Vol. 6(10) October 2013
Editorial
Studies of the past as the key to the future? Geological
and historical reconstructions provide valuable support for future trend prediction
of natural disasters
Habil. Sebastian Lüning
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Stability Analysis of Hsien-du-shan Rock Slope during
the Earthquakes
Lin Hung-Ming, Wu Jian-Hong and Sunarya Erik
In this paper, the impacts of the Chi-Chi Earthquake
(1999) and the Heng-Chun Earthquake (2006) to the stability of the Hsien-du-shan
rock avalanche slope in Taiwan are investigated. The residual shear strength parameters
of the sliding surface with high water content are c=0.0 and =24.3° using direct
shear tests. In addition, the stress paths of the sliding surface calculated based
on the simplified physical model with the impacts of both earthquakes are below
the failure envelope. Therefore, this study validated that the Hsien-du-shan slope
was stable during the Chi-Chi Earthquake and the Heng-Chun Earthquake.
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Impact of Climate Change on Flood Risk in the Muar
River Basin of Malaysia
Ching Yun Chen, Baharudin Y., Mohd Ekhwan T., Lee Yook Heng, Maimon A. and Salmijah
S.
Twenty-nine flood events have been reported for the last
31 years in the Muar River Basin area of Peninsular Malaysia during the North East
Monsoon. This study aims to analyze a 31-year period (from 1980 to 2010) of climatic
data from 25 meteorological stations in the Muar River Basin and to identify causes
of flooding events in the area. The mean annual rainfall of the 22 rainfall stations
in the area was 1707.2 ± 250.2 mm/year and the mean monthly rainfall was 146.2 ±
30.9 mm/month. On average, the maximum rainfall was recorded in November and December.
The mean annual rain days in the area were 118.4 ± 12.4 days and the mean annual
non-rainy day were 233.6 ± 14.3 days while the mean monthly rain day in the area
was 9.34 ± 1.72 days. Daily temperature in the area ranged from 21.2oC to 37.7oC.
The mean relative humidity was 63.0% and 94.0% during day time and night time respectively.
The average evaporation rate of the area was 3.8 mm/day. Results of this study are
useful for understanding the climate change in extreme weather events for hydrological
and agricultural planning and for flood risk management in the Muar River Basin.
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Leakage Analysis considering Unsaturated Seepage of
the Ground Water on Mengxi River
Ji Youjun*, Zhang Linzhi and Lai Yangchuan
Leakage of surface water can cause the waste of water
resources and the pollution of ground water. Aiming at the existing problem that
Mengxi River could not hold water for a long time, geology investigation and numerical
simulation analysis were carried out. The three dimension topography was drawn according
to data of topographic survey by Total-station instrument. The double-ring infiltrometer
was used to test the hydraulic conductivity of soil. Build the geologic model by
3D modeling software. A numerical model which is based on the unsaturated seepage
equation was developed to investigate the seepage field of riverbed and bank. The
study reveals the seepage mechanism of ground water in MENGXI River and compares
the effect of various impervious materials.
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Research on the Propagation Characteristics of Shock
Waves and Gas Flow during Coal and Gas Outbursts in Cross Roadway
Wang Kai and Zhou Aitao
In order to study the propagation law of shock waves
and gas flow during coal and gas outburst, first, we analyzed the formation process
of outburst shock waves and gas flow. Afterwards, we established the numerical simulation
models of the roadways with 45° intersection by which we conducted real-time simulation
of the propagation of outburst gas flow and the process of gas transport. Experimental
models have been carried out to investigate the outburst shock waves and gas flow
at the roadways with the similar shapes as the simulated ones. The results show
outburst shock wave and gas flow can diffract and reflect at intersection; the intensity
will attenuate to a large extent due to the split of shock wave and gas flow; turbulent
flow has influence mainly on branch roadway.
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Anchorage behavior of mechanically under-reamed anchors
in silty sand
Hsu Shih-Tsung and Tang Yu-Geng
An under-reamed anchor can meet the requirements of having
a short length and high anchorage capacity in a limited space or a restricted thickness
of an anchored stratum. Furthermore, the anchor can provide more ductility to resist
seismic force. To investigate the anchorage mechanisms of this anchor, a numerical
program was adopted to perform the numerical analyses. The results from field anchor
tests were compared with those calculated by numerical analyses to enhance the applicability
of the numerical program. Three failure modes on end bearing were identified according
to the embedded depth of the under-reamed anchor. These included general shear failure
for a shallow anchor, local shear failure for a transited anchor and punching shear
failure for a deep anchor. No progressive yield occurred along the interface between
the fixed length and soil for the anchors with length/diameter ratios (L/D) of less
than 25. Therefore, the anchorage capacity increased at an increasing rate with
the fixed length.
