Faculty Profiles - KOMATSU Mitsuru

擬似飽和体積含水率と降雨強度の関係性に関する一考察

Relationship between quasi-saturated volumetric water content and rainfall-induced slope deformation based on a model slope experiment Reviewed

K.Koizumi, K.Sakuradani, K.Oda, M.Komatsu, S.Itoh

Journal of GeoEngineering, Taiwan Geotechnical Society, 13 ( 4 ) 179 - 186 2018.12

空気圧を用いた連通試験に関する水平一次元要素結果の評価 Reviewed

西原直也, 小松満

地盤と建設 36 ( 1 ) 39 - 46 2018.12

河川堤防の弱点箇所を抽出する空気圧による連通試験手法の開発 Reviewed

新村卓也, 藤吉秀彰, 舘川逸朗, 齋藤雅彦, 珠玖隆行, 小松満, 西村伸一, 西垣誠

地盤と建設 36 ( 1 ) 71 - 78 2018.12

透水性基礎地盤に起因する河川堤防のパイピング進行性破壊に関する模型実験 Reviewed

小松満, 増山博之, 新村卓也, 舘川逸朗, 西垣誠

地盤と建設 36 ( 1 ) 111 - 118 2018.12

都市域山岳NATM施工時における軟弱地山対する補助法の採用事例 Reviewed

高橋啓介, 光増朝久, 吉本治憲, 大金隆宏, 小松満

地盤と建設 36 ( 1 ) 153 - 160 2018.12

初期擬似飽和体積含水率（IQS）測定手法の一提案

西村美紀, 喜多浩志, 小泉圭吾, 小松満, 小田和広

地下水地盤環境・防災・計測技術に関するシンポジウム論文集（Kansai Geo-Symposium 2018） - 235 - 238 2018.11

山本健史, 小泉圭吾, 櫻谷慶治, 小松満, 伊藤真一, 小田和広

地下水地盤環境・防災・計測技術に関するシンポジウム論文集（Kansai Geo-Symposium 2018） - 191 - 194 2018.11

Fundamental study of the effect of water level lowering in the groundwater drainage work utilizing siphon Reviewed

Yamamoto, T, Y. Minamiguchi, K. Koizumi, M. Komatsu, K. Oda, A. Tohari

8th Int. Conf. on Geotechnique, Construction Materials and Environment,Kuala Lumpur, Malaysia, Nov. 20-22 300 - 305 2018.11

Methods to measure the initial Quasi-saturated volumetric water content of soil Reviewed

Nishimura, M, H. Kita, M. Komatsu, K. Koizumi, K. Oda, K. Sakuradani

8th Int. Conf. on Geotechnique, Construction Materials and Environment,Kuala Lumpur, Malaysia, Nov. 20-22 306 - 310 2018.11

Evaluation of the calibration accuracy of soil moisture using a new microchip sensor Reviewed

Komatsu,M, M. Futagawa, Y. Fuwa

8th Int. Conf. on Geotechnique, Construction Materials and Environment,Kuala Lumpur, Malaysia, Nov. 20-22 306 - 310 2018.11

A fundamental experiment on pneumatic tomography of unsaturated soil ground using a horizontal one-dimensional column Reviewed

Nishihara, N, M. Komatsu

8th Int. Conf. on Geotechnique, Construction Materials and Environment,Kuala Lumpur, Malaysia, Nov. 20-22 549 - 554 2018.11

Relationship between quasi-saturated volumetric water content and slope deformation based on a model slope experiment Reviewed

SAKURADANI Keiji, KOIZUMI Keigo, ODA Kazuhiro, ITO Shinichi, KOMATSU Mitsuru

Japanese Geotechnical Journal 13 ( 3 ) 183 - 192 2018.9

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：公益社団法人地盤工学会

The authors hypothesized that displacement on a model slope would not occur unless the initial quasi-saturated volumetric water content was exceeded. This prediction was based on a past experiment using a small model slope for the purpose of predicting slope failure beforehand. However, in previous experiments, the soil-layer thickness of the slope was as thin as 100 mm, so the behaviors of sensors installed at the upper, middle, and lower slopes were nearly the same. Also, the size of the model slope was small, and the characteristics of each point could not be grasped. Therefore, in this study, we verified whether the hypothesis obtained from past experimental results was valid even when the topsoil-layer thickness to 300mm and the model size are increased. The following findings were obtained. Displacement was confirmed to occur in the vicinity of the toe of the slope after the volumetric water content exceed the initial quasi-saturated volumetric water content. On the other hand, in the middle part of the slope, while still below the initial quasi-saturated volumetric water content, displacement was confirmed. Thus, depending on the installation position, the displacement may occur before the initial quasi-saturated volumetric water content is exceeded.

DOI： 10.3208/jgs.13.183

Study of a Semiconductor Type pH Sensor to Measure Low Water Content Soils in Real-time Reviewed

Futagawa Masato, Uemura Keisuke, Nomiyama Kumiko, Hirano Harutoyo, Watanabe Minoru, Komatsu Mitsuru

IEEJ Transactions on Sensors and Micromachines 138 ( 9 ) 417 - 422 2018.9

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：一般社団法人電気学会

Real time measurement of soil pH is demanded in precision agriculture. Therefore, pH measurement capability in low water content soil was needed to confirm. In this paper, we fabricated an ISFET type pH sensor which can be inserted into soil. The sensor performed to measure two type of experiments. First, we experimented with changes in sensor output due to soil water content. The sensor output voltages were changed by changes in the soil pH value. In contrast, the voltages didn't be changed by changes in the soil water content. Secondly, we experimented whether the output of the sensor shows the same change when the soil pH changes during the measurement. The sensor could detect the pH value of soil which was changed dramatically by passing water. We confirmed that the ISFET type pH sensor can directly measure soil pH in real time.

地下水流動の調査技術と留意点 (特集基礎工と地下水処理・対策)

小松満

基礎工 = The foundation engineering & equipment, monthly : 土木・建築基礎工事と機材の専門誌 46 ( 6 ) 21 - 24 2018.6

Fabrication of a low leakage current type impedance sensor with shielding structures to detect a low water content of soil for slope failure prognostics Reviewed

Masato Futagawa, Shin Ogasahara, Tatsumi Ito, Mitsuru Komatsu, Yasushi Fuwa, Harutoyo Hirano, Ippei Akita, Kenichiro Kusano, Minoru Watanabe

Sensors and Actuators, A: Physical 271 ( 271 ) 383 - 388 2018.3

Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier B.V.

