Study on characterization of colloidal silica grout for rock excavation under saline groundwater

Tsuji, Masakuni*; Nakashima, Hitoshi*; Saito, Akira*; Okihara, Mitsunobu*; Sato, Toshinori

45th Annual Waste Management Conference (WM 2019); Encouraging Young Men & Women to Achieve Their Goals in Radwaste Management, Vol.7, p.4749 - 4763, 2020/01

A rock excavation grouting technology has been recently studied as significant technology for reducing the ingress of water into the deep repository. However, it has not been studied for applying to the coastal region, where it is discussed to be a more suitable region for the geological disposal in Japan. The latest material called colloidal silica grout (CSG) is good for sealing narrow fractures but is known to be sensitive to the salinity of groundwater because of its gelling property with salt accelerator. Although the gelling of CSG can be controlled by adding an acidic pH adjuster, the methodology for delivering the appropriate grout is not well established for such conditions of saline groundwater. Therefore, this research project was established to enhance the existing rock grouting technology for deep repositories.

Characterisation of colloidal silica grout under saline groundwater; Overall results for 3-year research project

Tsuji, Masakuni*; Aoyagi, Kazuhei; Nakashima, Hitoshi*; Okihara, Mitsunobu*; Sato, Toshinori

Proceedings of the Nordic Grouting Symposium 2019 (Internet), 15 Pages, 2019/09

This paper shows an overall result of the 3-year study on the characterisation of the colloidal silica grout (CSG) under saline groundwater, aiming to enhance the existing rock grouting technology, especially for the CSG under the saline groundwater. As a first step, we performed the survey of the latest grouting technology of CSG. We developed a feasible mixing methodology and have obtained the various CSG's properties impacted by the salty mixing water or submerged by saline water. Moreover, we proposed a theory for the grout penetration under saline water and performed the injection tests. In the second workshop in the final year, our overall findings in this study were recognised to attain some progress in the development of the grouting technology.

Evaluation of combined pre- and post-excavation grouting for reducing water inflow under high water pressure condition

Mikake, Shinichiro; Ikeda, Koki; Matsui, Hiroya; Tsuji, Masakuni*; Nishigaki, Makoto*

Doboku Gakkai Rombunshu, C (Chiken Kogaku) (Internet), 74(1), p.76 - 91, 2018/03

https://doi.org/10.2208/jscejge.74.76

Pre-grouting of shafts and galleries had been conducted during the construction of MIU in the aspect of reducing water inflow. After excavating GL.-500m gallery, a post-grouting was performed on section of the pre-excavation grouting area under high water pressure condition (max: 4MPa). The post-grouting experiment was performed outside of the pre-grouting zone with designs, applying colloidal silica grouting material and complex dynamic grouting. It was estimated that the inflow after post-grouting was reduced by 1/100 of the case that pre- and post-grouting were not performed. These results indicate that the applied combined pre- and post-grouting methodology is effective in reducing water inflow and it can be applicable under high water pressure condition. Then, this paper states the theoretical evaluation of relationship between reduction of hydraulic conductivity and the grouting zone is very convenient and useful for grouting design and estimate of water inflow.

Rock grouting technology for reducing groundwater inflow in deep underground

Tsuji, Masakuni*; Ikeda, Koki; Mikake, Shinichiro; Matsui, Hiroya

Tunnelling Activities in Japan 2018, P. 23, 2018/00

We have recently conducted pre- and post-grouting works at a gallery in 500m depth of MIU. The groundwater pressure was maximum 4.0MPa. As a result, water ingress was reduced to a one-hundredth of an assumed amount with no grouting were performed, which is reduction from approx. Moreover, after a later post-grouting work repeated in the most wet section of the relevant gallery, all dripping spots turned out to be lower than 1 L/min. Especially for the post-grouting technologies, three new concepts were demonstrated and found to be effective; which is the Colloidal silica grout for a new material, Complex dynamic grouting method for a new injection method, and sealing outer area of pre-grouted zones for a new grouting area as design concepts.

Study on engineering technologies in the Mizunami Underground Research Laboratory (FY 2015); Development of design and construction planning and countermeasure technologies (Contract research)

Toguri, Satohito*; Kobayashi, Shinji*; Tsuji, Masakuni*; Yahagi, Ryoji*; Yamada, Toshiko*; Matsui, Hiroya; Sato, Toshinori; Mikake, Shinichiro; Aoyagi, Yoshiaki

JAEA-Technology 2017-005, 43 Pages, 2017/03

JAEA-Technology-2017-005.pdf:4.4MB

The study on engineering technology in the Mizunami Underground Research Laboratory (MIU) project roughly consists of (1) development of design and construction planning technologies, (2) development of construction technology, (3) development of countermeasure technology, (4) development of technology for security, and (5) development of technologies regarding restoration and mitigating of the excavation effect. In FY2015, as a part of the important issues on the research program, water-tight grouting method has been developed. Grouting methods utilized in the MIU were evaluated and the post-excavation grouting at the -500m Access/Research Gallery-South was planned based on these evaluation results. Also, technology development from the viewpoint of geological disposal was summarized, and information on the alternative method to the grouting method was collected and organized.

