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GEOSLICIER AND ITS APPLICATION FOR SOIL STRATA ANALYSIS T. Harianto; T. Hino; R. Jia; K. Ohgushi; T. Ichihara
Lowland Technology International Vol 15 No 1, June (2013)
Publisher : International Association of Lowland Technology

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Many "nogoshi" i.e, lower sections of the river bank that allow upstream floodwater overflow, have been built on the Jobaru River in Kyushu Island, Japan. The soil strata in the floodpain adjacent to the Yago Nogoshi of the Jobaru River were studied using a Geoslicier. The sedimentary facies and the sedimentary ages of the soil strata were determined using Geoslicier samples. The sedimentary environmental of the test site was defined, and soil strata formed by sediments during large floods were identified. The layers below ground level (G.L.) -1.50 to -1.70 m are river channel deposits, and the layers above G.L. -1.50 to -1.70 m are back marsh deposits. The result of radiocarbon dating show that the river channel deposits were formed before AD 1500. The lower layers of the back marsh deposits, which contain a considerable quantity of plan roots, were formed at approximately AD 1600. The upper layers of the back marsh deposits, which contain a small quantity of plant roots, were formed after AD 1600. The time of artificial land alterations was deduced based on the results of the sample analyses.

Mitigations of flooding and soil erosions Geo-Disasters in Thailand and Laos due to climate change: From Mountains to Lowlands D. T. Bergado; S. Chaiyaput; P. Voottipruex; T. Hino; N. Chanmee
Lowland Technology International Vol 19 No 1, June (2017)
Publisher : International Association of Lowland Technology

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In 2011, Thailand has suffered from devastating flooding due to climate change. During this time, 2 typhoons from the Pacific area went straight across Vietnam to Northern Laos and Northern Thailand instead of the usual path to Taiwan and Japan. Subsequently, huge flooding damaged many infrastructures and overtopped flood protection dikes of many industrial estates and educational institutions in the Central Plain of Thailand such as at Hi-Tech Industrial Estate, Bang Pa- In Industrial Estate, Navanakorn Industrial Estate and Asian Institute of Technology, to name a few. The same phenomenon also occurred in neighboring Laos PDR which caused unusually heavy rains and widespread river flooding. Consequently, riverbank erosions accompanied by slope failures occurred at Xedon River in Pakse, Southern Laos due to saturation caused by high water levels accompanied by high velocity flow of the flooded river. To evaluate the stability of these mitigation structures, finite element and limit equilibrium methods were utilized. PLAXIS 2D software was used to analyze the slope protection schemes at low and high water levels incorporating the various supporting and reinforcing materials. Moreover, the PLAXIS 2D software was also utilized to predict the vertical deformations of improved flood control dikes with increased embankment height at different cases of flood water levels. In addition, the SLIDE software was used to predict the factor of safety by using limit equilibrium method for the various riverbank erosion protection structures. Furthermore, RESSA software was utilized to evaluate the slope stability of the erosion protection structures with geosynthetic reinforcements of Xedon riverbank in Pakse combined with gabions and mattresses. Laos PDR is mountainous with high elevations.

MEASURED BEHAVIOR OF A TRIAL EMBANKMENT ON FLOATING COLUMN IMPROVED SOFT ARIAKE CLAY DEPOSIT Y. Igaya; T. Hino; J.-C. Chai
Lowland Technology International Vol 13 No 1, June (2011)
Publisher : International Association of Lowland Technology

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A 6.5m height trial embankment was constructed on soft Ariake clay deposit improved by the floating soil-cement columns. At the test site, the thickness of the soft soil was about 10 m, and the length of the column was 8.5 m and the area improvement ratio was about 31%. To check both the mechanical and geoenvironmental performance, the embankment was monitored for more than 2 years. The measured results indicate that the behavior of the trial embankment satisfies the performance requirements for constructing a highway around Ariake Sea, in Kyushu, Japan, i.e. settlement and lateral displacement at the toe of the embankment are less than 50 mm, and residual settlement is less than 0.3 m. The observed results also show that the column improvement not only reduced the settlement but also accelerated the consolidation rate of the deposit. The results of groundwater monitoring indicate that at the test site, in terms of groundwater level, flow velocity, pH value and the concentrations of some key ions, there was no effect on the groundwater quality due to the installation of soil-cement columns into the ground.

