Editorial

Integrated approaches to explosive volcanic eruptions

Doronzo Domenico M.

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Assessment of LID-BMPs for Urban Runoff Control in Newly Developing Zones: the Case of Yanming Lake Residential District, China

Min Liu, Chuanbin Zhou* and Rusong Wang

The best management practices for low impact development (LID-BMPs) have been widely applied to control stormwater runoff. LID-BMPs using bio-retention and bio-filtration swales were planned to control the urban runoff in the studied case of the Yanming Lake Residential District which is a developing urban zone. The control of runoff by the LID-BMPs was simulated and assessed by applying the following methods of scenario analysis, SCS-CN model and GIS tool. The three scenarios studied were the existing background (EB), a conventional stormwater drainage system (CSD) and an ecologically designed stormwater system (EDS). We found that the land use types affected rainfall-runoff, with the runoff depth decreasing in the following land use types: road > commercial land > residential land > arable land > woodland > green/grassland. The different stormwater controlling systems, in the same land use type, also affected the runoff amount, with the runoff from EDS being 77.2% to 87.7% less than CSD. EDS had a “system-wide” reduction of runoff volume. The runoff volume of EDS (3.50 106 m3) was 25% less than EB (4.69 106 m3) and 36% less than CSD (5.49 106 m3). EDS showed the best performance on flood control, the submerged area was reduced by (1.84 106 m2) (24.0%) and (2.09 106 m2) (25.5%) compared to EB and CSD respectively.

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Laboratory study of unloading rate effects on rockburst

He Manchao1, 2* and Zhao Fei1, 2

Unloading rate is one of the most important factors that affect rock properties in rockburst tests. In this paper, a series of granite rockburst experiments at different unloading rates were performed. Several investigations have been made to study the influence mechanism of unloading rate including macroscopic failure modes of specimens, volumetric features of fragments as well as evolution regularities of AE frequency spectrum and energy releasing characteristics. The tests results indicate that unloading rate has great influence on failure modes of specimens. With the increasing of unloading rates, the failure modes of specimens change from general damage to spalling damage until violent rockburst which is accompanying with large amounts of fragments ejection and total destruction of specimen body. The effect on fragment structure is also highlighted by the findings that the fragment exhibited from blocky structure to platy structure with the unloading rate transition from a high value to a low value. As the unloading rate is higher, the AE activity and the frequency spectrum characteristics will be more pronounced.

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Numerical studies on seismic interference of two nearby embedded shallow footings

Ghosh Priyanka

In the present study, an attempt is made to model the seismic response of two perfectly rough embedded square or rectangular footings placed in close spacing on layered soil deposit resting on strong bed rock by using the explicit finite difference code FLAC3D. Each footing carries equal static working load without violating the ultimate bearing capacity under static condition. The soil is assumed to obey the Mohr-Coulomb failure criteria with non-linear failure envelope. The results are presented in terms of horizontal x-acceleration response on the top of the footings, the ultimate bearing capacity, the settlement of footings under both static and seismic conditions with the variation in clear spacing between two footings and the stresses developed at the base of each footing under seismic excitation. The present theoretical investigation indicates that the settlement of closely spaced footings under seismic condition is generally found to be higher than that of single isolated footing.

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Computer simulation of dynamic influence of outburst gas flow on mine ventilation network

Wang Kai1,2, Zhou Aitao1,2* and Li Shan1

Based on the theories of fluid dynamics and network, a mathematical model of unsteady flow in mine ventilation network is established and an unsteady ventilation network calculation program is developed in Visual C++ programming language. Then dynamic influences of outburst gas on mine ventilation network in different roadways are simulated with the program. The simulation results show that under the influence of outburst gas pressure, gas flow in the branches beside the branch filled with outburst gas may be reversed in the upward ventilation and that gas flow in the branch filled with outburst gas may be reversed in the downward ventilation. Gas flow in the downward ventilation is more harmful than that in the upward ventilation. Thus, the upward ventilation shall be adopted in the coal and gas outburst mine.

