Prediction of the Bullet Effect for Rockfall Barriers: a Scaling Approach

The so-called “bullet effect” refers to the perforation of a rockfall protection mesh by impact of a small block, which has a kinetic energy lower than the design value, where the design value is determined through tests with relatively large blocks. Despite playing a key role in the overall performance of a flexible rockfall barrier, this phenomenon is still poorly understood at present. An innovative approach for quantitatively characterizing this effect based on dimensional analysis is proposed in this paper. The analysis rests on a hypothesis that the relevant variables in the impact problem can be combined into three strongly correlated dimensionless parameters. The relationship between these dimensionless parameters (i.e., the scaling relationship) is subsequently investigated and validated by means of data generated with a finite element model. The validation process shows that the dimensionless parameters are apt and that the proposed scaling relationship characterizes the bullet effect with a reasonable level of accuracy. An example from the literature involving numerical simulation of a full rock barrier is considered, and satisfactory agreement between the calculated performance of the barrier and that predicted by the established scaling relationship is observed.     

A Bay–River Coupled Model for Storm Surge Prediction Along the Andhra Coast of India

The paper describes a two-dimensional bay–river coupled numerical model for storm surges along the Andhra coast of India. The effect of the Krishna and Godavari rivers on the surge development is analysed. A comparative study of the surge generated by a tropical cyclone with and without the inclusion of rivers is done in detail. Three cyclones that struck the Andhra coast in November 1977, May 1990 and November 1996 were used for the simulation studies. It is found that the idealized model without a river overestimates the sea-level elevation as compared to a more realistic bay–river coupled model. The temporal variation of surge values at the mouth of the rivers is also studied for all three cyclone cases. It is found that the effect of the presence of rivers depends on the strength of the cyclone, its point of landfall and the location of the rivers with respect to the landfall point.     

Rockfall hazard assessment at Ajanta Cave,Aurangabad, Maharashtra,India

The Ajanta caves are situated in Deccan Trap basalt and declared as one of the World Heritage Sites by UNESCO. The present study aims to investigate and understand the damage of caves and to protect the life of the visitors from the rockfall phenomenon at and around the caves. Information related to the detached rock mass/block was acquired by using Barton–Bandis model in Universal Distinct Element Code. Parameters for rockfall simulation were determined by rigorous field study and laboratory experiment and then calibrated some of the parameters by back analysis. RocFall 4.0 program has been used to calculate maximum bounce heights, total kinetic energies, and translational velocities of the falling blocks of different weights. The maximum bounce height varies from 14.0 to 19.0 m for the weight of the block size ranging from 500 to 2,000 kg, whereas the maximum velocity and maximum kinetic energy are 30.0 m/s and 917.66 kJ, respectively. Finally, the results of simulation have been used to find out the position of the barrier and its capacity to design the protection barrier. The barrier capacity was found to be 325 kJ for 2,000 kg of falling blocks at a height of 50.0 m.     

Ichnofossils from the Miocene Middle Bhuban Formation, Mizoram,Northeast India and their Paleoenvironmental Significance

An ichnofossil assemblage is preserved in sediments of the Middle Bhuban Formation,Surma Group,of Miocene age from the Durtlang and Chanmari sections,Aizawl district,Mizoram,northeastern India.The studied sections comprise a thick,bioturbated and thinly bedded sandstone–silty shale facies.The preserved ichnofossils show high density and low diversity with the assemblage represented by feeding and resting traces,i.e.,Psilonichnus upsilon Frey et al.,1984,Ophiomorpha isp.,Teichichnus spiralis Mikulá.1990,Skolithos isp.,Palaeophycus isp.,and other horizontal burrows.Sedimentary structures associated with these traces are mainly cross bedding,flaser bedding and slump structures.Considering the distribution of the Psilonichnus ichnogenus across an integrated ichnological–sedimentological framework,the stratigraphic interval of the Middle Bhuban Formation,in which they occur,are interpreted to have been deposited under a shallow,marginal-marine channel complex dominated by tidal channels developed in quiet,brackish-water portions of a delta plain.     

