FR2810350A1 - METHOD FOR CONTROLLING THE STATIC STABILITY OF A CONCRETE FOUNDATION OF AN OVERHEAD LINE PYLON - Google Patents

Abstract

To control the static stability of a concrete foundation (2) supporting an angle post (1) of an overhead line pylon made according to a lattice design, a force pulse (3) is exerted on the post d angle (1) and the reaction of the environment is measured using seismographic sensors (4) and analyzed.

Description

: 1 The invention relates to a method for controlling static stability

  of a concrete foundation supporting a corner post of an overhead line pylon made in a lattice design, using a force applied to the corner post. Over the past few years, overhead pylons have been knocked down by storms. During appraisals, it was sometimes found that the concrete foundations of the overhead truss pylons had failed. The concrete foundations of pylons for high-voltage lines are based on the principle that the corner posts transmit the force to the concrete studs by means of cleats or by friction by adhesion. To optimize costs, many foundations have a stepped structure, so that the weight of the earth located above the different stages of the concrete block also comes into play when the block is stressed in tension. For old airlines, the available study documents are sometimes insufficient. Assembly errors can also be responsible for an insufficient bearing capacity of the foundations. Operators of overhead lines are, however, required to guarantee the static stability of the pylons during their entire operating life. The weak points of the foundations having been highlighted - by the storms - they must be checked. In the context of known measurements of the type indicated in the introduction, we exerted on the corner post continuous traction forces with a traction device bearing on the ground a few meters to the left and right of the foundation to control. The tensile forces necessary for control can reach 3,000 kN. Because of its geometry and the high level of forces, the installation on the ground of such a traction control device is very complicated. This technique has therefore mainly been used only for approval tests. If you want to control a large number of overhead pylon foundations already in place, it is necessary for economic reasons

  to develop a more efficient process.

  The object of the invention is to achieve faster, simpler and safer control of static stability

  of pylon foundations of overhead lines.

  To this end, the present invention provides in a method of the type indicated in the introduction that a force pulse is exerted on the corner post and that the reaction of the environment is measured using

  seismographic sensors and analyzed.

  As the transmission of the force to the foundation takes place via the corner post, we have as a physical model a damping system with elastic mass. Due to the transmission of the force pulse to the corner post, this elastic mass system will provide a corresponding reaction response which can be

  recorded by appropriate sensitivity sensors.

  The masses can be deduced from it by corresponding calculation methods, which ultimately provides information on the static lift of the foundation pad. In the end, the method according to the invention allows the desired control to be carried out very quickly and efficiently, so that entire lines and, respectively, entire networks

  can be safely controlled.

  According to a preferred embodiment, the force pulse is oriented in the direction of the axis of the angle post. If the force pulse is oriented in the direction of the axis of the corner post upwards away from the foundation, the earth load also acts as mass. Ideally, the control will be carried out on an angle upright which is dissociated from the whole of the pylon by opening the assembly gussets. As during this

  time the pylon must nevertheless remain anchored and that the main-

  work is considerable, comparative checks can be carried out through comparative measurements without dissociating the individual angle amount from the set

  of the pylon. If the force pulse is just transmitted

  above the foundation, a sufficiently long propagation time of the reflections coming from the pylon may correspond to a well dissociated transient response

in terms of measurement.

  In the simplest case, the force pulse can be delivered with a pulse hammer, sensors can be integrated into the head of the hammer; we can then use modal analysis and seismic analysis models. In the presence of large foundations, it may however be necessary to give the force impulse a fairly high intensity. This can be achieved by exploding a propellant charge or by preloading an elastic mass system, which operates with mechanical, electrical, pneumatic or hydraulic drive. Again, there are, as seismographic sensors, displacement, vibration and / or acceleration sensors or pressure or acoustic sensors. As the earth load is differently compacted and can be made of various materials, such as for example silt, sand, pebbles, etc., it may be necessary to collect the transient response not only at the level of the angle post or directly on the concrete block, but also around the pylon on the ground surface. Through measurements made at different distances on each corner post, we can

  also determine the earth charge cone.

  The invention will be explained in detail below with reference to a drawing, the single figure of which schematically shows an overhead line pylon produced according to a lattice design. The overhead line pylon is supported by individual foundations 2 via at least three corner posts 1. To control the static stability, a force pulse 3 is delivered using a pulse hammer , on the corner post 1 located on the left in the figure, in the direction of the axis of the corner post 1 upwards. The reaction of the environment is measured using seismographic sensors 4, which are located on the corner post 1, on the foundation 2 and on the ground 5 in the area of the earth load cone, and is

  analyzed using known methods.

Claims (7)

  1. Method for controlling the static stability of a concrete foundation (2) supporting an angle post (1) of an overhead line pylon made according to a lattice design, using a force applied to the corner post, characterized in that a force pulse (3) is exerted on the corner post and the reaction of the environment is measured using   seismographic sensors (4) and analyzed.   2. Method according to claim 1, characterized in that the force pulse is oriented in the direction of the axis of the corner upright.   3. Method according to claim 1 or 2, characterized in that the force pulse is oriented in the direction of the axis of the corner post upward away from the foundation.   4. Method according to one of claims 1 to 3,   characterized in that the force pulse is delivered when the angle post is dissociated from the rest of the pylon of airlines.   5. Method according to one of claims 1 to 4,   characterized in that the force pulse is delivered using an impulse hammer or a mass system prestressed elastic.   6. Method according to one of claims 1 to 5,   characterized in that the seismographic sensors used are sensors for travel, displacement, vibrations and / or acceleration or sensors for pressure or acoustic.   7. Method according to one of claims 1 to 6,   characterized in that the seismographic sensors are installed on the corner post, on the foundation and / or in the area of the foundation earth cone.