GOST 5686-2012 Soils. Methods of field testing with piles

Understanding the underlying soil is essential to constructing sturdy and dependable structures. Here’s where GOST 5686-2012 is useful. This standard offers instructions on how to use piles to test soil in the field, a crucial technique for determining the properties of the soil before building starts.

An integral component of geotechnical investigations is field testing involving piles. They aid engineers in figuring out the behavior of soil under load, which is essential to guaranteeing the stability of foundations. The procedures for conducting these tests, which guarantee accurate and dependable results, are outlined in GOST 5686-2012.

In addition to providing procedure details, this standard guarantees uniformity amongst various testing scenarios. Engineers can confidently evaluate soil conditions and make well-informed decisions regarding the design and construction of foundations by adhering to GOST 5686-2012. Knowing this standard can help you in every way, whether you’re working on a big commercial development or a small residential project.

Section	Description
Introduction	Overview of field test methods for soil using piles according to GOST 5686-2012.
Scope	Details the standards and conditions under which soil tests with piles should be conducted.
Equipment	Lists the necessary tools and devices for carrying out pile tests.
Procedure	Step-by-step guide on how to perform the soil tests using piles.
Data Recording	Instructions on how to document the test results accurately.
Safety Measures	Precautions and safety protocols to follow during testing.

Terminology

Three categories of supporting elements are allowed to be used for testing according to the standard:

• A full-scale sample, which is a real product used in conventional construction. The geometric dimensions, the material from which it is made, as well as the installation method fully correspond to the actual conditions of the construction site. In particular, if a full-scale sample is planned for testing a bored pile foundation, then its installation must be carried out taking into account the rules and technology for installing similar elements. In this case, drilling of the shaft, installation of formwork, reinforcement, pouring of concrete must be carried out.
• A reference pile made of a composite metal rod that imitates a standard driven-type product and has a diameter of 114 mm. A standard assembled from individual segments has a length of 12 meters.
• Probe pile made of composite metal elements with a diameter of 127 millimeters. It has a pole tip and is equipped with a friction clutch. The assembled probe is 16 meters long.

Figures A.1 and A.2 display the reference pile and probe pile design diagrams.

Figure A.1: The probe pile’s design diagram

The reference pile’s design diagrams are shown in Figure A.2.

Stages of work

At the following stages, GOST controls both required static tests and dynamic tests of piles:

• at the stage of surveys and implementation of design activities in order to determine the cross-section, dimensions, and also to assess the bearing capacity provided for by the project. Based on the results of the measurements taken, specialists make a conclusion about the correct calculation of the parameters, and in case of discrepancy, they perform a re-calculation;
• during the immersion and extraction of piles, which allows you to compare the real ability to absorb forces with the design data.

Types of pile structures listed in a table

The accuracy of the measurements that are obtained as a result of static control is higher. Compared to data acquired through the dynamic method, they are more trustworthy.

Problems solved by static checking

Testing operations are conducted in the field for the following reasons:

• Selecting the design of products planned for use at the facility being built, determining their geometric parameters and ability to withstand forces.
• Determining in practice the possibility of driving piles to the depth specified by the project for a given type of soil, assessing its homogeneity.
• Determination of the amount of movement of piles in proportion to the applied influences during a time specified by the standard.

Static load testing is done on piles to verify that the products can actually withstand the total forces specified in the building design.

GOST 5686-2012 provides important guidelines for evaluating soil stability and load-bearing capacity and describes how to test soil in the field using piles. Because it offers an organized method for assessing soil conditions on the construction site, this standard is crucial for engineers and other construction industry professionals. You can guarantee the dependability of foundation designs as well as the general durability and safety of structures by adhering to these procedures.

Methods of static testing

Static tests are conducted by applying alternating loads to the tested product, depending on the force application method chosen. Depending on the loading technique, the required apparatus is chosen:

• a special loading device, which is a hydraulic jack or a platform with a load, the weight of which can be adjusted. It is allowed to use special tension couplings, winches;
• a prefabricated structure made of metal beams and reinforced concrete slabs with anchors, transmitting forces to the tested structure;
• a measuring device for monitoring the amount of immersion under the influence of force. The device consists of a group of measuring devices combined into one complex. The accuracy of measurements must be ensured up to 0.01 mm.

