Piling pipe include steel piling pipe and prestressed concrete piling pipe. These piling pipe are widely used in various construction projects and are favored for their advantages of saving materials, high bearing capacity, good penetration and low soil squeezing effect. However, as a semi-squeezing pile, the soil squeezing effect of open piling pipe still limits its application range. The length of the soil plug formed during the pile sinking process is usually 1/3 to 2/3 of the pile length, and the volume of soil discharge is still large.
Methods to solve the soil squeezing effect of open piling pipe
At present, there are mainly the following methods to solve the soil squeezing effect of open piling pipe:
Pre-drilling construction: pre-drilling holes at the pile position, usually with a diameter of 2/3 of the pile diameter and a depth of 2/3 of the pile length. Although this method is very effective, the construction cost is high.
Water jetting construction: a high-pressure water gun is set in the piling pipe, and high-pressure water jetting is used to break up the soil structure during the pile sinking process to reduce the pile-soil friction. At the same time, the vibration pile sinking during the water jetting process is more conducive to the discharge of soil and mud. This method has a high construction cost, and the discharge of mud will pollute the construction site and have a certain impact on the bearing capacity of the pile. It is usually used in the construction of large prestressed concrete piling pipe in bridge projects.
Trench protection: dig trenches or fill in loose materials around the construction site to reduce the squeezing effect of the surface soil and effectively protect shallow buried pipelines. This method has limited effect and can only reduce the harm of the soil squeezing effect, but fails to truly reduce the soil squeezing effect of the piling pipe.
Mechanism of soil squeezing effect of piling pipe
The stress condition of soil plug in piling pipe is as follows: During the pile sinking process, the bottom reaction force P is greater than the sum of friction force F and gravity G. When the bottom reaction force of pile cannot overcome the strong resistance (F+G), soil plug is formed. If the reaction force provided by the soil at the bottom of pile is greater than the friction force and gravity of soil plug, soil plug will slide in piling pipe; if the soil at the bottom of pile is destroyed, soil plug will no longer slide. By calculating the ultimate bearing capacity of the soil plug, the height of soil plug can be calculated.
Numerical simulation of soil squeezing effect of piling pipe
When the reaction force provided by the soil at the bottom of the pile is greater than the friction and gravity of the soil plug, the soil plug slides in the pipe; if the soil at the bottom of the pile is destroyed, the soil plug will no longer slide. According to the ultimate bearing capacity of the soil plug, the height of the soil plug can be calculated. For example, when the friction coefficient u=0.4 and the length of the soil plug is 5 meters, the reaction force at the bottom of the pile is about 2214kPa. At this time, the soil at the bottom of the pile is usually destroyed and the soil plug is generally not more than 5 meters. Under actual geological conditions, the length of the soil plug can be calculated layer by layer. When considering the effect of groundwater, the effective stress calculation is adopted. The excess pore water pressure during the piling process will increase the calculated length of the soil plug.
When choosing a piling pipe, the following factors should be considered:
1. Steel pipe strength: Piling requires greater pressure and impact, so it is necessary to choose a high-strength steel pipe. Common materials include Q195, Q235, Q345, etc.
2. Steel pipe diameter and wall thickness: Select the appropriate steel pipe diameter and wall thickness according to the project requirements. Generally speaking, larger diameters and thicker walls can provide better bearing capacity. For example, SSAW steel pipe or large-diameter seamless steel pipes, these steel pipes have strong stability and better bearing capacity
3. Steel pipe corrosion protection measures: If piling is carried out in water or soil, corrosion issues need to be considered. Steel pipes with anti-corrosion coatings or hot-dip galvanized treatments can be selected.
4. Construction conditions and environment: Select suitable steel pipes according to specific construction conditions and environments. For example, straight seam welded steel pipes can be used in soft soil areas; seamless steel pipes can be used in rock formations.
Summary
Prestressed concrete piling pipe are widely used in industrial buildings, civil buildings, bridges, railways and other infrastructure projects due to their high bearing capacity, light weight, low cost and good penetration, especially in coastal soft soil areas. Through effective methods such as pre-drilling construction and water jetting construction, the soil squeezing effect of open piling pipe can be significantly reduced, thereby increasing its application range.
English
Español
بالعربية
Phone : 
Whatsapp : 
Email : 