Quality assessment of potable water in the town of Kolasib,Mizoram (India)

The potable water for the residents of the town of Kolasib in Mizoram state, India, is supplied by the Public Health Engineering Department (PHED) of the Government of Mizoram without any notable treatment. The source of water is the Tuichhuahen River, flowing from north to south in the area. Water samples were analyzed for their physicochemical and bacteriological characteristics in order to obtain the current quality level of the potable water in the twon. The samples were collected from two different sources, i.e., the supply from the government agency (PHED) and from the naturally occurring springs (tuikhurs). The results suggest that the water supplied by the PHED is better than that from the tuikhurs; however, the quality of water from both sources, which are used for drinking and domestic purposes, were found to be more or less within the tolerance limits.     

A Simplified Numerical Approach for the Prediction of Rainfall-Induced Retrogressive Landslides

Retrogressive landslides are common geological phenomena in mountainous areas and on onshore and offshore slopes. The impact of retrogressive landslides is different from that of other landslide types due to the phenomenon of retrogression. The hazards caused by retrogressive landslides may be increased because retrogressive landslides usually affect housing, facilities, and infrastructure located far from the original slopes. Additionally, substantial geomorphic evidence shows that the abundant supply of loose sediment in the source area of a debris flow is usually provided by retrogressive landslides that are triggered by the undercutting of water. Moreover, according to historic case studies, some large landslides are the evolution result of retrogressive landslides. Hence the ability to understand and predict the evolution of retrogressive landslides is crucial for the purpose of hazard mitigation. This paper discusses the phenomenon of a retrogressive landslide by using a model experiment and suggests a reasonably simplified numerical approach for the prediction of rainfall-induced retrogressive landslides. The simplified numerical approach, which combines the finite element method for seepage analysis, the shear strength reduction finite element method, and the analysis criterion for the retrogression and accumulation effect, is presented and used to predict the characteristics of a retrogressive landslide. The results show that this numerical approach is capable of reasonably predicting the characteristics of retrogressive landslides under rainfall infiltration, particularly the magnitude of each landslide, the position of the slip surface, and the development processes of the retrogressive landslide. Therefore, this approach is expected to be a practical method for the mitigation of damage caused by rainfall-induced retrogressive landslides.     

Deformation History of the Kunavaram Complex, Eastern Ghats Belt, India: Implications for Alkaline Magmatism Along the Indo-Antarctica Suture

The Kunavaram alkaline complex is a NE-SW trending elongate body located along a major lineament, the Sileru Shear Zone (SSZ) that is regarded as a Proterozoic suture related to Indo-Antarctica collision. The complex is hosted within migmatitic quartzofeldspathic gneisses, mafic granulites retrogressed to amphibolites, and quartzites. The structural evolution of the country rocks and the alkaline complex are similar. The first phase of deformation, D₁, produces a pervasive segregation banding (S₁) in all rock units within and outside the complex. A second deformation phase D₂ isoclinally folded S₁ along subvertical axial planes with shallow plunging axes. F₂ isoclinal folds are ubiquitous in the country rocks and the eastern extremity of the complex. In the interior of the alkaline body, D₂ strain decreases and S₁ is commonly subhorizontal. While amphibolite to granulite facies conditions prevailed during deformation, post-D₂ annealing textures testify to persisting high grade conditions. In the west, a NNE-SSW trending dextral shear zone with strike-slip sense (D₃) truncates the complex. Within this shear zone, quartzofeldspathic country rocks are plastically deformed, while hornblende-K-feldspar assemblages of the complex are retrogressed to biotite and plagioclase. Warping related to D₃ shears also resulted in fold interference patterns on the subhorizontal S₁ foliation in low D₂ strain domains. Based on its steep dip, north-easterly trend, and non-coaxial nature with dextral strike-slip sense, the D₃ shear zone can be correlated with the SSZ. Since this shear zone, i.e., the SSZ, is not associated with primary igneous fabrics and resulted in solid state deformation of the complex, it cannot be considered as a conduit for alkaline magmatism, but is probably responsible for the post-tectonic disposition of the pluton.     

