【Excerpts】How should I decide on the pile selection?

Usually, pile foundation can be used in the following cases

       1、Pile foundation can be used when the foundation is soft and weak and the natural foundation cannot meet the requirements of foundation strength and deformation.

       2、Pile foundation should be used when there are strict requirements for building deformation.

       3、Pile foundation should be used when towering buildings or structures have special requirements for limiting tilt.

       4、Pile foundation should be used when there is mutual influence on the neighboring buildings due to foundation settlement.

       5、Heavy single-storey industrial plants with large tonnage heavy working system cranes, crane load, frequent use, more equipment platforms in the workshop, dense foundation, and generally have ground load, and thus the foundation deformation is large, then pile foundation can be used.

       6、precision equipment foundation and power machinery foundation, due to the deformation and allowable amplitude has high requirements, usually also use pile foundation.

       7、In the seismic zone, in the liquefiable foundation, pile foundation is used to cross the liquefiable soil layer and reach into the lower dense and stable soil layer, which can eliminate or reduce the hazard of liquefaction to the building.

Selection of pile type

       The selection of pile type should take into account various factors, including the type of building (structure) structure, the nature and size of the load, the type and nature of the soil layer and pile end, groundwater, construction environment, construction capacity, local experience in the use of pile foundations and cost, etc.

       Generally speaking, for frame and frame structure buildings (structures), when the bedrock or hard thick soil layer is not too deep, often use the end-bearing-based infill piles to obtain a higher bearing capacity and eliminate or reduce building settlement, such as the use of large-diameter drilling (punching) piles or hand-dug piles, designed as a single-pile single-column foundation, the foundation structure design is simplified. For general industrial and civil buildings, the choice of pile type is mainly based on site conditions, construction capacity, the number of floors, the size of the load, nature and cost, such as the number of floors to determine the pile type, the following 10 floors can be considered to use about 400-500mm diameter piles or side length of 250-300mm prefabricated piles, 10 to 20 floors available diameter 600-1000mm or 400-500mm prefabricated piles, 20-30 layers of 700-1200mm diameter piles or 400-600mm prefabricated piles, 30-40 layers of 800-1500mm diameter piles, etc.

       In dense urban construction areas, the vibration and noise pollution brought by driven pile construction is getting more and more attention, the sunken pile extrusion or vibration may also endanger the safety of neighboring buildings and underground pipelines, then the pile type should be selected according to the site conditions and the surrounding environment, such as the use of drilling (punching) piles or hand-dug piles and other non-extruded piles, but at the same time to pay attention to the disposal of waste mud and abandoned soil, as well as the pile construction of the grouting Quality and stability problems, such as in the high water table of sandy soil layer, especially in the saturated fine sand layer in the construction of hand-dug piles, prone to sand flow and lead to the collapse of the well hole, and in the thick layer of silty soil in the construction of bored piles, when the wall mud ratio is not appropriate, easy to collapse the hole and cause the pile body broken pile, mud or shrinkage.

       When there are dense interlayer or large isolated rocks or unweathered veins in the residual layer, prefabricated piles, especially prestressed pipe piles, should be selected carefully, otherwise the hammering is either unable to penetrate or cause high pile breakage rate; in the surface layer without weathering layer or weathering layer of thin hard rock as the pile end bearing layer, prefabricated piles should not be used, because the pile tip can not enter the rock and easy to break when hammering, such as limestone strata; for soil layers The prefabricated pile is not suitable for unevenly distributed strata because the prefabricated length of the pile is difficult to control; and the prefabricated pile is also not suitable when the slope of the bearing layer is large because the pile tip may slip and cause the pile body to break when sinking the pile; at this time, the infill pile should be considered.

——Source: Inverse Works Engineering Center

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