Digital Photogrammetric Mapping

Appendix A

Technology and Environment DirectorateRoad and Traffic Engineering Branch

Document No. 67/08/90Issue Date 01/2003

EARTHWORK VOLUME CALCULATIONS

This document is owned and controlled by the Survey & Mapping Manager.

The Data Manager is the delegated custodian.

All comments for revision should be submitted to the Data Manager.

Authorisation

As Executive Director of the Technology and Environment Directorate of Main Roads, I authorise the issue and use of this standard.

......................................................................EXECUTIVE DIRECTOR TECHNOLOGY AND ENVIRONMENT

Date: ___/ ___/ ___

No controlled copies are issued for this standard.

The latest copy of this standard is located on the Main Roads Internet site.

REVISION STATUS RECORD

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Authorised by: ________________________________Date____/____/____Survey & Mapping Manager

MAIN ROADS WAEarthwork Volume CalculationsPage 1 of 1667-08-90 Earthwork Volume Calculations_Rev_1.docDocument 67/08/90

CONTENTS1.PURPOSE42.SCOPE43.REFERENCES44.DEFINITIONS AND INTERPRETATIONS45.GENERAL55.1Survey55.2Software55.3Tender Volumes55.4Embankment Foundation Surface65.4.1Rock Excavation65.4.3Unsuitable Material65.5Stockpiles, Levees and Borrow Pits66.CAPTURE OF DIGITAL TERRAIN MODELS FOR VOLUME CALCULATIONS66.1Embankment Foundation Surveys (Stripped Ground Surveys)66.2Rock, Unsuitable Material, Borrow Pit, Stock Piles and Levees.76.2.1Existing Surface76.2.2New Excavated/Fill Surface77.METHODOLOGY FOR VOLUME CALCULATIONS87.1Design Models87.2Boundary Strings97.2.1Embankment Volume Calculations97.2.2Rock (Embankment Foundation) Calculations117.2.3Borrow Pits, Unsuitable Material, Stockpiling Calculations117.3Volumes127.3.1Embankment Construction Limits127.3.2Rock (Embankment Foundation)137.3.3Borrow Pits, Unsuitable Material and Stockpiling148.VOLUME VERIFICATION149.VOLUME AND DATA LODGEMENT15

PURPOSE

The purpose of this Standard is to define the methodology required for all work related to the calculation of Volumes. All work shall be performed and presented in accordance with the following requirements to ensure that Main Roads has continuity in standard, quality and procedure.

SCOPE

This standard shall be used where earthwork volume calculations are required for Main Roads projects.

Advice and further information can be obtained by contacting:

Haydn BuftonData ManagerRoad and Traffic Engineering Branch

Phone - 9323 4655Email - haydn.bufton@mainroads.wa.gov.au

REFERENCES

The following documents relate to this procedure:

Tender Document Preparation (TDP) - Specification 302 Earthworks

Main Roads Survey & Mapping Standard 67-08-43 Digital Ground Survey

DEFINITIONS AND INTERPRETATIONS

The following terms used in this procedure have the specific meanings indicated:

Superintendent Main Roads contract representativeContractor - the party named to perform the ServicesDTM - Digital Terrain ModelMX Software Road design Software (formerly known as MOSS)SUP - Shared Use PathNoise Bund - Earth embankment acting as a noise barrierRoad Formation - The surface of the finished earthworks, excluding cut or fill battersTDP - Tender Document Preparation for Major Works. Document 67/05/2102

GENERAL

Main Roads requires the computation of earthwork volumes for payment.

Research has shown that discrepancies resulting from operator interpretation and methodology are the major cause of differences in volume calculations.

The objective of this document is to define a standard methodology for the calculation of volumes.

1.1 Survey

All levels used to define digital terrain models for volume calculations shall be captured in accordance with Main Roads Survey and Mapping Standard 67-08-43 Digital Ground Survey.

Digital Terrain and Design models that are used to calculate volumes shall be accompanied with Metadata Statements detailing the coverage and what surface each file represents.

1.2 Software

Only software that has the functionality of prismoidal methodology shall be used to undertake volume calculations for payment for Main Roads projects.

Conversion of Digital Terrain and Design Models to a suitable format that allows importing into a software package is acceptable however once the data has been imported, verification is required as to the integrity of the imported data against the original information.

