Saturday, March 23, 2013

Procedures for Excavation, Pipe laying & Jointing


PIPE LAYING-INTRODUCTION


1.0 INTRODUCTION
The water supply projects/water distribution system may consist of pipe laying work either Ductile Iron Pipes or PVC pipes. The civil engineering background behind implementing pipe laying work shall be depending on the various circumstances.  But here we are introduced brief methodology of pipe laying work.

This has been prepared to describe the effective and safe working procedure of trench excavation, narrow road excavation, rock excavation, excavation in the vicinity of services, dewatering, supporting of excavation, backfilling and removing of trench supports.  Date of commencement and expected date of completion of work shall be informed to the engineer and Work Program shall be handed over by the time of implementation of pipe laying work.
Definitions
1.    Contractor – Big Contractors Joint Venture
2.    Client – National Water Supply & Drainage Board
3.    Engineer – Qualified engineer who represents the client
4.    Site Engineer – Qualified Engineer who represents the contractor

Pipe Laying-Approval from Authority                                


Pipe laying work has to be carried out along the paved roads most of the time, Therefore paved roads belong to the government authorities and some of the service lines available underneath of paved surface or both sides of the roads. The service lines has to be relocated or pipe line may change their trace according to the spaces available to relocation, cost estimation, time taken to it etc.. The best solution may commence after considering all the facts. in addition to the some of the other authorities has to be connect and it will vary geographically. The approval of the following authorities has to take officially most of the times for the pipe laying works.

The Authorities to take Approval

       Road Development Authority (for major roads)
      Provincial Road Development Authority (for secondary roads)
      Residents in the vicinity
      Irrigation Department etc..

Contractor coordinates the above listed authorities and relevant other parties through the employer and obtains permission for the excavation and pipe laying. SLTB and Private Bus Companies shall be informed at least one week earlier if any traffic re-routing happens due to the excavation and pipe laying work. In such case alternative routes shall be provided and at the both ends of the closed roads signs shall be placed. Traffic Police shall be informed and arrow symbols shall be shown the alternative route for the road users.

 

Pipe Laying – Material & Equipments

MATERIAL
Other than backfilling soil all the materials shall be transported and stored as per the manufacturer’s recommendation in a proper storage yard. In the case of exceeding the storage space in the storage yard stores, rented/hired lands shall be used for the material store purpose. Details of such lands shall be provided to the Engineer for the prior approval.
All the material other than soil shall be handled as per the manufacturer’s recommendation by using sling wires, cranes and excavators depending on the type of the material, weight, space available, location of the site and other factors to be considered.
Material that can be blown away by the wind during the transportation (soil, sand, etc.) shall be transported by covered trucks. Pipes and fittings shall be inspected before they are transported to the site and records shall be maintained. Engineer shall be notified for the inspection of such material before dispatching to the pipe laying site. Excavated materials that can be used for the backfilling shall be stored in suitable location protecting from weather in a practical manner.

MACHINERY AND EQUIPMENTS

However as a minimum requirement the sub contractor expect to provide a set of survey instruments, crane (if necessary) and a trailer on sharing basis. Excavator/JCB, dump truck, pile driving equipment, water pump, plate compactor, generator shall be generally provided to the sites as the requirement. These equipments shall be maintained periodically by a separate crew. Crew Cab shall be utilized for the transportation needs. Other transportation shall be provided depending on the type of the machinery/equipment to be transported.
Parking of the vehicle, storing material/equipment shall be done at the main yard. But in a case of this premises shall not be practicable, a land shall be arranged by the officer-in-charge after discussing with the Construction Manager. However in a case of cease work for a considerable period all the equipment/machinery shall be stored at the main yard site.
The Engineer shall be informed to inspect shoring material, etc before using them. Such materials shall be listed and the list shall be submitted to the Engineer in advance.

Pipe Laying – Excavation

EXCAVATION

Usually open excavation shall be done with braced cut. Excavated soil shall be directly loaded dump trucks/tractors and transported to separate yard approved by the Engineer. The excavated soil suitable for backfilling shall be stock piled in the site/separate locations as. Any unsuitable excavated shall be disposal yard.
Excavation for structures such as thrust blocks, valve chambers shall be allowed 800mm working spaces in minimum.

Excavation length shall depend on,
      Duration of ground water lowering
      Effect of settlements to adjoining properties
      Width of the road and traffic density
      Existing services.

PRIOR TO THE EXCAVATION

Before starting excavation in any road, the approval shall be obtained from the Engineer and the relevant authorities (RDA) shall be informed with the detailed work program and the relevant details (chainage of the roads, date of commencement, completion date of backfilling, planned dates of completion of temporary reinstatement and the date of handing over).
Excavation work shall be started only after,

      Granting the approval for the program by Engineer/relevant authorities.
      Granting the approval for the pipe and fittings.
      All the required plants are available for speedy work.

