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Disaster Advances

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Disaster Advances





Improvement of solar irradiance estimates based on COMS-MI satellite images over Korea

Jeongho Lee, Suyoung Seo,* Minyoung Jung, Nuri Lee, Yongil Kim and Changyeol Yun

Although previous research has been conducted to estimate the solar irradiance over Korea using satellite imagery, most of this work has employed foreign satellite imagery. In the present study, we provide improved estimates of global horizontal irradiance over Korea using satellite images obtained from the Communication, Ocean and Meteorological Satellite - Meteorological Imager (COMS-MI), Korea’s first geostationary satellite. The Kawai and Kawamura methodology, which is considered adequate for studies of East Asia, is applied to estimate solar irradiance under both clear and cloudy conditions. We modified this method in two ways, using training data to improve the estimates of solar irradiance. First, the biases of irradiance under clear conditions were offset by applying the correction coefficient derived from the relationship between the satellite-based estimations and the ground-based observations made by the Korea Meteorological Administration. Second, the coefficient of cloud attenuation, Look-Up Table (LUT) was newly derived from the relationship between the satellite-estimated clear sky and ground-observed cloudy sky irradiances. Using this method, the instantaneous global horizontal irradiance over Korea was estimated for every fifteen minutes from May 2011 to April 2012. We evaluated the hourly and daily means of these estimations by comparing them with the observations made at twenty-four stations. The estimations and observations showed a strong correlation and the application of the correction coefficient and the modification of the LUT improved the accuracy of the solar irradiance estimations. The root mean square errors of the hourly and daily mean irradiances decreased from 44.5% to 22.6% and from 41.2% to 16.5% respectively.

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Experimental model for Computation of Flow Energy Dissipation over Labyrinth Weirs

Ghare A. D.*, Pote A. S. and Khode B. V.

There is worldwide need presently being felt to increase the safety of several old existing overflow structures against floods that exceed the original design flood. Unless the discharge capacity of the existing spillway is increased, there is a greater possibility of dam break and the consequent disasters. There are various approaches to achieve this and the choice of a solution is affected by the prevailing physical and economic conditions. Provision of Labyrinth weirs is one of the popular choices which offers a distinct advantage of providing increased discharge capacity than that of a linear weir with the same upstream head and the same waterway width. Several studies on discharge characteristics on labyrinth are found in the literature. This paper presents the results of laboratory experimental studies carried out to formulate the expressions for the estimation of relative energy loss of flow over labyrinth weirs, with side wall angles varying between 6o to 16o. The proposed expressions are expected to facilitate the engineers dealing with the design of labyrinth weirs.

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Improved Dual Strength Reduction Method of Slope Stability Analysis

Liang Gui-lan and Wang Xin*

The Dual Strength Reduction Method (DSRM) works with two strength reduction coefficients: SRF1 and SRF2. For slope, its shearing strength parameters (internal frictional angle and cohesion ) are respectively divided by these two coefficients until it arrives to destabilization under gravity and external forces. The DSRM regards the average value of SRF1 and SRF2 as the final safety factor of the slope. This paper aims at the ratio of to and has deduced the mathematic function between this ratio and the slope safety factor by analysis of several models. By this function, Most Conservative Safety Factor (MCSF) is proposed and that is a significant improvement of DSRM.

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Computing Stress and Displacement Response of Composite plates under blast

Matsagar Vasant A.

The present study investigates the performance of composite plates as sacrificial blast walls subjected to impulsive loading. Three dimensional nonlinear dynamic analyses of composite plates under blast loading have been performed using finite element software Abaqus 6.11. Non-composite plates made up of steel and composite plates made up of stiffened and unstiffened sandwich panels of different core materials e.g. polyurethane, dytherm, aluminium alloy syntactic foam and sand with different core thicknesses have been examined under the blast loading. Strain rate dependent properties of all the materials have been used in the analyses. Blast induced impulse load is applied in the form of pressure-time history curve calculated using the TM5-1300 manual and the modified Friedlander’s equation. Stress and peak displacement response of the composite plates have been computed and studied. It is observed that the composite sandwich panels having aluminium alloy syntactic foam as core material show lesser stress and peak displacement and thus higher blast response reduction capability.

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Comparison among different scaling methods for earthquake records used for seismic nonlinear analysis of structures

Magliulo G.*, Maddaloni G. and Petrone C.

Current Italian and European seismic codes allow evaluating the dynamic nonlinear behaviour of structures using time-history analysis. In this case one of the main issues to be solved is the selection of the accelerograms according to the code prescriptions. The choice of seismic input should be addressed with natural records: in this way it is possible to represent the earthquake with its main characteristics i.e. its amplitude, frequency and energy content, duration and phase. If natural accelerograms are adopted, the above mentioned prescriptions strongly condition the search for the "best" seismic input and they often require the real accelerograms to be altered by scaling techniques. In the current paper, the influence of different scaling methods is evaluated. Seven methods of scaling are taken into account and the variation coefficients (CoV), calculated in terms of spectral ordinates for sets of elastic and inelastic spectra, are evaluated and compared. It is concluded that if the CoV of the structural response must be contained, it is convenient to refer to scaling procedures that explicitly consider the fundamental period of the structure e.g. Kappos intensity and Matsumura intensity.