Cross section volume calculations are only to be used for verification purposes or in the case of Tender Volumes for Mass Haul Analysis.

5.3Tender Volumes

Where volumes are to be calculated for the inclusion in Schedule of Rates contracts, the use of the prismoidal methodology shall apply. However as these volumes are calculated prior to the construction phase an allowance for topsoil removal, from the existing surface, is to be included in the volume calculations. Depending on the software used, this may necessitate the lowering of the existing surface model by the topsoil allowance.

This allowance for topsoil removal shall be the amount defined in Specification 302, Topsoil Removal Within Limits of Clearing clause.

No allowance is to be made for foundation compaction.

If required, Cross Section volumes shall also be calculated and supplied to the Superintendent, for Mass Haul Analysis. These volumes shall take into account the topsoil allowance with the cross section interval the same as the chainage interval of the master alignment string.

5.4Embankment Foundation Surface

For the purpose of this standard, the Embankment Foundation Surface shall be the prepared surface on which the embankment is constructed.

Volumes shall be calculated based on levels taken after embankment foundation compaction has been completed.

5.4.1Rock Excavation

The base level used for the calculation of the volume of excavated rock shall not exceed the depth below Subgrade as defined in Specification 302 Earthworks - Rock Excavation.

Rock excavated outside the design limits shall not be measured.

5.4.3Unsuitable Material

Where unsuitable material is excavated within the area bounded by the Embankment Foundation Surface, any areas of unsuitable material shall not be included in the stripped ground survey until backfilled and compacted to the required level.

5.5Stockpiles, Levees and Borrow Pits

A Digital Terrain Model defining the existing surface shall be captured prior to the stockpiling or excavation of any material that the contract requires to be measured.

CAPTURE OF DIGITAL TERRAIN MODELS FOR VOLUME CALCULATIONS

6.1Embankment Foundation Surveys (Stripped Ground Surveys)

Embankment Foundation Surveys are performed by the Superintendent to define the base surface of the prepared area for construction on which earthwork volume calculations are based.

Embankment Foundation Surveys shall be performed after the clearing, removal of topsoil and compaction of the embankment foundation and prior to the commencement of any earthworks. Refer Specification 302 Earthworks - Survey.

Before any volume calculations are undertaken, the contractor undertaking the calculations shall review the stripped ground model to ensure full coverage of the designated area requiring volume calculations. If coverage is not sufficient it may be necessary for additional survey to be carried out.

The stripped ground survey shall cover the embankment foundation between the interface strings for the length of embankment foundation required to have volumes calculated.

The methodology described at Section 7 shall apply for interim or full embankment volume calculations.

6.2Rock, Unsuitable Material, Borrow Pit, Stock Piles and Levees.

6.2.1 Existing Surface

Where a survey of the existing surface prior to excavation or stock piling is not available, the extremities (edge of cut/fill) of the survey defining the new surface shall be used to represent the original surface prior to cut or fill. That is, the surveyed points or strings that define the base of the stockpile or edge of the excavation shall be used to represent the pre-existing surface. These points/strings shall define the boundary of these earthworks.

A boundary shall be derived from the strings that define the interface of the existing surface and the edge of cut or fill. Where these breakline strings are not available, additional survey will be required to be undertaken, to adequately define the boundary of the cut or fill surface.

6.2.2New Excavated/Fill Surface

Where rock or unsuitable material has been excavated for embankment construction and the survey defining the new surface extends outside the interface strings, then only the surface within these strings shall be used for calculations. Refer to Section 7.3.

METHODOLOGY FOR VOLUME CALCULATIONS

7.1Design Models

The design model used for volume calculations shall be a clean model without any erroneous strings, such as:

Boundary strings

Construction strings

Discontinuous strings

Discontinuous strings are the most common causes of erroneous strings. Strings in a design model may require breaks to allow the inclusion of side roads into the model. When a discontinuity is inserted, the original string is divided into segments with the same label. The first point on the discontinuity is stored with a negative X coordinate and the last point with a negative Y coordinate as shown in Figure 1.

