Construction method for improved lock catch steel pipe pile cofferdam formed by covering stratum with lean sand large-particle-size pebbles

Abstract

The invention discloses a construction method of an improved lock catch steel pipe pile cofferdam with a poor sand large-particle-size pebble covering stratum. The construction method comprises the following steps that an upper structure of a drilling platform is dismantled; measuring and setting out a pile position of the lock catch steel pipe pile cofferdam, sinking and positioning the steel pipe pile cofferdam by adopting a crawler crane and a vibratory hammer, and preliminarily entering a pebble bed; driving a pipe pile to a set elevation by utilizing a hydraulic impact hammer; for a steel pipe pile which is difficult in drilling footage or provided with boulders at the bottom, an XR280 rotary drilling guide hole is adopted; the steel pipe piles are smoothly closed; cofferdam water pumping; a small excavator is adopted for internal excavation, slag is discharged in a long arm excavation up-and-down transfer mode, a local rock stratum is firstly crushed and then excavated through a crushing hammer, water is pumped to the position 70 cm below an inner support of the road, and after the inner support is installed, water pumping continues to be conducted; and bottom sealing, pile head breaking and pile cap construction are carried out. By means of the construction method, the problems that the double-wall steel cofferdam is difficult to put down and level, and the site requirement is high can be effectively solved; the defects that a long steel sheet pile cofferdam is low in rigidity, prone to deformation and poor in water stopping effect are overcome. Through the cofferdam construction technology of the hydraulic impact hammer and the guide hole in the pipe of the rotary drilling rig, the hydraulic impact hammer is used for driving the steel pipe pile, the guide hole in the pipe of the rotary drilling rig and the pile-forming construction of a single pipe pile only need 10 minutes, and the construction period is greatly shortened.

Description

Technical field:

[0001] The present invention relates to the technical field of bridge abutment cofferdam construction, and in particular to an improved locking steel pipe pile cofferdam construction method under geological conditions of sand-poor and large-grained pebble formation covering in a high-velocity environment. Background technology:

[0002] With the emerging development of my country's bridge industry, large-span bridges across canyons, reservoirs, lakes and shallows have been widely used. In the process of water-crossing bridge pier cap construction, in order to ensure the quality and safety of construction, it is inevitable to involve the construction of cofferdam caps; currently, steel box cofferdams or steel hanging box cofferdams are often used for deep-water cofferdams, and steel box cofferdams, steel sheet pile cofferdams and steel pipe pile cofferdams are mostly used for cofferdams with a water depth of about 3m to 8m. Steel box cofferdams have the characteristics of good water-stopping effect and high safety, but they have high requirements for the site, and piles must be added and the platform must be modified. The rock layer must be flat, the inclined rock layer must be leveled in advance, the cost of base treatment is high, and underwater blind excavation has many uncertain factors. It is difficult to locate the cofferdam in a flowing water environment, the lowering technology of the cofferdam is high, and the construction period is long, which affects the construction period; the Larsen steel sheet pile cofferdam has the characteristics of low rigidity, easy deformation, poor water-stopping effect, and good construction safety, but in a sand and gravel layer environment, holes must be drilled first, then replaced and driven in, and a large number of steel casings are invested, underwater holes are drilled, and positioning is difficult. The steel casings must be vibrated and sunk first, and then removed, and a large number of holes are drilled; the drilling and replacement of holes causes severe environmental pollution, which is not conducive to protecting water sources and has a long construction period.

