DEP SPECIFICATION
MOBILE MOBIL E CRANE FOUNDATION ASSESS A SSESSMENT MENT
DEP 60.00.10.13-Gen. February 2012
DESIGN AND ENGINEERING PRACTICE
© 2012 Shell Group of companies All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, published or transmitted, in any form or by any means, without the prior written permission of the copyright owner or Shell Global Solutions International BV.
DEP 60.00.10.13-Gen. February 2012 Page 2
PREFACE DEP (Design and Engineering Practice) publications reflect the views, at the time of publication, of Shell Global Solutions International B.V. (Shell GSI) and, in some cases, of other Shell Companies. These views are based on the experience acquired during involvement with the design, construction, operation and maintenance of processing units and facilities. Where deemed appropriate DEPs are based on, or reference international, regional, national and industry standards. The objective is to set the standard for good design and engineering practice to be applied by Shell companies in oil and gas production, oil refining, gas handling, gasification, chemical processing, or any other such facility, and thereby to help achieve maximum technical and economic benefit from standardization. The information set forth in these publications is provided to Shell companies for their consideration and decision to implement. This is of particular importance where DEPs may not cover every requirement or diversity of condition at each locality. The system of DEPs is expected to be sufficiently flexible to allow individual Operating Units to adapt the information set forth in DEPs to their own environment and requirements. When Contractors or Manufacturers/Suppliers use DEPs, they shall be solely responsible for such use, including the quality of their work and the attainment of the required design and engineering standards. In particular, for those requirements not specifically covered, the Principal will typically expect them to follow those design and engineering practices that will achieve at least the same level of integrity as reflected in the DEPs. If in doubt, the Contractor or Manufacturer/Supplier shall, without detracting from his own responsibility, consult the Principal. The right to obtain and to use DEPs is restricted, and is granted by Shell GSI (and in some cases by other Shell Companies) under a Service Agreement or a License Agreement. This right is granted primarily to Shell companies and other companies receiving technical advice and services from Shell GSI or another Shell Company. Consequently, three categories of users of DEPs can be distinguished: 1)
Operating Units having a Service Agreement with Shell GSI or another Shell Company. The use of DEPs by these Operating Units is subject in all respects to the terms and conditions of the relevant Service Agreement.
2)
Other parties who are authorised to use DEPs subject to appropriate contractual arrangements (whether as part of a Service Agreement or otherwise).
3)
Contractors/subcontractors and Manufacturers/Suppliers under a contract with users referred to under 1) or 2) which requires that tenders for projects, materials supplied or - generally - work performed on behalf of the said users comply with the relevant standards.
Subject to any particular terms and conditions as may be set forth in specific agreements with users, Shell GSI disclaims any liability of whatsoever nature for any damage (including injury or death) suffered by any company or person whomsoever as a result of or in connection with the use, application or implementation of any DEP, combination of DEPs or any part thereof, even if it is wholly or partly caused by negligence on the part of Shell GSI or other Shell Company. The benefit of this disclaimer shall inure in all r espects to Shell GSI and/or any Shell Company, or companies affiliated to these companies, that may issue DEPs or advise or require the use of DEPs. Without prejudice to any specific terms in respect of confidentiality under relevant contractual arrangements, DEPs shall not, without the prior written consent of Shell GSI, be disclosed by users to any company or person whomsoever and the DEPs shall be used exclusively for the purpose for which they have been provided to the user. They shall be returned after use, including any copies which shall only be made by users with the express prior written consent of Shell GSI. The copyright of DEPs vests in Shell Group of companies. Users shall arrange for DEPs to be held in safe custody and Shell GSI may at any time require information satisfactory to them in order to ascertain how users implement this requirement. All administrative queries should be directed to the DEP Administrator in Shell GSI.
