In urban deep foundation pit projects, pile support is a common support method. The pile support structure usually consists of steel pipe piles, steel sheet piles, long spiral drilled cast-in-place piles, etc. These piles are arranged in a certain design during construction to form a support structure that can withstand soil pressure and stop water. Below we will introduce the piling method of steel pipe piles in detail from several aspects.
1. Hammering method
The impact energy of the pile hammer is used to overcome the resistance of the foundation to the steel pipe pile and drive the pile to a predetermined depth. It is suitable for soft plastic or plastic cohesive soil layers. The main equipment used includes pile frames, pile hammers, power equipment, etc. Commonly used pile hammers include drop hammers, single-action steam hammers, double-action steam hammers and diesel hammers. The body of the falling hammer is made of cast iron and weighs 250 to 2000 kilograms. It is lifted by workforce or a winch, and the pile is driven by the impact energy of the free-falling hammer's body.
The advantage is that the structure is simple, but the piling speed is slow. The single-action steam hammer uses the energy of steam or compressed air to lift the hammer body, and relies on the impact energy of the free fall of the hammer body to drive piles; the weight of the hammer body is 1,500 to 10,000 kilograms, and the number of hammering times per minute is 25 to 30 times, which is more commonly used. A pile hammer.
The double-action steam hammer has a cylinder fixed on the top of the pile, and relies on the energy of steam or compressed air to push the hammer's body up and down in the cylinder: because of its high impact frequency, it can not only drive piles, but also pull out piles, and is widely used in piling construction. There are two types of diesel hammers: rod type and cylinder type. Its working principle is similar to that of a diesel engine cylinder. It has high piling efficiency and is also a commonly used pile hammer. The weight of the pile hammer is an important parameter in piling construction.
Piling should be driven lightly with a heavy hammer, and the falling distance should not be too large to avoid cracking the top of the steel pipe pile or causing horizontal cracks within 1/3 of the pile length below the top of the pile;. Hammering lightly and hard will result in a large hammering kinetic energy. Part of it is absorbed by the pile body, which results in low work efficiency and it is easy to break the pile head. Therefore, the hammer weight should be carefully selected according to the soil quality, pile weight and pile type.
When driving steel sheet piles, in order to prevent the pile driven first from being pushed by the pile driven later and causing horizontal displacement, the pile driving sequence must be reasonably arranged. When there are multiple rows of piles, the direction of advancement can be changed row by row; for the same row of piles, they can be driven at intervals; when driving piles in a large area, they are generally driven from the center first and gradually advanced to the surroundings.
2. Vibration method
When piling, a high-power vibration pile driver is installed on the top of the pile, and the vibration force is used to reduce the resistance of the foundation soil to the pile. It is very efficient at piling sandy soil and can also be used to sink and pull out steel sheet piles and steel pipe piles.
3. Water jet method
The water jet method is also called the water jet pile sinking method. It is an auxiliary method to the hammering method and vibration method. The high-pressure water flow is used to loosen the soil layer around the pile tip through the water injection pipe installed on the side of the pile or in the hollow pile, to reduce the sinking resistance of the pile. It is generally used in sandy soil layers and is very efficient. When the pile tip sinks to about 1 to 1.5 meters away from the design elevation, the water injection should be stopped, and the pile should be sunk to the design elevation using hammering or vibration.
4. Piling method
With the help of the pile frame's own weight and the pressure on the pile frame, the pile is pressed into the soil through the pulley reversal. The pile pressing method can reduce the noise and vibration of the foundation soil and adjacent buildings during hammering or vibration pile driving, and is suitable for relatively homogeneous soft soil foundations. In sandy soil and other hard soil layers, it is not suitable to be used due to excessive resistance.
Due to the limitation of the height of the pile-pressing frame, each pile needs to be pressed in sections, so there are many joints. The new pile-connecting technology using sulfur cement as the cementing agent has been successful and popularized.
1. Hammering method
The impact energy of the pile hammer is used to overcome the resistance of the foundation to the steel pipe pile and drive the pile to a predetermined depth. It is suitable for soft plastic or plastic cohesive soil layers. The main equipment used includes pile frames, pile hammers, power equipment, etc. Commonly used pile hammers include drop hammers, single-action steam hammers, double-action steam hammers and diesel hammers. The body of the falling hammer is made of cast iron and weighs 250 to 2000 kilograms. It is lifted by workforce or a winch, and the pile is driven by the impact energy of the free-falling hammer's body.
The advantage is that the structure is simple, but the piling speed is slow. The single-action steam hammer uses the energy of steam or compressed air to lift the hammer body, and relies on the impact energy of the free fall of the hammer body to drive piles; the weight of the hammer body is 1,500 to 10,000 kilograms, and the number of hammering times per minute is 25 to 30 times, which is more commonly used. A pile hammer.
The double-action steam hammer has a cylinder fixed on the top of the pile, and relies on the energy of steam or compressed air to push the hammer's body up and down in the cylinder: because of its high impact frequency, it can not only drive piles, but also pull out piles, and is widely used in piling construction. There are two types of diesel hammers: rod type and cylinder type. Its working principle is similar to that of a diesel engine cylinder. It has high piling efficiency and is also a commonly used pile hammer. The weight of the pile hammer is an important parameter in piling construction.
Piling should be driven lightly with a heavy hammer, and the falling distance should not be too large to avoid cracking the top of the steel pipe pile or causing horizontal cracks within 1/3 of the pile length below the top of the pile;. Hammering lightly and hard will result in a large hammering kinetic energy. Part of it is absorbed by the pile body, which results in low work efficiency and it is easy to break the pile head. Therefore, the hammer weight should be carefully selected according to the soil quality, pile weight and pile type.
When driving steel sheet piles, in order to prevent the pile driven first from being pushed by the pile driven later and causing horizontal displacement, the pile driving sequence must be reasonably arranged. When there are multiple rows of piles, the direction of advancement can be changed row by row; for the same row of piles, they can be driven at intervals; when driving piles in a large area, they are generally driven from the center first and gradually advanced to the surroundings.
2. Vibration method
When piling, a high-power vibration pile driver is installed on the top of the pile, and the vibration force is used to reduce the resistance of the foundation soil to the pile. It is very efficient at piling sandy soil and can also be used to sink and pull out steel sheet piles and steel pipe piles.
3. Water jet method
The water jet method is also called the water jet pile sinking method. It is an auxiliary method to the hammering method and vibration method. The high-pressure water flow is used to loosen the soil layer around the pile tip through the water injection pipe installed on the side of the pile or in the hollow pile, to reduce the sinking resistance of the pile. It is generally used in sandy soil layers and is very efficient. When the pile tip sinks to about 1 to 1.5 meters away from the design elevation, the water injection should be stopped, and the pile should be sunk to the design elevation using hammering or vibration.
4. Piling method
With the help of the pile frame's own weight and the pressure on the pile frame, the pile is pressed into the soil through the pulley reversal. The pile pressing method can reduce the noise and vibration of the foundation soil and adjacent buildings during hammering or vibration pile driving, and is suitable for relatively homogeneous soft soil foundations. In sandy soil and other hard soil layers, it is not suitable to be used due to excessive resistance.
Due to the limitation of the height of the pile-pressing frame, each pile needs to be pressed in sections, so there are many joints. The new pile-connecting technology using sulfur cement as the cementing agent has been successful and popularized.