Formation Mechanism of Mud Bank Along the Southwest Coast of India

Mud bank formation during the southwest monsoon along the southwest coast of India remains an enigma to the researchers and coastal community in spite of several earlier studies. The present study attempts to unravel the mystery through a high-frequency, season-long time-series observation at Alappuzha, located at the southern part of the west coast of India, a region of frequent occurrence of mud bank. Using 7-month-long weekly time-series observation, we identified strong winds and high waves associated with onset of the southwest monsoon and subsequent three episodic atmospheric low-pressure events (LPEs).With the help of in situ time-series data, we show that the strong winds and high waves associated with southwest monsoon pre-conditions the near shore bottom sediment to bring it into suspension. The high amplitude waves associated with the southwest monsoon, while propagating from the deep water to shallow water region, interact with the bottom initiating bottom-sediment movement and its suspension due to wave refraction and shoaling. The sporadic occurrence of the atmospheric LPEs enhances the process of suspension of bottom sediment in the near shore region leading to the formation of fluid mud. Simulations with a cohesive sediment transport model yielded realistic estimates of sediment transport, in the presence of an onshore current, a pre-requisite for transporting the fluid mud toward the coast. The prevailing onshore upwelling current during the southwest monsoon provides the favorable pre-requisite conditions for transporting the fluid mud through depression channel network towards the coast. Once sufficient quantity and thickness of fluid mud is accumulated in the near shore region, it acts as a wave damper for subsequent high monsoon waves, as indicated by the time-series wave data, leading to the formation of tranquil mud bank region. Depression channel networks extending from the shelf to the coast off Alappuzha, Kochi, Ponnani, Beypore, and Ullal were found in the bathymetric charts, thus explaining why mud banks occur only at few locations in spite of the prevalence of similar monsoon conditions.     

A GIS Approach to Prediction of Copper Deposits

INTRODUCTIONGeo-anomaly (GA) ,according to the Geo-Anomaly The-ory proposed by Professor Zhao Pengda,is the geological bod-ies or the combination of the geological bodies that are obvi-ously different from their surrounding geological bodies instructure,formation and genetic sequence.The ore body is avery special type of GA.The examination of the GA environ-ment is the basis of ore-prospecting,the premise of ore-find-ing and the criterion of target selection (Chi et al.,1 997) .The G…     

青藏公路沿线多年冻土变化及环境意义(英)

The permafrost on the Qinghai-Tibet Plateau(QTP) is unstable and sensitive to thermal disturbance due to the combined influences of anthropogenic forcing and global warming on the unique environmental background for permafrost development and preservation. Observations in about 40 years show natural and engineering environments of permafrost region along Qinghai-Tibet Highway(QTH)have changed significantly. The change of permafrost environments on the plateau will result in the remarkable shifts of physical geography and engineering geological environments. In addition, permafrost on the QTP responses actively and feedbacks to global climatic changes significantly. The study of permafrost on the plateau is no less important than the Arctic and Antarctic, and also provide a valuable linkage of climatic and environmental change studies between the other two poles. As the development of the plateau and adjacent areas in large scale is eminent, permafrost as the most important natural environmental factor, its stability and possible changes are extremely important in regional economical development. Therefore, the prediction of these changes and reasonable assessment of permafrost engineering conditions on the plateau based on permafrost monitoring are indispensable for the healthy and sustainable economical development in these regions.     

Status of arsenic contamination in potable water of Northern areas of Mizoram State and its adjoining areas of Southern Assam, India

A reconnaissance survey was conducted to examine the physicochemical properties of the potable water of Northern parts of the State of Mizoram, India, as well as the adjoining southern parts of the State of Assam, India. Groundwater samples were taken from those sources of water which were used as potable water source in the area. All the samples were analyzed for ionic concentrations of potassium (K⁺), sodium (Na⁺), calcium (Ca²⁺), magnesium (Mg²⁺), chlorine (Cl^?), sulfate (SO ₄ ^2? ), manganese (Mn), iron (Fe), and arsenic (As). Parameters such as pH, electrical conductivity, total dissolved solids, and total hardness were also measured in situ using digital instruments. The aim of the present work is to study the various physicochemical parameters following the recommendations of World Health Organization in order to test whether these sources are safe enough to be used as potable water resources. Furthermore, present work will throw light on the probable causes of presence of arsenic in Silchar City of southern Assam and total absence of it in neighboring state of Mizoram.     