DEP 60.00.10.13-Gen. February 2012 Page 3 TABLE OF CONTENTS 1. 1.1 1.2 1.3 1.4 1.5 1.6
INTRODUCTION ........................................................................................................4 SCOPE........................................................................................................................4 DISTRIBUTION, INTENDED USE AND REGULATORY CONSIDERATIONS .........4 DEFINITIONS .............................................................................................................4 CROSS-REFERENCES .............................................................................................4 COMMENTS ON THIS DEP .......................................................................................5 DUAL UNITS...............................................................................................................5
2. 2.1 2.2 2.3 2.4
GENERAL CONSIDERATIONS.................................................................................6 INTRODUCTION ........................................................................................................6 BASIC REQUIREMENTS ...........................................................................................6 ROLES AND RESPONSIBILITIES .............................................................................6 UNITS OF MEASUREMENT ......................................................................................6
3.
TECHNICAL CONSIDERATIONS .............................................................................7
4. 4.1 4.2 4.3 4.4
ASSESSMENT PROCESS FOR GROUND STABILITY ...........................................8 GENERAL...................................................................................................................8 ASSESSMENT OF APPLIED LOADS........................................................................8 SITE INVESTIGATION ...............................................................................................8 GEOTECHNICAL ASSESSMENT..............................................................................9
5. 5.1 5.2 5.3
5.4 5.5
MITIGATION MEASURES .......................................................................................10 GENERAL.................................................................................................................10 USE OF LOAD-SPREADING PLATES OR MATS................................................... 10 GROUND IMPROVEMENT OF EXISTING SUBGRADE FOR A PERMANENT SITUATION...............................................................................................................10 INSTALLATION OF WORKING PLATFORMS.........................................................10 REINFORCMENT .....................................................................................................10
6. 6.1 6.2
SITE PREPARATION ...............................................................................................11 CRANES WITH OUTRIGGERS................................................................................11 CRAWLER CRANES................................................................................................11
7.
MONITORING DURING LIFTING ............................................................................12
8.
REFERENCES .........................................................................................................13
DEP 60.00.10.13-Gen. February 2012 Page 4 1.
INTRODUCTION
1.1
SCOPE This new DEP specifies requirements and gives recommendations for the assessment of the foundation stability of mobile cranes during lifting operations. Failure of the ground is a common cause of incidents during the operation of mobile cranes. This document sets out procedures for the assessment of ground conditions and the loading conditions applied by mobile cranes. It then presents a methodology for the design of appropriate measures to allow safe operation.
1.2
DISTRIBUTION, INTENDED USE AND REGULATORY CONSIDERATIONS Unless otherwise authorised by Shell GSI, the distribution of this DEP is confined to Shell companies and, where necessary, to Contractors and Manufacturers/Suppliers nominated by them. Any authorised access to DEPs does not for that reason constitute an authorisation to any documents, data or information to which the DEPs may refer. This DEP is intended for use in oil refineries, chemical plants, gas plants, exploration and production facilities and supply/distribution installations. This DEP may also be applied in other similar facilities. When DEPs are applied, a Management of Change (MOC) process shall be implemented; this is of particular importance when existing facilities are to be modified. If national and/or local regulations exist in which some of the requirements could be more stringent than in this DEP, the Contractor shall determine by careful scrutiny which of the requirements are the more stringent and which combination of requirements will be acceptable with regard to the safety, environmental, economic and legal aspects. In all cases, the Contractor shall inform the Principal of any deviation from the requirements of this DEP which is considered to be necessary in order to comply with national and/or local regulations. The Principal may then negotiate with the Authorities concerned, the objective being to obtain agreement to follow this DEP as closely as possible.
1.3
DEFINITIONS
1.3.1
General defini tio ns
The Contractor is the party that carries out all or part of the design, engineering, procurement, construction, commissioning or management of a project or operation of a facility. The Principal may undertake all or part of the duties of the Contractor. The Manufacturer/Supplier is the party that manufactures or supplies equipment and services to perform the duties specified by the Contractor. The Principal is the party that initiates the project and ultimately pays for it. The Principal may also include an agent or consultant authorised to act for, and on behalf of, the Principal. The word shall indicates a requirement. The word should indicates a recommendation. 1.3.2
1.4
Specific defini tion s Term
Definition
Mobile Crane
Mobile crane consists of a lattice or telescopic boom mounted on a mobile platform capable of travelling laden or unladen without the need for fixed runways and which relies on gravity for stability.
