RU2190865C2 - Method determining length of current-conducting pile buried in medium and device for its realization - Google Patents

Abstract

FIELD: measurement technology, determination of length of current-conducting pile of bearing structures of ground and sea installations buried in medium. SUBSTANCE: vertical distribution of specific conductance of medium by way of its electromagnetic sounding is found in advance. After this low-frequency current is transmitted through medium between pile and grounding electrode and its value in pile is measured. Length of part of pile buried in medium is evaluated by value of current in pile and known distribution of specific electric conductance of medium. Device for realization of method has voltage source in the form of low-frequency generator connected to pile and grounding electrode and instrument current transformer. Instrument current transformer has split magnetic core embracing pile. Method makes it possible to determine length of buried part of individual pile and supporting structures comprising several piles electrically interconnected independent of properties of medium. EFFECT: raised functional reliability of method and device. 2 cl, 1 dwg

Description

 The invention relates to measuring the length, in particular, of an electrically conductive pile immersed in an environment, mainly single and several piles, combined into a single structure, for example, supporting structures of land and offshore structures.

 A known method and device for determining the length of a pile or other elongated object in the process of driving into the ground with a hammer or similar device, based on the principles of propagation of acoustic waves in a pile and environment [1]. To implement the method, measure the time of reception of the acoustic signal that occurs at the time of impact on the object, and compare it with the reference signal. The results of a comparison of these signals indicate the depth of advancement of the pile into the ground. Its main disadvantages include the ability to determine the length of the buried part of the pile only in the process of driving it into the ground and the inability to determine the length of the buried part of each of several piles combined in a single design.

 A known method and device for determining the length of an electrically conductive pile (metal rod electrode) buried in the medium [2]. The method and device allows to determine its length by the known specific electrical resistance of the medium into which the pile is buried, and by the constant electric potential measured on the surface of the medium. The method is based on measuring the electric potential on the surface of the medium from piles (metal rod electrode) and a grounding electrode. For its implementation, a rod metal electrode (pile) is buried in the ground and a direct current is supplied to it, and another electrode, the ground electrode, is placed at a very significant distance from the pile. At a sufficiently large distance from the metal rod electrode, a constant electric potential is measured, and the length of the buried metal electrode is determined from the calculated grounding resistance of the electrode and the known electrical resistivity of the medium. This method and device have disadvantages determined by the features of the physical method used, which do not allow determining the length of the electrode without knowing the electrical resistivity of the medium from the measured electric potential, it is impossible to determine the lengths of the buried part of each of several metal electrodes if they are combined into a single design in which each the electrode is electrically connected to others.

 The technical task to be solved is the development of a method and device for determining the length of an electrically conductive pile buried in the environment, which allows measurements of the geometric dimensions of individual buried piles and supporting structures, consisting of several electrically conductive piles that are electrically interconnected and buried in the medium, regardless of the properties of this medium ( loose, waterlogged deposits, bedrock on the shore or water area).

 The essence of the method for determining the length of an electrically conductive pile buried in the medium is that the electromagnetic sounding of the medium is preliminarily carried out and the vertical distribution of the electrical conductivity of the medium is determined, then a ground electrode is placed in the medium and an alternating low-frequency alternating current is passed between it and the electrically conductive pile, while measuring the magnitude of the current flowing along the pile, the magnitude of which and the known distribution of the specific electrical conductivity and the medium judges the length of the pile immersed in the medium, and the distance between the ground electrode and the pile is chosen so as to ensure uniformity of the electromagnetic field in the medium.

 A device for determining the length of an electrically conductive pile buried in the medium according to the patented method comprises a voltage source, one clamp of which is connected to the conductive pile, and the second to a grounding electrode located in the pile zone, the source of electromagnetic excitation of the medium located on the surface of the medium in the pile zone, a signal receiver , distorted by the probed medium, as well as the receiver signal processing unit, converting it into values of specific electrical conductivity. The voltage source is made in the form of a low-frequency voltage generator, and the device comprises a current measuring transformer with a detachable magnetic circuit enclosing a pile, the secondary winding of which is connected to a current meter.

The drawing shows one of the possible embodiments of the device, where the numbers indicate:
1 - source of electromagnetic excitation of the medium;
2 - receiver of electromagnetic excitation of the medium;
3 - block conversion of the signal of the receiver into the values of electrical conductivity;
4 - low frequency voltage generator;
5 - conductive pile;
6 - grounding electrode;
7 - measuring transformer with a secondary winding;
8 - a detachable element of the magnetic circuit;
9 - current meter.

