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ENERGIX-Stort program energi

Norwegian in-situ Rock Stress for Sustainable Development of Hydroelectric Power

Alternative title: Norsk in-situ Bergspenning for bærekraftig utvikling av vannkraft

Awarded: NOK 13.7 mill.

Project Number:

320654

Project Period:

2021 - 2025

Funding received from:

Norwegian HEP has a worldwide reputation for cost efficiency, environmental sustainability, and a proven design & construction concept. Some special features of the Norwegian HEP are lake taps, unlined tunnel, air-cushion surge chambers, unlined pressure shafts, and underground powerhouses. An essential part of this design concept is the utilisation of in-situ rock stress to prevent hydraulic jacking/fracturing situations, minimum steel lining. Thus, understanding & obtaining accurate information of in situ rock stress is of crucial. The existing methods for obtaining in situ rock stress are analytical, empirical, numerical, and in situ measurement. In analytical methods, vertical in-situ stress is estimated based on gravity & rock overburden. Horizontal stress is estimated based on the vertical stress with a ratio. Empirical methods are "rule of thumb" and equations proposed by different authors from their experience & research for the purpose of estimating minimum rock stress to prevent hydraulic failure in unlined pressured tunnels/shafts. Despite of comprehensive investigations/evaluations of in-situ rock stress being made, hydraulic failures still have happened in some HEPs, which have caused different levels of damage to the tunnels system, and some have serious consequences. To improve the situation, NoRSTRESS aims for: 1. Improve the knowledge on in-situ rock stress as a regional stress (deep stress), and as local stress variations (shallow stress) due to local geological, topographical, and geo-tectonic features. 2. Identify the behaviour of the rock mass on stress related instability along the waterway system under the condition of frequent load/unload scenarios. 3. Establish rock stress database for the successful evaluation of in-situ rock stress in HEP and other rock engineering projects during planning, construction, and operation. Machine learning process can be included to form an "intelligent database" that can be extended & improved with future data.

In summary, research in NoRSTRESS is aimed to fulfil the following three main objectives: 1. Improve the knowledge front on in-situ rock stress as a large picture of regional stress (deep stress), as well as local stress variations (shallow stress) due to local geological, topographical, and geo-tectonic features. 2. Research the behaviour of the rock mass to stress related instability along the waterway system under the condition of frequent cycles of load/unload scenarios that is being emerged and will be the operation scenario in the days to come due to different renewable sources of energy in the grid and its relationship with the in-situ stress. Through research, the Norwegian unlined tunnel solution for developing HEP projects is strengthening in Norway as well as internationally. 3. Establish rock stress database for the successful evaluation of in-situ rock stress in HEP as well as other rock engineering projects during planning, construction and operation. Machine learning process can be included to form an "intelligent database" that can be extended and improved with future data.

Funding scheme:

ENERGIX-Stort program energi