As the construction industry pays more and more attention to construction environmental protection and efficiency, traditional construction methods are gradually becoming insufficient due to long construction periods and environmental damage. In contrast, the steel sheet pile construction method, which has been relatively mature in the market, stands out for its environmental protection and high efficiency. However, the lateral stiffness of steel sheet piles is relatively low, which leads to its limitations in deformation control and is usually suitable for excavation depths of no more than 7 meters. In foundation pit projects with high requirements for the surrounding environment or large excavation depths, the application of steel sheet piles is relatively small.
In order to expand the scope of application of steel sheet piles, China has begun to combine steel sheet piles with H-shaped steel or pipe piles to form a combined steel sheet pile foundation pit support structure. This article will briefly summarize the relatively mature combined steel sheet pile construction methods at home and abroad for reference. In the process of design and construction plan formulation, this information can serve as an important reference.
The predecessor of the PC method pile is the traditional Larsen steel sheet pile. The simple steel sheet pile, whether it is U-shaped, Z-shaped or straight-belly type, must require a multi-layer support and anchor structure when used in deep foundation pits due to its small cross-sectional stiffness, which increases the difficulty of construction and leads to the continuous development of its advantages of fast and efficient. In order to increase the cross-sectional rigidity, our engineering and technical personnel thought that Larsen piles could be combined with steel pipes to form various cross-sectional combinations for retaining and water stopping;
As a reusable green and environmentally friendly building material, PC construction piles (combination of steel pipes and Larsen piles) are highly valued and favored by the foundation pit industry for their high strength, light weight, stable material, reliable quality, good durability, good weather resistance, water stopping, pollution-free construction, convenient inspection and acceptance, simple and reusable, and good economy;
PC construction method combined steel pipe piles are combined retaining piles that connect steel pipe piles with Larsen steel sheet piles by setting a small tongue-and-groove connection. This pile is suitable for the support structure of foundation pit engineering, and can be used as a reference for construction engineering, municipal engineering, port engineering, onshore parts of water conservancy engineering, and foundation pits adjacent to water.
Steel sheet piles have relatively small lateral rigidity and large deformation. They are generally suitable for excavation depths of no more than 7m. They are rarely used in foundation pit projects with high requirements for the surrounding environment and large excavation depths. In order to expand the application field of steel sheet piles, steel sheet piles and H-shaped steel are used to form a combined steel sheet pile foundation pit support structure, referred to as HSW method (H shaped steel & Steel sheet pile Wall). Steel sheet piles can retain soil and stop water; H-shaped steel has high rigidity, and the overall rigidity of the combined structure is large. H-shaped steel and steel sheet piles can be flexibly set in length according to engineering and geological characteristics, that is, the length setting of steel sheet piles meets the needs of seepage stability (water-stop curtain depth), overall stability, overturning, and uplift verification; and the length of H-shaped steel needs to meet the strength and deformation needs of the support structure.
There are mainly two connection methods. One is that H-shaped steel is placed on the inside of the steel sheet pile, and the steel sheet pile is constructed first, and then the H-shaped steel is constructed, and the removal is related. The steel sheet pile and H-shaped steel are constructed separately, and the soil resistance is small during construction, the operation is flexible, and it is convenient to recycle. The other is that the H-shaped steel is placed on the outside of the steel sheet pile. At this time, the steel sheet pile and the H-shaped steel must be consolidated. The two are connected by welding or bolts to form a whole, and the construction and removal are completed at one time. H-shaped steel is placed outside the steel sheet pile, the overall rigidity of the structure is large, the ability to control deformation is strong, but the disadvantage is that it is difficult to drive in and remove.
The combined structure can give full play to the advantages of steel sheet piles and H-shaped steel, with large structural rigidity, soil retaining and water stopping functions, fast and simple construction, easy quality control, recyclable and cost-saving.