A low-leakage-current-type impedance sensor chip with shield structures has been fabricated. The low limit detection of soil-water-content measurement was improved compared with that of the other semiconductor-type sensors. The shield structures were fabricated under the impedance sensor areas. To measure the weak signal current eliminated by the leakage current, we proposed a new operation circuit to separate the leakage current. Our sensor was able to measure low water content of 10% or less. The sensor could detect the change of water content in the slope of mountain when it rained.

DOI： 10.1016/j.sna.2017.12.022

Laboratory experiments on initiation of rainfall-induced slope failure with moisture content measurements

Adrin Tohari, Makoto Nishigaki, Mitsuru Komatsu

ISRM International Symposium 2000, IS 2000 2018

Language：English Publishing type：Research paper (international conference proceedings) Publisher：International Society for Rock Mechanics

A series of laboratory slope failure experiments was conducted to elucidate the initiation of rainfall-induced slope failures from moisture content measurement records. The change in moisture content during the infiltration of rainwater and at initiation of slope failures was monitored by moisture sensors (Amplitude Domain Reflectrometry type). Prior to experiments, numerical unsteady seepage analyses were also conducted to identify the hydraulic response of the soil slope models to rainfall. The experiment results showed that slope failures were initiated by the increase in moisture content of the soil at the toe of the slope. Moisture content of the soil was noted to reach its saturated value at the time of failure. This indicates that rainfall-induced slope failure is a consequence of instability of the toe of the slope induced by saturation process under drained condition, and the major portion of the sliding mass may still be in an unsaturated condition. The experiments reported in this Paper also indicated that the direct measurements of change in moisture content could provide a great possibility in predicting the critical time of the initiation of rainfall-induced slope failures. Therefore, the results of applying any moisture sensors to predict and to monitor slope movements are encouraging.

試験孔内での注水による現場飽和状態及び有効間隙率の測定方法に関する研究 Reviewed

小松満, 喜多浩志, 小泉圭吾

地盤と建設 35 ( 1 ) 225 - 232 2017.12

地盤内の弱点箇所を調査する空気圧連通試験に関する水平一次元カラムを用いた基礎的実験 Reviewed

小松満, 西原直也, 新村卓也, 舘川逸朗, 西垣誠

地盤と建設 35 ( 1 ) 101 - 108 2017.12

Column based infiltration experiment for considering initial Quasi-saturaeted volumetric water content due to defferences of water spray intensity and grain size distribution Reviewed

H.Kita, K.Koizumi, K.Oda, M. Komatsu

Third International Conference on Science, Engineering & Environment (SEE-USQ 2017), GEOMATE International Society 13 - 16 2017.11

Fabrication of a low leakage current type impedance sensor to monitor soil water content for slope failure prognostics Reviewed

Masato Futagawa, Shin Ogasahara, Tatsumi Ito, Mitsuru Komatsu, Yasushi Fuwa, Harutoyo Hirano, Ippei Akita, Kenichiro Kusano, Minoru Watanabe

TRANSDUCERS 2017 - 19th International Conference on Solid-State Sensors, Actuators and Microsystems 1136 - 1139 2017.7

Language：English Publishing type：Research paper (international conference proceedings) Publisher：Institute of Electrical and Electronics Engineers Inc.

A low-leakage-current type impedance sensor chip with shield structures has been fabricated. The low limit detection of soil-water-content measurement was improved compared with that of the other semiconductor type sensors. The shield structures were fabricated under the impedance sensor areas. To measure weak signal current eliminated the leakage current, we proposed a new operation circuit to separate the leakage current. Our sensor achieved to measure low water content 10 % or less.

DOI： 10.1109/TRANSDUCERS.2017.7994253

Fundamental study on siphon drainage method for landslide mitigation Reviewed

Y. Minamiguchi, K. Koizumi, K. Oda, S. Kobashi, M. Komatsu, T Adrin

15th REAAA CONFERENCE 226 - 232 2017.3

基礎技術講座現場透水試験

小松満

地質と調査 2017 ( 1 ) 51 - 56 2017.1

An example of test methods for permeability of bentonite-based material

小松満

地盤工学シンポジウム論文集地盤工学会編 60 29 - 32 2016.12

Characterization of soil permeability in Prambanan Temple Yard based on development of in situ test

A. Rifa'i, Y. Takeshita, M. Komatsu

International Journal of GEOMATE 11 ( 26 ) 2620 - 2625 2016.10

模型土層にサイフォンを用いた際の内径と排水量，水位に関する研究 Reviewed

南口優貴, 小泉圭吾, 小田和広, 小橋俊也, 小松満, Adrin Tohari

土木学会西部支部第8回土砂災害に関するシンポジウム 247 - 250 2016.9

Determination of unsaturated soil permeability based on geometric factor development of constant discharge model Reviewed

A. Rifa'i, Y. Takeshita, M. Komatsu

World Academy of Science, Engineering and Technology，International Journal of Environmental, Chemical, Ecological, Geological and Geophysical Engineering 10 ( 9 ) 2016.9

Extending Water Retention Curves to a Quasi-Saturated Zone Subjected to a High Water Pressure up to 1.5 Megapascals

Toshihiro Sakaki, Mitsuru Komatsu, Ryuji Takeuchi

VADOSE ZONE JOURNAL 15 ( 8 ) 2016.8

Language：English Publishing type：Research paper (scientific journal) Publisher：SOIL SCI SOC AMER

On closure of an underground facility, recovery of the geoenvironmental conditions is one of the essential issues for ensuring proper implementation of closure. At the Mizunami Underground Research Laboratory, Gifu, Japan, a tunnel flooding test is underway in which a section of a deep underground tunnel is filled with groundwater and the existing desaturated zone with trapped air is subjected to high water pressure. Water saturation in the unsaturated zone as a function of capillary pressure is well understood. However, the process of a saturation increase due to a further increase in water pressure is less well studied. In this study, a simplified laboratory setup using test sands with trapped air was established in a pressure chamber. The relationship between the positive water pressure up to 1.5 MPa and saturation was measured and the effect of the compression of trapped air bubbles on the change in saturation was investigated. The experimental results showed that the saturation increased further from the initial saturation of about 0.85 at zero suction. Most of the saturation increase occurred up to a water pressure of 0.5 MPa, at which the saturation reached 0.98. At 1.5 MPa, the air bubbles were compressed to a non-detectable level so that the sands were fully saturated. A mathematical model was established based solely on Boyle's law to define the water retention curve in a broad sense for the domain where the water pressure is positive. The measured water pressure-saturation data closely followed the relationship estimated with the established model.