[0003] Therefore, in view of the geological conditions of poor sand and large-grained pebble strata covering in a high-velocity environment, it is very important to propose an economical, applicable and environmentally friendly method for the construction of a cap cofferdam under the premise of limited construction period and ensuring the safety of the cofferdam structure. Summary of the invention:

[0004] Disadvantages of traditional technology: Traditional cofferdams mainly include steel pipe pile cofferdams, steel hanging box cofferdams, steel sheet pile cofferdams and steel box cofferdams. For cofferdams with a water depth of about 3m to 8m, steel box cofferdams, steel sheet pile cofferdams and steel pipe pile cofferdams are mostly used. Steel box cofferdams have the characteristics of good water stopping effect and high safety, but they have high requirements for the site, and piles must be added and the platform must be modified. The rock layer must be flat, and the inclined rock layer must be leveled in advance. The cost of base treatment is high, and there are many uncertain factors such as underwater blind excavation. It is difficult to locate the cofferdam in the flowing water environment, the technical requirements for lowering the cofferdam are high, and the construction period is long, which affects the construction period; Larsen steel sheet pile cofferdam has the characteristics of low rigidity, easy deformation, poor water stopping effect, and good construction safety, but the sand and egg layer environment requires first drilling, then replacement, and then driving. The number of steel casings is large, and underwater drilling is difficult to locate; the steel casing is first vibrated and then removed, the number of holes is large, and the environmental pollution of drilling and replacement is large, which is not conducive to protecting water sources and has a long construction period. Although the previous locking steel pipe pile cofferdams have the characteristics of high rigidity of steel box cofferdams and low site requirements of steel sheet pile cofferdams, the construction method is usually to first drill holes and then construct the pipe pile cofferdam, which leads to greater water pollution after the drilling holes are replaced. Under conventional locking conditions, the water-stopping performance of the cofferdam in the later stage is poor.

[0005] The purpose of the present invention is to propose a method for cofferdam construction with improved locking steel pipe piles in sand-poor and large-size pebble-covered strata in view of the above-mentioned deficiencies in cofferdam construction under specific conditions. This method combines the stress characteristics of conventional locking pipe piles, and achieves a good water-stopping effect by improving the locking buckle of the pipe piles. The pipe piles are driven in with a hydraulic impact hammer, and during the construction process, the pipe piles are first driven in and then partially bored. The pipe piles also serve as steel casings, reducing the investment in steel casings, especially in sandy and pebble layers and inclined rock formations. The construction is barrier-free and investment-saving, and it is applicable to both still water and flowing water environments. The construction period is short while ensuring the quality and safety of the structure, and the goals of saving construction time and protecting the environment are achieved.

[0006] Principle of the present invention:

[0007] A method for constructing an improved locking steel pipe pile cofferdam in a sand-poor, large-size pebble-covered stratum, characterized in that: 1. after the pile foundation construction is completed, the upper platform of the bored pile is dismantled, and the net width around the platform after the platform is dismantled is preferably 1m to 1.5m greater than the diameter of the cofferdam which is twice the width of the pedestal, and the pile position of the locking steel pipe pile cofferdam is measured and laid out, and the improved steel pipe pile cofferdam is sunk and positioned using a crawler crane and a vibrating hammer. 2. the hole end and the locking buckle of the conventional locking steel pipe pile are improved, and steel plates of the same thickness are additionally welded within a length range of 50cm at the top and bottom of the locking pipe pile 2, wherein the bottom steel plate is thickened and polished to form a 45-degree groove; the commonly used "CO" and "CT" locking forms are changed at the connection part between the locking buckles, and the Larsen steel plate form is referred to, and the inner inclination angle of the locking buckle is increased to form an improved locking buckle. 3. Use crawler crane and vibratory hammer to sink and position the improved steel pipe pile cofferdam, and initially enter the sand-poor large-grained pebble layer; the main construction purpose of crawler crane and vibratory hammer is to initially sink the butt-jointed pipe piles between the lock buckles of the lock buckle steel pipe piles, which plays a guiding and positioning role. Use hydraulic impact hammer to drive the pipe pile to the set elevation. The impact stroke height of the hydraulic impact hammer gradually changes from 1.2m to 0.6m. The verticality is fine-tuned by manual traction rope during the impact process. 4. For the sand-poor large-grained pebble formation with a diameter greater than 200mm or the pipe pile encounters a rock layer with a uniaxial compressive strength greater than 15MPa after entering the muddy siltstone. In the case of difficulty in driving, the lock buckle pipe pile is used as a casing, and the XR280 rotary drilling rig is used to guide the hole in the pipe. 5. When there are 1 to 2 locking piles left before the pipe piles are closed, the distance between the closure hole and the bottom of the hole should be measured according to the on-site injection of the pipe piles, and the locking position and inclination of the closure hole should be adjusted according to the spacing. Finally, the last 2 to 3 locking piles should be impacted and sunk by the impact hammer in rotation to close the cofferdam. 6. After the cofferdam is closed, water should be pumped out of the cofferdam. The first water pumping volume of the cofferdam should be 1.5 to 2.0 times greater than the water seepage in the cofferdam. For excavation inside the cofferdam, small excavators are used for internal excavation and long-arm excavation for up and down transfer to remove slag. Local rock formations are first crushed and then excavated by breaker hammers. 7. Installation of internal supports. Pump water from the cofferdam to the designed support position and then start to install the internal supports after 70cm. When installing the internal supports of the cofferdam, first construct the cofferdam corbels, place the cofferdam purlin profiles on the corbels for welding, construct the cofferdam purlin horizontal internal supports, install the horizontal support flat joints, install the small triangular diagonal braces, and construct the large triangular diagonal braces. To prevent the purlin support from being too deflected, set vertical supports at the steel connection nodes, continue pumping water and excavation until the excavation reaches the designed height. Finally, carry out the cofferdam bottom sealing concrete, cofferdam internal leveling, pile head breaking, and foundation construction.