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GIS-based Landslide Susceptibility analyses and Cross-Validation
using a Probabilistic Model on Two Test Areas in Korea
Kim Jinsoo, Choi Chuluong and Park Soyoung
Landslides are major natural geological hazards that
are responsible each year for a high amount of property damage involving both direct
and indirect costs. Over the last few decades, many researchers have produced landslide
susceptibility maps using various techniques. This paper presents the results of
the cross-validation of a probability model using remote sensing and geographic
information system for landslide susceptibility on the Wumyon and Inje areas in
South Korea. Landslide locations were identified from aerial photographs. The 13
landslide-related factors, slope, aspect, curvature, soil thickness, soil drainage,
soil texture, soil material, soil topography, timber type, timber age, timber density,
timber diameter, land cover, were calculated and extracted from the spatial database.
Using 13 factors, landslide susceptibility was analyzed by probability model. For
validation and cross-validation, analytical results were compared in each study
area with actual landslide locations. Wumyon based on its frequency ratio presented
the base prediction accuracy (76.38%) whereas Wumyon based on the Inje frequency
ratio presented the worst (70.11%). Qualitatively, the cross application model yields
reasonable results which can be used for preliminary landslide hazard mapping.
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Seismic liquefaction and related damage to structures
during the 2013 Lushan Mw6.6 earthquake in China
Liu Yufa and Huang Runqiu
On 20th April, 2013, a Mw6.6 earthquake hit Lushan county
of Yaan city, Sichuan province, southwestern China. We immediately conducted a field
survey after the earthquake. During the survey, we observed many liquefaction features
in and near Shuangshi town such as sand blow, lateral spread and settlement. The
liquefaction resulted in the damage to buildings, road and infrastructures, including
lateral displacement, uneven settlement, subsidence and impact failure. Particularly,
the liquefaction in gravel was in less than 7.0 magnitude earthquake in Chinese
mainland.
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Cloudburst and Landslides in Uttarakhand: Nature’s
Fury?
Mishra Ashutosh
Cloudburst is one of the major natural disasters in Uttarakhand
State of India and this brings flash floods, landslides and massive destruction
of property and lives almost every year in the state. The present paper discusses
about flood and landslides which occurred due to cloud burst and heavy downpour
in between 14 to 17 June, 2013 in the state. Uttarakhand is very susceptible to
landslides and almost three fourth of the total geographical area of the state comes
under severe to high landslide risk zone. The catastrophe started with cloud burst
near Rambara in Rudraprayag district and due to torrential and continuous rainfall,
almost all the major rivers and especially the Mandakini and the Alaknanda swelled
up. Overflowing water reservoirs of the region catalysed the severity of the event.
About one tenth of the upper catchment area of Mandakini river swept away due to
flood and landslide. This was the deadliest hazard in 80 years’ history of the state
which affected about 80,000 people. The paper reflects the nature`s supremacy over
human potentials and advocates the balanced man-nature relationship, especially
in such terrains which are most fragile and critically balanced. It suggests the
judicious use of Himalayan resources and use of environment friendly techniques
in implementing the development plan for the region.
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A Case Study of the Perceived Socio-Environmental
Problems caused By Illegal Gold Mining in Gwanda District, Zimbabwe
Bhebhe D., Kunguma O., Jordaan A. and Majonga H.*
This study assessed the perceived impact of illegal gold
mining on the environment and the people of Gwanda District, Zimbabwe. The research
applied qualitative and quantitative methods using face-to-face interviews, questionnaires
and observations. Purposive sampling techniques were used and 94 respondents were
interviewed drawn from informal gold miners, non-miners and stakeholders comprising
local government officials, environmental manage-ment authorities and officials
from local mining organisations. Non-miners included those people living with informal
gold miners along the riverbanks and neighbouring communal settlers. The study established
that informal gold mining activities were poverty driven, contributed to environmental
problems such as deforestation, river siltation, soil erosion and water pollution
due to disposing waste materials and the use of chemicals such as mercury and cyanide.
The study recommends that a coordinated approach be used to create a certification
scheme so that informal gold miners are provided with basic training in environmental
and disaster risk reduction management skills. This will assist in reducing the
environmental problems and other related disasters emanating from illegal gold mining.
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Study on Numerical Simulation of Wind Field around
Buildings over Complex Terrain
Li Lei1, Chan Pak-Wai, Yang Lin3 and Zhang Lijie
The complexity of underlying surfaces has always been
one of the main challenges facing wind field numerical simulations, especially when
there are both complex terrains and buildings inside the simulation domain. There
are almost no existing singular models that can simulate fine-scale wind fields
in details under such cases. In order to simulate detailed wind field around buildings
over complex terrain, this study presents a coupling method using both a mesoscale
RAMS model and a FLUENT computational fluid dynamics (CFD) model, in which RAMS
simulation results are extracted to initiate FLUENT simulations. In this study,
wind field around the Hong Kong International Airport during Typhoon Nuri was simulated
and analyzed. Simulation result was compared with observed data from 6 automatic
weather stations (AWSs) located beside the two airport runways. The comparison showed
that simulated wind directions and wind speeds agreed well with those from AWSs.
