Geology and Trenchless Technology

Abstract

Even though there are significant benefits in utilising Trenchless Technology for the installation of new pipelines it brings its own set of challenges and risks that need to be appropriately managed for a successful outcome. One of the major risks with the use of any trenchless technology is the geology. To be able to manage this risk two key elements need to be considered. 1. Determination of the likely geotechnical conditions that will be tunnelled/ drilled through. 2. Management of unexpected variances in the likely conditions both from a client and Contractors’ perspective. Drawing on experience as a Contractor, a Client and a Consultant, this paper discusses the various strategies that can be implemented to best manage these risks. It utilises real industry project examples, where unexpected ground conditions were encountered during the construction phase of HDD and microtunnelling trenchless installations. These strategies encompass measures that can be put in place during the planning, design, procurement, and construction stages. These strategies intend to enable project risks to be reduced or managed so providing a successful outcome for both the Client and Contractor. What is critical here is providing clear contractual pathways to deal with both known, perceived, and unexpected risks. Recently completed example projects discussed are: • Urban Utilities - HDD crossing of Centenary Hwy, Jindalee QLD. Page 1 of 22 No-Dig Down Under 2021 Geology and Trenchless Technology A real life perspective on how geotechnical conditions can vary and discussion of Risk Management strategies to deal with this. Adam Shayler • Yarra Valley Water – Microtunnelling sewer installation, Donnybrook 2, Donnybrook VIC. • Unity Water - HDD Crossing Fishermans Road, Sunshine Coast QLD. • Ausgrid - HDD Crossing for cable installation at Scotland Island, Pittwater NSW. Some of the areas discussed, where strategies can be implemented, are as follows: • Scope of geotechnical investigation based on likely trenchless methodology; • Appropriate assessment of the geotechnical investigation to determine potential risks; • Appropriate project contract structure; • Project budget cost estimation and applying appropriate risk allowances; • Robust documentation (Scope of Work, Tender Documents, and Specification) addressing actual, perceived, and unexpected risks; and, • The importance of detailed oversight and record-taking during delivery.