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The classification of non-pressure pipes is traditionally produced in terms of the standard dimensional ratio ( SDR.), and by the class of ring rigidity ( SN.). Fundamental difference SDR. and SN. that SDR. - this is a geometric characteristic of the pipe (the ratio of the external diameter of the pipe to the thickness of its wall), while SN. - This is a mechanical characteristic.

Ring rigidity SN. Allows you to judge the properties of the pipe to resist the pressure of the soil and is defined as the load on the pipe (KN / M2), in which the pipe is squeezed by 3% of its diameter. Value SN. It depends not only on the diameter of the pipe and the thickness of its wall, and also from the modulus of elasticity E. Material with compression.

Pipe labeling cable line should include pipe diameter D., wall thickness e., ring rigidity SN., limiting effort of these F. 1max , long permissible temperature T.At which the annular rigidity remains no less than the service life of the cable.

Parameters D., e., SN. and T. Must be monitored when the pipes are delivered to the objects under construction. Value F. 1max It may be necessary later - already at the stage of performing work on tightening pipes in the drilling channel, when the installation GNB operator will control the actual effort of the tension F. and interrupt the tightening process of a beam from N. Pipes in the case F. > 0,5 · N. · F. 1max In order to prevent the tube break.

Choosing a diameter and thickness of the pipe wall

Figure 1 shows the external diameter tube D. and wall thickness e.within which the cable is laid an external diameter d.. According to regulatory documents, when choosing an external pipe diameter, follow the following rule:

Pipe wall thicknesse. Determined in the course of mechanical calculations based on the basic information on the conditions of the pipe laying and relies on the concept of ring rigiditySN..

Figure 1. Polymer pipe with cable: without soil pressure ( but), with the pressure of the soil ( b.)

The connection of the wall thickness and ring rigidity is set by the expression:

where E.- Module of the elasticity of the pipe material during compression.

Pipe wall thicknesse. (mm) depending on the pipe diameterD. (mm) and ring rigidity SN. (KN / m 2)

* Are made in one-layer execution

Note: The external diameter of pipes ProtectorFoflex® is specified without taking into account the thickness of the protective coating.

There are two main ways to place pipes in the ground - this is the laying in a pre-prepared trench (Figure 2 but) or tightening pipes into the ground into the prepared channel, which is often performed by horizontal directional drilling (Figure 2 b.). In both cases, the calculation of the pipe is built on the concept of ring rigidity SN., on the basis of which it is possible to determine not only the thickness of the pipe wall, but also the limiting force of the pipes of the pipe when it is burned in the drilling channel.

Figure 2. Basic methods for laying polymer pipes: trench ( but), GNB method ( b.)

Selecting pipe rings

The vertical pressure of the soil (and transport) on the pipe is the force applied to the pipe and seeking to cause its ovality, but the emerging "soil repulsion", located on the sides of the pipe, seeks to return the form cross section Pipes to the source round. Tight soil on the sides of the pipe is a factor that increases its mechanical strength.

where q. and SN. are measured already in kn / m2, and E " S. - Factor of the stiffness of the soil, which is called the securing unit of the soil (MPa).

Section Module Soil E " S. Depends on the type of soil, which covers the pipe, and the degree of its seal. As a rule, sand is used for these purposes, and then it is recommended to use data to the table.

The vertical load on the pipe (KN / M2) is made up of three components:

where q. R. - load from the weight of the soil (KN / m 2); q. AT. - Load from vehicles (KN / m 2 );

Load from the soil in the most unfavorable case when the entire head of the soil is pressed on the pipe N,

where ρ R. - the proportion of the soil (usually not more than 2 t / m 3); g \u003d 9,81 m / s 2 - acceleration of gravity; H. - Depth of the location of the pipe underground (M).

Transport load can be defined as

Results of calculating the limiting depth of pipes N.dases in the table below. It can be seen that when laying pipes in trenches, it is dangerous to use pipes with ring rigidity of less than 8 and there is no need to apply pipes with SN. More than 64.

Limit depthH. (m) when laying open way under the lawn/ Squares / highways

Selection of limit efforts

When laying the PC GNB method are subjected to two types of influences: first, the longitudinal forces of the fusion F that occur when the pipes occur in the drill canal; Secondly, vertical pressure Soil and transport already during the operation of the pipe. The choice of ring rigidity and wall thicknesses is determined mainly by the efforts of the tension.

Through the effort of the pipe F. Creates friction forces arising due to the weighting of the pipe under the action of the soil clouded onto the soil pipe due to poor fixing the walls of the drill canal with drilling fluids (bentonite) or even the full impossibility of fixing (floating, heavy script).

where q.r. - soil weight in kN / m2; D.Ek. - the equivalent diameter of the flip of pipes of pipes; µ - The friction coefficient of the polymer pipe of the soil (usually equal to 0.2).

Check the permissibility of efforts F.arising when tightening the pipe (plweet pipes) in the drill canal, performed as follows

where 0.5 is the reserve coefficient; N. - the number of pipes in the plenty (one or four); F. 1max - the limit effort of this pipe (KN), which can be found as

where D. and e. - the outer diameter and the wall of the pipe (in mm); σ - The yield strength of the pipe material (MPa).

Terminal efforts F. 1max shown in the table below

Terminal PipeF. 1max (CN) depending ondiameter pipe D. (mm) and ring rigiditySN. (KN / m 2 )

Note. When tightening the polymer pipe in the ground, the efforts of the tension is recommended to limit the safe level of 0.5 F. 1max .

The maximum length of the pipe that can still be tightened into the drilling channel without the risk of its unacceptable stretching or even a cliff,

The table below shows the estimates of the limit length of the drilling channel L. GNB Depending on the number of pipes and the drilling scenario.

Estimates of the limit length of the drilling channel L. GNB (m) depending on the number of pipes N.

This indicator is specified in characteristics Under each product on the site.

Ring hardness pipe PE 100 and PE 80

This indicator is specified incharacteristics Under each product on the sitee.

PVC pipes and Corsis pipesfor sewage

also have ring rigidity. This parameter for equal to 4kN / m 2, for equal to 8 kN / m 2.

Ring rigidity pipes ( SN) - This is one of the physicial and mechanical indicators of pipe strength characterizing the ability of the pipe to withstand external load without significant deformation. Unit of measurement - kN / m2..

The external load includes the loads of the soil when dripping the trenches and transport loads (passenger, cargo cars).

The value of the indicator is indicated in technical conditions to the pipe and is established by the quality control department manufacturing enterprise, as well as the organization for certification of goods, where, on the basis of a positive result of the pipe test, the manufacturer receives a certificate of conformity.

To determine the ring rigidity of the pipe, special testers of various brands are used, depending on the diameter (mm) and the power of pipe compression (KN).

To calculate the indicator, these loads and deformation of the pipe are needed with a 4% deformation of the test sample and the sample length itself. The value is set to the medium-ray based on the three values \u200b\u200bof the ring rigidity of the test pipes obtained from one batch. The final result is rounded in a smaller side.

Ring rigidity is the main indicator of the quality of polymer pipes in the underground construction of non-pressure drainage and sewage systems. The higher the value of this indicator, the greater the loads can withstand the pipe in the external environment.

The absence of this pipe indicator will be reflected primarily on the cheapness of the product, due to the use of low-quality materials.