Trace fossils from Bhuban Formation,Surma Group (Lower to Middle Miocene) of Mizoram India and their palaeoenvironmental significance

A detailed ichnological study performed on the Bhuban Formation, Surma Group (Lower to Middle Miocene) of Mizoram, India reveals the occurrence of rich and diverse trace fossils. These have been collected from the two localities in Aizawl, i.e., Bawngkawn and Ropaiabawk, where sandstone—shale sequence is well exposed. Total 20 ichnospecies of 14 ichnogenera have been identified which include Arenicolites isp., Cochlichnus anguineus, Helminthopsis abeli, Laevicyclus mongraensis, Ophiomorpha borneensis, Palaeophycus tubularis, Palaeophycus heberti, Palaeophycus sulcatus, Palaeophycus alternatus, Pholeus abomasoformis, Pholeus bifurcatus, Planolites beverleyensis, Planolites annularis, Polykladichnus irregularis, Rhizocorallium isp., Skolithos linearis, Taenidium satanassi, Teichichnus rectus, Thalassinoides horizontalis and Thalassinoides paradoxicus. Ethologically these ichnogenera display dwelling and feeding activities of the infaunal organisms. Arenicolites, Ophiomorpha, Polykladichnus and Skolithos are the members of the Skolithos ichnofacies while Palaeophycus, Planolites, Rhizocorallium and Thalassinoides are the members of the Cruziana ichnofacies. The presence of Skolithos ichnofacies indicates sandy shifting substrate and high energy conditions in foreshore zone while the Cruziana ichnofacies indicate unconsolidated, poorly sorted soft substrate and low energy condition in the shoreface/offshore zone. These ichnogenera indicate foreshore to shoreface-offshore zone of shallow marine environment for the deposition of the rocks of the Bhuban Formation of Mizoram.     

Rockfall hazard and risk analysis for Monte da Lua,Sintra, Portugal

The prediction of rockfall trajectories below a rock cliff is essential in susceptibility, hazard and risk maps, particularity close to populated areas. The Monte da Lua hill area in Portugal, a tourist destination close to the historic city of Sintra (UNESCO World Heritage), is a typical granite boulder chaos landscape where from time to time rockfalls occur, the last such event having occurred on 29 January 2002. This area is therefore suitable to develop a rockfall study in order to provide hazard and risk maps a basis for mitigation measures. A preliminary investigation of the area leads to the identification of 188 potentially dangerous boulders. Detailed locations and geotechnical characteristics in terms of geometry, strength and context were sampled for each boulder. Digital elevations at 1 × 1 m resolution, known rockfall trajectory and building locations are provided in a GIS project for the study together with the spatial database of boulder characteristics. The modelling approach was conducted in two steps: (1) discrimination of the boulders in terms of static and dynamic mobility behaviour with multivariate analysis; (2) stochastic simulation of rockfall trajectories. The rockfall trajectory algorithm proposed is straightforward and is only dependent on elevation data, initial location of boulders and a friction angle. Due to the slope of the area, it assumes that rockfall is always of the rolling or sliding type. The friction angle was calibrated on the basis of the rockfall travel distance recorded on 29 January 2002 and generates simulated “realistic” trajectories. A smaller friction angle increases all simulated trajectories, leading to more “pessimistic” scenarios. The combined analysis of trajectories and potential damage to buildings and discrimination in terms of static and dynamic behaviour provides a final table in which all 188 sampled boulders are classified in one of the five risk grades.     

