Japanese Geotechnical Society Research Articles

Strength characteristics of cement-treated soil cured under extremely low temperatures

This paper discusses the strength characteristics of cement-treated soil cured at extremely low temperatures ranging from 5°C to −20°C. To examine how extremely low curing temperatures affect the strength of cement-treated soil, a field study of cement stabilisation executed in the severe winter of Hokkaido, Japan, is presented in the first part of this paper. This study reveals that extremely low air temperatures prevented the shallow part of the cement-treated ground at the site from solidifying sufficiently. Then the influence of extremely low curing temperatures on the strength characteristics of cement-treated soil is discussed, based on the results of laboratory cement mixing and other tests. It is found that cement-treated soils cured at lower temperatures (−20°C, −5°C, 0°C and 5°C) have lower unconfined compressive strengths (UCSs) than that cured at 20°C (a standard curing temperature according to the Japanese Geotechnical Society Standard). Cement-treated soils cured at −5 and −20°C showed almost no gain in UCS. For cement-treated soils cured at 0°C or above, the UCS increased with an increase in maturity. Finally, based on the above experimental results, points to be noted in the construction of cement stabilisation in winter in cold regions are proposed.

東日本大震災と資格制度「地盤品質判定士」 －公益社団法人地盤工学会の活動と運営（2011～2015）-

東日本大震災と資格制度「地盤品質判定士」 －公益社団法人地盤工学会の活動と運営（2011～2015）-

Damage Related to the 2011 Tohoku Earthquake in and Around Kamaishi City – Beyond the Tsunami Disaster –

Widespread damage was caused in eastern Japan as a result of the earthquake and tsunami which occurred in 2011 off the Pacific coast of Tohoku (hereinafter, the 2011 Tohoku Earthquake). A large tsunami struck the coastal area of eastern Japan and caused damage to buildings, breakwaters, tide embankments and river levees. The joint reconnaissance team of the Tohoku and Kyushu branches of the Japanese Geotechnical Society investigated the geotechnical damage in the south-central coastal area of Iwate Prefecture from the beginning of April to September 2011. This report summarizes the geotechnical hazards and the damage to port structures, roads, railways, river levees, and buildings caused by the earthquake motion and tsunami in the 2011 Tohoku Earthquake in the south-central coastal area of Iwate Prefecture. Major investigation areas are Kamaishi City (Koshirahama Port, Touni-Chou), the coastal area of Ofunato City (Sanriku-Chou Yoshihama, Sanriku-Chou Okirai), and Rikuzentakata City. In the 2011 Tohoku Earthquake, many people could not or did not evacuate from the tsunami. However, students at junior high and elementary schools started tsunami evacuation quickly, resulting in what is known as the “Kamaishi Miracle.” This study focused on the tsunami evacuation of children in Unosumai district, Kamaishi City.

膨潤性粘土鉱物の特徴 : 鉱物としての見方(地盤工学会・技術者交流特別セッション)

膨潤性粘土鉱物の特徴 : 鉱物としての見方(地盤工学会・技術者交流特別セッション)

The Fifth World Landslide Forum—Implementing and Monitoring the ISDR-ICL Sendai Partnerships 2015–2025

The outline of the Fifth World Landslide Forum (WLF5) was examined at the Steering Committee meeting of ICL and the launching meeting of the Organizing Committee of the Fifth World Landslide Forum was held on 5–6 March 2017 in the Disaster Prevention Research Institute, Kyoto University, Japan. Three participants from UNESCO, one from UNISDR, one from IRDR, 12 ICL, and IPL members from abroad, and 32 Japanese members from ICL headquarters in Kyoto, Kyoto University, the Japan Landslide Society, the Japanese Geotechnical Society, and the Japan Society for Natural Disaster Science (JSNDS) attended the meeting. The general outline of WLF5 was developed in the meeting. The first organizing committee meeting of the WLF5 took place on 1 April, 2017 at the forum venue—Kyoto International Conference Center, Kyoto, Japan. The second organizing committee meeting by ICL-IPL members will take place on 29 May 2017 at the University of Ljubljana in Ljubljana, Slovenia. The upcoming WLF5, the concept of “Kyoto 2020 Commitment of the World Landslide Community” and “The 2017 Ljubljana Declaration on Landslide Risk–Contributing to the Sendai Framework for Disaster Risk Reduction” will be discussed at the high-level panel discussion: Strengthening Intergovernmental Network and the International Programme on Landslides (IPL) for “ISDR-ICL SENDAI PARTNERSHIPS 2015-2025 for global promotion of understanding and reducing landslide disaster risk” on 30 May 2017 during the Fourth World Landslide Forum, Ljubljana, Slovenia.