[0008] The advantages of the patent of this invention are: 1. A rapid construction process for cofferdams in sand-poor and large-grained pebble formations is proposed. The new type of locking steel pipe pile cofferdam form effectively solves the difficulties in lowering and leveling the double-walled steel cofferdam and the high site requirements. At the same time, it also makes up for the shortcomings of long steel sheet pile cofferdams, such as low rigidity, easy deformation, and poor water-stopping effect. 2. A hydraulic impact hammer plus rotary drilling rig cofferdam construction technology is proposed. The hydraulic impact hammer drives the steel pipe piles, and the rotary drilling rig guides the holes. The construction of a single pipe pile only takes 10 minutes, which greatly shortens the construction period. 3. The traditional PU400×170 Larsen steel plate is improved, the inclination angle of the locking mouth is increased, and the risk of poor bite of the conventional PU400×170 locking mouth is reduced. Referring to the locking form of the Larsen steel plate, the commonly used "CO" and "CT" locking mouths are further designed to achieve small deformation and good water-stopping effect. 4Through the impact operation of the locked steel pipe piles, the surrounding strata are closely attached to the pipe piles, achieving a good water-stopping effect on the cofferdam foundation pit. The pipe piles also serve as steel casings, avoiding large excavation of the riverbed and saving investment. 5Compared with the double-wall steel cofferdam excavation and the steel sheet pile cofferdam pipe external lead hole, this method maximizes the environmental pollution-free and is conducive to protecting water sources. Description of the drawings:

[0009] The accompanying drawings are used as a part of the present invention for further understanding of the present invention. The implementation examples in the present invention are only used to illustrate the present invention and do not constitute an improper limitation of the present invention.

[0010] Figure 1 This is a construction flow chart of an improved locking steel pipe pile cofferdam construction method for a sand-poor, large-size pebble-covered stratum; the chart mainly focuses on the process of the locking steel pipe pile cofferdam from construction preparation to completion of the cofferdam construction to the foundation construction.

[0011] Figure 2 This is a general drawing of the improved lock connection in the construction method of an improved lock steel pipe pile cofferdam in a sand-poor and large-grained pebble-covered stratum.

[0012] Figure 3 This is a plan view of the cofferdam in an improved locking steel pipe pile cofferdam construction method for sand-poor and large-size pebble-covered strata.

[0013] Figure 4 This is a front elevation layout diagram of the cofferdam in an improved locking steel pipe pile cofferdam construction method for sand-poor and large-size pebble-covered strata.