The available details of underground services shall be obtained by the relevant authorities and respective residence. The Contractor shall protect the underground services and utilities as far as possible.

CONTROL OF WATER
The Contractor shall keep the excavation free from water during the time of the construction and pipe installation by installing and operating all necessary machinery, appliances and equipment  Disposal of water shall not damage any private property, or should not create any nuisance to the public.
A suitable de-watering system shall be used for the excavation depths passes the water table level and for the excavation in the rainy season. The de watering system shall be supervised and monitored by appropriate qualified personnel. De-watering system shall be inspected by the Engineer if he/she needs.

EXCAVATION IN NARROW ROADS

Police permission shall be obtained in a rerouting of traffic. Special consideration shall be paid to reroute traffic and make provisions to access adjoining building. Before start of the excavation the existing situation shall be photographed with the consent of property owner. Possible damages to the boundary walls and other properties, the possibilities of repairing such damages with the least inconvenience to the owners and cost effective manner shall be discussed with the owners. The vicinities shall be informed at least one week earlier about the excavation. Excavation length along such roads shall be limited to the minimum. Excavation shall be carried out with an optimum care. Parking spaces and security for the parking premises shall be provided for the residents in case if they cannot use their usual parking place due to construction.

EXCAVATION NEAR UTILITIES

Edges of the trench shall be marked on the ground, cut with asphalt cutter and removed by JCB/Excavator. Details of house connections for shops, etc shall be inquired and marked on the ground prior to the excavation work.
All services lines crossing or along the trench shall be exposed. Such services shall be temporary rerouted/modified wherever possible, to perform trenching operation. Every precaution shall be taken to avoid any damage to the existing services. Under the worst scenario they will be left as they are by providing the supports without disturbing to such services.
In case of interrupting water supply due to Contractor’s work, such situation shall be coordinated with the NWS&DB to rectify the situation immediately.
Overhead electric wires shall be protected from the construction vehicle operations. Temporary disconnecting the electric services/temporary shifting of electrical wires shall be arranged by coordinating with the relevant authority.

EXCAVATION NEAR EXISTING STRUCTURES

Any existing structures that cannot be temporarily relocated shall be preserved prior to the excavation proceed in the opinion of the Engineer. Above mentioned structures shall be carefully protected from damages by the Contractor.
In order to protect existing structure, the Contractor shall do shoring where required. The shoring method shall be submitted for the approval of the Engineer. For deep excavation very near to the existing structure, sheet pile shoring shall be used to protect the structures.
The arrangement made shall be approved by the Contractor and work should be hold until the Engineer’s decisions are issued.

ROCK EXCAVATION
Weathered rocks shall be removed by mechanical means as far as possible. Hard rock shall be removed by other means as agreed with the Engineer/reroute the pipeline trace.

HANDLING OF EXCAVATED MATERIAL
Excavated materials shall be dumped only in locations approved by the Engineer and relevant local authorities.

Materials that can be reused for back filling shall be approved by the Engineer. Such material shall be protected from weather as far as possible.

All the other material shall be dumped legally.

 

Borrow Excavation

Introduction
The borrow excavation shall consists the operations such as site clearing, stripping of the overburden and stockpiling. Excavation would only be proceeded where those sites have been approved as borrow sites to be used in the construction work.

Abbreviation
QAE      - Quality Assurance Engineer
SE        - Site Engineer
TO        - Technical Officer
QAS      - Quality Assurance System
ME        - Materials Engineer (Contractor)
TS        - Technical Specification

Resource Allocation

Man power
·         1 No Supervisor.
·         Un skilled labours
·         Operators

Equipments

·         Track Back-hoe loaders
·         Dump trucks

Quality Control Procedures
Sampling and testing 
Samples of soil would be taken from the borrow location and those samples would be placed in a polythene bag providing identification tag. All required tests would be carried out in the materials testing laboratory to confirm that those materials are in which category. After testing and with the satisfying results, excavation would be preceded and those materials would be stock piled at the site.

Even the materials are properly stock piled at the site the materials in the stock pile would be tested before issuing for the construction purpose. No materials would be allowed to execute in the construction work until the required tests are completed and satisfied.
Inspection Check list
To ensure that the all activities being performed with the expected quality, an inspection check list would be filled by the person in charge for the borrow excavation in case of preconstruction, during construction. The inspection check list shall include the specific requirements, safety and environmental measures. 

Dimension control

In case of the excavation of borrow materials, it is essential to have the designated limits of the borrow site to maximize the quality of the borrow materials. When the excavation is beyond the designated limit, it tends to mix with unsuitable materials.