Literature Survey and Experimental Study on the Direct Tension Test on Rocks

Abstract Direct tension tests are indispensable for obtaining an accurate understanding of the deformation and failure characteristics of rocks in tension. For this technical note, the authors collected original papers published in international journals and surveyed the previously reported methods and results of direct tension tests on rocks. Some important factors affecting the strength and stress–strain curve are discussed, such as the shape, size, anisotropy, and water content of the specimen; the loading rate; and the confining pressure. The relationship between the results of the direct tension tests and those of other tests also is discussed. Although various types of testing apparatuses have been adopted in direct tension tests on rocks, the dependence of test results on the apparatuses has not been investigated. In this study, direct tension tests were conducted using various testing apparatuses in seven laboratories. The results of the direct tension tests showed that direct tensile strengths were not dependent on the type of test apparatus used or whether a flexible linkage system was used. The results of the tuff in this study showed that the coefficient of variation of the direct tensile strengths is smaller than that of the Brazilian tensile strengths. Moreover, the results revealed that the coefficient of variation of the direct tensile strengths is comparable to that of the uniaxial compressive strengths of the tuff. The authors noted that to obtain the stress–strain curve from the pre-failure region to the post-failure region, it is necessary to conduct a test with a high-stiffness machine and without a flexible linkage system. This technical note summarized the results of the standardization activity by the authors in the Japanese Geotechnical Society.

Qualification of residential land from the viewpoint of liquefaction vulnerability

While the assessment of liquefaction potential by using borehole data has a long history since 1970s, its target users are still limited to professional engineers and experts. This situation is not favored by ordinary people who are seriously concerned with the reliability and preservation of their real estates during strong earthquakes. The demand of the people is that the liquefaction vulnerability of their residential land is precisely and clearly but concisely demonstrated so that people without engineering background can understand the real extent of risk. In this regard, the authors, under the governmental support, proposed a simple manifestation of the extent of liquefaction vulnerability of private houses in terms of the thickness of the surface unliquefiable crust and the vertical weighted average of the factor of safety or its equivalence. This achievement was made possible by introducing the ageing effects of soil on liquefaction resistance in addition to using geotechnical data base of subsoil conditions. During the work, it was found that existing borehole data may not be fully reliable and that experts who have sufficient knowledge of the local subsoil should assess the vulnerability. This requirement is satisfied by the qualification of special engineers that has been initiated by the Japanese Geotechnical Society in conjunction with several other institutions. The proposed method of subsoil qualification is used not only for individual residential land but also for regional hazard assessment.

Identification method for travel time based on the time domain technique in bender element tests on sandy and clayey soils

Based on the bender element (BE) international parallel tests, conducted from 2003 to 2005 using Toyoura sand, a standard test method for BE tests was proposed by Yamashita et al. (2009). The proposed method showed that any of the different identification methods would give a comparable travel time if the frequency of the transmitted wave were approximately equal to the frequency of the received wave. The proposed test method, however, did not show any specific procedure for choosing the input frequencies or for calculating the travel time. In the present study, therefore, with reference to the results from several previous studies on BE testing, a conditional expression for determining the input frequency and a calculation formula for the travel time have been defined, and BE testing using 13 different sandy and clayey soils has been conducted. After the testing, it was confirmed that the testing method is able to determine the shear wave velocity of sandy and clayey soils having widely different stiffnesses. Furthermore, the study has found that a reevaluation of the International Parallel Test results using this method has resulted in less variation as compared to the results from the reevaluation by Yamashita et al. (2009). This method is recommended in the "Method for laboratory measurement of shear wave velocity of soils by bender element test" standardized by the Japanese Geotechnical Society (JGS) in 2011 (Japanese Geotechnical Society, 2011).