[0014] Figure 5 This is a side elevation layout diagram of the cofferdam in an improved locking steel pipe pile cofferdam construction method for sand-poor and large-size pebble-covered strata.

[0015] In the figure: 1-improved lock, 2-locking pipe pile, 3-purlin corbel, 4-purlin, 5-purlin horizontal inner support, 6-horizontal support flat link, 7-small triangular diagonal brace; 8-large triangular diagonal brace, 9-vertical support, 10-sand-poor large-grained pebble stratum, 11-mudstone siltstone, 12-bottom sealing concrete. Specific implementation method:

[0016] In order to make the purpose, construction method and advantages of the examples of the present invention clearer, the following is combined with the drawings of the examples of the present invention. The implementation methods described in the examples of the present invention do not represent all implementation methods consistent with one or more embodiments of the present specification. They are only method examples consistent with some aspects of one or more embodiments of the present specification as detailed in the attached claims.

[0017] A method for constructing an improved locking steel pipe pile cofferdam in a sand-poor and large-size pebble-covered stratum comprises the following steps:

[0018] After the pile foundation construction is completed, the upper platform of the bored piles will be dismantled. After the platform is dismantled, the net width around it should be 1m to 1.5m greater than the diameter of the cofferdam, which is twice the width of the foundation. The position of the locking steel pipe pile cofferdam is measured and marked out, and the improved steel pipe pile cofferdam is sunk and positioned using a crawler crane and a vibrating hammer.

[0019] The hole end and lock of the conventional lock steel pipe pile are improved. Steel plates with the same pipe thickness are additionally welded within a length of 50 cm at the top and bottom of the lock pipe pile 2. The bottom steel plate is thickened and polished with a 45-degree groove. The commonly used "CO" and "CT" lock forms are changed at the connection between the locks, referring to the Larsen steel plate form, and the inner inclination angle of the lock is increased to form an improved lock 1.

[0020] The crawler crane and vibratory hammer were used to sink the improved steel pipe pile cofferdam and position it, and initially enter the sand-poor large-size pebble layer 10; the main construction purpose of the crawler crane and vibratory hammer was to initially sink the butt-jointed pipe piles between the lock buckles of the lock buckle steel pipe piles, which played a guiding and positioning role. The hydraulic impact hammer was used to drive the pipe piles to the set elevation. The impact stroke height of the hydraulic impact hammer gradually changed from 1.2m to 0.6m. During the impact process, the verticality was fine-tuned by manual traction ropes.

[0021] For sand-poor and large-grained pebble formations with a diameter greater than 200mm, or for rock formations with a uniaxial compressive strength greater than 15MPa encountered after the pipe piles enter the muddy siltstone 11, in the case of difficulty in injection, the locking pipe piles are used as casings, and the XR280 rotary drilling rig is used to drill holes inside the pipe.

[0022] When there are 1 to 2 locking pipe piles left before the pipe piles are closed, the distance between the closing hole mouth and the hole bottom should be measured according to the on-site injection of the pipe piles, and the locking position and inclination of the pipe piles at the closing hole should be adjusted according to the distance. Finally, the last 2 to 3 locking pipe piles should be impacted and sunk in rotation using an impact hammer to close the cofferdam.

[0023] After the cofferdam is closed, water is pumped out of the cofferdam. The first pumping volume of the cofferdam should be 1.5 to 2.0 times greater than the water seepage volume in the cofferdam. For excavation inside the cofferdam, small excavators are used for internal excavation and long-arm excavation for up and down transfer of slag. Local rock formations are first crushed and then excavated using a breaker.