Against the background of rapid economic development and the continuous expansion of infrastructure and civil construction, the development and utilization of underground space in dense urban centers has become a necessity. Some foundation pits with shallow excavation depth and good soil conditions often use Larsen steel sheet piles as retaining and water-stopping structures, such as breakwaters, revetments, docks, docks, artificial islands, ship locks, underground tunnels, embankments, retaining walls, anti-seepage walls, foundation reinforcement and other permanent projects and cofferdams, foundation pit enclosures and other temporary projects. However, when constructing cofferdams in rivers and surrounding soft clay areas, the rigidity of Larsen steel sheet piles often cannot meet safety requirements; while other support forms, such as bored piles and SMW methods, can meet design requirements, but the construction cost is significantly increased and it is difficult to construct in mudflats and rivers.
In order to solve the support of foundation pits and cofferdams in soft clay areas, combined steel sheet piles can be used, such as steel plates combined with H-shaped steel, Larsen steel sheet piles combined with H-shaped steel, etc. (see figure), through the continuous locking overlap of steel plates or Larsen steel sheet piles to form a continuous sealed water stop structure, and at the same time, a row of H-shaped steel is constructed on the inside of the steel sheet piles to meet the rigidity and stability requirements of the entire support structure.
HUW method (H steel U steel continuous Wall) is a new technology that can replace Larsen steel sheet piles (especially the 18m-30m long No. 6 Larsen piles used in deep-water foundation pits), SMW method piles, cast-in-place piles and other foundation pit retaining systems.
HUW combined Larsen steel sheet pile continuous wall is a steel sheet pile continuous wall that uses H-shaped steel with stoppers and U Larsen steel sheet piles with stoppers to be injected and connected through a positioning frame. It has the advantages of excellent water-stopping effect, high strength, fast construction progress, environmental protection, high efficiency, energy saving, and convenient material acquisition. It is deeply favored by the majority of owners, general contractors and construction units.
Advantages of HUW method:
(1) Cost saving
Compared with traditional foundation pit retaining technology such as No. 6 steel sheet piles, SMW method, cast-in-place piles in deep-water foundation pits, the cost of HUW method can be saved by 5%-20%.
(2) Shorten the construction period
The HUW method uses a fully automatic horizontal positioning frame to feed the piles first and then use a vibrating hammer to deliver the piles, so the daily construction progress can be guaranteed to be more than 20 linear meters. Compared with the SMW method and cast-in-place piles, the construction period can be saved by more than 30 days.
(3) Convenient material acquisition
Since the structure of the materials used in the HUW method is relatively simple, it mainly uses domestic steel materials such as H-shaped steel, 14mm rolled plate, 60*10 seamless steel pipe, 28φ round steel, etc., which can be processed and used, so the material acquisition is very convenient.
HUC combined steel sheet piles are a new type of deep foundation pit support technology. It is the abbreviation of "H-pile and U-pile Connected", which is a combination of H-shaped steel and U-shaped steel sheet piles. This combination inherits the advantages of steel sheet piles and solves the problems of insufficient rigidity of conventional steel sheet piles, large foundation pit deformation, difficult to control verticality, and poor waterproofing effect. HUC composite steel sheet piles have the characteristics of fast construction speed, tight locking, good waterproof performance, and strong reusability.
The main advantages of HUC composite steel sheet piles include:
(1) High rigidity and diversified specifications
Compared with U-shaped steel sheet piles, HUC composite steel sheet piles have greater rigidity and can better control the deformation of foundation pits.
(2) Excellent water-stopping performance: Due to the use of hot-rolled steel sheet piles, the locking hot rolling forming process has high precision, so the water-stopping effect is good.
(3) Diverse construction methods, fast and convenient construction
Similar to traditional steel sheet pile construction, a variety of construction machinery can be used, the construction efficiency is high, and the construction period is greatly shortened.
(4) Recycling, economic reduction, and green environmental protection
HUC composite steel sheet piles can be reused after pulling out the piles, which reduces the total cost and has little impact on the environment.
(5) High reliability
HUC composite steel sheet piles can be used not only for temporary support, but also for permanent structure construction, with high reliability.
In addition, the construction technology, measures and methods for solving problems encountered during construction of HUC composite steel sheet piles have also been applied and summarized in engineering practice. This method has shown its advantages in deep foundation pit support in ultra-deep silt layers, especially under conditions of site restrictions and high environmental protection requirements.