DOI： 10.2136/vzj2015.12.0165

小型半導体チップ型センサによる地盤の間隙変化の計測方法に関する基礎的実験 Reviewed

小松満, 竹下祐二, 二川雅登, 不破泰, 鈴木彦文, 熊倉信行, 吉野晃

地盤と建設 33 ( 1 ) 163 - 168 2015.12

静電容量センサによるベントナイト系材料の水分量計測に関する基礎的研究（共著） Reviewed

小松満, 佃明恵, 榊利博

地盤と建設 33 ( 1 ) 37 - 44 2015.12

河川堤防の法面における遠隔水分量モニタリングに向けた実証研究（共著） Reviewed

小松満, 竹下祐二, 二川雅登, 不破泰, 鈴木彦文, 熊倉信行, 吉野晃

地盤と建設 33 ( 1 ) 169 - 174 2015.12

Development of in situ permeability test using constant discharge method for sandy soils Reviewed

A. Rifa’i, Y. Takeshita, M. Komatsu

World Academy of Science, Engineering and Technology, International Journal of Environmental, Chemical, Ecological, Geological and Geophysical Engineering 9 ( 11 ) 1264 - 1268 2015.11

Fabrication of a Hydrophilic Property Impedance Sensor to Stably Monitor Soil Water Content for Slope Failure Prognostics Reviewed

Masato Futagawa, Tatsumi Ito, Hikofumi Suzuki, Yasushi Fuwa, Arumi Kunii, Yuji Takeshita, Mitsuru Komatsu, Minoru Watanabe

2015 IEEE SENSORS 1445 - 1448 2015

Language：English Publishing type：Research paper (international conference proceedings) Publisher：IEEE

To minimize the damage caused by slope failure, knowledge of the increase in water content in mountain soil is important. Our group has been studying miniaturized impedance sensor for multipoint measurements in the soil. To improve contact characteristics between sensor surface and free water in soil, SiOx film of hydrophilic property covered on our conventional sensor chip. For contact property test, the sensor chip measured impedance of model soils. The proposed sensor achieved to stable contact the free water in the soil. Moreover, the chip operated for long period of time in mountain slope. The sensor could measure nearly theoretical outputs which responded to rainfalls. We succeeded to fabricate the stably soil monitor sensor with hydrophilic film SiOx.

Realization of a Safe and Secure Society using ICT in Shiojiri-City, Nagano Prefecture, Japan -Towards the Creation of a Smart Citie- Reviewed

Hikofumi Suzuki, Yasushi Fuwa, Masato Futagawa, David K. Asano, Eiki Motoyama, Mitsuru Komatsu, Yuji Takeshita, So Seryu, Haruo Kaneko

2015 2ND INTERNATIONAL CONFERENCE ON INFORMATION AND COMMUNICATION TECHNOLOGIES FOR DISASTER MANAGEMENT (ICT-DM) 186 - 192 2015

Language：English Publishing type：Research paper (international conference proceedings) Publisher：IEEE

For some time, we have been working toward the "Realization of a Safe and Secure Society using ICT in Shiojiri-City, Nagano Prefecture." This is a project comprised of two phases: information gathering, and dissemination of information. For information gathering, we are developing systems to confirm the whereabouts of children and the elderly, who are vulnerable in disasters, and systems to gather information on the situation in mountainous regions, rivers etc. For dissemination of information, we are developing systems using broadcast technology for disseminating information to residents, such as disaster information and evacuation warnings derived from the gathered information. This presentation will describe the project goals, the background of the project thus far, and an overview of the developed system. The current situation and plans for the future will also be discussed.

Behavior of trapped air in the unsaturated zone located below the water table: A secondary drainage cycle after resaturation

SAKAKI Toshihiro, KOMATSU Mitsuru

Journal of Groundwater Hydrology 56 ( 1 ) 27 - 34 2014.2

Language：Japanese Publisher：公益社団法人日本地下水学会

Fluctuations in water table height tend to generate an unsaturated zone located below the water table. It is not well understood how water saturation is affected by trapped air in this unsaturated zone. In this study, water characteristic curves for primary drainage, wetting, resaturation (under the water table), and secondary drainage cycles were measured using a one-dimensional sand-filled column. It was assumed that the pore air pressure was atmospheric and that the effect of air pressure in the discrete air bubbles could be neglected. The experimental results showed that, in the resaturation cycle, the water saturation under positive water pressure increased with water pressure and exceeded that of the water table level whereas, in the secondary drainage cycle, the saturation change was rather small indicating that the water pressure – saturation relationships in resaturation and secondary drainage cycles below the water table were irreversible. Under the conditions considered in this study, the increase of water saturation in the resaturation cycle was found to be largely controlled by the upward movement of trapped air bubbles. The obtained water retention data for the secondary drainage cycle indicated that the relationships can be affected by the maximum resaturation level that the soil has experienced. This suggests that a unique definition of the secondary drainage curve may not be appropriate when the soil has experienced resaturation.

