Large Scale Rainfall induced Potential Landslide Analysis and Monitoring from DInSAR– A Case Study after Heavy Rainfall Event in 2006, Central Taiwan

Kuo-Lung Wang, Jun-Tin Lin, Meei-Ling Lin, Ching-Wee Lin, Hongey Chen, Tien-Chien Chen and Chih-Ming Tseng

About 70% coverage in Taiwan is mountain area. As Taiwan locates at the collision zone of Philippine seaplate and Eurasian plate, hazard induced by earthquake always happens. Also Pacific Ocean is nearby, thus tropical cyclone in summer can produce typhoon or heavy rainfall which induces high accumulated or high intensity rainfall in recent years. Despite of already slip landslide investigation, potential landslide is also very important for control priority of landslides. A heavy rainfall event in June, 2006 is selected in this research. Differential Interferogram Synthetic Radar (DInSAR) is adopted for search potential deformed landslides. Detail discussion of these potential deformed landslides and their relationship with following events is performed in this study. Moreover, ground landslide displacement monitoring results in three selected landslide sites selected to discuss the validity of this method and suggestion to further research.

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Migration characteristics of mixed gas after high concentration gas instantly pouring into roadway

Chengwu Li , Wei Yang , Shanyang Wei, Zhen Li and Teng Li

Mine gas is one of the main natural factors which pose serious threat to coal mine safety production. In order to analyze the propagation law of high concentration gas in roadway after coal and gas outburst, similarity test system was established based on principle of similitude and diffusion theory. An im-proved mathematical model of turbulent diffusion was proposed. Afterwards, the influences of the explosive quantity, air velocity and monitoring distance on migration of high concentration gas were also studied. In addition, the variation trend of field monitoring data was analyzed. Similarity test results indicate that the fitting results by using improved turbulent diffusion model basically tally with the experimental data. The monitoring distance has an effect on gas generation quantity, the initial rising moment and peak moment. With the increase of monitoring distance, the influence of the explosive quantity on rising slope or decreasing slope of moni-toring curves is gradually weakening. Meanwhile, the display degree of flow and diffusion characteristics of high concentration gas depends on the air velocity. Furthermore, the overall variation trend of field monitoring data is consistent with the experimental data. Research results can provide theoretical basis for both the dynamic identification and the decision of the disaster scope after coal and gas outburst.

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A simplified method for deformation analysis of deep excavation considering small-strain characteristics of soils

Chien-Chih Wang, Chih-Wei Lu, Gordon Tung-Chin Kung, Sin-Yi Lin, Gargh S. L. and Mungray Arvind

This paper proposed a simplified method capable of considering the small strain characteristics of soils in the numerical analysis of excavation using the conventional hyperbolic model. The commercial code PLAXIS is employed in the intended analysis. The sensitivity analysis was first conducted to investigate the sensitivity of various soil parameters using a series of hypothetical cases established based on a well-documented excavation case history. The MAPE method was incorporated into evaluating the sensitivity of soil parameters. Then, the optimization method is adopted to back figure the reasonable value of the normalized undrained strength, su/v. Based on the results of numerical analysis in the TNEC case, the value of (Eu/su)initial was 4-6 times of Eu/su. This value would be used in the practical excavation engineering. This study then incorporated the RSPE (Root square percentage error) method into further examining the results of optimization analysis. The RSPE values can be effectively reduced by optimizing the su/v stage by stage. The su/v-H/Hf regression curve may has the potential to be a practically useful analysis method for implementing the excavation design. The results revealed that the developed simplified method could reasonably estimate the excavation-induced wall deflection and ground surface settlement.

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Experimental study on water absorption and strength degradation effect of shale at great depth

He Manchao and Zhang Na

In the present study, water absorption experiments were carried out on shale samples collected from a deep coal mine in China using a computer-automated water absorption tester. The experimental results showed that the water absorbed by the shale samples increases with time while the absorption rate decreases with time. Regression analysis indicated that the water absorption curves of the shale samples can be well fitted by an exponential function. Comparison of the water absorption capacities of the shale samples with and without water pressure suggested that water pressure can significantly increase the water absorptivity. Based on statistical analyses, positive correlation relationships were found between the water absorption capacity and the clay mineral content which indicated that the clay minerals, specifically illite in this case, play an important role in water absorption process of the shale samples. However, negative correlations were found between water absorption capacity and porosity (d > 0.2 µm) and the reasons for these negative relationships were discussed from a micro-structural perspective. It is inferred that the increase of porosity could be one of the important reasons for strength attenuation of the hydrated shale samples.

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Coastal erosion in the South of Italy

Barbaro Giuseppe, Foti Giandomenico and Sicilia Carmelo Luca

The Calabria region, located in the South of Italy, has a coastline longer than 700 km and it plays a crucial role in economic growth. Unfortunately, all the coasts were affected by strong erosive phenomena during the last century. Since 2012 the Regional Environmental Office (Autorità di Bacino) has been conducting an integrated program to restore the existing beaches in the so-called “APQ (Framework Programme Agreement) on Coastal Defence” in association with the “Mediterranea” University of Reggio Calabria. This paper is concerned with the first part of the programme which involves the cognitive phase and is divided into two parts, the first one pertains to the historical evolution of the Calabria shoreline, evaluated by a cartographic analysis and the second one pertains to the evaluation of the causes of the erosion.