[0024] Installation of internal support: After pumping water from the cofferdam to the designed support position, 70cm below the support, the internal support will be installed. When installing the internal support of the cofferdam, the cofferdam corbel 3 is constructed first, the cofferdam purlin 4 profile is placed on the corbel for welding, the cofferdam purlin horizontal internal support 5 is constructed, the horizontal support flat joint 6 is installed, the small triangular diagonal brace 7 is installed, and the large triangular diagonal brace 8 is constructed. In order to prevent the purlin support from being too deflected, vertical support 9 is set at the steel connection node, and water is pumped and excavated continuously until the excavation reaches the designed height. Finally, the cofferdam bottom sealing concrete 12 is constructed, and internal leveling, pile head breaking, and foundation construction are carried out.

Claims

1. A method for constructing an improved locking steel pipe pile cofferdam in a sand-poor, large-size pebble-covered stratum, characterized in that: The following steps are involved: Dismantle the upper structure of the drilling platform 1; measure and mark out the positions of the locking steel pipe pile cofferdam, and improve the hole end and lock of the conventional locking steel pipe pile 2; use crawler crane and vibratory hammer to sink and position the improved steel pipe pile cofferdam, and initially enter the pebble layer 3; use hydraulic impact hammer to drive the pipe pile to the set elevation 4; for steel pipe piles that are difficult to drive or have boulders at the bottom, use XR280 rotary drilling rig to drill holes in the cofferdam pipe piles 5; close the steel pipe piles 6; pump out the cofferdam 7; excavate the inside of the cofferdam 8; excavate the cofferdam, level the cofferdam bottom, break the pile heads, and construct the foundation.

2. According to claim 1, the position of the locking steel pipe pile cofferdam is measured and laid out, and the improved steel pipe pile cofferdam is sunk and positioned using a crawler crane and a vibrating hammer, characterized in that The net width around the pile foundation platform after demolition should be 1m to 1.5m greater than the diameter of the cofferdam which is twice the width of the foundation.

3. According to claim 2, the hole end and the lock of the conventional locking steel pipe pile are improved, characterized in that Within a 50cm length range at the top and bottom of the lock pipe pile, additional steel plates of the same pipe thickness are welded, of which the bottom steel plate is thickened and polished with a 45-degree groove; the connection between the locks is changed from the commonly used "CO" and "CT" lock forms, referring to the Larsen steel plate form, and the lock inner inclination angle is increased.

4. According to claim 3, the improved steel pipe pile cofferdam is sunk and positioned by using a crawler crane and a vibrating hammer to initially enter the pebble layer, characterized in that The main construction purpose of the crawler crane and vibratory hammer is to initially sink the connecting pipe piles between the lock buckles of the locking steel pipe piles, which plays a guiding and positioning role.

5. According to claim 4, the pipe pile is driven into the set elevation by using a hydraulic impact hammer, characterized in that During the square impact process, the impact stroke height of the hydraulic impact hammer gradually changes from 1.2m to 0.6m, and the verticality is fine-tuned by manual traction rope.

6. According to claim 5, for steel pipe piles that are difficult to drive or have boulders at the bottom, an XR280 rotary drilling machine is used to drill holes in the cofferdam pipe piles, characterized in that For large-size pebbles with a diameter greater than 200mm or rock formations with a uniaxial compressive strength greater than 15MPa, when injection is difficult, lock-in pipe piles are used as casings to drill holes inside the pipe.

7. According to claim 6, the steel pipe pile closure is characterized in that When there are 1 to 2 locking pipe piles left before the pipe piles are connected, the distance between the connection hole mouth and the hole bottom should be measured according to the on-site injection situation of the pipe piles, and the locking position and inclination of the connection hole pipe piles should be adjusted according to the distance. Finally, the last 2 to 3 locking pipe piles should be impacted and sunk in rotation using an impact hammer.

8. According to claim 7, cofferdam pumping, characterized in that The first pumping out volume of the cofferdam should be 1.5 to 2.0 times greater than the water seepage volume inside the cofferdam.

9. According to claim 8, excavation in the cofferdam, characterized in that The slag is removed by internal excavation with a small excavator and up and down transfer with a long arm. The local rock formations are first crushed with a breaker hammer before excavation.

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