What is a four class pile and what is a three class pile?

The four types of piles refer to:Pile foundation inspectionThe pile foundation that fails to pass the inspection in the process and has serious defects in the pile body.

The pile foundation detection results are divided into four categories, the first and second types of piles indicate that the pile is no problem, the third type of pile is problematic, and the next process construction can only be carried out after treatment, and the fourth type of pile must be reworked for processing.

Construction features:1. Compared with the hammering method sunk into the pile, the construction noise and vibration are much smaller.

2. It can build piles that are much larger than the diameter of prefabricated piles.

3. It can be used on all kinds of foundations.

4. The quality of construction has a great impact on the bearing capacity of the pile.

5. Because the concrete is poured in muddy water, the quality of the concrete is difficult to control.

6. It is labor-intensive and time-consuming, the hole forming speed is slow, and the mud slag pollutes the environment.

The first type of pile and the second type of pile refer to the quality of pile foundation inspection.

The classification of intermediate pile foundation is divided into 4 categories, as follows.

Stake-like. The pile body is complete like a pile.

There are slight defects in the pile body, which will not affect the normal play of the bearing capacity of the pile structure.

The pile has obvious defects, which has an impact on the bearing capacity of the pile structure.

There are serious defects in the pile.

Generally, Class 1 and 2 piles mean that the pile is fine, Class 3 piles are problematic and must be treated before the next process can be constructed, and Class 4 piles must be reworked for treatment. Pile foundation inspection

Generally, there are large and small strains and ultrasonic testing, and the most accurate and troublesome is core drilling.

See: page 18 of the Technical Code for Building Foundation Pile Detection JGJ106-2003

The evaluation of test results and the test report stipulate:

Pile-like piles are intact.

Pile-like piles have slight defects, which will not affect the normal play of the bearing capacity of the pile structure.

Pile-like piles have obvious defects, which have an impact on the bearing capacity of the pile structure.

Pile-like piles have serious defects.

Pile foundation inspection quality.

The pile foundation inspection specification is only right.

The proportion of the third and fourth types of piles is explained, but it is not correct.

The proportion of Class 1 and 2 piles.

There are instructions. Class II piles are only slightly defective in integrity and do not affect the bearing capacity. However, if you want to apply for high-quality projects, such as provincial and national high-quality projects, the proportion of first-class piles should not be less than 94%. That is to say, no more than 6% of the second-class piles.

The basic inspection is done for pulse flaw detection, and it is divided into a class of piles and a class of two piles according to the echo plant. Four types of piles, etc.

The basic situation of this type of pile is that the detected waveform is basically straight, and there is a reflection in phase with the incident wave between the piles, but the reflection signal is not strong, the reflection signal at the bottom of the pile is clear, and the propagation speed of the stress wave in the concrete is normal.

The reflection at the end of the pile is clear, but there is a reflected signal generated by local defects, and the concrete wave velocity is in the normal range.

Class I piles, Class II piles, Class III piles, and Class IV piles are commonly used pile foundation classifications in civil engineering, and their differences mainly lie in the design and use requirements of piles. The specific differences are as follows:

1.Class I piles: Class I piles refer to piles with high quality requirements in the design and construction process.

It is usually used for projects that bear large loads or have high lateral force resistance, such as the foundation of large buildings, bridges, port terminals, etc. The design and construction requirements are relatively strict, and detailed design calculations and safety performance testing are required.

2.Class II piles: Class II piles refer to piles with moderate quality requirements during the design and construction process.

It is usually used in the foundation, road, embankment and other works of small and medium-sized buildings. Compared with the first type of pile, the design and construction requirements are relatively simple, which can be calculated and selected by empirical formulas.

3.Class 3 piles: Class 3 piles refer to piles with low quality requirements during design and construction.

It is usually used for independent pile foundation construction, slope protection, earthwork cushion reinforcement and other projects. The design and construction requirements are relatively simple, and the pile length and diameter specified in the code are often used for selection.

4.Four types of piles: Four types of piles refer to non-load-bearing piles. They are not subjected to horizontal loads or other significant loads and are often used for auxiliary works, drainage works, anti-floating piles, etc. The design and construction requirements are relatively simple, mainly considering the corrosion resistance and durability of the pile.