CROSS-REFERENCES Where cross-references to other parts of this DEP are made, the referenced section number is shown in brackets ( ). Other documents referenced by this DEP are listed in (8).
DEP 60.00.10.13-Gen. February 2012 Page 5 1.5
COMMENTS ON THIS DEP Comments on this DEP may be sent to the Administrator at
[email protected], using the DEP Feedback Form. The DEP Feedback Form can be found on the main page of “DEPs on the Web”, available through the Global Technical Standards web portal http://sww.shell.com/standards and on the main page of the DEPs DVD-ROM.
1.6
DUAL UNITS This DEP contains both the International System (SI) units, as well as the corresponding US Customary (USC) units, which are given following the SI units in brackets. When agreed by the Principal, the indicated USC values/units may be used.
DEP 60.00.10.13-Gen. February 2012 Page 6 2.
GENERAL CONSIDERATIONS
2.1
INTRODUCTION The safe operation of mobile cranes requires careful planning which entails consideration of several critical factors. A disproportionate number of incidents occur as a result of incorrect assessment of ground conditions, leading to the bearing capacity failure or excessive settlement beneath outriggers or tracks. Stringent regulations apply regarding the assessment of loads within the structure of a mobile crane, yet guidance on the assessment of ground conditions and the possible need for working platforms is less well defined in National and International Standards. This document presents the methodology that shall be used for the assessment of ground conditions for the use of mobile cranes at the Principal’s facilities.
2.2
BASIC REQUIREMENTS This DEP shall be applied to the use of all mobile cranes. Supplementary to this DEP, all work shall be carried out in accordance with recognised and accepted codes of practice and standards, and the principles of good engineering practice. Examples of acceptable standards and codes of practice are given in this DEP.
2.3
ROLES AND RESPONSIBILITIES Several parties are likely to be involved in the specification, management and operation of lifting operations; these are likely to include the Principal, Contractor, the permanent works designer and the mobile crane sub-contractor. Responsibilities shall be clearly defined such that operations are undertaken in a safe and efficient manner in accordance with the lift plan. However, one person shall be appointed and have responsibility for, and overall control of, the lift operation (the Appointed Person or Person-in-Charge). It shall be ensured that the working platform from which the lifting operations are undertaken is fit for purpose.
2.4
UNITS OF MEASUREMENT SI units shall be used for all surveys and related activities in accordance with DEP 00.00.20.10-Gen. unless agreed otherwise by the Principal.
DEP 60.00.10.13-Gen. February 2012 Page 7 3.
TECHNICAL CONSIDERATIONS
Failure of the ground is responsible for a large proportion of incidents involving mobile cranes. In most cases, this is due to inadequate consideration being given to the bearing capacity and settlement characteristics of the ground. Under normal lifting conditions, the consequences of failure are often severe; however, within an operating environment the hazards may be even greater. The aim of this document is to avoid the risk of failure without incurring excessive expenditure. This is straightforward to achieve but requires planning and assessment before lifting operations commence. The key elements that lead to foundation failure of mobile cranes are: 1.
The presence of weak subgrade, which leads to general failure due to inadequate bearing capacity.
2.
Localised failure of variable subgrade due to the presence of weaker zones.
3.
“Punching” failure where a thin crust of apparently competent material overlies a weaker layer.
4.
Localised “hard spots” caused by buried structures that incur differential settlement.
5.
The presence of sloping or uneven ground that induces localised failure under mobile crane loading.
6.
Edge failure of working areas due to crane loading.
7.
Inadequate crane load definition.
In most cases, these issues can be addressed using simple measures.
DEP 60.00.10.13-Gen. February 2012 Page 8 4.
ASSESSMENT PROCESS FOR GROUND STABILITY
4.1
GENERAL For assessment purposes, the mobile crane foundation shall be regarded in the same way as any type of structural foundation. Assessment of the performance of the foundation shall therefore be undertaken in accordance with DEP 34.11.00.12-Gen. The basis of the assessment shall comprise two elements: •
•
4.2
Calculation of the loads applied by the crane to the subgrade under all relevant working conditions. Assessment of the performance of the ground based on appropriate site investigation data.