Rules-of-thumb for predicting air-entry value of disturbed sands from particle size Reviewed

Toshihiro Sakaki, Mitsuru Komatsu, Manabu Takahashi

Soil Science Society of America Journal 78 ( 2 ) 454 - 464 2014

Language：English Publishing type：Research paper (scientific journal) Publisher：Soil Science Society of America

With the goal of finding empirical direct relationships between the air-entry values (AEV) and characteristic particle diameters (i.e., d 10, d20, d30, d90,) determined from the particle-size distribution, we examined the AEV values for a variety of disturbed sands. It was found that the AEVs were, in general, strongly correlated to the characteristic diameters. The correlation was more distinct for uniform sands with uniformity coefficient of 2 or smaller. For those with larger uniformity coefficient values, the AEVs were highly correlated to smaller characteristic particle sizes d10 to d50 but less with larger characteristic particle sizes, d60 to d90. For all the sands examined in this study, the AEVs showed the least scatter when plotted against d30. The large particles do not necessarily control the AEVs because the pores between the large particles are often filled with smaller particles. The following best-fit power functions with respect to the frequently used characteristic particle diameters were found to have high r2 values
AEV = 8.2 d30 -0.99and AEV =9.5 d50 -1.05(with AEV in cm and d in mm). The exponent close to -1 in both relationships confirms a strong "inverse" proportionality. The effective pore diameter, de′, estimated from the AEVs agreed closely with the mean pore diameters measured with mercury porosimetry and X-ray micro-tomography. All these findings suggest that the AEVs are strongly controlled by the particle sizes which determine the mean pore size, and that the capillary rise theory is applicable in terms of the effective pore diameter. Finally, easy-toimplement rule-of-thumb expressions, AEV [cm] = 8/d 30[mm] and AEV [cm] =10/d50[mm] were proposed with some limitations for a quick but reasonably accurate prediction of the AEV. © Soil Science Society of America.

DOI： 10.2136/sssaj2013.06.0237n

What controls carbon dioxide gas phase evolution in the subsurface? Experimental observations in a 4.5 m-long column under different heterogeneity conditions Reviewed

Toshihiro Sakaki, Michael R. Plampin, Rajesh Pawar, Mitsuru Komatsu, Tissa H. Illangasekare

INTERNATIONAL JOURNAL OF GREENHOUSE GAS CONTROL 17 66 - 77 2013.9

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

In order to assess the risk of CO2 leakage affecting the groundwater quality in aquifers, it is important to understand the mechanisms of CO2 gas release when brine carrying dissolved CO2 migrates to the shallow subsurface from sequestrated zones of deep geologic formations. As the brine with dissolved CO2 elevates where the water pressure is lower, development of a gas phase starts with evolution of gas out of liquid, followed by gas phase growth and movement. However, conditions under which CO2 gas evolution is triggered, how the gaseous phase CO2 migrates and/or gets entrapped in the naturally heterogeneous formations are not well understood due to the difficulties involved with obtaining detailed experimental data. In this study, our goal was to identify the conditions under which dissolved CO2 forms a gas phase and to understand how the formed CO2 gas migrates through the saturated soil formation. In particular, we put emphasis on the critical gas saturation (at which the onset of gas phase migration occurs) and how this is explained by the theoretical and modeling studies reported in the literature. We have performed a series of experiments in the laboratory using a highly instrumented long column under highly controlled conditions that are not feasible in field settings. The 4.5 m-long vertical column setup was instrumented with automated sensors to continuously monitor phase saturation, electrical conductivity (EC), temperature, and water pressure distribution along the column length as well as the rates of water and gas outflow at the upstream end of the column. The observations showed that (1) concentration of dissolved CO2 influenced the vertical extent of the gas phase formation, (2) the gas formation pattern was different if the saturation pressure was lower or higher than the static water pressure at the injection port which results largely from the gravity and viscous forces somewhat competing under the conditions in the experiments, (3) the mass transfer-dominant period where bubbles grew and water outflow increased was relatively short, (4) gas outflow was detected at the column outlet only after a continuous gas phase was formed and breakthrough had occurred, (5) the critical gas phase saturation at which the generated gas phase gets mobilized was always about 0.3-0.4 in homogeneous cases, (6) for the heterogeneous cases, a gas saturation higher than the critical gas saturation was observed due to accumulation of gas phase under a finer layer, (7) the injection rate did not affect the gas formation behavior whereas the temperature variation did, and (8) in some cases formation of gas appeared to be triggered by heterogeneities. These observations are expected to improve our understanding of gas evolution for better conceptualization and model development. (C) 2013 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ijggc.2013.03.025

Behavior of trapped air in the unsaturated zone located below the water table : A slow resaturation cycle

SAKAKI Toshihiro, KOMATSU Mitsuru

Journal of Groundwater Hydrology 55 ( 3 ) 269 - 277 2013.8

Language：Japanese Publisher：公益社団法人日本地下水学会

The water characteristic curve is one of the important properties of soil required for the evaluation of groundwater flow in the unsaturated zone. Unsaturated zones occur below the water table when there is fluctuation of the water table depth. In such zones, it is not well understood how the trapped air behaves and how it affects water saturation. In this study, we estimated the water characteristic curves based on the water pressure and water saturation. The water saturation was monitored for wetting and re-saturation cycles where the water pressure was gradually increased up to 5.5 kPa using a one-dimensional sand-filled column. In the wetting cycle, the water characteristic curve was obtained assuming that the pore air pressure was atmospheric. In the re-saturation cycle, how the water characteristic curve would extend was estimated by neglecting the effect of air pressure in the discrete air bubbles. The experimental results showed that the water saturation under positive water pressure, i.e., below the water table, increased with water pressure and exceeded that at the water table level. It was concluded that the rate of increase of water saturation resulted not only from the discrete air bubbles being compressed but also being forced up as the water table gradually moved up. Not considering the increase in water saturation in the unsaturated zone below the water table could result in a significant underestimation of hydraulic conductivity in such a zone.

DOI： 10.5917/jagh.55.269

Research on the ｃonstruction of an Ad-Hoc Network System for ｆlexibly ｄealing with ｄisasters Reviewed

Suzuki, H, D. K. Asano, M. Komatsu, Y. Takeshita, K. Sawada, M. Futagawa, H. Nose, Y. Fuwa

International Technical Conference on Circuits/Systems, Computers and Communications 2013 (ITC-CSCC 2013) 24 - 27 2013.7

Construction of a sensor network to forecast landslide disasters: Sensor terminal development and on-site experiments Reviewed

Hikofumi Suzuki, Daichi Kuroyanagi, David K. Asano, Mitsuru Komatsu, Yuji Takeshita, Kazuaki Sawada, Masato Futagawa, Hiroaki Nose, Yasushi Fuwa

Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) 7889 180 - 191 2013

Language：English Publishing type：Research paper (international conference proceedings)

We believe it is extremely important to quickly communicate information - on matters such as the extent of the damage and the safety of affected persons - when a large-scale earthquake or other disaster occurs. However, if electric power is lost, communication will be impossible with existing information networks. For this reason, we have built an Ad-Hoc network in Shiojiri City enabling communication even if electric power is lost due to a large-scale disaster. Using this Ad-Hoc network, we are building a sensor network to forecast landslide disasters. Among the various sensors installed to the sensor terminals, this paper reports in particular on observation results with EC sensors. © 2013 Springer-Verlag.