中国-巴基斯坦喀喇昆仑公路Ghulkin冰川百年进退变化

巴基斯坦喀喇昆仑山的Ghulkin冰川是距离中国-巴基斯坦喀喇昆仑公路最近的典型冰川之一,其冰川的进退变化影响着喀喇昆仑公路改建工程的线路设计与工程施工.为了追溯Ghulkin冰川的活动历史和查明近期进退变化,对过去200 a的相关文献和记录进行统计分析,并开展了2008-2011年野外定点观测,总结与分析了Ghulkin冰川冰舌的活动历史与近期变化.研究表明：Ghulkin冰川在1885-1980年近百年间经历了3次前进和3次后退,在此期间冰川波动了625 m;1913-1925年冰川处于显著的前进状态,1966-1978年冰川有小段距离的前进;2008-2011年K676+660处泥石流沟道逐年抬升,2011年南坡冰川融水由K676+660改道至K676+450;2010年的南坡冰舌较1994年后退了300余米,2011年的南坡冰舌较2010年后退了15.066 m,可见在2010-2011年期间冰川处于局部短期后退状态. 中巴公路冰川泥石流等灾害不但受区域气候的影响,而且还受冰川变化的影响.未来气候变暖将会导致冰川的强烈消融和后退,冰川融水携带大量冰碛体,形成大型的冰川泥石流,对公路的安全运营造成严重威胁.     

Petromineralogic and rock magnetic aspects of clastic sedimentation in the Surma basin, Mizoram

We present here comprehensive petromineralogic, mineral magnetic and lithologic observations from five stratigraphic sections representing the Barail Group, Middle and Upper units of Bhuban Formation, Bokabil Formation and Tipam Group in the Mizoram area. These stratigraphic units mainly display interplay of the grey and buff colored sandstones of the clast compositions varying from sub-lithic to lithic arenites (Q₇₉F₄L₁₇ to Q₅₅F₃L₄₂) including sedimentary, meta-sedimentary and subordinate igneous rock fragments. The buff sandstones with higher lithic fragments [Q₆₉F₄L₂₇ (Ls₆₁Lm₃₈Lv₁)] are dominated by recycled components with higher clast angularity (VA₁A₁₅SA₅₁SR₂₄R₈WR_0.4) relative to the grey sandstones. Mineral magnetic studies decipher bimodal (ferri- and antiferromagnetic) mineralogy with higher concentration in buff sandstones relative to the unimodal ferrimagnetic nature of the grey sandstones. The study infers that the buff sandstones mark the regressive phases driven by hinterland uplifts; whereas the growth of the grey sandstone facies is marked by transgressive basinal processes. Gradual increase in the frequency and appearance of the buff sandstones in the Surma stratigraphy, therefore, can be related to the evolution of the Indo-Burmese ranges.     

高速公路软土路基沉降量的人工神经网络预测

针对高速公路建设中广泛存在的软土路基最终沉降量预测这一迫切需要解决的技术难题,提出了改进的BP神经网络预测模型,并归纳出影响软土路基沉降量的主要因素.通过对模型的建立、训练和验证,以及与其他方法的对比表明,改进的BP神经网络模型在非线性建模方面具有泛化性强、计算精度高、操作简便的独特优势,具有广阔的工程应用前景.     

Rockfall hazard in the Daisekkei Valley, the northern Japanese Alps, on 11 August 2005

This paper describes a rockfall event in the Daisekkei Valley of Mount Shirouma-dake (2,932 m), the northern Japanese Alps. The rockfall occurred on a steep cliff comprising well-jointed felsites and produced debris of ≥8,000 m³. Most debris was deposited on an elongated snowpatch located immediately beneath the cliff, and it caused casualties among people who were trekking along a trail on the snowpatch. Additionally, a large rock block slipped 1 km on the snowpatch. The rockfall could have been due to the differential retreat of the rockwall, which contains areas of high- and low-density joints. Seasonal and diurnal freeze–thaw activities and snow avalanches and wash appear to be important factors responsible for the retreat. Although some rock blocks that can collapse further remain on the rockwall, the position of the mountain trail in the Daisekkei Valley is fixed. Fundamental reform of tourism systems for climbers, including education on natural hazards, is required.