3D FEM investigation on bending failure mechanism of column inclusion under embankment load S. Shrestha; J.-C. Chai; D. T. Bergado; T. Hino; Y. Kamo
Lowland Technology International Vol 17 No 3, Dec (2015)
Publisher : International Association of Lowland Technology

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Bending failure mechanism of column inclusions in soft clay deposit under embankment loading has been investigated by three dimensional (3D) finite element analyses. Firstly the effectiveness of the numerical procedure has been verified by comparing the simulated and the measured results of a centrifuge model test reported in the literature in terms of lateral displacement, settlement, and the bending moment in the column. Then the effects of the size of the column improved area from the toe toward the center of the embankment, stiffness of the column, the length of the column on the maximum bending moment in the column have been investigated numerically. The numerical results indicate that increase the size of the improved area, reduced the bending moment in the upper part (near ground surface) of the column; increase the stiffness of the column increased the maximum bending moment; and the maximum bending moment occurred at the end of the column in the case of an end bearing column, and in the upper part of the column for a floating column. The numerical results also indicate that when the whole area under the embankment is improved by end bearing columns with an area improvement ratio of 28 % and tensile strength of the column of 100 kN/m2, the embankment load can be applied with a factor of safety of about 2 for bending failure of the columns is about 13 times of the initial undrained shear strength of the soft deposit.

A Study on Jobaru River Basin Management by Numerical Simulations of Flooding and Sediment Deposition with Field Survey K. Ohgushi; H. Nakashima; T. Hino; T. Morita; T. Jansen
Lowland Technology International Vol 18 No 1, June (2016)
Publisher : International Association of Lowland Technology

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River basin management in Japan in the early modern period can be considered as providing a prototype of possible countermeasures for present-day flood exceeding the design level. The river basin management in the Saga region of Japan was established by Naritomi Hyogo in the early Edo era. This study evaluates characteristics of river basin management in Jobaru River Basin located in the eastern Saga Plain using numerical simulations and geotechnical surveys. A flood flow of Jobaru River was calculated using a 1-D flow numerical simulation. Overflow discharges from Nokoshi, open levee and no-levee intervals are estimated and these discharges are specified as boundary conditions for quasi 3-D inundation flow simulations. 2-D sediment transport by water flow is also simulated. A Geoslicer is used for field surveys that uncover clues of how the sediment has been deposited in the past. The ages of the sampled stratums was measured by using radiocarbon dating methods. The classified sediments columns and estimated ages of the stratum by the radiocarbon dating correspond to the simulated flood flow behavior in the retarding basin after overflow from the Nokoshi and open levee. Moreover, No.1 open levee reproduced by the geotechnical survey's result is used for the flow simulation successfully.

Influences of Long-Term Tectonic and Geo-Climatic Effects on Geotechnical Problems of Soft Ground - Ulaanbaatar, Mongolia S. Manandhar; T. Hino; K. Kitagawa
Lowland Technology International Vol 18 No 1, June (2016)
Publisher : International Association of Lowland Technology

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Ulaanbaatar city situates in Ulaanbaatar Folded System with presence of Mongolo-Baikal seismic zone. The presence of the Tuul River Valley dissected the basin with the formation of soft sediments transported by fluvial and Aeolian environments. The presence of scattered permafrost soil due to geo-climatic condition has led to freeze-thaw phenomena by physical weathering of the ground. This study reveals the influences of long-term tectonic and geo-climatic effects have brought up geotechnical problems in the area. Further it is advised that special attention need to be given in settlement of the area associated with mechanical disintegration of the ground, characterizing similar with lowlands along the valley bottom.

Damages and causative factors of 2015 strong Nepal Earthquake and directional movements of infrastructures in the Kathmandu Basin and along the Araniko Highway S. Manandhar; T. Hino; S. Soralump; M. Francis
Lowland Technology International Vol 18 No 2, Sep (2016)
Publisher : International Association of Lowland Technology