DOI： 10.1007/978-3-642-38401-1_14

Fabrication of a slope failure prediction sensor using miniaturized EC sensor

Masato Futagawa, Mitsuru Komatsu, Hikofumi Suzuki, Yuji Takeshita, Yasushi Fuwa, Kazuaki Sawada

IEEJ Transactions on Sensors and Micromachines 133 ( 9 ) 5 - 283 2013

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：一般社団法人電気学会

To minimize the damage caused by slope failure, knowledge of the increase in water content in mountain soil is important
however the current technology for monitoring this is insufficient. In this study, an EC sensor chip with an insulation layer with increased thickness, designed to reduce leakage current, was fabricated. Utilizing the chip, a wireless sensor terminal was constructed for long term continuous monitoring of the water content in mountain soil. The usefulness of the EC sensor for predicting slope failure was confirmed.

DOI： 10.1541/ieejsmas.133.278

飽和砂質地盤における空気侵入値の定量的評価手法に関する研究 Reviewed

小松満, 榊利博

地盤と建設 30 ( 1 ) 39 - 46 2012.12

Developing the Soil Moisture Sensor using Optical Fiber Technique (Joint Research)

小松満, 西垣誠, 瀬尾昭治

JAEA-research 2012 ( 1 ) 1 - 77,巻頭1-2 2012.9

浅層帯水層への気体注入及びその移動現象に関する研究 Reviewed

小松満, 藤田知大, 榊利博

地盤と建設 29 ( 1 ) 27 - 37 2011.12

坑道の掘削影響に対する修復技術としてのベントナイトグラウトの適用性に関する評価 Reviewed

藪内聡, 國丸貴紀, 岸敦康, 小松満

土木学会論文集C(地圏工学) 67 ( 4 ) 464 - 473 2011.11

原位置土中水分計測による浅地層における降雨浸透量の評価方法 Reviewed

小松満, 西垣誠, 瀬尾昭治, 戸井田克, 田岸宏孝, 竹延千良, 山本陽一

地下水地盤環境に関するシンポジウム2011－水環境の保全と育水－発表論文集 17 - 29 2011.11

MONITORING OF PORE WATER PRESSURE AND WATER CONTENT AROUND A HORIZONTAL DRIFT THROUGH EXCAVATION - MEASUREMENT AT THE 140m GALLERY IN THE HORONOBE URL -

YABUUCHI Satoshi, KUNIMARU Takanori, KISHI Atsuyasu, KOMATSU Mitsuru

Journal of Japan Society of Civil Engineers, Ser. C (Geosphere Engineering) 67 ( 4 ) 464 - 473 2011

Publisher：公益社団法人土木学会

&nbsp;Japan Atomic Energy Agency has been conducting the Horonobe Underground Research Laboratory (URL) project in Horonobe, Hokkaido, as a part of the research and development program on geological disposal of high-level radioactive waste. Pore water pressure and water content around a horizontal drift in the URL have been monitored for over 18 months since before the drift excavation was started. During the drift excavation, both pore water pressure and water content were decreasing. Pore water pressure has been still positive though it continued to decrease with its gradient gradually smaller after excavation, while water content turned to increase about 6 months after the completion of the excavation. It turned to fall again about 5 months later. An unsaturated zone containing gases which were dissolved in groundwater may have been formed around the horizontal drift.

Study on using Capillary Barriers to Control the Amount of Water that Permeates Landfills

二酸化炭素の浅層帯水層への注入に関する基礎的研究 Reviewed

小松満, 藤田知大

地盤と建設 28 ( 1 ) 137 - 143 2010.12

Measurements of Soil Water Content Using Dielectric Methods

竹下祐二, 小松満

地盤工学会誌 = / the Japanese Geotechnical Society 58 ( 7 ) 44 - 45 2010.7

On the value of lithofacies data for improving groundwater flow model accuracy in a three-dimensional laboratory-scale synthetic aquifer Reviewed

Sakaki, T, C. C. Frippiat, M. Komatsu, T. H. Illangasekare

45 2009.10

Creation of artificial aquifers in aquitard or aquiclude environment Reviewed

Nishigaki,M, J. A. Akudago, L. P. Chegbeleh, M. Komatsu

XXXVI IAH 2008 Proceedings, Oct.26-Nov.1, Toyama International Conference center, 2008.10. 2008.10

Filter choice and its relation to well construction and sustainability in rural water supply Reviewed

Akudago, J. A, M. Nishigaki, L. P. Chegbeleh, M. Komatsu

XXXVI IAH 2008 Proceedings, Oct.26-Nov.1, Toyama International Conference center, 2008.10. 2008.10

Geologic model construction in groundwater flow model calibration: A transitional probability approach for a non-stationary heterogeneous aquifer Reviewed

Sakaki, T, C. C. Frippiat, T. H. Illangasekare, M. Komatsu

XXXVI IAH 2008 Proceedings, Oct.26-Nov.1, Toyama International Conference center, 2008.10. 2008.10

Control of contaminant migration through bentonite grouting: - A laboratory investigation Reviewed

Chegbeleh, L. P, M. Nishigaki, J. A. Akudago, M. Komatsu, Md. A. Alim

XXXVI IAH 2008 Proceedings, Oct.26-Nov.1, Toyama International Conference center, 2008.10. 2008.10

SAKAMOTO Atsushi, SUZUKI Masato, NISHIGAKI Makoto, KOMATSU Mitsuru, IMAI Jun, SATOH Yasushi, YOKOTA Suehiko

Journal of the Japan Society of Material Cycles and Waste Management 19 ( 5 ) 318 - 327 2008.9

Language：Japanese Publisher：Japan Society of Material Cycles and Waste Management

The achievement of reclamation conditions suitable for waste stabilization is expected when controlling the amount of water permeation through the cover layer at final landfill sites. The structure of a capillary barrier, which is one method to control the amount of water permeation, was examined from the viewpoint of water permeation control. Based on this examination, it was found that analytical predictions accurately corresponded to measurement results, thus, the prediction of water permeation was quite reliable. Therefore, it was determined that capillary barriers are effective in controlling water permeation.

