Gladding, McBean

Gladding, McBeana division of PABCO Building Products, LLC.

Anatomy of a Pipeline Failure

Anatomy of a Pipeline Failure

Who are the Players?Owner - CityDesign EngineerGeotechnical Engineer Pipe SupplierManhole SupplierContractorConstruction Project Manager

Construction InspectorConstruction Manager

Different Geotechnical firm who provided Construction Backfill/Earthwork Observation/Testing

Pipeline

2,450 linear feet of 27-inch Vitrified Clay Pipe2,700 linear feet of 30-inch Vitrified Clay Pipe

12,550 linear feet of 42-inch Vitrified Clay Pipe13 to 20 feet of cover23 Manholes spaced at 800 feet (typ), cast in place (including 2 junction structures)

Contract Values

$1,785,320 Purchase of Vitrified Clay Pipe$2,575,120 Construction Contract$4,360,440 Total

$1,274,100 Manhole Repair Contract46% of original construction contract

Project SpecificationsVitrified Clay Pipe Specified and prepurchased by the City12-inches of crushed stone under the pipe barrelFull Geotextile EncasementCast-in-place Manholes Acceptance testing witnessed

History

Pipeline installed during summer of 2001December 2001, entire pipeline tested and accepted by construction management teamFebruary 2002, City found pipeline full of water.

Also discovered some manholes leakingThen found several cracked pipe sections

What Now??

MeetingsMeetingsLets repair the problem

Pipeline Repairs

April/May 2002, City started repairs.During this process found a number of other issues.City asked contractor to fully evaluate pipeline condition:June 2002 the contractor reported finding:

34 individual pipe sections leaking (1% of pipe segments installed)No Manhole issues

Oh No – Now what??

More repairs than anticipated

What are our choices??

DesignMaterialsConstruction

Lets look at…

Design &Materials

Fugro West Report – July 2002Observations – based on three repairs

Trench width exceeded design parametersNo (crushed stone) gap observed under the bell (bell hole) Less than the specified 12-inches of bedding One bell observed placed directly on native materialBedding material (crushed stone) not consolidated to a “non-yielding condition” as per specificationsNo evidence of erosion of trench walls or bottom observed.

Fugro West Report – July 2002Pipe Test

Four sections of 42-inch diameter pipe removed from the job site and testedAll exceeded specificationsOne tested to failure

18% over specification

Fugro West Report – July 2002Design Review

Reviewed design method, reviewed design & reviewed: earthquake ground motions; groundwater effects; hydrostatic forces and buoyancy; expansive soils; other loadsFound the calculated design safety factor for the 42-inch pipe was 1.53 to 1.80Found the actual safety factor at location of pipe failure was 2.09

Fugro West Report – July 2002Conclusions

“ The design approach employed a standard widely used method where reasonable to conservative design parameters were used”The pipe failures occurred in various locations including areas where the computed factors of safety were in excess of 1.5. For those conditions, small incremental loads alone should not have caused pipes to crack.”

Fugro West Report – July 2002Conclusions continued pg 2

“ The most likely primary causes of, or primary contributors to, distress to the pipe segments are:

The pipe segment bell was placed on the bedding or on the native soil without being “dug out”, and thus carried load that the barrel of the pipe was supposed to carry.The crushed stone pipe bedding was not compacted sufficiently to provide the full design load factor….Trench width was greater than specified in some locations, causing the load on the pipe to be greater than anticipated.”

Options

Now that both the design and materials are validated, lets look at:Construction

A firm was hired to perform a condition assessment of the entire pipeline.

Their findings are:

Condition Assessment - Pipeline

Longitudinal Cracks33 observed

Chips (1-inch or greater)107 observed

Joint spacing (3/4 to 1 1/3-inch)158 observed

Contractor repairs312 observedExamples;

18”L x 3”W x 1”D9”L x 1 ½”W x 1 ½”D

Condition Assessment - Manholes

Defects located on every manhole

No small matter

Let the games beginLawyers hiredPipe experts hired Forensic evaluations performed$$$$

Project forensic photosPipe line repairsManhole barrel jointsManhole – pipe connectionsUnauthorized repairs to manhole – pipe connectionsGrouting of flowline in first barrel section

Pipeline forensic photosPipe line repairsMost repairs associated with manholes

Pipeline forensic photosPipe joint leaksFound to be improper installation

Manhole barrel jointsThe manhole

joints were exposed and examined.

Manhole Joint issuesTwo different joint types used on job site, both in the same manhole.

Manhole Joint issuesRamneck improperly installed

Manhole Joint issuesManhole base installed upside down

Manhole – Pipe ConnectionsBoots improperly installedUnauthorized repairs

Manhole – Pipe ConnectionsBoots improperly installed

Manhole – Pipe ConnectionsUnauthorized repairs

Manhole Improper grouting of first flow channel

PVC liner not installed properlyNo consolidation of concrete

Pipeline issues identifiedCracks

Overload TypeNo bell hole

JointsBedding material found inside joint

Manhole issues identifiedManhole joint issues:

PVC liner improperly installed and leakingTwo different (barrel) joint types used on same manhole.Ramneck improperly installedManhole base installed upside down

Manhole – pipe connectionsBoots improperly installedUnauthorized repairs performed

Manhole flowline improperly grouted

ConclusionsDesign

ConservativePipe

Materials exceeded all specificationsConstruction

Manholes improperly installedPipe improperly installed

Construction inspection/testingImproper certification of pipe & manhole acceptance test results

Lessons LearnedVerify experience of consultantsProvide independent verification of critical items

Pipeline air testManhole vacuum test

Listen to warnings from team members

Any suggested design change?Yes – manhole connections

Use a VCP Bell and grout in place instead of the rubber boot

differential settlementASTM Standards, hydrostatic capabilities

“BLESSED ARE THE TROUBLE MAKERS,

FOR THEY SHALL PREVENT LETHERGY.”

Amster HowardJune 2008

Any questions?