodiment (Example 2) of the present invention. In this embodiment, the height of the caisson body 1 is 22.751 meters. As can be seen in the figure, the structure of this embodiment is basically the same as the previous embodiment, except that the number of sections of the caisson body 1 in this embodiment is different. In this embodiment, the caisson body 1 includes a first well body 11, a second well body 12, a third well body 13, a fourth well body 14, a fifth well body 15, and a sixth well body 16; a waterstop steel plate 3 with a size of 60mm×60mm×3mm is provided at the junction of the first well body 11 and the second well body 12, the junction of the second well body 12 and the third well body 13, the junction of the third well body 13 and the fourth well body 14, the junction of the fourth well body 14 and the fifth well body 15, and the junction of the fifth well body 15 and the sixth well body 16. To prevent water seepage from the well wall of the caisson body 1, a 10mm thick waterproof mortar cake is provided on the outer periphery of the waterstop steel plate 3 and covered with waterproof glue.

[0115] The caisson body 1 is still a rectangular parallelepiped structure with a height of 22.751 meters, a length of 9.8 meters, and a width w1 of 8.3 meters. The blade foot 2 is a wide-upper-narrow-lower structure, and the bottom 2 of the blade foot is a flat structure. The height of the blade foot 2 is 3.7 meters, and the thickness of the blade foot 2 is 1.8 meters. The thickness of the connection between the blade foot 2 and the caisson body 1 is greater than the thickness of the well wall of the caisson body 1. The wall thickness of the caisson body 1 will also be designed differently according to the actual construction conditions, and the wall thickness of the caisson body 1 in different sections will be different. The thickness d2 of the well wall of the first well body 11 and the second well body 12 is 1.2 meters; the thickness d1 of the well wall of the third well body 13, the fourth well body 14, and the fifth well body 15 is 0.9 meters.

[0116] As in the previous embodiment, during the actual construction process, the body of the caisson body 1 is also manufactured in sections. The caisson body of the caisson structure is manufactured according to the design requirements, and the first body 11, the second body 12, the third body 13, the fourth body 14, the fifth body 15 and the sixth body 16 are manufactured in sections; then the caisson structure 1 is sunk in sections; after the first body 11 is manufactured, the first body 11 is sunk first and then the second body 12 is manufactured; after the second body 12 is sunk, the third body 13 is manufactured; after the third body 13 is sunk, the fourth body 14 is manufactured; after the fourth body 14 is sunk, the fifth body 15 is manufactured and sunk; after the fifth body 15 is sunk, the sixth body 16 is manufactured and sunk.

[0117] The structures of the sand cushion layer and the plain concrete cushion layer laid on the sand cushion layer in this embodiment are the same as those in the previous embodiment, and will not be described again here.

[0118] like Figure 8FIG2 is a schematic diagram of another embodiment (Example 3) of the present invention. In this embodiment, the height of the caisson body 1 is 36.2281 meters. As can be seen in the figure, the structure of this embodiment is basically the same as the previous embodiment, except that the caisson body 1 in this embodiment has a different number of sections. The caisson body 1 in this embodiment includes eight sections, which can be suitable for deeper caisson operations. In this embodiment, the caisson body 1 includes a first well body 11, a second well body 12, a third well body 13, a fourth well body 14, a fifth well body 15, a sixth well body 16, a seventh well body 17, and an eighth well body 18. A waterstop steel plate 3 with a size of 60 mm × 60 mm × 3 mm is installed at the junctions of the first well body 11 and the second well body 12, the second well body 12 and the third well body 13, the third well body 13 and the fourth well body 14, the fourth well body 14 and the fifth well body 15, the fifth well body 15 and the sixth well body 16, the sixth well body 16 and the seventh well body 17, and the seventh well body 17 and the eighth well body 18. To prevent water seepage from the well wall of the caisson body 1, a 10 mm thick waterproof mortar cake is installed on the periphery of the waterstop steel plate 3 and covered with waterproof glue.