DOI： 10.3985/jswme.19.318

Other Link： https://jlc.jst.go.jp/DN/JALC/00321631778?from=CiNii

液状化防止を目的とした地盤の不飽和化に関する実験的研究 Reviewed

坂本篤, 鈴木正人, 西垣誠, 小松満, 今井淳, 佐藤泰, 横田季彦

廃棄物学会論文誌 19 ( 5 ) 318 - 327 2008.9

不飽和地盤の調査事例

小松満, 西村拓, 竹下祐二

地盤工学会誌 = / the Japanese Geotechnical Society 56 ( 7 ) 77 - 83 2008.7

キャピラリーバリアによる廃棄物処分場の浸出水の制御に関する研究 Reviewed

西垣誠, 小松満, 藤井直, 大内正敏

土木学会論文集C 64 ( 2 ) 340 - 352 2008.6

不飽和地盤の調査と浸透特性値の計測

竹下祐二, 小松満

地盤工学会誌 = / the Japanese Geotechnical Society 56 ( 6 ) 62 - 69 2008.6

Value of borehole data on geologic model construction for improving model calibration accuracy Reviewed

Sakaki, T, C. C. Frippiat, T. H. Illangasekare, M. Komatsu

Proceedings of the MODFLOW and More 2008, May 19-21 439 - 443 2008.5

亀裂性岩盤におけるグラウトの注入範囲と有効間隙率の評価

西垣誠, 見掛信一郎, 小松満, Kwabena KANKAM-YEBOAH

土木学会論文集 No.743 ( III-64 ) 199 - 212 2008

A Fundamental Study on Prediction of Slope Failure Induced a Heavy Rain Reviewed

NISHIGAKI Makoto, KOMATSU Mitsuru, RYUMAN Kousei

55 ( 6 ) 24 - 26 2007.6

Language：Japanese Publishing type：Research paper (scientific journal)

In the south area in Cyugoku region, residual granite soil is distributed widely and it induced many slope failures at heavy rain. In this study, it showed the each process that reached model of slope failure, and for the establishing the system which could grasp a change of the slope stability that it monitored in the real slope. This method is technique to assume the arrival time of wetting front to base impermeable layer or water table with monitoring of water content changing. Furthermore, it performed numerical seepage analysis and examined consistency with monitoring data. It is understood that effective of the water content measurement as long-term method, but, for completion of a prediction system, some problem remained in measurement results and analysis precisions.

Other Link： http://dl.ndl.go.jp/info:ndljp/pid/10445158

Laboratory rainfall-induced slope failure with moisture content measurement Reviewed

Adrin Tohari, Makoto Nishigaki, Mitsuru Komatsu

JOURNAL OF GEOTECHNICAL AND GEOENVIRONMENTAL ENGINEERING 133 ( 5 ) 575 - 587 2007.5

Language：English Publishing type：Research paper (scientific journal) Publisher：ASCE-AMER SOC CIVIL ENGINEERS

The development of a physically based warning system for rainfall-induced slope failures requires a comprehensive understanding of the failure process. A set of laboratory-scale soil slopes was subjected to instability, through three different modes of raising water level, to clarify the process of failure initiation. Hydrologic responses of the model slopes to the saturation process were recorded by volumetric soil moisture content sensors. The results of model tests show that failures of the model slopes were essentially initiated by the development of an unstable area near the slope toe, upon the formation of the seepage area, with shallow noncircular sliding being the dominant failure mode. The volumetric moisture content of the slope region where localized failures initiated was noted to reach a nearly saturated value. However, the major portion of soil slopes involved in overall instability was still in an unsaturated condition. Based oil the observed moisture content response of the model slopes, a concept for prediction methodology of rainfall-induced slope failures is introduced.

DOI： 10.1061/(ASCE)1090-0241(2007)133:5(575)

IN-SITU METHOD FOR MEASURING HYDRAULIC CONDUCTIVITY OF THE BENTONITE MIXTURED SOIL LINER Reviewed

NISHIGAKI Makoto, KOMATSU Mitsuru

Journal of Japan Society of Civil Engineers, Ser. C (Geosphere Engineering) 63 ( 1 ) 299 - 311 2007.3

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japan Society of Civil Engineers

The purpose of this study is proposing for the test method for measuring the hydraulic conductivity of bentonite mixtured soil used as a seal liner of waste disposal site after the construction in situ. Concretely, it is a method for building in the moisture sensor in which the measurement in the pinpoint was possible for Air Entry Permeameter, which exists in situ permeability test method. In results of this study, by catching fall time of wetting front, 10^-8(m/s) order of hydraulic conductivity could be measured in about 10 minutes. And, the validity of this proposed method was verified by carrying out the one-dimensional infiltrating test, and measuring moisture profile and pressure distribution in the test-piece.

DOI： 10.2208/jscejc.63.299

EVALUATION ON APPLICATION OF BENTONITE SLURRY GROUT FOR EXCAVATION DISTURBED ZONE IN ORDER TO RECOVER LOW PERMEABLE ROCK MASSES

Proposed geophysical method for investigating the seabed for a landfill project in Okayama, Japan Reviewed

Nishigaki,M, M.Komatsu, M.Inoue, K.Kankam-Yeboah, S.Mattersteig, J.A.Akudago

Environmental Geotechnics(5th ICEG), H.R.Thomas(eds) 1495 - 1502 2006.6

NISHIGAKI Makoto, KOMATSU Mitsuru, MIKAKE Shin-ichiro, NAKASHIMA Tomohiro, KANAYA Kensei, TATSUTA Keisuke

Doboku Gakkai Ronbunshu ( 806 ) 55 - 66 2005.12

Language：Japanese Publisher：Japan Society of Civil Engineers

The purpose of this paper is to improve technologies of the grouting for excavation disturbed zone in order to recover low permeable rock masses for research and development on geological disposal of high-level radioactive waste. In this study, experiments of grouting injection test are performed on bentonite slurry mixes with saline and ethanol in the laboratory. From the results of the tests, low viscous and high density bentonite slurry is found to be able to inject the concentrated bentonite slurry and to recover low permeable in the fine fractured aperture. In conclusion this bentonite slurry is able to be expected the grouting effects for excavation disturbed zone in order to recover low permeable rock masses.