Report on a reconnaissance survey of damage in Kathmandu caused by the 2015 Gorkha Nepal earthquake

Nepal was hit by the M7.8 Gorkha earthquake on April 25, 2015, which was the largest earthquake in Nepal’s history since 1934. The recent report presented by the Government of Nepal indicates that the recorded death toll has reached about 8800.Following the earthquake, the Japanese Geotechnical Society (JGS), Asian Technical Committee of ISSMGE on Geotechnical Natural Hazards (ATC3), Japan Society of Civil Engineers (JSCE) and Japan Association for Earthquake Engineering (JAEE) decided to jointly dispatch a survey team to Nepal to conduct a reconnaissance survey of the major damage caused by the earthquake. This report summarizes the results of the survey of the geotechnical and structural damage in the Kathmandu valley, which were observed by the survey sub-team between May 1 and 8, 2015. Geotechnical and geological characteristics of a deep soil profile up to 600m and a shallow profile up to 30m are also described with the help of the database system established by Bhandary et al. (2012). In order to study the correlation between building damage ratios and the predominant period of ground vibration, a partial exhaustive type survey was conducted along NS line where microtremor measurements had been previously conducted in 2008. The predominant period of ground vibration was short at the ridge of the valley and long at its center, ranging from 1.2 to 4.5s. A total of 532 buildings were assessed and more than 90% were classified as “No damage” or “Negligible to slight Damage” (Grade 0 and Grade 1), whereas only 5% of buildings were assessed as “Substantial to heavy damage” to “Destruction” (Grade 3 to Grade 5).Five locations were identified where the soil had liquefied. Liquefaction-induced damage to structures at these locations was not found, except at Nepal Engineering College where minor settlement of the college building was observed. During the 1934 earthquake, foundation liquefaction was observed in Tundhikhel area, but in the 2015 earthquake no evidence of liquefaction was detected in this area.The Kathmandu–Bhaktapur Road of Araniko Highway was heavily damaged in the Lokanthali area. The subsidence of soft soils and their lateral spreading in this area may have exacerbated the damage to this road.

Field Evaluation of the Vertical Bearing Capacity of a Screw Pretensioned Spun High-Strength Concrete Pile

This study has evaluated the vertical bearing capacity by conducting static load tests for noise-free and vibration-free screw pretensioned spun high-strength concrete (PHC) piles installed using two different methods (end-squirting shoe and pre-boring methods). Vertical bearing capacity differences seem to occur due to the displacement of soils near the external circumference of a pile, depending on the installation method. A method by which to evaluate the bearing capacity of screw concrete piles is suggested by considering the equations that already have been used to calculate the bearing capacity of piles. Based on static load tests and analysis, the pile installed using the end-squirting shoe method was assumed to be a bored pile and it was reasonable to use the equation proposed by the Japanese Geotechnical Society. At the same time, the pile installed using the pre-boring method was deemed a low soil displacement pile and so it was reasonable to apply the equations proposed for calculating the bearing capacity of the driven pile suggested by the Architectural Institute of Japan.

わが国で開発・改良された初期地圧測定法の基準化と国際化

The techniques of initial stress measurement were developed and improved in Japan. It is recommended to standardize some dominant methods in domestic market at first, and then encourage related organizations to promote them to international standard, in order to take an advantageous position of the methods in the international market. Currently, stress relief method and hydraulic fracturing method are considered to be valuable and practical methods. The compact conical-ended borehole overcoring method, one of the stress relief methods, was assigned as the standard of the Japanese Geotechnical Society in 2012. In addition, the new committee has been organized recently for standardizing the high stiffness testing method, an improved hydraulic fracturing technique. If international standard methods that are not the method used in Japan were assigned in future, we may be at a disadvantage for international bids. We may lose opportunities to apply our valuable technical resources such as engineers, instruments, established standards, and know-how in international market. And our techniques may become irrelevant in the international market. Our methods havebeen applied in many domestic foundation investigation fields such as construction of underground power plants, nuclear power plants, and large scale tunnels. It is in our best interest to have our techniques become the international standard as we expect an increase of requirement of those techniques in developing countries in future.

Japan’s Nation-Wide Electronic Geotechnical Database Systems by Japanese Geotechnical Society

On October 15, 2010, the Japanese Geotechnical Society (JGS) announced the public release of ‘Nation-wide Electronic Geotechnical Database Systems,’ which provides geotechnical information to the public on the internet. The information the system provides is a collection of ground models at 250 m by 250 m in plan built by using data from various geotechnical information databases. The paper first describes historical development of the geotechnical information databases in Japan, and introduces a 5-year project, ‘Integrated Geophysical and Geological Information Database in Japan,’ led by the National Research Institute for Earth Science and Disaster Prevention (NIED), and participated by the JGS. The paper then presents the JGS’ ‘Nation-wide Electronic Geotechnical Database Systems,’ and describes why such system was proposed and built, followed by the presentation of the examples for possible application of the system.