HZ+AZ combined steel sheet piles are a new type of support structure, widely used in deep foundation pits, docks, shipyards and other projects. The following is some key information about HZ+AZ combined steel sheet piles:
(1) Structural composition:
HZ+AZ combined steel sheet piles are composed of HZ steel sheet piles and AZ steel sheet piles. HZ steel sheet piles are the main piles, bearing the main soil pressure; AZ steel sheet piles are the auxiliary piles, connected to HZ steel sheet piles through locks, sharing part of the load.
(2) Construction technology:
In the grain and general terminal project in Nansha Port Area of Guangzhou Port, China, the construction of HZ/AZ combined steel sheet piles adopted the pile sinking technology of vibrating hammer pile insertion and diesel hammer re-driving. This technology enables all HZ and AZ steel sheet piles to reach the designed elevation, and the pile sinking effect is good.
(3) Application cases:
In the second phase of the new dock project at Tuas South Jurong Shipyard in Singapore, HZ+AZ composite steel sheet piles were used in the construction of quayside wharfs. The project adopted HZ1080MB+AZ26 steel sheet pile concrete breast wall and AZ26 steel sheet pile anchor wall, combined with an anchor system consisting of a φ90 tie rod and riprap system.
(4) Structural features:
HZ+AZ composite steel sheet piles have the characteristics of high bending strength, reasonable structural force, and good adaptability to loads and geology. HZ-type steel sheet piles are used as main piles to mainly bear horizontal loads, while AZ-type steel sheet piles are connected through locks to coordinate deformation and share part of the load.
(5) Applicability:
HZ+AZ composite steel sheet piles are suitable for pile sinking technology of high-grade, deep-water quayside wharfs. They have the best bending performance and the least steel consumption, but the vertical bearing capacity is relatively small, which is suitable for situations where the vertical bearing capacity requirements are not high.
In order to expand the scope of application of steel sheet piles, China has begun to combine steel sheet piles with H-shaped steel or pipe piles to form a combined steel sheet pile foundation pit support structure. This article will briefly summarize the relatively mature combined steel sheet pile construction methods at home and abroad for reference. In the process of design and construction plan formulation, this information can serve as an important reference.
1. Hat-type H-shaped steel plate combined steel sheet piles
Hat-type H-shaped steel plate combined steel sheet piles are a new type of steel structure with high bearing capacity and seismic performance, and are widely used in buildings, bridges, docks and other fields. This type of composite pile is formed by connecting the hot-rolled wide-width hat-shaped steel sheet pile and the H-shaped steel through a simple interlocking device to form a hat-shaped H-shaped steel interlocking composite pile. Its main features include rich combination forms, small impact on the surrounding environment, short construction period, simple process, convenient transportation, large bending stiffness, good water-stopping performance, lightweight, green and recyclable, etc.
2. PC method pile
The predecessor of the PC method pile is the traditional Larsen steel sheet pile. The simple steel sheet pile, whether it is U-shaped, Z-shaped or straight-belly type, must require a multi-layer support and anchor structure when used in deep foundation pits due to its small cross-sectional stiffness, which increases the difficulty of construction and leads to the continuous development of its advantages of fast and efficient. In order to increase the cross-sectional rigidity, our engineering and technical personnel thought that Larsen piles could be combined with steel pipes to form various cross-sectional combinations for retaining and water stopping;As a reusable green and environmentally friendly building material, PC construction piles (combination of steel pipes and Larsen piles) are highly valued and favored by the foundation pit industry for their high strength, light weight, stable material, reliable quality, good durability, good weather resistance, water stopping, pollution-free construction, convenient inspection and acceptance, simple and reusable, and good economy;
PC construction method combined steel pipe piles are combined retaining piles that connect steel pipe piles with Larsen steel sheet piles by setting a small tongue-and-groove connection. This pile is suitable for the support structure of foundation pit engineering, and can be used as a reference for construction engineering, municipal engineering, port engineering, onshore parts of water conservancy engineering, and foundation pits adjacent to water.