DOI： 10.2208/jscej.2005.806_55

Some aspects of groundwater drawdown and seepage flow rate in tunnels Reviewed

Nishigaki,N, M. Komatsu, A. Irie

Construction and Operation of Long Tunnels , To Celebrate the Breakthrough of the 12.9Km Hsuehshan Tunnel 1 259 - 271 2005.11

A NEW METHOD FOR PREDICTING GROUND SETTLEMENT USING GROUNDWATER FLOW ANALYSIS Reviewed

NISHIGAKI Makoto, IMAI Toshikazu, KOMATSU Mitsuru, NAGAI Izumi

Doboku Gakkai Ronbunshu ( 799 ) 1 - 12 2005.9

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japan Society of Civil Engineers

To estimate the degree of consolidation settlement, the soil mass conservation principle was used in this analysis. The specific storage coefficient was treated as a function of effective stress and void ratio. With this method, the behavior of consolidation from over-consolidation state to normal-consolidation state is easy to analyze. To evaluate its validity, results from the new method were compared with those from laboratory tests and Terzaghi's one-dimensional analysis. From these comparisons, it was shown that the principle is very accurate and reliable for estimating ground settlement. The new method was also used to analyse field conditions and to estimate settlement arising from (a) dewatering (pumping), (b) double-step load landfill phenomenon and (c) the disruption of groundwater flow during underground construction.

DOI： 10.2208/jscej.2005.799_1

A new Method to Estimate the Permeability of Soil with Considering Particle Size Distribution and Compaction Rate Reviewed

MORITA Yukio, TSUBOTA Kuniharu, NISHIGAKI Makoto, KOMATSU Mitsuru

53 ( 7 ) 5 - 7 2005.7

Language：Japanese Publishing type：Research paper (scientific journal)

For a long time, the permeability of soil is estimated from particle size distribution using D_<10> and D_<20> values. Still, there are some problems associated with this method. In this paper, a new method for estimating the permeability of soil is proposed. This is based on particle size distribution and compaction rate data that were obtained from laboratory tests. Under practical field conditions, the estimation of either porosity or void ratio is difficult. Therefore, from the N values, the compaction rate is estimated. Though the permeability values obtained from the new method are smaller than those obtained from other methods, the new method is fairly reliable.

Other Link： http://dl.ndl.go.jp/info:ndljp/pid/10444150

SIMPLE METHOD FOR PREDICTING CHANGES OF GROUNDWATER DISTRIBUTION CAUSED BY A CONSTRUCTION OF A MOUNTAIN TUNNEL DIGGING AND ITS APPLICABILITY Reviewed

NISHIGAKI Makoto, KOMATSU Mitsuru, IRIE Akira, YONO Koichiro, OTA Takuro

Doboku Gakkai Ronbunshu 2004 ( 778 ) 125 - 137 2004.12

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japan Society of Civil Engineers

In order to predict the range of groundwater level fluctuation and the flow rate of spring water in a tunnel, which are caused by digging a mountain tunnel, some simple methods were proposed. In this paper, the preconditions of these conventional simple methods are clarified. And new simple method, which can treat rainfall intensity and a coefficient of permeability that are not handled in these methods, is proposed by analyzing the results of a vertical-section-2-dimensional-finite-element-method. Moreover, based on results of new methods, the new method to set a range, which should be investigated and modeled for numerical analysis before excavation, is proposed.

DOI： 10.2208/jscej.2004.778_125

THE STUDY ON BENTONITE SLURRY GROUT WITH ETHANOL FOR FRACTURED ROCK Reviewed

NISHIGAKI Makoto, KOMATSU Mitsuru, MIKAKE Shin-ichiro, TAOKA Hiroshi, NAKASHIMA Tomohiro

Doboku Gakkai Ronbunshu 2004 ( 764 ) 221 - 233 2004.6

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japan Society of Civil Engineers

The purpose of this paper is to propose the grouting material and method for fractured rock masses. So experimental study is executed in order to grasp that the properties of grouting material is stable and impermeable. In this study, experiments of hydraulic test and grouting injection test are performed on bentonite slurry mixes in the laboratory. From the results of the tests, a mixer of ethanol and bentonite is found to be very suitable for a grouting material. Also, dynamic grouting method is able to inject the concentrated bentonite slurry in the fractured aperture.

DOI： 10.2208/jscej.2004.764_221

A basic study on monitoring method of contamination of soil and groundwater by using Frequency Domain Reflectometry method Reviewed

NISHIGAKI Makoto, KOMATSU Mitsuru, KIM Man-il

Journal of groundwater hydrology 46 ( 2 ) 145 - 157 2004.5

Visit to Valuable water springs (65) Valuable waters in Tarim basin, Xinjiang, western part of China

SHIMANO Yasuo, NISHIGAKI Makoto, KOMATSU Mitsuru, SUN Yao

Journal of groundwater hydrology 46 ( 2 ) 159 - 174 2004.5

Underground dam technology in some parts of the world Reviewed

西垣誠, K.Kankam-Yeboah, 小松満

46 ( 2 ) 113 - 130 2004.5

Field monitoring of hydraulic response of a residual soil slope to rainfall

A.Tohari, M.Nishigaki, M.Komatsu, K.Kankam-Yeboah, S.Daimaru

Lacerda, Ehrlich, Pont0ura & Sayao (eds):Landslides: Evaluation and Stabilization, Balkema 749 - 754 2004

Proposed New Equation for Estimating the Permeability of Soil Cosidering Particle Size Distribution and Compaction

Morita Yukio, Tsubota Kuniharu, Nishigaki Makoto, Komatsu Mitsuru

Proceedings of the Japan National Conference on Geotechnical Engineering 39 1159 - 1160 2004

A study on the development of a preventive method for reducing the effects of liquefaction during earthquake by creating unsaturated sandy ground

Yoshioka Seiji, Nishigaki Makoto, Komatsu Mitsuru, Ouchi Masatoshi, Onodera Takayoshi, Fujii Nao

Proceedings of the Japan National Conference on Geotechnical Engineering 39 1235 - 1236 2004