Figures B.1 and B.2 depict installation schemes for testing soils under static indentation loads.

Schemes of installations for using piles to test soils, sheet 1 (Figure B.1)

Sheet 2, Figure B.2

Technology of static tests

As per the standard’s requirements, pile testing is performed using the subsequent algorithm:

• A program and methodology for performing the test are developed, containing information on the maximum force transmitted to the structure, the load distribution step, which should be 10% of the mass of the calibrated load.
• The design organization determines the number of products for testing soils with piles, the places of their driving.
• On the future pile field, a group of piles is driven in zones corresponding to the worst, most unfavorable conditions or places where failures occurred during driving.
• The loading structure is installed, a set of equipment ensuring the transfer of forces.

Static pile testing

There are three steps involved in checking piles with a static load:

• preparation of the support being tested;
• testing;
• processing of the obtained information.

As per GOST, the process of preparation allows for a "rest" period, which lasts for the following duration:

• 1 day, if immersion is carried out in dense layers of sand or large-fragment massifs.
• 3 days for sandy foundations.
• 6 days for clayey surfaces and heterogeneous masses.
• 10 days for water-saturated and fine sands.
• 20 days for fluid, plastic and soft clay fractions.

Pile testing, according to the provisions of the document, is a sequential increase in load. The amount of immersion in a dense soil mass during the first loading cycle can be one fifth of the total mass of the calibrated load. The force is applied when stabilizing the position after the previous cycle of load application. Control of the settlement value is checked with watch-type deflection meters and electronic devices, the division value of which is 0.1 millimeter. Before applying the force, the data of all devices are reset to zero and after each cycle of exposure to the load, the readings of all devices are monitored. The criterion for stabilizing the position is a movement of no more than 0.1 millimeters over the last 60-120 minutes of observation.

The full-scale sample sags more than 40 millimeters during the test when peak force values are applied, and reference products are pushed at least 20 millimeters into the ground. The specific ultimate resistance is equal to the force at which the loading is halted.

Measurement outcomes are noted in the observation log. Graphs that enable inferences regarding the necessary number of supports, their geometry, and the depth of embedment are created once the tests are finished. The future building’s foundation is designed using the measurement data as a basis.

Dynamic test

It is performed with specialized immersion equipment. The level of soil immersion is tracked during testing for every hammer impact cycle. As it slowly sinks into the soil, the support begins to feel the resistance. It is demonstrated by the idea that failure gains less significance as one gets deeper. The foundation of this test is the relationship between the structure’s bearing capacity and the impulse of the equipment’s operating component.

In the course of testing, experimental driving is done. Based on the results, the ideal length for the supports is established, and the conformance of the theoretical and real values of failure is evaluated. By using these measurements, you can identify the soil’s bearing layers, identify weak areas in the pile field, and calculate the forces that the driven supports are likely to experience. When the dynamic control is finished, the results are graphically displayed and describe the position’s coordinates with respect to the applied forces.

Pile dynamic testing with additional weight installed on them

This approach has several benefits over the static testing method, including:

• minor costs associated with the use of equipment available at the construction site;
• speed of work, which can be completed within one working day;
• the ability to use any type of product for testing, regardless of their ability to withstand applied forces.

The potential for overestimating resistance to loads when the tip, which penetrates heavy soils, enters an easily compressed, deformable soil layer is the drawback of the dynamic testing method.

It is recommended by the standard to compare the indicators of static tests with the data from dynamic measurements. On light sand soils, pile foundation construction does not employ this testing technique.

It is essential for anyone working in construction or soil testing to comprehend GOST 5686-2012. The methods for conducting pile field tests, which are crucial for figuring out how well a pile will function in different soil conditions, are outlined in this standard. It’s important to make sure that the pillars upon which our structures are built are sturdy and trustworthy, not merely to adhere to a set of regulations.

Engineers and construction experts can accurately assess pile behavior and soil properties by adhering to GOST 5686-2012. By doing this, it is ensured that the piles used in construction will be able to sustain the intended loads and weather conditions. A methodical approach to testing is provided by the standard, which helps avert future issues.

In the end, following these rules contributes to preserving the durability and stability of infrastructure and buildings. It’s a step in the direction of building projects with improved quality and safety. Professionals who adhere to the guidelines provided in GOST 5686-2012 enhance the general dependability and success of their projects.

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