It should be noted that the specific pile foundation type and classification may vary depending on the region, engineering requirements and other factors. Therefore, in the actual project, it is necessary to select and use the pile foundation according to the engineering design requirements and local specifications.

"Technical Code for Building Pile Foundation Detection" JGJ106-2003 J256-2003, pile foundation classification is divided into 4 categories, of which three types (class III) piles are: the pile body has obvious defects, which has an impact on the bearing capacity of the pile structure. Pile defects refer to pile fractures, cracks, mud inclusions, cavities, honeycombs, looseness, etc.

Four categories (class): the pile body has serious defects. For defective foundation piles, it is necessary to choose the appropriate treatment method.

The foundation pile with defects in the upper part is excavated, and the pile position must be re-determined to make up the foundation pile if the defect is in the middle (or in the upper part and cannot be excavated); If the defect is in the lower part, the vertical ultimate bearing capacity of the single pile can be verified by the high strain method (if the measured bearing capacity meets the design requirements, it can be used directly.) Otherwise, engineering must be done.

If it is a pipe pile, check the depth of the injured part, and then follow the depth, put a reinforcement cage in the pile, the depth exceeds the injury depth of not less than 2 meters, and then pour high-grade micro-expanded cement concrete.

1. Foundation pile treatment method: the pile with defects in the upper part is excavated, and the pile position needs to be re-determined to supplement the foundation pile if the defect is in the middle (or in the upper part and cannot be excavated); If the defect is in the lower part, the vertical ultimate bearing capacity of the single pile can be verified by the high strain method (if the measured bearing capacity meets the design requirements, it can be used directly.) Otherwise, engineering must be done.

2. Pipe pile treatment method: check the depth of the injured part, and put the reinforcement cage in the pile according to the depth.

The depth exceeds the depth of injury not less than 2 meters, and then pour high-grade micro-expanded cement concrete, if it is a cast-in-place pile.

If it is disconnected or the depth of the injury is not deep, you can use an excavator to dig to the injured place, cut off the pile, and then hit the steel bar and reconnect the steel bar formwork to pour concrete.

3. Friction pile.

It is the use of the friction between the formation and the foundation pile.

It can be divided into pressure piles and tensile piles, which are generally used in the formation without a hard bearing layer or a deep bearing layer.

4. End bearing pile: the foundation pile is located on the bearing layer (rock plate) so that the structure can be loaded.

5. Prefabricated piles: through pile drivers.

Prefabricated reinforced concrete piles are driven into the ground. The advantage is that the material is saving, the strength is high, and it is suitable for buildings with higher requirements, and the disadvantage is that the construction difficulty is high, and the construction time is long due to the limitation of the number of machinery.

6. Cast-in-place pile: drill holes on the construction site, and put the steel bars into the pouring concrete when the required depth is reached. The advantage is that the construction difficulty is low, especially the manually dug piles.

It can be constructed at the same time without the limitation of the number of machinery, which greatly saves time, and the disadvantage is that the bearing capacity is low and the material is expensive.

The first type of pile is the waveform law of the reflected wave, clear, no defective reflected wave, the reflection at the bottom of the pile is obvious, the wave speed is normal, the second type of pile is the basic rule of the reflected waveform, there is a weak reflected wave, but there are no multiple reflections, and the reflected wave at the bottom of the pile can be distinguished.

According to the on-site concrete pouring record, the oversealing height of bored pile concrete pouring is generally 60-80cm, and the technical guide for the construction of passenger and freight co-linear railway bridge and culvert engineering stipulates that the oversealing height is 50cm-100cm, although the oversealing height meets the requirements of the guide, but the highway is generally close to the lower limit, resulting in the strength of the pile top is not high, and it is also one of the reasons for the generation of the second-class pile of the highway.

The first type of pile belongs to the pile without defects, and the second type refers to the pile with slight defects, but can continue to be used after simple treatment, and is counted as a qualified pile. The three types of piles belong to waste piles and must be treated with certain measures.

There is no problem with a class of piles.

The second type of pile is a slight problem, but it does not affect the use, and it is also a qualified pile, if it is a third type of pile, it is a big problem, which may affect the use, and it is necessary to carry out a static load test or high strain to confirm whether it can be used.

Four types of piles, unqualified, directly fill the pile.

Class perfect pile, class good pile, class treatment pile, class scrap pile.