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IM-based hazard assessment on debris flows in the upper reaches of Min River

Ding Mingtao

With the upper reaches of Min River as the study area, field survey as the foundation and the high resolution remote sensing visual interpretation as the method, a systematic analysis on the forming conditions of debris flows in the upper reaches of Min River is launched in this study. Employing the ArcGIS Software and the Information Model (IM) and taking the 8 influencing factors including slope aspect, slope gradient, stratum lithology, fault belts, human engineering activities, river scouring action, seismic intensity and precipitation as the assessment index parameters, the hazardous area has been divided into three zones: high, middle and low hazard. Furthermore, the assessment result is in conformity with that of the field survey, indicating that GIS-based IM will effectively provide parameter reference for the study of hazard zoning of the debris flows in the upper Min River and that such assessment result will help resolve the existing problems such as poor efficiency, low resolution, painstaking and time-consuming process so as to realize the scientific hazard assessment.

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Energy Dissipation and Release during Rock Burst

Chen Xuguang1,2* and Wang Yuan1

Abstract The geological environment and structure of rock decide the shear failure is the most common failure mode. Failure of underground cavities such as rock bursts are mostly damaged as shear failure. Shear cracks differ from tensile cracks in that the rock can release larger amounts of energy in the shear failure mode. The relationship of the strain-stress cannot reflect the essence of the deformation and failure of rock because of the mechanical parameters weakening during failure process. Consequently, research on changes in energy during the deformation and failure of rock is important. Based on theoretical calculations of energy dissipation and energy release, energy changes are studied and a model of uniaxial compression shear failure is taken as an example. The relationships among different types of energy are studied and the proportions of energies released after rock failure are computed. The present study is meaningful in realizing the proportions of different types of energy after stress re-distribution and the magnitudes of kinetic energy and rock burst.

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The psychology and well-being of adult survivors after the 2008 Wenchuan earthquake

Yuan He1, 2* and Jiuping Xu1

The powerful earthquake of May 12, 2008 wrought incalculable havoc on lives and properties in Wenchuan, Sichuan Province, China. The catastrophic earthquake not only created tremendous changes in the external environment but also caused stress and difficulties for the people in the affected areas which were felt long after the event. In this study, we attempt to examine the consequences of the earthquake to assess level of exposure to the disaster and well-being after this event. 2,080 survivors from nineteen counties freely participated in the survey which used self-report psychological questionnaires, including SF-12-v2, stress risk and social psych resources. We estimated regression models to identify stress risk and social psych resources associated with the presence of mental symptoms after the disaster. Disaster exposure did have a lasting impact on variation in local resident well-being. Experiencing negative life events and disease related to poorer physical health and better social psychological resources had improved mental health and decreased PTSD symptom. Female respondents or respondents aged 40-50 were more likely to suffer from poorer mental health compared male and other aged groups. Survivors aged 40-50 should take recuperation therapy. Local educators, psychological workers and volunteers should be trained on psychology intervention and government should make mental health policies.

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Tension Measurements for Xinbei Cable-Stayed Bridge with Ambient Vibrations and an EM Tension Sensor

Chih Kun Chu1, Che-Way Chang1*, Min-Jian Huang2, Qi-Wei Zhang2 and Chen-Hua Lin1

This research studies the XINBEI Bridge, which is a cable-stayed bridge that has a pylon symmetric cable configuration with a total span of 400 meters, 200 meters on each side of the pylon, along the embankment of the Sanchong area. The no infill HDPE sheathed stayed cables in this cable-stayed bridge are very important to the structure because they carry the deck of the bridge. To ensure the structural health of these cables so that they can work properly and will not fail due to overload, measurements of the load supported by the cable should be performed. Due to the nature of the cable-stayed bridge, the force inside the cable will be an axial force. In this paper, the conducted field observation results will be compared using an FBG based accelerometer and a cable tension sensor instrument, all for no infill HDPE sheathed based stayed cables, which are different from traditional stayed cables in which the inside cable and the sheathing are not in contact with each other. The results can be useful in cable-stayed bridge design and analysis, as well as structural health monitoring systems for cable-stayed bridges.

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Sediment Characteristics and Hydrodynamic Setting of Kanyakumari, South India

Natesan Usha*, Om Prakash M. and Deepthi K.

