چکیده مقاله
Tunnelling is the Art of dealing with Geologic Uncertainties Tunnel designers decide the future success at an early project stage Designers are the managers of tunnel construction Designers choice of design and contract model is the managing tool in construction Contract & Risk Management of Underground Works for both conventional and mechanized tunnelling shall follow procurement developments Fundamental requirements for tunnel design and construction contracts are • Evaluation/classification of ground conditions and particular project requirements• Design with subdivisions in stages, following the project and construction development • Construction Methods suitable for standard plant, equipment and material• Risk Management Plan RMP in context with Geotechnical Baseline Report GBR • Flexible Contractual Models for fair remuneration Demand for proper designed and contracted Underground Works is continuously growing Conventional and TBM Tunnelling are both well suited for tunnelling in difficult, complex and rapidly changing geological and geotechnical conditions It is paramount to maximize safety and to minimize construction cost by selecting optimum driving cross section, driving methods and suitable lining during the design and construction phases During tunnel excavation simultaneous and joint decision by the contract partners must be realized within predetermined limits to manage flexible response to changing ground and ground behaviour conditions While information exchange happens increasingly fast to the benefit of projects, the most important feature of a tunnel project remains contract model and geotechnical baselines Contract models are based and do depend on valuable professional traditions where the project shall be implemented Tunnel Construction is facing conditions of distributed teams and requires around the clock collaboration and coordination as well as the ability to successfully navigate throughout the life cycle of the project Today’s projects and program managers need tools that deliver the necessary project schedule and budget commitments They need the ability to integrate project and program resources with other departments and at other locations to ensure project success With tools to accurately forecast project completion dates and costs against estimates, strategic adjustments can be made throughout the project lifecycle and confidently make and keep commitments to the customers With real time key performance indicators, metrics, and financial data, deep analytical capabilities and advance warnings are received to reduce the risk of cost and schedule overruns and any resulting contract penalties Suggestions for efficient risk and safety management, payment and contract penalty clause are aimed at ensuring data collection and interpretation gets done on a realistic useful time scale, so as to constantly update understanding of ground response during actual construction and thereby plan against the potential for unexpectedly intersecting problem ground conditions ahead of the tunnel drive A comprehensive risk matrix is to be prepared and to be included in the Tender documents In any project, various risks have to be grouped into several risk categories • Design risks • Geological risks • Technological risks • General Risks The risks have to be allotted appropriately either to the Contractor or to the Employer so that the same can be suitably taken into account by the Contractor at the bidding stage Allocation of various risks during the design & execution of the project is given in the risk register, which should be a part of the contract document For addressing geological risks, Geotechnical Baseline Report GBR is the solution The GBR describes the conditions expected to be encountered during tunnel construction and other rock excavations It represents the Employer’s best judgment of geotechnical conditions anticipated in the excavations Actual conditions encountered during the execution may differ from those specified in GBR The experience from all of the tunnelling projects that have been examined in detail from project works in mountainous high cover situations, both TBM and DBM, shows clearly, that adverse conditions if encountered unexpectedly can lead to major collapse problems with delays of years sometimes being incurred With tools to accurately forecast project completion dates and costs against estimates, strategic adjustments can be made throughout the project lifecycle and confidently make and keep commitments to the customers With real time key performance indicators, metrics, and financial data, deep analytical capabilities and advance warnings are received to reduce the risk of cost and schedule overruns and any resulting contract penalties Lessons learned in design and in construction show that Geotechnical Baseline Report and Risk Management Plan shall be part of any contract document Contracting trends from practice show that project owners tend to shift the geotechnical risk of adverse geology to the contractor The clear distinction of risk ownership shall contribute to project success To make use of EPC Engineering Procurement Contracts requires more geotechnical investigations and related expenses than conventional contracts
کلیدواژهها
نویسندگان
Harald Wagner
Consulting Engineer & ITA EXCO Expert, Bangkok/Vienna
شیوه ارجاع
Wagner, Harald,1394,Solving Complexities in Tunnel Budget & Schedule Control with Geotechnical Baselines & Risk Management,The Second Regional Conference and the Eleventh Iran Tunnel Conference,Tehran
ارائهشده در
مجموعه مقالات دومین کنفرانس منطقه ای و یازدهمین کنفرانس تونل ایران11 آبان 1394 · تهران