Retrospective Overview on Developments of “Soils and Foundations”

To look back at the traces of the development of “Soils and Foundations” and write up a synthesized story of evolution is, needless to say, beyond the capacity of the author. It is rather easy to retrospectively describe the achievements of old times, but it becomes increasingly difficult to deal with more recent advances because of the vast majority of events taking place—too many to digest— and also because it is all but impossible to simply explain such complex work. Yet, in the course of time, while less important events are put gradually out of our memories, only the noteworthy and most significant achievements remain. It is the telling of these memories that survive the passage of time that establishes them as of commonly recognized milestones. As such, it would be wise to rely upon the natural screening process as just described and not dare to touch on the most recent development in details. In this context, the intention of this article is mainly to unveil the progress in the early period of the Japanese Geotechnical Society (JGS) and to clarify the situations culminating in the birth and subsequent evolution of the English journal, “Soils and Foundations”. Regarding the events related to more recent developments, only a bird's eye view will be presented herein.

Professor Ioannis Vardoulakis (1949–2009)

Professor Ioannis Vardoulakis (1949–2009)

Interpretation of International Parallel Test on the Measurement of Gmax Using Bender Elements

This report summarizes the results of international parallel test on the measurement of the elastic shear modulus at very small strains, Gmax, using bender elements which was carried out from 2003 to 2005 by technical committee, TC29 (Stress-strain and Strength Testing of Geomaterials) of the International Society of Soil Mechanics and Geotechnical Engineering. The purpose was to evaluate the consistency of the bender element test results obtained by applying the exactly similar test material as well as the test method besides identifying the various existing hardware and software being used in this test. It was decided that the domestic TC29 group of Japanese Geotechnical Society (TC29-JGS) was expected to lead this international co-operation. By 2005, reports of the test results were obtained from 23 institutions from 11 countries. This report has been prepared by TC29-JGS taking a leading role from the beginning. A standard test method is proposed here in order to obtain more accurate data from the bender element test by examining various test methods adopted at different institutions worldwide and the effects of various factors on the test results.

花崗岩地域の地盤変動(地盤工学会・技術者交流特別セッション)

花崗岩地域の地盤変動(地盤工学会・技術者交流特別セッション)

Introduction to the Clay Science Society of Japan(Special Session of the Japanese Geotechnical Society)

Introduction to the Clay Science Society of Japan(Special Session of the Japanese Geotechnical Society)

Groundwater, Microbial Mats and Clays Reflect the Landslide Areas(Special Session of the Japanese Geotechnical Society)

Groundwater, Microbial Mats and Clays Reflect the Landslide Areas(Special Session of the Japanese Geotechnical Society)

Damage Survey Report on May 27, 2006, Mid Java Earthquake, Indonesia

On May 27, 2006, the Mid Java Earthquake hit around Jogjakarta City in Java Island, Indonesia. In this report, results from field investigations on geotechnical issues conducted by the Japanese Geotechnical Society survey team are summarized. At several sites where liquefaction occurred in lowland areas, subsurface soil conditions consisting of high groundwater table with soft soil deposits were identified. The liquefaction caused frequent plugging of wells. In these lowland areas, high collapse ratio of houses was reported, which may be linked to the directivity of earthquake motions affected by the earthquake fault location and/or their amplification in the soft soil deposits. In mountainous areas, a large scale landslide and a large number of slope failures and rock falls occurred. Earth fill dams suffered from cracking at the crest, while the rate of the leakage water from the toe of the downstream slope was not changed. Some recommendations are made in conducting detailed analyses and executing rehabilitation works on the damaged dams.

Investigation and Restoration Countermeasure Work for the Slope Disaster Induced by the 2005 West off Fukuoka Earthquake

The slope disaster and damage in Genkaijima, induced by the 2005 West Off Fukuoka Earthquake, have been investigated and studied by the investigating commission organized by the Japanese Geotechnical Society. The slope disasters in this island are classified into three areas: (1) damages of the housing site foundations and the retaining walls of steep slopes in the resident area, (2) landslides over the circumference road of the island, (3) small-scale collapses and cracks on the eastern slope from the Genkai elementary school to the Genkai junior high school. For each area, the results from on-site inspections, filed tests, indoor tests, measurements and analysis are reported together with the suggestion on restoration countermeasure work in this paper.