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Developing processes of rainfall-induced flow slides in laboratory flume tests

Zhiqing Zhang and Jian Zhou*

Small-scale flume tests were carried out to investigate the developing processes of rainfall-induced flow slides. The particle motion was taken by two high resolution digital cameras and the captured images were then analyzed with the aid of digital photography measurement and analysis technique. The displacement fields in the photographed region and velocity profile of soil mass were then obtained to verify the existing macro behavior of flow slides and reveal more detailed properties of flow slides. For the retrogressive sliding mode, it was found that the continuously larger deformation first generates in the upper front part of the slope and then gradually develops towards the lower and rear part of the slope. For the flow sliding mode, the continuously larger deformation first generates in the upper rear part of the slope and then gradually develops towards the lower and front part of the slope. The whole soil mass initially moves almost at the same time and the velocity of soil mass in the upper layer is always higher than that in the lower layer during the sliding process. The sliding velocity of soil mass in the lower part of the slope is relatively uniform but that in the upper part of the slope shows larger fluctuation at different positions.

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Mechanical behavior of steel fiber reinforced concrete investigated by one-stage light gas gun experiment

Guoping Jiang

This paper presents shock Hugoniot compression data for several concrete materials by using flat plate impact experiments. The manganin pressure gauge was used to measure the pressure-time curves of the samples. The physical quantities were all obtained by the Lagrange method. Moreover, it is observed from the measured pressure-time curves that the rate-sensitivity of dynamic response for the concrete is not negligible, showing marked stress relaxation and dissipation. Based on the polynomial Grüneisen equation, the parameters of high-pressure equation of state of concrete were obtained. The steel fiber reinforced affect was analyzed.

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3D Geological modeling approach based on Cross-Section of the Space Unit Division

Chen Guoliang* and Cui Zhen

A Divide-and-Rule modeling method based on cross-section data has been put forward in this article. This method divided the cross section data into several space cells, then it created geological block model in each cell. Finally it merged all cells within the geological model into overall geological model. The geological interface created in the building process of geological model within a single cell can guarantee the geometry and topological consistency of the geological model. The use of the method makes many people participate in the building process of geological model and thus avoid the drawbacks of the modeling process. This modeling approach can effectively improve the efficiency of large-scale geological model construction.

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Prediction of Outburst Intensity based on Support Vector Regression Machine

Zhou Aitao, Wang Kai* and Li Shan

Outburst intensity is an important index of destructive consequence caused by coal and gas outburst. However, outburst intensity is affected by ground stress, the soft layer thickness and coal strength. Outburst intensity is the complex nonlinear relationship with the influence factors; therefore, it is difficult to quantify the outburst intensity induced by coal and gas outburst. In order to obtain the outburst intensity value, the -SVR, -SVR, LS-SVR and BP neural network prediction models are compared. Finally, the -SVR coal and gas outburst intensity prediction model is chosen as the best model for predicting outburst intensity and the performance of the model is validated by the laboratory data. The result shows that SVR has a good performance of classification and regression.

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Prediction model of rock mass quality classification based on TBM boring parameters

Feng Ji*, Junfu Lu and Yuchuan Shi

TBM method is a fast, high-quality and secured method. It is very important to predict the rock mass quality of tunnel using these boring parameters which can reflect the geological condition of tunnel, especially to avoid serious damage of exposed tunnel when the cutter head is advancing to ensure the safety of the designer and to adjust the support measures timely. Meanwhile, this is a key technical problem in TBM construction technology. There are four buried deepest tunnel of the world in Jinping Hydropower Station. Among them, 2 tunnel diameter 13m were excavated by TBM produced respectively by Robinson and Herrenknecht AG. A large number of geological data and TBM boring parameters have been collected. The results showed that(1) In predicting the classification of rock mass quality, if the regression equation is established and solely based on on TBM boring parameters, the fitting goodness is poor and the reliability is lower;(2) On the basis of TBM boring parameters, when the factor of rock strength is included, the score range of prediction model is wider and the reliability of the prediction model is significantly improved;(3) Established a prediction model of rock mass quality classification and (4)Through the verification of a length of 1600 m tunnel, prediction accuracy of the model reaches 90.30%.,

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Stability analysis of silty clay slope in wetting-drying alternate environment

Zuliang Zhong* , Yiliang Tu1, Xinrong Liu, Yuanxue Liu and Jingwei Liao

To study the stability of soil slopes in wetting-drying alternate environment, a laboratory simulation of wetting-drying cycles on silty clay slope is conducted in this paper. The law of shear strength and its parameters of silty clay varying with the number of wetting-drying cycles are investigated by triaxial compression test. Based on this, a theory for calculating safety factor of silty clay slope in wetting-drying alternate environment is derived. Then this theory and a modified instability criterion of slope are both applied in the stability analysis of a silty clay slope by numerical simulation. Its safety factor is obtained. It can supply the basic theory and can provide engineering reference for the stability analysis of similar soil slope engineering.

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