A Consideration on the value on geological investigation focusing on water inrush in discontinuous rock masses from viewpoints of construction contract

Otsu, Hiroyasu*; Arizono, Hiroki*; Saegusa, Hiromitsu

Doboku Gakkai Rombunshu, F4 (Tokushugo), Vol.66, No.1, p.77 - 90, 2010/12

This paper focused on the value on geological investigation from a viewpoint of construction contract, focusing on the risk caused by water inrush into underground structures such as tunnels/shafts constructed in discontinuous rock masses. In detail, water inrush evaluation using Discrete Fracture Network Model has been conducted focusing on the Mizunami Underground Research Laboratory construction project carried out by the Japan Atomic Energy Agency. Finally, it is pointed out that the accumulation of geological information help to mitigate losses due to geotechnical risk, and the contract of construction projects including unforeseeable geological condition should be regarded as incomplete contract, considering necessity of negotiation.

A Study on risk assessement approach of water inflow into a shaft in fractured rock mass

Motoshima, Takayuki*; Onoe, Hironori*; Ijiri, Yuji*; Otsu, Hiroyasu*; Saegusa, Hiromitsu

Doboku Gakkai Rombunshu, C, 66(2), p.370 - 386, 2010/06

https://doi.org/10.2208/jscejc.66.370

Since water inflow into a tunnel significantly impacts construction costs and schedules, it is important to estimate the impact on these factors quantitatively based on prior information about hydrogeological properties. A simplified formula is proposed in order to estimate water inflow volume into tunnel and is validated through comparing the results of DFN model. This formula is able to calculate water inflow risk more quickly than DFN model. Monte Carlo simulation and sensitivity analysis about water inflow risk are performed by using this formula. Then relationships between water inflow risk and amount of information about fracture properties are obtained based on the sensitivity analysis.

Applicability of the concept of Fractal to Fracture Network Model in Rock Mass

; Otsu, Hiroyasu*; Nishiyama, Satoshi*; Ijiri, Yuji*

ISRM Regional Symposium, 1, p.203 - 210, 2002/00

None

None

*; *; *

JNC TY8400 2000-006, 45 Pages, 2000/03

JNC-TY8400-2000-006.pdf:5.73MB

None

Development of risk management approach for underground facility construction in granite

Shimono, Masato*; Motoshima, Takayuki*; Ijiri, Yuji*; Otsu, Hiroyasu*; Sakai, Ryosuke*; Sakai, Kazuo*; Sato, Toshinori; Mikake, Shinichiro

no journal, , 

It is considered that the uncertainty of construction cost due to geological heterogeneity is quite large. Therefore, it is crucial to make a long-term consistent budget plan for a construction period of tens years and to have engineering strategies for reducing a total budget. In this study, a risk management approach for construction in a heterogeneous fractured rock is developed. In this approach, methodologies of calculating construction costs for excavating drifts and taking countermeasures at high-hydrostatic pressured fracture zones in a heterogeneous rock are established. The cost for excavating drift is calculated from the heterogeneity of rock strength estimated from a geostatistical modeling approach. The cost for taking countermeasures is calculated from the heterogeneity of large fracture zone estimated from a probabilistic discrete fracture network modeling approach. In addition, a risk for a construction is assessed by a risk cost curve commonly used in the financial business.

Risk evaluation and management method for high-pressure inflow, 2; Management of high-pressure inflow risk during the shaft construction using the groundwater level in the boreholes

Motoshima, Takayuki*; Ijiri, Yuji*; Onoe, Hironori; Saegusa, Hiromitsu; Watanabe, Tadashi; Otsu, Hiroyasu*

no journal, , 

no abstracts in English

A Study of risk assessment of rapid inrush of water into the underground facility at the Mizunami Underground Research Laboratory project, 1; Development of risk assessment methodology of water inrush using discrete fracture network model

Motoshima, Takayuki*; Ijiri, Yuji*; Onoe, Hironori; Saegusa, Hiromitsu; Otsu, Hiroyasu*

no journal, , 

Since the groundwater inflow into a tunnel has a large impact on a construction cost and a schedule. It is important to estimate the influences of groundwater inflow on the cost and schedule quantitatively based on prior information about hydrogeological properties. In this study, the hydrogeological structure of fractured granite distributed at the Mizunami Underground Research Laboratory was modeled by a stochastic Discrete Fracture Network, and the risk of water inrush is evaluated probabilistically based on the model. The effects of parameter value uncertainties derived from field data on the risk of water inrush were also discussed.

A Study on the meaning of geological investigation focusing on water inrush from viewpoint of geological risk

Otsu, Hiroyasu*; Okawa, Junnosuke*; Takeuchi, Ryuji; Saegusa, Hiromitsu; Ota, Yasutaka*

no journal, , 

This study focused on the meaning of geological investigations on the geological risk, focusing on the risk caused by water inrush into underground structures such as tunnels/shafts constructed in discontinuous rock masses. In detail, water inrush evaluation using Discrete Fracture Network Model has been conducted focusing on what kind of geological investigation contributes to mitigation of losses due to geological risk. As a result, it is pointed out that it becomes possible to reduce a geological risk by accumulation of the further geological investigation although the risk increases temporarily by some geological investigation.