(Image: Defect in the Sewer)

Question 1: Which is the correct main code?

(Image: Defect in the Sewer)

Question 1: Which is the correct main code?

► Cracking (BAB)

Question 2: Which is the correct characterisation?

(Image: Defect in the Sewer)

Question 1: Which is the correct main code?

► Cracking (BAB)

Question 2: Which is the correct characterisation 1?

► Gaping crack (C)

Question 3: Which is the correct characterisation 2?

(Image: Defect in the Sewer)

Question 1: Which is the correct main code?

► Cracking (BAB)

Question 2: Which is the correct characterisation 1?

► Gaping crack (C)

Question 3: Which is the correct characterisation 2?

► Complex cracking (C)

Question 4: Which is the correct quantification?

(Image: Defect in the Sewer)

Question 1: Which is the correct main code?

► Cracking (BAB)

Question 2: Which is the correct characterisation 1?

► Gaping crack (C)

Question 3: Which is the correct characterisation 2?

► Complex cracking (C)

Question 4: Which is the correct quantification?

► e.g. 5 mm (can only be roughly estimated from the picture)

Question 5: Location on the perimeter?

(Image: Defect in the Sewer)

Question 1: Which is the correct main code?

► Cracking (BAB)

Question 2: Which is the correct characterisation 1?

► Gaping crack (C)

Question 3: Which is the correct characterisation 2?

► Complex cracking (C)

Question 4: Which is the correct quantification?

► e.g. 5 mm (can only be roughly estimated from the picture)

Question 5: Location on the perimeter?

► 2 to 4 o'clock

Question 6: Is the pipe connection affected?

(Image: Defect in the Sewer)

Question 1: Which is the correct main code?

► Cracking (BAB)

Question 2: Which is the correct characterisation 1?

► Gaping crack (C)

Question 3: Which is the correct characterisation 2?

► Complex cracking (C)

Question 4: Which is the correct quantification?

► e.g. 5 mm (can only be roughly estimated from the picture)

Question 5: Location on the perimeter?

► 2 to 4 o'clock

Question 6: Is the pipe connection affected?

► Yes (A)

The consequences of cracks occurring in sewers are essentially influenced by:

• orientation of the crack (horizontal / inclined crack, crack starting at one point, or formation of broken fragments)
• depth of the crack (at the surface or through the wall of the structural component)
• width of the crack
• pipe material (reinforced or non-reinforced)
• position of the crack (in or above the water-bearing area) – position of the pipeline (in or above groundwater)

(Image: Picto Infiltration)

All continuous cracks, i.e. also transverse cracks, represent a priori leaks with the specific damage consequences. The infiltrations or exfiltrations - that may be associated with this - change the bedding conditions of the defective pipe area, so that positional deviations associated with new crack formation or further deformations of the cracked pipe can occur until it collapses. (Image: Picto Schäden) (Image: Environmental …

This load redistribution to areas next to the pipe causes an increase in the horizontal earth pressure (ǭ h ) and supports the possibility of achieving a state of equilibrium by activating the bedding reaction pressure (qh* ), in which the deformed system of pipe quarter segments and soil can then be permanently stable.

(Image: Rigid pipe under load in accordance with Stein, Kentgens and Bornmann) (Image: Cracked rigid pipe: Soil-supported four-joint …

(Image: Picto Statik)

(Image: Four joint ring crack)

Investigations at the Ruhr University Bochum [Stein94b] have shown that pipes cracked in this way with intact bedding can bear an earth load which, depending on the input values, is 2 to 8 times higher than the breaking load responsible for the occurrence of the longitudinal cracks in the quarter points.

In those cases where the crack edges are not displaced, i.e. the joint mechanism is still intact, …

(Image: Deformation process for a longitudinally cracked pipe up to its collapse in accordance with the Sewerage Rehabilitation Manual)

What can be done operationally to slow down further damage?

The deformation development can also be facilitated by a change in the operating conditions, high-pressure cleaning, leak-tightness testing with water, or short-term overload/flooding.

Thus, until sewer rehabilitation work can be conducted, preventive measures …

According to EN 13508-2, pipe break is defined as the displacement of pipe segments (pieces) and missing of individual, more or less large segments (pieces) of the pipe wall.

The following defect patterns are examples of the coding break / collapse.

(Table: Pipe break – Segments of the pipe are displaced, but not missing)

(Table: Pipe break – Segments of the pipe are displaced, but not missing)

(Table: Pipe break – Segments of the pipe are displaced, but not missing)

The following defect patterns are examples of the coding break / collapse.

(Table: Pipe break – Missing parts in the pipe wall)

(Table: Pipe break – Pipe segments are displaced, but not missing and missing parts in the pipe wall)

(Table: Collapse)

A pipe break is caused by an additional disturbance or changed internal or external load on a pipe that has already been damaged by cracking or fragmentation. Furthermore, a pipe break can occur as a consequence of leakage, mechanical wear, and corrosion.

A collapse represents the final and most severe stage in the temporal development of the following types of defect:

• Infiltration (BBF) / exfiltration (BBG) (leakage)
• Surface damage (BAF) (mechanical …

Further causes are wrong material choices caused by a non-observance or misinterpretation of exterior or interior loads and their possible changes during service life [WRC78] – or the use of faulty or damaged components, such as:

• concrete pipes with rock pockets and an insufficient compaction of the concrete

• pipes made of concrete and reinforced concrete with shrinkage cracks that exceed the permissible tolerances

• reinforced concrete pipes with …

The pipe fragments that have fallen into the pipe cross-section also create drainage …