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The strong earthquake on April 25, 2015 (7.8 Mw) and the aftershock on May 12, 2015 (7.3 Mw) claimed the lives of 8,659 people, plus 21,150 people injured and huge economic loss together with serious damages on eight World Heritage sites. Our two field surveys in the month of from May 9-21, 2015 and 19-23 July, 2015 revealed understanding of damages to traditional towns, historical monuments, and modern buildings. Regionally, damages on buildings are confined to the traditional houses which are remnants of or renovated after the 8.1 magnitude 1934 AD earthquake. Widespread cases of inadequate engineering and construction practices for RCC (Reinforced Cement Concrete) buildings and renovated old buildings have been severely affected. The affected region includes the main shock along the 150 km long rupture zone towards east. The aftershock reached farther south at a shallower depth towards the end of the eastern rupture zone. As a result damages inflicted in the structures from both quakes revealed different shaking directions. The April 25 main shock caused eastward leaning structures while May 12 aftershock caused southward leaning and/collapsed structures. It is important to identify whether the direction is due to aftershock at the end of initial rupture zone or if it represents a newly exposed fault.

Georisks during road tunneling in weathered quartz sand rock with faults under high-head of groundwater B. Yuan; Y.S. Xu; S.L. Shen; T. Hino
Lowland Technology International Vol 18 No 3, Dec (2016)
Publisher : International Association of Lowland Technology

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This paper presents an investigation of georisks during mining tunnel construction in weathered quartz sand rock with faults at Fuyang, which is located at the southwest of Hangzhou, Zhejiang Province, China. Fuyang is a hilly region, where volcanic and intrusive rock masses are irregularly distributed, with the extensive development of fault zones and joint fractures. The Park Road Tunnels in Fuyang City will pass through the mountain in the city center and will be excavated in the lightly to weakly weathered quartz sand rock. The rocks are mainly crushable and are affected by fault zones and joint fractures. The fault zones and joints have large cavities filled with loose fragments and rich of fissure water. The rocks are classified into three grades based on the design code for road tunnels in China. The strength of the rock gradually decreases under the softening effect of abundant fissure water during construction. It was found that water ingress occurred at the entrance and the exit of the tunnel, the faults, and the contact zone between the hard and soft rock. Landslides had also occurred at the entrance and the exit of the tunnel in this case study.

Investigation of the safety factor and reliability of the embankment in soil cement column improved ground on Saga lowland Y. Jabeur; S. Manandhar; S. Shrestha; T. Hino; M. Mbodji; T. Himeno
Lowland Technology International Vol 20 No 4, March (2019): Special Issue on: Green Technology for Sustainable Infrastructure Develop
Publisher : International Association of Lowland Technology

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Saga plain constitutes thick deposited soft marine clay which is susceptible for the construction of any civil engineering structures with reference to large and differential settlement problems in the area. This paper presents the case study of the Ariake sea coastal road project failure on Ashikari region in Saga lowland. In this region, the group of soil cement columns as ground improvement technique is adopted for the construction of the highway embankment. The estimation of probability of failure of the embankment on the stabilized soils is approached through the probabilistic analysis for this research. The assessments of total safety factor (Fs) and reliability rely on random variables of geotechnical parameters. These random variables considered for this study are the unit weights of the soil materials (γ) (fill and clay), the undrained shear strength (cu) in the embankment fill material and undrained shear strength of the stabilized soil and soft soil. Furthermore, the paper also delineates judgment of the geotechnical risk assessment based on real site condition.

Study on effects of specimen size of unconfined compressive strength of improved soil T. Himeno; K. Takatani; T. Hino; S. Mandhar; S. Shrestha
Lowland Technology International Vol 20 No 4, March (2019): Special Issue on: Green Technology for Sustainable Infrastructure Develop
Publisher : International Association of Lowland Technology

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Deep mixing method (DMM) is one of the countermeasures for long-term stability of the soft ground area, specifically highly applicable in coastal lowland. With the economic growth in ASEAN countries, this technology has become more popular in order to develop stable infrastructures through mega projects. In this paper, discussions are carried out through conducted laboratory mixing tests by where samples were extracted from the site in order to maintain the quality of soil-cement column by using DMM based on designed methodology. In Japan, samples are extracted continuously from the vertical direction using a thin-walled sampler. It can be connected from considering characteristics of strength development of each depth grouped into three sections from the tube into upper, middle and lower portions. However, the case of non-uniformity and the total amount of sample taken from the site is not enough, there will be the possibility to encounter a difficult situation to conduct laboratory mixing test using standard specimen size of D 50 mm × H 100 mm. Therefore, the characteristics of strengths appeared in the standard size of D 50 mm × H 100 mm laboratory mixing test is compared and discussed with newly defined laboratory test of specimen size D 25 mm × H 50 mm.

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