[0119] The caisson body 1 is still a rectangular parallelepiped structure with a height of 36.2281 meters, a length of 9.8 meters, and a width w1 of 9.3 meters. The blade foot 2 is a wide-upper-narrow-lower structure, and the bottom 2 of the blade foot is a flat structure. The height of the blade foot 2 is 5.1 meters, and the thickness of the blade foot 2 is 2.0 meters. The thickness of the connection between the blade foot 2 and the caisson body 1 is greater than the thickness of the well wall of the caisson body 1. The wall thickness of the caisson body 1 will also be designed differently according to the actual construction conditions, and the wall thickness of the caisson body 1 in different sections will be different. The thickness d3 of the well wall of the first well body 11 and the second well body 12 is 1.4 meters; the thickness d1 of the well wall of the third well body 13, the fourth well body 14, and the fifth well body 15 is 1.1 meters; the thickness of the sixth well body 16 and the seventh well body 17 is 0.9 meters.

[0120] As in the previous embodiment, during the actual construction process, the body of the caisson body 1 is also manufactured in sections. The caisson body of the caisson structure is manufactured according to the design requirements, and the first body 11, the second body 12, the third body 13, the fourth body 14, the fifth body 15, the sixth body 16, the seventh body 17 and the eighth body 18 are manufactured in sections; then the caisson structure 1 is sunk in sections; after the first body 11 is manufactured, the first body 11 is sunk first and then the second body 12 is manufactured; after the second body 12 is sunk, the third body 13 is manufactured; after the third body 13 is sunk, the fourth body 14 is manufactured; after the fourth body 14 is sunk, the fifth body 15 is manufactured and sunk; after the fifth body 15 is sunk, the sixth body 16 is manufactured and sunk; after the sixth body 16 is sunk, the seventh body 17 is manufactured and sunk; after the seventh body 17 is sunk, the eighth body 18 is manufactured and sunk.

[0121] In this embodiment, the structures of the top plate structure 4, the sand cushion layer and the plain concrete cushion layer laid on the sand cushion layer are the same as those in the previous embodiment and will not be described again here.

[0122] The present invention also provides a caisson construction structure, comprising the caisson structure provided by the present invention, and a caisson template detachably arranged on the caisson structure.

[0123] As shown in Table 4 below, the caisson structure provided by the present invention can be applied to ultra-deep caisson construction operations and various complex terrains.

[0124]

[0125] It is suitable for construction in various complex terrains.

[0126] Table 4 Caisson parameters

[0127] The caisson construction structure provided by the present invention includes a caisson template that is detachably mounted on the caisson structure to facilitate construction of the caisson structure provided by the present invention, ensuring construction safety and structural stability. The caisson structure provided by the present invention adopts a segmented structure, which is simple and easy to construct. Workers can observe and correct deviations in real time during construction, which facilitates effective control of the angle and depth of the caisson construction. The caisson structure is suitable for ultra-deep caisson construction and can be applied to various complex terrains.

[0128] In the above embodiment, after the pipe jacking construction is completed, the well wall and top plate are poured.

[0129] The caisson structure for composite strata provided by the present invention can be used for composite terrain operations, is suitable for ultra-deep caisson operations, and is suitable for various construction occasions.

[0130] The construction method of the caisson structure provided by the present invention is simple to operate, adopts a segmented sinking method to ensure smooth construction, and can correct deviations in real time during the construction process to ensure construction quality.

[0131] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0132] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0133] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A construction method for a caisson structure for composite terrain, comprising the following steps: 1) Measure and locate the caisson position according to the design drawings; 2) Lay out a caisson pit sample on the ground at the location of the caisson position, and dig out the caisson pit; 3) Make the blade foot of the caisson structure according to the design requirements; 4) Make the caisson body of the caisson structure in sections according to the design requirements, and then sink the caisson body in sections, wherein the caisson structure includes the caisson body and the blade foot arranged at the bottom of the caisson body, and the caisson body includes the caisson wall and a plurality of well bodies made in sections, and the making and sinking of the plurality of well bodies are carried out alternately; 5) Sink to the design elevation by its own weight. When the caisson is about to sink into place, when the self-sinking rate is less than the first speed, seal the bottom of the caisson; 6) After the caisson bottom sealing concrete construction is completed, the bottom plate construction is carried out; and 7) Quality inspection of the caisson project is carried out.

