A Case of Utilizing Results

The Technique of Planned and Effective Investigationand Judgment of Sewer Pipes
YOKOTA Toshihiro, Head
FUKATANI Wataru, Head Researcher
SUEHISA Masaki, Researcher
Wastewater System Division, Water Quality Control Department(Key words) facility of sewer pipe, stock management, vinyl pipe, degradation judgment criteria
1.

Introduction
Recently the number of decrepit pipes is increasing;
therefor there are growing concerns about occurrencesthat has a serious influence on social activities and daily
lives, such as road cave-ins and stop of sewage services.
To prevent these accidents, it is an important issue ofmunicipality to make and follow the maintenancemanagement plan for prevention and preservation, andthe adequate practice of reconstruction and repair. On
the other hand, along with the strained state of municipal
finances, the rate of annual sewer pipe investigations is
as low as 1% of total extension. Therefore more
effective investigation methods of sewer pipes arenecessary.
To prolong the lifespan of facility, the precise grasp of
the present state of degradation (substantiality) isrequired. However, the length of undergrounded vinylpipes that consist 60% of the length of total sewer pipes,
we do not have much knowledge of deficiency nor of
the mechanism of degradation. And there is concern that
we do not have degradation judgment criteria comparedto other materials. Based on this, National Institute ofLand and Infrastructure Management has proceeded
these two researches towards the promotion ofmaintenance management of prevention andpreservation to prevent the fatal damage of sewer pipes
and the adequate practice of reconstruction and repair.
①
Screening research method by utilizing polecamera.
②
The standardization of degradation judgmentof vinyl pipes,etc.
The Research of Screening Method by Utilizing PoleCamera
A pole camera is a piece of investigation equipmentthat has an extendable operation pole with a camera andlight on its top. (photo1) We can inspect andinvestigate sewer pipes by inserting the pole into a
manhole and using zoom functions while staying on thesurface. The merit is that the cost of this form inspection
is lower than the present detail inspection (TV camerainspection) and more sewer pipe investigations areconducted during a short term. We determined therange of camera eyesight by using experiment
instruments and grasped the trend of deficiency that

happens inside a pipe and estimated how much
deficiency the pole camera can detect. Based on theseresults we evaluated the systematic screening method by
combining the present detail inspection (TV camerainspection) and the pole camera. We developed amore effective judgment method for accurate
investigation, daily progressing amount and expense.
3.

Standardization of Degradation Judgment of Vinyl
Pipe, etc.
NILIM is experimenting to grasp of capability of vinyl
pipes with deficiencies. We are also making thejudgment criteria of vinyl pipes based on the trend of thedeficiency (photo2) through the results of present TV
camera inspection, etc. In the judgment criteria, we aregoing to include the appraisal method of the cracks that
occur following the axis, flattening and the deformationthat are characteristic for vinyl pipes instead ofconventional judgment of reinforced concrete pipe. The
result of this study will be proposed into the guide ofsewage maintenance management we are considering torevise.

2.

Photo1 Pole camera
Photo2 Example of damage to a vinyl pipe
4. Summary
By utilizing these research results, fatal damage ofsewer pipes that are caused by road cave-ins can be
avoided, the extension of endurance and the reduction ofmaintenance management cost are expected.