ASSESSMENT OF APPLIED LOADS Critical to the assessment of the working stability of mobile cranes is the determination of the loads applied to the ground by tracked plant and under outriggers for wheeled cranes, under the full range of working conditions. The loads shall be provided by the Contractor to determine the maximum ground pressures that can be exerted by the equipment. This includes loads generated during rigging and derigging of the crane, boom up and boom down and the various lifting radii that will be used from the crane position. The loads shall include environmental loads and dynamic lift factor effects. The Contractor shall supply complete and accurate details of the actual loads applied by a mobile crane and verify against the loading conditions assumed in the foundation assessment before lifting operation commences. Foundation loads shall be calculated using the approach set out in ISO 4305:1991. Wind loads shall be assessed in accordance with ISO 4302:1981. Load calculations shall make due allowance of the use of any load-spreading pads that are to be used during lifting operations.
4.3
SITE INVESTIGATION Reference is made to DEP 34.11.00.10-Gen. The correct assessment of the site is essential at an early stage in the design of lifting operations. Appropriate and sufficient ground data in the upper 4 m (13 ft) of the ground across the likely working area is generally vital to ensure an accurate assessment of the crane stability. The level of site investigation information that is required varies depending on: a) Location b) Static, dynamic crane movement c)
The size and type of crane
d) The weight to be lifted e) The potential consequence of ground failure f)
The level of knowledge of the prevailing ground conditions at the site
g) The likely need to develop mitigation measures or ground improvement works to ensure lifting stability on poorer ground For many of the Principal’s facilities, a significant amount of ground data may already exist associated with other aspects of site development. There is no requirement for additional
DEP 60.00.10.13-Gen. February 2012 Page 9 geotechnical site investigation to be undertaken before the lifting work commences provided that: •
•
there is confidence that the ground conditions in the lifting zone are similar to those identified by the available data and that no significant modification to site conditions has occurred since the data was gathered. the existing site investigation data is adequate to undertake the ground assessment.
The strength and variability of the near-surface ground is critical to the performance of a working platform. Where a geotechnical site investigation is deemed necessary, this shall include a requirement to investigate the ground across the likely working area, as follows: •
•
Careful description of soils in accordance with DEP 34.11.00.10-Gen. Determination characteristic values of soil strength for near-surface (<4 m (<13 ft) depth) strata.
Made ground (non-engineered fill) can be extremely difficult to assess due to its variability. Assessment not only of its in-situ strength but also of composition is therefore essential. 4.4
GEOTECHNICAL ASSESSMENT Calculations shall be undertaken using the methodology proposed for shallow foundations as set out in DEP 34.11.00.12-Gen. The assessment shall be undertaken by a qualified geotechnical engineer. Calculations shall consider both Ultimate Limit State (ULS) conditions and Serviceability Limit State (SLS) conditions.
4.4.1
Alt ernative codes of practi ce
Section 2.2.2 included in DEP 34.11.00.12-Gen. shall be adopted.
DEP 60.00.10.13-Gen. February 2012 Page 10 5.
MITIGATION MEASURES
5.1
GENERAL Where existing ground conditions are inadequate for the proposed crane loading or where the crane needs load distribution due to the use of caterpillar tracks, a number of options exist to enable safe working. These include: 1.
The use of enlarged outrigger mats or “spreaders” to reduce the pressures applied beneath outriggers.
2.
Dragline mats to reduce the soil pressures applied beneath crawler tracks.
3.
The use of ground improvement over the whole area.
4.
The installation of an engineered working platform.
5.
The use of soil reinforcement.
6.
Selective excavation and replacement of “soft spots” with compacted fill.
7.
The breaking down of any “hard spots” and their replacement with compacted fill for a permanent situation.
8.
The construction of a temporary working platform across operational areas.
Selection of mitigation measures will depend on the site-specific conditions and should be done in consultation with an experienced Geotechnical Engineer. Any mitigation measures should be such that, once implemented, the modified conditions meet the requirements set out in (4). 5.2
USE OF LOAD-SPREADING PLATES OR MATS Mats or spreader plates shall have adequate structural stiffness and strength to avoid intrinsic failure under loading. Set-up of the crane outriggers shall be such that sliding off the spreader plates under load is prevented. Crane mats shall be placed perpendicular to the caterpillar tracks.