Figure 1 - Discontinuous String

Not all software programs treat these strings in the same way and in some cases may treat them as one continuous string. This may result in strings incorrectly crossing each other, particularly at intersections. Design strings that are used for volume calculations are to be compared to the design drawings to confirm they are correct. If, because of software capabilities, discontinuous strings are not properly represented then the strings are to be extracted from the model and broken down into its individual components (at discontinuity points) and reinserted into the model.

For string names used to define the embankment foundation refer to the contract drawings.

If the supplied design model does not contain the design strings required to calculate the required volumes, the Superintendent is to be advised that the design model is not complete.

7.2Boundary Strings

The prismoidal method of volume calculations compares the triangulation of two surfaces to derive a volume. For all Main Roads projects the prismoidal method shall be used to determine volumes and all calculations shall be done within a boundary string that defines the extremity of the volume area.

This boundary string shall be derived from existing coincident strings (interface or breaklines) and, where required, from strings interpolated from the defined surface. When creating the boundary string from existing strings, copies of these strings should be used so as not to degrade the integrity of the existing data. To ensure that the boundary string is not included in volume calculations it is to be assigned a null elevation (-999.000).

When the boundary string has been created, each surface used for volume calculations shall contain a three dimensional string that is coincident with the boundary string and shall reflect the true height of the surface at the boundary location. This shall apply to all volume calculations for Main Roads projects.

7.2.1Embankment Volume Calculations

For embankment construction volumes, the boundary shall be created from the interface strings of the design model that define the limits of construction. Where embankments are constructed separate to the main road formation (eg: Noise Bunds, SUPs, Levees) separate boundary strings shall be created.

To have a continuous boundary string, the copies of the interface strings must be joined across the design and stripped ground. In some cases, joining these strings across the embankment foundation may result in the boundary string not intersecting defined points and this may result in areas of embankment being excluded from the volume calculation. This is because prismoidal triangles are only generated from individual point or linear features and most programs only generate the prismoidal triangles within a boundary area. This applies to both surfaces being used for volume calculations.

For example Figure 2 shows five design strings that are defined by 25 points. If the boundary is defined by points A, B, C and D when prismoidal volumes are calculated, only points 6 20 are triangulated. This is because there are no intersection points along the boundary between A B and C D. This will result in the two hatched areas being excluded from calculations.

Figure 2 - Triangulation

As defined in Section 7.2 three dimensional strings are to be coincident with the boundary for each surface used. In the case of Figure 2, a three dimensional string intersecting the five design strings shall be defined (cross section) along sections A B and C D of the boundary string. The resultant strings shall be included in the design surface.

If the 25 points in Figure 2 define the stripped ground, these points are to be triangulated and a three dimensional string (cross section) between A B and C D is to be created from the triangulation with the resultant two strings being included in the Embankment Foundation (stripped ground) surface.

Figure 3 shows the resultant triangulation when these cross section strings between A B and C D are created and included in the models.

Figure 3 Full Triangulation

For any volume calculations for Main Roads projects, where the coincident string along the boundary (Refer Section 7.2) does not reflect the shape of the surface, the generation of cross section strings detailed above shall apply. This shall particularly apply to surfaces defined by spot heights.

7.2.2Rock (Embankment Foundation) Calculations

Where rock is excavated wholly within the area of embankment, the boundary shall be defined as the extremity of the rock surface at the level defined by Specification 302 Earthworks - Rock Excavation.

Where part of the area of rock to be excavated falls outside the toe of batter of the embankment (interface string), the boundary shall consist of the area of rock within the embankment and the line of the interface string. Refer Figure 5.

7.2.3Borrow Pits, Unsuitable Material, Stockpiling Calculations

Where volumes are to be calculated on borrow pits, unsuitable material, rock excavation (non foundation) or stockpiles, the boundary shall be defined as the interface of the existing surface and the edge of the new excavation or stockpile.

7.3Volumes

Only software packages that use the prismoidal method shall be used for volume calculations and must use the following inputs:

An existing surface and a fill/cut surface Boundary string of the area under consideration Each surface shall have a three dimensional string coincident with the boundary string, defining the level of the respective design and stripped ground surface.

7.3.1Embankment Construction Limits

For embankment construction, the volume is to be based on the area defined by the design interface strings. (Refer to Section 7.1)

The area of stripped ground used for volume calculations is defined by dropping a vertical line from the design interface strings to the stripped ground as shown in Figure 4. That is, once the boundary string has been created using the interface strings, that boundary is used for both surfaces. As a result the coincident string on the boundary for the stripped ground should also be coincident with the design interface strings although at different level depending on each surface level.