Simulation result also described the crosswind change over the south runway (07R/25L)
caused by airport buildings which explained why two planes experienced tough landings
during Typhoon Nuri.
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Material parameters of D-P yield criterion in 3D stress
space based on non-associative flow rule
Tianwen Dong
Drucker-Prager (D-P) yield criterion was widely used
in the FEM (Finite Element Method) analysis of geotechnical engineering in present.
For limitation of complex characteristic of geotechnical material, the results of
analysis that used D-P criterion do not meet for the practical engineering sometimes.
According to the potential theory of plasticity in geotechnical plastic mechanics,
the plastic volumetric strain factor (u) and the rate of plastic shearing strain
to plastic volumetric strain () are advanced. The total plastic strain of frication
material is expressed as two kinds of plastic strain caused by the deviatoric stress
and spherical stress respectively. u and considered the level of plastic deformation
caused by the invariant of the deviatoric stress and spherical stress. At the same
time, also reflects the plastic strain coupling of the deviatoric stress invariant
and the spherical stress invariant for the different material and different loading
level on the view of macroscopic. Submitting the u and into two yield surface
criterion, the material parameters of D-P in 3D stress space are built. Comparing
with the material parameters of different solutions, it shows that the plastic deformation
is relative to u, , cohesion (c), internal frication angle () and the angle of
stress direction () and it fits for the deformation characteristic of geotechnical
material.
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Wave Forces on Upright Breakwater, Evaluation and
Case Study
Giuseppe Barbaro*, Giandomenico Foti and Carmelo Luca Sicilia
A correct prediction of the horizontal force exerted
by sea storms on structures is necessary for proper design of upright breakwaters.
In this paper the horizontal force on breakwaters is analyzed. Two cases in two
different locations are proposed, the first one concerns Italian coasts (Ortona),
the second one is in the USA (Alaska). The aim of this paper is to compare recent
methods for calculating force on structures with the well-known Goda’s model. Wave
climate was studied through the ISPRA (Istituto Superiore per la Protezione e la
Ricerca Ambientale) and NDBC (National Data Buoy Center) measurements.
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Tensile strength and suction of naturally available
saturated clays with modified tensile testing apparatus and their relationships
with unconfined compressive strength
Tamrakar S. B., Mitachi T. and Kung G. T. C.
Tensile crack development at the back of slope top is
one of reasons for the slope failure. Tensile strength measurement for the analysis
of such failure is very important. Here, tensile strength measuring apparatus developed
by Tamrakar el al11,12 is modified so that suction (-uw) could be measured along
with tensile stress from the start to the end of the test. Unconfined compression
(UC) tests are also done with suction measurements. Commercially available Kasaoka
and Fujinomori clays are used as test specimens. Ratios of tensile strength (qt)
to pre-consolidation pressure (P'c) found for Kasaoka and Fujinomori clays are around
0.16 and 0.07 respectively. Ratios of unconfined compressive strength (qu) to P'c
for Kasaoka and Fujinomori clays are around 0.50 and 0.24 respectively. Similarly,
strength ratios (qu/qt) calculated for Kasaoka and Fujinomori clays are equal to
2.90 and 3.66 respectively. In case of tensile test, increment in suction value
is seen around tensile failure zone. In contrary to this, in UC test, suction value
decreases around unconfined compression failure. Suction values at failure in both
tests are also compared and it is observed that the suction values at failure in
both tests show similar values, their ratio being in the range 0.8 to 1.2.
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Multiclass Support Vector Classification to estimate
Typhoon Rainfall Distribution
Shien-Tsung Chen
The prediction of typhoon rainfalls provides important
information for mitigating disasters. Different from models based on regression,
this study proposes a classification methodology for typhoon rainfall estimation.
A multiclass support vector classification with a one-against-one scheme is applied
to develop the model. Using important typhoon characteristics, including the minimum
central pressure, maximum central wind velocity, cyclonic radius and moving track
as input variables, the multiclass classification model is able to predict the classes
of rainfall depth, duration and type. The methodology combines the predicted classes
of three rainfall parameters to estimate typhoon rainfall distribution. Calibration
and validation results pertaining to data from 98 typhoon rainfall events in Alishan,
Taiwan, show the ability of the proposed classification methodology to estimate
typhoon rainfall distribution. Moreover, the proposed typhoon rainfall estimation
model can potentially be updated into a real-time forecasting model by including
relevant variables.
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