3. HSW construction method
Steel sheet piles have relatively small lateral rigidity and large deformation. They are generally suitable for excavation depths of no more than 7m. They are rarely used in foundation pit projects with high requirements for the surrounding environment and large excavation depths. In order to expand the application field of steel sheet piles, steel sheet piles and H-shaped steel are used to form a combined steel sheet pile foundation pit support structure, referred to as HSW method (H shaped steel & Steel sheet pile Wall). Steel sheet piles can retain soil and stop water; H-shaped steel has high rigidity, and the overall rigidity of the combined structure is large. H-shaped steel and steel sheet piles can be flexibly set in length according to engineering and geological characteristics, that is, the length setting of steel sheet piles meets the needs of seepage stability (water-stop curtain depth), overall stability, overturning, and uplift verification; and the length of H-shaped steel needs to meet the strength and deformation needs of the support structure.There are mainly two connection methods. One is that H-shaped steel is placed on the inside of the steel sheet pile, and the steel sheet pile is constructed first, and then the H-shaped steel is constructed, and the removal is related. The steel sheet pile and H-shaped steel are constructed separately, and the soil resistance is small during construction, the operation is flexible, and it is convenient to recycle. The other is that the H-shaped steel is placed on the outside of the steel sheet pile. At this time, the steel sheet pile and the H-shaped steel must be consolidated. The two are connected by welding or bolts to form a whole, and the construction and removal are completed at one time. H-shaped steel is placed outside the steel sheet pile, the overall rigidity of the structure is large, the ability to control deformation is strong, but the disadvantage is that it is difficult to drive in and remove.
The combined structure can give full play to the advantages of steel sheet piles and H-shaped steel, with large structural rigidity, soil retaining and water stopping functions, fast and simple construction, easy quality control, recyclable and cost-saving.
Against the background of rapid economic development and the continuous expansion of infrastructure and civil construction, the development and utilization of underground space in dense urban centers has become a necessity. Some foundation pits with shallow excavation depth and good soil conditions often use Larsen steel sheet piles as retaining and water-stopping structures, such as breakwaters, revetments, docks, docks, artificial islands, ship locks, underground tunnels, embankments, retaining walls, anti-seepage walls, foundation reinforcement and other permanent projects and cofferdams, foundation pit enclosures and other temporary projects. However, when constructing cofferdams in rivers and surrounding soft clay areas, the rigidity of Larsen steel sheet piles often cannot meet safety requirements; while other support forms, such as bored piles and SMW methods, can meet design requirements, but the construction cost is significantly increased and it is difficult to construct in mudflats and rivers.
In order to solve the support of foundation pits and cofferdams in soft clay areas, combined steel sheet piles can be used, such as steel plates combined with H-shaped steel, Larsen steel sheet piles combined with H-shaped steel, etc. (see figure), through the continuous locking overlap of steel plates or Larsen steel sheet piles to form a continuous sealed water stop structure, and at the same time, a row of H-shaped steel is constructed on the inside of the steel sheet piles to meet the rigidity and stability requirements of the entire support structure.
4. HUW combined steel sheet piles
HUW method (H steel U steel continuous Wall) is a new technology that can replace Larsen steel sheet piles (especially the 18m-30m long No. 6 Larsen piles used in deep-water foundation pits), SMW method piles, cast-in-place piles and other foundation pit retaining systems.HUW combined Larsen steel sheet pile continuous wall is a steel sheet pile continuous wall that uses H-shaped steel with stoppers and U Larsen steel sheet piles with stoppers to be injected and connected through a positioning frame. It has the advantages of excellent water-stopping effect, high strength, fast construction progress, environmental protection, high efficiency, energy saving, and convenient material acquisition. It is deeply favored by the majority of owners, general contractors and construction units.
Advantages of HUW method:
(1) Cost saving
Compared with traditional foundation pit retaining technology such as No. 6 steel sheet piles, SMW method, cast-in-place piles in deep-water foundation pits, the cost of HUW method can be saved by 5%-20%.
