Faculty Profiles - KOMATSU Mitsuru

Papers - KOMATSU Mitsuru

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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

<p>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. </p>

DOI： 10.3208/jgs.13.183

CiNii Article

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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

<p>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.</p>

CiNii Article

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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

Scopus

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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.

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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

Scopus

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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

Web of Science

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