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Post-hazard System Reliability Analysis of Complex Interacting Networks based on the Logical Expansion of Recursive Decomposition Algorithm

Kim Youngsuk and Kang Won-Hee

This paper proposes to solve sophisticated reliability problems of complex systems using the Logical Expansion of the Recursive Decomposition Algorithm (LE-RDA), a non-simulation-based network reliability analysis method. These problems include the reliability analysis of k-out-of-n system event definitions and importance assessment of the interaction effect between interdependent networks in terms of overall system reliability. These problems are defined by a complex mixture of events with correlation caused by shared components. This study also proposes a new reliability-based approach to evaluate the contribution of network component groups which are defined by their functions, to system events e.g. disconnection of water to an area. These new approaches are applied to a bench mark electric power grid and water network in Memphis/Shelby County to demonstrate the capabilities and effectiveness of the new approaches. The significance of interdependency effect is addressed and the network component groups’ priorities are identified according to given earthquake magnitudes and interdependency level for decision support in hazard mitigation planning and disaster prevention management.

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Study on the effects of compressed-air self-help system in mine fires

Kun Li and Xuyang Xie

Smoke gas from the mine fire was the main reason in-ducing to high death rate of the mine workers. Based on the 3D tunnel model and the compressed air self-help system model, the influence of the compressed air self-help system on ventilation, smoke gas distribution and safety area (the smoke concentration less than 24ppm) has been investigated when the tunnel was fulfilled with smoke gas. The results show that the scale of the gas flow influenced by the compressed air increased linearly as the compressed air velocity increased. The compressed air flow had a little influence on the whole tunnel flow structure. Furthermore, along with the compressed air velocity increasing, the safety area increased first and when the compressed air velocity was larger than a certain value, the safety area got a constant value. Under the same compressed air velocity, when the vertical deflection angle (VDA) was -30°or the horizontal deflection angle (HDA) was 30°, the scale of gas flow influenced and the safety area in the tunnel would get its maximum value.

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Surface Subsidence caused by Solid Backfilling Mining

Zhu Xiaojun, Guo Guangli and Zha Jianfeng

Surface subsidence is the most common disaster in mining areas and has resulted in a series of environmental geology problems. Solid backfilling mining is a newly developed mining technology that not only reduces solid waste pollution but also controls surface subsidence. On the basis of the subsidence data for the HuaYuan mine in China, the final and dynamic characteristics of the surface subsidence basin caused by solid backfilling mining are analyzed. The characteristics of backfilling mining are different from those induced by caving mining in some respects. Further, partial subsidence prediction parameters of solid backfilling mining are different from those of caving mining. This study may provide a technical reference for subsidence disaster prevention and evaluation of solid backfilling mining characteristics.

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Relative Permeability Analysis of Unsaturated Hard Rock

Yongfeng Du, Jiang Guoping and Xiao Sanxia

Correlations between permeability and porosity are often tested for fractal unsaturated hard rocks in relation to petroleum geology and reservoir characterization. The capillary pressure and relative permeability are the key parameters that affect air and water transport through fractured rocks. In this paper, a fractal model to predict air and water permeabilities with porosity of unsaturated fractured rocks can be expected. The fractal technique is used to predict the relative permeability of unsaturated hard rock which considered the effect of tortuosity of capillaries and capillary pressure. The presented fractal model is completely derived from the properties of geometric and physical concepts. The predicted relative permeability determined by the presented model has a good agreement with the experimental results reported in the literature.

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Provisions for Geotechnical Aspects and Soil Classification in Indian Seismic Design Code IS-1893

Anbazhagan P., Gajawada Prabhu, Moustafa Sayed S. R., Arifi Al Nassir S. and Parihar Aditya

Seismic codes are important guidelines for urban planning and infrastructure development. Seismic codes are mainly used for earthquake resistant design of new structures and retrofitting existing structures. The geotechnical aspects play a crucial role in the development of response spectra for a site/region which is the basis for any earthquake resistant designs. In this study an attempt has been made to study the geotechnical provisions in the Indian earthquake code of “Criteria for earthquake resistant design of structures”17. The first version of this code was released by the Bureau of Indian Standards in the year 1962 and followed by many revisions soon after major earthquakes in the country. The modification in the zonation map of India with occurrence of significant earthquakes shows that the assessment of hazard on a regional scale is not consistent with local variation. India has diverse geology and geotechnical material (soil and rock) properties with typical borelogs from different parts of India. Seismic code groups the geology/geotechnical variation in three categories i.e. hard, medium and soft soil in order to account site and induced effects of earthquakes. In IS 1893, soil types are classified based on the standard penetration test (SPT) N-value and soil classification using grain size distribution. It is mentioned to take the N- value but the depth option for which the SPT must be considered is not clearly mentioned. Many international standards have soil shear wave velocity as the main factor to categorize the subsurface materials missing in the Indian standard. This paper also presents a comparison of design response spectra, as per Indian standard and modern international seismic standards like International Building Code (IBC) and Eurocode for similar earthquake, site and building conditions. Design spectral values given in the Indian code do not match with modern codes for similar seismicity, building type and site condition.

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Quantitative study of the separation of intrinsic and scattering seismic attenuation in southeastern Korea using the Monte Carlo simulation method

Chung Tae Woong

Coda observations from 765 seismograms recorded in southeastern Korea were quantitatively fitted by the Monte Carlo (MC) simulation method to separate intrinsic (Qi-1) and scattering (Qs-1) attenuation. Since the MC simulation method assumes a single source, this study examined several focal depths for the uniform velocity model (UVM) and found the least misfit-function at a depth of 10 km which is the dominant focal depth of data. On the other hand, the decrease of the misfit-function from the UVM to the best fit depth-dependent velocity model is only one-tenth that of the previous study for Korea as a whole. This small decrease would seem to be caused by the lateral heterogeneity of the velocity structure of the Moho depth. The shorter hypocentral distance than C2010 seems to enhance not only the effect of lateral heterogeneity but also the attenuation value, reflecting the high Q-1 values in the shallow crust.

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