(2) Shorten the construction period
The HUW method uses a fully automatic horizontal positioning frame to feed the piles first and then use a vibrating hammer to deliver the piles, so the daily construction progress can be guaranteed to be more than 20 linear meters. Compared with the SMW method and cast-in-place piles, the construction period can be saved by more than 30 days.
(3) Convenient material acquisition
Since the structure of the materials used in the HUW method is relatively simple, it mainly uses domestic steel materials such as H-shaped steel, 14mm rolled plate, 60*10 seamless steel pipe, 28φ round steel, etc., which can be processed and used, so the material acquisition is very convenient.
5. HUC combined steel sheet piles
HUC combined steel sheet piles are a new type of deep foundation pit support technology. It is the abbreviation of "H-pile and U-pile Connected", which is a combination of H-shaped steel and U-shaped steel sheet piles. This combination inherits the advantages of steel sheet piles and solves the problems of insufficient rigidity of conventional steel sheet piles, large foundation pit deformation, difficult to control verticality, and poor waterproofing effect. HUC composite steel sheet piles have the characteristics of fast construction speed, tight locking, good waterproof performance, and strong reusability.The main advantages of HUC composite steel sheet piles include:
(1) High rigidity and diversified specifications
Compared with U-shaped steel sheet piles, HUC composite steel sheet piles have greater rigidity and can better control the deformation of foundation pits.
(2) Excellent water-stopping performance: Due to the use of hot-rolled steel sheet piles, the locking hot rolling forming process has high precision, so the water-stopping effect is good.
(3) Diverse construction methods, fast and convenient construction
Similar to traditional steel sheet pile construction, a variety of construction machinery can be used, the construction efficiency is high, and the construction period is greatly shortened.
(4) Recycling, economic reduction, and green environmental protection
HUC composite steel sheet piles can be reused after pulling out the piles, which reduces the total cost and has little impact on the environment.
(5) High reliability
HUC composite steel sheet piles can be used not only for temporary support, but also for permanent structure construction, with high reliability.
In addition, the construction technology, measures and methods for solving problems encountered during construction of HUC composite steel sheet piles have also been applied and summarized in engineering practice. This method has shown its advantages in deep foundation pit support in ultra-deep silt layers, especially under conditions of site restrictions and high environmental protection requirements.
6. HZ+AZ combined steel sheet piles
HZ+AZ combined steel sheet piles are a new type of support structure, widely used in deep foundation pits, docks, shipyards and other projects. The following is some key information about HZ+AZ combined steel sheet piles:(1) Structural composition:
HZ+AZ combined steel sheet piles are composed of HZ steel sheet piles and AZ steel sheet piles. HZ steel sheet piles are the main piles, bearing the main soil pressure; AZ steel sheet piles are the auxiliary piles, connected to HZ steel sheet piles through locks, sharing part of the load.
(2) Construction technology:
In the grain and general terminal project in Nansha Port Area of Guangzhou Port, China, the construction of HZ/AZ combined steel sheet piles adopted the pile sinking technology of vibrating hammer pile insertion and diesel hammer re-driving. This technology enables all HZ and AZ steel sheet piles to reach the designed elevation, and the pile sinking effect is good.
(3) Application cases:
In the second phase of the new dock project at Tuas South Jurong Shipyard in Singapore, HZ+AZ composite steel sheet piles were used in the construction of quayside wharfs. The project adopted HZ1080MB+AZ26 steel sheet pile concrete breast wall and AZ26 steel sheet pile anchor wall, combined with an anchor system consisting of a φ90 tie rod and riprap system.
(4) Structural features:
HZ+AZ composite steel sheet piles have the characteristics of high bending strength, reasonable structural force, and good adaptability to loads and geology. HZ-type steel sheet piles are used as main piles to mainly bear horizontal loads, while AZ-type steel sheet piles are connected through locks to coordinate deformation and share part of the load.
(5) Applicability:
HZ+AZ composite steel sheet piles are suitable for pile sinking technology of high-grade, deep-water quayside wharfs. They have the best bending performance and the least steel consumption, but the vertical bearing capacity is relatively small, which is suitable for situations where the vertical bearing capacity requirements are not high.