 The device contains a source of electromagnetic excitation of the medium (1), a receiver of electromagnetic excitation of the medium (2) and a unit for converting the signal of the receiver to the values of specific electrical conductivity (3), a low-frequency voltage generator (4) connected by wires to the electrically conductive pile (5) and the ground electrode (6), a measuring transformer with a secondary winding (7) by means of a detachable element of the magnetic circuit (8) is worn on an electrically conductive pile and connected to a current meter (9).

 The method for determining the length of an electrically conductive pile buried in the environment is as follows: in the immediate vicinity of the buried pile, electromagnetic sounding of the medium is carried out using a medium electromagnetic excitation source, a receiver and a signal converter, and the vertical distribution of the specific electrical conductivity of the medium is determined, to one terminal of the low-frequency voltage generator by a wire they connect an electrically conductive pile, and to the second terminal a ground electrode, which is earthed medium at a distance that ensures field uniformity in the medium, and an alternating electric current is passed, the frequency of which is selected, in particular, not higher than 100 Hz, a measuring transformer with a secondary winding is put on a pile by means of a detachable magnetic circuit element, connected to a current meter and the current value is measured, flowing along the pile, by the magnitude of the measured current and the known distribution of the electrical conductivity of the medium, judge the length of the pile immersed in the medium. In the case when there is a structure of several electrically connected piles, a measuring transformer with a secondary winding is put on each of the piles, the current flowing through each pile is measured, and the length of each of the piles immersed in the medium is judged by the known distribution of electrical conductivity of the medium .

A device for determining the length of an electrically conductive pile buried in the medium operates as follows: in the pile zone, an electromagnetic field is excited in the medium using a source of electromagnetic excitation of the medium (1), which is received by the electromagnetic excitation receiver (2) and converted using the signal conversion unit of the receiver (3) in the values of the specific electrical conductivity of the medium, the low-frequency voltage generator (4) is stabilized in frequency and provides a constant voltage value maintained in a circuit consisting of an electrically conductive pile (5), a grounding electrode (6), a medium and wires leading to the pile, an electrically conductive pile on which a measuring transformer (7) is worn with a detachable element of the magnetic circuit (8), is its primary winding, in which an alternating electric current flows, generated by a low-frequency voltage generator (4), the magnitude of the current transformer induced in the secondary winding is measured using a current meter (9) operating at the same frequency as the low-voltage generator frequencies
The source of electromagnetic excitation of the medium, the receiver of electromagnetic excitation of the medium, and the converter of the signal of the receiver to the values of the electrical conductivity of the medium can be specifically implemented in standard geophysical equipment for determining the electrical parameters of geological sections. Standard devices can be used as a low-frequency generator and a low-frequency current meter.

 A method and apparatus for determining the length of an electrically conductive pile buried in the environment were implemented in a laboratory simulator. Taking into account the principles of electromagnetic similarity at a geometric scale of 1: 100, a model was made of one of the four pillars of an offshore drilling platform. The underwater platform of the support with a diameter of 35 mm had eight piles with a diameter of 1.5 mm each from 115 to 150 mm long, was immersed in a concentrated salt solution. Using a generator with a frequency of 20 kHz connected to a support model and a grounding electrode, a current was generated in the model, the value of which on the longest pile was 0.22 μA. The measuring transformer was wound on a ferrite ring (330 turns, wire diameter 0.05 mm), which was worn on each of the piles to measure the strength of the flowing current. Studies have shown that in laboratory conditions at this installation it is possible to determine the change in the length of the pile with an error not exceeding 3%.

Sources of information
1. Patent for invention 2251943, UK.

 2. Matveev B.K. Electrical Intelligence, M .: Nedra, 1990, pp. 31-32 (prototype).

Claims (2)

 1. A method for determining the length of an electrically conductive pile buried in the environment, based on the measurement of the physical parameters of the conductive pile, characterized in that the electromagnetic sounding of the medium is preliminarily carried out and the vertical distribution of its specific electrical conductivity is determined, after which a ground electrode is placed in the medium and between it and the conductive pile pass an alternating electric current of low frequency, while simultaneously measuring the amount of current flowing along the pile, the magnitude of which and from the known distribution of the electrical conductivity of the medium is judged on the length of the pile immersed in the medium, and the distance between the grounding electrode and the pile is chosen sufficient to ensure uniformity of the electromagnetic field in the medium.  2. A device for determining the length of an electrically conductive pile buried in the medium, containing a voltage source, one clip of which is connected to the electrically conductive pile, and the second to an electrode located in the pile zone, a source of electromagnetic excitation of the medium installed on the surface of the medium in the pile zone, a signal receiver, distorted by the sensed medium, as well as the receiver signal processing unit, converting it into values of electrical conductivity, characterized in that the voltage source is made in the form of a generator low frequency and the device contains a measuring current transformer with a detachable magnetic circuit enclosing a pile, the secondary winding of which is connected to a current meter.