What Are Pile Foundations?

A deep foundation (see figure) consisting of a pile and a pile cap (referred to as the cap) connected to the top of the pile or a single pile foundation connected by a column to the pile foundation, referred to as the pile foundation. If the pile body is completely buried in the soil and the bottom of the cap is in contact with the soil, it is called a low cap pile foundation; if the upper part of the pile body is exposed to the ground and the cap bottom is above the ground, it is called a high cap pile foundation. Building pile foundations are usually low cap pile foundations. In high-rise buildings, pile foundations are widely used.

Main classification

According to the principle of foundation force, it can be roughly divided into friction pile and bearing pile.

1.Friction pile

It uses the friction between the ground and the foundation pile to support the structure and can be divided into pressure piles and tension piles. It is generally used for the ground without hard bearing layers or deep bearing layers.

2, end bearing pile

The foundation pile is placed on the bearing layer (on the rock plate) so that the structure can be carried.

According to the construction method, it can be divided into precast piles and cast-in-situ piles.

1.Precast pile

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Static test of pile foundation

The pile foundation static load test technology has been developed with the increasing use of pile foundations in building design. After the founding of the People's Republic of China, the static testing technology of pile foundations has gradually developed. The traditional static load test is performed by manual pressure, manual operation and manual recording. After the 1980s, with the pace of reform and opening up, the scale of basic construction has increased year by year, especially the widespread application of cast-in-situ piles, and China's pile foundation static load testing technology has also entered a brand-new development period. So far, the pile foundation static load test is established as a method, and theoretically there is no disputed pile foundation detection technology. ^[1]

Low strain treatment of pile foundation

In the 1980s, the low strain method based on the wave equation entered a rapid development period. Various low strain methods have been researched and practiced in basic theory, mechanism, instrument research and development, field testing and signal processing technology, engineering pile and model pile verification. In terms of accumulation of experience, many valuable results have been achieved.

High strain application of pile foundation

Research on the high strain dynamic test method in China started in the 1980s

In the middle and late period, by the early 1990s, relevant software and hardware were available, and the actual application effect was not weaker than that of foreign countries. In terms of dynamic testing of cast-in-place piles, domestic instruments and software have reached the international advanced level, and some aspects show Chinese characteristics .

Pile foundation acoustic transmission method

Acoustic transmission detection of concrete cast-in-situ piles was developed on the basis of structural concrete acoustic detection technology. By the 1970s, the acoustic transmission method was used to test the integrity of concrete cast-in-situ piles.

Pile foundation drilling and coring method

In the 1980s, the core drilling method was mainly used for the inspection of bored piles. At the same time, it was also used to detect the construction quality of underground diaphragm walls in areas with mature technical conditions. Core drilling method is a kind of detection method of micro damage or partial damage, which is scientific, intuitive and practical. ^[2]