What is the core pulling of rotary digging piles? Pile foundation borehole core pulling inspection?

The pile foundation is the main load-bearing part of the structure, and its quality is directly related to the safety and longevity of the structure, so the pile foundation is detected.

It is especially important. At present, pile foundation detection technologies include low strain, acoustic transmission method, static load, drilling coring, high strain, etc. This article shares the drilling coring method.

1. Basic principle and purpose of testing.

The drilling and coring method mainly uses a drilling machine (generally with 10mm inner diameter) to carry out core sampling on the pile foundation, and according to the core sample, the length and concrete strength of the pile foundation can be determined.

The thickness of the sediment at the bottom of the pile and the bearing layer.

The situation and so on to make a clear judgment.

2. Scope of application.

The drilling coring method is suitable for detecting the length of the pile foundation, the strength of the concrete, the thickness of the sediment at the bottom of the pile, the condition of the bearing layer, etc., and is often used in the detection of rock-socketed piles.

Drill core core samples.

3. Analysis of advantages and disadvantages.

The bored coring method is more intuitive, and it can not only understand cast-in-place piles.

It is the only reliable way to test the concrete strength of cast-in-place piles. However, this method is limited by the view of one hole, and the judgment of local defects and horizontal cracks of pile foundation is not necessarily very accurate, and is generally combined with other detection methods. The cost of drilling and coring method is related to the length of the pile, which is about 10,000 yuan per pile.

The above is the detailed analysis of the drilling coring method of the pile foundation detection method, have you learned? Geotechnical engineering.

The construction design and construction are also different according to the geological conditions of each region, and the geotechnical people need to learn more, and at the same time, they should also learn more about the latest norms and standards, and update them in time. Pay attention to the geotechnical knowledge channel of the construction industry, share more construction geotechnical knowledge related to the drilling and coring method of pile foundation detection methods, and learn and progress with you!

The core pulling test of pile foundation boring is suitable for testing concrete cast-in-place piles (the pile diameter is generally not less than and the pile quality of the underground diaphragm wall (such as the concrete cementation condition of the pile body, whether there are porosity, segregation, looseness, broken pile, mud inclusion, honeycomb, dog hole, etc.), concrete compressive strength, sediment thickness, contact relationship between concrete and bearing layer and rock (soil) properties of the bearing layer at the bottom of the pile, etc.

The quality evaluation of piles should be carried out according to a single pile. When one of the following situations occurs, it should be judged that the inspected pile does not meet the design requirements:

l. Pile integrity category is W type pile;

2. The representative value of the compressive strength of the core sample sample of the inspected pile concrete is less than that of the pile with the design strength grade on the concrete

3. The pile length and the thickness of the sediment at the bottom of the pile do not meet the requirements of the design or specification

4. Piles whose properties (strength) or thickness do not meet the requirements of the design or specification on the bearing layer rock at the end of the pile.

5. When the core hole deviates from the pile, only the core sample part of the drill is evaluated.

It is suitable for testing the concrete strength, integrity, pile length, ballast thickness at the bottom of the pile, and the properties of the rock and soil layer at the bottom of the pile of the concrete cast-in-place pile with a pile diameter of 800mm.

The concrete cementation properties of the core sample, the type and uniformity of the aggregate, and the properties of the rock and soil layer at the bottom of the pile should be observed, and the compressive strength test should be carried out on the core sample.

The integrity of the pile should be classified according to the characteristics of the concrete core sample on site, combined with the core drilling records and test results, according to the relevant regulations and specifications, combined with experience.

Measurement project parameters and allowable deviations:

1.Average diameter: Vernier calipers measure the middle of the core sample with a measurement error of 1 mm and a permissible deviation of 2 mm from the average diameter

Core height: measured by steel plate ruler.

Perpendicularity: Vernier protractor measurement.

Flatness: Measured by steel plate ruler and feeler gauge.

2. It shall be carried out in accordance with the provisions of the compressive test of the cube test block.

3. Calculation of conversion value: fc cu= (4f) (d2) fc cu—conversion value of concrete strength of core sample, mpa; f—the maximum pressure measured by the compressive test of the core specimen, n; d—the average diameter of the core sample, mm; —Correction coefficients for the conversion strength of concrete of different height-diameter ratio core specimens.

4. Correction of conversion value: CECS 03:88: Correction of height-diameter ratio JGJ106-2003: Avoid correction of height-diameter ratio, requiring not less than D or not greater than D

5. The core sample that cannot be tested for compression: Height: less than the average diameter, greater than the average diameter of the average diameter, and the deviation from the average diameter is greater than 2 mm perpendicularity

>2° Unevenness: Cracks and large defects within 100 mm over mm.

Rotary digging pile refers to the pile type constructed by the rotary drilling rig, the full name is rotary boring bored pile, and the project is referred to as rotary drilling pile.

In China, it is a more advanced pile foundation construction technology that has only been popularized in recent years, and is widely used in the foundation pile construction of roads, railways, bridges and large buildings. In the early days, most of the rotary drilling rigs used were imported from Germany and Italy or second-hand rotary drilling rigs from Japan. In recent years, with the promotion of projects such as the Qinghai-Tibet Railway and the Beijing Bird's Nest, foreign imported brands have continued to pour in, and similar products in China have gradually developed.

Cause analysis.

1. The concrete pouring time is too long, the concrete is poured first and is close to the final setting time, and the reinforcement cage is vibrated and segregated, and the effluent is poured along the pipe wall and then poured into the fresh concrete to form a cavity.

2. When lifting the conduit, it was not noticed that the conduit was blocked by concrete, resulting in the cavity left on the upper part of the pile after the conduit was pulled out and not filled with concrete.