2. The construction method of a caisson structure for composite terrain according to claim 1, characterized in that: The position of the foundation pit is determined according to the coordinates in the design drawings. The piles and center piles are controlled according to the axis of the caisson, and the caisson foundation pit sample is placed on the ground. The plane size of the foundation pit bottom is equal to the width of the blade foot sand cushion layer; the excavation depth of the foundation pit is about the first distance, and the slope is laid according to the first ratio. The distance from the edge of the foundation pit to the caisson wall is about the second distance; after the foundation pit is excavated, fixed guardrails are set on all sides for protection.

3. The construction method of a caisson structure for composite terrain according to claim 1, characterized in that: After the excavation of the foundation pit is completed, ensure that there is no water accumulation at the bottom of the pit, lay a sand cushion layer, and lay a plain concrete cushion layer on the sand cushion layer; the concrete cushion layer is 1.5m thick and 5.5m wide, and is laid in layers, with each layer not exceeding 30cm in thickness, and water is added layer by layer to ensure the optimal moisture content.

4. The construction method of a caisson structure for composite terrain according to claim 1, wherein: In order to prevent water seepage in the caisson wall, the bolt holes of the tension screws are waterproofed after the formwork is removed; small wooden blocks are chiseled out from the inner and outer ends of the bolt holes of the tension screws, and the recessed parts are smoothed with 1:2 cement mortar, and the outer layer is made into a 10mm thick waterproof mortar cake, and then 2 layers of waterproof glue are applied to cover it.

5. The construction method of a caisson structure for composite terrain according to claim 1, characterized in that: Before the caisson sinks, a first number of vertical lines are symmetrically popped out on the inner and outer walls of the caisson to measure the inclination of the caisson when it sinks; and a plumb bob is hung at the top of the first number of vertical lines on the inner wall of the caisson, and a mark plate is set at the blade foot. During the caisson sinking construction, the caisson deflection is observed at any time so that it can be corrected in time; and on the outer wall of the caisson, a horizontal measuring ruler is drawn along the first number of vertical lines to measure the sinking amount and sinking deviation of the caisson.

6. The construction method of a caisson structure for composite terrain according to claim 1, wherein: When the caisson sinks, the cushion concrete is first broken, and then a long-arm excavator is used to dig the soil. When digging, the surrounding areas are dug first and then the middle. The excavation is carried out in layers, and the thickness of each layer is 40 cm. The soil surface in the middle part should always be higher than the soil surface around it, in the shape of an inverted pot, so that it cuts the soil and sinks. The sinking is controlled at about 20 cm each time.

7. The construction method of a caisson structure for composite terrain according to claim 1, characterized in that: During the initial sinking stage of the caisson, the position, elevation or settlement value, and verticality of the caisson should be measured in a timely manner, at least twice every 8 hours and once every 3m of sinking, and records should be kept. Continuous observation should be carried out and corrections should be made in a timely manner when necessary.

8. The construction method of a caisson structure for composite terrain according to claim 1, characterized in that: During the final sinking stage of the caisson, measurements should be taken at least once every hour. If the caisson still cannot stop after excavation has stopped, measures should be taken immediately to control the sinking of the caisson.

9. The construction method of a caisson structure for composite terrain according to claim 1, characterized in that: Furthermore, when the caisson sinks close to the design elevation, observation should be strengthened. When the cumulative settlement of the caisson within 8 hours is no more than the third distance, the bottom should be sealed.

10. The construction method of a caisson structure for composite terrain according to claim 1, characterized in that: When the caisson sinks to the designed elevation, a fixed guardrail is set 1m outside the caisson.

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