Density dependent transport analysis saturated-unsaturated porous media Eulerian Lagrangian method considered salinity change for consolidation phenomenon

otaki ikumi, nishigaki makoto, komatsu mitsuru, imai toshikazu

Proceedings of the Japan National Conference on Geotechnical Engineering 39 1187 - 1188 2004

Study on grouting against crack rock using bentonite

nakashima tomohiro, nishigaki makoto, komatsu mitsuru

Proceedings of the Japan National Conference on Geotechnical Engineering 39 1211 - 1212 2004

誘電率計測法による地盤の汚染度及び有効間隙率の測定方法に関する研究 Reviewed

西垣誠, 小松満, 金萬鎰

環境制御 25 ( 25 ) 19 - 24 2003.3

An experimental approach for estimating the porosity and effective porosity of porous media by permittivity methods

Nishigaki, M, M. komatsu, M. Kim

Proceedings of International Symposium on the Fusion Technology of Geosystem Engineering, Rock Engineering and Geophysical Exploration, Soul, Korea 2003

The State of MTBE Contamination in Japan

Makoto Nishigaki, Mitsuru Komatsu, Kwabena KANKAM-YEBOAH, Kim Man-il

1ST European Conference on MTBE at Dresden University of Technology 2003

Study on infiltration behavior of in-situ method for measuring coefficient of permeability of the bentonite composite soil

Ebara Tomoko, Nishigaki Makoto, Komatsu Mitsuru

Proceedings of the Japan National Conference on Geotechnical Engineering 38 1175 - 1176 2003

Study on measuring method of the effective porosity of a porous media by using Dielectric Method

Komatsu Mitsuru, Nishigaki Makoto, Kim Man-il

Proceedings of the Japan National Conference on Geotechnical Engineering 38 1171 - 1172 2003

the study on the standard characteristics of ethanol-bentonite slurry

Nakashima Tomohiro, Nishigaki Makoto, Komatsu Mitsuru, Mikake Sinitirou, Taoka Hiroshi

Proceedings of the Japan National Conference on Geotechnical Engineering 38 1173 - 1174 2003

地下水・土壌汚染の予測・評価技術

西垣誠, 小松満, 菱谷智幸

環境技術 31 ( 10 ) 766 - 769 2002.10

Study on the Properties of Seepage Flow and Injection in the Grouting for Fractured Rock Masses. Reviewed

NISHIGAKI Makoto, KOMATSU Mitsuru, YAMAMOTO Hiroshi, MIKAKE Shin-ichiro

Doboku Gakkai Ronbunshu No.715 ( III-60 ) 311 - 321 2002.9

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japan Society of Civil Engineers

The purpose of this study is to improve the grouting method for fractured rock masses. So experimental study is executed in order to understand the properties of grouting injection and seepage flow in hydraulic fractured aperture. This paper grasps the effect of the properties of grouting stage due to the various conditions such as width of the aperture, viscosity of the grout, water cement ratio and injection flow rate using flat plate fractured model in a laboratory experiment. From the results, it is proposed to select the relationship between the most suitable grout mix (water cement ratio) and width of the aperture to be injected according to the properties of grouting stage.

DOI： 10.2208/jscej.2002.715_311

Study on in situ method for measuring coefficient of permeability of the bentonite composite soil

Study on in-situ measuring system of subsurface contamination using Frequency Domein Reflectometry Reviewed

Komatsu M, M.Nishigaki

Environmental Geotechnics(4th ICEG), de Mello & Almeida (eds) 521 - 526 2002.3

Nishigaki Makoto, Komatsu Mitsuru, Ohtaki Ikumi

Proceedings of the Japan National Conference on Geotechnical Engineering 37 2423 - 2424 2002

The research of simple in situ unsaturated hydraulic conductivity of the bentonite composite soil.

Mizuno K., Okada T., Hongo T., Hugiwara T., Nishigaki M., Komatsu M.

Proceedings of the Japan National Conference on Geotechnical Engineering 37 2421 - 2422 2002

Study on Measuring System of Subsurface Contamination using Complex Dielectric Method Reviewed

Komatsu Mitsuru, Nishigaki Makoto

Journal of the Faculty of Environmental Science and Technology,Okayama University 6 ( 1 ) 47 - 52 2001.2

Laboratory Experiments on Initiation of Rainfall Induced Slope Failure with Moisture Content Measurements Reviewed

Tohari T, M.Nishigaki, M, Komatsu

An International Conference on Geotechnical & Geological Engineering (GeoEng2000) Australia 2000.11

Study on Measuring System of Subsurface Contamination using Frequency Domain Reflectometry with Vector Network Analyzer Reviewed

Nishigaki M, M.Komatsu

Physical Modeling and Testing in Environmental Geotechnics, J.Garnier, L.Thorel & E.Haza, LCPC 2000.5

Monitoring Method of Subsurface Salinity Contamination Using Dielectric Constant Measuring System Reviewed

Nishigaki Makoto, Komatsu Mitsuru, Kumamoto Sou, Ninomiya Isao

47 ( 10 ) 17 - 20 1999.10

Predicting rainfall-induced slope failures from moisture content measurement Reviewed

M Nishigaki, A Tohari, M Komatsu

SLOPE STABILITY ENGINEERING, VOLS 1 & 2 1 465 - 469 1999

Language：English Publishing type：Research paper (international conference proceedings) Publisher：A A BALKEMA PUBLISHERS

This paper presents the results of a series of laboratory slope failure experiments conducted to examine the effectiveness of monitoring moisture content to predict the occurrence of rainfall-induced slope failure. Numerical seepage analyses were also conducted prior to the experiments to identify the hydraulic response of the model slopes to the simulated rainfall. The changes in moisture content and pore-water pressure were monitored during rainfall infiltration and at the initiation of failures. The experiments showed that moisture content of soil slope increased to the saturated value at the time of failure. This indicated the possibility in predicting the critical time of failure initiation by monitoring the change in moisture content. Upon advantages of moisture sensing instruments over pore-pressure measuring instrument, therefore, monitoring of moisture contents during rainfall is more effective and more reliable than that of pore pressures to predict failure occurrences. The results of precise monitoring of moisture contents in the field to predict the rainfall-induced slope failures are encouraging.