Deep cementing gravel bed double-wall steel cofferdam sinking construction method

Abstract

The invention provides a sinking construction method for a double-wall steel cofferdam of a deep and thick cementitious gravel layer. The sinking construction method comprises the following steps that S1, construction positioning is conducted, specifically, the installation position of the cofferdam is subjected to positioning marking; s2, a platform is built, specifically, the construction platform is built according to the position of the positioning mark; s3, a walking type three-shaft mixing pile machine is installed, specifically, the walking type three-shaft mixing pile machine is installed on the platform; s4, bottom layer pretreatment is conducted, specifically, a three-shaft stirring pile machine is adopted for drilling construction to conduct pre-stirring loosening on the stratum within the cofferdam projection range; s5, the stratum is vibrated and loosened, specifically, a hydraulic vibration hammer is used for clamping the steel sheet piles or the steel pipe piles to conduct zoning and layered vibration loosening on the hard stratum in the cofferdam; s6, a soil taking platform is built, specifically, a telescopic boom excavator is arranged for soil taking operation; and S7, cofferdam assembling and sinking are conducted, specifically, the cofferdam stably sinks to the designed elevation by adopting the mode of combining sectional assembling, water injection sinking and mud suction and soil taking, and the problems that in the cementing high-strength dense gravel stratum, excavation construction is difficult, and cofferdam sinking is difficult are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the sinking construction technology field of double-wall steel cofferdam, especially to the sinking construction method of double-wall steel cofferdam in deep and thick cemented gravel layer. BACKGROUND

[0002] In deep water bridge foundation construction, double-wall steel cofferdam is a common construction structure. The traditional sinking method of double-wall steel cofferdam includes: first, the temporary hanger is lowered into the water and bedded, then the gravel layer is loosened by using the grab cone to grab the gravel in the cofferdam and auxiliary water jet, and the cofferdam is sunk to the position by using the counter-pressure measure of the jack; second, the steel casing is used to build the walking construction platform of the excavator, the excavator is located in the cofferdam to take the soil, and the cofferdam is sunk; third, after the construction platform is removed, the cofferdam is assembled and sunk in sections on the leveled site. The three schemes have certain adaptability to the soil taking of the fine round gravel layer in the cofferdam, but they have great limitations due to the operation space for the engineering with large cofferdam, small gap between the casing and the cofferdam, low soil taking efficiency in the fine round gravel layer with high cementation strength, long construction period, and large investment, which is not conducive to the construction cost control. SUMMARY

[0003] In view of the deficiencies in the prior art, the present application provides a sinking construction method of double-wall steel cofferdam in deep and thick cemented gravel layer, which solves the problems of great difficulty in excavation construction in the dense gravel layer with high cementation strength and difficult sinking of the cofferdam in the prior art.

[0004] According to the embodiment of the present application, the sinking construction method of double-wall steel cofferdam in deep and thick cemented gravel layer includes the following steps: S1, construction positioning: the installation position of the cofferdam is positioned and marked; S2, platform building: the construction platform is built according to the position of the positioning mark; S3, installation of walking three-axis mixing pile machine: the walking three-axis mixing pile machine is installed on the platform; S4, bottom layer pretreatment: the stratum in the projection range of the cofferdam is pretreated by hole drilling construction of the three-axis mixing pile machine, the steel casing is followed to protect in the process of hole drilling, and the hole drilling speed and quality are ensured; S5, vibration and loosening of the stratum: the hard stratum in the cofferdam is partitioned and layered vibration and loosening by using the hydraulic vibration hammer clamping steel sheet pile or steel pipe pile; S6, building of soil taking platform: the Bailey beam platform is built on the top of the steel casing, and the telescopic arm excavator is arranged to take soil; S7, cofferdam assembly and sinking: the cofferdam is stably sunk to the design elevation by using the combination of sectional assembly, water injection sinking, and mud suction soil taking.

[0005] Compared with existing technologies, this invention has the following advantages: This construction method, following the steps of: stratum pretreatment → vibration loosening during lowering → foundation clearing and leveling, enables soil extraction from cemented high-strength dense gravel strata and successfully achieves cofferdam sinking. The method combines platform treatment and cofferdam treatment into two working spaces using different construction machinery combinations, ensuring rapid and efficient soil extraction within the cofferdam. This overcomes the difficulty of soil extraction by mechanical equipment due to the hard strata of the casing and cofferdam, solves the problem of difficult excavation and sinking in cemented high-strength dense gravel strata, and avoids the problem of torsional deformation of the cofferdam caused by unbalanced bending moments during hard strata excavation.

[0006] Furthermore, in step S4, a skip-hole operation method is adopted for construction. That is, after the Nth hole is completed, the drilling is moved forward to the N+2th hole, and after the N+1th hole is completed, the drilling is moved back to the N+1th hole.

[0007] Furthermore, in step S5, the hydraulic vibratory hammer includes APE130 and APE200 models, which are used for vibratory loosening of the strata around and in the middle of the cofferdam cutting edge, respectively.

