What is self balancing pile foundation detection?

Self-balancing methodPile test, first of all, calculate the balance point. The pressure box is placed here, and the bearing capacity of the upper section pile and the lower section pile is equal, that is, balanced, and the sum of the bearing capacity of the upper and lower sections of the pile measured at this time is the bearing capacity of the single pile. Of course, taking into account the following reasons, the reduction factor is usually multiplied by the ultimate load of the pile in the upper section.

In the usual pile test, the load is added to the top of the pile. For friction end-bearing piles, the axial direction of the pile is due to the gradual decrease of the pile pressure with the depth of the pile.

The compression also decreases with depth, so when the upper part of the pile reaches the limit value of side friction, the side friction of the lower part of the pile is far from reaching the limit value. Therefore, the self-balancing method, for friction piles controlled by deformation.

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Precautions for pile detection.

It is necessary to pay attention to the implementation of low-energy transient or steady-state excitation on the top surface of the pile, so that the pile can do elastic vibration in the elastic range, and thus produce the longitudinal propagation of stress waves, and at the same time, the integrity of the pile is evaluated by using the wave and vibration theory. The main use of pile low strain detector.

High strain method. It is a detection method to determine whether the vertical compressive bearing capacity of a single pile meets the design requirements and evaluates the integrity of the pile by measuring and calculating by carrying out a heavy hammer on the top of the pile, so that the dynamic displacement of the pile is close to the settlement of the conventional static load test pile, so that the rock and soil resistance around the pile can be fully exerted. The main use of pile high strain detector.

The self-balancing method is different from the traditional stacking method and the anchor pile method, the technology is to place the load box made according to the requirements of the pile bearing capacity parameters at the bottom of the pile body in the construction process, connect the pressure tubing and the displacement measurement device at the top of the pile, and after the concrete is cured to the standard age, the bottom load box is pressurized by the top high-pressure oil pump to obtain the bearing capacity of the pile end and the total friction resistance of the pile side.

Technical advantages – simple test environment.

The self-reaction method no longer requires an external loading force, so it can complete the test that cannot be completed or is difficult to complete by the traditional loading method when facing some pile foundations (difficult piles) where the test environment is very difficult.

Here, difficult piles refer to super-large tonnage pile foundations, pile foundations in slope, water, deep excavation and other environments, as well as some other pile foundations that do not have stacking and anchoring pile conditions.

The advantage of the self-reaction method makes it possible to complete the pile foundation test, which makes an irreplaceable contribution to the quality assurance of architectural design and construction, and reflects its huge technical value and social value.

Technical disadvantage – complex technical details.

Compared with the traditional method, the self-reflexive method has a short development history and low technical maturity and popularity, so there are still many problems in the details of experimental implementation and key technologies. For example: the determination and selection of pile test methods, the selection and installation of load boxes, the safety protection and repair measures of pile bodies, the accuracy assurance of displacement measurement methods, etc., these technical details need to be continuously developed and improved through a lot of practice and research.

At present, the static load test of pile foundation mainly includes the following types of loading methods: stacking method, anchor pile method and self-balancing method or self-reaction method.

Among them: the stacking method, which is to pile enough counterweight on the ground to provide the loading reaction force to achieve the loading of the pile foundation. It is a traditional test method.

The anchor pile method is a traditional test method that uses the auxiliary pile near the test pile as the reaction support, and the load test on the pile foundation.

The self-reaction method is a method of self-loading in the pile foundation with its own bearing capacity as the loading reaction force and realizing self-loading, which is a new experimental technology developed in recent years.

Of course, in practice, the "comprehensive method" can also be used, i.e. a combination of the above test methods.

The detection principle is to --- a special loading device into the load box, bury it in the corresponding position in the pile together with the reinforcement cage before the concrete is poured, and lead the pressurized pipe of the loading box and other test devices required from the pile body to the ground, and then pour into the pile. There is a pressurized pump in the ground like a load box pressurized loading, so that the pile body inside the load force, through the calculation and analysis of the relationship between the load force and these parameters, we can not only obtain the bearing capacity of the pile foundation, but also can obtain a series of data such as the lateral resistance coefficient of each layer of soil, the side resistance of the pile, the bearing force at the end of the pile, etc., this method can be used to provide data basis for the design, and can also be used for the inspection of the bearing capacity of the engineering pile. This method is called the self-balancing method or the self-reflex method.

The self-balancing method is a static load test method based on seeking the loading reaction force inside the pile foundation. Correspondingly, the implementation technology of this test method is called "self-reflex method pile measurement technology" or "self-equilibrium method pile measurement technology". According to the existing verifiable archival records, the method of detecting the bearing characteristics of pile foundation by the embedded loading equipment in the pile, which is named the "self-balancing method" in China, was first proposed and implemented by the Israeli company Afarvasela in the 1960s.

According to the patent information, this method is called "a new bearing capacity test method", commonly known as the "Tongmo static load method". Different from the traditional stacking method, this technology is to place the load box that is made according to the requirements of the pile bearing capacity parameters at the bottom of the pile body in the construction process, connect the pressure tubing and the displacement measurement device at the top of the pile, and after the concrete is cured to the standard age, the bottom load box is pressurized by the top high-pressure oil pump to obtain the bearing capacity of the pile end and the total friction resistance of the pile side.

- By loading the pile foundation in sections, the performance of the pile foundation and each soil layer is fully mobilized by using the reaction force of each section of the pile foundation, and the performance parameters are accurately recorded.

Through scientific data analysis, the real characteristics of the test pile foundation and each soil layer are obtained.

According to the characteristics of the pile foundation and each soil layer, a series of safety conclusions such as the ultimate bearing capacity of the pile foundation are derived.