Methodology
Clearing of the borrow site
1.    The location and dimensions of the borrow pits would be identified as instructed by the Engineer.
2.    All ordinary jungles, stumps and roots would be removed by a manual mean or using any other suitable equipment within the approved borrow area.
3.    All removed matters would be collected to a place and then they would be disposed to a suitable disposal location or burned at the site with the judgment of the Engineer.

Stripping of the overburden
1.    The overburden would be removed up to the required depth by using suitable mechanical devise and those materials would not be allowed to mix with other materials classified as suitable for filling.
2.    The all unsuitable materials would be disposed to a suitable disposal location by means of tipper trucks.

Excavation
1.    Borrow excavation would be carried out using a Back-hoe loader and would be properly stock piled with well-drain facilities. The material from the borrow pits would be blasted, ripped and excavated in a manner that will ensure the effective breaking down of the material in the borrow pit before it is loaded.
2.    Rippable material which tends to break into large blocks would be cross ripped. Borrow materials would be confirmed to the requirement before the application. Dump trucks would be applied for the transportation of borrow material.

 

Channel Excavation

How to do a channel, Side Drain, Side Ditches etc..

1.0  Introduction
This works consist of excavation for all channels, drains, ditches where in side and out side of the right of way showing on the Drawing or as instructed by the Engineer. The proper drainage shall be provided by constructing, shaping, finishing or backfilling where necessary involved in conformity with the required alignment, levels, grades and cross sections.

2.0  Abbreviation
QAE    - Quality Assurance Engineer
QAI    - Quality Assurance Inspector
QCI    - Quality Control Inspector
SE    - Site Engineer
SEO    - Safety and Environmental Officer
TO    - Technical Officer
QAS    - Quality Assurance System
ME    - Materials Engineer (Contractor)
3.0  Resource Allocation
Man power
QAI
QCI
Site  Engineer -01
Supervisor-01
Flagmen ( If necessary)-02
Surveyor-01
Surveyor helpers-05
SK/USK  labours-08
Operators- As required
3.2   Equipment & Tools
Back-hoe loader
Wheel Loader( If necessary)
Dump trucks(15 tons)
Rammers
Tractor Trailer
Compacting rollers
Level instrument
Mortar pans
Mamoties
Pick axes
Crow-bars
Wheel barrows
Shovels
Safety Inventory

1.    10 No of barrels
2.    02 No of signal Men
3.    10No Traffic Jackets with Retro reflective patches/stripes
4.    Sufficient barricade tapes.
5.    05 No barricade boards with Retro reflective stripes
6.    02 No Stop and Go signs
7.    03 No Road works ahead
8.    01 No Road Works ahead, End
9.    05 No of traffic cones
10.  04 No. of Blinking Lights


4.0 Quality Control Procedures
4.1 Sampling and testing
Embankment Filling Material:
Samples would be collected from the work execution areas and would be placed in a polythene bag providing identification tag. All required tests would be carried out in the materials testing laboratory for identification suitability of the Excavation Materials. The areas where backfilling is required for the conformity of the design levels, the works would be carried out with approved filling materials in layer by layer as described in technical specifications. Required test would be carried out after placing and compacting to check the degree of compaction.

4.2  Inspection Check list
To ensure that the all activities being performed with the expected quality, an inspection check    list would be filled by the person in charge for the Channel excavation in case of  covering  pre construction, during construction. The inspection check list shall include the specific requirements, safety and environmental measures.
4.3  Dimension Control
Channel excavation would be carried out according to the designed cross sections conformity with typical section issued for construction. The required shape, depth and offset of the excavation would be properly maintained during construction and those requirements would be checked with the inspection check list.
5.0  Setting Out
·         The setting out would be carried out in the area where the Engineer’s approval is given for channel excavation.
·         Levels of excavation would be marked by the surveyor using pegs.
·         The line of the Excavation would be marked with lime powder or any other proper manner

 Excavation and Shaping
·         The set out area would be subjected for the excavation with machinery or in manual manner conformity with designed line and levels
·         The shape of the drain would be maintained to satisfy the typical sections issued for the construction.
·         All materials suitable for embankment Construction removed from excavations would be used in Embankment construction or any other filling specified to fill with Embankment Materials.
·         Materials deemed not suitable for embankment filling  would be disposed of to approved disposal locations
·         Any area backfilling have to be done to form earth drains, filling would be done using approved filling material instructed by the Engineer

 

Pipe Laying – Shoring Methods

Trenches excavation shall be carried out without shoring/with light shoring/with heavy shoring depending on the stability of the ground. Light shoring/no shoring shall be used for shallow trenches in stable ground with lower ground water table. Arrangements for heavy shoring shall be submitted for the approval to the Engineer before using them.
Excavated surfaces too steep shall be protected and supported as necessary to safeguard the work and workmen, to prevent sliding or settling of the adjacent ground.
      Sheeting
      Bracing
      Shoring
      Other support installation
The Contractor shall remove all the supporting installation once the work is finished. Trenches shall be effectively supported including sheet piles where necessary to prevent any fall/run from any portion of the ground outside the excavation into the trench and to prevent settlement/damage to structures adjacent to the excavation. Where battered sides shall be elected there shall be provided with stable slope (height at a slope of not steeper than one to one from point of 300mm above the pipe).