[0008] Furthermore, in step S6, the soil extraction platform can be vertically adjusted by removing the steel casing to adapt to the soil extraction needs at different sinking stages.

[0009] Furthermore, in step S7, the cofferdam is assembled in sections. When assembling the first section, the upstream and downstream short-side cofferdam unit blocks are installed first, followed by the long-side cofferdam unit blocks on the large and small mileage sides. The bottom compartment is installed last. After the first section of the cofferdam sinks to a self-floating state, water, sand, or concrete are poured into the cofferdam compartment to assist in sinking. After sinking to a certain height, the top of the previous section of the cofferdam is then assembled. The subsequent cofferdam assembly sequence is the same as that of the first section.

[0010] Furthermore, the bottom section of the cofferdam is equipped with a limit guide device to prevent large horizontal displacement caused by wind, waves, and water flow during the lowering process.

[0011] Furthermore, in step S7, after the entire cofferdam has landed, the cofferdam is lowered using an air suction dredger. First, the middle compartment is suctioned, and then the compartments on the upstream and downstream sides are suctioned. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the planar installation structure of the guide device of the present invention.

[0013] In the above attached diagram: 1. Cofferdam; 2. Base; 3. Connecting bolt; 4. Mounting seat; 5. Guide wheel; 6. Auxiliary support steel column. Detailed Implementation

[0014] The technical solutions of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0015] This invention proposes a construction method for sinking a double-walled steel cofferdam in a deep cemented gravel layer, comprising the following steps: S1, Construction Positioning: Marking the installation location of the cofferdam; S2, Platform Construction: Constructing a construction platform according to the marked location; S3, Installing a Walking Triaxial Mixing Pile Machine: Installing the walking triaxial mixing pile machine on the platform; S4, Subsurface Pretreatment: Using a triaxial mixing pile machine to drill holes and loosen the strata within the cofferdam's projection area, with steel casing following and protecting the strata during drilling to ensure drilling speed and quality; S5, Vibration Breaking of Strata: Using a hydraulic vibratory hammer to clamp steel sheet piles or steel pipe piles to vibrate and loosen the hard strata inside the cofferdam in sections and layers; S6, Construction of a Soil Extraction Platform: Constructing a Bailey beam platform on top of the steel casing and deploying a telescopic boom excavator for soil extraction; S7, Cofferdam Assembly and Sinking: Using a combination of segmented assembly, water injection sinking, and mud suction to achieve a stable sinking of the cofferdam to the design elevation.

[0016] This construction method, following the strategy of: stratum pretreatment → vibration loosening during lowering → foundation clearing and leveling, successfully achieved soil extraction from cemented, high-strength, dense gravel strata and facilitated the sinking of the cofferdam. The method combined platform treatment and cofferdam internal treatment with different construction machinery to ensure rapid and efficient soil extraction within the cofferdam. It overcame the difficulty of using mechanical equipment to extract soil from the hard strata of the casing and cofferdam, and solved the problem that conventional cutter suction hoppers and grab buckets could not effectively extract soil from deep, hard strata when the cofferdam entered cemented, high-strength, dense gravel strata. Simultaneously, it avoided the torsional deformation of the cofferdam caused by unbalanced bending moments resulting from excavation of hard strata.

[0017] In step S4, a skip-hole drilling method is adopted. After the Nth borehole is completed, the drilling proceeds to the (N+2)th borehole, and then back to the (N+1)th borehole. This means odd-numbered piles are drilled first, followed by even-numbered piles, with a 30cm overlap between odd and even piles, ensuring complete loosening of the soil at the cofferdam location. Compared to traditional cutter suction dredgers, this method allows for pre-loosening of the soil, saving construction time. After the cofferdam is lowered into the bed, the cutter suction head is used for rapid foundation clearing, ensuring the cofferdam's smooth and continuous sinking.

[0018] In step S5, the hydraulic vibratory hammer includes APE130 and APE200 models, which are used for vibratory loosening of the strata around the cutting edge of the cofferdam and in the middle, respectively.

[0019] In step S6, the soil extraction platform can be vertically adjusted by removing the steel casing to adapt to the soil extraction needs at different sinking stages.

[0020] In step S7, the cofferdam is assembled in sections. When assembling the first section, the upstream and downstream short-side cofferdam unit blocks are installed first, followed by the long-side cofferdam unit blocks on the large and small mileage sides. The bottom compartment is installed last. After the first section of the cofferdam sinks to a self-floating state, water, sand, or concrete are poured into the cofferdam compartment to assist in sinking. After sinking to a certain height, the top of the previous section of the cofferdam is then assembled. The subsequent cofferdam assembly sequence is the same as that of the first section.

[0021] Furthermore, during the final assembly of the cofferdam's closure blocks, deviations may occur in the closure section due to assembly and manufacturing errors. For larger deviations, after the cofferdam is lowered, reinforcing plates are welded to the inner and outer wall panels and ring ribs at the vertical joints to seal the joints. For smaller deviations, the spacing between the closure sections is measured. After measurement, the cofferdam joints are adjusted by cutting off some wall panels and ring ribs to ensure the cofferdam can be lowered. After lowering, vertical welds are then welded.