In most cases this will differ to what is shown on Typical Cross Sections and Detail drawings, as these drawings are compiled prior to the removal of topsoil and where applicable the removal of the existing seal and/or existing pavement.

Figure 4 Embankment Cross Section

7.3.2Rock (Embankment Foundation)

For calculation of rock volumes, only the excavated rock within the interface between the original surface and the design model is used. This shall include table drains where applicable.

The volume is determined from the survey that defined the original rock surface and the level of the rock after excavation as defined in Specification 302 Earthworks - Rock Excavation.

Figure 5 shows the area (hatched) used for volumes, with the boundary being defined by the extremity of the rock within the interface between the original surface and the design model, in this case the right hand interface string.

Figure 5 Rock Excavation

Figure 6 Rock Excavation Cross Section

7.3.3Borrow Pits, Unsuitable Material and Stockpiling

Excluding areas of road works, all other volumes shall be calculated between the existing surface, obtained before excavation or fill occurs, and the final excavated/fill surface. The volume area is defined by the boundary created as per Section 7.1.3

However if unsuitable material within the embankment foundation extends outside the area defined by the design interface strings, only the volume within the foundation area is to be calculated. Where this occurs a vertical line shall be dropped from the interface string/s to the excavated surface to form part of the boundary as per Sections 7.2.1 and 7.2.2.

VOLUME VERIFICATION

To minimise the possibility of operator error, and to provide confidence in the volumes calculated, verification volumes shall be undertaken. In each case volumes are calculated within the boundary defined at Section 7.1.

The verification can be done in one of two ways:

Where supported by the software used to calculate the volumes, and where it is not used to calculate the original volumes, a prismoidal volume can be calculated from each surface used (strip ground, design, existing or cut/fill surface) to an arbitrary level. This level is to be a value lower than either surface.

Once the two volumes have been obtained, subtract the volume derived from the stripped ground or existing surface from the volume obtained from the design model, new fill or excavated surface.

If the resultant value is negative then the project is in a cut situation. If the value is positive then the project is in a fill situation and this resultant value is to be used as a check of the original calculated volume. From research undertaken, the variation between the original and verification volume should not exceed 1%. Where the software used does not support volume calculations to a base level, end area volumes are to be calculated to verify the original volumes. Where the volumes are for embankment foundation the interval for the end area calculations will be the same as the interval of the design master string. All other end area calculations will be at an interval of 1 metre.

VOLUME AND DATA LODGEMENT

At the completion of volume calculations (interim or final embankment) a Volume Report shall be completed. Refer Appendix A for a Proforma. This report shall be submitted to the Superintendent with the following:

Electronic and Hard copy of

Cross Section (End Area) volumes for Mass Haul Analysis and prismoidal volume verification.

For Tender volumes, Cross Section drawings of the subgrade design surface and existing surface at the interval of the master alignment string. Required for visual verification of volume surfaces.

As these drawings may be included in tender documents, no allowance for topsoil removal is to be included in the drawings.

For final volumes, Cross Section drawings of the subgrade design surface against the stripped ground surface, at the interval of the master alignment string. Required for visual verification of volume surfaces.

Digital data used for calculations which may consist of:

- Design

-Stripped ground and/or existing surface

-Boundary strings used for calculations

Where required to lodge electronic copies of the above information, the following formats shall apply.

Cross Section VolumesWord 2000 compatible

Cross Section DrawingsAutocad R14/2000 compatible

DesignMX design model or MX compatible input file

Stripped ground and/or existing surfaceMX design model or MX compatible input file

Boundary stringsMX design model or MX compatible input file

VOLUME REPORT

CONTRACT NUMBER:

PROJECT LOCATION:

Notes:

1. Topsoil allowance (if applicable) as per Specification 302 Topsoil, Clause 302.17 Removal From Designated Areas.

2. No embankment compaction factor to be used.

UNIT

VOLUME

Prismoidal Volumem3

Topsoil Allowance (if applicable)mm

METADATA

Version of Design model usedDate

Stripped ground or existing surface captureDate

Software used Name

Operator and Company nameName

Date of calculationDate