Modern Methods of Excavation Support

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Harvey Hensley
5 years ago
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1 Modern Methods of Excavation Support Presented by Duncan Pearson Technical Services Manager Helen Aird Technical Sales Engineer

2 Agenda Company Introduction / Technical Services Introduction to proprietary shoring Why excavations fail SiteSafe Solutions Load monitoring of hydraulic struts / case studies 6. Bad practice slides 7. Questions

3 Company Introduction

4 Established 1954 Annual turnover of 147m Circa 1500 employees

5 Strategic depot network Comprehensive equipment portfolio Dedicated sales & operational support

6 Technical Services

7 ction u d o r t n ffice I O n g i s De Twelve E Design xperienced Engine ers Specia list Ma jor Pro Team jects Dedica te Suppo d Technical S rt ales ISO acc reditati on P.I. Co ver - 5m Docum en checkin ted design a nd g proce dure

8 Client Design Brief Complementary design service Safe, practical & cost effective solutions

9 rvices e S g n i Train Traini ng Op tions Office based apprec course iation s Practic al site training Toolbo x Talk DVD produc ed in c on with th e Natio junction nal Constr uction College Bircham, Newton

10 Introduction to Proprietary Shoring a) What is proprietary shoring? b) Why do we shore excavations? c) What are its advantages?

11 Examples of Traditional methods of support

12 Examples of Proprietary systems

13 Proprietary systems

14 Why Support Excavations? Avoid death and injury Protect colleagues and Public outside the dig Comply with Health And Safety Legislation WHY SUPPORT EXCAVATIONS? Avoid damage to Existing services Time and Cost savings Protect adjacent structures

15 Why Support Excavations? Average of 7 fatal accidents each year. 7 Deaths 60 Major Incidents 1500 Minor Incidents??? Near Misses?

16 1 Rapid installation and removal 2 3 On-site adjustment and versatility 4 5 No on-site welding The ability for pre-load to limit deflections Re-use of components 6 Improved safety Advantages of proprietary shoring

17 Why do excavations fail? Causes of failure in excavations and how we can prevent them

18 a near miss!!

19 small water leak in cofferdam leads to..

20 Examples of Failure Pile toe failure - due to over digging Over loading of frame

21 Surcharges (Additional external loadings not taken into account)

22 Groundwater Loss of fines

23 Causes of Failure SITE ISSUES Design Brief Inadequate or poor quality information Verbal soil information Missing surcharges Incomplete assessment of site conditions Execution Lack of communication Ignoring changes in conditions Poor workmanship / Failure to follow design DESIGN ISSUES Design Lack of consideration of limit states Lack of adequate design risk assessment Poor interpretation of SI Underestimation of surcharges Underestimation of effects of groundwater Over reliance on software

24 Causes of Failure / Accidents HUMAN ISSUES Ignorance Bullying Idleness Neglect Irresponsibility Complacency Forgetfulness

25 Collapse of Excavations Collapse of unsupported or inadequately supported excavation walls. Often with disastrous consequences This was the aftermath scene of a recent trench collapse recent fatality

26 Modes of Failure

27 Failure due to boiling

28 Modes of Failure Slope failure of Battered Excavation

29 Modes of Failure Cross-strut removal / frame overload

30 s n g i S g n i n r a W De flection Te nsion c racks So il move ment

31 SiteSafe Solutions

32 ions t u l o S e Sitesaf System s includ e Box Ha ndrail S ystems Ladder safe R ange Stepsa fe Edgesa fe Endsaf e Surrou ndsafe Fallsaf e

33 On board load monitoring of proprietary struts

34 Wireless Load Monitoring Overview Calibrated load / swivel pin Hydraulic strut assembly Wireless telemetry unit and transmitter

35 Wireless Load Monitoring Overview

36 Typical results graph Trigger levels

38 Case Study Tyne Tunnel 2 72 Struts 96 Struts 10 Struts 14 Struts This 260m project was one of the largest infrastructure projects in the UK. The main Contractor was Bouygues Travaux Publics (UK)

39 Design Challenges High design axial prop loads ranging from 1,500kN 13,000kN Design specification included: Loss of prop condition 50kN accidental loading 35 temperature range (60% restraint) Overcome a reluctance to use hydraulic props Huge amount of bespoke fabrication Provide a cost effective solution over long rental period