[0022] When the steel cofferdam is lowered, a limiting guide device is installed at the bottom section of the cofferdam. The bottom section of the cofferdam has two layers of guide devices, with eight guide devices in each layer. The purpose of the guide device is to prevent large horizontal displacement caused by wind, waves and water flow during the lowering process.

[0023] like Figure 1 As shown, each guiding device includes a base 2, a mounting seat 4, and a connecting screw 3. The base 2 is inclinedly set on the inner wall of the cofferdam 1, with the angle between the base and the inner wall of the cofferdam 1 being 30-45°. The connecting screw 3 is threaded to the base 2 in the axial direction of its extension. The mounting seat 4 is fixed to the end of the connecting screw 3, and a guide wheel 5 is provided on the mounting seat 4. Furthermore, to prevent deformation and damage to the inner wall of the cofferdam at the guiding point due to large impact forces, 12mm steel plate stiffening ribs are used to reinforce the wall plate inside the cofferdam at the guiding device. Furthermore, the verticality of the steel casing is measured before the cofferdam sinks. During the sinking process, the length of the connecting screw 3 extending from the base 2 is adjusted according to the inclination of the casing to ensure the distance between the guide wheel 5 and the steel casing. This prevents excessive displacement of the steel casing due to pile foundation construction, which would hinder the sinking of the cofferdam and ensure the smooth sinking of the cofferdam. An auxiliary support steel column 6 is also provided between the base 2 and the inner wall of the cofferdam 1.

[0024] In step S7, after the cofferdam has fully landed, the cofferdam is lowered using an air suction dredger. First, the middle compartment is suctioned, and then the compartments on the upstream and downstream sides are suctioned.

[0025] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A construction method for sinking a double-walled steel cofferdam in a deep cemented gravel layer, characterized in that... Includes the following steps: S1. Construction Positioning: Mark the installation location of the cofferdam; S2. Platform Construction: Construct the construction platform according to the location marked on the positioning markers; S3. Install the walking triaxial mixing pile machine: Install the walking triaxial mixing pile machine on the platform; S4. Pre-treatment of the bottom layer: The strata within the projection range of the cofferdam are pre-mixed and loosened by drilling with a three-axis mixing pile machine. During the drilling process, steel casing is followed for protection to ensure the drilling speed and drilling quality. S5. Vibration breaking of loose strata: Using a hydraulic vibratory hammer to clamp steel sheet piles or steel pipe piles to break up hard strata in sections and layers. S6. Construct a soil extraction platform: Construct a Bailey beam platform on top of the steel casing and deploy a telescopic boom excavator for soil extraction operations. S7. Cofferdam assembly and sinking: The cofferdam is smoothly sunk to the design elevation by adopting a combination of segmented assembly, water injection sinking, and mud removal.

2. The construction method for sinking a double-walled steel cofferdam in a deep cemented gravel layer as described in claim 1, characterized in that, In step S4, the skip-hole operation method is adopted. That is, after the Nth hole is completed, the drilling is moved to the N+2th hole, and after the N+1th hole is completed, the drilling is moved back.

3. The construction method for sinking a double-walled steel cofferdam in a deep cemented gravel layer as described in claim 1, characterized in that, In step S5, the hydraulic vibratory hammer includes APE130 and APE200 models, which are used for vibratory loosening of the strata around the cutting edge of the cofferdam and in the middle, respectively.

4. The construction method for sinking a double-walled steel cofferdam in a deep cemented gravel layer as described in claim 1, characterized in that, In step S6, the soil extraction platform can be vertically adjusted by removing the steel casing to adapt to the soil extraction needs at different sinking stages.

5. The construction method for sinking a double-walled steel cofferdam in a deep cemented gravel layer as described in claim 1, characterized in that, In step S7, the cofferdam is assembled in sections. When assembling the first section, the upstream and downstream short-side cofferdam unit blocks are installed first, followed by the long-side cofferdam unit blocks on the large and small mileage sides. The bottom compartment is installed last. After the first section of the cofferdam sinks to a self-floating state, water, sand, or concrete are poured into the cofferdam compartment to assist in sinking. After sinking to a certain height, the top of the previous section of the cofferdam is then assembled. The subsequent cofferdam assembly sequence is the same as that of the first section.

6. The construction method for sinking a double-walled steel cofferdam in a deep cemented gravel layer as described in claim 1, characterized in that, The bottom section of the cofferdam is equipped with a limiting guide device to prevent large horizontal displacement caused by wind, waves and water flow during the lowering of the cofferdam.

7. The construction method for sinking a double-walled steel cofferdam in a deep cemented gravel layer as described in claim 1, characterized in that, In step S7, after the cofferdam has fully landed, the cofferdam is lowered using an air suction dredger. First, the middle compartment is suctioned, and then the compartments on the upstream and downstream sides are suctioned.

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