Post-grouting with colloidal silica at great depth of the Mizunami Underground Research Laboratory, Japan

Tsuji, Masakuni*; Kobayashi, Shinji*; Sato, Toshinori; Mikake, Shinichiro; Matsui, Hiroya

Proceedings of 8th Nordic Grouting Symposium, p.171 - 185, 2016/09

This paper presents the application of a durable liquid-type colloidal silica grout (CSG), to the great depth of the Mizunami Underground Research Laboratory (MIU). The CSG had been invented decades ago in Japan for the purpose of the ground improvement. A post-grouting experiment with the CSG carried out in 300 m depth of MIU confirmed its applicability and good durability at a great depth more than 3 years. Furthermore, a comparison study of applying the CSG between this experiment and a Swedish project indicated good applicability of the Swedish theoretical design to MIU. The CSG with the Swedish design were applied to the post-grouting campaign in a gallery at 500 m depth for further reducing water ingress and for developing the latest grouting methodology. The grouting was successful in reducing the abundant inflow from the rock with many fractures. The conductivity of the grouted rock mass of the latter fans is estimated to be lower than 10 m/s.

Study on engineering technologies in the Mizunami Underground Research Laboratory (FY 2014); Development of design and construction planning and countermeasure technologies (Contract research)

Kobayashi, Shinji*; Niimi, Katsuyuki*; Tsuji, Masakuni*; Yamada, Toshiko*; Aoyagi, Yoshiaki; Sato, Toshinori; Mikake, Shinichiro; Osawa, Hideaki

JAEA-Technology 2015-039, 170 Pages, 2016/02

JAEA-Technology-2015-039.pdf:37.73MB

The researches on engineering technology in the Mizunami Underground Research Laboratory (MIU) plan consists of (1) development of design and construction planning technologies, (2) development of construction technology, (3) development of countermeasure technology, (4) development of technology for security, and (5) development of technologies regarding restoration or reversal and mitigating of the excavation effect. To develop design and construction planning technologies, and countermeasure technology, the analysis of measured data during earthquake and seismic movement characteristics at deep underground, and the examination of grouting method were carried out. For the characteristics of earthquake ground motion, measurement data obtained by seismometers installed in the Mizunami Underground Laboratory were analyzed, and the comprehensive assessment of the relationship between the measurement data and the geological condition at each depth was performed. As for "Study on grouting method at deep underground ", post grouting was carried out and evaluated based on the Construction plan in FY2013. Furthermore, target of the future R&D was proposed.

Grouting for reducing groundwater inflow into a gallery at 500m depth of the Mizunami Underground Research Laboratory, Japan

Tsuji, Masakuni*; Kobayashi, Shinji*; Sato, Toshinori; Mikake, Shinichiro

Proceedings of the ISRM Regional Symposium EUROCK 2015 & 64th Geomechanics Colloquium; Future Development of Rock Mechanics, p.35 - 41, 2015/10

Rock grouting has been an essential measure to reduce water ingress into the deep underground during the excavation of Mizunami Underground Research Laboratory project in Japan. This paper shows an overview of grouting works performed at a gallery of 120 m at 500 m depth. After completion of its excavation with the pilot borehole investigation and pre-grouting mainly by Super-fine Portland cement, the inflow from the whole gallery was 200-220 Liter/min within the requirement. Then, at a limited section of 16 m, post-grouting was performed with new designs, applying colloidal silica grout, complex dynamic grouting, and grouting outside of the pregrouted zone. These designs were effective and the inflow at the section reduced from 35 to 11 Liter/min. These experiences must be fruitful for advancing the present technology and there should have been potential for reducing further inflow if any of the new designs are applied from the pre-grouting phase.

Pre-excavation grouting design, results and evaluation of a gallery at great depth in Mizunami Underground Research Laboratory

Tsuji, Masakuni*; Kobayashi, Shinji*; Sato, Toshinori; Mikake, Shinichiro

Dai-43-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koenshu (CD-ROM), p.7 - 12, 2015/01

Pre-excavation grouting of shafts and galleries has been conducted during the construction of Mizunami Underground research laboratory in the aspect of safe works and reducing the discharge treatment of the water inflow. The grouting methodology has been simultaneously studied an developed as there is less experience of grouting in low conductive rock with high water pressure, especially in Japan. Ahead of excavating GL.-500m gallery on the ventilation shaft side, grouting design was performed based on the estimation of water inflow by the pilot-boring investigations and the design was properly revised during the campaign. The gallery satisfied the inflow requirement with good sealing effect.

Comparison of grouting with silica sol in the sp Hard Rock Laboratory in Sweden and Mizunami Underground Research Laboratory in Japan

Tsuji, Masakuni*; Funehag, J.*; Kobayashi, Shinji*; Sato, Toshinori; Mikake, Shinichiro

Proceedings of 8th Asian Rock Mechanics Symposium (ARMS-8) (USB Flash Drive), 10 Pages, 2014/10

Silica sol is a material that seems to fulfill the non-hazardous requirement and capable of penetrating into narrow fractures. The rock grouting strategy with silica sol has been studied and applied for some recent projects in Sweden. The design methodology is based on the determination of the fracture transmissivity distribution and the theoretical penetration length. In 2008, grouting with silica sol was applied in the construction of a short tunnel at 450 m depth in the sp Hard Rock Laboratory, the TASS-tunnel. In 2010, a grouting experiment with silica sol was performed in a gallery at 300 m depth in the Mizunami Underground Research Laboratory (MIU experiment). It can be suggested that Swedish methodology can be applied to design and evaluate the grouting works in Japanese rock with higher intensity of fractures in general. Furthermore, an additional pumping time or the use of Japanese silica sol might improve the grouting quality in Sweden.