Kanyakumari is an area, unique in nature wherein two seas - Bay of Bengal and Arabian Sea and the Indian Ocean converge. MIKE 21, a 2D numerical model was applied to the 68 km coastal stretch of Kanyakumari to assess the seasonal variations in hydrodynamics for a period of 15 days (spring tide) in 2009. The sediment grain size distribution was also used to determine its hydrodynamic setting. The sediment characteristics reveal a high wave energy environment. The strong winnowing action has led to the removal of fine sediments leaving the coarser sediments in the foreshore. Hydrodynamic variations such as surface elevation, water depth and current velocity are relatively high during monsoon season when compared to fair weather conditions. Current speed of 0.75 m/s to 1m/s is observed during northeast monsoon which reduces to 0.5 to 0.6 m/s during southwest monsoon with the least in summer and post monsoon (0.01m/s to 0.2m/s). With the use of numerical modeling, it is quite possible to obtain more information on the marine conditions of the area even when the field data is limited. Numerical models offer engineers very useful tools to cope with the limited data in calibration and verification stages. Results from the model will serve as a baseline and help coastal managers in decision making for future developmental activities in Kanyakumari coast.

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A Dynamic Design Method for Highway Sub-grade to Prevent Disaster due to Long-Term Traffic Loads

Lu Zheng* and Yao Hailin

In order to prevent disaster due to progressive failure of highway induced by long-term repeated traffic loads, a dynamic design method for highway sub-grade is proposed in this paper. Based on the field test data of pavement roughness, the influencing factors on vehicle loads are analyzed considering moving velocity and vibration frequency of the traffic loads. A simplified three-layer structure of highway is obtained by adopting the method of Ode mark equivalent hypothesis of modulus-thickness. The computation expression of dynamic deformation of sub-grade is deduced with elasto dynamics theorem and Fourier transform method. Combining the expression of dynamic deformation and the pavement deflection control standard of current specification, the control value of dynamic deformation of sub-grade top and the determination method is derived in the context of compatibility of deformation between pavement and sub-grade. According to the control standard, a new design method of sub-grade on control deformation is advanced and three typical asphalt pavement structures are designed for illustration using this method.

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Application of new nonlinear elasticity and nonlinear dynamics tools in real time monitoring of large engineering constructions (case of high arc Enguri dam)

Chelidze T.,1, 2* Matcharashvili T.1, 2 and Abashidze V.1, 2

Large engineering constructions (dams, bridges, high towers etc.) are complex structures with nonlinear dynamic behavior. Engineers often are forced to assess their safety based on the available incomplete data which is extremely difficult. This important problem can be solved with the modern theory of complex systems. It is possible to derive characteristics of the whole unknown dynamics of a structure using few data sets of certain carefully selected representative parameter(s). We created a cost-effective Monitoring Telemetric System for Dam Diagnostics (DAMWATCH) which consists of sensors (tiltmeters), terminal and central controllers connected by the GSM/GPRS Modem to the diagnostic center. The tilt data recorded for varying reservoir level are compared with static design model of dam deformations computed by a finite element method (FEM) for the dam-reservoir-foundation system. Besides, recently developed linear/nonlinear data analysis and prediction schemes may help to quantify fine dynamical features of the dam behavior using monitoring time series. The software package DAMTOOL has been developed for this purpose. The differences between measured and theoretically predicted response parameters of the dam may signal abnormal behavior of the object. The data obtained already by testing of the DAMWATCH/ DAMTOOL system during operation of the high Enguri arc dam and its reservoir (Georgia) show interesting long-term and short-term patterns of tilts in the dam body which can be used for diagnostics. Of course main principles of both the real-time monitoring system and analysis approach can be applied to any large engineering construction. Thus, in following we will use the word “dam” as a collective term for large engineering constructions. The 271 m high Enguri arch dam, still the highest (in its class) dam in the world, was built in the canyon of Enguri river (West Georgia) in the 1970s. The high seismic and geodynamical activities together with a high population density of the adjoining region made the Enguri dam a potential source of a major technological catastrophe in Georgia. That is why in 1996 the European Centre “Geodynamical Hazards of High Dams” with the Enguri Dam International Test Area (EDITA) was organized in Georgia by the Council of Europe. From the very beginning in EDITA the unique geotechnical, geodynamical and geophysical monitoring system was functioning1. The database of observations (tilts, strains etc) contains information accumulated during more than 30 years.

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