REMOVING OF TRENCH SUPPORT
Removing of trench support shall be done simultaneously with the backfilling. Lowest bracing shall be removed once completed the backfilling up to that level. So on for bracing for higher levels.
The Contractor shall be responsible for removing all the supporting systems that are used for the pipe laying process.

Pipe Laying Procedures
Pipe laying between two adjacent manholes/chainages shall be started from the lower elevation to higher elevation for easy draining of ground water in the trench. However there can be case where need to lay pipes in opposite direction also.

      All pipes shall be laid to lines and grades shown on the drawings.
      Open ends of the installed pipes shall be plugged with a watertight plug/other approved way when there is no pipe laying in progress.
      When the pipes are to be ready for joining the plug shall be taken off.
      Material used for plugging shall be approved type that shall adequately protect the pipe from damage, prevent dirt, debris and water from entering the pipe.
      All pipes shall be checked for defects and cleaned before joining.

DUCTILE IRON PIPE LAYING
      All pipes shall be carefully inspected for defects before installation.
      Proper installation of pipe shall be carried following steps.
o    Excavation
o    Preparation of the bed for pipe
o    Placing the pipe without damage
      The section of the pipe shall be fitted together correctly.
      Pipe shall be laid true to line and grade.
      As far as possible pipe shall be lowered by a crane.
      Whenever the work cease for any reason the unfinished end of the pipeline shall be securely closed.
      Where the water table is encountered, shall be kept below the sockets when joining by pumping or any other mean.
      Concrete Protection: Encased Concrete for pipes shall not be placed until the joints at each end of the pipe have been completed.

UPVC PIPE LAYING
      Pipes shall be stored out of direct sunlight but ventilation shall be provided.
      Cutting of the pipe shall be kept to a minimum.
      Cuts shall be perpendicular to the axis of the pipe and smooth.

 PIPE LAYING IN RAILWAY CROSSINGS
Shop drawings shall be approved by the engineer before commencing work at every railway crossing.

 

 

 

 

 

 

 

 

 

 

Pipe Laying-Traffic Control Plan

Individual traffic arrangement shall be provided with coordination of Police, Traffic Division. Night work shall be introduced to the highly congested roads. For the other roads one lane shall be  Closed for the pipe laying work.
Maximum speed for the vehicle shall be 30kmph where the pipe laying work going on.
Where necessary only single lane traffic shall be allowed and the road shall be closed for the other way traffic for the pipe laying work.

Sign Boards
Sign boards shall be used for the road users to inform about the pipe laying.
Following sign boards shall be used mainly.

Men at Work Road Narrow



Method of Traffic Control
Vehicles shall be controlled at the both ends of the construction part of the road. Two men (Traffic Controllers) shall be allocated at the both ends to signal the vehicles to move/not to. They will carry “GO” and “STOP” boards and shall have communicative equipments (walky-talky) according to the site location and the distance. The traffic will move when the Traffic Controller shows the board “GO”, and the traffic will stop and allow the opposite traffic to flow while Traffic Controller shows the board “STOP”.

The boards shall be used both the day and the night time due to its property of reflecting the light, but where the Engineer requests for another arrangement for the night shifts, reflecting lighting guns shall be used for the traffic control. 


Pipe Laying-Setting Out
Setting out on the ground will be done by a competent person with total station/ theodolite as per approved construction drawings. Correct coordinates and levels shall be taken referring to TBMs established along the road.
Pipe line trace shall be marked on the ground as per the construction drawings and agreed by the Engineer. After finalizing the trace, trial pit investigation and other studies shall be carried out.
Final setting out work shall be done as per the Engineer instructions after the trial pit excavation.

Procedure to Setting Out

      The line and the level of the trenches shall be as per the drawing.
      The route of the trenching shall be pegged out accurately.
      Strong sight rails shall be fixed and maintained at every change in gradient.
      Any deviation of the line and/or grade shall be permitted by the Engineer.
      Nominal trench width shall be as indicated in the drawings.




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1 comments:

  1. I learned a lot by reading your blog and pipe line laying. Thanks for sharing.
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