5.3
GROUND IMPROVEMENT OF EXISTING SUBGRADE FOR A PERMANENT SITUATION Reference is made to DEP 34.11.00.12-Gen. for guidance on ground improvement.
5.4
INSTALLATION OF WORKING PLATFORMS The procedure presented in BRE Special Publication 470 shall be adopted when installing working platforms.
5.5
REINFORCMENT Reference is made to DEP 34.11.00.12-Gen. for guidance on ground reinforcement. In addition to this DEP, where geosynthetic materials are to be employed, the recommendations made in Section 3.4 of BRE Special Publication BR470 shall be adhered to and, where necessary, the approaches outlined in CIRIA Publication SP123 (1996) shall be followed.
DEP 60.00.10.13-Gen. February 2012 Page 11 6.
SITE PREPARATION
6.1
CRANES WITH OUTRIGGERS In many cases, before any lifting operations commence, the existing formation will require a degree of preparation. This shall include:
6.2
1.
Removal of any soft superficial material and backfill with compacted granular fill.
2.
Levelling the ground surface, so that all outrigger mats are resting on a flat horizontal plane.
3.
Breaking down of any hard spots (formed by old basements or substructures) and backfilling the resulting voids with well compacted granular fill (for a permanent situation).
4.
Identification of any abandoned underground services and mitigation (either removal and backfill with compacted granular fill, or backfilling with suitable lean-mix concrete, grout, etc.).
5.
Identification of natural or man-made voids, culverts, live services, etc. that cannot be backfilled. Mitigation measures such as the use of protective plates or transfer slabs to bridge over such features may be possible; alternatively these areas should be clearly marked and isolated from operational areas to prevent damage due to crane activity.
6.
Deterioration of the exposed subgrade before platform installation should be prevented by the implementation of effective surface water drainage to prevent ponding and softening of surface materials.
CRAWLER CRANES Before any lifting operations commence, the existing formation will require a degree of preparation for crawler cranes as well. This shall include levelling the ground surface, so that the crane mats are resting on a flat horizontal plane.
DEP 60.00.10.13-Gen. February 2012 Page 12 7.
MONITORING DURING LIFTING
Where high-risk lifts are being undertaken, settlement of outriggers shall be observed during the first lift operation. A regular inspection of mats is suggested to monitor settlement of one or all outriggers for routine lifts. Monitoring is recommended when ground conditions may change, e.g., due to rain or nearby excavation. Where progressive settlement beyond that expected under the outrigger loads is observed, the lift shall be terminated immediately, made safe, and appropriate mitigation measures shall be deployed. Once the crane is properly set up, and before the first lift, the crane uppercarrier should be slewed 360 degrees. Ground settlement should be monitored during this operation.
DEP 60.00.10.13-Gen. February 2012 Page 13 8.
REFERENCES
In this DEP, reference is made to the following publications: NOTES:
1. Unless specifically designated by date, the latest edition of each publication shall be used, together with any amendments/supplements/revisions thereto. 2. The DEPs and most referenced external standards are available to Shell staff on the SWW (Shell Wide Web) at http://sww.shell.com/standards/.
SHELL STANDARDS
The use of SI quantities and units (endorsement of ISO/IEC 80000)
DEP 00.00.20.10-Gen.
Onshore and nearshore site investigations
DEP 34.11.00.10-Gen.
Geotechnical and foundation engineering - Onshore
DEP 34.11.00.12-Gen.
BRITISH STANDARDS AND DESIGN GUIDES
Working platforms for tracked plant, Good practice guide to the design, installation, maintenance and repair of ground-supported working platforms
BRE BR470 (2004)
Issued by: Building Research Establishment Limited (BRE), UK
Soil reinforcement with geotextiles
CIRIA SP123 (1996)
Issued by: CIRIA (Construction Industry Research and Information Association), UK
INTERNATIONAL STANDARDS AND DESIGN GUIDES
Cranes - Wind load assessment
ISO 4302 (1981)
Mobile cranes – Determination of stability
ISO 4305 (1991)
